Energy yield of thin-film PV modules and the relevance of low irradiance, spectral and temperature effects

The electrical performance and energy yield of 25 PV modules were studied in the laboratory and under moderate climate conditions. The study compares thin-film technologies (a-Si, a-Si/μc-Si, a-Si/a-Si, CIS, CIGS and CdTe) and crystalline silicon technologies (mono- and polycrystalline). Intensive laboratory tests were performed before and after the outdoor exposure with regard to low irradiance behavior as well as sensitivity to spectrum and module temperature. Measurements according to IEC 61853-1 provide information about the nonlinear behavior of thin-film modules in respect to irradiance and temperature. The spectral response was determined in the module plane according to IEC 60904-8. Combining the measured spectral response and the measured spectral solar irradiance data, an automated spectral mismatch correction could be implemented to improve monitoring. Additionally, the average photon energy factor was used to determine the dependency of the photo current on spectral shifts for the module technologies under investigation. In a final ranking the energy yield of all tested specimens is compared and the influence of spectrum, temperature and low irradiance behavior on the energy yield is quantified for moderate climate conditions.