Is an exact backside irradiance modelling essential for bifacial PV systems?

Abstract

Backside irradiance modelling for photovoltaic (PV) modules is not simple and straightforward as it highly depends on the situation of an actual system. In addition, the irradiance conditions can change from one side of a PV system to the other due to the reflections from the ground or surroundings. Currently, all available models are based on analytical methods. Here, we present a new empirical model for backside irradiance for fixed PV systems modelled by a Gaussian function on the backside irradiance share and compare the results with an analytical model. Furthermore, we have applied different backside irradiance calculations to a PV performance rating model and compared the results. Our calculations, verified with the data from three different locations in Europe, have shown that for common PV systems, where the backside irradiance share is relatively low, annual PV performance calculations can be performed with a fixed backside irradiance share value.