Energy performance of different photovoltaic module technologies under outdoor conditions

A comparative study is performed to obtain the energy performance of four different photovoltaic module technologies, when they are exposed to the same real sun conditions over a one-year period under the meteorological conditions of Southern Spain. Modules of thin film technologies were analysed: amorphous silicon (a-Si), tandem structure of amorphous silicon and microcrystalline silicon (a-Si/μc-Si) and cadmium telluride (CdTe). In addition, a polycrystalline silicon module (pc-Si) was studied. The modules were characterised by measuring their I–V curve. Thin film modules show changes of the peak power at STC (Standard Test Conditions) throughout the year. This variation is more remarkable in a-Si modules. The performance comparison shows that the perfomance of thin film modules is better than that of pc-Si modules for this location. However, CdTe and pc-Si modules present better performances during the winter months with higher daily yield values and lower total losses, while a-Si and a-Si/μc-Si modules perform better in summer. This paper also presents an empirical model that allows the daily energy performance of different module technologies to be calculated according to the daily irradiation and to the daily average temperature of the module. The proposed empirical model has an average relative error under 5% for all analysed modules.