Transparent Refractory Aerogels in High Temperature Solar Environments

Transparent aerogels have the potential to improve solar collection in a range of concentrating solar thermal (CST) systems, especially those targeting higher temperatures. Our previous work demonstrated transparent aerogels that exhibited high-temperature stability and a record-high receiver figure-of-merit (FOM) at 100 suns and an absorber temperature of 700°C. However, the dimensions of those aerogels were too small for CST applications. Here, we demonstrate high performance aerogel tiles at sufficiently large areas for integration in fielded CST receivers. The work leverages a scaled-up process for sol-gel synthesis and adapts our previous atomic layer deposition (ALD) technique with the aid of predictive reaction-transport modeling. The density of the aerogels is controlled to improve solar transmittance. After aging for 10 days at 700°C, the large-area tiles exhibit a solar-weighted transmittance of 95.6% and a thermal emittance of 0.31, corresponding to a FOM of 80% at 100 suns and 700°C. The observed sintering rates at 700°C are comparably low to our benchmark one-inch aerogels, suggesting long-term stability under relevant operating conditions. The study indicates that refractory aerogels are scalable materials for efficient photothermal conversion at high temperatures.