In this paper, recent patents along with recent published literature on functional coatings generated on different substrates for solar thermal applications are reviewed with a special focus on coatings derived by the sol-gel method. In solar thermal power plants, solar radiation is used to heat a thermic fluid in the primary circuit, which is subsequently used to run a turbine for generation of electric power. Functional coatings on components of a solar thermal device, viz. focusing aluminum mirrors, stainless steel absorber tubes and borosilicate cover glass tubes, improve the efficiency of the solar to thermal energy conversion. Though, currently there are several coating techniques available, most of them are based on vapor deposition that require high vacuum and are cost-intensive. Therefore, it is necessary to adopt an environmental- friendly and cost-effective coating process such as hybrid sol-gel coating technique that is also amenable to scaleup in addition to providing multi-functional properties.
Keywords: Absorber coatings, antireflective coatings, borosilicate glass, cermet, easy-to-clean coating, grooved surface, high temperature applications, protective coating, resistant surface, sol-gel, solar mirrors, solar selective coating, solar thermal applications, spectral solar selective surfaces, stainless steels, textured surface, thermal treatment.