High-Efficiency Selective Solar Absorber from Nanostructured Carbonized Plant Raw Material

Abstract

The results of investigation into the absorptivity of carbonized rice-husk plant material with regard to solar radiation have been given. It has been shown that an absorber based on leached carbonized rice husk has higher solar absorptivity than an absorber based on carbonized apricot pits with an Apricus coating and an absorber based on a commercial Chinese-made coating. The results of investigation into the physical and chemical properties of carbonized rice husk have been presented. It has been shown that the carbon content in the initial unleached rice husk powder is 82.3%, and after leaching, the percentage of carbon rises up to 93.3%. Based on the results of a BET (Brunauer–Emmet–Teller) analysis, it has been established that leached rice husk has a more developed specific surface (447–641 m2/g) and a higher specific volume of pores (0.27–0.392 cm2/g) than unleached rice husk (127–160 m2/g and 0.054–0.127 cm2/g respectively). The advantage of the considered plant-based carbon materials compared to the exiting coatings lies in their porous structure. Cavities are known to be a model of a blackbody, which is a decisive factor in using a material as an absorber, and, simultaneously, a porous structure has a heat-insulating property.