Programm Photovoltaik Ausgabe 2002

Transcription

Forschung
Dezember 2012
Überblicksbericht, Liste der Projekte
Jahresberichte der Beauftragten 2011
ausgearbeitet durch:
NET Nowak Energie & Technologie AG
Auftraggeber:
Bundesamt für Energie BFE
Forschungsprogramm Photovoltaik
CH-3003 Bern
www.bfe.admin.ch
Auftragnehmer:
Waldweg 8, CH-1717 St. Ursen
Tel. +41 (0)26 494 00 30, Fax. +41 (0)26 494 00 34
[email protected]
Autor:
Dr. Stefan Nowak, NET Nowak Energie & Technologie AG
[email protected]
BFE-Bereichsleiter:
Dr. Stefan Oberholzer
BFE-Programmleiter:
Dr. Stefan Nowak
BFE-Vertrags- und Projektnummer: SI/500020-02
Für den Inhalt und die Schlussfolgerungen ist ausschliesslich der Autor dieses Berichts verantwortlich.
Titelbild: Bildquelle NET
Forschung
Inhalt
S. Nowak
Überblicksbericht des Programmleiters
Seite 7
Jahresberichte der Beauftragten
Seite
Solarzellen
C. Battaglia, M. Despeisse, F.-J. Haug, S. Nicolay, L.-E. Perret-Aebi, F. SculatiMeillaud, R. Tscharner, C. Ballif
New processes and device structures for the fabrication of high efficiency
thin film silicon photovoltaic modules – SI/500031 / SI/500031-01
31
F. Sculati-Meillaud, S Nicolay, G. Parascandolo, G. Bugnon, C. Ballif
PEPPER: Demonstration of high performance processes and equipments for thin
film silicon photovoltaic modules produced with lower environmental impact and
reduced cost and material use – PEPPER 249782
45
S. Nicolay
N2P: Flexible production technologies and equipment based on atmospheric
pressure plasma processing for 3D nano structured surfaces – N2P 214134-2
52
F.-J. Haug, C. Ballif
SILICON LIGHT: Improved material quality and light trapping in thin film silicon
solar cells – FP7 241277
57
Interface texturing for light trapping in solar cells
– SNF 200021-125177/1 / 200020-137700/1
61
1/394
S. De Wolf, L. Barraud, A. Descoeudres, F. Zicarelli, C. Ballif
THIFIC: Thin film on crystalline Si – Axpo Naturstrom Fonds 0703
65
Z. Holman, S. De Wolf, C. Ballif
20 Percent efficiency on less than 100μm thick industrially feasible c-Si solar
cells – 20plμs 256695
69
Ch. Hollenstein, M. Chesaux, A.A. Howling
A new low ion energy bombardment PECVD reactor - Deposition of thin film
silicon for solar cell applications – KTI 9675.2
73
D. Gablinger, R. Morf
Zweidimensionale Nanostrukturen für Silizium-Solarzellen
– SI/500141 / SI/500141-01
74
C. Niederberger, J. Michler
ROD-SOL: All-inorganic nano-rod based thin film solar cells on glass
– NMP-2008-2.6.1 / 227497
79
R. Verma, A. Chirila, S. Buecheler, S. Nishiwaki, A.N. Tiwari
FEBULAS: Flexible CIGS solar cells and mini-modules on polymer without - or
with alternative buffer layer – SI/500394 / SI500394-01
87
F. Pianezzi, A. Chirila, S. Buecheler, S. Nishiwaki, A.N. Tiwari
IMPUCIS: Influence of impurities on the performance of CIGS thin film solar cells
– SI/500417 / SI500417-01
96
S. Buecheler, A. Chirila, P. Blösch, A.N. Tiwari
HIPO-CIGS: New concepts for high efficiency and low cost in-line manufactured
flexible CIGS solar cells – HIPOCIGS 241384
102
Y.E. Romanyuk, A.R. Uhl, C. Fella, A.N. Tiwari
NOVA-CIGS: Non-vacuum processes for deposition of CI(G)S active layer in
PV cells – NOVACIGS 228743
107
P. Blösch, S. Bücheler, A.N. Tiwari
Multifunctional back electrical contact for flexible thin film solar cells
– KTI 10245.1
113
B. Ruhstaller, N. A. Reinke, M. Neukom, S. Züfle, R. Ritzmann, G. Nisato,
T. Offermans, J. Schleuninger, M. Chrapa, M. Turbiez, M. Düggeli, M. Wienk,
R. Janssen, S. Kuijzer, K. Sastrowiardjo, G. Garcia-Belmonte, J. Bisquert, P. Boix,
APOLLO: Efficient Areal Organic Solar Cells via Printing
– SI/500122 / SI/500122-01
J. Heier, J. Groenewold
HIOS-CELL: Nanoscale structuring of heterojunction ionic organic solar cells by
liquid-liquid dewetting – SI/500297 / SI/500297-01
R. Hany, F. Nüesch
FABRI-PV: Transparent fabric electrodes for organic photovoltaics – KTI 9995.1
2/394
119
127
136
T. Geiger, Y. Shcherbakova, S. Hochleitner, F. Nüesch, T. Meyer
Neuartige Sensibilisatoren für Farbstoffsolarzellen: Squarain- und
Heptamethinfarbstoffe mit einer grossen spektralen Vielfalt oberhalb 700nm
– KTI 10584.1
140
T. Meyer, F. Oswald
ORION: Ordered inorganic-organic hybrids using ionic liquids for emerging
applications – FP7-229036
144
F. Nüesch, R. Hany, G. Wicht, A.N. Tiwari, S. Bücheler, C. Gretener, C. Ballif,
F. Sculati-Meillaud, S. Hänni, M. Stückelberger, S. Pélisset, M. Grätzel,
S.M. Zakeeruddin, F. Duriaux Arendse, G. Nisato, T. Offermans, T. Friesen,
B. Ruhstaller, M. Schmid, O. Schumacher
DURSOL: Exploring and improving durability of thin film solar cells
– CCEM-DURSOL
151
J. Elias, L. Philippe, J. Michler
ETA SOLAR CELL: Extremely Thin Absorber Solar Cell based on
electrodeposited ZnO Nanostructures – SI/500426 / SI/500426-01
156
M. Loeser, K. Lapagna, B. Ruhstaller, J. Elias, L. Philippe
Numerical Simulation, Design and Fabrication of Extremely Thin Absorber
Solar Cells – SI/500613 / SI/500613-01
164
A. Fontcuberta i Morral
UPCON: Ultra‐high Purity nanowires for energy CONversion
– UPCON 239743
173
T. Meyer, F. Oswald
INNOVASOL: Innovative materials for future generation excitonic solar cells
– FP7-227057
178
T. Meyer
SOLAMON: Plasmons generating nanocomposite materials (PGNM) for
rd
3 generation thin film solar cells – FP7-226820
186
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Module und Gebäudeintegration
F. Ruesch, L. Omlin, S. Brunold
Solarglas PV – SI/500614 / SI/500614-01
197
T. Szacsvay
SmartTile II - Pilotanlage: Innovative Photovoltaik Indachlösung
– SI/500388 / SI/500388-01
L.-E. Perret-Aebi, P. Heinstein, V. Chapuis, S. Pélisset, K. Lumsden, R. Tween,
M. Mottet, Y. Leterrier, J.-A. E. Månson, M. Joly, V. Le Caër, S. Mertin, A. Schüler,
C. Roecker, M. Edelman, G. Stoll, J.-L. Scartezzini, M. Bätschmann, V. Ritter,
H. Leibundgut, P. Mirzaee, K. Ghazi Wakili, J. Carmeliet, C. Ballif
ARCHINSOLAR: Unique and Innovative Solution of Thin Silicon Films Modules
Building Integration – SI/500474 / SI/500474-01
Y. Leterrier, M.A. González Lazo, R. Teuscher, P. Velut, R. Tween, K. Lumsden,
J.-A.E. Månson, C. Calderone, A. Hessler, P. Couty, Y. Ziegler, F. Galliano, D. Fischer
Conformal photovoltaic modules – KTI 9903.1
M. Despeisse, C. Ballif
SUNSIM: Large Area solar simulator integrating power Light Emitting Diodes for
performance measurement of new generations of photovoltaic modules
– KTI 10880.2
204
212
218
225
A. Virtuani
MPVT: Multi-Purpose PV module tester – KTI 9626.1
230
E. Langenskiöld, M. Stoll
Photovoltaik im Verbund mit Dämmstoff Foamglas – SI/500582
235
F. Galliano, D. Fischer
PV-GUM: Manufacturing technologies and equipment to produce low-cost PV
bituminous-modified roofing membrane with full integration of high efficiency
flexible thin-film silicon PV modules – PV-GUM 249791
240
Systemtechnik
F. Frontini, K. Nagel, V. Tettamanti, G. Panzera, M. Ferrazzo, D. Chianese
BiSol: Building Integrated Solar Network-BRENET – SI/500339 / SI/500339-01
F. Frontini, A. Chatzipanagi
BiPV Tools: Interactive tools and instruments supporting the design of building
integrated PV installations – 103220 / 154244
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249
254
Building Integrated Photovoltaics Thermal Aspects – 103155 / 154147
G. Friesen, M. Pravettoni
Optimization of thin film module testing and PV module energy rating at SUPSI
– SI/500691 / SI/500691-01
U. Muntwyler
Photovoltaik Systemtechnik – various projects
261
267
275
Application de modules PV flexibles sur le site de production Flexcell
– 103202 / 154220
280
F. Bertrand, L. Perret
Photovoltaïque et neige: horizon des solutions pour l'installation sur les toits
dans les régions enneigées – SI/500568 / SI/500568-01
288
F. Baumgartner, N. Allet, T. Hobi, H. Kessler
Solar Wings: Seil-basiertes Photovoltaik-Nachführsystem 2-achsig
– SI/500466 / SI/500466-01
294
H. Häberlin, Ph. Schärf, L. Borgna
Autonomous cleaning robot for large scale photovoltaic power plants in Europe
resulting in 5% cost reduction of electricity – PV-SERVITOR 232062
303
T. Nordmann, L. Clavadetscher, T. Vontobel
Messkampagne Photovoltaik Schallschutzanlage Münsingen
– SI/500361 / SI/500361-01
310
C. Bucher
Distribution grid analysis and simulation with photovoltaics
– DIGASP SI/500549 / SI/500549-01
318
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Internationale Koordination
P. Hüsser
Schweizer Beitrag zum IEA PVPS Programm, Task 1 – SI/400516 / SI/400516-01
S. Nowak, N. Guthapfel, A. Mastronardi
REPIC: Swiss Interdepartmental Platform for Renewable Energy and Energy
Efficiency Promotion in International Cooperation – SECO UR-00123.03.01
327
333
K. Flury, M. Stucki, R. Frischknecht
356
T. Nordmann, L. Clavadetscher
362
P. Renaud, L. Perret, J. Fahrni
IEA PVPS, Task 14 - High penetration of PV systems in electricity grids
(Swiss contribution) – IEA PVPS Pool II 2011.01
366
J. Remund
IEA SHC, Task 36 – Solar resource knowledge management
– 101498 / 151784/151761
375
P. Toggweiler, T. Hostettler
Normenarbeit für PV Systeme – SWISSOLAR 17967
379
S. Nowak, M. Gutschner
PV-ERA-NET: Networking and Integration of National and Regional Programmes in
the Field of Photovoltaic (PV) Solar Energy Research and Technological
Development (RTD) in the European Research Area (ERA) – CA-011814-PV ERA NET
6/394
387
Erneuerbare Energien / Sources d‘Énergie Renouvelables
Überblicksbericht 2011
Forschungsprogramm
Photovoltaik
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Energieforschung 2011 – Überblicksberichte
1
Photovoltaik
Titelbild:
Vom Gebäude zum Kraftwerk: Photovoltaik auf Dach und Fassaden
Der mit dem Solarpreis 2011 ausgezeichnete, neue solare PlusEnergieBau der
Heizplan AG in Gams ist im wahrsten Sinne des Wortes ein Kraftwerk. Eine Photovoltaik-Anlage mit rund 61 kW Leistung (Dach: 37 kW monokristallin, Südfassade 13 kW monokristallin, Ostfassade 7 kW amorph, Tracker 4 kW multikristallin) liefert deutlich mehr elektrische Energie, als im Gebäude gebraucht wird.
Thermische Solarkollektoren auf dem Dach und eine Luft-Wasser-Wärmepumpe
sorgen für die nötige Heizenergie. Ein 2‘000-Liter Solarspeicher steht in der Energiezentrale und komplettiert die Heizungsanlage (Bildquelle: Heizplan).
BFE Forschungsprogramm Photovoltaik
Überblicksbericht 2011
Auftraggeber:
CH–3003 Bern
Programmleiter BFE (Autor):
Dr. Stefan Nowak, NET Nowak Energie & Technologie AG ([email protected])
Bereichsleiter BFE:
Dr. Stefan Oberholzer ([email protected])
www.bfe.admin.ch/forschungphotovoltaik / www.photovoltaic.ch
Für den Inhalt und die Schlussfolgerungen ist ausschliesslich der Autor dieses Berichts verantwortlich.
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2
Recherche énergétique 2011 – Rapports de synthèse
Einleitung
Die Photovoltaik erfährt in aktuellen
nationalen und internationalen Energieszenarien eine immer grössere Beachtung. Dabei wird diese sehr dynamische Energietechnologie sowohl aus
wissenschaftlich-technischer Sicht, als
auch industriell und marktbezogen viel
diskutiert. Vor dem Hintergrund einer
rasch wachsenden, global orientierten
Industrie findet weltweit eine intensive
Forschung statt, welche als Hauptziel
eine weitere Kostenreduktion und die
rasche Industrialisierung der Photovoltaik verfolgt. In den technologisch
besonders wichtigen Ländern wie
Deutschland, Japan und USA werden
die Photovoltaikforschung intensiviert
und ambitiöse Ziele formuliert [1,2].
Ähnlich ist Europa mit der Solar Europe Industry Initiative bestrebt, weiterhin eine führende Rolle auf diesem
Gebiet zu spielen. Parallel dazu findet
marktseitig eine rasante Kostenreduktion statt, welche einerseits die Wettbewerbsfähigkeit der Photovoltaik mit
anderen Energieträgern laufend erhöht, andererseits innerhalb der Photovoltaikindustrie zu einem stark verschärften Wettbewerb führt.
In der Forschung geht es um die anhaltende Weiterentwicklung der bestehenden Photovoltaik-Technologien
sowie die Entwicklung neuer Materialoptionen und Konzepte. Nebst dem
Kerngebiet der verschiedenen Solarzellen-Technologien beinhaltet die Photovoltaikforschung auch technologiespezifische Themen auf der Systemebene,
z. B. der Gebäudeintegration, der elektrischen Systemtechnik oder der Um-
weltindikatoren und des Recyclings.
Mit der derzeit anhaltenden Kostenreduktion bilden System übergreifende
Aspekte wie die Netzintegration, die
Speicherung oder energetische Konzepte im Gebäude immer wichtigere
Themen der Forschung. Neue Erkenntnisse und Resultate aus der Forschung
werden möglichst rasch in die Industrie
übergeführt.
Die Photovoltaik als möglicher wesentlicher Pfeiler einer nachhaltigen Stromversorgung hat in relevanten Szenarien
weiter an Bedeutung gewonnen: Die
im Jahr 2010 publizierte PhotovoltaikRoadmap der Internationalen Energie
Agentur IEA [3] spricht bis 2050 von
einem möglichen Beitrag von mehr
als 10 % zur weltweiten Stromversorgung, ein Wert der von vielen Akteuren aus der Photovoltaik als untere
Grenze angesehen wird. In aktuellen
Schweizer Energieszenarien wird von
der Photovoltaik bis 2050 ein Beitrag
von mindestens 10 TWh Elektrizität als
möglich erachtet [4].
In den letzten 25 Jahren hat sich eine
starke Schweizer Position in verschiedenen Gebieten der Photovoltaikforschung herausgebildet: Im Vordergrund
stehen die Entwicklungen von verschiedenen Dünnschicht-Technologien, welche schon immer den Schwerpunkt
der Schweizer Photovoltaikforschung
bildeten. Ausgehend von Arbeiten an
neuen Solarzellen-Konzepten wurden diese sukzessiv in die industrielle
Umsetzung übergeführt. Heute findet
neben der Forschung an Instituten und
Hochschulen auch seitens der Industrie
IEA Klassifikation:
3.1.2 Photovoltaics
Schweizer Klassifikation:
2.1.2 Photovoltaik
eine intensive Technologieentwicklung
statt, welche mittlerweile zu einer entlang der ganzen Wertschöpfung der
Photovoltaik bedeutenden Schweizer
Industrie geführt hat.
Laufende Aktivitäten in Forschung und
Entwicklung sowie Projekte im Bereich
von Pilot- und Demonstrationsanlagen umfassen im Berichtsjahr 2011
rund 70 Projekte, wobei alle der Programmleitung bekannten Projekte mit
einer Förderung der öffentlichen Hand
berücksichtigt sind. Nebst den durch
das Bundesamt für Energie (BFE) geförderten Projekten und den Schwerpunkten einzelner Hochschulen und
Forschungsinstitute spielen KTI- und
EU-Projekte im Forschungsprogramm
Photovoltaik eine tragende Rolle.
Das Forschungsprogramm Photovoltaik des BFE verfolgte in der Periode
2008–2011 die folgenden Ziele [5,6]:
• Senkung der Kosten der Solarzellen
und -module;
• Steigerung des
(Solarzellen);
Wirkungsgrades
• Senkung des Material- und Energieeinsatzes;
• Vereinfachung und Standardisierung der elektrischen Systemtechnik; Steigerung der Lebensdauer
und Zuverlässigkeit von Wechselrichtern;
• Erhöhung der Verfügbarkeit und
der Vielfalt industrieller Produkte.
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3
Photovoltaik
Programmschwerpunkte
Das Forschungsprogramm Photovoltaik ist in folgende fünf Bereiche aufgeteilt (die in Klammern angegebene
Klassifizierung bezieht sich auf die Liste
der Projekte, Seite 11 ff.):
Solarzellen (1a-e)
Verschiedene materialspezifische Ansätze zu Dünnschichtsolarzellen stellen hier den wichtigsten Schwerpunkt
dar (Silizium, Verbindungshalbleiter,
organische Materialien). Verstärkt
werden Heteroübergänge zwischen
Dünnschicht- und kristallinem Silizium
untersucht. Organische und Polymersolarzellen als mögliche langfristige
Technologieoptionen gewinnen an
Bedeutung. Ausserdem findet Grundlagenforschung an elektrochemisch
abgeschiedenen Schichten statt.
(2a-e)
Das Gebiet der Solarmodule ist im Forschungsprogramm Photovoltaik eng
mit der Anwendung der Gebäudeintegration verbunden. Im Vordergrund
stehen Modultechnologien, welche
mit den in der Schweiz entwickelten
Solarzellen einhergehen.
Elektrische Systemtechnik (3)
Bei der elektrischen Systemtechnik,
insbesondere bei Wechselrichtern,
steht die Qualitätssicherung im Vordergrund, einschliesslich entsprechender
Normen. Ein in Zukunft wichtiger werdendes Thema ist die Wechselwirkung
mit dem elektrischen Netz und die Integration der Photovoltaik ins Netz.
Institutionelle internationale Zusammenarbeit (5)
Sie erfolgt einerseits projektbezogen
auf allen Gebieten und andererseits
im Rahmen des Implementing Agreements Photovoltaic Power System
Programme (PVPS) der Internationalen
Energieagentur (IEA), der Europäischen
Photovoltaik-Technologieplattform,
der europäischen PV-ERA-Net-Kooperation (ERA: European Research Area),
der neuen Solar Europe Industry Initiative (SEII) im Rahmen des SET-Plans und
der Normen festlegenden Internationalen Elektrotechnischen Kommission
(IEC).
Rückblick und Bewertung 2011
Gemessen an der Anzahl laufender
Projekte mit öffentlicher Finanzierung
und der gesamthaft gemeldeten Forschungsprojekte [7] kann eine Verstärkung der Photovoltaik-Forschungsaktivitäten beobachtet werden. Allerdings
ist diese Erhöhung weiterhin in erster
Linie auf Erfolge mit KTI- und EU-Projekten zurückzuführen. Die zur spezifischen Förderung der Photovoltaik verfügbaren Mittel des BFE sind im Jahr
2011 weiter zurückgegangen. Diese
Entwicklung ist insofern Besorgnis erregend, als die BFE-Mittel primär zur
Wahrung des Kompetenzvorsprungs
der beteiligten Institute auf ihren Spezialgebieten eingesetzt werden. Ausserdem steht diese Entwicklung im
Widerspruch zu den jüngsten energiepolitischen Signalen; sie ist damit für
die Forschungsgemeinschaft schwierig
nachvollziehbar.
Begleitende Themen (4)
Zum einen geht es hier um relevante
technische und nicht technische Themen zur Marktentwicklung (z. B. Hilfsinstrumente, Monitoring, Umweltaspekte). Andererseits sind hier auch auf
andere Energiethemen übergreifende
Projekte (z. B. Gebäude, Mobilität,
Speicherung) angesiedelt.
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4
Ausblick
Es zeichnet sich anfangs der Dekade 2011–2020 immer mehr ab, dass
dieses Jahrzehnt für die Photovoltaik
weltweit eine kritische Zeit ist, welche
massgebend über den mittelfristigen
Erfolg dieser jungen Energietechnologie bestimmen wird. Für die Photovoltaikindustrie hat der Wettbewerb im
letzten Jahr deutlich zugenommen und
erste Insolvenzen grösserer Unternehmen leiten eine Konsolidierungsphase in der Industrie ein. Dies mag aus
Sicht des wachsenden Marktes mit der
damit einhergehenden raschen Kostenreduktion eine willkommene Entwicklung sein. Sie stellt aber die Photovoltaikindustrie weltweit vor gewaltige
Herausforderungen. Dazu kommt die
schwierige globale Wirtschaftslage,
welche zusätzliche Herausforderungen
nach sich zieht.
Aus Schweizer Sicht gilt es deshalb
umso mehr, diesen Zeitraum optimal zu
nutzen, um die Photovoltaikforschung
als innovative Kompetenz-Grundlage
der Schweizer Photovoltaikindustrie
zu positionieren und in dieser Hinsicht
weiter zu verstärken. Optimal wird dies
mittels einer Stärkung der Forschung
und der institutionellen Kapazitäten
zur raschen Umsetzung von Forschung
in die Industrie erreicht. Dahingehende
Initiativen sollten so rasch wie möglich
konkretisiert und auf eine mittelfristig
feste Grundlage gestellt werden. Eine
starke Schweizer Photovoltaik braucht
mehr denn je auch eine starke Photovoltaikforschung.
Highlights aus Forschung und Entwicklung
Seit vielen Jahren setzt sich das Forschungsprogramm Photovoltaik zum
Ziel, zu den einzelnen Teilbereichen
Kompetenzzentren mit nationaler
und internationaler Ausstrahlung zu
fördern. Im Jahr 2011 sind dies das
Photovoltaik-Labor (PV-Lab) an der Eidgenössischen Technischen Hochschule
Lausanne (EPFL) (Silizium-DünnschichtSolarzellen), das Institut of chemical
sciences and engineering (ISIC) an der
EPFL (Farbstoff-Solarzellen), die Empa
(Verbindungshalbleiter- und organische Solarzellen), die Scuola universitaria professionale della Svizzera italiana
(SUPSI, Solarmodule und Gebäudeintegration) und die Berner Fachhochschule HTI Burgdorf (elektrische Systemtechnik).
Forschung und Entwicklung auf kristallinen Solarzellen ist in der Schweiz
weit gehend Sache der Industrie. Ein
Grossteil der öffentlichen Photovoltaikforschung befasst sich mit neuen Solarzellen auf der Grundlage von Dünnschicht-Technologien. Die wesentlichen
Technologieansätze betreffen Dünnschicht-Silizium (zur Hauptsache am
PV-Lab der EPFL) sowie DünnschichtVerbindungshalbleiter CIGS und CdTe
(Empa). Die rasche Kostenreduktion
bei den kristallinen Solarzellen zwingt
die Vertreter der Dünnschicht-Technologien, ihre Konzepte kosten- und effizienzmässig noch rascher weiter zu
entwickeln.
Wachsende Tätigkeiten finden zudem
auf dem Gebiet der organischen Solarzellen (Empa, ZHAW) statt. Auf der
exploratorischen Ebene werden neue
Solarzellen auf der Grundlage von
elektrochemisch abgeschiedenen, sehr
dünnen Absorberschichten erforscht.
Die Qualitätssicherung hat seit vielen
Jahren ihren festen Stellenwert in der
Photovoltaik
Forschungslandschaft.
Die Prüfung von Solarmodulen und
deren Verhalten bei unterschiedlichen
Betriebsbedingungen ist die Kernkompetenz des Istituto sostenibilità applicato all’ambiente costruito (ISAAC) an
der SUPSI. Komplementär dazu wird
an der Fachhochschule in Burgdorf das
Verhalten von Wechselrichtern und
Systemen untersucht. Beide Institute
betreiben Prüflabors, in welchen Solarmodule oder Wechselrichter gemäss
gängigen Normen geprüft werden
können.
Figur 1: Neues PECVD Depositionssystem Octopus von Indeotec am PV-Lab des IMT
mit automatischer Beladung von 10 Proben (Bildquelle: PV-Lab, IMT, EPFL).
Im Folgenden werden aktuelle Resultate aus den bedeutenden Arbeitsgebieten der Dünnschichtsolarzellen vertieft.
Dünnschicht Silizium – mit
Nanostrukturen und neuen
Materialkombinationen zu
höchsten Wirkungsgraden
Auf dem Gebiet des DünnschichtSiliziums hat sich am PV-Lab der EPFL
in Neuchâtel im Verlauf der Zeit ein
Cluster von Projekten herausgebildet,
welcher verschiedenste Materialvarianten und Prozessschritte beinhaltet: Zur
Optimierung der Dünnschicht-Siliziumsolarzellen in ihren verschiedenen Ausprägungen stehen zahlreiche Parameter zur Verfügung. Neben Art, Anzahl
und Umfang der aktiven Schichten,
welche zur Hauptsache aus amorphem
und mikrokristallinem Silizium bestehen, spielen Dotierung, Fenster- und
Zwischenschichten, Art der Deposition,
usw. wichtige Rollen. Ziel der laufenden Optimierung und neuer Ansätze
ist es letztlich, den Wirkungsgrad der
Solarzellen zu erhöhen. Eine wachsende Rolle spielen dabei kontrollierte Strukturen und Zwischenschichten
im Nanometerbereich. Entsprechend
komplex ist der Weg zu verbesserten
Solarzelleneigenschaften, welche auch
noch den Anforderungen an grossflächige industrielle Prozesse gerecht
werden müssen.
Am PV-Lab der EPFL finden eng verwandte Forschungsprojekte zu ver-
schiedenen Fragestellungen rund um
die Dünnschicht-Siliziumsolarzellen auf
den Substraten Glas und Kunststoff sowie in Kombination zu kristallinen Siliziumsolarzellen statt. Die zu beantwortenden Forschungsfragen beinhalten
das grundlegende Verständnis einzelner Prozesse und Schichten ebenso wie
den Aufbau ganzer Solarzellen und
neuerdings auch von Kleinmodulen.
Die Übertragbarkeit der Forschungsergebnisse auf den industriellen Massstab bildet eine zentrale Aufgabe, bei
welcher eine zunehmende Anzahl von
Industrieunternehmen mit dem PVLab zusammenarbeitet. Damit wachsen auch die Anforderungen an eine
leistungsfähige
Labor-Infrastruktur,
welche in der Lage sein muss, rasch
reproduzierbare Resultate zu liefern
(Figur 1).
Wichtige Arbeiten im Sinn der Kernkompetenz am PV-Lab finden im BFEProjekt Silizium-Dünnschichtsolarzellen
und -module zur weiteren Verbesserung der mikromorphen Solarzelle
(Kombination aus amorphem und mikrokristallinem Silizium) statt. Die laufende Phase dieses Projektes wurde im
Berichtsjahr abgeschlossen. Im vierten
und letzten Projektjahr stand die Verwendung von fortgeschrittenen Materialien und optischen Nanostrukturen
im Vordergrund. Die Struktur der nanokristallinen Siliziumoxid-Zwischenschichten, welche aufgrund ihrer positiven Eigenschaften inzwischen in den
meisten Laborzellen eingesetzt werden, konnte analysiert und damit besser verstanden werden (Figur 2). Für die
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Photovoltaik
Dünnschicht-Siliziumsolarzellen
auf
Kunststoffsubstraten bilden weiterhin
ein Thema am PV-Lab. Auch hier sind
Materialeigenschaften und Lichteinfang die zentralen Fragestellungen,
welche im EU-Projekt Si-LIGHT untersucht werden. Mikromorphe Tandemsolarzellen erreichten 11,8 % stabilisierten Wirkungsgrad.
Figur 2: Elektronenmikroskopische Aufnahme von dotierten nanokristallinen SiOx
Schichten, welche bessere optische und elektrische Eigenschaften von mikromorphen
Silizium-Dünnschichtsolarzellen ermöglichen (Bildquelle: PV-Lab, IMT, EPFL).
transparenten leitenden Oxidschichten
wurde ein neuer Nanoprägeprozess
von Zinkoxidschichten entwickelt. Damit gelingt es, das Zusammenspiel
zwischen
Oberflächenmorphologie,
Lichteinfang und elektrischen Eigenschaften der Zelle gezielter zu beeinflussen. Durch die Kombination einer
transparenten, nanogeprägten Textur
aus Indiumoxid, einer dotierten Zinkoxidschicht mit kleinskaliger Textur
konnte eine mikormorphe Laborzelle
mit einem neuen Rekord-Anfangswirkungsgrad von 14,1 % erzeugt werden. Mit optimierten Schichten konnte
zudem für eine Einfachzelle aus mikrokristallinem Silizium ein Laborrekord
von 10,9 % erreicht werden. Diese Arbeiten werden durch das neue anwendungsnahe EU-Projekt PEPPER ergänzt.
Die nachgewiesenen Optimierungsmöglichkeiten durch die Erzeugung
von Strukturen im Nanometerbereich
stellen nicht triviale Anforderungen
für deren Umsetzung im industriellen
Massstab. Das EU-Projekt N2P (Nano
to Production) befasst sich mit dieser
Fragestellung und untersucht insbesondere die Möglichkeiten von Plasmaprozessen bei Atmosphärendruck.
Im Vordergrund steht für das PV-Lab
das Wachstum von strukturierten Zinnoxid-Schichten als leitende Oxidschicht
(TCO).
Figur 3: Hocheffiziente flexible CIGS Dünnschichtsolarzellen: Entwicklung des Wirkungsgrades, neuer Weltrekord 18.74 % (Bildquelle: Empa).
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Als weitere Stossrichtung der Solarzellenforschung am PV-Lab kommt das
bekannte Konzept eines Heteroübergangs zwischen verschiedenen Schichten aus kristallinem und amorphem
bzw. mikrokristallinem Silizium zur Anwendung (HIT-Zelle). Mit diesem Ansatz lassen sich hoch effiziente Solarzellen herstellen. Im EU-Projekt 20PLUS
erreichte das PV-Lab hierzu einen Wirkungsgrad von 21,2 %.
cIGS Solarzellen – neuer
Wirkungsgrad-Weltrekord
für flexible Solarzellen
Die derzeit wichtigsten Vertreter der
Verbindungshalbleiter-Solarzellen
sind CIGS und CdTe. Letztgenannte
Technologie hat sich in den vergangenen Jahren als weltweit führende
Dünnschichttechnologie etabliert mit
einer Produktion im GW-Massstab
(First Solar) und ist der Referenzwert für die Wettbewerbsfähigkeit
von Dünnschicht-Solarzellen. CIGSSolarzellen werden erst in kleinerem
Umfang produziert, bergen aber ein
grosses Effizienzpotenzial. Nebst diesen Hauptvertretern der Verbindungshalbleiter-Solarzellen werden weltweit
neue Materialvarianten erforscht, insbesondere in der Materialklasse der
Kesteriten.
In der Schweiz hat sich auf diesem
Gebiet das Labor für Dünne Schichten und Photovoltaik an der Empa
als leistungsfähige Forschungseinheit
etabliert. Das Labor arbeitet im Rahmen von BFE-, EU-, KTI- und weiteren
Projekten an unterschiedlichen Fragestellungen zu CIGS-Solarzellen. Dabei
interessieren auch bei dieser Technologie die Materialeigenschaften, Depositionsprozesse und -temperaturen
(sowohl unter Vakuum, als auch bei
Atmosphärendruck), die notwendigen
Pufferschichten und die Substratwahl.
Von besonderem Interesse sind flexible
Solarzellen auf Kunststoffsubstraten.
Hier erfolgt eine intensive Zusammenarbeit mit dem Empa-Spin-off-Unternehmen FLISOM.
Im BFE-Projekt FEBULAS werden mit
dem Ziel Cd-freier Solarzellen die
Möglichkeiten von und die Solarzelleneigenschaften mit alternativen Pufferschichten zu CdS untersucht. Mit einer
Pufferschicht auf der Grundlage von
In2S3 wurde bisher ein Wirkungsgrad
von 12,6 % erreicht. Dieser reicht allerdings noch nicht an die Eigenschaften der mit CdS Schichten realisierten
Solarzellen, für welche Mini-Module
mit 13,3 % Wirkungsgrad erreicht
wurden. Dieses Resultat steht stellvertretend für die Forschung an Cd-freien
CIGS-Solarzellen.
Im EU-Projekt HIPO-CIGS wurde mit
CdS ein neuer Rekordwirkungsgrad
für flexible Solarzellen von 18,7 %
(Figur 3) erzielt. Damit konnte gezeigt
werden, dass für flexible Solarzellen
hohe Wirkungsgrade möglich sind
und der Höchstwert wohl noch nicht
erreicht ist.
Als kostentreibender Faktor gelten
die bei CIGS Solarzellen notwendigen
Ausgangsmaterialien und deren Depositionsprozesse (z. B. Verdampfen, Molekularstrahlepitaxie MBE). Im BFE-Projekt IMPUCIS wird in Zusammenarbeit
mit dem belgischen Industriepartner
Umicore der Einfluss von unterschiedlichen Materialreinheiten erforscht. Im
Berichtsjahr wurde der Einfluss von
Eisenverunreinigungen
untersucht,
welche einen besonders starken Einfluss auf die Solarzellen-Eigenschaften
haben. Die bisherigen Resultate von
hohen Wirkungsgraden mit Ausgangsmaterialien geringerer Reinheit konnten bestätigt werden. Mit der neuen
Molekularstrahlepitaxie-Anlage wurden CIGS Solarzellen bei unterschiedlichen Temperaturen (450 und 600 °C)
abgeschieden. Es konnte gezeigt werden, dass auch bei der tieferen Temperatur mit geeigneten Prozessen hohe
Wirkungsgrade möglich sind.
Als Alternative zu den aufwändigen,
vakuumbasierten Verfahren zur Herstellung von CIGS Solarzellen werden vermehrt die Möglichkeiten von
vakuumfreien Prozessen untersucht.
Das EU-Projekt NOVA-CI(G)S befasst
sich mit dieser Fragestellung. Im Berichtsjahr wurden mit ersten CIGS
Figur 4: Stromspannungskennlinien von Polymer-Solarzellen durch Spin Coating (ausgezogene rote Linie, Wirkungsgrad 5,5 %) und Inkjet Druckverfahren (unterbrochene
Linie, Wirkungsgrad 4,4 %) (Bildquelle: ZHAW).
Solarzellen auf der Grundlage von Nanopartikel-Precursor-Dispersionen ein
Wirkungsgrad von 4,8 % erreicht.
Organische und andere
neue Materialansätze –
Neuste Grundlagenresultate
Während sich die bekannten Solarzellentechnologien immer stärker in
Richtung industrielle Prozesse und Umsetzung bewegen, entwickeln sich in
der Grundlagenforschung neue Materialansätze, welche das Spektrum der
künftigen
Photovoltaiktechnologien
ergänzen können. Auch wenn diese
Ansätze die Photovoltaikanwendun-
gen der nächsten Jahre noch nicht
unmittelbar beeinflussen werden, ist
die Erforschung neuer Lösungen mittel- und langfristig dennoch wichtig.
Die folgenden Beispiele zeigen neue
Forschungsresultate, welche in den
mehr grundlagenorientierten Gebieten
der organischen Solarzellen und der
elektrochemisch abgeschiedenen ETASolarzellen erzielt wurden. Mehrere
Projekte kamen in diesem Bereich im
Berichtsjahr zum Abschluss:
Die Abteilung Funktionspolymere an
der Empa entwickelte im BFE-Projekt
HIOS-CELL im Rahmen der europäischen PV-ERA-NET Zusammenarbeit
eine neue Bulk-Heterojunction zwischen Cyanin-Farbstoffen und PCBM
Fullerenen. Als Resultate der grund-
Figur 5: Elektronenmikroskop Aufnahmen von elektrochemisch abgeschiedenen Zinkoxid Nanostrukturen als Grundlage für ETA (extremely thin absorber) Solarzellen (Bildquelle: Empa).
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Photovoltaik
legenden Arbeiten konnten Morphologie, Ionenlöslichkeit und ein Modell
des neuen Systems erarbeitet werden.
Erste Solarzellen mit tiefen Wirkungsgraden von < 1 % wurden ebenfalls
hergestellt, wobei das vorliegende System materialspezifisch weiter entwickelt werden muss.
Näher an den bereits erprobten Ansätzen der organischen Solarzellen war
das BFE-Projekt Apollo an der ZHAW,
in welchem ebenfalls im internationalen PV-ERA-NET Kontext aufgrund
von Erfahrungen aus der Kunststoff-
elektronik neue Ansätze für druckbare organische Solarzellen mittels Tintenstrahldrucker entwickelt wurden.
Durch Spin-Coating abgeschiedene
Solarzellen erreichten Wirkungsgrade
von 6 %, die gedruckten organischen
Solarzellen zeigten beachtliche Wirkungsgrade bis zu 4,5 % (Figur 4). Zudem konnten Tandemzellen mit bis bis
zu 6 % Wirkungsgrad erreicht werden.
Ein grundlegend anderer Ansatz wurde im BFE-Projekt ETA Solar Cell an der
Abteilung Werkstoff- und Nanomechanik der Empa verfolgt. Hier wurden auf
Polystirol-Kugeln durch Atomic Layer
Depostion ZnO-Nanoschichten und
anschliessend elektrochemisch Nanodrähte abgeschieden. Dadurch wurden
hohe spezifische, igelartige Oberflächen erzielt (Figur 5). Als Lichtabsorber
wurden darauf CdSe Schichten und
anschliessend CuSCN abgeschieden.
Die optischen Eigenschaften dieses
Materialsystems wurden bestimmt und
erste Solarzellen gebaut. Dabei wurde
ein Wirkungsgrad von 1,3 % erreicht.
Pilot- und Demonstrationsprojekte
Als Schwerpunkt stehen neue Ansätze
im Bereich der Photovoltaik Gebäudeintegration im Vordergrund. Typische
Themen sind hier der Unterbau und
das Montagesystem, der Aufbau des
Solarmoduls, ein hoher Integrationsgrad oder Zusatzfunktionen am Bau.
Photovoltaik-Indachsysteme übernehmen neben der Stromproduktion die
Funktion der Wasser führenden Dachhaut.
Das ISAAC an der SUPSI hat zum Thema der Photovoltaik-Gebäudeintegration einen Schwerpunkt gesetzt und
erarbeitet in mehreren übergreifenden
Projekten umfassende Analysen und
Lösungsansätze. Dieses Wissen wird
im BRENET-Netzwerk weiter entwickelt
(www.bipv.ch).
Im neuen BFE-Projekt PV Foamglas sollen die Photovoltaikmodule neben der
Stromproduktion und der Funktion der
Dachhaut auch die Wärme- und Schalldämmung übernehmen. Dieser Ansatz
stellt insbesondere in Bezug auf das
thermische Verhalten der Photovoltaikanlage eine Herausforderung dar.
Hierzu erarbeiten die Partner Basler
& Hofmann und Pittsburgh Corning
Schweiz geeignete Lösungen, welche
anschliessend in einer Demonstrationsanlage realisiert werden sollen.
Einen grundlegenderen Ansatz verfolgt
das P+D-Projekt Archinsolar, welches
verschiedene Partner und Förderorganisationen (BFE, swisselectric research,
SIG, CCEM) vereint. Es geht darum,
Silizium-Dünnschichtsolarmodule mittels kolorierten Interferenzfiltern so zu
gestalten, dass unterschiedliche Farben
möglich werden. Damit soll eine neue
und energetisch effizientere Art der
Farbgebung von Solarmodulen erzielt
werden. Im Berichtsjahr konnte ein erstes Terra-Cotta-farbiges Demonstrationsmodul realisiert werden. Neben der
ästhetischen Funktion werden auch
die Aspekte der Zuverlässigkeit und
der Lebensdauer des neuen Ansatzes
untersucht.
Photovoltaik Gebäudeintegration – ästhetische und
funktionale Integration
2011 schloss 3S Swiss Solar Systems
das BFE-Projekt SmartTile eines neuen
Photovoltaik-Indachsystems mit den
Messungen eines ganzen Betriebsjahrs
einer Pilotanlage ab (Figur 6). Mit diesem Ansatz können Photovoltaik und
Solarthermie in einem System vereint
werden. Für die Photovoltaik-Anlage
von 9,6 kWp Leistung konnte ein jährlicher Energieertrag von 11‘225 kWh
ermittelt werden, was einem spezifischen Ertrag von 1‘169 kWh/kWp entspricht.
Figur 6: Gebäudeintegrierte Photovoltaik-Pilotanalge (9,6 kWp) mit dem neuen SmartTile System (Bildquelle: 3S Swiss Solar Systems).
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Nationale Zusammenarbeit
Im Berichtsjahr wurde die vielfältige nationale Zusammenarbeit in verschiedenen, zum Teil übergreifenden
Projekten weiter gepflegt. Damit findet innerhalb der
Schweizer Photovoltaik-Gemeinschaft aus Forschung,
Industrie und Anwendung ein reger Austausch statt. Die
Zusammenarbeit mit Industrieunternehmen konnte weiter intensiviert werden, sowohl in neuen Projekten mit
der KTI, als auch in der Form von direkten Mandaten
der Industrie an ausgewählte Forschungsinstitute. Auf
Programmebene wurde die Zusammenarbeit mit vielen
Stellen des Bundes, der Kantone und der Elektrizitätswirtschaft weiter gepflegt.
Die weltweit sehr dynamische Entwicklung der Photovoltaik, die jüngsten energiepolitischen Entwicklungen im
Zusammenhang mit der Fukushima-Katastrophe sowie
die KTI-Sondermassnahmen Starker Franken haben für
die Schweizer Photovoltaik für viel Hektik gesorgt und
zahlreiche Diskussionen sowie neue Projekte ausgelöst.
Eine Arbeitsgruppe mit Vertretern der führenden Forschungsinstitute und der Industrie hat sich intensiv mit
dem Masterplan Photovoltaik 2020, welcher auf der
Grundlage des Masterplans Cleantech erarbeitet werden soll, befasst. Aufgrund der raschen Änderung der
Randbedingungen auf allen Ebenen konnte dieses Strategiepapier noch nicht abgeschlossen werden. Es soll im
ersten Halbjahr 2012 weiter konkretisiert und einer breiten Vernehmlassung unterzogen werden.
Internationale Zusammenarbeit
Die institutionelle Zusammenarbeit innerhalb der IEA,
der IEC und der europäischen Netzwerkprojekte wurde
im Berichtsjahr kontinuierlich fortgesetzt. Auf der Projektebene konnte die Zusammenarbeit innerhalb der EU in
bestehenden und neuen Projekten sehr erfolgreich fortgesetzt werden. Im Jahr 2011 waren es 23 Projekte im
7. Rahmenforschungsprogramm der EU.
Die Beteiligung am Photovoltaikprogramm der IEA (IEA
PVPS) wurde im Berichtsjahr fortgesetzt, sowohl auf der
Projektebene als auch im Executive Committee (ExCo).
Die Firma Nova Energie vertritt die Schweiz in Task 1 des
Implementing Agreements (IA) PVPS der IEA, welcher
allgemeine Informationsaktivitäten zur Aufgabe hat. Im
Berichtsjahr wurde ein weiterer nationaler Bericht über
die Photovoltaik in der Schweiz bis 2010 [8] ausgearbeitet. Auf dieser Grundlage wurde die 16. Ausgabe des
jährlichen internationalen Berichtes (Trends Report) über
die Marktentwicklung der Photovoltaik in den IEA-Ländern erstellt [9].
Im Rahmen der interdepartementalen (SECO, DEZA,
BAFU, BFE) Plattform REPIC zur Förderung der erneuerbaren Energien und der Energieeffizienz in der internationalen Zusammenarbeit [10] leistet das Beratungsunternehmen Entec den Schweizer Beitrag zum IA PVPS Task 9
über die Photovoltaik-Entwicklungszusammenarbeit.
Dieses Projekt befasst sich mit der nachhaltigen Verbreitung der Photovoltaik in Entwicklungsländern und thematisiert auch Aspekte der solaren Wasserversorgung.
ESU Services vertritt die Schweiz im IA PVPS Task 12 zu
Umwelt-, Sicherheits- und Gesundheitsaspekten der
Photovoltaik. In diesem Projekt sollen industriell möglichst aktuelle, relevante und international abgeglichene
Informationen zu diesem bedeutenden Thema aufgear-
beitet und publiziert werden. Im Berichtsjahr erschien
eine neue Publikation zu Lebenszyklusanalysen (LCA) der
Photovoltaik [11].
TNC vertritt die Schweiz im neuen IA PVPS Task 13 zu
Performance und Zuverlässigkeit von Photovoltaikanlagen. Eine Arbeitsgruppe unter Leitung von Planair vertritt die Schweiz im neuen IA PVPS Task 14 zur hohen
Penetration von PV-Anlagen in elektrischen Netzen.
Das Unternehmen Meteotest und die Groupe Energie an
der Universität Genf erbringen zusammen den Schweizer Beitrag zum Task 36 Solar resource knowledge management. Task 36 ist Bestandteil des IA Solare Wärme
und Kälte (SHC) der IEA, inhaltlich ist es jedoch für alle
Solartechnologien relevant. Dementsprechend erfolgt
eine Zusammenarbeit mit den weiteren IA zur Solarenergie (IA PVPS und IA SolarPACES). In diesem Projekt wird
die Qualität verschiedener Strahlungsmodelle und daraus abgeleiteter Produkte verglichen und optimiert.
Ähnlich erfolgt im Task 41 Solar Energy and Architecture
des IA SHC eine Mitwirkung der Schweiz durch die HSLU
(CCTP) und das ISAAC an der SUPSI. Auch hier finden
Photovoltaik-relevante Aktivitäten statt.
Basler & Hofmann vertritt die Schweiz im Auftrag von
Swissolar im TC 82 der IEC zu Photovoltaik-Normen.
Die Beteiligung am EU-Projekt PV-ERA-Net, welches Programmkoordinationsstellen und verantwortliche Ministerien unter dem ERA-Net-Schema zusammengeführt
hatte, wurde im Berichtsjahr von den beteiligten Ländern als selbst getragenes Netzwerk weiter verfolgt [12].
Das Sekretariat ist bei der Programmleitung Photovoltaik
angesiedelt.
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Die Schweiz ist in der Europäischen Photovoltaik-Technologie-Plattform sowohl im Steuerungsausschuss, als
auch in der Mirror Group vertreten [13]. Die von der
Europäischen Kommission lancierte Solar Europe Industry Initiative soll im Rahmen eines neuen Solar ERA-Net-
Projektes konkretisiert werden. Die Programmleitung
Photovoltaik koordiniert dieses Vorhaben, welches im
Februar 2012 bei der Europäischen Kommission eingereicht wird.
Referenzen
[1] Forschung für eine umweltschonende, zuverlässige und
bezahlbare Energieversorgung, Das 6. Energieforschungsprogramm der Bundesregierung, BMWi (2011).
[2] SunShot Vision Study, US DOE (2012).
[3] IEA Technology Roadmap Solar photovoltaic energy,
OECD/IEA, (www.iea.org/papers/2010/pv_roadmap.pdf)
(2010).
[4] Grundlagen für die Energiestrategie des Bundesrates, BFE
(2011).
[5] Konzept der Energieforschung des Bundes 2008 bis
2011, CORE/BFE (2007).
[6] Energieforschungsprogramm Photovoltaik für die Jahre
2008–2011, BFE (2008).
[7] Projektliste der Energieforschung des Bundes 2008–
2009, BFE (2011).
[8] National Survey Report of PV Power Applications in Switzerland 2010, BFE (2011).
[9] Trends in Photovoltaic Applications, Survey Report of
selected IEA countries between 1992 and 2010, IEA-PVPS
T1–20 (2011).
[10] Interdepartementale Plattform zur Förderung der erneuerbaren Energien und der Energieeffizienz in der internationalen Zusammenarbeit, REPIC (www.repic.ch).
[11] Life Cycle Inventories and Life Cycle Assessments of
Photovoltaic Systems, IEA-PVPS T12-02 (2011).
[12] The Photovoltaic European Research Area Network, PVERA-Net (www.pv-era.net).
[13] European Photovoltaic Technology Platform (www.
eupvplatform.org).
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Laufende und im Berichtsjahr abgeschlossene Projekte
(* IEA-Klassifikation)
•
New processes and device structures for the fabrication of high efficiency thin
film silicon photovoltaic modules
Lead: EPFL STI IMT-NE PV-LAB
Contact: Ballif Christophe
R+D (1a)
3.1.2*
Funding: BFE
[email protected]
Period: 2007–2011
Abstract: New processes and device structures for the fabrication of high efficiency thin film silicon photovoltaic modules. Focus is on layers with
new or better properties, on improved processes, on improved devices and on enhanced cells and modules reliability.
•
PEPPER – Processes and equipments for thin film silicon PV modules produced with
lower environmental impact and reduced cost and material use
R+D (1a)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2010–2013
Abstract: The FP7 EU PEPPER project aims at achieving high efficiency (11%) micromorph (amorphous/microcrystalline silicon tandem) modules at
low cost (CoO ≤ 0.5 €/Wp) while reducing the environmental impact of fabrication processes.
•
Flexible production technologies and equipment based on atmospheric pressure
plasma processing for 3D nano structured surfaces (N2P)
R+D (1a)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2008–2012
Abstract: The overall objective of the project “N2P” (Nano to Production) is to develop and substantially enhance the position of Europe in the
science, application and production technologies of surface 3D nano-structuring.
•
Improved material quality and light trapping in thin film silicon solar cells
(SILOCON_LIGHT)
R+D (1a)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2010–2012
Abstract: The project Si-Light is devoted to the investigation of n-i-p solar cells on flexible substrates with focus on material quality, interface
properties, and light management.
•
R+D (1a)
3.1.2
Funding: SNF
[email protected]
Period: 2009–2011
Abstract: The project is devoted to a fundamental understanding of the light trapping process in solar cells.
•
A new low ion energy bombardment PECVD reactor for the deposition of thin film
silicon for solar cell applications.
Lead: EPFL CRPP
Contact: Hollenstein Christoph
R+D (1a)
3.1.2
Funding: KTI
[email protected]
Period: 2008–2012
Abstract: A novel electrode configuration is proposed for improved plasma-enhanced chemical vapour deposition of films such as amorphous
silicon and micro-crystalline silicon.
•
R+D (1a)
Lead: PSI Paul Scherrer Institut
Contact: Gobrecht Jens
3.1.2
Funding: BFE
[email protected]
Period: 2008–2012
Abstract: Numerische Simulation von zweidimensionalen Nanostrukturen für Silizium-Solarzellen.
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Photovoltaik
•
All-inorganic nano-rod based thin-film solarcells on glass (ROD-SOL)
Lead: EMPA Thun
Contact: Michler Johann
R+D (1a)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2009–2011
Abstract: The ROD-SOL project aims at the synthesis of Si nano-rods, densely packed at sufficiently large diameters (few 100 nm's) and lengths
(>1µm) directly on cheap substrates like glass or flexible metal foils.
•
High efficiency thin-film passivated silicon solar cells and modules – THIFIC: Thin
film on crystalline Si
R+D (1b)
3.1.2
Funding: Axpo Naturstrom
[email protected]
Period: 2007–2011
Abstract: The THIFIC project aims at developing a new kind of ultra-high efficiency (20-22%) solar cells by depositing very thin silicon layers of
amorphous and/or microcrystalline silicon on top of silicon wafers.
•
20 percent efficiency on less than 100 µm thick industrially feasible c-Si solar
cells (20PLµS)
R+D (1b)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2010–2013
Abstract: The guiding principle of the 20PLµS project is to develop new and innovative process steps for wafer fabrication and solar cell and
module manufacturing, taking into consideration the transfer of the processes to a pilot production line.
•
Ultra-high conductivity metallization pastes for heterojunction solar cells
(TCOC)
R+D (1b)
3.1.2
Funding: KTI
[email protected]
Period: 2009–2011
Abstract: The TCOC project aims at developing nano-enabled low temperature curable silver pastes exhibiting very low resistivity compatible with
high efficiency heterojunction solar cells (HJC).
•
FEBULAS
R+D (1c)
Lead: EMPA Dübendorf
Contact: Tiwari Ayodhya N.
3.1.2
Funding: BFE
[email protected]
Period: 2009–2011
Abstract: FEBULAS – Flexible CIGS Solar Cells and Mini-Modules on polymer without – or with alternative buffer layer. Focus is on Cd-free buffer
layers.
•
IMPUCIS
R+D (1c)
3.1.2
Funding: BFE
[email protected]
Period: 2009–2012
Abstract: Influence of impurities on the performance of CIGS thin film solar cells. Focus is on achieving good performace CIGS solar cells with
reduced material quality.
•
HIPOCIGS – New concepts for high efficiency and low cost in-line manufactured
flexible CIGS solar cells
R+D (1c)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2010–2012
Abstract: The HIPO-CIGS project aims at the development of cost efficient flexible solar cells and modules based on the compound semiconductor
CIGS.
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•
NOVA-CI(G)S – Non-vacuum processes for deposition of CI(G)S active layer in PV cells
R+D (1c)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2010–2013
Abstract: NOVA-CI(G)S proposes alternative, non-vacuum deposition processes for thin film CI(G)S photovoltaic cells. The low capital intensive,
high throughput, high material yield processes are expected to deliver large area uniformity and optimum composition of cells.
•
Contact: Tiwari Ayodhya Nath
R+D (1c)
3.1.2
Funding: KTI
[email protected]
Period: 2009–2011
Abstract: The project will demonstrate development of next generation of high efficiency CIGS flexible thin film solar cells and monolithically
interconnected modules based on 'alternative multilayer electrical back contact' that provides multi-functionality and overcomes the
problems of conventionally used electrical back contact.
•
All Laser Scribing of CIGS Photovoltaic Panels on rigid Substrates: Feasibility
Study
Lead: BFH
Contact: Romano Valerio
R+D (1c)
3.1.2
Funding: KTI
valerio.romano@bfh
Period: 2011
Abstract: All laser based scribing of thin film photovoltaics such as CIGS or CdTe would represent an enormous step forward from the cost and
technological points of view. This study should demonstrate the feasibility of all laser CIGS scribing as a first step for an efficient all laser
scribing machine.
•
APOLLO – Efficient Areal Organic Solar Cells via Printing
R+D (1d)
Lead: ZHAW ICP
Contact: Ruhstaller Beat
3.1.2
Funding: BFE
[email protected]
Period: 2008–2011
Abstract: This project aims to combine plastic electronics expertise in Europe for realizing organic solar cells for empowering printed electronics
applications.
•
HIOS-Cell
R+D (1d)
Contact: Heier Jakob
3.1.2
Funding: BFE
[email protected]
Period: 2009–2011
Abstract: The project explores nanoscale structuring of heterojunction ionic organic solar cells by liquid-liquid dewetting.
•
FABRI-PV -Transparent fabric electrodes for organic photovoltaics
Contact: Nüesch Frank
R+D (1d)
3.1.2
Funding: KTI
[email protected]
Period: 2009–2011
Abstract: Solar cells require at least one transparent electrode which are commonly made of transparent conducting metal-oxide films (TCOs) since
they ally excellent conductivity and high optical transmission in the visible domain. The project explores transparent fabric electrodes for
organic photovoltaics (FABRI-PV).
•
Heptamethinfarbstoffe mit einer grossen spektralen Vielfalt oberhalb 700 nm.
R+D (1d)
3.1.2
Funding: KTI
[email protected]
Period: 2009–2012
Abstract: Was für die Pflanzen bzw. für die Photosynthese die komplexen Chlorophyllmoleküle sind, sind für Solarzellen heutzutage photosensitive
anorganische und organische Materialien, die in gleicher Weise wie das Chlorophyll effizient Licht absorbieren und in Energie umwandeln
können. Die Entwicklung solcher organischer Materialien für Farbstoffsolarzellen ist das Ziel des Projektes.
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•
ESCORT – Efficient Solar Cells based on Organic and hybrid Technology
Lead: EPFL ISIC-LPI
Contact: Graetzel Michael
R+D (1d)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2010–2013
Abstract: The project's objectives are to exploit the joint leadership of the top European and Indian academic and industrial Institutions to foster
the wide-spread uptake of Dye-Sensitized Solar Cells technology, by improving over the current state of the art by innovative materials
and processes.
•
MOLESOL – All-carbon platforms for highly efficient molecular wire-coupled dyesensitized solar cells
Lead: EPFL ISIC-LPI
R+D (1d)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2010–2013
Abstract: The proposed project comes with a visionary approach, aiming at development of highly efficient molecular-wire charge transfer
platform to be used in a novel generation thin film dye-sensitized solar cells fabricated via organic chemistry routes. The proposed
technology combines the assembled dye monolayer’s, linked with organic molecular wires to semiconducting thin film deposited on
optically transparent substrates.
•
Ordered inorganic-organic hybrids using ionic liquids for emerging applications
(ORION)
Lead: Solaronix SA
Contact: Meyer Toby
R+D (1d)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2009–2013
Abstract: The ORION project puts together a multidisciplinary consortium of leading European universities, research institutes and industries with
the overall goal of developing new knowledge on the fabrication of inorganic-organic hybrid materials using ionic liquids.
•
DURSOL – Exploring and improving durability of thin film solar cells
Lead: EMPA
R+D (1d)
3.1.2
Funding: diverse
[email protected]
Period: 2011–2013
Abstract: The project's objectives are focused towards the understanding of fundamental degradation phenomena in thin film solar cells and
enhancement of lifetime.
•
Numerical Simulation, Design and Fabrication of Extremely Thin Absorber Solar
Cells
Lead: ZHAW EMPA Thun
Contact: Loeser Martin
R+D (1d)
3.1.2
Funding: BFE
[email protected]
Period: 2011–2012
Abstract: This joint research focuses on combining both numerical and experimental methods to analyze and improve the optical efficiency of
extremely thin absorber (ETA) solar cells.
•
UPCON – Ultra-Pure nanowire heterostructures and energy CONversion
Lead: EPFL
Contact: Vaccaro Luciana
R+D (1d)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2010–2014
Abstract: This proposal is devoted to the synthesis of ultra pure semiconductor nanowire heterostructures for energy conversion applications in
the photovoltaic domain.
•
SANS – Sensitizer Activated Nanostructured Solar Cells
Lead: EPFL ISIC-LPI
R+D (1d)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2011–2013
Abstract: Plastic electronics and solution-processable inorganic semiconductors can revolutionise the photovoltaic industry due to their relatively easy
and low cost processability (low embodied energy). The project aims at achieving significant progress in the materials for this type of solar cells.
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DEPHOTEX – Development of photovoltaic textiles based on novel fibres
Lead: Greatcell solar AG
R+D (1d)
3.1.2
Funding: SBF/EU
Contact: Brooks Keith
Period: 2008–2011
Abstract: The goal of the project is to research and develop photovoltaic cells in order to get flexible photovoltaic textiles based on novel fibres
allowing taking benefit from the solar radiation so as to turn it into energy.
•
MESOLIGHT – Mesoscopic Junctions for Light Energy Harvesting and Conversion
Lead: EPFL
Contact: Vaccaro Luciana
R+D (1d)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2010–2015
Abstract: Research will focus on the generation of electric power by mesoscopic solar cells. The target is to increase the photovoltaic conversion
efficiency from currently 11 to over 15 percent rendering these new solar cells very attractive for applications in large areas of photovoltaic
electricity production.
•
ETA SOLAR CELL – Extremly Thin Absorber Solar Cells based on electrodeposited
ZnO nanostructures
Lead: EMPA Thun
Contact: Laetitia Philippe
R+D (1e)
3.1.2
Funding: BFE
[email protected]
Period: 2009–2011
Abstract: The aim of the "ETA solar cells" project is to study separately the different materials used for the fabrication of this kind of photovoltaic
device in order to improve the solar efficiency.
•
NANOSPEC – Nanomaterials for harvesting sub-band-gap photons via
upconversion to increase solar cell efficiencies
Lead: Universität Bern, Dep. Chemie & Biologie
Contact: Krämer Karl
R+D (1e)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2010–2013
Abstract: Fundamental loss mechanisms limit the maximum achievable efficiency: around 20% of the incident power is lost, because photons with
energies below the band-gap are transmitted. Upconversion of two low energy photons into one usable photon reduces these losses.
In this project we will realize upconversion with the help of nanostructures and nanotechnoloy-based materials and show a significant
improvement in solar cell efficiency.
•
Innovative Materials for Future Generation Excitonic Solar Cells
Lead: Solaronix SA
Contact: Meyer Andreas
R+D (1e)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2009–2012
Abstract: The main objective is to leapfrog current limitations of third-generation PV devices through a drastic improvement of the materials used
for assembling excitonic solar cells.
•
Plasmons generating nanocomposite materials (PGNM) for 3rd Generation thin
film solar cells (SOLAMON)
Lead: Solaronix SA
Contact: Meyer Toby
R+D (1e)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2009–2011
Abstract: The objective of the SOLAMON project is to develop high potential Plasmon Generating Nanocompo-site Materials (PGNM) which will
pave the way to the generation III solar cells (high efficiency & low cost).
•
Advanced Lasers for Photovoltaic INdustrial processing Enhancement (ALPINE)
Lead: Oclaro (Switzerland) AG
Contact: Schmid Manuel
R+D (1e)
3.1.2
Funding: SBF/EU
www.oclaro.com
Period: 2009–2012
Abstract: ALPINE aims to push forward the European research and development of fiber laser systems for the scribing of photovoltaic modules,
joining together two exciting challenges: the fiber laser development for advanced industrial processing and the solar energy exploitation.
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•
Solarglas PV
R+D (2a)
Lead: SPF / HSR
Contact: Stefan Brunold
3.1.2
Funding: BFE
[email protected]
Period: 2011–2012
Abstract: In this project the existing certificate for "solar glass", originally developed for solar thermal collectors, is adapted to the special properties
of crystalline solar cells, which are directly laminated onto the tested glass. For the certification different factors are defined in order to
classify the tested glasses in several performance groups.
•
SmartTile: Innovative Photovoltaik Indachlösung
Lead: 3S Swiss Solar Systems AG
Contact: Szacsvay Tamás
P+D (2a)
3.1.2
Funding: BFE
[email protected]
Period: 2008–2011
Abstract: Die zunehmende Industrialisierung der Fertigungsprozesse von Photovoltaik (PV) Modulen eröffnet neue Möglichkeiten für die
Massenfertigung. Im Projekt SmartTile wird ein neues Solardachelement nach neusten Erkenntnissen entwickelt.
•
Unique and Innovative Solution of Thin Silicon Films Modules Building Integration
P+D (2a)
3.1.2
Funding: BFE
[email protected]
Period: 2010–2013
Abstract: This project aims to develop and test a new generation of photovoltaic building elements based on thin film silicon technology (single
amorphous and tandem amorph/microcrystalline cells).
•
Profiled photovoltaic modules
R+D (2a)
Lead: EPFL-STI-IMX-LTC
Contact: Leterrier Yves
3.1.2
Funding: KTI
[email protected]
Period: 2009–2012
Abstract: The objective of this collaboration is to develop a materials system and process for profiled encapsulation of thin film silicon photovoltaic
devices with improved efficiency for structured roofing elements.
•
technologies and equipment for low-cost PV bituminous-modified roofing
membrane with integration of flexible thin-film silicon PV modules (PV-GUM)
Lead: VHF Technologies SA
Contact: Fischer Diego
R+D (2a)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2010–2013
Abstract: The PV-GUM project aims at developing new manufacturing technologies and equipments which will produce a low cost highly efficient
flexible BIPV solar cell on a bituminous roofing membrane.
•
Building Integrated Photovoltaics Thermal Aspects
Lead: SUPSI ISAAC
Contact: Frontini Francesco
R+D (2a)
3.1.2
Funding: BFE
[email protected]
Period: 2009–2011
Abstract: PV industries offering products that can be integrated as building materials represent so far a niche but promising market. The intentions of this
project are to: Analyze building integrated PV products in order to define their electrical and thermal cha-racteristics. Analyze the interaction
between these materials and the building. Demonstrate what BiPV modules look like and how to integrate them into the building con-cept.
•
Large Area solar simulator integrating power Light Emitting Diodes for
performance measurement of new generations of photovoltaic modules (SUNSIM)
R+D (2b)
3.1.2
Funding: KTI
[email protected]
Period: 2009–2011
Abstract: High precision solar simulators will become crucial to characterize the next generation of low cost PV modules. In this project, a new
large area characterization tool, satisfying criteria on homogeneity, spectrum, and temporal stability will be developed, prototyped and
tested.
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•
Lead: SUPSI ISAAC
Contact: Friesen Gabi
R+D (2c)
3.1.2
Funding: BFE
[email protected]
Period: 2011–2014
Abstract: This project aims to improve the measurment accuracy for thin film technologies throgh th definition of new test procedures and the
up-grade of the test equipment.
•
Mobiles PV Messsystem
P+D (2c)
Lead: ZHAW IEFE
Contact: Baumgartner Franz
3.1.2
Funding: diverse
[email protected]
Period: 0
Abstract: Ein Messsystem für PV-Module ist auf einem Kleinbus montiert und erlaubt so Messungen von PV-Modulen an einem beliebigen Ort.
Damit können langwierige Transporte von grösseren Mengen von zu testenden Modulen vermieden werden.
•
Photovoltaik im Verbund mit Dämmstoff Foamglas
P+D (2d)
Lead: Basler & Hofmann AG
Contact: Bucher Christof
3.1.2
Funding: BFE
[email protected]
Period: 2010–2013
Abstract: In diesem Projekt soll mindestens ein Produkt aus PV und FOAMGLAS entwickelt werden.
•
Lead: VHF Technologies SA
Contact: Fischer Diego
P+D (2d)
3.1.2
Funding: BFE
[email protected]
Period: 2009–2012
Abstract: The goal of this project to develop, install and monitor various building integrated PV products and installation solutions based on
Flexcell's technology on buildings of Flexcell's production site in Yverdon.
•
dans les régions enneigées
Lead: Planair SA
Contact: Perret Lionel
P+D (2d)
3.1.2
Funding: BFE
[email protected]
Period: 2011–2014
Abstract: Seven different photovoltaic fields and three snow clearing solutions were implemented. Measures on different parameters such as
production and consumption of each field will occurre during the winters of 2012, 2013 and 2014. The evaluation of the measures will
enable to determine snow impact and compare different photovoltaic technologies and snow clearing solutions.
•
BiSol – Building Integrated Solar Network – BRENET
Lead: SUPSI ISAAC
Contact: Rudel Roman
R+D (2e)
3.1.2
Funding: BFE
[email protected]
Period: 2008–2011
Abstract: The aim of the BiSol project is to create a competence network between specialists from various stakeholders so as to maximize solar
energy integration into the built environment and overcome the related technical and non technical issues.
•
BiPV Tools
WTT (2e)
Lead: SUPSI ISAAC
Contact: Frontini Francesco
3.1.2
Funding: BFE
[email protected]
Period: 2009–2011
Abstract: The BiPV Tools project is addressed specifically to architects. Its aim is to provide information and tools which will allow a correct and
appropriate integration of photovoltaics into the building design concept.
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•
Textile Photovoltaics: Integration of Miniaturized Solar Modules on textiles by
Embroidery Techniques
Lead: NTB
Contact: Gutsche Martin
R+D (2e)
3.1.2
Funding: KTI
[email protected]
Period: 2010–2012
Abstract: Im Projekt Textile Photovoltaik werden durch die Kombination von bestehenden Techniken miniaturisierte Solarmodule hergestellt und
mittels Sticktechnik zu einem neuen Gewebeverbund verarbeitet. Die erarbeiteten Techniken erlauben es zum ersten Mal, vollflexible
Flächengebilde mit photovoltaischer Funktion zu erzeugen.
•
Photovoltaik Systemtechnik 2007 – 2010
R+D (3)
Lead: HTI Burgdorf
Contact: Häberlin Heinrich
3.1.2
Funding: BFE
[email protected]
Period: 2007–2011
Abstract: Bau eines neuen Solargenerator-Simulators von 100 kW zusätzlich zu den bisherigen Geräten von 20 kW und 25 kW. Wartung und
laufende Weiterentwicklung der Mess-Software der vorhandenen Solargenerator-Simulatoren.
•
Lead: PAMAG Engineering
Contact: Kessler Hugo
P+D (3)
3.1.2
Funding: BFE
[email protected]
Period: 2009–2011
Abstract: Im Pilotprojekt Solar Wings wird erstmalig das Verhalten eines Seil-basierten 2-achsig nachgeführten Photovoltaiksystems erprobt und
mit einer fix installierten Anlage verglichen.
•
Autonomous cleaning robot for large scale photovoltaic power plants in
Europe resulting in 5% cost reduction of electricity (PV-SERVITOR)
Lead: HTI Burgdorf
Contact: Häberlin Heinrich
R+D (3)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2009–2011
Abstract: The PV-Servitor project focuses on concepts for a fully autonomous cleaning robot for ground mounted large scale photovoltaic power
plants consisting of several 100 kW units. The PV-Servitor shall be able to automatically clean glass surfaces of solar modules in several
areas of up to 2,500 square meters in an unrestricted way.
•
PV Testanlage Dietikon
P+D (3)
Lead: ZHAW IEFE
Contact: Baumgartner Franz
3.1.2
Funding: diverse
[email protected]
Period:
Abstract: In einer Testanlage werden verschiedene Photovoltaik-Modultechnologien erprobt und miteinander verglichen.
•
Simulation Approach to Investigate the Impact of Distributed Power Generation
with Photovoltaics on a Power Grid (PV ERA NET Project PV+Grid_06_DPVG)
Contact: Bucher Christof
R+D (3)
3.1.2
Funding: BFE
[email protected]
Period: 2010–2012
Abstract: Simulation Approach to Investigate the Impact of Distributed Power Generation with Photovoltaics on a Power Grid. The project
addresses the important topic of grid integration of variable production from phovoltaics.
•
Lead: TNC Consulting AG
Contact: Nordmann Thomas
P+D (4)
3.1.2
Funding: BFE
[email protected]
Period: 2009–2011
Abstract: In dieser Messkampagne wird das Verhalten der bifacialen Photovoltaik Schallschutzanlage beim Bahnhof Münsingen (Kt. BE) analysiert.
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Resource- and cost-effective integration of renewables in existing high-rise
buildings (COST-EFFECTIVE)
Lead: Emmer Pfenninger Partner AG
Contact: Emmer Andreas
R+D (4)
3.1.2
Funding: SBF/EU
[email protected]
Period: 2008–2012
Abstract: The main focus of the project is to convert facades of existing “high-rise buildings” into multifunctional, energy gaining components.
This goal will be achieved by: development of integrated building concepts, development of new multi-functional façade components
and development of new business and cost models.
•
Normenarbeit für PV Systeme
WTT (4)
Contact: Toggweiler Peter
3.1.2
Funding: Swisssolar
[email protected]
Period: 2007-
Abstract: Normen sind ein wichtiges Instrument zur Qualitätssicherung sowie zum sicheren und zuverlässigen Betrieb von PV-Anlagen. Das Projekt
umfasst den Schweizer Beitrag zu den entsprechenden Arbeiten im IEC Technischen Kommittee 82.
•
Schweizer Beitrag IEA PVPS Task 1 – Exchange and Dissemination of Information on
Photovoltaic Power Systems
Lead: Nova Energie GmbH
Contact: Hüsser Pius
R+D (5)
3.1.2
Funding: BFE
[email protected]
Period: 2011
Abstract: IEA PVPS Task 1 befasst sich mit Informationsaufgaben zum Stand der Photovoltaik in den Mitgliedländern des IEA PVPS Programms.
Dazu leistet dieses Projekt den Schweizer Beitrag, insbesondere zur Entwicklung von Industrie und Markt sowie des regulatorischen
Kontextes.
•
Schweizer Beitrag im IEA PVPS Projekt Task 9 „Photovoltaic Services for Developing
Countries“
Lead: Entec
Contact: Arter Alex
R+D (5)
3.1.2
Funding: REPIC
[email protected]
Period: 1999–2012
Abstract: Gestützt auf die umfangreichen weltweiten Erfahrungen mit Photovoltaik Anlagen in Entwicklungsländern, strebt dieses Projekt
die Erhöhung von erfolgreich und nachhaltig betriebenen Anlagen dieser Art für unterschiedliche Zwecke an. Die internationale
Expertengruppe umfasst auf diesem Gebiet eine breite Projekterfahrung und konzentriert ihre Arbeit insbesondere auf die nichttechnischen Aspekte dieser Anwendungen.
•
Schweizer Beitrag IEA PVPS Task 12 – PV Environmental Health & Safety Issues
Lead: ESU-Services AG
Contact: Frischknecht Rolf
R+D (5)
3.1.2
Funding: BFE
[email protected]
Period: 2011
Abstract: IEA PVPS Task 12 befasst sich mit Umweltaspekten der Photovoltaik ausgehend von Analysen in den Mitgliedländern des IEA PVPS
Programms. Dazu leistet dieses Projekt den Schweizer Beitrag, insbesondere zur Lebenszyklusanalyse (LCA) von PV-Systemen.
•
Schweizer Beitrag IEA PVPS Task 13 – Performance and Reliability of PV systems
Lead: TNC Consulting AG
Contact: Nordmann Thomas
R+D (5)
3.1.2
Funding: IEA PVPS Pool
[email protected]
Period: 2011–2012
Abstract: IEA PVPS Task 13 befasst sich mit Performance und Zuverlässigkeit von PV-Kompenten und PV-Anlagen in den Mitgliedländern des IEA
PVPS Programms. Mit diesem Projekt wird der Schweizer Beitrag zu diesem neuen internationalen Vorhaben vorbereitet.
•
Schweizer Beitrag IEA PVPS Task 14 – High penetration of PV systems in electricity
grids (Swiss contribution)
Lead: Planair
Contact: Renaud Pierre
R+D (5)
3.1.2
Funding: IEA PVPS Pool
[email protected]
Period: 2010–2014
Abstract: The main purpose of Task 14 is to analyze the role of grid connected PV as an important source in electric power systems on a high
penetratin level where additional efforts may be necessary to integrate the dispersed generation in an optimum manner. The aim of
these efforts is to reduce the technical barriers to achieve high penetration levels of distributed renewable systems on the electric power
system.
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Photovoltaik
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Solarzellen
C. Battaglia, M. Despeisse, F.-J. Haug, S. Nicolay, L.-E. Perret-Aebi, F. SculatiMeillaud, R. Tscharner, C. Ballif
New processes and device structures for the fabrication of high efficiency
thin film silicon photovoltaic modules – SI/500031 / SI/500031-01
31
F. Sculati-Meillaud, S Nicolay, G. Parascandolo, G. Bugnon, C. Ballif
PEPPER: Demonstration of high performance processes and equipments for thin
film silicon photovoltaic modules produced with lower environmental impact and
reduced cost and material use – PEPPER 249782
45
S. Nicolay
N2P: Flexible production technologies and equipment based on atmospheric
pressure plasma processing for 3D nano structured surfaces – N2P 214134-2
52
SILICON LIGHT: Improved material quality and light trapping in thin film silicon
solar cells – FP7 241277
57
– SNF 200021-125177/1 / 200020-137700/1
61
THIFIC: Thin film on crystalline Si – Axpo Naturstrom Fonds 0703
65
20 Percent efficiency on less than 100μm thick industrially feasible c-Si solar
cells – 20plμs 256695
69
Ch. Hollenstein, M. Chesaux, A.A. Howling
A new low ion energy bombardment PECVD reactor - Deposition of thin film
silicon for solar cell applications – KTI 9675.2
73
– SI/500141 / SI/500141-01
74
C. Niederberger, J. Michler
ROD-SOL: All-inorganic nano-rod based thin film solar cells on glass
– NMP-2008-2.6.1 / 227497
79
FEBULAS: Flexible CIGS solar cells and mini-modules on polymer without - or
with alternative buffer layer – SI/500394 / SI500394-01
87
27/394
IMPUCIS: Influence of impurities on the performance of CIGS thin film solar cells
– SI/500417 / SI500417-01
96
HIPO-CIGS: New concepts for high efficiency and low cost in-line manufactured
flexible CIGS solar cells – HIPOCIGS 241384
102
NOVA-CIGS: Non-vacuum processes for deposition of CI(G)S active layer in
PV cells – NOVACIGS 228743
107
P. Blösch, S. Bücheler, A.N. Tiwari
– KTI 10245.1
113
B. Ruhstaller, N. A. Reinke, M. Neukom, S. Züfle, R. Ritzmann, G. Nisato,
T. Offermans, J. Schleuninger, M. Chrapa, M. Turbiez, M. Düggeli, M. Wienk,
R. Janssen, S. Kuijzer, K. Sastrowiardjo, G. Garcia-Belmonte, J. Bisquert, P. Boix,
APOLLO: Efficient Areal Organic Solar Cells via Printing
– SI/500122 / SI/500122-01
J. Heier, J. Groenewold
HIOS-CELL: Nanoscale structuring of heterojunction ionic organic solar cells by
liquid-liquid dewetting – SI/500297 / SI/500297-01
R. Hany, F. Nüesch
FABRI-PV: Transparent fabric electrodes for organic photovoltaics – KTI 9995.1
119
127
136
T. Geiger, Y. Shcherbakova, S. Hochleitner, F. Nüesch, T. Meyer
Heptamethinfarbstoffe mit einer grossen spektralen Vielfalt oberhalb 700nm
– KTI 10584.1
140
T. Meyer, F. Oswald
ORION: Ordered inorganic-organic hybrids using ionic liquids for emerging
applications – FP7-229036
144
F. Nüesch, R. Hany, G. Wicht, A.N. Tiwari, S. Bücheler, C. Gretener, C. Ballif,
F. Sculati-Meillaud, S. Hänni, M. Stückelberger, S. Pélisset, M. Grätzel,
S.M. Zakeeruddin, F. Duriaux Arendse, G. Nisato, T. Offermans, T. Friesen,
B. Ruhstaller, M. Schmid, O. Schumacher
DURSOL: Exploring and improving durability of thin film solar cells
– CCEM-DURSOL
ETA SOLAR CELL: Extremely Thin Absorber Solar Cell based on
electrodeposited ZnO Nanostructures – SI/500426 / SI/500426-01
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151
156
M. Loeser, K. Lapagna, B. Ruhstaller, J. Elias, L. Philippe
Numerical Simulation, Design and Fabrication of Extremely Thin Absorber
Solar Cells – SI/500613 / SI/500613-01
164
A. Fontcuberta i Morral
UPCON: Ultra‐high Purity nanowires for energy CONversion
– UPCON 239743
173
T. Meyer, F. Oswald
INNOVASOL: Innovative materials for future generation excitonic solar cells
– FP7-227057
178
T. Meyer
SOLAMON: Plasmons generating nanocomposite materials (PGNM) for
rd
3 generation thin film solar cells – FP7-226820
186
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Eidgenössisches Departement für
Umwelt, Verkehr, Energie und Kommunikation UVEK
NEW PROCESSES AND DEVICE STRUCTURES FOR THE FABRICATION OF HIGH
EFFICIENCY THIN FILM SILICON PHOTOVOLTAIC MODULES
Annual Report 2011
Author and Co-Authors
C. Battaglia, M. Despeisse, F.-J. Haug, S. Nicolay,
L.-E. Perret-Aebi, F. Sculati-Meillaud, R. Tscharner, C. Ballif
Institution / Company
EPFL, IMT, PV-Lab
Address
Rue A.-L. Breguet 2, 2000 Neuchâtel
Telephone, E-mail, Homepage +41 32 728 33 30, +41 32 718 32 01
Project- / Contract Number
SI/500031 / SI/500031-01 (101191 / 153032)
Duration of the Project (from – to) 1.12.2007 - 31.12.2011
Date
23.12.2011
ABSTRACT
This project has four axes which focus on layers with new or better properties (e.g. new materials to
be i ncorporated into devices), on i mproved processes ( e.g. ne w plasma r egimes l eading t o higher
quality layers), on improved devices, and on enhanced cell and module reliability. The final objective
is to contribute to the field by findings that lead to increased module efficiencies while ensuring lower
costs and long-term stability.
In the fourth and final year, the project focused on the use of advanced materials and optical structures to increase device efficiency. Nanocrystalline silicon oxide layers are now implemented in most
devices and we were able to reveal their nanoscale filamentary structure responsible for their interesting properties. A better un derstanding of the impact of pl asmas on the growth on r ough substrates
was acquired. Strong accent was also on improving cell stability by minimizing light induced degradation and gain better control over the morphology evolution which is important for the growth of high
quality silicon layers.
A ne wly developed nanomoulding process allowed for t he fabrication of zinc ox ide layers with ar bitrary s urface morphologies, which opens many new venues for studying the interplay between l ight
trapping, el ectrical c ell per formance and zinc oxide surface morphology. An innovative m ulti-scale
electrode architecture, c ombining a t ransparent na noimprinted large-scale texture, a hi gh-mobility
indium oxide layer and a non-intentionally doped zinc oxide layer with a small-scale texture enabled a
lab r ecord t andem micromorph c ell with an initial efficiency of 14. 1%. A n i mproved c ell des ign and
optimized layers also resulted in a lab record microcrystalline silicon single junction solar cell with an
efficiency of 10. 9%. I n the s ubstrate c onfiguration, micromorph t andems w ith ef ficiencies of up t o
11.8% were achieved.
Globally t he findings of the pr ojects s hould contribute to l ower the cost of thin f ilm silicon modules,
while continuing increasing efficiencies. Production costs of 0.35 to 0.44 €/W p should soon be possible.
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Introduction
In 2011, the economic situation for thin film silicon companies was delicate, as most of them are still
operating at relatively low production volumes but with high initial investments. However, several tens
of companies are now producing routinely amorphous and micromorph modules with efficiencies of up
to 10% using mass production tools. The best modules even reach 10.8% stable efficiency at the pilot
line l evel, e. g. a t O erlikon S olar, S anyo or A MAT. N evertheless bec ause of t he s trong pr essure on
modules prizes, the cost of thin film silicon has to be reduced further through gains in efficiency and
through faster and/or cheaper processes. Incorporating several elements developed at IMT, or developed c urrently e.g. in the f rame of t he E U-FP7 Pepper pr oject, O erlikon S olar was r ecently able t o
propose an aggressive cost reduction roadmap. This is illustrated in Table 1, which shows that even at
a modest production volume of 120 MW, thin film silicon proves to be highly competitive in terms of
production c osts. As es thetic bu ilding e lements ( see al so r eport o n A rchinsolar) or c omponents of
large power plants in sunny areas, thin film silicon remains one of the very attractive options.
Table 1: Example cost structure for a 120 MW production line amortized over 7 years with a residual value of 20%
for a Thin Fab line in China, ordered in 2012-2013. Data provided by R. Benz, Oerlikon Solar
Contribution
Amount (€/Wp)
Type of cost
Capital investment
0.08-0.12
fixed
Labour
0.01
fixed
Materials
0.12-0.15
variable
Gas
0.07-0.08
variable
Utilities
0.03
variable
Maintenance
0.04
variable
Yield loss
0.01
variable
Total module manufacturing cost
0.35-0.44
Project goals
In the general economic context, the present project remains fully relevant, as its global objective is to
allow for a lowering of the cost of solar electricity based on thin film silicon. In particular, this project
aims at dev eloping m aterials, pr ocesses an d d evice s tructures f or t he f uture g eneration of t hin f ilm
silicon modules, based on amorphous silicon or silicon-germanium alloys, and microcrystalline silicon.
The objective of this “technology push” project is, hence to make the necessary breakthroughs that will
allow in the medium to long term, to further reduce module production costs at elevated efficiencies,
while ensuring perfect module reliability.
Short project description (2008-2011)
The pr oject has f our m ajor r esearch ax es, and t wo t ransversal d omains, sketched i n Figure 1. The
project’s goa ls ar e, hence, t o be achieved b y introducing i nnovation a nd o ptimisation in f our m ajor
areas:
• Layers with new or better properties (e.g. new materials with higher transparency)
• Improved processes (more stable, faster processes, yielding higher quality layers)
• Increased device and module efficiency
• Enhanced cell and module reliability
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OFEN 101191, C. Battaglia, EPFL, IMT, PV-Lab
For 2011, the major objectives have been to
• Integrate and optimize silicon oxide based layers into solar cells
• Improve cell stability with respect to light induced degradation
• Develop ne w s uper- and s ubstrates pr oviding s trong l ight t rapping, while r especting
morphological constraints for optimum layer growth
• Isolate performance metrics of top and bottom cell in micromorph tandem cell
• Optimize zinc oxide layer transparency and electrical properties
• Improve test criteria to quantify main failure mechanism of modules.
Figure 1: Summary of workpackages of SFOE-EPFL PV-Lab project 2008-2011.
The detailed scientific results are reported in the publications listed in the references at the end of the
report, which the reader is invited to consider.
Work performed and results achieved in 2011
In the last part of this four years project, a focus point was the achievement of better substrates and
superstrates, which combined with doped oxides layers and improved plasma processes, allowed us
to not only gain understanding of the devices, but also to further improve the device efficiencies.
1. Materials
1.1 Nanocrystalline silicon oxide layers
A key result of this project period is the elucidation of the nanostructure of silicon oxide layers using
energy filtered transmission electron microscopy, in which only electrons which underwent a characteristic energy loss ar e us ed f or i maging [1]. With t his no vel nanoscale i maging t echnique, c ontrast
between s ilicon-rich and o xide-rich r egions i s obtained, which allowed f or t he observation of p hase
separation o ccurring in s ub-stochiometric s ilicon ox ide l ayers gr own b y plasma-enhanced c hemical
vapor deposition (see Figure 2). Most interestingly, we could reveal the existence of silicon filaments
embedded in an amorphous silicon oxide matrix, which explain well the unique properties of this highly
tunable f unctional m aterial s uch as its an isotropic c onductivity. N anocrystalline s ilicon ox ide layers
further al low f or t he dec oupling of t he opt ical and e lectrical pr operties, w hich makes them per fectly
suited as window l ayers a nd i ntermediate r eflector l ayers. I n addition s ilicon ox ide l ayers h ave a lso
proven extremely useful for shunt quenching on highly textured substrates and have been instrumental for achieving the new record efficiencies.
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Figure 2: TEM cross-section of three silicon oxide layers encircled in the inset graph, with the same refractive
index of 1.8, but different nanostructure due to different input gas ratios used for deposition. The layers are grown
onto a microcrystalline silicon layer to ensure a good electrical contact for transverse conductivity measurements.
1.2 ZnO bilayers
Even t hough s tandard boron-doped L P-CVD Z nO with i ts c haracteristic p yramidal f eatures remains
the standard material for front and back contacts in our lab, the ZnO bilayer approach, introduced in
the previous project period, has been further investigated. ZnO bilayers, consisting of a highly borondoped nuc leation l ayer f ollowed by a no n-intentionally doped bulk Z nO l ayer, enable t he gr owth of
larger p yramids at equ ivalent t hickness r esulting i n enha nced l ight s cattering and i mproved c arrier
mobility [1][3]. We also observed that bilayers are more resilient to damp heat degradation compared
to non -intentionally d oped films w ith e quivalent sheet r esistance, which r epresents an add itional important advantage f or the integration in industrial modules. In t he f rame of the E U-FP7, ZnO bilayer
processes were transferred to Oerlikon Solar were they could replace the standard ZnO layers in the
Thin Fab production lines.
1.3 ZnO nanomoulding
We also developed a new elegant nanomoulding technique, which allows the fabrication of ZnO layer
with arbitrary surface morphology (see Figure 3) [5][6]. The method is related to the nanoimprinting
technique es tablished i n pr evious project per iods [7][8][8][10], but t he s tamp i s used as a m ould on
which the ZnO is deposited. The ZnO film carrying the structure of the mould is then transferred onto a
glass substrate using a UV curable resin for anchoring. Amorphous silicon single junction as well as
micromorph tandem junction solar cells on nanomoulded ZnOs, with efficiencies as high as on stateof-the-art ZnO substrates were demonstrated. In addition, a honeycomb texture, based on anodically
textured aluminum, w as t ransferred ont o Z nO v ia n anomoulding and s uccessfully integrated i nto
amorphous silicon solar cells.
Nanomoulding of ZnO can also be used to decouple interlinked ZnO growth parameters. For example,
doping reduces the average pyramid size. By means of nanomoulding, we fabricated ZnO films with
the same thickness and pyramid size, but with varying doping and studied the influence of free carier
absorption on m icromorph s olar c ells, without i nterference f rom v arying light scattering properties.
Furthermore, w e r eplicated t he m orphology of a morphous s ilicon f ilms on Z nO p yramids v ia Z nO
nanomoulding, t o isolate the i nfluence of t he s urface m odification on t he e lectrical p erformance of
microcrystalline silicon cells used as bottom cell in the micromorph tandem. Unfortunately, due to the
relatively sharp pinches appearing when amorphous silicon is deposited on ZnO, a high fidelity mould
is difficult to fabricate. An alternative approach to decouple the bottom cell performance using filtered
micromorph cells is described below.
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Figure 3: SEM images of master test structures and their corresponding nanomoulded ZnO replicas: a) A onedimensional periodic grating fabricated by interference lithography, b) a nanotextured aluminium surface with a
quasi-periodic hexagonal dimple pattern prepared by anodic oxidation of aluminum, c) random pyramid network of
ZnO grown by low-pressure chemical vapor deposition, d-f) images of the corresponding nanomoulded ZnO replica. Image size 6 µm x 4 µm.
1.4 ZnO nanorods
We further dev eloped Z nO nan orod arrays gr own by hydrothermal synthesis from an aqueous s olution. Initially, drop casted zinc nitrate layers were used as seed layers on glass. Trials with spray coated zinc n itrates gave m ore un iform r esults. T he most uni form nanor od ar rays were obtained us ing
sputtered ZnO layers. Deposition of LP-CVD ZnO on these ZnO nanorods yielded improved mobilities
and s lightly higher h aze values. H owever, integration of s uch nanorod ar rays covered with L P-CVD
ZnO into micromorph cells lead to additional reflection losses at the glass-ZnO interface, as the volume filling ratio of the ZnO nanorods is below ½ resulting in an effective refractive index below 1.5. In
addition, as the ZnO nanorods are undoped, the lower apparent band gap due to the Burstein-Moss
effect also reduces the blue response of the cell.
As a s econd potential route for t he integration of Z nO nanorods into solar c ells, w e investigated the
possibility to use the ZnO nanorods as skeleton to modulate a LP-CVD ZnO layer on the micrometer
scale. P atterning of the sputtered ZnO seed layer was achieved via our in-house laser scribing s ystem. We were able to demonstrate successfully the patterned growth of the ZnO nanorods on areas
where the l aser did not ablate t he seed layer. To ac hieve a sufficient m odulation of a LP-CVD ZnO
layer with a typical thickness of 2 um, ZnO rods with a height of at least the same order of magnitude
or i deally h igher r ods must be gr own. H owever, gr owing s uch h igh r ods r equires r e-supplying t he
growth solution with zinc acetate as subcritical saturation leads to an equilibrium between rod growth
and dissolution. Work on this topic is still in progress.
1.5 Nanocones and nanocavity substrates
An optimized periodic honeycomb structure on glass for amorphous silicon solar cells was developed
using nanosphere l ithography i n collaboration w ith S tanford University [11]. S imilarly as f or t he Z nO
morphology, we observe that a compromise between optical and electrical cell performance must be
respected. For a direct comparison of the periodic honeycomb texture with LP-CVD ZnO, we replicated t he r andom p yramidal ZnO morphology us ing n anoimprint l ithography. T his al lows us t o i solate
scattering effects from the influence of material properties. In combination with high-mobility conformal
indium oxide [12], developed in the previous project period, amorphous silicon cells with an excellent
short-circuit current of 17.1 mA/cm2 and an initial efficiency of 11.2% were fabricated, demonstrating
that p eriodic s tructures m ay r ival di rectly with t he r andom p yramidal m orphology of LP -CVD Z nO.
Nanosphere lithography was also used to fabricate substrates with hexagonal arrays of nanocones for
the substrate (n-i-p) configuration and resulted in efficiencies of 9.6% [13].
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Figure 4: SEM image of micromorph record cell on novel multi-scale electrode architecture.
1.6 Multiscale electrode architecture
To c ircumvent t he trade-off between o ptical and electrical performance i n micromorph tandem c ells,
we further investigated a novel multiscale electrode architecture (see Figure 4) [14]. In this approach,
small s harp m orphological f eatures, used f or o ptimum l ight i ncoupling, ar e c ombined with l arge
smooth features which provide light scattering in the red and infrared part of the solar spectrum. In a
first realization of this approach, a strongly smoothened ZnO layer, with large pyramids, was covered
with a t hin am orphous silicon l ayer to i nterrupt ep itaxial growth. On top, a t hin ZnO layer with small
sharp pyramids was grown. Micromorph cells grown on such front electrodes clearly demonstrated the
potential to obtain excellent electrical cell performance, characterized by the open-circuit voltage and
fill factors of the cells. However, the relatively thick ZnO required to obtain large pyramids, causes a
parasitic abs orption, which c ompromises t he bot tom c ell c urrent. Consequently, i n a s econd i mplementation, the thick ZnO pyramids were replaced by a nanoimprinted replica, with no parasitic absorption. In order to further minimize parasitic absorption a thin undoped ZnO layer was used for the small
pyramids. Between the nanoimprinted replica and the thin ZnO layer, the high mobility hydrogenated
indium oxide layer was applied to minimize resistive losses during carrier extraction at minimum parasitic abs orption. T his ap proach l ed t o a m icromorph c ell with a n ew l ab r ecord i nitial efficiency of
14.1% (see section 3.2 and refs [15][16][17]).
1.7 New antireflective scheme
In the new record cell, a novel antireflection concept on the air-glass interface is implemented, consisting of a nanoimprinted array of pyramids [18]. The master for these pyramids was obtained by alkaline
etching of a Si(100) wafer, resulting in well-oriented pyramids with Si(111) facets, which differ from the
pyramid s tructure of LP -CVD Z nO. T he s tructure is well k nown i n t he c rystalline s ilicon c ommunity,
where it is the industrial standard to reduce reflection losses. A careful analysis for their transparent
counterpart app lied t o our thin-film s ilicon s olar c ells r evealed t hat s uch p yramids r educe r eflection
thanks t o a do uble-rebound. I n ad dition t he p yramidal s tructure i s be neficial a s i t provides an ant iescape effect based on total internal reflection.
1.8 Backreflectors
A c omparison b etween different backreflector des igns f or c ell i n s uperstrate c onfiguration was p erformed. The combination of LP-CVD ZnO and the standard white dielectric backreflector clearly yields
the b est r esults. Sputtered Z nO i n c ombination with an aluminum bac kreflector resulted i n excellent
yield and electrical performance, but lead to substantial current losses. So far tests with sputtered Ag
backreflectors, which are expected to improve optical performance, lead to massive problems in yield
especially after annealing. These problems do not only appear when using ZnO as a buffer layer, but
also when using ITO. Further work is required to understand this problem in more detail.
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In t he s ubstrate c onfiguration t he r eflectivity of t he s ilver bac kreflector on r ough L P-CVD Z nO was
improved significantly [20][30]. As deposited silver films exhibit strong parasitic plasmonic absorption
leading to massive current losses. A simple annealing step leads to a subtle but important modification
of the silver layer morphology and a substantial increase in the silver grain size (see Figure 5). Both
aspects do not only result in a substantial increase in the reflectivity, whose effect is directly observable as an increase in the external quantum efficiency, but also to improved electrical cell performance.
Figure 5: Morphological modification of thermally roughened silver back reflector upon annealing resulting in
improved reflectivity.
1.9 Plasmonics
In t he pr evious pr oject per iod, we f abricated pl asmonic s ilver na noparticles an d i ntegrated t hem as
backreflector i n am orphous s ilicon s olar c ells i n s ubstrate c onfiguration [21]. While a c lear c urrent
enhancement due to light scattering was observed, the approach could not rival the standard texturing
methods. It is well know that a tight particle size distribution is absolutely mandatory for optimum performance as too small particles lead to strong parasitic absorption, while too large particles exhibit a
very low s cattering cross s ection. T o i mprove the particle s ize distribution and g ain control over t he
particle shape, we performed first tests with silver nanoparticle arrays fabricated via nanostencil lithography in collaboration with Prof. Jürgen Brugger’s group.
2. Processes
2.1 Improved p-i interface stability
Optimization of the p-layer in amorphous silicon solar cells lead to improved cell stabilities with respect
to l ight induced de gradation [22][23][24]. I n t he s mall P E-CVD s ystems, an i mproved s tabilized f ill
factor of 68% was achieved in a cell with an i-layer of 220 nm by reducing the boron doping and the
thickness of the p-type s ilicon c arbide l ayer. I n t he KAI system, we tried to i mprove the f ill f actor b y
reducing the deposition rate of the p-type silicon carbide layer. With this approach, we were not able to
achieve fill factors above 66%. Subsequently, the p-type silicon carbide layer was replaced by a p-type
silicon oxide layer. To achieve open-circuit voltages comparable to the standard carbide layer, a relatively high boron doping had to be applied, resulting in amorphization of the carbide layer. Stabilized
fill factors of 65% and 66% were achieved with this approach for absorber thicknesses of 250 nm and
180 nm respectively. An even higher fill factor of 67% was obtained for a cell with a 180 nm absorber
by further replacing the intrinsic carbide buffer layer with an intrinsic oxide.
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2.2 Improved i-layer stability
Cell s tability was al so i nvestigated with r espect t o t he abs orber t hickness [25]. Fill f actor s tability is
clearly improved at reduced i-layer thickness. Deposition at higher temperatures is an alternative route
to improve fill factor stability, but also leads to a lower open-circuit voltage. Strong accent was therefore put on improving t he product of op en-circuit voltage a nd f ill f actor. I nitial o pen-circuit v oltages
above 1 V were achieved, resulting in maximum open-circuit voltage-fill factor products of up to 0.73
V. Further work will concentrate on further improving these values, also in the stabilized state.
2.3 Intermediate reflector
In t he K AI s ystem, t he r efractive i ndex of s ilicon ox ide bas ed i ntermediate r eflector l ayers c ould be
pushed down to 1.66. These new layers are used in the new lab record micromorph cell with 14.1%
initial efficiency.
2.4 Intrinsic vs extrinsic defects in microcrystalline silicon
An extensive study was also conducted to improve our understanding of the fundamental mechanism
involved in the growth of microcrystalline silicon layers on highly textured substrates [26]. The impact
of i ntrinsic a nd extrinsic defects must be c arefully distinguished. While t raditional an alytic m ethods
such as Fourier transform infrared spectroscopy and Fourier transform photocurrent spectroscopy are
sensitive to the intrinsic material properties, they do not detect the influence of extrinsic effects such
as l ocalized porous r egions ( “cracks”), appear ing on r ough s ubstrates, and which we h ave s hown
earlier to be detrimental to the electrical device performance. Here we fabricated microcrystalline solar
cells with the same intrinsic bulk material quality, but with increasing extrinsic defect densities, which
negatively affect efficiencies. The impact of extrinsic effects on the electrical cell performance can be
reduced by adapting s urface m orphology ( U-shaped valleys r ather t han V-shaped on es) and /or i mplementing nanocrystalline s ilicon ox ide layers ( shunt quenc hing), or as shown i n the context of this
work by lowering the hydrogen flow during deposition.
2.5 ZnO at high deposition rate
Thanks to the use of higher flow rates and higher deposition temperatures, the deposition rate of LPCVD Z nO c ould be increased from 4. 5 nm /s t o 9 n m/s, w hile m aintaining s imilar o pto-electrical f ilm
properties. Annealing of ZnO films without a cap layer was confirmed to lead to an increased mobility,
accompanied b y a l oss i n carrier c oncentration, leading t o h ighly t ransparent, b ut r elatively r esistive
ZnO films. Post-deposition plasma treatments were found to strengthen the electrical properties with
respect to damp heat degradation.
2.6 Laser scribing
Amorphous and micromorph cell stacks were monolithically interconnected to mini-modules via laser
scribing. O n c ommercial A sahi SnO2 substrates, am orphous c ells i solated via a P 3 s cribe ( Voc=923
mV, F F= 69%) s howed s lightly improved op en-circuit voltages and f ill f actors c ompare t o c ells pa tterned via the standard lift-off process (Voc=919 mV, FF=67%). Also on the mini-module with 12 segments, an ex cellent per formance w as ac hieved ( Voc= 918 m V, F F= 67%). O n our i n-house L P-CVD
ZnO (2 um thick), laser patterning reveals to be much more delicate. Compare to a cell patterned by
lift-off ( Voc= 902 m V, F F= 77%), a P3 s cribe leads to m arked per formance l osses ( Voc= 827 m V,
FF=515) and also the m ini-module h as t o be o ptimized ( Voc= 784 m V, F F= 50%). A s imilar t rend is
observed for micromorph mini-modules with 8 segments.
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3. Devices
3.1 New microcrystalline record cell
New lab record efficiencies above 10% were achieved for microcrystalline single junction solar cells in
both the small PE-CVD reactors and the KAI system (see Figure 6) [27][28]. In both systems, we optimized the p-type silicon oxide layers. In addition, the introduction of a higher resolution in the control
of the silane gradient during i-layer deposition, lead to improved performance. An efficiency of 10.6%
was achieved at a deposition rate of 0.3 nm/s for an absorber layer thickness of 2 um. With the newly
developed antireflective coating, an efficiency of 10.9% was measured for the same cell.
Figure 6: Current density-voltage characteristics and external quantum efficiency of microcrystalline silicon record
cell with an efficiency of 10.9%.
3.2 New micromorph record cell
As m entioned a bove, a n ew initial ef ficiency record was al so obt ained f or a m icromorph cell on the
new multi-scale electrode architecture (see Figure 7) [15]. A 290 nm thick top cell, combined with a 60
nm low-refractive-index intermediate reflector, on silicon oxide basis, and a 2.6 um bottom cell as well
2
as t he n ew a ntireflection scheme yielded a n i mpressive m atched c urrent of 14 m A/cm , ex cellent
open-circuit voltage of 1.41 V and a fill factor of 71.5%, resulting in an initial efficiency of 14.1%. Our
multi-scale approach has a strong potential to yield even higher efficiencies, as the morphology of the
nanoimprinted structure is still s uboptimal f or the growth of hi gh-quality microcrystalline layers. Considering the thickness of the top cell a degradation in the range of 12-13% should be achieved for
Figure 7: Current density-voltage characteristics and external quantum efficiency of micromorph record cell with
an initial efficiency of 14.1%.
such kind of devices. More work is required though, because of postoxidation process, to realise the
full potential of such structures in the stabilized state. One of the remaining issue, is to further reduce
the i mpacts of c racks i n t he m icrocrystalline c ell, c reated b y t he m orphology i nduced b y the am orphous Si cell. First strategies have been attempted (section 3.3.)
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3.3 Valley filling after amorphous cell growth
To optimize the bottom cell performance in the micromorph tandem solar cell, we investigated possibilities to smoothen the sharply pinched morphology resulting from the deposition of an amorphous silicon layer on the ZnO pyramids. The pinches are responsible for regions of porous, low density material (called cracks), which are detrimental for the electrical performance of the bottom cell. Three approaches are under investigations. We report here on two approaches.
a) Valley filling via ZnO spray deposition
A first approach to actively influence the growth environment for the microcrystalline bottom cell consists of smoothening t he p inches via s pray deposition of a zinc acetate salt solution on the top cell,
which undergoes calcination into ZnO at 230°C. A setup for spray deposition has been installed and
first pr omising r esults i ndicate t hat t he pinches ar e s uccessfully f illed, a lthough uniformity issues r emain to be addressed.
b) Valley filling via chemical-mechanical polishing
A second approach focuses on i mproving the bot tom c ell in the s ubstrate (n-i-p) c onfiguration. Here
the m icrocrystalline s ilicon bottom c ell is deposited di rectly o n t he Z nO b ackcontact, followed by the
amorphous s ilicon t op c ell [19]. T o pr ovide a s mooth morphology f or t he bot tom c ell, w hich av oids
crack formation, an amorphous silicon layer is deposited to fill the valleys between the ZnO pyramids.
Chemical-mechanical polishing results in a flat surface consisting of patches of amorphous silicon and
polished ZnO pyramids. This approach resulted in high open-circuit voltages and an infrared response
similar to what is observed on a textured ZnO. From a scattering point of view, amorphous silicon is
the i deal valley filling material as the hi gh r efractive index contrast between t he ZnO and t he silicon
filling leads to excellent light scattering. Another advantage of using amorphous silicon as filling materials is its t ransparency in t he i nfrared r egion, where t he m icrocrystalline s ilicon s till abs orbs l ight.
However, parasitic absorption in the electrically dead amorphous silicon filling layer causes a marked
dip in the spectral response at 700 nm resulting in current losses. This dip can be partially reduced by
suppressing the doping in the amorphous silicon. Further work is required to develop filling layers with
transparencies ranging into the visible.
3.4 Filtered micromorph cells
We also introduced filtered micromorph cells to isolate the influence of the amorphous cell morphology
on the open-circuit voltage of the bottom cell. For this purpose, an Ohmic amorphous silicon layer was
deposited on LP-CVD ZnO, followed by the deposition of a microcrystalline bottom cell. The role of the
amorphous layer is to mimick the morphology of a full amorphous cell and to filter the solar spectrum,
such t hat t he m icrocrystalline bot tom cell onl y s enses t he r ed and i nfrared par t of t he s pectrum, as
would be the case in a complete micromorph cell. With such a filtered cell stack, only the bottom cell
contributes to open-circuit voltage generation. Comparing filtered and non-filtered micromorph cells on
substrates of increasing roughness, a clear correlation between open-circuit voltage of the bottom cell
and the open-circuit voltage of the micromorph cell could be established.
3.5 New record cell on flexible substrate
In the substrate configuration, amorphous/amorphous tandem junctions with initial and degraded efficiencies of 9.6 and 8.6% were achieved, which is a record for amorphous material on plastic. These
cells ar e de posited on n anoimprinted p lastic s ubstrates t o enha nce l ight t rapping and m ake us e o f
nanocrystalline s ilicon oxide w indow layers ada pted specifically f or c ells i n s ubstrate c onfiguration.
Micromorph cells with initial efficiencies of 11.8% were also fabricated. In order to boost the top cell
current an asymmetric intermediate reflector developed in previous project periods was implemented.
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4. Reliability
4.1 Electrode stability
Stability tests of conducting t apes and transparent conductive oxide were performed with the a im of
improving contacting schemes for modules [31]. Conductive tapes consist of a metallic ribbon coated
on one side with a conductive pressure sensitive adhesive. In order to ensure long lifetime and high
reliability of photovoltaic modules, the contacting scheme should be able to withstand typical IEC degradation tests such as damp-heat tests (85°C, 85% relative humidity) or thermal cycling tests (cycles
between -40°C and 85°C). Contact resistance measurements have been performed for different conductive tapes applied on a ZnO layer deposited on a 3 mm thick low-iron glass. The ZnO and the contacts w ere s ubsequently e ncapsulated using a layer of et hyl v inyl acetate ( EVA) and another 3 m m
thick glass as backsheet. The samples were subjected either to damp-heat (up to 600 h) or thermal
cycling conditions (up to 240 cycles of 4 h each). With respect to the amplitude of the degradation in
damp-heat (see Figure 8) and thermal cycling (not shown here), the tin-plated copper is the best contacting option among al l tested conductive t apes. H owever, i t is to be noticed t hat t he initial c ontact
resistances of the conductive tapes is rather high: further research will now be done in order to provide
conductive tapes using acrylic pressure sensitive adhesives (PSA) that exhibit a lower initial resistivity.
Figure 8: Evolution of contact resistance through damp-heat degradation. The first point represents resistance
before lamination, the second point after lamination, but still before degradation. Resistance is normalized to its
initial value after lamination (second point).
4.2 Encapsulation
A lot of efforts were expended to understand and monitor ZnO degradation in damp heat depending
on t he polymer us ed as enc apsulant. We dev eloped a m easurement s ystem al lowing a c ontinuous
monitoring of t he r esistance v alue in t he damp heat . Figure 9 s hows t he r esults obt ained f or t hree
different polymers, EVA, PVB and an Ionomer. The PVB sample shows a huge increase in resistivity
in the beginning of the aging. Only after 100 h of damp heat, the resistance was already in the order of
50, while the resistances of the EVA and Ionomer samples were much lower at the same time. These
results give important information on the barrier effect of the polymers against the water vapor ingress,
which is known to cause thin film silicon modules to fail. Further experiments are in progress, to understand more deeply the interaction and compatibility of ZnO layers with the encapsulants as well as
to further improve the module reliability in general by defining the most appropriate encapsulation design (edge sealant, frame, polymers, glass, foil, etc).
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Figure 9: Damp heat degradation of TCOs encapsulated with various polymers.
5. Infrastructure
5.1 Large area ZnO LP-CVD
A large-area LP-CVD deposition system has been installed, including a load-lock chamber, a transfer
chamber, w ith a utomated transfer r obot and t he possibility t o c onnect t hree de position c hambers. A
first depos ition c hamber h as bee n p ut into s ervice and f irst t ests h ave s hown that Z nO l ayers with
uniform optical and electrical properties can be grown. Optimization of the process parameters to establish standard recipes is ongoing.
5.2 PE-CVD cluster tool
In t he O ctopus c luster s ystem, bas e r ecipes f or s ingle j unctions ( amorphous and m icrocrystalline)
have b een s uccessfully developed both i n s uperstrate an d s ubstrate c onfiguration. Amorphous an d
microcrystalline cells with an efficiency of 10.4% and 9.9% were obtained respectively. Recombination
junctions for m icromorph t andem and t riple c ells were al so s uccessfully d eveloped r esulting i n zero
voltage loss in multi-junctions compared to reference single junctions. Hard- and software adjustments
were required to adapt the system to specific deposition regimes, notably an extension of the pressure
range to 12 mbar and a m odification of the pumping conductance and butterfly valves to allow for stable deposition conditions over a large pressure range. Furthermore the resistive heating system experienced several breakdowns, but is working stable now, although heat management must still be further optimized for optimum uniformity. A source of boron contamination due to boron residues in the
gas supply lines could be identified and eliminated. To this point, experimental work was carried out
exclusively at 80 MHz. The use of alternative frequencies was made delicate by coupling issues between the match box and generator, which could be solved recently. The system is now operational
with 6 chambers at 13, 40 and 80 MHz.
5.3 Current-matching machine and Voc separator
To i nvestigate c urrent m atching i n m icromorph c ells, w hich s trongly influences t he f ill f actor, w e
deviced an add-on setup for the Wacom IV simulator allowing to adjust the blue and red content of the
illumination spectrum. T he J -V c haracteristics of t he m icromorph c ells c an b e m odeled us ing an
equivalent network model with a two-diode model for the bottom cell and a Merten’s collection function
in the generated-recombination terms for the top and bottom cells. The model predicts an increase in
fill factor for both a blue rich and red rich spectral mismatch. Minimum fill factor is achieved when current m atching is es tablished. T hese t heoretical pr edictions could b e verified ex perimentally with t he
new current matching machine. In parallel, we are also developing a new setup that will enable measurement of the open-circuit voltage of top and bottom cell of a micromorph tandem independently. Part
of the work was done in collaboration with IPP Prahah.
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5.4 Degradation systems
A new system for light induced degradation at one sun was installed and is fully operational. The new
system provides a stable and uniform light distribution on a large area and a precise temperature control. We are currently also developing a 3-5 sun degradation system, which will enable rapid degradation experiments with faster feed-back loop.
5.5 Mass spectrometer
A quadruple mass spectrometer with a mobile pumping station was acquired allowing not only to fingerprint the residual gas content of the deposition chambers, but also to actively monitor process gas
composition. A s an alternative ap plication, t he m ass spectrometer c an al so be used i n c ombination
with a heating station for thermal desorption experiments.
National and international collaborations
Regular academic contact/scientific and sample exchanges continued to be maintained throughout the
project both with national and international entities (ETH Zürich, Zürich University of Applied Sciences
[32], C SEM Neuchâtel, F orschungszentrum Jülich, F riedrich-Schiller U niversität J ena [33], H elmoltz
Zentrum Berlin, Academy of Science Prague, University of Delft [34], Energy Research Center Netherlands, University of Utrecht, Trinity College Dublin, Stanford University [11][13], Caltech, National University of Singapore [35][36][37], AIST Japan …)
PV-Lab continues to be involved in several European projects (N2P, Silicon Light, Pepper, Hetsi and
20 p lus) as well as n ational projects ( Dursol, A xpo, Archinsolar, Velux in c ollaboration with C SEM)
and be nefits f rom t he s upport of t he N ational S cience F oundation. A s trong s ynergy i s or c ould be
realized between all these projects and this running SFOE project. National and industrial collaborations with industrial par tners ar e ong oing, e ither i n t he f rame of C TI pr ojects or through direct m andates, e. g. with O erlikon S olar [1], VHF T echnologies, R oth & R au S witzerland, 3S P hotovoltaics,
Pasan, Me talor, S olneva, Essemtech, I ndeotech, B osch S olar, S chott Solar, I BM, A ir L iquid, G adir,
Centro Ceramico, Photosolar, ...
