Research on the influence and optimization of sunshade effect on radiative cooling performance

Intense solar radiation is the main reason why radiative cooling is difficult to achieve during the daytime, as the radiative heat flux from the sun will offset the heat emitted by the cooler. Most previous studies have focused on providing coolers with high solar reflectance and high mid-infrared spectral emissivity by designing photonic structures. In this study, a macroscopic sunshade device based on the solar visual motion trajectory is proposed to reduces the direct solar radiation received by the cooler surface through setting a blocking on the solar path, while hardly affecting the radiative capacity of the cooler. Here, we built a three-dimensional sunshade device simulation model based on the surface-to-surface radiative heat transfer module in COMSOL Multiphysics® software, which can effectively improve the cooling performance of the cooler. Then, using polished aluminum plates, black paint-coated cooler, and reflective radi-cool film to test the impact of macroscopic sunshade device based on the solar apparent motion trajectory on improving the cooling performance of difference coolers. The results verified the effectiveness of the proposed sunshade devices in improving radiative cooling performance, and the results showed that the maximum temperature reduction could reach 3.35 °C, 26.96 °C, and 3.42 °C, respectively.