Preparation and performance study of highly transparent SiO2 aerogel for solar high-temperature thermal utilization

Monolithic SiO2 aerogel, as a transparent insulation material, has extensive potential in the field of concentrated solar power. However, challenges still persist when it comes to the high-temperature solar thermal utilization of transparent SiO2 aerogel. In this study, a supercritical CO2 extraction drying process was employed to fabricate monolithic and highly transparent SiO2 aerogels. The impacts of high temperature (500-900 degrees C) on the light transmission, thermal insulation, thermal stability, and microstructural features of the aerogels were thoroughly investigated. The results indicate that the aerogel can achieve 93.8 % solar spectral weighted transmittance with small-scale mesopores (5-10 nm) after 5-h thermal treatment at 500 degrees C. High temperature can enhance the transmission of solar radiation through the aerogel, but it simultaneously decreases its thermal insulation performance. The effective thermal conductivity is 0.08 W/(m & sdot;K) at 100 degrees C and increases as the temperature rises. The aerogel is not suitable for high-temperature conditions above 900 degrees C as its nanoporous characteristics will be significantly diminished. Experimental tests under concentrated solar radiation reveal that the aerogel can achieve a stagnation temperature of 640 K at a concentration ratio of 5, which is 24.3 % higher than that of quartz glass, demonstrating its superior transparent thermal insulation performance.