U.S. Department of Energy - Energy Efficiency and Renewable Energy
Photovoltaic Module Reliability Workshop 2012
February 28–March 1, 2012
The Photovoltaic (PV) Module Reliability Workshop was held in Golden, Colorado, on Feb. 28–March 1, 2012. The objective was to share information to improve PV module reliability because such improvements reduce the cost of solar electricity and give investors confidence in the technology. NREL led the workshop, which was sponsored by the U.S. Department of Energy (DOE) Solar Energy Technologies Program (Solar Program).
The following documents are available. The entire proceeding of the PV Module Reliability Workshop (Files) will be available for download soon.
In addition, a detailed agenda is available.
The presentations are grouped by topic and session:
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Plenary Session: Silicon
Chairs/Discussion Leaders: Jay Johnson (Sandia) and Chris Flueckiger (UL)
Discussion summary (safety issues):
- The challenge is to construct a rooftop PV system that simultaneously keeps the panels cool and achieves a Class A fire rating.
- When ANSI adopts IEC 61730, harmonizing the U.S. and International safety standards, national differences will be retained to include spread-of-flame tests of PV systems mounted on roofs.
- Addressing series arc faults is useful, but will increase the issues with parallel arc faults. We should address both, and the technology for addressing the parallel arcs may be available soon.
- Solar ABCs will work to develop a standard for inspecting older PV systems this year.
- Suggestion for DOE to support a program to inspect old PV systems through SunShot and the RTCs.
Reliability Predictions through Analytical Modeling
Chairs/Discussion Leaders: Glenn Alers (UC Santa Cruz), David Meakin (Fraunhofer CSE)
Discussion summary (modeling):
- Modeling far into the future tends to exaggerate testing anomalies and uncertainties.
- Modeling helps us:
- Improve product design
- Explore our understanding
- Extrapolate to longer times
- We still need field experiments for:
- Gathering statistics for manufacturing variations
- Understanding combinations of factors
- Stochastic approaches allow modeling of complex systems with less computational time.
- We often take diodes for granted. We should explore this as an industry, especially considering the 25% failure rate seen in the Japanese study.
Potential Induced and Other Bias-Related Degradation
Chairs/Discussion Leaders: Mike Kempe (NREL), Jenya Meydbray (PV Evolution Labs)
Discussion summary (PID):
- PID is observed in both mono- and multi-crystalline systems.
- Could we develop a test for encapsulants that identifies whether they will help the mitigation of PID?
Regional meeting of PV QA Task Group #1
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Poster Session: Silicon
- Highly Accelerated UV Aging of Organic Luminescent Materials, Glenn Alers (Univ. California, Santa Cruz)
- Photovoltaic Module Outdoor Analysis and Power Estimation, Dohyun Baek (Samsung)
- PV Standards. What New Things Does the IEC Have for You?, Howard Barikmo (Sunset Technology)
- Exploring Highly Accelerated Aging on c-Si Modules, Didier Binesti (Electricité de France)
- Evaluating Backsheets without Fluoropolymer Sun-Facing Layers, Jim Bratcher (Honeywell Performance Materials)
- Outdoor High-Voltage Bias Testing of PV Modules, Neelkanth Dhere and Ashwani Kaul (FSEC)
- Performance and Reliability Test Methodology, Thai Phuong Do (REC Solar)
- Improved Plastic Materials for Application in PV Modules, Dan M.J. Doble, Andrew Kodis, Rob deJong, Karen van de Wetering and Bala Ambravan (Sabic Innovative Plastics)
- Spectral Effects in Performance Ratio Measurement: Comparing PV Reference Devices and Pyranometers, Lawrence Dunn and Michael Gostein (Atonometrics)
- Task Statement/Japan Regional Task Group, Yoshihito Eguchi (Sharp)
- Current PV Standards – Polymeric Requirement and Test Methods, Chris Flueckiger (UL)
- Material Characterization in PV Modules, William Gambogi, Katherine Stika, Alex Bradley, Babak Hamzavy, and Rebecca Smith (Dupont)
