: 7th PVPMC Energy Rating and Module Performance Modeling Workshop, 30-31 March, 2017 in Lugano, Switzerland

1. © Fraunhofer ISE
ACCURATE INDOOR DATA FOR ENERGY
RATING
J. Hohl-Ebinger, I. Geisemeyer, B.
Müller, C. Reise, A. Schmid
Fraunhofer Institute for Solar
Energy Systems ISE
PVPMC Workshop
Supsi Canobbio-Lugano,
31.03.2017
www.ise.fraunhofer.de

2. © Fraunhofer ISE
2
 Angle-of-incidence (AOI) effects
 Spectral response
 Absolute module temperature
 Irradiance and temperature coefficients
PV MODULE RATINGS
STC
Nominal power 1
+ = $$$
Realistic
conditions
 Standardized testing for energy rating (e.g. IEC 61853)
?

3. © Fraunhofer ISE
3
 PV Modules
 Irradiance and temperature coefficients
 Angle-of-incidence (AOI) measurement
 PV Cells (Lower the uncertainty)
 Temperature coefficients
 Angle-of-incidence (AOI) measurement -
A Study on front texturization
OUTLINE

4. © Fraunhofer ISE
4
 Power Rating Matrix:
 mandatory (dark green)
 at CalLab PV Modules (light green)
 on request (grey)
Characterization of PV Modules
Power Rating measurements in accordance to IEC 61853
Temperature in °Ct
Irradiance in W/m²
15 25 NOCT 50 75
1100
1000 (incl. TC) STC HTC
900
800 NOCT
700
600
500 LTC
400
300
200 LIC
100
 CalLab PV Modules:
IV(T) 15-75°C in 1K
steps

5. © Fraunhofer ISE
5
Characterization of PV Modules
Power Rating measurements in accordance to IEC 61853

6. © Fraunhofer ISE
6
Power Rating is characterization of modules by …
…determination of the
irradiance dependency
…evaluation of the
temperature coefficients
…determination of incident
angle dependency
Characterization of PV Modules
Power Rating measurements in accordance to IEC 61853

7. © Fraunhofer ISE
7
Characterization of PV Modules
Power Rating measurements in accordance to IEC 61853
Power Rating is characterization of modules by …
…determination of the
irradiance dependency
…evaluation of the
temperature coefficients
…determination of incident
angle dependency

8. © Fraunhofer ISE
8
Characterization of PV Modules
Power Rating measurements in accordance to IEC 61853
Power Rating is characterization of modules by …
…determination of the
irradiance dependency
…evaluation of the
temperature coefficients
…determination of incident
angle dependency

9. © Fraunhofer ISE
9
Characterization of PV Modules
Angular Response Measurement
 Part of standard IEC 61853-2
 Test set up to rotate module
in fixed steps (~7° increments)
 Measurement on one single
cell, either with electrical
connection or by shading this
cell
 Measured short circuit current
is normalized to relative
transmittance 𝜏(𝐴𝑂𝐼), which is
the „incidence angle modifier
(IAM)“ used e. g. in PVSyst
Measured and normalized angular response of a
typical PV module

10. © Fraunhofer ISE
10
Characterization of PV Modules
Angular Response Measurement
View from inside of
the simulator on the
tilted module

11. © Fraunhofer ISE
11
 PV Modules
 Irradiance and temperature coefficients
 Angle-of-incidence (AOI) measurement
 PV Cells (Lower the uncertainty)
 Temperature coefficients
 Angle-of-incidence (AOI) measurement -
A Study on front texturization
OUTLINE

12. © Fraunhofer ISE
12
Temperature Coefficient Determination on Cells
T-Dependent Spectral Response
400 600 800 1000 1200
0
2
4
6
8
10
12
14
16
18
15 °C
25 °C
50 °C
75 °C
SpectralResponse[mA*m²/W]
Wavelength [nm]
200 400 600 800 1000 1200
-2
0
2
4
6
8
10
12
14
TC(SR)[%/K]
Wavelength [nm]

13. © Fraunhofer ISE
13
Temperature Coefficient Determination on Cells
T-Dependent Spectral Mismatch
0.0 0.2 0.4 0.6 0.8 1.0 1.2
0
20
40
60
80
Count
MM [%]
MM Max-Min
*Osterwald et al., Temperature-Dependent Spectral Mismatch Corrections,
IEEE JOURNAL OF PHOTOVOLTAICS
 MM Change (T 15°C->75°C) Class A Simulator Spectrum

