2014 PV Performance Modeling Workshop: Results from Flash Testing at Multiple Irradiance and Temperatures across Five Photovoltaic Testing Labs: Junaid Fatehi, Yingli Green Energy Americas

1. RESULTS FROM FLASH TESTING AT MULTIPLE IRRADIANCES AND
TEMPERATURES ACROSS FIVE PHOTOVOLTAIC TESTING LABS
3rd PV Performance Modeling Workshop
May 5, 2014, Santa Clara, CA
Junaid H. Fatehi1, Cherif Kedir2, Charles Tumengko3, Nick Riedel4, John L. R. Watts5
1Yingli Green Energy Americas, San Francisco, CA
2Renewable Energy Test Center, Fremont, CA
3Intertek Testing Services, Lake Forest, CA
4CFV Solar Test Laboratory, Albuquerque, NM
5PV Evolution Labs, Berkeley, CA
Published by Sandia National Laboratories with the permission of the authors.

2. Background
• For reliable system energy yield modeling, it is important to
characterize the dependence of PV module performance on
irradiance and operating temperature, for conversion into module
performance models used in energy simulation
• This study was coordinated by Yingli Green Energy Americas and it
investigates the contribution of data source in the measurement and
understanding of PV module behavior
• Three light-stabilized multicrystalline silicon PV modules from Yingli
Solar were sent to five testing labs for round robin characterization

3. Participating Labs
• CFV Solar Test Laboratory
– Albuquerque, NM
• Intertek Testing Services
– Lake Forest, CA
• Renewable Energy Test Center
– Fremont, CA
• PV Evolution Labs
– Berkeley, CA
• Yingli Americas PV Testing Lab
– South San Francisco, CA
All labs are assigned a random number for anonymous reporting.

4. Testing Scope
• Multiple Irradiance Testing
– Testing between 100 W/m2 and 1,000 W/m2
– Minimum testing interval of 100 W/m2
– Fixed testing temperature of 25 oC
• Temperature Coefficient Testing
– Testing between 25 oC and 65 oC
– Maximum testing interval of 5 oC
– Fixed testing irradiance of 1,000 W/m2

5. Testing Notes
• All five participating labs:
– Conducted electroluminescence imaging to
screen for transportation damage (none reported)
– Conducted temperature coefficient testing indoors
– Calibrated with a module tested at Fraunhofer
ISE and traceable to PTB

6. Standard Test Conditions
1,000 W/m2, 25 oC, AM 1.5g

7. Module S/N: 124804060126
Lab Isc (A) Voc (V) Imp (A) Vmp (V) Pmp (W)
1 8.785 45.69 8.281 36.53 302.5
2 8.756 45.60 8.211 36.43 299.1
3 8.826 45.55 8.256 36.41 300.6
4 8.799 45.60 8.264 36.60 302.5
5 8.874 45.59 8.300 36.77 305.1
Lab Isc Voc Imp Vmp Pmp
1 -0.26 % 0.18 % 0.22 % -0.05 % 0.18 %
2 -0.59 % -0.01 % -0.63 % -0.33 % -0.96 %
3 0.21 % -0.12 % -0.08 % -0.37 % -0.45 %
4 -0.10 % -0.01 % 0.02 % 0.15 % 0.18 %
5 0.75 % -0.04 % 0.45 % 0.60 % 1.05 %
Test Results:
Difference from the Mean:

8. Module S/N: 124804060149
Lab Isc (A) Voc (V) Imp (A) Vmp (V) Pmp (W)
1 8.768 45.67 8.272 36.55 302.3
2 8.732 45.56 8.185 36.51 298.9
3 8.788 45.59 8.224 36.62 301.1
4 8.753 45.61 8.245 36.69 302.5
5 8.860 45.61 8.285 36.86 305.4
Lab Isc Voc Imp Vmp Pmp
1 -0.14 % 0.13 % 0.36 % -0.26 % 0.10 %
2 -0.55 % -0.10 % -0.69 % -0.36 % -1.05 %
3 0.09 % -0.04 % -0.23 % -0.07 % -0.30 %
4 -0.31 % 0.00 % 0.04 % 0.11 % 0.15 %
5 0.91 % 0.01 % 0.52 % 0.58 % 1.10 %
Test Results:
Difference from the Mean:

