High temperature stability of transparent silica aerogels for solar thermal applications
Author(s)Strobach, Elise M.; Bhatia, Bikramjit S; Yang, Sungwoo; Zhao, Lin; Wang, Evelyn
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Solar thermal energy systems combined with low-cost thermal storage provide a sustainable, dispatchable source of renewable energy. One approach to increase the attractiveness of these systems is to use high-performing solar transparent, thermally insulating silica aerogel to significantly increase efficiency. Several past works have proposed using these ultra-nanoporous materials to reduce thermal losses in the receiver, but only recently have aerogels reached the high solar transparency necessary to be considered for concentrated solar applications (>97%). However, the durability and stability of optically transparent silica aerogels at the operating conditions of solar-thermal receivers has not been examined. Here, we investigate the high temperature stability of transparent silica aerogel for use in concentrated solar thermal energy applications. Transparent samples (visible transmission >95% at 4 mm thickness) were annealed for several months at 400, 600, and 800 °C to investigate the relative change in nanostructure, solar transparency, and effective thermal conductivity. Results showed that at 400 and 600 °C, the temperature-dependent changes reach a plateau within 30 days of continuous annealing, but at 800 °C, samples are structurally unstable. A simple receiver efficiency model was used to show stable performance at 400 and 600 °C temperatures, even after months of exposure. This work validates that transparent silica aerogels can be used in solar thermal receivers below 800 °C, yielding appreciable increases in efficiency for solar energy harvesting operation.
DepartmentMassachusetts Institute of Technology. Department of Mechanical Engineering
Strobach, Elise M. et al. "High temperature stability of transparent silica aerogels for solar thermal applications." APL Materials 7, 8 (August 2019): 081104 © 2019 Author(s)
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