2021 Annual Meeting
The Role of Surface Hydroxyl Groups in the Thermal Transport of Silica Aerogels
Concentrated solar thermal (CST) is a promising carbon-free technology which generates high-temperature heat by using large optics to focus sunlight onto a solar receiver. One major engineering challenge is to develop selective receivers that capture sunlight but limit thermal losses due to thermal re-radiation. Silica aerogels are a great candidate for providing insulation to reduce these losses due to its low density and high solar transparency. However, the performance of silica aerogels is susceptible to changes in relative humidity. Current literature suggests there is a linearly proportional relationship between increasing heat capacity of silica and thermal transport. Here, it is demonstrated there is also a linear relationship between the surface concentration of hydroxyl groups and heat transfer properties. We subject the aerogel to relative humidity greater than 70% while measuring the optical properties and surface chemistry of silica aerogels. To do this, we use UV-Vis and FTIR spectroscopy, and transient plane source conductivity analysis. Our results indicate there is a direct relationship between water concentration and thermal transport, giving insight on the nanostructure of silica aerogels and its potential for long term use in CST systems.