- Comparing Anti-Soiling Reliability and Performance on Glass, ETFE, Structured Glass and Film Structured Fusion on PV Panels, Melissa Grossman, Mark Raymond, Seth Weiss, and Hector Porras (Genie Lens)
- Effect of Simultaneous UV Radiation, Temperature and Moisture on Degradation of PV Polymers, Xiaohong Gu, Yongyan Pang, Kaipeng Liu, Tinh Nguyen and Joannie W. Chin (NIST)
- Lifetime Prediction of Silicon Crystalline Photovoltaic Ribbon Wire in Three Local Weathers, Changwoon Han, Nochang Park, and Jaesung Jeong (Korea Electronics Technology Institute)
- Observing Mini PV Module Degradation through Successive Damp Heat Testing and Thermal Cycle Testing Procedure, Kusato Hirota, Takashi Arai, Ryuhei Metabi, Michiko Tanaka, Takao Amioka, and Miki Terada (Toray Industries)
- Hotspot Detection for Cell Production Lines, G.S. Horner, J.E. Hudson, J. Schmidt, L.A. Vasilyev, and K. Lu (Tau Science Corporation)
- Thermoanalytical Characterization of Ethylene Vinyl Acetate Copolymer (EVA) for Lamination Process Simulation and Gel Content Determining in Photovoltaic Modules, Yen-Shan Hsu and Steven R. Aubuchon (TA Instruments – Waters LLC), Yi-Hung Chou, Wen-Yao Chou, Yu-Chen Chien, and Shr-Ming Shiu (Delsolar)
- Introduction to the SunFarm Outdoor Test Facilities at the Solar Durability and Lifetime Extension Center in Case Western Reserve University, Yang Hu, Joseph Karas, and Roger H. French (Case Western Reserve University), David A. Hollingshead, Scott A. Brown, and Mark A. Schuetz (Replex Plastics)
- Arc-Fault Detection and Mitigation in PV Systems – Industry Progress and Future Needs, Jay Johnson (Sandia National Laboratories)
- TenKsolar Cell-to-Grid Redundant PV System Delivers High System Availability, Timothy Johnson (tenKsolar)
- Test Chamber Brainstorming: Consider All of the Options, David Jung (ESPEC)
- Junction Box and Wiring Issues in Reliability, Juris Kalejs (American Capital Energy)
- Fluoropolymer Coated Backsheet for Photovoltaics, Yi Kang (Avery Dennison)
- Validation of Real Life Silicone Array Efficiency Gains, Anna Keeley (Dow Corning)
- Quality Control during the Manufacturing of PV Backsheets: A Fundamental Key Component to the Long-Term Performance of PV Modules, Robin Kobren (Dunmore)
- The Challenges of Testing the UV Impact on PV Modules, Michael Kö hl (Fraunhofer ISE)
- Enhanced Protection of Photovoltaic Systems, Charles J. Luebke, Birger Pahl, and Thomas J. Schö pf (Eaton Corporation) Jerome K. Hastings (Electric Power Management Consulting)
- Increasing Investor Confidence in PV Power Plants through Latent Defect Screening (LDS), Alex C. Mayer and Jenya Meydbray (PV Evolution Labs)
- Salvage Operation Determines Value of Used Photovoltaics, Joseph McCabe (SRA)
- A Novel Insulated Solder Tail Assembly for Use with Aluminum Core Backsheets, Michael McNeeley (Transform Solar)
- Characterization of Potential Induced Degradation Sensitivity of Crystalline Silicon Modules, Jenya Meydbray (PV Evolution Labs) and Wenda Zheng (Canadian Solar)
- Manufacturing Quality Systems Guidelines, Alex Mikonowicz (Powermark)
- Silicone Potting Materials to Reduce PV Module Field Failures, Clarissa Miller (Momentive)
- Quantifying Adhesion and Debonding of Encapsulants for Solar Modules, Fernando Novoa and Reinhold H. Dauskardt (Stanford University), David Miller, Mike Kempe, Nick Bosco, and Sarah Kurtz (NREL)
- Ranking PV Materials for Weathering Performance, Gregory S O'Brien, Amy Lefebvre, Steven Hahn, and Anthony Bonnet (Arkema)
- Estimation of Amount of Free Acetic Acid Desorbed in EVA Encapsulant with Infra-Red Spectrum, Kaoru Ohshimizu (Mitsui Chemical)
- Development of a Visual Inspection Checklist for Evaluation of Fielded PV Module Condition, Corinne Packard (Colorado School of Mines; NREL), John Wohlgemuth, and Sarah Kurtz (NREL)
- Performance & EL Studies on Single Crystalline Silicon Modules from Three Different Manufacturing Sites Exposed to TC 500 and Damp Heat 2000 Hours, Paul Robusto (Intertek)
- Impact of Module Construction in Providing Reliability Redundancy through Accelerated Lifetime Testing, M.W. Rowell, S.J. Coughlin, D.W.J.Harwood, (D2Solar)
- Variability in NOCT Standard Test Results as a Function of Day, Time of Day, and TC location, Fatih Sabuncuoglu, Larry Pratt, and Martin Plass (CFV Solar)
