Analyzing the effectiveness of various coatings to mitigate photovoltaic modules soiling in desert climate

Abstract

In this work, two different anti-soiling coatings (ASC) and anti-reflection coatings (ARC) were developed and tested under real operating conditions in Doha, Qatar, and compared with uncoated glass (UNC) to identify the best coating properties for mitigating solar photovoltaic (PV) module soiling. Soiling was measured in terms of loss in light transmittance, measured by UV–Vis spectroscopy, and increase in surface coverage area, measured using optical microscopy. The results indicate a decrease in light transmittance and an increase in surface coverage area over time due to dust accumulation. ASC coupons show higher hydrophilicity and, therefore, less soiling. ASC/ARC leads to a higher loss in light transmittance, while UNC results in a higher surface coverage area compared to the other coupons. Over 25 weeks of outdoor exposure and 12 cleaning cycles, analysis of 13,320 light microscopy images revealed mean dust surface coverage areas for ASC, ASC/ARC, and UNC glass coupons of 14.6 %, 13.6 %, and 15.8 %, respectively. Unlike the ASC/ARC and UNC coupons, the ASC recovers to its initial condition immediately after cleaning. Therefore, ASC was found to maintain a cleaner glass surface compared to ASC/ARC and UNC. However, the differences in transmittance loss among the three coupons are not significant. The results were compared to findings from similar studies conducted in Saudi Arabia to evaluate regional differences in coatings performance. For the same coatings, a significant light transmittance loss was measured in Doha (Qatar) compared to Uyaynah (Saudi Arabia). The combination of high humidity and heavy dust in Qatar's extreme conditions reduces the effectiveness of both ASC/ARC and ASC coatings.