Photovoltaic module failures after 10 years of operation in the tropics

Abstract

This paper presents a case study of photovoltaic (PV) module failures after over 10 years of operation in the tropical climate of Singapore. Three types of modules (two samples from each type) were analysed: multi-crystalline silicon (multi-Si), mono-crystalline silicon (mono-Si), and copper indium selenide (CIS). Visual inspection revealed several problems, including encapsulant discoloration (to different extents), backsheet yellowing, and soiling among others. Different degradation behaviour of the samples was observed from current-voltage (IV) and electroluminescence characterization. The maximum power of the multi-Si samples degraded by more than 9% (on average), likely due to corrosion around the cell edges. The mono-Si modules suffered a catastrophic power reduction (>40%) that could be ascribed to a combination of encapsulant discoloration, potential-induced degradation (PID), and corrosion. While one CIS module was primarily affected by encapsulant discoloration and possibly corrosion, the other sample also exhibited signatures of PID and experienced about 45% power drop. Furthermore, external quantum efficiency measurements of the multi-Si modules identified cell mismatch and changes to the additives in the encapsulant. Overall, PID, corrosion and encapsulant degradation are found to be the most detrimental degradation processes for PV modules in the tropical climate of Singapore.