Comparative study of Potential Induced Degradation approaches in multicrystalline Si PV modules

Abstract

Potential Induced Degradation (PID) causes major reliability issues, since it results in significant performance degradation and negatively affects the durability of cells, modules and PV systems. In this work three methods are used to induce PID on three modules (A, B and C) by applying a voltage of 1000V to the frame, an aluminium sheet and a plate respectively. In the first method the voltage is applied to the aluminium frame while the temperature is kept at 35 °C ± 1°C and humidity levels at 70% RH ± 5% RH. In the second method, an aluminum sheet covers the glass surface without touching the frame and acts as a positive terminal connection, temperature of 35 oC ± 1 oC and humidity of below 40%RH. The third method, involves a smaller aluminium plate which only covers one cell under the same environmental conditions as for method 2. The extent of degradation is determined by measuring the maximum power before and after the PID stress and using Electroluminescence (EL) Imaging taken at a current corresponding to 10% of Isc. The power dropped by 29.6% in 288 hours, 88.7% in 48.0 hours and 6.2% in 96.0 hours in the three separate methods respectively. This study showed that certain modules may not be easily susceptible to PID, unless subjected to a high system voltage over a long period of time such as modules deployed over a long period of time in the field.