Enabling Highly Efficient Solar Thermal Generation with 800{\deg}C-Stable Transparent Refractory Aerogels

Although spectrally selective materials play a key role in existing and emerging solar thermal technologies, temperature-related degradation currently limits their use to below 700C in vacuum, and even lower temperatures in air. Here we demonstrate a solar-transparent refractory aerogel that offers stable performance up to 800C in air, which is significantly greater than its state-of-the-art silica counterpart. We attribute this improved stability to the formation of a refractory aluminum silicate phase, which is synthesized using a conformal single-cycle of atomic layer deposition within the high-aspect-ratio pores of silica aerogels. The transparent refractory aerogel achieves a record-high receiver efficiency of 77% at 100 suns and an absorber temperature of 700C based on direct heat loss measurements at this temperature. Such performance and stability can enable the use of advanced supercritical CO2 power cycles and lead to a ~10% (absolute) improvement in solar-to-electrical conversion efficiency. Transparent refractory aerogels may also find widespread applicability in solar thermal technologies by enabling the use of lower-cost optical focusing systems and eliminating the need for highly evacuated receivers.