Lifetime Prediction of Antisoiling Coatings Undergoing Degradation due to Rain

ABSTRACT If not cleaned, energy loss due to soiling can go up to 50% in 4 months in parts of India. Such losses significantly impact the economic viability of PV deployments in sunbelt countries like the Middle East and India. Antisoiling coating offers a cost‐effective dust mitigation strategy. However, as the coating is applied on the outer surface of the PV module, it has to endure various environmental stressors. Our previous studies have shown that rain is one of the most significant stressors that degrade the antisoiling coatings. This study estimates the lifetime of antisoiling coatings when subjected to rain, considering the pH of the rainwater as the stressor. The study was done on four commercial hydrophobic antisoiling coatings (A–D). Coated samples were exposed to water immersion tests; thus, the effect of the impact of the raindrop is not considered in this study. Characteristic times to failure were estimated using the Weibull distribution. The activation energy and pH dependence factor (N) were calculated using the Arrhenius‐modified Pecks model. The activation energy of Coatings A–D were calculated to be 0.09, 0.43, 0.09, and 0.56 eV, respectively. Positive activation energy indicated that the coating life decreases with increased temperature. The pH dependence factor (N) for Coatings A–D was estimated as 3.6, 1.4, 0.28, and 1.31, respectively. Based on the modelled equation, we predict the life of the coatings based on Miner's rule at two different locations. All coatings showed lower coating life irrespective of the pH when exposed at a tilt angle lower than their respective roll‐off angle. PV plant developers can use these data to predict coating life against this stressor at different locations, which can help identify coatings that work for specific weather conditions. It may also act as the starting point to model the effect of the combination of stressors.