Performance Measurements of CIS Modules: Outdoor and Pulsed Simulator Comparison for Power and Energy Rating

A method for energy yield prediction under development in this laboratory has proved to be accurate for crystalline Si modules, however, in the determination of an energy rating of CIS modules, it was found to be difficult to accurately predict the module performance based on simulator measurements. The Energy Rating (ENRA) procedure is based on determining the maximum power point P_max as a function of the irradiance and the module temperature using standard pulsed simulator measurements. Long term outdoor measurements have been performed to test the method´s accuracy. It has been observed that the power measured on the simulator is in general lower than that measured outdoors and this is a significant cause of the difficulties in the energy predictions. The short circuit current has not been found to be significantly different, rather the difference is mainly due to lower open circuit voltage and fill factor. It is known that pre-conditioning CIS modules by light soaking can increase these parameters, and a study has been made of the short term effect of light soaking on the module. It has been found that the light soaking does increase the power measured on the simulator, but the light soaking effect relaxes very quickly, and it is therefore important to measure the module immediately following light soaking