Hydrophilic anti-soiling coating for improved efficiency of solar reflectors

The reflector is the first key component in the energy conversion process of concentrating solar technologies as any solar radiation that is not reflected by the mirror in the direction of the receiver is lost to the system. Due to the outdoor exposure, solar reflectors are subjected to constant soiling deposition (including dust, sand and/or dirtiness), which severely decreases the output power of the solar concentrating collectors, as it reduces the amount of radiation that can be reflected towards the receiver (associated to the absorption and scattering effects of light). Most of the Concentrating Solar Power (CSP) plants are installed in regions of high Direct Normal Irradiance (DNI) with arid and semi-arid climate, involving the existence of an important amount of dust and sand in the ambient. Collector cleanliness represents one of the most costly expenses of the solar-plant operation and maintenance (O&M). Consequently, minimizing this cost is an important issue for the solar-plant economic feasibility. Anti-soiling coatings deposited on the surface of silvered-glass reflectors are a powerful tool that can help in repelling all sort of dust, sand and particles. This technological solution presents the following benefits: (i) the maintenance cost is driven down by reducing washing times, (ii) the water consumption is drastically diminished and (iii) the efficiency is increased since the average reflectance of the solar field remains higher. This work presents the behavior of a new anti-soiling coating with improved durability and high efficiency.