![From: F. Brill, “EnviroPolitics Blog: PSEG building solar farms--and not just in
New Jersey,” 16-Nov-2012. [Online].
From: E. Lorenzo, R. Moretón, and I. Luque, “Dust effects on PV array
performance: in-field observations with non-uniform patterns,”
Progress in Photovoltaics: Research and Applications, 2013.
0.700
0.750
0.800
0.850
0.900
0.950
1.000
0% 5% 10% 15% 20% 25% 30% 35%
SoilingRatio
Edge Cells Soiling Level
SRIsc (12 cells)
SRPmax (12 cells)
SRPmax (6 cells)
SRIsc (6 cells)
From: Gostein, Littmann, Caron, Dunn, Proceedings of the 39th IEEE Photovoltaic
Specialists Conference (PVSC), Tampa, FL, June 2013.
Accurately Measuring PV Soiling Losses
Using Module Power Measurements
M. Gostein and B. Stueve, Atonometrics, Inc.
Non-uniform PV soiling can’t be measured by short-circuit current alone.
• In some conditions, soiling
may accumulate non-
uniformly on PV modules
• Wind, rain, condensation,
temperature, and gravity all
affect soiling distribution
• Often, soiling is
concentrated at module
edges
• “Soiling Ratio” (SR) metric
can be based on losses in
measured current (Isc) or
power (Pmax)
• Isc measurement simpler,
but only approximates true
power loss in case of uniform
soiling
• Experiment shows Isc
measurements can severely
over- or under-estimate true
power loss for non-uniform
soiling on c-Si PV modules
• Soiling measurement: use
“soiled” module and “clean”
control
• “Clean” control: may use
automatically cleaned
reference cell
• For “soiled module” use
actual PV module
representative of site, to
capture module-specific
effects and non-uniformities
• Should measure both
module current and power
Example of edge soiling
on utility-scale tracking system:
Examples on ground and
roof-mount systems:
Non-Uniform PV Soiling
Pmax vs. Isc as Soiling Metric
Soiling Measurement System
Soiling Underestimated
ResultsExperiment with Simulated Soiling
72-cell c-Si module, two orientations
Soiling Ratio Metrics
Explanation: Module has 3 internal bypass diodes. Shaded 12-cell
string on long edge is bypassed by internal diode, so Isc is not
limited by shading; but shading 6 cells across all strings results in
the shaded cells controlling and limiting Isc.
Soiled Reference Module
Washed
Ref Cell
Measurement
Electronics
Wash
Unit
Stand-alone system Utility plant monitoring system
Washed
Ref Cell
Measurement
Electronics
Wash
Unit
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Accurately measuring pv soiling losses using module power measurements
- 1. From: F. Brill, “EnviroPolitics Blog: PSEG building solar farms--and not just in New Jersey,” 16-Nov-2012. [Online]. From: E. Lorenzo, R. Moretón, and I. Luque, “Dust effects on PV array performance: in-field observations with non-uniform patterns,” Progress in Photovoltaics: Research and Applications, 2013. 0.700 0.750 0.800 0.850 0.900 0.950 1.000 0% 5% 10% 15% 20% 25% 30% 35% SoilingRatio Edge Cells Soiling Level SRIsc (12 cells) SRPmax (12 cells) SRPmax (6 cells) SRIsc (6 cells) From: Gostein, Littmann, Caron, Dunn, Proceedings of the 39th IEEE Photovoltaic Specialists Conference (PVSC), Tampa, FL, June 2013. Accurately Measuring PV Soiling Losses Using Module Power Measurements M. Gostein and B. Stueve, Atonometrics, Inc. Non-uniform PV soiling can’t be measured by short-circuit current alone. • In some conditions, soiling may accumulate non- uniformly on PV modules • Wind, rain, condensation, temperature, and gravity all affect soiling distribution • Often, soiling is concentrated at module edges • “Soiling Ratio” (SR) metric can be based on losses in measured current (Isc) or power (Pmax) • Isc measurement simpler, but only approximates true power loss in case of uniform soiling • Experiment shows Isc measurements can severely over- or under-estimate true power loss for non-uniform soiling on c-Si PV modules • Soiling measurement: use “soiled” module and “clean” control • “Clean” control: may use automatically cleaned reference cell • For “soiled module” use actual PV module representative of site, to capture module-specific effects and non-uniformities • Should measure both module current and power Example of edge soiling on utility-scale tracking system: Examples on ground and roof-mount systems: Non-Uniform PV Soiling Pmax vs. Isc as Soiling Metric Soiling Measurement System Soiling Underestimated ResultsExperiment with Simulated Soiling 72-cell c-Si module, two orientations Soiling Ratio Metrics Explanation: Module has 3 internal bypass diodes. Shaded 12-cell string on long edge is bypassed by internal diode, so Isc is not limited by shading; but shading 6 cells across all strings results in the shaded cells controlling and limiting Isc. Soiled Reference Module Washed Ref Cell Measurement Electronics Wash Unit Stand-alone system Utility plant monitoring system Washed Ref Cell Measurement Electronics Wash Unit This poster contains no confidential information.