Review on the Sources of Power Loss in Monofacial and Bifacial Photovoltaic Technologies

An evaluation of the degradation effects on photovoltaic modules is essential to minimise uncertainties in the system operation. Bifacial photovoltaic technology is attracting attention due to the capacity of generating energy from the front and rear sides. This paper presents a review of degradation factors, for both conventional monofacial and bifacial photovoltaic modules, to highlight how the current and voltage characteristics of these technologies are affected by degradation. Microcracking, encapsulant discoloration, and light induced degradation seem to have similar effects on both modules. Contrarily, bifacial modules are more prone to potential induced degradation as the electromagnetic shielding is affected by the bifaciality. Bifacial devices are less affected by light and elevated temperature induced degradation. The degradation (1.3%) is similar for both technologies, up to 40 kWh/m2 of solar radiation. Above this value, monofacial degradation increases faster, reaching values of 7%. For tilted systems, the front side soiling degradation of 0.30% per day is similar for both technologies. For vertical systems, soiling loss for bifacial is considerably lower with values of 0.02% per day.