Influence of environmental conditions on UV fluorescence imaging in the field

The potential of ultraviolet (UV) fluorescence as a field technique for photovoltaic module defect detection has been demonstrated recently. In the field during daytime, environmental parameters are not controllable. We assess in this work the influence of environmental temperature on the quality and reproducibility of UV fluorescence measurements. The kind of lamination material and its aging history very much influences the fluorescence intensity. During the measurement, the temperature of the module influences the fluorescence emission. A module at nominal operating cell temperature range (45°C to 50°C) can show from 3% up to 30% less fluorescence intensity compared to a module at a temperature of 25°C. The temperature dependence of the excitation UV light source itself has also some effect on the imaging quality but the influence of the camera temperature is negligible.