Why and How of Testing Solar PV Emona Instruments Mustafa Keskin

Why and How of Testing Solar PV
Emona Instruments
Mustafa Keskin
Overview
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Why Test Solar PV
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How to Test Solar PV
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Basic tests required for Solar PV- Seaward PV150
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IV testing
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Visual Inspections on Solar PV
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Thermal Imaging on Solar PV
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Performance Verification- Array DC Output
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Performance Verification -Inverter Efficiency
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Performance Verification- AC output
Conclusion
Basic Tests Required for Solar PV
AS/NZS 5033 specifies tests to verify safety and correct system operation.
Basics Tests Required for Solar PV
Effect of Temperature and Irradiance
Effect of Temperature on Voltage Output
Effect of Irradiance on Current Output
Manufacturer specification for voltage and current are at Standard Test Conditions (STC) – 25 deg C and 1000 W/m2
Basics Tests- Seaward PV-150 Video
I-V Test Basics
I-V Curve is the voltage current characteristic based on a variable loads
Parameters listed on the data sheet of a module,
Isc,Voc,Pmax,Vmp,Imp,FF
IV Curve model applies to cell, module, whole array
IV Curve Impairments
1. Series losses: (loss of slope)
:Increased Series resistance
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Breaks, Connection faults
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Corrosion
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in-correct dimensioning
2. Shunt Losses: (downward tilt near Isc)
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Imperfection in cell material.
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Cracked or damaged cells.
3. Mismatch Losses: (notches or steps)
Source: SolarPro Aug 2011
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Shading, Uneven soiling
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Cracked cells,
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Faulty bypass diode
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Mismatch module
4. Reduced current: (height of curve)
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Uniform soiling
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low irradiance.
5. Reduced Voltage: (width of curve) affected by module temp
Equivalent circuit model for Solar Cell
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Poor air circulation
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shorted bypass diodes
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other system problems
Reasons for Decreased Output and Yield for Solar Generators
No power generated
Check metering
Turn switch to on position
Visual Inspections on PV Modules
IV tests on 250 modules
to measure degradation
Discoloration
Delamination:back blistering
Browning around junction box
Delamination: front
Arc Fault
Electrochemical Delamination or Corrosion
Burnt housing and 3 broken substrings
and 4 broken bypass diodes
Ref:University of Arizona: IV Analysis of PV modules deployed Tucson 2012 Emily Kopp
Infrared Imaging- Solar PV
Ref :SolarPro Magazine
Patchwork Pattern-defective bypass diode
Red spots-faulty connections
Source:: ZAE Bayern e.V,”Quality Testing in Photovoltaics modules using infrared imaging” 2007
Infrared Imaging- 20 year old Solar PV installation-Patras Greece
Ref: Kaplani-International Journal of Photoenergy
Mortar (induced shading)
Siemens M55 Modules
Severe browning causing blisters on back
Corrosion of busbars and contacts
Back
Back
Front
Front
Back
Back
Back
Hotspots around junction box front and back
Severe browning causing hotspots front and back
Hotspot more than 170 deg.
Infrared Imaging- Installation
Faulty Connector
Can test all parts of the installation : Inverters, Fuses, Cables, Connectors
Performance Verification -Array DC Output
23 Modules (235Watt) in Series
Pstc
Watts
A
V
V
INSTALTEST PV REPORTS
Performance Verification -Array DC Output
23 Modules (235Watt) in Series
INSTALTEST PV REPORTS
Performance Verification -Array DC Output
IV Characteristic and Power Graph- 235 Watt Module-1 Cell Shaded
STC
INSTALTEST PV REPORTS
Performance Verification -Inverter Efficiency
Inverter Conversion Efficiency= Pac/Pdc
Inverter Efficiency Curve - SMA Sunny Boy 2500
INSTALTEST PV
Inverter efficiency affected by temperature should be mounted in shade.
Performance Verification-Inverter
Maximum Power Point Tracking Efficiency
Power Curve Module with Shaded Cell
P
INSTALTEST PV REPORTS
INSTALTEST
INSTALTEST PV
Verifying AC Output for PV Systems
INTERACTIVE PV SYSTEM PERFORMANCE WORKSHEET
PV Array DC Power Rating at STC - 1000 W/m2, 25 °C (kW) .. ......................................................................................
10 kW
Derating Factors
Nameplate Ratings ..........................................0.95
Inverter & transformer.....................................0.95
Module Mismatch.............................................0.98
DC Wiring .........................................................0.98
AC Wiring .........................................................0.99
Soiling
Age
(dusty area's 20% or more) ...................1.00
0.5 to 1 % per year...................................1.00
Combined Derating Factor ................................................................................................... 0.86
Estimated System AC Power Output at STC - 1000 W/m2, 25 °C ................................. ………………………… 8.6 kW
Temperature Adjustments
Array Power-Temperature Coefficient (%/°C) . ................................................................
...-0.5
Measured Array Operating Temperature (°C) . ..(60-25)X0.5=17.5%....................................................60
Estimated System AC Power Output at 1000 W/m2 and Operating Temperature ..............................................7.1 kW
Solar Radiation Adjustments
Measured Solar Irradiance in Plane of Array (W/m2)
...................................................... 850
Estimated System AC Power Output at Operating Temperature and Solar Irradiance ………………….....................
6.0 kW
Conclusion
Seaward PV150 -Quickly verify correct system operation.
Multifunction Tester:
IV Testing Benefits:
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True array Pmppt
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Degradation rates over time (voltage/power)
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Changes in Rs/Rshunt
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Identify wiring problems , module or bypass diode failures.
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Analyze effects of shading.
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Losses due to module mismatch and array wiring methods.
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Establish array ratings for performance guarantees.
Thermal Imaging -
See much more than the eye.
Emona Instruments:
Seaward,Metrel,PVE,Trotec, Amatrol Solar Trainers (IV testers,Cameras $2k)
New Installations:
Last 4 years more than 1 million Solar PV installations have come online.