STE plants with parabolic trough collectors: Loreto Valenzuela

Transcription

STE plants with
parabolic trough collectors
Loreto Valenzuela
Concentrating Solar Thermal Systems
CIEMAT, Plataforma Solar de Almería
[email protected]
STE plants with parabolic trough collectors
3rd SFERA Summer School, Solar Thermal Electricity Generation
Almería, 27-28 June, 2012
Contents
Basic principles in parabolic-trough collectors technology
• Main components
• Energy balance: simplified analysis
• Seasonal dependence of thermal energy production
Configuration of STE plants with PTCs (oil based
technology)
• STE Plants without Thermal Energy Storage (TES) system (SEGs-type plant)
• STE Plants with TES system (ANDASOL-type plant)
• Solar fields integrated in Combined Cycle Systems (ISCCS) (KURAYMAT-type plant)
2
Basic principles in PTC
technology
y
Directrix
Elements:
tracking)
• Reflectors
• Receivers (Heat-Collection
Structure
r = 2f/(1+cos(p))
x = y2/(4·f)
Vertex
• Trough collector (single-axis
r
p
x
Line of
(-f,0)Parabolic-trough
(f,0) reflector
simetry
HCE
Elements)
• Drive system, tracking
system, pylons
Source: Plataforma Solar de Almería, DISS
3
technology
How does a PTC work?
It is positioned to guarantee the aperture plane is perpendicular to the
plane containing the sun vector
Plane perpendicular to the collector axis
Vector perpendicular to the aperture area
Sun vector
Incidence angle, θ
Aperture area
Source: CIEMAT, EZM
4
technology
How does a PTC work?
It tracks the sun in a single axis to
transfer the energy to the fluid
circulating through the absorber
pipe (HCE)
Sunrise
Sunset
Source: CIEMAT, EZM
5
Elements:
Structure and reflectors
In charge of concentrating solar radiation
Reflectors:
• most current designs use back-silvered glass mirrors
• barriers for polished aluminum mirrors reflectance and durability
Source: Plataforma Solar de Almería
Torque-box structure-type
EuroTrough (ET) collector
ET-type PTC with FLABEG RP3 glass mirrors
(Focal length = 1710 mm; Thickness = 4 mm;
Dimensions = 1700x1501 mm2(outer) /1700x1641 mm2(inner))
6
Structure and reflectors:
Basic parameters
Reflectance (ρ):
• fraction of incident energy (solar radiation) reflected by a surface
• depends on wavelength, direction and nature of the incident
radiation, surface finish and surface temperature
• typical solar hemispherical reflectivity glass-silver mirrors ~ 93%
Intercept factor (γ):
• ratio of the energy intercepted by the receiver to the energy reflected
by the parabolic trough reflector
• typical values in commercial mirrors > 98%
7
Elements:
Receivers (Heat Collection Elements)
Composed by:
Absorber pipe: Steel pipe with an external coating that:
• Increases absorptance of solar radiation
• Minimizes thermal losses
Glass cover: Borosilicate glass cover with an antireflective coating to
increase solar transmittance
Characteristics:
Vacuum in the annular cavity
Getters for absorbing hydrogen and improve vacuum lifetime
Glass-to-metal seal
8
Receivers:
Design characteristics
Vacio entre el vidrio
Evacuated
annulus
y el absorbente
Glass-metal
seal
Unión Vidrio-Metal
Flange
Brida
Source: Pilkington
Oliva
de evacuación
Evacuation
nozzle
Tubo absorbente de acero
Steel absorber
con recubrimiento selectivo
Glass
cover
Cubierta
de vidrio
”Geter”
for mantenimiento
vacuum
'Geter' pra
e indicación del vacio
maintenance
Schott PTR70
Thermal
Dilatador expansion below
Siemens UVAC3
9
Receivers:
Optical and thermal parameters
Absorptance (α):
• fraction of incident energy (solar radiation) absorbed by a surface
• depends on wavelength, direction of the incident radiation, surface finish and
surface temperature
• maximum solar absorptance values ~ 95%
Thermal emittance (ε):
• amount of energy emitted in all spatial directions by an area at a given
temperature (T)
• current values ≤ 14% @400°C
Transmittance (τ):
• fraction of incident energy (solar radiation) transmitted by the glass cover
• maximum solar transmittance values ~ 96%
10
Elements:
Flexible connections
To connect single PTCs to the headers or PTCs to each other are used:
• Flexible hoses: High pressure drop, stainless steel bellows, and limited flexibility
for high temperature
• Ball joints: provided with inner graphite sealing to reduce friction and avoid leaks
Flexible hose
Ball joint
11
Elements:
Drives & Tracking systems
Tracking system: Light-sensing or intelligent tracker
Hydraulic drive system
12
Heat transfer fluids in PTCs
Mineral or synthetic oils
• Therminol VP-1 (Solutia) / Dow A (Dow Chemical)
(@400°C)
Water:
• Pressurized hot water
• Direct steam generation (@500°C)
Other proposals (Feasibility?):
• Molten salts in parabolic trough collectors
• Pressurized gasses
13
Parabolic-trough collector:
View of a collector unit
Ball joint
Parabolic-trough concentrator
HCE
Hydraulic drive pylon
Collector module
14
Parabolic-trough collectors:
Solar field configurations
Direct return
Indirect return
Central feed
Source: CIEMAT, LVG
15
Basic principles in PTC technology:
Energy balance
Type of losses in PTCs:
• Optical losses
• Geometrical losses
• Thermal losses
17
performance parameters
Optical efficiency (o)
• ratio of the radiant power absorbed
by the receiver to the useful radiant
Direct normal radiation

