Radiative transport in transparent aerogels for solar thermal energy applications

Abstract

Solar-thermal energy conversion systems hold great promise to meet our diverse energy demand by a renewable source. Converting sunlight into thermal energy requires solar radiation to be absorbed and transformed into heat effectively while minimizing system thermal loss to the ambient environment. Traditional solar-thermal systems utilize high optical concentration and vacuum enclosure to reduce the impact of heat loss. However, the cost of sophisticated optical and thermal components limits their market adoption to date. In this thesis, we explored the development of transparent aerogels for enhancing solar-thermal energy conversion. We established and validated a modeling framework to understand the fundamental light transport within an aerogel sample and yield helpful guidance for material development. We performed synthesis recipe optimization through a systematic parametric study and discovered a facile procedure to fabricate low-scattering aerogel samples with >95% solar transmittance. We then incorporated the developed aerogel in solar-thermal collectors and tested the performance. Under unconcentrated sunlight, stagnation temperature beyond 265 °C can be reached and saturated steam above 120 °C can be generated without vacuum enclosures or selective surfaces. The improvements enabled by the low-scattering aerogels promote a new pathway of solar energy utilization for domestic, industrial, and power generation applications..