Development and application of a UV light source for PV-module testing

Photovoltaic (PV)-modules are exposed to solar irradiation, which includes Ultra-violet (UV) light. UV light is wellknown as degradation factor for polymeric materials, as used for encapsulation of PV-cells. Therefore they are protected by UV-filtering glass or UV protecting additives. The UV-stability is only tested on a very low level (total UV energy of 15 kWh/m(sup 2)) according to the actual type approval standards (IEC 61215, IEC61646, e.g.). An undefined acceleration is provided by the testing temperature of 60°C. The real UV-dose can reach more than 120 kWh/m(sup 2) per year, however. The module-temperature during high UV-irradiation ranges between 40°C and 60°C, usually. The main reason for the inadequate test conditions is the lack of well-defined and inexpensive UV-light sources and therefore small test capacities. We developed an UV-radiation unit based on fluorescence tubes, which have the advantage of low visible and NIR irradiation avoiding overheating of the samples. The spectral irradiation is solar-like in the short-wavelength UV and lower in the long-wavelength UV, with a limited number of disturbing emission-lines. The design of the unit has been optimized for high UV-intensities up to 5X and usage on both sides. Our prototype has an area of 1.7 m * 3 m, which yields an usable testing area of 6 m *1.7 m. The unit is designed for usage in humid ambient in a temperature range up to 90°C for the future development of combined damp-heat and UV tests, in order to get the tests closer to reality.