Source: CIEMAT, EZM
HCE-glass cover
(transmittance  )
solar power at the collector
Peak-optical efficiency (o,peak)
• optical efficiency when the
HCE-absorber pipe
(absorptance  )
incidence angle is zero (= direct
Parabolic-trough reflector
(reflectance  )
the collector aperture plane)
solar radiation is perpendicular to
𝜂𝑜,𝑝𝑒𝑎𝑘 = 𝜌 ∗ 𝛾 ∗ 𝜏 ∗ 𝛼 = 𝜂𝑜,𝜃=0°
𝜂𝑜 = 𝜂𝑜,𝜃≠0° = 𝜂𝑜,𝜃=0° ∗ 𝐼𝐴𝑀
18
performance parameters
Incidence angle modifier (IAM)
• Performance factor that:
• includes the change of optical and
1.0
geometrical parameters when
IAM /(-)
0.8
incidence angle is not 0°
0.6
• does not include the cosine effect
0.4
• changes from 0 to 1 (a value of 1
occurs when θ = 0°)
0.2
0.0
0
10
20
30
40
50
60

70
80
incidence angle,  ( )
Source: CIEMAT, LVG
19
Geometrical losses
Sol
Front
view
perfil
Vista de
Shady
Superficie
surface
sombreada
ED
Top
en planta
Vistaview
W
Source: CIEMAT
Sol
Source: CIEMAT
Collector geometrical end losses
Shadows between adjacent rows
20
Heat losses
Steel absorber
𝑸env,rad
𝑸abs,cond/conv
𝑸abs,rad
𝑸env,conv
𝑸c,cond
𝑄𝑃𝑇𝐶→𝑒𝑛𝑣 = 𝐻𝑙 𝑇𝑎𝑏𝑠 , 𝑇𝑒𝑛𝑣 ∗ 𝐿
Hl
L
Thermal-losses function dependent on
absorber and environmental temp. (W/m)
Absorber-pipe length (m)
Glass cover
Source: CIEMAT
21
Parabolic-trough Collectors:
Energy balance
global
𝑄𝑠𝑢𝑛→𝑃𝑇𝐶 =
𝑄𝑃𝑇𝐶→𝑓𝑙𝑢𝑖𝑑
𝐴𝐶 ∗ 𝐷𝑁𝐼 ∗ cos 𝜃
o, peak
IAM
Opt. & Geom. losses
(θ=0°)
th
𝑄𝑃𝑇𝐶→𝑒𝑛𝑣
Opt. & Geom. losses
(θ>0°)
𝑄𝑃𝑇𝐶→𝑓𝑙𝑢𝑖𝑑 = 𝐴𝐶 ∗ 𝐷𝑁𝐼 ∗ cos 𝜃 ∗ 𝜂𝑜,𝑝𝑒𝑎𝑘 ∗ 𝐼𝐴𝑀 ∗ 𝐹𝑐 − 𝑄𝑃𝑇𝐶→𝑒𝑛𝑣
•
Thermal losses in EuroTrough prototype (PSA) with Schott receivers:
𝑄𝑃𝑇𝐶→𝑒𝑛𝑣 = 0.00154 ∗ ∆𝑇 2 + 0.2021 ∗ ∆𝑇 − 24.899
+
0.00036 ∗ ∆𝑇 2 + 0.2029 ∗ ∆𝑇 + 24.899 ∗
𝐷𝑁𝐼
∗ cos 𝜃
900
∗𝐿
22
Contents
• Main components
technology)
23
STE Plants with PTC:
Seasonal dependence of energy production
Thermal energy produced by a solar field with PTCs whose axis is North-South
oriented varies a lot during the year. Three to four times more energy is delivered
daily during summer months than in winter months. Thermal energy delivered by
PTCs with axis oriented east-west does not vary as much from summer to winter.
24
Z
Z
W
C
W
N
Y
S
N
C
Y
S
X
S
E
a) Axis oriented North-South
Tracking East-West
X
Source: CIEMAT
S
E
b) Axis oriented East-West
Tracking North-South
25
2
4
6
8
10
12
14
16
18
20
22
2
Irradiancia Solar Directa (W/m )
1000
Junio
Diciembre
900
24
1100
1000
900
800
800
700
700
600
600
500
500
400
400
300
300
200
200
100
100
0
0
2
4
6
8
10
12
14
16
18
20
22
0
24
Hora Solar
Source: CIEMAT, EZM
0
1100
Typical daily DNI profile in June and December (PSA)
26
Influence of the axis orientation in the seasonal behaviour
ET-100 thermal power (kW)
Simulation of the behavior of a ET-100 PTC-type located at the PSA
2
4
6
8
10
12
14
16
18
20
22
24
350
350
300
300
300
250
250
250
250
200
200
200
200
150
150
100
100
Orientación Norte-Sur
Orientación Este-Oeste
150
150
100
100
50
50
0
0
2
4
6
8
10
12
14
16
18
20
22
0
24
0
Pcolector->fluido (kW)
Pcolector->fluido (kW)
0
350
2
4
6
8
10
12
14
16
18
20
22
Orientación Norte-Sur
Orientación Este-Oeste
24
350
300
50
50
0
0
Hora Solar
2
4
6
8
10
12
14
16
18
20
22
0
24
Hora Solar
Source: CIEMAT, EZM
Sunny day in June
Sunny day in December
27
PTCs with axis oriented East-West does not vary as much from summer to winter.
The yearly thermal energy output of a North-South-type solar field is greater than
the output of a East-West-type solar field .
28
January
Enero
February
