Radiative cooling with multilayered periodic grating under sunlight

Abstract

Radiative cooling is an energy-saving cooling technology and is achieved when the grating structure emits infrared radiant heat energy into outer space through an atmospheric window (8∼13μm). The radiation cooling effect is low for the simple grating structure due to its low absorptivity, thus was a novel multilayered composite grating structure proposed in the paper, an aluminum substrate composite whose top layer is polycarbonate coating and intermediate layers are composed of SrTiO2, SiO and Al2O3. The influencing factors of the absorptivity of the simple grating structure were analyzed by rigorous coupled wave analysis (RCWA), which consider grating period (1∼5μm), grating height (1∼20μm), duty cycle (0.75∼1) and angle of incidence (0∼75°), it was found that grating height is the crucial factor and increasing grating height can improve the absorptivity of the grating structure Hence, the proposed composite grating structure was studied with 20μm grating height and 0.5 to 2μm thickness of the polycarbonate (PC) coating, 1μm thickness polycarbonate structure was found to have good absorptivity, most is over 0.9, and the net cooling power of this grating structure could reach 71.39 W/m2 at ambient temperature.