Effects of cyclic heat-treatment in air on optical performances of AlCrSiO-based solar selective absorber

Abstract

Higher working temperatures could help to improve the solar-electricity efficiency of concentrating solar power plant. However, the high temperature also induces structure variations and optical degradation of solar absorbers, and how the structure evolutions affect the optical performances remains largely unclear. To address the problems, we conducted cyclic heat-treatment on the AlCrSiO-based solar selective absorbers at a temperature of 650 °C. Then the microstructures and optical properties of the absorbers before and after annealing were systematically investigated. Finite-Difference Time-Domain simulations were used to establish the relationships between the microstructures and optical properties. The results showed that the absorber can maintain its multilayered structure after cyclic heat-treatment at 650 °C in air with a solar selectivity of 0.928/0.171. Oxidation of micro-droplets on surface can enhance solar absorption in the UV–Vis region due to the reduction of backscattering. The weak oxidation of the absorbing layers would lead to the enhancement of interference effects in the whole solar spectrum. The combination of the above effects can actually enhance the solar absorptance. The diffusion of carbon from the substrate into the infrared reflective Cr layer would slightly improve the thermal emittance. These results suggested the AlCrSiO-based solar selective absorber can be a possible candidate for applications in the next-generation concentrating solar power plant system.