- Systematic Approaches to Determining Degradation Rates from Continuous Meteorological and System Production Data, Kenneth Sauer (Yingli Americas)
- Solar Wind: Reproducing the Effects of Wind-Induced Field Vibration on PV Modules in the Laboratory Without the Requirement of a Wind Tunnel, Herbert Schueneman (Westpak), Kent Whitfield (Solaria), Tanya Dhir (MiaSolé), and Matt Muller (NREL)
- Silicon Cracking in Plated c-Si Solar Cells, Oliver Schultz-Wittmann (Tetrasun)
- Influence of Elastic Modulus of Encapsulant on Solder Bond Failure of c-Si PV Modules, Tsuyoshi Shioda and Hirofumi Zenkoh (Mitsui Chemicals)
- The Effect of Na on the Electrical Breakdown of EVA, N. R. Sorensen, J. R. McElhannon, and M.A. Quintana (Sandia National Laboratories)
- The Influence of Various c-Si Module Encapsulants on WIR Performance, Chris Stapelmann (SolarWorld Industries)
- Photovoltaic Module Reliability Testing: 400°C/hr, Tadanori Tanahashi (ESPEC)
- 15-year Review of Field Performance of EVA-based Encapsulants, Ryan Tucker and Joseph Woods (STR Solar)
- Japanese TG4 activities of QA Forum, Yasunori Uchida (JET)
- Construction of a Hail Gun for Solar PV Module Testing, Robert Uselton (Lennox Industries)
- EVA Adhesion Test Method,180o-peel vs. T-peel, in PV applications, Hugh Yang (Avery Dennison)
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Plenary Session: Standards
Chairs: Kurt Scott (Atlas), Michael Koehl (Fraunhofer ISE)
Quality Assurance Overviews of Proposed Tests
Proposed Test Protocols — IEC 61215 on Steroids
Proposed Test Protocol — Accelerated Simulation of the Weather
Proposed Test Protocols — New Tests
PV Quality Assurance Task Force Plans
Quality Assurance Rating Test Development Discussion
- Summary of Proposed Test Methods (see handout), Ian Aeby (Emcore)
- Consensus Building — Can we agree on general items? What we can learn from proposed tests? Can we agree on detailed inputs for the Task Groups?
Discussion summary (QA standards):
- The combination of stresses is most important. Any test we design should include combinations of stresses.
- Testing concerns include:
- The methods in which the tests are applied can yield different results.
- Tests will take too long.
- Tests may not reflect actual failure mechanism.
- Tests may require frequent, expensive retesting.
- New guideline could be confused with IEC 61215.
- Rankings will not be related to product value in a way that customers can understand.
- With faster temperature cycling, modules in the middle of the chamber would not be stressed as much as those close to the thermal control.
- It is difficult to define a standard method for making a test coupon for UV testing.
- UV testing for full-size modules is expensive.
- UV testing could be accelerated too much, changing the failure mode.
- Testing to IEC 61215 and to a new standard will increase costs.
- Suggestions include:
- Use a triangle or a circle and colors to communicate rating.
- Design the highest rating to be for the most extreme stresses found on the earth.
- Modify IEC 61215 instead of creating a new document.
- Only the range of temperature change will affect the acceleration factor for Cu ribbon, while solder joints will additionally be influenced by ramp rate and dwell time.
- Combine UV and mechanical testing.
- UV test both full-size module (to test interconnects) and test coupons (to screen new materials).
- Use weatherometer testing to identify yellowing problems.
- Create a task force to collect field data.
- Require every module manufacturer to bring data to the workshop next year.
- Find other ways to require companies to share failure data.
- Consider testing mechanical load at low temperature.
- Consider illuminated stress testing of minimodules.
- Participants agreed that:
- Comparative testing is preferred over pass/fail testing because durability can be assessed for different climates. For example: 5 stars is better than 4 stars is better than 3 stars, etc.
- Comparative testing is the first step to predicting module lifetime for a specific application or location.
- Testing results should be communicated both in a short summary that can be recorded on the module and detailed data that is communicated in a report.
