Evolution of Leakage Current Paths in MC-Si PV Modules From Leading Manufacturers Undergoing High-Voltage Bias Testing

The evolution of leakage currents in photovoltaic modules undergoing outdoor high-voltage bias testing is studied using data from high-voltage bias testing of multicrystalline silicon modules from leading manufacturers. An analysis of the module leakage currents as a function of environmental conditions including temperature, relative humidity, rain, and wetness is carried out. The behavior of the modules was found to be dependent on the module construction and the materials used. The Arrhenius model was used to fit the experimental data and activation energies were computed for various relative humidity values. The effect of dew and rain (wetness) on the front glass was investigated. Changes in the leakage current during dry conditions were studied using the temperature dependence of resistivity of bulk soda-lime glass. Because of the approximately tenfold increase in leakage currents during the wet conditions, it is suggested that the accelerated tests should not be limited exclusively to noncondensing environments but should also be complemented with tests that include wet conditions.