Physics based modeling of dust accumulation on a bifacial solar PV module for generation loss estimation due to soiling

Abstract

In this paper, a physics-based model for dust accumulation on the front and rear surfaces of a bifacial module is presented. The accumulation on both the surfaces is assessed considering deposition, rebound and resuspension phenomena. The lift-off phenomenon of dust particle from ground is included additionally for the rear surface. This composite model is utilized to estimate soiling on both sides, which is extended to analytically assess the energy loss of the bifacial module. Experimentation has been carried out in four phases on a 10 kWp rooftop solar PV power plant. In the first phase, result shows soiling is less on glass than on the transparent back sheet-based rear surface. In the second phase, it is observed that surface density of dust on back surface for 34 days is 0.08 g/m², for 79 days 0.6 g/m² and for 126 days 1.8 g/m² which are deviated from model based calculated ones by 10%, 33.33% and 4.4% respectively. The surface density of dust accumulated on the glass-based rear surface is about (1/6)^th of the front glass surface, which is validated by the model also. The measured transmittance reduction is 3.2% for the back glass substrate and 29.6% for the front glass without manual cleaning for the test period. The model leads to the interesting result that the average energy generation loss for the bifacial plant is 1.4%/day compared to 1.7%/day for the monofacial plant since the generation enhancement from the rear surface more than compensates for the soiling loss from the back surface.