Thermal or photovoltaic rear sides? A parametric comparison between photovoltaic thermal and bifacial technology

Abstract

The photovoltaic generation has experienced high growth in recent years. However, more effort is needed to get on track with the net-zero scenario. The use of the photovoltaic modules' rear part can increase their electricity generation by controlling their temperature (hybrid photovoltaic/thermal solutions) or by adding conversion capability to the backside (bifacial modules). However, which solution is more effective in increasing energy yield, and under what conditions? To answer these questions, the authors conducted a worldwide comparative parametric study considering a wide range of site conditions and photovoltaic module specifications. Two relevant results came from the study. The first is a global technical competitive analysis to determine favorable site and module specifications for each rear-side utilization alternative. The second is the mathematical expression of a new parameter named “critical bifaciality,” which expresses the minimum bifaciality rate required to obtain a performance superior to similar monofacial photovoltaic-thermal modules. This parameter serves as a design rule for the selection specification of the bifacial system, which depends on both the location’s climate and site conditions. It also permits determining the feasible locations for adopting either technology based on electricity production. The study concludes that using bifacial modules is the most effective way to increase electricity generation. For typical site conditions (albedo = 0.3), module specifications (cell efficiency = 20%, and Temperature coefficient (-0.3%/°C), the energy benefit can range from 1 to 5% near the equator and more than 25% near the poles.