14. © Fraunhofer ISE
14
Temperature Coefficient Determination on Cells
MM(T) vs MM(const)
 Assumtion: 1% MM Change
(T 15°C->75°C)
10 20 30 40 50 60 70 80
3600
3800
4000
4200
4400
4600
4800
5000
P[mW]
T [°C]
Pmpp(Ti, MM(const)) [mW] -> -19.6mW/K; 0.413%/K
Pmpp(Ti, MM(T)) [mW] -> -18,96mW/K;0.400%/K
9200
9250
9300
9350
9400
9450
Isc[mA]
MM(const) -> 2.1mA/K; 0.023%/K
MM(T) -> 3.7mA/K; 0.040%/K
0 100 200 300 400 500 600 700
0
2000
4000
6000
8000
10000
Current[mA]
Voltage [mV]
15°C
25°C
50°C
75°C

15. © Fraunhofer ISE
15
Texturization Study
 Angular spectral response
 Measurement setup
 Uncertainty analysis
 Test samples (cells & modules)
 Different front surface textures
 Energy rating
Cells Modules
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

16. © Fraunhofer ISE
16
Measurement of AOI Effects
Integral vs. Spectrally Resolved
 Why spectrally resolved?
 Understand differences
 Validate simulation models
 Low measurement uncertainty
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

17. © Fraunhofer ISE
17
Angular Spectral Response (SR)
Measurement Setup
 Filter monochromator
 Two light sources
 Lock-in procedure
 Fully illuminated sample
Cells Modules
 Rotary measurement unit
 T-control
 Rotating bias light
 Separates injection-dep.
 One axis of rotation
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

18. © Fraunhofer ISE
18
Angular Spectral Response (SR)
Uncertainty Analysis
 Based on measured data
 Spectral content
 Polarization
 Uniformity
 Angular response
of different cells
and modules
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

19. © Fraunhofer ISE
19
400 600 800 1000 1200
10-1
100
101
102
U95
(SR/SR0
)/%
1%
wavelength / nm
AOI = 30°
400 600 800 1000
0
25
50
75
100
wavelength / nm
Uncertainty/%
AOI = 30°
Change in Angular SR
Uncertainty Analysis
 AOI = 30°: 95% confidence level
typically below 1%
 UV: Out-of-band radiation,
bandwidth, etc…
 Visible/: Position of sample and
NIR associated uniformity
correction
 NIR: Temperature
Cells
Uniformity
Temperature
OOB etc.

20. © Fraunhofer ISE
20
Change in Angular SR
Uncertainty Analysis
 AOI = 30°: 95% confidence level
typically below 1%
 UV: Out-of-band radiation,
bandwidth, etc…
 Visible/: Position of sample and
NIR associated uniformity
correction
 NIR: Temperature
 AOI = 60°: Increasing influence of
adjustment of rotating
frame (AOI adjustm.)
10-1
100
101
102
400 600 800 1000 1200
10-1
100
101
AOI = 60°
1%
U95
(SR/SR0
)/%
AOI = 30°
1%
U95
(SR/SR0
)/% wavelength / nm
Cells
0
25
50
75
100
Uncertainty/%
AOI = 30°
400 600 800 1000
0
25
50
75
100
AOI = 60°
Uncertainty/%
wavelength / nm
Uniformity
Temperature
OOB etc.
AOI adjustment

21. © Fraunhofer ISE
21
400 600 800 1000 1200
10-1
100
101
102
U95
(SR/SR0
)/%
1%
wavelength / nm
AOI = 30° Cells
Change in Angular SR
Uncertainty Analysis
 AOI = 30°: 95% confidence level
typically below 1%
 UV: Out-of-band radiation,
bandwidth, etc…
 Visible/: Position of sample and
NIR associated uniformity
correction
 NIR: Temperature
 AOI = 60°: Increasing influence of
adjustment of rotating
frame (AOI adjustm.)
400 600 800 1000
0
25
50
75
100
wavelength / nm
Uncertainty/%
AOI = 30°
Uniformity
Temperature
OOB etc.