Evaluation of 2011 and perspectives for 2012
In 20 11, k ey r esults h ave been ac hieved with t he e lucidation of t he nanostructure of t he f unctional
silicon oxides, with the integration of improved plasma processes and with the testing of new optical
structures, some of which proved remarkable for achieving better efficiencies. The results of the group
have a strong visibility in the field, and several findings are transferred or are in the process of being
st
transferred t o industry. P V-Lab a lso r eceived a wards at the I EEE PVSC ( M. Boccard) and t he 21
Asian PVSEC (M. Despeisse) for its work. However, even though the initial efficiencies of the microcrystalline cell and micromorph cell increased noticeably, the stable efficiency of the micromorph technology needs to be further increased beyond the current status of best efficiencies for tandems being
around 11.5 to 12.3% (at IMT and in advanced industrial labs for the highest values). In this respect
the coupling of the amorphous and microcrystalline cells in tandem devices must be improved. Indeed,
the deposition of the top cell changes the substrates morphology to a point where the bottom cell suffers (in the initial state but even more in the degraded state). The new processes and materials introduced have allowed a mitigation of this effect, but we expect that, by further addressing this issue, it is
possible to gain over 2% absolute efficiency in tandem devices (going up to 13.5% stable). In parallel,
at an industrial level, if the current cost calculations are correct, the micromorph technology represents
a promising low cost option of special interest, e.g. for the sunny areas of the globe. However, to remain competitive in the long run, further material and device research is required to allow stable efficiencies well above 13% at the cell level and above 12% at the module level.
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Acknowledgements
All t he PV-Lab c ollaborators, w ho c ontributed t o t he r esults presented in t his r eport, are warmly
acknowledged. In par ticular w e acknowledge t he c ontributions of A . B illet, R . Biron, M. Boccard, M.
Bonnet-Eymard, G. Bugnon, V. Chapuis, M. Benkhaira, C. Bucher, N. Castillo, M. Charrière, P. Cuony,
J. C urrit, C . Pahud, J . Escarré, L. D ing, J . F onjallaz, S . H änni, F .-J. H aug, J.-L. K umin, H .-Y. Li, L.
Löfgren, X . N iquille, G . Parascandolo, S . Pélliset, B . Perruche, P. P ettoruto, K . Söderström and M.
Stückelberger. We also thank D. Alexander, A. Hessler, M. Dadras and M. Leboeuf for assistance and
support in electron and scanning probe microscopy.
References
Most of t he r eferences bel ow ac knowledge s upport f rom S FOE under pr oject 1011 91. Preprints of
most papers are available from http://pvlab.epfl.ch.
[1]
P. Cuony et al., Advanced Materials, accepted (2011)
[2]
L. Ding et al., Solar Energy Materials and Solar Cells, accepted
[3]
L. Ding et al., IEEE J. Photovoltaics, accepted
[4]
S. Nicolay et al.,
[5]
C. Battaglia et al., Nature Photonics 5, 535 (2011)
[6]
C. Battaglia et al., OSA meeting, Technical Digest, Texas (2011)
[7]
J. Escarré, Solar Energy Materials and Solar Cells 95, 881 (2011)
[8]
C. Battaglia et al., Nano Letters 11, 661 (2011)
[9]
J. Escarré, J. Optics, accepted
[10] C. Battaglia et al., Energy Procedia, accepted
[11] C. Battaglia et al., submitted
[12] C. Battaglia et al., J. Appl. Phys. 109, 114501 (2011)
[13] C.-M. Hsu et al., submitted to Advanced Energy Materials
[14] M. Boccard et al., IEEE J. Photovoltaics, accepted
[15] M. Boccard et al., submitted
[16] C. Ballif et al., PVSEC-21 Technical Digest, Fukuoka, (2011)
[17] C. Ballif et al., Proceedings of the 26th EU-PVSEC, Hamburg (2011)
[18] J. Escarré et al., Solar Energy Materials and Solar Cells, accepted
[19] K. Söderström et al., in preparation
[20] K. Söderström et al., Solar Energy Materials and Solar Cells, 95, 3585 (2011)
[21] C. Eminian et al., Prog. Photovolt.: Res. Appl. 19, 260 (2011)
[22] M. Despeisse et al., Phys. Status Solidi A, 208, 1863 (2011)
[23] P. Cuony et al., Proceedings MRS meeting, San Francisco (2011)
[24] M. Despeisse et al., PVSEC-21 Technical Digest, Fukuoka, (2011)
[25] M. Stuckelberger et al., J. Non-Crystalline Solids, accepted
[26] G. Bugnon et al., Proceedings of the 37th IEEE PVSC, Seattle (2011)
[27] S. Hänni et al., Proceedings of the 26th EU-PVSEC, Hamburg (2011)
[28] G. Bugnon et al., submitted
[29] G. Parascandolo et al., submitted
[30] K. Söderström et al., Proceedings MRS meeting, San Francisco (2011)
[31] H.-Y. Li et al., Progress in Photovoltaics: Research and Applications (2011)
[32] T. Lanz et al., J. Appl. Phys. 110, 033111 (2011)
[33] C. Rockstuhl et al., Appl. Phys. Lett. (2011)
[34] O. Isabella et al., PVSEC-21 Technical Digest, Fukuoka, (2011)
[35] J. Wang, Proceedings of the APVIA, Singapore, (2011)
[36] M. Peters et al., Proceedings of the 26th EU-PVSEC, Hamburg (2011)
[37] M. Peters et al., Energy Procedia, accepted
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DEMONSTRATION OF HIGH PERFORMANCE
PROCESSES AND EQUIPEMENTS FOR THIN
FILM SILICON PV MODULES PRODUCED
WITH LOWER ENVIRONMENTAL IMPACT AND
REDUCED COST AND MATERIAL (PEPPER)
Annual Report 2011
F. Sculati-Meillaud, S. Nicolay, G. Parascandolo, G. Bugnon,
C. Ballif
EPFL, Photovoltaics and thin film electronics laboratory, Institute of
Microengineering IMT
Address
Rue A.-L. Breguet 2, CH-2000 Neuchâtel, Switzerland
Telephone, E-mail, Homepage 021/718.33.19, [email protected], http://pvlab.epfl.ch/
PEPPER/ 249782
Date
23.12.11
ABSTRACT
The FP7 EU PEPPER project aims at achieving high efficiency (11%) micromorph (amorphous/microcrystalline silicon tandem) modules at low cost (CoO ≤ 0.5 €/W p) while reducing the environmental impact of fabrication processes. The project thus includes development of a new generation of
Plasma Enhanced Chemical Vapor Deposition (PECVD) reactors for high rate deposition (up to 15 A/s) of
intrinsic µc-Si:H thin films. PVLAB participates in assessing the most favorable process parameters space
for high rate deposition. PVLAB also contributes, together with the University of Patras, Greece, to the
development of a model linking layer quality to deposition parameters and plasma dynamics.
One of the major outcomes for the first year of the project was the possibility to clearly improve the material
quality and device efficiency by hardware modification (inter-electrode distance reduction) of PVLAB KAI-M
PECVD reactor. Inter-electrode distance reduction indeed allowed increasing process pressure while maintaining powder free conditions, leading to 1 µm thick single-junction µc-Si:H solar cells with a conversion
efficiency of 8.6% at 12 Å/s. It was furthermore highlighted that µc-Si:H i-layers deposited with a low input
silane concentration typically exhibit a much higher density and severity of porous defective material than
the one deposited with higher silane concentration; nevertheless use of silicon oxide doped layers permit
to mitigate performance losses due to these defective zones.
PEPPER project also focuses on improving transparent conductive oxides (TCOs) used as front and back
electrode in micromorphs. PVLAB has here shown that the well-known transparency conductivity/trade off
could be drastically relaxed leading to the possibility to decrease the TCO film thickness at equivalent device performance. This was achieved by developing a bilayer approach (i.e. a highly doped nucleation
layer providing sufficient free electron conduction followed by a lowly doped bulk providing higher total
transparency) that led in micromorph solar cells to a total efficiency gain for a front contact 25 % thinner
than standard 2 µm front electrode. Further work is under way on reducing defective zones density in µcSi:H as induced by the roughness of the front contact. Several approaches are already envisaged: use of
an ethanol based cap layer to smoothen the surface of the TCO film or exploration of new growth regimes
leading to improved surface features morphologies.
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Short project description
The global goal of the project is to demonstrate and partially implement cost-effective high efficiency
processes to prove the feasibility of thin film micromorph (amorphous/microcrystalline silicon tandem)
module production. Its objectives are to:
 Increase the module power to 157 W p stabilized (corresponding to 11% conversion efficiency)
 Maintain low Cost of Ownership (CoO) for micromorph module fabrication at 0.5 €/W p
 Reduce the environmental impact of the fabrication process with the target of 20% lower energy
payback time
To meet these goals, different topics are addressed, among which 2 concern PVLAB directly:
advanced transparent conductive oxide (TCO) properties allowing better light trapping (Work Package
WP 2) and higher deposition rates while maintaining high quality intrinsic microcrystalline silicon
(µc-Si) material (WP3).
An optimized front electrode is a prerequisite to cost-effective and efficient micromorph modules. The
key is to have one that enables good light scattering and at the same time still allows high quality microcrystalline silicon growth. Thus, in PEPPER project, various approaches are addressed with the
aim to achieve a rough surface structure featuring wide valleys which benefit the microcrystalline
growth. Furthermore, for production cost rationalization, it is important to decrease the thickness of the
TCO films to reduce tact time and material consumption.
During the first year, different deposition concepts and regimes have hence been evaluated, among
which most promising ones should now be selected and studied in more detail during the next two
years.
The specified objectives concerning TCO development are the following:
 Layers with a nanomorphology allowing reduced defective zone (crack) density by a factor 2 as
compared to the current process at Oerlikon Solar.
 Reduced deposition time by 10% for ZnO layers with similar sheet resistance without increasing
free carrier absorption (equivalent to better control of nucleation).
Regarding plasma processes and high deposition rates development for µc-Si:H silicon, the first year
was focused on studying the impact of the inter-electrode distance of a KAI-M Plasma Enhanced
Chemical Vapor Deposition (PECVD) reactor on the process parameter space for high rate deposition
of µc-Si:H. In this frame, process conditions leading to low powder formation and high material quality
were identified and device efficiency at high deposition rate improved.
Our main results during the first year are the following:
 High deposition rate for µc-Si:H:
First, we studied the impact of the inter-electrode distance (dgap) of a Plasma Enhanced Chemical
Vapor Deposition (PECVD) reactor on the process parameter space for high rate deposition of intrinsic
microcrystalline silicon (µc-Si:H) thin films. In this frame, we identified process condition leading to low
powder formation and high material quality/device performances. We began by reducing dgap in our
medium-size KAI reactor (KAI-M, VHF = 40.68MHz) from 25 mm to 11 mm. The narrow gap configuration allows high pressure processing with reduced powder formation, leading to improved bulk material
quality of the deposited µc-Si:H films and enhanced solar cell performances. dgap then determines the
maximum deposition rate (Rd) achievable and the optimum value for process pressure.
Full p-i-n devices with typically 1µm thick intrinsic layer were thus deposited in the KAI-M reactor on
0.5 mm thick SCHOTT AF45 glasses coated with naturally textured in-house Low-Pressure CVD
(LPCVD) zinc oxide (ZnO) that serves as front Transparent Conductive Oxide (TCO). After Si layers
deposition, the device is capped with a similar LPCVD ZnO back TCO and 16 (or 6) solar cells with
2
2
0.25cm (or 1.2 cm ) active area are patterned on the substrate by lift-off. The plasma dynamic is monitored in-situ via a Tunable Diode Laser Spectrometer (TDLS) measuring the SiH4 consumption efficiency, an Optical Emission Spectrometer (OES) identifying different chemical species present into the
plasma and a Laser Light Scattering (LLS) setup quantifying the production of powder during the process. The bulk material quality is studied via X-Ray Diffraction (XRD), Fourier Transform Infrared
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PEPPER 249782, F. Sculati-Meillaud, EPFL/IMT
Spectroscopy (FTIR) and Fourier Transform Photocurrent Spectroscopy (FTPS). The presence of
defective regions in the films was further evidenced via Scanning Electron Microscopy (SEM). Currentvoltage (J-V) curves were measured with a dual lamp (Xe-Ha) solar simulator (WACOM) and average
values of open circuit voltage (Voc) and fill factor (FF) over 16 (or 6) cells are reported, unless otherwise stated. The short circuit current Jsc is evaluated via external quantum efficiency measurement
performed on the best cell.
High Rd of µc-Si:H films is achieved when a large amount of SiH4 molecules (high input SiH4 flow) is
efficiently dissociated (via high feed-in power density and excitation frequency, i.e. VHF) and deposited on the substrate. In these conditions, high process pressure leads to long residence time for effective gas utilization and eventually reduces the ion bombardment of the growing surface, thus enhancing the bulk quality of the deposited film. Nevertheless, as soon as all these conditions are met, secondary gas-phase reactions lead to the formation of powder, which is detrimental to film homogeneity
and, to some extent, to the device quality. Moreover, large quantity of powder can harm the pumping
system of the reactor. If the surface to volume ratio of the reactor is increased, the probability of a SiH4
radical contributing to film growth, rather than creating powder by interacting in the gas phase, increases. In a parallel plate reactor, the surface to volume ratio scales as 2/dgap (dgap is the interelectrode distance). Thus, powder formation can be reduced by means of a simple geometric adjustment, i.e. reducing dgap, allowing high pressure processing. Moreover, at high pressure and small dgap
a stable plasma discharge can be maintained at lower power densities [1].
In Figure 1, the Voc ·FF product of single-junction µc-Si:H solar cells is plotted as a function of Rd
(black symbols, left hand scale). The devices were deposited either in wide (25mm, squares) or narrow (11mm, dots) gap reactor configuration. The process pressure was fixed to 3.3mbar and 5.5mbar
in wide and narrow gap configuration, respectively. For each device, the “bulk” defect absorption coefficients at 0.8eV (α0.8eV) measured via FTPS is plotted as well (red symbols, right hand scale).
0.42
7
0.40
6
0.36
5
0.34
4
0.32
α0.8eV(10-3cm-1)
Voc⋅FF
0.38
3
0.30
wide i-e gap, 3.3 mbar
narrow i-e gap, 5.5 mbar
0.28
5
2
10
Rd(Å/s)
Figure 1: Voc ·FF product (black symbols, left hand scale) as obtained from J-V curves of µc-Si solar cells deposited i n w ide ( squares) and na rrow ( dots) ga p r eactor c onfiguration and corresponding “ bulk” def ect absorption
coefficients at 0 .8eV measured v ia F TPS ( red symbols, r ight han d s cale) versus t he d eposition r ate o f t he a bsorber i-layer.
Figure 1 summarizes the following results:
i) For each value of dgap, the product Voc ·FF decreases versus Rd while α0.8eV increases, indicating
that the deterioration of the bulk material quality is responsible for electrical performance losses
at increasing deposition rate.
ii) At fixed Rd, narrow gap configuration enhances electrical performances, due to reduced ion bombardment on the growing surface at high pressure.
iii) At narrow gap, high Rd = 12Å/s is achieved compared to Rd = 7Å/s at wide gap. This is due to the
intensive formation of powder that takes place in the wide gap reactor, which overcomes film
deposition.
Note that the average product Voc ·FF of devices deposited at 12Å/s with dgap = 11mm is 20% higher
than that of devices deposited at 7Å/s with dgap = 25mm, even if comparable defect density are meas-3
-1
ured for the two samples (i.e. α0.8eV ≈ 7·10 cm ). This suggests that the bulk material quality as measured via FTPS only partly accounts for the electrical performances of the device, as will be further
discussed later on.
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Once the geometrical configuration of the reactor was fixed, we investigated the parameter space for
high rate deposition of µc-Si:H films. The optimal process pressure (p) window being determined by
dgap, the film Rd and Raman crystalline fraction (Ic) are a function of the input gases flows and of the
feed-in power density (Pd). Looking for processes leading to Rd = 10Å/s and Ic ≈ 60%, we developed
PECVD processes at three values of pressure, namely p = 4.5/5.5/7.0 mbar. For each pressure the
input SiH4 flow, [SiH4], was fixed while we varied the input hydrogen flow, [H2], and adjusted Pd by a
few percent to fulfill the desired conditions on Rd and Ic
Figure 2a shows that the solar cell conversion efficiency linearly increases versus p, the silane concentration being here fixed at c = 9.1%. Even if, as explained in the previous section, the pressure
increase favors the powder formation, it also reduces the ion-bombardment on the growing surface,
which promotes higher solar cell performance [2]. Using standard µc-Si doped layers, a maximum
initial efficiency of 7.9% was achieved at p = 5.5mbar and c = 29%, as shown in Figure 2b.
Efficiency (%)
7.6
7.2
6.8
6.4
4.5
5.0
5.5
6.0
6.5
pressure (mbar)
7.0
Figure 2: Conversion efficiency of µc-Si solar cells (a) versus i-layers deposition pressure, p, with constant input
silane concentration, c= 9.1%, and ( b) versus c at p = 5.5mbar. In (b), black and red lines are guide to the eyes
for devices using µc-Si and SiOx doped layers, respectively (see text). All i-layers are deposited at 10Å/s and
have comparable Raman crystalline fraction.
Figure 2b additionally demonstrates a linear efficiency growth with increased input silane concentration c for p = 5.5mbar (black squares). This is rather unexpected because low input gas flow enhances
powder production but, differently from the case of pressure increase, no reduction of ion bombardment is obtained in turn. EPFL has recently shown that replacing standard µc-Si doped layers with
microcrystalline silicon oxide doped layers improves the electrical properties of different types of thinfilm silicon based solar cells [3, 4]. In Figure 2b, the conversion efficiency of devices using SiOx doped
layers is also plotted (red dots): using such doped layers improve electrical performances for all c, with
a higher relative improvement (up to 29%) the lower the input silane concentration so that the performances are leveled up to remarkable values over 8% and comparable for all c.
The bulk material quality of the cells in Figure 2b was then studied via XRD, FTIR and FTPS [5]. None
of these techniques was able to highlight significant differences in the bulk of the films deposited at
increasing silane concentration. On the other hand, the SEM images in Figure 3 shows that the µc-Si
i-layer deposited with the lowest c exhibits a much higher density and severity of porous zones than
the one deposited with the highest c.
Figure 3: Scanning Electron Microscope pictures of µc-Si:H solar cells deposited at p = 5.5mbar with using c =
5.7% and c = 28.6%.
These defects act as bad recombination diodes and contribute along with bulk defects to define the
overall cell efficiency. These results suggest that adequate plasma conditions may hinder the development of porous zones in µc-Si:H films of very similar bulk electrical properties. By using SiOx doped
layer, contributions of defective zones to performance loss can be mitigated [4] and initial efficiencies
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up to 8.6% for single-junction solar cells with an absorber layer of 1 µm deposited at
12 Å /s have been achieved. When such cell is implemented in a micromorph with an amorphous top
cell of 220 nm, 12.3% initial efficiency is reached. IVs of single-junction and micromorph cells are
shown in Figure 4. The micromorph stabilized at 9.8% after 1000h of light-soaking, demonstrating a
higher relative degradation than expected.
Figure 4: IV measurement of state-of-art single-junction microcrystalline silicon solar cell with 1 µm thick i-layer
@ 12 Å /s and micromorph tandem with a top a-Si:H of 220 nm.
 TCO developments:
In the first year of the PEPPER project, the transparency/conductivity tradeoff has been addressed to
improve the transparency for a given sheet resistance. In order to reach this goal, we used a highly
doped nucleation layer providing sufficient free electron conduction followed by a lowly doped bulk
providing higher total transparency, i.e. a bilayer approach [6]. The results of this approach are shown
in Figure 5 and table 1.
1.0
std
2um: (0.12) bulk
1.5 um: (0.12) bulk
0.8
EQE
0.6
0.4
0.2
0.0
300
450
600
750
900
1050
1200
Wavelength (nm)
substrate:
d (µm)
Haze
600nm
(%)
BL (0.12):1.9
JEQE (mA/cm²)
Eff
(%)
Voc
(V)
FF
top
bot
49
13.1
12.5
11.5
1.29
0.71
BL (0.12):1.5
35
13
12.3
11.5
1.30
0.72
Std:2
32
12.7
11.5
11.2
1.30
0.75
Figure 5 and Table 1: External q uantum ef ficiency r esponse an d I V m easurements o n m icromorph c ells
co-deposited on standard LPCVD ZnO (2 µm thick) and bilayers of 1.9 and 1.5 µm thick.
It is clearly seen that the high transparency of the bilayer leads to a gain in photogenerated current as
well as a drop in FF, mainly attributed to different matching condition between the top and bottom part
of the micromorph. However, this loss in FF is overcompensated by the gain in current which leads to
an absolute efficiency gain of 0.3% for a front contact 25 % thinner than the standard 2 µm film.
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In order to test this process on large scale modules in a production environment, the bilayer approach
has been transferred to Oerlikon Solar. Figure 6 shows the evolution of photogenerated current on 1.4
2
m modules while using this approach: a current gain of up to ∼0.03 A can be observed which can be
translated into a total output power gain of more than 3 W p per module.
1.26
Isc(A)
1.24
1.22
1.20
1.18
Std. ZnO
Bilayer
Bilayer
Cell opti.
Std. ZnO
Figure 6 : Current ga in at t he m odule s cale w hile us ing t he bi layer appr oach. A n abs olute gai n o f
current can be observed between the module on standard front ZnO and an optimized module on bi-layer which
corresponds to a total output power gain of more than 3 Wp per module.
These results are very promising given the very simple and very low cost implementation procedure of
this new TCO film design.
Finally, the PVLAB is in charge of the dissemination of the project: a brochure has been edited and
th
distributed at the 26 EU PV conference in Hamburg, and a website was created with details on the
project, partners, publication list, etc.: http://pepper.epfl.ch/.
National and inernational collaboration
In the frame of this project, the PVLAB is directly collaborating with Oerlikon Solar for TCO developments and the University of Patras for plasma modeling.
Evaluation for 2011 and perspectives for 2012
 High deposition rate for µc-Si:H:
Our study of maximum deposition rate and material quality as a function of inter-electrode distance
and the reduction of the latter in our KAI-M reactor has permitted to:

Highlight the fact that PECVD processes may give same bulk quality assessment but differences in the development of porous zones (non-bulk defects)

Improve µc-Si:H quality and, hence, solar cell efficiency while increasing deposition rate to 12
Å/s.
We have obtained 12.3% initial efficiency stabilizing at 9.8%, whereas 11% stable is planned for
month 24 of the project with the µc-Si:H i-layer at 12 Å /s. Further reduction of the inter-electrode distance is currently under test. We should now further investigate what are the clear contributions of
plasma conditions, substrate morphology and deposition rate to bulk and non-bulk defects.
 TCO developments:
In the first year of the PEPPER project, the transparency/conductivity tradeoff has been addressed
and successfully lifted since we were able to obtain a total efficiency gain in micromorph tandems for a
front contact 25 % thinner than the standard 2 µm film.
Now, further work should comprise developments of layers allowing reduced defective zone (crack)
density (milestone: reduction by a factor of 2), as compared to standard front contact. First tests have
been conducted with significant crack density reduction (as observed by SEM) but unfortunately poor
electrical performances.
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References
[1] G. Parascandolo, R. Bartlome, G. Bugnon, T. Söderström, B. Strahm, A. Feltrin, C. Ballif. Applied P hysics Let ters 96,
233508 (2010).
[2] G. Bugnon, A. Feltrin, F. Meillaud, J. Bailat, C. Ballif. Journal of Applied Physics 105, 064507 (2009).
[3] P. Cuony, M. Marending, D. T. L. Alexander, M. Boccard, G. Bugnon, M. Despeisse, C. Ballif. Applied Physics Letters 97,
213502 (2010).
[4] M. Despeisse , C. Battaglia, M. Boccard, G. Bugnon, M. Charrière, P. Cuony, S. Hänni, L. Löfgren, F. Meillaud, G.
Parascandolo, T. Söderström and C. Ballif,,Optimization of thin film silicon solar cells on highly textured substrates, Physica
status solidi (a) 208: 1863–1868 (2011)
[5] G. Bugnon, G. Parascandolo, T. Söderström, R. Bartlome, P. Cuony, S. Hänni, M. Boccard, J. Holovsky, M. Despeisse, F.
Meillaud, C. Ballif, Proceedings of the 37th PVSC, Seattle (2011)
[6] L. Ding, M. Boccard, G. Bugnon, M.Benkhaira, M. Despeisse, F. Meillaud, S. Nicolay, P.A. Losio, O. Kluth, P. Carroy, O.
Caglar and C. Ballif, accepeted for publication in IEEE Journal of Photovoltaics.
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Département fédéral de l’environnement,
des transports, de l’énergie et de la communication DETEC
Office fédéral de l’énergie OFEN
FLEXIBLE PRODUCTION TECHNOLOGIES
AND EQUIPMENT BASED ON ATMOSPHERIC
PRESSURE PLASMA PROCESSING FOR
3D NANO STRUCTURED SURFACES (N2P)
Annual Report 2011
Address
S. Nicolay
Ecole Polytechnique Fédérale de Lausanne
Institute of Microengineering IMT
Telephone, E-mail, Homepage 032 718 33 11, [email protected], http://pvlab.epfl.ch/
CP-IP 214134-2 N2P
Duration of the Project (from – to) 01.06.2008 – 31.12.2012
Date
12.2012
ABSTRACT
Although important progresses have been made in the development of novel structures for 3D
nanosurfaces applications, their use at large scale is still partly limited by lack of high throughput suitable manufacturing technologies.The overall objective of this project “N2P” (Nano to Production) is to
develop and substantially enhance the position of Europe in the science, application and production
technologies of surface 3D nano-structuring. In this project, the consortium develops innovative in-line
high throughput manufacturing technologies based on atmospheric pressure vapour phase surface
and plasma processing technologies. Both approaches have significant potential for 3D nanostructuring, but their effective simultaneous combination is particularly promising. It is proposed to
merge the unique potential of atmospheric pressure based plasma-chemical etching with vapour
phase based nucleation and growth.
The role of the PV-lab is to guide the development of SnO2 TCO layers for thin film silicon photovoltaic activities by working in close collaboration with the University of Salford (USAL) and CVD Technologies Limited, both specialists in atmospheric CVD. Regarding photovoltaic applications, the goal is
to optimize the TCO film in order to achieve energy conversion efficiencies higher (>7% relative) than
the ones obtained with in-line produced industrially available TCO.
Another part of the photovoltaic related development of the project consists in developing atmospheric plasma etching for surface post treatment of the TCO films, which is needed to allow the deposition
of a good quality absorber material. Both these objectives are pursued by carefully correlating the
optical, electrical and morphological properties of the TCO films with the performances of the cells
deposited on these films.
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Project Goal
Although important progresses have been made in the development of novel structures for 3D
nanosurfaces applications, their use at large scale is still partly limited by lack of high throughput suitable manufacturing technologies. The overall objective of this project “N2P” (Nano to Production) is to
develop and substantially enhance the position of Europe in the science, application and production
technologies of surface 3D nano-structuring.
Regarding the thin film silicon development, the main goal of the project is to develop the atmospheric
CVD (ACVD) process for in-line TCO (SnO2:F) on glass production in order to achieve a relative increase of 7% solar cell efficiency compared to industrially available in-line products on both single
junction and micromorph devices. Another goal is to demonstrate the possibility to use atmospheric
plasma etching as an efficient way to modify the surface morphology of TCO films allowing developing
high efficiency cells by combining at the same time high photo-generated current and high FF and
1
Voc .
Since the beginning of the project it has been shown that a relative efficiency increase of 18 % could
be achieved by using the TCO developed by University of Salford (USAL) compared to the standard
in-line industrial available TCO. Based on these promising results it was decided to further develop the
TCO in order to achieve higher efficiency compared to cells deposited on off-line high quality/high
price product thanks to the improvement of the USAL in-line process. In addition the atmospheric
plasma etching surface process also has to be further developed in order to avoid particle redeposition that was observed in the previous years. Eventually, we also started depositing tandem aSi/µc-Si cells on the new TCOs in order to evaluate their suitability as front contacts for cells including
µc-Si:H material which is well known to be sensitive to too rough TCO surface morphologies.
Description of the project
The project takes place in the framework of the FP7 theme 4: Nanosciences, Nanotechnologies, Materials and new Production Technologies. Compatible with the call, the research focus is on the application of basic research results for the development of new manufacturing processes and equipment for
new science based products in order to create potentially disruptive products and production systems.
The project relies on strong collaborations between teams in charge of depositing the TCO films
(Universit of Salford (USAL), UK), equipment development (CVD Tech (UK), Manchester University
(UK)), evaluation (EPFL) and demonstration (Nuon Helianthos (NL)) as shown in Fig. 1.
Figure 1: Structure of the project (N2P project proposal)
Work and results after 36 months
In order to achieve higher efficiency compared to the off-line industrial standard (AGC U), it was
decided to concentrate on process solutions allowing for better cell Voc and FF in stead of higher
photo-generated current. Indeed, it was already shown that higher current could be easily achieved
but this was at the detriment of the electrical properties. The implementation of a SiOx doped layer
(developed at IMT) in the PIN stack allowed to decrease the cell sensitivity on the roughness of the
TCO surface leading to an increase of the cell Voc and FF. However, this was true for both the
industrial standard and USAL TCO and therefore did not bring a specific competitive advantage for the
process developped in this project.
Still, in the first part of the past year, it was demonstrated that the use of well established preparation
procedures could strongly reduce the result statistical scattering and leads to higher mean efficiencies
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Project N2P, S. Nicolay, EPFL
on standard samples. The first micromorph cell was also deposited which EQE measurement is
shown in Figure 2 along with the EQE measured on the industrial off-line TCO.
172 top J = 11.69 mA/cm^2
172 bottom J = 10.81 mA/cm^2
AGC top J = 11.41 mA/cm^2
AGC bottom J = 10.32 mA/cm^2
0.8
EQE
0.6
0.4
0.2
0.0
300 400 500 600 700 800 900 1000 1100 1200
Wavelength (nm)
Figure 2: EQE measured on USAL TCO (black) and industrial off-line standard (green)
It is seen that USAL TCO leads to higher photo-generated current especially in the IR part which is
attributed to better light trapping thanks to larger surface features. However, as it is seen in the following tables (Sample 172 is the standard USAL sample achieved after one year while AGC is the industrial offline standard) exhibiting the result of the IV measurements on these two cells, such larger features also led to dramatic decrease in FF.
172
Isc
mA/c
m²
Voc
(V)
10.95
1.377
FF
Rsc
Ohm.cm²
Roc
Ohm.c
m²
Imax
mA/cm²
Vmax
(V)
Eff
(%)
Isc 0.4
mA/c
m²
Voc
0.4
(V)
FF
0.4
Rsc 0.4
Ohm.cm²
0.701
14320.249
10.310
9.482
1.118
10.599
0.030
0.372
0.339
22923.242
30495.07
9.056
AGC
10.15
1.360
0.768
9.456
1.122
10.609
0.029
0.907
0.684
1059001.6
Table 1: I-V cell characteristics of “standard” USAL TCO sample and AGC U type TCO
Such decrease compensates the gain in current which led to efficiency of 10.4 % measured on the
USAL TCO versus 10.8% on industrial off-line TCO. Still, this is a promising result as it was the first
trial of a micromorph deposition on USAL samples.
In the second part of the past year, it was decided to focus on process aiming at producing cell with
improved electrical properties. One of the proposed solution is to play on the water to Tin (Sn) precursor ratio as it is known that it can strongly alter the surface feature morphology. First results show that
using higher water content (sample 237) leads to an increase of the total transmittance of the layers
as shown in figure 3 for films with different tin/water ratio. Note that the USAL standard is deposited
with a 1/5 ratio.
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90
80
70
TT, TD
60
236 1:1 Sn/water
237 1:50 Sn/water
240 std low FCA
50
40
30
20
10
0
300
600
900
1200 1500 1800 2100
wavelength (nm)
Figure 3: Total and diffuse transmittance as a function of the water/tin ratio.
In the same time it is seen that the diffusive transmittance is also reduced as the water to tin ratio is
increased.
Eventually, TiO2 was added at the end of the growth (sample 241) in order to decrease the reflection
at the TCO/cell interface as well as in the nucleation stage in order to investigate the possibility to
enhance the grain size at the surface to achieve higher haze (sample 242). Results are shown in Figure 4.
90
80
70
TT, TD
60
50
240: standard
241: 20 nm TiO2 on top of FTO
242: FTO on top of 40 nm TiO2
40
30
20
10
0
300
600
900
1200 1500 1800 2100
wavelength (nm)
Figure 4: Total and diffuse transmittance for layers with TiO2 in the nucleation or at the surface.
It seen that the transparency is increased when TiO2 is put on the surface while using TiO2 in the
nucleation leads to stronger light absorption in the TCO for the whole wavelength range. This is ascribed to the higher reflectivity at the glass/TiO2 interface due to the higher index of refraction jump
compared to standard SnO2 on glass. Regarding cell properties, it is seen in table 2 that the use of
higher water to tin ratio and TiO2 on the TCO surface leads to better Voc and FF while keeping good
photo-generated current. Note that samples 238 and 239 were deposited with water flushes (with
different water flows) between several pass in front of the coating head.
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sample
JEQE
237
Eff EQE
surf
cm²
Isc
mA/cm²
Voc
(V)
FF
Rsc
Ohm.cm²
Roc
Ohm.cm²
Imax
mA/cm²
Vmax
(V)
Eff
(%)
0.4
mA/c
0.4
(V)
FF
0.4
Rsc 0.4
Ohm.cm²
0.101
0.25
17.311
0.915
0.731
2491.361
5.480
15.524
0.742 11.513 0.045 0.340
0.000 13912.064
235
14.4 0.0651188
0.25
15.49
0.873
0.518
372.273
14.311
11.463
0.609
6.981 0.070 0.045
0.000
616.774
236
15.12 0.0876741
0.25
17.963
0.899
0.645
958.699
5.716
14.749
0.706 10.420 0.044 0.060
0.000
1326.306
238
15.87
0.094125
0.25
18.105
0.900
0.659
661.455
5.856
15.111
0.711 10.744 0.044 0.042
0.000
932.405
239
15.76 0.1006763
0.25
18.321
0.901
0.709
1943.738
4.613
16.039
0.729 11.692 0.046 0.230
0.000
6696.234
0.458 32693.170
15.1
240
15.03 0.0951098
0.25
14.242
0.904
0.700
3979.410
8.222
12.627
0.711
241
15.43 0.0988508
0.25
17.359
0.910
0.704
1817.118
5.800
15.271
0.728 11.117 0.044 0.229
0.000
242
13.37 0.0682732
0.25
14.397
0.885
0.577
548.855
6.597
10.717
0.690
7.392 0.037 0.031
0.000
758.150
0.0945
0.25
18.475
0.908
0.703
921.458
4.388
15.832
0.746 11.814 0.049 0.074
0.000
1526.687
AGC
14.8
8.978 0.067 0.632
Table 2: I-V cell characteristics of USAL TCO films deposited with different tin/water ratio
and with TiO2 cap or nucleation layer.
The use of the high water/tin ratio leads to an efficiency gain 0.5 % absolute value ( 237 vs AGC
or 239 (alternating high water flow with smaller tin flow in the chamber) vs AGC) while the use
of a TiO2 cap layer leads to a gain of 0.4% (241 vs AGC).
As a conclusion future work will concentrate on further developing USAL films by determining the optimum water to tin ratio as well as by finding the optimal TiO2 cap thickness.
International Collaboration
As stated above, the N2P project relies on strong cross cutting activities between equipment development, process optimization, device evaluation and final transfer towards a demonstrator. General
assembly meetings bringing together all the partners involved in the project are organized every 6
months. In addition, for the thin film PV cells, a strong collaboration between EPFL and USAL/CVD
Tech (UK) is ongoing in the form of regular intermediate technical meetings to ensure an optimum
follow up of the progress. Eventually, the PV-lab also works in close collaboration with the Fraunhofer
IWS in Dresden, coordinator of the project, for the development of plasma etching technique on
LPCVD ZnO.
2011 evaluation and prospects for 2012
First, it has been shown that the TCO developed in the framework of this project are suitable for
micromorph deposition. In addition, the use of high water/tin ratio and TiO2 cap layer allowed us to
achieve ef ficiency 0.5 % higher th an th e i ndustrial o ff-line p roduct w hile u sing a n in lin e d esigned to ol a nd p rocess. This o pens i nteresting p rospective fo r the c ommercialization o f th e
developed coating tool. And as a reminder it has to be noted that this is well above expected project
deliverables.
For the coming year, the development of atmospheric plasma surface treatment should be developed
as it was not touched since month 24. In addition micromorph demonstrator and mini-module should
be achieved with the improved process parameters.
Références
[1] Bailat J. et al, Proc. of the 4th WCPEC Hawaii, 2006, p.1533
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7158.951
SILICON-Light – IMPROVED MATERIAL
QUALITY AND LIGHT TRAPPING IN THIN
FILM SILICON SOLAR CELLS
FP-7 PROJECT 241277
Annual Report 2011
Address
Telephone, E-mail, Homepage
Duration of the Project (from – to)
Date
EPFL, Institute of Microengineering, PVLab
Rue A. L. Breguet 2, Neuchâtel
032 718 3325, [email protected]
241277
01.01.2010 – 31.12.2012
15.12.2011
ABSTRACT
Open circuit voltage
(mV)
ITO work function
(eV)
The project SILICON-Light is devoted to the investigation of n-i-p solar cells on flexible substrates
with focus on material quality, interface properties, and light management. During the second year
three main aspects were investigated; firstly, based on work from the previous period, a model was
developed for relating the open circuit voltage to properties of the p-layer and the transparent front
electrode. One of the theoretical findings, an improvement of the open circuit voltage with the work
function of the ITO front electrode, was subsequently tested during a screening of novel front electrode materials.
5.3
5.2
5.1
ITO 90/10
920
900
880
0
1
2
Relative oxygen partial pressure (%)
Finally, amorphous cells with improved performance were combined with microcrystalline bottom cells
into tandem cells, reaching initial efficiencies up to 11.8%.
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EU FP7 Project Silicon Light
The EU project SILICON-Light started in January 2010. Its main aspects are flexible thin film silicon
solar cells in n-i-p configuration. The consortium consists of:
•
•
•
•
•
•
•
•
•
ECN (National Energy Research Laboratory of Holland, large area silicon deposition,
coordination
EPFL PV-Lab (high efficiency devices)
University of Ljubljana (optical modeling)
Technical University of Denmark (TEM analysis)
Polytechnic University of Valencia (Mastering of nano-structures)
Shanghai Jiatong University (Mastering of nano-structures)
Umicore AG (Liechtenstein, manufacturer of sputtering targets)
nanotpics GmbH (Germany, roll-to-roll processing of textured plastic substrates)
VHF technologies S.A. - Flexcell (integration into modules)
Work performed in the reporting period 2011
MODELLING THE WINDOW LAYERS OF AMORPHOUS SINGLE JUNCTION SOLAR CELLS
The combination of front electrode and p-doped layer is often referred to as “window layers” because
all illumination must pass though these films. Electrically, the junction between the n-type TCO and the
p-type film represents a p-n diode whose blocking direction is opposed to solar cell operation. The
blocking effect can be reduced by strong doping which facilitates tunnelling transport or by choosing a
TCO material whose work function is high enough to make Ohmic contact to the p-layer [1,2].
Together with the partner Umicore, a variety ITO of materials was screened with respect to their work
function, their electric conductivity, and their optical transmission.
5
4
ITO 80/20
ITO 90/10 ITO 95/5
ITO 97/3
ITO 100/0
Resistivity (10−3 Ωcm)
3
2
1
0 1 2
0 1 2
0 1 2
0 1 2
0 1 2
FIGURE 1: RESISTIVITY OF DIFFERENT ITO COMPOSITIONS, THE NUMBERS REPRESENT THE
WEIGHT RATIO BETWEEN IN2O3 AND SNO2. FULL AND OPEN SYMBOLS DENOTE
VALUES BEFORE AND AFTER ANNEALING, RESPECTIVELY.
Figure 1 shows the electric resistivity of different ITO compositions and their dependence on the oxy-3
gen content during sputtering. State of-the-art films should exhibit resistivity below 10 Ωcm. Most of
the films show that a minimum oxygen content is required for reaching such low values, however,
towards high oxygen content, the resistivity of all films increases due to passivation of oxygen vacancies that act as donors in these films. The figure illustrates also that low tin content results in high resistivity, but the exact mechanism of tin doping in ITO is still debated. Additional measurements of the
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EU-FP7 project Silicon-LIGHT, F.-J. Haug, EPFL PV-Lab
Hall effect showed that high tin content and low oxygen partial pressure during deposition translate
directly into high carrier densities. FIGURE 2 shows the work functions of the samples with high tin
content. There is a clear relation towards low work function for conditions that produce high carrier
density.
Work function (eV)
5.3
5.2
5.1
ITO 80/20
5.0
0
ITO 90/10
ITO 95/5
1 2
0 1 2
0 1 2
FIGURE 2: VARIATION OF THE WORK FUNCTION FOR SELECTED ITO COMPOSITIONS.
The figure on the title page shows a clear improvement the Voc with increasing work function. More
details can be found in ref. [3].
HIGH EFFICIENCY TANDEM CELLS
Amorphous cells with improved performance then integrated into tandem cells, using microcrystalline
bottom cells on a 5 μm thick ZnO film with pyramidal texture. Prior to the deposition of the amorphous
top cell a 2.5 μm thick ZnO layer is deposited which acts as textured intermediate reflector.
1.0
Current density (mA/cm2)
5
0.8
EQE
0.6
0.4
0.2
0.0
12.58 mA/cm2
12.79 mA/cm2
400 500 600 700 800 900 1000 1100
Wavelength (nm)
0
Voc: 1.39 V
Jsc: 12.6 mA/cm2
FF: 67%
Efficiency: 11.8%
-5
-10
-15
-0.5
0.0
0.5
1.0
Voltage (V)
1.5
FIGURE 3: EQE (LEFT) AND J-V CHARACTERISTIC OF A MICROMORPH N-I-P TANDEM CELL WITH
INITIAL EFFICIENCY CLOSE TO 12%.
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Summary of 2011 and outlook for 2012
The project as a whole is within schedule except for the screening of the ITO materials where the PVLab had to take over some task from ECN. After finishing this extra task in October of the reporting
period, EPFL will focus now on high efficiency tandem cells where a delay of about three months is
expected. The current results with tandem cells close to 12% are encouraging and suggest that the
delay can be recovered in the coming period.
References
[1]
R. Biron et al., Window layer with p doped silicon oxide for high Voc thin film silicon n-i-p solar cells, accepted in J.
Appl. Physics
[2]
R. Biron et al., p-doped s ilicon oxide c ontaining s ilicon na no-crystals as w indow l ayer for H igh V oc n -i-p so lar
cells, presented at the 24th ICANS, Nara, Japan, paper submitted to J. Noncryst. Mat.
[3]
F.-J. Haug et al., Improvement of t he ope n c ircuit v oltage b y modifying t he t ransparent i ndium-tin-oxide f ront
electrode in amorphous n-i-p solar cells, presented at the 26th EU-PVSEC, Hamburg. Out of more than 1700 abstracts,
this contribution was selected as one of 20 papers for the conference edition of Progress in PV.
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INTERFACE TEXTURING FOR LIGHT TRAPING
IN SOLAR CELLS
SNF PROJECTS 200021 / 125177/1
AND 200020 /137700/1
Annual Report 2011
Address
Date
Rue A. L. Breguet 2
200021_125177/1
01.10.2009 – 30.09.2013 (2 + 2 years)
15.12.2011
ABSTRACT
The project granted by the Swiss National Science foundation is devoted to a fundamental understanding of the light trapping process in thin film silicon solar cells. The first phase finished successfully in September 2011. Within the project it was possible to show for the first time that enhanced
absorption is related to the excitation of guided modes in the silicon film.
In a subsequent study of the metallic back reflector it emerged that a simple annealing step improves
the quality of silver.
The improvement is due to a reorganization of the polycrystalline material and the formation of larger
grains with fewer grain boundaries, resulting in better reflection and devices with higher performance.
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SNF project “Interface texturing”
The project is a joint collaboration between the PV-Lab and the group of Advanced Optics. Two PhD
students work on the development of optical simulation tools and experimental analysis of interface
textures.
EXPERIMENTAL WORK
In experiments it was noted that the reflection of the silver back reflector is surprisingly weak when it is
deposited by sputtering at room temperature. Better performance was obtained by depositing on heated substrate or alternatively when a short annealing treatment was performed. The underlying changes are illustrated in Figure 1 where three identical copies of a master surface are shown with different
covering layers. Sample A) shows the pyramidal texture of LP-CVD ZnO covered with a very thin silver
film which is necessary for imaging of the insulating UV-lacquer. The surface morphology of the master is well reproduced because the thickness of the silver film is not sufficient to develop changes of
the surface morphology.
Figure 1: morphologies of silver films on identical texture replications; a) substrate with thin silver film,
b) same substrate with thick film, c) same substrate with thick film after annealing [1].
After deposition of a thick silver film the pyramidal morphology is still visible, but some of the finer details are overgrown or filled with small round grains of silver. After annealing, the small grains have
disappeared completely and the pyramids of the substrate texture are no longer visible. Instead, the
film recrystallized into large round grains which exhibit clearly defined domain boundaries. The reflection losses of the annealed silver film are drastically reduced. Additional measurements of the structural properties with X-ray diffraction suggest the formation of much larger grains and consequently
fewer grain boundaries that potential impede the movement of electrons as they follow the oscillating
field of an electromagnetic wave. The improved material quality of the silver film is thus translated into
better reflection.
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SNF project Interface Textures, F.-J. Haug, EPFL PV-Lab
Figure 2: changes in surface morphology (left) and smoothing of the interface (right) after antnealing [2].
The cross sectional analysis in Figure 2 shows that V-shaped valleys of the ZnO surface become
more pinched in the as-deposited films while they are smoothed in the annealed films. Despite the
smoother morphology after annealing, the reduction of parasitic losses yields better photocurrent in
devices on this type of substrate. Moreover, the smoother morphology results in better cell performance as evidenced by a gain of 20 to 40 mV in the open circuit voltage [1].
The improved substrates were instrumental to achieving amorphous single junction solar cells with
initial efficiencies beyond 10% [2].
THEORETICAL WORK
Theoretical work on the limits of absorption enhancement in thin film solar cells is often based on as2
sumptions that do not exactly apply; for example, the well known 4n limit was derived for wafer based
cells (Yablonovitch et al., IEEE Trans. El. Devices, 1982). Later work showed that this bulk limit cannot
be achieved in thin films with random surface textures (Stuart et al., J. Opt. Soc. Am. A, 1997) while
thick films with periodic interface texture can exceed the limit in a narrow wavelength range (Yu et al.,
Opt. Express, 2010). The latter two approaches describe the solar cell as idealized waveguides that
consist of a thin silicon film suspended in air or on a substrate.
In the previous reporting period, light coupling in amorphous silicon solar cells with periodic interfaces
was successfully described with a realistic waveguide model and we were able to demonstrate an
experimental validation. In this period, we applied the argument of Yu et al. to our realistic waveguide
model [3, 4]. Figure 3 shows the spectrally resolved enhancement factors for the case of 1D periodici2
ty; note that the 1D limit is not 4n but πn. The sawtooth line illustrates that the enhancement factor
can potentially exceed the bulk limit in certain spectral regions at the cost of other regions where the
enhancement is reduced below the bulk limit (represented by the dashed line). The gray bars illustrate
statistical distribution of energy among discrete modes. If either film thickness or period is increased,
the bars become denser and will eventually approach the sawtooth line.
The red and blue bars denote results of the realistic model that takes additionally into account the
differences due to TE and TM polarization, respectively. Overall, the realistic model promises slightly
higher values than the idealized model. This aspect is currently under further investigation [5].
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Wavelength [nm]
4000 2000
1000
500
833 nm
6
Enhancement (πn)
4
2
0
6
560 nm
4
2
0
0.5
1.0
1.5
2.0
2.5
Photon energy (eV)
3.0
Figure 3: enhancement factor for 1d periodicities of 833 (top) and 560 nm (bottom) [4].
The first phase of the project was finished successfully in September 2011, a follow-up project was
granted for the coming two years.
References
[1]
K. Söderström et al., Highly reflective nano-textured sputtered silver back reflector for flexible high-efficiency n-i-p
thin-film silicon solarc ells, Sol. En. Mat. 95(12), 3585 (2011)
[2]
K. Söderström et al., Reflectance I mprovement b y T hermal Annealing o f S puttered Ag/ZnO B ack Reflectors i n a Si:H Thin Film Silicon Solar Cells, Proc. MRS Spring Meeting (2011)
[3]
F.-J. Haug et al. Resonances an d ab sorption en hancement i n t hin f ilm si licon so lar cel ls with periodic i nterface
texture, J. Appl. Phys. 109, 084516 (2011)
[4]
F.-J. Haug et al. Excitation of plasmon and guided-mode resonances in thin film silicon solar cells, Proc. MRS Fall
Meeting (2011)
[5]
A. Naqavi et al. Angular behavior of the absorption limit in thin film solar cells, in preparation
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THIFIC: THIN FILM ON CRYSTALLINE SI
Annual Report 2011
Institute of Microengineering (IMT)
Ecole Polytechnique Fédérale de Lausanne (EPFL)
Address
Rue A.L. Breguet 2, 2000 Neuchâtel
Telephone, E-mail, Homepage +41 32 718 33 78, [email protected], http://pvlab.epfl.ch/
Axpo Naturstrom-Fonds 0703
Date
09.12.2011
ABSTRACT
Silicon het erojunction ( SHJ) s olar c ells hav e a h igh e nergy-conversion ef ficiency pot ential at a r easonable cost. Axpo Naturstromfonds launched in 2007 a 4 year project named THIFIC (Thin film on
crystalline s ilicon) w ith t he i ntention of br inging t his t echnology to an i ndustrial level i n S witzerland.
For this, the Institute de Microtechnique’s (IMT, now part of Ecole Polytechnique Fédérale de
Lausanne (EPFL)) high expertise in plasma processes and thin-film silicon deposition was applied to
crystalline-silicon t echnology. T he T HIFIC project was s pecifically f ocused on w afer texturing, l ayer
development, cell technology up-scaling and module fabrication.
This r eport pr esents t he m ajor r esults obt ained. A k ey r esult i s t he f abrication of l arger-area s olar
cells pr epared with f ully industrial c ompatible t echniques. T his i ncludes t he us e of l arge-area f ilm
deposition r eactors, s creen printed m etallisation gr ids, and textured wafer s urfaces. As such, inter2
mediate sized (4 cm ) solar cells with an aperture-area conversion efficiency of 21 % have been
2
realised with open-circuit voltages higher than 720 mV. Also, on larger area substrates of 100 cm ,
efficiencies of up to 20.2 % have been obtained. The achieved results are among the best reported
by research institutes for SHJ devices. As all processing steps are simple and as thin silicon wafers
can be used, we expect that the research results can be transferred to commercial modules allowing
the production of low cost solar electricity. It is estimated that 20% module at production costs well
below 1€/Wp is possible considering the project results. This could lead to solar electricity price of 1020 cts/kWh in Switzerland depending on the assumptions made.
Next to this, improved understanding of the physics of SHJ devices was obtained, with a main focus
on t he electronic passivation of t he ul trathin amorphous silicon layers and their plasma processing.
These r esults w ere presented a t s everal pr estigious c onferences, i ncluding i nvited t alks, and d escribed in scientific papers in high-ranking journals.
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Introduction / Project Goals
The specific scientific and technological project objectives of this project were to demonstrate:
• the fabrication of ultra-high-efficiency silicon heterojunction solar cells (>20%), based on a combination of amorphous/microcrystalline layers and thin crystalline wafers (down to 100μm).
2
• that t he pr ocess i s up -scalable t o l arge-area s olar c ells ( > 100 c m ) w hich s hould ac hieve ef ficiency over 20%.
• a new metallization/encapsulation process capable to lead to a fabrication of high-efficiency and
lightweight reliable solar modules.
• a roadmap towards the mass fabrication of such modules at very low-cost (<0.7€/Wp) allowing,
with suitable module integration, electricity costs down to 12-15 cts.
Project description and approach
The “ core” t echnology f or t his pr oject was t hin-film p assivation of crystalline s ilicon us ing very h ighfrequency p lasma depos ition ( VHF-PECVD) with typical frequency f rom 40 t o 70 MH z. The pr oject
was divided into four work packages (WP), which address all issues that need to be solved in the 4
years timeframe. In WP 1, interfaces were improved and high-efficiency devices with contacts on both
sides are realized. In WP 2, innovative device structures were studied by putting all the contacts at the
back o f t he dev ices. T his allows, i n pr inciple, t he ac hievement of hi gher ef ficiencies. I n WP 3 , t he
know-how gained in the first two work packages was transferred to larger deposition reactors and also
to l arger area solar c ells. The goal was to fabricate high-efficiency s olar c ells on l arge area. Finally,
WP 4, innovative metallization techniques were tested and applied to devices fabricated in the first two
work packages. A lightweight encapsulation process was developed in the last work package as well.
To complement these work packages, our process development was focused on the upscaling of
lab-scale devices to a more industrial product (see Fig. 1), while maintaining also an emphasis on the
fundamental understanding of the physics underlying the device.
Figure 1: Typical example of solar cells before (left) and after (middle and right) the THIFIC project. The middle
2
wafer represents the record 2x2 cm devices we fabricated, with an efficiency of 21 %. The right cell is a large
2
area device (12.5x12.5 cm )
Results
In t his pr oject we f ocused on the “ technology” s ide of het erojunction s olar c ells. This c omprises t he
processes for texturing of wafers, large-area deposition, screen-printing, and annealing.
The key-result that we obtained is a successful transfer from small-area cells fabricated in R&D reactors (which did not feature a metallic front contact), to larger area cells prepared in industry-compatible
reactors, with screen printed contacts.
2
In particular, solar cells of 4 cm area, with screen-printed contacts, with a total-area conversion efficiency as h igh as 21 % have be en r ealised on random-pyramid t extured wafers [4]. Also, on l arger
2
area substrates of 100 cm , efficiencies of up to 20.2 % have been obtained, both in collaboration with
Roth & Rau Switzerland.
This result followed dedicated work on several fronts. For the a-Si:H films, a careful optimization study
was performed on flat polished Si surfaces, assuring even with very thin films good passivation in large area reactors. In a next stage, these processes have been transferred onto random-pyramid textured wafers, f eaturing < 111> f acets [ 5,6]. These s urfaces, i ncluding t heir c hemical pr e-deposition
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THIFIC, S. De Wolf, EPFL
preparation, were developed in our new state-of-the-art wetbench, located in our new heterojunctiondedicated cleanroom facilities. Also here, excellent passivation of surfaces was obtained, as evidenced in Fig 2 for several types of film stacks. The same figure gives an example of 15 nm thin p- and n15
-3
type l ayers de posited o n t he r espective wafer s urfaces. A t an excess c arrier dens ity of 10 cm , a
carrier lifetime of less than 0.1 ms is obtained, a remarkable drop in passivation indeed. Under 1 sun
illumination, t his c orresponds t o an i mplied-Voc value of onl y 613 mV. T he ph ysical r eason f or s uch
drastic passivation losses is almost certainly related to doping-related defect generation in the
amorphous host matrix [7]. This effect is the most severe for p-type films, but can also play a role in ntype films. Figure 3 shows the defect formation energy as function of the position of the Fermi-level in
amorphous silicon, which explains reduced passivation for doped films.
2
In order to extend the high-efficiencies obtained from small cells (< 1 cm ) to larger cells, new metallization and c ell s tructuring pr ocesses were r equired. For t his go od progress h as been m ade b y us
within t his pr oject on s creenprinting of de dicated low-temperature pastes f or f ront-grid f ormation o n
2
our 2x2 cm devices [8], but also larger-area cells (see Fig. 1). In addition, efforts on stencil p rinting
have been done as well, which has resulted in very fine printed lines, as narrow as 35 micron (see Fig
5), with very good aspect ratios, as high as 1:1 [8].
Combining all these developments has allowed us already to reach, with the support of Roth and Rau
Switzerland for wafer preparation, an excellent 21 % aperture area efficiency on intermediate sized (4
2
cm ) solar cells with open-circuit voltages higher than 720 mV. Also, on larger area substrates of 100
2
cm , efficiencies of up to 20.2 % have been obtained.
Figure 2: Passivated wafers, including solar precursor,
consisting of device-relevant a-Si:H stacks. The wafers
are random-pyramid textured n-type FZ-Si, with a resistivity of about 3 Ohm.cm. The indicated voltages correspond to the implied Voc under 1 sun illumination.
Figure 3: Defect formation energy as function of the
position of the Fermi-level in amorphous silicon, which
explains reduced passivation for doped films.
Figure 4: Examples of fine-line printing with low-temperature pastes, combined with stencil printing technology.
Narrow lines down to 30-35 microns are obtained under laboratory conditions. Double print technology allows the
achievement of narrow lines with high aspect ratio.
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THIFIC, De Wolf, EPFL
Collaborations
IMT is active in collaboration internally with the EPFL for advanced transmission electron microscopy
(TEM) s ample pr eparation, s upporting t he textured h eterojunction s olar c ell i mprovement. IMT has
also an important partnership with Roth&Rau Switzerland (RRS) on the development of industrial processes for heterojunction devices. We acknowledge the technical support of RRS for this project and
achieving the THIFIC milestones. In addition, IMT was from 2008 to 2011 also taking part in the European project Hetsi, and since the fall of 2010, in a second European project, 20plµs, focusing on solar
cells fabricated on ever thinner wafers. Both projects connect the major European Institutes and Universities working on similar devices.
Evaluation 2011 and Outlook 2012
THIFIC was launched in mid-2007. Crucial parameters were identified in this project to fabricate successfully devices on textured wafers, which has been demonstrated successfully in 2011 by efficiencies higher than 21%. For this, an industrial compatible wetbench was commissioned in our completely new c leanroom f acilities, ded icated f or het erojunction d evices s tudies. T he s ame f acilities h ost a
fully operational new multi-chamber PECVD system for further device development. A reliable baseline process is now established for larger area solar cells. This baseline includes screenprinted grids,
with a special focus on fineline printing. Overall, the THIFIC project sponsored by Axpo
Naturstromfonds has be en hi ghly s uccessful. B ased on t hese results, Axpo has dec ided t o s ponsor
IMT for a follow-up project, called NODHID, focusing on new device architectures to obtain ever higher
device efficiencies.
References
[1]
L. Fesquet, S. Olibet, E. Vallat-Sauvain, A. Shah, C. Ballif: High quality surface passivation and heterojunction fabrication by VHF-PECVD deposition of amorphous silicon on crystalline Si: Theory and experiments, to be published
in the Proceedings of the 22th EU-PVSEC, Milano, Italy, 2007.
[2]
J. D amon-Lacoste, L . F esquet, S. O libet, and C . Ballif, Ultra-high qua lity su rface p assivation of cr ystalline si licon
wafers in large area parallel plate reactor at 40 MHz Thin Solid Films (2008).
[3]
J. Damon-Lacoste, L. Fesquet, S. De W olf, and C. Ballif, Influence of oxygen impurity on the performances of
heterojunction solar cells, 23rd ICANS, Utrecht, the Netherlands, 2009.
[4]
A. Descoeudres, L. Barraud, S. De Wolf, B. Strahm, D. Lac henal, C. Guérin, Z.C. Holman, F. Z icarelli, B. Demaurex, J .
Seif, J. H olovsky, and C . B allif, Improved am orphous/crystalline si licon i nterface p assivation b y H 2 plasma t reatment, Appl. Phys. Lett. 99, 123506 (2011).
[5]
L. Fesquet, S. Olibet, J. Damon-Lacoste, S. De Wolf, A. Hessler-Wyser, and C . Ballif, Modification of textured silicon
wafer surface morphology for fabrication of heterojunction solar cell with open circuit voltage over 700mV, Proc.
34th IEEE PVSC, Philadelphia, Pennsylvania, 2009.
[6]
S. Olibet, E. Vallat-Sauvain, L. Fesquet, C. Monachon, A. Hessler-Wyser, J. Damon-Lacoste, S. De Wolf, C. Ballif, Properties of interfaces in amorphous/crystalline silicon heterojunctions, 23rd ICANS, Utrecht, the Netherlands, 2009. Invited talk.
[7]
S. De Wolf and M. Kondo, Nature of doped a-Si:H/c-Si interface recombination, J. Appl. Phys. 105, 103707 (2009).
[8]
F. Zicarelli, A. Descoeudres, G. Choong, P. Bôle, L. Barraud, S. De Wolf and C . Ballif, Metallisation for silicon heterojunction solar cells Proc. 5th World PV conference, Valencia, Spain (2010).
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THIFIC, S. De Wolf, EPFL
20 PERCENT EFFICIENCY ON LESS THAN
100 µM THICK INDUSTRIALLY FEASIBLE
C-SI SOLAR CELLS
Annual Report 2011
Address
IMT-PVLAB / EPFL, Neuchâtel
Rue A.L. Breguet 2, 2000 Neuchâtel
+41 32 718 33 30, +41 32 718 32 01, [email protected],
http://pvlab.epfl.ch/
20plµs 256695
Date
10.12.2011
ABSTRACT
20plµs (20 percent efficiency on less than 100 µm thick industrially feasible c-Si solar cells) is a project sponsored by the European Commission. This project links together world-class EU companies
and institutes with experience in the field of crystalline silicon solar cells. The guiding principle of this
project is to develop new and innovative process steps for wafer, solar cell, and module fabrication on
wafers less than 100 µm thick, taking into consideration transfer of the processes to a pilot production
line. The project’s goal is to demonstrate the industrial feasibility of high-efficiency solar cells on very
thin wafers in Europe. For this, both high- and low-temperature processes are being studied and
compared. Our laboratory is focusing on amorphous silicon (a-Si:H) / crystalline silicon (c-Si)
heterojunction solar cells processed at low temperatures. Our target is to demonstrate ultra-high efficiency (up to 23%) a-Si:H/c-Si heterojunction solar cells on thin wafers.
At the Institute of Microengineering of the Ecole Polytechnique Fédérale de Lausanne (formerly the
University of Neuchâtel), we started activity in 2005 in the field of silicon heterojunction solar cells.
Based on extensive plasma diagnostics and materials characterization, we have developed both a
comprehensive physical understanding of the passivation mechanisms in silicon heterojunction solar
cells and the know-how to reproducibly fabricate devices with open-circuit voltages in excess of 710
mV. We can now fabricate 20% efficient solar cells on (thick) textured wafers with industrially relevant
technologies, in particular with PECVD deposition at 40 MHz. Our efforts are shifting to understanding
and improving optical and electrical losses in the devices, and, in the framework of the 20plµs project,
to light trapping in thin wafers. In this report we show, among other results, that the transparent conductive oxide (TCO) and a-Si:H layers that comprise the front of heterojunction solar cells cause significant current loss due to parasitic absorption. While 30% of light absorbed in the front intrinsic layer
is collected as current, all light absorbed in the TCO and doped a-Si:H layer is lost as heat. By reducing the a-Si:H layer thicknesses and employing a high-mobility TCO, we reach short-circuit currents
and efficiencies in excess of 38 mA/cm 2 and 21%, respectively, on 4 cm2 cells.
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Goals of the project
The overall objective of the 20plµs project is the development of 20% efficient silicon solar cells
with thicknesses below 100 µm. The developed processes will be transferred to an industrial pilot
line with the aim of achieving a yield comparable to that obtained in standard solar cell production and
2
a conversion efficiency of 19.5% on 100 µm thick 156 x 156 mm wafers. The Institute of Microengineering (IMT) is concentrating on reaching this objective using the silicon heterojunction solar cell
design. Within the project, IMT’s goals for 2011 included the development of amorphous silicon (aSi:H) passivation layers suitable for high open-circuit voltage (Voc) on thin wafers, identification and
mitigation of parasitic absorption losses to enable high short-circuit current (Jsc), and demonstration of
fine-line screen printing for reduced front reflection.
Brief description of the project
The 20plµs project consists of ten work packages covering all aspects of crystalline silicon solar cell
manufacturing ranging from wafering to cell fabrication on an industrial pilot line. IMT is a principal
contributor to the work packages related to emitter formation, passivation, light trapping, metallization,
and prototype cell fabrication. Consequently, we are developing new scientific understanding and fabrication processes for each of these topics as they relate to silicon heterojunction solar cells, focusing
on achieving 20% efficient cells on wafers less than 100 µm thick.
2
At the start of 2011, IMT’s record efficiency for a 2 x 2 cm silicon heterojunction solar cell was 19.9%,
2
with Voc = 715 mV, Jsc = 37.4 mA/cm , and fill factor (FF) = 74.3% [1].
Within the framework of the 20plµs and Axpo projects, we studied the effects of the deposition conditions during plasma-enhanced chemical vapor deposition (PECVD) of a-Si:H on the resulting surface
passivation, which is directly linked to Voc. Of particular interest, interupting a-Si:H film growth with
hydrogen plasma treatment steps was shown to dramatically improve the passivation quality of
a-Si:H / crystalline silicon (c-Si) interfaces [2]. This treatment pushes the a-Si:H film towards the amorphous-to-crystalline transition without risking detrimental epitaxial growth [3], and increases the higher
hydride content. Minority carrier effective lifetimes exceeding 10 ms were achieved on wafers coated
with a-Si:H layers as thin as 12 nm [2].
EQE, 1-reflection, and Asi (%)
As wafer thickness is reduced in solar cells, less long-wavelength light is absorbed and Jsc consequently decreases. One way that we
100
100
investigated to regain this lost current is
(b)
(a)
90
90 to identify and e lliminate p arasitic
absorption—absorption that does not
80
80
produce current. We desconstructed and
70
70 reassembled the front side of
heterojunction solar cells layer by layer,
60
60
allowing us to identify and quantify all
p-layer
50
50 current losses in the front a-Si:H and
thickness
transparent conductive oxide (TCO)
0 nm
40
40
films [4]. Figure 1 shows an example of
2.0 nm
30 this analysis and demonstrates that we
30
3.9 nm
4.7 nm
can reproduce the external quantum
20
20
14.2 nm
efficiency (EQE) spectra (symbols) of
22.7 nm
10
10 heterojunction cells using a simple modwith i-layer
without i-layer
el (lines). We found that all light ab0
0
sorbed in the TCO and doped a-Si:H
300
400
500
300
400
500
600
layers is lost, but that 30% o f l ight a bWavelength (nm)
sorbed i n th e fr ont i ntrinsic a -Si:H is
Figure 1: EQE (symbols), 1-reflection (dashed lines), and
collected as current. By minimizing
modeled absorption in the wafer for heterojunction solar cells
absorption in these layers, up to
(a) without and (b) with front intrinsic layerd, and with doped players of varying thickness. The modeled absorption should
2 mA/cm2 of additional current can be
reproduce the experimental EQE data (as in (a)) if all the ab-
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20plµs, Z. Holman, IMT Neuchâtel
gained. Reducing layer thicknesses is one route to mitigate parasitic absorption, but limits are imposed by the films’ roles as passivation layer and emitter. An alternative approach currently being
investigated is to develop new materials with low absorption to replace a-Si:H.
Long-wavelength absorption in the front and rear TCO layers of silicon heterojunction solar cells also
2
erodes Jsc by as much as 1 mA/cm . These optical losses can be reduced with traditional TCOs by
lowering the free carrier concentration, but this simultaneously increases electrical losses. We developed hydrogenated i ndium o xide (IO:H) as a new, high-mobility TCO and integrated it into high2
efficiency heterojunction cells. We achieved mobilities exceeding 100 cm /Vs, resulting in IO:H films
that are both h ighly c onductive a nd highly tr ansparent. We observe a gain i n b oth J sc and F F
when IO:H films replace traditional indium tin oxide (ITO) films in solar cells, improving efficiency by as
much as 0.5% absolute.
A final topic to which we devoted considerable work within the 20plµs project was fine line printing.
The metallic electrode grid at the front of silicon solar cells reflects 4–8% of incident light, correspond2
ing to a current loss of 1–3 mA/cm . We investigated the use of stencil technology to print fingers that
are both narrow and tall, thereby reducing reflection without incurring additional resistance losses [5].
We successfully printed fingers 65 µm wide and 65 µm tall, achieving an aspect ratio of one. Standard screen-printed fingers are approximately half as tall and one and a half times as wide; our fingers
reduce reflection by over 30% and reduce resistance losses by 40%.
Through the scientific and technological achievements described above, we i ncreased t he o verall
efficiency of our silicon heterojunction solar cells by over 1% absolute in 2011. Figure 2 shows
2
the current-voltage characteristic and EQE of a 21.2% ef ficiency, 2 x 2 cm silicon heterojunction
2
solar cell with Voc = 723 mV, Jsc = 37.9 mA/cm , and FF = 77.5%.
100
90
80
70
60
50
40
30
20
10
0
(a)
30
20
Voc = 723 mV
10
Jsc = 37.9 mA/cm2
FF = 77.5%
Eff. = 21.2%
0
0.0
0.2
0.4
0.6
Voltage (V)
(b)
EQE and 1-reflection (%)
Current density (mA/cm2)
40
0.8
400
600 800 1000 1200
Wavelength (nm)
Figure 2: (a) Current-voltage characteristic and (b) EQE (solid) and 1-reflection (dashed) of a high-efficiency
2
2 x 2 cm silicon heterojunction solar cell.
National and international collaboration
Due to the nature of this European Project, IMT is in collaboration with many of the the major European institutes, universities, and companies working on crystalline silicon solar cells. These partners
include University of Konstanz, Fraunhofer Institut für Solare Energiesysteme, Q-Cells, and PSE AG
from Germany; New and Renewable Energy Centre Limited (Narec) from the United Kingdom; Eni
S.p.A. from Italy, Photovoltech NV from Belgium; and Mechatronics Systemtechnik GmbH from Austria. Moreover, in Neuchâtel, IMT also has an ambitious collaboration with Roth & Rau on the development of production technology for silicon heterojunction solar cells.
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Evaluation of 2011 and perspectives for 2012
2011 was a successful year for IMT in the 20plµs project. All deliverables, milestones, and internal
goals were met, and we developed new scientific understanding and technological know-how to make
excellent solar cells. Although we began experiments on wafers 160 µm thick (our standard wafers are
250 µm thick) and obtained promising results, we have not yet fabricated solar cells on wafers less
than 100 µm thick because our partner institutes in 20plµs were given the first year to develop the
technology to cut wafers so thin. As we have already achieved efficiencies well in excess of 20% (the
target efficiency of 20plµs) on thick wafers and small areas, 2012 will be dedicated to fabricating
heterojunction solar cells on wafers less than 100 µm thick and on large areas. We anticipate that
most of our processes will transfer directly to thin wafers; special attention will be given to trapping
long-wavelength light within the thinner absorber layer.
References
[1]
A. Descoeudres, et al., "The silane depletion fraction as an indicator for the amorphous/crystalline silicon interface
passivation quality," Appl. Phys. Lett., vol. 97, 183505, Nov. 2010.
[2]
A. Descoeudres, et al., "Improved amorphous/crystalline silicon interface passivation by hydrogen plasma treatment,"
Appl. Phys. Lett., vol. 99, 123506, Sep. 2011.
[3]
S. De Wolf and M. Kondo, "Abruptness of a-Si:H/c-Si interface revealed by carrier lifetime measurements," Appl. Phys.
Lett., vol. 90, 042111, Jan. 2007.
[4]
Z. Holman, et al., "Current losses at the front of silicon heterojunction solar cells," IEEE J. Photovoltaics, in press.
[5]
F. Zicarelli, et al., "Metallisation for silicon heterojunction solar cells," presented at the 25th European Photovoltaic Solar
Energy Conference and Exhibition, Sep. 2010.
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A NEW LOW ION ENERGY BOMBARDMENT
PECVD REACTOR
DEPOSITION OF THIN FILM SILICON FOR
SOLAR CELL APPLICATIONS
Annual Report 2011
Address
Date
Ch. Hollenstein, M. Chesaux, A. A. Howling
CRPP / EPFL
Bâtiment PPH, Station 13, CH-1015 Lausanne
KTI 9675.2
01.1.2009 – 31.12.2011
12.12.2011
ABSTRACT
A novel electrode configuration is proposed for improved plasma-enhanced chemical vapour deposition of films such as amorphous silicon and micro-crystalline silicon. The new electrodes are designed
to de-couple the film deposition from the plasma generation zone. The deposited films are thus protected from damage by plasma ion bombardment, which is crucial for the manufacture of highperformance photovoltaic material. The new plasma reactor concept is being optimised in laboratory experiments and has been developed into a R&D industrial pilot reactor. Tests of film and device quality
tests are currently underway.
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ZWEIDIMENSIONALE NANOSTRUKTUREN
FÜR SILIZIUM-SOLARZELLEN
Annual Report 2011
Address
Date
Paul Scherrer Institut
5232 Villigen PSI
+41 56 310 5328, [email protected], www.psi.ch
SI/500141 / SI/500141-01 (102807 / 153611)
01.10.2008 – 15.12.2011
14.12.2011
ABSTRACT
The main goal of the project is the development of efficient numerical methods to solve the Maxwell equations in order to calculate the optical properties of crossed gratings rigorously.
The structures shall be optimized for broad-band absorption of b oth polarizations in thin films.
This optimization should take into account the various experimental limitations. Prototypes should be
fabricated with e-beam lithography by the LMN of PSI, and experimental characterisation of the structures, as well as a prototype solar cell fabrication is to be done by the IMT in Neuchâtel.
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Einleitung / Projektziele
In diesem Projekt sollen zweidimensional-periodische Nanostrukturen durch numerische Berechnungen untersucht werden. Diese sind von besonderem Interesse für die Photovoltaik, da sie es ermöglichen, die Lichtabsorption in dünnen Schichten stark zu verbessern. Dabei sollen solche Strukturen für
eine möglichst breitbandige Absorption beider Polarisationen optimiert werden.
Die Motivation für das Projekt ergibt sich aus Resultaten sowohl für die TM Polarisation der Absorption bei eindimensionalen Gittern (z.B. [1],[2]), wie auch aus Resultaten für schmalbandige totale Absorption bei zweidimensionalen Gittern (z.B. in [3]). Deshalb wird eine spürbare Effizienzsteigerung
von Dünnschichtsolarzellen bei relativ geringen Zusatzkosten erwartet.
Zunächst soll ein Computerprogramm geschrieben werden, das die Analyse zweidimensionaler
Strukturen erlaubt. Dabei wird ein Schwerpunkt auf die Untersuchung von idealisierten Strukturen
gelegt, um numerisch exakte Referenzresultate für reale Strukturen zu erhalten. Parallel zur Arbeit
von A. Naqavi am IMT Neuchâtel werden verschiedene Strukturen untersucht, vor allem solche, die
sich später für kostengünstige Massenfabrikation eignen könnten. Die gezielte Suche nach optimalen
Strukturen wird voraussichtlich am IMT durchgeführt, um diese konkret an die realen Verhältnisse anzupassen. Unter anderem sollen die Halbleitereigenschaften der Materialien nicht tangiert werden.
Dabei sollen in Zusammenarbeit mit dem IMT und dem Labor für Mikro- und Nanotechnik Strukturen
mit Hilfe von Elektronenstrahl-Lithographie konkret realisiert werden, und mit diversen Methoden untersucht werden.
Kurzbeschrieb des Projekts
Im Allgemeinen existieren zwei Ansätze für die Berechnung stationärer elektromagnetischer Felder.
Einerseits sind dies Methoden, bei denen der Raum diskretisiert wird mit Auflösung Δ bei fixer Approximationsordnung k, zum Beispiel bei der Methode der finiten Differenzen, oder bei einer finiten Elementmethode mit variabel gewähltem Gitter. Die Konvergenz ergibt sich bei diesen Methoden indem
die Auflösung Δ kleiner und kleiner gewähl t wird. Andererseits kann die Approximationsordnung k bis
zur Ordnung 1/Δ erhöht werden, dies entspricht einer Spektral - oder Galerkinmethode. Wird die Differenzialgleichung in Eigenmoden entwickelt, so spricht man von einer modalen Methode mit Ordnung
d. Diese Eigenmoden werden oft in einer Basis der Ordnung n approximiert.
Für das vorliegende Problem wird eine Methode gewählt, die das Beugungsgitter in Schichten aufteilt,
und die Beugungsgitter durch Treppenstufen approximiert. Dies bringt zwar gewisse Herausforderungen für glatte Strukturen mit sich, bietet aber
viele Vorteile, wenn ganze Klassen von Strukturen mit unterschiedlicher Tiefe effizient gerechnet werden sollen (siehe fig.1), wobei die
Erhöhung für die einzelnen Schichten unabhängig gewählt werden kann. Innerhalb solcher Schichten basiert unser Code auf einer
modalen Methode, indem das elektromagnetische Feld nach Eigenfunktionen der Helmholtz-Gleichung entwickelt wird. Wie man eine
modale Methode auf ein beliebiges, eindimensionales Beugungsgitter anwendet, findet sich
zum Beispiel in [4,5]. Hierbei ist festzustellen,
dass es einen numerischen Unterschied gab
Figure 1: Diese drei Strukturen lassen sich mit sehr wenig
bei der Polarisation des Lichts, wenn die Eizusätzlichem Aufwand berechnen, wenn die Rechnung für
genfunktionen nach Fourier-Moden entwickelt
eine der Strukturen bereits gemacht wurde.
wurden.
Es
konvergierten
transversal
elektrische (TE) und transversal magnetische
(TM) Polarisation nicht gleich schnell. Für eine derartige Entwicklung sinkt der Fehler für die TE
3
2
Polarisation wie 1/n , für die TM Polarisation wie 1/n , und für konische Diffraktionsprobleme sind die
beiden Polarisationen gekoppelt und daher wird die Konvergenz durch die langsamer konvergierende
Polarisation begrenzt.
Die Verallgemeinerung auf zweidimensionale Strukturen wurde in [6] behandelt, für die die
Rechnungen noch langsamer konvergieren weil E- und H-Feld immer gekoppelt auftreten, und damit
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Zweidimensionale Nanostrukturen für Silizium-Solarzellen, D. Gablinger, Paul Scherrer Institut
die langsamere Konvergenz des H-Falls immer limitierend wirkt. Konkret konvergieren die Eigenwerte
auf Grund der quadratisch wachsenden Moden- und Basisfunktionszahlen sogar nur wie 1/n. In den
Ref. [7],[8] wurde eine Methode gefunden, um die Konvergenz von quadratisch auf kubisch zu
verbessern. Eine Analyse der Methode findet sich in [9]. Diese Verbesserung ist entscheidend, denn
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nun sinkt der Fehler wie 1/n in zwei Dimensionen. In [10] wurde diese Methode mit zusätzlichem
Formalismus für zwei Dimensionen und nicht-rechtwinklige Elementarzellen verallgemeinert. Unter
Berücksichtigung von Symmetrien kann der Rechenaufwand reduziert werden, wie in [11] dargelegt
wird, in [12] für hexagonale Symmetrien, und in [13] für quadratische Symmetrien, wobei die
Konvergenz im Prinzip nicht verändert wird.
Die Diskussion der Konvergenz ist wesentlich im Rahmen des verbesserten Lichteinfangs, weil die zu
untersuchenden Solarzellen zum einen aus stark reflektierenden Metallen an den Kontakten, und zum
anderen aus sehr dünnen, schwach absorbierenden Halbleiterschichten bestehen. Die Herausforderung besteht darin, dass die Absorptionskonstanten in dem Wellenlängenbereich sehr gering sind, wo
der Lichteinfang besonders benötigt wird. Die geforderte hohe Absorption in schwach absorbierende
Materialien bedingt die Nutzung von Resonanzeffekten, um die Intensität der elektromagnetischen
Felder zu optimieren. Dabei soll möglichst nur die Absorption in der optoelektrisch aktiven Schicht erhöht werden. In diesem Bereich hoher Resonanz ist es anspruchsvoll, die Maxwell'schen Gleichungen
numerisch exakt zu lösen, da die Anzahl der Moden d zunimmt, die berücksichtigt werden müssen.
Daher haben traditionelle Verfahren in diesem Bereich Mühe, numerisch exakte Resultate zu erhalten.
Bei der Entwicklung der Eigenfunktionen nach einer Basis kommen weitere Schwierigkeiten hinzu.
Einerseits sind nur ungefähr n/3 Eigenfunktionen akzeptabel genau in der Basis dargestellt, und
andererseits gibt es auch O(1) Moden, die zwar das algebraische Eigenwertproblem lösen, aber keine
Lösungen der Differentialgleichung sind. Diese Artefakte wurden eingeführt, als der Differentialoperator ersetzt wurde durch einen Operator, der auf einen n-dimensionalen Raum wirkt.
In [14] wurde eine Methode vorgestellt, die aufgrund ihrer exponentiellen Konvergenz diesen Anforderungen an numerische Exaktheit genügt. Die Methode aus [14] wird deshalb in dieser Arbeit auf zwei
Dimensionen verallgemeinert. Hierbei wird das elektromagnetische Feld in Eigenfunktionen der Helmholtzgleichung dargestellt. Diese Eigenfunktionen werden dann in Regionen mit jeweils konstanter
Permittivität nach Legendre-Polynomen entwickelt. An den Grenzflächen müssen die E- bzw. H-Felder
die exakten Randbedingungen erfüllen, das heisst, dass sowohl die Felder stetig sein müssen, als
auch dE/dn und (1/ε)dH/dn, wobei n die Normale auf die Grenzschicht bezeichnet. Dank dieser Trennung in Regionen mit konstanter Permittivität gelingt es, die exponentielle Konvergenz bezüglich der
Ordnung n der Entwicklung zu garantieren, wie es eben nach der Approximationstheorie möglich sein
muss für Systeme, in denen das Feld überall unendlich oft differenzierbar ist mit Ausnahme der
Grenzflächen des Gebiets der Entwicklung.
Durchgeführte Arbeiten und erreichte Ergebnisse
Im Berichtsjahr wurde vor allem an vier Themen gearbeitet. Erstens wurde versucht die letztes Jahr
entdeckten komplexen Eigenwerte besser zu verstehen, welche für die TM Polarisation auftreten
können. Diese entstehen bei Rechnungen mit rein negativen Permittivitäten, was einem idealisierten,
absorptionsfreien Metall entspricht. Diese Rechnungen sorgen für ein besseres Verständnis der für
unsere Zwecke interessanten Strukturen, die meist aus sehr gering absorbierenden Halbleitern und
metallischen Schichten bestehen.
Numerische Rechnungen für die TM Polarisation zeigten komplexe Eigenwerte. Diese konnten auch
in analytischen Rechnungen nachgewiesen werden, was im Widerspruch zu Aussagen in den
Publikationen [15-17] steht. In diesen Arbeiten wurden Argumente gegeben, die die
Selbstadjungiertheit des Operators zeigen sollen und somit auf reelle Eigenwerte führen würden. Wir
konnten den Fehler in diesen Argumenten zeigen.
Zweitens wurde dieses Jahr die Legendre-Polynom-Methode erstmalig in einer Dimension für beliebig
viele Materialienübergänge in einer Schicht implementiert, was eine notwendige Voraussetzung für die
zweidimensional-periodischen Rechnungen ist. Erfahrungsgemäss setzt die exponentielle Konvergenz
in ca. n/3 der Eigenwerte und Eigenfunktionen ein. Die Übrigen bleiben ungenau, und einige, das
heisst O(1), gehorchen der Differentialgleichung nicht. Diese müssen herausgefiltert werden, weil die
Rechnung massiv verfälscht werden kann, sowohl wenn physikalisch relevante Eigenfunktionen
weggelassen werden, wie auch wenn Artefakte der spektralen Methode mitgenommen werden.
Hierzu wurden verschiedene Verfahren geprüft, zum Beispiel der Vergleich zweier Rechnungen
verschiedener Ordnungen, oder die Anzahl Knoten der Eigenfunktionen niedriger Ordnung sowie das
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Kriterium der Konditionszahlen des algebraischen Eigenwertproblems. Als einfachstes Verfahren
bietet sich das folgende an: Zusätzlich zum Spektralen Operator, der zur präzisen Lösung des
Eigenwertproblems verwendet wird, wird ein lokaler finiter Differenzen Operator gebildet, der auf die
präzise berechneten Eigenfunktionen angewendet wird. Zeigen die so erhaltenen Schätzwerteλ(x) für
die Eigenwerte, die aus λ(x)=ℋ(Δ)ψ(x)/ψ(x) berechnet werden, wo ℋ(Δ) der Helmholtzoperator in finiter Differenzapproximation mit Auflösung Δ ist, eine starke räumliche Abhängigkeit, so handelt es sich
um ein Artefakt der spektralen Methode.
Drittens wurde eine leicht modifizierte Variante der Legendre Methode implementiert. Bis anhin wurde
der Lösungsraum direkt eingeschränkt auf einen Unterraum, der die Randbedingungen zwischen
verschiedenen Regionen mit konstantem Brechungsindex erfüllt. Die modifizierte Methode verwendet
stattdessen eine Projektion auf den Raum, der die Randbedingungen erfüllt. Eine Motivation für
dieses Vorgehen findet sich in [18]. Dies bietet einerseits den Vorteil, dass die Menge der so
entstehenden Basisfunktionen für den eingeschränkten Raum orthogonal ist, im Gegensatz zur bisher
angewandten Methode, welche mit einer asymptotisch orthogonalen Basis arbeitet. Andererseits
bietet diese neue Methode auch Vorteile bei der Implementation für allgemeinere Geometrien.
Viertens wurde am Algorithmus zur Lösung des Randwertproblems zwischen den Schichten
gearbeitet. Der in [14] beschriebene Algorithmus wurde jetzt erstmals für eine beliebige Zahl von
Schichten implementiert. Das ist notwendig, weil die hohe numerische Empfindlichkeit der zu
untersuchenden Strukturen eine unbedingte Stabilität und grosse Genauigkeit bedingt, insbesondere
wenn viele Schichten überlagert werden müssen, um eine glatte, dünne Struktur zu berechnen. Für
die Feldamplituden in jeder Schicht entsteht ein lineares Gleichungssystem, welches durch eine
Matrix mit Bandcharakter dargestellt wird. Hierbei wurde festgestellt, dass die Bandbreite der in [14]
beschriebenen Bandmatrix mittels algorithmischer Tricks reduziert werden kann auf eine Weise, die
tiefenunabhängig ist, indem andere Variablen für die Amplituden verwendet werden, und erst zum
Schluss auf die ursprünglichen Amplituden zurückgerechnet wird. Dies ermöglicht die Verwendung
von Teilmatrizen, die sich so zerlegen lassen, dass diese Zerlegung nur ein mal für alle Schichttiefen
gerechnet werden muss, während gleichzeitig die günstige Asymptotik für das Randwertproblem des
in [14] beschriebenen Algorithmus erhalten bleibt. Dies ergibt die vermutlich effizienteste Methode für
die Berechnung der spektralen Eigenschaften von Klassen von Strukturen, die sich nur in der
Gittertiefe unterscheiden. Asymptotische Konditionszahlen der Bandmatrix des Randwertproblems für
beliebig tiefe Gitterstrukturen lassen sogar erwarten, dass eine doppelt genaue FliesskommaRechnung für stabile Resultate nicht unbedingt erforderlich ist. Um später die Absorption in der
optoelektrisch aktiven Schicht optimieren zu können, werden nun mit dem neuen Code auch die
elektromagnetischen Felder und der Poynting Vektor für die Bestimmung der lokalen Absorption im
Inneren des Gitters mitberechnet.
Bewertung 2011 und Ausblick 2012
Um das Projekt 2012 erfolgreich abschliessen zu können wurde vor allem an neuen methodischen
Grundlagen gearbeitet. Die erfolgreiche Implementation des Randwertproblems ist von entscheidender Bedeutung, insbesondere wird die Minimierung des numerischen Aufwandes ohne Beeinträchtigung der Stabilität dabei sehr nützlich sein, ganze Klassen von Gitterstrukturen zu studieren. Dies ist
vor allem auch interessant im Rahmen der bereits existierende Zusammenarbeit mit A. Naqavi vom
IMT Neuchâtel, welche es im kommenden Jahr ermöglichen wird, unsere Rechnungen für numerisch
exakte Referenzresultate mit experimentellen Resultaten und A. Naqavis Rechnungen für realen
Strukturen vergleichen zu können.
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Referenzen
[1]
C. Heine und R. H. Morf: 1995 Submicron gratings for solar energy applications, aus Appl. Opt. 34, 2476–2482, 1995
[2]
C. Heine, R. H. Morf and M.T. Gale: Coated Submicron Gratings for Broadband Antireflection in Solar Energy Applications, aus J. Modern Optics, 43, 1371-1377, 1996.
[3]
E. Popov, D. Maystre, R.C.McPhedran, M. Nevière, M.C. Hutley and G.H Derrick: Total absorption of unpolarized light
by crossed gratings, Optics Express, 16, 6146, 2008
[4]
L. Li, Multilayer modal method for diffraction gratings of arbitrary profile, depth, and permittivity, J. Opt. Soc. Am.
A, Vol. 10, No. 12, p. 2581, 1993
[5]
L. Li, A modal analysis of lamellar diffraction gratings in conical mountings, J. Mod. Opt., Vol.40, No. 4, p. 553-573,
1993
[6]
E. Noponen, J. Turunen, Eigenmode method for electromagnetic syn thesis of d iffractive el ements w ith threedimensional profiles, J. Opt. Soc. Am. A, Vol. 11, No. 9, p. 2494, 1994
[7]
P. Lalanne, G.M. Morris: Highly i mproved c onvergence of t he c oupled-wave m ethod f or TM po larization, J. Opt.
Soc. Am. A, Vol. 13, No. 4, p. 779, 1996
[8]
G. Granet, B. Guizal, Efficient implementation of t he c oupled-wave m ethod f or metallic l amellar g ratings in T M
polarization
[9]
L. Li, Use of Fourier series in the analysis of discontinuous periodic structures, J. Opt. Soc. Am. A, Vol 13, No. 9, p.
1870, 1996
[10] L. Li, New formulation of the Fourier modal method for crossed surface-relief gratings, J. Opt. Soc. Am. A, Vol. 14,
No. 10, p. 2758, 1997
[11] B. Bai, L. Li, Reduction of computation time for crossed-grating problems: a group-theoretic approach, J. Opt. Soc.
Am. A, Vol. 21, No. 10, p. 1886, 2004
[12] B. Bai, L. Li, Group-theoretic approach to enhancing the Fourier modal method for crossed gratings with hexagonal symmetry, J. Mod. Opt., Vol. 53, No. 10, 1459–1483, 2006
[13] B. Bai, L. Li, Group-theoretic approach to enhancing the Fourier modal method for crossed gratings with square
symmetry, J. Opt. Soc. Am. A, Vol. 23, No. 3, p. 572, 2006
[14]
R. H. Morf: Exponentially convergent numerically efficient solution of Maxwell’s equations for lamellar gratings,
aus J. Opt. Soc. Am. A, 12, 1043-1056, 1995.
[15] L. C. Botten, M. S. Craig, R. C. Mcphedran, J. L. Adams, J. R. Andrewartha, The dielectric lamellar diffraction grating,
aus Opt. Acta 28, pp. 413-428 (1981).
[16] L. C. Botten, M. S. Craig, R. C. Mcphedran, J. L. Adams, and J. R. Andrewartha, The finitely conducting lamellar diffraction grating, aus Opt. Acta 28, pp. 1087-1102 (1981).
[17] L. C. Botten, M. S. Craig, R. C. Mcphedran, Highly conducting lamellar diffraction gratings, aus J. Mod. Opt. 28: 8, pp.
1103-1106
[18] G. H. Golub, Some Modified Matrix Eigenvalue Problems, aus SIAM Rev., Vol. 15, No. 2, pp. 318-334
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ROD-SOL
ALL-INORGANIC NANO-ROD BASED THINFILM SOLAR CELLS ON GLASS
Annual Report 2011
Christoph Niederberger, Johann Michler
Empa, Swiss Federal Laboratories for Materials Science and
Technology
Address
Feuerwerkerstrasse 39, CH-3602 Thun, Switzerland
Telephone, E-mail, Homepage +41 58 765 6254, [email protected],
www.rodsol.eu
NMP-2008-2.6-1 / 227497
Date
04.05.2012
ABSTRACT
Thin film solar cells, based on non-toxic, abundant and air-stable silicon (Si) will probably, based on
forecasts, dominate the photovoltaic market in the future and thus replace bulk Si from its leading
position. This prognosis is fostered by the strong cost reduction potential due to highly effective
materials utilization at low energy consumption. However, thin film Si suffers from inherently small
grains, which limits efficiencies to ~10% due to carrier recombination at grain boundaries.
A radical innovation of the Si thin film materials synthesis route is needed to circumvent this problem.
The FP7 European Project ROD-SOL aims at the synthesis of Si nano-rods, densely packed at
sufficiently large diameters (few 100 nm's) and lengths (>1µm for sufficient carrier absorption in
indirect semiconductors) directly on cheap substrates like glass or flexible metal foils. The idea is to
grow Si nano-rods from the gas phase that are inherently defect free, with a wrapped around pnjunction that bares the potential to decouple absorption of light from charge transport by allowing
lateral diffusion of minority carriers to the pn-junction, which is at most a few hundred nm away, rather
than a few µm as in conventional thin film solar cells. That way, efficiencies as in bulk Si are
expectable, however, with the advantage that the 'nano-rod carpet' layer, is at most a few µm thick. A
'nano-rod carpet' that thin shows a strongly increased optical absorption.
Thus, the 'nano-rod carpet' is not only the active solar cell element but at the same time its own light
trapping structure. For synthesis of the nano-rods, development of suitable contact materials and
characterization of physical and structural properties four experienced research institutes have joined
forces. Despite the fundamental materials research to be in focus, three companies joined the
consortium to directly test and implement the novel materials and processes in a well proven,
industrially viable thin film solar cell concept.
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Introduction / Objectives
Globally, the FP7 European Project ROD_SOL project aims at making available to the markets novel
materials and nanomatrials for energy applications and a thin film solar cell based on silicon nanorods
(NRs).
Materials developments and optimization based on NRs are one of the major tasks in ROD-SOL next
to the integration of these NRs in working thin-film solar cell devices, their testing and the
benchmarking of the solar cell parameters. The leading European materials oriented research groups
contribute to this task.
Innovation will take place in areas of materials processing of NRs such as adequate preferably radial
doping; NR contacting based on conformally wrapped around transparent conducting oxide (TCO)
layers. These materials developments will be guided by device simulations.
To support the strategic objective to enable the European thin film PV community to commercialize a
new innovative thin film cell based on semiconductor NRs with potential for enhanced efficiencies at
competitive costs, solid materials developments with huge innovation requests at the nanoscale need
to be carried out. From this, the following scientific objectives are derived.
1. Semiconductor (mostly Si) NR deposition or integration on glass or foil substrates need to be
developed and among different options of deposition/synthesis such as bottom-up and top-down
methods the most promising one with the potential for best materials/device properties, best upscalability at lowest production costs needs to be identified;
2. Identification of the most suitable material based on numerical and physical device simulations
and experimental solar cell parameter extraction based on electrical measurements (ensembles
and single processed NRs) is needed;
3. Establishment of physical device simulations for the novel 3D NR-based solar cell using the
COMSOL and r-soft and ATLAS simulation software;
4. Establish parameter extraction from electrical measurements that need to be established for single
processed NRs and NR ensembles (preferably also at an end user test site-BISOL);
5. Materials optimization based on combined structural, electrical, optical and mechanical
characterization by TEM and SEM techniques, I-V measurements based on 4-point-probe
measurements or AFM-tip based contacting of single NRs in an SEM and contacting processed
NR ensembles, as well as optical characterization in an integrating sphere of wavelength
dependent light absorption or optical standard characterization for solar cells at the end users site
as well as mechanical tests of stability of single processed NRs and reliability tests of embedded
NR-based thin films with respect to delamination, bending, cracking and disintegration of
components.
These developments are carried out by researchers at six different research institutions involved in
this project.
The integration of selected processes in a technological process or processing environment (upscaling) with the potential to yield a highly efficient and cost effective fabrication route to produce thin
film NR based solar cells on cheap substrates are carried out by the four industry/SME partners.
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Projekt ROD-SOL, C. Niederberger, Empa
Short description of the project
The goal of the FP7 European Collaborative Project ROD_SOL is to realize optimized thin film
material systems based on semiconductor NRs that show photovoltaic behavior and properties
optimized for that application. Detailed information about materials and devices cannot be disclosed
since we are required to keep confidentiality. Figure 1 presents one possible layout of the targeted
solar concept. The SiNRs are not only the light trapping structure but at the same time the active solar
cell element. The SiNRs, p or n doped are covered by a n or p-type transparent conductive oxides
(TCO) respectively as to build a p/n junction necessary to convert the solar radiation in electric energy.
sunlight
N doped TCO
P-doped SiNRs
Figure 1: Possible layout of a SiNR based solar cell concept.
For an economically viable concept, SiNR array need be realized on glass of foil substrates. For the
generation of SiNR arrays, two processing approaches are looked at in the project. The first is the socalled bottom up approach. In the bottom-up approach, SiNRs are grown by the vapor-liquid-solid
(VLS) process on glass substrates. The VLS growth process is based upon a droplet of a
metal/semiconductor alloy that catalyzes the local growth of a NR which is a shaft of the
semiconductor material (cf. Fig. 1, left). This NR crystallizes with the diameter of the catalyzing droplet
and the NR pushes the metal alloy droplet away from the substrate when, upon supersaturation with
semiconductor species from the gas phase (e.g. silane, DTBS) the semiconductor shaft crystallizes on
the substrate. The position of the SiNRs grown by the VLS process is determined by the position of
the necessary metal catalyst particles. Therefore, the first step in a VLS growth process is the
patterning of the metal templates. Another possibility for the generation of SiNR arrays is the so-called
top down approach. In the top-down approach, NR arrays are etched into silicon by metal assisted
chemical etching. A metal catalyst laser is deposited onto a Si surface. Upon immersion into an
etching solution, the Si below the metal dissolves. Depending on the pattering of the metal layer, SiNR
arrays can be generated. Top-down arrays can be realized on bulk Si and then depilated, transferred
and reintegrated on glass or foil substrates, or the SiNR arrays can directly be etched into crystalline
Si thin films.
In order to realize a p-n junction, the possibility of both axial and radial p-n junctions within the SiNRs
is investigated in the project. In addition, devices with p-n junctions between the SiNR array and a
conformal layer of a transparent conducting oxide (TCO) are realized. The deposition of conformal
TCO layers around SiNR arrays for both realizing p-n junctions and for contacting the arrays is a key
subject of the project. Three different methods are investigated for this step: magnetron sputtering,
atomic layer deposition (ALD) and electrochemical deposition. Different TCO materials are
investigated, and the deposition methods and materials are benchmarked against each other. The
development of SiNR arrays, p-n junctions and TCO layers are accompanied by numerical
simulations, and extensive characterization of structures, materials and defects.
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The project is structured in 10 work packages. Empa is involved in 4 work packages and is work
package leader in one work package. The main tasks of Empa include:

The development of metal templates (Au, Al, Cu, Pd, …) for the VLS-growth of SiNR arrays
allowing higher density and larger diameter NRs on Si wafer substrates and glass substrates,

The development of a process for the chemical etching of Si nanorod (SiNR) arrays into Si wafers
or crystalline Si thin films as well as a depilation, embedding and reintegration process for
embedded SiNRs onto glass or foil substrates.

The development of a process for the deposition of TCO layers by electrochemical deposition on
flat surfaces and on SiNR arrays.

Structural, electrical, optical and mechanical characterization of individual SiNRs, TCO layers and
devices. In particular, this includes the structural characterization of NRs by SEM and EBSD, the
measurement of of electrical properties (I-V, EBIC and derived parameters) of individual
processed NRs. In addition, the mechanical properties of individual and embedded ensembles of
NRs are assessed, and the strength and resistance against delamination of the thin film solar
cells are investigated.
Performed work and results obtained
The development of a process for the chemical etching of Si nanorod (SiNR) arrays into Si as
well as a depilation, embedding and reintegration processes
NR arrays can be generated by metal assisted chemical etching. Under the effect of noble metal
catalyst particles, an etchant solution dissolves the Si substrate (bulk silicon or crystalline thin film)
which is in contact with the metal particle. By patterning the metal catalyst on a Si substrate, ordered
structures can be etched into the Si. One task of Empa within the Rod-Sol project is to develop a
process route allowing the generation of SiNR arrays having a defined length, inter-rod spacing and
rod diameter. In a first step, an array of polystyrene (PS) spheres is deposited onto the Si surface. In a
thermal treatment, the PS spheres are bonded to the substrate and shrunk so that a metal layer can
be deposited in between the spheres. After the etching step where the silicon below the metal layer is
dissolved, a regular array of Si pillars remains standing where the PS spheres avoided the deposition
of the metal catalyst layer. The diameter and the interdistance of the NRs can be controlled by
adjusting the heat treatment parameters on the PS sphere template. By varying the etching time, NRs
of different aspect ratio can be realized, see Figure 3.
Figure 2: Process sequence of the templated etching of Si NRs. (a) a one dimensional array of PS spheres is
deposited. ( b) a m etal l ayer i s de posited b etween t he P S spheres ei ther by el ectroless plating or by
magnetron sputtering. (c) the silicon under the metal layer is etched. (d) the metal and the PS spheres
are removed.
Figure 3: NR arrays with different lengths and aspect ratios.
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A preliminary study on the embedding of Si NWs in polydimethylsiloxane or polyetoxy derivates
showed promising results. We used the polymer to stabilize the Si NWs and depilate them from the
single crystalline silicon wafer as shown in the SEM micrograph in Figure 4. However, the reintegration
of the depilated Si NW array into a working thin film solar cell device proves to be difficult. As an
alternative approach for the production of thin film PV devices, the top-down etching Si NW/NR arrays
into macro-crystalline Si thin films is a promising option.
Figure 4: SEM m icrograph o f t he et ched w et chemically etched S iNWs transfered i nto pol ydimethlysiloxane
(PDMS) by the depilation of etched nanostructures form the single crystralline silicon wafer.
The development of a process for the deposition of TCO layers by electrochemical deposition
Within the Rod-Sol project, Empa has the task to develop an electrochemical deposition technique for
layers of ZnO and Al-doped ZnO (AZO). Electrochemical Deposition (ECD) appears as a judicious
choice for ZnO growth, because of its numerous advantages over the other synthesis techniques: i) no
vacuum system needed, ii) low temperature process (<100°C), iii) precise control of the film thickness
and morphology by playing on the process parameters, iv) easy scaling-up, v) relatively high
deposition rate, vi) process less hazardous and environmentally friendly, vii) low cost of equipment
and viii) the possible use of conductive substrates thermally sensitive. Figure 3 schematically shows
the setup of the ECD experiment. The depositon process can be divided in three steps, (1) the
reduction of the oxygen precursor on the electrode surface, (2) the precipitation of zinc hydroxide and
(3) the dehydration and formation of ZnO.
Figure 5: Schematic diagram of the electrochemical deposition setup.
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Parameters such as precursor concentration, temperature, and especially applied potential were
varied in order to obtain good quality ZnO compact layers. The deposition time is very fast: less than 1
min and 5 min are necessary to obtain 250nm and 1μm of thickness, respectively. The ZnO layers
shown in Figure 4 a to c have been deposited on FTO coated glass substrates, whereas, Figure 6 d to
f show that electrodeposition on B-doped Si is equally possible
Figure 6: SEM pictures of ZnO layers electrochemically deposited. (a) top view, on F TO coated glass. (b) and
(c) cross-sections on F TO c oated gl ass. (d) and (e) top v iews of Z nO dep osited on S i:B. (f) cross
section, on Si:B.
Mechanical characterization on individual Si nanowires
Mechanical testing on individual VLS-grown Si nanowires was performed inside a scanning electron
microscope (SEM) with a micromachined tensile stage, as shown in Fig. 3 (a). An individual Si
nanowire was mounted on the device (i.e. bridging the gap A) by in-situ nanomanipulation and fixed at
its two ends via focused electron beam induced deposition, as shown in the inset of Fig. 7 (b).
Phosphorous-doped Si nanowires with lengths of >15 μm and diameters of ~ 200 nm were grown by
the VLS technique, which show an average Young’s modulus of (170.0±2.4) GPa and a tensile
strength larger than 8.3 GPa. Fig. 7 (b) is a representative engineering stress-strain curve of the
tested wires.
(a)
(b)
Figure 7: (a) A SEM image of the developed micro tensile testing stage. (b) A representative engineering stressstrain curve of a phosphorous-doped Si nanowires grown by the VLS technique.
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Structural characterization of individual SiNR by electron backscatter diffraction (EBSD)
An electron backscatter diffraction (EBSD) procedure for the determination of the crystal orientation of
VLS-grown individual SiNR has been developed. For this purpose, the EBSD setup in a high
resolution SEM has been modified such that STEM imaging is possible in parallel thereby enabling the
extraction of EBSD signal from small quantities of matter. In this way, mappings of the crystal
orientation become possible in SiNRs. Fig. 8 shows an example of a mapping of a SiNW, for which the
growth direction was determined to be along [111]. An important finding is, that SiNWs grown on Si
wafer substrates (CVD growth at 510°C) generally exhibit a growth direction of <111> type as it is
visualized in Figure 8.
100 nm
111
a
001
101
〈111〉
b
c
d
Figure 8: (a) EBSD inverse pole figure mapping of a VLS-grown SiNW. The SiNW is shown in pink and the Au
catalyst dr oplet i n b lue. ( b) and ( c) E BSD pat tern r ecorded i n t he S iNW and t he A u dr oplet,
respectively. 〈111〉 pole figure of the SiNW (blue) and the Au droplet (red). The encircled 〈111〉 pole of
the SiNW is perfectly aligned with the wire growth direction visible in (a).
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National and international cooperation
ROD-SOL is a FP7 European Collaborative Project, in which 6 research institutions and 4 industrial
partners from 6 European countries are participating, see table 1. The project is coordinated by the
Institut für Photonische Technologien in Jena, Germany. Empa collaborated closely with IPHT Jena in
the field of metal assisted chemical etching for the generation of SiNR arrays and for the development
of a EBIC characterization methods for individual SiNRs. In addition Empa collaborated with ARC
(Austria) for the development of metal templates for SiNW growth by the VLS, mechanism, with VTT
(Finland) for the characterization of electrodeposited ZnO and AZO coatings and with MFA (Hungary)
for the characterization of structures by TEM.
Table 1: Project partners in the FP7 European project ROD-SOL
Evaluation 2011
During the last year, the etching procedure to generate ordered large area arrays of SiNRs with
controllable length, diameter and inter-rod spacing has been further developed. In parallel, a process
for the electrodeposition of TCO layers, namely Al-doped ZnO, onto silicon has been successfully
developed. These two achievements are promising for NR based solar cell concepts that can be
produce in an economic way as both processes are based on wet chemical approaches that do not
require vacuum or other expensive process steps. At the same time, nanowires and nanowire
structures generated by project partners have been characterized. Namely mechanical properties, the
crystal orientation (EBSD) and electrical properties (EBIC of individual NWs) have been assessed in
collaboration with other project partners.
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FEBULAS: FLEXIBLE CIGS SOLAR CELLS
AND MINI-MODULES ON POLYMER WITHOUT
OR WITH ALTERNATIVE BUFFER LAYER
Annual Report 2011
Address
Date
EMPA, Laboratory for Thin Films and Photovoltaics
Überlandstr. 129, 8600 Dübendorf
+41 44 823 4130, [email protected], www.empa.ch/tfpv
SI/500394 / SI500394-01 BFE 103317/154375
01.07.2009 – 31.01.2012
12.12.2011
ABSTRACT
The objective of this R&D project included the investigation of flexible Cu(In,Ga)Se2 (CIGS) solar cells
with alternative In2S3 buffer layer deposited using an in-line deposition compatible vacuum based
techniques. The research on alternative buffer layers for CIGS solar cells was strongly challenged by
the observed irreproducibility in the solar cell performance. It turned out that the layer were always
non-stoichiometric with respect to In2S3 composition, which in fact was critical issue for obtaining reproducible results. A systematic study of the evaporation of In2S3 material over a large number of
deposition runs was performed. The absorption coefficients of the layers indicated the growth of layers with varied optical band gaps related to successive deposition runs. Despite our intensive efforts,
the chemical disorder in the evaporated buffer layer persisted. An in-depth analysis of optical, chemical and structural properties of Flash-In2S3 layers was performed. The maximum conversion efficiency of 12% was obtained for flexible CIGS solar cell with InxSy buffer layer and metastabe effects of
such solar cells were investigated. An important objective in the reporting period was the development of CIGS mini-modules with CdS as well as alternative buffer layers. Within FEBULAS project
2
CIGS mini-modules (~13cm ) with 13.3% (CdS buffer layer) and 10.6% (InxSy buffer layer) efficiency
were developed.
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1. Introduction and Project Goals
1.1 Introduction and Project Goals
Roll-to-roll processing of flexible solar cell has high potential to further reduce the module cost significantly. Additionally, physical attributes such as the easy adaptability to uneven surface at applications
site and lightweight of flexible modules significantly add to its level of acceptance as a future technology [1]. Recently, our research team at EMPA successfully developed an 18.7% efficient CIGS/CdS
solar cell on flexible polyimide (PI) substrate [2] pushing the efficiency boundaries farther close to conventional glass based rigid solar cells [3]. However, considering the industrial scale production large
area solar module, it is desired to conserve the vacuum in the whole production line which gets interrupted due to use of non-vacuum chemical bath deposition for growing n-type CdS layer on p-type
CIGS absorber. Hence, the replacement of CBD method by an alternative, preferably, vacuum based
thin-film deposition technique and CdS layer by an alternative buffer layer of suitable optical and electronic characteristics are highly desired alternatives and have been explored worldwide.
III-VI compound In2S3 has been studied as a one of the most suited replacements of CdS buffer layer
in CIGS technology. The efficiency as high as 16.4% with atomic layer chemical vapor deposition
In2S3 [4] and 15.2% for thermally evaporated In2S3 buffer layers has already been demonstrated [5].
Despite the encouraging results obtained on glass substrate, there is practically no report on flexible
CIGS/In2S3 solar cell. Our initial efforts in direction towards the development of flexible CIGS/In2S3
yielded very promising results (conversion efficiency ~10 %). Alongside, the research on thermally
evaporated In2S3 buffer layer indicated the growth of S-deficient layer which may be the prime factor
limiting the solar cell performance. The control over chemical composition of the evaporated layer and
the source material used in evaporation crucibles are matter of concern for achieving reproducible
results which is linked to anomalous evaporation behavior of In2S3 compound [6]. An alternative method, flash evaporation, has potential to overcome the problem of nonstoichiometry in the deposited
layer. Flash evaporation deals with an instant evaporation of the source material and layers of stoichiometric composition can be grown under suitable experimental conditions [7-9]. Moreover, it is a high
growth rate and an in-line deposition compatible technique, relevant for industrial production of large
area solar modules.
The project was aimed at the development of flexible CIGS/In2S3 solar cells, determining the most
suited evaporation technique which is capable of yielding reproducible solar cell performance. Since,
CIGS/In2S3 is extremely sensitive to chemical and electronic changes occurring due to elemental interdiffusion across absorber/buffer interface [10], the CIGS growth process needed to be optimized in
view of its In2S3 junction partner. Finally, the efforts were combined towards development of minimodules with CdS and In2S3 buffer layers.
2. Experimental Details and Results
2.1 Thermally Evaporated In2S3 Buffer Layer:
2.1.1 Chemical Analysis: The thermal evaporation of In2S3 layers was carried out by evaporation of
In2S3 compound powder (99.999% metal basis, Alfa Aesar) in a vacuum chamber at a base pressure
-6
of 1x10 mbar. Figure 1 shows the chemical composition, as derived from EDX analysis, of the source
material subjected to an extended period of evaporation. As apparent from the figure, a large degree
of chemical inhomogeneity was observed in the source material. A careful look at the evaporation
behavior and phase diagram of In2S3 compound indicates the S-loss in the material [6]. As a result of
S-loss from the source material the layers were expected to grow S-deficient with respect to stoichiometric In2S3 composition. Thus, the accurate determination of buffer layer composition was important
to analyze the influence of S-loss in source materials on final layer composition. Rutherford backscattering (RBS) measurements were performed on the layers grown with different evaporation runs. Table 1 lists the chemical composition of buffer layer grown on Si substrate. It can be observed that the
layers were always nonstoichiometric with respect to In2S3 composition.
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FEBULAS Project, R. Verma, Lab. for Thin Films and Photovoltaics, Empa, Dübendorf
Figure 1: EDX analysis of In2S3 source materials with time of evaporation.
Table 1: Buffer layer composition as a function of evaporation runs (cf. annual report 2010).
Evaporation Run
In2Sy composition: y
1
2.75
2
2.74
3
2.71
4
2.74
5
2.7
6
2.49
2.1.2 Solar Cell Performance: The solar cells with In2S3 buffer layer were produced and characterized by measuring their J-V characteristics. The direct impact of non-stoichiometry associated with
In2S3 buffer deposition runs, with single filling of evaporation crucible, on the solar cell performance is
shown in Figure 2. As indicated in the figure, an appreciable variation in the PV parameter, primarily
due to variation in Voc and Jsc, was observed. It is important to emphasize that the CIGS was obtained
from single deposition run, thus ensuring the identical properties of CIGS absorber layer throughout.