9. Module S/N: 124804060310
Lab Isc (A) Voc (V) Imp (A) Vmp (V) Pmp (W)
1 8.741 45.62 8.220 36.51 300.1
2 8.718 45.50 8.144 36.42 296.6
3 8.725 45.50 8.158 36.61 298.6
4 8.740 45.49 8.204 36.56 299.9
5 8.858 45.51 8.232 36.77 302.7
Lab Isc Voc Imp Vmp Pmp
1 -0.18 % 0.22 % 0.34 % -0.17 % 0.17 %
2 -0.44 % -0.05 % -0.58 % -0.42 % -1.00 %
3 -0.36 % -0.06 % -0.41 % 0.09 % -0.32 %
4 -0.19 % -0.07 % 0.16 % -0.04 % 0.11 %
5 1.16 % -0.04 % 0.49 % 0.55 % 1.04 %
Test Results:
Difference from the Mean:

10. Multiple Irradiance Testing
25 oC, AM 1.5g

11. Relative Efficiency Metrics
• Relative Efficiency
– 𝐸𝑓𝑓𝑅𝑒𝑙 𝐺
=
𝑃𝑚𝑝 𝐺∗
1000 𝑊/𝑚2
𝐺
𝑃𝑚𝑝1000
− 1
• Self-Referenced Relative Efficiency
– 𝐸𝑓𝑓𝑆𝑒𝑙𝑓_𝑅𝑒𝑙 𝐺
=
𝑃𝑚𝑝 𝐺∗
𝐼𝑠𝑐1000
𝐼𝑠𝑐 𝐺
𝑃𝑚𝑝1000
− 1

12. Absolute Efficiency Metrics
• Absolute Efficiency
– 𝐸𝑓𝑓𝐴𝑏𝑠 𝐺
=
𝑃𝑚𝑝 𝐺
𝐴𝑟𝑒𝑎 ∗𝐺
• Self-Referenced Absolute Efficiency
– 𝐸𝑓𝑓𝑆𝑒𝑙𝑓_𝐴𝑏𝑠 𝐺
=
𝑃𝑚𝑝 𝐺
𝐴𝑟𝑒𝑎 ∗
𝐼𝑠𝑐 𝐺
𝐼𝑠𝑐1000
∗1000 𝑊/𝑚2

13. Module S/N: 124804060126
100 200 300 400 500 600 700 800 900 1000
-8
-7
-6
-5
-4
-3
-2
-1
0
1
Relative Efficiency
Irradiance (W/m2
)
ChangeinEfficiency(%)
Lab 1
Lab 2
Lab 3
Lab 4
Lab 5
100 200 300 400 500 600 700 800 900 1000
-8
-7
-6
-5
-4
-3
-2
-1
0
1
Self-Referenced Relative Efficiency
Irradiance (W/m2
)
ChangeinEfficiency(%)
Lab 1
Lab 2
Lab 3
Lab 4
Lab 5
100 200 300 400 500 600 700 800 900 1000
14.2
14.4
14.6
14.8
15.0
15.2
15.4
15.6
15.8
Absolute Efficiency
Irradiance (W/m2
)
Efficiency(%)
Lab 1
Lab 2
Lab 3
Lab 4
Lab 5
100 200 300 400 500 600 700 800 900 1000
14.2
14.4
14.6
14.8
15.0
15.2
15.4
15.6
15.8
Self-Referenced Absolute Efficiency
Irradiance (W/m2
)Efficiency(%)
Lab 1
Lab 2
Lab 3
Lab 4
Lab 5

