Investigation of the Temperature Sensitivity of 20-Years Old Field-Aged Photovoltaic Panels Affected by Potential Induced Degradation

One effect of moisture ingress on solar panels is potential induced degradation (PID). Solar panels affected by PID experience large leakage currents between the solar cells and the module's frame, which leads to substantial power degradation. In the present work, the temperature coefficients of 3 old PV panels affected by PID were investigated. In the electroluminescence images, solar cells nearer to the edge of the modules appear darker due to ohmic shunting. IR thermal images acquired under clear sky outdoor conditions show that the majority of the warmer cells (hotspots) were located closer to the edge of the modules. The difference in cell temperature ( increment T) due to PID effect ranges from 7 degrees C to 15 degrees C for the 3 field-aged modules. The average temperature coefficient of efficiency (beta(eta m)) was found to be -0.5%/degrees C. Also, it was observed that the temperature coefficients of open circuit voltage (beta(Voc) = -0.4%/degrees C), maximum power point voltage (beta(Vmpp) = -0.5%/degrees C), and fill factor (beta(FF) = -0.2%/degrees C), were the underlying factors for the degradation in the P-max of the old solar panels affected by PID. This accounted for an average 1.2%/year overall degradation in the efficiency of these modules. Most notably, it was discovered that the PV modules affected by PID show negative temperature coefficients of maximum power point current (beta(Jmpp)) due to large leakage currents. This observed negative beta(Jmpp) we believe is characteristic of PV panels affected by PID.