Cobalt-rich spinel oxide-based wide angular spectral selective absorber coatings for solar thermal conversion applications

Abstract

Solar energy conversion technologies attain enormous attention to create more efficient energy production sources to meet the current world's demand. The solar thermal conversion system converts solar energy to heat, and the receiver tube is crucial for achieving high photo-thermal conversion efficiency. The absorber coatings with high solar absorptance at normal and wide incidence angles of solar radiation improve the performance of concentrated and non-concentrated solar thermal systems. To achieve high photo-thermal conversion efficiency in the solar thermal conversion system, a novel spinel structured cobalt-rich transition metal oxide-based absorber coating was developed by a cost-effective wet chemical route. The developed absorber coatings with sub-micron scaled surface protrusions with porous structure (size 0.75 μm) exhibit an excellent spectral selectivity (α/ε = 0.91/0.13). In addition, the coatings show an excellent wide angular solar absorptance of 0.97–0.96 at incidence angles of 10°–40°. Extensive characterization has been carried out to analyze the structural properties of the absorber coatings and correlated to the spectral selectivity and wide angular solar absorptance property. The stability of the absorber coating at 400 °C for 100 h in an open-air atmosphere assessed by the performance criteria (PC) function value of 0.015 indicates the ability of the optimized absorber coatings to employ in solar thermal systems.