14. Module S/N: 124804060149
100 200 300 400 500 600 700 800 900 1000
-8
-7
-6
-5
-4
-3
-2
-1
0
1
Relative Efficiency
Irradiance (W/m2
)
ChangeinEfficiency(%)
Lab 1
Lab 2
Lab 3
Lab 4
Lab 5
100 200 300 400 500 600 700 800 900 1000
-8
-7
-6
-5
-4
-3
-2
-1
0
1
Self-Referenced Relative Efficiency
Irradiance (W/m2
)
ChangeinEfficiency(%)
Lab 1
Lab 2
Lab 3
Lab 4
Lab 5
100 200 300 400 500 600 700 800 900 1000
14.2
14.4
14.6
14.8
15.0
15.2
15.4
15.6
15.8
Absolute Efficiency
Irradiance (W/m2
)
Efficiency(%)
Lab 1
Lab 2
Lab 3
Lab 4
Lab 5
100 200 300 400 500 600 700 800 900 1000
14.2
14.4
14.6
14.8
15.0
15.2
15.4
15.6
15.8
Self-Referenced Absolute Efficiency
Irradiance (W/m2
)Efficiency(%)
Lab 1
Lab 2
Lab 3
Lab 4
Lab 5

15. Module S/N: 124804060310
100 200 300 400 500 600 700 800 900 1000
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
1
Relative Efficiency
Irradiance (W/m2
)
ChangeinEfficiency(%)
Lab 1
Lab 2
Lab 3
Lab 4
Lab 5
100 200 300 400 500 600 700 800 900 1000
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
1
Self-Referenced Relative Efficiency
Irradiance (W/m2
)
ChangeinEfficiency(%)
Lab 1
Lab 2
Lab 3
Lab 4
Lab 5
100 200 300 400 500 600 700 800 900 1000
14.0
14.2
14.4
14.6
14.8
15.0
15.2
15.4
15.6
15.8
Absolute Efficiency
Irradiance (W/m2
)
Efficiency(%)
Lab 1
Lab 2
Lab 3
Lab 4
Lab 5
100 200 300 400 500 600 700 800 900 1000
14.0
14.2
14.4
14.6
14.8
15.0
15.2
15.4
15.6
15.8
Self-Referenced Absolute Efficiency
Irradiance (W/m2
)Efficiency(%)
Lab 1
Lab 2
Lab 3
Lab 4
Lab 5

16. Temperature Coefficient Testing
1,000 W/m2, AM 1.5g

17. Short Circuit Current Temperature Coefficient
Lab 1 Lab 2 Lab 3 Lab 4 Lab 5
0.045
0.050
0.055
0.060
%/C Isc
Module S/N: 124804060126
Module S/N: 124804060149
Module S/N: 124804060310

18. Open Circuit Voltage Temperature Coefficient
Lab 1 Lab 2 Lab 3 Lab 4 Lab 5
-0.345
-0.340
-0.335
-0.330
-0.325
-0.320
-0.315
-0.310
-0.305
%/C Voc
Module S/N: 124804060126
Module S/N: 124804060149
Module S/N: 124804060310

19. Maximum Power Temperature Coefficient
Lab 1 Lab 2 Lab 3 Lab 4 Lab 5
-0.47
-0.46
-0.45
-0.44
-0.43
-0.42
-0.41
-0.40
%/C Pmp
Module S/N: 124804060126
Module S/N: 124804060149
Module S/N: 124804060310

20. Conclusions
• Self-referencing irradiance results in smoother
efficiency curves and better relative efficiency
agreement between labs
• Three out of five labs have good agreement on
Voc temperature coefficients and moderate
agreement on Pmp temperature coefficients

21. Thank You
Contact Junaid H. Fatehi at juanid.fatehi@yingliamericas.com for questions and comments.

22. For Discussion
* Annual energy yield estimates were performed in PVsyst for a fixed system design and using .PAN files created from each participating lab’s measurement
data in accordance with “Systematic Approaches to Ensure Correct Representation of Measured Multi-Irradiance Module Performance in PV System Energy
Production Forecasting Software Programs”, presented at Sandia's 2013 PV Performance Modeling Workshop by Kenneth J. Sauer and Thomas Roessler.
Deviation in estimated annual energy yield from the mean for each location.*
-0.8%
-0.6%
-0.4%
-0.2%
0.0%
0.2%
0.4%
0.6%
Antofagasta, Chile Berlin, Germany Phoenix, USA Trivandrum, India
Lab 1
Lab 2
Lab 3
Lab 4
Lab 5