Enhancing Radiative Cooling Efficiency with a Novel Metal-Dielectric Grating System

Abstract

Recent developments in passive radiative cooling technology have shown promising potential for reducing energy consumption. Passive radiative cooling is achieved when radiators emit heat radiation into outer space through the atmospheric window between 8-13μm. In this study, an advanced metal dielectric grating has been designed to enhance the intensity of infrared radiation and improve the ability of radiation cooling. The cooling device consists of two heat-emitting layers made up of 1D BN gratings and SiO2 on top of a multilayer bottom reflector comprising seven alternating layers of TiO2 and CaCO3 on an Ag substrate. The effects of grating geometrical parameters, incidence angle, and coating layers on spectral characteristics have been analyzed in detail. Numerical results show that tuning the grating parameters can achieve a broad spectral distribution over a wide wavelength range. This spectral feature is caused by several effects, including excitation of surface phonon polariton, coupling effect between the grating and multilayer, and the combination of material properties. The optimized design emits more than 86% of infrared radiation while the solar absorption remains less than 2%, leading to an efficient passive radiative cooling potential of 100 W/m² at ambient temperature. Furthermore, the design displays an exceptional cooling effect, even when subjected to thermal exchange mechanism, demonstrating its high potential for advancing passive cooling applications.