(331g) Engineering Multicomponent Nanoporous Materials for Spectral Filtering of Heat

Lenert, A., University of Michigan
Kim, H., University of Michigan
Berquist, Z., University of Michigan
Brown, B., University of Michigan
The ability to selectively control the spectrum of heat by manipulating materials chemistry and nanoscale structure holds promise for a range of energy applications including power generation and thermal management of buildings. Here, I will discuss a new mechanism for spectral filtering of heat that mimics the greenhouse effect but enhances it using resonant absorption and scattering within highly-insulating nanoporous materials.

One thrust of our work focuses on nanocomposites that are opaque in the visible spectrum but selectively transparent in the long-wave IR, overlapping the atmospheric IR transparency window. In our published work (J. Opt., 2018), we proposed a new approach for passive radiative cooling using these materials and developed a model describing the multimodal heat transfer mechanisms. Using the model, we have shown that unprecedented cooling power (>125 watts per meter squared) and low temperatures (35 degrees below ambient) are achievable with our approach. The model represents an important framework that can be used for materials selection and design. We are currently experimentally validating our prediction using a scalable polyethylene-based nanoporous materials.

Second, we are studying multicomponent plasmonic aerogels to enhance the greenhouse effect for applications in concentrated solar power (CSP). In our published work (ACS Appl. Mats and Interfaces, 2018), we developed silica aerogels with high solar transmission and tunable hydrophobicity. More recently, we have incorporated ultrathin coatings of plasmonic oxides using atomic layer deposition to enhance the absorption in the mid-IR and suppress losses from thermal re-radiation at high temperatures. These materials have the potential to decrease heat losses by about 67%, which would have a major impact on the efficiency and cost of CSP.