Degradation of photovoltaic modules at medium voltage with different types of encapsulants

Enhancing the electrical efficiency of photovoltaic (PV) systems, particularly by increasing voltage, improves their performance and cost-effectiveness, while lowering the levelized cost of energy (LCOE). However, as PV modules transition to medium voltage applications (|U| > 1500 V DC ), potential induced degradation (PID) has emerged as a significant challenge in power plant PV systems. At medium voltages, the electrical properties of encapsulants, particularly the conductivity, can differ from those at low voltages. In this study, we investigate the evolution of encapsulant conductivity under different electric fields. Additionally, we conducted PID tests on PERC modules at −1500, −3000, and −6000 V (the highest voltage reported in the literature) for 96 h. The degradation increased with the absolute value of voltage, correlating with the evolution of conductivity under the electric field, indicating that PID degradation will be exacerbated as system voltage increases. In the second part of our study, we tested PV modules with different encapsulants at −3000 V to assess their degradation behavior at medium voltage. While modules made with POE encapsulant exhibited the lowest I-V losses, using encapsulants such as ionomer, EVA, and TPO with higher conductivities resulted in significant power losses. Furthermore, we identified a new degradation phenomenon: partial discharge, inherent to increased voltage, which led to the formation of electrical trees in the PV modules. We propose a potential mechanism to limit the initiation of these phenomena.