Febrero
March
Marzo
April
Abril
Mayo
May
Junio
June
350
250
Net power
Potencia Térmica Útil
300
200
150
50
0
4
6
8
10
12
14
16
18
20
Hora Solar
Solar
time
Daily profile of the net power delivered to the grid by
a PTC solar field (North-South oriented)
Source: CIEMAT, EZM
100
29
Daily profile of incidence angle in PTCs with axis oriented North-South (PSA coordinates)
60
30
January
February
March
55
50
April
May
June
25
45
20
Incident Angle
Incident Angle
40
35
30
25
20
15
10
15
10
5
5
0
0
6
8
10
12
14
16
18
20
22
6
8
10
Local Time (hh.hhh)
14
16
18
20
22
Local Time (hh.hhh)
40
65
July
August
September
35
October
November
December
60
55
30
50
45
25
Incident Angle
Incident Angle
12
20
15
10
40
35
30
25
20
15
5
10
0
6
8
10
12
14
16
18
20
22
6
Local Time (hh.hhh)
Source: CIEMAT, EZM
8
10
12
14
16
Local Time (hh.hhh)
18
20
22
30
The size of the solar field depends on the nominal electric power of the STE plant
but also on the existence or not of a thermal energy storage (TES) system and on
its capacity.
31
Thermal power produced (calculated) by Andasol-I and Ibersol solar fields
(sunny day in June)
Andasol-I:
0
2
4
6
8
10
12
14
16
18
20
22
300
300
Andasol
Ibersol
250
Potencia Térmica Util
Campo solar (MW)
24
250
200
200
150
150
100
100
50
50
0
0
Source: CIEMAT, EZM
2
4
6
8
10
12
14
16
18
20
Hora Solar
22
0
24
• 50 MWe nominal electric
power
• 510000 m2 of PTCs (155
collector loops; 4 PTCs per
loop)
• Thermal storage 1000 MWh
Ibersol:
• 50 MWe nominal electric
power
• 288000 m2 of PTCs (88
collecor loops; 4 PTCs per
loop)
• NO thermal storage system
Thermal power required by
the power block (50 MWe)
32
Thermal energy produced by a solar field with PTCs whose axes are North-South
The size of the solar field depends on the nominal electric power of the STE plant
but also on the existence or not of a thermal energy storage (TES) system and on
its capacity.
A TES system with capacity to guarantee 2 to 3 hours of power plant operation at
nominal power is an excellent help to fulfill the requirements of the electricity
transmission grid manager, specially during partly cloudy days.
33
Contents
• Main components
technology)
34
STE Plants without TES system:
SEGS-type plant
Solar field with PTCs
Steam at 104 bar/371 ºC
supplying thermal energy to
Oil at 390 ºC
Super-heater
Steam turbine
the steam generator of a
Rankine cycle (unfired boiler
HTF fluid: Thermal oil
Solar Field
Oil circuit
steam generator)
Condenser
Steam generator
.
Solar field coupled to the
steam boiler, superheater
Auxiliar heater
and/or reheater
Oil at 295 ºC
Medium grid stability
boiler)
Re-heater
Oil expansion vessel
SEGS VIII & IX Scheme
SEGS Plant
(Hybridization with fossil
fuel - solar field or steam
Deaerator
Source: CIEMAT, EZM
Scheme of SEGS VIII & SEGS IX STE Plants
•
•
•
Reheat regenerative steam power cycle (steam cycle efficiency ~ 37.6%)
Nominal electric power = 80MWe (solar to electricity annual efficiency ~ 13.6%)
SEGS-I to SEGS-IX built by the Luz Company of United States between 1985 and 1991
35
STE Plants with TES system:
ANDASOL-type plant
PTCs solar field
supplying thermal
energy to the SG of a
Rankine cycle and to a
TES system
High grid stability
Standard configuration:
• Oil based technology
• 2-Tank molten salt TES system
• Central feed configuration for
the solar fields (> 500,000 m2 of
mirror surface for 50 MWe and