Therefore, the analysis clearly indicates the strong influence of S-loss originating from evaporation
behavior of In2S3 compound on the solar cell performance. Interestingly, the air annealing treatment of
the deices at 200°C for 20 min was found to have positive effect on the PV parameters leading to a
large increase in FF and Voc. Thus, the negative effect of non-stoichiometry on the solar cell performance of as-deposited devices can be annihilated by air annealing treatment.
To ascertain the above finding and verify the reproducibility of the results, another set of experiments
with even more prolonged evaporation steps was carried out with single filling of evaporation crucible.
It should be noted that contrary to solar cell performance in the first case, a large scattering in PV parameters was observed in second set of experiments. From the analysis it appeared that there was an
optimal point, corresponding to Run-12, after which the device performance degraded mainly due to
the collective drop in FF and Voc. The positive effect of air annealing was again observed. The second
set of experiments was planned in a way such that layer on glass substrate was also deposited for
optical analysis. The absorption coefficient of layers obtained from Run-1 till Run-22 was calculated by
recording their transmission and reflection spectra in spectral range of 300-1500 nm. Figure 4 shows
the absorption spectra of In2S3 layers grown in successive evaporation runs.
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Figure 2: PV parameters of best solar cells with In2S3 layer grown in successive evaporation runs.
Note that in case of Run 8 a layer of around 150 nm was deposited in CIGS absorber.
Figure 3: PV parameters of the best solar cell with successive evaporation runs until all the source
materials got consumed in evaporation.
Figure 4: Absorption coefficient of In2S3 layer deposited on SLG substrates in successive
evaporation runs.
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As evident from the Fig. 4, the absorption edge was found to be scattered over the photon energy
range, suggesting deposition runs dependent absorption characteristics of the layer, and hence the
solar cell performance is expected to be influenced by change in the absorption characteristics of the
buffer.
2.2 Flexible Solar Cells with In2S3 Buffer Layer:
The flexible CIGS solar cell with In2S3 buffer layer were developed by depositing CIGS layer on Mo
coated PI substrate following a modified 3-stage process as described in Ref. [12]. Since, PI is Na-free
substrate; CIGS growth on polyimide foil requires an external source of Na. The supply of Na to CIGS
was ensured by applying a post-deposition treatment (PDT) of NaF. In2S3 buffer layer was deposited
by thermal evaporation technique. The preliminary results on the flexible solar cell with In2S3 buffer
layer were very encouraging, yielding a 10% efficient solar cell (Fig. 5). A set of experiments, comprising of two identical absorbers processed in the same deposition run subjected to water cleaning and
ammonia etching prior to deposition of ~50 nm In2S3 layer, was performed to study the effect of intermediate layer. The direct impact of CIGS surface treatment was seen in J-V characteristics of the device. Figure 5 provides a detailed picture of PV parameters of devices with untreated and treated
CIGS surface before and after annealing of the device.
Figure 5: PV parameters of device produced on unetched and etched CIGS absorber.
The influence of air annealing (200°C, 20min) is also shown.
The comparison study of PV parameters of solar cells with and without CIGS surface treatment suggests the critical role of residual layer on the device performance. The increase in efficiency in case of
surface treated devices was due to increase in Jsc and FF. The ubiquitous beneficial effect of air annealing was also observed resulting in increase in efficiency from ~5% to 10% (NH3 treated device).
However, the wet chemical surface treatment of CIGS surface is not desirable in in-line deposition
sequence of solar cell processing. In view of this, a different scheme of Na incorporation was adopted
rd
in which co-evaporation of NaF precursor layer was carried out during 3 stage. The solar cell with Na
incorporation under co-evaporation and PDT schemes were developed and compared. Figure 6
shows the PV parameters of the two solar cells with CIGS receiving co-evaporation and PDT of NaF. It
is important to note that a fairly better performance of the solar cell were observed in as-deposited
state where maximum efficiency was ~9.5%, comparable to solar cell with PDT-CIGS absorber. A
maximum efficiency of 12% was obtained after air annealing at 200°C for 30min.
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Figure 6: PV parameters of flexible CIGS/In2S3 solar cells in which Na was supplied via
co-evaporation and PDT schemes.
2.2.1 Influence of Cu concentration in the CIGS
CIGS absorber layers were grown by co-evaporation of the elements on Mo coated polyimide substrates with varying final y=Cu/(Ga+In) content. The final Cu/(Ga+In) content is determined by XRF
measurement which reflect the average value over the entire CIGS thickness. With Cu rich CIGS
samples (y=0.92) a conversion efficiency of 4.9% was obtained. The efficiency decreased after air
annealing at 200 °C for 15 min to 1.9%. In contrast with Cu poor CIGS samples (y=0.83) the obtained
conversion efficiency in the not annealed state is 9.2%. Further stable and metastable states of such
samples are described in the following section. From the measured results it can be concluded that
CIGS absorbers should be grown Cu poor if thermally evaporated InxSy is employed as buffer layer
material.
2.2.2 Metastable conditions of CIGS solar cells with In2S3 buffer layer
Flexible CIGS thin film solar cells with InxSy buffer layer deposited by PVD were tested for metastable
effects. In previous chapters it was mentioned that air annealing of the finished devices for several
minutes has significant impact on the PV perfomance. In figure 7 the effect of different conditions of
two CIGS samples with InxSy buffer layer is illustrated. In both cases the air annealing at 200°C of the
finished device has a beneficial impact on all PV parameters. Those observed changes in
performance due to air annealing are stable conditions and not reversible. Also shown in figure 16 is
the impact of preconditioning of the solar cells by light soaking under 1 sun as well as reverse voltage
bias on the PV performance. The impact of reverse bias voltage together with white light soaking is
described in more detail in the following section.
Figure 7: Current density – voltage characteristics of CIGS solar cells with InxSy buffer layer
in different stable and metastable conditions.
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Reverse bias plus illumination:
Figure 8a illustrates the impact of applying reverse bias voltage of 3 V in combination with illumination
for 30 seconds to a CIGS solar cell with InxSy buffer layer deposited by high vacuum evaporation. The
2
device shows an enormous increase of the short circuit current density from 23.3 mA/cm to 30.9
2
mA/cm . Simultaneously the Voc decreases from 570 mV to 522 mV. In the relaxed as well as in the
metastable state no voltage dependency of the current density was observed. It is important to note
that this effect is only observed if both the reverse bias voltage and the illumination are applied at the
same time. The external quantum efficiency curve of the relaxed state of that device is displayed in
figure 8b. In this state the solar cell shows low response in the whole relevant wavelength spectrum
which increased if a reverse bias voltage together with white light bias is applied.
Figure 8: (a) J V c haracteristics of C IGS s olar cell w ith InxSy buffer layer i n t he r elaxed as w ell as i n
the met astable s tate. ( b) E xternal qu antum ef ficiency of t he s ame d evice w ith a nd w ithout
reverse bias voltage.
A possible reason for the low current density in the relaxed state can be high recombination of
+
photogenerated minority carriers at the interface. This can happen in case of a p /n heterojunction, i.e.
if bulk minority carriers remain minorities at the interface and majority carriers are abundant at the
interface [13]. Applying reverse bias voltage together with illumination can change the charging state
of acceptor like defects in the CIGS surface region reducing the p-type doping concentration and with
this decreasing the interface recombination of photogenerated charge carriers which in turn increases
the current density of the device [14].
Reduced interface recombination in the metastabe state is confirmed by the increased activation energy as derived from temperature dependent JscVoc measurements. In the relaxed state the device
shows activation energy of 0.93 eV, i.e. well below the energy band gap of the absorber material. This
activation energy increases to 1.15 eV in the metastabel state, which is within the error margins equal
to the energy band gap of the absorber layer in the SCR.
These findings open new possibilities in engineering the interface region of the CIGS as well as the
buffer and i-ZnO layers for further increasing the performance of CIGS solar cells with alternative buffer materials.
2.3 Flexible Mini-Module:
For solar module preparation solar cells are monolithically interconnected by laser scribing technology.
The main advantages of monolithical interconnection compared to the shingling approach used in
wafer based silicon technology are the high level of automation and large scale practicability. The
advantage of using laser patterned monolithical interconnection is the possibility to apply the technique on flexible substrate material as well as to significantly reduce loss areas between the P1 to P3
scribe lines. The industrial partner Flisom developed a laser scribing equipment which allows accurate
positioning of the scribe lines on flexible substrate material.
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Figure 9: J-V characteristics of CIGS mini-modules with CBD-CdS (red line) and HVE-InxSy
buffer layers.
For CIGS device with CdS buffer layer deposited by chemical bath deposition, the extensive efforts in
1
process optimization of CIGS growth and Na incorporation steps yielded a mini-module efficiency of
2
13.3% on 13 cm area (fig.9).
Figure 9 also shows the JV characteristics of a CIGS mini-module with InxSy buffer layer deposited by
high vacuum thermal evaporation. The mini-module with InxSy buffer layer reaches a remarkable con2
2
version efficiency of 10.6% on 13 cm area.
National and International Cooperation
Active collaboration with project partner Flisom AG on mini-module development. Also there is some
synergy in EU FP7 project hipo-CIGS (a joint project comprising of 8 European R&D institutes and
industries).
Evaluation 2011
st
The FEBULAS project started on July 1 , 2009. A detailed chemical composition analysis of evaporated buffer confirmed the ubiquitous S-deficiency in the layer. As result of extensive research a strong
understanding of properties of thermally evaporation In2S3 buffer layer was developed. Large impact of
chemical instability in the thermal- In2S3 buffer layer on solar cell performance was observed for large
period of buffer evaporation. With an aim of preserving chemical composition (stoichiometry) in the
thermally evaporated In2S3 layer, a novel Flash evaporation technique was developed and implemented in our laboratory. However, it turned out that S-loss from the layer was unavoidable. Despite that,
the detailed study Flash-In2S3 layers yielded in-depth understanding of growth and properties of the
layer. Nevertheless, a 12.6% efficient solar cell was successfully realized with Flash evaporation In2S3
buffer layer. The flash evaporation chamber has seen various stages of improvement during the
course of this work and at present the current design offer possibility of performing in-line deposition
by thermal and flash evaporation techniques in the same vacuum chamber. Initial attempts on flexible
CIGS/ In2S3 solar cell yielded a promising ~10% efficient cell, which was further improved to 12% as a
consequence of process engineering associated with Na incorporation in CIGS. A successful development of 13.3% efficient mini-module was realized with our optimized CIGS process using CdS buffer layers and of 10.6% using evaporated InxSy material as buffer layer. It turned out that the deposition
conditions of the i-ZnO also critically influence the performance of CIGS solar cells with alternative
buffer layer. Here the partial pressure of oxygen in the working gas has to be accurately controlled.
As such In2S3 buffer layers has good potential but our current results have not yet attained the expected high efficiencies. Further research is needed to investigate the efficiency limiting reasons as
well as the reasons for the reproducibility problems observed in this project.
1
2
Partial financial support from CTI, BFE and EU-FP7 projects
Measured under STC after 140 min light soaking
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References
[1]
D. Brémaud, D. Rudmann, G. Bilger, H. Zogg, A. Tiwari, Proceedings of the 31st IEEE Photovoltaic Specialists
Conference, Orlando, (2005), p. 223-226.
[2]
A. Chirila et al., Nature Materials, 10, 857-861, 2011
[3]
M. Green et al., Progress in Photovoltaics: Research and Applications, 19, 565-572, 2011.
[4]
N. Naghavi, S. Spiering, M. Powalla, B. Cavana and D. Lincot, Progress in Photovoltaics: Research and Applications 11,
7, pp. 437–443, 2003
[5]
P. Pistor, R. Caballero, D. Hariskos, V. Izquierdo-Roca, R. Wächter, S. Schorr, R. Klenk, Solar Energy Materials & Solar
Cells 93 (2009) 148–152.
[6]
D. FERRO, V. PIACENTE and P. SCARDALA, J. Mater. Sei. Lett. 7 (1988) 1301.
[7]
H.L. Hwang, C.C. Tu, J.S. Maa and C.Y. Sun. Sol. Energy Mater. 2 (1980), p. 433.
[8]
N. Romeo, V. Canevari, G. Sberveglieri, O. Vigil and L. Zanotti. Sol. Energy Mater. 3 (1980), p. 367.
[9]
R.D.L. Kristensen, S.N. Sahu and D. Haneman. Sol. Mater. 17 (1988), p. 329.
[10] S. Spiering, A. Eicke, D. Hariskos, M. Powalla, N. Naghavi and D. Lincot, Thin Solid Films 451-452, pp. 562–566, 2004
[11] Rajneesh Verma, Debjit Datta, Adrian Chirila, Dominik Güttler, Julian Perrenoud, Fabian Pianezzi, Ulrich Müller,
Satyendra Kumar, and Ayodhya N. Tiwari, J. Appl. Phys. 108, 074904 (2010)
[12] A. Chirila, D. Guettler, D. Brémaud, S. Buecheler, R. Verma, S. Seyrling, S. Nishiwaki, S. Haenni, G. Bilger, A. N. Tiwari,
Proceedings of 34th IEEE PVSC, June 7–12, 2009, Philadelphia, USA.
[13] R. Scheer, H.-W. Schock, Chalcogenide Photovoltaics: Physics, Technologies, Thin Film Devices, Wiley-VCH Verlag
GmbH & Co KGaA, Weinheim, 2011
[14] M. Igalson et al. Thin Solid Films, 515, p 6142, 2007
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IMPUCIS: INFLUENCE OF IMPURITIES ON
THE PERFORMANCE OF CIGS THIN FILM
SOLAR CELLS
Annual Report 2011
Address
Date
Überlandstr. 129, 8600 Dübendorf
0448234130, [email protected], www.empa.ch/tfpv
SI/500417 / SI/500417-01 103259 / 154296
01.03.2009 – 31.12.2011
15.12.2011
ABSTRACT
The main objective of this project is to better understand the influence of impurities on the
performance of Cu(In,Ga)Se2 (CIGS) solar cells. Impurities can be introduced in various ways into the
CIGS layer: using less pure source material, intentionally adding them from a different evaporation
source, or allowing them to diffuse into the CIGS layer from the substrate.
During this year the influence of Fe impurities in CIGS was investigated by using a stainless steel
substrate such that Fe can diffuse through the back contact into the absorber. Fe is found to have a
detrimental effect on the PV performance and admittance spectroscopy showed that a defect at
around 320 meV is formed.
Furthermore, the purity of an evaporation source material was reduced to intentionally introduce
impurities into CIGS. However, no noticeable influence on the PV performance of the solar cells was
observed. A chemical analysis of these solar cells with ToF-SIMS showed that impurities were not
incorporated into CIGS, or their concentration would be below the detection limit of the measurement.
After installing a new vacuum evaporation system last year, processing parameters were optimized to
achieve high efficiency during this year. For the high temperature process where temperatures up to
600°C are applied during CIGS growth a high efficiency of 16.6% was achieved without an additional
anti-reflective coating. For the low temperature growth process where the temperature is limited to
450°C during CIGS growth solar cells with efficiency up to 15.3% (without anti-reflective coating) were
produced on soda lime glass.
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Introduction and Project goals
The Cu(In,Ga)Se2 (CIGS) compound is an excellent material for production of solar cells because of
its high light absorption coefficient as well as the possibility to adjust the band gap of the material by
varying the In/Ga ration in the layer. To improve the efficiency of such CIGS solar cells it is necessary
to understand the underlying electronic transport properties of the device. In this context the role of
defects in the CIGS layer becomes important because defects influence the electronic properties (e.g.
doping and recombination) substantially. Defects may appear as a consequence of atomic vacancies
or anti-sites, but also impurities can form defects when introduced into the material.
The objective of this project is to better understand the role of impurities in the CIGS layer. Impurities
do not necessarily act detrimentally on the device performance – some of them (e.g. Na) even
improve it. Impurities can be introduced into the layer by using less pure source material, by
intentionally adding them from a different source, or by allowing them to diffuse into the CIGS layer
from the substrate. During this year the processing parameters of the new vacuum evaporation system
for CIGS processing that has been installed last year were optimized to achieve high efficiency solar
cells. Furthermore, the effect of iron impurities on the CIGS properties was investigated and the
concentration of impurities in the absorber was investigated by a chemical analysis.
Work and Results
1. Effect of iron impurities on CIGS solar cells
A controllable method to introduce iron impurities into the CIGS layer is to grow the CIGS solar cell on
a stainless steel substrate. During the CIGS growth iron diffuses through the back contact into the
CIGS film. The amount of iron atoms incorporated in the absorber depends on the properties of the
Mo back contact. For this study two different back contact layer thicknesses of 100 nm and 500 nm
were used [1]. CIGS, as well as the buffer and the window layers were processed identically. For
CIGS growth a high temperature process (maximum substrate temperature Tsub = 600°C) was used to
enhance the diffusion of impurities from the substrate into the absorber. A schematic of the layer
properties of the two devices is given in Figure 1.
TCO
CdS
TCO
CdS
CIGS
CIGS
Mo
Mo
Ti
Ti
Stainless steel
foil
Stainless steel
foil
Figure 1: Schematic device structures of two devices on stainless steel substrate with different back contact
thickness.
The PV parameters of the two devices are given in table 1. The solar cell with thin Mo back contact
clearly shows degraded PV performance compared to cell with thick back contact. Especially, the Voc
is reduced by 125 mV, which indicates increased recombination of the generated charge carriers.
Admittance spectroscopy was used to detect defect levels in the absorber of these two devices. For
the measurement the temperature of the device was varied from 120 K to 350 K in a cryostat cooled
with liquid nitrogen.
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Back contact
Tsub [°C]
Voc [mV]
Jsc [mA/cm ]
FF [%]
η [%]
100 nm Mo
600
502
29.4
61.2
9.0
500 nm Mo
600
627
31.3
68.4
13.4
2
Table 1: PV parameters of two cells on stainless steel substrate with 100 nm Mo and 500 nm Mo back contact.
Figure 2 shows the resulting defect spectrum of both solar cells. The device with 100 nm Mo back
contact shows 2 distinct defect levels. The level at 120 meV is the so called N1 defect, commonly
observed in CIGS devices. It has been observed in numerous of CIGS devices processed on different
substrates and with different CIGS growth parameters. Therefore, this level is most likely not attributed
to impurities. Its origin is however still not identified. A special feature is that its energetic position
varies depending on the sample. As shown in Figure 2 for the sample processed with 500 nm Mo the
N1 level was not detectable.
The defect level at 320 meV instead is probably caused by impurities because it is not found in the
samples with 500 nm back contact and in other samples with similar CIGS growth parameters. Such a
deep defect level leads to enhanced recombination and therefore to degraded efficiency.
1E+17
1E+17
100 nm Mo
1E+16
500 nm Mo
NT [cm-3eV-1]
NT [cm-3eV-1]
1E+16
1E+15
1E+15
1E+14
0.0 0.1 0.2 0.3 0.4 0.5 0.6
ET [eV]
1E+14
0.0
0.1
0.2
0.3 0.4
ET [eV]
0.5
0.6
Figure 2: Defect levels of devices on stainless steel. Left: Defects at 120 meV and 320 meV of the device with
thin Mo back contact are shown. Right: No clear defects appear in the spectrum of the solar cell with
thick Mo back contact.
In addition to the characterization of the electronic properties a chemical analysis was carried out with
ToF-SIMS. The iron concentrations in CIGS of the samples with 100 nm and 500 nm Mo back contact
shown in Figure 3 were calculated by integrating the Fe signal over the absorber layer thickness and
normalizing by the integrated Cu signal over the same interval and the number of sputter cycles
needed. This does not give quantitative values of the Fe concentration in the CIGS but relative
numbers can be compared. The CIGS absorber layer of sample with 100 nm Mo shows one order of
magnitude higher Fe concentration compared to the sample with 500 nm Mo and is therefore
consistent with the interpretation that Fe impurities form a defect level at around 320 meV observed in
admittance spectroscopy.
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Figure 3: Integrated Fe concentration in the CIGS layer for a device processed on 100 nm Mo (left) and
500 nm Mo (right) back contact. The Fe concentration in the device with thin back contact is
one order of magnitude higher.
2. Chemical analysis of CIGS produced from impure source material
CIGS solar cells were produced with reduced source material purity and the device performance was
compared to samples processed in the same way but with higher quality evaporation material.
Surprisingly, the reduced In purity did not degrade the efficiency of the solar cells noticeably.
Therefore, during this year a chemical analysis was performed on these samples to investigate the
amount of impurities in the absorber layers. Time-of-flight secondary ion mass spectroscopy (ToFSIMS) was chosen because impurities in ppm concentration can be investigated.
The two devices discussed in section 1 were actually produced with the lower purity source material.
The SIMS data indicate that in both samples the only detectable impurity is Fe. The concentration of
all other elements was below the detection limit of SIMS. To make sure that Fe in CIGS is not coming
from the In source, but from the stainless steel substrate, also a device grown on polyimide substrate
was investigated with SIMS. Indeed in this case also the Fe signal was below the detection limit. The
reason, why no impurities could be detected in the CIGS layer is most probably the different vapor
pressure of the elements in the In source material.
3. Progress with new vacuum evaporation system
After installing the new system for CIGS growth last year the processing parameters were optimized
during this year. The growth parameters for CIGS processing at high substrate temperature were
investigated in a first step. The same procedure was done for the processing at low substrate
temperature, which becomes important when substrates are used that do not allow high processing
temperatures, such as polyimide. The electronic properties and the performance of CIGS solar cells
from these two different processes are presented in the following sections.
3.1 Low temperature CIGS growth
In this context a low temperature growth process means that the maximum substrate temperature
during CIGS processing is kept below 450°C such that temperature sensitive substrates (such as
polyimide) can be used. Overall, the production of CIGS solar cells with such a low temperature
growth process is more challenging compared to the high temperature process because of the
different interdiffusion of the elements and the crystal growth. Nevertheless, we could show that highly
efficient solar cells can be produced with the low temperature process by changing the standard three
stage co-evaporation process used for high temperature growth to a multi-stage process [2].
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To achieve highly efficient solar cells with the new evaporation system this means that the processing
parameters such as the evaporation rate of the individual sources have to be very well known. During
this year it was possible to achieve an efficiency of 15.3% on soda lime glass (Figure 4) and 14.4% on
polyimide. Both values were achieved without an additional anti-reflective coating.
80
J [mA/cm2]
Voc = 680 mV
60
Jsc = 30.5 mA/cm2
40
FF = 73.8%
Eff. = 15.3%
20
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
-20
-40
Voltage [V]
Figure 4: J-V curve of the best cell processed at high substrate temperature with the new system.
No anti-reflective coating was applied.
Compared to the high efficiency of 18.7% (with AR coating) [2] achieved with the old system, there is
still room to improve the CIGS process for low substrate temperature. The optimum In/Ga ratio depth
profile as well as a better control of the Se source are expected to be crucial to further improve the
efficiency with the new system.
3.2 High temperature CIGS growth
Similar to the growth of CIGS at low substrate temperature the optimization of the CIGS process at
high temperature (600°C) is still in progress. The high temperature growth process is usually done on
soda lime glass substrates but it can also be applied on stainless steel foils.
During this year it was possible to improve the efficiency of the solar cells from an initial level of about
13% to 16.6%, as shown in Figure 5. This high efficiency was achieved without an additional antireflective coating. Therefore, even higher efficiency can be expected by reducing the optical losses.
80
Voc = 684 mV
60
J [mA/cm2]
Jsc = 32.7 mA/cm
2
40
FF = 74.5%
20
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
-20
-40
Voltage [V]
Figure 5: J-V curve of the best cell processed at high substrate temperature with the new system.
No anti-reflective coating was applied.
3.3 Characterization of electronic transport properties
CIGS solar cells produced with the new system were characterized by capacitance measurements to
better understand the electronic transport properties as well as the reasons for the still lower efficiency
of these cells compared to the best cells from the old system. Figure 6 shows a typical defect
spectrum of a CIGS solar cell grown with the low temperature process. Two distinct defects can be
observed.
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NT [cm-3eV-1]
1E+17
1E+16
1E+15
1E+14
0
0.1
0.2
0.3 0.4
ET [eV]
0.5
0.6
Figure 6: Defect spectrum of a typical CIGS solar cell grown at low substrate temperature with the new
evaporation system.
The shallow defect at 110 meV is again attributed to the N1 defect (as already mentioned in
section 1). The defect located deeper inside the band gap at 250 meV is not present in the best
performing CIGS solar cells. Therefore, it could be one limiting factor to achieve higher efficiencies.
From admittance spectroscopy it cannot be determined whether the measured defect is located
250 meV away from the conduction band or from the valence band. DLTS measurements could be
used in future to learn more about this defect and to identify its origin.
The investigation of the role of defects on the electronic properties of CIGS solar cells was carried out
in collaboration with the University of Gent, Belgium. Especially, the capacitance measurements as
well as the analysis and the modelling of the defects were assisted by J. Lauwaert, H. Vrielinck, K.
Decock and M. Burgelman.
Appraisal 2011 and Outlook
We could show that a reduced source material purity does not affect the performance of state of the
art CIGS solar cells. The chemical analysis shows that the concentration of impurities in the final
device is below the detection limit of the measurement (ToF-SIMS). Therefore, even lower purity
material could be used in principle.
Furthermore, Fe has been identified to be a detrimental impurity in CIGS. Already a small amount of
Fe degrades the efficiency of the solar cell. Allowing impurities to diffuse through the back contact into
the CIGS layer is found to be an appropriate method to study their effect on the device properties. In a
similar way we are currently investigating the effect of Sb on the CIGS layer, by intentionally adding it
to influence the CIGS microstructure and cell performance.
References
[1]
F. Pianezzi et al., Electronic properties of Cu(In,Ga)Se2 solar cells on stainless steel foils without diffusion barrier.
Progress in Photovoltaics: Research and Applications, 2011, accepted for publication
[2]
A. Chirilă et al., Highly efficient Cu(In,Ga)Se2 solar cells grown on flexible polymer films.
Nature Materials 2011; 10: 857–861. DOI:10.1038/nmat3122
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HIPO-CIGS: NEW CONCEPTS FOR HIGH
EFFICIENCY AND LOW COST IN-LINE
MAUFACTURED FLEXIBLE CIGS SOLAR
CELLS
Annual Report 2011
Address
Date
Überlandstrasse 129, 8600 Dübendorf
044 823 6107, [email protected], www.empa.ch/tfpv
HIPOCIGS / 241384
01.01.2010 – 31.12.2012
15.12.2011
ABSTRACT
The EU project hipo-CIGS project aims at the development of cost efficient flexible solar cells and
modules based on the compound semiconductor CIGS. Efficiency and cost limitations in state-of-theart flexible CIGS solar cells have been identified and solutions were elaborated for each step in production and each layer of the multilayer structure in order to overcome these limitations. For accomplishing these tasks a European consortium of leading R&D institutes and industries was established.
A key issue for cost reduction is the improvement of efficiency and therefore the output yield in production. An important milestone of the hipo-CIGS project is the achievement of cell efficiency higher
than 16% on flexible substrate by optimizing the multistage deposition process for the CIGS layer.
The low temperature deposition process for the CIGS layer was optimized in terms of timing and of
elemental fluxes during the various stages. This led to improved grain growth in the polycrystalline
CIGS layer. Furthermore, the composition grading of group three elements is flattened and more similar to high efficiency devices obtained on glass substrates. This reduces recombination losses in the
solar cell and hence improves the efficiency. A certified efficiency of 18.7% has been achieved on
flexible polyimide substrate which is a new world record and an important step towards the project
objectives.
Further activities during this project are the evaluation of suitable substrate materials as well as the
development of crack free electrical back contacts which provide sufficient adhesion of the CIGS to
the selected substrate materials.
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Introduction and Project Goals
The Cu(In,Ga)Se2 (CIGS) on glass technology is already heading towards industrial maturity, but to
meet the production cost target of below 0.6 Euro/Wp in mid-term and below 0.4 Euro/Wp in longterm, development of highly efficient flexible modules is an attractive option.
The ultimate advantage of thin-film technologies is the possibility of monolithically connected flexible
modules produced with high speed roll-to-roll manufacturing systems. Transfer of a “static deposition”
process to “in-line deposition” on moving substrates brings additional challenges for control of layer
composition and interfaces. Choice of an appropriate substrate and deposition process to overcome
problems related to thermal mismatch induced stress are important for high performance and
monolithic cell interconnection.
The main goal of the project is to develop innovative flexible substrates and deposition processes that
are suitable for the in-line and/or roll-to-roll production of highly efficient solar modules using thinner (<
1 micron) CIGS absorbers and with potential for production costs below 0.6 Euro/Wp in future. The
objective will be achieved by developing novel concepts in growth of “high quality” layers and interfaces for efficiency improvement, aiming a new world record efficiency of 16% on PI and low-cost
metal (mild steel and alumina) foils. Also, the implementation of in-line compatible buffer layers, improvements in interconnection technologies and application of multifunctional top layer will lead to an
advancement towards roll-to-roll manufacturability of integrated solar modules. This project will help
research institutions to maintain a global lead in the CIGS field and will enable the European industries
to implement the research excellence in industrial production of low cost flexible CIGS solar modules
in future.
In order to achieve the challenging aims and objectives of this project a European consortium consisting of 8 partners from R&D and industry was established and is coordinated by ZSW (Zentrum für
Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg, Germany).
The project is divided into seven work packages covering activities on flexible substrates (WP1), back
contact and Na supply (WP2), CIGS deposition (WP3), buffer layers (WP4), interconnections (WP5),
TCOs (WP6), and assessment of results (WP7). Empa is contributing to WP1-4 with the following
goals for the reporting period:
•
Crack-free back contacts with sufficient adhesion on various flexible substrate materials.
•
Investigation of influence of NaF doping during different growth stages on the CIGS morphology and device performance.
•
Find optimum low-temperature CIGS growth procedures for solar cell efficiency above 16% on
flexible substrate.
These tasks for achieving high efficiency CIGS flexible cells are complemented by research activities
within BFE project Febulas (103317) and the CTI project on Multifuncional back contacts (CTI10245.1).
Work and Results
1. Flexible and lightweight substrate materials
Low temperature (450°C) CIGS solar cells were processed on commercial stainless steel, low carbon
steel and commercial aluminium foils. Solar cells on all three tested metallic substrates showed very
promising results with efficiencies of 17.7%, 14%, and 14.1%, respectively.
High temperature (600°C) CIGS solar cells were processed on enameled low carbon steel TATA steel
and Pemco). The achieved efficiency of 18.2% is very close to the soda lime glass (SLG) reference
(18.8%) of the high temperature process at Empa.
Medium temperature (500°C) CIGS layers were deposited on enameled Al substrates supplied by
Pemco. The enamel cracked after CIGS deposition and back contact/CIGS structure delaminated from
the substrate. Furthermore, the end point detection was not possible to determine the stoichiometric
point during the CIGS processing.
Polyimide foils with different thicknesses have been procured from four independent suppliers. The
study includes polyimide of 25 µm, ~37 µm, and 50 µm. 25 µm thick polyimide is used as standard
substrate at Empa for low temperature CIGS processing.
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hipoCIGS, Stephan Buecheler, Empa
2. Crack free back contact
Single-layer experiments
Investigations of Ti, TiN, and Mo single layers on polyimide foils in terms of residual stress, electrical
resistivity, optical reflectivity and stoichiometry were performed. In case of Mo, a strong influence on
the residual stress was found when total pressure and sputtering power were varied together: Mo
sputtered at low Ar partial pressure at high power leads to a film with low resistivity and high density,
but high compressive stress. Mo sputtered at high Ar partial pressure at low power leads to a film with
high resistivity and low density, where the layer is under small tensile stress.
Multi-layer back contact experiments for CIGS solar cells on Polyimide foils
Mo based back contacts were optimized to fulfil the following requirements:
• High conductivity (due to the high moisture absorption in polyimide foil, the first Mo layer must
prevent further oxidation of the whole back contact and therefore must have a compact microstructure deposited with high metal flux)
• Adhesion (both the adhesion of the Mo back contact on the polyimide substrate and the adhesion
of the CIGS on the back contact stack must be considered)
• Residual stress (the consequence of high residual stress is bending of the polyimide foil as well
as increasing probability for micro-cracks and local loss in adhesion. The residual stress after the
back contact deposition must be compressive to compensate thermally induced stress during the
CIGS deposition process)
During the development of the low temperature CIGS process at Empa, a multilayer back contact
stack was developed using a combination of two Mo layers deposited at different sputtering conditions. The first layer was sputtered at high power and low Ar pressure leading to a dense layer with
high conductivity but strong compressive stress. A second layer sputtered at moderate power at high
Ar pressure shows slightly tensile stress and higher conductivity. In combination the back contact has
a sheet resistance of ~0.3 Ω/square and is under compressive stress (between -0.5 and -1 GPa when
polyimide foil is used) and the back contact layers are crack-free. The total thickness of the Mo bilayer
is ~500 nm. To enhance the adhesion of the Mo back contact stack, a plasma treatment of the polyimide foils was performed prior to the deposition process. This back contact was also tested on enameled mild steel substrates, where a crack-free layer was achieved on the steel sample.
Additionally, alternative materials within multilayer back contact structures were investigated on polyimide foils. An approach of a Ti/TiN/Mo stack, which should lead to a multifunctional and adjustable
back contact, was analysed. This back contact structure showed a significant improvement in CIGS
adhesion and residual stress compared to the Mo based back contacts (but at lower sheet resistance
of 0.6 Ω/square). However, the solar cell performance was about 10% lower (relative) compared to a
Mo bilayer reference cell (same CIGS run). Further optimizations on the both the back contact design,
including its sputtering processes, and the CIGS deposition process must be performed to maintain
the solar cell performance.
Barrier-layers on different substrates
The barrier performance of different materials (TiN, Si3N4 and Mo) was tested on stainless steel foils.
The impurity barrier performance of these contacts was evaluated using two different CIGS processes,
a low and high substrate temperature process with Na post-deposition treatment. Additionally, a thin
Mo single layer as a back contact was added for the experiment, where the Mo bilayer contact was
used as a reference contact. For all contacts a thin Ti layer was sputtered onto the steel substrate to
ensure good adhesion of the back contact films.
Results of this investigation show no increase in solar cell performance when contacts with TiN and
Si3N4 were compared to the Mo bilayer reference. This indicates that the Mo bilayer contact acts sufficiently as an impurity diffusion barrier against iron. However, the thin Mo single layer back contact
showed a significant decrease in solar cell performance, while this decrease was stronger with the
high temperature CIGS process. Further investigations on the impurity diffusion behaviour of Mo was
performed for solar cells manufactured at low temperature CIGS process where it was confirmed by
SIMS that the iron concentration measured in the CIGS layer directly depends on the density of the
Mo film. With the use of a Mo bilayer stack (combination of high and low sputtering power), a good
impurity diffusion performance was achieved at low residual stress in the back contact film leading to
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best cell efficiencies of 17.7% (with ARC) on stainless steel foils without the need of an additional impurity diffusion barrier.
On pure aluminum foils (without any treatments or coatings) a Mo bilayer back contact was deposited
by sputtering (again with a thin adhesion layer of Ti). After the CIGS solar cell processing the solar
cells did not yield any efficiency due to strong Al diffusion into the CIGS layer (measured by EDX).
With an additional impurity diffusion barrier (<200 nm) the Al diffusion could be prevented and solar
cell efficiencies of 14.1% were achieved. No cracks in both the CIGS and back contact films were
visible.
3. Low temperature growth procedure
Extensive process development has been carried out for the growth of high quality absorber layers at
low substrate temperature. An efficiency of 17.6% on polyimide has been achieved over the course of
2010 and has now been further improved to 18.7% this year [1-3]. Furthermore, the process has also
proven to be suitable for stainless steel substrates where a certified record efficiency of 17.7% has
been achieved. It is remarkable that this has been achieved without any additional diffusion barrier
layer between the steel substrate and the back contact and thus, proves the high potential of processing CIGS at low temperature.
The record devices mentioned above are typically achieved with about 3 µm thick CIGS layers. The
process has been scaled down proportionally in time by a factor of 2 and compared to a baseline reference sample (fig. 1). Even though an efficiency decrease of about 10% relative is observed, a
15.5% efficiency device with 1.4 µm thick CIGS has been achieved. Future work will be carried out in
this direction to increase efficiencies with such thin absorber layers.
Figure 1: J-V and E QE m easurements of s olar c ells o n pol yimide c omparing a ba seline de vice ( 2.8 µm)
with an absorber of reduced thickness (1.4 µm).
The same low-temperature CIGS process as used for the 18.7% record device on polyimide has as
well been applied on Al foil. Initial experiments resulted in a 14.1% efficiency device on Al-foil. Figure 2
shows the corresponding J-V curve. On that sample, no apparent cracks or delamination was observed.
Figure 2: J-V measurement of the initial device obtained on Al foil.
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Further work concerning high deposition rates has been carried out at Empa. To gain preliminary insights into the critical growth phases, an investigation has been carried out on glass substrates at a
low temperature suitable for polyimide foils. A basic three stage process has been used and the deposition rates during either the 2nd stage or the 3rd stage have been increased drastically to about 500600 nm/min CIGS growth rate [4]. In both cases the relative efficiency loss as compared to a baseline
process was found to be in the range of only about 10% as shown in figure 3. Further investigations
will be carried out to develop an overall drastically faster deposition process together with thinner absorber layers.
Figure 3: J-V parameters of solar cells with different deposition times during the 2nd stage (left) and during the
3rd stage (right) of a three stage process.
National / international Cooperation
The consortium of the EU-FP7 hipo-CIGS project consists of four R&D partners ZSW (Germany) TNO
(Netherlands), Technical University of Warsaw (Poland), and Empa (CH) and four industrial partners
Flisom (CH), Tata Steel (Netherlands), Pemco (Belgium), and Würth Solar (Germany). Some of the
tasks in this European project overlap with activities in complementary BFE project Febulas (103317)
and a CTI project on Multifuncional back contacts (CTI-10245.1), where direct partners are companies
FLISOM AG and W. Blösch AG, respectively.
Appraisal 2011 and Outlook 2012
With the achievement of 18.7% efficiency on flexible PI substrate an important milestone of the hipoCIGS project was accomplished. This result demonstrates the high potential of low temperature processed CIGS devices. It was obtained by combining efforts on the development of crack free back
contacts for reduced residual stress and improved adhesion of the CIGS layer, on the investigation of
the optimum Na treatment procedure, and ultimately in reducing recombination losses by modified
band gap grading in the low-temperature CIGS absorber.
The results and findings of 2011 are an ideal basis for the challenging tasks of increased deposition
speed of the absorber which are planned for 2012. In collaboration with ZSW and the Technical University of Warsaw an important aim is to gain deeper understanding on relevant critical stages of the
growth process for low substrate temperature on various substrate materials including mild steel and
alumina foil. Further on, the issue of in-line buffer layer deposition and the development of modules by
laser scribing will be important activities.
References
[1] A. Chirilă et al., 35th IEEE PVSC, Honolulu, 2010, pp. 657-660.
[2] A. Chirilă et al., 25th EUPVSEC / 5th WCPEC, Valencia, Spain, 3BV.2.68, 2010.
[3] A. Chirilă et al., Prog. Photovolt. DOI: 10.1002/pip.1077.
[4] A. Chirilă et al., Prog. Photovolt. DOI: 10.1002/pip.1122.
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NOVA-CIGS: NON-VACUUM PROCESSES
FOR DEPOSITION OF CIGS ACTIVE LAYER
IN PV CELLS
Annual Report 2011
Address
Date
Überlandstrasse 129, 8600 Dübendorf
0587654130, [email protected], www.empa.ch/tfpv
NOVA-CIGS / 228743
01.01.2010 – 30.06.2013
15.12.2011
ABSTRACT
Current production methods for thin film photovoltaics typically rely on costly, difficult to control (over
large surfaces) vacuum-based deposition processes that are known for low material utilisation of 3070%. EU project NOVA-CIGS proposes alternative, non-vacuum deposition processes for thin film
Cu(In,Ga)Se2 (CIGS)photovoltaic cells. The low capital intensive, high throughput, high material yield
processes will deliver large area uniformity and optimum composition of cells.
The overall project goal is to develop an ink based, simple and safe deposition process of the CIGS
absorber layer for highly efficient low cost solar cells. Major scientific breakthroughs of the project
include improved materials control in novel precursor materials by using nano-sized precursors of
specific chemical and structural characteristics and innovative ink formulation, to enable coating by
printing processes while avoiding the use of toxic gases or solvents in subsequent process steps.
Specifically, research work at Empa is focused on the deposition and activation of CIGS layers from
formulated precursor suspensions and solutions, providing a feedback to the project partners engaged in precursor materials and ink formulation, and preparing background for large area solar cells
and industrial implementation.
During the second project year, selected Cu-, In, and Ga-containing nanoparticle dispersions were
received from projects partners, and deposited on rigid substrates by means of knife-coating and
printing, and activated in selenium atmosphere to yield the CIGS absorbers. Several coating problems, such as insufficient wetting, large crystallites, local precursor oxidation, have been solved by
optimizing coating and drying parameters. The precursor layer thickness could be tailored by
multipass deposition. Selenization conditions are critical for the precursor conversion, so that increased selenization time improves the CIGS quality. Both increased Se flux and time accelerate the
formation of MoSe2. Finally, first solar cells were processed from the formed CIGS absorbers. Future
experiments will focus on improving solar cell performance with optimized ink chemistry, and faster
precursor conversion will be performed with rapid thermal processing.
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Introduction and project objectives
Concept
Photovoltaics (PV) is a key technology option to meet the rising demand for energy and counter rising
energy prices whilst reducing CO2 emissions and encouraging energy independence in Europe.
However, the dominating crystalline silicon (c-Si) technology remains expensive, and it is also comparatively energy intensive to manufacture and results in rigid and heavy devices. A radically different
step-change concept is required to become competitive with fossil-based energy.
With 100 times thinner absorbers than conventional c-Si wafers, the emerging inorganic Thin Film
(TF) PV technology uses only small quantities of semiconductor material to achieve viable cell efficiencies, allowing light weight and flexible modules. There are three major families of inorganic TF
PV: i) amorphous / micro crystalline silicon (a-Si/micro-Si), ii) Cadmium Telluride (CdTe) and iii) Copper Indium Gallium Diselenide (CIGS) and Copper Indium Sulfide (CIS).
The current deposition process for TF PV relies on well-known vacuum-based sputtering or coevaporation technologies. Whilst allowing controlled deposition of high purity thin layers, these techniques experience limitations such as high investment and operating costs, low throughput, low materials yield and high energy consumption, amongst others. This leads to TF PV module costs of about
1-1.5 $/Wp.
However, TF PV has significant cost reduction potential. Thin layers can be applied by non-vacuum
deposition processes such as printing, which are low capital intensive, exhibit high throughput, high
material yield and are suitable for roll-to-roll processes that deliver large area uniformity and optimum
composition. The EU PV Technology Platform suggests that development of such technology should
lead to medium term (2013-2020) TF module cost of around 0.8 $/Wp.
The feasibility of this method was shown by companies ISET and Nanosolar that reported CIGS solar
cells with 13.6% and 14.5% efficiency, respectively [1,2] by printing pastes containing oxide nanoparticles. Kaelin et al. reported 6.7% efficient cells in 2005 [3] by selenization of metal salt solution
pastes, which has been recently improved to 7.7% by Uhl et al. [4]. Mitzi et al. utilized hydrazine as a
solvent reaching an efficiency of 12.8% [5], but the industrial implementation might be hindered due
to the toxic and explosive nature of hydrazine.
Global project objectives
The goal of NOVA-CI(G)S is to develop an ink based non-vacuum, simple, and safe deposition process of the CIGS absorber layer for highly efficient low cost solar cells. The CIGS absorber is the core
of the solar cells, and also the most scientifically challenging and most cost intensive layer to produce. The project aims to demonstrate the following:
1. Non-vacuum deposition of the CIGS layer is possible whilst maintaining high efficiency.
2. Non-vacuum deposition of CIGS layers can be realized at high speed on rigid and flexible
substrates whilst maintaining acceptably high efficiency on assembled cells.
The overall aim being to make a significant impact on reducing the cost of the CIGS layer and pave
the way to future development addressing the device’s adjoining layers with a similar fully integrated
low cost deposition process ultimately achieving a CI(G)S TF module cost of below 0.8 €/Wp.
Specific research objectives at Empa
Research work at Empa is focused on the deposition and activation of CIGS layers from formulated
precursor suspensions and solutions, providing a feedback to the project partners engaged in precursor materials and ink formulation, and preparing background for large area solar cells and industrial
implementation. Three specific work packages at Empa are:
1. Layer deposition
2. Layer activation
3. Solar cell processing and characterization
The layer deposition will be optimized individually for each precursor material for a good adhesion of
the precursor layers and homogeneous film formation. This work is important for large-area deposition and the development of solar modules. The starting point is the raw precursor material which has
to be converted effectively into an efficient photoactive layer upon thermal annealing, with or without
addition of chalcogen. The deposition process is a means to transfer the precursor to the substrate to
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NOVA-CIGS“, Y.E. Romanyuk, Empa
achieve a thin precursor layer. By nature printing processes are likely to introduce potential contaminants, which need to be accounted for. Therefore, an intensive iterative process will take place
throughout the project for the materials synthesis, ink formulation layer conversion and deposition
process to ensure that the layer is correctly applied, that there is minimal interference by ink formulation chemistry, the layer has adequate adherence, has optimal chemistry and crystallography / phase
structure.
The layer activation via thermal treatment is required in order to transform printed precursor layers
into crystalline CIGS absorbers with correct composition, homogeneity and morphology. Usually a
two-step method is applied to first sinter the precursor at 200-300°C in order to remove solvent and
binder material and to densify the precursor. In most cases an additional selenization/sulfurization
step at higher temperatures (500-600°C) in a closed reactor furnace with Se/S atmosphere will be
necessary. The selenization conditions (partial pressure of Se, temperature ramps, annealing time,
etc) must be optimized to obtain single phase CIGS layers of optimum structural and opto-electronic
properties. Depending on the precursor material, especially depending on its selenium content (pure
metals without selenium or binary selenide compounds) the selenisation or conversion process has to
be adapted. Rapid thermal processing (RTP), which offers fast heating rates, will be tested in order to
avoid detrimental reaction pathways during layer activation and increase processing speed.
Methodology
The non-vacuum deposition of CIGS absorbers can be divided into four steps (see Figure 1). A suitable precursor paste is formulated from either true metal solutions or particle dispersions. The paste is
then transferred on a molybdenum coated substrate by means of a non-vacuum technique, i.e. doctorblade, screen printing, slot-die, ink-jet or spray-coating. Consecutive drying on a hotplate or drying
lamp in ambient or inert atmosphere facilitates the evaporation of solvents and chemical additives. In a
last step CIGS phase is obtained via a heat treatment at 500-600°C in selenium atmosphere. While all
steps are important for a successful absorber deposition this work will mainly focus on the paste formulation and optimization of the CIGS conversion.
Figure 1 : CIGS f ormation steps: 1) pa ste f ormulation, 2) non-vacuum d eposition, 3) drying i n ambient at mosphere to remove solvents, 4) selenization step to convert precursor into final absorber layer.
Performed work and results
Nanoparticle dispersions
A series of individual Cu-, In-, Ga-containing nanoparticle dispersions, as well as their binary and ternary mixtures, formulated with different solvents, stabilizers and weight loads were received from projects partners. Because of pending IP and a potential commercialization of the nanoparticle inks, it is
not possible to disclose formulation details at this moment.
Precursor deposition
Dispersions were applied on molybdenum coated soda-lime glass (SLG) by knife blading technique or
ink-jet printing. Various coating defects were observed for dried precursor films, and respective
measures were taken in order to obtain a homogeneous, pin-hole free layer. For instance, microscopic
uncovered areas were observed on spots, where either organic contamination or insufficient Mo layer
thickness prevented sufficient wetting (Fig 2a). Degraded and unfiltered nanoparticle dispersions often
yielded large crystallites on the surface of the precursor layer, Fig. 2b). These crystallites should be
avoided by filtering and using stable dispersions, because they can result in shunt passes in selenized
absorber layers. Finally, local or even complete oxidation of the precursor layer can occur when drying
at elevated temperatures in air, Fig. 2c). Again, these defects should be avoided, because fully oxidized precursors can be hardly converted in high-quality CIGS films but require harsh reducing and
selenization treatment, e.g. with H2 and/or H2Se treatment.
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Figure 2: Top-view optical microphotographs of nanoparticle precursor layers, showing possible coating defects:
a) uncovered spot because of inhomogeneous wetting of the Molybdenum layer; b) large crystallite formations
from unfiltered, degraded inks; and c ) whitish spots stemming from local oxidation of the nanoparticle precursor
during high-tempareture drying in air. Optical magnification factors are given.
Once the coating conditions are optimized, single or multipass coating can be applied to tailor the total
layer thickness, Fig. 3. It was found out, that an intermediate drying between individual passes is
beneficial for the layer quality, because it reduces the risk of crack formation.
Figure 3 : C ross-section SEM micrographs of pr ecursor l ayers, f ormed by o ne, t wo and three i ndividual k nifeblading steps layers with drying beween steps. Desired precursor thickness can be achieved.
Layer activation
Standard selenization was carried out in a two temperature zone tubular furnace. XRD of selenized
films confirmed the formation of the CIGS phase in most cases. For Cu-rich precursor compositions,
often traces of the Cu2-xSe phase were detected, whereas excessive overheating of precursors in air
caused the formation of (In,Ga)2O3 phases.
To investigate the effect of selenization time, the substrate heated to 550°C was dwelled for various
times under constant selenium supply. Figure 4b) shows an exponentially decreasing full-width-at-halfmaximum (FWHM) of the CIGS (112) reflection with prolonged selenization which is associated with
larger crystallite size due to grain growth and coalescence. The conversion of Mo to MoSe2 is also
taking place, which can be seen in the ratios of XRD peak intensities. In the case of complete selenization it also led to a delamination of the film from the glass substrate. An optimal trade-off between
sintering and MoSe2 formation was determined to be 35 minutes.
To investigate the effect of Se flux, i.e. Se partial pressure, three experiments were carried out with a
varying Se zone temperature resulting in three various Se consumptions, Figure 4a). No significant
impact on film morphology and FWHM could be observed. The formation of MoSe2 is accelerated for
higher Se flux.
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b)
a)
Figure 4: Variation of the FWHM of the CIGS (112) peak, and the intensity ratio of MoSe2/Mo peaks for a) different Se consumptions and b) different selenization times.
Rapid thermal annealing (RTP)
In order to reduce the activation duration, as well as avoid the formation of undesired binary phases on the way towards the CIGS
phase, a custom-designed rapid-thermal processing (RTP) system
has been built and installed, Fig. 5. Preliminary experiments indicated, that the CIGS phase can be obtained very fast, only within
30-60 seconds after starting the RTP. However, numerous parameters, such as temperature profiles, Selenium supply, operation pressure should be optimized to obtain the fastest and full
conversion into CIGS layer.
Figure 5: Custom built RTP system for selenization of nanoparticle precursors at Empa.
Solar cell fabrication
Selected CIGS absorbers were coated with a CdS buffer layer by chemical bath deposition and an iZnO/ZnO:Al window bi-layer transparent contact by RF magnetron sputtering. After mechanical scribing to define individual cells, current-voltage (I-V) and quantum efficiency (QE) measurements were
performed under simulated AM1.5 global illumination. Figure 6 shows one of the first solar cells, based
on the CIGS absorber processed from nanoparticle precursor, yielding 4.8% conversion efficiency.
Current Density (mA/cm2)
50
40
Active Area Quantum Efficiency (%)
60
a) Voc (mV)
433
Jsc (mA/cmÂ²) 24.8
FF(%)
44.7
Eff (%)
4.80
Rp (Ohmcm²) 168
Rs (Ohmcm²) 3.22
30
20
10
0
-10
-20
-30
-400
-200
0
200
Voltage (mV)
400
600
0.8
b)
0.6
0.4
J=24.8 mA/cm2
0.2
0.0
400
600
800
Wavelength (nm)
1000
1200
Figure 6: a) I-V characteristics and b) QE response of a CIGS solar cell processed from nanoparticle precursors.
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The project Consortium includes four academic-research partners and four industrial partners:
* Umicore S. A., Brussels, Belgium (coordination)
* Eidgenössische Materialprüfungs- und Forschungsanstalt (Empa), Switzerland
* FLISOM AG, Switzerland
* Zentrum für Sonnenenergie und Wasserstoffforschung (ZSW), Stuttgart, Germany
* Würth Elektronik Research GmbH, Stuttgart, Germany
* VTT Technical Research Center of Finland
* Technische Universität Chemnitz, Germany
* Xennia Technology Ltd., Letchworth, UK
Empa is collaborating intensively with ZSW to elaborate different routes for post deposition annealing
and selenization, as well as concepts of defining optimum structural, compositional and electronic
properties of absorber layers.
Conclusions 2011 and Outlook 2012
 Coating parameters of selected nanoparticle dispersions have been optimized to obtain homogeneous and pin-hole-free precursor layers.
 Selenization conditions, such as process time, selenium pressure and flux, rector design are critical to obtain the full and fast conversion of nanoparticle precursor.
 Rapid thermal processing (RTP) system has been built and successful experiments performed to
form CIGS phase in short (<5 min) time.
 First CIGS solar cells based on nanoparticle-derived absorbers have been produced.
In 2012 several new sets of pre-formulated inks will be received from the project partners. Future experiments will focus on better sintering of inks. A new rapid thermal annealing (RTP) set-up will be
installed in order to study the effect of rapid heating on the CIGS phase formation and the absorber
uniformity. Fabrication and characterization of CIGS solar cell devices will be done.
References
[1]
V. Kapur, A. Bansal, P. Le, O.I. Asensio, Non-vacuum processing of CuIn1−xGaxSe2 solar cells on rigid and flexible
substrates using nanoparticle precursor inks, Thin Solid Films 431-342, 53-57, 2003.
[2]
J. K. J. van Duren, C. Leidholm, A. Pudov, M.R. Robinson Y. Roussillon, The Next Generation of Thin-film Photovoltaics, Materials Research Society Symposium Proceedings 1012, 259, 2007.
[3]
M. Kaelin, D. Rudmann, F. Kurdesau, H. Zogg, T. Meyer, A.N. Tiwari, Low-cost CIGS solar cells by paste coating and
selenization, Thin Solid Films 480–481, 486–490, 2005.
[4]
A. R. Uhl, C. Fella, A. Chirila, M. R. Kaelin, L. J. Karvonen, A. Weidenkaff, C. N. Borca, D. Grolimund, Y. E. Romanyuk, A.
N. Tiwari, Non-vacuum deposition of Cu(In,Ga)Se2 absorber layers from binder free, alcohol solutions, Progress in
Photovoltaics: Research and Applications, 2011, DOI: 10.1002/pip.1246
[5]
W. Liu, D.B. Mitzi, M. Yuan, A.J. Kellock, S.J. Chey, O. Gunawan, 12% E fficiency CuIn(Se,S)2 Photovoltaic D evice
Prepared Using a Hydrazine Solution Process, Chemistry of Materials 22, 1010, 2010.
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MULTIFUNCTIONAL BACK ELECTRICAL
CONTACT FOR FLEXIBLE THIN FILM SOLAR
CELLS
Annual Report 2011
Address
Date
P. Blösch, S. Bücheler, A. N. Tiwari
EMPA, Laboratory for Thin Films and Photovoltaics, Swiss
Federal Laboratories for Materials Science and Technology
Überlandstrasse 129, CH-8600 Dübendorf
058 / 765 4152, [email protected], www.empa.ch/tfpv/
CTI - 10245.1 PFNM-NM
01.06.2009 – 30.09.2011
15.12.2011
ABSTRACT
Flexible Cu(In,Ga)Se2, called CIGS, solar cells provide high efficiencies with low cost potential. The
aim of this CTI project is to develop concepts and optimize deposition processes for multifunctional
back el ectric c ontact l ayers s uitable f or r oll-to-roll m anufacturing. Lo w electrical r esistance, t hermal
and mechanical stability, impurity barrier properties for long-term solar cell performance stability, and
suitable film stress comprise the multifunctional contact.
The c onventional M o bas ed bac k contact w as c ompared t o an a lternative a nd m ultifunctional bac k
contact design, which is a multilayer stack of Ti, TiN and Mo. The solar cell performance with an optimized alternative back contact on polyimide foils showed about the same solar cell efficiency compared to the Mo based cell, but with reduced residual stress.
On stainless steel foils, different back contact designs were tested with both low and high temperature C IGS pr ocess. I n c ase of s teel s ubstrates, an i mpurity diffusion b arrier layer m ust be us ed t o
prohibit iron diffusion into the CIGS absorber, because a small iron concentration in CIGS decreases
the solar cell performance. The performance of Mo based back contacts as an impurity diffusion barrier against iron was evaluated and compared to back contacts with an additional TiN and Si3N4 diffusion barrier layer. Best cell efficiencies of 17.3% were obtained on a Ti/Mo/Mo back contact design.
Solar m odules were developed o n p olyimide f oils with monolithical s eries interconnection b y l aser
2
2
patterning. Two different module sizes were successfully fabricated: 13 cm and 144 cm , where the
2
13 cm mini-module showed a performance of 13.6%.
Further, a r otatable c athode w as i ntegrated i nto t he magnetron s puttering s ystem of E mpa. I nitial
tests with both Ti and TiN showed an improved conductivity of the Ti layer, but some challenges to
sputter stoichiometric TiN without a real-time N2 gas flow control-loop system.
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Introduction / Project Goals
Production of flexible thin film solar cells and modules with roll-to-roll deposition methods offer several
advantages f or p otentially low c ost m anufacturing. H owever s uitable eq uipment f or w eb ( roll-to-roll)
coating including r elevant processes ar e not c ommercially available. A ppropriate web coating equipment together with a baseline deposition process is essential to facilitate manufacturing of next generation of high performance Cu(In,Ga)Se2 (called CIGS) thin film solar modules. The project will demonstrate development of next generation of high efficiency CIGS flexible thin film solar cells and monolithically c onnected m odules bas ed o n “ alternative multilayer e lectrical back c ontact” t hat provides
multi-functionality and overcomes the problems of conventionally used electrical back contact. Sputtering processes will be used to grow these stacked layers and based on a specific process know-how a
proprietary design will be developed to configure a roll-to-roll coating system with rotatable cylindrical
magnetron sputtering targets appropriate for cost-effective industrial production in future.
Short Project Description
This project is structured in four work packages:
- WP 1 : Deposition a nd c haracterization o f th e m ultilayer b ack c ontact An in line sputtering
deposition system with four cathodes is used to deposit metals, nitrides, and transparent contacts
for thin film solar cells using DC or pulsed DC magnetron sputtering technology. Multilayer contacts
are dep osited and o ptimized i n c onductivity, f ilm s tress, and l ong-term s tability. F or m etal s ubstrates, contacts w ith impurity di ffusion bar rier pr operties were deposited. I nvestigated m aterials
are Mo, Ti, TiN, SiN, ZnO, and ZnO:Al.
- WP 2 : Processing o f f lexible so lar c ells Solar c ells with a lternative m ultilayer bac k c ontacts
were processed on v arious flexible s ubstrates. T he back contact needs t o f ulfill t he a bove m entioned demands for these different substrate materials. It was found that sodium, which is present
in the commonly used soda lime glass, acts as dopant material when diffusing from glass substrate
into CIGS. Since our flexible substrates do not contain sodium, a suitable method for sodium doping was tested and applied.
- WP 3: Laser scribing and patterning for modules The development of monolithically connected
solar cells requires a process with several sequential steps of layer deposition and selective layer
removal b y l aser s cribing. In t his pr oject, t he l aser s cribing beha vior of t he al ternative m ultilayer
back contacts on flexible substrates was investigated. The principle is shown in Fig. 1.
Figure 1: Schematic of a monolithic integrated CIGS – solar cell. The back contact is connected to
the front contact (serial connection of cells). [Source: ZSW, Stuttgart, Germany]
- WP 4: Design and testing of the rotatable cylindrical magnetron sputtering system A rotatable c ylindrical m agnetron was tested in the s ame s puttering c hamber t o c ompare t he s puttering
behavior t o t he generally used pl anar m agnetrons. These t ests were performed b y s puttering T i
and TiN.
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Accomplished Project Tasks and Results
1. Deposition and Characterization of Alternative Multilayer Back Contacts
In this work package the conventional back contact of a CIGS solar cell has been replaced by an alternative design, with the motivation to build a tunable and multifunctional back contact optimized for
polyimide substrates.
Combinatorial Design of Alternative Back Contact
The bac k c ontact des ign suitable f or CIGS s olar c ells on flexible pol yimide substrates has t o be
adapted to the polyimide and CIGS material properties. Moreover, the temperature cycles during the
whole solar cell production must be considered (mainly the high temperature step during CIGS deposition). Finally, the back contact must fulfill the following requirements:
-
Conductivity: The conductivity of the back contact is given by the sum of each layer of the stack,
and must be as a rule of thumb <1 Ω/square for modules and <0.4 Ω/square for lab solar cells.
-
Residual stress: Residual stress management is important because stress can result in cracking of
the films and, especially on polyimide foils, leads to deformation of the substrate (the foils bend to a
cylindrical shape). The thermally induced stress is also important due to the subsequent high temperature CIGS process (>450°C) and can be optimized by the material choice.
-
Interface formation: During CIGS growth, Mo is partially transformed to MoSe2, which forms a quasi-ohmic electrical interface between the back contact and the CIGS absorber. Therefore, a (thin)
Mo top layer is required in the multilayer back contact stack.
-
Stability: An impurity diffusion barrier can be used to improve the stability (e.g. against moisture) of
both the back contact. Additionally, this barrier layer also prevents impurity diffusion into the CIGS
absorber during the solar cell production and over the whole device lifetime.
In this project, two different approaches were used to meet the back contact requirements: (i) Modification of the conventional Mo-based back contact design and (ii) introduction of alternative materials
such as Ti and TiN. The multilayer back contact design was developed using results from single layer
experiments discussed in the next subsection.
Single Layer Experiments
The t rends obs erved f or an i ncrease i n s puttering p arameters ( power, pr essure, substrate bias an d
temperature) to the film properties (residual stress, resistivity, average reflectivity and stoichiometry) of
Ti, TiN and Mo are s hown in Tab. 1 . Ti shows l ow a nd mostly tensile residual stress due t o its l owdensity m icrostructure. T he app lication of a s ubstrate bi as l eads t o c ompressive s tress and a d ecrease in film resistivity. In case of TiN a significant improvement in stoichiometry was obtained when
applying a substrate bias. Mo is generally under compressive stress with nicely defined columnar and
dense microstructure. Changing both the power and pressure of the sputtering process can control the
residual stress of the Mo film, whereas the resistivity increases strongly with increasing pressure.
Ti
TiN
Mo
Increase in…
Power
Pressure
Substrate Bias
Temperature
Power
Substrate Bias
Temperature
Power
Pressure
Stress
↓ (t)
→
↑↑ (c)
↓ (c)
↓↓ (c)
↑↑↑ (c)
→
↑↑ (c)
↓↓ (c)
Resistivity
↓↓
↑
↓↓
(↑)
→
↓↓
↓
↓
↑↑
Reflectivity
↑
↓
↑↑↑
(↓)
→
↑↑
↑
↑
↓
Stoichiometry
↑↑
↑
-
Table 1: Summary of single layer experiments. The arrows show the tendency of the change in film parameters,
e.g. ↓: small decrease, ↑: small increase, ↑↑: moderate increase, ↑↑↑: strong increase, →: stays constant, -: not
evaluated. Values in brackets are no definitive trends. For the residual stress, (t) denotes tensile, (c) compressive
stress.
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In a ddition t o t he sputtering parameters, also the substrate m ovement during the deposition was investigated ( in-line deposition m ode). A summary of Ti film properties is shown in Tab. 2, where stationary, single- and multi-pass depositions are compared. The results show an improvement in Ti layer
quality w hen either multi-pass or stationary i s us ed instead of s ingle-pass dep osition. SEM c rosssection i mages for eac h depos ition mode show significant differences in m icrostructure (results not
shown here).
Substrate Movement
Mode
Single-pass
Multi-pass (28x)
Stationary
Stress
[MPa]
0
-78
-301
Resistivity
[µΩ cm]
87
75
52
Av. Reflectivity
(0.4-1.3 µm) [%]
27
39
60
Roughness
(RMS) [nm]
16.25
15.75
4.00
Table 2: Summary of Ti film properties resulting from different substrate movements during the sputtering deposition. All layers were sputtered at 2 kW.
Optimization of Alternative Multilayer Back Contact Design
The multilayer back contact optimization was performed applying the knowledge acquired in the single
layer experiments. The alternative back contact designs are fundamentally different compared to the
conventional design, because not only different sputtering conditions are used but also different materials are combined. Each material has its unique property, so that in combination this alternative back
contact superposes all these properties leading to a multifunctional back contact design.
In this work, Ti, TiN, and Mo was put into a
multilayer back contact stack, where
- Ti r elaxes t he r esidual s tress of t he bac k
contact du e t o i ts m atched C TE and d ifferent grain structure compared to TiN an
Mo
- TiN is a well-known impurity diffusion barrier, which protects t he b ack contact from
corrosion and the CIGS absorber from indiffusion of impurity
- Mo is strongly conductive and forms
MoSe2 during CIGS growth, which provides a quasi-ohmic interface between the
back contact and the CIGS absorber.
Figure 2: Three different back contact designs on polyimide
foils: t he m odified conventional M o bac k c ontact P I-1 w as
used a s a r eference and w as c ompared t o t he a lternative
back contacts PI-2 and PI-3.
In Fig. 2, a summary of different back contact designs is shown. PI-1 is a slightly modified conventional Mo back contact design and represents the reference contact, whereas PI-2 and PI-3 are alternative
back contact designs.
2. Processing of Flexible CIGS Solar Cells
The CIGS absorber is deposited with a multi-stage p rocess done by co-evaporation of the elements
Cu, In, Ga, and Se. Due to the lack of sodium in the polyimide and stainless steel foil, a post deposition treatment with NaF was used to improve the solar cell efficiency [1].
Empa has de veloped t wo different C IGS pr ocesses: a l ow and hi gh t emperature pr ocess. T he l ow
temperature pr ocess ( ~450°C) i s s uitable f or v arious s ubstrates, w here E mpa r ecently published a
new world record in efficiency of 18.7% on polyimide foils [2]. The 18.7% cell not only shows the highest efficiency value on polyimide, but also the best performance compared to any published result on
flexible solar cells. The low temperature CIGS process was developed at Empa within several projects
financed b y CTI, B FE and EU-FP7 and is s uitable f or polyimide, s tainless s teel, and a luminum substrates. The hi gh temperature pr ocess ( ~550°C) c an be us ed on ei ther s tainless s teel f oils or s odalime glass.
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Performance of CIGS Solar Cells with Alternative Back Contacts on Polyimide Foils
The per formance of C IGS s olar c ells pr ocessed o n polyimide f oils with t he c onventional (PI-1) and
alternative back contact designs (PI-2, PI-3) were investigated (see Fig. 2 for details). The PI-2 back
contact structure showed a significant improvement in CIGS adhesion and residual stress compared
to the PI-1 (Ref) back contacts (but at lower sheet resistance of 0.6 Ω/square). However, the solar cell
performance w as abo ut ~10% l ower ( relative) c ompared t o a Mo b ilayer r eference c ell ( same C IGS
run) [3]. Further i mprovements of t he al ternative bac k c ontact des ign ( PI-3) as w ell as on t he C IGS
process resulted in a improvement in solar cell performance, where only a loss in performance of ~3%
(relative) in comparison to the reference contact could be measured. The performance of the TiN layers as a barrier against moisture has still to be verified.
CIGS Solar Cells on Stainless Steel Foils
On stainless steel foils, different back contact designs were tested with both low and high temperature
CIGS process. For both processes a NaF post deposition treatment was done. In case of steel substrates, an impurity diffusion barrier layer must be used to prohibit iron diffusion into the CIGS absorber. It is well known that even a small iron concentration in the CIGS absorber leads to a decrease in
the s olar c ell per formance. I n t his w ork t he per formance of Mo based back c ontacts as an i mpurity
diffusion barrier against iron was evaluated and compared to back contacts with an additional TiN and
Si3N4 diffusion barrier layer. Solar cells on contacts with TiN and Si3N4 barrier coating showed no improvement in performance compared with the cells on Ti/Mo/Mo triple-layer contact, regardless of the
CIGS deposition temperature. The variation of the Mo back-contact designs with no impurity diffusion
barrier s howed a s ignificant d ecrease in s olar c ell p erformance w hen thin Mo c ontacts w ere used.
Furthermore, capacitance to voltage measurements showed a decrease in the carrier concentration in
CIGS gr own o n t hin Mo c ontacts compared with t he l ayers f or s olar c ells on Ti/Mo/Mo t riple layer
structures. Best cell efficiencies of 17.3% were obtained using a Mo back-contact with a thin Ti adhesion layer, in combination with a low-temperature CIGS deposition process with no additional oxide or
nitride impurity diffusion barrier layer on stainless steel foils. [4]
Deposition of ZnO:Al by Inline Pulsed-DC Magnetron Sputtering
ZnO:Al (also called AZO) is a transparent and conductive oxide (TCO) used as the front contact material f or CIGS s olar cells. In this project, the conventionally used RF magnetron s puttering pr ocess is
replaced by a pul sed-DC s puttering pr ocess, which i s bet ter s uited f or industrial production at l arge
scales. Due to the high sensitivity of CIGS to sputter damage and heat, the AZO process has to be
done under s pecial c onditions, which
will be evaluated during the project.
In F ig. 3 the r esistivity versus the
transmittance qua lity f actor ( TQF) for
single A ZO layers ar e s hown. T he
TQF r epresents a m easure f or the
transparency weighted by the spectral
response of a typical C IGS s olar c ell.
The resistivity of the samples deposited in s tationary mode is s ignificantly
lower c ompared t o layers gr own in
single-pass mode. This e ffect c an be
explained by sputter damage of negative ox ygen i ons r esulting f rom t he
race-track of the AZO target, which
lead t o a large r esistivity distribution
over the deposition area [5].
Both the r esistivity an d T QF was improved b y i ncreasing t he s ubstrate
temperature. Due t o t he s ensitivity of
the CIGS absorber, a maximum deposition t emperature of 150° C was chosen.
Figure 3: Summary of AZO single layer results (on glass). The
deposition t emperature s howed a s ignificant ef fect on bo th t he
conductivity and t ransparency. Further the conductivity is strongly
enhanced in stationary deposition mode.
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3. Laser Scribing and Patterning of Modules
The development of monolithical series interconnection by laser patterning required the minimization
of all losses introduced by this technique. First of all, it necessitates very precise positioning of each
scribing step with respect to the previous one, since the area between the P1 scribe line (done after
back contact deposition) and the P3 scribe line (done after front contact deposition) does not contribute t o c urrent g eneration and is t hus t o b e m inimized. The industry par tner Flisom has des igned
equipment to perform this detection and positioning process with high accuracy.
An important result of this work was the successful fabrication of monolithically (laser-)interconnected
2
2
2
modules of different sizes (13 cm and 144 cm ). The 13 cm 8-cell modules feature a multi-layer Mo
back-contact. An example module is presented in Fig. 4.
2
Figure 4: Left: 13 cm 8-cell m odule m anufactured c ollaboratively bet ween Empa (material d eposition) an d
2
Flisom ( laser scribing). T he active ar ea is 12 cm . R ight: Performance measurement of an 8 -cell module ( independently measurement by ZS W in G ermany). The overall ef ficiency is 13.6% and t he active area ef ficiency is
14.7%.
4. Integration of Rotatable Cylindrical Magnetron Sputtering System
W. Blösch AG as the main industry partner developed in collaboration with the company Pivot A.S. the
design of the rotatable cathode including its integration-chamber. This system was built and integrated
to the sputtering machine at Empa. The rotatable cathode was tested with a Ti target, where layers of
Ti and TiN were deposited under various conditions. In comparison to the planar cathode, the Ti layers
showed slightly improved quality (conductivity). However, it was found that stoichiometric deposition of
TiN is more challenging t o c ontrol, because of the c onstant change in v oltage a rose f rom the target
rotation. A plasma emission monitor (PEM) system could be used to overcome this problem.
National / International Cooperation
In t his C TI pr oject, t he La boratory f or T hin F ilms and P hotovoltaics at E MPA in D übendorf worked
close together with its industry partners, which are: W. Blösch AG as the main industry partner, and
Flisom AG as the second industry partner. Furthermore, this project has a small overlap with EU-FP7
hipoCIGS project, where six additional European R+D and industrial partners are involved.
References
[1] D. Güttler, et. al : Influence of N aF I ncorporation d uring C u(In,Ga)Se2 Growth on Microstructure a nd P hotovoltaic
Performance, 35th IEEE Photovoltaic Specialists Conference (PVSC), 3420-4, 2010.
[2] A. Chirilă, et. al: Highly efficient Cu(In,Ga)Se2 solar cells grown on flexible polymer films, Nature Materials, 10, 857861, 2011.
[3] P. Blösch, et. al : Optimization of Ti/TiN/Mo back contact properties for Cu(In,Ga)Se2 solar cells on polyimide foils,
Thin Solid Films, 519, 7453-7457, 2011.
[4] P. Blösch, e t. a l: Comparative Study o f D ifferent B ack-Contact D esigns f or H igh-Efficiency CIGS Solar C ells o n
Stainless Steel Foils, IEEE Journal of Photovoltaics, accepted for publication, DOI: 10.1109/JPHOTOV.2011.2166589.
[5] K. Ellmer: Magnetron sputtering o f transparent co nductive zinc oxide: relation b etween the sputtering p arameters
and the electronic properties, Journal of Physics D: Applied Physics 33, R17–R32, 2000.
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APOLLO
EFFICIENT AREAL ORGANIC SOLAR CELLS
VIA PRINTING
Annual Report 2011
Author
Authorand
andCo-Authors
Co-Authors
Address
Project- / /Contract
Number
Institution
Company
Date
Address
1
1
1
1
1
B. Ruhstaller , N. A. Reinke , M. Neukom , S. Züfle , R. Ritzmann ,
2
2
2
2
G. Nisato , T. Offermans , J. Schleuninger , M. Chrapa ,
3
3
4
4
4
M. Turbiez , M. Düggeli , M. Wienk , R. Janssen , S. Kuijzer ,
4
5
5
5
K. Sastrowiardjo , G. Garcia-Belmonte , J. Bisquert , P. Boix
1
2
3
ZHAW, Winterthur / CSEM, Basel / BASF, Basel
4
5
TU Eindhoven, Netherlands / Universitat Jaume I, Spain
1
Wildbachstrasse 21, 8401 Winterthur
Mattenstrasse 22, 4058 Basel
ABSTRACTE-mail, Homepage 1 +41 58 934 7836, [email protected], www.zhaw.ch
Telephone,
Project/ Contract
SI/500122 der
– SI/500122-01
/ 102738/153575
Das Abstract
soll Number
eine Zusammenfassung
Ziele und der
wichtigsten Resultate des Projekts in
Duration
of theenthalten.
Project (from
to) darf
01.11.2008
– 01.04.2011
kurzer Form
Der–Text
nicht länger
sein als das vorgegebene Feld. Das Abstract ist in
Date
01.10.2011
englisch zu verfassen.
2
ABSTRACT
Bitteproject
beachten
für die Erstellung
des Berichts
folgende
Richtlinien:
This
aimsSie
to combine
plastic electronics
expertise
in Europe
for realising organic solar cells for
empowering
printed
electronics
applications.
Existing
solar
cell
technologies
cannot
theProjekpoten•
Passen Sie das vorgegebene Inhaltsverzeichnis nach Bedarf an Ihr Projekt
anprovide
(bei P+D
tial attributes
such
as
printability
in
ambient
conditions,
flexibility
and
low
cost.
These
research
ten kann z.B. häufig auf das Kapitel 'nationale / internationale Zusammenarbeit' verzichtet topics
wercarry den).
high innovation potential and unique selling points for Europe. If successful they open up new
markets for the European high-tech industry allowing for Europe to take a leading position in printed
•
Seitenzahl:
maximal
electronics
and solar
cells. 8 Seiten pro Bericht (Titelblatt inbegriffen).
• far,Illustrationen:
ein oder
mehrere
Fotos,
und Diagramme
sind vorteilhaft.
So
the development
of organic
solar
cells Schemata
was to a large
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trial-and-error process,
in which organic
semiconducting
materials were selected on the basis of their known or partially
•
Schriftart:
Arial 10
pt.
known separate properties. It has recently become clear that this provides an insufficiently sound basis
• a further
Ränder:
links 3cm und
2 progress,
cm frei lassen
(entsprechend approach
dem vorliegenden
for
development.
Forrechts
further
an interdisciplinary
with newText).
materials, device
concepts,
modelsd,and
methods is critical.
•
Sprachen:
f, i,characterisation
e
The focus of this project is on single cells and tandem cells with record efficiency that feature ease of
production and proof-of-principle for the interdisciplinary research approach. The detailed understandDie Jahresberichte sind dem Programmleiter wie folgt einzureichen:
ing of device operation allows for steady improvements in efficiency.
- 1 Version als Word- und als pdf-Datei.
119/394
Introduction
Polymer solar cells convert sunlight directly into electricity via a complex sequence of events (cf. Figure 1), starting with the absorption of light (1), followed by creation of an exciton (2), dissociation of the
exciton (3), transport (4,5) and collection of charges. The expectation that lightweight, flexible, and
large-area polymer solar cells can be produced at low cost, in combination with high energy efficiencies spurs a worldwide fast-growing interest in this area. Not all of these attractive properties have
materialised and although evidence is building up that polymer solar cells may live up to this appealing
scenario in the future, new inventions have to be made. Presently, state-of-the-art polymer solar cells
have reached power conversion efficiencies of 8% [1]. Projected efficiencies of 10% seem within
reach and expectations for the future are even higher.
Figure 1: Standard device setup of a polymer bulk heterojunction solar cell.
The active layer is the P3HT:PCBM layer.
Most polymer solar cells rely on a photo-induced charge-transfer reaction at the interface of an acceptor and a donor type organic semiconductor which are combined into a bulk heterojunction to generate
charges in a process that mimics natural photosynthesis. Following this event, charges must escape
from recombination, separate spatially, migrate to the appropriate electrode and finally be collected.
Each of these processes poses intriguing scientific questions and exciting challenges to materials
design to make the overall conversion both quantum and energy efficient. With the continuing increase
in power conversion efficiency, it is clear that the field of polymer solar cells has progressed in the last
five years from a scientific curiosity to a stage that it is now on the brink of a breakthrough technology
2
for the future. Yet, the transfer from test-type devices that are typically 5-100 mm in size to real large
2
areas (1 m ) does require new concepts in cell design and large-area processing.
The power conversion efficiency of any polymer solar cell depends critically on the quantum efficiency
of photon-to-electron conversion that determines the current and the potential energy efficiency that
describes how much of the initial photon energy (eV) is preserved at the operating voltage of the cell.
The past years we have witnessed a strong innovation in the development of polymers that have a
small bandgap and are able to absorb up to the near infrared. Despite their high and promising efficiencies, the maximum EQE of these cells is still lower compared to the cells that absorb light in the
visible region only. If for these low-bandgap cells the quantum efficiency could be improved, cells with
10% efficiency or more are within reach.
Tasks of the collaboration partners
New materials (BASF, TUE): BASF competence in synthesising tailor-made materials for a variety of
dye applications is crucial for this project. The challenge in the design of synthetic organic semiconductors for solar cells is to optimise the absorption spectra (for matching the illumination), the transport
energy levels and mobilities (for low electrical losses) as well as the electron-hole binding energy (for
efficient dissociation). Solubility and printability concerns add additional constraints.
A new series of small-bandgap donor-type polymers with high intrinsic charge carrier mobility and
energy levels that are optimised for charge carrier generation in combination with PCBM need to be
synthesised. Of the most promising materials multi-gram quantities will be available for further studies
and printing at the other partners.
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APOLLO, B. Ruhstaller, ICP ZHAW
Cell o ptimisation a nd n ew c oncepts (T UE, CSEM): Even though the excited-state energy of the
absorbing solar cell material can be as high as 2 eV, the open-circuit voltage is typically as low as
0.6V. This represents a loss by a factor of 3 and is one example of the room for improvement. While
high efficiencies and innovative concepts were demonstrated with multi-cell stacks at TUE, in this project we will focus on low-complexity cell concepts that are feasible for printing. Solution-processed
organic solar cells rely on bulk heterojunctions that must separate the charges effectively. These
blends must be optimised for high efficiency, open-circuit voltage and fill-factor. Combinatorial device
fabrication by use of a high-throughput pipetting robot (cf. Figure 2) and automatic characterisation
has proven highly useful for OLED research and development at CSEM and shall be explored for solar
cells.
The active layers need to be fully characterised with respect to their morphology and optical absorption. The IQE, EQE, and J-V characteristics of the devices will be characterised to determine the major
loss mechanisms and –hence – identify opportunities for further optimisation.
Figure 2: CSEM’s ink-jet printer (left) and the high throughput fabrication robot (HTF-7)
for polymer devices based on a modified pipetting robot (right).
Cell c haracterization m ethods and to ols (U JI, TUE, C SEM, Z HAW): Electrical characterisation of
solar cells by impedance spectroscopy has been pioneered at UJI for dye sensitised solar cells.
Equivalent circuit models are physically motivated and able to reveal loss mechanisms. While impedance spectroscopy has also been employed in the past to study OLEDs, little is known in the context
of organic solar cells and the numerical modelling thereof.
Cell modelling (ZHAW, UJI): A comprehensive device model for the study of operation mechanisms
and the interpretation of measured data will be developed. It will cover the whole process chain from
light absorption, exciton dissociation, charge carrier transport and collection by electrodes. The ZHAW
has expertise in numerical modelling of opto-electronic processes in transient and steady-state in
OLEDs. The maximum achievable short-circuit current will be addressed with optical simulations that
provide the spatial exciton generation rate density. It is intended to distinguish the detrimental effects
of charge trap, recombination and collection losses by the use of drift-diffusion simulations.
Cell prototyping (CSEM): CSEM has established organic layer deposition by spinning, ink-jetting (cf.
Figure 3), screen printing as well as hot-embossing of 3D structures as part of an EU-project
(“ROLLED”) on roll-to-roll OLED fabrication. The printing challenges arise with viscosity constraints,
interface roughness, thickness non-uniformity etc. and lead to a reduction of the record efficiencies
compared to spin-coated devices.
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Performed work and achievements
WP1 (Materials: BASF, TUE)
BASF has been focusing on synthesizing new donor materials for organic bulk heterojunction cell architectures. The materials were distributed to CSEM and TUE for device fabrication. BASF emphasises on printing technologies and investigations on suitable solvents. Figure 3 shows the EQE (external
quantum efficiency) of two cells built with the new donor material and two different acceptor materials.
This example shows the superior performance of the cell with the [70]PCBM acceptor.
Figure 3: EQE measurements for cells comprising the new material as donor and [60]PCBM (red)
respectively [70]PCBM (black) as acceptor.
WP2 (Cell optimisation and new concepts: TUE, CSEM, ZHAW)
The Technical University of Eindhoven and the Centre Suisse d'Electronique et de Microtechnique
fabricated spin-coated solar cells based on materials provided by BASF. The influence of the fabrication parameters such as the choice of solvents and the layer thickness on the blend layer morphology
was analysed by various techniques such as AFM (atomic force microscopy), TEM (transmission electron microscopy) and electron tomography.
Maximum power conversion efficiencies close to 6% were achieved. Moreover new concepts for tandem cells were investigated and an algorithm for cell optimisation was developed at TUE. This algorithm allows to estimate key figures such as the short-circuit current, the fill factor and the maximum
power point based on single cell units and simulations with the software SETFOS. The predictions
could be validated experimentally. Tandem cells with an open-circuit voltage of 1.4 V and a power
conversion efficiency slightly above 6% were achieved, which are very promising results. Several scientific publications in this context were published recently by TUE [2-6].
Concerning single cells, TUE and CSEM extensively investigated the influence of different solvents
and solvent mixtures with varying mixing ratios with regard to fabrication issues and cell performance.
Thus, optimum solvent mixing ratios could be obtained that not only lead to high efficiencies but also
allow for inkjet-printed processing. Figure 4 exemplarily shows how crucial the solvents influence the
solar cell parameters.
Figure 4: JV measurements on OSC fabricated at TUE with varying content of o-DCB in Chloroform.
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WP3 (Cell characterisation methods and tools: UJI, TUE, CSEM, ZHAW)
The Zurich University of Applied Sciences and the University Jaume I in Castelló extracted device and
material parameters by advanced experimental methods for solar cells that were fabricated at CSEM
Basel.
At UJI the focus was set on impedance spectroscopy, where a DC offset voltage modulated by a
small-amplitude sine voltage is applied to the cell and the transient current response is measured.
Thus the capacitance of the device can be obtained. UJI developed various models in order to extract
the charge carrier densities, estimate the electrical field profile, defect density-of-states, the dielectric
constant, and series resistance (shown in Figure 5).
Figure 5: The measured complex impedance Z as a function of frequency is illustrated as a polar plot.
Extraction of the series resistance from the high-frequency limit (right).
At the ZHAW an integrated measurement system for steady-state, transient and photo-CELIV characterisation for model-based parameter extraction was developed. The measurement setup includes an
integrated amplifier for both illumination and photocurrent at extremely low series-resistances (1 Ω)
and a significantly improved signal-to-noise ratio by on-board high-frequency connectors. The measurement system allows to extract material parameters such as field-dependent mobilities and to investigate electrical loss mechanisms.
A second measurement setup was built in order to vary the cell temperature, as it is known that many
device and material parameters such as charge carrier mobilities and injection barriers are strongly
temperature-dependent. The variation of the temperature from 15 to 65 °C was achieved using a
Peltier module. Figure 6 shows the measured JV-characteristics as well as the temperaturedependence of the open-circuit voltage.
Figure 6: Temperature-dependent dark JV-characteristics in a semi-logarithmic plot (left).
Dependence of the open-circuit voltage on temperature and light intensity,
as measured and fitted using an analytical formula (right).
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WP4 (Cell modelling: ZHAW, UJI)
At UJI various models to analyse the measurements were developed accounting for inhomogeneous
electric fields and defect states as well as doping. Defect states might have negative effects on the
solar cells performance. Charged defects within the bandgap alter the electrical field-profile and might
reduce the drift-driving force for carrier transport, and consequently diminish carrier collection at the
contacts. In extreme cases, the electrical field can be even suppressed in a significant portion of the
active layer. UJI analysed polymer gap-states as a function of temperature by impedance spectroscopy and transient measurements of the open-circuit voltage. The variation of Voc was obtained by
varying the illumination intensity. The results obtained by UJI have been published recently [11].
An accurate determination of the charge carrier mobilities is essential to model and improve organic
solar cells. A frequently used method to determine charge carrier mobilities is the CELIV technique
(charge extraction by linearly increasing voltage). In this technique a voltage ramp is applied to the
device in order to extract free charge carriers inside the bulk. The free charge carriers can be created
by injection or by a short light flash (photo-CELIV). With a simple analytical formula the mobility is
commonly estimated on the basis of the temporal position of the current peak. We simulate the photoCELIV experiment with a fully-coupled electro-optical model and measure dark-CELIV, photo-CELIV,
transient photocurrents and steady-state current-voltage curves of an organic bulk heterojunction solar
cell. By fitting our numerical model to the multiple transient and steady-state curves we show that important material parameters like the electron mobility, hole mobility, charge generation and recombination efficiency can be determined using numerical parameter extraction [7,8].
The series resistance of the experimental setup strongly influences the transient response as well as
the steady-state characteristics of the device and can therefore not be neglected in the simulation
[7,8]. It can be extracted by applying a small voltage pulse and measuring the slope of the responding
displacement current. The dielectric constant of the organic material can be analysed from the equilibrium current in the CELIV measurements. By varying the light intensity, an effective photon-to-charge
conversion efficiency can be obtained from the JV-curves, which is implemented in the simulation. Any
other parameters such as charge carrier mobilities, recombination efficiency, injection barriers and
density of chargeable sites are extracted by a fitting algorithm comprising a nonlinear least-square
method. Thus, multiple curves of different measurement techniques with several light intensities, offset
voltages or voltage ramps can be fitted simultaneously with a single set of parameters.
Figure 7: Measured and simulated measurements for various measurement techniques established at ZHAW.
All measurements have been fitted simultaneously with a single set of parameters, thus minimizing
correlations and enhancing accuracy.
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In Figure 7 a result of such a measurement and simulation procedure is shown. Here, measurements
of four different techniques, each with variation in one parameter (light intensity or voltage ramp, respectively) have been fitted simultaneously resulting in a unique set of parameters that represents the
device. We could show that assuming constant charge carrier mobilities and thereby neglecting any
field-dependence already gives very good results for the investigated devices. Also, no trapping of
charge carriers is considered here. Our CELIV analysis results were published recently [7,8].
WP5 (Cell prototyping: CSEM)
Structural ordering of the polymer chains and the resulting improvement of the carrier mobility is favourable in achieving efficient solar cells. Direct evidence of crystallinity in our polymer films is given
by x-ray diffraction (XRD) data. Measurements made at CSEM show the structural ordering corresponding to the inter-chain spacing and the π-π stacking between the molecules.
The morphology on a larger length-scale resulting from de-mixing of the polymer and the fullerene in
the blended film is critical for efficient device performance. AFM can give some indication about the
morphology of the film. The morphology of the active layer is influenced by the choice of solvent, annealing conditions, drying rate, and the deposition method. This affects the optical parameters of the
cell.
CSEM achieved ink-jet printing of polymer blends with a good layer-uniformity by tuning solventmixture composition, concentration, print-head velocity and dot-spacing. Polymer solar cells have
been fabricated based on the ink-jet printed active layer. By optimising the printing parameters, power
2
2
conversion efficiencies of ~4.5% for 0.04 cm inkjet-printed cells and ~3.4% for 1 cm inkjet-printed
cells have been achieved. Figure 10 shows AFM images of layers processed with two different solvent
mixing ratios. The obtained results on printed solar cells were published recently [9,10].
Figure 8: Absorbance of solvents with different mixing ratios.
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Assessment of achievements
In the first project year, the consortium was quickly getting up to speed with respect to fabricating devices based on new polymers from BASF. In the second year the characterization of basic material
properties has indicated that the new materials enable potentially very good solar cell performance.
The project partners that do not have device fabrication facilities available received cells fabricated by
CSEM and investigated them further by dynamic electrical characterization techniques and modeling.
The spin-coated cells were optimized to achieve nearly 6 % power conversion efficiency while the inkjet-printed cells reach up to 4.5%. An efficiency of 3.4% was achieved for solar cells printed by CSEM
2
with relevant cell sizes of 1 cm . Moreover, optimized tandem-cells with power conversion efficiencies
above 6% were achieved. Defect states in organic solar cells have been analyzed by impedance
spectroscopy. Novel experimental and numerical characterization tools based on the photo-CELIV
method were developed at the ZHAW which allow extraction of material parameters in organic solar
cells.
It is noteworthy, that in addition to the scientific and technological achievements this project was also
successful in terms of extending international collaborations. In fact, the project partners are part of a
new, bigger consortium that launches a European research project on organic solar cells in the
framework of FP7 in Fall 2011.
References
[1]
Record power conversion efficiency of 8.3% reported in a Konarka press release, November 2010
[2]
J. C. Bijleveld, A. P. Zoombelt, S. G. J. Mathijssen, M. M. Wienk, M.Turbiez, D. M. de Leeuw, and R. A. J. Janssen,
“Poly(diketopyrrolopyrrole-terthiophene) for ambipolar logic and photovoltaics”, J. Am. Chem. Soc. 2009, 131, 1661616617.
[3]
J. Gilot, M. M. Wienk, and R. A. J. Janssen, “Optimizing polymer tandem solar cells”, Adv.
[4]
J. C. Bijleveld, V. S. Gevaerts, D.Di Nuzzo, M. Turbiez, S. G. J. Mathijssen, D. M. de Leeuw, M. M. Wienk, and
R. A. J. Janssen, “Efficient solar cells based on an easily accessable
diketopyrrolopyrrole polymer”, Adv. Mater.
2010, 22, E242–E246.
[5]
G. Lakhwani, R. Roijmans, A. J. Kronemeijer, J. Gilot, R. A. J. Janssen, and S. C. J. Meskers,
“Probing charge
carrier density in a layer of photodoped ZnO nanoparticles by spectroscopic
ellipsometry”, J. Phys. Chem. 2010,
114, 14804-14810.
[6]
J. Gilot, M. M. Wienk, and R. A. J. Janssen, “Measuring the external quantum efficiency of
dem solar cells”, Adv. Funct. Mater. 2010, 20, 3904-3911
two-terminal polymer tan-
[7]
M. Neukom, N.A. Reinke, K.A. Brossi, B. Ruhstaller, “Transient Photocurrent Response of
tion Solar Cells”, Proc. SPIE 2010, 7722 30
Organic Bulk Heterojunc-
[8]
M. Neukom, N.A. Reinke, B. Ruhstaller, “Charge extraction with linearly increasing voltage: A numerical model for parameter extraction”, Sol. Ener. 2011, 85, 1250-1256
[9]
T. Offermans, J. Schleuniger, G. Nisato, “Inkjet Printing of Polymer Solar Cells”,
Proceedings of the Large-area, Organic & Printed Electronics Convention 2010
ISBN 978-3-00-029955-1 © OE-A 2010
Mater. 2010, 22, E67-E71.
(LOPE-C 2010), pages 99-102.
[10] T. Offermans, J. Schleuniger, G. Nisato, “Ink-jet printing of polymer solar cells”, Plastic Optoelectronics workshop June
2010, Basel CH
[11] G. Garcia-Belmonte, P. P. Boix, J. Bisquert, M. Sessolo, H. J. Bolink, “Simultaneous determination of carrier lifetime
and electron density-of-states in P3HT:PCBM organic solar cells under illumination by impedance spectroscopy”,
Sol. Ener. Mat. Sol. Cells 2010, 94, 366-375
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HIOS-CELL
NANOSCALE STRUCTURING OF HETEROJUNCTION IONIC ORGANIC SOLAR CELLS
BY LIQUID-LIQUID DEWETTING
Annual Report 2011
Jakob Heier, EMPA
Jan Groenewold, University of Utrecht, Netherlands
EMPA Dübendorf
Address
Überandstrasse 129, 8600 Dübendorf
Telephone, E-mail, Homepage 044 823 55 11, [email protected], www.empa.ch
SI/500297 – SI/500297-01
Date
27.03.2011
ABSTRACT
To enable the use of highly light absorbing cyanine dyes for organic solar cells, we investigated the
possibility to establish bulk heterojunction film morphology of cyanine dye / PCBM blends. We could
develop a comprehensive model that explains how the interactions between counter ions and PCBM
determine the phase domain size. The phase morphology evolves through liquid-liquid dewetting, a
mechanism that may play a role in numerous systems where blend films are produced from solution,
but is not recognized as such. In our case, net charges (counter ions diffusing into the PCBM phase)
stabilize a transient layer system. Depending on the affinity of the counter ion to PCBM, the phase
dimensions can be controlled. We investigated one cyanine dye chromophore (1,1’-diethyl-3,3,3’,3’tetramethylcarbocyanine) with the five different counter-ions iodine (I¯ ), perchlorate (ClO4¯ ),
hexafluorophosphate (PF6¯ ), tetraphenylborate (B(Ph)4¯ ) and a nickel-complex¯. The range of
phase dimensions spans more than 2 orders of magnitudes, with structures in the micrometer range
(iodine) down to 20 nm (nickel-complex).
A particular feature of cyanine dyes is their ability to form aggregates. Using liquid-liquid dewetting as
structure determining mechanism, dye aggregation can now be controlled. Delocalization of the excited state makes aggregates potentially useful for photovoltaic applications.
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Objectives
To manufacture organic thin film photovoltaic devices, a generally followed approach is to blend an
organic absorber with an electron accepting material in solution and then coat one electrode with that
solution. Cyanine dyes are cationic dyes, and their demixing behaviour may differ from conventional
phase separation. This work aims at understanding and tuning the self-organisation properties of molecular ionic blends in thin films, and to straighten the path to use these materials in all-organic solar
cells.
During solvent evaporation, phase separation sets in (solvent quench) and a phase separated structure is immobilized. By blending cyanine dyes with the soluble electron acceptor PCBM, the phase
morphology develops via a process called liquid-liquid dewetting. Liquid-liquid dewetting can generate
phase morphologies with lateral dimensions in the range of the exciton diffusion length, but the process as such, especially the conditions that lead to phase structures on a nanoscale level, is not understood at all.
The complexity stems from the fact that during solvent evaporation the individual interactions between
the molecules become increasingly important, while solvation effects have less and less influence.
That is especially important as we are dealing with cationic dyes where solvated counter ions introduce electrostatic interactions.
Furthermore, the particular features of cyanine dyes, such as aggregation and mobile counter ions can
have desired but also averse effects for photocurrent generation in organic solar cells. We are aiming
at pointing at approaches how to utilize these particularities.
In order to achieve the project goals, the following scientific objectives were addressed:
1. A detailed investigation of the liquid-liquid dewetting process.
2. Identification of the processing window that allows adjusting a nano-scale phase morphology.
3. Implement the findings in thin film solar cell geometries.
4. Investigate aggregation and ion diffusion and its influence on solar cell performance.
Experimental
Sample preparation: Materials were purchased from Solenne B.V. (PCBM), FEW Chemicals (the dyes
CyI, CyP and CyB with the counter ions I¯, PF6¯ and B(Ph)4¯ , respectively) or synthesized in our
own laboratory (CyC, CyNi with the counter ions ClO4¯ and nickel complex).
Dye and PCBM were dissolved in the common solvent chlorobenzene (CB) and then spin coated onto
ITO coated glass substrates. Thicknesses were adjusted by varying the concentration and spin speed.
PCBM was selectively removed by immersing the samples in hexane for up to 3 minutes in an ultrasonic bath, the dyes were selectively removed by immersing in 2,2,3,3-tetrafluoropropanol (TFP) for 3
seconds. Al was deposited by vacuum thermal sublimation.
The morphology of the samples was determined with Scanning Force Microscopy (SFM). The instrument used was a Nanosurf Mobile S in tapping mode at a resonance frequency of 170 kHz.
Attenunance spectra were measured on a Varian Cary 50 UV-Vis spectrophotometer.
Current-voltage (J-V) characteristics were measured under simulated solar irradiation using the spectrum of a 300 W Xe lamp together with an AM1.5G filter set. The light intensity was calibrated in order
to correspond to standard solar irradiation at 100 mW cm-2 for full sun. A monochromator was used
together with the Xe lamp to measure the incident photon-tocurrent conversion efficiencies (IPCE).
Rutherford b ackscattering (RBS) was used to quantify the amount of counter ions present in the
PCBM phase. The sample surface is bombarded by a beam of 4He ions at an energy of 2MeV and the
energy of elastically scattered beam particles is measured in a detector under a backward angle. The
scattering cross-sections are tabulated and quantitative information on the presence of counter ions is
obtained.
Conductometry was performed on a conductometer KNICK703 and a 4-Pol-Cell KNICK SE204. The
conductivity range of the instrument is in the range of 1.00 μS cm-1 bis 500 mScm-1. The value of the
-1
cellconstant is about kz ≈ 0.5 cm .
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HIOS-CELL, J. Heier, EMPA
Approach
Figure 1 shows the chemical structure of the materials our investigation is based on. The dye with the
counter ion ClO4¯ and PF6¯ has been successfully used in a bilayer solar cell with C60 as an electron
acceptor and acts as our starting material. The energy levels of the dye, C60 and PCBM for comparison are depicted in Figure 2. We believe that the energy differences in HOMO- and LUMO-levels between C60 and PCBM should not dramatically change the exciton dissociation properties at the donoracceptor interface. Blending the dye with the counter ion ClO4¯ and PCBM leads to a laterally phase
separated morphology resulting from a liquid-liquid dewetting process [12].
Figure 1: Chemical structure of PCBM and the dye chromophore 1,1’-Diethyl-3,3,3’,3’tetramethylcarbocyanin Cy. The dye is accompanied by a counter ion X.
Figure 2: HOMO and LUMO levels of the dye CyC, C60 and PCBM
In a first step the chemical structure of the dye was modified such that a phase morphology on a
nanometer level could be obtained. What will remain a challenge are the facts that any modification in
structure may change HOMO and LUMO levels; even worse, we realized that counter ion diffusion into
the PCBM phase occurs and introduces vacuum energy level shifts between the two phases.
In phase 2 we envisioned two device geometries that account for the specific properties of cyanine
dyes and allow examining the photovoltaic properties.
A first envisioned device concept is of type “enhanced interface bilayer heterojunction” whereby the
morphology develops during a single spin coating step from a blend solution of a cyanine dye and
PCBM through self-organization. By realizing different morphologies in a controlled manner, we hoped
to gain insight into structure – performance relations.
The second envisioned architecture can be described as a “dye-sensitized doubleheterojunction” device. Here, the cyanine was sandwiched between two materials that act as an electron donor and as
acceptor with respect to the cyanine, respectively. We demonstrated already that a device of that type
can be manufactured in three consecutive coating steps from different solvents. We intended to simplify the device fabrication to a two-step process where a cyanine-acceptor mixture is coated on a
suitable donor layer. During the course of the project, we realized that liquid-liquid dewetting induces
dye aggregation at the PCBM interfaces. This “new” species can has interesting photo-physical properties and can eventually be exploited for PV. Ultimately, the envisioned device architecture dyesensitized double-heterojunction can be realized that way in a single spin coating step.
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Results and Discussion
MORPHOLOGY
As a first result we could show that by simply changing the counter ions, a rich variety of morphologies
can be obtained. This can be rationalized with differences in solvation behavior, and consequently
differences in ion association which in turn leads to differences in the entropic contribution to the free
energy of mixing.
This is an important insight as it allows us to focus on one dye chromophore that showed promising
results in bilayer cells with C60 as an electron acceptor.
Chemical structures of the tested counter ions are summarized in Figure 3 and examples of observed
morphologies for all counter ions are depicted in Figure 4. We notice that the morphologies differ
markedly, and most importantly with respect to an envisioned application in photovoltaics, we note
huge differences with respect to the lateral dimensions. While the lateral phase features observed with
the counter ions I¯, ClO4¯ and PF6¯ seem not suited for PV, the scales reached with the counter ion
Ni-complex are very close, if not even sufficient to support a bulk heterojunction morphology.
Figure 3: Chemical structure of the counter ions iodine (I¯), perchlorate (ClO4¯), hexafluorophosphate (PF6¯),
tetraphenylborate (B(Ph)4¯ ) and a Nickel-complex¯.
In the following we investigated which properties of the counter ions cause that large difference in
blend structure; we want to note that this is not a trivial problem as there are numerous parameters
(such as interaction parameter, solubility, ion dissociation) that can influence structure formation in
various stages of the process (in the dilute solution, in a final solid state). We finally were able to show
that for all dyes the basic underlying structuring mechanism is the same.
We hereby focused on the differences between the counter ion groups I¯, ClO4¯, PF6¯ (group A) and
B(Ph)4¯, Ni-complex (group B). As film formation strictly spoken starts from a diluted solution, we have
to assume that the solution properties are of importance, if they do not even fully determine the evolution of the final morphology.
ION DISSOCIATION & SOLUBILITY
Ion dissociation in solution was measured by conductometry. The results are shown in Figure 5 for the
counter ions ClO4¯ (group A) and B(Ph)4¯ (group B). Analytical models are available for the two limiting cases of a strong and a weak electrolyte. Unfortunately, none of the curves follows any of the
models, suggesting that in both cases an intermediate state is present. Consequentially, we cannot
easily extract any equilibrium constants, but from the slopes we can estimate the fraction of dissociated counter ions. We find one out of 1000 counter ions is dissociated in the case of ClO4¯ (group A),
while 1 out of 200 counter ions is dissociated in the case of B(Ph)4¯. Solution concentration dependent
peak shifts in NMR are also suitable to detect ion dissociation, and they confirm the measured weak
ion dissociation.
Ion dissociation in the solid state has been investigated with ion beam techniques and UVV is spectroscopy. Blend films have been prepared and the dye phase has been removed with a selective solvent. With UV-Vis, the fraction of PCBM that also has been removed and the fraction of dye chromophore that remained in the sample has been determined. In the same samples, the amount of counter
ions remaining in the PCBM could be determined. For the film samples we can hereby confirm the
results of very low ion dissociation for the group A counter ions from the solution results. We find significant ion dissociation for the nickel complex.
Dye solubilities show an interesting behaviour when PCBM is added. While the solubility of the pure
dyes does not differ much from counter ion to counter ion, pronounced differences in behaviour between group A and B become visible. Adding a small amount of PCBM to the solution leads to a significant increase in solubility for dyes of the group B.
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Figure 4: Differences in conductivity of one dye from the group A (counter ion ClO4¯) and B (counter ion B(Ph)4¯)
as a function of solution concentration. The higher conductivity of dye CyB indicates a higher ion
dissociation
The experiment as such had been motivated by the conductometry measurements (Figure 4), there
we already noted that blending PCBM increases the conductivity: even though the curves seem to fall
on top of each other, the blend film has a higher viscosity, therefore similar conductances can only
stem from higher ion dissociation. These findings point to an affinity of the counter ions of group B to
PCBM. This affinity then seems to be the cause for increased dissociation of counter ions (into PCBM)
in this counter ion group.
MODELLING
We here summarize the findings of the property differences between the two groups of counter ions.
To then further deepen our understanding of the processes at play, these findings entered molecular
modelling and simulations on the system (University of Utrecht).
- For both groups, in a diluted solution of chlorobenzene, the ions are neither fully dissociated nor
fully associated; from the slopes of the conductance plots we estimate a degree of dissociation
of 1/1000 for group A, and 1/200 for group B.
- That is consistent with a very weak ion dissociation suggested by NMR.
- Ion beam techniques allow an estimation of the fraction of counter ions that are present in the
PCBM phase in the solid film.
- The solubilities of all dyes are rather similar, but the most remarkable fact is that for the counter
ions of group B we observe an increase of solubility upon adding PCBM. We thus can postulate
an attractive force between these counter ions and PCBM.
The simulations suggest that the thinning films will develop a layer system. The periodicity of the layer
structure depends on the amount of counter-ions that dissociate from the chromophore and are located within the PCBM containing phase. By only making a few assumptions, we can develop a model
that accounts for all morphologies.
- Counter ions can dissociate from the dye chromophore and can be located in the PCBM rich
phase.
- The quantity of counter ions located in the PCBM phase depends on a specific interaction
between counter ion and PCBM.
- This specific interaction is increasing from group A to B.
- This charge transfer will stabilize a layered morphology in the thinning film.
- The periodicity of the layer system depends on the amount of counter ions within the PCBM phase.
- Unless the layer periodicity is very small, the layers will align parallel to the interfaces.
- The layered system will eventually break up by interfacial instabilities.
- An unstable layer will lead to a droplet phase. The lateral dimensions of the droplets are a measure
of the thickness of the layer that has been destabilized.
In the following we elaborate how this model can account for the differences in morphology of dyes of
group A and B. In Figure 7 we demonstrate the existence of a linear relation between droplet wavelength and film thickness for the counter ion ClO4 ¯. This is a known relation for dewetting sytems, but
in our case it shows that the dye CyC will remain in a double layer configuration, no matter how thick
the film is. That then corresponds to an infinite value for the equilibrium layer periodicity. Differently, for
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the counter ion PF6¯, a kink in the wavelength – thickness plot indicates a transition from a double- to
a triple or quadruple layer once the thickness gets larger than one stable period. In our case that corresponds to a layer periodicity in the range of 120 nm (corresponding to the critical PCBM thickness of
60nm, indicated in Figure 5). The behaviour can be best compared to the formation of lamellae in thin
block copolymer films.
Figure 5: Dependence of the lateral feature dimensions on the averaged PCBM film thickness for dyes with the
counter ions ClO4¯ and PF6¯. For ClO4¯ we observe a strict linear relation, for PF6¯ the wavelength
levels off for thicker films.
We have thus strong evidence for layering, the PCBM / CyC system can form a very thick bilayer, the
charge transfer of counter ions into the PCBM is negligible. Differently, in PCBM / CyP, a thick bilayer
is energetically less stable than a multilayer, the reason are the dissociated ions that effectively charge
the PCBM phase negatively, and the dye phase positively. It is thus an electrostatic interaction that
stabilizes a lamellar phase structure. There are several pathways and mechanisms that can account
for the formation of a lateral phase structure from layered systems, as for example the one described
by us earlier [12], but also other mechanisms could account for that observation.
When we turn to the dyes with the counter ions B(Ph)4¯ and Ni-complex, the picture changes. We
anticipate a higher PCBM – counter ion affinity, correspondingly, the layer periodicity is much smaller
and we do not find a droplet structure anymore, but a more or less bicontinuous phase structure with
lamellae that are not aligned parallel to the substrate. The driving force for lamellae alignment parallel
to the substrate is not dominant anymore. Additionally, stabilizing electrostatic forces seem strong
enough to counter balance layer destabilization.
SOLAR CELLS
While we were successful in understanding the morphologies observed in cyanine dye / PCBM
blends, the anticipated improvement in device performance with decrease in phase structure was not
happening. For both counter ions of group B we were able to identify the reason for that failure. Ni of
the Ni-complex has unfavourable oxidation states interfering with photocurrent generation at the dye /
PCBM interface. Similarly, an electron transfer reaction from B(Ph)4¯ to the photo-excited dye leads to
a decomposition of B(Ph)4¯ into B(Ph)3¯ and a phenyl-radical. Within the frame of the project, we
were not able to replace the counter ions; but the knowledge we gained now allows us to design suitable counter ions.
AGGREGATION
One of the most striking features that accompanies liquid-liquid dewetting of a PCBM / cyanine dye
blend is the controlled H-aggregation of the cyanine molecules. Aggregates carry outstanding optical
properties which are advantageous for light harvesting, namely efficient exciton coupling and fast energy migration. The possibility to employ H-aggregates as light harvesting complexes has been reported in the literature [13,14,15]. Aggregation of cyanine dyes is a phenomenon that is well known
from aqueous solutions, similarly, dye aggregates have been successfully employed as spectral sensitizers in the photographic process. Much less is known about aggregates in their function as light harvesting antennas in amorphous films, we believe that this phenomenon has not been fully exploited
because of lack of reliable manufacturing methods. We here for the first time report controlled aggregation in an organic film in combination with an organic electron acceptor.
The advantage of dye aggregation is two-fold: ordering of dye molecules into precisely ordered structures leads to an extra-ordinarily high cross section for light absorption (Haggregation peak in the absorbance spectrum), in case of H-aggregates this peak is blueshifted compared to monomer absorbance, thus expanding the absorption range of the dye. Secondly, aggregates are characterized by a
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large exciton delocalization length that means the excitation energy is available at any place where it
could be used for photo-induced electron transfer.
The effect of aggregation is summarized in Figure 6, for simplicity only aggregations of 2 monomers to
a dimer are considered. H-aggregates are characterized by almost parallel molecular dipoles. When
summing the transition moments of the dimer, we obtain the S+ state with the associated transition
from the ground state (indicated by an arrow). When the momentums zero each other out, we obtain
the S- state, whereby the transition from the ground state to this state is forbidden. The consequence
of this geometry is most attractive: the excited state will relax by internal conversion into the lower
excited level. The return from the lower excited state to the fundamental state is less likely, and the
excitation can diffuse over relatively long distances. Exciton diffusion length of ~ 100 nm are expected,
which is large compared to the exciton diffusion length of 10-20 nm which is normally assumed for
organic systems. The exciton can then dissociate at a donor-acceptor interface, or the excitation can
be eventually transferred to the monomer. Both pathways would benefit the photovoltaic effect.
Figure 6 (left): Schematic diagram of the energy levels in an H-aggregated dye
Figure 7 (right): Attenuance spectra of blend films of PCBM and CyC for different thicknesses. With increasing
film thickness enhanced attenuation is observed towards lower wavelength, which turns into a
sharp H- aggregate peak in a narrow film thickness range. Figure reproduced with permission
from Ref 16. Copyright ACS 2011.
H-aggregation is observed in thick PCBM / dye layers that destabilize via a liquid-liquid dewetting
route [16]. In Figure 7 we show attenuance spectra of PCBM / blend films of different thickness. For a
total film thickness of 400 nm, the signature of H-aggregation is most dominant and visible as a sharp
peak in attenuance.
The height of the peak is a direct measure of the interaction of the aggregated molecules with light, it
is obvious that H-aggregate absorbance contributes largely to the overall dye absorption. Haggregation is linked to a thickness regime where dye remains within cavities of PCBM. In Figure 11
we visualize the aggregation process and show a schematic diagram of the film morphology. A necessity of H-aggregation is the formation of nano-cavities within the PCBM. That can be made visible by
slightly ablating the PCBM domains.
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SOLAR CELLS
The discovery of H-aggregates in PCBM / dye blend films suggest to test the photo current generation
of that sample. First experiments proved the diode character with an improved Voc (Figure 8).
Figure 8: I-V characteristics of a photodiode with an H-aggregate layer at the PCBM interfaces.
HIOS-CELL is a transnational project within the PV-ERA NET call POLYMOL between EMPAin Switzerland and the University of Utrecht (Dr Jan Groenewold). POLYMOL is funded by the Bundesamt für
Energie (Switzerland) and SenterNovem (the Netherlands). The project greatly benefits from collaborations with Cambridge University (UK).
Sample preparation and characterization has been performed in the laboratories of the group Functional Polymers at EMPA. Modelling and computer simulations have been performed at the University
of Utrecht. For a basic understanding of the dynamics of film formation during spin coating we greatly
benefited from knowledge at Cambridge University.
