Hierarchically designed radiative cooling glass with enhanced thermal emittance by moisture capillary condensation

Abstract

Transparent radiative cooling (T-RC) using photonic structures is limited by its high processing cost of inorganics and poor weather resistance of polymer in existing applications. Here, we develop a hierarchically designed T-RC glass that can promote nearly 8.5 % conversion efficiency in relative terms of solar cells at the nominal operating temperature. A micro-nano structure comprising micro-scale etched pits and nano-scale etched pores on the surface obviously improves the emissivity (∼0.97) in atmospheric window (8–13 μm) and the transmittance (∼97 %) in solar spectrum of the glass. Both the realistic measurements and multi-physics simulations demonstrate that when capillary condensation water is generated in nanopores, the emissivity of T-RC glass will further increase. Compared to the common glass, this glass exhibits exceptional heat dissipation with a temperature drop of 1.1 °C in indoor heating measurement and a temperature drop of 2.4 °C on average, with its peak at 3.3 °C in field measurement. This invention makes it possible to fabricate T-RC materials on a large scale, especially in the form of glass for semiconductor device heat dissipation, building and automobile energy-saving windows.