22. © Fraunhofer ISE
22
10-1
100
101
102
10-1
100
101
400 600 800 1000 1200
10-1
100
101
AOI = 75°
AOI = 60°
1%
U95
(SR/SR0
)/%
AOI = 30°
1%
U95
(SR/SR0
)/%U95
(SR/SR0
)/%
wavelength / nm
1%
Change in Angular SR
Uncertainty Analysis
 AOI = 30°: 95% confidence level
typically below 1%
 UV: Out-of-band radiation,
bandwidth, etc…
 Visible/: Position of sample and
NIR associated uniformity
correction
 NIR: Temperature
 AOI = 60°: Increasing influence of
adjustment of rotating
frame (AOI adjustm.)
 AOI = 75°: AOI adjustment
dominates
Cells
0
25
50
75
100
Uncertainty/%
AOI = 30°
0
25
50
75
100
AOI = 60°
Uncertainty/%
400 600 800 1000
0
25
50
75
100
AOI = 75°
Uncertainty/%
wavelength / nm
Uniformity
Temperature
OOB etc.
AOI adjustment

23. © Fraunhofer ISE
23
 Differences in measurement
uncertainty for cells and modules
 AOIs > 60°: angle adjustment
more critical
 UV: low signal due to EVA 10-1
100
101
102
1%
U95
(SR/SR0
)/%
Change in Angular SR
Uncertainty Analysis
10-1
100
101
102
1%
U95
(SR/SR0
)/%
AOI = 30°
10-1
100
101
AOI = 60°
1%
U95
(SR/SR0
)/%
400 600 800 1000 1200
10-1
100
101
AOI = 75°U95
(SR/SR0
)/%
wavelength / nm
1%
400 600 800 1000 1200
10-1
100
101
102
U95
(SR/SR0
)/%
wavelength / nm
10-1
100
101
102
1%
U95
(SR/SR0
)/%
Cells
400 600 800 1000 1200
10-1
100
101
102
wavelength / nm
Modules
AOI / °
15 30 45 60 67.5 75 80 85
1)
2)
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

24. © Fraunhofer ISE
24
 Differences in measurement
uncertainty for cells and modules
 AOIs > 60°: angle adjustment
more critical
 UV: low signal due to EVA
 Change in JSC:
 Monte Carlo simulation
 Random walks for correlations
w.r.t wavelength
 Lowest measurement uncertainty
reported for relative measurement
Change in Angular SR
Uncertainty Analysis
400 600 800 1000 1200
10-1
100
101
102
U95
(SR/SR0
)/%
wavelength / nm
Cells
400 600 800 1000 1200
10-1
100
101
102
wavelength / nm
Modules
1)
2)
0 15 30 45 60 75 90
0.4
0.6
0.8
1.0
JSC
/JSC,0
AOI / °
0 15 30 45 60 75 90
0.1
1
10
U95/%
0.5
AOI / °
15 30 45 60 67.5 75 80 85
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

25. © Fraunhofer ISE
25
Samples
Cells and Modules
 Six cells
 Small area 5 x 5 cm²
 p-type Al-BSF
 Contacted via micromanipu-
lators with Kelvin probes
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

26. © Fraunhofer ISE
26
Samples
Cells and Modules
 Six cells
 Small area 5 x 5 cm²
 p-type Al-BSF
 Contacted via micromanipu-
lators with Kelvin probes
 Modules
 Planar glass
 Dummy half cells
 Open rear
 El. conductive tape
 Th. conductive gray pad
Side view
Front view Rear view
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

27. © Fraunhofer ISE
27
Texture Substrate
PLANAR
(chemically polished)
Cz-Si
RANDOM PYRAMIDS
(alkaline-textured)
Cz-Si
ISOTEXTURE
(acidic-textured)
mc-Si
NIL-HC
(nano-imprinted honeycombs)
*Volk et al., IEEE JPV 5, 1027-1033, 2015
mc-Si
LW-HC
(laser-structured honeycombs)
*Volk et al., 28th EUPVSEC, 1024-1028, 2013
mc-Si
NANO
(shallow nano-textured)
*Kafle et al., Solmat 152, 94-102, 2016
mc-Si
Samples
Front Surface Textures
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