- We need an option for subjecting the module to greater thermal-cycling stress than IEC 61215 (TG2).
- We want to do more UV testing in test coupons that represent full package
- The ranking must to be tied to field performance.
- The new test standard should use a different number rather than be considered Part 2 to IEC 61215.
- We need to apply mechanical stress before thermal cycling.
- The majority expressed a preference for a rating system that describes module durability for a list of stresses (temperature, humidity, UV); some preferred describing the durability with respect to climates (hot and dry, hot and humid, etc.).
- A key question is whether ultimately all of the manufacturers will make their products achieve the highest rating in the system. Cases in which a lower rating could enable lower costs:
- Reduced thickness of glass when mechanical (snow/wind) load is not an issue
- Low voltage systems, which use fewer bypass diodes
- Locations requiring special (expensive) glass to avoid abrasion from the sand.
- Manufacturers do not determine where the modules are located, so it may be best to have one design that works everywhere.
- We need field data to better understand what tests are needed. If PV owners can share data confidentially, this may help guide the designs of the tests. For example, are we seeing failures related to humidity?
- PID is observed less often in the U.S. because of the grounding. The new proposed test would allow modules to fail the test, but then be able to pass it simply by modifying the data sheet to require the system to be grounded.
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Oral Session: Thin-Film Modules
Chairs/Discussion Leaders: Chris Deline (NREL), Govindasamy Tamizhmani (TUV)
Keeping the Moisture Out
Chairs/Discussion Leaders: Dennis Coyle (GE), Arrelaine Dameron (NREL)
Discussion summary (thin films):
- We need appropriate measurement techniques for metastable thin-film modules. We should retain the stabilization procedure in IEC 61646 as a general thin-film test procedure. Testing labs need to understand the limitations of the devices that they are testing, and, for example, measure the CIGS modules very quickly after the light soaking stabilization, as they have a fast relaxation time.
- Responding to a statement at the DOE Metrology workshop, participants discussed whether the topic of metastabilities is still a priority, considering that the best CIGS modules show only very small metastabilities. Participants agreed that metastabilities are still a vital topic, but generalizing may be difficult due to the dependence on certain processing methods and conditions. For example, each product may respond differently to light and dark exposure.
- We can increase stability by:
- Annealing CdS after deposition
- Increasing CdS thickness
- Sometimes, higher efficiencies show smaller metastability.
- We could question the relevance of the 85/85 damp heat test, but data is not available to define the necessary test.
Reliability Issues with Thin-Film Modules
Chairs/Discussion Leaders: Shubhra Bansal (DOE), Tony Sample (JRC)
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Poster Session: Thin-Film Modules
- PV Standards. What New Things Does the IEC Have for You?, Howard Barikmo (Sunset Technology)
- The Effect of Copper on Accelerated Life Test Performance of CdTe Solar Cells, Dennis Coyle (GE)
- Test-to-Failure Program for Photovoltaic Modules, Tanya Dhir and Brian McNamara (Miasole)
- Derivation of Quality Specifications of Glass by Probabilistic Evaluation of Mechanical Module Reliability, Sascha Dietrich, Martin Sander, Matthias Pander, and Matthias Ebert (Fraunhofer CSP)
- Edge Sealing Tape with Getter for PV Modules: Very Long Breakthrough Time and Mechanical Properties at High Temperature, P. Gallina, A. Bonucci, and R. van der Wel (SAES Getters)
- Adhesion of Encapsulating Films Used in PV Module Manufacturing, Christian Honeker, Maryann Kenney, and Ricky Santoso (Saint-Gobain)
- Data Filtering Impact on PV Degradation Rates and Uncertainty, Dirk Jordan (NREL)
- Meeting IEC 61646 Climatic Chamber Test Requirements with OPV, Elsa Kam-Lum, Fadong Yan, Jorma Peltola, Stephen Wicks, Srini Balasubramanian (Konarka)
- Flexible CIGS Modules – Selected Aspects for Achieving Long-Term Stable Products, M. Münch, Mike Röllig, A. Reithe, M. Wachsmuth, and M. Meißner (Solarion)
