Abrasion resistance of spray coated anti-soiling coatings during waterless cleaning of PV modules

Abstract

Dust deposition on photovoltaic (PV) modules leads to remarkably high energy loss, which has an enormous economic impact on PV plants. Anti-soiling coatings have been extensively studied as a cost-effective dust mitigation strategy in the PV market. However, such coatings applied to the top surface of the PV modules should be resilient to environmental stressors. Coated modules would also need periodic cleaning; thus, such anti-soiling coating must be abrasion-resistant. This article investigated the abrasion-resistant property of 4 types of commercial hydrophobic anti-soiling coatings. The study emulates the effects of different brush designs on the degradation of anti-soiling coatings under low soiling conditions. The samples were subjected to dry brush cleaning. We tested the samples with 3 different brush designs (linear brush 1, linear brush 2 and rotary brush) with a varying packing density of brush bristles. Linear brush 1 had 3.5 times higher packing density of brush bristles than linear brush 2 and rotary brush. By increasing the packing density of brush bristles by 3.5 times, the degradation rates were enhanced by factors varying from 1.2 X to 4.4 X in coated samples when cleaned with linear brush 1, compared to linear brush 2 and rotary brush. Phenylsilicone based coating shows higher degradation rates (varying from 2.9 X to 11.2 X) than fluoropolymer-based coatings. The result indicates a decline of the anti-soiling property as we see an increase in roll-off angle (compared to Mumbai, India’s tilt angle = 19º) with the increase in number of cycles. The results also show that compared to the structural brush design, the packing density of the brush bristle has a strong impact on the coating life. However, the actual coating life in the field would also be dependent on other environmental factors like the amount of dust deposit, moisture etc.