This paper presents a study of long‐term outdoor performance of a‐Si and hybrid modules mounted in the same location over several years. The modules were also characterized indoors using standard measurement methods employing pulsed solar simulators at the European Solar Test Installation (ESTI). The present study is intended to contribute to future standards on energy rating by presenting a common procedure for correcting the outdoor performance measurements to standard test conditions and comparing the resulting module performance at real and laboratory conditions. A seasonal variation in output, higher in the summer and lower in the winter, suggests that the module performance improves due to annealing when the module temperature is higher. The total output energy per month for these two technologies and a reference c‐Si technology is also presented. Copyright © 2010 John Wiley & Sons, Ltd.

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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 Pmax 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.