Effects of microstructure and moisture content on the radiative properties of porous films for radiative cooling

Global warming is a major concern, and active cooling technology, which consumes substantial energy, contributes to global warming. Radiative cooling (RC) is a form of passive cooling. An optically selective porous film can provide cost-effective and efficient radiative cooling. This study aims to investigate the theoretical effects of the structural parameters on the cooling performance of porous films. An improved diffusion-limited cluster aggregation (DLCA) algorithm is established to reproduce porous structures with moisture content. A combination of discrete dipole approximation and Monte Carlo method was employed to predict the structure related solar reflectance and "sky window"emissivity. An optimal design of a porous RC film was developed. The results demonstrate that the BaSO4 porous film can achieve high solar reflectance (' 97%), high "sky window"emissivity (' 99%), and a net cooling power of 102 W/m2 during the day. In particular, the effect of moisture content on the cooling performance of the porous RC film was analyzed. Moisture content enhances the cooling performance at night but decreases it during the daytime. The results provide guidance for designing optically selective porous films for radiative cooling.