Although silica aerogels have led to improvements in solar collection efficiency at low to intermediate temperatures, there remains an incomplete understanding of thermal stability at temperatures necessary for next-generation CSP (>700 °C). A few studies suggest that silica aerogels experience significant degradation at these temperatures such as decreased spectral selectivity and increased thermal conductivity which results in lower receiver efficiency. Here, we experimentally investigate the degradation in aerogel-based receiver efficiency as a result of prolonged exposure to elevated temperatures. We investigate conventional silica aerogels as well as multicomponent aerogels that are specifically designed to decrease outgoing re-radiation losses. To stabilize the structures at elevated temperatures, we explore the use of atomic layer deposition (ALD) with various oxides and coating process parameters. We characterized the effects of the ALD coating on the optical and thermal properties of the aerogels using UV-Vis-NIR, ellipsometry, FTIR, and hot-disk techniques. Furthermore, we report on our methods to develop a uniform and conformal ALD coating by analyzing the diffusion and precursor limitations of ALD on aerogels. Lastly, we compare the experimentally determined receiver efficiencies with our simulations of coupled radiative and conductive heat transfer. Our results reveal that ALD coatings may slow down the rate of efficiency degradation if properly optimized for these applications.


Investigating the Thermal Stability of Silica Aerogels at Gen3 Csp Temperatures

Division / Sponsor:
Advanced Energy Systems Division (AESD) & Solar Energy Division (SED)

Paper Proceedings: https://asmedigitalcollection.asme.org/ES/ES2020/volume/83631

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