The design, construction and put in operation of a laser reflectomer (film development) and spectroscopic light scattering set-up (scattering properties of the films) was done at the department of metreology at EMPA.
Fruitful collaborations emerged with the ETH Zürich (Ion-Beam Analysis, Conductometry) and the EPF
Lausanne (Electron spin resonance).
Thanks to the research results obtained during this project, we were granted the SNF-project “Structured templates of PCBM for applications in photovoltaics and photonics”, 200021- 132502, starting
st
1 November 2011, where we will continue working on that topic and further exploit POLYMOL findings.
Conclusion
With the POLYMOL project we explored the potential to realize cyanine – PCBM bulk heterojunctions
for organic photovoltaics. We developed a comprehensive model how structure formation proceeds in
ionic dye / PCBM blends. The phase morphology evolves via a liquidliquid dewetting process, which is
conceptually different from phase separation normally observed in blend systems. We could demonstrate that liquid-liquid dewetting is suitable to generate a phase morphology with characteristic length
scales in the order of 20nm. Molecular simulations suggest that the morphology evolves from a transient lamellar system stabilized by counter ions diffusing into the PCBM phase. The characteristic
phase dimensions can thus be controlled by the PCBM – counter ion interactions.
The role of the dye counter ion should not be underestimated; efficient solar cells could not be manufactured because of averse effects induced by the counter ion.
The process of liquid-liquid dewetting offers the possibility to organize dye molecules into dye aggregates.
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Referenzen
[1]
[2]
[3]
[4]
B. C.Thompson et al., Organic photovoltaics - Polymer-fullerene composite so lar cel ls, Angew. Chem. Int. Ed. 47,
58, 2008.
B. Walker et al., Small Molecule Solution-Processed Bulk Heterojunction Solar Cells, Chem. Mater. 23, 470, 2011.
F. Hamer, The Chemistry of Heterocyclic Compouds, vol 18, The Cyanine Dyes and related compounds, WileyInersciences, New York, 1964.
H. Mustroph et al., Current developments in optical data storage with organic dyes, Angew.Chem. Int. Ed. 45, 2016,
2006.
[5]
K. Sayama et al., Efficient sensitization of nanocrystalline TiO2 films with cyanine and merocyanine organic dyes,
Sol. En. Mat. Sol. Cell. 80, 47, 2003.
[6]
T. Geiger et al. Low-Band Gap Polymeric Cyanine Dyes Absorbing in the NIR Region, Macromol.Rapid Comm. 2008,
29, 651, 2008.
V. Y. Merrit, IBM J. Res. Develop. Organic P hotovoltaic Materials: Squarylium an d C yanine-TCNQ D yes 22, 353,
1978.
[7]
[8]
B. Fan et al., Improved p erformance o f c yanine so lar cel ls w ith p olyaniline an odes, J. Materials Chem. 2010, 20,
2952.
[9]
H. Benmansour et al., Ionic Space Charge Driven Organic Photovoltaic Devices, Chimia 2007, 61, 787.
[10] F. Meng et al., Cyanine dye acting both as donor and acceptor in heterojunction photovoltaic devices, Apl. Phys.
Lett. 2003, 82, 3788.
[11] K. Saito, Sensitization of t he P hotocurrent in C 60/merocyanine J -Aggregate H eterojunction P hotovoltaic C ells,
Jpn. J. Appl. Phys. 1999, 38, L1140.
[12] J. Heier, J. Groenewold, F. Nüesch, R. Hany, Nanoscale S tructuring of S emiconducting Moelcular B lend Fi lms in
the Presence of Mobile Counterions, Langmuir, 2008, 24, 7316.
[13] A. Moliton et al., How to model the behaviour of organic photovoltaic cells, Polymer International 55, 583, 2006.
[14] S. Das et al., Can H-Aggregates Serve as Light-Harvesting Antennae? J. Phys. Chem. B, 103, 209, 1999.
[15] S. Kirstein et al. J-Aggregates of Amphilic Cyanine Dyes: Self-Organization of Artificial Light Harvesting Complexes, International Journal of Photoenergy, Article 20363, 1, 2006.
[16] J. Heier, R. Steiger, F. Nüesch, R. Hany, Fast assembly of cyanine dyes onto [6,6]-phenyl C61-butyric acid methyl
ester surfaces from organic solvents, Langmuir 2010, 26, 3955.
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FABRI-PV: TRANSPARENT FABRIC ELECTRODES FOR ORGANIC PHOTOVOLTAICS
Annual Report 2011
Address
Date
R. Hany, F. Nüesch
EMPA, Lab. for Functional Polymers
Überlandstr. 129, CH-8600 Dübendorf
KTI 9995.1
01.04.2009 – 01.04.2011
09.12.2011
ABSTRACT
New generations of optoelectronic devices require cheap, electrically conductive and optically transparent electrodes. Flexibility adds new possibilities to products such as displays, touch screens, organic light emitting devices and organic solar cells. In these systems, the transparent electrode communicates with t he environment, as it is used to c ollect or emit l ight, and to inject current into or to
transport electrical charge out of the device. Flexible organic photovoltaic devices may soon find applications in various fields, such as portable electronics or building-integrated PV, occupying market
niches that are currently not covered by the prevailing PV technology based on silicon and other inorganic materials. For these applications, there is an urgent need to replace the commonly used indium
tin oxide by t ransparent and el ectrically conductive materials that can be processed cost-effectively
by l arge-area c ompatible p rinting a nd c oating pr ocesses. T ogether w ith our i ndustrial partner S efar
AG, we developed such an improved flexible electrode based on a woven precision fabric, embedded
into a t ransparent p olymer l ayer with m inimal m etal wire ex posure. U sing the benchmark P 3HT /
PCBM active materials, we demonstrated organic solar cells on t hese woven f abric electrodes with
power conversion efficiencies of 3.1%.
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Organic photovoltaic (OPV) cells based on semiconducting small molecules and polymers have rapidly i mproved ov er t he last f ew years, and p ower c onversion ef ficiencies ( η) greater t han 8% h ave
2
been reported. In most cases, record efficiencies were obtained on small device areas (≤ 1 cm ) using
a glass/indium tin oxide (ITO) substrate as the transparent and conducting electrode. This device architecture, however, does not necessarily capture the true merits of OPVs, since cells will ultimately be
fabricated via simple coating and printing processes on flexible and light-weight large substrates, offering an attractive and cost-effective source of renewable energy.
For l arge-area O PV a pplications on f lexible t hin p lastic s ubstrates, al ternatives t o I TO ar e u rgently
needed. ITO is costly and scarce, and demand keeps increasing. In addition, ITO is brittle and easily
forms c racks w hen ben t, w hich er odes t he c onductivity. D epending on t he f abrication pr ocess, th e
high c onductivity of I TO o n gl ass t ypically d evelops onl y af ter a hi gh-temperature an nealing s tep,
which i s i ncompatible with l ow c ost pl astic-based s ubstrates; i ndeed, r esistive l osses for I TO/plastic
electrodes are limiting when OPV devices are up scaled.
Promising alternative materials to ITO have been presented in the form of carbon nanotube and graphene films, as well as (nano-)structured metals, including metallic nanowires and ultrathin metal films.
ITO-free s olar cells hav e al so be en f abricated us ing t ransparent, c onductive pol ymers, t he m ost
prominent be ing po ly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PEDOT:PSS). H ighly c onductive PEDOT:PSS has been used as a stand-alone electrode, or in various combinations using current-collecting metal grids. It is anticipated that for large-area, up scaled organic solar cells, resistive
power losses with any of the existing transparent electrode materials will require the use of a currentcollecting grid.
Work performed / Results obtained
Together with our industrial partner Sefar AG, we have introduced a flexible, s table and t ransparent
electrode f or O PV c ells c onsisting of pol ymer f ibres and c urrent-collecting m etal wires woven i nto a
mesh. To provide a stable support for the thin OPV active film (~ 150 nm), the holes in the mesh struc2
ture (~ 0.07 mm ) were filled with a curable transparent polymer emulsion in such a way that one side
of the fabric was fully embedded in the polymer, while metal wires were exposed by ~ 10-15 μm to air
at the other side. We fabricated woven fabric/PEDOT:PSS(~ 1-1.5 μm)/P3HT:PCBM/Al solar cells with
η = 2.2%, and demonstrated that the photocurrent can be transported practically loss-free over a distance of several cm at least, a relevant distance for a large-area OPV cell applications [1,2].
We t hen showed that t he OPV performance us ing t he woven f abric e lectrode c an b e c onsiderably
improved (η = 3.1%) by further decreasing the distance (~ 5 μm) between the protruding metal wires
and the plane of the polymer-filled holes [3]. For reduced metal wire exposure, thinner but still covering PEDOT:PSS layers could be used; this resulted in increased light transmittance reaching the active layer, and translated in an associated increase in the short-circuit current density (Jsc) and η.
Fabrics c onsisted throughout [1-3] of ~ 40 μm thick molybdenum metal wires and semitransparent
polymer fibres, woven into a mesh with a distance of ~ 0.27 mm between individual threads. The mesh
opening was ~ 76%, defined as the ratio between the area of the transparent holes and the total electrode area. Fig. 1a shows a side view image of a fabric electrode. Metal wires are woven in the mesh
unidirectionally in the absence of polymer fibres (metal-to-polymer ratio 1:0). However, to minimize the
shadowing effect of the non-transparent metal wires, a metal-to-polymer ratio of 1:3 was used for the
fabrication of s olar c ells. A fter w eaving, t he m esh w as e mbedded into a liquid, transparent po lymer
emulsion an d s tabilized b y c uring. T he k ey pr ocessing s tep i s t o pr ecisely adjust t he height of t he
polymer filling, such that the holes of the mesh are filled and provide a smooth surface for the overlaying solar cell, while retaining a minimal distance for the metal wires to emerge to the air surface (Fig.
-1
1a, exterior wires, and Fig. 1b). The sheet resistivity (~ 1-8 Ω sq ) and light transmittance (~ 76-85%
at 500 nm) vary with the chosen polymer-to-metal ratio (between 0:1 and 3:1) in the mesh structure.
The production of the woven substrate electrode is fully integrated into a technological roll-to-roll process (fabric width ~ 120 cm, 10 metres per minute) at Sefar AG. The production system is rather flexible, since the mesh structure (open area), metal (nature, wire diameter, wire distances) or the polymer
filling (nature, additives) can be varied within the limits of the technological process.
Fabric samples were rinsed with purified water, sonicated in ethanol, and were then dried with a flow
of ni trogen gas . P EDOT:PSS films with average thicknesses between 300 nm and ~ 1.5 μm were
bladed on to t he f abric, a nd w ere then dr ied. F or t he pr eparation of reference d evices, P EDOT:PSS
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KTI 9995.1, FABRI-PV, R. Hany, Empa
was applied in the same way onto cleaned glass/ITO substrates. The role of PEDOT:PSS is to further
smoothen the fabric surface, to prevent electron leakage current to the anode, and to transport holes
to the protruding current-collecting metal wires. To prevent shorts in the final solar cell, a certain PEDOT:PSS thickness is required to fully cover the metal/polymer edge of the fabric. However, the layer
thickness should be kept minimal, since PEDOT:PSS itself absorbs a fraction of the incoming sunlight
(Fig. 2a) which is then not available for the photocurrent generation process.
Active l ayers were spin coated f rom chlorobenzene solutions c ontaining poly(3-hexylthiophene)
(P3HT), 1 -(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM), and 5 v ol-% of ni trobenzene. As a
top electrode, aluminum was evaporated through a shadow mask, defining active cell areas of 3 and 7
2
mm , respectively (Fig. 1c and 1d).
Current-voltage (J-V) characteristics were measured under simulated solar irradiation. The light intensity was calibrated in order to correspond to standard 1 sun solar irradiation. Fig. 2b displays J-V curves f or di fferent P EDOT:PSS t hicknesses. B elow 4 00 nm , t he c ell performance er odes ( low o pencircuit v oltage ( Voc) and f ill f actor (FF), hi gh r everse phot ocurrent) w hich we at tribute t o s hunts. F or
thicker PEDOT:PSS layers, diode behaviour develops. Comparing solar cells with PEDOT:PSS
thicknesses between ~ 400 nm and ~ 750 nm, the Voc = (0.54-0.55) V and FF = (0.47-0.49) remained
-2
almost constant, and the short-circuit currents (Jsc = 9.3, 10.5, and 11.8 mA cm ) increased for thinner
PEDOT:PSS ( 750, 600, an d 400 nm , r espectively). Performance values f or the best fabric solar cell
-2
(Fig. 2b, no. 2) were Jsc = 11.8 mA cm , Voc = 0.55 V, FF = 0.48, η = 3.1%, only slightly lower than the
-2
values for the reference glass/ITO/PEDOT:PSS cell, Jsc = 12.1 mA cm , Voc = 0.52 V, FF = 0.58, η =
3.6%. As expected, we observed that for very thick PEDOT:PSS films (~ 1 μm), the influence of the
distance of the protruding metal wire diminished, and fabric solar cells with a metal exposure distance
of 10-15 μm and ~ 5 μm performed similar.
As s unlight is r eaching t he ac tive l ayer t hrough t he f abric el ectrode s ide, t he d istance bet ween the
shadowing m etal wires s hould be as l arge as p ossible. O n t he ot her ha nd, t his di stance has t o be
-1
matched to the sheet resistivity (~ 1 kΩ sq ) of PEDOT:PSS, to minimize the fractional electrical loss
-2
in hole transport to the metal wires. Assuming a cell performance with a current density of 9 mA cm
and a voltage of 0.35 V, both taken at the maximum power point (Fig. 2b, no. 2), the best compromise
between fractional shadowing and electrical losses is calculated to be at a metal-to-metal distance of ~
1.1 mm, close to the actual distance of 1.2 mm in our devices.
Figure 1: (a,b) Cross section optical microscopy pictures of woven mesh electrodes; (a) shows a section of three
metal wires (black), two of the metal wires are exposed to air (above) and the light would reach the active layer of
the solar cell from below through a t hin, supporting polymer foil (thickness ~ 50 μm); (b) closer view of a s ingle
metal wire (white). The inert hole-filling polymer wets the metal wire, and the effective metal-to-air exposure distance is ~ 5 μm. To increase the visual contrast, the fabric was covered with a thin layer of a conductor (faint
white line, e.g. PEDOT:PSS, traced by a broken line on the right side of the metal). (c, d) Microscopy pictures of
circular finished solar cells, (c) top view onto the aluminium electrode, and (d) view from below through the transparent fabric electrode, where the hole-collecting and charge-transporting metal wires (polymer : metal wire ratio
3 : 1) are clearly visible. (Figure reproduced from [3]).
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Figure 2: (a) Selected transmission spectra of PEDOT:PSS-coated fabrics. To detect both the directly transmitted
and diffusively scattered light, samples were placed at the entrance of an integrating sphere. For comparison, the
spectrum of a glass/ITO/PEDOT:PSS (400 nm) sample is included. (b) J-V curves of fabric organic solar cells (no.
1-4) with bladed PEDOT:PSS layers of different average thicknesses. For comparison, a glass/ITO device (no. 5)
with bladed PEDOT:PSS (400 nm thickness) is included. (Figure reproduced from [3]).
Project evaluation
Our results demonstrate t he po tential of a woven f abric el ectrode f or or ganic s olar c ell ap plications
and provide some directions for further improvement. Weaving a fabric with even greater mesh openings than used here with constant mechanical stability is technologically difficult, but, contrary to expectation, m ay also not be necessary. Spatially r esolved ph otocurrent c urrent mapping ex periments
[3] showed that the photocurrent is highest on the grid of the transparent polymer fibres; therefore, it
might w ell be t hat a woven el ectrode using a f abric w ith a s maller ge ometrical ope n ar ea per forms
better. A pparently, f urther reduction of t he m etal ex posure f rom t he f abric pl ane w ould al low t o us e
thinner P EDOT:PSS l ayers and i t s eems t hat hi gher phot ocurrents c ould b e ge nerated. F inally, t he
distance b etween t he s hadowing m etal wires h as t o be f urther increased. T herefore, P EDOT:PSS
formulations with higher conductivities and low electric resistivity for hole current transport to the metal
are needed.
It is expected [4] that the woven fabric electrode is best suited for thin film solar cell applications, including pure organic and dye-sensitized solar cells. By filling the mesh pore with a polymer emulsion
in s uch a w ay t hat t he m etal wires ar e s till ex posed to ai r on bo th s ides, i t i s pos sible t o us e t hese
electrodes as interlayer recombination layers in tandem solar cells. The polymer emulsion filling acts
not only as a support for the thin active film, but presents a barrier layer for water vapour and oxygen
at the same time. Additives can be added to the polymer emulsion to improve and adjust the barrier
properties. In a n umber of r elated pr ojects, Sefar A G dem onstrated t hat t his woven f abric el ectrode
can find use in other thin film applications as well, such as electroluminescence devices and organic
light-emitting diodes.
References
[1] W. Kylberg et al., “Woven electrodes for flexible organic photovoltaic cells”, Advanced Materials 2011, 23, 1015.
[2] “See-through electrodes”, Nature Materials 2011, 10, 82.
[3] W. Kylberg et al., „Spatially resolved photocurrent mapping of efficient organic solar cells fabricated on a woven mesh electrode“, Progress in Photovoltaics 2011, accepted for publication.
[4] P. Chabrecek, “Polymer-Gewebeelektrode für Dünnschicht-Solarzellen“, Plastics.now! Okt. 2011, 30.
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NEUARTIGE SENSIBILISATOREN FÜR
FARBSTOFFSOLARZELLEN
KTI 10584.1 PFIW-IW
Annual Report 2011
1
1
1
1
T. Geiger , Y. Shcherbakova , S. Hochleitner , F. Nüesch ,
2
T. Meyer
1
Empa, Überlandstrasse 129, 8600 Dübendorf
2
Adresse
Solaronix SA, Rue de l'Ouriette 129, 1170 Aubonne
Telephone, E-mail, Homepage www.empa.ch, www.solaronix.ch
KTI 10584.1 PFIW-IW
Date
14.12.2011
ABSTRACT
In the CTI-Project the company Solaronix and Empa focus on the development of new unsymmetrical
squaraine and heptamethine dyes for application in dye sensitized solar cells. Because of their outstanding physical properties (e.g. high extinction coefficient and absorption maximum over 700 nm),
these dyes are very promising sensitizers. By skilful combination of different heterocycles and squaric
acid or d ianil der ivatives, it w as pos sible t o s ynthesise and c haracterise various f unctionalised unsymmetrical s quaraine and hept amethine d yes. F urthermore, t he ef ficiency of dy e s ensitized s olar
cells pr epared with s uch s ensitizers i s u p t o 2% . R emarkably, d ye s ensitized s olar c ells with h eptamethin dyes, which absorb light in the NIR, almost appear in light yellow, the colour of the electrolyte.
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Was für di e Pflanzen b zw. f ür di e Photosynthese d ie k omplexen C hlorophyllmoleküle s ind, s ind f ür
Solarzellen heutzutage photosensitive anorganische und organische Materialien, die in gleicher Weise
wie das C hlorophyll ef fizient Li cht a bsorbieren un d i n E nergie um wandeln k önnen. D ie E ntwicklung
solcher or ganischer Ma terialien f ür F arbstoffsolarzellen i st das Z iel des P rojektes. I m F okus s tehen
neuartige Sensibilisatoren aus der K lasse der asymmetrischen Squarain- und H eptamethinfarbstoffe
mit einer grossen spektralen Vielfalt oberhalb 700 nm. Die Synthese und die Charakterisierung dieser
Farbstoffe, der Bau und Charakterisierung von Solarzellen mit diesen Farbstoffen sowie deren Markteinführung sind zentrale Aufgaben in diesem Projekt.
Für ei ne ef fiziente Stromproduktion, wird i n d er F arbstoffsolarzelle (dye s ensitized s olar c ell, D SC)
eine m onomolekulare F arbstoffschicht auf ei nen na noskaligen H albleiter m it gr osser B andlücke ( oft
TiO2-Partikel mit ei nem D urchmesser v on c a. 20 nm) auf gezogen. D iese p hotosensitive S chicht a bsorbiert Photonen, wobei der F arbstoff aus ei nem k urzlebigen a ngeregten Z ustand ei n Elektron a uf
den Halbleiter üb erträgt. Der H albleiter s einerseits l eitet das Elektron zur Anode, d ie m it e inem
Verbraucher v erbunden i st. N ach dem V erbraucher f liesst das E lektron über di e K athode zu ei nem
Redoxsystem (z.B. Iodid/Triiodid), das den Farbstoff reduktiv regeneriert und diesen in seinen energetischen Ausgangszustand überführt. Damit ist das System wieder bereit für die Absorption von weiteren P hotonen u nd d er K reislauf s chliesst s ich. D abei s ind hoc heffiziente F arbstoffe s owie k inetisch
günstige Elektronentransferprozesse innerhalb der DSC der Schlüssel für die effiziente Umwandlung
der Photonenenergie zu Strom.
Obwohl der Wirkungsgrad von DSCs bereits die 10% Hürde überwunden hat, wird weiterhin die Optimierung der Zellbestandteile, w ie Halbleiter, R edoxsystem, E lektroden und na türlich auc h di e F arbstoffe, vorangetrieben, mit dem anspruchsvollen Ziel höhere Wirkungsgrade zu erreichen. Gerade auf
dem Gebiet der Farbstoffe bietet sich ein sehr grosses Entwicklungspotential. Die etablierten metallorganischen Farbstoffe basierend auf Ruthenium-Komplexen, mit den bekannten Varianten N3, N719,
Z907 und Black dye, absorbieren Sonnenlicht im gesamten UV-Vis Bereich mit eher geringen molaren
Absorptionskoeffizienten. Neben dem oft erwähnten hohen Rohstoffpreis des Rutheniums, bieten der
geringe Absorptionskoeffizient u nd die be grenzte s pektrale V ariabilität der R utheniumfarbstoffe im
nahen Infrarot (NIR) Ansatzpunkte für eine Entwicklung von neuen organischen Farbstoffen, die eine
sinnvolle Ergänzung zu den metallorganischen Sensibilisatoren darstellen können.
Für den Einsatz in Farbstoffsolarzellen sind die Farbstoffklassen der asymmetrischen Squaraine und
Heptamethine (Fig. 1 ) mit ihren her ausragenden ph ysikalischen E igenschaften von sehr gr ossem
Interesse. S quaraine s ind K ondensationsprodukte der Q uadratsäure m it H eterozyklen ( z.B. I ndol-,
Benzindol-, Thiazolin-, Azulen-, Chinolin- oder Pyryllium-Derivate) und im Gegensatz dazu sind
Hepthamethine Kondensationsprodukte von z.B. zyklischen Bisaldehyden mit den erwähnten Heterozyklen. Beide F arbstoffklassen zeichnen s ich da durch aus , das s ei n Absorptionsmaximum über 700
nm mit sehr hohen molaren Absorptionskoeffizienten (bis zu 300'000 dm 3mol-1cm-1 in Lösung) erreicht
wird.
Figur 1: Prinzipielle Struktur der Squaraine (links) und der Heptamethine (rechts),
beide mit einer Ankergruppe ( –⊂ )
Beide F arbstoffklassen l assen s ich d urch e ine ges chickte R eaktionsführung asymmetrisch mit ei ner
funktionellen Gruppe, d.h. einer Ankergruppe, aufbauen. Diese Ankergruppe bindet den Farbstoff an
den Halbleiter.
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KTI 10584.1 PFIW-IW, T. Geiger, Empa
Im P rojekt w urden dur ch die Kombination von v erschiedenen H eterocyclen m it Q uadratsäure u nd
Dianilen eine Vielzahl v on S quarainen un d H eptamethinen s ynthetisiert und charakterisiert. Dabei
wurde bewusst nach Syntheserouten gesucht, die mit einfachen Reaktionsführungen und Reinigungsmethoden (ohne Chromatographie) auskommen. Somit ist auch eine industrierelevante Durchführung der Synthesen in einem grösseren Massstab (10 Gramm und mehr) vorstellbar.
Spektroskopische U ntersuchungen der F arbstoffe z eigen e indrücklich di e s pektrale Vielfalt, die m it
den Squarainen und Heptamethinen erreicht werden kann. In Figur 2 sind die UV-Vis Spektren einer
Auswahl v on Squarainen und Heptamethinen und d as solare S pektrum aufgeführt. Entsprechend
ihrem molekularen Aufbau absorbieren die Farbstoffe maximal im Bereich von 700 bis nahezu 900 nm
und somit kann auch Strahlung auc h aus serhalb d es s ichtbaren Li chtes in elektrische E nergie umwandelt werden
1.8
UV
Vis
1.6
NIR
AM1.5
1.2
1.4
1.0
1.2
1.0
0.8
0.8
A / a.u.
Spectral Irradiance / Wm-2nm-1
1.4
Dyes in solution
0.6
0.6
0.4
0.4
0.2
0.2
0.0
-0.2
300
400
500
600
700
800
900
0.0
1000
wavelenght / nm
Figur 2:
Absorptionsspektren einer Auswahl verschiedener Squaraine und
Heptamethine und das solare Spektrum (AM1.5).
Im A nschluss w urden di e F arbstoffe mittels klassisch auf gebauter F arbstoffsolarzellen
(Glas/FTO/TiO2/Farbstoff/Iodid-Triiodid(Acetonitril)/Pt/FTO/Glas) get estet. D ie I mmobilisierung d er
Farbstoffe auf der H albleiteroberfläche er folgte aus alkoholischer L ösung un ter dem Einfluss e ines
-2
Co-Adsorbenz (Chenodeoxycholsäure). Die Grösse der aktiven Solarzellenfläche betrug 0.72 cm für
die Laborsolarzellen bis hin zu mehreren Quadratzentimetern für grosse Demonstratoren (Figur 3).
Figur 3. Von links nach rechts: Laborsolarzelle, 10x10cm Demonstrator, 30x30cm Demonstrator
Für er ste F arbstoffsolarzellen m it S quarainen u nd H eptamethinen mit ei nem Absorptionsmaximum
von über 700 nm konnte ber eits ein Wirkungsgrad bis an nähernd 2 % gem essen w erden. Bemerkenswert i st, das s bei Solarzellen m it H eptamethinen, d ie nahezu k eine A bsorption i m S ichtbaren
aufweisen, annährend nur noch die Färbung des Elektrolyten zu sehen ist.
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Die erfolgreiche Synthese der asymmetrischen Squaraine und Heptamethine, die ein Absorptionsmaximum bi s in den Bereich des nahen Infraroten zeigen, und di e nac hgewiesene Funktionstüchtigkeit
der Sensibilisatoren in Farbstoffsolarzellen sind Grund genug die Arbeiten im dritten Jahr des Projekts
weiter zu führen. Der Fokus der Arbeiten liegt jetzt auf der Optimierung der Solarzelle selbst. Ein erster Ansatz ist das Zusammenspiel zwischen Halbleiter und Farbstoff oder Elektrolyt und Farbstoff besser zu verstehen und dann zu optimieren, um letztendlich eine höhere Performance der Zelle zu Erreichen.
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ORION
ORDERED INORGANIC-ORGANIC HYBRIDS USING
IONIC LIQUIDS FOR EMERGING APPLICATIONS
Annual Report 2011
Address
Date
F. Oswald, T. Meyer
Solaronix SA
Ouriette 129 CH-1170 Aubonne
021 821 2280, [email protected], www.solaronix.com
FP7-NMP-2008-LARGE-2-229036
1.10.2009 – 30.09.2013
24.04.2012
ABSTRACT
ORION puts together a multidisciplinary consortium of leading European universities, research institutes
and industries with the overall goal of developing new knowledge on the fabrication of inorganic-organic
hybrid m aterials us ing ionic l iquids. Maximum r esearch ef forts w ithin O RION will b e addressed t o
achieve i norganic-organic hybrids with an or dered nanostructure an d t o u nderstand and c haracterize
the next generation of inorganic-organic hybrids for energy conversion and storage. The final goal is to
optimize the best possible materials and processing methods for increasing the performance of batteries and innovative solar cells.
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Aims of the project
The main concept of the project is the development of a new family of functional inorganic- organic hybrid
materials characterized by an ordered morphology. The hybrids will be composed of an inorganic material
such as (TiO2, SiO2, ZnO, Si, Sn, LiCoO2) and a new functional ionic liquid as the organic component. At
high i norganic ox ide c ontents t he preferred s tructures w ill be ordered na noporous i norganics f illed with
ionic liquids hybrids.
At low inorganic oxide contents, nanoparticle, nanotube and nanowire arrays embedded in ionic matrixes
will be searched. At intermediate compositions bi-continuous and lamellar structures will be presumably
obtained. T he phas e di agram of t he or dered i norganic-organic h ybrids i s s hown bel ow. T he or dered
geometry of the final hybrid will allow a synergic combination of the properties of each individual
component, ensuring good electrochemical and photonic performance.
Two di fferent c omplementary ge nerations of h ybrids w ill be developed. F irst, Generation 1 i norganicorganic h ybrids will b e s ynthesized f or app lications in lithium bat teries. A lthough t he c omplete p hase
diagram will be investigated, the expected morphologies of choice will be nanoporous structures because
of t heir h igher c harge c apacity and en hanced c harge/discharge r ate pos sibilities. O n t he ot her ha nd,
Generation 2 inorganic-organic hybrids will be developed for application in innovative solar cells. In this
case, a t hird c omponent n amed l ight s ensitizer ( dye, s emiconducting p olymer or qua ntum dot ) w ill b e
added to the inorganic component/ionic liquid system. Generation 2 will prefer nanoparticle and nanowire
array morphologies. This will facilitate electronic and ionic transport and will allow the introduction into the
hybrid of a third component (light sensitizer) which will be added to bring optical activity to the hybrid.
Generation 1
Generation 2
Illustration of the synthetic approaches to Generation 1 Ordered Inorganic-Organic Hybrids.
Graphical presentation of generation 2 hybrid architectures (inorganic nanoparticle or nanowires
surface functionalized with a light sensitizer and
embedded into ionic liquid media).
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ORION, T. Meyer, Solaronix SA
SCIENTIFIC AND TECHNICAL OBJECTIVES:
ORION captures the main goal into the next particular scientific and technical objectives to be achieved in
the project:
- Design and processing of ordered inorganic-organic hybrid materials for energy applications.
- Understanding of self-assembling methods for the synthesis of ordered inorganic-organic hybrids using
ionic liquids.
- Development of new m ethods f or or dering i norganic-organic h ybrids us ing f unctional a nd p olymeric
ionic liquid block copolymers as structure directing agents.
- New functional Ionic Liquids and polymeric ionic liquid block copolymers including chemical functional
groups such as triethoxysilane, carboxylic, phosphoric and thiol functionalities enabling the ionic liquids
to act as functional templates in the synthesis of ordered inorganic-organic hybrids.
- Development of or dered hybrid m aterials c omposed of an i norganic c omponent an d i onic l iquid f or
battery applications. (Generation 1)
- Synthesis of light sensitizers (organic dyes, quantum dots and semiconducting polymers) with adequate
functionality to be added to the inorganic-organic hybrids.
- Development of c omplex or dered hybrid m aterials c omposed of an i norganic c omponent, ionic l iquid
component an d a t hird c omponent nam ed l ight s ensitizer ( organic d ye, s emiconducting po lymer or
quantum dot) for innovative solar cells.(Generation 2)
- Complete c haracterization of i nnovative hybrid materials: m orphological c haracterization,
electrochemical and t ransport studies including ionic, electrical a nd hole c onductivities, and f unctional
performance (half-cell devices).
- Theoretical m odeling of ne w inorganic-organic m aterials a nd prediction of t heir pr operties a nd
performance in devices.
- Processing of i norganic-organic h ybrids b y different m ethods i ncluding i nk-jet pr inting and s creen
printing.
- Development and optimization of innovative inorganic-organic electrode materials for lithium batteries.
To propose a high storage capacity battery with a l ong lifetime (respectively>200 Wh/kg, 30%
improvement).
- Development and o ptimization of i nnovative inorganic-organic hybrids f or s olid s olar c ells with h igh
efficiencies (>10%) and high cyclability (10’000 h) (30% improvement).
- Evaluation of organic/inorganic hybrids in other applications (supercapacitors, sensors and light-emitting
devices).
Project partners & role of Solaronix
ORION is a Large Scale Collaborative Project involving 17 partners with duration of 48 months. The work
program is divided into 7 logical Work packages (WPs), covering RTD, Management, Demonstration and
Training activities
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Work performed and results obtained
In WP2, novel polymerizable ionic liquids received from the project partners are investigated:
The dye solar cell with the best performance use volatile solvents in their electrolytes, which may be prohibitive for outdoor solar panel in view of the need for robust encapsulation. Solvent free quasi solid gel
electrolytes have been pursued as an attractive solution to this dilemma. Gelation of the liquid electrolytes
mitigates the potential instability against solvent leakage under thermal stress.
Using ionic liquid monomer and various cross linker to form a gel electrolyte or a gelling agent that can be
added to an ionic liquid electrolyte will add extra levels of smartness to this approach:
- gel electrolyte will avoid cell leakage,
- with proper formulation gel electrolyte could be screen printed avoiding the annoying step of filling electrolyte through a drilled hole,
- once po lymerized, ionic l iquid m onomers could f orm preferential c hannels f or c harge t ransport, t hus
enhancing cell performance.
Several polymerization tests using an ionic liquid monomer (EVIBFSI) supplied by SOLVIONIC and various cross linker supplied by CNRS-LCPO were performed in presence of AIBN. However iodine containing electrolyte inhibits the radicals formation needed for monomer polymerization. To solve this issue, the
electrolytes w ere formulated w ithout i odine; i t w ill b e introduced onl y onc e t he polymer electrolyte is
formed.
CNRS-LCPO cross linker on the left and SOLVIONIC monomer on the right
Preliminary results are encouraging and confirm the validity of this concept. Various ionic liquid polymers
were obtained. Finding the optimum composition to form a screen printable electrolyte is ongoing and will
require fine tune of the ratio ionic liquid electrolyte / monomer / cross linker.
Various ionic liquid polymers obtained
In WP3, the best ionic-liquid based cells are developed on the basis of the «spot-cells» having an active
area of 0.36 cm2 (6x6 mm TiO2 square). Using organic-solvent-based electrolyte to achieve high conversion efficiencies has impaired large-scale production and outdoor application for DSSC. Organic solvents
not only present challenges for sealing but also permeate across plastics, excluding their use in flexible
cells. In contrast, the vapor pressure of molten salts and their permeation rate across plastics are negligible at the typical operating temperature of photovoltaic devices. SOLARONIX tested these promising new
class of material in order to evaluate the potential of ionic liquid based electrolytes in terms of efficiency
and stability.
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To test the performance of the state of the art ionic liquid electrolyte (coded Z-952), which consists in a
mixture of di methylimidazolium i odide ( DMII) /
ethyl-methylimidazolium i odide ( EMII) / et hylmethylimidazolium t etracyanoborate ( EMITCB) / iodine / n-butylbenzimidazole ( NBB) / guanidinium
thiocyanate ( GuNCS) i n t he f ollowing m olar r atio 12:12:16:1.67:3.33:0.67, s everal m esoporous t itania
2
photo anod es ( 0.36 c m ) were pr inted on F TO glass ( 2.2mm t hick and 15 O hm/sq). The l ayering us ed
was as followed: around 7 microns of 18 nm TiO2 nanoparticles and 3 microns of over 100 nm TiO2 nanoparticles. These photoanodes were then s ensitized using t he Z-907 d ye ( 0.3 mM solution in acetoni2
trile). The characteristics of the cell were found to be Voc = 529 mV, Jsc = 7.69 mA/cm and FF = 65%
leading to a disappointing PCE of 2.97 %, which is far from to the highest efficiency published using Z952 electrolyte. Several optimizations on the titania nanoparticle size (see WP2, task 2.2.1), on the layer
porosity and on the layer quality (introduction of a TiCl4 pre- and a post-treatment) allowed to improve this
low PCE to 4.91%.
Further i mprovements w ere ac hieved b y c hanging t he d ye ( use of D 5 or ganic d ye or N -719 r uthenium
complex) and fine tuning the sensitization conditions (going from methanol solution to ethanol/tert-butanol
3:1).
2
Finally, a state of art cell was prepared with several titania photo anode (0.36 cm ) printed on FTO glass
(2.2mm thick and 15 Ohm/sq).The layering used was as followed (see SEM cross section below): around
11 microns of 18 nm TiO2 nanoparticles and 3 microns of over 100 nm TiO2 nanoparticles.
SEM cross section of mesoporous titania photo anode
A T iCl4 pre- and a p ost-treatment w as per formed t o opt imize t itania’s por osity and s pecific ar ea. T he
counter electrode was prepared by paint brushing three layers of SOLARONIX‘ Platisol T, leading to the
formation of a platinized catalyst layer after firing at 400 °C. The photoanodes were then sensitized using
the C-106 dye (0.5 mM solution in ethanol/tert-butanol 3:1) in presence of chenodeoxycholic acid (5 mM).
The w orking and c ounter electrode were j oined t ogether us ing a 25 m icron s pacer t o m inimize m ass
transport limitation due to the viscosity of the ionic liquid mixture. The cell was then backfilled with electrolyte Z-952. Figure 1 show the I-V performance of these cells measured in full sun (AM 1.5G). The charac2
teristics of the cell were found to be Voc = 628 mV, Jsc = 14.33 mA/cm and FF = 69 % leading to a PCE
of 6.24 %, which is close to the highest efficiency published using Z-952 electrolyte, especially considering that only industrially available raw material were used to prepare theses cells.
Figure 1: I-V performance of an ionic liquid electrolyte spot-cell
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Ionic l iquid el ectrolyte cell s tability w as tested. Cells m ade with N -719 d ye and Z -952 el ectrolyte, w ere
placed under constant illumination, one sun AM 1.5G, at 55 °C during the first 2’000 hours and at 65 °C
for the rest of the experiment. All cells exhibit good stability with less than 2% efficiency loss after 3’000
hours and less than 5% after 5’000 hours in these conditions (see graph below).
This remarkable stability f eature makes ionic liquids g ood candidate to build s table devices for out door
applications.
In WP6, the performance of the state of the art ionic liquid electrolyte Z-952 was tested in W-module configuration. T he el ectrodes (front pl ate a nd b ack pl ate) w ere pr inted o n F TO gl ass ( 2.2mm thick and 7
Ohm/sq). The titania electrodes consisted in about 7 microns of 18 nm TiO2 nanoparticles. SOLARONIX
Platisol T/SP was used to print the counter electrodes. The benefits of a TiCl4 treatment are evaluated.
The phot oanodes were then s electively sensitized using the N -719 d ye ( 0.5 m M s olution in e thanol) in
presence of chenodeoxycholic acid (5 mM in in ethanol) during 15 hours. The characteristics of the resulting module were found to be Voc = 6.7 V and Isc = 54 mA leading to a encouraging PCE of 3.1% after
TiCl4 treatment, whereas untreated modules only reach a PCE of 2.2% (Voc = 6.6 V; Isc = 44 mA).
Further performance optimizations and stability testings are now under investigation.
Future work will consist in developing thin glass based modules as well as investigating solid state devices.
I-V characteristics of TiCl4 treated (on the left) and untreated modules (on the right).
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Projects related to the work described here:
Running of the 3 years "KTI-Project" N° 10584.1 PFIW-IW with the EMPA Dübendorf (Switzerland) on the
topic of near infrared absorbing organic sensitizers.
FP7-Project "INNOVASOL" – coordinated by Dr. Leo Marchese of the SiSTeMI center at the University of
Piedmont, Italy.
INNOVASOL aims to increase the efficiency of exitonic solar cells to 15 % by using innovative approaches in cell designs and novel materials (see www.innovasol.eu)
FP7-Project "SOLHYDROMICS" - coordinated by Prof. Guido Saracco at the Politecnico Torino, Italy.
This project aims to build a photoelectrochemical water splitting device based on organic (or biological)
catalysts f or l ight c ollection ( PSII s ystem) and hydrogen e volution m aterials without n oble m etals ( see
http://solhydromics.org/).
Evaluation of 2011 and outlook for 2012
During 2011, improved ionic liquid based spot-cells were fabricated showing for the first time efficiencies
above 6% and 10x10 cm sized mini-modules were also investigated.
Novel ionic liquid electrolytes are studied using polymerizable components provided by the project partners. Stability testing for over 5’000 hours at 65°C under constant artificial sun illumination of ionic liquid
filled s pot c ells s how less t han 5% performance l oss of t he d evices un der t est - this r emarkable r esult
opens the way for outdoors application of dye solar cells based on advanced ionic liquid electrolytes.
In 2012, the production of 30x30 cm (or bigger) sized modules (semi-transparent or monolithic type) will
show the production improvements achieved thanks to the ORION works.
References
http://www.cidetec.es/ORION/index.html
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DURSOL – EXPLORING AND IMPROVING
DURABILITY OF THIN FILM SOLAR CELLS
Annual Report 2011
*F. Nüesch, *R. Hany, G. *Wicht , *A.N. Tiwari, *S. Bücheler,
*C. Gretener (*Empa, Dübendorf)
°C. Ballif, °F. Sculati-Meillaud, °S. Hänni, °M. Stückelberger,
°S. Pelisset (°IMT, EPFL)
“M. Grätzel, “S.M. Zakeeruddin, “F. Duriaux Arendse (“LPI, EPFL)
^G. Nisato, ^T. Offermans (^CSEM Basel)
T. Friesen (SUPSI, Trevano)
´B. Ruhstaller, ´M. Schmid, Ó. Schumacher (´ZHAW, Winterthur)
*Empa, Lab for Functional Polymers
Address
Überlandstr. 129, CH-8600 Dübendorf
Telephone, E-mail, Homepage 058 765 4740, [email protected]
CCEM-DURSOL
Date
03.12.2011
ABSTRACT
The project objectives are focused towards the understanding of fundamental degradation phenomena i n thin film s olar c ells and enhancement of lifetime. D egradation is due to c omplex mechanisms
related t o inherent m aterial s tability; interdiffusion ac ross j unctions and du e t o external i nfluences
such as ambient atmosphere and solar light, and depends on the type of semiconductors being used
in the devices and how the solar cells are encapsulated. The way degradation processes are identified relies on the observation of the temporal evolution of device performance and its relationship to
microscopic changes in device materials and morphology. The goal of this project is to use the competences of the partners in micromorph silicon, compound semiconductors, dye sensitized and organic thin film solar cells, solar cell testing and modeling to scrutinize durability of thin film photovoltaic
devices.
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Thin film technologies occupied a remarkable market share of roughly 12 % in 2008 which was predicted to account for as much as 20% in 2010 [1]. As a matter of fact, thin film module production increased significantly during these years, but due to the considerable production increase of Chinese
crystalline silicon modules (about 9 GWp in 2010), the thin film market share reached much the same
value in 2010 which it had in 2008 [2]. CdTe based thin film solar cells are leading the field ahead of aSi. This can be attributed to a defeating production cost of 1.1 US$/Wp at the beginning of 2008 [3],
which in 2010 has tumbled to impressive 0.85 $/Wp. Even though the way for thin film technologies is
paved b y s uch breakthrough, l arge s cale d issemination an d g eneral ac ceptance ha ve s till t o b e i mproved. Above all, there is much less lifetime experience in this rather young technology as compared
to wafer silicon photovoltaics, especially when flexible solar cells are concerned. Only a few standards
and codes of best practice exist for particular thin film technologies hindering market introduction. Durability and degradation mechanisms are still topics of scientific debate and require further systematic
studies.
Several world c lass S wiss r esearch institutes do work on t he m ost pr omising thin f ilm phot ovoltaic
technologies such as µc-Si, CdTe, CIGS, DSC and OPV. Efforts have primordially been focussed on
enhancing de vice ef ficiency and pr ocessing m ethods, as f or ex ample i n t he ongoing S wiss pr oject
entitled “ThinPV”, s upported b y t he Swiss C ompetence Centre f or Energy and Mobility (CCEM) and
swisselectric research [4]. Materials aspects have been in the centre of these investigations and have
led to a profound understanding of structure and physical properties. Yet, the long term behaviour of
device performance and its dependence on the fundamental physical and chemical properties of the
materials has so far not been addressed in detail. This proposal specifically aims at a full investigation
and un derstanding of dev ice l ifetime b y ad dressing t he m icroscopic pr ocesses involved i n de gradation. T he i nvestigations w ill not on ly s crutinize c hemical an d s tructural c hanges of t he ac tive phot ovoltaic material occurring under thermal activation or light bias, but will equally address long term failure at electrical contacts or encapsulation materials. In the latter case, sealing welds and barrier properties will be in the focus of investigations.
The findings of this pr oject will be used by t he different research gr oups to improve d evice performance and reliability, by implementing the gained knowledge in new device structures and materials. As
an additional merit the acquired results shall be available to set the base for establishing testing standards and codes of good practice.
Work performed / Results obtained
- CIGS and CdTe thin film solar cells
Electrical back contacts for CdTe/CdS solar cells are commonly based on copper, which is known to
cause s evere s tability pr oblems due t o di ffusion of C u i nto t he active s olar c ell layers. T herefore, a
combination of Sb2Te3, MoO3, NiO and combinations of these materials with Sb, Te and Cu were investigated as back contact buffer layers and the solar cell parameters and the layer properties were
examined. Preliminary stress tests carried out in air under illumination of 0.5 sun at a temperature of
40°C indicate the stability of the Cu free devices with MoO3 and Sb2Te3.
Improvements w ere a lso obtained i n t he s ynthesis of t ransparent c onducting ox ide f ront c ontacts.
Aluminum doped ZnO (AZO) thin films were deposited by ultrasonic spray pyrolysis without any postdeposition t reatment. T he influences of solution ac idity, do pant c oncentration a nd f ilm t hickness on
film morphology, resistance and transmittance were studied.
- Microcrystalline silicon solar cells
Concerning light-induced degradation of amorphous silicon based solar cells, new regimes have been
tested an d s imulations per formed t o bet ter und erstand t he d egradation b ehavior ( i.e. t he Staebler
Wronski e ffect) of s ingle-junction a -Si:H s olar c ells. T he c oncentration of dang ling bo nds ( db) w ithin
the i-layer of a-Si:H solar cells has been simulated before and after light soaking for different absorber
layer thicknesses.
Damp-Heat s tability tests of c onducting t apes an d t ransparent c onductive ox ide ( TCO) s tacks w ere
performed with the aim of improving modules contacting schemes. The conductive ribbon consists of a
metallic ribbon coated on one side with a conductive pressure sensitive adhesive.
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CCEM-DURSOL, F. Nüesch, Empa
The abs orber l ayer c rystallinity R c is c ommonly l inked t o t he pr esence/density of por ous material in
microcrystalline s ilicon: t he hi gher R c, t ypically the h igher t he de nsity of por ous zones. V oc stability
between annealed state (180°C under N2 rich atmosphere for 1.5 hours after solar cell deposition) and
after 4 months atmospheric storage without encapsulation was investigated for different cell architectures. Much increased stability was observed for cell designs implicating SiOx layers.
Different kinds of front electrode morphologies have been tested to better clarify the front electrode’s
roughness influence on µc-Si:H growth quality and, more particularly, density of defective zones. The
front electrode roughness has a direct influence on the apparition/density of zones of porous material,
with, typically, a large density of porous material on very rough front electrodes
- Organic/Polymer solar cells
The s tability of ul trathin c yanine dye ( Cy3) f ilms w ith di fferent d ye c ounterion were investigated by
absorption spectroscopy. No degradation and no counterion dependence was found for films irradiated o ver 50 d ays u nder inert at mosphere. A lso, t he f ilm morphology of C y3 was f ound t o be s table
when heated at 110°C for 60 minutes.
The s tability of cyanine/C60 s olar c ells was evaluated by looking at t he effect of anode buffer layer.
Thin 10nm to 30nm thick layers of MoO3 were benchmarked against commonly used conducting polymer PEDOT:PSS. An initial performance decrease over 15 days was observed for both buffer layers
and contrasts with the stability of the cyanine films.
Polymer solar cells have been realized where PEDOT:PSS was replaced by V2O5. The novel devices
gave c omparable or s lightly better performance as t he r egular de vices. Spectral r eflectometry n ad
electroabsorption measurements were started.
- Dye sensitized solar cells
For realizing flexible dye sensitized solar cells, ionic liquids provides an attractive solution to the problem of solvent penetration through plastic foils. The addition of molecular solvents like sulfolane as a
plasticiser t o t he eutectic melt i onic liquid e lectrolytes i ncreases t he ph otoconversion ef ficiency and
durability. In this context the concentration of sulfolane was varied for solar cells based on ionic electrolyte and s ensitizer C 106. A s the c oncentration of t he s ulfolane i n t he e lectrolyte increases f rom
“0%” to “50%” the Jsc and Voc values increases and consequently the overall photo conversion efficiency ( PCE) i ncreased t o 8% ef ficiency. A t l ow l ight i ntensity t he P CE was i ncreased as hi gh as
9.4%. Long term stability under full sunlight soaking at 60°C was achieved for more than 1000h (see
Figure 1).
- Physical simulation of solar cells
Electroabsorption (EA) experiment was successfully set up, allows to better extract material parameters and to c onfirm results from el ectrical de vices simulations. The EA signal of a polymer s olar cell
was consistently modeled on the basis of the software SETFOS.
A scalar light scattering model was extended for coherent layers and experimentally validated for microcrystalline/a-Si solar cells. The planar cell is compared to the one with a structured ZnO interface.
Improved absorption is observed for the cell with a rough ZnO interface. The simulations agree nicely
with the experiment.
Main Achievements;
• Several pieces of testing equipment for testing solar cell aging and degradation phenomena have
been installed including:
- Climate chamber for accelerated solar cell and mini-module testing
(Empa, TFPV). See Figure 2
- Two accelerated OPV aging units (CSEM, Polymer Optoelectronics)
- Electroluminescence analysis set up consisting of camera and darkroom
(SUPSI, Photovoltaic Testcenter)
- Maximum Power Point Tracker (MPPT) system suitable for mini modules
(SUPSI, Photovoltaic Testcenter)
- Evaluation of a corrosion testing system
- Mechanical stress device for small and large flexible PV modules
(SUPSI, Photovoltaic Testcenter). See Figure 3.
- Bend test setups have been constructed to accelerate the aging of novel substrates
(CSEM, Polymer Optoelectronics)
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• Accelerated stress tests on CdTe devices using MoO3 back-contact layer showed stable behavior
over 150 h
• Aluminium doped ZnO films were doped with AlCl3 and shoed >74% optical transmittance and a
-3
resistivity of 3*10 Ωcm for 3 μm thick films
• Modeling s tudy o n a -Si:H s olar c ells r eveals t hat light s oaking i ncreases t he c oncentration o f
charged dangling bonds. Positively charged bonds dominate at the i-n interface.
• The open circuit voltage of cyanine solar cells was increase from 0.6 V to 0.9 V replacing
PEDOT:PSS by MoO3.
• A po wer c onversion efficiency of 9.4% was achieved using i onic liquid e lectrolytes with sulfolane
plasticizer.
• Results were communicated in form of publications and conference contributions.
Figure 1: Long term stability under full sunlight soaking at 60°C of a dye sensitized solar cell based
on C-106 dye using sulfolane based electrolyte.
Figure 2: Scheme of the chamber for accelerated solar cell testing and photo of the chamber
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Figure 3: Mechanical device to stress flexible modules
Project evaluation
In course of the first project year the planned tasks have been addressed and the work carried out is
on s chedule. Bilateral ex change of knowhow, m aterials and pr ocesses has be en i nitiated and has
taken place between the partners of the project. Industrial contributions in the form of materials supply
(chemicals and barrier foils) are greatly acknowledged.
In or der t o organize the exchange of knowledge and know-how, 4 thematic modules have be en defined which are discussed in regular topical meetings:
1)
2)
3)
4)
Chemical alteration of the PV device components by external influence (Module 1)
Improving morphological stability of the PV device layers (Module 2)
Mechanical effects of stress on device lifetime (Module 3)
Barrier properties of encapsulation materials (Module 4)
The pr oject has now been running almost one year. The k ick-off meeting as well as the first topical
meeting focusing on Mo dule 1 have b een c arried out ac cording t o t he pl an. The next w orkshop will
provide an overview of the durability of thin film solar cells given by a prestigious panel of international
th
speakers. The meeting has been fixed on April 4 2012 and will take place at Empa Akademie.
References
[1] Trends in photovoltaic applications, IEA-PVPS T1-18:2009.
[2] Trends in photovoltaic applications, IEA-PVPS T1-20:2011.
[3] Semiconductors TODAY, Compounds and Advanced Silicon, Vol 3 (7), 2008, 74.
[4] http://thinpv.empa.ch/
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ETA SOLAR CELL
EXTREMELY THIN ABSORBER SOLAR CELL
BASED ON ELECTRODEPOSITED ZNO
NANOSTRUCTURES
Annual Report 2011
Address
Date
EMPA – Materials Science and Technology
Schachenweg 24, 3250 Lyss
032 391 11 11, [email protected], www.3-s.ch
SI/500426 / SI/500426-01 – 154374/103296
01.10.2009 – 31.12.2011
05.01.2012
ABSTRACT
In this project, systematic and fundamental studies on the synthesis of new nanostructured semiconducting materials have been performed by electrochemical deposition approach combined with natural lithography and at omic l ayer d eposition. T he ef fect of na nostructure’s d imensions a nd ar chitectures on the optical engineering through the n-type semiconductors (ZnO) have been studied in order
to control the light scattering for application in nanostructured solar cells particularly for extremely thin
absorber (ETA). A dramatic improvement of light diffusion has been found by using the present new
ZnO architecture, namely urchin-like.
A clear correlation between the light scattering engineering and the light absorption has been demonstrated after the deposition of an ultrathin layer of a light absorber (CdSe) on the ZnO nanostructures.
In a later stage of the project, control of the CdSe thickness has been assessed in order to obtain an
optimal thickness for charge separation and avoiding recombination. This was followed by a full control of the p-type semiconductor (CuSCN) thickness over the core-shell ZnO/CdSe arrays.
Finally, ETA solar cells including the optimized thicknesses of light absorber and p-type semiconductor have been fabricated with different ZnO urchin-like dimensions. A perfect correlation between the
dimensions, the light diffusion, the light absorption and solar cells efficiency have been obtained. As
results, the l ight d iffusion of t he ur chin-inspired nanowire ar rays was varied from 15% t o 35% . H omogenous abs orption in t he wavelength range of 400-800 nm of up to 90% was obt ained. F irst results show ~1.33% solar conversion efficiencies. This will open important rooms of improvement for
ZnO urchin-like based nanostructured solar cells in general and particularly for ETA.
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Introduction / Project goals
In this project, the objective was to make a highly innovative contribution by suggesting and exploring
a novel concept for thin film solar cells (SC) based on low-cost electrodeposited arrays of ZnO nanostructures ( as a n-type s emiconductor) be aring t he p otential f or s olar c ell ef ficiencies ex ceeding t he
15% limit in a micrometer thin layer due to structural and cell design peculiarities [19]. These peculiarities are: ( i) t he nanostructures of ZnO ar e inherently free of extended l attice d efects and (ii) t he p-n
junction in the solar cell for charge separation can be realized radially (in the case of 1D nanostructured ZnO) so, that light absorption and generated carrier diffusion to the p-n junction can be decoupled into orthogonal directions and diffusion distances are short.
Being fully explored and developed, such a nanostructured (including nanowires, nanorods, and complex architectures) based solar cell represents a major break-through in thin film photovoltaic on cheap
glass or foil substrates [20]. Thus, the nanostructured photovoltaic concepts are free of the usual thin
film problems that hamper good solar cell efficiencies such as low grain size, high defect density and
thus limited diffusion lengths and high carrier recombination. It is, however, essential for the industrial
solar c ell implementation t hat s uch a process will not be m ore ex pensive t han the established p ure
solid ph ase c rystallization (SPC) of am orphous s ilicon ( a-Si) f ilms on gl ass t hat s erves as a benchmark. This is why the electrochemical synthesis is the obvious solution to circumvent the use of high
cost high vacuum synthesis methods.
An increase in European competitiveness for the field of thin film photovoltaic is targeted by the project
and will affect Swiss photovoltaic module manufacturers, equipment manufacturers and the scientific
community since the electrochemical deposition has the potential to be cheaper than any other deposition method (see next) and Switzerland benefits from a long tradition in plating industry that could be
implemented directly to the PV market once proof of concepts of electrodeposited solar cells has been
made.
As described earlier, single crystal ZnO layers and NWs have been already electrochemically synthesized in our previous works and a simple cell concept with all materials issues already solved will be
assessed directly. It is now important to increase the efficiency of the solar cell by focusing on different
parameters such as:
(a) Dimensions, organization and morphology control of ZnO nanostructures
(b) Controlling the light scattering through the ZnO nanostructures
(c) Controlling the light absorption after depositing an ultra-thin layer of narrow band-gap
semiconductors on ZnO.
(d) Correlating the light scattering (ZnO) and the light absorption (ZnO/light absorber).
(e) Correlating (d) with the conversion efficiency after the deposition of a p-type material
on the core-shell ZnO/light absorber.
In the following are represented the achievements that have been made during this project based on
the above goals.
Accomplished project tasks and results
Since t his s olar c ells c oncept i nvolves d ifferent t ypes of materials, di fferent k ind of el ectro-chemical
and chemical methods have been employed for the synthesis. A schematic view of ETA solar cells is
presented in Figure 1 in order to illustrate the involvement of each material in the fabrication process.
Figure 1: Schematic view of an ETA solar cell based on ZnO nanostructures
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ETA Solar CELL, J. Elias, EMPA
HOLE BLOCKING LAYER
Generally, f or t his kind of solar cells, a ho le-blocking layer barrier is needed in order to avoid s hortcircuits and contacts between the transparent conductive oxide (TCO) electrode and the p-type semiconductor. Therefore we have used the Atomic Layer Deposition (ALD) for the first time.
For t he deposition process w e h ave us ed c ommercial T CO s ubstrates ( glass/SnO2:F, 1 0 Ω/sq) purchased from Solaronix, Switzerland. The bare TCO were cleaned thoroughly by sonication with soap
in water, trichloroethylene (CH3Cl3), acetone (CO(CH3)2) and isopropanol (CH3CH(OH)-CH3), consecutively, for 15 minutes at 70 °C. After each immersion in each solvent, TCO substrates were rinsed with
ultra-pure water and dried in air.
The c leaned TCO s ubstrates have been c overed by a thin ZnO nanocrystalline layer by ALD, using
diethylzinc (DEZ) and dionized water as zinc oxide (ZnO) precursors. The deposition was performed in
6 steps cycles: a first 0.1 s pulse of DEZ, 20 s of exposure, 45 s of purge (N2), 1 s pulse of H 2O, 20 s
of exposure and 60 s of purge (N2). Each cycle was lasting 2 min and 26.1 s and deposition of 20 nm
of ZnO requires 100 cycles.
ELECTRODEPOSITION OF ZNO
ZnO nanowire arrays
The electodeposition of ZnO NWs arrays was performed in a three-electrode electrochemical cell using the T CO substrate covered b y ZnO b uffer layers as the cathode, a P t spiral wire as the counter
electrode an d a Saturated C alomel E lectrode ( SCE) as t he r eference e lectrode. We hav e us ed t he
method of oxygen reduction to obtain ZnO NWs. This method consists on an aqueous oxygen saturated solution containing zinc precursor (ZnCl2) and supporting electrolyte (KCl). The temperature was
°
kept constant at 80 C during the deposition and the potential we applied at -1 V by potentiostat (mi-5
-3
cro-Autolab). The electrolyte was an aqueous solution containing a mixture of ZnCl2 (5x10 -1x10 M)
and KCl (0.05-3.4 M), saturated with bubbling oxygen 10 min before and during the experiment. The
ultrapure water ( 18 MΩ.cm) was provided by a Millipore setup. Anhydrous ZnCl 2 salt ( Flucka, pur ity
2+
>98.0 %) was used as the Zn precursor. KCl (Flucka, purity >99.5 %) served as a supporting electro2
lyte. The charge density was varied between 1 and 40 C/cm .
Electrodeposition of ZnO urchin-like arrays
A novel approach to fabricate hollow urchin-like ZnO NWs with tailored dimensions has been developed during this project. The method combines the formation of a polystyrene (PS) microsphere colloidal monolayer, an Atomic Layer Deposition of a thin buffer layer of ZnO and the electrodeposition of
ZnO nanowires arrays, f ollowed by the elimination of the PS microspheres (which pl ay t he r ole of a
template). The deposition process is shown in the schematic view of Figure 2.
Figure 2: Process steps for the fabrication of ZnO urchin structures:
(a) Polystyrene spheres coating on TCO substrate by spin coating; (b) Size reduction of the PS
spheres by oxygen plasma etching; (c) Deposition of ZnO buffer layer by Atomic Layer Deposition;
(d) Electrodeposition of ZnO nanowires (n-type); (e) PS spheres elimination in toluene.
ELECTRODEPOSITION OF CDSE
CdSe was deposited electrochemically from an aqueous alkaline selenosulfate solution at room temperature (0.05 M cadmium acetate, 0.1 M nitrilotriacetic acid trisodium salt and 0.005 M selenosulfate,
with excess sulphite). The pH of the solution was adjusted by acetic acid to~8-9. CdSe was deposited
2
galvanostatically ( J= -3 m A/cm ) i n a t wo-electrode el ectrochemical c ell with t he T CO/ZnObuffer/
ZnONWs samples as cathode and a spiral wire of Pt as a counter electrode. CdSe electrodeposition is
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2+
based on the reduction of selenosulfate ions and the further chemical reaction between Se
ions [26].
2+
and Cd
The different thicknesses of deposited CdSe on the ZnO nanostructures can be obtained by control2
ling precisely the charge density (from 0.25 to 0.65 C/cm ) based on the estimated surface area of the
ZnO nanostructures. The deposited CdSe samples were then annealed in air at 350 °C for 1 hour.
SOLUTION CASTING OF CUSCN
-2
The C uSCN l ayer is d eposited f rom a s aturated s olution of C uSCN ( ~5.75×10 M, A ldrich, pur ity
~99%) in n-propyl sulfide. The TCO/ZnOBuffer/ZnONWs/CdSe samples were preheated at 100 °C on a
hot pl ate. After heat ing, the C uSCN saturated s olution was i nfiltrated through the core-shell ZnO u rchin-CdSe by using a micropipette set to automated bench.
2
The amount of solution used in the CuSCN deposition process varied between 0.10 and 0.25 ml/cm
depending on the needed thickness over the ZnO nanostructured arrays. The volume corresponding
to the CuSCN thickness was calculated by using the following equation:
VCuSCN = 0.0637 x (LNW + ThCuSCN)
-2
Where VCuSCN is the volume of the CuSCN solution in mL.cm , LNW is the length of NWs in μm and
ThCuSCN is the thickness of CuSCN from over the urchin structures in μm.
SPUTTERING OF GOLD BACK CONTACTS
To complete the fabrication of ETA-solar cells and provide the electrical contact between the cell and
the TCO, 100 nm thin layer of gold was deposited onto the TCO/ZnObuffer/ZnONWs/CdSe solar cells by
using plasma sputtering machine (Balzers Union SCD 040). 10 min of sputtering is required to obtain
about 100 nm of thickness.
Results and discussion
CONTROLLED SYNTHESIS OF ZNO
Different systematic studies have been carried out in this part of the project. The drawn conclusions
from the control of the nanostructure dimensions as a function of the different parameters of the process are summarized below:
- The interspace between the Urchins can be precisely controlled by controlling the
PS sphere sizes.
- The increase in charge density at low supporting electrolyte concentration leads to a
preferential growth along the c-axis of the NWs and results in the control of the length
and the density of NWs.
- The concentration of zinc precursor plays an essentially role on the diameter variation.
- The concentration of the supporting electrolyte affects both the length and the diameter
of the NWs and plays an important role on the global architecture of the Urchin-like
structures.
The aim of these studies was to control the dimensions of the ZnO NWs arrays and the morphology of
the global structure. The obtained results enable for the first time a precise control of the diameter and
the length of the NWs as well as the interspace and the architecture of the Urchin-like structures.
LIGHT SCATTERING OF ZNO URCHIN-LIKE STRUCTURES
By c ombining O -plasma t reatment, A LD, a nd electrodeposition, the ur chin l ike Z nO bu ilding b locks
can be engineered in numerous designs and in a very precise manner. In order to study the geometry
influence of t he Z nO building-blocks on t he light s cattering, t he s pectral dependence of t he optical
reflectance (R) of the samples obtained in the previous part of the project has been measured.
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a)
b)
NWs on flat surface
c)
d)
Figure 3 : Optical r eflectance of t he s amples: a) V ariation of i nterspacing between t he urchin-like st ructures; b)
Increasing NW length by keeping constant the sphere interspace (3.3 µm) and the ZnO NW diameters (~100 nm);
c) Varying NW diameters and keeping constant the NW lengths (~300 nm) and the sphere interspace (3.3 µm); d)
Zoom into the region of UV absorbance edges of Figure 3c.
In order to reflect the importance of the three-dimensional architecture based on urchin-like buildingblocks, a ZnO NW carpet was electrodeposited onto a flat FTO substrate that had been covered by a
20 nm t hin A LD layer of Z nO. T he r eflectance of t his pl anar c arpet ar chitecture was m easured
(dashed c urve, f igure 3b) and c ompared t o t he c orresponding ur chin architecture ha ving t he s ame
NWs’ di mensions ( Figure 3b; di ameter~100 nm , l ength~450 nm ). A n i ncrease of about 50% of t he
reflectance was observed throughout the entire visible range. For constant NW lengths (~300 nm) and
sphere i nterspace (3.3 μm), t he variation of t he NW diameter had no ef fect on the m aximum reflectance value ( Figure 3c), h owever a r edshift with increasing d iameter was observed ( dashed l ines,
Figure 3d). According to Mie theory [29] the size, the shape, and the distance between the irradiated
particles ar e t he m ain par ameters t hat c over t he multiple s cattering of t he i ncident l ight. D ue t o t he
complexity of the 3D urchin-like architecture, the reflectance spectra (Figure 3) can be, for instance,
interpreted qualitatively b y c onsidering NWs as s cattering c enters. Regardless o f t he NWs s ize, the
increase of t he interspace bet ween t he ur chin-like s tructures dec reases pr ogressively the m ultiple
scattering (Figure 3a). This tendency can be explained by the decrease of the size of the urchin-like
structures and t he l arger i nterspace bet ween t hem. I n ot her words, when t he s ize of t he ur chin-like
structures decreases less light is trapped by a single structure. Additionally, the target of the reflected
light from one structure to another increases with increasing interspace, which leads to a loss of scattered light, and, therefore to a reduction of the total reflectivity of the urchin-like substrates (Figure 3a).
Same tendency, but more pronounced, has been found in the case of constant NW diameter and interspace with an increased NW length (Figure 3b). A recent experimental study concerning the effect
of ZnO NW size on the light scattering showed that the length of vertical NWs in carpet architecture
increases the reflectivity only for a certain wavelength range (400-600 nm). In our urchin-like architecture, the increase of the total reflectivity is found to cover a large wavelength range 400-800 nm. This
is most probably due to the fact that NWs are exposed to the incident light from all the directions (i.e.
angles) in urchin-like building blocks thus enhancing even more the light scattering. While the increase
in t he N Ws l ength e nhances t he m aximum of t he t otal reflectivity at f ixed wavelength ( 400 nm), t he
increase in the diameter size results in a redshift of the whole spectrum (Figures 3c and 3d). We relate
this shift to the scattering of the long wavelength visible radiation due to the augmentation of the size
of the scattering center when the NWs diameter increases [27].
OPTIMIZATION OF DIFFERENT LAYER THICKNESSES
The optimization of the absorber (CdSe) and the p-type semiconductor (CuSCN) thicknesses are necessary f or ha ving i deal c harge s eparation and t ransport t hrough an d within t he di fferent i nterfaces
(ZnO/CdSe and CdSe/CuSCN). It has been shown that the deposited CuSCN thickness over the top
of the nanowires arrays is an important factor regarding the efficiency of the complete solar cell. [30]
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-
+
Similarly a c ompromise bet ween t he h igh photon a bsorption and t he l ow e -h pair s eparation an d
recombination requires an ideal thickness for the absorber.
Optimization of the thickness of CdSe
Solar c ells bas ed on t he c ore-shell Z nO-CdSe s tructures hav e bee n c ompleted b y infiltration of an
-2
equal amount of CuSCN (0.172 ml.cm ) leading to a thickness over the structures (ZnO/CdSe coreshell) of about ~2 μm. Finally a gold thin layer of about 100 nm was deposited on the previous deposited semiconductors in order to provide an electric contact for the ETA solar cell. The J-V characteris2
tics of eac h c ell ha ve been m easured under ha lf s un ( 500 W/m ). T he variation of C dSe t hickness
from 12 t o 84 nm has no not iceable i nfluence on t he ope n c ircuit voltage ( Voc) t hat r emains m ainly
constant between 0.42 and 0.48 V. On the other hand, the values of the Short Circuit current density
2
(Jsc) increase from 1.13 to 1.56 mA/cm when the thickness increases from 12 to 34 nm, respectively.
Thicker t han 34 nm , t he J sc decreases gr adually with t he i ncrease of t he t hickness. The ph otogenerated electron-hole pairs cannot be well separated which lead to a recombination increase, therefore, to a dramatic drop of the Jsc.
0.6
η (%)
0.4
0.2
0.0
20
40
60
80
CdSe thickness (nm)
Figure 4: Conversion efficiency (η) as a function of CdSe thickness
As a partial conclusion for this study, the solar cell with about 30 nm CdSe thin layer gives rise to the
optimal J sc and allows an enhancement in the conversion efficiency up to 0.53% (Figure 4). Therefore,
in the following studies the CdSe thickness will be fixed to about 30 nm.
Optimization of CuSCN thickness
Different t hicknesses of C uSCN have b een o btained b y infiltrating d ifferent amount of s aturated
CuSCN solution.
The above solar cell devices were completed by depositing a gold thin layer and the J-V curves were
measured under half sun. As results, Voc and the fill factor (FF) do not present significant evolution and
remain in the range of 0.45 V and 34%, respectively. The differences obtained for the conversion efficiencies are mainly due to the variation of Jsc. The efficiency was increased from 0.23 to 0.53% when
the CuSCN layer thickness increased from 0.68 to 1.85 μm above the nanostructured ZnO/CdSe urchins. The efficiency decreases when the thickness was higher than 1.85 μm. This optimal thickness
is most probably related to the complete filling of the structure. The loss of current density and solar
efficiency for the cells having thicknesses above 2.1 μm can be due to the increase of the electronic
diffusion length which consequently leads to an increase in the carrier recombination. In the following
parts of the project the CuSCN thickness was fixed to 1.85 μm above the urchin structures.
ROLE OF NANOSTRUCTURATION ON ETA PERFORMANCE
Light absorption
To study the effect of light scattering on the sensitization of the urchin-like building blocks we coated
the s eries of di fferent NW lengths with a C dSe absorber f ilm of c onstant t hickness ( ~30 nm ). C ompared to the reflectance graph in figure 3b a clear correlation was detected for the absorbance after
adding t he C dSe layer, indicating t hat m ultiple s cattering i n t he ur chin-like s tructures en hances t he
optical absorption through ZnO/CdSe core-shell urchins. A quantification of these absorption spectra
is made by calculating the effective absorption in the region where CdSe absorbs (400-800 nm). An
increase of AE from ~52% to ~90% is already obtained by increasing the NW lengths from 0.3 to 1µm.
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In order to confirm the NW dimension effect on the scattering and the absorption, we fixed the length
of NWs to ~450 nm and varied the thickness of CdSe absorber layer from 11 to 90 nm. Even by increasing the thickness up to 90 nm, the absorbance values were still lower than the one with the thinner CdSe layer (~30 nm) and longer NWs (~1 µm). This proves that the absorption of ZnO/CdSe coreshell building-blocks can be efficiently enhanced by our approach.
ETA performance
The final ZnO/CdSe/CuSCN ETA solar-cells were obtained by covering the core-shell ZnO/CdSe urchin-like building-blocks with CuSCN and a gold sputtered layer. It is clearly seen that Jsc values followed the same behaviour as AE. The values of the open-circuit voltage (Voc) a nd fill factor (FF) are
almost constant with increasing NW length (Figure 4).
Figure 4 a) Short circuit current densities Jsc of solar-cells based on urchin-like building blocks having different
lengths of ZnO NWs. For a direct comparison effective absorbance values (AE) are displayed together; b) are
the current density-voltage curves as a function of nanowire’s length measured under half sun. All the solar
characteristics are included in the graph.
The c ombination of t hese c haracteristics l eads t o an al most l inear i ncrease of t he c onversion ef ficiency (Figure 4a) from 0.37% to higher than 1.3% by only increasing the ZnO nanowire lengths from
300 to 1050 nm. These r esults pr ove, f or t he f irst time, t hat s olar-cells c an be m ade b y threedimensional, urchin-like ZnO nanowire building blocks. Although our actual best solar-cell efficiency is
still s lightly lower with r espect t o the f ew pu blished works c oncerning Z nO/CdSe/CuSCN s olar-cells
(1.33% vs 2%), we strongly believe that there is a big potential for solar cell improvement by further
optimizing the geometry of urchin-like ZnO nanowire building-blocks as well as for the optimization of
absorber layer and hole collector layer thicknesses and materials.
Conclusion
In t his pr oject, we h ave es tablished a n ovel low-cost synthesis r oute t o pr oduce l arge areas of pe rfectly-ordered h ollow s elf-stabilized ur chin-like Z nO nanowire bu ilding-blocks by a c ombination of
polystyrene s phere pat terning, a tomic l ayer dep osition, and e lectrodeposition. T he pr ocess al lows a
wide control of the dimensions of arrays of urchin-inspired building building-blocks and their constituting ZnO nanowires. This method opens the door for investigations of a large class of semiconducting
and m etallic m aterials in more c omplex t hree-dimensional ar chitectures f or d ifferent t ype of ap plications, like short-wavelength lasers, piezoelectric nanogenerators, nanogenerators, electroluminescence, and field-emission devices. For the first time, we proved the functionality of this unique architecture in extremely thin absorber solar-cells. A clear correlation between the geometry of the urchinlike building block, the optical properties, and the solar efficiency has been stated offering promising
applications of such building-blocks in different types of nanostructured solar-cells (organic, hybrid and
dye sensitized solar-cells) as well as in applications where specific architectures of high surface area
structures are an asset like for wettability, gas sensing, and biofuel cells. Although the actual efficiency
still relatively low, many rooms of investigation are planned in the future research to improve the performance.
First we believe that we had a full control in terms of control of the architecture of the n-type semiconductor (ZnO) and the optimal thickness of CdSe. In the following steps, the focus will be on the interfacial r ecombination and s eparation a t t he n -type|absorber i nterface. While s pontaneous dec ay of
charge carrier, recombination within the absorber may be efficiently suppressed due to the ETA-solar
cell c onfiguration; t he s ubstantially enlarged s urface ar ea i s ex pected t o l ead to a c onsiderable increase of interface recombination probability (as compared to a flat surface of the same optical den7/8
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sity). Therefore, the aim is to add a shell passivation layer of transparent and wide band gap semiconductors (allowing light to reach the absorber) with low conductivity (through which electron tunneling
can occur) on the core ZnO nanostructures in order to control/slow-down the active interface recombination kinetics. On the other hand, similar study will be performed at the absorber|p-type interface. In
addition, we believe that the determination of the fundamental requirements for dopant incorporation
into the p-type material will improve efficiently the performance of ETA solar cells. Ultimately, we hope
to de termine an optimal des ign of E TA s olar c ell enabling r ise of c onversion e fficiency c lose t o t he
predicted one.
References
[1] B. Jalali, S. Fathpour, Silicon photonics, Journal of Lightwave Technology 24, 12, 4600-4615, 2006.
[2] J. Zhao, A. Wang, M.A. Green, 24.5% efficiency silicon PERT cells on MCZ substrates and 24.7% efficiency PERL cells on
FZ substrates, Progress in Photovoltaics: Research and Applications, 7, 6, 471-474, 1999.
[3] Y. Li ang, D . F eng, Y . Wu, S . T sai, G . Li , C . R ay, L. Y u, H ighly ef ficient solar c ell pol ymers dev eloped v ia f ine-tuning of
structural and electronic properties, Journal of the American Chemical Society 131 22, 7792-7799, 2009.
[4] B. O'Regan, M. Grätzel, Low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films, Nature 353 (6346),
pp. 737-740, 1991.
[5] http://solarcellsinfo.com/dyecell/node/5713
[6] http://www.oled-display.net/organic-solar-cells-reach-6-confirmed-efficiency/
[7] Y. Li, J. Xiang, F. Qian, S. Gradečak, Y. Wu, H. Yan, D.A. Blom, C.M. Lieber, Dopant-free GaN/AlN/AlGaN radial nanowire
heterostructures as high electron mobility transistors, Nano Letters, 6, 7, 1468-1473, 2006.
[8] X. Wang, J. Song, P. Li, J.H. Ryou, R.D. Dupuis, C.J. Summers, Z.L. Wang, Growth of uni formly al igned Z nO nano wire
heterojunction arrays on GaN, AlN, and Al0.5Ga0.5N substrates, Journal of the American Chemical Society 127, 21, 79207923, 2005.
[9] Huang, M.H. et al. Room-temperature ultraviolet nanowire nanolasers. Science 292, 1897-1899 2001.
[10] Wang, Z.L. & Song, J.H. Piezoelectric nanogenerators based on zinc oxide nanowire arrays. Science 312, 242-246 2006.
[11] Park, W.I. & Yi, G.C. Electroluminescence in n-ZnO nanorod arrays vertically grown on p-GaN. Adv. Mater. 16, 87-+ 2004.
[12] Tseng, Y.K. et al . C haracterization and f ield-emission pr operties of needl e-like z inc ox ide nano wires gr own v ertically on
conductive zinc oxide films. Advanced Functional Materials 13, 811-814 2003.
[13] F.M. Ross, J. Tersoff, M. Reuter, Sawtooth faceting in silicon nanowires, Physical Review Letters 95 14, 146104, 1-4, 2005.
[14] S. P eulon, D . Li ncot, C athodic el ectrodeposition f rom aqueous s olution of dens e or open -structured z inc o xide f ilms, Advanced Materials, 8, 2, 166-170, 1996.
[15] J. E lias, R. T ena-Zaera, C . Lév y-Clément, E lectrochemical depos ition of Z nO nanow ire ar rays with t ailored di mensions,
Journal of Electroanalytical Chemistry 621, 2, 171-177, 2008.
[16] C. Lévy-Clément, R. T ena-Zaera, M.A. Ryan, A. Katty, G. Hodes, CdSe-sensitized p-CuSCN/nanowire n-ZnO het erojunctions, Advanced Materials, 17, 12, 1512-1515, 2005.
[17] R. Könenkamp, R.C. Word, C. Schlegel, Vertical nanowire light-emitting diode, Applied Physics Letters 85, 24, 6004-6006,
2004.
[18] Z.L. Wang, ZnO nanowire and nanobelt platform for nanotechnology, Materials Science and Engineering R: Reports 64, 3-4,
33-71, 2009.
[19] K. Taretto, U. Rau, J.H. Werner, Method to extract diffusion length from solar cell parameters - Application to polycrystalline
silicon, Journal of Applied Physics 93, 5447-5455, 2003.
[20] S. Chu, D. Li, P.-C. Chang, J.G. Lu, Flexible Dye-Sensitized Solar Cell Based on Vertical ZnO Nanowire Arrays, Nanoscale
Research Letters 6, 1-4, 2011.
[21] J.-S. Na, B. Gong, G. Scarel, G.N. P arsons, S urface pol arity s hielding and hi erarchical ZnO nano-architectures produced
using sequential hydrothermal crystal synthesis and thin film atomic layer deposition ACS Nano 3, 3191-3199, 2009[22] J. E lias, R . T ena-Zaera, C . Lév y-Clément, E ffect of the c hemical nature of t he ani ons on t he el ectrodeposition of ZnO
nanowire arrays, Journal of Physical Chemistry C 112, 5736-5741, 2008.
[23] J. Elias, C. Lévy-Clément, M. Bechelany, J. Michler, G.-Y. Wang, Z. Wang, L. Philippe, Hollow urchin-like ZnO thin films by
electrochemical deposition, Advanced Materials 22, 1607-1612, 2010.
[24] J. Elias, R. Tena-Zaera, C. Lévy-Clément, Electrodeposition of ZnO nanowires with controlled dimensions for phot ovoltaic
applications: Role of buffer layer, Thin Solid Films 515, 8553-8557, 2007.
[25] J. E lias, R . T ena-Zaera, C . Lév y-Clément, E lectrochemical depos ition of Z nO nanow ire ar rays with t ailored di mensions,
Journal of Electroanalytical Chemistry 621, 171-177, 2008.
[26] R. Tena-Zaera, J. Elias, C. Lévy-Clément, ZnO nanowire arrays: Optical scattering and s ensitization to solar light, Applied
Physics Letters 93, art. no. 233119, 2008.
[27] R. Tena-Zaera, J. Elias, C. Lévy-Clément, Role of chloride ions on electrochemical deposition of ZnO nanowire arrays from
O2 reduction, Journal of Physical Chemistry C, 111, 16706-16711, 2007.
[28] V. Srikant, D.R. Clarke, On the optical band gap of zinc oxide, Journal of Applied Physics, 83, 5447-5451, 1998.
[29] C. F. Bohren and D. R. Huffman, Absorption and Scattering of Light by Small Particles Wiley, New York, Chap. 4, 1998.
[30] J. Elias, Ph.D. Réseaux de nanofils et de nanotubes d'oxyde de zinc de dimensions contrôlées obtenus par voie électrochimique : application aux cellules solaires nanostructurées, 1998.
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NUMERICAL SIMULATION, DESIGN AND
FABRICATION OF EXTREMELY THIN
ABSORBER SOLAR CELLS
Annual Report 2011
1
1
1
M. Loeser, K. Lapagna, B. Ruhstaller,
2
J. Elias, L. Philippe
1
ZHAW School of Engineering
2
EMPA, Thun
Address
Technikumstrasse 9, CH-8401 Winterthur
Telephone, E-mail, Homepage 058 934 78 06, [email protected]
SI/500613 / SI/500613-01
Date
30.11.2011
2
ABSTRACT
Our joint research focuses on combining both numerical and experimental methods to analyze and
improve the optical efficiency of extremely thin absorber (ETA) solar cells. As a first step we produce
and measure various reference devices with simplified geometries that are used as benchmark examples. On the computational side we are extending our novel and cutting-edge three-dimensional
full-wave optical simulation software OPUS 3-D in such way, that it allows for the numerical simulation of ETA solar cells and returns data that can directly be compared to experimental results. By
showing that experimental and numerical data do not only agree for simple structures but for many
classes of devices with increasing geometric complexity we aim at establishing a combined framework for the analysis and design of next-generation ETA solar cells. It is a unique approach as the
optical characteristics of ETA solar cells are systematically being analyzed by combining elaborate
experimental and numerical methods.
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Introduction
The overall project goal is the development of a combined formalism that can help to both analyze and
design ETA solar cells. To this end we aim at proving that our in-house three-dimensional full-wave
software tool can reproduce and predict measured absorption, transmission and reflection spectra for
ETA solar cells with a very broad range of designs.
The goals for the first eight months of the project are two-fold. On the experimental side the focus is –
as outlined in Work Package 1 – the production a nd e xperimental characterization o f v arious
reference d evices with different degrees of complexity. Typical designs feature planar double- and
multi-layer structures with varying thicknesses. These devices are then used for benchmarks. On the
software side, the focus is on enhancing the simulator OPUS 3-D in such way, that ETA solar cells
can be numerically analyzed. In detail the deliverables include implementation of plane-wave sources
(so far, only dipole sources could be accounted for), perfectly matched layer (PML) boundary
conditions to avoid spurious and unphysical solutions, and novel post-processing mechanisms that
allow a direct comparison between measured and experimental data. The extension of OPUS 3-D also
includes the comparison of numerical simulation results with analytic reference solutions.
The results obtained so far lay a sound foundation for a large-scale analysis between measured and
experimental data and allow achieving the overall goals of the project.
By uniquely combining elaborate experimental and numerical tools, this project focuses on
systematically analyzing and designing next-generation ETA solar cells.
Performed Work and Achievements
STATUS RE PORT O N W ORK P ACKAGE 1: FABRICATION AND C HARACTERIZATION O F
SAMPLE DEVICES.
Following the procedure outlined in the proposal, various simple reference structures were produced,
and their optical characteristics were obtained experimentally. As the focus of this work package lies
on benchmarking, we chose planar and nanostructured designs for which we measured both the
transmission and reflection coefficients for a large range of optical frequencies.
1. Production of structures. Two classes of devices have been produced and measured within Work
Package 1 – both device designs are shown in Figure 1. The first reference design consists of a
transparent glass substrate with a transparent conducting oxide (TCO) contact on top. For our
purposes we have chosen a SnO2:F layer with a thickness of 1mm as TCO (see cross sections
SEM view in Figures 1c and 1d). The second class of devices additionally features an array of
ZnO nanowires (NWs) on top of the TCO that serves as large band-gap n-type material for the
electron transport. The TCO substrates (SnO2:F/glass) were purchased from Solaronix, Switzerland. The electrodeposition of ZnO NW was performed in a three-electrode electrochemical cell
with the substrate (conducting glass) as the cathode, a Pt spiral wire as the counter electrode and
a saturated calomel electrode (SCE) as the reference electrode. The electrolyte was an aqueous
-4
solution of ZnCl2 (5x10 M) and KCl (0.1 M), saturated with bubbling oxygen. The ultrapure water
(18 MΩ.cm) was provided by a Millipore setup. The ZnCl 2 salt (Flucka, purity >98.0%) acts as a
2+
Ω/square) glass/SnO
Zn precursor. The substrates were conducting (10
2:F from Solaronix,
2
Switzerland. For each working electrode, a geometric surface of 2 cm was masked off prior to the
electrodeposition experiments. As a first step, they were covered by a nanocrystalline ZnO buffer
2
2
layer galvanostatically electrodeposited at room temperature (J = -0.15 mA/cm , Q = 0.4 C/cm )
-3
using ZnCl2 and KCl concentrations of 5x10 and 0.1 M, respectively. On top of the nanocrystalline
ZnO buffer layer, the ZnO nanowire arrays were electrodeposited at 80 °C under –1 V constant
2
potential. The charge density was 20 C/cm [1,2].
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Fabrication and Numerical Analysis of ETA Solar Cells, J. Elias + M. Loeser, ZHAW/EMPA
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Figure 1: Sem micrographs of ZnO NW arrays electrodeposited on SnO2:F substrates. a) and b) are the low
and high magnification t op view i mages, r espectively. c) and d) ar e t he l ow and h igh magnification c rosssectional view images, respectively. This sample was produced and measured at the Empa in Thun.
In order to set the measured reflection and transmission spectra on a broader footing, the
thickness of the ZnO layer has been varied between 670nm and 3360nm for the second class of
devices. Thus, experimental data has been obtained for five different layer thicknesses. The
variation of the layer thickness is depicted in Figure 2.
Figure 2: A series of reference devices featuring a ZnO-layer with t hicknesses between 670nm and
3360nm. These devices were also produced and measured at the Empa in Thun.
2. Measurement of reflection and absorption spectra. After processing, the optical transmission (T)
and reflectivity (R) spectra of the samples were measured at room temperature using an Ocean
Optics HR2000+ES spectrophotometer connected to an integrating sphere. An Ocean Optics DH2000-BAL served as light source. A schematic view of the setup is shown in Figure 3. Two
different integrating spheres have been used: one for the transmission (left scheme) and the
other for the reflectivity (right scheme) measurements. When incident light passes through the
sample (depending on its position) it can be diffracted in all directions inside the integrating
spheres. A detector then collects the sum of all diffractions through an optical fiber, and this is
how transmission or reflectivity spectra were obtained. After the measurements of T and R the
absorption A can be obtained according to the Beer–Lambert law: A= 1 –T–R. The measured
reflection, transmission and absorption spectra are shown in Figure 4.
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Figure 3: Schematic view of the configuration used to measure the total transmission (left) and
reflectivity (right).
Figure 4: Spectral measurement of transmission, reflection, and absorption. The top figure shows the results
for a two-layer structure (glass substrate and TCO) whereas the bottom figure shows the same results for a
three-layer structure (glass substrate, TCO, and ZnO nanowires).
As a next step we will make the transition towards more complex structures. First, we will analyze
planar structures with multiple layers that represent a simplified model of the entire ETA solar cell.
Then, we focus on devices featuring advanced geometries such as structured layers or textured
surfaces.
Summing up, important aspects of Work Package 1 have been fulfilled, whereas further activities
are still ongoing. As outlined in the project proposal the devices and measured data created in
Work Package 1 are currently being used as an input for other work packages, above all in Work
Package 3.
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STATUS R EPORT O N WO RK P ACKAGE 2 : EXTENSION O F SO FTWARE F EATURES I N T HE
EXISTING SIMULATOR OPUS 3-D.
1. Sanity check of the simulator – comparison to analytical reference solutions. Prior to enhancing the
capabilities of OPUS 3-D we aimed at showing that the three-dimensional full-wave simulation
results are both qualitatively and quantitatively accurate. To this end they were compared to
analytical reference solutions. The benchmark problem we have chosen consists of a dipole
radiating into free space. This seemingly simple model poses severe computational challenges, as
the dipole – in a mathematical sense – forms a singularity and is therefore a strong challenge for
any kind of numerical simulation tool [3]. Figure 5 shows a comparison between the numerical
computation and the analytical reference solution for both the electric and the magnetic fields E
and H. In both cases the gray lines represent isoclines of the electric and magnetic field that have
been obtained using the numerical simulation software. For a direct comparison the green lines
represent the same isoclines that have been obtained from the analytical solution. Although there
are some minor deviations in very close proximity to the singularity the plots indicate that both
solutions are nearly identical.
Figure 5: Electric field component Ex (left), and magnetic field component Hz obtained with numerical
simulation. The gray lines indicate isoclines of the numerical solution (E = 700 v/m, H=2 a/m), the green lines
show the same isoclines for the analytical solution.
The excellent agreement between analytical and numerical solution for both the electric and the
magnetic field – obtained for a problem featuring a singularity in the simulation domain – shows the
software’s numerical stability and accuracy.
2. Implementation of P erfectly Mat ched Lay ers ( PML) as abs orbing boundary c ondition. It is well
known from literature that standard absorbing boundary conditions that so far have been utilized in
OPUS 3-D, can lead to numerical reflections at the boundary of the simulation domain. This, in
turn, leads to a non-physical standing wave pattern. There are several typical situations where
these spurious patterns can occur, for example when calculating the emission beam of an antenna
or a dipole. To further challenge the validity of the simulator we also computed the emission beam
corresponding to the dipole problem. This beam analysis is not an academic purpose but helps to
verify that the novel boundary conditions – the PML – work properly and efficiently. Figure 6 shows
the emission beam that has been obtained after implementing the PML.
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Figure 6 : Numerically c omputed em ission beam of a di pole r adiating into f ree s pace. T he s lice shows t he
electric field in a plane perpendicular to the dipole axis – the isoclines of the electric field are concentric circles
and are used to prove that the beam features rotational symmetry.
The plot clearly illustrates the rotational symmetry and doughnut-like emission beam that we would
expect from theory. The use of PML can decrease the numerical error of the simulation by a factor
of five [3], and obtaining the correct beam shape is impossible without utilizing PML. Thus, PML are
an important means to boost both accuracy and numerical stability of the simulator.
3. Implementation of plane wave s ources. As OPUS 3-D was originally designed for the analysis of
emission problems, the initial version could only deal with dipole sources inside the simulation
domain. As we are aiming at numerically investigating structures that are irradiated with plane
waves the simulator had to be extended in such way, that plane wave propagation can now be
accounted for. In a first step, the idea of utilizing arrays of dipoles to mimic an incident plane wave
was explored. Yet, it turned out that this approach has only limited applicability for two reasons.
First the resulting field (created with 900 dipoles) does still not produce a plane wave. Second, the
use of many distributed dipole sources mandates locally strongly refined meshes, and this
outbalances the computational efficiency, as the entire formalism is designed too yield accurate
results on coarse meshes. Thus, in an alternative approach, plane wave sources have been
incorporated as special boundary conditions. This solution leads to significantly improved results
while reducing numerical issues that would arise during the treatment of singularities. Figure 7
gives an example of what the free-space solutions look like when the novel boundary condition is
employed. As opposed to the dipole array much higher field uniformity can be achieved with this
novel boundary condition. At the same time – alleviating the necessity of strong mesh refinement –
both computation time and memory consumption were significantly reduced.
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Figure 7: Field produced by a plane wave source at the boundary of the 3-D simulation domain. The slices
show the propagation of t he electric f ield, t he ar rows i ndicate poynting’s v ector and t hus r epresent both the
power flow in each point and the propagation direction of the plane wave.
4. Advanced pos t-processing. To compare simulated data with spectral measurements, OPUS 3-D
needs to be extended in such way that it allows to extract both reflection and transmission spectra
from the simulation. As we so fare focused on enabling plane wave radiation and ensuring both
efficiency and accuracy, this work is currently ongoing. However, the previous implementations and
extensions of the simulation software have laid the foundation for developing efficient postprocessing schemes.
STATUS RE PORT O N W ORK P ACKAGE 3: BENCHMARKING WITH S IMPLE R EFERENCE
STRUCTURES.
Prior to comparing the reflection and absorption spectra obtained from spectral measurements and
three-dimensional optical simulations we need to ensure that we employ the correct material
parameters (above all, the refractive indices) in our numerical analysis. Obtaining these parameters is
quite challenging task for several reasons. First, due to process variations and uncertainties, the
manufacturer of the glass substrate cannot exactly indicate the exact index of refraction, but rather
gives quite large an interval in which this index should lie. Second, both the TCO and the ZnO layer
are not made of bulk but nanostructured material. As a consequence it is unclear, which index of
refraction to employ when modeling these nanostructures as bulk layers with an effective index of
refraction. Therefore we extracted the refractive indices of the relevant materials from the measured
data. The procedure of parameter extraction is based on fitting absorption and transmission spectra
that are obtained from one-dimensional transfer-matrix calculations to the measured spectra. Here, we
employ the commercial Software tool Setfos [4] that has proven to yield very viable results for a very
broad range of applications. During the fitting procedure a conjugate-gradient optimization algorithm is
applied to determine the optimal parameters for a Sellmeier refractive index model that describes both
refractive index n and absorption coefficient k of a material as a function of the optical wavelength. A
direct comparison between fitted and measured curves for the FTO-coated glass sample is shown in
Figure 8. The numerical values that were obtained for n and k agree well with what is reported in
literature.
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Figure 8: Fitting of the reflection and transmission curve for the FTO-covered glass to extract the refractive indices. The green curves indicate measured data, the red curves represent the fits. The error is below 3%.
The agreement between experiment and simulation is good, even though the angle of incidence in the
simulation is strictly zero whereas it varies in the experimental integrating sphere configuration (see
Fig. 3). From the fit, an FTO layer thickness of 807 nm is obtained, which is slightly below the
thickness as estimated by the SEM (see Fig. 1).
In Figure 9 we proceed with the analysis of the layer structure glass/FTO/ZnO (c.f. Figure 1c and 1d).
Here, the nanowire ZnO layer is modeled with an effective index approach and the FTP layer is
treated incoherently. The FTO thickness and refractive index were assumed to be identical to what
was obtained from Figure 8. Thus, only the refractive index dispersion of the ZnO layer and its
thickness were fitted.
Figure 9 : Fitting of the transmission and absorption spectra for the layer structure glass/FTO/ZnO. The FTO
thickness and r efractive index ex tracted i n f igure 8 w ere fixed an d t he ZnO refractive i ndex a nd l ayer t hickness
were fitted.
Summing up, Work Package 3 has successfully started and is still ongoing.
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National Collaboration
The entire project is based on a national cooperation between the EMPA Thun and the Zurich
University of Applied Sciences. Whereas specific work packages such as the production and
measurement of reference devices, or software-based tasks such as implementation of postprocessing procedures into OPUS 3-D can be carried out rather independently, there are other work
packages such as the extraction of the refractive indices from measured data that require close
collaboration and efficient communication between all partners. In order to guarantee that solutions
are found most efficiently all strategic questions such as which devices produce and which measured
data are compared to simulation results have been decided upon by all partners.
Assessment of Achievements and Outlook for 2012
During the first eight months the project made substantial progress. On the experimental side we now
have a broad spectrum of reference devices with varying geometries and complexities at hand. On the
computational side the simulation software OPUS 3-D made significant progress with respect to
computational efficiency and treatment of ETA solar cells. Here, the most important progress is the
implementation of Perfectly Matched Layers and plane wave sources. Although the software still
needs additional extensions – above all advanced post-processing capabilities – the foundation for a
comparison between numerical and experimental data has now been laid. At present, we do not see
any major obstacles and are positive that we will obtain good agreement between simulated and
measured data.
References
[1] J. Elias, R. Tena-Zaera, C. Lévy-Clément: Electrochemical deposition of ZnO nanowire arrays with tailored
dimensions, Journal of Electroanalytical Chemistry, Volume 621, Issue 2, 15 September 2008, Pages 171-177
[2] J. Elias, C. Lévy-Clément, M. Bechelany, J. Michler, G.-Y. Wang, Z. Wang, L. Philippe: Hollow urchin-like ZnO thin films
by electrochemical deposition, Advanced Materials , Volume 22, Issue 14, 12 April 2010, Pages 1607-1612
[3] T. Huttunen, M. Malinen, P. Monk: Solving Maxwell’s Equations using the Ultra-Weak Variational Formulation, from –
Journal of Computational Physics, Edition 223, pages 731 – 758, 2007.
[4] Setfos 3.2 software by Fluxim AG, Switzerland, www.fluxim.com , 2011.
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UPCON: ULTRA‐HIGH PURITY NANOWIRES
FOR ENERGY CONVERSION
Annual Report 2011
Address
Telephone, E-mail,
Homepage
Date
Anna Fontcuberta i Morral
EPFL
LMSC, Station 12, 1015 Lausanne
021 693 73 94, anna.fontcuberta‐[email protected],
wttp://lmsc.epfl.ch
UPCON 239743
01.01.2010 - 31.12.2015
31.12.2011
ABSTRACT
This proposal is devoted to the synthesis of ultra pure semiconductor nanowire heterostructures for
energy conversion applications in the photovoltaic domain. Nanowires are filamentary crystals with a
very high ratio of length to diameter, the latter being in the nanometer range. They have become a
major research di rection i n nanot echnology o ver t he pas t dec ade. F rom a fundamental poi nt of
view,semiconductor nanowires are of significant interest owing to their large surface-to-volume ratio
and low dimensional properties due to the confinement of carriers in two dimensions. From a technological perspective, they constitute attractive building blocks for the assembly of novel nano-electronic
and nan ophotonic systems, as well as f or nov el energy c onversion s ystems. The m ost w idely e mployed growth method relies on the use of a catalyst -commonly gold- which is known to be an impurity limiting mobility and carrier lifetime in semiconductors. It is generally realized that if nanowires with
higher purity were obtained, the limits of fundamental studies and applications could be pushed further.
This project combines t wo complementary and essential aspects of semiconductor nanowires:
(i) synthesis in ultra clean conditions and (ii) their application to new concepts of photovoltaic devices.
The proposed research is based on the past research of the applicant both as a team leader at the
“Technical University of Munich” and as a postdoctoral fellow at the “California Institute of Technology”. The first part involves the use of ultra-clean Molecular Beam Epitaxy (MBE) system for the synthesis of III-V semiconductor nanowires and heterostructures. Special emphasis will be given in the
synthesis of new heterostructure designs, i.e. across the nanowire radius and along the growth axis.
The fabrication of ordered arrays of nanowires and devices on large areas and on silicon substrates
will also be investigated. In the second part, the nanowires will be used for photovoltaic applications.
Nanowire based solar cells will be designed, fabricated and characterized. Particular emphasis will be
given in understanding the role of geometry and interfaces in the energy conversion efficiency of the
solar cells. Here, the high cleanliness and precise heteroepitaxial growth of MBE will allow us to perform f undamental studies; gener ating gr ound-breaking k nowledge on t he m icroscopic pr ocesses i n
the energy conversion. This project will foster the use of nanotechnology in the energy challenges of
the XXI century.
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Introduction/Objectives
Nanowires are filamentary crystals with a large aspect ratio and the radius ranging from few to tens of
nanometer. I n a world, w here t he technological pr ogress i s l inked t o t he s hrinking of el ectronic an d
optoelectronic devices, semiconductor nanowires are the object of many new fundamental and applied
studies. Their uni que ge ometry and t he possibility of c onfinement of carriers provide an opportunity,
both t o test fundamental quantum m echanics and r elated ph enomena, as well as t o develop no vel
device concepts.
The method mainly used for the synthesis of nanowires was developed about four decades ago for the
fabrication of whiskers, which at that time had diameters in the micron range. The whisker growth process involves the use of a metal catalyst – usually gold- which gathers and decomposes the growth
precursors. Upon saturation, the growth precursor precipitates below the catalyst in the form of a nanowire. This method has proven to be very powerful for the synthesis of various types and compositions
of nanowires.
The drawback is that gold is usually considered a contaminant for semiconductors. Synthesis of nanowires un der ex tremely c lean conditions ( as e. g. pr ovided b y Molecular B eam E pitaxy: M BE) an d
avoidance of gol d is of gr eat importance f or future nanowire r esearch and a pplications. I n s emiconductors high purity avoids unintentional doping and promotes better performance. Using MBE for the
synthesis of nanowires has an additional positive point, because it enables the design of new
heterostructure forms. This will extend the functionality of the nanowires, in particular in the domain of
energy conversion applications.
Figure 1: Transmission Electron Micrograph of asilicon nanowire nucleatedwith gold as a catalyst [1].
In this project we exploit the advantages of extremely high purity and the atomic precision of the Molecular Beam Epitaxy technique for the synthesis of novel heterostructures at the nanoscale and apply
them to energy conversion applications.
The objectives of the proposal are four-fold:
(i) Synthesis of novel nanowire heterostructures, using the extremely high purity and accuracy
at the atomic scale provided by the MBE technique.
(ii) Deterministic localization of the nanowires at the nanoscale onto 2’’ GaAs and Si wafers.
(iii) Application of the novel nanowire structures to photovoltaic energy conversion concepts
and devices.
(iv) Understanding of the physical processes enhancing and/or limiting conversion efficiencies.
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UPCON, Anna Fontcuberta i Morral, EPFL
The following is a general scheme of the project that helps to visualize the time schedule of each of
the missions and the interaction between the different areas. In yellow –two at the top-, the synthesis
related activities are schematized, while in green –the four bottoms-, the activities related to the photovoltaic devices are shown:
The pr oject will start with the s tudy of the s ynthesis of nano wire het erostructures in extremely clean
conditions. P arallel with t his, t he use of t hese s tructures f or s olar en ergy c onversion will b e s tudied
from the theoretical point of view, in order to find the designs that should lead to the best conversion
efficiency.
Then, the fabricated heterostructures will be used for the fabrication of nanowire solar cell devices and
they will be characterized. At the same time, the effect of materials and interfaces quality on the efficiency will be s tudied. I n p arallel with t his, t he understanding on t he nuc leation and gr owth m echanisms of the nanowires will be used to grow ordered arrays of nanowires onto 2’’ GaAs and Si wafers.
The general goals of this five year project are summarized as follows:
1. Mastering in the axial and coaxial nanowire heterostructures.
2. Synthesis of ordered nanowire arrays on 2’’ Si and GaAs substrates.
3. Fabrication of GaAs based nanowire solar cells with efficiency of at least 12%.
4. Understanding of the factors leading to a high efficiency in nanowire solar cells.
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Results
• Synthesis of nanowires on silicon substrates
The first c hallenge t hat w e f aced w as t he un derstanding of the m echanism for t he gr owth of s elfcatalyzed GaAs nanowires grown on silicon. One of the challenges is the crystal polarity mismatched,
which can lead t o the gr owth of nanowires with m any orientations with respect t o the substrate. We
demonstrated that these orientations can be explained with the formation of secondary seeds due a
threedimensional twinning phenomenon.
This mechanism c an be t uned as a f unction of t he growth conditions b y c hanging t he r elative s ize
between the GaAs seed and the Ga droplet. We also demonstrated how a further optimization of the
2,3
growth conditions results in a 100% yield of vertical nanowires, as shown in the figure here below.
Figure 2: Representative SEM micrograph of a field of nanowires grown at 645oC under a V/III
BEP ratio of 60 (top) and in cross-section (bottom).
• Fabrication of single nanowire photovoltaic devices
Nanowire based d evices based on a r adial pn j unction were fabricated. The structure consisted of a p‐type doped core and a n‐type doped
shell. The schematic drawing of such structure is shown in Fig 3.a. We
started b y growing t he GaAs nano wires i n pr esence of a s ilicon f lux,
with the objective of achieving incorporation of this element nanowire
core. T hen, w e t ested whether t he n anowires were doped and what
kind of doping they exhibited. We achieved this by contacting the nanowires and measuring the gate dependence of the conductivity. After
learning t hat p ‐doping was obtained, we pr oceeded to fabricate samples with a doped s hell. Our nano wires ex hibit a h exagonal s ection
with f acets of t he c rystal family of { 110}. F or gr owing t he n do ped
shell, we applied the gr owth pr ocess appl ied t ypically t o ( 110) f acets
and from our previous growth studies of growth of heterostructures on
the n anowire f acets [ 4]. This r equires a r elatively low t emperature
(465oC) an d a h igh ar senic f lux ( 5x10‐5mbar). I n or der t o t est t hat
effectively we had created a pn junction, we fabricated electrical contacts on the c ore a nd external part of s ingle n anowires. A diode b ehavior was obtained.
A typical current‐voltage characteristic (I‐V) of a nanowire device with
a p‐i‐n structure is shown in Fig. 3b. In this case, we added an intrinsic
layer between the p and n layers in order to demonstrate the creation
of a photocurrent upon illumination. The I‐V curve in the dark shows a
typical di ode beh avior. Mo reover, upon illumination a phot ocurrent is
clearly created. We hav e measured t he light c onversion efficiency of
such a device upon illumination of 1 sun (1.5 AM conditions) and we
have obt ained an ef ficiency of 4. 5% [ 5]. T hese r esults i ndicate t hat:
(i) dop ing i s s uccessfully achieved b y t he t wo s trategies a nd ( ii) t he
interfaces between the two doped regions are of high quality.
Figure 3: a) Drawing of a core
shell pin junction b) Current
voltage characteristics of such
a structure.
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• Fabrication of nanowire array photovoltaic devices:
We developed a process for contacting nanowire arrays. For this, we took silicon micro-pillars that we
fabricated by etching silicon through a mask. The fabrication process is indicated in Figure 4.
Figure 4: Fabrication schematic of radial p–n junction Si micropillar arrays: (a) Patterning of a p–type Si wafer by
means of phot olithography; ( b) deep r eactive i on et ching t o obt ain p –core pi llar arrays; ( c) P OCl3 di ffusion t o
create an n –shell; (d) ITO and Al sputtering as front and rear contacts, respectively; and (e) evaporation of Ti/Au
contacts around the arrays. A detail of the resulting cross-section is also depicted. (f ) SEM image of a fabricated
micro-pillar array viewed at 30° tilt.
The or dered ar rays of micropillars ar e f abricated b y a c ombination of opt ical l ithography and d eep
reactive ion etching on a 3 80 μm thick Czochralski <100> p–doped Si wafer. Hexagonally packed 45–
μm long pillars with diameters of 1.86, 2.4 and 3.1 μm, spaced 7, 8 and 10 μm, respectively, are obtained. 3 substrates with different resistivities are used: 0.1–0.5 Ω·cm, 1–5 Ω·cm and 1–10 Ω·cm. The
n-shell is formed by a POCl3 diffusion at 850◦ C and 900◦ C. In order to diminish the defects conce ntration at the surface of the pillars caused by the etching process, a thermal oxidation step is added
right af ter t he diffusion. T he ox ide layer i s stripped of f by an HF wet etching. A conformal I TO layer
with a nominal thickness of 70 nm is sputtered on the front side as an n –contact and 200 nm of Al as
a rear contact.
Optical a nd electrical pr operties of ITO were measured with an ellipsometer (Sopra GES–5E) and a
resistivity meter four–point measurements, respectively, obtaining a transmittance in the visible range
of 96% and a resistivity of 0.2–0.4 mΩ·cm, which proves ITO as a suitable front contact. In order to get
a better contact for electrical measurements, four Ti/Au pads (10/200 nm) are evaporated around the
array. The surface of the arrays is 5,4 x 5,4 mm 2 . We optimized the design of the pn junction (dimensions and doping concentration) and reached a device efficiency of 10%.6
References
[1] A .Fontcuberta i Morral et al. Adv. Mater. 19, 1347-1351 (2007)
[2] E. Uccelli, J. Arbiol, C. Magen, P. Krogstrup, E. Russo-Averchi, M. Heiss, G. Mugny, F. Morier-Genoud, J. Nygard,
J.R. Morante, A. Fontcuberta i Morral, Nano Lett. 11, 3827 (2011)
[3] E. Russo-Averchi, M. Heiss, L. Michelet, P. Krogstrup, J. Nygard, C. Magen, J.R. Morante, E. Uccelli, J. Arbiol,
A. Fontcuberta i Morral, accepted in Nanoscale (2012)
[4] A. Fontcuberta i Morral, Small 4, 899-903 (2008); M. Heigoldt et al, J. Mater. Chem. 19, 840 (2009)
[5] C. Colombo et al, Appl. Phys. Lett. 94, 173108 (2009)
[6] A. Dalmau-Mallorqui, A. Fontcuberta i Morral et al, submitted (2012)
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INNOVASOL
INNOVATIVE MATERIALS FOR FUTURE
GENERATION EXCITONIC SOLAR CELLS
Annual Report 2011
Address
Date
Dr. Toby Meyer & Frédéric Oswald
Solaronix SA
021 821 2280, [email protected] www.solaronix.com
FP7-ENERGY-NMP-2008-1-227057
01.04.2009 – 31.03.2012
15.06.2012
ABSTRACT
The main o bjective is t o leapfrog c urrent l imitations of t hird-generation P V devices t hrough a dr astic
improvement of the materials used for assembling XSCs.
The f irst step i s t he s ubstitution of t he l iquid electrolytes, c urrently used in dye sensitized s olar c ells,
with solid-state hole conductors. In parallel, semiconductor quantum dots (QDs) with tuned band gap,
designed to enhance the photon capture efficiency, will replace the organic dyes as light absorbers.
A striking improvement is expected from multi exciton generation (MEG) effects, overcoming the Shockley-Queisser efficiency limit of 31% for the PV conversion. In a second step, highly innovative QDs with
supramolecular hierarchical nanostructure will be designed and synthesized: the QDs will be covered
by s elf-assembled monolayers of a mphiphilic d ye m olecules, m imicking t he phot osynthetic an tenna
system. The dye molecules will act as molecular relays (MRs), which connect the QDs to the transparent c onductive oxide ( TCO). N ovel T CO ar chitectures w ill b e de veloped f or ef ficient interface ener gy
transfer and electron diffusion.
Six ac ademic i nstitutions g uarantee a n i nterdisciplinary r esearch, bas ed on t op l evel t heoretical an d
experimental approaches.
The high degree of knowledge of solid-state physics and chemistry, nanoscience and nanotechnology
of the researchers assures that the new concepts and the objectives proposed will be successfully developed/pursued.
Fiat research center and Solaronix, a SME leader in the XSCs production, will provide proof-of-concept
prototypes t o v alidate t he i nnovative m aterials dev eloped b y t he ac ademic par tners. Mat erials an d
technological solutions of INNOVASOL ar e or iginal a nd w ill pave the way for future generation X SCs
alternative to devices so far developed both inside and outside Europe.
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Aims of the project
INNOVASOL a ims t o dev elop r adically new n anostructured m aterials f or phot ovoltaic ( PV) ex citonic
solar cells (XSCs) really competitive with traditional energy sources.
INNOVASOL f ulfills entirely the S&T obj ectives r elated t o t he t opics addr essed b y t he c all “ Novel
materials for energy applications” in that it focuses on basic innovative material research approaches,
which will involve the following tasks and milestones: i) use of semiconductor quantum dots (QDs) as
the l ight har vesting un its, with a f ine t uning of t he optical c ross s ection an d of t he band gap ( by
modifying bo th the c hemical composition, e.g. PbS, PbSe, e tc…, and the size of t he nanoparticles);
ii) synthesis of suitable amphiphilic dye molecules (e.g. cyanines, squaraine dyes, zinc phthalocyanine
and d ipolar S tilbene–like dy es), des igned t o ac t as m olecular r elays ( MRs) t hat connect th e Q Ds to
electron c onductor m aterials ( Figure 2) ; i ii) d evelopment of nov el s olid-state e lectrolytes ( and qu asisolid electrolytes) as p-type hole conductors, such as layered (Figure 3) or porous materials suitable to
host anionic redox couples (e.g. I-/I3-); iv) development of specifically designed n-type semiconductor,
e.g. the mesoscopic oxide film or the transparent conductive oxides (TCO), such as ZnO nanorods or
TiO2 nanofibers and nanotubes (Figure 6), with architecture, morphology and surface structure
suitable to m aximize t he ef ficiency of the charge transfer pr ocesses at the QD/MR/SC i nterface and
electron transport in the nanocrystalline TCO films. Innovative materials and device architectures will
be characterized by low production cost, high stability to UV and high light harvesting efficiency.
