Inter-laboratory comparison of UV-light sources for testing of PV-modules
Durability assessment of materials exposed to natural weathering requires accelerated testing for verification of the ultraviolet (UV) stability, especially for polymeric material. The type approval testing of photovoltaic (PV) modules according to the standards International Electrotechnical Commission (IEC) 61215 and IEC 61646 includes a so-called UV-preconditioning test with a total UV dose of 15kWh/m2 corresponding to natural weathering of about 3months only. A serious UV test representing the service life needs to apply a much stronger UV-intensity in a comparable way. Fraunhofer Institute for Solar Energy Systems performed an inter-laboratory comparison of UV-light sources in 13 accredited test labs and test centres of major PV module manufacturers. The most important topic was the spectral radiometric measurement of the used UV sources. Another main issue was the comparison with the integral measurements by the sensors used for control of the tests. Errors up to 120% were found.