4. 1 PV Module Design, Manufacture, Performance and Reliability
PV Modules, Degradation, Polymer, Backsheet
Summary / Abstract:
During the last years PV-modules fail very often due to their backsheet material, and cause inverter issues. IV-curves and power measurements are not affected and therefore other methods are necessary to disclose the errors. We carried out time-series of wet leakage current measurements and imaging methods on field-aged PVmodules with various backsheets. The backsheet material was identified with field-suitable near infrared absorption spectroscopy. We found three main behaviours: 1) high leakage resistances (LR) and LR decrease for modules with double fluoropolymers, 2) medium LR and moderate LR decrease for modules with polyamide backsheets and 3) medium LR and strong LR drop for those with single-fluoropolymer backsheets, especially with thin fluorinated coatings (FC). We show that with water ingress into the backsheet and encapsulant the leakage current increases. Furthermore, UV-fluorescence is able to differentiate different backsheet materials, no differences were observed for electro- or photoluminescence. The fact that modules with FC backsheets increasingly show electrical insulation issues during operation makes the relevance for field operation clear.