28. © Fraunhofer ISE
28
Texture Substrate
PLANAR
(chemically polished)
Cz-Si
RANDOM PYRAMIDS
(alkaline-textured)
Cz-Si
ISOTEXTURE
(acidic-textured)
mc-Si
NIL-HC
(nano-imprinted honeycombs)
*Volk et al., IEEE JPV 5, 1027-1033, 2015
mc-Si
LW-HC
(laser-structured honeycombs)
*Volk et al., 28th EUPVSEC, 1024-1028, 2013
mc-Si
NANO
(shallow nano-textured)
*Kafle et al., Solmat 152, 94-102, 2016
mc-Si
Samples
Front Surface Textures
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

29. © Fraunhofer ISE
29
Texture Substrate
PLANAR
(chemically polished)
Cz-Si
RANDOM PYRAMIDS
(alkaline-textured)
Cz-Si
ISOTEXTURE
(acidic-textured)
mc-Si
NIL-HC
(nano-imprinted honeycombs)
*Volk et al., IEEE JPV 5, 1027-1033, 2015
mc-Si
LW-HC
(laser-structured honeycombs)
*Volk et al., 28th EUPVSEC, 1024-1028, 2013
mc-Si
NANO
(shallow nano-textured)
*Kafle et al., Solmat 152, 94-102, 2016
mc-Si
Samples
Front Surface Textures
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

30. © Fraunhofer ISE
30
Texture Substrate
PLANAR
(chemically polished)
Cz-Si
RANDOM PYRAMIDS
(alkaline-textured)
Cz-Si
ISOTEXTURE
(acidic-textured)
mc-Si
NIL-HC
(nano-imprinted honeycombs)
*Volk et al., IEEE JPV 5, 1027-1033, 2015
mc-Si
LW-HC
(laser-structured honeycombs)
*Volk et al., 28th EUPVSEC, 1024-1028, 2013
mc-Si
NANO
(shallow nano-textured)
*Kafle et al., Solmat 152, 94-102, 2016
mc-Si
Samples
Front Surface Textures
50 µm
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

31. © Fraunhofer ISE
31
Texture Substrate
PLANAR
(chemically polished)
Cz-Si
RANDOM PYRAMIDS
(alkaline-textured)
Cz-Si
ISOTEXTURE
(acidic-textured)
mc-Si
NIL-HC
(nano-imprinted honeycombs)
*Volk et al., IEEE JPV 5, 1027-1033, 2015
mc-Si
LW-HC
(laser-structured honeycombs)
*Volk et al., 28th EUPVSEC, 1024-1028, 2013
mc-Si
NANO
(shallow nano-textured)
*Kafle et al., Solmat 152, 94-102, 2016
mc-Si
Samples
Front Surface Textures
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

32. © Fraunhofer ISE
32
Texture Substrate
PLANAR
(chemically polished)
Cz-Si
RANDOM PYRAMIDS
(alkaline-textured)
Cz-Si
ISOTEXTURE
(acidic-textured)
mc-Si
NIL-HC
(nano-imprinted honeycombs)
*Volk et al., IEEE JPV 5, 1027-1033, 2015
mc-Si
LW-HC
(laser-structured honeycombs)
*Volk et al., 28th EUPVSEC, 1024-1028, 2013
mc-Si
NANO
(shallow nano-textured)
*Kafle et al., Solmat 152, 94-102, 2016
mc-Si
Samples
Front Surface Textures
0 1 2 3 4 5 µm
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

33. © Fraunhofer ISE
33
0.6
0.8
1.0
1.2
400 600 800 1000 1200
0.6
0.8
1.0
1.2
SR/SR0
SR/SR0
wavelength / nm
RANDOM PYRAMIDS
PLANAR
Results
Change in Angular SR
AOI / °
15 30 45 60 67.5 75 80 85
MODULESCELLS
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

34. © Fraunhofer ISE
34
0.6
0.8
1.0
1.2
400 600 800 1000 1200
0.6
0.8
1.0
1.2
0.6
0.8
1.0
1.2
400 600 800 1000 1200
0.6
0.8
1.0
1.2
SR/SR0
SR/SR0
wavelength / nm wavelength / nm
RANDOM PYRAMIDS
PLANAR
Results
Change in Angular SR
MODULESCELLS
AOI / °
15 30 45 60 67.5 75 80 85 Module level
 More similar characteristics
 Effects of texture still
observable
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