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INNOVASOL, Toby Meyer, Solarnix SA
A p ossible architecture of I NNOVASOL de vice; the i nset d isplays a s chematic m odel s howing t he
supramolecular entity (QD covered by molecular relays, MRs) that are adsorbed via anchoring groups
on a mesoscopic TCO film serving as electron collector.
1. Photon capture and generation of multiple excitons by light excitation of quantum dots (quantum
yield >100%);
2. Energy transfer to a surface adsorbed MR;
3. Electron injection from excited MR into conduction band of the TCO film.
QDs have already demonstrated to be very efficient in the photon capture, with optical cross sections
which can be far greater than the molecular dyes currently used in dye-sensitized solar cells (DSCs).
A revolutionary improvement can be achieved by multiple exciton generation (MEG) processes, where
more t han one ex citon i s gener ated b y a s ingle hi gh ener gy ph oton, l eading t o quan tum ef ficiency
larger than 100%. Such processes have been observed in colloidal silicon QDs, and in small band-gap
IV-VI s emiconductors l ike P bS an d P bSe. I NNOVASOL w ill ex plore this r adically ne w ap proach t o
increase the XSC performance, by designing, producing and testing suitable QDs and QD/MR
composites.
INNOVASOL c onsortium i s f ormed o f five par tners of t hree E U Member S tates (Italy, G ermany a nd
United K ingdom), t wo par tners of an A ssociated C ountry ( Switzerland) a nd on e par tner of a T hird
Country of Emerging Economy (Brazil).
Six internationally recognized academic institutions, a large company and an SME, namely
- Nano-SISTEMI Interdisciplinary Centre, Università del Piemonte Orientale, Italy (UNIPMN)
- Centre of Excellence Nanostructured Interfaces and Surfaces Università di Torino, Italy (UNITO)
- Centro di Ricerche Fiat, Torino, Italy (CRF)
- Physical Chemistry/ Electrochemistry, Technische Universität Dresden, Germany (TUD),
- Nanoscience Centre, University of Cambridge,U.K. (UCAM),
- Solaronix SA, Aubonne, Switzerland (SOLARONIX),
- Laboratory for Photonics and Interfaces, Ecole Polytechnique Federale de Lausanne (EPFL),
- Instituto de Química, Universidade Estadual de Campinas, Brasil (UNIPMN),
which are l eading gr oups i n d ifferent ar eas of s olid-state ph ysics an d c hemistry, na noscience an d
nanotechnology, are joined together for the development of radically new materials, nanomaterials and
architectures f or f uture g eneration m ulti-exciton s olar c ells a pplications. T he ex perience of t he academic researchers in the design, modeling and synthesis of inorganic, organic and hybrids nanostructured m aterials, a nd i n t heir c haracterization both with ex perimental and c omputational t ools, i s e xpected to g uarantee a substantial br eakthrough of knowledge based on nanotechnologies t o be disseminated u pon c ompletion of t he pr oject. T he r esearch i s or iented t o go be yond c onventional a pproaches and the materials and concepts developed will pave the way for long term innovation.
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Work performed and results achieved
After that the «spot cell» based testing tool was setup in 2010-2011, various electrolyte additive materials supplied by the project’s partners were evaluated in these lab cells.
The additives are chosen among these classes of materials:
-
Talcs
Hydrotalcites
Saponites
Silicas
The objectives of this screening were to collect more data on these materials in dye solar cells and to
sort out the most promising class of materials.
Excerpt from the list of investigated materials, showing that saponites (e.g. DC Sap 70) may be
a good choice as solidifying agent in DSC electrolytes.
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In parallel to the work on new electrolyte materials, SOLARONIX developed liquid and gel electrolyte
based prototypes. These prototypes consisted in serially interconnected dye sensitized solar cells to
form a module. W-type modules were first investigated. W-type modules are semi-transparent bifacial
devices where the counter and the working electrodes are alternately printed on the same side creating the serial connection with the other side.
2
The state of the art W-module (10 x 10 cm, 65 cm active area) based on liquid electrolyte and N-719
dye reached an active area power conversion efficiency (PCE) of 7.86 % (Voc = 8.3 V; Isc = 106 mA)
under on e s un ( AM1.5G). This dev ice was m easured at v arious s un i ntensities (see t able an d I /V
curves below) to evaluate the performance in situation matching real outdoors conditions. Under one
third of sun the PCE was as high as 9.19 %.
This high efficiency is impressive especially considering the fact that the titania layer was only around
8 m icrons t hick w hile be ing s till s emi t ransparent, a nd t he m odule was m ade w ith only industrially
available raw materials.
J
Voc
Eff.
1 Sun
106 mA
8.3
7.86 %
0.6 Sun
71 mA
8.1
8.62 %
0.5 Sun
58 mA
8.1
9.03 %
0.3 Sun
40 mA
7.9
9.19 %
I-V characteristics of the state of the art module 10 x 10 cm 11-cell W-module giving 7.86% PCE at 1 sun and
2
9.19 % PCE at one third of sun, all efficiencies calculated with an active area of 63 cm .
Y-axis is the current in mA), x-axis is the voltage in V.
Liquid electrolyte cell stability was tested for prolonged periods using mostly the laboratory spot cells
2
(0.36 cm active area). Cells made with N-719 dye and the 3-methoxypropionitrile based Z-946 elec2
trolyte were placed under constant illumination of 1’000 W/m AM 1.5G, at 55 °C during the first 4’000
hours and at 65 °C for the rest of the experiment. All cells exhibited good stability with less than 2%
efficiency loss af ter 1 ’000 hours an d ar ound 20% after 8’ 000 hours i n these c onditions ( see gr aph
below).
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Liquid electrolyte based cell performance over more than 8’000 h - represented in relative units
(1 at start), cell efficiency was 6 % initially.
The s tability of s ome 10 x 10 c m 11 c ell W-modules w as t ested i n t he s ame ex perimental c ondition
than the ones previously described. The module exhibited good stability over 2000 h. Some (predictable) defects in the sealing finally lead to the module death after this time.
Liquid electrolyte based module performance over more than 2’000 h - represented in relative units
(1 at start), module efficiency was 4.5 % initially.
Further work consisted in developing thin glass based modules to build INNOVASOL prototype. The
idea was to apply t he process pr eviously developed f or high efficiency modules t o hundred m icrons
thick flexible glass (see pictures below).
Hundred microns thick flexible glass module tests.
A new design to fit FIAT specifications was created and consisted in an W-type interconnected module
of seven individual cells on a 7 x 10 cm substrate. Several steps needed to be optimized for this thin
glass like:
- FTO deposition
- Two glass lamination
- Hole drilling
- Titania printability and adhesion
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All t hese s teps were s uccessfully tested a nd t uned. The hol es w ere dr illed us ing C O2-laser ab lation
(see picture below).
30 µm holes drilled by CO2-laser ablation in 100 µm glass.
The classical FTO process was applied and leaded to a FTO layer which quality allowed to print only
thin layers of titania with good adhesion properties.
Unfortunately making modules using 0.1 mm glass is a real challenge. Due to the high fragility of this
thin glass, some modules were produced but none of the final desired size to fit FIAT requirements.
The process was then successfully applied on 1 mm glass. Several module using this thin glass and
including INNOVASOL materials were made and sent to FIAT for integration in the final demonstrator.
These modules using 1 mm glass were the first ever made at SOLARONIX.
Comparison between thick 2 x 2 mm module (on the left) and 2 x 1 mm thin module (on the right).
To conclude, INNOVASOL lead to several achievements:
- Test cells went from around 7 % to above 9 %.
- Ionic liquid cells went from around 2.5 % to above 6 %.
1
- W modules went from around 3 % to around 8% and even above 9 % under /3 of sun.
- First thin glass modules at Solaronix were obtained.
- High stability cells were obtained (one year under 1 sun during 24 h/day, corresponding to over
5 years of outdoors conditions).
All these results were obtained using only industrially available raw materials or techniques and summing up the various improvements developed during INNOVASOL.
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Running of the 3 years "KTI-Project" N° 10584.1 PFIW-IW with the EMPA Dübendorf (Switzerland) on
the topic of "Squaraine" and «Heptamethine» based organic sensitizers.
FP7-Project "ORION" – coordinated by Dr. David Mecerreyes at the CIDETEC, San Sebastian, Spain.
This project investigates the development of a new family of functional inorganic-organic hybrid materials ( for ex ample m etal ox ide – ionic l iquid) c haracterized b y an or dered m orphology ( see
http://www.cidetec.es/ORION/index.html).
This project aims to build a photoelectrochemical water splitting device based on organic (or biological) catalysts for light collection (PSII system) and hydrogen evolution materials without noble metals
(see http://solhydromics.org/).
Evaluation 2011 and outlook for 2012
During 2011, hundreds of electrolyte additives were tested on behalf of the project partners, and as
example the saponite compound «DC Sap 70» gave promising results with an increased open-circuit
voltage while keeping good current levels.
The laboratory spot-cell based stability tests were running for over a year, and 3-methoxypropionitrile
based cells performed surprisingly well during this time period with ca. 20 % loss of efficiency.
The W-Module manufacturing has been streamlined to provide test samples of 10x10 cm to 30x30 cm
for performance and stability investigations, using the materials elaborated within the project, and first
thin glass based W-module prototypes have been delivered to the project partner FIAT.
For 2012, latest improvements are expected as the projects finishes by end of March in that year.
References
http://www.innovasol.eu/
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SOLAMON
PLASMON GENERATING NANOCOMPOSITE
MATERIALS (PGNM) FOR 3RD GENERATION
THIN FILM SOLAR CELLS
Annual Report 2011
Address
Date
Dr. Toby Meyer
Solaronix SA
021 821 2280, [email protected] www.solaronix.com
FP7-ENERGY-NMP-2008-1-226820
01.02.09 – 31.01.11
24.04.2012
ABSTRACT
The objective of the SOLAMON project is to develop high potential Plasmon Generating Nanocomposite Materials (PGNM) which will pave the way to the generation III solar cells (high efficiency & low
cost). The objective is an augmentation in the External Quantum Efficiency resulting in an increase of
20% in the short circuit current density of the thin film solar cells.
To achieve such an ambitious goal, the project will focus on the development of fully tailored building
block nanoparticles able to generate a plasmon effect for enhanced solar absorption in thin film solar
cells. Such nanoparticles designed for an optimum absorption will be integrated in solar cells matrix
using a recently developed room temperature deposition process designed by Mantis Deposition. This
step will result in the specific design of PGNM for solar cells using a knowledge based approach coupling modeling (University of Ljubljana) at both scales: nanoscopic (plasmonic structure) and macroscopic (solar cells). SOLAMON will address three different classes of solar cells: a-Si:H thin films (TU
Delft), organics (CEA) and dye sensitised (Solaronix, University of Ljubljana).
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Aims of the project
Objectives: The objective of SOLAMON is to develop high potential nano-composite materials (matrix +
metal nano-particles) that will generate a Plasmon resonance effect which will pave the way to the generation III solar cells (high efficiency & low cost). The aim is to enhance the External Quantum Efficiency
resulting in an increase of 20% in the short circuit current density of three types of thin film solar cells: aSi:H, organic and dye-sensitized solar cells.
Description of the work: To achieve such an ambitious goal, SOLAMON tackles a range of difficulties remaining to be completed for the optimization of the Plasmon resonance effect in thin film solar cells. It
includes the development of dedicated numerical codes able to determine the characteristics of optimized
nano-particles, identify their best localization in the solar cell and predict the optical and electrical responses of solar cells. It also deals with the development of advanced nanotechnologies to fully tailor the
nano-particles (nature, size, shape and surface density) embedded in a matrix chosen to generate a
Plasmon resonance effect that can enhance solar absorption in a specific wavelength range.
The approach developed in SOLAMON, by strongly coupling theory (optical and electrical modelling) and
experiments (finely controlled nano-particles deposition and characterization) will improve the basic understanding of localized surface Plasmon resonance effect versus the characteristics of the nanoparticles that can be experimentally investigated (nature, size distribution, shape, surface density and
surrounding medium). The SOLAMON approach will allow the development of reliable advanced models
through a systematic confrontation between theoretical and experimental properties of the plasmonic
structures investigated.
Expected results: As scientific results, SOLAMON aims at theoretically and experimentally assess various
solar cells configurations utilizing Plasmon Generating Nanocomposite Materials in 3 real cases of solar
cells. Beyond Photovoltaics, the results of SOLAMON should be also usable for other applications such
as biological or chemical sensing, highly efficient organic and inorganic LEDs.
Further research needs: For schedule and budgetary reasons, the present project is not investigating
core-shell nano-particles, although such systems could be very useful to solve charge carriers recombination issues that can limit the interest of Plasmon resonance effect in solar cells. Future technological
and theoretical investigations in that field could be very interesting to open the field of plasmonic applications to new device concepts like Plasmon resonance assisted up-conversion or Plasmon resonance enhanced radial p-n junction (nano-wire solar cells), for instance.
Basic principle of surface plasmon effect:
When a small spherical metallic nanoparticle is irradiated by light, the oscillating electric field causes the
conduction electrons to oscillate coherently. When the electron cloud is displaced relative to the nuclei, a
restoring force arises from the Coulomb attraction between electrons and nuclei that results in oscillations
of the electron cloud relative to the nuclear framework. The collective oscillation of the electrons is called
the dipole surface plasmon resonance. The resonance frequency on metal particles depends on the size,
shape, particle material, and refractive index of the surrounding medium.
The incident light, in the region of the resonance wavelength of the particles is strongly scattered or absorbed, depending on the size of the particles. The extinction of the particles is then defined as the sum
of the scattering and absorption due to the enhancement of the electric field in and very close to the metallic nanoparticle.
Scattering and absorption depend mainly on the size of the particles. Metallic particles that are much
smaller than the wavelength of light tend to absorb more and hence extinction is dominated by absorption
in and very close to the metal particles. As the size of the particles increases, extinction is dominated by
scattering.
Both scattering and absorption can contribute to the enhancement of light absorption in the active layer of
thin film solar cells.
- Scattering will induce enhanced absorption throughout the whole thickness of the photoactive active
layer; in that case, one defines the scattering efficiency as the relative contribution of scattering to the
total extinction;
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SOLAMON 2011, Toby Meyer, Solaronix SA
- Absorption includes absorption in the metal nanoparticles (negative effect in the present case) but also
enhanced absorption at the very close vicinity of the nanoparticles which can lead to enhanced absorption in the active layer provided that nanoparticles are close enough to the active layer.
The objective of the SOLAMON project, as illustrated below, is to develop high potential Plasmon Generating Nanocomposite Materials (PGNM) which will pave the way to the generation III solar cells (high efficiency & low cost).
The objective is an augmentation in the External Quantum Efficiency resulting in an increase of 20% in
the short circuit current density of the thin film solar cells.
To achieve such an ambitious goal, the project will focus on the development of fully tailored building
block nanoparticles able to generate a plasmon effect for enhanced solar absorption in thin film solar
cells. Such nanoparticles designed for an optimum absorption will be integrated in solar cells matrix using
a recently developed room temperature deposition process designed by Mantis Deposition1. This step
will result in the specific design of PGNM for solar cells using a knowledge based approach coupling
modeling (University of Ljubljana2) at both scales: nanoscopic (plasmonic structure) and macroscopic
(solar cells).
SOLAMON will address three different classes of solar cells: a-Si:H thin films, organics and dye sensitized. Developing the PGNM on these three classes aims at maximizing the project impact and not to
compare them because scientific background acquired on these technologies could be easily transferred
to other ones. As a matter of fact, a-Si:H technology targets mainly the BuiIding Integrated PV (BIPV)
market (large surfaces) whereas the two others are most suitable for the consumer good market (nomad
applications).
The project workprogram, the critical path and the contingencies plans are designed to maximize both
social and economic impact. For this reason, the BIPV applications (i.e. a-Si:H based technology) will be
firstly considered when a strategic choice occurs, keeping in mind that, even of large economic importance, the two other technologies do not have the same key BIPV environmental and social impact.
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SOLAMON gathers the key actors to address material knowledge based development, material modeling
and material synthesis process. The complementary partners will therefore answer the needs of all 3
types of systems: organic (CEA1), a-Si:H thin film (TUD2) and Dye Sensitized Solar Cells (Solaronix).
Clearly focused on a Concept to Feasibility approach, SOLAMON combines the most promising technique of nanoparticles deposition with an integrated modeling study. The partnership is aware of the ambitious challenge of the project and will dedicate a concentrated effort (189,5 PM over 24 months).
SOLAMON will use the exclusive expertise of the World leader in the field of plasmonic theory: the University of New South Wales (Australia).
The project partners are:
Partner
Beneficiary Name
CEA
Commissariat à l’Energie
Atomique et aux Energies France
Alternatives
Mantis
Technische Universiteit
Delft
Mantis Deposition Ltd.
UL
University of Ljubljana
SOLAR
SOLARONIX SA
University of New South
Wales, Sydney
TUD
UNSW
Country
Role
Project coordination.
Optical modelling.
Nanotechnology study and characterization.
Organic solar cell development.
a.Si:H solar cell development.
The Netherlands
Optical and electrical characterization of cells
United Kingdom Nanotechnology provider
Numerical modelling and simulation of cells
Slovenia
(optical and electrical).
DSSC cell development.
Switzerland
DSSC cell provider.
Australia
Expert on plasmonic systems.
These workpackages and their dependencies are summarized in the diagram below:
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Work performed and results obtained
During the second project year, ending in January 2011, the work focused on building solar cells having
these 900 nm thin TiO2 electrodes, being either colored with «D5», a highly absorbing organic dye, or
with the classic Ruthenizer 535-bisTBA, and having either the well studied acetonitrile based electrolyte
Iodolyte AN-50 or the new corrosion safe T /T2 formulation. The idea is to compare them with cells having
the silver particles coated on top of the TiO2 layer (= best position according to the modeling). The silver
particles containing samples are to be processed at Mantis Deposition Ltd, in the UK, using their proprietary sputtering process (www.mantisdeposition.com).
A first set of 900 nm thin TiO2 electrodes were sent to Mantis to get coated in their next production cycle,
while the second set acted as reference electrodes (without any PGNM deposited). Complete dye solar
cells were built to have all the data to be able to compare with the ones having the PGNM silver particles
built-in, once they come back from Mantis.
Ruthenium dye «N-719»
ε = 12’000 /Mcm at 535 nm
Organic D5 dye
ε = 37’000 / Mcm at 476 nm
tri-iodide/iodide electrolyte Iodolyte AN-50
-
T /T2 electrolyte
(iodine free)
Completed reference cells with 900 nm thick nano-TiO2 layer,
lefthand set is colored with N-719 ruthenium sensitizer, the
righthand set is stained with the organic dye D5.
The molecular structures of the investigated sensitizers are shown below:
N719 dye
D5 dye
These 4 sets of reference cells were characterized by their I-V plot using a calibrated solar simulator
2
(SolarSim-150 Class B, set to 1000 W/m at 20°C sample temperature) and by their quantum efficiency
using a filter wheel based spectrometer (Solaronix SR-IV F312) ranging from 300 to 1200 nm:
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-
Quantum efficiency (IPCE) plots of the reference cells colored with N719 and D5, in AN-50 and T /T2
electrolytes:
For both dye and both electrolytes, the current integral of the quantum efficiency spectrum is comparable
to the observed short-circuit currents:
Dye
Short-circuit current Isc
N719 Iodolyte AN-50
3.28 mA/cm
2
3.39 mA/cm
2
N719 T2/T electrolyte
-
2.95 mA/cm
2
2.88 mA/cm
2
D5 Iodolyte AN-50
7.65 mA/cm
2
7.72 mA/cm
2
5.05 mA/cm
2
5.19 mA/cm
2
-
D5 T2/T electrolyte
Current integral from quantum
efficiency spectrum
The I-V plots of all the cells were compiled in the table below:
Spot ID
Composition
2
Area (cm ) Isc (mA) Voc (V)
2
FF
J (cm /mA)
Efficiency
Sp01-200111FO N719 / AN-50 0.72
2.63
0.724
0.73
3.65
1.93 %
Sp02-200111FO N719 / AN-50 0.72
2.44
0.716
0.73
3.39
1.76 %
Sp03-200111FO D5 / AN-50
0.72
5.58
0.684
0.66
7.75
3.50 %
Sp04-200111FO D5 / AN-50
0.72
5.60
0.686
0.69
7.77
3.68 %
Sp05-200111FO D5 / AN-50
0.72
5.56
0.678
0.70
7.72
3.66 %
-
0.72
2.05
0.728
0.60
2.85
1.24 %
-
0.72
2.08
0.736
0.59
2.88
1.26 %
-
0.72
2.02
0.725
0.60
2.80
1.21 %
Sp09-200111FO D5 / T /T2
-
0.72
3.74
0.621
0.55
5.19
1.77 %
-
0.72
3.50
0.600
0.49
4.89
1.43 %
0.72
3.65
0.621
0.54
5.06
1.70 %
Sp06-200111FO N719 / T /T2
Sp07-200111FO N719 / T /T2
Sp08-200111FO N719 / T /T2
Sp10-200111FO D5 / T /T2
-
-
Sp11-200111FO D5 / T /T2
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The ~ 900 nm thick TiO2 test cells colored with the highly absorbing organic D5 dye show a quite high
efficiency of ca. 3.6 %, compared with only ca 1.8 % produced by the classic ruthenium sensitizer N719
when using the iodine containing electrolyte Iodolyte AN-50. When using the T /T2 containing electrolyte,
an efficiency of ca 1.6 % is achieved with the D5 dye, whereas N719 brings about 1.24 %.
An important aspect is the reproducibility in current density, as the photocurrent is the parameter being
most sensitive to the presence of the plasmon generating particles within the cell. From the table above,
the standard deviations (and their percentage) in current density and in efficiency can be extracted:
Spot ID
Composition
Current
density
2
(cm /mA)
Standard de- Efficiency
viation / (%)
(%)
0.13
(4.5 %)
Sp01-200111FO
N719 / AN-50
3.65
Sp02-200111FO
N719 / AN-50
3.39
Sp03-200111FO
D5 / AN-50
7.75
0.085 (9.6%)
1.76 %
3.50 %
0.02
(0.26 %)
D5 / AN-50
7.77
Sp05-200111FO
D5 / AN-50
7.72
3.66 %
Sp06-200111FO
N719 / T /T2
-
2.85
1.24 %
Sp07-200111FO
N719 / T /T2
-
2.88
Sp08-200111FO
N719 / T /T2
-
2.80
1.21 %
Sp09-200111FO
D5 / T /T2
-
5.19
1.77 %
Sp10-200111FO
D5 / T /T2
-
4.89
Sp11-200111FO
D5 / T /T2
-
/
1.93 %
Sp04-200111FO
-
Standard
deviation
(%)
0.033
(1.1 %)
0.123
(2.4 %)
5.06
3.68 %
1.26 %
1.43 %
0.08
(2.22 %)
0.02
(1.66 %)
0.146
(8.9 %)
1.70 %
The smallest standard deviation percentage of < 1 % in short-circuit current is obtained with the Iodolyte
AN-50 filled D5 colored cells, followed by the value (1.1 % ) from the cells made with the iodide free T /T2
electrolyte and the ruthenium dye N-719. From these small observed standard deviations, we think that
our reference cell building technique is probably good enough to distinguish the light absorption improvements expected with the plasmon generating nanoparticles loaded samples.
Unfortunately, we never could complete the experimental study as Mantis could not process the samples
due to technical difficulties in their specialized equipments. This rather short 2 year high risk project ran
out of time to have that part of the work completed.
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Projects related to the work described here:
Running of the 3 years "KTI-Project" N° 10584.1 PFIW-IW with the EMPA Dübendorf (Switzerland) on the
topic of near infrared absorbing organic sensitizers.
FP7-Project "ORION" – coordinated by Dr. David Mecerreyes at the CIDETEC, San Sebastian, Spain.
This project investigates the development of a new family of functional inorganic-organic hybrid materials
(for example metal oxide – ionic liquid) characterized by an ordered morphology (see
http://www.cidetec.es/ORION/index.html).
FP7-Project "INNOVASOL" – coordinated by Dr. Leo Marchese of the SiSTeMI center at the University of
Piedmont, Italy.
INNOVASOL aims to increase the efficiency of exitonic solar cells to 15 % by using innovative approaches in cell designs and novel materials (see www.innovasol.eu)
This project aims to build a photoelectrochemical water splitting device based on organic (or biological)
catalysts for light collection (PSII system) and hydrogen evolution materials without noble metals (see
http://solhydromics.org/).
Evaluation of the year 2011
The 2011 works aimed to produce specially adapted dye solar cells to test the concepts of the SOLAMON
project. These cells have an extra-thin 900 nm nano-TiO2 layer, required to observe the expected light
absorption improvements due to the presence of plasmon generating nanoparticles. Silver nanoparticles
(ø 20 nm) deposited by Mantis on top of the TiO2 layer would generate the most favorable plasmons according to the models developed within this project.
The usage of a highly absorbing organic dye («D5») afforded rather efficient reference cells, having a
small standard deviation in their electrical characteristics. But the experimental work could not be completed within this limited project time as we never got back the test samples from Mantis, in charge of the
delicate deposition of the tightly controlled silver particles (troubles due to equipment issues).
References
http://www.solamon.eu/
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197
Solarglas PV – SI/500614 / SI/500614-01
T. Szacsvay
SmartTile II - Pilotanlage: Innovative Photovoltaik Indachlösung
– SI/500388 / SI/500388-01
L.-E. Perret-Aebi, P. Heinstein, V. Chapuis, S. Pélisset, K. Lumsden, R. Tween,
M. Mottet, Y. Leterrier, J.-A. E. Månson, M. Joly, V. Le Caër, S. Mertin, A. Schüler,
C. Roecker, M. Edelman, G. Stoll, J.-L. Scartezzini, M. Bätschmann, V. Ritter,
H. Leibundgut, P. Mirzaee, K. Ghazi Wakili, J. Carmeliet, C. Ballif
ARCHINSOLAR: Unique and Innovative Solution of Thin Silicon Films Modules
Building Integration – SI/500474 / SI/500474-01
Y. Leterrier, M.A. González Lazo, R. Teuscher, P. Velut, R. Tween, K. Lumsden,
J.-A.E. Månson, C. Calderone, A. Hessler, P. Couty, Y. Ziegler, F. Galliano, D. Fischer
Conformal photovoltaic modules – KTI 9903.1
SUNSIM: Large Area solar simulator integrating power Light Emitting Diodes for
performance measurement of new generations of photovoltaic modules
– KTI 10880.2
204
212
218
225
A. Virtuani
MPVT: Multi-Purpose PV module tester – KTI 9626.1
230
Photovoltaik im Verbund mit Dämmstoff Foamglas – SI/500582
235
PV-GUM: Manufacturing technologies and equipment to produce low-cost PV
bituminous-modified roofing membrane with full integration of high efficiency
flexible thin-film silicon PV modules – PV-GUM 249791
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Solarglas PV
Annual Report 2011
Address
Telephone, E-mail,
Homepage
Date
SPF-HSR
Oberseestrasse 10; 8640 Rapperswil
0041 55 222 48 31, [email protected]
www.solarenergy.ch
SI/500614 / SI/500614-01
01.04.2011 - 28.02.2012
29.11.2011
ABSTRACT
The SPF certificate “solar glass” was developed in 2002 to guarantee the quality of glazings for the
use as t ransparent c overs f or s olar thermal collectors. Mor e t han 100 glasses have bee n c ertified
since the implementation of this certificate. Although it was explicitly de veloped for thermal applications, it became widely used in the pv-module industry. However, the existing certificate can result in
misleading conclusions when applied to glass for pv-modules. In this project the existing certificate is
adapted to the special properties of crystalline solar cells, which are directly laminated onto the tested
glass. F or t he c ertification different f actors w ill b e def ined i n order t o c lassify t he t ested glasses i n
several per formance groups. T hese ar e: a) t ransmittance f actor, b) degr adation f actor, c ) i ncident
angle modification factor.
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Seit d er E inführung des SPF Z ertifikats „Solarglas“ im J ahr 2002, wurden über 170 G läser unterschiedlicher Hersteller weltweit in das Zertifizierungsverfahren aufgenommen. Obwohl dieses Zertifikat
ausdrücklich nur für Gläser in solarthermischen Kollektoren vorgesehen ist, findet es zunehmend auch
Verbreitung im Bereich der PV Modulherstellung. Dies ist jedoch nicht zulässig, da die Solarglas Klassifizierung speziell für thermische Kollektoren entwickelt wurde. Angewendet auf PV Module kann dies
zu falschen Folgerungen führen. Im Rahmen des vorgestellten Projekts wird das SPF Zertifizierungsverfahren „Solarglas“ erweitert um dem von Gläsern als Abdeckung von PV-Modulen gerecht zu werden. D azu wird der E influss a) des s olaren T ransmissionsgrades, b) d er Ä nderung d es s olaren
Transmissionsgrades auf grund v on S olarisation sowie c) des w inkelabhängigen s olaren Transmissionsgrades auf den Jahresertrag einer PV-Anlage ermittelt, um eine Zuordnung des zu zertifizierenden
Glases zu einer Leistungsklasse vornehmen zu können. Hauptunterschied zwischen der Anwendung
als Kollektorabdeckung und der Anwendung in PV-Modulen liegt in der direkten Lamination der c-Si
Zellen auf die Glasrückseite, womit der Reflexionsverlust an dieser Stelle quasi wegfällt. S owohl die
Transmissionsmessung aber vor allem auch die incident angle modifier (IAM) Messung muss an diese
Gegebenheit angepasst werden. Für letztere muss auch eine neue Gewichtungsroutine definiert werden, welche sich nach den jährlichen Energieerträgen von PV-Anlagen richtet.
Transmissionsgrad
Für die Zertifizierung von Solarglas für Solarthermische Kollektoren wird das (direkt – hemisphärische)
Transmissionsspektrum der P rüflinge an einem FTIR-Spektrometer v on Bruker gemessen [1]. Dabei
treten R eflexionsverluste bei de n Ü bergängen Luft-Glas an d er V orderseite und G las-Luft a n d er
Rückseite s owie Absorptionsverluste i m Glas auf . F ür den Einsatz v on G läsern i n PV-Modulen wird
der Reflexionsverlust an der R ückseite unbedeutend, da die Zellen direkt an das Glas laminiert und
somit optisch gekoppelt werden. Anhand von drei Messungen (Transmission in Luft; Reflexion in Luft;
Reflexion mit optisch gekoppelter Lichtfalle, siehe auch Fig. 1) kann die für PV-Anwendungen relevante T ransmission ohne Reflexion an der R ückseite bestimmt werden. Für unstrukturiertes Glas ohne
Antireflexschicht s ollte di e Reflexion an der R ückseite ex akt der R eflexion d er V orderseite entsprechen. Dieses Verhalten wurde in der Mes sung, welche in Fig. 1 dargestellt ist, bestätigt. D ie beiden
Reflexionsspektren an der Vorder- und Rückseite können im Diagramm schlecht auseinandergehalten
werden, da sie fast genau aufeinander liegen. Diese Übereinstimmung bestätigt die Qualität der Messungen und die Richtigkeit der daraus folgenden Berechnungen.
Analog z ur Zertifizierung für t hermische Anwendungen wird aus dem Transmissionsspektrum, durch
eine Faltung m it einem Gewichtungsspektrum, ein T ransmissionswert bes timmt. Dabei m uss s owohl
die spektrale Verteilung der Solareinstrahlung, als auch die spektrale Effizienz von c-Si Zellen berücksichtigt werden. In Fig. 1 wird das verwendete Gewichtungsspektrum dargestellt. Der damit gewichtete
Transmissionswert ( nach A bzug d er R eflexion an d er G lasrückseite) l iegt f ür t ypische G läser oh ne
Antireflexschicht im Bereich von 95%.
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SI/500614, F. Ruesch, SPF-HSR
Fig. 1: Spektrale Messungen an ei nem glatten (nicht s trukturierten) 3 mm dicken Solarglas. G emessen w urden
drei Spektren; die Transmission in Luft (T_Luft/Glas/Luft), die Reflexion in Luft (R_Luft/Glas/Luft) und die Reflexion der G lasvorderseite ( T_Vorderseite, g emessen m it ei ner opt isch g ekoppelten L ichtfalle). D araus w urde d ie
Transmission ohne Reflexionsverluste, di e Reflexion der R ückseite un d d ie f ür di e A nwendung i m P V-Modul
wichtige Transmission bis zur Rückseite (T_für PV) berechnet. Ebenfalls dargestellt ist das verwendete Gewichtungsspektrum, welches sich aus der Faltung eines AM1.5 Solarspektrums (ISO 9845) mit der spektralen Empfindlichkeit einer typischen c-Si Zelle ergibt.
Fotodegradationsfaktor
Der Fotodegradationsfaktor wird anhand des Transmissionsverlustes durch Solarisation mit UVStrahlung analog zum Zertifizierungsprozess für thermische Anwendungen bestimmt.
Winkelgewichtungsfaktor
Der Hauptunterschied in der Anwendung von Solarglas i n PV-Modulen im Vergleich zu solarthermischen K ollektoren l iegt be i der Bewertung des Einflusses d er un terschiedlichen Einfallswinkel
der S olarstrahlung a uf das P V-Modul. Dazu w urde ei ne Messeinrichtung entwickelt und i n B etrieb
genommen, mit welcher die Effizienz als Funktion des Einfallswinkels bestimmt werden kann und theoretische Untersuchungen zur Bewertung dieser Messungen durchgeführt.
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Messsignal
Messsignal
-
-
+
+
c-SI Zelle
c-SI Zelle
Glassubstrat
Glassubstrat
EVA
EVA
Prüfglas
Prüfglas
Polarisation der
Laserstrahlung
Glycerin 99%
Polarisation der
Laserstrahlung
Laser strahlt orthogonal auf das Prüfglas.
α
Glycerin 99%
Laser strahlt im Winkel α auf das Prüfglas.
Fig. 2: Skizze des Messaufbaus: Messzelle mit optisch gekoppeltem Solarglas (Prüfglas).
Messaufbau
Auf ei nem G lassubstrat ist e ine c -Si Z elle in d er G rösse 15. 5 x 15.5 c m in ei ner EVA
2
(Ethylenvinylacetat) Schicht ei nlaminiert. Im Zentrum dieser c-Si Z elle wurde eine 2 x 2 c m grosse
„Si-Messzelle“ durch Laserbearbeitung elektrisch isoliert. Von dieser Si-Messzelle wird das Messsignal (Kurzschlussstrom) mitttels zwei nach aussen geführten Anschlüsse abgenommen. Das Messsignal wird zu nächst mit ei nem Transimpedanzverstärker v orverstärkt und danach mit ei nem Loc k-In
Verstärker weiter verstärkt, gefiltert und gemessen.
Damit das Prüfglas ohne Lufteinschluss optisch an das EVA gekoppelt werden kann wird eine dünne
Schicht Glycerin (Reinheit 99%) zwischen P rüfglas u nd E VA-Schicht a ufgebracht. G lycerin ha t f ast
den g leichen Brechungsindex w ie EVA un d gar antiert daher ei ne o ptimale op tische K opplung, w ie
diese bei einer direkten Lamination vorliegen würde. Mit einer Klemmvorrichtung (nicht eingezeichnet)
wird das Prüfglas zusammen mit dem Glycerin auf das EVA gepresst.
Messablauf
Mit einem Laser der Wellenlänge 650nm wird ein homogenes kollimiertes Strahlenbündel erzeugt. Um
unerwünschte Randeffekte zu vermeiden wurde der Durchmesser des Strahlenbündels deutlich grösser gewählt als d ie Diagonale der Si-Messzelle. Durch die Verwendung eines modulierten Lasersignals zusammen mit Lock-In Verstärkertechnologie i st di e Messung weitestgehend un empfindlich gegenüber F remdlicht. D er L aser i st auf ei nem s chwenkbaren A rm montiert u nd kann s omit in e inem
beliebigen Winkel α zwischen 0° und +/-70° bezüglich der Normalen des Prüfglases positioniert werden. Der winkelabhängige IAM Wert wird aus dem Verhältnis der Messung unter einem Einfallswinkel
α zur Messung bei senkrechtem Einfall bestimmt.
Da der Laser einen polarisierten Lichtstrahl erzeugt, müssen für jede Winkelposition zwei Messungen
durchgeführt werden, wobei d ie Polarisationsebenen der be iden Mes sungen orthogonal zueinander
stehen muss. Der Mittelwert dieser beiden Messungen wird dann zur Bewertung weiterverwendet.
Erste Messresultate
Im Fig. 3 wird eine am SPF Teststand gemessene incident angel modifier (IAM) Kurve, mit Werten aus
der Literatur verglichen. Die intern gemessene IAM Kurve wurde an einem 3mm dicken unstrukturierten Glas durchgeführt. Von DeSoto et al. [2] werden gemessene IAM Verläufe von realen Modulen in
Form von gefitteten Kurven (Polynom 4. Grades) publiziert. Anhand dieser Angaben wurden die IAM
Werte v on v ier ge testeten Modu len f ür di e M esspunkte des Teststandes ( von -70° bis 70°) a usgerechnet und zum Vergleich dargestellt. Durch die Interpolationsart als Polynom ist bei den Literaturdaten m it ei ner ge wissen Abweichung zu r echnen un d die Werte über eins m üssen k ritisch bet rachtet
werden.
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Fig. 3: Vergleich e iner am S PF gem essenen I AM-Kurve eines hochtransparenten unstrukturierten Solarglases
mit Outdoormessungen an realen Modulen [2].
Die am SPF gemessene IAM Kurve zeigt eine gute Übereinstimmung mit den publizierten Daten von
ganzen Modulen. Die maximale Abweichung liegt in der Grössenordnung der Streuung der Literaturdaten. Dass der gemessene IAM im oberen B ereich der Literaturwerte oder au ch darüber liegt, entspricht den E rwartungen, da es s ich b ei dem dar gestellten Beispiel um ei n hochtransparentes u nd
sehr dünnes Glas (3 mm) handelt. Die Glasdicken der vermessenen Module sind zwar nicht bekannt,
aber in der Vergangenheit wurden tendenziell eher dickere Gläser verbaut. Daraus lässt sich folgern,
dass das momentane Messverfahren im Grundsatz richtig und erfolgsversprechend für die Zukunft ist.
Der E influss unterschiedlicher E inbettungsmaterialien s owie de r Einfluss der opt ischen Koppelung
durch Glycerin w ird noch untersucht und bis zum Projektende quantifiziert. Dazu wird ein bereits erstelltes Modell eines PV-Modules im Raytracing-Programm OptiCAD [3] eingesetzt werden.
Gewichtungsfaktoren
Mit der Software Polysun 5 [4] wurde die jährliche Strahlungsverteilung in Abhängigkeit des Einfallswinkels berechnet. Polysun 5 greift dabei auf Wetterdaten von Meteonorm [5] zurück. Die Summe der
Einstrahlung, die während eines Jahres aus einem bestimmten Winkel auf das Modul triff, ergibt die
Gewichtung des IAM bei diesem Winkel. Der gemessene IAM Wert des Glases bei einem bestimmten
Einfallswinkel w ird a lso mit der S trahlungssumme ge wichtet, welche während e ines J ahres aus d iesem Winkel auf das Modul eintrifft. Bei den Berechnungen wurde der Einfluss unterschiedlicher Ausrichtung und unterschiedlicher Standorte untersucht. Dabei hat sich gezeigt, dass die Unterschiede in
den resultierenden Gewichtungsfaktoren über Standorte von Madrid bis Stockholm relativ gering sind.
Auch unterschiedliche Ausrichtungen führten, mit Ausnahme der vertikalen Orientierung (Fassadenintegration), zu r elativ äh nlichen G ewichtungsfaktoren. Zusätzlich wurde e ine Abschätzung üb er d en
Einfluss der Mod ultemperatur und di e spektrale V erschiebung der E instrahlung durchgeführt. A uch
diese Einflüsse liegen nur im unteren Prozentbereich.
Daraus wird der S chluss g ezogen, das s ei ne B ewertung u nabhängig v om S tandort m öglich i st un d
dass das R esultat dab ei f ür ei nen weiten B ereich a n Anwendungen e ine gr osse R elevanz au fweist.
Die ausgewählten Gewichtungsfaktoren werden mit dem Abschluss des Projektes mit einer Testanleitung publiziert.
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Fig. 4: Anteil der gesamten jährlichen Einstrahlung aufgeteilt auf unterschiedliche Einstrahlungswinkel.
Von Marrakech bis Stockholm ist diese Verteilung über ein ganzes Betriebsjahr aufsummiert relativ ähnlich.
Nationale / internationale Zusammenarbeit
Die eingesetzte Messzelle wurde von einem der weltweit grössten Hersteller von PV-Modulen speziell
angefertigt un d f ür di eses P rojekt z ur V erfügung ge stellt. Z usätzlich b estehen K ontakte zu e inem
Deutschen und einem Norwegischen Forschungsinstitut, welche zu einer losen Zusammenarbeit geführt haben.
Die Methode zur Messung der Transmission wurde zur Bewertung von Glas als transparente A bdeckung von PV-Modulen angepasst. Eine Messapparatur zur Messung des IAM von Gläsern mit angekoppelter c-Si Zelle wurde aufgebaut und getestet. Letzte Kontrollen zur Abschätzung der Messunsicherheit und Ä nderungen zur V erbesserung des Handlings werden n och d urchgeführt. Simulationen
zur A bschätzung des E influsses unt erschiedlicher E instrahlungswinkel auf den Jahresertrag wurden
durchgeführt. D abei k onnte ge zeigt werden, d ass di eser E influss f ür unt erschiedliche S tandorte u nd
Montagewinkel in der gleichen Grössenordnung liegt. Die genauen Gewichtungsfaktoren müssen aber
noch auf B asis der berechneten D aten definiert werden. Ein Modell einer c-Si Z elle w urde i n einem
Raytracing [3] Programm erstellt. D ieses M odell d ient i m näc hsten S chritt da zu di e Sensitivität de r
Bewertungsmethode auf u nterschiedliche Z elltypen u nd Einbettungsmaterialien sowie der o ptischen
Koppelung m ittels Gl ycerin z u qua ntifizieren. D ie genaue B eschreibung der Test- und B ewertungsgrundlagen, s owie die D efinition der S tufen f ür di e Beurteilung d er G läser, folgt mit dem A bschluss
des Projektes.
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Referenzen
[1] S. Brunold + U. Frei, „Was ist Solarglas?“, presented at the OTTI-Symposium Thermische Solarenergie,
Bad Staffelstein, Deutschland, 2002.
[2] W. De Soto, Masterarbeit betreut von W. Beckman und S. Klein; „Improvement and Validation of a Model for Photovoltaic
Array Performance“. Solar Energy Laboratory University of Wisconsin-Madison, 2004.
www.nrel.gov/analysis/sam/pdfs/thesis_desoto04.pdf
[3] Opti CAD. Opti CAD Corporation, Santa Fe, USA; www.opticad.com
[4] Polysun 5. Velasolaris, 8400 Winterthur; www.velasolaris.ch
[5] Meteonorm. METEOTEST, 3012 Bern; www.meteonorm.com
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SMARTTILE II - PILOTANLAGE
INNOVATIVE PHOTOVOLTAIK INDACHLÖSUNG
Annual Report 2011
Address
Date
Tamás Szacsvay
3S Swiss Solar Systems AG
Schachenweg 24, 3250 Lyss
032 391 11 11, [email protected], www.3-s.ch
SI/500388/500388-01 / 153473/102682
01.08.2008 – 30.09.2011
22.12.2011
ABSTRACT
The intention of the project „SmartTile“ is to finalize the development of roof integrated photovoltaic
building elements, which had started within the framework of the EU-research Project “BIPV-CIS”.
Instead of pursing the original project idea of using plastic to produce the integration frame of the PVelement in a moulding process, the actual focus of the project lies on finalizing the development of the
®
MegaSlate II mounting system, and complementing it with thermal collectors and skylights.
The present document is the final report relating the pilot plant, including thermal collectors, which are
mounted in the same pattern as the PV-modules.
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Dieser B ericht b eschreibt die Ausführung u nd d ie M essergebnisse des P ilotprojektes z um P rojekt
„SmartTile: Innovative Photovoltaik-Indachlösung“.
Als Pilot- und Messprojekt wurde eine Anlage auf einem Neubau in Altwis (Luzern) gewählt. Mit der
PV-Anlage wird mehr als das fünffache des Eigenbedarfs an Strom gewonnen, und mit den Kollektoren auch ein erheblicher Anteil an der Wärmeversorgung.
®
Die Pilotanlage dient dazu, di e Praxistauglichkeit d er neu en Me gaSlate II S ystemkomponenten aus
der Serienfertigung vor der breiten Anwendung an einem realen Objekt zu testen, sowie Erkenntnisse
zu e lektrischem E rtrag, Lei stung un d T emperaturverhalten zu gewinnen. A ls weiterer P unkt s oll di e
Integration v on t hermischen K ollektoren m it gl eichem R astermass w ie das d er P V-Module er probt
werden.
BAU DER ANLAGE
Die A nlage wurde v on d er B auherrschaft s owie e ines Teams seitens 3 S gep lant und im Mär z/April
®
2010 er richtet. Abbildung 1 zeigt d ie m ontierte U nterkonstruktion des Mega Slate II I ndachsystems,
welche bereits aus den neuen Komponenten (Profile, Auflager, Haken) aufgebaut ist.
Abbildung 1: Montierte Unterkonstruktion
Zur Montage der Haken wurde eine Montagelehre eingesetzt. Nach der Unterkonstruktion wurden die
Module verlegt. Deren Montage verlief ohne Probleme. Mehr Mühe bereitete die Verlegung der Thermiepanele, di e be i di esem P rojekt z um er sten Mal zum E insatz k amen. D ie A usrichtung der P rofile
sowie der Anschluss der Thermiepanele gestaltete sich anspruchsvoller als erhofft, weshalb ein halber
Arbeitstag für die 6 Stück benötigt wurde, da zwischendurch wieder einige demontiert werden mussten. D ie Abdichtung der h ydraulischen Verrohrung ge lang er st i m dr itten A nlauf, w as mittlerweile zu
grundsätzlichen Verbesserungen und Vereinfachungen des Systems geführt hat . Nach Montage d er
Thermiepanels w urden d ie r estlichen PV-Module installiert. Bilder d er f ertigen Anlage und e ine G esamtansicht des Gebäudes sind in Abbildung 2 und Abbildung 3 dargestellt.
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SmartTile II, T. Szacsvay, 3S Swiss Solar Systems AG
Abbildung 2: PV unten, Thermie oberste Reihe
Abbildung 3: Gesamtansicht des Gebäudes
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Elektrische Komponenten und Messsystem
Die Anlage verfügt über 64 monokristalline Indachmodule mit je 150Wp. Dies ergibt eine Gesamtleitung von 9.6 kWp. Die Anlage ist elektrisch in 4 Felder aufgeteilt, die über einen Fronius IG 120 Plus
Wechselrichter i ns Netz e inspeisen. D ie D atenerfassung erfolgt m ittels 2 Fronius S ensorboxen u nd
einem Fronius Datalogger Web. Die Daten sind per Internet abrufbar.
Mit den Messgeräten w erden di e el ektrischen Le istungs- und Ertragsdaten er fasst, s owie folgende
weitere Messgrössen:
•
•
•
•
•
Temperatur Rückseite unterstes PV-Modul
Temperatur Rückseite oberstes PV-Modul (Abbildung 7)
Temperatur Luft im Unterdach unten (Lüftungsgitter an Traufe, Abbildung 8)
Temperatur Luft im Unterdach oben (nähe First, Abbildung 9)
Einstrahlungssensor (Abbildung 10)
Die Ertrag der thermischen Solaranlage wir mit einem Wärmezähler erfasst.
Messwerte
SOLARTHERMIE
Der Ertrag der thermischen Anlage im ersten Betriebsjahr mit kompletter Erfassung betrug 2074 kWh.
Dieser teilte sich wie folgt auf die einzelnen Monate auf:
Monat
Ertrag in kWh
November 2010
Dezember 2010
Januar 2011
Februar 2011
März 2011
April 2011
Mai 2011
Juni 2011
Juli 2011
August 2011
September 2011
Oktober 2011
37
27
78
131
243
279
170
228
225
283
223
150
Von April bis September wurde keine weitere Wärmequelle für Raumheizung und Warmwasser benötigt.
PHOTOVOLTAIK
Der elektrische Ertrag von Nov. 2010 bis Oktober 2011 betrug 11'225 kWh, was einem spezifischen
Ertrag von 1 ’169 k Wh/kWp/Jahr e ntspricht. A bbildung 4 zeigt d ie m onatliche Verteilung d er E rträge
sowie die Performanz. Aufgrund des Teilausfalls des Strahlungssensors fehlt die Performanz im April
2011; der Strahlungssensor lieferte erst ab Februar 2011 plausible Werte.
Die maximale Anlagenleistung bewegte sich zwischen 3,8 kW im Dezember und 9,1 kW im Juni. Somit wurden im realen Betrieb ca. 95% der Nominalleistung erreicht.
2
Die höchste gemessene Einstrahlung betrug 1158 W/m ; gleichzeitig wurde eine elektrische Leistung
von 8,1 kW gemessen. Der entsprechende Tag ist in Abbildung 13 dargestellt.
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Abbildung 4: Monatliche Erträge eines Betriebsjahres
Abbildung 5: Temperaturen, Leistung und Einstrahlung am 6. Juli 2011
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Die höchste registrierte Anlagenleistung wurde am 19. Juni gemessen, bei recht tiefen Modultempera2
turen und einer Einstrahlung von 1040 W/m , vgl. Abbildung 6.
Abbildung 6: Temperaturen, Leistung und Einstrahlung am 19. Juni 2011
Die höchste Temperatur wurde am Messmodul in der Nähe des Firstes gemessen. Diese lag knapp
über 80°C. Eine Maximaltemperatur von knapp über 80°C wurde im Juni, Juli und August an 1 bis 5
Tagen registriert. Der 22. August 2011 als einer der wärmsten Tage ist in Abbildung 7 dargestellt.
Abbildung 7: Temperaturen, Leistung und Einstrahlung am 22. August 2011
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Interessant ist e ine B etrachtung d er m it der ak tuellen L eistung gewichteten Temperaturmittelwerte.
Ohne Gewichtung enthalten die Mittelwerte keine relevante Information in Bezug auf das Betriebsverhalten.
Abbildung 8: Maximale und gewichtete Temperaturen Luft und Module
Abbildung 8 stellt die M esswerte d er T emperaturen dar. D abei e ntspricht d ie durchschnittliche Luf ttemperatur an der Traufe (Lüftungsgitter) der Umgebungstemperatur. „gew. Ø Mod. Traufe“ stellt die
durchschnittliche gewichtete Temperatur eines Moduls an der Traufe dar, „gew. Ø Mod. First“ diejenige be im F irst. F erner s ind noc h di e m onatlichen Ma ximalwerte d er Modul und Luf ttemperatur Nähe
First angegeben, sowie die maximale Differenz zwischen dem jeweiligen Wert an Traufe und First. Da
die Mo dultemperaturen an der Modulrückseite gemessen werden, entsprechen s ie nicht ex akt de n
Zelltemperaturen, u nd s ind v ermutlich etwas s tärker von d en Luf ttemperaturen im U nterdach beei nflusst als die Zelltemperaturen.
Analysiert wurde a uch d ie K orrelation zwischen Einstrahlung und T emperaturdifferenz zwischen e inem Modul t rauf- zu f irstseitig, s owie der Erhöhung der Luf ttemperatur i m U nterdach ( Differenz einströmende Luft und Luft im Unterdach gegen den First hin). Zu diesem Zweck wurden die Temperaturdifferenzen vs. Einstrahlung in einem Streudiagramm aufgetragen und mittels linearer Regression
ein linearer Zusammenhang gefittet. Wenngleich die Werte naturgemäss stark streuen – die Einstrahlung variiert wesentlich schneller al s die Temperaturdifferenzen – ergibt sich bei der Z usammenstellung der einzelnen Monatswerte ein recht einheitliches Bild, vgl. Abbildung 9 und Abbildung 110. Die
Geraden verlaufen fast durch den Nullpunkt beider Achsen, was Sinn macht, da sich ohne Einstrahlung auch die Temperatur nicht erhöht.
Die Temperaturdifferenz der Module nimmt im Schnitt von unten nach oben etwa 2,2° pro 100 W/m
2
zusätzliche Einstrahlung zu. Die Luft erwärmt sich um etwa 2,5° pro 100W/m erhöhte Einstrahlung.
2
Die Entwicklung der I ntegration der t hermischen S olarkollektoren i n d as Meg aSlate®II Dachsystem
erfolgt in Zusammenarbeit mit der Firma H+S Solar in Rebstein.
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Abbildung 9: Zusammenhang Modultemperaturdifferenzen vs. Einstrahlung
Abbildung 10: Zusammenhang Lufttemperaturdifferenzen vs. Einstrahlung
Zusammenarbeit
Die Entwicklung der Integration der thermischen Solarkollektoren in das MegaSlate®II Dachsystem
erfolgt in Zusammenarbeit mit der Firma H+S Solar in Rebstein.
Bewertung
Die I nstallation der P ilotanlage mit den neu en Systemkomponenten sowie des Mes ssystems konnte
erfolgreich dur chgeführt w erden, und l ieferte keinen A nlass, signifikante Anpassungen am Montagesystem oder an den Solarmodulen ins Auge zu fassen. Die Praxistauglichkeit von MegaSlate®II wurde
bestätigt. Mehr Schwierigkeiten bereitete die Montage und Abdichtung der MegaSlate Thermiepanels,
jedoch hat dieses Pilotprojekt ermöglicht, Schwachstellen aufzudecken und installationsfreundlichere
Lösungen zu entwickeln. Dank der Messungen an der Pilotanlage konnten wichtige Informationen zu
Temperaturverhalten und Stromertrag einer MegaSlate®II Indachanlage gewonnen werden.
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UNIQUE AND INNOVATIVE SOLUTION OF
THIN SILICON FILMS MODULES BUILDING
INTEGRATION
ARCHINSOLAR
Annual Report 2011
L.-E. Perret-Aebi, P. Heinstein, V. Chapuis, S. Pélisset, K. Lumsden, R. Tween, M. Mottet, Y. Leterrier, J.-A. E. Månson, M. Joly,
V. Le Caër, S. Mertin, A. Schüler, C. Roecker, M. Edelman,
G. Stoll, J.-L. Scartezzini, M. Bätschmann, V. Ritter, H. Leibundgut, P. Mirzaee, K. Ghazi Wakili, J. Carmeliet, C. Ballif
IMT-PVLAB / EPFL, Neuchâtel, IMX-LTC / EPFL, LESO-PB /
EPFL, ETH, EMPA
Address
Telephone, E-mail, Homepage 032 718 33 56, [email protected];
http://pvlab.epfl.ch
SI/500474-01, Swiss Electric Research
Date
10.12.2011
ABSTRACT
The Archinsolar project is based on the vision that, for a wide-scale development, photovoltaic (PV)
products have to become “commodity objects”. This project aims to develop a new generation of photovoltaic elements based on thin film silicon technology (single amorphous and tandem
amorph/microcrystalline c ells). T hese new e lements w ill be u ltra-reliable. T hey w ill m ake v ery low
manufacturing c osts and u nique ar chitectural integration possible, a nd be respectful of the environment, landscape, buildings and traditions.
•
A survey was submitted to more than 1800 architects with the aim of understanding the key
features necessary for a well admitted product on the building integrated PV market.
•
The first terra-cotta colored PV modules were developed and a new multi-functional solar tile
with a molded backstructure in composite was demonstrated.
•
A first series of reliability tests (accelerating aging and mechanical) on small size samples
were performed in order to ensure the full module a lifetime over 25 years.
•
Indoor and outdoor demonstration roofs were constructed at the PVLAB to present the new
developments.
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Goals of the project
The Archinsolar project aims to develop a new generation of photovoltaic elements based on silicon
thin film technology, ultra-reliable and manufacturable at a very low cost, allowing a unique architectural integration, respectful of the built environment and landscape. This project aims at developing
the science, technologies and methodologies allowing:
• to conceive innovative elements, able to widely pass IEC standards, with the objective of ensuring a lifetime of over 25 years,
• to propose aesthetically revolutionary elements (in a variation of colors and textures) that will fit
from an ar chitectural p oint of v iew as well as b eing respectful of t he landscape an d en vironment,
• to s implify t o a m aximum the i nterconnections on t he r oof w hile r especting t heir m echanical
constraints and security, and increasing their functionality,
• to demonstrate, even with the mentioned constraints, competitively low prices.
Short project description
The project is divided in 3 main workpackages:
• WP1 ” PV en gineering design of r eliable e lements“ es tablishes t he design c riteria, s elects
appropriate materials and carries out the first concepts of module design,
• WP2 ”Colored filters and multifunctionality“ develops the colored films and specific coatings
and t extures w hich w ill modify t he v isual aspect of the modules as w ell as t he innovative
electrical and roof interconnections.
• WP3 „ Integration, d esign, architecture“ realizes the ar chitectural i mplementation an d i dentifies the various constraints (e.g. linked to mounting, security, certification).
Architecture and Photovoltaics
A survey was sent to more than 1800 architects, in order to characterize the architectural sensitivity
regarding freedom in choosing module size, colors, texture and the willingness to pay for these features. T his s howed t hat ar chitects ar e v ery i nterested i n i nstalling ph otovoltaics but ar e l ooking f or
specific c haracteristics r arely a vailable o n t he m arket: p ossibilities of c hoosing d imensions, c olour,
type of surface and jointing. This study also showed that they were ready to accept to pay the price
(extra cost or reduced efficiency) for a suitable product.
Figure 1: Simulation of a traditional roof covered with the innovative
colored solar modules developed within the framework project
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SI/500474-01, L.-E. Perret-Aebi, EPFL-IMT-PVLAB
Most traditional roofs throughout central and southern Europe, due to a long tradition of typical terracotta roof tiles, represent a considerable market potential for modules having an appearance that better match traditional tiles. Hence, enlarging the offer by proposing various colored modules, from black
or dark brown towards a terracotta tone represents one of the main technical challenges of this project, as i t r equires a c omplex s cientific a nd t echnical pr ocess. T herefore, t wo d ifferent r outes have
been followed to reach this aim, the use of interferential colored filters laminated on the top glass of a
classical thin film module, such as developed by the LESO group and another technique, developed
by the PVLAB related to the module encapsulation.
Design of innovative thin silicon film PV Modules
With the purpose of developing a new multifunctional PV element, the possibility to remove the traditional back glass of the module and to replace it by a composite structure has been studied. Activities
including the selection of the material and of the process method, the analysis of the bonding between
the composite backing and the glass module, and the production of prototype elements were carried
out.
A cost and life cycle assessment of alternative composite backing solutions was carried out.
Four functional prototypes of a new solar tile were designed and produced. A small roof has been
constructed at IMT to demonstrate these new elements.
Figure 2: Moulded back structure and demonstration roof of the new integrated Archinsolar tile
With the aim to produce colored modules that could esthetically fit with the traditional ceramic tiles of a
roof, two di fferent r outes hav e be en f ollowed f or t he m odule c oloration: 1) t he us e of i nterferential
colored f ilters depos ited o n a gl ass l aminated o n t he or iginal m odule, as dev eloped b y the L ESO
group, 2) a new procedure combining encapsulation elements and technical aspects of the cell design
(This innovative technique is in the process of being patented, therefore this method will be described
more deeply later in 2012.)
With this purpose, colored filters deposited on glass have been simulated and produced with a special
focus on t he terra-cotta c olor. This c olored glass will be t hen l aminated to the t op of an amorphous
solar cell, changing the original brownish color of the amorphous cell.
The amorphous silicon photovoltaic modules combined with the interferential colored filters have been
characterized. A first version of these selective filters was tested on amorphous silicon (a-Si:H) thinfilm modules. E ach c ombination of c ell, filters, b ack-reflector and texturized glass was characterized
by means of quantum efficiency and current-voltage characteristic measurements.
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Figure 3: Orange interference filters developed at the LESO.
Figure 4: Terra-cotta solar modules developed at the PVLab
Reliability testing
Replacing the back glass of a standard glass/glass PV module by a polymer-based composite structure is a key toward low-weight m odules. Moreover, the composite bac k-structure can be shaped t o
include fixation anc hors that facilitate t he m ounting on r oofs r educing thus t he f inal c osts of the P Vsystem. However the main concern when replacing the back glass by a polymer-based material is the
protection of the active layers (TCO and cells) against moisture ingress which needs to be tested.
Therefore, ZnO layers have been deposited on glass and encapsulated with an EVA. Different composites where us ed as ba cksheets and, i n s ome c ases, a but yl ed ge s ealant ( es) w as app lied. T he
tested composites include Epoxy with 40% of glass fibers (GF), Polyester with 40% GF and Polypropylene ( PP) with 40% G F. T he s amples hav e t hen been s ubjected to damp-heat c onditions ( 85°C,
85%RH) and t he T CO s heet r esistance has b een measured us ing a c ontactless t echnique ( Sinton
tester) at different degradation times.
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Photovoltaics in Buildings
Local production of energy (heat and power) is an important element to realize this kind of buildings.
The integration of Photovoltaic (PV) within the building skin (BIPV) is of high relevance. The consolidation of s everal f unctions i n o ne e lement has not only ae sthetic, bu t also ec onomic ben efits. F urthermore, indirect emissions and grey energy can be reduced due to less construction and installation materials.
Typically, the direct combination of PV onto thermal building insulation causes high module temperatures (> 85°C). This af fects the material pr operties (notably E VA) of t he P V module n egatively a nd
reduces the persistence of the module. T he electrical ef ficiency also d ecreases with increasing c ell
temperature. This di sadvantage o ccurs i n crystalline technology i n a hi gher ex tend t han i n o ther
technologies. The solar heat absorbed on the PV module needs to be removed in order to increase
the lifetime of PV as well as to minimize the decrease of the electrical efficiency, depending on technology. This is done in conventional BIPV constructions by natural convection with an air gap on the
backside of the P V module. A n a lternative solution i s to us e a n active i nstead of a p assive cooling
system, which a Photovoltaic/Thermal-collector (PV/T) provides. The cell cooling function of a PV/Tcollector ha s t he advantage of a c ontrolled c onduction of t he heat. T herefore P V/T is beneficially
applicable for the direct combination of PV with thermal building insulation material.
The largest pot ential of t hose appl ications i s in t he f ield of f lat r oof r efurbishment. S ince 67.5% of
Swiss b uildings are built or refurbished be fore 1 980 an d need to be refurbished w ithin the n ext 10
years due t o average persistence of t he building s ystem a nd r oof c onstruction. In t hose r efurbishments the aspect of increasing thermal insulation and installation of solar energy generating systems
are essential.
In a first p hase, a P V/T-collector based on c rystalline t echnology, as c omponent of t he Z E-LowExbuilding t echnology has bee n developed. A f ield of 3 0m2 P V/T h as b een installed in April 2 011 including a monitoring system.
Figure 5: Installed PV/T panels
To determine the moisture loading of PV modules installed on roofs, it is necessary to know the climatic c onditions ar ound t he m odules and t he r esulting l ocal heat a nd m ass t ransfer pr ocesses at t heir
surface, in the cavity underneath and into the PV modules themselves. A multi-stage approach based
on both, experiments and simulation was used in order to predict the heat and mass transfer processes and perform adequate accelerated aging tests.
First a Computational Fluid Dynamics (CFD) model was developed in order to study the heat, vapor
and ai r f low around the m odules a nd t o per form a par ametric s tudy f or t he opt imization of t he PV
module composition and its installation. In the second step, the heat and moisture transport in the PV
module itself is modeled using the boundary conditions determined in the CFD model. Moreover, in a
third step the durability using an adequate moisture performance indicator will be evaluated. The outcome of the CFD study will provide the required information on the hygrothermal loading for the accelerated aging tests in which the aim is to determine and optimize the durability of the PV modules, including glass/PVB/glass, glass/EVA/glass, and glass/colored filter/PVB/colored filter/glass. Moreover,
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this study intends to propose recommendations for the installation of the PV modules, e.g. for promoting cavity ventilation in order to reduce the hydrothermal loading of the PV modules. Parametric studies ar e per formed i ncluding t he i nfluence of r oof i nclination, r oof or ientation, t he di mension of gaps
and overlaps between panels and the width of the cavity.
Figure 6: (Top) wind flow pattern (bottom) pressure contours
National and inernational collaboration
Beside t he s trong partnership bet ween a ll t he s cientific par tners i nvolved i n t he pr oject, t his pr oject
allows al so f ruitful c ollaboration with S wissInso f or t he pr oduction of t he c olored gl asses and with
Pramac for the production of the micromorph modules.
Evaluation for 2011 and perspectives for 2012
In 2011, most project deliverables were met in time. The first terra-cotta modules and a fully integrated
solar tile with a backsheet composite were demonstrated.
Even t hough, f urther development w ill be do ne i n t he aesthetic aspects b y de veloping new colored
filters and textured patterns for the glass. A strong effort will be done to understand the module reliability issues but still need to be deeply studied. Indeed the mechanisms and environmental influences
that cause module performance degradation are yet poorly understood. Among them are the interlayer
adhesion and c ohesion within t he layers, t he glass i nstability i n t he t hin film modules r elative t o t he
adhesion of the TCO layer on the glass, the effect of moisture, hot spot damage, encapsulant yellowness and interconnect f ailures. T he em phasis of t his r esearch i n t he n ext year w ill b e t o d evelop a
better understanding on what changes (use of new materials like composites, colors filters) may have
impact on these different aspects (adhesion of the encapsulant, TCOs degradation, mechanical stability…) and more generally, on the modules reliability over time. Finally, the next prototypes will be presented on a real outdoor demonstration roof in Neuchâtel and in Zürich.
Acknowledgments
Swiss E lectric R esearch ( SER), the Services I ndustriels G enevois (SIG) a nd t he C enter of C ompetence Energy and Mobility (CCEM) are thanked for their co-financing support.
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CONFORMAL PHOTOVOLTAIC MODULES
Annual Report 2011
1
1
1
1
Y. Leterrier, M.A. González Lazo, R. Teuscher, P. Velut,
1
1
R. Tween, K. Lumsden, J.-A.E. Månson
2
2
C. Calderone, A. Hessler
3
3
3
P. Couty, Y. Ziegler, F. Galliano, D. Fischer
1
Laboratoire de Technologie des Composites et Polymères
LTC-IMX-EPFL, Station 12, CH-1015 Lausanne
Address, Telephone,
Tel. 021 693 4848, http://ltc.epfl.ch
E-mail, Homepage
2
Centre Interdisciplinaire de Microscopie Electronique
CIME-EPFL, Station 12, CH-1015 Lausanne
Tel 021 693 4830, http://cime.epfl.ch
3
VHF-Technologies SA
Avenue des Sports 26, CH-1400 Yverdon les Bains
Tel. 24 423 08 90, http://www.flexcell.com
CTI 9903.1
Date
16.12.2011
1
ABSTRACT
The objective of this collaboration between EPFL and Flexcell is to develop a materials system and
process f or pr ofiled e ncapsulation of t hin f ilm s ilicon phot ovoltaic (PV) devices w ith i mproved efficiency f or s tructured, building i ntegrated P V r oofing el ements. T he pr oject s tarted on March 1s t,
2009. T wo i nnovative c oncepts w ere ex plored and i mplemented i n industrial de monstrators. F irstly,
light-trapping textures for the back reflector of the solar cells were produced in hyperbranched polymer ( HBP) s ilica nanocomposites us ing a U V-nanoimprint lithography ( UVNIL) r eplication m ethod,
either i n bat ch or roll-to-roll processes. A nickel template was used to imprint nanocomposites c ontaining u p t o 20 vol% of s ilica n anoparticles on a polyethylene n aphthalate ( PEN) s ubstrate. T he
hardness of t he H BP was f ound to increase b y a lmost 2 times with increasing nanoparticle loading
and its adhesion to the PEN was excellent. A replication quality better than 80 % was achieved in all
cases. Thin film silicon solar cells were deposited on the textured substrates using a large-area rollto-roll process. The phot ocurrent was m ore than 20% hi gher than t he r eference value of a flat c ell.
Secondly, a polymer composite material system and process for encapsulation of thin film solar cells
was developed for profiled roofing elements. The process technology includes a pre-forming step of
the laminated P V de vice a nd combined composite injection and bon ding s teps. T hese t hree s teps
were opt imized i n v iew of i ndustrial i mplementation with at tention pai d t o i dentify laminate des igns
and process windows compatible with the thermo-mechanical limits of the fragile active PV layers. A
large-scale dem onstrator w ith s tandard 1 m x 1.8 m c orrugated r oofing pr ofile and 60 W of out put
power was pr oduced. The env ironmental i mpact of t his no vel BIPV m odule was found t o be m ore
than 2 times lower than standard crystalline silicon modules. With such lightweight prefabricated PV
products Flexcell can now offer a completely new product to profiled roof panel manufacturers and to
system installers.
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Project Goals
The main objective is to develop a materials system and process for profiled encapsulation of thin film
silicon photovoltaic devices with improved efficiency for structured building integrated PV (BIPV) roofing elements. Two innovative concepts, namely a multifunctional textured coating and a full composite
backing were explored with specific objectives:
2
i) Increasing cell current density (> 13 mA/cm ) and module yield and durability with novel nanotextured photon-trap polymer-based coatings.
ii) Producing the photon-trap coatings in a roll-to-roll process (rate up to 10 m/min).
iii) Optimizing t he f orming o f an appr opriate c omposite m aterial as s tructural bac king with
appropriate design freedom to be adaptable to a range of roofing geometries.
Key challenges were to avoid premature cracking of the brittle PV stack during forming and to achieve
a high replication fidelity of thin organic coatings during photo-polymerization in a dynamic roll-to-roll
operation. A f urther c hallenge was t o gu arantee t he integrity of t he layered s tructure with v ery h igh
thermo-mechanical contrast bet ween layers, and a high dimensional s tability under severe durability
conditions.
Back Reflector Light Trapping Textured Coatings
Texturation of the back reflector of a PV module is a way to enhance light absorption by keeping the
thickness of the active material to its minimum (Deckman, H.W., et al., Optically enhanced amorphous
silicon solar cells. Appl. Phys. Lett., 1983, 42, 968-970). Thin film silicon cells deposited on a random
pyramidal r elief s howed a n i mproved ef ficiency c ompared with c ells depos ited on a f lat s ubstrate
(Söderström, K., et al., UV-nano-imprint lithography technique for the replication of back reflectors for
n-i-p thin film silicon solar cells. Prog. Photovoltaics: Res. Appl., 2011, 19, 202-210). UVNIL is an effective al ternative t o hot embossing t o produce ac curate s ub-micron t extures. I t was f ound to be a
viable and low cost method for the replication of nano-scale patterns using a HBP and silica nanoparticles (Geiser, V., et al., Nanoimprint lithography with UV-curable hyperbranched polymer nanocomposites. Macromol. Sympos., 2010, 296, 144-153). Particle-based polymer nanocomposites have
shown significant improvement in mechanical properties with respect to unfilled polymers (Hussain, F.,
et a l., Polymer-matrix na no-composites, pr ocessing, manufacturing, an d a pplication: a n ov erview. J .
Compos. Mat er., 2 006, 4 0, 1511 -1575). T he addi tion of nanopar ticles to t he t extured bac k r eflector
should thus improve the mechanical integrity and durability of the fragile PV device, especially when
using polymers as substrates. The objective of this work was to study the influence of nanosized silica
fillers and process pr essure on t he ac curacy of t extures r eplicated f rom a metal m aster and on t he
hardness of the composites and the efficiency of thin film silicon devices deposited on the textures.
Experimental
A U V-curable f ormulation of an ac rylated H BP with up t o 5 0 vol% ( 65 wt%) of 13 nm di ameter S iO2
particles and a 50 µm thick PEN substrate were used. Vickers microhardness tests were performed on
approximately 300 µm t hick coatings pr epared on glass s lides. Adhesion to t he PEN was m easured
using f ragmentation t ests. Texturation of appr oximately 100 mg nanoc omposite s amples w as pe rformed using a nickel replicate of a pyramidal texture of ZnO grown by CVD. The samples were covered with a PEN film and a glass slide to ensure a homogeneous pressure across the sample surface.
Pressures of 1, 3 and 6 bar were tested with SiO2 fractions up to 20 vol%, using a UVNIL tool built inhouse. A ll samples were irradiated dur ing 3 min. at t he maximum lamp i ntensity. The t opography of
the textured samples was examined by scanning electron microscopy (SEM). The root mean square
(RMS) roughness and the coherence length (L) value were computed from the micrographs. For optical characterization, all samples were coated with a 100 nm thick sputtered aluminum film. Angle resolved scattering (ARS) measurements were carried out in reflection mode using an in-house set-up,
using a red light laser (637 nm). The haze parameter was calculated from the ratio of scattered light
and t otal r eflected light values, which were m easured us ing a 1 0 W hal ogen lamp, an i ntegrating
sphere and a spectrometer (AvaSpec-2048).
Results & Discussion
The microhardness of the composites was found to increase by almost 2 times, up to 280 MPa with
increasing nan oparticle loading. T he i nterfacial s hear s trength bet ween t he c oating a nd a pl asmatreated PEN was close to 50 MPa for all investigated compositions, which corresponds to a very high
adhesion.
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CTI 9903.1, Y. Leterrier, EPFL
In all investigated cases very high replication fidelity was achieved (see Figure 1). The RMS/L ratios of
all textures were equal to that of the master within the experimental error of 20%. No significant effect
of process pressure during photo-polymerization was observed, which implies that a pressure as low
as 1 bar was sufficient to ov ercome the viscous s tress, ev en i n t he high v iscosity, paste-like
nanocomposite with 20%vol of s ilica, a nd ensure c omplete f illing of t he t extured m old. T he a ngular
distribution of the scattered light and the haze parameter of all nanocomposite textures were comparable within experimental scatter to the Nickel template, although a small loss in the amount of scattered light was detected.
Fig. 1: SEM m icrographs of t he N ickel template ( left) and a t extured nanoc omposite c oating bas ed on a U V c urable HB P
with 20 vol % silica produced at a pressure of 1 bar (right). The RMS/L of each texture is also indicated.
Figure 2 shows t he cr oss-section of a t extured na nocomposite with 10 vol% of s ilica na noparticles
produced using a pressure of 6 bar. The light-grey layer on the top corresponds to the platinum protective layer a nd t he dark layer o n t he b ottom corresponds t o t he P EN substrate. The nanoparticles
are well dispersed in the HBP across the whole coating thickness, with some degree of heterogeneity
at the micron level. The uppermost bright coating layer is an artifact resulting from charging effects at
the platinum interface.
Fig. 2 : Electron m icrograph of a FIB cross-section of a t extured nanoc omposite c oating w ith 10 vol% of s ilica nanopar ticles
produced with a pressure of 6 bar during UVNIL.
A 18 cm wide web roll-to-roll line equipped with a coating unit, a textured Ni roll and a UV lamp was
developed (Figure 3). Several 100 m of an imprinted PEN film was produced with the unfilled HBP at a
speed of about 7 cm/min. A 50 µm Mayer bar was used to meter the formulation coating, leading to a
final thickness of 3 µm, measured by optical microscopy. A sample of imprinted film of 12.5 cm x 10
cm on the 18 cm wide PEN substrate is shown in Fig. 3. A very high and homogeneous haze effect is
evident.
Fig. 3: Left: Roll-to-roll pilot process (18 cm wide web). Right: Textured HBP coating on a 18 cm wide PEN foil. The inset is a
top view of the texture.
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Thin film amorphous s ilicon solar cells were de posited on these large ar ea textured substrates. T he
2
highest ph otocurrent dens ity ac hieved with t he pr esent r oll-to-roll pr ocess w as 13. 5 mA/cm , wh ich
2
was more than 20% higher than the reference photocurrent of 11.0 mA/cm of a flat cell (Figure 4).
Fig. 4: External Quantum Efficiency (a) and (b) JV curves (b) of roll-to-roll manufactured cells on flat and textured HBP coated
PEN substrates. The inset in Figure 8b is a PV reference cell array.
The morphology of the device shown in Figure 5 is characterized by a good conformal coverage with
smooth interfaces and absence of a-Si growth defects in the bottom of the valleys. Such morphology
based on a texture with RMS roughness close to 100 nm and rather wide pyramidal angles is optimal
for cell performance.
Fig. 5: Electron micrograph of a FIB cross-section of a roll-to-roll processed a-Si device on textured HBP coating.
Conformal demonstrator modules
New building integrated photovoltaic (BIPV) roofing markets are estimated to be of 5 b€ in 2015. The
general objective of the present project is to develop a materials system and process for profiled encapsulation of flexible thin film PV for structured roofing elements. This opens a new market of profiled
roofs w ith integration s olutions eas ily ac cepted b y the ar chitects. F ocus of t he research was on the
development of a c ost-effective f orming pr ocess of a c omposite m aterial (e.g., M. W akeman et al.,
Manufacturing c ost c omparison of t hermoplastic an d t hermoset RTM f or a n a utomotive f loor pan,
Composites Part A , 2 006, 37, 9 -22) as s tructural backing f or t hin f ilm P V d evices w ith ap propriate
design freedom adapted to a range of roofing geometries. The key challenge was to avoid premature
cracking of the brittle PV stack during forming.
Materials and Processes
The multilayer P V de vice ( transparent electrode, a-Si, al uminium el ectrode) was de posited on the
50 µm thick PEN substrate and laminated at 150°C with a fluorinated polymer top foil and a thermoplastic back sheet, using an ethylvinyl acetate adhesive. On the outer side of the back sheet a polypropylene felt was added in order to provide an effective anchoring substrate for resin injection. The
laminated s tructure was s ubsequently f ormed i nto t he s elected pr ofile, a nd t he c omposite bac king
structure was injection molded onto the profiled laminate as detailed in following sections.
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Thermomechanical Analysis of Critical Radius of Curvature
A fracture mechanics model to predict the influence of temperature and mechanical stress on the failure of the PV layers was developed. This information was essential to calculate the critical radius of
curvature of the fragile device and enable forming the PV laminate. The model included the thermoelastic contrast between the stiff PV layers and the soft PEN substrate and was validated using temperature-controlled tensile tests in situ under a microscope. The crack onset strain (COS) data were
modeled as a linear superposition of an intrinsic COS and the process-induced internal strain taking
into consideration the r espective i nfluences of t emperature d ependent energy r elease r ate f or c rack
propagation and thermal expansion behavior (Figure 6). The COS decreased up to 200°C due to increased thermal strain and softening of the PEN. Above 200°C the additional shrinkage of the polymer
led to an increase in COS.
Fig. 6: Predicted crack onset strain (COS, solid line) vs.
measured COS (dots) for PV/PEN films as a function of temperature. Internal strain εi and intrinsic COS* predictions are
also shown.
Forming Process Optimization
A two-step manufacturing process was developed: the first step was a pre-forming of the laminate into
the selected profile and the second step was a resin transfer molding (RTM) of a thermoset resin on a
glass fiber fabric to the back side of the preformed laminate. A COS of less than 0.5% at 150°C puts
severe limits in terms of pre-forming the laminate foil under pressure. Failure of the device systematically occurred at 130°C under a pressure as low as 2 bars. A solution was found to enable forming to
radii of c urvature down t o 8 mm, t hrough t he optimization of the position of the neutral ax is w ith tailored thickness and stiffness of the thermoplastic backing layer and the use of a metal frame designed
2
for in-plane confinement of the laminate. The admissible flexural rigidity (2.8 N.mm ) and heat deflection temperature of the polymer (70°C for the selected 0.3 mm thick TPO sheet with excellent dielectric and waterproof properties) are insufficient for use as a structural backing. A glass/polyester composite was thus developed, with 30%vol fibers for optimal processability and mechanical performance.
With the light RTM technology, vacuum in the mold pulls the resin into the glass mat reinforcement.
The vacuum was set at 0.8 bar to avoid evaporation of the polyester resin solvent at higher vacuum
levels. T he t emperature c ycle an d f ormulation of t he polyester r esin, ac celerator and c atalyst w ere
also opt imized using c hemorheological analyses, with at tention paid to the gel time, which limits the
time for the injection step. Special attention was moreover paid to the adhesion of the TPO to the polyester composite. A range of polypropylene felts were anchored in the TPO under different pressures
and temperatures and their adhesion strength was measured using a 180° peel test. The impregnation
of the best felt with the liquid polyester resin guaranteed a durable interface between the PV laminate
and the composite backing.
This part of the work led to a joint Flexcell-EPFL Patent (see publications and patent section)
Demonstrators
®
A full-scale 1 m x 1.8 m demonstrator replicating a commercial SP44/333 Montana roofing profile was
produced us ing t hree i ndividual 5 0 cm w ide laminate P V f oils ( Figure 7) . T he d emonstrator module
weights 4. 5 kg and provides an out put p ower of 60 W. C omparison of t he I -V c haracteristics of t he
individual f lat l aminates ( prior t o f orming) and of t he f inal m odule ensured t hat no de gradation o ccurred during forming process (fill factor equal to 62% in all cases). The long-term endurance of the
conformal PV laminates with composite backing was also validated using standard damp-heat cycling
tests.
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Fig. 7: Full size profiled composite aSi solar module (1.8 m x 1 m, 4.5 kg,
60 W) and I-V characteristics of the
module and of the three individual flat
laminate PV foils used to produce the
module.
An evaluation of the life-cycle costs and environmental impacts of the present novel profiled modules
was moreover carried out using the Swiss Ecoinvent database and the Simapro software for the latter.
Figure 8 compares the environmental impacts related to the manufacture of the solar modules according to four i mpact c ategories, and to four di fferent scenarios, namely flat vs. conformed, and with or
without textured back reflector. The data are normalized with respect to the impacts for standard c-Si
modules produced using electricity mix based on 78% coal production.
It i s ev ident that i n a ll investigated c ases the a -Si modules enab le very large environmental savings
compared to the standard c-Si technology. The profiling of the flat module leads to a relatively large
increase of the environmental impact due to some extent to the reduced active area and essentially to
the addition of the composite backing, i.e., the addition of building integrated functionality. In spite of
this increase, the profiled module compatible with full BIPV is more than 2 times more environmental
friendly than the c -Si m odule. In c ontrast, t he bac k r eflector t exture (and corresponding i ncrease of
efficiency) enables an additional 5-10% environmental savings.
Fig. 8: Environmental impact assessment of the influence of back reflector texturation and profiling into conformal BIPV
modules. The data are normalized with respect to the impact of a standard c-Si module.
Conclusions
HBP-silica nanocomposite coatings were developed to produce light-trapping textures using a UVNIL
replication method. A microhardness of 280 MPa and interfacial shear strength with a PEN substrate
close t o 50 MPa were achieved. Both HBP a nd HBP nanocomposites r eplicated the nickel template
with f idelity better t han 8 0%. T he s ame l ight s cattering per formance i n t erms o f angul ar distribution
and haze parameter was reproduced for all tested compositions and process pressures. A roll-to-roll
process w as m oreover d eveloped f or c ost-effective production of l arge ar ea t extured c oatings. T hin
film silicon solar cells were deposited on these roll-to-roll textured substrates, with an increase of 23%
in photocurrent compared to a flat cell.
A novel polymer composite backing process method was developed, which enables fast profiling into
stable and complex shapes. The developed material and process system offers a low-cost and energetically robust alternative to standard building-integrated PV products based on crystalline silicon.
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Evaluation 2011 and Outlook 2012
The project started in the spring 2009 and the main objectives of the project, namely the development
of back reflector light trapping textures and of a profiled composite backing process method have been
achieved in 2011. The project will end in February 2012, and ongoing activities focus on further optimization of the roll-to-roll coating process, and on refined cost and environmental evaluations.
Publications and Patent
• Rion J., Leterrier Y., Månson J.-A.E., Blairon J.M., ‘Ultra-Light Asymmetric Photovoltaic Sandwich
Structures’ Compos. Part A., 40, 1167-1173 (2009)
• Leterrier Y., M ottet A., Bouquet N ., G illiéron D ., D umont P ., P inyol A ., L alande L ., Waller J .H.,
Månson J .-A.E., ‘ M echanical I ntegrity of T hin I norganic C oatings on P olymer S ubstrates und er
Quasi-Static, Thermal and Fatigue Loadings’, Thin Solid Films, 519, 1729-1737 (2010).
• Waller J .H., La lande L. , L eterrier Y., M ånson J .-A.E., ‘ Modelling t he Effect of Temperature on
Crack O nset S train of Brittle C oatings on Polymer S ubstrates’, T hin S olid F ilms, 519, 424 9-4255
(2011).
• Velut P., Tween R., Lumsden K., Leterrier Y., Månson J.-A. E., Galliano F., Fischer D., ‘Conformal
Thin Film Photovoltaic Modules’, 21st International Photovoltaic Science & Engineering Conference
(PVSEC), Fukuoka, Japan, Nov. 28-Dec. 2 (2011).
• González La zo M., T euscher R ., Let errier Y., Må nson J .-A. E ., C alderone C ., Hessler-Wyser A .,
Couty P., Ziegler Y., Fischer D., ‘Large Area Roll-to-Roll Texturation with Hyperbranched Polymer
Nanocomposites f or Li ght-Trapping A pplications’ 21s t I nternational P hotovoltaic S cience & Engineering Conference (PVSEC), Fukuoka, Japan, Nov. 28-Dec. 2 (2011).
• González La zo M., T euscher R ., Let errier Y., Må nson J .-A. E ., C alderone C ., Hessler-Wyser A .,
Couty P., Z iegler Y., F ischer D ., ‘UV-Nanoimprint Li thography and Large Area R oll-to-Roll
Texturation with Hyperbranched Polymer Nanocomposites for Light-Trapping Applications’, submitted to Solar Energy Materials and Solar Cells.
• ‘A Photovoltaic Element’ (Joint EPFL-FLEXCELL Swiss patent application, Dec. 23, 2010)
Acknowledgements
The authors would like to acknowledge the Commission for Technology and Innovation (CTI, project
9903.1 PFIW-IW) and VHF Technologies SA for financial support.
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LARGE AREA SOLAR SIMULATOR INTEGRATING POWER LIGHT EMITTING DIODES
FOR PERFORMANCE MEASURMENT OF NEW
GENERATIONS OF PHOTOVOLTAIC MOULES
(SUNSIM)
CTI PROJECT 10880.2
Annual Report 2011
Address
Date
Rue A. L. Breguet 2, Neuchâtel
CTI 10880.2
01.01.2010 – 30.06.2012
15.12.2011
ABSTRACT
The project granted by the Commission for Technology and Innovation is devoted to the development
of a ne w generation of f lat-bed l arge-area s olar simulator t echnology. T he f irst phas e f inished successfully in June 2011 with the demonstration of the high potential of the developed solution utilizing
an hybrid mix of light emitting diodes and halogen lamp sources. The first demonstrator, with an ac2
tive area of ~ 0. 8 m , showed hi gh s pectrum fidelity to t he A M1.5g spectrum, low non uniformity of
irradiation (< 2 % ) and l ow temporal non uniformity (class A AA). Characterization of high efficiency
crystalline silicon and of thin film PV modules carried out with the developed first prototype confirmed
the h igh p otential of t he developed technology. T he monitored v ariable s pectrum, i ntensity an d the
long pulse duration are some of the decisive advantages provided by the flat-bed simulator.
The des ign of t he 1.5 m × 2 m f inal prototype c ould therefore b e t riggered. T echnical c hoices and
launch of parts construction were finalized in December 2011.
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CTI PROJECT “SUNSIM”
The project is a joint collaboration between the PV-Lab and the company PASAN SA. A team of engineers and of post-doc from both the PV-Lab and PASAN SA collaborate to build a large-area flat-bed
solar simulator.
Commercial large-area solar simulators are principally in the form of Xenon flashers, which intrinsically
have a short flash duration time, typically 100 ms at low spectrum quality and 10 ms at high spectrum
quality. This implies measurement time constraints not adapted to the characterization of new generations of ph otovoltaic m odules s uch as h igh-efficiency c rystalline s ilicon, which can e xhibit t ransient
effects l eading t o m easurement ar tifacts. Mor eover, t hin f ilm t echnologies r equire a high s pectral
match and pos sibly a v ariable s pectrum o f t he i llumination s ource f or t he ac curate po wer-rating of
multi-junctions bas ed s olar modules. A n a lternative large-area s olar s imulator s olution i s t herefore
developed in this project for the power rating and the diagnostic of such generations of solar modules.
The t argeted f lat-bed simulator m akes us e of a c ombination of di fferent po wer LE Ds a nd h alogen
lamps in a particular matrix configuration. In 2011, the work consisted in the construction and characterization of the first demonstrator (1 m × 1 m flat-bed simulator with mirrors), and in the characterization of different PV modules technology to assess the potential of the developed solution.
DEMONSTRATOR CONSTRUCTION AND CHARACTERIZATION
The constructed prototype makes use of a combination of different power LEDs and halogen lamps in
a particular matrix configuration, integrated into a 1 m × 1 m table with mirrors. A picture of the constructed simulator is shown in Figure 1.
Figure 1: Left: 1m×1m flat-bed demonstrator. Right: LEDs and halogen lamps arrangement in the demonstrator.
A class A spectral match is provided with different LED types for the low wavelength regions (< 700
nm) and principally halogen lamps for the high wavelength region (> 700 nm). The spectral match is
solely limited in the present demonstrator in the 400 nm to 480 nm wavelength region, due to a lack in
light intensity around 420 nm, compensated by a higher intensity at 460 nm wavelength. For the final
prototype, this will be corrected thanks to the recent availability of 420 nm wavelength power LEDs.
Technical solutions were found to overcome the difficulty related to the spatial non-uniformity on large
area, so that it was measured systematically below 2 %, while biasing schemes of the lamps and m echanical design ensure a class A in temporal stability. The uniformity was automatically measured for
each type of light source and found to be below 2 %, therefore guaranteeing uniform spectrum over
the simulator illumination area.
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CTI 10880.2 SUNSIM, M. Despeisse, EPFL PV-Lab
Relative unit
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
380
AM1.5
Spectrum
480
580
680
780
880
980
Wavelenght [nm]
Figure 2: Left: Spectrum measured on the prototype active area compared to the AM1.5g solar spectrum. Right:
Uniformity distribution measured on the prototype active area: non-uniformity < 2 % in both spectrum and intensity
are guaranteed.
The pos sibility t o adjust t he bi ases independently f or eac h t ype of l ight s ource allows f or c ontrolled
variations of the spectrum. While this permits to assess the module performance under illuminations
corresponding to different outdoor conditions, variable spectrum measurements can also be important
to es timate t he limiting j unction in m ulti-junction m odules. Mod ule di agnostic can al so b e r ealized
through v ariable i llumination measurements, as al ready us ed f or t hin f ilm silicon t echnologies. T hin
film silicon tandem junctions (micromorph) could be tested with the prototype solar simulator, demonstrating a close matching to results obtained with a small-area WACOM dual lamp system.
CHARACTERIZATION OF NEXT GENERATION PV MODULES
From an electrical point of view, the main characteristic of high-efficiency crystalline silicon solar cells
and m odules, s uch as he tero-junction phot ovoltaic devices, i s t he h igh d iffusion c apacitance pr esented by the cell under normal operating forward voltages. This capacitance increases for increasing
forward v oltage, an d i ntroduces c harge s torage ef fects w hich pr event r apid c hanges of v oltage, as
they then lead to measurement artefacts which depend on the I-V sweep speed and direction. For fast
sweeping, the charge or discharge of the diffusion capacitance during the measurement will respectively l ower or i nflate t he measured c urrents f or f orward ( increasing voltage) or r everse ( decreasing
voltage) directions of the I -V s weep. T his hi gh c apacitance ef fect i s a di rect c onsequence of t he increased performance of the s olar c ells, w ith t ypically i ncreased ef fective m inority c arrier l ifetime, r esulting f rom i mproved bulk-material, r ear passivation, but al so i mproved f ront s ide pr operties. The
performance v ariations of hetero-junction a -Si/c-Si, “standard” di ffused mono-crystalline and thin film
silicon solar modules with respect to the sweeping time and direction were therefore carefully studied
using a state-of-the-art PASAN flasher and the newly developed LED based flatbed sun simulator.
The incidences of the I-V measurement sweep time on MPP are detailed in Figure 3, keeping similar
scales for the 4 modules relative MPP data.
The di scharge of t he c ell c apacitance a nd t herefore t he reverse di rection measurement i s shown t o
lead t o m ore pr onounced t ransient ef fects t han t he direct m easurements. F or eac h het ero-junction,
very similar transient effects are measured using the flasher, the flatbed and the corrected dark conditions measurements, showing that pre-illumination, which is occurring during the measurements with
the flatbed and not with the flasher or in dark conditions, does not impact the transient behaviour of
the measured hetero-junction modules.
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Figure 3: MPP variations of the monocrystalline silicon module 5 (top left), of the hetero-junction modules 1 and 3
(top right and bottom right) and of the micromorph module 7 (bottom left) for 10 ms to 1 s I-V sweep duration as
measured with the flasher, the table (IMT flatbed [7]) and in dark conditions.
Then, f rom F igure 3, i t c an be s een t hat t he v ariations w ith t he s weep t ime i s qui te s imilar f or t he
hetero-junction m odules 1 and 3, which ar e r espectively f rom two di fferent manufacturers, A and B .
This is clearly confirmed by direct comparisons in Figure 4 of the relative difference between the MPP
measured in the forward and in the reverse directions, referred to as ΔMPP in the following. Interestingly, t he per fect m atch bet ween t he t wo m odules t ransient be haviour c orrelates w ith s imilar V OC
measured for t he c ells i n t hese t wo m odules f rom di fferent manufacturers. I n order t o pr ovide a n
accurate measurement, one can consider that ΔMPP must be below ± 0.5 %. This condition is met for
hetero-junction modules 1 and 3, w hich ha ve similar cell V OC, for similar sweeping times abov e 12 0
ms, even though they were developed by different manufacturers.
Figure 4: Relative variations between MPP measured in forward and in reverse directions in hetero-junction modules, expressed in %, for different I-V sweep durations. Hetero-junction modules 1 and 3, which are from different
manufacturers, have similar cells VOC and similar transient behaviour with a similar minimum sweep time of about
120 ms. Hetero-junction module 4 implements cells with a higher VOC (+ 20 mV), and exhibit stronger transient
effects, with a minimum sweep time of about 300 ms.
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Similar analysis of the relative MPP difference between forward and reverse direction ΔMPP was conducted on t he hetero-junction m odule 4, which i mplements c ells w ith a higher VOC than t he c ells i n
modules 1 and 3 (typically ~ 20 mV more per cell). Results compared in Figure 4 clearly demonstrate
more pronounced transient effects on this module than on modules 1 and 3, with a minimum sweep
time of about 300 ms to allow for ΔMPP < ± 0.5 %. This can be explained by higher effective minority
carrier lifetime in the cells of module 4, yielding an increased VOC, and an enhanced diffusion capacitance, which in turn results into more pronounced transient artefacts during the measurement. These
final r esults s how t hat b y further enh ancing the c ells per formance, t he m easurement ar tefacts ge t
even more pronounced, and imply the use of further enhanced minimum sweeping time, clearly showing that t he transient b ehaviours i n high efficiency m odule power r ating will get more and more pronounced in the f uture. This problem also ar ises f or very high efficiency b ack-contact ce lls, will also
start to arise for diffused solar cells with enhanced VOC, following the introduction of selective emitters
and backside passivation.
Noticeably, reproducible ISC were measured over the experiments on the tandem module, showing a
good repeatability of spectrum and irradiance of the developed flatbed sun simulator and that proper
thermal control can be realized. Long sweeping times (> 120 ms for modules 1 and 3 and > 300 ms for
module 4) were then demonstrated to be needed for an accurate measurement of the hetero-junction
modules. Long-pulse is the method of choice, but can be very sensitive to thermal errors, due to the
heating of the module in test. However, quite stable VOC measured in this study even for modules on
the flatbed simulator; show that a good thermal control can be achieved with these small area modules.
The project w as successfully advanced in 20 11, with t he f inalization of t he f irst f lat-bed l arge-area
hybrid s imulator, a nd its f ull c haracterization d emonstrating a c lass A AA. PV m odules c haracterizations also clearly demonstrated that the project development will become a method of choice for the
future. The final large-area prototype will be constructed and evaluated in 2012.
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MPVT PROJECT
MULTI PURPOSE PHOTOVOLTAIC
MODULE TESTER
Annual Report 2011
Address
Date
Alessandro Virtuani
SUPSI-DACD- ISAAC
Via Trevano, CH-6952 Canobbio (Lugano, TI)
058 666 63 14, [email protected], www.isaac.supsi.ch
CTI 9626.1 PFIW-IW
01.10.2008 – 31.03.2011
13.12.2011
ABSTRACT
The aim of the MPVT ( Multi-Purpose P V M odule Tester) project was to developed an extremely
versatile measurement equipment for the indoor testing of PV modules by upgrading and integrating
new functionalities into an existing solar-simulator (flasher) based IV measurement set-up.
The newly developed MPVT set-up should be able to realize IV measurements at standard test conditions, temperature coefficients (TCO’s) and measurement at different irradiance levels. In addition, a
set-up to measure spectral response (SR) of large-area module will be implemented in the system.
The MPVT system will be adapted to the needs of the different PV technologies present today on the
market, which require a larger flexibility in terms of electrical measurement conditions (highvoltage/low-current thin film PV and high-current/low-voltage c-Si technologies).
Moreover, traditional or alternative solutions will be implemented to overcome problems - related to
the short duration of the light pulse -which some technologies may encounter when performing power measurements with flashers, as for example, high efficient c-Si modules, which are characterized
by high cell capacitances.
The outcomes of the project are briefly reviewed.
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Aims of the project
The MPVT (Multi-Purpose PV Module Tester) project is funded by KTI-CTI (project number 9626.1
PFIW-IW) and has a duration of 24 months. The industrial partner is PASAN SA (Neuchatel) – manufacturer of solar simulators and measurement equipments for photovoltaic (PV) devices – and the
research partners are two research institutes of SUPSI (Scuola Universitaria Professionale della
Svizzera
Italiana):
SUPSI-DACD-ISAAC
(www.isaac.supsi.ch)
–
and
SUPSI-DTI-ISEA
(www.dti.supsi.ch). ISAAC (Institute for Applied Sustainability to the Built Environment) is involved in
the project with its Photovoltaics Sector (testing of PV devices and systems). ISEA is the Institute for
Systems and Applied Electonics.
The main goal of the project was to adapt the measurement equipment (solar simulator set-up) for the
current-voltage (IV) characterization under standard test conditions (STC: 1000W/m², 25°C, AM1.5) of
PV modules and solar cells to the needs of the market, characterized by an increasing number of
technologies commercially available – which require different measurement procedures and/or approaches - and by a continuously increasing size of the PV devices.
Besides the flah lamp, the heart of a solar-simulator set-up is the electronic load, which has to respond
to all requirements of a multipurpose solar simulator. The newly developed MPVT electronic load will
be offered at testing and research laboratories worldwide and will be the basis for the development of
a high efficient and cost effective in-line testing for PV module manufacturers.
The motivations to develop a new electronic load can be summarized as follows:
• Need for a larger range of electrical test conditions
The size of PV modules – both c-Si based and thin film (TF) technologies - is continuously increasing,
challenging the existing test equipment, which was mainly developed for standard crystalline silicon
2
PV modules. E.g. the largest thin film PV modules (5.2 m ) present on the market are approaching
powers close to 500 W.
There is therefore a need for more flexible measurement equipment able to test high voltage (TF) and
high current (c-Si) devices.
The power unit of the new MPVT electronic load will be adapted to this requirements.
• Testing conditions different from STC
An increasing awareness in recent years about the need to optimize PV modules for their energy production (kWh) under real operating conditions rather just than for their power (Wp) measured at
standard test conditions, has led to a growing demand for test equipment capable of characterizing a
module under different irradiance, temperature and spectral conditions.
Very few of the existing solar simulator manufactures offer a light generator and electronic suitable for
IV testing at STC, different temperature and irradiance levels in one solution; and none of these offers
a system for the measurement the spectral response (SR) of the PV device.
The future adoption by IEC (International Electro-technical Committee) of an Energy Rating standard
(IEC 61853, currently under draft) will further increase these requirements.
The new MPVT electronic load (HW and SW) could easily be adapted to test TCO (temperature coefficients) and IV curves at different irradiances.
• Need for a commercial spectral response (SR) system for large-area PV modules
The SR curve of a module is crucial for a correct calibration of PV devices and for precise
energypredictions under real operating conditions where the spectral composition of the light changes
continuously. Presently no existing solar simulator manufacturer offers a full solution for the testing of
SR of large-area modules.
The new MPVT system (HW and SW) will offer the possibility to perform SR measurements on these
devices.
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MPVT Project, A. Virtuani, ISAAC-DACD-SUPSI
• Need for specific solutions for thin film and high efficiency c-Si modules
Larger and more efficient PV technologies entering the market are challenging the existing test
equipment, which was mainly developed for standard crystalline silicon PV modules.
Current equipment offered by manufacturers is not always capable of measuring these technologies.
E.g. one of the typical problems encountered with pulsed solar simulators is the difficulty to test high
efficiency c-Si modules, which are characterized by high cell capacitances.
Standard measurement approaches do not allow the discharge of this capacitance within the duration
of the light pulse, therefore, introducing strong measurements artifacts in the IV measurements of
these technologies. This measurement artifacts may lead to strong over- or underestimation of the
measured power (up or down to more than 20%, respectively).
Traditional approaches to overcome these problems – as sectional and point-by-point multi-flash IV
measurement approaches - are generally time consuming and costly.
The newly developed MPVT system will implement these traditional approaches (as the multi-flash
one) but also investigated specific alternative solutions to overcome these problems (as the measurement of dark IV curves or the use of modified voltage profiles) If these solutions will provide ease of
implementation and will result in an increased time- and cost effectiveness they will be implemented in
the final MPVT measurement set-up.
Results
The prototype of a novel electronic load (EL) – shown in Fig.1 - was manufactured by PASAN and
handed over to ISEA and ISAAC in July 2010 for integration tests. The software (SW) is still under
development at PASAN, though the first release is now ready and the EL can be governed by a lowlevel SW interface for testing purposes.
The validation of the entire system – including for example the testing of modified voltage profiles for
highly capacitive devices – was carried out in the period January - March 2011. Figures 2 and 3 show
the results of initial testing of highly capacitive devices (SANYO HIT). By applying – during the duration of a single 10-ms light pulse - a triangular voltage profile at the terminals of the modules, it is possible to drive the module from short-circuit (Isc) to open-voltage (Voc) conditions and vice versa. The
asymmetrical behavior of the measured current in Fig. 2 and the fact that the two IV curves in Fig. 3
do not overlap, are an indication that the module is capacitive.
Figure 1: prototype of the novel MPVT electronic load (EL) manufactured by Pasan SA.
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Voltage (V), Current (A)
50
40
30
measured voltage
20
imposed voltage
Isc
10
current
0
-10
0
1000
2000
3000
Measurement points
Figure 2: Imposed and measured voltage and measured current upon applying a triangular voltage profile
at the terminals of a capacitive PV module.
Voltage V (V)
7
5
3
Current
1
-1 0
20
40
Cuurrent I (A)
60
Figure 3: IV characteristics obtained by plotting data contained in Fig.2. By applying a triangular voltage profile
at the terminals of the modules, during the duration of a single 10-ms light pulse - it is possible to drive the module from short-circuit (Isc) to open-voltage (Voc) conditions and vice versa. The fact that the two IV curves do not
overlap, are an indication that the module is capacitive.
WP5 (validation of the newly developed system with particularly significant PV technologies: highefficient c-Si and thin-film modules) has provided relevant results. Focus was been dedicated to the
testing of highly-efficient (highly-capacitive) c-Si PV modules. Novel methods for the testing of these
devices were validated (customized voltage profile and dark Iv measurements), though further testing
is required.
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Dissemination
Virtuani, Friesen, Chianese, Dozio, Rigamonti, Pegurion, Beljean, THE M PVT ( MULTI-PURPOSE
PV M ODULE TESTER) PR OJECT - A HI GHLY I NNOVATIVE AND V ERSATILE S OLAR SIMULAth
TOR, presented at the 25 European Photovoltaic Solar Energy Conference and Exhibition, Valencia
6-10 September 2010.
Meza, Virtuani, Chianese, EVALUATION OF MODELS FOR THE INTERNAL CAPACITANCE OF A
PV MODULE FOR THE DESIGN AND SIMULATION OF POWER CONVERTERS, presented at the
th
25 European Photovoltaic Solar Energy Conference and Exhibition, Valencia 6-10 September 2010.
A.Virtuani, G. Friesen, D. Chianese, G. Rigamonti, and P.R. Beljean, MAJOR OUTPUTS of the MPVT
(MULTI-PURPOSE PV MODULE TESTER) PROJECT - A HIGHLY INNOVATIVE AND VERSATILE
th
SOLAR SI MULATOR, presented at the 26 European Photovoltaic Solar Energy Conference and
Exhibition, Hamburg 5-9 September 2011.
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PHOTOVOLTAIK IM VERBUND MIT
DÄMMSTOFF FOAMGLAS
Annual Report 2011
Address
Duration of the project (from–to)
Date
Pittsburgh Corning (Schweiz) AG,
Schöngrund 26, 6343 Rotkreuz
044 387 13 86, [email protected]
SI/500582 / TP Nr.:8100146-02
01.12.2010 – 31.12.2013
13.12.2011
ABSTRACT
As a pure electrical power producer, the photovoltaic technologies are established. The development
of “ In-roof-systems” has pr oved to b e ef fective. Besides t he e lectrical po wer pr oduction, I n-roofsystems s erve al so as r oof panel s and water pr otection. U nknown ar e s ystems, w here t he ph otovoltaic in addition to the power production and the water protection has the function of thermal insulation. T he scope of this project is the development and realisation of building integrated photovoltaic
(BIPV) including the feature of thermal insulation. A pilot plant with modules combined of photovoltaic
modules and Foamglas insulation shall be built.
The project “Photovoltaic with Foamglas insulation” was initiated in spring 2010 and was started officially in December 2010. Work on the project in 2011 progressed as planned. Following results were
achieved in 2011:
•
An overview of the market prices situation was elaborated
•
•
Applications were selected and concepts were evaluated
Desk research investigated on the temperature influence from the insulation on the module
efficiency has been done
•
•
A new insulated hybrid collector concept was found and given to the industry (3S)
Contacts to adhesive industries and PV-module manufacturers were established and first adhesions tests were performed.
Short summary of the targets for 2012:
•
Evaluation and execution of mechanical load tests and aging tests
•
•
Evaluation, specification und start of construction of a pilot project
Conceptual development of the cable and plug connection
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Marktpreisanalyse
In der folgenden Tabelle sind die geschätzten Marktpreise als Beispiel Deutschland für die komplette
Gebäudehülle inkl. PV-Unterkonstruktion, Material und Arbeit. Die Bezugsgrösse der folgenden Kom2
ponenten ist 200 m :
•
•
•
•
Dämmung, Dampfsperre
Dichtung
Witterungsschutz
PV-Befestigungssystem ohne PV Module (PVUK)
Die Preise stellen für die Entwicklung von Lösungskonzepten die Zielgrösse dar, welche unterschritten
werden muss, damit das Produkt auf dem Markt lebensfähig ist (Targetpricing).
Marktpreis Neubau
Fassade
Flachdach Beton
Starke Dämmung
Mittlere Dämmung
U: 0.15
U: 0.24
2
Leichte Dämmung
U: 0.35
2
2
126.00 EUR/m
115.00 EUR/m
110.00 EUR/m
U: 0.15
U: 0.20
U: 0.30
2
2
2
156.00 EUR/m
141.00 EUR/m
125.00 EUR/m
Flachdach Leichtbau
(Trapez, Holz)
U: 0.15
U: 0.20
U: 0.30
153.50 EUR/m
138.50 EUR/m
122.50 EUR/m
Schrägdach
unten Holz, oben
Ziegel
U: 0.15
U: 0.20
U: 0.30
126.50 EUR/m
120.00 EUR/m
111.70 EUR/m
Schrägdach
unten Beton,
oben Falzblech
U: 0.15
U: 0.20
U: 0.30
156.00 EUR/m
138.50 EUR/m
138.50 EUR/m
Schrägdach
unten Trapezschale,
oben Falzblech
U: 0.15
U: 0.20
U: 0.30
Schrägdach Sandwich
2
2
2
2
2
2
2
2
100.50 EUR/m
U: 0.15 70.00 EUR/m
2
2
2
2
2
94.00 EUR/m
85.70 EUR/m
U: 0.20
U: 0.30
2
64.00 EUR/m
2
60.00 EUR/m
Tabelle 1: Überschicht Abschätzung Marktpreise für Isolation, Witterungsschutz und PV Montagesystem
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Photovoltaik im Verbund mit Dämmstoff FOAMGLAS, E. Langenskiöld, Basler & Hofmann AG u. M. Stoll Pittsbugh Corning Schweiz AG
Fokussierung auf Applikationen
Aufgrund der Marktpreissituation wurden die Potentiale für eine PV Lösung mit Foamglas auf folgende
Felder fokussiert:
Integriert / geformt
(verklebt)
(verklebt)
abgesetzt
Fassade
Schrägdach
Flachdach
Integriert
Tabelle 2: Fokus der Anwendungen aufgrund der Marktpreise
Klebeversuche
Ertste
Klebeversuche
mit
Foamglas
wurden
durchgeführt. Die Zusammenarbeit mit der Firma
Henkel wurde aufgebaut und Klebeversuche mit realen
Modulen der 3S sind zur Zeit in Arbeit.
(Bild 1: Foamglasblock mit angeklebter Modulattrape)
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Temperatur und Wirkungsgrad der PV Module: Resultat Deskresearch
Der direkte Verbund von Photovoltaikmodulen und FOAMGLAS verschlechtert die Wärmeableitung im
Vergleich zu h interlüfteten I nstallationen. Die r esultierenden hohen T emperaturen f ühren be i den
meisten Solarzellen zu einem Leistungsverlust, der je nach Zellentyp verschieden hoch ist (2-8%). Bei
den amorphen Zellen kann dieser Verlust durch das Annealing teilweise oder ganz kompensiert werden. Beachtet sollte werden, dass die Solarzellen meistens nur bis 85°C getestet werden und deshalb
keine Garantie auf fehlerfreie Funktion bei höheren Temperaturen geben.
Hybridkollektoren mit Foamglas
Das D ach des G ebäudes B 35 von H errn Leibundgut in Z ürich wurde m it F oamglas i soliert und
anschliessend m it B itumen und F olien abgedichtet. D ie 3S H ybridmodule ( PVT) w urden mit e imen
Chromstahlbefestigungsträger (Krallenplatte) im Foamglas verankert.
Ein neues Konzept wurde aufgezeigt, welche mehrere PVT Hybridmodule und Foamglas Isolation in
grösseren v orgefertigten B euteilen kombiniert. Das Potential der R ationaliserung der v erschiedenen
Gewerke auf de m B au hat än liche D imensionen w ie d ie Einführung d er Sandwichpanele bei
Leichtbauhallen. Bei S andwichpanelen werden T ragkraft, D achhaut u nd I solation als 6 x 1 Meter
Bauteilen sehr r asch un d i n e inem A rbeitschritt auf der Baustelle v erbaut und führen zu m assiven
Kostenreduktionen.
Die Weiterentwicklung dieses Konzeptes würde jedoch den Rahmen dieses Projektes sprengen. Das
aus diesem P rojekt gebor ene neue K onzept wurde mit der F iram 3S bes prochen und i st dort i n d ie
Entwicklung eingeflossen.
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Die A nforderungserfassung und d ie Konzeptphase s ind weitgehend ab geschlossen ( sieht gr üne T ätigkeiten in der untigen Tabelle)
Für die kommenden Jahre ist das Vorgehen gemäss dem Meilensteinplan ("Fast Prototyping") vorgesehen:
Deliverables
Q1
Anforderungen
- Anforderungen an die Lösung
Verbindung PV-FOAMGLASS
- Anforderungen
- Konzept - Variantenentscheid
- Konstruktion
- Labortest
- Feldtest
Kabelführung u. Steckverbindung
- Anforderungen
- Konstruktion
- Labortest
- Feldtest
2011
Q2 Q3
Q4
Q1
2012
Q2 Q3
Q4
Q1
x
x
2013
Q2 Q3
Q4
x
x
x
x
x
x
x
x
x
x
x
Eigenschaften (Wirkungsgrad.....)
- Anforderungen
- Konstruktion
- Labortest
- Feldtest
x
x
x
x
Befestigung der Elemente
- Anforderungen
- Konstruktion
- Labortest
- Feldtest
x
x
x
x
x
Demo Anlagenbau
- Anforderungen
- Variantenentscheid
- Konstruktion / Bau
- Langzeittest
x
x
x
x
Wirtschaftlichkeit und Einsatzgebiet
- Betrachtung Markt
x
x
Tabelle 3: Zeitplan
Referenzen
Dieser Jahresbericht referenziert ausschliesslich auf den Projektantrag " Photovoltaik im Verbund mit
Dämmstoff FOAMGLAS".
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MANUFACTURING TECHNOLOGIES
AND EQUIPMENT TO PRODUCE LOW-COST
PV BITUMINOUS-MODIFIED ROOFING MEMBRANE WITH FULL INTEGRATION OF HIGH
EFFICIENCY FLEXIBLE THI-FILM SILICON
PV MODULES (PV GUM)
Annual Report 2011
Address
Date
VHF Technologie SA
Av. Edouard Verdan 2, 1400 Yverdon-les-Bains
024 423 08 90, [email protected], www.flexcell.ch
PV-GUM / 249791
01.12.2010 – 30.11.2012
14.12.2011
ABSTRACT
With millions of square meters of available flat roof surfaces with PV conversion potential, PV roofing
membranes have a huge potential for mass deployment. However, currently, major issues still hinder
this deployment: adhesives or barrier encapsulants of the existing flexible PV roofs don’t meet yet the
same reliability as standard construction materials and BIPV is still expensive. The PV-GUM project
aims at developing new manufacturing technologies and equipments which will produce a low cost
highly efficient flexible BIPV solar cell on a bituminous roofing membrane (thanks to their proven sustainability, bituminous membranes remain predominantly used for waterproofing flat roofs). The PVGUM membrane should be very close to the usual bituminous roofing membrane in terms of size,
installation process and quality to highly increase the penetration power of PV-GUM in the building
market. The PV-GUM membrane will be based on the “Derbibrite” white-coated bituminous membrane technology of Imperbel, PV-GUM coordinator, and the Flexcell flexible PV modules technology.
