Optical properties and thermal stability evaluation of solar absorbers enhanced by nanostructured selective coating films
In the last decades, many drastic efforts have been undertaken to attain solar selective absorber coatings with high thermal stability and performance for better solar energy capture. Nanomaterials that are attached at the back-side, front-side, or inside of laminated absorber coatings play a determinative novel role, thus improving the thermal performance of solar harnessing systems. To cite a general example, a deficiency of stationary non-concentrating solar power technologies, as one of the potentials to eliminate traditional fossil fuels, is the lack of high performance absorbing materials at high temperatures. Such enhancement is an obviously requirement for tracked concentrating solar collectors as well. In this comprehensive review article, the main focus is on the novel structures of solar selective absorber coatings with nanoparticle-based layer, which is added to improve the solar cell efficiency following their potential of directing the light transmission and reflection. Another concern of this paper is the different operating temperature range of solar selective coatings with an awareness of the highly desirable property of high-temperature applications, having thermal stability at temperature levels of more than 400 °C. According to the reported results, noticeable augmentation of optical properties such as solar absorption of higher than 0.97 touching upon different levels of thermal stability for low, mid, or preferable high-temperature applications have been achieved. At the same time, it is noted that, ZnO, SiO2, CuO, Al2O3, and carbon derivatives nanomaterials applied for copper, silicon, SiO2, aluminum, and stainless steel substrates are the most applicable promising combination of various types of nano-based solar selective absorber coatings. Referring to the remarks as mentioned above, it is a crucial concern that for next generations of solar thermal systems, the surface temperature of the receivers must operate up to 600–700 °C or more. In contrast, the nanomaterials’ usage is one of the passive promising approaches in this avenue of commercialized-oriented research.