Wrinkled surface microstructure for enhancing the infrared spectral performance of radiative cooling.

Abstract

Radiative cooling is a passive cooling method that does not consume additional energy and has broad application prospects. In recent studies, the surface microstructure was found to have a significant influence on improving the emissivity in infrared spectra for radiative cooling. Accordingly, in this paper, an innovative wrinkled surface microstructure without any periodicity is proposed for enhancing the infrared spectral performance of radiative cooling. The effects of the height and number of wrinkles as well as the radius and volume fraction of particles on the infrared spectral performance of radiative cooling are investigated. The radiative cooling performances of the plane, pyramid, moth-eye, and wrinkled microstructures are comparatively investigated using the finite-difference time-domain (FDTD) method. The results show that the mean emissivity of innovative radiative cooling films with the wrinkled surface microstructure reaches 99.58% in the "atmospheric window" wavelength range. The mean emissivity of the wrinkled microstructure is improved by 19%, 22.16%, and 8.41% over those of the plane, pyramid, and moth-eye microstructures, respectively. This indicates that the wrinkled microstructure exhibits a better performance for radiative cooling than single periodic surface microstructures. Furthermore, the wrinkled microstructure has no periodicity so it has low production cost, which makes it possible to replace other periodic surface microstructures.