7,5 h TES capacity-Spanish STE
plants)
Source: Solar Millenium AG
Scheme of Andasol-type STE Plants
•
•
•
•
•
Reheat regenerative steam power cycle (steam cycle efficiency ~ 37.5%)
Nominal electric power = 49.9 MWe
TES system:
• Storage medium: Nitrate salt mixture (60% NaNO3 – 40% KNO3)
• Capacity 7,7 h @ 50MW (28500 Tons of molten salts)
Andasol power plants promoter: Solar Millenium AG
Technology integrators involved in Andasol-I and Andasol-II: Flagsol GmbH, ACS Cobra, Sener,…
36
Integrated Solar Combined Cycle Systems:
(ISCCS)
Option 2 – Solar Field for Low Pressure Steam
Hybrid STE plant with PTCs
Thermal oil
making use of the ISCCS
Expansion
Vessel
LP Steam
scheme
Steam
Generator
Feed water
Steam turbine
The solar field is integrated
GT Exhaust gas
combined-cycle gas-fired
HGSG Exhaust
in the bottoming cycle of a
Gas Turbine
Heat Recovery Steam
Generator (HRSG)
HP Steam
power plant for:
Thermal oil
• High-Pressure Steam  HRSG 
HP-stage of Steam Turbine (ST)
Expansion
Vessel
• Low-Pressure Steam  LP-stage
Steam
Generator
Feed water
Option 1 – Solar Field for High Pressure Steam
of ST
Source: CIEMAT, LVG
37
Integrated Solar Combined Cycle Systems:
Kuraymat-type plant
Hybrid STE plant with PTCs
making use of the ISCCS
scheme
The solar field is integrated
in the bottoming cycle of a
combined-cycle gas-fired
power plan for:
• High-Pressure Steam  HRSG 
HP-stage of Steam Turbine (ST)
Source: Fitchner Solar GmbH
(Option 1) *
*Brackmann et al., Construction of the ISCCS Kuraymat,
SolarPACES2009, Berlin, Germany.
38
STE plants with PTCs in Spain
35 STE plants connected to the grid:
• 30 PTCs solar fields (14 with TES system)
• 1500 MWe of 1581 MWe come from PTCs
solar fields (oil based technology)
17 STE plants under construction:
Source: Protermosolar (www.protermosolar.com)
• 16 STE plants with PTC solar fields
Standard configuration of STE plants
with PTCs solar fields:
• Nominal power: 50 MWe
• TES system capacity: 7,5 h@ 50 MWe
Large part of key CSP players are
Spanish companies:
• Abengoa Solar, Acciona Energía, ACS Cobra,
Sener, Torresol Energy, ...
Date: June 24, 2012
39
Additional comments
The SEGS experience was essential to explain what is happening today…
STE plants with PTC has turned into reliable renewable energy power stations
Spain has played a key role in the commercial development of the technology
during the last five years (Spanish RD 661/2007)
Dimensions and configuration of current PTCs are mainly imposed by:
• A limited selection in reflectors and receivers for commercial application whose size are
conditioned by basis configuration of the LS-3-type collector (installed in SEGS plants)
• As a result, there are many similarities between PTCs currently installed in STE Plants
Future developments of PTC technology for STE Plants involve new designs of PTCs
(bigger sizes), the replacement of the heat transfer fluid in the solar field (DSG
technology?), and new types of TES systems
40
Gracias
Thank you
Danke schön
Merci beaucoup
41
Geometrical end losses
42
Parabolic-trough Collectors:
Equations for incidence angle
 PTC axis oriented East-West:
 = arccos 1  cos2 ·(cos2s 1) 


 PTC axis oriented North-South:
 = arccos cos · cos·cos s + tang ·sen 2 + sen2s 


43

STE plants with parabolic trough collectors: Loreto Valenzuela

Transcription

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