Solid nanostructured materials and solar collectors for efficient absorption of intense solar radiation and their application

Abstract

Solar collectors (absorbers) in which the solar radiation energy is absorbed by liquid working body have been presented in the end of previous century. Optics of pure water and water-based liquids were analyzed for the purpose of their use in solar absorber, but their absorptive properties are not enough to achieve high efficiency of absorbers. After that, various nanoparticles (nanostructures) were used to increase the absortive properies of working liquid absorbers and their optical properties of nanoparticles immersed in water were discussed. Unfortunately, the temperature range in which absorbers with liquid working fluid operate is limited to a value of no more ∼400 K, which, in turn, limits the efficiency of the absorbers. Solid based solar absorbers in which the solar radiation energy is absorbed by solid working body (glass, cermets, ceramics, etc.) have been offered recently. The use of solid-state solar absorbers based on thermal stable solid materials such as glass, ceramics or cermets expands their operating temperature range to 1000 K and more, thereby increasing the efficiency of solar energy collection and opening up the possibility of using high-temperature processes. The optical properties of pure glass and ceramics-based materials are analyzed and the need to use additional absorbers like nanostructures are analyzed. The results of comparative analysis of the influence of optical properties of various metallic and other nanoparticles depending on their material and thermo-optical parameters, solar radiation characteristics and parameters of various hosts (water, glass, Perlucor ceramics) are presented, allowing to select their parameters for increasing the efficiency of solar absorption. Particular interest was shown in the optical absorption properties of homogeneous Ti, Ni nanoparticles in the range of 50–125 nm radii, embedded in silica glass, and they showed the corresponding properties for efficient absorption of solar radiation in the wavelength spectrum of 200–2500 nm. The high temperature stability and efficiency enhancement of solid-state nanostructured materials are significantly higher compared to traditional liquid absorbers, especially taking into account the unique optical properties of Ti/Ni nanoparticles in glass or ceramics. Applications of solid-state solar collectors, thermal energy storage devices, air collectors, as well as solar distillers and desalinators, containing nanoparticles, in various fields are analyzed. Moreover, the high temperature up to thousands of kelvins realized in solid absorbers allows implementing various subsequent high-temperature processes for using the absorbed solar energy. The unique performance advantages of solid absorbers are confirmed by significant achievements currently available. The development and future application of high-temperature nanostructured solid-state solar absorbers promise perspective future effective achievements in different areas.