Harnessing photovoltaics for electrical generation can make it to the big time only if cells and modules meet stringent standards and pass safety tests.All across the globe, solar power is gaining ground. The movement has been sparked by feed-in tariffs, tax breaks and other government incentives and lower costs, not to mention advances in the technology itself. The world is discovering that solar works and is safe; however, coming to this realization was no small task. Over time, myriad standards have evolved, and labs around the world perform a variety of tests to ensure that each cell is up to the job of harnessing the sun’s energy in the most efficient way possible.Three standardsThere are three basic sets of standards: the International Electrotechnical Commission (IEC), the American Society for Testing and Materials (ASTM) and the Japanese Industrial Standards (JIS). All standards are classified as either Class A or B, with Class A indicating that the photovoltaic (PV) cell or module meets, as closely as possible, the standards of all three organizations. According to Chris Ball, business development manager for Oriel products at Newport Corp. in Irvine, Calif., the three sets of standards are similar, but specifications vary a bit on the three main tests, which are for spectral match, spatial uniformity and temporal stability. The IEC, for example, has a tighter spec on spatial uniformity than the others, and the JIS has a tighter spec on temporal stability.Solar manufacturers have several labs to turn to for testing. For example, private companies can send their PV cells to a lab such as the Photovoltaic Testing Laboratory at Arizona State University in Mesa. The lab provides IEC and IEEE certification testing, Underwriters Laboratories (UL) and IEC safety testing, long-term exposure testing and more. The Arizona State University facility tests amorphous as well as single- and polycrystalline silicon, along with cadmium telluride and CIGS materials. Concentrator PV modules can be evaluated there, and environmental assessments that take advantage of the extreme sunshine in Mesa also can be run. The lab has a hail-impact tester for customers who want to know whether their designs will hold up to extreme weather conditions.Underwriters Laboratories has a new PV testing facility in San Jose, Calif., that analyzes modules according to US, Canadian and IEC standards. PV cells, already packaged with the modules they receive, are sorted by peak watt rating. Both UL and IEC testing can detect the potential problem of mismatched cells in a module, which could cause a “hot spot” failure.The National Renewable Energy Lab (NREL) in Golden, Colo., also performs indoor and outdoor reliability tests, either accelerated stress or actual field conditions. NREL generally serves the research community in testing materials, cells, and mini- and full-size modules as well as prototypes.Test results help the manufacturer or researcher to adjust current and future designs as well as to gain the certification necessary for export purposes. The specifications are needed also for various requirements set by governmental and nongovernmental incentive programs, by local inspectors, and by banks and other funding agencies. According to Ball, testing marked by what Newport refers to as “intelligent flexibility” – stringent standards backed by cutting-edge research – will continue to be critical to success in an industry poised to make a significant contribution to the low-carbon future of so many global industries.
Photosensitizers