Irradiance Effect on the Bifaciality Factors of Bifacial PV Modules

Bifacial photovoltaic (PV) modules are seen as a promising way to increase the power density and output of solar PV systems. Since a relatively new technology, there is little knowledge on the electrical model of bifacial modules and its dependence on operating conditions. This paper looks into the bifaciality factors of such a module by means of several ex-perimental measurements in controlled environment. It is found that, contrary to the common assumption of constant values, the bifaciality factors in fact vary with the solar irradiance. This irradiance effect is approximated via a linear model and a newly introduced irradiance coefficient. A comparative assessment to the bifaciality factors provided in the datasheet shows that the proposed model more accurately provides these values both at STC and other conditions.