GreenField Solar:
Testing and Reliability needs of CPV Systems
Dr. Sagar Gadkari, Quality Engineer
Mico Perales, Business Development
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What is CPV?
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Our proprietary PhotoVoltTM Concentrated PV cell
(PV = Photovoltaics)
“Cells”
“Modules”
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Water-cooled
“Receivers”
CPV: two broad approaches
Dense Array vs. Distributed Array
Triple-junction
cells difficult to
densely pack
Distributed Array:
Many concentrators (one per cell)
PhotoVoltTM cells can
be densely packed
Dense Array:
Many cells share one concentrator
GreenField’s Dense array design advantages:
• Simpler optical alignment & relaxed tracking tolerances =>
o Lower O&M costs
o Lower manufacturing costs
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GreenField’s Dense Array Design Optical Approach
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Optical design results in light uniformity in axis of serial
connections
West
East
Reliability Advantages
• Light uniformity easily achieved in one direction
• Greater acceptance angle East-West
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• Tracker north-south movements only required once a day
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Industry-wide issues - Solar
Issues from the field:
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Lower power output over time
By-pass diode/solder failures
Connectors and junction box
Encapsulation failures
Inverter reliability
Solder fatigue
Junction box failures
Encapsulant
browning
connector failures
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source: nrel.gov/pv/pvmrw.html
Industry-wide issues - Solar
Failure to accurately predict performance
– Lack of field data
– Understanding failure mechanism
– Replicating failure modes for accelerated
testing
– Developing models
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Additional Reliability challenges for CPV System
Extreme environment operation
• Receiver Module
– Coatings
– Thermal interface material
– Module packaging (solder joints, epoxy, encapsulants,
diodes)
• Optical Components
– Mirror bonding
– Outdoor exposures over time (backing materials
degradation)
• Tracking, Control system and Power conversion
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– Power system components reliability
– Tracking motor reliability
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Testing Requirements for CPV Module Reliability
Indoor Environmental testing requirements
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High intensity continuous light source exposure
High dose UV impact on materials
Temperature cycling
Humidity effects
• Response to multiple environmental factors
• Outdoor Exposure tests
– Real time DNI, temperature, spectral data and module
performance
– Correlating outdoor data with the indoor tests
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Developing in-house reliability testing capabilities
- Thermal imaging as module production testing tool
- UV test set up for accelerated testing at high
intensities
- Concentrated source 20 sun simulator
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SDLE enhances our testing capabilities
• Cell/Module reliability
– XT-30 200-1000sun concentration exposure
– Time vs performance study
• Cell/Module Coatings reliability
– ART study for the coatings used and their
performance over time – surface analysis
• Environmental chamber testing
• Mirror degradation
– Loss in reflectance over time
– Corrosion
• Real time DNI/AM spectral data
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Thank You!
Driving solar energy into mainstream
deployment, without subsidies
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