The full integration of the flexible PV modules in the membrane will be performed at the manufacturing stage by a new standardized roll-to-roll encapsulation process to produce PV-laminates followed
by a roll-to-roll bitumen impregnation of the PV-laminates.
In parallel, a new standardized PECVD reactor and process will be implemented to increase the
Flexcell PV cells efficiency to 8% at least and achieve technology superiority over other providers in
US, like Unisolar, remaining the main supplier for this market. The PV-GUM project targets a PVlaminates production capacity of 20 MW. The high degree of integration of the PV modules and the
roll-to-roll lamination allowing process automation will highly decrease the costs /Wp. Furthermore,
sustainability, quality procedures and monitoring in-line, compliance to BIPV standards, as well as
fully recyclability of the whole product are associated priorities of the PV-GUM project.
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Goal of the project
2
Building Integrated Photovoltaic (BIPV) potential is estimated to 23 billion m (source: Report IEA –
PVPS T7-4:2002-Suitable existing roofs and facades with good sunshine exposure in selected 14 IEA
countries). In terms of building integrated photovoltaic’s (BIPV), compared with pitched roofs, flat roofs
have the advantage of good accessibility, easy installation, an almost limitless choice of orientation for
the PV units and in addition, usually part of commercial, industrial or public buildings, flat roofs offer an
important surface for PV exploitation. Thus flat and low-pitched roofs provide ideal locations to integrate PV plants. This BIPV potential, however, is still underused.
The market leading BIPV product is the flexible photovoltaic roof system originally developed by Solar
Integrated Technologies (US) which uses flexible thin film modules made by UNI-SOLAR, combined
with a polymeric roofing system. But this integrated solar roof system still has limitations. Polymeric
membrane roofing systems made from PVC or TPO account for only 20% of the commercial roofing
membrane market. The majority of commercial roofing still uses asphalt based roofing technologies in
the form of single or multiple APP or SBS asphalt roof membranes.
Thus, in order to meet the growing demands of the BIPV market, and make it more attractive to builders and building owners to install, the PV-GUM project aims at developing new manufacturing technologies which will produce a low cost highly efficient flexible BIPV solar cell fully integrated on a bituminous roofing membrane, which remains the main used roofing technology.
The start point of the project is the DERBISOLAR FLEX product: Flexcell and Imperbel have already
started to jointly develop an integrated product called DERBISOLAR FLEX which is based on the integration the integration of Flexcell a-Si PV cells on the Derbibrite white-coated bituminous membrane to
provide a PV module of 1 m wide x 3,5 m long integrated on a 1,2 m wide x 4,7 m long membrane
corresponding to a surface of 5,64 m2 with a maximum power point of 132 W per module (efficiency
at 4,2%), which corresponds to a power of 42 Wp/m2. The connectors are placed over the membrane.
Based on this first successful collaboration, the main concept of the PV-GUM project is to develop a
PV roofing bituminous membrane very close to the usual bituminous roofing membrane in terms of
size, installation process, sustainability and waterproofing performances, quality and recyclability to
increase the penetration power of the new BIPV product in the building market and to fully exploit the
flat and low-pitched roofs PV potential. At the same time, it is necessary to develop the Flexcell technology to provide highly efficient (at more than 8%) and cost-effective PV laminates to compete with
other providers throughout the world.
The complete integration of the flexible PV cells in the roofing membrane will be performed at the
manufacturing stage by a new roll-to-roll process that will be developed to produce the laminated PV
cells: the flexible PV cells will be continuously laminated between the polymeric transparent “encapsulant” sheet (front side: EVA, ETFE, or other…) and the reinforcement sheet of the bituminous membrane (back side), then the laminated PV cells will be impregnated by the bitumen to provide a fully
integrated PV roofing bituminous membrane.
In parallel, a new standardized PECVD reactor and process will be implemented to increase the Flexcell production capacity and PV cells efficiency thanks to Flexcell’s work described in the WP2.
The expected decrease of cost will be mainly generated by the high degree of integration of the PV
modules in the product with the new roll-to-roll laminating process and the high speed of silicon deposition generated by the new standardized PECVD reactor and process.
At the end of the project, the new developed PV membrane will be ready to market: the new product
will be compliant with all electrical and building standards, and the production capacity will be wellsuited with the demand. Furthermore, sustainability (wind, rain, UV resistance with constant efficiency
of the PV cell), quality procedures and fully recyclability of the PV bituminous roofing membrane product are associated priorities of the project that will give an important added-value to the final product.
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PV GUM , F. Galliano, VHF-Technologies SA
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Overall objective
Reducing overall production costs of the new PV roofing bituminous membrane with increased degree
of integration of PV module, increased PV module efficiency, high quality and fully recyclability
The analysis, step by step, of this current manufacturing chain will allow ways to reduce costs and
increase performance of the product and the process:
- Step 1: Should enhance silicon deposition rate to increase PV modules efficiency and length without increasing production costs (the equilibrium between deposition throughput and PV modules efficiency remains an important challenge).
- Steps 1 & 2: Should improve the white-coated reinforcement sheet (fibres+ acrylic) of the Derbibrite roofing bituminous membrane to allow lamination of the PV module with this back sheet.
- Step 3: Should replace the current batch lamination process that limits the PV laminates length at
3.5 meters by a new continuous lamination process (roll-to-roll) to provide 10 meters long PV laminates.
- Step 4: Should define an adapted bitumen impregnation process of the PV laminates.
- Step 5: Should adapt the connector fitting to the new PV modules.
- Step 6: Should validate the product performance and sustainability in real conditions by pilot installations.
This constant concern for finding equilibrium between costs and performance will be a guideline
throughout the project to achieve a really cost-effective BIPV product with world class manufacturing
processes
The development o f steps 1 ( silicon d eposition) and 3 (l amination) a re strategic g oals of the
project:
- The new deposition equipment and process will allow significant improvement of the electrical and construction specifications of Flexcell PV modules (upscale efficiency and length
of the module) without significantly increasing costs. This will make Flexcell the world leader
in the flexible PV module market.
- The new roll-to-roll l amination p rocess (encapsulation o f the PV modules) will reduce production costs through a high degree of integration, high throughput and low-cost raw materials and processing. The roll-to-roll encapsulation implies research on the continuous lamination
process and equipment associated to adequate encapsulant (front sheet), adhesive and back
sheet (reinforcement of the membrane). This new encapsulation process will enable production of
PV laminates at low cost and integration in roofing membranes, which is a strong commercial asset
for both Flexcell and for Imperbel.
In addition to the new or optimized processes, new quality procedures should be defined with associated in-line quality monitoring: currently no standardized quality procedures exist to check quality of
the new upscale PV laminates, as well as to check the whole PV roofing membrane through testing of
its outdoor PV performances and weather resistance for building integration.
In line with the quality control, the requirements for compliance to building and electrical standards
should be taken into account from the start of the project to achieve a certified and marketable BIPV
product.
The main asset of the bitumen is its ability to be fully recyclable, and there is a need to investigate and
implement processes to recycle the PV roofing bituminous membrane and connectors.
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Weathering film
Derbibrite reinforcement sheet (Imperbel):
Encapsulants
ETFE
(Meyer)
(Nolax)
Acrylic+fibre
Laminator
Adhesives
(Nolax)
PV Laminates ready to be
impregnated by bitumen
(Imperbel)
Continuous lamination
(Roll-to-roll)
Flexcell
Figure 1: production lay out for PV-GUM
Results from 2011
Flexcell was mainly involved in steps 1 & 3.
Step 1: Increase in cell efficiency
The first push-pull electrode prototype has been installed in a PECVD at Flexcell production site for
testing. In the Flexcell PECVD equipment a plastic foil normally pass through 3 identical standard
electrodes. One of the standard electrodes has been replaced by the push-pull electrode.
Figure 2: Left- first argon plasma light in the push-pull electrode prototype
Right- schematic principle of the push-pull electrode prototype realized
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Testing of the new push-pull electrode has been started with argon plasma. Figure 2 shows a picture
of the first plasma lights in push-pull mode in the electrode prototype. For demonstration purpose, the
front grounded cover for plasma confinement has been removed in order to be able to see the plasma,
and only a partial view of the electrode is possible from the front door window.
From the picture of figure 2, it can be seen that the first and third RF electrodes starting from the top
have more intense plasma emission than the second and fourth RF electrodes. This is revealing an
asymmetry problem in the push-pull excitation mode. It has been found that this asymmetry is caused
by parasitic capacitive coupling in the VHF transformer used for this test. Work is under progress to
redesign the VHF transformer in order increase the symmetry of the RF push-pull excitation.
Step 3: Roll to roll lamination
An important part of the activity in 2011 was focused on the achievement of the roll to roll lamination.
The main points under study were the search for an appropriate thermoplastic encapsulant (in collaboration with Nolax) and the development of a vacuum continuous laminator (in collaboration with Meyer
Machines GmbH).
The main results can be resumed as follows:
•
After long term adhesion test and lamination trials, at least one potential encapsulant (polyolefine based) was selected as potential candidate on both ETFE and PVDF.
•
Vacuum continuous laminator was completed by Meyer in Oct 2011 with a vacuum of 500
mbar. Fine tuning of the process parameters is on going. The first results are very encouraging and the development of a better vacuum system is still under way
Peeling after 21d in Outdoor
200
180
160
Force (N/50mm)
140
120
100
*Break
Silicone
Polyolefine
UV curable EVA
80
60
40
20
0
Nolax
Flexcell
Nolax
ETFE
Flexcell
PVDF
Peeling after 40d in Outdoor
200
180
160
Force (N/50mm)
140
120
100
*Break
(Apolhya)
80
Silicone
Polyolefine
UV curable EVA
60
40
20
0
Nolax
Flexcell
Nolax
ETFE
Flexcell
PVDF
Figure 3: outdoor testing after 21 and 40 days for selected encapsulant with different frontsheets
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Figure 4: R2R lamination trials with vacuum machine
Conclusion and perspectives
The design and construction of the first push-pull 80MHz electrode prototype has been realized by
Flexcell. This prototype has been installed in Flexcell roll-to-roll PECVD equipment for testing and a
first argon plasma has been lighted.
Work is under progress in order to improve the VHF transformer’s symmetry and efficiency used to
deliver the power to the RF electrodes. Once this electrical problem will be solved, study of a-Si i layer
deposition rate and lateral uniformity and device quality will be started.
In the PECVD equipment, the prototype electrode is in series with 2 standard Flexcell electrodes.
Therefore, the quality of the a-Si i layers deposited by this new electrode will be studied by incorporating the layer in solar cells deposited with the standard flexcell electrode and recipe.
Concerning R2R lamination and choice of the encapsulant, the machine is now ready for testing and
one main candidate has been selected. Work is now in progress to lower the pressure in the machine
to 300-400 mbar (actually limited to 500 mbar) and to produce a colaminate frontsheet/encapsulant to
optimise the lamination behaviour of the materials and their adhesion performances. Reliability testing
on real scale samples will be then launched on the selected materials/machine parameters.
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Systemtechnik
F. Frontini, K. Nagel, V. Tettamanti, G. Panzera, M. Ferrazzo, D. Chianese
BiSol: Building Integrated Solar Network-BRENET – SI/500339 / SI/500339-01
BiPV Tools: Interactive tools and instruments supporting the design of building
integrated PV installations – 103220 / 154244
Building Integrated Photovoltaics Thermal Aspects – 103155 / 154147
G. Friesen, M. Pravettoni
– SI/500691 / SI/500691-01
U. Muntwyler
Photovoltaik Systemtechnik – various projects
249
254
261
267
275
– 103202 / 154220
280
dans les régions enneigées – SI/500568 / SI/500568-01
288
F. Baumgartner, N. Allet, T. Hobi, H. Kessler
– SI/500466 / SI/500466-01
294
H. Häberlin, Ph. Schärf, L. Borgna
Autonomous cleaning robot for large scale photovoltaic power plants in Europe
resulting in 5% cost reduction of electricity – PV-SERVITOR 232062
303
– SI/500361 / SI/500361-01
310
C. Bucher
Distribution grid analysis and simulation with photovoltaics
– DIGASP SI/500549 / SI/500549-01
318
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BISOL
BUILDING INTEGRATED SOLAR NETWORK
- BRENET
Annual Report 2011
F. Frontini, K. Nagel, I. Zanetti, V. Tettamanti, G. Panzera,
M. Ferrazzo, D. Chianese
ISAAC-DACD-SUPSI
Address
Campus Trevano, 6952 Canobbio
Telephone, E-mail, Homepage 058 666 63 50, [email protected], www.isaac.supsi.ch
SI/500339 – SI/500339-01
Date
31.10.2011
ABSTRACT
The B RENET N etwork ( Building and R enewable E nergies N etwork o f Technology) i s a r ecognized
Confederation of the Swiss research network between SUP universities, institutes of the ETH domain
and independent private institutions in the field of building technology and renewable energies. It i s
recognized b y t he K TI/CTI. The BR ENET i s f ocused on f ive d ifferent t opics: “ Building r enovation”,
“Active House”, “Simulation”, “Trends & Foresight” and the “BiSol-Building Integrated Solar Network”.
The B iSol project was specifically addressed t o all t he stakeholders involved i n s olar energy de velopment such as architects, engineers, building material manufacturers, solar system manufacturers,
designers, contractors, public sector and researchers. The aim of the project was to initiate a competence network among different specialists to promote the integration of solar energy into building environment and to overcome the actual technical and non technical issues.
In order to encourage communication among these professionals of different sectors and to identify
the issues linked to building integration of solar systems and their possible solutions, thematic multidisciplinary workshops were planned and carried out during the whole period of the project.
Four di fferent w orkshops were organized and a f ifth one was p lanned b ut unf ortunately du e t o f ew
inscriptions was not held.
The first two workshops were organized together with Swissolar (so to be closer to installers and industries) and with EPFL-LESO PB for their competence in solar thermal integrated into buildings.
The outcomes of each workshop are the encouragement of collaborations between the different actors and t he identification of pr oblems and t heir r esolution t hrough eventual n ew pr ojects an d t he
creation of one or more working groups that will develop and manage these projects.
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Project goals
The market o f s olar s ystems o f phot ovoltaic m odules and t hermal c ollectors i s i ncreasing v ery f ast.
This increase has encouraged producers, installers and designers to develop products that are more
adequate for building integration. This is also because of the European directive that all new buildings
after 2020 must be nearly Net Zero Energy Buildings (nZEB). Different researches demonstrated that
this is possible but to do that in a more cost effective way solar energy must be integrated in the building i tself. H owever, b arriers t o t he di ssemination of s olar t hermal and P V integration ar e numerous
and concern various aspects: architectural, planning, constructive, economical and educational.
AIM
In order to confront and overcome the different aspects of these barriers, the BiSol Workshops aimed
to act as the platform that brings together the different sectors and encourage communication among
them creating a competence network between specialists (stakeholders) for maximizing solar energy
integration to the built environment.
METHODOLOGY
Between Mar ch 2009 a nd F ebruary 2 011, t he B iSol gr oup or ganized 4 m ultidisciplinary workshops
specifically addressed t o a rchitects, en gineers, building m aterial producers, s olar s ystem pr oducers,
designers, contractors and researchers.
Different people, coming from various research institutes, universities, industries, architecture offices,
and technicians participated to the different workshop.
Work carried out and achieved results
WORKSHOPS
Four di fferent w orkshops were or ganized and a f ifth one was p lanned but u nfortunately d ue t o f ew
inscriptions was not held. The different topics of the workshop were:
1. Facilitate the acceptance of solar installations in the built environment”,
hosted in Luzern the 23rd and 24th of march 2009
2. Interactive tools and assistance for the architectural integration of solar installations”,
hosted in Lugano the 16th and the 17th of November 2009
3. “Opportunites of collaboration between the building and solar sectors”,
hosted in Trübbach the 1st and 2nd February 2010
4. “Quality and reliability of building integrated pv modules and thermal collectors”,
hosted in Lugano the 23rd and 24th of August 2010
RESUME OF THE FOUR BISOL WORKSHOPS
1st Workshop: Facilitate the acceptance of solar installations in the built environment
In Switzerland, the t opic of t he i ntegration of s olar s ystems i n t he b uilt environment i s v ery t opical
/relevant. T heir i nstallation i s r egulated t hrough t he procedures i n f orce b y t he l aw on c onstruction,
which pr incipally c onsiders t he r espect of ar ticle 1 8a enc losed i n the r evision o f t he f ederal l aw o n
town an d l andscape p lanning. T his l aw s tipulates t hat i n t he ar eas t o be bu ilt, c arefully i ntegrated
(roofs and façades) solar installations are authorized if they do not spoil cultural assets or natural sites
of any cantonal or national importance (original text in F, D and I).
The goal of this particular workshop was to find solutions to facilitate the acceptance of solar installations an d t heir di ffusion i n t he bui lt e nvironment. U nder t he aus pices of t he w orking gr oup B iSol, a
“Facilitate t he acceptance of s olar i nstallations i n t he bui lt e nvironment” Workshop was he ld at t he
University of Applied Sciences and Arts in Lucerne on the 23rd and 24th of March 2009. The Workshop was attended by 36 professionals from different Swiss Cantons (AG, BE, BL, FR, GE, LU, TG,
TI, VD, ZG, ZH), Germany and Singapore. These professionals were mainly architects and engineers
working in diverse fields such as the private and public sector (3 canton representatives and 1 national
representative).
The main outcome of Workshop 1 was the identification of future projects:
•
•
•
Architectural quality standard for solar installations
Implementation of recommendations, examples and products
(on the basis of the www.bipv.ch website).
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BiSol, F. Frontini, SUPSI
•
•
Extension of the recommendations at the Swiss level
Adaptation of the recommendations of the Canton of Bern with formal recommendations
2nd Workshop: Interactive tools and assistance for the architectural integration of solar
installations
The different actors involved in the design/planning of building integrated solar installations; often require tools that will facilitate the promotion, the design and the realization of these systems in an optimal way. These “instruments” come in the form of software for supporting the process of dimensioning, visualization ( photomontage or C AD el ement) and f inancial es timation of i nstallations, or ot her
sources such as websites, advices concerning the integration, books, a reference of integrated installations and “guidelines” for the formulation of construction demands.
Under the auspices of the working group BiSol, a “Interactive tools and assistance for the architectural
integration of s olar i nstallations” Workshop w as he ld i n Lugano on t he 16th an d 17t h of N ovember
2009. The Workshop was attended by 34 professionals from different Swiss Cantons, Germany and
Italy. These professionals were mainly architects and engineers working in diverse fields such as the
private sector and university related research centers.
The goal of this workshop was to analyse the existent supports (software, information, education, recommendations, etc.) through the presentations on the first day, and to identify and evaluate the limits
of these supports and propose solution by discussions in multidisciplinary groups.
The main outcomes of Workshop 2 was the identification of solutions for the recognized problems:
•
•
•
•
•
“Teaching Net”: sharing of study cases, experience sharing within schools/institutes,
example database
CAD object for solar thermal
Group of experts that could give feedback to software producers
Planning guide (with norms, reference offices, procedures
Development of new directives for products
3rd Workshop: Opportunities of collaboration between the building and solar sectors.
Pushed by the global warming concern and new energy regulations, the market of building integrated
solar plants is growing very fast. To help architects and installers increase the quality of these plants,
new or improved products developed as constructive/architectural elements are needed.
The goal of this workshop was to give a chance to specialists from the building and solar sectors to
get together and discuss the issues and wishes, concerns and solutions related to the integration of
solar systems in buildings. Particularly, the importance that PV and STH become a more used building
material was stressed.
The Workshop w as at tended b y 35 pr ofessionals f rom di fferent S wiss C antons, G ermany and I taly.
These professionals were mainly architects and engineers working in different fields such as the private s ector, i ndustry and university r elated r esearch c enters. T he main out come of t his par ticular
workshop was the identification of a series of issues and observations concerning the difficulty of obtaining a compromise between standardization (producer’s wish) and flexibility (architect’s necessity)
(see the Annex).
The main outcomes can be summarized in the following points:
•
•
•
•
•
•
•
Architects would like to maintain some kind of “artistic” flexibility when working with PV
and STH as a building material
Producers would like to standardize the products especially for reducing the fabrication
process and costs
Crystalline silicon modules are available in different sizes from different producers.
On the contrary, amorphous silicon modules on glass are proposed in standard sizes
(1.3 x1.1m / 2.2 x 2.6m)
Fastening systems should be compatible to all PV module size to allow, with the use of interface elements and dummies, more flexibility for completing the façade and/or roof raster
BiPV modules are dealing with electrotechnical and building codes
Lack of tests for flexible PV modules (problems of compatibility with existing norms)
Lack of uniformity for electrical security and fire tests at the international level
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•
•
•
•
•
•
Need of research/state of the art on building material tests for proposing similar tests on
BiPV systems (ex. tests on waterproofing membranes could be reproduced on PV waterproofing membranes)
Lack of tests on fastening systems
For further information on tests on new PV products: www.pv-performance.org (SP 6);
a brochure are available on the website
The function/position of STH and PV façade planner does not yet exist
It is essential to form STH and PV façade planners!
CSFF and Swissolar could co-organize courses for professionals
4th Workshop: Quality and reliability of building integrated PV Modules and
thermal collectors.
The Workshop was attended by 31 professionals from different Swiss Cantons and Italy. These professionals were mainly engineers and architects working in different fields such as the private sector,
industry and university related research centers. The main outcome of workshop 4 was the highlighting of the need of tests on the whole system (modules + fastening system) rather than single parts; the
need of more collaboration between the producers, the installers and researchers for defining the necessary tests; and the need of product development such as modules with diode bypass, modules with
MPPT (maximum power point tracker), back sheet + integration of other functions, coloured encapsulation and more types of dummy modules.
Building integration of photovoltaic modules and thermal collectors leads to some very important considerations such as compliance with building standards, safety, waterproofing systems and mechanical strength. The goal of t his workshop was to illustrate t he v ariety of i ssues l inked to solar pr oduct
quality and reliability and the state of the art regarding norms and regulations on these same products.
The main outcomes can be summarized in the following points:
•
•
•
•
•
Lack of tests on: modules together with fastening systems, waterproofing systems, how the
temperature influence the module lifetime and modules characteristics. Necessity of tests
on the whole system (modules + fastening system) rather than single parts = more security;
separated tests and norms for BAPV and BIPV; more collaboration between the producers,
the installers and researchers to define tests requested; Lifetime test with higher temperature; lifetime: define when a module is “dead” and need to be changed; need for testing
changes in characteristics: colour, transparency, form, weight, dimensions.
Need of product development. Modules with diode bypass; Module with MPPT (maximum
power point tracker); back sheet + integration of other functions; coloured encapsulation,
more type of dummies modules.
Lack of research on shadowing effect (in relation to technologies and application). Necessity
of developing research, type of technology less sensitive in shadow (longer and thinner cells
rather than larger cells), standardized measurements, results use by dimensioning tools
(PVSyst).
Risks for firemen when dealing with PV. Necessity of fireproof norms including PV (as a
building component); specific PV (DC) training for firemen; mapping of buildings with PV.
Lack of training: ventilation, building standard, inverter configuration. Necessity of training;
stages and collaborations between industries and research institutes; change the mentalities: PV is a building element!
For eac h workshop, a detailed r eport was written. T hese ar e a vailable on r equest t hrough
[email protected] and in 2012 the documents will be available for download on the BiSol website.
All t he P owerPoint presentations pr esented during t he workshops are available at t he internet s ite
build up for the workshop: www.bisolnet.ch.
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National collaboration
The BiSol team involved different partners:
•
•
•
•
•
Swissolar
EPFL LESO-PB
BRENET
OERLIKON SOLAR
Swiss PV module test center.
During the last two years the BiSol outcomes and results were presented in the framework of the IEA
Task 41 S olar Energy and A rchitecture, where d ifferent i nternational institutes and of fices ar e pr esented. The BiSol workshops are also part of a deliverable of the SubTask A and C of the IEA Task
41.
Outcomes and achieved results
The main outcomes of the BiSol were the creation of a network of all the stakeholders working in the
field of solar energy and its integration into buildings:
•
•
•
•
•
•
•
Architects
Planners
Manufacturers
R&D institutes
Universities
Test laboratories
Building owners and private holders
This network is mainly from Swiss stakeholders. They have created a discussion group on the main
problems or criticism concerning the integration of solar energy systems into the building. This discussion sometimes was the starting point for a common project or research program. Also the dissemination and the education of the stakeholders were an outcome of this project.
Still a lot of work has to be done. The downside is that the BiSol Team has found some difficulty t o
concretize all the good ideas, emerged during the workshops, and all the propositions highlighted during t he m eetings. M ore t ime and r esources ar e nee ded t o organize k ickoff meetings w ith the interested parties and launch new projects. Hence, discussions, propositions, etc. fall short after the Workshops have taken place.
References
[1] G. Panzera, I. Zanetti, K. Nagel, V. Tettamanti, BISOL - Building Integrated Solar Network – Workshops to optimize the
integration of solar systems in buildings, 24th EUPVSEC, 5BV.2.59, 2009
[2] I. Zanetti., K. Nagel, G. Panzera, D. Galimberti, P. Kaeh, Results of one-week workshop with students in architecture,
24th EUPVSEC, 5BV.2.57, 2009
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Départmenet fédéral de l’environnement,
BiPV TOOLS
INTERACTIVE TOOLS AND INSTRUMENTS
SUPPORTING THE DESIGN OF BUILDING
INTEGRATED PV INSTALLATIONS
Annual Report 2011
Address
Date
ISAAC-DACD-SUPSI
Campus Trevano, CH-6952 Canobbio (TI)
058 666 63 20, [email protected], www.bipv.ch
103220/154244
01.07.2009 – 01.07.2011
09.12.2012
ABSTRACT
The BiPV Tools project was addressed specifically to architects and its aim was to provide information a nd t ools, which al low a c orrect an d a ppropriate i ntegration of ph otovoltaic t echnology in t he
building design concept. Its purpose was to define and analyze a series of needs especially pertaining to architects (and architecture students) who don’t have a strong technical knowledge in PV but
who would like to be able to integrate photovoltaic systems into their architectural design.
The website www.bipv.ch has been the backbone tool of this project. It was developed in a previous
SUPSI project with the intent of making it an informative website specifically for architects. Thanks to
the B iPV T ools pr oject i t was pos sible t o m ove up t o a f ollowing ph ase of dev elopment w here t he
contents of the website were examined, updated and optimized with a list of examples of BiPV installations and with a CAD l ibrary which include a 3D p arametric CAD obj ect whose development was
also included in this project. Nowadays the website is constantly visited by architects, planners and
researcher, from all over the world.
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Aims of the project
In or der t o pr event an i ndiscriminate us e of photovoltaic applications an d t o i nvest ec onomic and
space resources in the most effective possible way, it is necessary to offer to architects and specialists
of t he b uilding s ector t ools and i nformation t hat ar e effectively d eveloped c onsidering t heir s pecific
needs and requests.
Consequently the distinctiveness of this project was the contribution of ideas, remarks and advices by
many different partners. Part of the pr oject ( selection of several BiPV installations par ticularly r epresentative) was done following the direction of the Solares Bauen Committee constituted by members
of Swissolar (Swiss Association of Solar Energy Professionals). The Swiss BiPV Competence Centre
also collaborates with the University of Applied Sciences of Southern Switzerland and with the Architecture Academy of Mendrisio. Thanks to this collaboration it was actively possible to test the developed m aterial on ar chitects, s tudents and s pecialists of t he ener gy f ield b y one-day c ourses, w orkshops and pr actical assignments. Mor eover, c onsidering t hat s ome of t he obj ectives ar e s imilar, an
exchange of resources with the IEA SHC Task 41 “Solar Energy and Architecture”[1] has been also
envisaged.
The main objectives of the project were the following:
1. Elaboration of a list of high quality BiPV installations in Switzerland and in Europe to be included
in the website www.bipv.ch.
2. Updating and development of the website www.bipv.ch.
3. Development and improvement of a PV CAD parametric object (determination of characteristics
and dynamics).
4. Configuration of a CAD library (nine standard PV modules were developed using a 3D CAD object; it will be possible to download them together with the 3D CAD object).
5. Analysis of various software.
Works carried out and results achieved
BiPV examples
Currently 41 buildings c haracterized b y ex cellent an d ex emplary BiPV i nstallations are l isted on the
website. Other referential cases will be regularly included on the examples section of the website.
The s elected B iPV ex amples, s orted by building t ypologies ( residential, c ommercial, historical bu ildings, etc.) are:
Residential Buildings (10x)
Erni House – 11 kWp
Untersiggenthal (AG-CH)
Schmölzer House – 3.2 kWp
Pratteln (BL-CH)
Rakusa House – 9.5 kWp
Ruvigliana (TI – CH)
On t he website 10 r esidential bu ildings are c urrently listed. F urther i nformation can be f ound in the
Final report of the project or directly on www.bipv.ch.
Administrative Buildings (7x)
FEAT Building – 3.8 kWp
Lugano (TI-CH)
Marché International – 44.6 kWp
Kemptthal (ZH-CH)
Novartis Gehry Building – 92.7 kWp
Basel (BS-CH)
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BiPV Tools, F. Frontini, ISAAC-DACD-SUPSI
On the website 7 administrative buildings are currently listed, other buildings are on the waiting list and
ready f or upl oad. F urther i nformation c an be f ound i n t he F inal r eport of t he p roject or di rectly on
www.bipv.ch.
Industrial Buildings (4x)
Böwe Cardtec – 9.65 kWp
Paderborn (D)
Riedel Recycling – 837 kWp
Moers (D)
Tobias Grau Lighting HQ – 18 kWp
Hamburg (D)
Four industrial buildings are present on the website today. Further information can be found directly on
the website www.bipv.ch.
Sport facility Buildings (4x)
Stade de Suisse – 1’342 kWp
Bern (BE–CH)
Paul Horn Arena – 43.7 kWp
Tübingen (D)
Kriegerhornbahn – 9.5 kWp
Lech (A)
On the website 4 sport facility buildings are currently listed. Further information can be found directly
on www.bipv.ch.
Agricultural Building (1x)
Urban structures (1x)
Pilotanlage Lauper 1 – 22.4 kWp
Gasel (BE-CH)
Town Hall Canopy – 19.1 kWp
Ludesh (A)
Historical Buildings (2x)
Paolo VI Chamber – 221.6 kWp
Vatican City (V)
Alès Tourist Offices – 9.6 kWp
Alès (F)
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Up to now only two historical buildings are listed on www.bipv.ch. We will keep looking for good example of PV integration in historical protected and unprotected buildings in order to give architects a
better idea of what is possible to do with historical or existing buildings.
Others Buildings (12x)
Dock E Midfield – 283 kWp
Kloten (ZH-CH)
Matterhorn Glacier Paradise
22 kWp - Zermatt (VS-CH)
Monte Rosa Hutte – 14 kWp
Zermatt (VS-CH)
Further information can be found directly on www.bipv.ch.
The case studies presented in the previous pages are divided geographically as follows: 15 are located in Switzerland, 9 in Germany, 3 in England, 3 in Italy, 4 in Holland, 2 in Austria, 2 in France, 1 in
Spain, 1 in Belgium.
The most significant characteristics of every example are collected in a table (location, latitude, completion year, ar chitect, building typology and c ategory, description of t he s urroundings, t echnology,
installed power, orientation, PV module, dimension), a couple of pictures and drafts are also shown in
the specific page.
Figure 1: Print screen of table and drafts for the onze lieve ospital.
BiPV website
The backbone and the main sharing channel of the project is the website www.bipv.ch.
The w ebsite www.bipv.ch is pr esented i n f our l anguages: I talian, G erman, E nglish an d F rench. I ts
purpose is to give a general insight into building-integrated photovoltaic (BiPV). Even though the structure and the contents of the website are well established, the web hierarchy and the information published i n t he website were r eorganized through 2011 i n order t o i mprove t he m anagement and the
updating process.
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Because the BiPV market and the knowledge are continuously changing and the users requests are
enormous there are an increasingly amount of information and data that need to be processed almost
daily and the website needs to be updated constantly.
The website is divided in seven main sections whose contents are the following:
1. home – BiPV, integration, news & events;
2. PV t echnology – photovoltaic, r equirements, en ergy aspects, c haracteristics, l egal aspects,
quality, potential;
3. examples – residential, administrative, industrial, sports, agricultural, urban structures, historic,
other, add example;
4. products – BiPV criteria, BiPV modules, BiPV fastening systems, other, add products;
5. material – virtual visit BiPV simulator, guidelines, software, publications, CAD objects, feed in
tariff, glossaries, tables, economic evaluation;
6. contact;
7. FAQ and prejudices regarding PV.
Further information about t he s tructure of the website can be f ound in the final report of the project.
CAD 3D object
Figure 2: Archicad 3d photovoltaic module object window. Source: isaac-dacd-supsi.
A 3D CAD object was developed throughout the BiPV Tools project. A screenshot of the programme is
presented in the Figure 2. This instrument was developed in collaboration with IDC AG, the national
Graphisoft distributor, which is the responsible for CAD object programming.
The ability to select building components before and during the design phase will benefit both the designer, who can design by using real objects, and the component manufacturers, who can successfully market their product at an earlier stage in the design process.
The c haracteristics of a standard P V product s uch a s the t ype of t echnology, the colour, the s hape,
the typology of the electrical contacts, the transparency and the reflection can be modified depending
on the product specification. Each of these factors corresponds to a GDL (Geometric Description Language) information which carries 2D and 3D geometry, product logic and behaviour, parameters, material definitions and a specific user interface. These features allow an effortless customization of the
CAD object to the requirements of every user, reproducing most of the products currently on the market using an ArchiCAD or AutoCAD software, two widely used modelling tools compatible with most of
the visualization tools.
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The 3D CAD object was developed in four languages: English, Italian, French, German, and it is possible to download it for free from the website www.bipv.ch.
ArchiCAD 13 rendering of BiPV sun shading elements.
Source: ISAAC-DACD-SUPSI
ArchiCAD 13 rendering of BiPV sun shading elements,
the 3D was refined with the software Artlantis 3.0.
Source: ISAAC-DACD-SUPSI
A s implified parametric C AD obj ect r eproducing a s tandard s olar t hermal c ollector w as al so d eveloped.
SWISSOLAR - Commission “Solares Bauen” (reference person: Peter Dransfeld)
BiPV Tools is a project that deals with the significant lack of communication between the actors of the
building sector, the general public and the PV sector. Having professionals with expertise in different
fields w orking t ogether f rom t he v ery f irst phas e of s olar i ntegration and d eveloping a c ommon an d
adapted jargon is by itself a success.
SUPSI / DACD - University of Applied Sciences of Southern Switzerland / Environment Construction
and Design Department
The Swiss BiPV Competence Centre actively collaborates with the University giving specific course in
two bachelor degree courses (architecture and civil engineering) and one DAS (Diploma in advanced
studies - Energy Management) course.
On request, specific lessons on the topic (Bi)PV are also given (e.g. AAM – Architecture Academy of
Mendrisio)
IDC AG Luzern - Swiss ArchiCAD distributor
IDC AG was the professional partner who developed the parametric CAD 3D tool.
IEA SHC Task 41 – Solar Energy and Architecture
Some of the subjects (collection of BiPV “good” examples, 3D CAD object) which were covered by this
project have aroused the interest of the IEA SHC Task 41 “Solar Energy and Architecture”. This task
and the BiPV Tools project (which started first) deal with very similar arguments and consequently for
both of them is very important to define tools and informative supports that will help the achievement
of high quality architecture for buildings through a correct integration of solar energy systems.
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2011 evaluation and future prospects
Overall the objectives of the project have been accomplished.
The development of the website has been very successful, especially considering that the new operating system enables to optimize resources and time. The new layout of the website allows to consistently implement in the website all the subjects, which have been elaborated in the BiPV Tool project,
thus leading to a better and faster dissemination of the achieved results. During the last two years the
BiPV website was visited by several international users, which also give their feedback and suggestions.
A paper and oral presentation regarding the project named “Building-integrated Photovoltaic TOOLS Interactive tools and instruments supporting the d esign of b uilding i ntegrated P V”, was presented at
the EUROSUN 2 010 ( International C onference on S olar Heating, C ooling and B uildings) w hich w as
held in Graz (Austria) from the 28th September to the 1st October.
The elaboration of a list of high quality BiPV installations has been successful. It was possible to find
several very interesting case studies that were more or less exhaustively displayed in internet. On the
other hand only few architects have answered to the short survey that was sent out at the end of April
2010.
In an y c ase, t hanks t o t he par ticipation i n t he S HC I EA T ask 41, i t has been p ossible t o m eet w ith
architects from Europe, Asia, Canada and Australia. During the IEA meetings many solar installations
were presented and this has allowed us not only to assess the level of solar technology integration in
the various countries but also to find many new interesting examples that are now listed in the bipv.ch
website.
Concerning the development of a CAD 3D tool (parametric object + library), the programming phase
ended i n 20 10. T he t esting par t t ook more t ime t han ex pected, i t has been necessary t o v erify t he
corrections and the changes several times.
Once the testing phase was ov er, t he t ool w as translated in English, French and German and i ntroduced into the website where it is possible to download it free of charge
The existing software investigation was partially done in the context of this project and partially within
the IEA SHC Task 41 “Solar energy and architecture“. This is because during the preliminary research
a hu ge number of s oftware was f ound. C onsequently it was not pos sible to t reat t hem exhaustively
within our competences and the timeframe of this project. As a result, an expert group (composed by
Task 41 members and c ollaborators of t he S wiss B iPV c ompetence c entre) was c reated a nd t he
anaysis was split between the partners.
This review covers a total of 56 computer pr ograms, classified according to t hree categories: CAAD
(computer-aided architectural design), visualization, simulation t ools. The a im of this e valuation is to
analyse the current software landscape for building projects with a focus on early design phase (EDP).
For more information the full report “State-of-the-Art of Digital Tools Used by Architects for Solar Design” is available for download [4].
All the information and data collected throughout the duration of the BiPV Tools project, properly selected and presented are now shown on the bipv.ch website.
The success of the CAD tool revealed the importance, especially for architects and planners, to have
implemented t he s olar t echnologies in t he project a lready dur ing the f irst des ign phas e. B uilding I nformation Models are becoming essential for many industries and companies and can be used to lower construction costs. BIM (Building Information Modelling) and CAD/CAM tools enable customisable
mass pr oduction by pr oviding t he c ell m aker, module i ntegrators and c ontractors w ith ac cess t o t he
same information.
References
[1] IEA SHC Task 41 “Solar Energy and Architecture” - www.iea-shc.org/task41
[2] Farkas K., Munari Probst M.C. and Miljana Horvat, Barriers and Needs for Building Integration of Solar Thermal and Photovoltaic, available on http://infoscience.epfl.ch/record/162426/files/eurosun.farkas.mcmp.10pdf.pdf
[3] R&D SFOE project 102579 (Définition des éléments photovoltaïque intégrés pour la RCP)
[4] State-of-the-Art of Digital Tools Used by Architects for Solar Design, Marie-Claude Dubois and Miljana Horvat, available on
www.iea-shc.org/publications/task.aspx?Task=41
[5] Zanetti, I . N agel, K . , B uilding-Integrated Photovoltaic - TOOL. I nteractive t ools and i nstruments s upporting t he des ign of
building integrated PV. Proceedings Eurosun 2010.
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Départmenet fédéral de l’environnement,
BUILDING INTEGRATED PHOTOVOLTAICS
THERMAL ASPECTS
LOW ENERGY HOUSE FOR TESTING BIPV
SYSTEMS
Annual Report 2011
Address
Date
ISAAC-DACD-SUPSI
Campus Trevano, CH-6952 Canobbio (TI)
058 666 63 20, [email protected], www.bipv.ch
103155/154147
01.07.2009 – 01.07.2011
09.12.2012
ABSTRACT
PV industries offering products that can be integrated as building materials represent so far a niche
but pr omising m arket. A t the m oment onl y a f ew s tudies ( see t he r eferences i n t he ann ual r eport
2009) have been carried out to assess the interaction between the PV modules and the building itself.
This fact may represent a barrier not only for the PV industry, but also for the building industry that
has yet to gain confidence in these new materials. The building sector must therefore possess a basic
knowledge in r elation t o what i s t echnologically a vailable an d ho w t o pr operly employ ph otovoltaic
integration in a building. Considering that in the near future PV will be used more and more often as a
building material, the intentions of this project are to:
• Analyze building integrated PV products in order to define their electrical and thermal characteristics.
• Analyze the interaction between these materials and the building.
• Demonstrate what BiPV modules look like and how to integrate them into the building concept.
The r eal working c onditions of a bui lding-integrated PV s ystem ar e gen erally different f rom t hose
reproduced i n a c ommon outdoor t est f acility. F or ex ample, pho tovoltaic insulated g lass will ex hibit
different electrical and thermal behavior compared to PV modules analyzed with a common outdoor
test f acility where ventilation, t emperature, h eat f lux and s tructure are d ifferent. C onsequently the
photovoltaic components for building integration require a special test facility. To test BiPV modules
closer to the real situation, a special stand was built on the roof of our institute with the objective of,
on the one hand, analyzing new prototypes or already existing commercialized modules and, on the
other hand, showing visitors what these new photovoltaic building elements really look like and which
building components can be replaced with PV.
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Aims of the project
The bui lding i ntegration photovoltaic sector becomes m ore popular da y after day and c onsequently
professional interest is increasing. The photovoltaic technology is the only way to achieve integrated
delocalized electrical production. The cost of the modules is decreasing more quickly than other building elements. In this case, the photovoltaic façades will become financially interesting in the near future. For this r eason, this project ana lyzes s everal PV elements us ed as b uilding components i n façades. For further details on the facility construction and modules technologies, see the annual report
2009.
The main goals of 2011 were the following:
•
•
•
•
•
•
Data acquisition
Improvement of the data acquisition system
Data Analysis
Discussion with manufacturers (confidential)
Test facility tour for building professionals, PV specialists and students
Presentation of the project and diffusion of the main results.
The objectives were reached with a small delay due to the large extend of the data to be processed
and a lso due to t he fact t hat the thermal characteristics of t he modules measured at E MPA n eeded
more time than expected.
This work was already presented at the 26th EUPVSEC in Hamburg (07.09.2011), as well as at the
Solar Power UK in Birmingham (27.10.2011) and will be part of other scientific publications.
Figure 1: Outdoor facility for the testing of BiPV systems
Works carried out and results achieved
The BiPV simulator was finalized and the last modules were installed in March 2010.
Data acquisition
The acquisition of data began with the simulator completion in March 2010. All electrical and thermal
data ar e r egistered o n daily basis with a f requency o f 1 per minute dur ing t he daylight p eriod. The
module oper ating e lectrical par ameters (voltage and c urrent), t he meteorological dat a ( irradiance,
outdoor temperature), the ambient t emperature inside t he house and the module temperature at the
back of each module are registered by 24 maximum power point trackers (MPPT) specially realized by
ISAAC for t his pr oject, p yranometers and P t100s. The one-year monitoring period started i n Mar ch
2010 and finished at the end of March 2011when four modules where dismantled and sent them to the
EMPA Laboratory in Dübendorf.
During the first months of monitoring, some improvements were made in order to improve the working
conditions of the simulator (see the Annual report 2010).
Intermediate analysis reports for manufacturers
Two intermediate reports after 3 and 6 months were sent to each of the five manufacturers who collaborated within this project. These individual analysis reports only show the results of the PV modules
provided by the producers themselves. A f inal report was prepared for eac h manufacture describing
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Building Integrated Photovoltaics – Thermal aspects, F. Frontini, ISAAC-DACD-SUPSI
the m ain r esult ac hieved a fter one year m onitoring f or t heir m odules. The c omparison be tween t he
different technologies (without naming the manufacturer) has been shown within the final report for the
BFE submitted in November 2011. This decision was taken in order to avoid the publication of values
that don’t a llow a f air c omparison d ue t o t he am biguous c hoice of t he nom inal pow er between t he
different technologies.
The Final Yield (FY) was used to compare the production of modules having different nominal power
but the same inclination and orientation (during a defined time period).
Prior as well as af ter t he m ounting/integration of t he modules on t he t est f acility, S TC po wer m easurements were performed at ISAAC. Moreover, at the end of the project, additional measurements like
Measurement of Temperature Coefficient (TCO), Performance at different Irradiance levels (GCO) and
Performance at Low Irradiance (PL) were carried out.
The indoor measurements were performed with a pulsed sun simulator (better than IEC class A). The
measurements of al l modules ar e I SO 170 25 ac credited b y t he S wiss A ccreditation S ervice ( SAS).
The module u nder t est has been m easured with a s pectral a dapted r eference cell f or eac h m odule
technology. This reduces the measurement error due to a lower spectral mismatch between module
and reference cell.
The t emperature coefficients of t he m odules were obtained b y p erforming t he T CO measurement.
2
According to it, the modules were measured at 1000 W/m and between 25°C and 65°C.
For the GCO measurements, the modules were measured at different irradiance levels between 100
2
2
W/m and 1000 W/m at 25°C.
Some summarized results extracted are (for further information please consider the Final report submitted to the BFE in November 2011):
• The c-Si modules have produced more energy per square unit area for the whole year.
2
• More particularly, the one integrated at 30° produced 40kWh/m and that is because of its more favorable inclination.
• The two a-Si/a-Si modules that were integrated at 90° produced less energy than the rest of a-Si/aSi modules whereas the most energy produced for this technology was from the integrated at 30°.
• Ultimately, as far as the flexible a-Si modules on different membranes and sheet materials are concerned, they all produced approximately the same energy per square unit area.
A very important par ameter t hat i nfluences t he behavior of m odules i s t he c ell t emperature ( during
working time). The fact that the working temperature of an integrated module is higher than that of a
mounted one is crucial to investigated how temperature affects the performance of a BiPV module.
Figure 2 pr esents t he c alculated m aximum E quivalent C ell T emperature (ECTmax) according t o I EC
IEC 60904-5 as well as the maximum ambient temperature (Tamb_max) for the whole monitoring period.
BIPVTP/22 (I, 90°)
BIPVTP/2 (I, 90°)
BIPVTP/20 (I, 90°)
BIPVTP/3 (V, 90°)
BIPVTP/18 (V, 90°)
Tamb max
80
70
ECT max [°C]
60
50
40
30
20
10
0
Figure 2: Calculated maximum Equivalent Cell Temperature (ECTmax) and maximum ambient temperature
(Tamb_max) for some modules for the whole period of monitoring.
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According to figure 2 and as expected, the integrated modules exhibited higher working temperatures
than the ventilated ones for the same inclination, at 90°.
For t he v entilated m odules, t emperatures ar e i n t he r ange of 45°C -55°C whereas f or t he i ntegrated
ones the range is 55°C-75°C.
As observed, the working temperatures of the modules have a smaller variation throughout the year in
comparison to the ambient temperature.
Finally during the summer 2011, in order to empirically assess the thermal characteristic of the BIPV
windows (U-value and g-value), four modules were tested at the Swiss Federal Laboratories for Materials T esting an d R esearch ( EMPA) l ocated in D übendorf ( Switzerland). M easurements o f t he s olar
gains through the windows were performed in a calorimetric outdoor test facility (test cell) [4].
The U-value was measured in a large guarded hot box facility.
From the acquired data it can be concluded that the g-value of the semi-transparent BIPV modules is
changing according to the windows and PV cells design. It is for all four modules less than 0.2.
The four t ested m odules hav e a t hermal c onductivity around 1. 1 W/m2K ( all t he B iPV transparent
modules are constructed in a form of a double glazing unit filled with argon gas).
Test facility tour for building professional, PV specialist and students
During 2010 and 2011, many visits of the BIPV simulator were organized for architects, actors of the
building sector, students, industries and associations. A virtual tour was also produced and uploaded
on our web site www.bipv.ch through a Zoom out/Zoom in application (that was not included initially in
the project) Ref. [1].
Presentations of the project and diffusion of knowledge about the concept and first results
th
• 25 EUPVSEC and W CPEC-5, Valencia, Poster and pap er: “Low energy house f or testing BiPV
systems”, September 2010.
• Status Seminar, Zurich, September 2010.
• Energy forum - solar skins, Bressanone, Oral presentation: “Temperature and module efficiency:
thermal and electrical behaviour of BIPV systems”, December 2010.
• Supplemento del corriere del trentino e dell’Alto Adige, article: “Stand di prova per elementi fotovoltaici integrati negli edifici”, November 2010.
• Metallglass, article: “Stand di pr ova p er e lementi f otovoltaici i ntegrati negli e difici”, December
2010.
th
• 26 EUPVSEC, Hamburg, Oral presentation and paper: “Evaluation of 1 year of monitoring results
of a testing stand for Building Integrated PV elements”, September 2011.
• RENEXPO A ustria, Invited speak: Niedrigenergiehaus als Testanlage für gebäudeintegrierte PVElemente: Untersuchungsergebnisse nach einem Jahr Salzburg 2011.
• SolarPower UK, Birmingham, Oral Presentation: “BIPV side-by-side trial results”, October 2011.
• Verres industriels, Moutier
• Galvolux, Bioggio
Marco Jelmini director
• Swiss laboratories for materials testing and research EMPA, Dübendorf
Ghazi Wakili Karim, Bruno Binder, Mr. Vonbank and Stephan Carl
• PV producers (confidential)
• AIT (Austria)
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2011 Evaluation and future prospects
Also in 2011, t his project has received a great response by architects, actors of the building s ector,
students, industries and research. In fact, building specialists encounter difficulties when they have to
choose am ong different t echnologies i n r elation t o t he a pplication of P V i nto the b uilding and ar e
pleased to know that this project will give more “usable” information on this subject.
The construction of t he s tand was de layed and the measurements at E MPA, due t o not f avorable
weather conditions took more time than expected.
The B iPV s tand was m ore ex pensive c ompared t o t he es timated c osts, bec ause of t he dec ision t o
give m ore v alue t o d emonstration b y making a small s cale house i nstead of hav ing boxes behind
modules.
In the final report the following considerations are analyzed.
• It has b een observed that temperatures and m odule inclination ha ve i nfluenced t he am ount of
energy produced by the modules as well as their performance.
• The modules integrated at 30° had higher energy production in comparison to the ones integrated
at 90°.
• The higher working temperatures of the modules integrated at 30° had a significant annealing effect on them which consequently resulted in a better performance, followed by the modules integrated at 90° and ultimately, the ventilated modules at 90° demonstrated the lowest performance,
as well as the lowest working temperatures throughout the whole monitoring period.
• The higher working temperatures of the integrated at 90° modules had a significant annealing effect on the a-Si modules which consequently resulted in a better performance.
• For the thermal part, all the measured modules demonstrated satisfactory U and g values due to
the technologies used. Its U-value and g-value were measured to be respectively around
2
1.1W/m K and l ower t han 0.16. A l ow g-value has a lso an impact on t he visual transmission of
the window.
In conclusion, it could be said that the performance of BiPV modules is influenced by the combination
of the:
•
•
•
•
type of integration,
inclination,
temperature coefficients of the modules and
annealing effects.
The working t emperature o f the photovoltaic part seems t o have a small influence on t he total solar
heat g ains. F urther i nvestigations have t o be d one in t his s ense i n or der t o a ssess i n adv ance t he
thermal characteristics of the BiPV windows (U-value and g-value). This point can be addressed to a
new research project in which the U-value and g-value characteristic of glazing systems with Photovoltaic cell integrated on it, is evaluated and compared with standard glazing unit or fritted windows. Up
to now there is no legislation or standard describing how to consider the photovoltaic effect on U and
g-values.
However, in addition to the aspects above, also the lifetime and long-term degradation of the modules,
aesthetics and cost must be taken into consideration.
Further investigation concerning the impact of BiPV module (especially semi-transparent modules) on
the indoor comfort and on the thermal behavior of the room would be of great interest. The following
points may be analyzed and investigated in future projects:
•
•
•
•
•
influence on day lighting,
influence on human behavior,
influence on glare in working space,
influence on heating and cooling demands,
how a different orientation of the module (not only south oriented PV modules) can have a role in
the electrical and thermal performance of the system (Module and Building).
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References
[1]
Zoom in / zoom out application on www.bipv.ch “materials” / “BIPV simulator”
[2]
[1] S .Dittmann et al ., E nergy Y ield M easurements at S UPSI - Importance of D ata Q uality C ontrol a nd i ts I nfluence on
kWh/Wp Inter-Comparison, 26th EPVSEC, Hamburg (D), September 2011.
[3]
[2] G. Friesen & S. Dittmann, et al.: Performance Intercomparison of 13 Different PV Models Based on Indoor and Outdoor
Tests, 25th EPVSEC, Valencia (ES), September 2010.
[4]
[3] H. Simmler, B. Binder, Experimental and numerical determination of the total solar energy transmittance of glazing with
venetian blind shading, Building and Environment, Volume 43, Issue 2, February 2008, Pages 197-204.
[5]
[4] P. G. Lout zenhiser et al l., Empirical validations of s olar gai n models f or a gl azing uni t with e xterior and i nterior bl ind
assemblies, Energy and Buildings, Volume 40, 2008, Pages 330-340.
[6]
[5] A. Chatzipanagi et all., Evaluation of 1 year of monitoring results of a testing stand for Building Integrated PV elements,
26th EUPVSEC, 5CO.12.3, Hamburg 2011.
[7]
[6] K. N agel et al l., Low ener gy house f or testing bu ilding-integrated P V el ements, 25 th E UPVSEC, 5B V.5.6, V alencia
2010.
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OPTIMIZATION OF THIN FILM MODULE
TESTING AND PV MODULE ENERGY
RATING AT SUPSI
Annual Report 2011
Address
Date
Gabi Friesen, Mauro Pravettoni
ISAAC-DACD-SUPSI
Via Trevano, CH-6952 Canobbio (TI)
058 666 63 57, [email protected]
REF-1081-00215/SI/500691-01
01.10.2011 – 31.03.2014
01.12.2011
ABSTRACT
This project aims to improve the measurement accuracy for thin film technologies through the definition of new test procedures and the up-grade of the test equipment. The focus is on the characterisation of m ulti-junction de vices and t he pr e-conditioning of t hin f ilm modules, w hich needs t o be i mproved to guarantee a higher comparability and repeatability of power measurements. The results, in
combination with long term outdoor monitoring data and modeling activities, will be used to increase
the understanding of thin film performance in comparison to the one of crystalline silicon technologies
and to verify the applicability of the current energy rating procedure to thin film modules. Side activities as measurement round robins and collaborations with industry and other test institutes will help in
the evaluation of the introduced changes.
The project is divided into 4 work-packages:
WP1 Characterisation of multi-junction modules
current-voltage characterisation and spectral response of large area modules
WP2 Stabilisation procedures
preconditioning of CIS/CdTe modules and stabilisation of amorphous silicon modules
WP3 Outdoor performance of thin film modules
yield inter-comparison and modelling of outdoor performance
WP4 Energy rating
validation of IEC61853 part1-3 standard
The project has started with promising results for the testing of multi-junction modules (WP1) and
the electrical characterisation of all outdoor exposed modules (WP3).
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1. Aims of the project
WP 1: Characterisation of multi-junction modules
Back-ground
In the specific case of multi-junction technologies, the proper calibration of the modules is complicated
by spectral mismatch errors and by the current limiting behavior of the sub-cells, which may change
when t he device is ex posed t o light s ources w ith different s pectral d istributions, s ay, d ifferent s olar
simulators or natural sun light. Moreover there exists today still no IEC standard describing test methods for m easurement of t he s pectral r esponse of m ulti-junction PV m odules a nd f or a s pectral m ismatch c orrection pr ocedure t o be app lied on t heir I -V c urve m easurement r esults. In it s s ide, th e
ASTM I nternational des cribes, in E 2236-10 [ 1], i terative pr ocedures f or adj ustment of t he bi as-light
intensity and of t he bias voltage to b e us ed for SR measurement. For I-V c urve m easurements, th e
ASTM s tates t hat a s pectral m ismatch c orrection c an be ap plied us ing t he s pectral r esponse of t he
limiting s ub-cell of the PV module, b ut it s uggests t hat i t is preferable to use a s pectrally adjustable
solar simulator and to ensure that the actual current balance within the individual sub-cells of the PV
module is c lose to AM1.5G c ondition. Indeed f rom s pectrometric I -V c urve m easurements, i t is well
known that variations of photo-generation within the sub-cells of a multi-junction device influence the
short-circuit current (Isc) but also notably the fill factor (FF) of the I-V curve [2, 3]. Therefore, depending
on the current limitation status of the multi-junction module, a simple correction of the I-V curve based
on a MM factor calculated using the SR of the limiting component cell is generally not sufficient.
[1] ASTM International 2010, “ Standard T est M ethods for M easurement of Electrical Performance and Spectral R esponse of
Nonconcentrator Multijunction Photovoltaic Cells and Modules”, ASTM Designation E 2236 – 10, 2010, West Conshohocken, PA.]
[2] M. Meusel,R. Adelhelm, F. Dimroth, A. W. Bett and W. Warta, "Spectral Mismatch Correction and Spectrometric Characterisation of Monolithic III–V Multi-junction Solar Cells", Prog. Photovolt: Res. Appl. 2002; 10:243–255.
[3] A. B öttcher, A . P rorok, N . F erretti, A . Preiss, S . Krauter and P . G runow, " Flasher t olerance of po wer m easurement on
micromorph tandem modules”, Proc. of the 25th EU-PVSEC, 2010, Valencia, Spain.
[4] F. Baumgartner, “Power rating multi-junction solar cells: Focus Thin Film”; Thin Film Industry Forum 2010, Berlin, April 22nd
2010.
Expected results
The target is to decrease the measurement uncertainty on Pmax from the current value of ±5-8%, assessed by a survey within different test laboratories [4], to an improved value of ±3-4%.
The l aboratory will be able t o of fer measurements o f s pectral r esponse of l arge ar ea m odules with
multi-junction structure.
Accreditation according ISO17025 of the new test allowing the laboratory to offer a full qualification of
multi-junction devices according IEC61646.
WP2: Stabilisation procedures
Back-ground
It is well known that in dependence on the exposure history of a module an indoor measurement can
lead to very different results [1, 2, 3]. The better understanding of these phenomena and the achievement of r eproducible r esults i s particularly important f or: ( 1) m odule qualification, where m easurements bef ore and after ag ing t ests ar e c ompared; ( 2) c alibrations of r eference modules and ( 3) t he
prediction of energy yield, especially in the case of amorphous silicon modules.
The typical effects, requiring the introduction of stabilisation procedures are here summarized for three
different families of technologies. (1) Crystalline silicon modules undergo an initial degradation of up to
1-5% of the initial power after a period of exposition to light of 5-60 kWh/m² due to the creation of boron-oxygen defects and/or the reduced transmittance of the glass after light exposure. (2) Polycrystalline thin film modules as CIS and CdTe can be i nfluenced by internal meta-stabilities, which m ay in
some c ases s trongly influence t heir s tate even af ter v ery s hort-exposure t imes (seconds, hour s) t o
light. If the devices are stored in the dark performance may decrease c onsiderably. (3) Amorphousbased thin film devices are subject to an initial degradation, which may account for a loss of power up
to 30% , o verlapped b y a seasonal os cillation, which extension i s influenced b y the t emperatures
reached by the module over the year. The scope of WP2 is to develop for each technology simple, fast
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Optimization of thin film module testing, G. Friesen, SUPSI
and reproducible stabilisation procedures (indoor and/or outdoor) for the proper preconditioning of PV
modules, i n or der t o per form c orrect S TC pow er m easurement. Mos t of t he pr e-conditioning pr ocedures are based on light soaking (LS) under load or open circuit conditions, but also annealing can be
required as, for example, for amorphous silicon technologies. Even if the project is focused on thin film
modules a small part will be also dedicated to the stabilisation of crystalline silicon modules.
[1] Rau U, Jasenek A, Herberholz R, Schock HW. The inherent stability of Cu(In, Ga)Se2 solar cells. Proceedings of the 2nd
World PVSEC, Vienna, 1998; 428–433.
[2] A. Virtuani, H . Muellejans* and E . D . D unlop, Comparison of i ndoor and out door per formance m easurements of r ecent
commercially available solar modules, Prog. Photovolt: Res. Appl. 2011; 19:11–20
[3] Virtuani A , P avanello D , K enny R, N ikolaeva-Dimitrova, M, D unlop E . C omparison of i ndoor and out door per formance
measurements on CIS thin film solar modules. Proceedings of the 22nd European PVSEC, Milan, 2007; 2421–2426.
Expected results
Definition a nd s uccessful validation of pre-conditioning pr ocedures for thin f ilm P V modules, which
may be performed indoors and/or outdoors prior of the execution of the definitive indoor measurement.
Definition of some reproducible stabilisation methods for a-Si modules, which output parameters can
be related to the site and integration dependent temperature and irradiation history of a module and so
help to predict its energy output.
Optimization and better understanding of the initial degradation procedure for c-Si modules.
WP3: Outdoor performance of thin film modules
Back-ground
The performance of thin film modules under real operating conditions is far from being understood as
well as the one of crystalline silicon modules. Each single technology behaves differently and depends
on the manufacturing process. Even samples coming from the same production line can behave differently. Mor eover, the m easurement ac curacies under c ontrolled test c onditions do not r each t he
same accuracy as for crystalline silicon modules and the test procedures aren’t as well defined. Despite of t his m any thin f ilm manufacturers c laim, t hat t heir P V m odules have a hi gher out put un der
diffuse or low irradiance c onditions r espect to crystalline silicon m odules. Independent test institutes
are asked to verify these statements. One approach is to compare the energy output of different technologies side by s ide b y mounting t hem on a test s tand an d by monitoring them for a l ong en ough
time.
[1] G. Friesen (2011), “Centrale di test ISAAC-TISO: final report 2007-2010”, contract n° OFES: 36508
Expected results:
The m ain outcome of this w ork-package will b e: (1) a hi gh num ber of hi gh q uality t hin f ilm module
outdoor data ( kWh and I-V c urves) i n combination with high quality meteorological dat a and module
parameters ex tracted f rom r egular indoor m easurements, a nd ( 2) a d eeper i nsight i nto the per formance of thin film modules.
The novelties respect to former test cycles performed by SUPSI [1] are: (1) the focus on thin film technologies, (2) the extended measurement period (minimum 2 years), (3) the implementation of spectral
irradiance data in combination with I-V curves and in-plane diffuse irradiance measurements and, (4)
the availability of high quality indoor measurements with spectral response curves for each module.
The outdoor and indoor data acquired during the measurement campaign will be used to:
-
compare the energy yield of thin film technologies with the crystalline silicon technologies and to
disseminate the results
investigate d ifferences w ithin modules of t he s ame t echnology (e.g. micro morph or CIGS), but
produced by different manufacturers
quantify the contribution of spectral effects for the different technologies
monitor the initial stabilisation of a large number of thin film technologies (c-Si, a-Si, µ-Si, CdTe
and CIS) and use this data for the validation of the stabilisation procedures defined within WP2
verify the applicability of indoor measured thin film performance data to predict outdoor data, by
applying the characterisation and stabilisation procedures defined within WP1 and WP2
validate the full IEC61853 energy rating standard within WP4
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WP4: Energy rating (IEC 61853)
Back-ground
The peak power at STC in W p is still the main parameter for the classification of PV modules on the
market. B esides it represents also the principal reference of many PV manufacturers, given t hat the
product value is directly related to its power (Euro/W p). However, what is obviously more important is
how many kWh the P V m odules will pr oduce under real operating c onditions. A ne w e nergy rating
standard, which s hould overcome t his problem, is t herefore under pr eparation at I EC level [1, 2 , 3 ].
The I EC 61853 e nergy r ating s tandard i s divided i nto 4 parts. T he f irst was published i n F ebruary
2011. The other parts are still under preparation and valuable input for the finalization of this document
can still be given.
[1] IEC 61853-1 edition 1.0. (2011). "Photovoltaic (PV) Module Performance Tasting and Energy Rating - Part 1: Irradiance and
Temperature Performance Measurements and Power Rating".
[2] IEC 61853 -2 D raft H . ( 2007). " Photovoltaic ( PV) M odule Performance T asting and E nergy R ating - Part 2: S pectral R esponse, Incidence Angle and Operating Temperature Measurements".
[3] IEC 61853-3 Draft E. (2007). "Photovoltaic (PV) Module Performance Tasting and Energy Rating - Part 3: Energy Rating of
PV Modules"
Expected results:
The goal of this work package is the full implementation of the IEC 61853 standard with an evaluation
of the uncertainties.
Improved energy prediction of cloudy days.
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2. Work carried out and results achieved in October /November 2011
The f ollowing t wo ac tivities hav e been started i n 20 11: 1) some pr eliminary tests on m ulti-junction
devices a nd 2) monitoring of t he stabilisation process of 11 different t hin f ilm t echnologies t ogether
with a detailed indoor characterisation of the single devices under test.
2.1 Test procedures for the characterisation of multi-junction devices (WP1)
The activity in WP1 in the first months of the project has been mainly devoted to upgrade the existing
spectral r esponse ( SR) m easurement s etup t o a llow measurements of multi-junction modules. T his
peculiar measurement requires using coloured bias light to “saturate” the junction(s) not being measured and drive the junction to be measured in a current-limiting status.
Preliminary results before the kick-off of the project highlighted the importance of a dedicated coloured
bias light system with intensity and uniformity high enough for modules of commercial size (order of 1
2
m ). Good results were obtained with coloured, high powerful LEDs shown in the picture below.
Fig. 1: Measurement set-up with bias light for the measurement of small devices.
To investigate over different solutions, which allow uniform coloured beam of square meter size, the
power output and spectral irradiance of commercial video projectors have been also analysed.
Fig. 2: Spectral irradiance distribution of different bias light combinations.
Figure 2 shows the spectral irradiance of the following colour combinations: primary colours red (R),
green ( G) and b lue ( B); s econdary c olours cyan ( C= G+B), m agenta ( M= R+B) and yellow ( Y= R+G);
and white (W=R+G+B).
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Both B, G and C spectra lie in the wavelength band of absorption of the top junction of both a-Si/a-Si
and a-Si/µc-Si commercial modules (300-600 nm). R spectrum (500-750 nm) instead lies in the region,
where both top and bottom junctions respond. A good selection for the bottom junction SR measurement i s t herefore an y c ombination of B , G a nd C , a s t he f ollowing c hart s hows. Similar ar guments
apply to the saturation of the bottom junction and SR measurement of the top junction and are under
investigation.
Fig. 3: Spectral response curves of a a-Si/µc-Si small size module measured with different
combinations of bias light.
2.2 Outdoor and indoor performance inter-comparison of 11 different thin film modules (WP3)
The measurements for WP3 started effectively already at the beginning of 2011 with the purchase and
initial characterisation of al l ne w m odules (test c ycle 12), and t he s tart of t he o utdoor measurement
campaign in February 2011. Modules manufactured by 11 different companies including all main thin
film t echnologies (a-Si, a -Si/a-Si, a -Si/µ-Si, C dTe. C IS, C IGS, C IGSS) are c ompared against each
other and to some crystalline silicon modules. Two modules of each type are exposed outdoors and
one is stored in the dark.
All modules were first subjected to a detailed indoor measurement sequence in order to characterise
their p erformance bef ore ex posing t hem t o t he s un or s toring t hem i n t he dar k. The f ollowing tests
were conducted: visual inspection, insulation test, wet leakage current test, performance at STC with
different r eference c ells, performance at d ifferent i rradiance l evels and t emperature c oefficient. The
first year data will be used to analyse the initial degradation and stabilisation process within the different technologies, whereas the following years data will be used to compare the energy output of the
modules. A second extended indoor measurement campaign was performed on all modules in October 2011 to quantify the changes in module performance respect to the initial measurement performed
at the begin. After this the modules have been installed again on the outdoor test facility. Indoor and
outdoor data are currently analysed and results will be published later on.
Table 1 lists the thin film modules tested in test cycle 12, the technology, the nominal power Pn and
tolerance given by the manufacture as well as the performance warranty.
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Manufacturer
Module type
Technology Pn [W]
Warranty Tolerance [%]
Avancis
PowerMax 110
CIGSS
110
--%/20y
±5
Solibro
SL1-75F
CI(G)S
85
--%/--y
+4, 0
Sulfurcell
55-HV-F
CI(G)S
55
90%/10y
±5
FirstSolar
FS-275
CdTe
75
90%/10y
±5
NexPower
NH-100AX-1
a-Si
100
90%/10y
±5
EPV Solar
EPV-5X
a-Si (2)
52
90%/10y
---
Schott
ASI 100
a-Si (2)
100
--%/20y
±5
Mitsubishi
MT130
a-Si/µ-Si
130
--%/--y
±5
Inventux
X 120
a-Si/µ-Si
120
90%/10y
±3
Bosch Solar
Vega-T 115
a-Si/µ-Si
110
--%/--y
±2.3
Pramac
Luce MCHP
a-Si/µ-Si
125
90%/10y
±5
Tab.1: List of the modules of test cycle 12
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3. Work to be performed in 2012
The next steps planned for 2012 are:
WP1
•
•
•
•
•
•
test of the appropriate bias light intensity for SR measurement of a large area module
calculation of measurement uncertainty.
implementation of the data acquisition system.
determination of the operating procedure.
round-robin tests with selected partners to validate the new setup.
up-grade of outdoor test facility for the measurement of module performance at close to STC conditions and inter-comparison to indoor STC measurements.
WP2
• up-grade of i ndoor light s oaking f acility ( temperature/irradiance un iformity a nd c ontrol s ystem,
spectrum, load and monitoring units, etc.).
• investigation of the sensitivity of the indoor stabilisation process to the applied to indoor test conditions and comparison to the stabilisation achieved outdoors’.
WP3
• analysis of indoor and outdoor data.
• upgrade of t he out door t est f acility with a n ew s pectrum r adiometer and a p yranometer f or t he
measurement of in-plane diffuse irradiance.
• continuation of indoor tests in regular intervals (approx. every 3-6 months).
• determination of spectral response curves and spectral mismatch factors.
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PHOTOVOLTAIK SYSTEMTECHNIK
Annual Report 2011
Urs Muntwyler
Berner Fachhochschule, Technik und Informatik,
Elektro- und Kommunikationstechnik, Burgdorf
Jlcoweg 1, 3400 Burgdorf
034 426 68 11, [email protected], www.pvtest.ch
Various projects
Address
Date
01/2012
ABSTRACT
In 2011, Research in the PV laboratories, with a focus on the "PV System Technology", of the Bern
University of Applied Sciences was in a transitional phase. The circumstances in energy politics
increased the importance of photovoltaics for stable, secure and affordable electricity supply in
Switzerland and affected the PV laboratory of the Bern University of Applied Sciences as well. The
demand for courses, student projects and R&D increased massively, but without the prospect of
additional financial support. Instead, it was even harder than before to obtain existing funds.
Also in human resources there has been a temporary situation caused by the imminent replacement
of the former head of the PV Laboratory Prof. Dr. Heinrich Häberlin by Urs Muntwyler. At least, during
the time overlap, more projects could be processed.
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Langfristige Strategie
In Zukunft sollen die Kernkompetenzen der Berner Fachhochschule optimal genutzt werden. Dabei
sollen die bisherigen Schwerpunkte „PV-Langzeitmessung“ und „Tests und Testmethoden von PVWechselrichtern“ erweitert werden. Dazu wurde neu der Bereich des „Projektentwurfes von PVAnlagen“ gestartet. Dies ergibt starke Synergien mit den bestehenden arbeiten und ist für die PVBranche der Schweiz sehr wichtig. Das Know-How wird u.a. in einem neuen Kurs für externe „Photovoltaik-Systemtechnik“ vermittelt. Er richtet sich an Berufsleute in der PV-Branche. Die ersten zwei
Kurse waren bereits ausgebucht. Ab 2012 wird auf der „Master of Engineering“ Ausbildungsebene
erstmals ein spezielles Modul über Photovoltaik angeboten. Im deutschsprachigen Modul stellt die
Berner Fachhochschule zwei der drei Dozenten.
Zur Bündelung der Forschungskompetenz wurde in der Berner Fachhochschule das „Institut für Energie, Mobilität und Verkehr IEM“ mit den drei Bereichen „Energie, Fahrzeuge und nachhaltige Technologien in Entwicklungsländern“ gegründet. Für den PV-Bereich ist dabei die Integration der Elektromobilität interessant. Dies ist eine Kernkompetenz der Berner Fachhochschule, welche 1985 mit dem
Bau der ersten Solarmobile startete.
Angelaufen ist 2010/2011 auch die Zusammenarbeit mit der Abteilung „Architektur und Holzbau
(AHB)“ der Berner Fachhochschule. Für die Verzahnung der Photovoltaik auf und am Gebäude bieten
sich gemeinsame Projekte und ein Austausch in der Lehre geradezu an.
Projektabschluss „Photovoltaik Systemtechnik 2007-2010"
Das Rahmenprojekt "Photovoltaik Systemtechnik 2007-2010" ist das Nachfolgeprojekt zum Projekt
"Photovoltaik Systemtechnik 2003-2006". Die wichtigsten Projektresultate: Auch im Laufe dieses Projektes wurde die Infrastruktur des Photovoltaiklabors ausgebaut und weiter verbessert. Für den Test
grosser Wechselrichter wurde ein hochpräziser, hochstabiler, automatischer Solargenerator-Simulator
mit einer MPP-Leistung von bis zu 101 kW (UOC ≤ 810 V, ISC ≤ 156 A) entwickelt und in Betrieb genommen. Für normgerechte Inseltests bis 100kW wurden 2010/2011 Resonanzkreise von 33 kVar
entwickelt und vier Stück gebaut. 2011 wurden Entwicklungen geplant für verbesserte FI-Tests,
Lichtbogen-Detektoren und automatische Resonanzkreise. Mangels Finanzen konnte mit den Arbeiten
2011 nicht begonnen werden.
Das Langzeit-Monitoring wurde 2011 nach längerer Stagnation ausgebaut. Gegenwärtig werden insgesamt 44 Anlagen mit total 74 Wechselrichtern überwacht (die meisten davon in Burgdorf). Die BFHTI besitzt mittlerweile fein aufgelöste PV-Messdaten von über 900 Wechselrichter-Betriebsjahren.
Ende 2011 waren 10 Anlagen mit einem Fein-Messsystem ausgerüstet. Die überwachten Anlagen
funktionierten mehrheitlich gut. Die Energieerträge der messtechnisch erfassten PV-Anlagen in Burgdorf (installierte Gesamtleistung 372kWp) weisen eine leicht sinkende Tendenz auf. Die Gründe hierfür liegen bei Degradation der Module, zunehmender Verschmutzung, Wechselrichterausfällen,
Strangausfällen durch Sicherungs- oder Klemmendefekte usw. Bei der CIS-Anlage Newtech 1 setzte
sich die 2004 begonnene, stärkere Degradation weiter fort. Die beiden amorphen Anlagen Newtech 2
und 3 zeigten dagegen neben der üblichen saisonalen Variation des Wirkungsgrades nur eine geringe
weitere Degradation. Seit 1992 wurden insgesamt 104 verschiedene Wechselrichter in einer Ausfallstatistik erfasst. Momentan werden 74 Geräte überwacht. Seit 1997 variiert die jährliche Ausfallrate
zwischen 0,07 und 0,21 Ausfällen pro Wechselrichter-Betriebsjahr (Mittelwert 0,122).
Da im Sommer 2010 vermehrt Berichte über die mögliche Gefährdung der Feuerwehr durch PV-Anlagen erschienen, wurde dieses Problem etwas näher untersucht und erste Messungen gemacht. Dazu
wurden 2011 verschiedene Fachartikel publiziert (siehe www.pvtest.ch  Publikationen).
Photovoltaik al s B estandteil einer si cheren, g ünstigen u nd zu verlässigen
Stromversorgung
Im Hinblick auf eine stark zunehmende Anwendung der Photovoltaik zur Sicherung einer stabilen,
sicheren und kostengünstigen Stromversorgung der Schweiz sollen die Nutzung der Ergebnisse der
Forschung im Bereich der „PV-Langzeitmessung“ eingesetzt werden. Ein zusätzliches Arbeitsfeld
waren 2011 die Arbeiten im Bereich der Planung von PV-Anlagen mit verschiedenen Planungsprogrammen. Mangels Finanzierung wurde das mittels BSc-Arbeiten gemacht:
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PVSYSTE 07-10, Urs Muntwyler, BFH-TI
- So konnte in einer Arbeit von Marc Hauser gezeigt werden, dass die Genauigkeit der Produktionsprognose mit dem Programm „PVSyst“ um bis zu 20% variieren kann. Referenzwerte bildeten Anlagen aus dem PV-Langzeitmessprogramm des PV-Labors der BFH-TI wie „Mont Soleil“, „Jungfraujoch“ und „Stade de Suisse“. Hier sind also zusätzliche Arbeiten nötig, ist dies doch ein unakzeptabler grosser Wert.
- In einer BSc-Arbeit verglich Thomas Heiniger verschiedene professionelle Auslegungs- und Freeware - Programme. Die Ertragsprognosen der Programme variieren bis zu 10 Prozent in ihren Resultaten. Dies stellt weniger versierte Anwender vor grosse Probleme, von denen sie bisher wohl
nichts wussten. Heiniger bewertete zusätzlich die Programme im Hinblick auf verschiedene Benutzergruppen.
- Das wohl spektakulärste Projekt bearbeiteten Nicole Reber und Daniel Bützer. Dabei galt es die
Sanierung von zwei 60 m hohen Hochhäusern in der Zürcher Sihlweid mit u.a. PVFassadenelementen von je 113 kWp Leistung planerisch zu begleiten. So musste herausgefunden
werden, wie die korrekte Beschaltung der mikromorphen Dünnschichtmodule gemacht werden
muss. Diese Module erlauben nur bestimmte Teilbeschattungen, die es in einer Fassade immer
gibt. Für alle vier Seiten, inklusive Nordseite, galt es eine wirtschaftliche Variante zu finden. Weil
die Hochhäuser nicht über die kostendeckende Vergütung KEV abrechnen, brauchte es dazu einige neue Ideen. Die BSc-Arbeit zeigte einige „weisse Flecken“ in der Planung von Dünnschicht-PVFassaden. Die Realisierung des ersten Hochhauses wird 2011 abgeschlossen. Es gibt weltweit
kaum Objekte in der Grösse und Komplexität der „Sihlweid“-Hochhäuser. Es bestehen Pläne, die
Anlage detailliert zu vermessen, falls eine Finanzierung dafür gefunden wird. Das Projekt hat grosses Interesse im In- und Ausland bekommen. Urs Muntwyler hat dazu einige Beiträge an Fachkongressen wie CISBAT, EUPVSEC, Solar World Kongress, PV-Konferenz Staffelstein 2012 etc. verfasst.
- Zusammen mit der ETH Zürich wurde im Rahmen des Projektes „Suncar“, einem „Plug-in-Hybrid“Fahrzeug ein Wohngebäude in Horw mit einer sehr kräftigen PV-Anlage versehen. Fokus der BScArbeit von Andreas Meier war die produktionsgerechte Ladung des Elektrofahrzeuges in Zeiten
von PV-Überschuss.
- Daran anknüpfend befasste sich Besnik Ajeti mit der Planung einer PV-Anlage für den Parkplatz
der BFH-TI in Burgdorf und den dazugehörenden E-Mobil-Parkplatz.
- Michael Diethelm bearbeitete eine Überbauung mit 8 je 17-eckigen Mehrfamilienhäusern mit verschiedenen Dachebenen und verschiedenen Aufbauten. Ziel war die Erreichung der „2‘000 WattRegel“, was die Produktion von mehr als 9‘500 kWh pro Gebäude erforderte. Von den evaluierten
Varianten ergab die „Ost-West“-Ausrichtung der Solarmodule die besten Werte.
Daneben arbeiteten die Studenten im Rahmen von Projektarbeiten an verschiedenen Planungen von
PV-Anlagen, wie dem neuen Fussballstadium der Stadt Biel (ca. 1, 2 MWp), verschiedenen Wohnund Gewerbegebäuden, sowie an Themen wie den „Plus-Energiehäusern“. Im Bereich der Hardware
wurde an einer Globalstrahlungs-Anzeige für ein Pyranometer, digitalen Sensoren für die PVLangzeitmessung und der Weiterentwicklung der Wechselrichter-Tests gearbeitet. Geplant ist der
Ausbau des Wechselrichter-Prüfstandes für Multi-Tracker PV-Wechselrichter. Hier fehlt noch die Finanzierung, um sich voll auf das Projekt zu konzentrieren.
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Langzeitmessung von PV-Anlagen
Die Langzeitmessung von PV-Anlagen wurde trotz fehlender Finanzierung 2011 fortgesetzt. Dank
internen Reserven des PV-Labors und Beiträgen der Studiengesellschaft „Mont-Soleil“ und dem lokalen Burgdorfer Stromversorger Localnet konnte die nun seit fast 20 Jahren laufende Messserie fortgesetzt werden. Im Hinblick auf die Zukunft wurden verschiedene Infrastrukturarbeiten vorangetrieben,
wie eine nun extern gehostete Webseite www.pvtest.ch, sowie ein neuer Server auf dem Stand der
Technik zur Datenerfassung der Feinmessungen. Die Wartungsarbeiten wurden intensiviert. Dank
einem Projekt der „Emmentaler Versicherung“ konnte eine 37 kWp Anlage mit CIGS-Solarmodulen in
das Messprojekt aufgenommen werden. Dies ist seit vielen Jahren der erste „Neuzugang“ in der
Messreihe. Vorbereitet und geplant für 2012 ist eine Ausweitung der Messungen auf neue Solarmodul-Technologien wie HIT, rückseitenkontaktierte m-Si Module und moderne p-Si und m-Si Technologien. Die PV-Anlagen stehen auf dem Alters- und Pflegeheim in Burgdorf. Für die Installation der
Messeinrichtungen fehlt es einzig noch an der Finanzierung. Mit diesen Mess-Installationen könnte
das PV-Labor der BFH-TI die aktuellen Technologien in der Messreihe abbilden.
Verschmutzung von Solarmodulen: EU-Projekt „Servitor“
Das Ziel im EU- Projekt PV-Servitor war einen autonomen Putz- und Serviceroboter für Freifeld-PVAnlagen zu entwickeln. Die Rolle des PV-Labors innerhalb des Projektes bestand darin, PV-Knowhow
zur Verfügung zu stellen. Im Speziellen im Bereich des korrekten Putzens und genauen Messens von
Anlagen. Beim finalen Projekt-Meeting in Castuera in Spanien war eine durch Staub visuell stark verschmutzte PV-Anlage anzutreffen. Nach Putzversuchen mit manuellem Putzgerät wie auch mit dem
Roboter, und vielen Messungen des PV-Labors ergab sich jedoch nur ein Leistungsgewinn von ca.
3%. Quintessenz: Der visuelle Eindruck kann täuschen! Im Bereich „Putzen“ muss noch viel geforscht
werden, wo und mit welchem Gerät wie viel geputzt werden muss. Unter Umständen ist der Aufwand
für das Putzen grösser als der wirtschaftliche Nutzen. Trotzdem macht es wahrscheinlich Sinn eine
Anlage periodisch zu putzen, damit sie nicht „verrottet“. Dies zu beurteilen ist eine Sache für Fachleute.
Für den Kanton Bern wurde ein Merkblatt kommentiert, das Vorschriften zum Putzen von Solaranlagen mit Flüssigkeiten macht. Es besteht die Befürchtung, dass Chemikalien zum Einsatz kommen, die
ungeklärt versickern könnten.
PV-WR-Testverfahren
Die Weiterentwicklung der Wechselrichter-Testverfahren litten 2011 unter dem Finanzmangel. Der
Bau der geplanten Multi-Tracker-Anlage musste daher zurückgestellt werden. Gearbeitet wird im Moment an der Zertifizierung der Messungen. Dafür wurde eine Ingenieurin aus der PV-Industrie angestellt.
KTI-Projekte
Zur Deckung der Finanzierungslücke und für einen verbesserten Transfer der Forschungsresultate
wurden 2010/2011 erstmals in der Geschichte des PV-Labors der BFH-TI Projekte bei der Kommission für Innovation und Technologie KTI eingegeben. Dabei konnte ein Projekt über eine „intelligente
Solarmodul-Dose“ weitgehend abgeschlossen werden. Das Produkt der Firma Esmolo AG wurde an
der PV-Ausstellung „Intersolar 2011“ in München als eine der 10 interessantesten Neuheiten vorgestellt. Im Rahmen der Sonderfinanzierung der KTI zur Behebung der „Frankenschwäche“ wurden
ebenfalls Projekte eingegeben. Eines der Projekte zum Praxistransfer eines Lichtbogen-Detektors
erhielt die Zusage. Das Projekt wird 2012 und 2013 bearbeitet.
Interne Projekte
Am PV-Labor der BFH-TI wurden verschiedene neue Projekte und Bereiche bearbeitet. Einer der
Bereiche ist die Zuverlässigkeit von PV-Anlagen. Zusammen mit dem SUPSI wollen wir die gesamte
Lebensdauer einer PV-Anlage abbilden. Die Forschungsanlage „Mont-Soleil“ kann dazu eine wichtige
Rolle spielen. Damit zusammen hängt auch der Bereich der „Brandgefahr von PV-Anlagen“. Hier
herrscht fallweise Konfusion bei Nichtfachleuten. Prof. Dr. Heinrich Häberlin hat hierzu einige klärende
Artikel verfasst, die in Fachmedien für Elektrotechnik und Feuerwehren publiziert wurden.
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Der PV - Normenbereich wurde 2011 ebenfalls bearbeitet. Dies durch Kontakte in der TK 82 und Kontakten mit Normenbehörden und –Fachleuten im In- und Ausland.
Eine Spezialität der BFH-TI ist das Hochspannungslabor. Der für den PV-Bereich relevante Teil wurde
2011 revidiert. Neu wird an allen PV- Praktikas eine Übung im Hochspannungslabor durchgeführt.
Dabei werden Aspekte des Blitzschutzes und der Vermeidung von Schäden durch Überspannungen in
PV-Anlagen bearbeitet. Dies soll 2012 noch ausgeweitet werden.
Neu: Off-Grid-Projekte
Der Bereich der dezentralen Stromversorgungen in Entwicklungsländern hat durch die Gründung des
IEM auch am PV-Labor der BFH-TI Einzug gehalten. Neben den „PV-Solarpumpen“ von Prof. Dr.
Andrea Vezzini sind vermehrt Projekte mit dezentralen Energieversorgungen an das PV-Labor herangetragen worden, so aus Indien, Madagaskar, Philippinen und Sumatra. Zur Ausbildung von PVFachleuten aus diesen Gebieten läuft aktuell eine Machbarkeitsstudie an der BFH-TI. In wie weit die
begrenzten Kapazitäten des PV-Labors eine Ausweitung und eine gesicherte Finanzierung erlauben,
wird die Zukunft zeigen.
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APPLICATION DE MODULES PV FLEXIBLES
SUR LE SITE DE PRODUCTION FLEXCELL
Annual Report 2011
Address
Date
VHF Technologie SA
Av. Edouard Verdan 2, 1400 Yverdon-les-Bains
024 423 08 90, [email protected], www.flexcell.ch
103202 / 154220
15.05.2009 – 31.12.2012
07.12.2011
ABSTRACT
The goal of this project is to develop, install and monitor various building integrated PV products and
installation s olutions bas ed on F lexcell’s t echnology o n t he b uildings of F lexcell’s pr oduction s ite in
Yverdon. The type of installation includes applications on insulated metal sandwich panels, on corrugated metal s heets, on gr avel c overed f lat r oofs, on bi tuminous f lat r oofs, and an appl ication as a
stand-alone roof.
During t he r eporting per iod, t he large 86. 4kWp roof appl ied on the s andwich p anels of t he s torage
hall (“stock”-site) was monitored for the second year of operation. Since the shut down of a part the
site in July 2010 due to quality problems, the installation produced according to the expected simulations for 1.5 years.
Two ne w s ites w ere i nstalled i n s ummer 2010 w here a main t echnological i mprovement w as i ntroduced to tackle an important reliability issue; the reliability of the contact film/copper ribbon. After 1½
years of monitoring the results are extremely positive and with the new technology this reliability issue
is considered as completely solved.
Further, during 2011, two new installations were added that set new important milestones for the development of the company: the first prototype of solar awning and the first site with tandem a-Si/a-Si
technology.
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Buts du projet
Sise à Y verdon-les-Bains, VH F-Technologies SA, développe, pr oduit et c ommercialise des m odules
solaires f lexibles connu s ous l a dénomination « Flexcell ». La technologie de dé position par plasma
haute f réquence de s ilicium a morphe en c ouches m inces s ur substrat pl astique initié à l ’IMT de
l’Université d e Neuchâtel est uni que a u m onde e t s ’adapte p articulièrement bien à la pr oduction de
module BIPV.
La diversité des toitures du site de production de l’usine Flexcell à Yverdon permet de réaliser différentes i nstallations ( de 1 à 85k Wp) pour at teindre u ne pui ssance PV i nstallée d e 1 32kWp. Les m odules F lexcell l égers s ’adaptent à d e nom breuses na ture de toiture: bac ac ier, panneaux s andwich,
membrane bi tumineuses et pol ymères. I ls s ont i nstallés s ans néc essairement r equérir d e s upport
spécifique, mais directement sur la toiture existante ou monté en remplacement de l’étanchéité.
Ce projet vise à caractériser les diverses modes d’installation et les différents type de modules photovoltaïques offert par cette technologie. Il s’agit plus précisément de :
1. Illustrer différentes nouvelles solutions BIPV
2. Etablir le détail des couts complets investis dans chaque toiture pv
3. Mesurer les productions d’énergie et calculer la performance de chaque site en fonction des
particularités architecturales et des spécificités des modes d’installations
4. Disposer d’un site démonstratif fonctionnel
ETFE
EVA
Film PV
EVA
Elément de toiture
Figure 1: décomposition de l'encapsulation d'un module Flexcell
En fonction du type de matériau ou d’élément de toiture utilisé à l’arrière (backsheet) on parle de produits du type :
•
TO : backsheet (1.8 mm en membrane base polyolefines - TPO)
•
MO : backsheet en Metal-TPO (0.6 mm en tôle zinguée + 0.6 mm de TPO)
•
EE: backsheet (0.1 mm en ETFE)
Les objectifs pour l’année 2011 du projet OFEN consistaient à procéder à la réalisation de plusieurs
installations, de tester d ifférents t ypes de produits et de technologie, à assurer l e s uivi é nergétique
des installations réalisées précédemment et à évaluer le rendement énergétique.
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Flexcell, F. Galliano, VHF-Technologies SA
2/8
Brève description des sites installés dans le cadre du projet OFEN
#1. Front End
Site de 9.45 kWp de MO sur toiture gravier. Installé en 2010 mais pas connecté pour raison liées à
l’exploitation du bâtiment du FE
#2. Admin 1 – Admin 2010
Site d e 4.3 kWp de TO posés sur t oiture gravier. Installé en aout 2 010, i njection da ns l e r éseau et
monitoring.
→ Nouvelle technologie de contact film/cuivre testée dans cette installation.
#3. Admin 2 – Admin 2010
Site de 4.3 kWp de TO posés sur toiture gravier. Installé en aout 2010 injection dans le réseau et monitoring.
→ Nouvelle technologie de contact film/cuivre et nouvelle pâte base Ag testée dans cette installation.
#4. Stock
Site de 86.4 kWp de MO vissés sur toiture en métal. Installé en 2009, reconfiguré après de problèmes
de qualité en juillet 2010, injection dans le réseau et monitoring.
#5. Garages
Site de 4. 7 kWp de MO vissés su r toiture en métal. Installé en 2 009, i njection dans l e r éseau m ais
sans monitoring.
→ Test d’onduleurs sans transformateurs avec la société Sputnik
#6. Poutrelles
Site de 7.3 kWp de MO vissés sur avant toit en métal. Installé en 2009, injection dans le réseau mais
sans monitoring.
#7. Bureau ingénieurs
Site de 2.4 kWp de TO posés sur toiture gravier. Installé en septembre 2010, injection dans le réseau
mais sans monitoring.
→ Nouvelle technologie de contact film/cuivre.
#8. Stand démo
Pas réalisé
#9. Bunker
Pas réalisé
#10. Halle prod
Pas réalisé
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#11. Chaufferie
Site de 3.8 kWp de TO posés sur toiture bitume. Installé en 2010 et déconnecté en janvier 2011 pour
de problèmes de connectique film/cuivre
#12. Garage vélo
Site de 1.6 kWp de MO vissés sur toiture métal. Installé en 2009, injection dans le réseau mais sans
monitoring
#13. Abri cafétéria
Site de 0.7 kWp de MO vissés sur toiture métal. Installé en juin 2010, injection dans le réseau mais
sans monitoring
#14. Store aile 18
Site de 0.3 kWp de EE soudés et intégrés à un store. Installé en mai 2011, injection dans le réseau et
monitoring
→ Nouveau produit (store solaire) né du développement Flexcell
#15. Atélier méca 1 – Admin 2011 TO
Site de 4.3 kWp de TO soudés sur toiture TO. Installé en septembre 2011, injection dans le réseau et
monitoring
→ Nouvelle technologie tandem a-Si/a-Si
#16. Atélier méca 2 – Admin 2011 EE
Pas réalisé
#17. Atélier méca -3 – Shading tandem/single
Site de 1.2 kWp de TO soudés sur toiture TO. Installé en novembre 2011, injection dans le réseau et
monitoring. Site destiné à de test d’ombrage partiel en 2012
→ Nouvelle technologie tandem a-Si/a-Si
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Figure 2: réalisation de l’abri cafeteria (site #13, haut à gauche), des garages (site #5, haut à droite),
du prototype TPO colle à chaud (site #11, bas à gauche) et des stocks (site #4, bas à droite)
#4
#5
#6
#7
# 13
# 14
#1
# 15
#3
#2
# 17
# 12
Figure 3: prise de vue aérienne du site Flexcell en septembre 2010 (pas de photo actualisée en 2011).
Les installations #14, #15, et #17 ont été réalisées pendant l’année 2011.
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Travaux effectués et résultats acquis
Stocks
La toiture des stocks a été la première réalisation dans le cadre de ce projet, avec la construction en
été 2009, et le branchement électrique en novembre 2009. Cette installation consiste de 864 modules
de type MO avec une puissance nominale de 100 Wp par module, vissés sur éléments sandwich métalliques du toit du bâtiment des stocks. La puissance nominale est donc de 86.4 kWp. Comme le toit
comporte deux orientations en quatre pans, deux onduleurs de 50 kW chacun groupent les strings est
et les strings ouest (72 strings de 6 modules pour chaque orientation) (voir Figure 2, section #4).
Suite à problème de f iabilité d u c ontact c uivre/film du à un c omposant p as ad apté, u ne partie de
l’installation a du être déconnectée (voir rapport OFEN 2010) pour arriver à 480 panneaux connectés.
La p uissance D C c onnectée de l ’installation a été d onc réduite. Pour é valuer correctement l a p uissance restante il faut considérer que la technologie Flexcell a suivi dans le temps une augmentation
de la puissance: les modules produits en 2009 étaient classés à 100 W (pour la taille 2s22p). En début 2010 ils s ont passés à 13 5 Wp pour m onter enc ore e n f in 2010 à 150Wp. T rès pr ochainement
(début 2012) ils devraient passer à 160W. Ceci dit les panneaux qui sont installés sur le stock ont été
produits juste avant la transition de 100Wp à 135Wp et présentent une puissance réelle plus proche
de 135W que de 100W. Pour cette raison, après déconnection de la partie plus ancienne de la toiture,
on peut considérer une puissance moyenne par panneaux de 135 Wp (à la place de 100 Wp) et par
conséquent une puissance totale de 64.8 kWp (480 x 135 Wp).
Sur toute l’année 2011, l’installation à injecté dans le réseau 66843 kWh (contre 70705 kWh en 2010)
(actualisé au 1.1.-15.12.), ce qui revient à un rendement énergétique de 1031 kWh/kWp (avec puissance de 135Wp/mod) ou 1160 kWh/kWp (avec une puissance de 120 Wp).
Si on tient compte de la simulation effectuée avec des modules de 135 Wp avec le logiciel PVSOL,
nous nous s erions attendus à une pr oduction de 59 994 kWh et un r endement éner gétique d e 927
kWh/kWp.
L’installation a produit donc en 2011 environ 11% de plus de la simulation et il est à noter qu’à nos
latitudes un rendement énergétique de 1031 kWh/kWp sur toiture pratiquement horizontale représente
un excellent résultat
Le PR se maintien a des excellent valeurs en 2011 comme en 2010, avec env. 90% en été à env. 60
% en hiver.
Admin 2010
La toiture ADMIN 2010 a été conçue pour :
• prouver que le problème de fiabilité du contact cuivre/film avait été réglé aussi pour les produits TO ;
• valider une nouvelle pate d’Ag avec performances accrues.
Au total 64 modules TO 2s22p ont été posés à plat sur une toiture gravier.
Ces produits, à vue de l’important coefficient de dilatation thermique du substrat (k d’une membrane
TPO est d’env. 100 um/(m*°C) ) présentent des contraintes sur le contact beaucoup plus accentuées
que l es pr oduits MO . Les efforts de c isaillement a u niveau d u c ontact f ilm/cuivre risquent de pr ovoquer la perte du contact électrique. Ce problème a été étudié en profondeur et un nouveau composant
a été validé qui permet de supporter ces contraintes sans aucune perte de contact.
Après une année la toiture ADMIN 2010 a donné des résultats satisfaisant avec 8368 kWh produits
sur 12 mois (aout 2010-juillet 2011), qui correspond à 972 kWh/kWp. Les valeurs de PR sont d’env.
85-88 % en été.
Aucun problème de perte de contact n’a été observé et cette technologie a été depuis implémentée en
production. Du même la nouvelle pate d’Ag a donné des résultats satisfaisant et a été, elle aussi, implémentée en production.
Cette toiture a été démontée en sept 2011 pour analyses et seulement une petite partie (16 modules
sur 64) a été réinstallée et injecte à nouveau.
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Production energie toiture stock (64.8 kWp)
12000
Energie AC (kWh)
10000
8000
2011
6000
2010
4000
2000
0
Janv
Févr
Mars
Avril
Mai
Juin
Juil
Août
Sept
Oct
Nov
Déc
Figure 4: énergie produite de l’installation « stock » en 2011 et 2010 jusqu’au 15.12.2011
(à partir du 07.11 puissance connectée = 64.8 kWp).
Performance ration toiture stock (64.8 kWp)
100.0
90.0
Perfomance ratio AC
80.0
70.0
60.0
2011
50.0
2010
40.0
30.0
20.0
10.0
0.0
Janv
Févr
Mars
Avril
Mai
Juin
Juil
Août
Sept
Oct
Nov
Déc
Figure 5 : PR de l’installation « stock » en 2011 et 2010 jusqu’au 15.12.2011
(à partir du 07.11 puissance connectée = 64.8 kWp)
AC performance ratio
100.0
Sol 1
Sol 2
Sol 1 - Dupont
90.0
80.0
AC perfomance ratio (%)
70.0
60.0
50.0
40.0
30.0
20.0
10.0
Figure 6: PR de l’installation « ADMIN 2010 » sur 12 mois
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sept.11
août.11
juil.11
juin.11
mai.11
avr.11
mars.11
févr.11
janv.11
déc.10
nov.10
oct.10
sept.10
août.10
0.0
Store aile 18
Un nouveau produit a été développé sur la base d’un module très souple (type EE) avec une construction s ymétrique bas ée sur l ’ETFE en 0.1 m m comme c ouche ex terne à l ’avant et à l’arrière du
module. Grace à la souplesse de cette construction un tel module est enroulable sur de diamètres > 5
cm sans aucune perte de fonctionnalité. Un procédé de soudure thermique a été optimisé pour pouvoir relier ensemble plusieurs produits du type EE 1s16p et l’élément obtenu a été intégré à un store
commercial. Les modules 1s16p ont été tous connecté en parallèle ensemble, pour pouvoir garder la
2
tension en dessous de 50V. Au final un store avec une surface de 2.5 x 3 m et 320 Wp a été installé
devant le bureau coté S de l’aile 18.
Depuis sa mise en service le 25.05.2011 le store a été sorti et rentré tous les jours ouvrables de beau
temps (environ 100 jours) et à produit 92.6 kWh ce qui corresponds à 289 Wh/Wp. Les valeurs de PR
sont très variables avec beaucoup de journée avec plus de 90%.
De tests effectués sur un store de test on permis de démontrer que après plus de 600 cycles de ouverture/fermeture du store (qui corresponds environ à deux ans de fonctionnement normale) la perte
de puissance mesurée ne dépasse pas le 14% attendu et qui dérive purement de la dégradation du
silicium amorphe. Aucun dégât supplémentaire a été causé par l’enroulement /déroulement
Store 1
1.05
1
Normalised Power
0.95
0.9
0.85
0.8
0.75
0.7
0.65
0.6
0
100
200
300
400
500
Nr of cycles roll/unroll
Figure 7: store solaire
600
700
Roll/unroll
Figure 8: évolution de la puissance avec le
cyclage d’un store
Admin 2011 TO
L’installation de 16 m odules TO av ec technologie tandem a -Si/a-Si (2.4 k Wp) et de 1 6 modules TO
avec t echnologie s ingle a-Si ( 2.4 k Wp) a ét é complétée en s ept 2 011 et c onnecté en oc t 2 011. Le
système de monitoring a été finalisé en nov 2011. A présent il est trop tôt pour évaluer les différences
entre les deux technologies.
Évaluation de l’année 2011 et perspective pour 2012
L’année 20 11 a per mis de réaliser trois installations supplémentaires : un n ovateur s tore s olaire et
deux installations TO de comparaison de technologie single et tandem. Maintenant tous les types de
module Flexcell (MO, TO et EE) sont installés et connectés sur le site Flexcell à Yverdon. Le rendement énergétique a été évalué sur plus d’un an avec des valeurs supérieures d’env. 10% aux simulations pour les modules MO et en ligne avec les simulations pour les TO sans aucun problème de fiabilité. Ceci permet à Flexcell d’utiliser ces installations comme vitrine pour des clients et d’autres intéressés dans la technologie BIPV de couche mince flexible.
L’année 2012 sera axée sur les analyses de production plus approfondies de toutes les installations
connectées.
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PHOTOVOLTAÏQUE ET NEIGE
HORIZON DES SOLUTIONS POUR
L’INSTALLATION SUR LES TOITS DANS
LES RÉGIONS ENNEIGÉES
Annual Report 2011
Address
Planair SA
Crêt 108, 2314 La Sagne
032 933 88 40, [email protected],
[email protected], www.planair.ch
SI/500568 / SI/500568-01
Duration of the project (from – to) 01.02.2011 – 30.07.2014
Date
15.11.2011
ABSTRACT
The educational project « PV and Snow » of the Secondary School Blaise Cendrars was installed
st
during the summer 2011 and inaugurated on October 21 , 2011.
Seven different photovoltaic fields and three snow clearing solutions were implemented. Measures
on different parameters such as production and consumption of each field will be occurred during the
winters of 2012, 2013 and 2014. The evaluation of the measures will enable us to determine snow
impact and compare:
• The different photovoltaic technologies (amorphous Flexcell’s cells, Bosch multicristallin cells and
Sanyo HIT cells),
• The different snow clearing solutions (Eulektra, Solutronic and Freso).
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Buts du projet
Le projet, en partenariat avec le canton de Neuchâtel, Viteos SA et Planair SA, se base sur une installation didactique sur les toits du Lycée Blaise Cendrars à La Chaux-de-Fonds.
Il est prévu de comparer la production de différentes technologies photovoltaïques dans les conditions
d’enneigement. Les différentes technologies ainsi que les systèmes de déneigement étudiés sont
répertoriés dans le paragraphe « technologies installées ».
La conception, l’installation des capteurs et des systèmes de déneigement se sont déroulés durant
l’année 2011.
Les mesures de productions/consommations des différentes technologies se dérouleront durant les
hivers 2012,2013 et 2014. L’évaluation de ces mesures sera effectuée au cours du mois de mai suivant l’hiver.
Brève description du projet / de l'installation
Technologies installées
Les technologies suivantes ont été installées sur le toit du Lycée Blaise Cendrars :
Technologie
Fabricant
Si Amorphe
Si Monocristallin
1
HIT Double
Si Polycristallin
Flexcell
Bosch
Sanyo
Trina
Puissance de
l’installation
1.35 kW p
1.41 kW p (x5)
1.47 kW p
1.41 kW p
Tableau 1: type de technologies des panneaux PV
La technologie amorphe a été choisie pour ses propriétés de sensibilité au rayonnement diffus, qui
devrait lui permettre de chauffer même avec une faible épaisseur de neige.
La technologie HIT Double a été choisie pour sa double couche photovoltaïque, qui devrait lui permettre de fonctionner et de monter en température par la réflexion de la lumière sur la neige environnante.
Les modules du fabricant Trina permettront de comparer la production de panneaux chinois et de
panneaux allemands de même puissance.
Les solutions de déneigement installées sur les différents champs de capteurs Bosch sont :
Type
Si Monocristallin,
1.41 kWp
Si Monocristallin,
2,82 kWp
Si Monocristallin,
1.5 kWp
Si Monocristallin,
1.5 kWp
Solution de déneigement
Sans déneigement
Solutronic (solution 1)
Eulektra (solution 2)
FRESO
(solution 3)
Remarques
Installation de référence
Inversion manuelle du courant dans les panneaux
Inversion automatique du courant dans les
panneaux
Application de polymère permettant de rendre
les surfaces hydrofuge.
Tableau 2: type de solution de déneigement (panneaux cristallins uniquement)
1
HIT : Heterojunction with Intrinsic Thin layer
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Photovoltaïque et neige, F. Bertrand, Planair SA
L’installation complète disposera de 8 champs d’environ 1.4 kWp chacun, soit une puissance totale
d’environ 11 kWp. La solution de déneigement Solutronic nécessite deux champs de capteurs : il n’y
a donc que 7 champs représentés.
Figure 1: vue d’ensemble de l’installation sur le toit du Lycée
Les 7 champs PV disposent de leur propre onduleur et d’un équipement de supervision (Solarlog)
permettant d’enregistrer les différents paramètres (production d’électricité, T° extérieure, ensoleille2
ment (W/m )).
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Aspect didactique
Les étudiants du Lycée Blaise Cendrars effectueront divers travaux d’études pratiques sur ces installations.
Différents documents ont été distribués au Lycée afin de suivre l’installation :
• protocole des opérations à effectuer,
• plan de mesure,
• tableaux de relevés.
Ces différents éléments permettront au personnel ainsi qu’aux élèves du Lycée de prendre part dans
le suivi et dans la marche optimum de l’installation.
Afin de communiquer sur l’installation, nous avons mis en place :
• un panneau didactique,
• un écran de visualisation en temps réel de la production électrique.
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Évaluation de l’année 2011 et perspectives pour 2012
L’intégralité de l’installation est à ce jour installée et en parfait état de fonctionnement afin de pouvoir
réaliser les mesures du premier hiver.
Les photos ci-dessous présentent l’installation :
Figure 2: capteurs Bosch avec et sans solution de
déneigement
Figure 5: capteurs Flexcell
Figure 4: capteurs Trina
Figure 6: capteurs Sanyo
Figure 3: local onduleurs
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Figure 7: panneau didactique
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SOLAR WINGS: MONITORING ZWEIACHSIGE
NACHFÜHRUNG – FLUMROC
Annual Report 2011
*F. Baumgartner, *N. Allet, °T. Hobi, °H. Kessler
°Flumroc AG, Flums
*ZHAW, Zurich University of Applied Science
Address
Technikumstrasse 9, 8401 Winterthur
Telephone, E-mail, Homepage 058 934 72 32; www.zhaw.ch/~bauf
SI/500466 / SI/500466-01
Date
01.08.2011
ABSTRACT
The performance of the 79kW PV plant, installed at the Flumroc AG site in Flums was measured and
analysed. This PV plant is based on the first two-axis Solar Wings tracking system, where the PV
module are mounted on module beams, 9 meters above the ground of the outdoor storage facility of
Flumroc. The DC power of a PV string, tracked by the Solar Wings system, was compared to the DC
output of a fixed flat-roof mounted PV string consists of the same number and type of monocrystalline silicon standard modules and the same 10kW PV inverter.
During the full first year of operation, from July 2010 till June 2011, a specific AC yield of the whole
system of 1360 Wh/Wp was measured (78.96 kWp nominal power including the 3.76 kWp of the fixed
reference system). This represents a 36% higher specific yield relative to the longtime average PV
yield of new large scale PV installations in Switzerland. Thus the yearly energy of this two-axis Solar
Wings System in Switzerland is in the same range like PV installations in southern Italy.
th
On the clear sky day 27 of June 2011 a detailed performance analysis shows 27% higher measured
DC power of the tracked modules compared to the fixed mounted reference system on the DC input
connectors of the inverter. The measured DC current at MPP of the tracked PV string was even 43%
higher before noon and only 19% higher in the second half of the day. This additional loos of energy
yield was found to be clearly attributed to the shading effects from the nearby high voltage transmission line, occurring in the afternoon. Total yearly losses of shading are estimate to about 4% only for
the tracked PV modules. Very high DC losses of about 4% were found for the tracked modules. The
measured gain in DC power due to tracking was 14% between Jan and June 2011. Without these
additional effects of local shading due to the power transmission line and without the higher DC cable
losses a gain of 22% due to tracking, was analysed for that two axis Solar Wings Plant.
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Dieses Projekt hat die Performanceanalyse des zweiachsig, seilbasierten Solarnachführsystem Solar
Wings zum Ziel, welches bei der Flumroc AG, Flums von der Firma Bartholet AG, Flums installiert
wurde. Dieser Bericht ist der Endbericht und analysiert die Messergebnisse in der Periode Juli 2010
bis Juni 2011. Die Erkenntnisse aus dem Zwischenbericht, mit Stand Dezember 2010, werden zitiert
aber hier nicht erneut dargelegt.[1]
Anlagenkonzept
Der Auftraggeber, Flumroc AG hat die Realisierung des ersten Solar Wings Kraftwerks mit zweiachsiger Nachführung auf dem Aussenlagergelände der Flumroc am Standort Flums in Auftrag gegeben.
Dieses Solarkraftwerk wurde Anfang 2010 gebaut und die Netzeinspeisung erfolgt seit März 2010.[1]
Die Forderung des Auftragsgebers mit dem Bau der Anlage auch den Doppelnutzen, der Solarstromereugung und des ungestörten Betriebs des Warenverkehrs mit LKW unterhalb der Solaranlage, ansprechend zu demonstrieren, bedingte die Beschattungswirkung durch die Hochspannungsleitung.
Referenz fix 30°
Tracking System
Abbildung 1: Links oben, Blick auf die Zufahrtstrasse Aussenlager, unterhalb des zweiachsigen Solar W ings
Kraftwerks der Flumroc AG. Je zehn Modulträger, mit jeweils 8 Solarmodulen, sind im Intervall von 3.2m auf den
Tragseilen z wischen den Z wischenstützenträgern m ontiert, w elche im A bstand von 35m platziert w urden. Das
obere r echte B ild, z eigt auc h da s zusätzliche R eferenzmesssystem, w elches oh ne Nachführung auf dem
benachbarten Hallendach installiert wurde. In der zweiten Bilderreihe ist der Tageslauf der Modulorientierung, von
Sonnenaufgang ( -30° Neigung der T räger zur Waagrechten nac h N ordost) bi s a bends siehe letztes Bild (-35°
Neigung der Träger nach Südwest).
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Monitoring Solar Wings Tracking System, F. Baumgartner, ZHAW 2011
Das PV Systemdesign bestand während der Messperiode aus dem Teil der Anlage mit 75.2 kW
(40x8x235Wp) nachgeführter kristalliner Silizium Solarmodule (Sharp NU-E235), während 3.8kW fest
auf dem benachbarten Hallendach als Referenz der Messung installiert waren (Abb. 1). Um den Einfluss der AC-Stromertrag durch Abschattung des Hochspannungsmasten zu minimieren wurde nicht
ein Zentralwechselrichter, sondern sieben einzelne dreiphasige Wechselrichter mit einer Nennleistung
von je 10kW (Sunways NT 10000) installiert.
Alle zehn Minuten erfolgt über eine chronologische Vorgabe die Nachführung der Module nach vorher
berechneten Jahresprogramm. Diese Modulnachführung wirkt mittels einer SPS Steuerung und der
Antriebsmotoren, die am Ende der Längssteuerseile und der Hauptquerbalken kraftschlüssig montiert
sind.
Das Messsystem
Technische Details zur eingesetzten Messtechnik, wie auch deren Kenngrössen für die zugeordnete
Messunsicherheit, sind im Zwischenbericht dargelegt. Jede Minute werden dazu die nachfolgenden
Messdaten aufgezeichnet:
• Je eine Strangspannung, für fix montierte und nachgeführte Solarmodule (zwei Modulbalken
Nr. 5 und 6, Nummerierung startet auf Südost Seite des PV Kraftwerks)
• Je ein Strangstrom fix montierter und nachgeführter Module (Modulwahl wie oben)
• Temperatur fix montierter und nachgeführter (wie oben) Module (gemessen mit PT100 Sensor
auf der Modulrückseite)
• Jeweils die Solarstrahlungsleistung mit Siliziumsensor (Spektron 310), gleicher Ausrichtung wie
die fest mit 30° nach Süden orientierter Module, sowie eines zweiter Siliziumsensor der auf den
nachgeführten Modulbalken montiert wurde.
