Search

A novel selective multilayered periodic grating radiator (MPGR) was proposed in the paper, which is composed of Al2O3, SiO and SiO2 on an Al substrate. The influence factors on the radiative cooling power of the selective structure were studied by orthogonal test method, including the grating period, duty cycle and grating height. The spectral absorptivity and electromagnetic field of the MPGR were analyzed by using the rigorous coupled wave analysis (RCWA). Moreover, the MPGR was optimized by using the particle swarm optimization (PSO) algorithm. The results shown that the grating height has the greatest impact on the periodic grating structure. The optimized MPGR obtained a wide and high absorption peak in the atmospheric transparency window, which due to the coupling between SPPs and MPs of different modes. The emissivity of the designed grating presents a weak dependence on the incident angle. The optimized selective MPGR achieves a net cooling power of 118.17 W/m2 at nighttime ambient temperature of 300 K.

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 ∼ 13 μ m ). 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 ∼ 5 μ m ), grating height (1 ∼ 20 μ m ), 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 20 μ m grating height and 0.5 to 2 μ m thickness of the polycarbonate (PC) coating, 1 μ m 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.