Multifunctional ice and snow repellent coatings for photovoltaic modules

Abstract: Implementation of solar power by photovoltaic modules in cold climates, such as northern Sweden, implies several challenges. Ice and snow coverage not only leads to reduction in energy production due to shading, but it also puts equipment at risk from additional weight. The goal of this thesis was to formulate a passive ice shedding coating for photovoltaics that could handle the demands of both high optical transmittance and durability. In addition, the coating should be environmentally friendly and low cost. For that purpose, a state-of-the-art, superhydrophobic sol-gel silica-based coating was selected with the focus on optimizing its transparency, wettability, and durability. Different concentrations of binder, tetraethyl orthosilicate (TEOS), and catalyst (HCl) in the sol were explored, as well as post-treatment temperatures and sol aging, Hydrophobization was done by self-assembly of a silane and plasma polymerization of a siloxane. The coatings were characterized by UV-Vis spectroscopy, contact angle measurements, Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), tape peel strength, freeze-thaw cycling, ice adhesion force and a field test. Superhydrophobic, anti-reflective coatings with high transmittance (88.5±1.9%) were achieved, with some of them retaining their superhydrophobic properties after 15 freeze-thaw cycles between room temperature and -20°C. The main findings were that the amount of TEOS in the sol has the largest influence on transmittance and strength, with more TEOS leading to less transparent but stronger coatings, and that calcination of the coatings greatly improves their durability.