In der Hälfte des Messjahres, Ende Dezember 2010, wurde als Referenzstrang für die DC Messung
das nachgeführte System, von der Mitte der Anlage, Strang 15 auf die Südseite zu Strang 1 verschoben um die dort vorherrschende Abschattungsverhältnisse durch die grössere Entfernung zum Hochspannungsmasten zu verifizieren. Ebenfalls wurde damit der Referenzsensor von der Mitte der Anlage
zum Strang 1 verschoben. (Vergleiche Abb. 3 im Zwischenbericht [1])
Messergebnisse
Mit dem Standardstromzähler des lokalen EW wurden 1360 kWh/kWp Wechselstromerträge, für das
vollständige Messjahr, von Juli 2010 bis Juni 2011, ermittelt. (siehe Tab. 1) Damit liegt diese spezifische Ertragskennzahl um 38% über dem spezifischen langjährigen Schweizer Durchschnittsertrag von
980 kWh/kWp für neue PV Anlagen grösser 30kW Nennleistung.[2] Bezogen auf den gesamten
Durchschnitt aller Anlagen in der Schweiz, entspricht dies sogar einem Mehrertrag von über 60%.
Damit hat die zweiachsig nachgeführte Solar Wings Anlage in Flums Jahresstromerträge produziert,
wie sie für Süditalien für nicht nachgeführte Anlagen erwartet werden.[3]
Der spezifische Jahresertrag der hier untersuchten Anlage, unterscheidet sich somit um etwa 4% vom
Jahresertrag, des ersten einachsigen Solar Wings Kraftwerks an der Nordgrenze der Schweiz, was
somit noch innerhalb der Messunsicherheit liegt. (Tab. 1) Die Daten beziehen sich auf den gleichen
Beobachtungszeitraum, wobei aber die unterschiedlichen Einstrahlungsbedingungen der Standorte
beachtet werden müssen. Dieser erste 650kW Solar Wings Solarkraftwerk, wurde auf einem 22° nach
Süd geneigten Hang einer Mülldeponie in Waldshut, ebenfalls als seilbasiertes aber einachsiges
Nachführsystem installiert (der Winkelstellbereich zur Seilrichtung beträgt beim Kraftwerk Waldshut
ebenfalls +/-45° wie in Flums auch). [4, 5]
Nachfolgend werden die Gründe, warum die zweiachsige Nachführung in Flums keinen deutlichen
Mehrertrag gegenüber der einachsigen Solar Wings Anlage in Waldshut hat, auf Basis der hier ermittelten Messdaten analysiert und entsprechend der nachfolgenden Einflussfaktoren diskutiert:
1. Die Anlage in Waldshut ist vollständig ohne externe Abschattung, wobei jene in Flums massive
Abschattungen durch die benachbarte Hochspannungsleitung im Südosten aufweist.
2. Die Seilausrichtung verläuft entlang der Zufahrtstrasse zum Freilager, welche parallel zur Hochspannungsleitung Richtung Südost verläuft und nicht optimal Ostwest orientiert ist. Am späten
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Nachmittag im Sommer kann somit keine senkrechte Einstrahlung auf die Modulebene mehr erzielt werden, da der Neigungswinkel der Hauptbalken auf 35° begrenzt ist.
3. Die DC Spannungsverluste auf der DC Leitung in Flums sind deutlich höher, da die Wechselrichter anders wie in Waldshut nicht direkt am Masten der Nachführung sondern ca. 300 Meter entfernt von der Anlagenmitte im Gebäude installiert sind und die Leitungsquerschnitte knapp bemessen wurden.
4. Dem Standort in Flums ist ein natürlicher Horizont gegeben, der im Westen einen Abschattungswinkel von ca. 22 Grad durch Berge (Juni Sonne erst ab 10 Uhr) und im Westen von 12°. (Die
Energieprognose vom renommierten europäischen Forschungsinstitut JRC [3] liefert für den
Standort Flums mit 30° Süd Orientierung inkl. natürlichem Horizont 1040kWh/kWp und 1230
kWh/kWp für unbegrenzte, zweiachsige Nachführung aber ohne Beschattungsgrenzen durch lokale Nachbarmodule. Potential der maximalen Ertragssteigerung an diesem Standort, durch
zweiachsiges Tracking gegenüber fixer Südorientierung, beträgt 19%
Der Vergleich der DC Erträge von nachgeführt und fest am Dach installiert, auf der Basis der vorliegenden Messung von jeweils einem String, gestaltet sich aufgrund der Unterschiede der lokalen Beschattung durch den Hochspannungsmasten als schwierig. Dies ist deutlich in Tab. 1 zu erkennen wo
die Stromerträge des AC Zähler durch die von einem Referenzstrang auf alle 20 Stränge hochgerechnet DC Erträge dargestellt sind. So unterscheidet sich dieses Verhältnis im Juli, Aug 2010 zu jenem
von Mai Juni 2011, bei ähnlicher Sonnenhöhe um bis zu 7%. Die Ursache liegt in der anderen Wahl
des Referenzstranges und die damit verbundene andere Wirkung der Abschattung durch die Hochspannungsleitung. Dies bedingt, dass diese Vergleiche über grössere Zeiträume nicht zielführend
scheinen und daher in der Folge auf die Betrachtung von Detailanalysen an schönen Tagen mit bekannten Abschattungsverhältnissen gemacht wird. Der DC Mehrertrag im Halbjahr 2011 beträgt energiegewichtet etwa 14% wobei die höheren DC Verluste der Nachführung zu beachten sind.
Tabelle 1: Ertragswerte des zweiachsigen Solarnachführsystems der Flumroc AG bezogen auf die gesamte PV
Nennleistung von 78.96kW wovon 3.76kW als Referenzsystem fix auf dem Dach des benachbarten Betriebsgebäudes installiert s ind. D ie A C E rträge w urden al s Messwerte d er Standardstromzählers aus d er S tromabrechnung der gesamten Anlage des EW übernommen (Landis & Gyr 1%, Industriezähler). Die erzielten Monatserträge
sind mit jenen der einachsigen Solar Wings Anlage in Waldshut verglichen.[6] Die unter Flums spez. DC tracking
geführten Daten, sind die Energieerträge des nachgeführten Strangs. Er wurde Ende Dez. 2010 von der Mitte der
Anlage (Strang 15) ans südliche Ende, auf Strang 1 versetzt, mit anderen Abschattungsverhältnissen. Die Angaben zum Tracking M ehrertrag gan z r echts be ziehen s ich a uf den D C- Leistungs- und D C-Strangstromverlauf.
(vgl. Abb. 2 u 5), da der Einstrahlungssensor Pin fix nicht immer ein stabiles Signal geliefert hat.
Monat
Jul 10
Aug 10
Sep 10
Okt 10
Nov 10
Dez 10
Jan 11
Feb 11
Mrz 11
Apr 11
Mai 11
Jun 11
Summe
Flums
Flums
Waldshut
Flums
Flums
TagesTracking Tracking
AC Ertrag spez. AC spez. AC spez. AC spez. DC PAC/ einstrah- MehrMehrPDC lung
Monat
Monat
Monat
Tag
Tag
ertrag Idc ertrag Pdc
kWh kWh/Wp/m kWh/Wp/m kWh/Wp/d kWh/Wp/d
kWh/m2/d
13767
174.4
185.2
5.62
5.97 0.94
7.23
121%
115%
9435
119.5
146.8
3.85
4.01 0.96
4.14
110%
108%
9494
120.2
140.4
4.01
4.11 0.98
4.82
115%
113%
7481
94.7
86.9
3.06
3.07 0.99
3.84
105%
103%
3839
48.6
36.4
1.62
1.67 0.97
2.45
2525
32.0
21.8
1.03
0.86
4568
57.9
30.1
1.87
2.12 0.88
2.24
107%
106%
5877
74.4
57.2
2.66
3.09 0.86
2.78
112%
111%
10842
4.43
4.73
0.94
4.69
137.3
137.2
115%
113%
14466
183.2
197.9
6.11
6.43 0.95
6.35
120%
118%
14045
177.9
210.3
5.74
5.62 1.02
6.57
116%
113%
11056
140.0
161.8
4.67
4.52 1.03
4.75
115%
113%
107395
1360.1
1412.0
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Abbildung 2: Detailergebnis für den 27.6.2011 mit den Minutenmesswerten der Einstrahlungsleistung des nachgeführten Siliziumsensors Pin_track (blau), sowie die beiden Strangströme des nachgeführten Strings Idc_track
(rot) und des fix montierten Strings Idc_fix (grün). Die jeweiligen Ursachen für die Ertragsreduktionen sind in der
Grafik beschrieben.
Mast
Isolator
Leitung
Abbildung 3: Darstellung des Einflusses der Beschattung durch die benachbarte Hochspannungsleitung mit
Nordpfeil (siehe auch Abb. 1) Links ist der Abstand des Hochspannungsmasten mit 20 M eter bis zum Rand der
Solaranlage dargestellt, sowie die Trajektorien der Länge des Schattens während dem 15 Juni, für
unterschiedliche Höhen auf dem Masten. (Der Abstand der Stützen beträgt 35m) Rechts ist der Schattenwurf des
Hochspannungsmasten, der Isolatoren am Mast und i m äus sersten r echten T eil, für die Hochspannungsleitung
selbst dargestellt.
Die Summe der gemessenen Einstrahlung war am 27.6.2011, für den Sensor der nachgeführten Module um 29% höher, als die Werte für den fest montierten Sensor. Wenn die Sonne um 6 Uhr morgens über den Gebirgszug im Osten steigt, herrscht sogleich eine Einstrahlungsleistung von über
2
750W/m , ein Wert den die festmontierten Module erst drei Stunden später erreichen. Von 6 Uhr bis
12 Uhr ist die leichte Zunahme der Strahlungsleistung, des nachgeführten Sensors und des Strangstroms für den nachgeführten Teil der Anlage, synchron. Der Strangstromverlauf gehorcht für das
konventionelle Referenzsystem auf dem Hallendach, dem bekannten Verlauf, wobei fast keine Einbrüche durch Wolken, auch nicht am Nachmittag erkennbar sind. Ab 13 Uhr zeigt hingegen die Sensorcharakteristik sieben steile Einbrüche um jeweils ca. 10%, die von den Schatten der einzelnen
Hochspannungsleitung, nicht des Hochspannungsmasten, hervorgerufen werden (siehe Schattenbild
in Abb. 3 rechts). Diese Schattenlinien der Hochspannungsleitungen kreuzen während des ganzen
Nachmittag jenen Strang (zwei Modulträger), der zur Messung Modulstroms eingesetzt wurde, wodurch sich ein ca. 10% Einbruch desselben ergibt. Ab 16 Uhr erfolgt ein zusätzlicher massiver Einbruch des Strangstroms, da dann der Schatten des Hochspannungsmasts (siehe Abb. 3 links), die
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zwei Modulträger in der Mitte des südöstlichsten Feldes erreicht hat. (andere Abschattung in Anlagenmitte, siehe Abb. 3 in [1])
Im Tagesmittel erreichte der Gleichstrom des nachgeführten Strangs für diesen 27. Juni 2011 einen
Mehrertrag von 31%. In der Zeit vor 12 Uhr ist der Mehrertrag sogar 43%, wobei er am Nachmittag
durch die oben beschriebenen Abschattungseffekte der Hochspannungsleitung bzw. –mast auf 19%
Mehrertrag abgesenkt wird. (Leistung siehe Abb. 5) Das Verhältnis der Strangströme entspricht eher
dem realen Energiegewinn durch Tracking, da so lokale Sensor-Abschattungen ausgemittelt werden.
Selbstverständlich ist zu beachten, dass obige Reduktionen der Effizienz der Nachführung, bzw. Steigerungen, falls die Abschattung nicht vorliegt, keine Jahresmittelwerte sind, sondern nur für diese
wolkenlosen Tage gelten, die in der Schweiz, zum Unterschied zu Südeuropa, nicht häufig auftreten.
Die Analyse der Gleichspannungen der beiden Stränge zur Mittagszeit zeigt in etwa den gleichen
Wert von 405V (siehe Abb. 4). Gleichwohl erreichen dann die nachgeführten Module auf der Modulrückseite Temperaturen von ca. 45°C. Zur gleichen Zeit zeigen aber die Module die auf dem Dach
montiert sind eine um etwa 18°C höhere Temperatur, was auf die ausgezeichnete Kühlung der auf
den Seilen montierten Module zurückzuführen ist. Wird die Modultemperatur mit der produzierten Leistung gewichtet, so ergibt sich eine mittlere Tagestemperatur von 53°C für die fest montierten und 13°C
weniger für die nachgeführten Module. Mit dem vom Hersteller angegebenen Temperaturkoeffizienten
für die Leistung, von -0.485%/°C für diese monokristallinen Siliziummodule (Sharp, NU-E235) ergibt
sich eine um 6.4% höhere Leistung der nachgeführten Module, aufgrund der geringeren mittleren
Modultemperatur an diesem Hochsommertag.
Entsprechend Abb. 2 stimmt um 12 Uhr auch der Modulstrom nahezu überein. Daher kann mit dem
vom Hersteller gegebenen Temperaturkoeffizient der Spannung von -0.35%/°C, auf eine Differenz der
Strangspannung von 25V geschlossen werden, oder 6% des Wertes. Dieser Wert entspricht in etwa
jenem Wert der Strangspannungsdifferenz, wie sie in der Detailanalyse im Zwischenbericht angegeben ist.[1] Dies kann nur mit einem drastisch höheren Spannungsabfall auf den langen DC Leitungen
(ca. 500m für Hin- und Rückleitung ) zwischen den Modulträger und den in der Halle installierten Inverter zugeschrieben werden.
Im Tagesmittel erreichte die DC Leistung des nachgeführten Stranges für diesen 27. Juni 2011 einen
Mehrertrag von 27%. (siehe Abb. 5) Der obige Mehrertrag des Strangstroms von 31% wird also durch
die Spannungsverluste auf den DC Leitungen auf 27% reduziert. (Messunsicherheiten ca. +/-2%)
Abbildung 4: Detailergebnis für den 27.6.2011 mit den Minutenmesswerten der beiden Temperaturen der Module sowohl nachgeführt Tmod_track (rot), sowie der Temperaturdifferenz, bzw. typischen Temperaturerhöhung der
fest m ontierten Module T mod_fix. D ie ebe nfalls d argestellten Messergebnisse d er bei den gem essenen S trangspannungen an den Klemmen des Wechselrichters, stimmen zur Mittagszeit nahezu überein.
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Abbildung 5 : Detailergebnis f ür den 27. 6.2011 m it den Minutenmesswerten der be iden Gleichstromleistungen,
sowie der Temperaturdifferenz der fest montierten gegenüber den nachgeführten Modulen.
Fazit der Messergebnisse die den Leistungsgewinn durch Tracking betreffen :
•
Abschattung im Juni des südlichen Teils der Anlage:
Die Messung am wolkenlosen Sommertag 27.6.2011 zeigte eine Reduktion des Leistungsgewinns durch Tracking von 43% auf 31% Mehrertrag im Strom, aufgrund der Abschattung
durch die Hochspannungsleitung im südlichen Bereich der Anlage. (siehe Abb. 2) Der gemessene DC Mehrertrag betrug an diesem Tag 27%. Die Temperatur der Solar Wings montierten
Modul war zur Mittagszeit 18°C geringer wie die Dachanlage.
An diesem wolkenlosen Junitag 27.6.2011 war die energiegewichtete mittlere Modultemperatur, für die mit Seilen montierten Module um 13°C geringer, als jene auf dem Flachdach. Daraus würde sich ein Energiegewinn von 6.5%, aufgrund der optimalen Kühlung durch die Solar
Wings Montage an diesem Sommertag ergeben, wie er typisch für Standorte in Südeuropa ist.
•
Abschattung im Juni des mittleren Teils der Anlage:
Die Referenzmessung am 23. Juni 2010, ein ebenfalls wolkenloser Tag, zeigt für den mittleren
Anlagenteil (siehe Anmerkung zum Messsystem betreffend Verschiebung des Referenzstrangs) nahe dem Hochspannungsmasten, keine drastischen Abschattungen durch die
Hochspannungsleitungen, obwohl der Sonnenstand fast identisch zu oben ist. (siehe Abb. 3 in
[1]) Die grosse Sonnenhöhe ergibt noch keine Beschattung durch den nahen Hochspannungsmasten. Der DC Leistungsgewinn lag an diesem Tag bei 26%. [1]
Die Temperatur der Solar Wings montierten Modul war zur Mittagszeit 10°C geringer wie die
Dachanlage. Aus dem Detailvergleich der beiden Juni Tag 2010 und 2011 haben sich jeweils
die gleichen DC Tagesgewinne ergeben, obwohl die Messungen der Modultemperaturdifferenz sich um 8°C unterschied, vermutlich durch den Einfluss der lokalen Windsituation.(Auch
die Langzeitstabilität der Haftung des Temperatursensors kann hier einen Einfluss haben.)
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•
Abschattung im August des mittleren Teils der Anlage:
Aufgrund der niedrigeren Sonnenhöhe erfolgt in dieser Jahreszeit eine deutliche Abschattung
am Nachmittag durch den Hochspannungsmasten (siehe Tab. 2 in [1]) Die relativen Leitungserträge, des durch den Masten abgeschatteten Strangs, sind dann bis zu 80% geringer. Dies
würde für die gesamte Anlage eine Minderung der Leistung um ca. 8% für die Zeitdauer der
Abschattung ergeben. [1]
•
Fazit Abschattung:
Sie variiert sehr stark nach Position der Anlage und der Jahreszeit aufgrund der komplexen
Struktur des Schattenwurfs durch den Hochspannungsmast und den Hochspannungsleitungen.(siehe Abb. 3 links ) Sie wird auf 4 bis 6% geschätzt.
•
Spannungsabfall:
Aus der Analyse der Modultemperaturen und der Strangspannungen um die Mittagszeit, wird
ein sehr hoher Spannungsabfall von 6% auf der DC Leitung für den nachgeführten Anlagenteil
ermittelt. Die nicht nachgeführte Dachanlage hat deutlich kürzere Leitungslängen und damit
typische DC Spannungsverluste von etwa 1%. Auch die Analyse im Zwischenbericht [1] hat
überhöhte DC Spannungsabfälle von 5% für Aug. 2010 ermittelt.(siehe die dortigen Bemerkungen zu den Kabeln, Seite 5)
•
Weitere geringfügige Ertragseinbussen:
Weitere eher geringfügige Ertragseinbussen erfolgen, wenn die Anlage zu Demonstrationszwecke bei Werksführungen für die Besucher bewusst aus der optimalen Orientierung gefahren wurde. Im März 2011 musste ein Antriebsmotor eines Querträgers gewechselt werden,
wodurch die Nachführung für ca. eine Woche nicht in Betrieb war, aber die Stromproduktion
selbstverständlich in konstanter Ausrichtung erfolgte.(kein Mehrertrag)
•
Einfluss des Referenzsystem auf dem Hallendach:
Ein gleichwertiger Vergleich von nachgeführtem und fix installierter Dachanlage darf nicht nur
eine einzelne Modulreihe beinhalten. Optimal müsste sich die gleiche Leistung beinhalten, also mehrere Modulreihen hintereinander anordnet sein. Daraus ergeben sich dann aber auch
Abschattungsverluste der auf einem Flachdach installierten Modulreihen zu Sonnenaufgang
und Sonnenuntergang, der ca. 3% beträgt (für einen typischen Reihenabstand bzw. Abschattungswinkel von 20%.
Weiteres ist bei einer einzelnen Modulreihe, wie hier verwendet, auch der grössere lokale Albedo, der verstärkten lokalen Reflexion durch das Kiesdach zu beachten.
Zusammenfassung - Endbericht
Die Performance des zweiachsig nachgeführten 79kW Solarkraftwerks, welches, auf der Basis der
Solar Wings Seilmontage realisierter wurde, betrug 1360 kWh/kWp für das untersuchte vollständige
Betriebsjahr, Juli 2011 bis Juni 2010. Dieser ins öffentliche Stromnetz eingespeiste Ertrag ist um 36%
höher als das Langjahresmittel, der von mit fest installierten neuen Grossanlagen in der Schweiz,
erreichten Erträgen.
An wolkenlosen Sommertagen sind typische ca. 27% Mehrerträge der Gleichstromleistung, am Wechselrichter Eingang, gemessen worden. Die Mehrerträge der nachgeführten Solarmodule, zu den fest
am Dach installierten Modulen, betragen für den Strangstromvergleich 31%, was auf 4% höhere Verluste durch die DC-Zuleitungsverbindung der nachgeführten Anlage schliessen lässt. Beim Vergleich
von zwei gleichwertigen Anlagen, sollten diese Werte identisch sein, was den hier gemessenen Mehrertrag unterschätzt.
Aufgrund der exzellenten Hinterlüftung der Solarmodule die in eine Höhe von 8 Metern über Boden
montiert sind, wurden an Sommertagen zwischen 10°C und 18°C° geringere Temperaturen um die
Mittagszeit gemessen. Auf die Stromproduktion bezogen entspricht dies einer Differenz von mittleren
4 bis 6°C über den Tag, was einem Leistungsgewinn von ca. 2 bis 3% bezogen auf fix aufgeständerte
Dachanlagen bedeutet.
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Die Abschattung durch die Hochspannungsleitung führt, jeweils am Nachmittag zu Verlusten, dann
wenn die Nachführung an klaren Sonnentagen den Mehrertrag gegenüber fix montierten Solarsystemen erzielt. Beispielsweise wurde im August an klaren Sonnentagen eine Minderung des Mehrertrags
von ca. 8% am Nachmittag gemessen (siehe Tabelle 2). Daraus wird eine Minderung des zusätzlichen
Trackergewinnes von täglich 4% abgeschätzt.
Fazit: Soll bei zukünftigen Installationen maximaler Ertrag erzielt werden, muss strikt auf einen abschattungsfreien Standort geachtet werden. Die Nähe zu Hochspannungsmasten und die Ausrichtung
der Leitungen kann zu deutlichen Ertragseinbussen führen, auch für nicht nachgeführte Anlagen.
Im Halbjahr 2011 wurde an diesem System ca. 14% Mehrertrag gegenüber dem fest montierten Referenzdach ermittelt. Ohne Abschattung durch den Hochspannungsmasten (ca. 4% Einbusse) und ohne
erhöhte DC-Leitungsverluste (ca. 4% Einbusse) wäre ein Tracking-Mehrertrag von ca. 22% für dieses
Solar Wings System am Standort Flums möglich.
Das zweiachsige Solar Wings Nachführsystem könnte allerdings noch deutlich mehr erwirtschaften,
wäre es nicht durch äussere Einflüsse, der Einbettung in die bestehende Bausituation bzw. Bergschatten – natürlichen Horizont begrenzt. Diese Verluste sind im Einzelnen:
• Würden die Tragseile nicht wegen der Zufahrtstrasse nach Süd-Ost orientiert sein, könnte
ebenfalls ein höherer Mehrertrag erzielt werden, da dann der Back-Tracking Modus reduziert
werden könnte, was zu Mehrerträgen von bis zu ca. 3% führen könnte
• Abschattung durch die nahe Bergkette im Nordosten und im Südwesten ca. 6%
• All die hier ermittelten Messwerte basieren auf einem unbeschatteten fix installierten Referenzsystems auf dem Industrieflachdach. Für einen gleichwertigen Vergleich müsste für grössere
Referenzanlagen eine typische lokale Reihenverschattung von ca. 3% abgezogen werden.
Es ist eine Tatsache, dass mittelfristig, wenn im öffentlichen Stromnetz, die photovoltaischen Erzeugungsanteile im Jahresvergleich bei etwa einem Zehntel liegen, an den verbrauchsschwachen Wochenenden, gerade um die Mittagszeit, ein Überangebot vorliegen wird.[7] Dann würden fest konventionell, ausgerichtete Solaranlagen Abschaltungen vornehmen müssen oder den Strom speichern,
was erst langfristig lokal zu günstigen Kosten möglich wäre. Dem stehen geringere Mehrkosten für die
Nachführung von Photovoltaikanlagen gegenüber, die dann in den Morgen- und Abendstunden (Abb.
2) ihre Mehrerträge noch unlimitiert einspeisen können und im Jahresmittel weniger Reduktion der
Solarstromproduktion durch Netzlimite, erfahren werden.
Referenzen
[1] Hugo Kessler, Nicolas Allet, Franz Baumgartner; BFE Jahresbericht Photovoltaik 2010; „SOLAR WINGS: MONITORING
ZWEIACHSIGE NACHFÜHRUNG – FLUMROC“; www.bfe.admin.ch/forschungphotovoltaik; Autor S. Nowak, Oberholzer
bzw. Hinweis auf diese Projekt auch auf Seite 263 in „Energieforschung Schweiz BFE 2010“, Autor Dr. Rolf Schmitz BFE;
www.energieforschung.ch / www.recherche-energetique.ch
bzw. download auch unter http://www.flumroc.ch/downloads/solar/BFE_bericht_de.pdf
[2] T. Hostettler, "Solarstromstatistik Schweiz 2009“; SEV Bulletin 05/2010; Seite 13
[3] Ertragsprognose mit dem Web-Rechner der EU Forschungsstelle, JRC Ispra; http://re.jrc.ec.europa.eu/pvgis/
Elektrizitätsertrage in Palermo 1400kWh/kWp, in Rom 1260kWh/kWp, jeweils 30 Grad Neigung nach Süd.
[4] F. Baumgartner, A. Büchel, R. Bartholet; 25th European Photovoltaic Solar Energy Conf. and 5th World Conference on
Photovoltaic Energy Conversion, Proceedings; Valencia; Spain; 6- 10 Sept 2010;
“Cable-based Solar Wings tracking system: two-axis and progress of one-axis system”
[5] F. Baumgartner; ep Photovoltaik – Jan 2010, S38-42; Hamburg; Germany; 21- 25 Sept 2009;
„Solar Wings – Skilifttechnik für die Modulnachführung“
[6] Öffentlicher Zugang zu den Messdaten des einachsigen Solar Wings Kraftwerks in Waldshut, Lonza Solarpark unter
http://www.sunways-ise.solar-monitoring.de
[7] F. Baumgartner, T. Achtnich, J. Remund, S. Gnos and S. Nowak; PROGRESS IN PHOTOVOLTAICS: RESEARCH AND
APPLICATIONS; Prog. Photovolt: Res. Appl. (2010); DOI: 10.1002/pip.1047
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AUTONOMOUS CLEANING ROBOT FOR
LARGE SCALE PHOTOVOLTAIC POWER
PLANTS IN EUROPE RESULTING IN 5%
COST REDUCTION OF ELECTRICITY
(EU-PROJECT PV-SERVITOR)
Annual Report 2011
Address
Date
H. Häberlin, Ph. Schärf and L. Borgna
Berner Fachhochschule, Technik und Informatik, Burgdorf
Jlcoweg 1, CH - 3400 Burgdorf
034 426 68 11, [email protected], www.pvtest.ch
PV-Servitor 232062 (www.pv-servitor.eu)
01.09.2009 – 31.08.2011
14.01.2012
ABSTRACT
Purpose and goals of the PV laboratory of BFH-TI in this project during 2011
- Ongoing coaching for the project partners in PV systems technology.
- Neutral assessment and documentation of the results and effectiveness of cleaning tests with PVServitor research robots built by the project partners MRU, DTI and Profactor doing the development part
in this project. Assessment, quantitative measurements and documentation of cleaning effectiveness of
robot prototypes B and C cleaning polluted PV modules during field tests.
Most important results in 2011
- Coaching of and consulting for project partners in PV systems technology.
- First cleaning tests with prototype B with basic functions (moving and cleaning) at BFH-TI’s PV test plant
in Burgdorf in March 2011 and at an i mproved prototype B on A pril 11 th and 12 th, 2011 with participation
of all project partners and representatives of the EU. With slow moving speed and appropriate revolution
speed and sufficient use of water, cleaning results were acceptable and nearly as good as with manual
cleaning, however the robot weight was too high.
- Based on t he results with prototype B, an improved prototype C was developed by the project partners,
which according to the project goals had to be abl e to clean a typical inclined free-field plant with a total
module length of 3.2m from the highest to the lowest point of the module rows. As it was difficult to find a
sufficiently polluted PV free-field PV plant in Germany, it was decided to perform the final cleaning test at
a remote plant in western Spain with clearly visible pollution.
- As it was difficult to bring all our specialised measuring equipment, which is not especially designed for
easy transportation, down to the remote test location in Spain, it was decided to assess the cleaning efficiency i n a m ore s imple w ay (string c omparison method). With t his method t he c urrents of t wo parallel
strings connected to the same inverter are compared before and a fter cleaning of one of the two strings
(the other string remains uncleaned).
- An as tonishing r esult w as t he f act t hat at t he P V pl ant i n S pain ( about 3 y ears ol d) c leaning o f P Vmodules with clearly visible pollution only increased their power in the order of about 3% compared to up
to 10% at many older plants in Switzerland. This is due to the fact that the kind of pollution seems to be
different (light and small bright particles instead of dark gray to black pollution at those plants in Switzerland) and especially because the distance between the module edges and the begi nning of the nearby
solar cells is much higher (e.g. > 15 mm instead of 0 – 2 mm like with M55 modules used in many very
old P V pl ants l ike t hat o f B FH-TI). T herefore a c ritical and y ield af fecting per manent edge pol lution i s
hardly f easible. T he hot l ocal c limate i s al so not f avourable f or m oss and l ichen which c an gr ow at
module edges in course of many years and gradually cover neighbouring cells.
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Aus Gründen der Geheimhaltung wegen noch nicht abgeschlossener Patentverfahren kann auf
Wunsch des K oordinators nur ei n e twas ge nauerer B ericht über d ie E rgebnisse der
Putzversuche a n einer Anlage in Spanien im Vergleich zu e inigen Anlagen in der S chweiz gegeben
werden. D ieser Beitrag w urde bereits a m 2 7. Symposium Photovoltaische S olarenergie i n S taffelstein/D publiziert.
Vergleich der Verschmutzung von PV Anlagen:
Alte Anlagen in der Schweiz im Vergleich
zu einer neuen Anlage in Spanien
Prof. Dr. Heinrich Häberlin, Luciano Borgna und Philipp Schärf
Berner Fachhochschule, Technik und Informatik (BFH-TI),
Elektro- und Kommunikationstechnik
Labor für Photovoltaik, Jlcoweg 1, CH-3400 Burgdorf / SCHWEIZ
Tel: +41 34 426 68 11, Fax: +41 34 426 68 13,
E-Mail [email protected]; www.pvtest.ch
1. Einführung
Bei Photovoltaikanlagen k ann s ich i m Lauf e der J ahre t rotz d er S elbstreinigung dur ch R egen u nd
Schnee eine gewisse permanente Verschmutzung entwickeln. Dies geschieht an manchen, aber nicht
an a llen O rten und ist v om A ufbau d er A nlage u nd d en l okalen V erhältnissen a bhängig. D iese V erschmutzung kann of t nur durch eine R einigung vollständig en tfernt werden [1], [2], [3]. Im Lauf e der
Zeit s ind auc h diverse F irmen ent standen, di e R einigungsmaterial f ür od er R einigungen v on P hotovoltaikanlagen anbieten [4]. Anlagen in Südeuropa werden oft in gewissen Zeitintervallen gereinigt [5].
Anlagen in ariden G ebieten v erschmutzen oh ne R einigung oft i nnerhalb von wenigen Mo naten beträchtlich [6], [7].
In F achkreisen bes tehen unterschiedliche Ansichten, ob, wann u nd wie h äufig PV-Anlagen gereinigt
werden sollen. Im Rahmen des EU-Projektes PV-Servitor (Projekt Nr. 232062, Entwicklung eines autonomen Serviceroboters zur Reinigung und Inspektion von PV-Anlagen, gefördert von der EU unter
FP7-SME) bestand die Möglichkeit, entsprechende Messungen an einer A nlage im Innern von Spanien auf c a. 39°N dur chzuführen un d q uantitativ a uszuwerten. I n diesem B eitrag werden die d abei
erhaltenen Messresultate mit den bisher vom PV-Labor der BFH an Anlagen in der Schweiz gemessenen Werten verglichen und Gründe für die festgestellten Unterschiede diskutiert.
2. Messungen an Anlagen in der Schweiz und Deutschland
In der Schweiz wurden viele PV-Anlagen bereits zwischen 1988 und 1995 errichtet. Oft wurden dabei
Module des damaligen Marktführers ARCO Solar resp. (nach der Übernahme) Siemens Solar eingesetzt. F ür d ie m eisten A nlagen wurde dabei das gerahmte Modu l M55 ( 55 Wp, Län ge 1,3 m, B reite
33 cm) verwendet. Bei diesen Modulen waren die Randabstände zwischen Solarzellen und Rahmen
auf den L ängsseiten zur Erzielung eines h ohen Modulwirkungsgrads auf d em D atenblatt s ehr k lein
(typisch 0 bis 2,5 mm). Bei vielen Anlagen wurden Anstellwinkel im Bereich von 30° gewählt und zur
Minimierung des Einflusses von Beschattungen bei tief stehender Sonne wurden die Module mit der
Längsseite parallel zur Horizontalen montiert ("Landschafts-Montage", siehe Bild 1 und 2).
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PV-Servitor (mainly part BFH-TI), Prof. Dr. Heinrich Häberlin, BFH-TI
Bild 1:
Ansicht eines Teils des
PV-Generators der
60 kWp-PV-Anlage
der BFH in Burgdorf
(β = 30°) [3].
Bild 2:
Detailansicht der Verschmutzung des PVGenerators von Bild 1 mit
gerahmten Modulen Siemens M55 [3].
Durch R egen und Schnee wird ei n grosser T eil der S chutzablagerungen (Staub, P ollen, V ogel- und
Insektenkot usw.) jeweils abgewaschen. Dabei bildet sich bei gerahmten Modulen beim unteren Rahmen w ie be i e iner F lussmündung e ine k leine Ablagerungszone für di esen Schmutz. I n d ieser f liesst
das Wasser nicht sofort ab, sondern es verdunstet allmählich und einen Teil des Schmutzes bleibt als
Ablagerungsschicht zurück. Falls der Abstand zwischen Zellen und Rahmen allzu klein ist (wie beim
M55), wird nach einer gewissen Zeit deshalb ein Teil der untersten Zellenreihe abgedeckt, was einen
entsprechenden Minderertrag des Moduls zur Folge hat (siehe Bild 1 und 2). Messungen an der 1993
erstellten 6 0 k Wp-PV-Anlage der BFH-TI i n B urgdorf mit c a. 1100 Modulen M 55 ( mit 4 Zoll Zellen,
meist in "Landschafts-Montage" mit A nstellwinkel 30°) zeigen denn a uch einen Minderertrag von bis
zu 10%, wenn seit der letzten Reinigung etwa 4 Jahre verstrichen sind [1], [2], [3] (siehe Bild 3).
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Measurement of an I-V Curve of PV Plant BFH-TI Burgdorf
Array 6W2B converted to STC, measured 28.6.2010 and 2.7.2010
Current [A]
Power [W]
13
1300
12
1200
11
1100
cleaned modules
polluted modules
10
9
1000
900
8
800
7
700
6
600
5
500
3
PMPP before cleaning = 1058 W
PMPP after cleaning = 1172 W
power reduction 9.7%
2
G and T measured with reference cell M1R
200
4
400
300
1
100
0
0
20
40
(Parameter b = 0.0045)
60
80
Voltage [V]
100
120
0
140
Bild 3:
Gemessene I-U- und P-U-Kennlinien (umgerechnet auf STC) eines Arrays der Teilanlage West der PV-Testanlage der
BFH-TI mit einer Nennleistung von 1310W (24 Module M55 mit 55W (±10%) minus etwa 10W Diodenverluste) vor und
nach der manuellen Reinigung Anfang Juli 2010.
Werden di e Mo dule dag egen m it der S chmalseite p arallel zur H orizontalebene ("Portrait-Montage")
und ei nem et was gr össeren A nstellwinkel v on 40° b is 50° montiert, i st di e V erschmutzungsneigung
wegen des gr össeren G efälles, der gr össeren G eschwindigkeit des Wassers b ei der R ahmenkante,
der kleineren Ablagerungszone und des grösseren Randabstandes zwischen Solarzellen und Rahmen
bei den gl eichen Modulen v iel g eringer. Bei gr össeren Mo dulen ist di eser E ffekt bei s onst g leichen
Bedingungen wegen der längeren Gefällstrecke noch ausgeprägter.
In einem Beitrag in der Nummer 4/2011 hat auch die Zeitschrift Photon das Verschmutzungsproblem
untersucht [4]. Dabei wurden aber vermutlich primär die Daten von vielen neueren Anlagen in
Deutschland verwendet. D a bei n eueren, gr össeren Modulen ni cht n ur Mod uldimensionen u nd d ie
Zellen (5 oder 6 Zoll), sondern auch die Randabstände (mindestens > 5mm auf der Längsseite, > 10
mm auf der S chmalseite, oft deut lich m ehr) meist gr össer s ind, i st d ie Verschmutzungsneigung b ei
solchen Modulen unter sonst gleichen Umständen deutlich geringer. Deshalb wurden in [4] für Anlagen i n D eutschland auc h viel ger ingere L eistungsverluste dur ch Verschmutzung v on b is ge gen 3%
angegeben.
3. Messungen an einer Anlage in Castuera/Spanien
In der Literatur wird oft von starken Verschmutzungen und regelmässigen Reinigungen bei Anlagen in
ariden Gebieten berichtet [5], [6], [7], jedoch oft nur mit wenigen oder gar keinen quantitativen Angaben. Im R ahmen des E U-Projektes P V-Servitor ( www.pv-servitor.eu) b ot s ich die interessante G elegenheit, a n d er von I BC vor e twa dr ei J ahren er stellten P V-Anlage v on 1, 728 MWp in C astuera/Spanien Ende A ugust 2 011 q uantitative M essungen v or u nd nac h Reinigungen v on A nlageteilen
durchzuführen. Die Anlage besteht aus 240 Teilanlagen zu 7,2 kWp, bestehend aus jeweils 2 parallelen Strängen mit je 16 Modulen IBC 225-TE (225 Wp) und einem Wechselrichter SMC 7000 HV. Die
Module sind in "Portrait-Montage" m it einem Anstellwinkel von e twa 30° montiert. Sie b esitzen auch
relativ grosse Randabstände (6 mm auf den Längsseiten, 20 mm auf den Schmalseiten), so dass die
Neigung zu Randverschmutzung sehr gering ist.
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Da wegen Transport- und Zollproblemen nicht allzu viele Messgeräte mitgenommen werden konnten
und Unterbrüche zwecks Kennlinienmessung aus Sicht der Betreiber unerwünscht waren, wurde der
Reinigungseffekt einerseits durch den Vergleich der Strangströme vor und nach der Reinigung eines
der b eiden S tränge a n e iner A nlage und a ndererseits dur ch d en V ergleich der am Wechselrichter
angezeigten Leistung benachbarter Anlagen beurteilt (Messung beider Anlagen vor und nach der Reinigung einer ganzen Anlage, Vergleichsanlage bleibt ungereinigt). Erstaunlicherweise betrug der Gewinn durch die Reinigung trotz deutlich sichtbarer Verschmutzung in der Fläche maximal etwa 3%. Bei
dieser Anlage fehlte eine Randverschmutzung, sie hätte aber wegen relativ grossen Randabständen
ohnehin keinen Einfluss gehabt. Bild 4 und 5 zeigen die in Castuera vorhandene Verschmutzung.
Bild 4:
Teilansicht einiger Module bei der PV-Anlage in
Castuera. Das Modul
rechts unten ist bereits
gereinigt.
Es ist keine Randverschmutzung erkennbar.
Bild 5:
Detail von Schmutzschicht und Rahmenabstand bei der PVAnlage in Castura/
Spanien.
Auch im Detailbild ist
keine Randverschmutzung erkennbar.
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Das Z iel des er wähnten EU-Projektes w ar di e E rforschung d er not wendigen G rundfunktionen und
erste Tests mit einfachen Funktionsmustern von autonomen Servicerobotern an realen Anlagen. Bei
der PV-Anlage in Castuera wurde ein Teil der Anlage mit einem solchen Funktionsmuster des von den
Projektpartnern e ntwickelten P V-Servitor-Roboters gereinigt. E in anderer Teil w urde z u V ergleichszwecken manuell gereinigt (siehe Bild 6). In den meisten Fällen wurde nur die untere Reihe geputzt
und die Reinigungswirkung durch Vergleich der Leistung der unteren und der oberen Reihe bestimmt.
Da n och n icht alle P atentanträge def initiv ber einigt s ind, k ann leider k ein Bild d es R oboters g ezeigt
werden.
Bild 6:
Manuelle Reinigung von
Teilen des Solargenerators der PVAnlage in Castuera.
In einem ersten Schritt
werden die Module mit
einer Bürste und Wasser
gereinigt (rechts), danach wird das Wasser
mit einem Gummischaber entfernt.
4. Fazit
Wie schon in früheren Publikationen erwähnt [3], kann keine generelle Aussage über die Verschmutzungsneigung gemacht w erden. D iese ist w esentlich von den lokalen Verhältnissen (Art und A nzahl
der Verschmutzungsquellen in der Nachbarschaft) und von der Art und Aufbau der Anlage (Modultyp,
Modulgrösse, Zellengrösse, Montageart, Randabstände, Neigungswinkel usw.) abhängig. Zur Beurteilung der W irtschaftlichkeit v on Reinigungen i st n icht nur di e H öhe der a llfälligen höh eren Leistung
nach d er R einigung und ihrer K osten, s ondern auch die Höhe d es E inspeisetarifs der bet reffenden
Anlage und eine allfällige Begrenzung der voll vergüteten Volllastsunden (wie in Spanien) zu berücksichtigen. Tendenziell lohnt sich eine Reinigung umso weniger, je neuer die Anlage (mit entsprechend
tieferem Einspeisetarif) ist und je tiefer eine allfällige Begrenzung der Volllaststunden in Bezug auf die
maximal möglichen Volllaststunden ist. Unter den heutigen Bedingungen dürfte sich deshalb bei vielen
Anlagen in Spanien eine Reinigung wirtschaftlich meist nicht lohnen.
Aus dieser Relativierung der Notwendigkeit der Reinigung auf Grund der Messungen an einer Anlage
in Spanien (nur etwa drei Jahre alt) mit deutlich sichtbarer, aber relativ heller Verschmutzung und der
an dieser Anlage festgestellten erstaunlich geringen Ertragssteigerung durch Reinigung von nur etwa
3% darf nun aber nicht gefolgert werden, dass die Reinigung von PV-Anlagen überhaupt nie notwendig sei. In W üstengebieten oder w üstenähnlichen R egionen mit starker Staubbelastung sind periodische Reinigungen nach wie vor sinnvoll [5], [6], [7].
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Literatur
[1] H. Häberlin und Ch. Renken: "Allmähliche Reduktion des Energieertrags netzgekoppelter Photovoltaikanlagen infolge
permanenter Verschmutzung“.14. Symposium PV-Solarenergie, Staffelstein, 1999.
[2] H. Häberlin und Ph. Schärf: Langzeitverhalten von PV-Anlagen über mehr als 15 Jahre.
25. Symposium PV-Solarenergie, Staffelstein, 2010.
[3] H. Häberlin: "Photovoltaik – Strom aus Sonnenlicht für Verbundnetz und Inselanlagen". Electrosuisse-Verlag,
CH-8320 Fehraltorf, 2010,
ISBN 978-3-905214-62-8 und VDE Verlag, Berlin, ISBN 978-3-8007-3205-0.
[4] A. Beneking: "Sauberkeit um jeden Preis?". Photon 4/2011.
[5] A. Dietrich: "Germany vs. Spain – Unterschiedliche Erfahrungen aus mehrjährigem Betrieb von Solarkraftwerken
in Deutschland und Spanien".
[6] M. Ibrahim, B. Zinser u.a.: "Advanced PV Test Park in Egypt for investigating performance of different module
and cell technologies".
[7] A. Wagner: "Photovoltaic Engineering“. Springer Verlag, Berlin, 2006,
ISBN-10 3-540-30-30732-X.
Weitere Informationen über das Photovoltaik-Labor der BFH in Burgdorf http://www.pvtest.ch.
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MESSKAMPAGNE PHOTOVOLTAIK
SCHALLSCHUTZANLAGE MÜNSINGEN
Annual Report 2011
Address
Date
TNC Consulting AG
General Wille-Str. 59 – CH 8706 Feldmeilen
044 991 55 77 – [email protected] - www.tnc.ch
SI/500361 / SI/500361-01
01.09.2009 – 31.12.2011
17.01.2011
ABSTRACT
On t he i mportant N orth-South r ailway l ine B ern-Lötschberg i n S witzerland the w orlds first bifacial
Photovoltaic pl ant integrated i n a noi se barrier al ong the railway h as been realized i n December
2008. For this project the originally planned transparent glass noise barrier elements have been substituted by bifacial PV modules based on a special glass-glass-structure to fulfill the noise protection
requirements.
Detailed measurements on the bifacial PV plant have been carried out from second half 2009. After
experience of one year of measurement 2010, in 2011 the time resolution of the measurement has
been improved to get more detailed measurements and continue the investigation of the behaviour of
this bifacial PV plant.
Practical ex perience of op erating a PV no ise b arrier pl ant o n a r ailway l ine with r egard to m aintenance h as be en g athered. T he case of a nec essary substitution of a P V m odule due to vandalism
was carried out successfully.
The estimated yield in the process of planning of this bifacial PV noise barrier plant of ′6 750kW h/a
has not been reached. The measured yield of the plant is at 5′076 kWh after one year of full operation
and of 5’339 kWh after the second year of operation have been analysed.
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Introduction and aims
With the construction of the first bifacial PV noise barrier on the motorway flyover in Aubrugg, Zürich,
the concept for bifacial PV noise barriers has been proofed. An intensive measurement campaign has
been carried out at the PV plant Aubrugg, which shows that the concept of gathering energy on two
vertical planes facing east and west equals energy yield of a south oriented and tilted plane PV system. D ifferent P V s pecific par ameters s uch as s hading, d irt de posits, inverter behaviour a nd s izing
have been examined and optimized. All of these experiences have been taken into the account during
the planning of the bifacial PV noise barrier plant along the railway in Münsingen.
The bi facial P V no ise bar rier i n Müns ingen i s t he f irst bi facial P V noi se bar rier al ong a r ailway l ine.
There are several railway specific issues such as shading by railway infrastructure or passing trains,
reduction of the yield through deposits of iron dust from the brakes of the trains, general maintenance
issues and of course the analysis of the economics of a bifacial PV noise barrier on a railway.
1. Description of the bifacial PV noise barrier on a railway line in Münsingen
On t he i mportant N orth-South r ailway l ine Bern-Lötschberg i n S witzerland, t he w orld’s f irst b ifacial
Photovoltaic plant integrated in a noise barrier along the railway has been realised in December 2008.
For this project, the originally planned noise r eflecting transparent noise barrier elements have been
substituted by bifacial PV modules based on a special glass-glass-structure to fulfil the noise protection r equirements. E conomical c onsiderations s uch as t he s ubstitution of c onventional gl ass noise
barrier elements b y PV m odules f ulfilling t he no ise protection r equirements c an be s tudied with t his
pilot project as well as technical questions concerning the use of bifacial PV modules in a noise barrier
along a r ailway line. D ifferent i ssues c oncerning t he operation of bi facial PV noise bar riers s hall be
evaluated by comparing several years of operation of the different bifacial PV noise barrier plants on
the railway in Münsingen and on the highway in Zürich.
Figure 1: The PV plant consists basically of two adjoining noise barrier sections, marked and labelled with Noise
Barrier 10 (LSW10) for the section which starts directly at the north end of the train station and the section Noise
Barrier 7 (LSW7), which starts at the north end of the LSW10. This results in a total area of 115m2 available for
the PV noise barrier elements for a given height of 1m.
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SI/500361, T. Nordmann, TNC Consulting AG
2. Maintenance and logistics
Unfortunately, one of the PV modules was destroyed in an act of vandalism. The glass was perforated
with b rute f orce and f irst s igns of hum idity e ntering t he m odule s howed o n t he bo nds of t he c ells
shortly after. The PV modules seemed to be still working nonetheless, but it was unclear for how long
it would work. The municipality of Münsingen as owner and operator of t he bi facial PV noise barrier
plant decided to exchange the module during 2011.
During planning and the ordering process of the bifacial PV modules, an amount of spare modules has
been manufactured and delivered. These glass-glass modules were delivered without frame. For the
exchange of the module, the broken PV module had to be dismounted, taken out of its frame and correctly disposed. In a second step, the replacement module had to be mounted in the frame and then
be installed i nto the noi se bar rier c onstruction. During t his work, the r ailway traffic was not to be a ffected.
Since the access to the modules in the noise barrier was not given any longer as during construction
phase, a r emote c ontrolled v ehicle was t o b e us ed f or t ransport an d i nstallation of t he m odule. T he
safety r equirements from the r ailway operator had t o be f ulfilled at any time. Thanks to the m odular
design of the PV noise barrier construction, the dismounting of the module was straight forward. With
the easy access to the wiring integrated in the frame construction, the electrical disassembly and installation of the replacement module could be done very fast.
Figure 2: T he r emote controlled vehicle f or r eplacing t he PV module is t he same vehicle as used for replacing
conventional transparent noise barrier elements and is also operated by the same people, allowing the use of
synergies in maintenance.
The costs of the replacement of the PV module were shared with the railway operator SBB, which had
to ex change a c onventional transparent n oise b arrier el ement at t he s ame t ime. T he safety pr ecautions and parts of the logistics were taken over by the maintenance part of the railway operator, since
the PV modules fulfil the purpose of transparent noise barrier elements, for which the railway operator
is responsible.
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Maintenance of plants along the railway line
The maintenance of the plants along the railway-averted side of the bifacial PV noise barrier is in the
responsibility of the land owner, in this case the community of Münsingen. Unfortunately the directly
adjoining land in the east is not used and therefore not well tended. This leads to the growth of different pl ants that r each more t han 1m hei ghts abo ve gr ound. T hese pl ants lead to a shadowing of t he
east side during the morning hours. Unfortunately, the exact time and place when this occurs cannot
be specified without visual inspection.
Figure 3: maintenance of the railway averted side (in the case of Münsingen the east side) is essential to avoid
shading by wildly growing plants. The influence is not severe, due to the bifacial nature of the solar cells.
During t he r eplacement of t he P V m odule, t he p lants w ere c ut d own. H ere t he dat e of t he m aintenance is known, a nd it is therefore possible to compare pr oduction bef ore an d after the i nfluence of
the plants.
Figure 4: normalized power output before the
cutting of the plants. The measurement points
in the lower right corner show the shadowing.
Figure 5: normalized power output after
the cutting of the plants.
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3. Measurement by TNC
The measurement equipment was installed in May 2009 by TNC.
In t he middle of s ection L SW 7 t hree t emperature compensated r eference c ells w ere installed. O ne
reference cell each is installed parallel to the modules, facing east and west. The third reference cell is
oriented south with an inclination of 35°. This allows the comparison of the solar irradiation of the two
sides to the east and the west in comparison to a south oriented plane. In addition there is a temperature sensor that is located with the three reference cells for the measurement of the ambient temperature.
To measure t he electrical parameters of t he P V p lant, 3 D C voltage m easuring uni ts ha ve be en installed, one before e ach i nverter f or the 3 arrays. Every inverter i s fed by two groups of modules in
parallel, consisting of the same amount of modules of the same type. Each of these groups of modules has a Hall sensor to measure the current on the DC side. This results in 6 DC current values. In
addition one single phase AC energy meter is installed per inverter on the output side of the inverter.
All sensors are connected to a data logger, which stores the input values. First calculations are done
by the data logger, based on a customized logger program developed and written by TNC for the bifacial PV plant in Münsingen. The data on the data logger is collected regularly by TNC using a GSM
modem connected to the data logger for remote access.
Figure 6 : I nstallation o f t he three t emperature compensated reference cells. Two are parallel to the modules facing east and west, one facing south with ◦35
inclination.
Figure 7: Each group of modules has one Hall sensor
measuring t he D C current ( blue on t he or ange pr int).
To the left the three DC voltage measurements of the
PV arrays are installed.
Figure 8: The data logger stores the input data and does basic calculations based on a customized logger program developed by TNC. The dat a l ogger has a separate pow er supply i ncluding a battery b ackup s ystem t o
prevent data loss in case of power outage.
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Data acquisition
The first full year of measured data was acquired in 2010. Now with the data of 2011 available, first
comparisons can be m ade. In add ition T NC has t he possibility t o ac cess the data of t he bifacial PV
noise barrier plant on the highway in Zürich for further comparison on a longer timescale.
Improvements in the measurement
In 2011 the Software on the data logger was expanded for more detailed analysis based on a higher
time resolution. This was done with the aim of achieving a more precise analysis of the facts already
found in the first year of the measurement campaign for confirmation and more detailed analysis. This
data is currently under evaluation. Some first results are shown in the following chapter.
Data loss in the measurement
Early 2011 the AC energy meters had a failure and had to be replaced. In the first two months of 2011
the AC energy was not separately measured, but had to be calculated from different other available
sources, such as DC measurement of energy, energy sums of the inverter intern measurements and
the c ounter on t he feed i n po int from the utility. This also means t hat t here ar e uncertainties on t he
overall yield of the plant for 2011. Based on the experience of 2010 and the available date, the estimation of the overall yield can be judged to be fairly precise.
4. Overview of two full years of operation
The estimated y ield in t he pr ocess of planning of this bi facial PV noise barrier plant of ′6 750kW h/a
has not been reached. The measured yield of the plant for 2010 is at 5′ 076 kWh and for 2011 at 5’339
kWh.
The forecast for the electrical energy expected has been originally made based on a simulation of the
solar irradiation available with the renowned Software MeteoNorm v5. Meanwhile, a newer version of
this software is available (MN v6). The data used for simulating an average year is basically still the
same, but the algorithms have been further improved. A comparison of the results for the bifacial PV
noise barrier plant in Münsingen with the same parameters for simulation has shown, that there is a
difference in the simulated solar irradiation available in the planes of the PV modules. The results are
shown in Table 1.
Simulation with MeteoNorm v6
Simulation with MeteoNorm v5
East side
West side
East + West
East side
West side
East + West
Winter
2
[kWh/m a]
171
253
424
166
240
406
Summer
2
[kWh/m a]
493
538
1’031
435
507
942
Total year
2
[kWh/m a]
664
791
1’455
601
747
1’348
111%
106%
108%
Difference
Table 1: C omparison of the simulation of t he available solar i rradiation for the bifacial P V noise barrier plant i n
Münsingen with MeteoNorm.
The difference in solar irradiation of approximately 5-10% is directly proportional to the expected electrical o utput. T hese ne w r esults ha ve t o b e t aken i nto c onsideration when c orrecting the m easured
values to a standard meteorological year. At the same time the expected yield would also be higher.
Electrical power generation cost calculations based on the standard meteorological year improve with
the new values.
The measured s olar i rradiation i n t he s um of bot h pl anes of t he P V modules f or 2011 i s at 1’ 266
2
2
kWh/m a. This is just a little below the solar irradiation of 2010, which was at 1’286 kWh/m a. Com2
pared to the simulated solar irradiation of 1’455 kWh/m a the year 2011 was below the standard meteorological year (87%) for the special case of the east and west oriented, vertical planes of the bifacial PV noise barrier plant in Münsingen.
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The influence of the shadowing of the east side of the northern most part of the bifacial PV noise barrier due to the adjacent trees has already been shown in the measurements of 2010. With the more
precise measurements now available based on the 1 minute measured data, this influence has been
re-evaluated. While the hourly data led to the calculation of the measured reduction of 65% of the yield
for t he af fected s tring dur ing t he m orning ho urs, t he ne w d ata s hows t hat this r eduction i s slightly
lower at a bout 60%. C ounter measures have been discussed with the municipality, but they are too
drastic, so the lower yield is accepted.
Figure 9: Based on the hourly data, a first estimation of the influence of the shading of the northern most string
of the bifacial PV noise barrier plants was made at approximately 65%.
Figure 10: The more precise data measured in 1 minute steps allows a more precise estimation of the reduction
of the yield of the string affected by shadow in the morning hours at about 60% reduction.
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5. International collaborations
During p lanning and c onstruction, s everal i nternational c ompanies were involved f or t he bifacial PV
noise barrier plant in Münsingen. Product development and project lead has been done by TNC Consulting. The bifacial solar cells have been provided by Hitachi from Japan. Hitachi has also provided
the technical specifications for the bifacial cells. For module construction several European companies
have been contacted. Scheuten Solar processed the bifacial solar cells to glas-glas modules fulfilling
the r equirements of transparent noise barriers on railways. Installation of t he modules and electrical
installations has been provided by local companies. Installation of the modules and the construction of
the frames of the modules for integration into the noise barrier has been carried out by Walo Bertschinger. E lectrical i nstallations hav e be en c arried o ut b y a team c onsisting of B aumannElektro and
SunTechnics Engineering.
6. Outlook
The newly gained data with the higher time resolution shall be exploited in details. The different influences shall be isolated and quantified where possible. Adaptions to the measurement shall be made
where necessary and useful. The comparison of the operational data of the plant in Münsingen will be
compared to the data available from Zürich, where the bifacial PV noise barrier on the highway is operational since 15 years. A comparison of the technologies over time is also possible.
Figure 11: In this figure, the solar irradiation for three summer days is shown. G_i (red) stands for the sum of the
solar irradiation in the planes of the bifacial PV modules, while g ( blue) stands for the solar irradiation in a tilted
south oriented plane. This shows t hat bifacial P V p lants can contribute t o a be tter di stribution of the av ailable
solar power by spreading the midday peak more over the day and therefore allow for a higher penetration of PV in
the power mix.
Referenzen / Publikationen
[1]
Th. Vontobel, Th. Nordmann, L.Clavadetscher: Erstmalige Realisierung einer in eine Schallschutz-Konstruktion voll integrierten bi facialen P hotovoltaik A nlage ent lang ei ner E isenbahnschiene i n der S chweiz, 24. S ymposium P hotovoltaische
Solarenergie, 4. - 6. März 2009, Staffelstein
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DISTRIBUTION GRID ANALYSIS AND SIMULATION WITH PHOTOVOLTAICS (DIGASP)
SIMULATION APPROACH TO INVESTIGATE
THE IMPACT OF DISTRIBUTED POWER
PRODUCTION WITH PV ON A POWER GRID
Annual Report 2011
Address
Christof Bucher
Basler & Hofmann
Forchstrasse 395, 8032 Zürich
044 387 13 80, [email protected],
www.baslerhofmann.ch
SI/500549 / SI/500549-01
Date
07.12.2011
ABSTRACT
The pr oject “ Distribution G rid Analysis an d Simulation with Photovoltaics ( DiGASP)” ( former nam e
“distributed PV generation") investigates the technical impact of distributed PV power production on
low- and medium voltage grids. The main questions to be answered in this task are the following:
• How much PV can be fed in the power grid at a certain point?
• What are the restrictions for feeding in PV power, and how can they be mitigated?
• What ef fects c an be expected, if c ertain m odifications ar e ap plied t o t he d istribution p ower grid
(such as active / r eactive power c ontrol, energy s torage, t ap c hanging transformers, ac tive load
control, …)
By modelling the grid with adequate algorithms for PV, these questions shall be answered, and in a
second step, be adapted to the distribution grid of ewz Zürich.
Given t he r esults of t his project, a di stribution system operator ( DSO) should k now t he pos sibilities
and limits of i ts gr id c oncerning distributed f eed-in of P V, an d ha ve a g uideline / m ethod where t o
place future investments in order to strengthen its grid for PV.
In 2011, the project made relevant progress in the following fields:
• Probabilistic load pattern generation
• Analysis of sampling rates in load patterns
• Framework of load flow simulation
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Einleitung
+
Dieses Projekt wird im Rahmen des PV Grid Calls des PV ERA NET mit den Projektpartnern Austrian
Institute of Technology und der Universität Oldenburg durchgeführt. Ein besonderes Gewicht hat deshalb der Wissenstransfer zwischen den beteiligten Institutionen: Dank der internationalen Kooperation
wird ein Mehrwert für das Projekt angestrebt, der bei der rein nationalen Projektbearbeitung nicht erreicht werden könnte.
Das Projekt bildet zudem den Beginn und einen integralen Bestandteil der Dissertation des Projektleiters. D ie eng e Z usammenarbeit m it dem I nstitut f ür Elektrische E nergieübertragung u nd H ochspannungstechnik (EEH) der Abteilung für Informationstechnologie und Elektrotechnik (D-ITET) der ETH ist
somit ein weiterer Pfeiler für das Projekt.
Projektziele
Die wesentlichen Ziele des Projekts sind die detaillierten und fundierten Antworten auf folgende Fragen:
• Wie gross ist die PV-Leistung, die in ein bestimmtes Verteilnetz eingespeist werden kann?
• Welches sind die Limitierungen für die Einspeisung von PV in ein Verteilnetz, und wie können diese beeinflusst werden?
Die Beeinflussung d er ph ysischen Einspeisebegrenzungen i st dabei ein wichtiges T hema. E s s oll
untersucht werden, mit welchen Massnahmen welche Effekte erzielt werden können. Folgende Massnahmen stehen heute zur Diskussion:
• Blindleistungsregelung am PV-Wechselrichter
• Verwenden eines Stelltransformators als Ortsnetztransformator
• Abregelung der Wirkleistung der PV-Anlagen
• Ausrichtung der PV-Analgen variieren
• Dezentrale Speicher
• Elektromobilität (Ladealgorithmus von vorangehender Dissertation ETH)
• Demand Side Management (Algorithmus von vorangehender Dissertation ETH)
• Optimum Power Flow: Wie müssen Regelparameter etc. gewählt werden, um das System zu optimieren?
Die Roadmap beschreibt das geplante weitere Vorgehen im Projekt.
Termin
Arbeitsschritt
Verantwortlich
Dokumentation
Dez 2011
Paper Lastprofilgenerator an PMAPS einreichen
B&H
Paper
Dez 2011
Entwurf Meteodatengenerator
Universität
Oldenburg
Matlab Code
Mrz 2012
Nationale PV-Tagung
Swissolar /
BFE
Präsentation
Mai 2012
Simulationsmodell mit integriertem Last- und Wettermodell
B&H
Kurzbericht
Jun 2012
PMAPS: Präsentation Lastprofilgenerator
B&H
Paper
Jul 2012
Erweiterung Lastprofilgenerator
B&H
Kurzbericht,
Paper?
Okt 2012
Vergleich Benefit Blindleistungsregulierung vs. Stelltransformator in Netzebene 6.
AIT
Kurzbericht,
Paper?
Okt 2012
Aufnahmekapazität Verteilnetz für PV als Index
B&H
Kurzbericht
Dez 2012
Simulationsresultate Teilnetz ewz
B&H
Kurzbericht
Winter
2012/13
Schlussbericht DiGASP
B&H
Bericht
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Distribution Grid Analysis and Simulation with Photovoltaics (DiGASP), C. Bucher, Basler & Hofmann
Die b isher d urchgeführten Arbeiten k onzentrieren s ich auf di e Arbeiten v on B asler & H ofmann. Die
folgende Liste stellt die Meilensteine der durchgeführten Arbeiten vor:
LASTPROFILGENERATOR
Ein Paper mit dem Titel „Generation of Domestic Load Profiles - an Adaptive Top-Down Approach“ zur
stochastischen G enerierung v on Las tprofilen wurde verfasst und zuhanden d er K onferenz PMAPS
2012 ( Probabilistic Met hods A pplied i n P ower Systems) ei ngereicht. D ort s oll es i m S ommer 2012
vorgestellt werden.
Das Konzept zur Generierung von Lastprofilen wird in Abb. 2 gezeigt. Abb. 3 zeigt ein Beispiel generierten Lastprofils.
Abb. 1: Konzept zur Generierung von stochastischen Lastprofilen.
Abb. 2: Lastprofil generiert mit dem „Adaptive Top Down Approach“.
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SIMULATION FRAMEWORK
Die Simulationen s ollten u rsprünglich m it N EPLAN durchgeführt werden. D a d ieses P rogramm z u
wenig Entwicklungsflexibilität bietet, wird im folgenden Projekt auf MATPOWER, einem freien Plug-In
zu M ATLAB g earbeitet. M ATPOWER bi etet Las tflussberechnungen und O PF ( optimum pow er f low)
auf Basis des „Unified Branch Models“.
Das F ramework bas iert au f den an der E TH unt er d em N amen „ Power N ode“ ent wickelten G rundstrukturen und wird im w eiteren Projektverlauf den spezifischen Bedürfnissen d ieses P rojekts ang epasst.
GRANULARITÄT LASTPROFILE
Mangels guter Referenzen in der Literatur wurde anhand öffentlich zugänglicher Lastmessungen mit
Sekundenauflösung die Effekte der Granularität (Sampling Rate) von Lastmessungen untersucht. Die
Resultate deuten darauf hin, dass Messwerte zu Minutenwerten aggregiert werden dürfen, ohne dass
sich die Charakteristik der Messungen wesentlich ändert. Werden die Daten darüber hinaus gemittelt
(z.B. auf Viertelstundenwerte), so gehen Informationen verloren.
Abb. 3 zeigt eine mögliche Auswertung / Bewertung von Granularitäten der Messungen.
Abb. 3: Lastperzentile für verschiedene Granularitäten (Sampling Rate). Werden die Daten mehr als eine Minute
gemittelt, verschieben sich die Perzentile. Das „99 Perzentil“ gibt z.B. die Last an, welche grösser ist als 99% der
tiefsten Lasten resp. kleiner als das Prozent der höchsten Last.
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Nationale Zusammenarbeit
Nationaler Austausch und nationale Zusammenarbeit hat insbesondere mit der ETH Zürich und dem
ewz stattgefunden.
ETH ZÜRICH
Intensive Zusammenarbeit besteht mit den Doktoranden und Studierenden, welche das „Power Node“
-Konzept entwickelten und weiterentwickeln [1]. Da auch sie mit MATPOWER arbeiten, können etliche
Programmcodeteile gemeinsam verwendet und gepflegt werden.
In verschiedenen Projekten wurden die Aspekte „Lastmanagement“ und „Speicher im Verteilnetz“ an
der ETH untersucht (u.a. im Zusammenhang mit Elektromobilität [2]). Die dabei gefundenen und untersuchten A lgorithmen s ollen s päter i m R ahmen di eses P rojekts implementiert und hi nsichtlich PV
bewertet werden.
In Projekten am D epartement I nformatik werden Smart Me ter D aten untersucht und ausgewertet. In
einer gemeinsamen Projektsitzung wurde nach möglichen Synergien gesucht und der Austausch von
Daten in Aussicht gestellt.
EWZ (ELEKTRIZITÄTSWERK DER STADT ZÜRICH)
Nebst der kontinuierlichen Unterstützung im Rahmen von Korreferaten und Rückmeldungen zu aktuellen Projektresultaten hat das ewz einer Messkampagne zur Charakterisierung von Haushaltslastdaten
zugestimmt. I m kommenden J ahr s oll e ine A nzahl Haushalte m it hoc hauflösenden Messungen ( 1Minutenwerte) ausgerüstet werden. Die Messungen werden die Basis für das Lastmodell bilden.
Die Internationale Zusammenarbeit hat sich neben den Projektpartner des PV ERA NET Projekts auf
die Hochschule Ulm erweitert.
UNIVERSITÄT OLDENBURG (PROJEKTPARTNER PV ERA NET)
An einer Startsitzung im Frühjahr wurden die Anforderungen an das Meteodatenmodell festgehalten.
Ein Entwurf dazu wurde im Folgenden geschrieben. Dieser soll im kommenden Jahr in das Simulationsmodell integriert werden.
AIT (PROJEKTPARTNER PV ERA NET)
Das Austrian Institute of Technology (AIT) beteiligte mit Informationsrecherchen und Korreferaten an
dem Projekt. Für das kommende Jahr ist ein Input (Bericht) zum Vergleich von Netzstützung mittels
Blindleistungsregelung an Photovoltaikwechselrichter versus der Netzstützung durch Stelltransformatoren auf Netzebene 6 vereinbart.
HOCHSCHULE ULM
An einer gem einsamen Sitzung mit Prof. G. Heilscher an der Hochschule Ulm, welcher in enger Zusammenarbeit mit d en Stadtwerken Ulm steht, wurden Synergien im Bereich der Projektauswertung
und Validierung von Modellen ausgemacht. Es besteht die Absicht, ein in einer Fallstudie untersuchtes Netzgebiet von Ulm mit den Methoden von DiGASP zu simulieren und die Konzepte miteinander
zu vergleichen.
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Nach einem eher verhaltenen Projektstart aufgrund der unklaren Finanzierungslage der Projektpartner
AIT und U niversität O ldenburg hat d as P rojekt i m L auf des J ahres an F ahrt auf genommen. Z war
musste di e R oadmap des P rojekts um ei n ha lbes- bis e in J ahr a ngepasst werden, j edoch wurden
inzwischen wichtige Teilresultate erzielt.
Für das Jahr 2012 ist insbesondere Folgendes zu erreichen:
• Fertigstellung des Lastprofilgenerators
• Fertigstellung des Meteodatengenerators
• Fertigstellung der Implementierung des Frameworks
• Diverse Auswertungen gemäss dem Kapitel „Projektziele“
Referenzen
Die in diesem Kapitel aufgeführten Referenzen verweisen auf ausgewählte Publikationen, auf welchen
das Projekt aufbauen wird.
[1] Kai H eussen, Stephan K och, Andreas U lbig and G öran A ndersson, Energy S torage i n P ower S ystem O peration: T he
Power Nodes M odeling F ramework, Presented a t the I EEE PES C onference on I nnovative S mart G rid T echnologies
Europe, Gothenburg, Sweden, 2010.
[2] Rashid A. Waraich, Matthias Galus, Christoph Dobler, Michael Balmer, Göran A ndersson and Kay W. A xhausen, Plug-in
Hybrid Electric Vehicles and Smart Grid: Investigations Based on a Micro-Simulation, The 12th International Conference of the International Association for Travel Behaviour Research, Jaipur, India, 2009.
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Internationale Koordination
P. Hüsser
REPIC: Swiss Interdepartmental Platform for Renewable Energy and Energy
Efficiency Promotion in International Cooperation – SECO UR-00123.03.01
327
333
K. Flury, M. Stucki, R. Frischknecht
356
T. Nordmann, L. Clavadetscher
362
IEA PVPS, Task 14 - High penetration of PV systems in electricity grids
(Swiss contribution) – IEA PVPS Pool II 2011.01
366
J. Remund
IEA SHC, Task 36 – Solar resource knowledge management
– 101498 / 151784/151761
375
P. Toggweiler, T. Hostettler
Normenarbeit für PV Systeme – SWISSOLAR 17967
379
S. Nowak, M. Gutschner
PV-ERA-NET: Networking and Integration of National and Regional Programmes in
the Field of Photovoltaic (PV) Solar Energy Research and Technological
Development (RTD) in the European Research Area (ERA) – CA-011814-PV ERA NET
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387
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SCHWEIZER BEITRAG ZUM
IEA PVPS PROGRAMM, TASK 1
Annual Report 2011
Author
Company
Address
Duration of the Project
Date
Pius Hüsser
Nova Energie GmbH
Schachenallee 29, 5000 Aarau
062 834 03 00, [email protected], www.iea-pvps.org
SI/400516 / SI/400516-01
01.02.2011 – 31.12.2011
13.12.2011
ABSTRACT
The Swiss contribution to the PVPS Programme includes:
• National Survey Report, a summary of developments in the market and political areas.
The report’s data is integrated into the IEA PVPS Trends in Photovoltaic Applications Report.
• Acquisition of Swiss contributions to PV Power, collecting subscribers for the new EmailNewsletter.
• Targeted search for new contacts in the PV area, maintain a network of contacts.
• Contributions/organizations to/of national and international workshops.
• PR work in Switzerland. Reference to the programme‘s international publications.
The results of these activities include:
• National Survey Report (NSR) based on the statistics provided by the Swiss Association
of Solar Professionals.
• Two Task 1 meetings in Istanbul and Amsterdam.
• Three workshops in Istanbul, Turkey, Hamburg, Germany and Fukuoka, Japan.
• Webmastering support for www.iea-pvps.org.
Ongoing work:
• Workshop organization at the PV conference in Frankfurt (Sept. 2011)
& China (Nov. 2011).
• Participation at Task 1 Meetings in Stockholm (April) and Aarhus (DK, September).
• National Survey Report 2012.
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Task 1 unterstützt die generelle Strategie des PVPS Programmes (Kostenreduktion, Potenzial erfassen, Barrieren beseitigen, Kooperation mit Nicht-IEA-Ländern) mit folgenden Produkten:
• PV POWER Update, seit April 2009 erscheinender E-Newsletter. 2 Ausgaben in 2011
• Trends Report (Trends in Photovoltaic Applications, Survey report of selected IEA countries Between 1992 and 2010), ein Jahresbericht zur Markt- und Technologie-Entwicklung der dem Programm angeschlossenen Länder
• Reports und Workshops zu spezifischen Themen der Photovoltaik
• Eigene Programm-Homepage unter www.iea-pvps.org.
Ziel ist es, die identifizierten Zielgruppen (Regierungen, EW’s, Industrie, Forschung usw.) mittels qualitativ hochstehenden Produkten zu informieren.
Der Schweizer Beitrag innerhalb des PVPS Programms (Task 1) konzentriert sich auf folgende
Schwerpunkte:
• National Survey Report [1], eine Zusammenstellung der Marktentwicklung und des politischen Umfeldes in der Schweiz. Diese Daten werden im Trends Report [2] zusammengefasst und publiziert.
• Organisieren von Schweizer Beiträgen in PV
Power sowie Mitarbeit im Editorial Board.
• Bewerbung der Anmeldemöglichkeit für den
E-Newsletter (als Ersatz für die gedruckte
Version)
• Gezielte Suche nach weiteren Kontakten
innerhalb der Zielgruppe
• Beiträge an Workshops und Konferenzen auf
nationaler und internationaler Ebene
• Organisation von Workshops
• Medienarbeit in der Schweiz: Hinweise auf
internationale Publikationen des Programms,
Publizieren von Marktstatistiken
• Unterstützung des ExCo beim Internetauftritt
.
Estimated world PV cell production (%)
by country in 2010
National Survey Report NSR
Der NSR bildet die Grundlage für den jedes Jahr erscheinenden ”Trends Report”. Als Basis für die
Statistiken dienen die jährlichen Erhebungen des Sonnenenergie Fachverbandes Swissolar, ergänzt
mit Daten der VSE-Statistik zu den netzgekoppelten PV-Anlagen. Die nachfolgende Tabelle gibt einen
Überblick über die erhobenen Marktzahlen.
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IEA-PVPS Task1, P. Hüsser, Nova Energie GmbH, Aarau
4 710
900
2200
70
1 540
1992
5 775
1 100
2900
100
1 675
1993
6 692
1 200
3 600
112
1 780
1994
TOTAL (kW)
centralised
connected
Grid-
distributed
connected
Grid-
domestic
non-
Stand-alone
domestic
Stand-alone
Sub-market
7 483
1 350
4 050
143
1 940
1995
8 392
1 350
4 850
162
2 030
1996
Auszug aus dem “National Survey Report”:
The cumulative installed PV power in 4 sub-markets
9 724
1 450
5 950
184
2 140
1997
11 500
1 470
7 630
190
2 210
1998
13 400
1 480
9 420
200*
2 300*
1999
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15 300
1 480
11 220
210*
2 390*
2000
17 600
1 560
13 340
220*
2 480*
2001
19 500
1 560
15 140
230*
2 570*
2002
21 000
1 560
16 440
260*
2 740*
2003
23 100
1 560
18 440
290*
2 810*
2004
Cumulative installed capacity as of 31 December 2010 (kW)
27 050
2 560
21 240
320*
2 930*
2005
29 700
2 560
23 740
350*
3 050*
2006
36 200
2 560
30 040
400*
3 200*
2007
47 900
2 560
41 540
3 800
2008
73 600
2 560
67 040
4 000
2009
110 900
2 560
104 140
4 200
2010
PV Power
PV Power update wurde im Berichtsjahr 2-mal als elektronische
Version versandt.
Zusätzlich wurden 200 Exemplare für die EUPVSEC-Konferenz
gedruckt und in Hamburg verteilt.
Die Schweiz ist zuständig für den Versand des Newsletters an
etwa 2500 Adressaten weltweit sowie an die nationalen Experten
im Netzwerk.
Trends Report 1992-2010
Basierend auf den Daten des "National Survey Reports" wurde
Ende Oktober 2011 der Trends Report publiziert. Zeitgerecht
konnten die wesentlichen Tabellen zu Beginn der Europäischen
PV-Konferenz in Hamburg auf dem Internet aufgeschalten werden. Die gedruckte Ausgabe wurde Anfang November ausgeliefert.
Die wichtigsten Daten aus dem Report sind im Internet unter
www.iea-pvps.org [3] einsehbar. Der ganze Report wie auch
einzelne Tabellen können als PDF-Dokumente heruntergeladen
werden.
WORKSHOPS
Task 1 war insgesamt an 3 Workshops beteiligt. 2 davon wurden in Eigenregie organisiert.
Wie in den Vorjahren war die Schweiz hauptverantwortlich für den EUPVSEC-Workshop, Japan organsierte den asiatischen Workshop, dieses Mal in Japan selbst.
16 February 2011: UFTP & IEA-PVPS Workshop, Istanbul, Turkey:
Advantages of and possible Issues Surrounding
Grid-Connected PV Power Systems
Die Kombination von Task 1 Meetings mit einem nationalen Workshop war wiederum sehr erfolgreich. Der
von der lokalen UFTP (Ulusal Fotovoltaik Teknoloji
Platformu) organisierte ganztägige Workshop mit türkischen und internationalen Referenten ermöglichte
einen sehr guten Austausch zwischen den Experten
von Task 1 und der PV-Industrie in der Türkei.
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7 September 2011: EUPVSEC, Hamburg, Germany
“Driving future PV deployment - electricity utility PV
business models?“
Gegen 100 Teilnehmer bekundeten ihr Interesse an diesem Workshop. Mit Referenten von EURELECTRIC,
SMA sowie Experten aus dem PVPS Task 1 Umfeld
wurde ein hochinteressantes Programm geboten. Dies
zeigte sich auch an der abschliessenden Diskussion, die
um mehr als 30 min überzogen wurde.
Aus der Schweiz stellte ein Vertreter des ewz die Solarstrombörse ewz vor.
1 December 2011: PVPS @ PVSEC, Fukuoka, Japan
PV trends i n e stablished a nd emerging m arkets
and developing countries
Task 1 ist es gelungen, namhafte Referenten aus den
aufstrebenden Märkten China, Indien und Taiwan für
eine Präsentation zu verpflichten. Obwohl die Teilnehmerzahl eher klein war im Vergleich zu Hamburg,
profitierten die TeilnehmerInnen von hervorragenden
Referaten zu den asiatischen, europäischen und USMärkten (Paula Mints, Navigant).
Konferenzen
EUPVSEC Hamburg: Posterpräsentation der Resulate des Trends Reports 2010.
Zusätzlich wurden für den PVPS-Stand (innerhalb des EPIA-Standes) Flyer mit den neusten Resultaten des Trends Reports aufgelegt. Der PVPS-Newsletter wurde in einer gedruckten Version (200 Exemplare) ebenfalls abgegeben.
PVSEC21 in Fukuoka, Japan: Oral Presentation [5] zum Trends Report 1992 – 2010. Zusätzlich
Workshop (siehe oben).
Neue Webseite PVPS (Sonderauftrag PVPS)
Betreuung/Koordination der Webseiten-Entwicklung (Struktur CMS) sowie Migration der Inhalte aus
der bestehenden Webseite.
PR und Networking
Mit-Organisation der Schweiz. Photovoltaik-Tagung 2011 von Swissolar in Fribourg. Mitglied des Programm-Komitees.
Leitung der Kommission Photovoltaik des Branchenverbandes Swissolar
Der direkte Draht zu den Swissolar-Mitgliedern ermöglicht auch das direkte Abrufen von spezifischen
Informationen zum PV-Markt in der Schweiz.
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Das erstmalige Task1-Meeting in Istanbul in Kombination mit einem nationalen Workshop war ein
voller Erfolg. Task 1 – Experten bestritten einen grossen Teil des ganztägigen Workshops.
Der Workshop in Hamburg war sehr gut besucht und wurde sowohl wegen den organisatorischen wie
auch inhaltlichen Qualitäten gelobt. Insbesondere ist es uns gelungen, Vertreter der Strombranche als
Referenten zu gewinnen (EURELECTRIC, ewz).
Der Fukuoka – Workshop wurde zwar etwas weniger gut besucht, inhaltlich war er aber ein absolutes
Highlight der Konferenz, da es gelungen war, je einen Vertreter aus den Märkten China, Indien und
Taiwan zu präsentieren. Die Referate befinden sich auf der Webseite www.iea-pvps.org.
Bereits hat die Planung für 2 weitere Workshops in Frankfurt (EUPVSEC) und China (nähe Shanghai,
PVSEC22) begonnen.
Ziel ist auch, den Trends Report etwas früher als bisher zu publizieren.
Referenzen
[1] P. Hüsser National Survey Report on PV Power Applications in Switzerland 2010, Mai/Aug. 2011
[2] Trends in Photovoltaic Applications in selected IEA countries between 1992 and 2010, IEA, PVPS, Task I – 20:2011
[3] Internet site www.iea-pvps.org
[4] I. Kaizuka, G. Watt, P. Hüsser, R. Bründlinger, Trends in Photovoltaic Applications - The Latest Survey Results on PV
Market, Industry and Policies from the IEA PVPS Programme
Poster Präsentation EUPVSEC, Hamburg, Sept. 2011,
[5] P. Hüsser, I. Kaizuka, G. Watt, R. Bründlinger, Trends in Photovoltaic Applications - The Latest Survey Results on PV
Market, Industry and Policies from the IEA PVPS Programme
Oral presentation, PVSEC21, Fukuoka, Japan, Nov. 2011.
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SWISS INTERDEPARTMENTAL PLATFORM
FOR RENEWABLE ENERGY AND ENERGY
EFFICIENCY PROMOTION IN INTERNATIONAL
COOPERATION (REPIC)
Annual Report 2011
Address
Date
Waldweg 8, CH-1717 St. Ursen
+41 (0) 26 494 00 30, [email protected], http://www.repic.ch
SECO UR-00123.03.01
01.04.2011 – 31.12.2013
April 2012
ABSTRACT
The Swiss State Secretariat for Economic Affairs (SECO), the Swiss Agency for Development and
Cooperation (SDC), the Swiss Federal Office for the Environment (FOEN) and the Swiss Federal
Office of Energy (SFOE) have been operating the interdepartmental platform for the promotion of
renewable energy in international cooperation since 2004. In 2011, phase III of the REPIC Platform
started and focuses now more on concrete application and possible multiplication of promising project
approaches. The REPIC-Platform contributes to the implementation of global climate protection
agreements and to a sustainable energy supply in developing and transition countries, as well as in
Switzerland, and represents an important part in the implementation of the Swiss policy for sustainable development on the international level. The REPIC-Platform thereby represents an important
contribution to the creation of a coherent policy and strategy in Switzerland, for the promotion of renewable energy in international cooperation. The specific goals of the REPIC-Platform in relationship
with renewable energy in international cooperation are:
1. Project promotion and project realisation
2. Information and communication
3. Coordination
The measures of the REPIC-Platform are subsidiary to national and international promotion instruments which already exist. The measures are meant to support these instruments, especially in the
area of finance (project lines of the governmental agencies involved, mixed credits, WB, IFC, GEF,
and similar) and climate policy instruments (Kyoto-mechanisms). Furthermore, the measures of the
REPIC-Platform should provide for synergies between activities from the private sector and the civil
society.
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Einleitung
Die seit 2004 bestehende REPIC-Plattform ist eine gemeinsame Initiative des Staatssekretariates für
Wirtschaft (SECO), der Direktion für Entwicklung und Zusammenarbeit (DEZA), des Bundesamtes für
Umwelt (BAFU) sowie des Bundesamtes für Energie (BFE) zur Förderung der erneuerbaren Energien
und der Energieeffizienz in der internationalen Zusammenarbeit – Renewable Energy and Energy
Efficiency Promotion in International Cooperation.
Die REPIC-Plattform stellt seit ihrem Bestehen eine neue Form der interdepartementalen Zusammenarbeit dar. Während früher die einzelnen an der REPIC-Plattform beteiligten Ämter in der Regel individuell und punktuell Projekte mit erneuerbaren Energien und Energieeffizienz in der internationalen
Zusammenarbeit gefördert haben, erfolgt heute dank dieser Initiative ein koordinierter Ansatz zur Förderung solcher Projekte. Damit werden eine bessere Koordination zwischen den beteiligten Ämtern
und ein einheitlicheres Vorgehen sichergestellt. Die REPIC-Plattform wirkt subsidiär zu bestehenden
Instrumenten der beteiligten Ämter und soll insbesondere dort Wirkung entfalten, wo früher keine oder
wenig Aktivitäten stattgefunden haben.
Die REPIC-Plattform leistet einen wichtigen Beitrag zur Umsetzung einer kohärenten Politik und Strategie der Schweiz zur Förderung der erneuerbaren Energien und der Energieeffizienz in der internationalen Zusammenarbeit. Sie trägt zur Umsetzung der globalen Klimaschutzvereinbarungen und zur
Förderung einer nachhaltigen Energieversorgung in Entwicklungs- und Transitionsländern ebenso wie
in der Schweiz bei und ist damit ein wertvoller Bestandteil der Umsetzung der schweizerischen Politik
der nachhaltigen Entwicklung auf internationaler Ebene. Der vorliegende achte Jahresbericht beschreibt die Projektaktivitäten, Resultate und Erfahrungen im achten Jahr der Plattform.
REPIC versteht sich als marktorientiertes Dienstleistungszentrum zur Förderung der erneuerbaren
Energien und der Energieeffizienz in der internationalen Zusammenarbeit. Unter Berücksichtigung der
vorhandenen Erfahrungen soll diese Plattform neue konkrete Projekte mit erneuerbaren Energien und
Energieeffizienz unter vermehrter Mitwirkung von Schweizer Unternehmen und Organisationen ermöglichen. Sie baut dazu ein Netzwerk zur Information und Sensibilisierung interessierter Kreise auf,
pflegt den Erfahrungsaustausch zwischen verschiedenen Akteuren und fördert die Kenntnis von lokalen Rahmenbedingungen und Projektmöglichkeiten. Zur Realisierung erfolgversprechender Projekte
kann die REPIC-Plattform Beiträge zu einer Anschubfinanzierung leisten. Darüber hinaus erfolgt über
die REPIC-Plattform die Mitwirkung in internationalen Netzwerken.
Die REPIC-Plattform umfasst die folgenden Arbeitsebenen:
1. Strategische Leitung, gebildet durch die Direktoren der beteiligten Bundesämter
2. REPIC-Steuergruppe, gebildet durch Vertreter der beteiligten Bundesämter
3. REPIC-Sekretariat, bei NET Nowak Energie & Technologie angesiedelt
Die einzelnen Ansprechpartner sind im REPIC-Leitfaden [1] aufgeführt.
Im Jahr 2010 wurde die zweite Phase von REPIC abgeschlossen und im Jahr 2011 die dritte Phase
gestartet. In dieser Phase wird verstärkt Gewicht gelegt auf konkrete Umsetzung und mögliche Multiplikation.
Schwerpunkte 2011, durchgeführte Arbeiten und Ergebnisse
Die Schwerpunkte der REPIC-Plattform lauteten für 2011 wie folgt:
1. Projektbezogene Aktivitäten
2. Information und Kommunikation
3. Koordination innerhalb der Trägerschaft, mit einschlägigen Finanzorganisationen
und mit internationalen Netzwerken
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REPIC, S. Nowak, NET AG
Projektbezogene Aktivitäten
Durch die Zurückstellung von Projektskizzen und -gesuchen im 2010 gab es nach dem Start der dritten Phase im 2011 eine hohe Anzahl Projektskizzen und -gesuche zu bearbeiten. Dementsprechend
wurden auch viele neue Projekte bewilligt und gestartet. Für die laufenden Projekte wurde ein reibungsloser Vollzug sichergestellt. Der Stand der einzelnen Projekte wird im Kapitel 6 ausführlich beschrieben.
Information und Kommunikation
Der verstärkte Fokus aus der zweiten Phase auf Veranstaltungen und Workshops wurde im 2011
etwas reduziert, denn der Fokus galt verstärkt der Multiplikation von erfolgversprechenden Projektansätzen.
Als erster thematischer Anlass des Jahres fand am 21. Juni 2011 ein Workshop zum Thema „Energetische Nutzung von Abfällen aus der Kaffeeherstellung in Mittel- und Südamerika“ [2] statt. Dieser
Workshop wurde von Ernst Basler + Partner und Swisscontact mit Unterstützung des REPICSekretariates organisiert. Rund 35 interessierte Personen nahmen teil.
Am 19. August 2011 nahm REPIC mit einem Stand an der Jahreskonferenz „Entwicklungszusammenarbeit - Innovativ in die Zukunft!“, einer Partnerausstellung der DEZA und SECO, teil. Die Konferenz fand im Palais de Beaulieu in Lausanne statt. Dabei konnten verschiedenste Kontakte geknüpft
werden.
Zudem wurden in der englischen Version des online-Adventskalenders nachhaltige Entwicklung 2011
einzelne REPIC-Projekte vorgestellt.
Die üblichen REPIC Kommunikationsaktivitäten wurden weitergeführt. Die REPIC Website
(www.repic.ch) wurde laufend aktualisiert, der Projektleitfaden [1] und der REPIC Flyer [3] standen
und stehen weiterhin zur Verfügung. Der Projektleitfaden [1] wurde zudem Anfang 2011 aufgrund der
Änderungen der dritten REPIC-Phase aktualisiert. Die Schlussberichte werden jeweils auf der REPICWebsite aufgeschaltet.
Koordination innerhalb der Trägerschaft, mit einschlägigen Finanzorganisationen und mit internationalen Netzwerken
Die REPIC Plattform wurde auch 2011 intensiv genutzt, um die Aktivitäten der beteiligten Bundesämter im Bereich der erneuerbaren Energien und der Energieeffizienz in der internationalen Zusammenarbeit auszutauschen und allenfalls abzusprechen. Im Hinblick auf eine verstärkte Umsetzungsorientierung und Multiplikationswirkung von Projekten gemäss der Strategie für die dritte REPIC Phase
wurden vermehrt Kontakte mit anderen Programmen und Initiativen aufgebaut und erweitert. Im 2011
betraf dies vor allem Organisationen im Bereich CO2-Kompensation. Zudem wurde am 10. Februar
2011 ein erstes Mal ein REPIC-Projekt-Tag im SECO in Bern durchgeführt, an dem ausgesuchte,
abgeschlossene REPIC-Projekte Interessierten innerhalb der REPIC-Bundesämter und einschlägigen
Finanzorganisationen vorgestellt und diskutiert wurden. Ziel war, die Resultate und Erfahrungen aus
den Projekten auszutauschen und die Projekte bekannter zu machen. Der Tag wurde von allen Beteiligten als äusserst positiv bewertet. Mit rund 30 Teilnehmenden war er sehr gut besucht.
Projektaktivitäten und Kennzahlen
Die Projektaktivitäten konnten 2011 mit der dritten Phase wieder intensiv weitergeführt werden. Das
Verfahren funktioniert gut und kann effizient und wirksam abgewickelt werden.
Das thematische Schwergewicht der Anfragen im Jahr 2011 liegt im Bereich der Photovoltaik. Bei den
laufenden Projekten sowie bei den genehmigten Gesuchen liegt es zu jeweils relativ gleichen Teilen
im Bereich der Energieeffizienz, der Photovoltaik und der Biomasse. Die erste Phase konnte im Jahr
2011 mit einem letzten Projekt komplett abgeschlossen werden. Von den insgesamt 30 Projekten aus
der zweiten Phase konnten acht abgeschlossen werden, sieben Projekte sind noch laufend. In der
dritten Phase wurden im Jahr 2011 23 Projekte gestartet. Im Kapitel 5 werden sämtliche im Jahr 2011
laufenden und abgeschlossenen Projekte ausführlicher erläutert. Über alle Phasen hinaus wurden bis
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Ende 2011 durch REPIC 67 Projekte gefördert. Gesamthaft gesehen sind mehrheitlich die Energietechnologien Photovoltaik und Biomasse betroffen. Die Figuren 1 und 2 geben einen Überblick über
sämtliche Projektaktivitäten aus allen REPIC-Phasen und deren Verteilung auf die verschiedenen
Energietechnologien.
Zu den betroffenen Ländern gibt Figur 3 einen Überblick über sämtliche geförderten Projekte.
Figur 1: Projektaktivitäten und Technologien aller REPIC Phasen bis Ende Jahr 2011
Figur 2: Geförderte Projekte und Anzahl Länder aller REPIC Phasen bis Ende Jahr 2011
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Figur 3: Verteilung aller ab 2008 bis Ende 2011 unterstützten Projekte aus allen Phasen
nach Region und Technologiebereich
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Stand der bewilligten REPIC-Projekte aus früheren REPIC-Phasen
Abgeschlossene Projekte mit Bezug zur Photovoltaik
• Nouvelle Planète, Madagaskar: Bau einer Photovoltaikanlage und eines dörflichen Stromnetzes
zur Speisung neuer Batterie- und Akkuladestationen in der ländlichen Gemeinde Ankaranana. Das
Projekt ermöglichte den 2'100 Einwohnern von Ankaranana den Zugang zu elektrischem Strom.
Der ökologische Nutzen dieses Projekts ist bedeutend durch das Einführen von aufladbaren Batterien, welche die Einwegbatterien ersetzen, die zuvor in der Natur landeten.
• Ecogeo, Brasilien: Solare Trinkwasserversorgung. Die Trunz Solar Water Systems Pilotanlagen
wurden in fünf Gemeinden des brasilianischen Nordostens erfolgreich getestet. Die Joint Venture
«Swiss Water Systems» zwischen Ecogeo und Trunz Water Systems wurde gegründet. Eine erste
Fertigungshalle im Nordosten Brasiliens ist im Aufbau.
Projekte in der Abschlussphase mit Bezug zur Photovoltaik
• UEZ, Bosnien & Herzegowina: Markteinführung von solaren Warmwasseranlagen in der Region
Tuzla
Laufende Projekte mit Bezug zur Photovoltaik
• Sahay Solar Solutions, Äthiopien: Aufbau eines Solar Kompetenz Zentrums, Arbaminch Universität
• Tritec, Madagaskar: Elektrifizierung der letzten Meile – Stromversorgung mittels Solarenergie in
abgelegenen Gebieten in Madagaskar
• INFRAS, Albanien: Markttransformation für solare Warmwasseraufbereitung
• Muntwyler Engineering, Indien: Demonstrationsprojekt Solare Elektrofahrzeuge im öffentlichen
Verkehr in Clean Air Island
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Bau einer Photovoltaikanlage und eines dörflichen Stromnetzes zur Speisung
neuer Batterie- und Akkuladestationen in der ländlichen Gemeinde Ankaranana in Madagaskar
Projektart
Schweizer Partner
Technologie
Beschreibung
Land
Schweizer Beitrag
Projektstatus
Infrastrukturorientiertes Projekt
Nouvelle Planète, Lausanne, www.nouvelle-planète.ch, Philippe Randin
Mizara, Corseaux, Philippe Meister
Photovoltaik
Mit dem Bau einer Photovoltaikanlage und einem Stromnetz in der madagassischen Gemeinde Ankaranana sollen neue Batterie- und Akkuladestationen
gespeist werden. Durch diese Ladestationen können Einwegbatterien durch
aufladbare ersetzt werden. Des Weiteren soll das Stromnetz ebenfalls der
Beleuchtung öffentlicher Plätze und des Spitals dienen. Dadurch werden die
Lebensbedingungen in der Gemeinde verbessert und so soll wiederum der
Landflucht vorgebeugt werden. Das Projekt soll ebenfalls die Machbarkeit
eines autonomen Stromnetzes in einer abgelegenen, ländlichen Region zeigen.
Madagaskar
Mit Nouvelle Planète wird das Projekt von einem Schweizer Unternehmen
initiiert, welches grosse Erfahrung in Projekten gegen Landflucht und Umweltschutz in armen Ländern hat. Das Projekt wird von Nouvelle Planète‘s Partnergruppe Mizara begleitet. Das Spezialgebiet des Projektleiters liegt im Bereich von aufladbaren Batterien, er war bereits in Madagaskar tätig und kennt
die Unterfangen von Nouvelle Planète sehr gut.
Abgeschlossen – Das Projekt ermöglichte den 2'100 Einwohnern von Ankaranana den Zugang zu elektrischem Strom. Das Dorf profitiert heute von einem
zuverlässigen und ökologischen Stromnetz von fast 2 km. Dank den beleuchteten Strassen hat sich die Sicherheit in der Nacht deutlich verbessert. Versammlungen im Gemeindehaus und anderen öffentlichen Gebäuden sind
dank der Beleuchtung viel angenehmer. Der ökologische Nutzen dieses Projekts ist bedeutend durch das Einführen von aufladbaren Batterien, welche die
Einwegbatterien ersetzen, die zuvor in der Natur landeten. Zudem hat die
Einführung der aufladbaren Batterien Arbeitsplätze geschaffen und Einnahmen in der Gemeinde generiert.
© Nouvelle Planète
Wirkungen
Dokumentation
Die ca. 25'000 Einwegbatterien, welche jährlich verbraucht wurden, werden
ersetzt mit aufladbaren Batterien.
Schlussbericht „Bau einer Photovoltaikanlage und eines dörflichen Stromnetzes zur Speisung neuer Batterie- und Akkuladestationen in der ländlichen
Gemeinde Ankaranana in Madagaskar [4], zu beziehen bei NET AG, Nouvelle
Planète oder www.repic.ch.
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Solare Trinkwasseraufbereitung in Brasilien
Projektart
Schweizer Partner
Technologie
Beschreibung
Land
Schweizer Beitrag
Projektstatus
Machbarkeitsstudie
Ecogeo GmbH, Bern, Ernesto Moeri
Photovoltaik
Die Versorgung mit sauberem Wasser ist ein elementares Grundbedürfnis,
das aber in vielen Gegenden Brasiliens, insbesondere im trockenen Nordosten und im Amazonasgebiet nicht befriedigt wird. Die brasilianische Regierungs-Initiative Água Doce hat die bestehenden Defizite bisher nicht beseitigen können, viele Brunnen wurden wegen Versalzung stillgelegt, weitere wegen Wartungsproblemen. Die fehlende funktionierende Wasseraufbereitung
führt zu Seuchen, Verarmung und Landflucht.
Das langfristige Ziel des Vorhabens besteht deshalb darin, mit moderner, wartungsarmer und energieautarker Technologie Abhilfe für die Probleme zu
schaffen. Dabei kommen solarbetriebene Entsalzungs- und Aufbereitungsanlagen mit einem Umkehr-Osmose-System aus Schweizer Produktion zum
Einsatz.
Als erster Schritt soll im Projekt die Technologie mit Hilfe einer Demonstrationsanlage ausgewählten Gemeinden in den betroffenen Gebieten nahe gebracht werden und in Zusammenarbeit mit diesen Gemeinden MusterProblemlösungen erarbeitet werden. Begleitet werden diese Aktivitäten von
Gesprächen mit Regierungsstellen und Finanzierungspartnern.
Brasilien
Schweizer Partner steuern zum einen die technische Lösung für das Projekt
bei, zum anderen wird das Projekt von einem brasilianisch-schweizerischen
Beratungsunternehmen umgesetzt.
Abgeschlossen – Im Laufe des Jahres 2010 und bis April 2011 wurden die
importierten Trunz Solar Water Systems Pilotanlagen in fünf Gemeinden des
brasilianischen Nordostens erfolgreich getestet. Mit der Auswahl von geologisch stark unterschiedlichen Orten konnte aufgezeigt werden, dass die Anlagen im Stande sind, auch unterschiedlichste Wasserarten problemlos aufzubereiten.
Das Pilotprojekt ist technisch sowie wirtschaftlich machbar und könnte dazu
beitragen, den aktuellen Einsatz von Tankwagen für die Trinkwasserversorgung der ärmeren Bevölkerung zu ersetzen. Der Betrieb der Versuchsanlage
stösst auf grosse Zustimmung der Leute und der lokalen Behörden in Brasilien.
© Ecogeo
Wirkung
Dokumentation
Die Joint Venture «Swiss Water Systems» zwischen Ecogeo und Trunz wurde
gegründet. Eine erste Fertigungshalle im Nordosten Brasiliens ist im Aufbau.
Schlussbericht „Solarbetriebene Trinkwasserversorgung in Problemgebieten
Brasiliens : Potenzial- und Marktstudie“ [5], zu beziehen bei NET AG, Ecogeo
GmbH oder www.repic.ch
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Demonstrationsprojekt Solare Elektrofahrzeuge im öffentlichen Verkehr in
Clean Air Island, Mumbai
Projektart
Pilotprojekt
Schweizer Partner
Berner Fachhochschule, Technik und Informatik, 2501 Biel, www.ti.bfh.ch ,
Prof. Urs Muntwyler
Technologie
Photovoltaik
Beschreibung
Die indische Partnerorganisation Clean Air Island ist seit mehreren Jahren
bestrebt, die Lebensqualität im Stadtzentrum Mumbais zu verbessern. Ihre
Aktivitäten stützen sich dabei hauptsächlich auf die drei Aktionsbereiche Begrünung von Strassen und Parks, Kompostierung von organischen Abfällen
und Einsatz von Elektrofahrzeugen.
Im Rahmen dieses Demonstrationsprojekts sollen nun zum ersten Mal Elektrofahrzeuge im öffentlichen Verkehr zum Einsatz kommen und gleichzeitig
sollen die Batterien der Elektrofahrzeuge mit Solarstrom gespeist werden. Der
elektrische Bus (30 Personen) und das elektrische Sammeltaxi (10 Personen)
werden auf einem Rundkurs zwischen zwei Bahnhöfen und dem Geschäftsviertel Nariman Point verkehren und damit einen Teil der tausenden von
Pendlern in diesem Gebiet transportieren. Auf dem Dach des Busdepots wird
die Photovoltaikanlage installiert. Die Fahrzeuge können dort jeweils ihre Batterien mit Hilfe eines Schnelladesystems aufladen oder leere Batterien gegen
eine geladene austauschen.
Indien
Land
Schweizer Beitrag
Der Schweizer Experte bringt mit seinen umfassenden Erfahrungen sowohl im
Bereich der Solarenergie als auch im Bereich der Elektrofahrzeuge eine optimale Kombination von Kenntnissen mit, um dieses Projekt zu unterstützen.
Weitere Schweizer Technologiepartner werden nach Bedarf einbezogen.
Projektstatus
Laufend – der Entwurf des elektrischen Bus ist abgeschlossen. Als nachhaltige Energiequelle wurden für das Schnelladesystem Lithium-Batterien ausgewählt, welche an eine PV-Ladestation angeschlossen werden können. Um die
Batterien manuell mittels Hubwagen auswechseln zu können sind spezielle
Stationen vorgesehen. Die Entwicklung des GPS-Systems und der elektronischen Zentralen ist abgeschlossen. Die Zentralen wurden erfolgreich geprüft.
Ein Mechanik-Ingenieur und ein Elektriker wurden angestellt, um das Projekt
weiterzuverfolgen.
© Clean Air Island
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Solarkompetenzzentrum an der Arba Minch Universität in Äthiopien
Projektart
Schweizer Partner
Technologie
Beschreibung
Land
Schweizer Beitrag
Projektstatus
Ausbildung und Qualitätssicherung / Finanzierungsmodell
Sahay Solar Solutions GmbH,Winterthur, www.sahay-solar.com; Max Pohl
ISAAC-SUPSI, Canobbio, www.supsi.ch, Roman Rudel
Photovoltaik
Der Aufbau von selbsttragenden Ausbildungs- und Marktstrukturen im Bereich
Solarenergie ist das gemeinsame Ziel der Arba Minch Universität (AMU) in
Äthiopien, der Fachhochschule der italienischen Schweiz (SUPSI) in Lugano,
sowie der Sahay Solar Solutions, einer gemeinnützigen GmbH aus Winterthur.
Der erste Schritt auf diesem Weg soll die Gründung eines äthiopischen Kompetenzzentrums für Solartechnik innerhalb der AMU sein. Das Kompetenzzentrum umfasst sowohl ein entsprechend ausgerüstetes Solarlabor für Forschungs- und Schulungszwecke als auch die Etablierung eines Lehrstuhls für
erneuerbare Energien für die fachliche Ausbildung von Studenten und Technikern. Parallel zum Kompetenzzentrum soll ein soziales Unternehmenskonzept
zur Realisierung von Solarelektrifizierungsprojekten entwickelt werden, um
sukzessive zukunftsfähige Arbeitsplätze für die ausgebildeten Fachkräfte zu
generieren und eine nachhaltige Entwicklung der Initiative unabhängig von
Drittmitteln zu ermöglichen.
Äthiopien
Mit der Schweizer Universität und der schweizerischen Sozialunternehmung
steht den äthiopischen Partnern sowohl im technischen als auch im unternehmerischen Bereich umfassendes Know-How zur Verfügung.
Laufend – Zwei erste Schulen wurden mit einer autarken PV-Anlage im Rahmen eines Stipendien-Programms an der AMU ausgerüstet. Das Ziel dieser
Aktivität war, die Studenten zunehmend in die praktische Planung und Umsetzung von kleineren Solarprojekten einzuführen.
Experten von ISAAC und Sahay führten die geplante PV-Grundlagenschulung für Mitarbeiter und Studenten am Kompetenzzentrum durch und
bearbeiteten verschiedenste Anfragen seitens äthiopischer Haushalte in Bezug auf Solarlösungen.
Die Arbeiten am neuen Laborgebäude gehen gut voran. Bis zur praktischen
Umsetzung arbeitet das ISAAC federführend an der Konzeptionierung der
Testanlage sowie der technischen Ausstattung der neuen Laborräume.
© Sahay Solar Solution
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Markteinführung von solaren Warmwasseranlagen in der Region Tuzla, Bosnien-Herzegowina
Projektart
Schweizer Partner
Technologie
Beschreibung
Land
Schweizer Beitrag
Projektstatus
Förderverein Umwelt- und Energiezentrum Tuzla, Basel, Ruedi Stauffer, Dorothée Dettbarn
Solarthermie
Das geplante Projekt zielt auf die vermehrte Nutzung von Solarenergie für die
Warmwasserproduktion in der Region Tuzla. Mit dem Projekt ist die praktische
Produktion und Installation von 10 Solaranlagen für Einfamilienhäuser vorgesehen. Das Projekt spricht lokale Unternehmen in der Markteinführung von
Solaranlagen an. Gleichzeitig soll privaten Interessenten geholfen werden,
ihre Solaranlage zu verwirklichen (Selbstbau und Einkauf). Bei dem Projekt
werden lokale Handwerker und Lehrkräfte der technischen Schule ausgebildet. Parallel führt das UEZ eine Medienkampagne durch um über die Nutzung
von Solarenergie für Warmwasser zu informieren.
Bosnien-Herzegowina
Der Schweizer Förderverein Umwelt- und Energiezentrum Tuzla verfügt über
10 Jahre Erfahrung bei der fachlichen und finanziellen Unterstützung von Projekten in Osteuropa.
In der Abschlussphase - Alle 10 geplanten Anlagen wurden gebaut, installiert
und erfolgreich in Betrieb genommen. Es ist gelungen, mit Hilfe von Medienkampagne, Lehrerfortbildung sowie der Gründung eines Runden Tisches mit
den Behörden das Thema auf mehreren Schienen bei unterschiedlichen Zielgruppen breit zu streuen und interessierte Personen von verschiedenen Institutionen und Berufsgruppen zu vernetzen. Die Regierung zeigte sich am Projekt interessiert. Die Öffentlichkeitsarbeit (Info-Material bis Fernsehberichterstattung) weckte sehr viel Interesse bei der Bevölkerung und in den technischen Schulen. Das UEZ empfiehlt eine gemeinsame Fortführung der Aktivitäten mit den ausgebildeten Handwerkern zur Optimierung der lokalen Produktionsweise von qualitativ hochwertigen und gleichzeitig kostengünstigen Anlagen sowie die Weiterführung der Ausbildungstätigkeiten und der Öffentlichkeitsarbeit.
© UEZ, Tuzla
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Markttransformation für solare Warmwasseraufbereitung in Albanien
Projektart
Schweizer Partner
Technologie
Beschreibung
Land
Schweizer Beitrag
Projektstatus
INFRAS AG, Zürich, www.infras.ch, Bernhard Oettli
Solarthermie
Über 80% des Warmwassers in den privaten Haushalten in Albanien wird mit
Hilfe von Elektrizität erzeugt. Dies entspricht zurzeit etwa 2/3 des gesamten
Elektrizitätsverbrauchs in Albanien. Mit seinem mediterranen Klima ist Albanien prädestiniert, den rasch wachsenden Strombedarf für die Warmwasseraufbereitung (WWA) soweit möglich durch solare WWA-Systeme zu ersetzen.
Die Nationale Energieagentur Albaniens hat bei der Global Environment Facility (GEF) ein Projekt vorgeschlagen, das auf eine rasche Entwicklung des
heute kaum existenten Markts für solare WWA-Systeme abzielt. Der Exekutivrat von GEF hat im Sommer 2006 das Projekt als erstes Länderprogramm
(Albanien) im Rahmen eines globalen WWA-Programms gutgeheissen. Nach
Erteilung der Bewilligung des Projektes bei GEF und der albanischen Regierung im November 2009 konnte das Projekt wieder aufgenommen werden.
Albanien
Der Schweizer Beitrag konzentriert sich auf die Ausbildung auf der
Angebotsseite und zielt darauf ab, die in der Schweiz vorhandenen
Erfahrungen im Bereich Schulung und Prüfung sowie im Aufbau von
Dachorganisationen zu nutzen.
Laufend – Im Juni 2011 erfolgte die Trainings- und Studientour albanischer
Produzenten in die Schweiz. Hauptziel war die Verbesserung der Qualität von
in Albanien hergestellten solarthermischen Komponenten. Neben einem Training beim Institut für Solartechnik in Rapperswil wurden Schweizer Produzenten und Anlagen besucht. Im November fand in Tirana das 1. durch Swissolar
durchgeführte Training für Solarinstallateure statt. Das 2. Training vor Ort ist
mit ein paar Anpassungen für Frühling 2012 vorgesehen.
© Swissolar
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Stand der bewilligten REPIC-Projekte aus der REPIC-Phase III
Abgeschlossene Projekte mit Bezug zur Photovoltaik
• Trunz WaterShop Consortium c/o IWÖ-HSG, Universität St.Gallen, Kenia: Entwicklung eines Business-Modells für solarbetriebene Watershops in Kenia. Mit dem Businessmodell konnte gezeigt
werden, dass ein Trunz-Watershop-Konzept machbar ist. 4 Pilotstandorte für nachhaltige, skalierbare Watershops konnten identifiziert werden. Die Gesamtzahl machbarer Watershops in Kenia
wird auf 300 geschätzt.
• Das IEA PVPS Projekt „Photovoltaic Services for Developing Countries“, welches bereits in der
ersten REPIC-Phase bewilligt und gestartet ist, wurde formell in der zweiten REPIC Phase weitergeführt und geht nun auch in der dritten Phase weiter.
Neue Projektunterstützungen im Jahr 2011 mit Bezug zur Photovoltaik
• Entec, International: Schweizer Beitrag im IEA PVPS-Projekt Task 9: Photovoltaic Services for
Developing Countries
• SUPSI-ISAAC, Nepal: Netzgekoppelte PV-Pilotanlage
• Swiss Fresh Water, Senegal: Pilotprojekt eines low-cost und dezentralen Entsalzungssystems im
Sine Saloum Delta in Senegal
• Trunz WaterShop Consortium c/o IWÖ-HSG, Universität St.Gallen, Kenia: Entwicklung eines
Business-Modells für solarbetriebene Watershops in Kenia
• WirzSolar, Haiti: Einführung von Solarpumpen zur Wasserversorgung in der Landwirtschaft
• Berner Fachhochschule, Indien: Mikro-Unternehmen und Kleinbäuerinnen im ländlichen Indien:
Innovation durch nachhaltige Energietechnologien, mit der „Swiss Solar Water Pump“
• DT-Power, Kenia: Mobisol – Solar Home Systeme mit GSM Modem für die ländliche Elektrifizierung
• SwissWaterKiosk Foundation, Bangladesch: Nachhaltige Implementierung von solarthermischen
Anlagen zur Wasseraufbereitung
Laufende Projekte mit Bezug zur Photovoltaik
• SUPSI-ISAAC, Nepal: Netzgekoppelte PV-Pilotanlage
• Swiss Fresh Water, Senegal: Pilotprojekt eines low-cost und dezentralen Entsalzungssystems im
Sine Saloum Delta in Senegal
• WirzSolar, Haiti: Einführung von Solarpumpen zur Wasserversorgung in der Landwirtschaft
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Entwicklung eines Business-Modells für solarbetriebene Watershops in Kenia
Projektart
Schweizer Partner
Technologie
Beschreibung
Land
Schweizer Beitrag
Projektstatus
Finanzierungsmodell, Aufbau von Marktstrukturen
Trunz WaterShop Consortium c/o IWÖ-HSG, Universität St.Gallen,
www.trunz.ch, www.iwoe.unisg.ch, Christoph Birkholz
Photovoltaik
Ziel des Projektes ist die Entwicklung eines Business Modells und anschliessend eines Businessplans für solarbetriebene Watershops in Kenia. Basierend
auf ersten Erfahrungen in einer Region (Ukunda/Diani) werden die Parameter
eines finanziell, sozial und ökologisch machbaren Business Case evaluiert,
um Pilotprojekte und ein späteres Scaling-Up der Watershops zu ermöglichen.