35. © Fraunhofer ISE
35
CELLS
MODULES
SIMULATION
Results
Change in JSC
Cells
 PLANAR: Stronger decrease
for AOI > 60°
 RP: Distinct near-linear
decrease for
AOI > 15°
Modules
 Differences in the range of 1%
 RP: Stronger AOI
dependence
0.4
0.6
0.8
1.0
0 20 40 60 80
0.4
0.6
0.8
1.0
0 20 40 60 80
20 30 40 50 60
0.92
0.94
0.96
0.98
1.00
1.02
0 20 40 60
0.85
0.90
0.95
1.00
1.05
JSC
/JSC,0
PLANAR
RANDOM PYRAMIDS
JSC
/JSC,0
AOI / °
PLANAR
RANDOM PYRAMIDS
AOI / °
EXPERIMENT
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

36. © Fraunhofer ISE
36
Energy Rating with Measured Data
Change in JSC
 Three different climate zones
 SolarGIS weather data
 10 years
 15 min resolution
 Separated direct and diffuse
(AOI 55°) irradiation
 Three module orientations
 Three inclination angles
0
1
2
3
4
5
6
Rafah, Egypt
Breisach, Germany
Inclination
SOUTH
AOIloss/%/a
PLANAR
ISO-TEXTURE
RANDOM PYRAMIDS
EAST
O
rientation
Norwich, UK
0
1
2
3
4
5
6
AOIloss/%/a
20° 40° 90° 20° 40° 90°
0
1
2
3
4
5
6
AOIloss/%/a
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

37. © Fraunhofer ISE
37
Energy Rating with Measured Data
Change in JSC
 Typically 2-4 % annual loss due to
AOI dependence
 Up to 1.5 % difference due to
front texture
0
1
2
3
4
5
6
Rafah, Egypt
Breisach, Germany
Inclination
SOUTH
AOIloss/%/a
PLANAR
ISO-TEXTURE
RANDOM PYRAMIDS
EAST
O
rientation
Norwich, UK
0
1
2
3
4
5
6
AOIloss/%/a
20° 40° 90° 20° 40° 90°
0
1
2
3
4
5
6
AOIloss/%/a
*Geisemeyer et al., Angle Dependence of Solar Cells and Modules: The Role of Cell
Texturization, DOI: 10.1109/JPHOTOV.2016.2614120

38. © Fraunhofer ISE
38
Energy Rating with Measured Data
Cell-to-Module Losses in JSC
 Convolution of SR with AM1.5g
(before and after encapsulation)
 Simulated annual AOI loss (based
on measured data)
 Cell-to-module:
 NIL-HC: -4.0 %
 RP: -2.7 %
 ISO: -1.1 %
 AOI losses:
 RP loses initial advantage over
ISO almost completely
NIL-HC LW-HC RP ISO PLANAR
32
33
34
35
36
37
38
JSC
/mA/cm2
JSC
cell
JSC
module
JSC
module with annual loss AOI
Norwich (UK), Orientation: South, Inclination: 40°
-4.0%
-2.7%
-1.1%
Small area laboratory cells
and mini modules!
-2.3%
-2.7%
-2.2%

39. © Fraunhofer ISE
39
Conclusion
 Measurement setup for angular SR:
Bias light rotating with the sample
400 600 800 1000 1200
10-1
100
101
102
U95
(SR/SR0
)/%
wavelength / nm
0 15 30 45 60 75 90
0.4
0.6
0.8
1.0
JSC
/JSC,0
AOI / °
0 15 30 45 60 75 90
0.1
1
10
U95/%
0.5
 Results for cells and modules:
Modules: Differences ≈ 1%
 Combination of CTM and AOI losses:
Random pyramids lose initial advan-
tage over isotexture
 Uncertainty analysis:
Change in SR: U95(AOI < 75°) < 1%
Change in JSC: U95(AOI < 60°) ≈ 0.5%

40. © Fraunhofer ISE
40
Acknowledgment
This work was partly funded by the German Federal Ministry for the
Environment, Nature Conservation and Nuclear Safety (Contract Number
0325447 OHM) and the EMRP ENG55 project “Towards an energy-based
parameter for photovoltaic classifi-cation”. The EMRP is jointly funded by
the EMRP participating countries within EURAMET and the European Union.
Jochen Hohl-Ebinger
www.ise.fraunhofer.de
jochen.hohl-ebinger@ise.fraunhofer.de
Thank You Very Much for Your Attention!