Outdoor performance of anti-soiling coatings in various climates of Saudi Arabia

Soiling can significantly reduce the energy yield of PV modules, especially in desert climates due to high airborne dust concentration, frequent dust storms, and rare rain events. The current vast deployment of PV in deserts requires adequate and economically feasible strategies for the mitigation of soiling. In this regard, anti-soiling coatings (ASCs) could be a promising solution as they could significantly reduce the accumulation of dust and resultant soiling losses. To assess the outdoor performance of different ASCs, an outdoor benchmark test setup was designed and installed at eight different locations in Saudi Arabia. The soiling losses have been determined by measuring the transmittance of the samples before and after outdoor exposure for monthly (2 locations) and quarterly (6 locations) exposure periods throughout one full year. Within this study, detailed results are presented for an uncoated reference glass and 3 out of 15 coatings, which have been tested. In addition, a general coating ranking based on average monthly and quarterly soiling losses of the full set of ASCs is also presented. The results indicate huge variations of anti-soiling functionality of the coatings depending on exposure period and location. Overall, both improved and decreased anti-soiling performances have been observed for coatings compared with an uncoated reference glass. An investigation on the correlation between the daily soiling loss and weather parameters indicates that besides precipitation and particulate concentration in the air, also dew and its interaction with the coatings is an important influencing parameter strongly affecting soiling rates. Looking at the two most promising coatings with very low-adhesive properties, the overall performance benefit is higher for a hydrophilic surface in high humid areas (coastal) and a hydrophobic surface in dry areas (central desert).