Ag/SiO<sub>2</sub> and Ag/TiO<sub>2</sub> Nanoscale-Thick Layers as Hyperbolic Metamaterials for Transparent Radiative Cooling Glass Design
Hai‐Feng Nan, Peng‐Qi Xiong, Gan‐Ji Zhong, Yue Li, Ruiqing Li, Jiahong Niu, Jun Lei, Zhong‐Ming Li
Abstract
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/SiO 2 and Ag/TiO 2 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/(m 2 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/m 2 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.