- Performance of CIGS Flexible Module Arrays on Different Field Mountings, S. Jayanarayanan, L. Cao, A. Kamer, N. Staud, D. Nayak, B. Metin, E. Lee, and M. Pinarbasi (Solopower)
- Which Polymer for Reliable Silicon Thin-Film PV Module? Laure-Emmanuelle Perret-Aebi, C. Schlumpf, V. Chapuis, H.-Y. Li, and C. Ballif (EPFL/IMT/PVLAB)
- Light Soaking Behavior and Alternate Stabilization Method For CIGS/CIS Modules, Adam Stokes, John Wohlgemuth, Chris Deline, Sarah Kurtz, Steve Rummel, Alan Anderberg, Matt Webber (NREL)
- Solar Edge Sealant with Optimized Sealing and Application Properties, Samar Teli (Adco Products)
- The Effects of Device Geometry and TCO/Buffer Layers on Damp Heat Accelerated Lifetime Testing of Cu(In,Ga)Se2 Solar Cells, Christopher Thompson, Steve Hegedus (University of Delaware) Peter Carcia, R. Scott McClean (DuPont)
- FLEXOSKIN — Front Barrier Film for Flexible Solar Modules, Doug Weishaar (Evonik)
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Oral Session: CPV
CPV Module Reliability — Accelerated Testing and Field Experience
Chairs/Discussion Leaders: Peter Hebert (Spectrolab), Paul Lamarche (Solar Junction)
Chairs/Discussion Leaders: Kenny Villegas (Solar Compliance), Robert MacDonald (Skyline Solar)
Modeling of CPV Reliability Issues
Chairs/Discussion Leaders: Nick Bosco (NREL), Scott Burroughs (Semprius)
- Testing at high fluxes is difficult. Will irregularities cause problems?
- Soiling and condensation cause problems in the modules, but are not addressed by IEC 62108. IEC 60068-2-68 has defined a vertical dust flow test.
- In the short term, trackers and inverters have more issues than modules, but module failure could be devastating in the long term.
- The tracker standard attempts to address tracker issues, but more data is needed to know whether the draft standard will be effective.
- Bypass diode testing should be defined as part of the cell-on-carrier test standard.
- We should test whether the lenses lose alignment at low temperatures. This test might be done as part of the energy rating.
- Most manufacturers do more testing than modeling because they don't have confidence that the modeling will give the correct result and believe that testing is a faster way to determine whether a design will work.
- Modeling can reveal ways to improve a design. For example, modeling shows that matching the thermal expansion coefficients can help to reduce damage accumulation in thermal fatigue.
- Company representatives value having the universities and national labs do modeling, allowing the companies to focus on testing their product, while gaining increased understanding from the modeling.
- Modeling may help us understand whether chambers packed with modules can ramp temperatures uniformly and quickly.
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Poster Session: CPV
- High Intensity Light-Cycling of HCPV Cell Assemblies Using the XT-30 Solar Simulator, R. Beal, S. Chow, F. Asselin-Guay, J.F. Wheeldon J.E. Haysom, K. Hinzer (University of Ottawa SUNLAB)
- Solar Cell Grid Finger Failure due to Micro-cracking, Ling Cheng (Semprius)
- Reliability Characterization of an Exposed Spherical Ball Lens in a Dish-Based CPV System, Blake Coughenour, Brian Wheelwright, David Lesser, and Roger Angel (University of Arizona)
- Acrylic Materials in PV Applications, Peter Colburn (Evonik)
- Solar Durability and Lifetime Extension Center at Case Western Reserve University: Degradation of Acrylic Polymer and Acrylic Mirrors, Roger H. French, Laura S. Bruckman, Myles,P. Murray, Samuel Richardson, and Esther Deena (Case Western) Scott A. Brown, Mark A. Schuetz (Replex Plastics)
- Use of Thermal Imaging as a Tool for CPV Module Development and Production Testing, Sagar Gadkari (Greenfield Solar)
- Reliability of Concentrix CPV Modules, Eckart Gerster (Soitec Solar)
- Abengoa Solar CPV Field Testing Capabilities, K. Kiriluk, P. Banda, J.A. Perez, A. de Dios, F. Celaya (Abengoa Solar)
- Reliability Testing of Triple Junction Solar Cells with a GaInNAs Bottom Layer using Dilute Nitrides, Paul LaMarche (Solar Junction)
- Reliability of PMMA under Concentration, Stefan Myrskog, Pascal Dufour, Yi Guo, Kristine Drew (Morgan Solar)
- Lessons Learned from Flat Panel that Can be Applied to CPV, Paul Norum (Amonix)
- CPV Standard Conditions, Sandheep Surendran (Surya Design)
- Overview of CPV Tracker Safety, Kenny Villegas (Solar Compliance)
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