Double-layer radiative cooling coating comprising a UV reflective layer and hollow TiO2

Abstract

Radiative cooling is a passive cooling strategy that requires no external energy input. It can provide continuous cooling for buildings and reduce energy consumption. In this study, a double-layer radiative cooling coating (DHRC) was designed with a bilayer structure. Fluorocarbon resins were used as film-forming substances for the coatings. Hollow rutile TiO₂ and 200 nm diameter ZrO₂ were used as fillers in the lower and upper layers, respectively. The cooling coating exhibited excellent reflective radiation performance, with a solar reflectance (R_solar) of 92.9 % and an emissivity (ε_{8-13 μm}) of 95.13 %. In outdoor tests, the average and maximum temperature reductions relative to ambient conditions were 8.44 ℃ and 12.3 ℃, respectively. The water contact angle was 98°, and after 25 days of UV irradiation, the R_solar only decreased by 1.09 %. The cooling power calculated using MATLAB was 123.44 W∙m⁻², which was 22.45 W∙m⁻² more than that of the commercial cooling coating. The EnergyPlus building energy consumption simulation results showed that among 15 cities around the world, buildings using cooling paints achieved energy saving rates of more than 7 % in 10 cities. The results showed that the DHRC effectively reduced temperature, improved energy efficiency in buildings, and exhibited resistance to staining and aging. This coating provides new ideas for future research on the design and innovation of building cooling coatings.