Die Watershops sollen von lokalen Unternehmern geführt werden. Die
zugrundeliegende Technologie von Trunz Water Systems ist bereits in über 35
Ländern erprobt und funktioniert.
Der Analysebereich wird auf weitere Orte im ganzen Land ausgedehnt (bspw.
Lake Turkana Region im Norden). Die wirtschaftliche und finanzielle Machbarkeit sowie die Schaffung von Arbeitsplätzen sind die hauptsächlichen Zugpferde für das Watershop-Konzept. Die Replizierung durch lokale MikroUnternehmen in einem Franchisesystem o.ä. ist das Herzstück des Projektes.
Es wird mitentwickelt durch Trunz Water Systems (Schweiz), Tomash International Ltd. (Kenya) und Forschern der Universität St.Gallen, der ETH Zurich,
des Copenhagen Business School und der Universität Freiburg i.Br.
Kenia
Die zugrundeliegende Technologie zur Wasseraufbereitung wurde vom
Schweizer Technologiepartner Trunz Water Systems entwickelt.
Abgeschlossen – 4 Pilotstandorte für nachhaltige, skalierbare Watershops
konnten identifiziert werden. Die Gesamtzahl machbarer Watershops in Kenia
wird auf 300 geschätzt. Das Konzept ist vor allem auf kleinere Städte und periurbane Gegenden ausgelegt. Ländliche Gegenden sind weniger geeignet.
Jeder Watershop soll durch einen lokalen Betreiber geführt und durch die
lokale Partnerorganisation unterstützt werden. Die Shops bieten Trinkwasser
in wiederverwertbaren und als Markenartikel gelabelten Kanistern zu einem
erschwinglichen Preis an. Zusätzlich sollen weitere Dienstleistungen wie das
Aufladen von Mobiltelefonen angeboten werden, um die Shops wirtschaftlich
betreiben zu können.
© IWÖ-HSG
Wirkungen
Dokumentation
Mit dem Businessmodell konnte gezeigt werden, dass ein Trunz-WatershopKonzept machbar ist. Das Pilotprojekt an den identifizierten Pilotstandorten
soll nun aufgegleist werden. Eine erste Skalierungsphase wird auf ca. 100
Watershops geschätzt.
Schlussbericht „Developing a Business Model for Solar-Powered Watershops
in Kenya“ [6], zu beziehen bei NET AG, IWÖ-HSG oder www.repic.ch.
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Schweizer Beitrag im IEA PVPS-Projekt Task 9
Photovoltaic Services for Developing Countries (PVSDC)
Projektart
Schweizer Partner
Technologie
Beschreibung
Land
Schweizer Beitrag
Projektstatus
Internationales Projekt im Rahmen der IEA-Zusammenarbeit
entec AG, St. Gallen; www.entec.ch, Alex Arter, Thomas Meier
Photovoltaik
Gestützt auf die umfangreichen weltweiten Erfahrungen mit Photovoltaik Anlagen in Entwicklungsländern, strebt dieses Projekt die Erhöhung von erfolgreich und nachhaltig betriebenen Anlagen dieser Art für unterschiedliche Zwecke an. Die internationale Expertengruppe umfasst auf diesem Gebiet eine
breite Projekterfahrung und konzentriert ihre Arbeit insbesondere auf die nichttechnischen Aspekte dieser Anwendungen. Durch den Status eines internationalen Netzwerkprojektes ist die Expertengruppe in permanentem Kontakt mit
zahlreichen internationalen Entwicklungsorganisationen.
Internationales Projekt
Die Schweizer Erfahrung in der internationalen Zusammenarbeit und das bei
entec verfügbare Know-how aus einem verwandten Gebiet (Kleinwasserkraft)
stellen wesentliche Beiträge zu diesem Projekt dar, insbesondere auch in
Bezug auf die Übertragbarkeit der Resultate auf andere Technologien.
Laufend – Der Schweizer Beitrag im 2011 fokussierte sich weiterhin hauptsächlich auf die Themen Photovoltaik und Wasserpumpen. Angesichts der
zunehmenden Bedeutung rund um das Thema Wasserversorgung (Trinkwasser und Bewässerung) setzt PVSDC hier die grösste Priorität der laufenden
und künftigen Aktivitäten. Im November 2011 nahmen verschiedene Experten
am Forum des Rural Water Supply Network (RWSN) in Uganda teil.
Zusätzlich zu einem Ausstellungsbeitrag wurde ein Workshop durchgeführt,
der mit rund 40 Teilnehmern einen sehr grossen Anklang fand. Ein erfolgreicher Dialog zwischen Energie- und Wasserexperten konnte initiiert und weitergeführt werden. Das bereits Ende 2010 im ersten Entwurf vorliegende Positionspapier zu Wasserversorgungsprojekten in Entwicklungsländern wurde im
2011 überarbeitet und am Task 9-Expertenmeeting vorgestellt. Die definitive
Publikation soll im Frühling 2012 vorliegen.
© PVPSTask 9
Dokumentation
Publikationen IEA PVPS Task 9, siehe
http://www.iea-pvps.org/tasks/task9.htm
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Elektrifizierung der letzten Meile – Stromversorgung mittels Solarenergie in
abgelegenen Gebieten in Madagaskar
Projektart
Schweizer Partner
Technologie
Beschreibung
Land
Schweizer Beitrag
Projektstatus
TRITEC International AG, Allschwil, www.tritec-energy.com, Giordano Pauli
Photovoltaik
87% der madagassischen Familien haben keinen Zugang zum Stromnetz und
benützen Kerzen oder Kerosinlampen um ihre Zimmer nachts zu beleuchten.
Soziale Infrastrukturen wie Schulen, Gesundheitszentren, Rats- oder Gemeindehäuser und öffentliche Plätze verfügen in ländlichen Gebieten oft über
keinen Strom. Das gemeinsam mit der madagassischen ADER (Agence de
Développement de l‘Electrification Rurale) und der Deutschen Gesellschaft für
Internationale Zusammenarbeit (GIZ) durchgeführte Projekt verfolgt die folgenden zwei Ziele:
1. Bereitstellung von Elektrizität für soziale Infrastrukturen in 4 prioritären ländlichen Gemeinden im Süden Madagaskars, betrieben durch eine lokale private
Firma.
2. Information und Ausbildung über die Vorteile von Solarenergie für einkommensschwache Haushalte in den ländlichen abgelegenen Gebieten durch
Mobil-Kommunikation.
Die Einheiten und der Zugang zu Pico-Solarsystemen erfolgen durch erschwingliche Verkaufs-/Mietsysteme. Das Projekt visiert ca. 20‘000 Haushalte
in den ärmsten ländlichen Regionen Madagaskars an, in denen heutzutage
noch keine modernen Energiedienstleistungen verfügbar sind.
Madagaskar
TRITEC ist seit über 20 Jahren ein Photovoltaik-Systemlieferant und hat anlässlich eines früheren Entwicklungsprojektes bereits an der Implementierung
von dezentralen Photovoltaiksystemen in Madagaskar mitgewirkt. Der
Schweizer Beitrag bezieht sich hauptsächlich auf das Training der lokalen
privaten Operateure und Mitarbeitern von ADER sowie auf das Solarmaterial
der ersten Gemeinde.
Laufend – Eine Bestandsaufnahme der für die Elektrifizierung in Frage kommenden Dörfer und Gebäude wurde durchgeführt, und die Solaranlagen für
die ausgesuchten Gebäude geplant. Die Solarstromanlagen werden kostenlos
installiert, den Strom müssen die Gemeinden jedoch selber bezahlen. Die
Grösse der Anlage und der Bedarf an Strom wurden mit dem Gemeinderat
und den Schuldirektoren ausführlich besprochen. Als Zielobjekte für beide
Gemeinden wurden prinzipiell die sozialen Einrichtungen wie Schulen und die
Krankenstation ausgesucht. Zusätzlich zu den Abklärungen in den Gemeinden wurden zwei Schulungen durchgeführt für ortsansässige Ingenieure und
Firmen, einmal in Tulear und einmal in Antananarivo.
© TRITEC, Madagaskar
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Netzgekoppelte PV-Pilotanlage in Nepal
Projektart
Schweizer Partner
Technologie
Beschrieb
Land
Schweizer Beitrag
Projektstatus
Pilotprojekt
SUPSI – ISAAC, Canobbio, www.isaac.supsi.ch, Domenico Chianese, Dr.
Roman Rudel
Photovoltaik
Das Projekt handelt von der Realisierung und dem Monitoring einer netzgekoppelten Photovoltaik-Pilotanlage im Kathmandu-Tal. Es hat sich weiterentwickelt aus den ermutigenden Resultaten der bereits durchgeführten REPICMachbarkeitsstudie zu netzgekoppelter Photovoltaik in Nepal. Der aktuelle
Mangel an einem zuverlässigen Stromnetz und die gestiegenen Bedürfnisse
der Nutzer (kleine und mittlere Unternehmen, Bevölkerung) kann durch eine
dezentrale und partiell autonome Stromversorgung gelöst werden.
Das Pilotprojekt sieht den Entwurf, den Bau und das Monitoring einer 1 kWp
netzgekoppelten PV-Anlage vor. Dazu gehört ein Back-Up-System, welches
als Mini-Grid funktionieren kann. Zusätzlich zur Realisierung der Pilotanlage
beinhaltet das Projekt Ausbildungskomponenten. Ein weiterer wichtiger Teil
besteht aus der Demonstration und Verbreitung der Installationsresultate und
der gesamten technischen Charakteristiken. Die Erfahrung aus dem Projekt
soll auch als Referenz für ähnliche mögliche Entwicklungen in anderen einkommensschwachen Ländern dienen.
Nepal
Der Schweizer Partner bringt breite Erfahrung im Bereich netzgekoppelter
Photovoltaik und Ausbildung mit. Die Photovoltaik-Abteilung des ISAAC ist ein
Schweizer Kompetenz-Zentrum für das Testen von PV-Modulen.
Laufend – Die Vorbereitungsphase des Projekts hat begonnen und die Entwurfsphase der Pilotanlage ist abgeschlossen. Die Ausschreibungen für die
Beschaffung von Baumaterial laufen. Einzig die Wechselrichter werden aus
der Schweiz importiert und den nepalesischen Bedingungen angepasst.
© ISAAC-SUPSI
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Pilotprojekt eines low-cost und dezentralen Entsalzungssystems im Sine Saloum Delta in Senegal
Projektart
Schweizer Partner
Technologie
Beschreibung
Land
Schweizer Beitrag
Projektstatus
Pilotprojekt
Swiss Fresh Water, Lausanne, www.swissfreshwater.com, Renaud de Watteville
Photovoltaik
Swiss Fresh Water (SFW) entwickelte ein low-cost Entsalzungssystem für
Salz- und Brackwasser, welches eine Produktion im kleinen Massstab (400 l
Trinkwasser/Tag) mit dem Einsatz von Sonnenenergie erlaubt. Das System
wurde für eine einfache Benutzung entwickelt, es ist einfach im Unterhalt und
konsumiert wenig Energie.
SFW hat entschieden, ein Pilotprojekt im Sine Saloum Delta durchzuführen, in
dem 225‘000 Menschen leben. Ausserhalb der Regenzeit, d.h. ca. 8-9 Monate
des Jahres, trinkt die Bevölkerung vor allem Wasser aus BrackwasserBohrungen. Dieses Wasser ist stark Fluor-belastet und bewirkt ernsthafte
Gesundheitsprobleme. Wenn es sich die Bevölkerung leisten kann, kauft sie
sich regelmässig importiertes Trinkwasser, welches per Boot, Auto oder Lastwagen zu den Inseln gebracht wird. Das Projekt von SFW will dazu beitragen,
die Auswirkungen der Wasserversorgung auf die Gesundheit und den Bedarf
an Zeit, Geld und Energie (Transport) zu verringern.
Gemäss den Erwartungen des SFW wird der Erfolg des Pilotprojektes bestätigen, dass das low-cost und dezentrale Konzept ein grosses Potenzial in Senegal hat. Dort wurden auch bereits andere Regionen identifiziert, welche sich
für eine Replikation des Projekts eignen würden.
Senegal
Swiss Fresh Water ist ein neues Start-up-Unternehmen der ETH Lausanne.
Die Leiter weisen breite Erfahrung im Projektmanagement und der Wasserbehandlung auf. Das Projekt wird in enger Zusammenarbeit mit der Firma Impact
Finance aus Genf durchgeführt. Sie ist auf die Entwicklung und Finanzierung
von Projekten in Entwicklungsländern spezialisiert.
Laufend – Die ersten zwei transportierten und installierten Maschinen funktionieren problemlos und ohne Ausfälle. Weitere 17 Maschinen sind in Vorbereitung und werden demnächst in die Dörfer des Sine Saloum geliefert. Als Regionalzentrum wurde Foundiongne bestimmt.
Die Präsentation der Maschinen beim Regionalrat, welcher die Vorgesetzten
und wichtigen lokalen Persönlichkeiten vereint, verlief erfolgreich. Verhandlungen mit den senegalesischen Verantwortlichen laufen bezüglich Steuererleichterungen aufgrund der öffentlichen Bedeutung des Projekts.
© Swiss Fresh Water
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Vorbereitung zur Multiplikation des Mali-Solarpumpenprojekts in Haiti
Projektart
Schweizer Partner
Technologie
Beschreibung
Land
Schweizer Beitrag
Projektstatus
Pilotprojekt
WirzSolar GmbH, Sissach, Fredy Wirz
Photovoltaik
In Haiti können Solarpumpen optimal und nachhaltig eingesetzt werden, um
das teure und weitverbreitete Verteilen von Trinkwasser mit Zisternenwagen
(Watertrucking) zu ersetzen und günstig mehr sauberes Trinkwasser auf bestehenden oder jetzt neu errichteten Brunnen zu fördern.
Dieses Projekt beinhaltet eine Abklärungs- und Vorbereitungsmission für ein
möglicherweise grösseres Solarpumpenprojekt ab 2012 in Haiti. Zusammen
mit den Wasserbehörden und UNICEF soll ein Programm zur nationalen Ausbildung von lokalen Technikern und Sensibilisierung aller Akteure erarbeitet
werden, bei welchem von den Erfahrungen von WirzSolar/ Solsuisse in Mali
profitiert werden kann. Daneben sollen durch den Einsatz von DemoSolarpumpensystemen und dem Austesten von 3 in der Schweiz entwickelten
Mini-Solarpumpen zum Ausrüsten von Handpumpen zusätzlich konkrete Verbesserungen in der Trinkwasserversorgung vor allem in Schulen im Erdbebengebiet Leogane erzielt werden.
Der vorgesehene Süd-Süd Know-How Transfer der Erfahrungen aus Mali mit
Ausbildung der nationalen Wasserbehörden DINEPA, UNICEF, WASH NGO
Partnern und der lokalen Wasserkomitees und lokaler Techniker durch Wirz
Solar und einen erfahrenen malischen Solsuisse Techniker sind Komponenten
zur erfolgreichen Weiterführung und zur Multiplikation der Erfahrungen aus
dem durch REPIC unterstützten Mali Solarpumpenprojekt.
Haiti
WirzSolar GmbH besitzt langjährige konkrete Erfahrung mit Solarpumpenprojekten in Entwicklungsländern, insbesondere in Mali, wo bereits solche
durch REPIC unterstützte Projekte stattgefunden haben.
Laufend – In einer ersten Mission konnten zusammen mit dem malischen
Techniker drei Tauchpumpenanlagen installiert und ein erster Test mit dem
neuen Solarmotor der Berner Fachhochschule für Handpumpen durchgeführt
werden. Gleichzeitig wurde ein kleines haitianisches Installationsteam aufgebaut und trainiert. Verzögerungen ergaben sich bei der Auslösung des Materials durch den haitianischen Zoll. Zudem sind von der Seite der Partner noch
nicht alle Bohrungen vorhanden. Als nächster Schritt sind bei einer zweiten
Teiletappe vor Ort die Installation weiterer Demoanlagen sowie die konzeptionelle Ausarbeitung eines Programmes mit den lokalen Wasserbehörden vorgesehen.
© Wirz Solar
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Mikro-Unternehmen und Kleinbäuerinnen im ländlichen Indien: Innovation
durch nachhaltige Energietechnologien, mit der „Swiss Solar Water Pump“
Projektart
Schweizer Partner
Technologie
Beschreibung
Land
Schweizer Beitrag
Projektstatus
Pilotprojekt
Berner Fachhochschule, Technik und Informatik, Biel, www.bfh.ch, Prof. Dr.
Eva Schüpbach
Photovoltaik
Das Ziel des Pilotprojekts ist die Einführung einer nachhaltigen Energietechnologie in kleinen indischen Landwirtschaftsbetrieben. Für den Anfang beschränkt sich das Projekt auf die Region Karnataka. Die angewandte Technologie « Swiss Solar Water Pump » ist ein einzigartiges, kleines und günstiges
Wasserpumpsystem, welches mit Strom aus 80W Photovoltaikanlagen gespeist wird. Diese Technologie wurde gemeinsam von der Universität Bern
und der Berner Fachhochschule entwickelt. Sie ist flexibel und von langer
Lebensdauer und kann lokal produziert und gewartet werden. Die Umsetzungsstrategie des Projekts richtet sich an Frauengruppen und Unternehmerinnennetzwerke. Der Wissenstransfer ist in Form von Seminaren und Arbeitsgruppen vorgesehen, woran auch die Hochschulen und Schweizer sowie
Indischen Unternehmen teilnehmen werden.
Indien
Das Labor für Industrieelektronik an der Fachhochschule Bern in Biel hat für
die Entwicklung der Wasserpumpe eng mit Fachpersonen der Entwicklungszusammenarbeit wie Caritas und Seecon zusammengearbeitet.
Frau Prof. Dr. Eva Schüpbach pflegt im Bereich der globalen Veränderungen
die regelmässige Zusammenarbeit mit den indischen Hochschulen.
Laufend – Das Projekt startet im Januar 2012.
© Berner Fachhochschule
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Mobisol – Solar Home Systeme mit GSM Modem für die ländliche Elektrifizierung
Projektart
Schweizer Partner
Technologie
Beschreibung
Land
Schweizer Beitrag
Projektstatus
Pilotprojekt
DT-Power, Zug, www.dt-power.me, Thomas Gottschalk
Photovoltaik
Die Entwicklung der Elektrifizierung in Kenia konzentriert sich hauptsächlich
auf das städtische Gebiet. Das Projekt Mobisol wurde entwickelt, um auch den
Bedarf in den ländlichen Gebieten zu decken. Mobisol SHS ist ein PV Modul
welches mit einem GSM Modem ausgerüstet ist und eine Fernkontrolle des
Produkts erlaubt. Das Angebot beinhaltet ein Zahlungssystem (pay-as-you-go)
welches speziell an die Zahlungsmöglichkeiten der lokalen ländlichen Bevölkerung angepasst ist. Für das Angebot, die Verteilung und das Monitoring wird
das Netz eines nationalen Mobiltelefonanbieters genutzt. Das Pilotprojekt hat
zum Ziel, die Vertrauenswürdigkeit der technischen Komponenten, der Vermarktung und die Wirtschaftlichkeit von 100 Mobisol-Systemen in Kenia zu
prüfen. Das Mobisol-Projekt versucht, ein System zur Verfügung zu stellen,
welches sowohl für die Kunden wie auch für die Investoren finanziell machbar
ist.
Kenia
DT-Power ist ein junges Unternehmen mit Rechtssitz in der Schweiz, welches
für das Produkt Mobisol gegründet wurde. Die Verantwortlichen haben mehrere Jahre Erfahrung im Bereich der erneuerbaren Energien.
Laufend – Das Projekt hat im Dezember 2011 angefangen.
© DT Power
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Nachhaltige Implementierung von solarthermischen Anlagen zur Wasseraufbereitung in Bangladesch
Projektart
Schweizer Partner
Technologie
Beschreibung
Land
Schweizer Beitrag
Projektstatus
Pilotprojekt
SwissWaterKiosk Foundation, www.swisswaterkiosk.org, und SPF Institut für
Solartechnik, Rapperswil, www.solarenergy.ch, Lars Konersmann
Solarthermie
SoWaDis (Solar Water Disinfection) ist ein solarthermisches System zur Desinfektion von Trinkwasser. Es wurde am Institut für Solartechnik SPF der
Hochschule für Technik Rapperswil entwickelt. Beim Pilotprojekt geht es darum, 10 Wasserkiosks als Anlagen-Verbund im ländlichen Raum im Süden von
Bangladesch aufzubauen. Dadurch soll ein nachhaltiges Betriebssystem für
diesen Anlagen-Verbund („Cluster“) getestet und implementiert werden. Die
technische Funktionalität der Wasseraufbereitung mittels SoWaDis sowie die
soziale Akzeptanz wurden bereits untersucht. Nun soll die Technologie erstmals als Anlagenverbund mit einem nachhaltigen Betriebs- und Wartungskonzept zur Anwendung kommen. Diese Wasserkioske sollen von lokalen Benutzergemeinschaften eigenverantwortlich und finanziell nachhaltig betrieben
werden.
Bangladesch
Das Institut für Solartechnik SPF der Hochschule für Technik Rapperswil entwickelte die Technik SoWaDis.
Bewilligt – Das Projekt startet im Januar 2012.
© SPF
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Beurteilung 2011 und Ausblick 2012
Nach dem Start der dritten REPIC Phase von auf Anfang 2011 kann als Zwischenstand ein erster
Vergleich mit den für Phase III formulierten Zielen gezogen werden.
Im Hinblick auf die Projektförderung und -realisierung wurden bereits im ersten Jahr mehr Projekte
gefördert als insgesamt für Phase III mindestens erwartet, nämlich total 23 bis Ende Jahr. Das bisher
in REPIC Phase III ausgelöste Projektvolumen ist über 3-mal grösser als die erfolgten Beiträge. Auch
wurden schon annähernd 50% der Mittel der REPIC-Plattform für konkrete Aktivitäten in Entwicklungsund Transitionsländer reserviert. Es zeichnet sich daher für 2012 bereits eine frühzeitige Vollverpflichtung der Projektmittel ab.
Konkrete Resultate und Wirkungen in Bezug auf umgesetzte Projekte und konkrete Fortsetzungen
können noch nicht bestimmt werden, sind die meisten Projekte doch noch in der Ausführungsphase.
Trotzdem konnte bereits an der der Art der geförderten Projekte beobachtet werden, dass der Fokus
verstärkt auf der Umsetzung und Multiplikationswirkung liegt. Es wurden vermehrt Pilotprojekte mit
konkreten Anlagen gefördert und durchgeführt. Zudem wurde darauf geachtet, dass die geförderten
Projekte ein möglichst hohes Multiplikationspotenzial aufweisen.
Die Qualität der Projektanträge hat sich im Verlauf der Zeit verbessert. Dies ist einerseits sicher einer
stärkeren Bekanntheit von REPIC und guter Netzwerkfunktion der Plattform zu verdanken, andererseits durch ausgeprägtere Erfahrung der Gesuchsteller und eine engere Begleitung mit spezifischer
Beratung aufgrund der Erfahrungswerte begründet.
Die REPIC-Plattform ist unter den relevanten Akteuren bekannt. Sie ist gut etabliert und spielt im
schweizerischen Kontext eine wichtige Rolle. Entsprechend wird die Plattform aktiv genutzt, was sich
auch in der Anzahl neu geförderter Projekte widerspiegelt.
REPIC war auch im 2011 bei relevanten Tagungen und Workshops im Bereich erneuerbare Energien
präsent und organisierte zwei REPIC-Anlässe. Dies entsprach den Erwartungen gemäss Zielsetzungen. Auf internationaler Ebene können und sollen die Netzwerkkontakte noch weiter ausgebaut werden. Im 2011 wurden die Kontakte bereits weiter vertieft und „Best Practices“ ausgetauscht.
Die Koordination zwischen den beteiligten Bundesämtern verlief wie bis anhin effizient. Die Qualität
der Projekte und Massnahmen ist mit wohl begründeten Entscheiden gesichert. Doppelspurigkeiten
konnten vermeiden werden.
Für 2012 steht die Weiterführung der REPIC Phase III im Vordergrund. Dazu gehört auch die verstärkte Vernetzung zu anderen Initiativen, Finanzierungsgebern und Akteuren im Bereich CO2-ZertifikateHandel. Unter Anderem ist wiederum ein REPIC-Tag zur Vorstellung abgeschlossener Projekte in
einem weiteren Kreis von Finanzierungsgebern und Akteuren vorgesehen. Auch der Austausch von
Erfahrungen und Projektanforderungen mit Investoren gehört dazu.
Im Kommunikationsbereich sollen weitere themenspezifische Veranstaltungen organisiert werden.
Insbesondere der Erfahrungsaustausch und die Vernetzung zwischen den Akteuren stehen dabei im
Vordergrund.
Referenzen
[1] REPIC-Leitfaden (REPIC)
[2] REPIC Workshop mit Ernst Basler und Partner (EBP): Energetische Nutzung von Abfällen aus der Kaffeeproduktion
in Süd- und Mittelamerika, Juni 2011 (Vorträge)
[3] REPIC-Flyer (REPIC)
[4] Nouvelle Planète, Bau einer Photovoltaikanlage und eines dörflichen Stromnetzes zur Speisung neuer Batterie- und
Akkuladestationen in der ländlichen Gemeinde Ankaranana in Madagaskar, Schlussbericht
[5] Ecogeo, Solare Trinkwasseraufbereitung in Brasilien, Potenzial- und Marktstudie, Schlussbericht
[6] Trunz WaterShop C onsortium, E ntwicklung e ines B usiness-Modells f ür so larbetriebene Watershops i n K enia,
Schlussbericht
Alle Publikationen sind bei NET Nowak Energie & Technologie AG oder unter http://www.repic.ch zu
beziehen.
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IEA-PVPS TASK 12: SWISS ACTIVITIES IN 2011
ÖKOBILANZEN VON SOLARSTROM UND
VON CHEMIKALIEN IN DER PHOTOVOLTAIKINDUSTRIE
Annual Report 2011
Address
Date
Karin Flury, Matthias Stucki, Rolf Frischknecht
ESU-services Ltd.
Kanzleistr. 4, 8610 Uster
Tel. 044 940 61 02, Fax 044 940 61 94
[email protected], www.esu-services.ch
SI/500052 / SI/500052-02
01.01.2008 – 31.12.2011
7.12.2011
ABSTRACT
Life c ycle as sessment ( LCA) i s an en vironmental m anagement t ool f or anal ysing, c omparing a nd
improving t he environmental impacts of products or technologies. The ecoinvent dat abase pr ovides
life cycle inventory data for currently more than 4000 unit processes. Amongst other datasets, photovoltaic life cycle inventory data are provided.
Within the Swiss contribution to the IEA PVPS Task 12, Subtask 2, the methodology guidelines were
revised, the dataset of ethylene-tetrafluoroethylene (ETFE) was updated. The consideration of latest
emission figures of the concerned industry results in a significant reduction of the environmental impacts in the ETFE production.
Furthermore, dat asets of t he pr oduction of a -Si-laminates were es tablished i n collaboration with a
Swiss m anufacturer. I t i s shown, t hat, f rom an en vironmental p oint of v iew, t hese laminates are
among the most favourable photovoltaic technologies. T his is due t o t he s mall amount of materials
needed and the non-use of a mounting system, since the modules are integrated in roof systems and
facades.
The investigation of PV recycling started in 2011. However, due to delays in the supply of information
from manufacturers, the LCI of PV recycling could not be completed yet.
Within another BFE commissioned project LCI data on important PV technologies is being updated in
view of the new national energy strategy 2050.
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Ökobilanzen s ind ein U mweltmanagement-Werkzeug, um di e U mweltauswirkungen von Produkten
und Technologien zu analysieren, zu vergleichen und zu verbessern. Eine wesentliche Grundlage für
Ökobilanzen sind S achbilanzdaten, w elche die E nergie- und Massenflüsse üb er di e verschiedenen
Lebensphasen des zu untersuchenden Objektes beschreiben. Die ecoinvent Datenbank stellt zurzeit
solche Sachbilanzdaten für mehr als 4'000 Einheitsprozesse bereit [1]. Diese Daten w erden i n allen
bedeutenden Ö kobilanz-Softwareprodukten a ngeboten un d von üb er 2'500 Nutzern in üb er 40 Lä ndern weltweit verwendet.
Die letzte Aktualisierung d er P hotovoltaik(PV)-Sachbilanzdaten i m R ahmen der ec oinvent Projekte
wurde i m F rühjahr 2009 durchgeführt [2-4]. D ie Sachbilanzdaten i m ec oinvent D atenbestand v 2.2
beschreiben di e S ituation der amerikanischen und e uropäischen P V-Industrie sowie d ie Anwendung
von 3 kWp PV-Anlagen auf Gebäuden in der Schweiz und in Europa im Jahr 2005.
Da sich der P V-Sektor r asch w eiterentwickelt un d s ignifikante V erbesserungen v erschiedener PVSysteme erreicht wurden, ist es von Interesse, diese Änderungen auch in den Sachbilanzdaten abzubilden.
Im Rahmen der IEA-PVPST Task 12, Subtask 2 werden verschiedene PV-Ökobilanz-Projekte durchgeführt. Die Schweizer Projektpartner stellten im Jahr 2009 neue Datensätze zu Freiflächen- und Photovoltaik-Grossanlagen für eine Implementierung in der ecoinvent Datenbank bereit [5]. 2010 wurden
die Solarstrommixe in 26 Ländern aktualisiert sowie verschiedene Chemikalien und Materialien, die in
der PV-Industrie verwendet werden, bilanziert.
Um die Wahrnehmung der Photovoltaik als umweltfreundliche Technologie aufrecht zu erhalten, sind
seit zwei Jahren Bestrebungen im Gange ein Sammelsystem von Modulen nach dem Anlagerückbau
zu e tablieren u nd ein Recyclingsystem für di e P hotovoltaik-Module auf zubauen. Mi t de n v on den
Schweizer P rojektpartnern der I EA-PVPS Task 12 g eplanten Arbeiten wird be absichtigt, diese E ntwicklung in den Ökobilanzdaten zu berücksichtigen.
Für das Jahr 2011 plante der Schweizer Projektpartner folgende Arbeiten durchzuführen:
• Erstellung von Sachbilanzdatensätzen zu Modul-Take-Back-Systemen und Modul-Recycling
• Aktualisierung des S achbilanzdatensatzes zu E TFE, das in der P hotovoltaik-Industrie v erwendet wird.
• Die Sachbilanzdaten des a-Si-Laminats eines Schweizer Herstellers werden erstellt und zur
Implementierung in ecoinvent zur Verfügung gestellt.
• Diskussion der Sachbilanzdaten mit IEA-PVSP Task 12 Projektpartnern.
Die Verantwortung über die Inhalte und Publikation der Sachbilanzdaten liegt bei ESU-services
GmbH. Es ist geplant, dass die Daten im Rahmen einer Aktualisierung des ecoinvent Datenbestand
publiziert werden (verantwortlich: ecoinvent Centre). Das Review der bereits 20 09 und 2010 neu erstellten und überarbeiten Datensätze durch ecoinvent ist hängig.
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Kurzbeschrieb des Projekts / der Anlage
Das Ziel des Gesamtvorhabens, Subtask 2 innerhalb des Task 12, LCA, ist das Erarbeiten von aktuellen Sachbilanzdaten zur Stromerzeugung mit Photovoltaikanlagen. In TAB. 1 sind die einzelnen Aktivitäten und die hauptverantwortlichen Personen aufgelistet.
Tab. 1: Aktivitäten im Subtask 2 des IEA-PVPS Task 12
Subtask 2. LCA
Country
Experts
Activity 2-0 Guidelines for common approach in LCI and LCIA
NL/CH/US
Erik Alsema / Matthias Stucki / Rolf
Frischknecht / Vasilis Fthenakis
Activity 2a Mono and multi- c-Si US
NL
Mariska de Wild-Scholten
Activity 2b Ribbon c-Si
NL
Mariska de Wild-Scholten
Activity 2c a-Si & tandem
US/NL
Activity 2d CIGS
DE/NL
Activity 2e CdTe
US/IT
Vasilis Fthenakis
Activity 2f Concentrator PV
ES/US/NL
Vasilis Fthenakis & Mariska de WildScholten
Activity 2g Production of Si feedstock
NO
Ronny Glockner
Activity 2h LCI data management and publication
CH
Matthias Stucki & Rolf Frischknecht
Vasilis Fthenakis & Mariska de WildScholten
Michael Held & Mariska de WildScholten
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Die Guidelines für Ökobilanzen von Solarstrom wurden dieses Jahr im Rahmen der IEA-PVPS Task
12, Subtask 2 aktualisiert. Das überarbeitete Dokument umfasst sowohl einen Leitfaden zum methodischen Teil der Ökobilanzen wie auch zur Berichterstattung der Ergebnisse und soll so zu einer grösseren Verständlichkeit und Transparenz beitragen.
1
Im R ahmen der Aktualisierung des ec oinvent D atenbestandes wurden f olgende A rbeiten d urchgeführt:
• Überarbeitung des Methodik-Leitfadens
• Aufdatierung des Sachbilanzdatensatzes für Ethylen-TetrafluorEthylen (ETFE)
• Erstellung e ines Sachbilanzdatensatzes eines a -Si-Laminats i n Z usammenarbeit m it ei nem
Schweizer Hersteller. Die Diskussionen über eine allfällige Bereitstellung der Daten in ecoinvent
sind am Laufen.
• Publikation eines Artikels zum Vergleich von Elektroautos mit PV Strom einerseits und Autos mit
Agrotreibstoffen anderseits [6].
Aufgrund von Verzögerungen bei der B ereitstellung der nöt igen Daten, war es ni cht möglich die geplanten Arbeiten zur Erstellung von Sachbilanzdaten des Modulrecyclings durchzuführen. Die Datenbeschaffung ist laufend und erfolgt in einer Zusammenarbeit mit Sylke Schlenker (Sunicon) und Lisa
Krüger (First Solar).
SACHBILANZINVENTAR ETHYLEN-TETRAFLUORETHYLEN (ETFE)
Zu ETFE, welches in der Produktion der PV-Anlagen benötigt wird, wurde die Sachbilanz weiter aufdatiert. Der T reibhausgasausstoss i n d er H erstellung bet rägt 1 69 kg C O2-äq/kg E TFE. Der C arbon
Footprint wird fast halbiert. Der nach wie vor hohe Carbon Footprint von ETFE steht im Zusammenhang m it f luorierten K ohlenwasserstoffen, w elche be i der H erstellung der R ohmaterialien (Teflon)
emittiert werden und als hochwirksame Treibhausgase wirken.
Gemäss neusten E rkenntnissen k önnte der T reibhausgasausstoss w eiter sinken. Entsprechend w ird
die Sachbilanz von ETFE nochmals überarbeitet und angepasst.
SACHBILANZINVENTAR A-SI LAMINAT
Die Sachbilanzdaten der Produktion von a-Si-Laminaten in der Schweiz wurden erhoben. Die Auswertung der Daten zeigt, dass diese Technologie bezüglich der Umweltbelastungen im Vergleich mit anderen Technologien sehr gut abschneidet. Dies ist auf den geringen Materialverbrauch in der Produktion und in der Installation zurückzuführen.
1
Photovoltaik Inventardaten von 2009, 2010 und 2011 können hier heruntergeladen werden:
http://www.esu-services.ch/data/public-lci-reports/
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Nationale / Internationale Zusammenarbeit
Auf nationaler Ebene erfolgt die Zusammenarbeit primär mit dem ecoinvent Zentrum, welches die Validierung der aktualisierten D atensätze übernehmen soll. Aufgrund der umfangreichen Anpassungsarbeiten an der ecoinvent Datenbank (inhaltlich und strukturell), war das ecoinvent Zentrum dieses Jahr
nicht in der Lage, die bereitgestellten Daten zu validieren.
Der Sachbilanzdatensatz der flexiblen a-Si-Laminaten wurde in Zusammenarbeit mit einem Schweizer
Produzenten erstellt.
In einem BFE Projekt im Zusammenhang mit der neuen Energiestrategie 2050 des Bundesrates werden der zeit di e Wertschöpfungsketten der w ichtigsten P V T echnologien ak tualisiert, nam entlich i n
Bezug auf Materialeffizienz, Materialherkunft und Wirkungsgrad.
Auf i nternationaler Ebene fanden i nsbesondere im R ahmen d er geplanten A rbeiten z u Mod ulRecycling Diskussionen statt. Wichtige Partner dabei sind Sylke Schlenker, Sunicon, Deutschland und
Lisa Krueger, First Solar, USA.
An der Europäischen Photovoltaik Konferenz (26th EU PVSEC) in Hamburg wurde die Studie
„Agrotreibstoffe versus Solarstrom“ präsentiert. Weiter hat Karin Flury an einer Sitzung der IEA PVPS
task 12, s ubtask 2 teilgenommen. D iskutiert w urde vor al lem di e Ü berarbeitung der G uidelines f ür
Ökobilanzen v on S olarstrom. Weiter w urde über e ine al lfällige V erlängerung d er Z usammenarbeit
diskutiert. Falls es eine solche geben wird, wird EPIA jedoch nicht mehr den Vorsitz übernehmen.
Diese Zusammenarbeit ermöglichte auch die Erarbeitung der Publikation „Life Cycle Inventories and
Life Cycle Assessments of Photovoltaic Systems“.
Die Durchführung der g eplanten Mo dellierung d er Modul-Take-Back-Systeme un d des ModulRecyclings war aufgrund der fehlenden Daten von Sunicon und First Solar nicht möglich. Für die Datenbeschaffung besteht weiterhin Kontakt zu Sylke Schlenker (Sunicon) und Lisa Krüger (First Solar),
so dass diese Arbeiten zu Ende geführt werden können.
Die Sachbilanzdaten von amorphem Silicon auf flexiblen Substraten eines Schweizer Herstellers sind
erstellt. Zurzeit läuft die Diskussion mit dem Hersteller über eine allfällige Implementierung der Daten
in ecoinvent.
Für Ende 2011 und 2012 sind folgende Arbeiten geplant:
• Erstellung von Sachbilanzdatensätzen zu Modul-Take-Back-Systemen und Modul-Recycling
• Einarbeitung der neusten Kenntnisse in die Sachbilanz von ETFE
• Überarbeitung der Daten zum Wasserverbrauch während des Betriebs (Reinigung) von Photovoltaik-Anlagen.
• Erstellung v on S achbilanzdatensätzen zu Mikromorphen Silizium P V-Modulen i n Z usammenarbeit mit einem Schweizer Hersteller. Die Diskussionen über eine allfällige Bereitstellung der Daten in ecoinvent sind am Laufen.
• Aktualisierung und Erweiterung der Sachbilanzdaten der Photovoltaik in der Schweiz.
Falls v on M itgliedern der I EA-PVPS Task 12 w eitere S achbilanzdaten zu P hotovoltaik-Technologien
zur Verfügung gestellt werden, wird angestrebt, diese für eine Implementierung in den ecoinvent Datenbestand aufzubereiten.
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Referenzen
[1] ecoinvent Centre, ecoinvent data v2.2, ecoinvent reports No. 1-25. 2010, CD-ROM, Swiss Centre for Life Cycle Inventories:
Duebendorf, Switzerland. Retrieved from www.ecoinvent.org.
[2] Jungbluth N , Bauer C , D ones R , & F rischknecht R , Life C ycle A ssessment for E merging T echnologies: C ase S tudies for
Photovoltaic and W ind P ower. Int J LC A, 2004. 10(1): p. 24 -34. dx .doi.org/10.1065/lca2004.11.181.3 or www.esuservices.ch.
[3] Jungbluth N, Life Cycle A ssessment f or Crystalline P hotovoltaics in the S wiss ec oinvent Database. Prog. P hotovolt. Res.
Appl., 2005. 2005(13): p. 429-446. www3.interscience.wiley.com/cgi-bin/jissue/82003028 or www.esu-services.ch.
[4] Jungbluth N , S tucki M , & F rischknecht R , Photovoltaics, in Sachbilanzen v on E nergiesystemen: G rundlagen f ür den
ökologischen V ergleich v on E nergiesystemen und den E inbezug von E nergiesystemen i n Ö kobilanzen f ür di e S chweiz,
Bauer C & Dones R, Editors. 2009, Swiss Centre for Life Cycle Inventories: Dübendorf, CH. p. 171. www.ecoinvent.org.
[5] Frischknecht R, Stucki M, & Buesser S, IEA-PVPS Task 12: Swiss activities in 2009 – Ökobilanzen von PV Freiflächen- und
Grossanlagen (Jahresbericht). 2009, ESU-services Ltd.: Uster. Retrieved from
http://data.solarch.ch/p415.php?PV=230&LoName=SolarProjekte.
[6] Stucki M , F rischknecht R , & J ungbluth N , Agrotreibstoffe v ersus S olarstrom: E in Vergleich der Ökobilanzen al ternativer
Treibstoffe. VSE Bulletin, 2011. 2011(2): p. 25ff. www.esu-services.ch/publications/energy/.
[7] Life Cycle Inventories and Life Cycle Assessments of Photovoltaic Systems, IEA-PVPS T12-02 (2011).
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SCHWEIZER BEITRAG ZUM IEA PVPS
PROGRAMM, IEA PVPS TASK 13
Annual Report 2011
Address
Date
Thomas Nordmann, Luzi Clavadetscher
TNC Consulting AG
General Wille-Str. 59, CH 8706 Feldmeilen
044 991 55 77, [email protected], www.tnc.ch
SI/500021 / SI/500021-03
2010 - 2013
11.07.2012
ABSTRACT
Switzerland takes part in the Photovoltaic Power Systems (PVPS) program of the International Energy Agency (IEA), Task 13: Performance and Reliability of Photovoltaic Systems, 2010 - 2014
The overall objective of Task 13 is to improve the operation, reliability and, thus, electrical and economic output of photovoltaic power systems and subsystems
• providing a common platform where quality aspects are elaborated and exchanged among the
stakeholders
• disseminating this knowledge to different market actors.
Task 13 is focusing on:
• Providing reliable statistical data for any kind of decision makers for different PV applications and
system locations (e.g. different countries, regions, climates).
• Technical issues such as adapting test methods and reliability assessments of PV modules, comparing the long-term behavior of systems and components, as well as performance analysis and
optimization of PV systems
Subtask 1: Statistical System Performance Analysis
Subtask 2: Analytical PV System Assessment
Subtask 3: PV Module Characterisation and Life Time Assessment
Subtask 4: Dissemination has been started as planned.
TNC Consulting AG is the responsible Subtask 1 leader and also the activity leader 1.1 Database and
Analysis of PV Systems.
In the Year 2011 an 'Input Tool' for the collection of plant- and operational was developed and distributed. By the end of 2011 datasets of 32 PV systems and a total of 73 years of operational data was
collected.
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Die Schweiz ist durch TNC Consulting AG im IEA Task 13 vertreten und leitet Subtask 1, 'Statistical
PV System Performance Analysis'. Der Beitrag ist im wesentlichen die Aktivität 1.1, 'Database and
Evaluation of PV Systems' und besteht im Einsammeln, der Bereitstellung und der Darstellung von
Anlagen- und Betriebsdaten von PV Netzverbundanlagen der Task 13 Mitgliedländern sowie von anderen Datenquellen. Das gewählte Datenformat entspricht weitgehend dem Format der der 'IEA PVPS
Task 2 Performance Database' und die Auswertung der Betriebsdaten ist vom IEC Standard
61724,1998 übernommen. Das ermöglicht eine normierte Auswertung und Darstellung von Betriebsdaten von unterschiedlichen PV Netzverbundanlagen in verschiedenen geografischen Regionen.
Allen Beteiligten wurde ein Werkzeug zur Verfügung gestellt, das ermöglicht die Daten im vorgeschriebenen Format einzugeben und zu prüfen. Durch eine Export-Funktion können die gesammelten
Daten an die Subtask 1 Verantwortlichen weitergegeben werden. Die gesammelten Daten werden
geprüft und in die Hauptdatenbank eingefügt. In der Zukunft werden diese Daten über ein WWW interface öffentlich zugänglich gemacht und das ermöglicht dem Benutzer interaktiv zusammenfassende
normierte Auswertungen von ausgesuchten PV-Netzverbundanlagen zu erstellen.
Am Task 13 Meeting vom 23. - 24. März 1211 in Madrid wurde das 'Input Tool' den Beteiligten vorgestellt.
Am 30. Mai 2011 wurde das 'Input Tool' fertig erstellt und steht nun allen Mitgliedern des Task 13 zu
Dateneingabe zur Verfügung (siehe Figur 1, 'Input Tool').
Figur 1: Input Tool
Am Task 13 Meeting vom 3. - 4. Oktober 2011 in Israel konnte das 'Input Tool' nochmals im Detail
erläutert und das weitere Vorgehen diskutiert werden.
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SI/50021 / SI/50021-03, Thomas Nordmann, TNC Consulting AG
Bis Ende 2011 sind Datensätze von insgesamt 39 Anlagen mit einem Total von 73 Jahren Betriebsdaten eingegangen (siehe Figur 2, Datasets).
Figur 2: Datasets
Ein Problem ist die zaghafte Bereitschaft von einzelnen Mitgliedländern zur Zusage und der Bereitstellung von Daten. Der Gründe sind, obwohl Daten vorhanden sind, zum Teil administrative und rechtliche Einschränkungen zur Veröffentlichung von Betriebsdaten.
Durch die Unterzeichnung des 'IEA PVPS Implementing Agreement' hat sich die Schweiz verpflichtet
einen internationalen Beitrag zu leisten. Die 'IEA PVPS Task 13 Performance Database' ist ein Werkzeug zur Analyse der Betriebsdaten von PV-Netzverbundanlagen von internationaler Bedeutung und
die Mitglieder des Task 13 leisten hiermit einen wertvollen Beitrag.
Mit der Bereitstellung des 'Input Tools' im Jahre 2011 wurde ein Werkzeug geschaffen, das allen Beteiligten eine problemlose Mitarbeit ermöglicht. Für das Jahr 2012 ist vorgesehen weitere Daten zu
sammeln und die WWW Hauptdatenbank öffentlich zugänglich zu machen.
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Referenzen
[1]
T. Nordmann, L. Clavadetscher: Reliability of Grid-Connected Photovoltaic Systems, the learning Curve in Yield and
System Cost, 23rd European Photovoltaic Solar Energy Conference and Exhibition, Valencia, Spain, 5BP.1.5 September 2008
[2]
COST AND P ERFORMANCE TRENDS IN GRID-CONNECTED PHOTOVOLTAIC SYSTEMS AND CASE STUDIES,
Report IEA-PVPS T2-06:2007 December 2007.
[3]
IEA PVPS Task 2, Country Reports on PV System Performance, Report IEA-PVPS T2-05:2004, December 2004.
Task 2 Datenbank
[4]
Performance Database, Version 1.19, Edition: Sept 2006, auf CD-ROM für EUR 20.- erhältlich bei der Taskleitung: Ulrike
Jahn, ZAE Bayern, D-91058 Erlangen, E-Mail: [email protected], als Download oder interaktiv auf der Task 2
Homepage: http://www.iea-pvps-task2.org
IEA PVPS
[5]
Info auf Webseite: http://www.iea-pvps.org/
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Département fédéral de l’environnement, des transports, de l’énergie et
de la communication - DETEC
IEA PVPS TASK 14 – HIGH PENETRATION
OF PV SYSTEMS IN ELECTRICITY GRIDS
SWISS CONTRIBUTION
Annual Report 2011
Address
Date
Planair SA
Crêt 108a, 2314 La Sagne
+41 32 933 88 40, [email protected], www.planair.ch
IEA PVPS Pool II No. 2011.01
01.03.2010 – 31.03.2014
19.12.2011
ABSTRACT
The main purpose of Task 14 is to analyze the role of grid connected PV as an important source in
electric po wer s ystems on a hi gh pen etration l evel where add itional ef forts may be nec essary t o
integrate the dispersed generation in an optimum manner. The aim of these efforts is to reduce the
technical barriers to achieve high penetration levels of distributed renewable systems on the electric
power system.
Switzerland is responsible of subtask 1 and contributes to other subtasks.
Cross-cutting s ubtask (Information G athering, A nalysis a nd O utreach) objective is t o r eview and
document w orldwide implementations of hi gh pe netration PV scenarios i nto el ectric po wer s ystems
and based on subtask work, to generalize and refine them to generate a set of convincing cases of
safe and reliable implementation.
Subtask 1 (PV generation in correlation to energy demand) objective is to show and determine how
with bet ter prediction t ools an opt imized l ocal en ergy m anagement, PV pe netration level c an be
improved in grid.
Subtask 2 (High penetration PV in local distribution grids) objective is to identify and evaluate the role
of PV in distribution grids, to analyze the impact of high penetration and to make recommendations
(Grid Codes, incentives, regulation).
Subtask 3 (High penetration s olutions f or c entral PV gen eration s cenarios) o bjective is t o en vision
the future power system with the integration of system-wide PV integration through the review of PV
generation output variation and its predictability, the power system operation and the power system
increase.
Subtask 4 (Smart inverter technology for high penetration of PV) objective is to highlight and define
inverter technology requirements for successful smart integration of a high penetration of PV
(technology, technical requirement, standards and system integration aspects).
The Swiss representation at the IEA-PVPS Task 14 meetings 2011 was ensured (Lisbon, Portugal –
May 2011 and Beijing, China – October 2011).
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Purposes of the project
The pr oject ai ms t o anal yze t he impact of a hi gh pene tration of phot ovoltaic ( PV) es pecially the
integration i n electricity gr id. The hi gh pen etration of r enewable ener gy s ystems ( RES) i s a r eal
challenge t o m aintain r eliability and s tability i n el ectricity gr ids. T he obj ective i s s o t o anal yze and
reduce the technical barriers restricting PV penetration in following fields:
• local energy management (load profiles and weather's effect  subtask 1,
• local distribution grids (optimized load management)  subtask 2,
• central PV generation  subtask 3,
• inverter technology  subtask 4.
The Task 14 results from a workshop on the role of photovoltaic in Smart Grids.
What are the opportunities and needs for an electricity grid with a high penetration of PV? In a number
of countries the PV has been grown rapidly with some problems and issues associated to a question
more and more current.
As t he i nitiative and r esponsibility of t he t ask w ere t aken ov er b y Austria, t he f ollowing c ountries
announced their i nterest t o par ticipate to t he t ask: Australia, C anada, S witzerland, Germany, Israel,
Italy, Japan, Korea, Portugal, USA, China and Thailand.
The main purpose of this task during four years (March 2010 to March 2014) is to promote the use of
grid c onnected P V as an i mportant s ource i n el ectric pow er s ystem on a hi gh pen etration l evel.
However, these dispersed generators require additional efforts and a great collaboration to be
integrated in an optimum manner. It will only be possible when the technical barriers will be reduced.
To ac hieve t his obj ective t he t ask 14 w ill f ocus on w orking w ith ut ilities, i ndustry a nd ot her
stakeholders to develop the technologies and methods enabling the widespread deployment of
distributed PV technologies into electricity grids.
The objective would be to:
1. develop and verify mainly technical requirements for PV systems and electric power systems to
allow high penetrations of PV systems interconnected with the grid,
2. discuss t he active r ole of P V s ystems r elated t o energy m anagement and s ystem c ontrol of
electricity grids.
To achieve these objectives the project was divided into five parts: four subtasks and a cross-cutting
subtask.
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IEA-PVPS Task 14 Swiss contribution, P. Renaud, L. Perret & J. Fahrni, Planair SA
Subtasks description, work done and results
CROSS-CUTTING SUBTASK
« INFORMATION GATHERING, ANALYSIS AND OUTREACH »
Subtask leader: Canada
The objective of this subtask is to collect, standardize and share existing information on high
penetration PV into electric power systems, based on other subtasks needs.
In a report, the existing IEC and CENELEC standards concerning PV are summarized and presented.
Furthermore an overview over planned standards and topics discussed in normative committees will
be given. Feedback of the Task 14 experts shall be disseminated to the normative committee (Basler
& Hofmann).
Activity CC1 (Canada)
In or der t o s hare pr oject i nformation an ex change pl atform has been s et up (Wiki: http://apps2ext.nrcan.gc.ca/t14/doku.php), as well as a number of model documents.
Swiss t eam has i ntroduced t he o bjectives an d r esults of hi s work on t his Wiki a nd w ill upd ate
information about studies and project progress.
Activity CC2 (USA)
In order to make and analyze state of the art of existing high PV penetration systems a questionnaire
was pr epared in c ollaboration with ac tivity 2.1 ( one common ques tionnaire f or bot h activities). The
objective i s that ev ery par ticipating country collects own hi gh PV pe netration systems for w hich t he
operators could potentially answer to the questionnaire.
In Switzerland few systems seem respond to questionnaire's standard but many projects are starting
and could be potentially interesting. It's also planned early in 2012 to contact Swiss electricity
companies and project leaders who could be involved in high penetration PV in electric grid in order to
present Task 14 and to generate interest to fill the questionnaire (VEIN Project, EWZ, SIG, RE, …).
Activity CC3 (USA)
A r epository with d ifferent t ools us ed by p articipants has been set u p. E very m ember c an share hi s
modeling and simulation tools and add methodically necessary information to the list. Simulation tools
and s ettings used in „ Distribution Grid Analysis a nd Simulation with P hotovoltaics (DiGASP)“ [1] are
presented and discussed by Basler & Hofmann.
Activity CC4 (Canada)
In this activity numerous models which had been collected in activity CC2, thanks to questionnaire, will
be refined and developed. Results and techniques developed in subtasks will be merged in order to
come up w ith a s et of per tinent cases/scenarios which can be us eful t o the industry a nd ut ilities
worldwide in solving PV integration issues.
The report « Successful method to reach high PV penetration » will be developed through a workshop
in which S witzerland will t ake par t. These c ases/scenarios will b e t horoughly d ocumented, modeled
and s imulated with r espect to t he par ameters of interest s uch as po wer qua lity, system stability and
economic impact.
SUBTASK 1
« PV GENERATION IN CORRELATION TO ENERGY DEMAND »
Subtask leader: Switzerland
The objective of this subtask is to show and determine how with better prediction tools an optimized
local energy management, PV penetration level can be improved in grid.
Activity 1.1 (Switzerland)
This activity concentrates on forecast tools and on their adaptation to anticipate the shift in local grid.
The goal is t o establish a link between weather f orecasts, prediction and monitoring tools and t o do
recommendations.
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Due to interactions with activity 3.1 (different scope, different users, but great similitude), and in order
to concentrate efforts, a joined report structure (draft table of contents) was presented, discussed and
accepted in the last international meeting in Beijing.
Joined part
Evaluation of forecast methodologies
Specific parts (different scale and forecast use)
Activity 1.1
Activity 3.1
Local energy management and forecast:
• local grid integration,
• small scale PV.
Areal management and power planning:
• power planning in transmission grid,
• large scale PV.
 Small utilities, households
Time horizon, accuracy and acceptable cost are not the same.
The i mportant criteria for t he e valuation of f orecast s ystems hav e be en d etermined an d brought
together in a common questionnaire "Use of solar and PV forecasts for enhanced PV integration" that
has been distributed to about 30 persons in order to collect different case studies.
The ques tionnaire i ncluded 7 bl ocks ( with a t otal o f 34 ques tions) abo ut m odel n ames, t emporal
range, pos t processing of dat a, add itional par ameters, spatial information and aggr egation, forecast
evaluation, uncertainty and r eferences. I t was aiming at s hortest ( 0 – 6 h) a s w ell as s hort t ime
forecasts ( 6 – 72 h) . Up t o no w 14 organizations f illed i n t he q uestionnaire. T he or ganizations ar e
coming from private and public sectors and are based in North America, Europa and Japan.
Source
Type
Global
model
Local
model
Resolution
[km]
Area
Time
horizon
[d]
Canmet (CAN)
NWP
GEM
-
15
Point
2
JWA (JP)
Cloud
motion*
-
-
1
Point
0.25
MeteoSwiss (CH)
NWP
ECMWF
Cosmo
2/7
Point
1/3
Univ. Oldenburg /
Meteocontrol (DE)
NWP / P
ECMWF
-
25
Point/
Regional
3
Univ. Jaen (ES)
NWP
ECM/GFS
WRF
3
Point
3
DTU IMM (DK)
NWP
ECMWF
Hirlam
-
Point
2
AIST / Waseda (JP)
NWP / P
JMA-GSM
NHM
5
Point
1.5
Univ. GIFU (JP)
NWP
JMA-GSM
MM5
2
Point
2
UCSD (USA)
Cloud
motion**
-
-
<0.1
Point
<0.1
Weather Analytics (USA)
NWP / P
GFS
-
1
Point
6
Bluesky Wetteranalyse (A)
NWP / P
GFS
Cosmo
-
Point
3
Irsolav (ES)
NWP / P
GFS
-
-
Point
3
Meteotest (CH)
NWP
GFS
WRF
10
Point
2.5
NWP = numerical weather prediction model, P = post processing, * = satellite images, ** = Sky imager
The results will be analysed and described in the report about “System-wide PV generation
forecasting” in the first half of 2012.
Activity 1.2 (Switzerland)
This a ctivity reviews and ana lyzes l ocal s torage an d dem and s ide m anagement s ystems t hrough
various case studies. The objective is to increase the penetration of PV in local grids.
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The report structure (draft table of contents) has been prepared and discussed in the last international
meeting in Beijing.
A test site is launched in Cernier (CHE) where Smart Meters will be installed in households and will
allow data transmission and remote consultation. This site will offer the possibility to study and analyze
PV local energy management with storage.
In order t o evaluate the situation i n other areas, the Task 14 participating countries w ill be asked to
provide typical data (typical load profiles and case studies selection). Some countries already manifest
interest: Belgium and Japan can provide case studies; Germany can provide information but noticed
that dat a's confidentiality i s critical; China and Denmark can provide typical load profiles. Planair SA
will contact them early in 2012 to collect information.
A fictional example (basis case study) has been described in order to illustrate what is needed and to
make t he c omprehension of appr oach eas ier. T his ex ample gives already interesting r esults. I t's
possible to evaluate the part of PV generation that can be completely used on site in standard case,
with DSM or/and with storage.
Considering t hat 15% of t he
household c onsumption can be
shifted at another time, PV
generation us ed on s ite c an be
increased of 60% . With a l ocal
storage (6kWh batteries), PV
generation us ed on s ite c an be
increased of 220%. Finally with
both solutions, PV generation used
on site can be increased of 250%.
On a verage Switzerland gets 90 01'000 k Wh/kWp a year. Based on
an a nnual pr ivate household
consumption of 4’ 000kWh i t’s
possible t o produce up t o 50% of
this consumption with PV without
additional penetration to the grid:
Power
of 4'000 kWh
yearly consumption
13 – 14 %
Generation
Basis
570 Wp
513 –
570 kWh
DSM
920 Wp
828 –
920 kWh
(+61%)
21 – 23 %
Storage
1'840 Wp
1'656 – 1'840 kWh
(+223%)
41 – 46 %
DSM + storage
2'020 Wp
1'818 – 2'020 kWh
(+254%)
45 – 51 %
Activity 1.3 (Portugal)
This activity reviews the e ffect on t he gr id with l arge s cale PV due to f ast an d v ery local weather
fluctuations (cloud, rain). It's first important to review the effect of large PV systems on the electric grid,
especially the characterization of temporal variability due to changing local weather and with a
significant impact. On this basis a standard method will be developed in order to analyze the variability
of di fferent P V s ystems a nd t o det ect anom alies. I t c ould be i nteresting t o v erify if t his s tandard
characterization can be applied to small and medium systems.
USA, Australia, China, Japan and Belgium manifest their interest for this activity. USA own elements
for the first par t of the r eport on t heoretical ef fects of l arge PV p lant on the grid. Portugal c ontacted
NREL to share information and to determine a standard analyze for variability of large PV systems.
Then these theoretical results will then be tested on large Portuguese installations. However the plants
owners have t o gi ve the agreement to get and use data ( even only power ou tput to ha ve a bas e of
comparison with standard variability). Portugal has difficulties to obtain data of the two largest
Portuguese plants (46 MW and 11 MW) because of confidentiality.
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A survey will be done in order to identify and select other large plants in different countries. Needed
information t o c ollect is: location, PV po wer, p roduction, m odule des cription, i nverter des cription,
substation description, monitoring method.
The ow ners of t he f ollowing five PV plants ha ve been c ontacted: Central F otovoltaica Hércules
(11MW), Central Fotovoltaica da Amareleja (46MW), Parque Solar de Almodôvar (2.15MW), Central
Fotovoltaica de Ferreira do Alentejo (12MW), Central Solar de Ferreira (10 MW). To this date only the
owner f rom t he Central F otovoltaica d e F erreira d o A lentejo has pr eliminary ac cepted t o s hare
information, however, terms are still under discussion. The other PV plants remain an option, as they
didn't give a final answer declining the request.
A par tnership with t he I nstituto S uperior T écnico ( Technical U niversity of Li sbon) has be en
established, in order to support the works of developing monitoring standards and the data analysis.
NREL h as s hared r elevant i nformation as i nputs f or s tandards de veloping. F urther c ontacts ar e
scheduled to discuss in greater detail the sent information.
SUBTASK 2
« HIGH PENETRATION PV IN LOCAL DISTRIBUTION GRIDS »
Subtask leader: Germany
The objective of this subtask is to identify and evaluate the role of PV in distribution grids and to make
an analyze cost-benefit for ancillary services. Especially this subtask focuses on the analyze of impact
of high PV penetration in distribution grids in order to make recommendations on Grid Codes,
incentives and regulation.
In t he pr oject D iGASP [1], B asler & H ofmann de velops a s imulation ap proach based on s tochastic
input data. The results will be discussed in this subtask and compared to other approaches. A more
detailed roadmap will be developed in the coming Subtask 2 meeting.
Activity 2.1 (USA)
This activity evaluates the current experience of distribution grid concerned by a high penetration PV
and analyzes the background in this field. This review will be conducted on basis of a survey among
participants and on collection of relevant case studies, and will identify challenges of PV integration.
The questionnaire for this activity has been produced in collaboration with activity CC2 (one common
questionnaire for both activities).
Swiss team tries to find interested Swiss participants to fill the questionnaire (see activity CC2).
Activity 2.2 (Germany)
This activity reviews actual op timization approaches and m akes simulations in or der t o c ompared
impacts of reactive power storage on country-specific grids. A cost-benefit-analysis will be conducted
on c ase s tudies of ac tivity 2. 1 with f ocus o n r eactive p ower balancing i n d istribution gr ids with PV
systems.
Activity 2.3 objectives are the same as 2.2 but with focus on active power control.
Activity 2.4 (Canada)
On bas is of ex isting ex ample, t his ac tivity c oncentrates on c hange f rom di stribution t o s upply gr ids,
with dynamic studies, simulations, and analyze of
• technical changes in grid planning and operation (e.g. reverse power flows),
• grid support by PV systems (impact on grid planning and operation, economic impacts, changes
in grid codes recommendations)
SUBTASK 3
« HIGH PENETRATION SOLUTIONS FOR CENTRAL PV GENERATION SCENARIOS »
Subtask leader: Japan
The subtask will envision the future power system with the integration of system-wide PV integration
through the review of PV generation output variation and its predictability including smoothing effect,
power system operation planning, and power system augmentation planning.
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Activity 3.1 (Canada)
This activity concentrates on existing technologies to analyze and predict the variability of system-wide
PV g eneration i ncluding s moothing ef fect. T he obj ective is t o e valuate a nd select on e or m ore
methodologies considering the applicability to different structures of power markets for different
forecast-range and accuracy.
Due to collaboration between activities 1.1 and 3.1 the Swiss group is strong involved in this activity
(especially Meteotest, see activity 1.1):
• common ques tionnaire in order t o c ollect r elevant c ase s tudies an d s imulations f or s elected
regions,
• interaction w ith IEA SH C T ask 3 6-46 “Solar R esource K nowledge Management” (solar
forecasting and resource assessment).
Activity 3.2 (Japan)
This a ctivity su rveys and reviews the existing m ethodologies f or l ong-term pow er s ystem oper ation
planning i ncluding PV integration and DSM/DR technologies for DSM/DR in order to develop criteria
and s cenarios f or c ase s tudies and s imulations in selected r egions ( including app licability of ne w
technologies such as power storage, generation load dispatch, and DSM/DR)
In this a ctivity, S wiss c ontribution would be di fficult and with s mall i nterest no wadays. T he
questionnaire seems to be inappropriate for Switzerland. Only Swissgrid would be able to fill out it and
for Swissgrid the problem isn’t in Switzerland but in Germany (at this time).
Activity 3.3 (Japan)
The obj ectives of t his t hird ac tivity ar e s imilar t o 3 .2 but for l ong-term pow er s ystem aug mentation
planning. For selected regions, t he c ase s tudies will include ne w generation technologies, fossil fuel
availability and price, power system demand, and energy policy
As for activity 3.2 a Swiss contribution would be difficult and with small interest nowadays.
SUBTASK 4
« SMART INVERTER TECHNOLOGY FOR HIGH PENETRATION OF PV »
Subtask leader: Austria
This subtask will highlight and define inverter technology requirements for successful smart integration
of a high penetration of PV: technology, technical requirements and standards, and system integration
aspects.
As funding of Austria has been delayed deliverables of this subtask are not defined yet. At Swiss level,
reports will be sent to Sputnik Engineering for validation.
Activity 4.1 (Austria)
This activity will review the interconnection requirements and standards in different countries, in order
to get an overview about control approaches, safety and functional requirements for PV inverters as
interface between s torage and grid (collection of results an d outcomes of research). The c orrelation
between gr id v oltage level, net work t opology a nd capabilities of gr id m anagement s ervices, an d t he
opportunities of PV inverters to be “smart” will be assessed and analyzed.
Basler & H ofmann will s ummarize an d a nalyze t he gr id c onnection r equirements an d a pplicable
standards for Switzerland.
This activity includes a collection of all at present existing inverter topologies and technologies for grid
management services. The suitability of the devices for these services will be analyzed and lined out,
where limiting factors come up and which hardware must be used for a proper function. Furthermore,
a main task in this activity is the assessment of the impact of reactive power on the design,
dimensioning and efficiency of PV inverters, especially in relation to a high PV penetration.
On t he bas e of an ex tended r eview of i nverter m odels, a gen eric i nverter m odel will be de veloped
and/or improved, which will then used in the activities of CC1 and ST2.
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Activity 4.3 (Spain)
The work in this subtask focuses on review of remote control architectures and interfaces between PV
inverters and ex ternal de vices (monitoring or c ontrol s ystems). I t r equires an i nvestigation of t he
suitability o f communication s tandards f or S mart I nverters, t aking i nto ac count d ifferent appl ications.
Security issues in regard to remote inverter operation and control will be discussed and new ideas for
communication of PV inverters and related systems will be developed.
Basler & Hofmann w ill c ontact s ubtask and ac tivity leaders t o s uggest a questionnaire t o evaluate
inverter c ommunication i ssues i n di fferent ut ilities. Swiss t eam w ill d isseminate an alysis t hrough
utilities for comments.
For S wiss par ticipation t o I EA-PVPS t ask 1 4 Pl anair SA allied with B asler & Hofmann A G and
Meteotest in order to provide quality services, Swiss developments and knowledge for task 14.
At international level Planair SA (subtask 1 leader) represents Switzerland during international
meetings, with Meteotest during European meetings (activity 1.1 leader and coordinator with IEA-SHC
Task 36/ 46 pr ogram). Work and r esults of s ubtask 1 ar e pr esented a nd d iscussed dur ing t hese
meetings.
At national level meetings are organized in order to present information received during international
meetings but also to evaluate the situation about Swiss progress and to fix expected objectives and
deliverables. A m eeting with P VPS P ool ( Swiss el ectrical s ociety) will be or ganized a t beg inning of
2012 (end of February) for technical dissemination.
Peter Toggweiler, PV expert of Basler & Hofmann, is the Swiss representative for IEC and CENELEC
norms concerning PV. It is a big opportunity for Task 14 to develop the link between this international
project and the norm editors. This topic doesn't concern Switzerland only, it's a general question in PV
business and it is worthwhile t o bring t he f eedback of t he T ask 14 ex perts b ack t o t he nor mative
committees. The i ntegration of this work i n c ross-cutting subtask is in discussion with the Operating
Agent.
Year 2011 evaluation and outlook for future work
Swiss t eam is s ubtask 1 leader and especially develops activities 1.1 (joined with 3.1) and 1.2. The
subtask is well-advanced in its results and deliverables:
• Activity 1.1 : results are being compiled and first part of the report will be written begin of 2012.
• Activity 1 .2 : basis c ase s tudy is r eady a nd r eal d ata will be c ollected begin of 2012 ( load
profiles)
Switzerland also contributes to other activities:
• CC subtask : normative work, update of wiki, participation to questionnaire, simulation tool and
settings of project DiGASP, participation to workshop
• Subtask 2 : participation to questionnaire, pr esentation of results of project DiGASP and
comparison with other approaches
• Subtask 3 : joined work and report among activities 1.1 and 3.1
• Subtask 4 : grid c onnection r equirements, appl icable s tandards f or S witzerland, pr oposition of
questionnaire to evaluate inverter communication in different utilities
Depending on budget allocation contribution to subtask 4 will be reinforced with a stronger work with
Swiss utilities about inverters communication.
Swiss team will ensure the Swiss dissemination of work and results in Task 14. A communication plan
is planned to organize dissemination.
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References
[1]
Christof B ucher: Distribution G rid Analysis a nd S imulation w ith P hotovoltaics ( DiGASP), J ahresbericht 2011 ,
Bundesamt für Energie, Schweiz, 2011
[2]
Kirsten D. Orwig, Marissa Hummon, Bri-Mathias Hodge, and Debra Lew:
Transmission Planning Studies, NREL, USA, 2011
Solar Data Inputs for Integration and
[3]
Sabreena Juneja: Demand Side Response – A discussion paper, OFGEM, UK, 2010
[4]
Dave Renné: Task 36 – Solar Resource Knowledge Management, NREL, 2010
[5]
Brian Seal: Standard Language Protocols for PV and Storage Grid Integration: Developing a Common Method for
Communicating with Inverter-based Systems, EPRI, 2010
[6]
F. P. Baumgartner, T. Achtnich, J. Remund, S. Gnos and S. Nowak: Steps towards integration of PV-electricity into
the GRID, Paper presented at 25th EU PVSEC WCPEC-5, Valencia, Spain, 2010
[7]
Elke Lorenz, Thomas Scheidsteger, Johannes Hurka, Detlev Heinemann and Christian Kurz: Regional PV Power
Prediction for Improved Grid Integration, Paper presented at 25th EU PVSEC WCPEC-5, Valencia, Spain, 2010
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IEA SHC TASK 36: SOLAR RESOURCE
KNOWLEDGE MANAGEMENT
GLOBAL RADIATION SHORT TERM FORCAST
AND TRENDS / AEROSOL CLIMATOOGY
Annual Report 2011
Address
Date
Jan Remund
Meteotest
Fabrikstrasse 14, 3012 Bern
031 307 26 26, [email protected], www.meteotest.ch
101498 / 151784+151761
01.07.2005 – 30.06.2011
15.12.2011
ABSTRACT
In the framework of IEA Solar Heating and Cooling (SHC) task 36 Meteotest investigates the possibilities and quality of global radiation forecast, the trend of recent global radiation data and distribution
of atmospheric aerosols.
th
In the 6 and final year 2011 of task 36 the work within the tasks has been finished and the final report has been started to write. The follow on task 46 has started in July 2011.
METEOTEST wrote two chapters in the final report, which will be published in 2012. One is dealing
about aerosol climatologies and one about long term trends of global radiation.
To c onclude t he work of t he l ast 6 years t hree c ontribution of METEOTEST are hi ghlighted: 1. the
new aerosol optical depth map, 2. the trend analysis of global radiation and 3. the benchmark of radiation forecast models.
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Introduction
In the framework of IEA Solar Heating and Cooling (SHC) task 36 “Solar Resource Knowledge Management” [ 1] Meteotest i nvestigates m ainly the pos sibilities and qu ality of gl obal r adiation f orecast.
The task 36 is divided into 3 main subtasks:
A) Standard qu alification f or solar r esource pr oducts ( includes be nchmarking of different r adiation
estimation models based on satellite measurements).
B) Common structure f or ar chiving and ac cessing s olar r esource pr oducts ( includes pr ototype of
online tool for accessing data).
C) Improved t echniques f or s olar r esource c haracterization and f orecast; improve s atellite r etrieval
methods for solar radiation products; conduct climatological analysis of solar resources.
The aim in the radiation forecast subtask is to define the quality of the existing models and to enhance
the quality.
Work done and results
The year 2011 was used to finalize the task and report about the work done. No additional work parts
have been started.
Final subtask deliverables as well as inputs for the Handbook on Solar Radiation of all three parts are
in pr eparation or n early f inished. The de lays are not due t o S wiss c ontributors, but t o t he s ubtask
leaders.
FINAL REPORT
METEOTEST wrote two chapters of the final reports, which will be published in 2012. One is dealing
with aerosol c limatologies and another with long t erm t rends of glob al r adiation ( see BFE J ahresbericht 2009 of IEA SHC Task 36).
To conclude the work of the last 6 years three contribution of METEOTEST are highlighted:
1. New aerosol optical depth map: Figure 1 shows the average aerosol optical depth map
2. Trend analysis of global radiation: Table 1 gives an overview of the global radiation trends
3. Benchmark of radiation forecast models: Table 2 shows the accuracy of the forecasted global radiation (hourly values, Switzerland).
Figure 1: Yearly mean of aerosol optical depth at 550 nm 2001-2008, based on Aeronet [2] and satellite data of
NASA. These values are used within Meteonorm Version 6.1 and 7. Aerosol optical depth has a big influence on
the amount of clear sky radiation reaching the ground.
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IEA SHC Task 36, J. Remund, Meteotest
Table 1: Result of linear trend analysis for the period 1985-2006 based on GEBA database [3]. Cursive values
are not significant (on a 95% level). Trends in Europe and Japan are clearly positive (effect is also known as
“global brightening”) and in China and India mostly negative [4, 5].
2
Region
Trend [W/m 10y]
all
1.82
Europe
4.13
Northern Europe
2.94
Germany / Austria
4.64
Switzerland
3.07
United Kingdom
1.52
Asia
1.43
Japan
5.25
India
-5.44
Canada
-0.21
Table 2: Root m ean s quared er ror ( rmse), m ean a bsolute er ror ( mbe) an d bi as f or t he f our f orecasting a pproaches and persistence, first forecast day, complete Swiss data set [6]. The uncertainty (rmse) ranges between
40 and 45% and is clearly lower than persistence.
approach (forecast model, operator)
rmse in
2
W/m
mae in
2
W/m
bias in W/m
ECWMF, Univ. Oldenburg
Germany
107
(39.6%)
70
(25.8%)
-1
(-0.3%)
BLUESKY Wetter,
Austria
109
(40.5%)
73
(27.0%)
-9
(-3.3%)
MOS, Meteomedia,
Germany
122
(45.0%)
85
(31.5%)
-18
(-6.6%)
WRF (GFS based),
Meteotest, Switzerland
119
(44.2%)
76
(28.0%)
4
(1.3%)
Persistence
(constant clearness index)
158
(58.4%)
104
(38.7%)
-17
(-6.3%)
2
NEW TASK
The kick off meeting of task 46 was held in Kassel in September 2011 (in combination with ISES SWC
2011). It will include the following four subtasks:
Subtask A: Solar Resource Applications for High Penetration of Solar Technologies
This s ubtask w ill d evelop t he nec essary data s ets t o al low s ystem pl anners an d ut ility o perators t o
understand s hort-term r esource variability c haracteristics, in p articular u p a nd down r amp r ates, t o
better m anage large p enetrations of solar technologies i n the grid system. A lthough this work i s primarily focused toward PV systems, which react almost instantaneously to cloud passages over individual pan els, the i nformation is also useful for s olar thermal and CSP s ystems where intermittence
resources can impact their ability to meet load demands.
• A-1: Solar variability, and specifically ramp rates, for particular systems
• A-2: Integration of solar with other RE technologies
• A-3: Spatial and temporal balancing studies of the solar and wind energy resource
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Subtask B: Standardization and Integration Procedures for Data Bankability
• B-1: Measurement best practices
• B-2: Gap-Filling, Quality control, flagging, data formatting
• B-3: Integration of different (short and long) data sources
• B-4: Evaluation of the use of TMY data
• B-5: Data uncertainties over various time frames
Subtask C: Solar Irradiance Forecasting
• C-1: Short term forecasting (1 – 7 days ahead)
• C-2: Integration of solar forecasts into operations
Subtask D: Advanced Resource Modelling
• D-1: Improvements to existing solar radiation retrieval methods
• D-2: D evelopment of gl obal s olar r esource d ata s ets for i ntegrated as sessment of gl obal an d
regional RE scenarios modelling, with a special focus on CSP and solar heating technologies
• D-3: Long term analysis and forecasting of solar resource trends and variability
National / international cooperation
The w ork w as done in t he f ramework of I EA S olar H eating a nd C ooling t ask 36. F rom S witzerland
there is also University of Geneva part of the task team.
Outlook
The task will be finished next year. The follow on task 46 has been approved in November 2010. The
new task started in July 2011 and will end in June 2016.
References
[1] Homepage of IEA Solar Heating and Cooling task 36: http://www.iea-shc.org/task36/
[2] http://aeronet.gsfc.nasa.gov/
[3] https://protos.ethz.ch/geba
[4] J. Remund, 2010: Zeitliche Entwicklung der Globalstrahlung von 1950 bi s 2099, 25. SYMPOSIUM "PHOTOVOLTAISCHE
SOLARENERGIE", Bad Staffelstein, Germany, 3. – 5. März 2010.
[5] J. Remund and S.C. Müller, 2010: Trends in global radiation between 1950 and 2100, EuroSun Conference, Graz, Austria,
Sep. 29th to Oct 1st 2010
[6] Lorenz et al . 2009, B enchmarking of di fferent appr oaches t o f orecast solar i rradiance, 24t h E uropean P hotovoltaic Solar
Energy Conference (EUPVSEC), Hamburg, Germany, Sep. 21st to 25th 2009.
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NORMIERUNG FÜR PV-SYSTEME
IEC-TC82 UND
NATIONALES TK 82 FÜR PV-SYSTEME
Annual Report 2011
Peter Toggweiler, Thomas Hostettler
Basler & Hofmann AG und
Swissolar, Fachverband für Sonnenenergie
Address
Forchstrasse 395, 8032 Zürich
Telephone, E-mail, Homepage 044 387 13 50, [email protected],
www.baslerhofmann.ch und www.swissolar.ch
Swissolar / 17967
Duration of the Project (from – to) 2008 Date
January 2012
ABSTRACT
In 2011 the TC 82 of the International Electrotechnical Commission (IEC) had the general meeting in
Shanghai, together with several working group meetings. There was again a high interest with more
than 100 participants. Also there is a much stronger influence of the Asian countries visible. The delegation of C hina c onsisted of up t o 40 par ticipants. Like i n ot her years, the S wiss c ontribution has
focused on ac tivities i n WG 3 ( PV systems) b y P eter T oggweiler a nd WG 6 ( BOS-components) b y
Michel Ryser from Sputnik Engineering.
A key focus on national level was the ongoing revision of the part 712 in IEC 60364-7-712 about PV
installations i n bu ildings. A C ommittee D raft ( CD) w as c irculated f or c omments and again a large
number of suggestions for improvements were collected. Thus the revision process is further delayed.
Within TC 82 seven standards were published as new or revised documents, about 17 are actually
under revision.
The preparation of the CENELEC standard for BIPV products has been issued as first draft (CD). By
acceptance of a new work item IEC has also started to prepare a BIPV standard, but with more focus
on systems and applications.
The collaboration with standards for grid connection issues shall be improved, in particular with TC 8.
For that purpose, the newly established collaboration with IEA PVPS Task 14 (High Penetration of PV
Systems in Electricity Grids) on a national level is helpful.
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Die Projektziele waren zum Teil ähnlich wie im Jahr zuvor, weil etliche Projekte eine mehrjährige Bearbeitungszeit aufweisen. Im Bericht werden die jeweiligen Aktivitäten kurz beleuchtet.
Nachfolgend die Übersicht über einige Schwerpunkte:
• PV und Feuerwehr: Risiken minimieren, Verhaltensvorschläge erarbeiten
• Blitzschutz, Ausarbeitung von Empfehlungen für PV-Anlagen
• Überarbeitung des Abschnitts 712 in der NIN 2010 (TK 64 Dokument)
• BIPV (Building Integrated PV)
• Bedürfnisse in den Entwicklungsländern berücksichtigen
• Lichtbogendetektor
• Normen für Kraftwerke
Normen und technische Regeln für die Photovoltaik sind erforderlich für die Sicherheit von Personen
und Material, für die zweckmässige Funktion und f ür einen fairen internationalen Markt. Das Projekt
wird in enger Zusammenarbeit mit Vertretern von Swissolar, der Electrosuisse und den internationalen
Normengremien dur chgeführt. Der S chwerpunkt liegt in der B etreuung und Le itung des nationalen
IEC-TK 82 und d er schweizerischen Vertretung i m I EC-TC 82, w elche zuständig s ind für di e P VNormen. Die IEC-Normen fokussieren sich auf die Elektrotechnik und zugehörige Themen wie Sicherheit, Brandschutz un d generelle Aspekte zur Qualität. Die Normen gelten für Produkte w ie auch di e
Systemtechnik, Installations- und Unterhaltsarbeiten.
Seit mehreren Jahren ist die Arbeit des IEC-TC 82 in 5 Arbeitsgruppen (Working Groups, WGs) aufgeteilt plus eine gemeinsame Arbeitsgruppe (JWG 1) mit Delegierten aus mehreren IEC-TCs.
WG 1
WG 2
WG 3
WG 6
WG 7
JWG 1
Glossary
Modules, non-concentrating
Systems
Balance-of-system components
Concentrator modules
Decentralized Rural Electrification(JWG TC 82/TC 88/TC21/SC 21A)
Schwerpunkt der A rbeiten bildeten d ie Ü berarbeitung und A ktualisierung v on bestehenden N ormen.
Im 2011 sind 7 neue resp. revidierte Normen in Kraft getreten und etwa 17 Dokumente sind in Arbeit.
Sie sind im Anhang 1 aufgeführt.
Die üblichen zwei internationalen WG 3 & WG 6-Meetings fanden in Shanghai und Zermatt statt. Ergänzend gab es wie ü blich z wei na tionale T K82-Sitzungen und weitere i nternationale M eetings m it
Schweizer B eteiligung, insbesondere zum Teil 7. 12 i n der N IN. Nachstehend i st der S tand zu d en
wichtigsten Themen zusammengefasst.
Meetings
WG 3 & 6 trafen sich im Mai in Shanghai und im Dezember in Zermatt.
Das Treffen in Zermatt war ein Höhepunkt: Einerseits habe es viele Teilnehmer geschätzt, einmal in
Zermatt zu sein und andererseits waren die meisten noch nie auf einem so hohen Berg. Der Besuch
der PV-Anlage auf dem K leinmatterhorn war nur möglich m it der Unterstützung der Zermatter B ergbahnen A G und Thomas Hostettler. An den b eiden Meetings k onnten m ehr a ls 40 T eilnehmer b egrüsst werden, was ist einen neuen Teilnehmerrekord darstellt.
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Swissolar: IEC-TC82, P. Toggweiler, Basler & Hofmann AG
Bild 1: IEC-TC 82-WG 3 & 6-Mitglieder auf dem Klein Matterhorn bei Zermatt, 8. Dezember 2011
Das Meeting in der Schweiz wurde unterstützt von Swissolar, Basler & Hofmann, Sputnik Engineering,
Oerlikon, Huber & Suhner und Multikontakt.
Das nat ionale TK 82 h atte zwei S itzungen. Die G ruppe besteht aus 18 aktiven Mitgliedern. D ie umsatzstarken Schweizer PV-Firmen sind mit Delegierten vertreten. Das Sekretariat führt Thomas Plattner von Electrosuisse. Swissolar begleitet die Normenarbeit mit Unterstützung durch die Kommission
Bildung & QS.
Brandschutz, Feuerwehren und Versicherungen
Das Thema "Feuer & PV-Anlagen" wurde intensiv auf diversen Ebenen national und international behandelt. In der Schweiz haben die neuen Regeln, welche einige Feuerpolizeibehörden voreilig angeordnet haben, unnötige Umtriebe verursacht. Diese Bestimmungen sind in die Baubewilligungen eingeflossen und wurden somit für den jeweiligen Fall rechtsverbindlich. Es zeigt sich an diesen Beispielen erneut deutlich, w ie w ichtig praxisbezogene und v erbindliche Normen s ind. Inzwischen ist das
koordinierte Vorgehen angelaufen. So arbeitet der Verband der Kantonalen Gebäudeversicherungen
(VKF) an einem neuen Basisreglement w elches 2012 i n Kraft t reten s oll. Swissolar, vertreten d urch
Thomas Hostettler, begleitet diese Arbeiten und verfasst weitergehende Empfehlungen.
Auf Stufe IEC wird kontinuierlich nach geeigneten Sicherheitsmassnahmen gesucht, um das Brandrisiko bei PV-Anlagen weiter zu reduzieren. Als Beispiel wurde der F unkendetektor i n der USInstallationsnorm ei ngefügt. Mangels v erfügbarer P rodukte dabei der Hinweis angebracht, dass di e
Anforderung er st dan n gi lt, w enn geeignete P rodukte v erfügbar s ind. D ies i st m omentan noc h n icht
der Fall. Einen weiter verbesserten Schutz soll auch die konsequente Anwendung der Isolationsüberwachung dar stellen. A uch bei Anlagen m it Wechselrichtern ohne T renntransformator kann w ährend
der Nacht und spätestens vor dem Einschalten die Isolationsüberwachung allfällige Fehler feststellen
und den Betreiber benachrichtigen.
Swissolar hat für den Umgang mit dem Thema Feuerwehreinsätze ein Merkblatt verfasst.
http://www.swissolar.ch/de/info/broschueren/
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PV in Buildings (BIPV)
Der CENELEC-BIPV-Normenentwurf zirkulierte im Sommer 2011 zur Vernehmlassung. Parallel dazu
hat die IEC einen eigenen Normierungsprozess zur Gebäudeintegration begonnen. Dieser soll stärker
auf di e S ystemaspekte ei ngehen. Der CENELEC-BIPV-Vorschlag bezieht s ich mehr auf Module f ür
Fassaden und D ächer. Beide Projekte s ind eng v erknüpft mit dem sich in Arbeit bef indenden D okument IEC 62548 (Design Requirements for Photovoltaic Arrays, Auslegerichtlinien für PV-Arrays).
PV-Norm als Bestandteil der Hausinstallationsnorm
(NIN)
Wegen den vielen neuen Kommentare und Ergänzungen ist das
Dokument 60364-7 7.12 immer noch in Bearbeitung. Peter Toggweiler ha t dazu im 2011 insgesamt an dr ei Meetings des T C64-MT9
teilgenommen. Der revidierte Normenvorschlag soll nun bis Mitte
2012 vorliegen. Ein Ergebnis sei hier vorweg genommen: Es soll eine
bessere Kennzeichnung bei m Z ähler- oder H ausanschlusskasten
verwendet werden. Eine mögliche Variante zeigt der nebenstehende
Vorschlag aus Deutschland (Bild 2). In der Schweiz bietet Swissolar
ein ähnliches Klebeschild an . F erner i st vorgesehen, das s P V-DCKabel gemäss dem Beispiel nebenan gekennzeichnet werden sollen
(Bild 3).
Das T C-64 für el ektrische H ausinstallationen und d as TK 82 h aben momentan nur eine informelle Form der Zusammenarbeit.
Mehrere Vertreter schlagen vor, die Zusammenarbeit zu erweitern,
vor a llem w egen den Überschneidungen m it de m TC82-"PVGenerator"-Dokument und neu auch mit Normenvorschlag für die
gebäudeintegrierte Photovoltaik (BIPV).
Bild 2: Hinweisschild bei Hausanschlusskasten © IEC-TC64
Bild 3: Hinweisschild für
PV-DC-Kabel
Normen und Guidelines für Entwicklungsländer
Für die Bedürfnisse der Entwicklungsländer ist die gemeinsame Arbeitsgruppe mit Vertretern aus drei
Technischen Komitees (TKs) zuständig:
JWG TC 82/TC 88/TC21/SC 21A) – Decentralized Rural Electrification
Leider s ind bisher k eine Ergebnisse v eröffentlicht worden. M it Le on A. D rotsche v on Eskom ( South
African Utility Company) wurde ein zweiter Leiter gewählt.
Smart Grid
China h at zwei V orschläge i m B ereich "Smart G rid User I nterface" e ingereicht. A m I EC-Meeting i n
Shanghai wurde betont, dass sich die IEC vermehrt dem Thema "Smart Grid" annehmen will. Es sind
verschiedene TKs involviert, inklusive das TK 82.
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Zusammenarbeit mit anderen Normengruppen
Mit folgenden TCs besteht eine regelmässige Zusammenarbeit:
SC 17B
TC 32
TC 57
TC 81
Low-voltage switchgear and control gear
Fuses
Power systems management and associated information exchange
Lightning protection
D-A-CH-CZ
Unter diesem Titel arbeiten die drei deutschsprachigen Länder und CZ eng zusammen, vor allem im
Bereich Stromverteilnetze. Von dieser Gruppe stammt der Vorschlag, dass bei einem Netzanschlusspunkt die Spannung als Folge der PV-Einspeisung maximal 3 % ansteigen darf. Nun liegt ein neuer
Vorschlag zum Thema "Schieflast" auf dem Tisch. Damit soll die maximal zulässige einphasige Einspeiseleistung auf 3 kW begrenzt werden. Der Vorschlag wird von den Normengremien zurzeit diskutiert.
Das 2011 l ief i m gl eichen Takt w ie di e J ahre zuvor. D as s chnelle Mar ktwachstum, di e r asante E ntwicklung der Technik und die vielen neuen Marktteilnehmer benötigen laufend neue und verbesserte
Normen. Trotz Knappheit an personellen wie finanziellen Ressourcen konnten die wesentlichen Zielsetzungen erreicht werden. Der Arbeitsaufwand für die Tätigkeiten in der Schweiz lag weit über dem
Budget. D ank der E igenleistungen, den Beiträgen v on S wissolar, E lectrosuisse, B asler & Hofmann
und den Sponsoren für das Meeting in Zermatt entstand schlussendlich keine Deckungslücke.
Die Liste der sich in Arbeit befinden Dokumente ist lang und zeigt deutlich, dass auch im Jahr 2012
viel Arbeit ansteht. Unter anderem soll auf nationaler Ebene die Zusammenarbeit mit dem TK 81 zum
Thema Blitzschutz bei PV-Anlagen vertieft werden, daraus soll wenn möglich ein Leitfaden publiziert
werden. Ein anderes Vorhaben betrifft die verbindlichen und praxisgerechten Richtlinien für di e Vorsorge bei Brandereignissen und zur Brandverhütung. Dies geschieht in Zusammenarbeit mit der Vereinigung der Kantonalen Feuerversicherungen(VKF).
Neu soll eine Norm für PV-Kraftwerke auf Freiflächen erarbeitet werden. Wegen dem Technologieexport ist das Thema auch für die Schweiz interessant.
Aktuell geplant und bekannt sind folgende internationale Meetings mit Teilnehmern aus der Schweiz:
•
Stockholm, Februar 2012, Arbeitssitzung zur Revision des NIN-Teils 712 (TC64-MT9)
•
USA, Mai 2012, WG3 & WG 6 Meetings
•
Juli 2012, TC64-MT9, Ort noch nicht bekannt
•
Oslo, Oktober 2012: TC 82 Meeting und WG3&6 Meetings
Referenzen
[1]
www.iec.ch
[2]
www.electrosuisse.ch
[3]
www.swissolar.ch
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Beilage 1: Auszug von neu publizierten Normen und Dokumenten in Arbeit
Im Jahr 2011 neu publizierte IEC-Normen zu PV:
IEC 62116
"Test procedure of islanding prevention measures for utility-interconnected photovoltaic inverters"
IEC 62253
"Photovoltaic pumping systems - Design qualification and performance measurements"
IEC 60904-5
Photovoltaic devices - Part 5: Determination of the equivalent cell temperature (ECT) of photovoltaic
(PV) devices by the open-circuit voltage method
IEC 62109-2
Safety of power converters for use in photovoltaic power systems - Part 2: Particular requirements for
inverters
IEC 61853-1
Photovoltaic (PV) module performance testing and energy rating - Part 1: Irradiance and temperature
performance measurements and power rating
IEC 60904-1
Photovoltaic devices - Part 1: Measurement of photovoltaic current-voltage characteristics
IEC 62509
Battery charge controllers for photovoltaic systems - Performance and functioning
TC 82 Dokumente per Anfang 2012 in Arbeit
Euronorm: CLC/TC82/Sec0110/DC
Proposed text for the standard - prEN 50XXX “Photovoltaics in buildings”
(EN-Norm)
IEC:
IEC-Nummer
Titel
Dokumenten-Nr.
IEC 60904-8 Ed. 3.0
Photovoltaic devices - Part 8: Measurement of spectral response of a photovoltaic (PV) device
82/535/MCR
IEC 61215 Ed. 3.0
Crystalline silicon terrestrial photovoltaic (PV) modules - Design qualification and type approval
82/684/CD
IEC 61683 Ed. 2.0
Photovoltaic systems - Power conditioners - Procedure for measuring efficiency
Amendment 2 to IEC 61730-1 Ed.1: Photovoltaic (PV)
IEC 61730-1 am2 Ed. 1.0 module safety qualification - Part 1: Requirements for 82/687/CDV
construction
IEC 61730-2 Ed. 2.0
Photovoltaic (PV) module safety qualification - Part 2:
Requirements for testing
82/663/CD
IEC 61829 Ed. 2.0
Crystalline silicon photovoltaic (PV) array - On-site
measurement of I-V characteristics
82/693/CDV
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IEC 61853-2 Ed. 1.0
Photovoltaic (PV) module performance testing and
energy rating - Part 2: Spectral response, incidence
angle and module operating temperature measurements
IEC 62109-3 Ed. 1.0
Safety of power converters for use in photovoltaic
power systems - Part 3: Controllers
IEC 62109-4 Ed. 1.0
Safety of power converters for use in photovoltaic
power systems - Part 4: Particular requirements for
combiner box
IEC 62548 Ed. 1.0
Design requirements for photovoltaic (PV) arrays
IEC 62670-1 Ed. 1.0
Concentrator photovoltaic (CPV) module and assembly performance testing and energy rating - Part 1:
82/630/CD
Performance measurements and power rating - Irradiance and temperature
IEC 62670-2 Ed. 1.0
Concentrator photovoltaic (CPV) module and assembly performance testing and energy rating - Part 2:
Energy rating by measurement
82/679/CD
IEC 62688 Ed. 1.0
Concentrator photovoltaic (CPV) module and assembly safety qualification
82/631/CD
IEC 62716 Ed. 1.0
Ammonia corrosion testing of photovoltaic (PV) modules
82/650/CD
IEC 62759-1 Ed. 1.0
Transportation testing of photovoltaic (PV) modules Part 1: Transportation and shipping of PV module
stacks
82/644/NP
IEC 62775 Ed. 1.0
Cross-linking degree test method for Ethylene-Vinyl
Acetate applied in photovoltaic modules - Differential
Scanning Calorimetry (DSC)
82/655/NP
IEC 62782 Ed. 1.0
Dynamic mechanical load testing for photovoltaic (PV)
82/676/NP
modules
IEC 62787 Ed. 1.0
Concentrator photovoltaic (CPV) solar cells and cellon-carrier (COC) assemblies - Reliability qualification
IEC/TS 61836 Ed. 3.0
Solar photovoltaic energy systems - Terms, definitions
82/538/MCR
and symbols
IEC/TS 62727 Ed. 1.0
Specification for solar trackers used for photovoltaic
systems
IEC/TS 62738 Ed. 1.0
Design guidelines and recommendations for photovol82/639/NP
taic power plants
IEC/TS 62748 Ed. 1.0
PV systems on buildings
82/642/NP
PNW 82-654 Ed. 1.0
Photovoltaic devices - Part11: Measurement of initial
light-induced degradation of crystalline silicon solar
cells and photovoltaic modules
82/654/NP
PNW 82-665 Ed. 1.0
Future IEC 6XXXX-1-2: Measurement procedures for
materials used in photovoltaic modules - Part 1-2:
Encapsulants - Measurement of volume resistivity of
photovoltaic encapsulation and backsheet materials
82/665/NP
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82/606/CDV
82/646/CDV
82/673/NP
82/651/DTS
PNW 82-666 Ed. 1.0
Future IEC 6XXXX-1-4: Measurement procedures for
materials used in Photovoltaic Modules - Part 1-4:
Encapsulants - Measurement of optical transmittance
and calculation of the solar-weighted photon transmittance, yellowness index, and UV cut-off frequency
82/666/NP
PNW 82-668 Ed. 1.0
Future IEC 6XXXX-1-3 Ed.1: Measurement procedures for materials used in photovoltaic modules Part 1-3: Encapsulants - Measurement of dielectric
strength
82/668/NP
PNW 82-669 Ed. 1.0
Future IEC 6XXXX-1-5 Ed.1: Measurement procedures for materials used in photovoltaic modules Part 1-5: Encapsulants - Measurement of change in
linear dimensions of sheet encapsulation material
under thermal conditions
82/669/NP
PNW 82-674 Ed. 1.0
Junction boxes for photovoltaic modules - Safety requirements and tests
82/674/NP
PNW 82-675 Ed. 1.0
Connectors for DC-application in photovoltaic systems
82/675/NP
- Safety requirements and tests
PNW 82-685 Ed. 1.0
System voltage durability test for crystalline silicon
modules - Qualification and type approval
82/685/NP
PNW 82-688 Ed. 1.0
Sealant for crystalline solar modules
82/688/NP
PNW 82-689 Ed. 1.0
Test method for total haze and spectral distribution of
haze of transparent conductive coated glass for solar
cells
82/689/NP
PNW 82-690 Ed. 1.0
Edge protecting materials for laminated solar glass
modules
82/690/NP
PNW 82-691 Ed. 1.0
Test method for transmittance and reflectance of
transparent conductive coated glass for solar cells
82/691/NP
PNW/TS 82-652 Ed.1.0
Specification for concentrator cell description
82/652/NP
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PV ERA NET
NETWORKING AND INTEGRATION OF NATIONAL
AND REGIONAL PROGRAMMES IN THE FIELD
OF PHOTOVOLTAIC (PV) SOLAR ENERGY RESEARCH AND TECHNOLOGICAL DEVELOPMENT
(RTD) IN THE EUROPEAN RESEARCH AREA
(ERA)
1
1
Nowak, M. Gutschner
Annual
Report 2011 S.
S. Oberholzer
2
1
NET Nowak Energy & Technology Ltd
Bundesamt für Energie
1
Address
Waldweg 8, 1717 St.Ursen
2
3063 Ittigen (Bern)
1
Telephone
+41 (0)26 494 00 30
1
1
E-mail, Homepage
[email protected], http://www.netenergy.ch;
2
+ 41 (0)31 325 89 20
2
2
[email protected], http://www.bfe.admin.ch
CA-011814-PV ERA NET
Date
December 2011
2
ABSTRACT
PV ERA NET is a European network of programme coordinators and managers in the field of photovoltaic solar energy (PV) research and technological development (RTD). The consortium comprises
major key stakeholders in the field of national and regional RTD programmes involving photovoltaics
(PV), which is considered a key technology and industry.
The general objectives of the network are to further enhance the cooperation between regional and
national RTD programmes in an efficient, pragmatic and flexible way, thereby providing substantial
added value to the individual programmes, to the network and to the European Research Area as a
whole. This cooperation shall result in further improving the effectiveness of the RTD programmes
both on an individual and global level in terms of programme management and RTD activities.
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Introduction and Goals
PV ERA NET is a European network of programme coordinators and managers in the field of photovoltaic solar energy (PV) research and technological development (RTD). The consortium comprises
major key stakeholders in the field of national and regional RTD programmes involving photovoltaics
(PV), which is considered a key technology and industry.
The Photovoltaic European Research Area Network PV ERA NET is open to any other interested
country or region in Europe, which carries out PV RTD programmes and projects.
PV ERA NET started in October 2004 as a project supported by the EC within the ERA-NET scheme.
After the official project end in 2009, the network continued its activities supported and managed by
the participating partners.
The general objectives of the network are to further enhance the cooperation between regional and
national RTD programmes in an efficient, pragmatic and flexible way, thereby providing substantial
added value to the individual programmes, to the network and to the European Research Area as a
whole. This cooperation shall result in further improving the effectiveness of the RTD programmes
both on an individual and global level in terms of programme management and RTD activities.
PV ERA NET is based on two premises: First, PV is seen as a relevant RTD area and a specific thematic focus is desired. Second, international cooperation is understood as a strategic element
strengthening the regional / national programmes.
PV ERA NET brings together expertise and ownership, i.e. stakeholders that can actually define and
implement concrete actions within and between RTD programmes in the European Research Area.
The working principles are:
• PV ERA NET develops and uses a set of tools that enable and facilitate information exchange and
implementation of PV RTD projects. The tools are pragmatic and target-oriented.
• PV ERA NET is complementary to other types of international bodies and flexible in providing essential contributions to international initiatives and activities in a highly dynamic context.
• PV ERA NET taps synergies and seizes opportunities for fomenting PV RTD activities between
programmes creating benefits for research and industry both on a national and international level.
• PV ERA NET operates on trustful face-to-face relationships and willingness to actively cooperate.
Nine states (eight countries and one region) are the founding members of PV ERA NET (see Table 1).
Any other interested country or region in Europe, which carries out PV RTD programmes and projects,
can become member of the network.
PV ERA NET members and other stakeholders responded to the EC Call “ENERGY.2012.10.1.2:
ERA-NET on Solar Electricity: Implementation of the Solar Energy Industry Initiative” launched on 20
July 2011, by submitting a proposal for a “SOLAR-ERA.NET - ERA-NET on Solar Electricity for the
Implementation of the Solar Energy Industry Initiative”. SOLAR-ERA.NET may become the follow-up
network of PV-ERA-NET, growing from nine to twenty-three members and covering as well topics in
the field of Concentrating Solar Power.
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PV ERA NET, S. Nowak, NET Nowak Energy & Technology Ltd
Brief Description of the Project
According to the objectives, six key activities and tools are identified for transnational cooperation:
1.
2.
3.
4.
To lead the update and to publish survey reports on regional/national PV RTD programmes
To coordinate the database on ongoing PV RTD projects
To publish relevant information on the Website
To co-organise and hold consortium meetings and workshops with external stakeholders (one or
two times a year according to the needs)
5. To support the implementation of RTD projects
6. To assist the identification of joint activities with other relevant RTD networks (e.g. smart grids;
materials)
The first four items are summarised as structured information exchange which is carried out by the
individual partners and managed by the PV ERA NETwork secretariat providing basic support and
guidance to keep the network running.
The fifth and sixth items lead to dedicated transnational activities (e.g. clustering of projects, joint calls,
pooling of experts and evaluators) involving the individual partners effectively interested. The PV ERA
NETwork secretariat supports the process of identifying, selecting and implementing RTD projects on
photovoltaics and related areas.
Table 1: PV ERA NET Partners and Contact Points
State
Partner
Contact
Austria
Federal Ministry for Transport, Innovation and Technology /
Bundesministerium für Verkehr, Innovation und Technologie (BMVIT)
Fritz Fahringer
Denmark
Energinet.dk
Jesper Bergholdt Soerensen
France
French Agency for Environment and Energy Management /
Agence de l’environnement et de la maîtrise de l’énergie
(ADEME)
Yvonnick Durand
Germany
Research Center Jülich GmbH /
Forschungszentrum Jülich GmbH (FZJ)
Hermann Bastek
Greece
General Secretariat for Research and Technology, Ministry
of Development (GSRT)
Γενική Γραμματεία Έρευνας και Τεχνολογίας, Υπουργείο
Ανάπτυξης (ΓΓΕΤ)
Chrysoula Diamanti
Centre for Renewable Energy Sources (CRES) /
Κέντρο Ανανεώσιμων Πηγών Ενέργειας (ΚΑΠΕ)
Stathis Tselepis
The Netherlands
NL Agency, Directorate Energy and Climate Change
Otto Bernsen
North-RhineWestphalia
Cluster EnergyResearch.NRW/
Cluster EnergieForschung.NRW
Stefan Rabe
Sweden
Swedish Energy Agency /
Statens energimyndighet
Sara Bargi
Switzerland
Swiss Federal Office of Energy (SFOE) /
Bundesamt für Energie (BFE) /
Office fédéral de l’énergie (OFEN) /
Ufficio federale dell’energia (UFE)
Stefan Oberholzer
NET Nowak Energy & Technology Ltd.
Stefan Nowak
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PV ERA NET, S. Nowak, NET Nowak Energy & Technology Ldt
The added value for participating programmes and states are:
• Direct and regular contacts to RTD programme peers
• First hand information and experience on PV, RTD and programming
• Compact and comprehensive information tools (survey, database)
• Strategic basics for RTD programme management and positioning
• Efficient assessment of synergies and opportunities for transnational activities
• More effective PV RTD projects and research by reaching critical mass, defragmentation, and
cross fertilisation
The network activities result in the following deliverables:
• Survey Report on regional/national PV RTD programmes (1 / year)
• Updated PV RTD Projects Database
• Update website
• Workshops for programme peers (1 - 2 times a year)
• International PV RTD projects
• Coordinated network
Work Performed
+
Transnational Call PV Grid
+
The transnational Call PV Grid – a dedicated
call on Simulation and System Requirements
for High Level Penetration of Photovoltaics in
the Electricity Grid with the participation of
Austria, Denmark, France, Germany, Greece,
North-Rhine-Westphalia, Sweden and Switzerland – was launched end of September 2009
and closed mid-March 2010.
Six full proposals were successfully submitted
amounting to a total budget of approximately
3,3 MEUR, of which 2,6 MEUR funding requested. The ranking of the proposals was
based on the evaluations done by two internationally renowned experts (provided by Austria
and Denmark) and on evaluations done within
the national (programme) framework.
Figure 1: More than 20 universities and companies are
about to launch new transnational RTD activities thanks
+
to the transnational call PV Grid.
Contracts were concluded between the project partners and national / regional RTD programme. The
transnational monitoring of the projects is done by the PV ERA NET Secretariat (see summaries are
available online on pv-era.net).
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All projects went through the negotiation process. The three funded by the participating states are
listed below. One project could not be started due to lack of (favourable) funding decision in one
member state. Intermediary reports are available in the annexes.
Requested funds
in kEUR
721
PV+Grid_06
_DiGASP
(formerly :
DPVG)
Distribution Grid Analysis and Simulation with
Photovoltaics (formerly: Simulation approach
to investigate the impact of distributed power
production with PV on a power grid)
442
240
Other
775
Switzerland
High-Penetration of PV Systems in Electricity
Grids
Sweden
PV+Grid_05
_HiPe-PV
NRW
797
Greece
1'094
France
Smart modelling of optimal integration of high
penetration of PV
Germany
PV+Grid_04
_SmoothPV
Denmark
Project full title
Austria
PV+Grid
Proposals
Project costs in
kEUR
Table 2: PV+ Grids Projects Funded
o = coordinating project partner; x = participating project partner(s)
Transnational Call POLYMOL
POLYMOL – a dedicated transnational call on Polymer and Molecular S olar P hotovoltaic C ells and
Modules with the participation of Denmark, Flanders (Belgium), the Netherlands, Sweden, Switzerland
and the United Kingdom – was launched late 2007 and resulted in four projects funded (see Table 3).
The transnational monitoring of the projects is done by the Secretariat. Three out of four projects
ended and their results are summarised in the annexes.
PolyStaR
Nanoscale structuring of hetrojunction ionic organic solar cells by liquid-liquid dewetting
Novel materials and processes for polymer solar
cells with improved stability and reliability
o = coordinating project partner; x = participating project partner(s)
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Requested funds
in kEUR
HIOS-Cell
Project costs in
kEUR
Polymer solar cells; stabilised morphology and
upscaling
Other
POLarge
United Kingdom
Efficient areal organic solar cells via printing
Switzerland
APOLLO
(Power
Plastic)
Sweden
Project full title
The Netherlands
POLYMOL
Proposals
Flanders
Denmark
Table 3: Ongoing POLYMOL Projects Funded by PV ERA NET Members
1'286
587
739
619
200
200
2'118
1’022
Reports
The Survey Report was partly updated and published in
October 2011. It presents key features of the PV ERA NET
states and their programmes, namely:
•
Organisations Involved in PV ERA NET and PV RTD
Programming
•
Set-up and strategy of the programme involved
•
Objectives
•
Priorities
The states and their programme(s) are presented side by
side in the same format. The goal of this report is to provide
an essential overview over each of the country and the programme(s) involved. The internal report sent to partners
provides some additional, mainly financial information.
Figure 2: T he S urvey R eport pr ovides concise i nformation on k ey
features of RTD programmes involved in PV ERA NET
Summary reports are available for all projects supported (see Table 4, for reports: pv-era.net).
Table 4: Final and intermediary reports from POLYMOL and PV+ Grid Projects
Project title
Project duration and type of report / summary
Apollo – Efficient areal organic solar cells via printing
11.2008 – 04.2011 – Final report
HIOS-Cell – Nanoscale structuring of heterojunction
ionic organic solar cells by liquid-liquid dewetting
01.2009 – 12.2010 - Final report
POLarge – Polymer solar cells, stabilized morphology
and upscaling
07.2008 – 06.2011 - Final report
PolyStaR – Novel materials and processes for polymer
solar cells with improved stability and reliability
04.2009 – 06.2012 - Intermediary report
DiGASP – Distribution Grid Analysis and Simulation with
Photovoltaics
10.2010 – 06.2013 - Intermediary Report
HiPe-PV – High-Penetration of PV Systems in Electricity
Grids
Smooth PV – Smart Modelling of Optimal Integration of
High Penetration of PV
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Database & Tools
The Projects Database is continuously completed and updated by the individual PV ERA NET partners. The number of projects assessed has grown to 513.
The website provided up-to-date information on the network’s ongoing activities and results. It also
lists the most recent related documents like PV Status Report, PV NMS NET Status Report, IEA PV
Roadmap.
Figure 3:
PV ERA NET Projects Database contains more than 400
PV RTD projects
from PV ERA NET
member and other
countries. The database is open to all
RTD programmes
and can be used as
an efficient tool
thanks to the search
options incorporated.
Coordination
Three PV ERA NET meetings were held throughout 2011. Main topics were:
• Status and follow-up of on-going joint activities (PV+ Grid, POLYMOL, database, etc.)
• Communication and administration issues of PV ERA NET
• (New) member issues
• Recent developments and open calls in the member countries
• Current developments in EU policy (SET plan, Solar Europe Industry Initiative (SEII), etc.)
• Strategic Positioning of PV ERA NET
• (New) Joint transnational activities
Major issue has become the proposal “SOLAR-ERA.NET - ERA-NET on Solar Electricity for the Implementation of the Solar Energy Industry Initiative” as a response to the EC Call “ENERGY.2012.10.1.2: ERA-NET on Solar Electricity: Implementation of the Solar Energy Industry Initiative”
launched on 20 July 2011.
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Outlook 2012
The Photovoltaic European Research Area Network PV ERA NET has been taking a key role in proposing a network for the Implementation of the Solar Europe Industry Initiative. If SOLAR-ERA.NET
should become reality, a new and strong network may carry the fundamental mission of PV ERA NET
by involving more programmes and states than ever before in the European Research Area.
The network will strive to corroborate its strategic position and European Research Area (ERA) dimension not only in terms of a broader membership basis but also in strengthening its coordinative
role in transnational PV RTD programming. The visibility of the network shall be improved with concrete new actions as best marketing approach considered. The further development of the Strategic
Energy Technology Plan (SET-Plan) and Solar Europe Industry Initiative (SEII) may become part of
the network as SOLAR-ERA.NET.
According to the areas of cooperation agreed in the Memorandum of Understanding, the following
activities are to be undertaken in 2012 potentially considered as a bridging year from “old” PV-ERANET to “new” SOLAR-ERA.NET. Basic activities remain the same:
a) Structured information exchange
• To exchange information and experience between the programme owners and managers (i.e. organise a coordination meeting)
• To provide key data and information on regional/national PV RTD programmes (i.e. to update and
complete the survey report but also regular information on new national calls offering opportunities
for international RTD cooperation)
• To keep up an overview on ongoing PV RTD projects (i.e. to update the projects database)
• To monitor ongoing projects initiated through the transnational calls POLYMOL and PV+ Grid
• To communicate with the target audiences (programme managers and owners, experts from industry and research) (i.e. to stay in touch with other networks and stakeholders’ groups)
b) Implementation of RTD projects
• To identify and define common subjects for RTD on photovoltaics and related areas
• To select project proposals with added value for RTD programmes involved
• To co-fund, implement and monitor common RTD projects
• To stimulate cooperation between research groups from different countries and increase competetiveness of stakeholders involved
Specific focus will be on the SOLAR-ERA.NET proposal and Solar Europe Industry Initiative activities.
Bibliography
The website www.pv-era.net provides information on participating RTD programmes and ERA NET
with respect to PV technology.
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Programm Photovoltaik Ausgabe 2002

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