Ag/SiO2 and Ag/TiO2 Nanoscale-Thick Layers as Hyperbolic Metamaterials for Transparent Radiative Cooling Glass Design

Radiative cooling glass with spectral selectivity is an effective energy-saving strategy for buildings and vehicles. Nevertheless, the current research still has limitations; for example, the absorption of ultraviolet light by the glass results in a large amount of heat generated inside the space, which affects the radiative cooling performance. Herein, distinct spectral bands of solar radiation are precisely controlled through independently designing epsilon-near-zero (ENZ) regions within the hyperbolic metamaterials (HMMs) composed of Ag/SiO2 and Ag/TiO2 nanoscale-thick layers, which exhibit outstanding spectral regulation capability. The HMM glass features a high visible light transmittance (0.654), superior near-infrared reflectance (0.858), and good ultraviolet reflectance (0.576), while also possessing a high infrared emissivity of 95.6% in the atmospheric window. Outdoor simulation results suggest that with a convective heat transfer coefficient of 6 W/(m2 K), the internal equilibrium temperature of the HMM glass can be reduced by 32.8 °C compared to that of normal glass. Furthermore, the HMM glass can save up to 91.8–216.4 MJ/m2 of cooling energy annually in China in comparison to normal glass. The radiative cooling glass showcased in this work, with its superior spectral regulation capabilities, plays a crucial role in energy conservation and fostering sustainable progress and thus makes it suitable for use in building glass curtain walls or roofs, vehicles windows, and so on.