Energy-saving all-weather window based on selective filtering of solar spectral radiation

Transparent planar solar absorber for winter thermal management

Indoor heating during winters accounts for a significant portion of energy consumed by buildings in regions of cold climate. Development of transparent coatings for windows that efficiently harvest solar energy can play a major role in reducing energy consumption and fuel costs incurred for winter heating. In recent years, there has been a great research effort towards designing transparent solar absorber coatings using nanophotonic structures. The potential of coatings based on planar multilayer structures, however, has received very little attention. In this work we investigate the performance of planar multilayer thin films using low-cost materials for design of transparent solar absorber window coatings. Our study led to the proposal of two planar multilayer designs. Simulation results predict that an increase in surface temperature by 27 K and 25 K, while maintaining mean visible transmittance of over 50% is possible using these designs. These results illustrate the great promise planar multilayer structures hold for winter thermal management of buildings.

Infrared-blocking plasmonic meta-glass for energy-saving passive windows

Passive windows that can concurrently block infrared radiation while allowing transmission of visible radiation help in significantly reducing global energy usage by cooling and lighting systems deployed in buildings and vehicles. This Letter reports a design of plasmonic "meta-glass" that blocks up to ∼87% of infrared radiation over a spectral window of 750-1800 nm, predominantly responsible for indoor radiative heating, while maintaining an average visible transmission of 60% for providing indoor illumination. Our polarization-independent design comprises a two-dimensional hexagonal array of tungsten nanorings placed on top of a silica glass substrate. By virtue of surface plasmons excitation in the infrared regime, we achieve selective suppression in the transmission spectrum, which is tailorable by adjusting the dimension of the nanorings. The theoretically calculated figure-of-merit indicates that our proposed meta-glass designs outperform some of the recently reported window glass varieties in the literature.