Impact of Aerogel as a Thermal Insulator in Concentrating Solar Systems: An Experimental Study

Abstract Concentrating solar thermal systems convert solar radiation into heat, but thermal losses limit their efficiency. This study evaluates silica aerogel, a lightweight material with low thermal conductivity (kaerogel = 0.02 W/(m · K)), high solar spectral transmittance (τaerogel, λ ≈ 80% average over 300–2500 nm, peaking at 93–95% near 650–750 nm), and infrared opacity (λ > 3 µm), as a thermal insulator for high-concentration solar receivers. We experimentally tested a point-focus solar receiver integrated with a Fresnel lens concentrator, achieving concentration ratios (CRs) of 79, 177, 440, and 710. The focus is on the aerogel gain ratio (ηaerogel), which quantifies the enhancement of heat flux compared to an air gap configuration. Results show significant heat flux increases with aerogel, ranging from 89% (CR = 79, ηaerogel = 1.89) to 18% (CR = 710, ηaerogel = 1.18), with a relative decrease in gain as CR increases due to radiative losses and Rayleigh scattering effects. The aerogel maintains stability at high fluxes and temperatures of 425–580 K. These findings highlight aerogel's potential to enhance energy capture efficiency and enable vacuum-free concentrated solar power systems for mid-temperature applications.