All-season thermal regulation with thermochromic temperature-adaptive radiative cooling coatings

Radiative cooling is a method of sustainable cooling without energy consumption; however, a strong cooling effect increases the energy consumption for heating in cold winters. Therefore, a temperature-adaptive radiative cooling coating (TARCC) consisting of a radiative cooling underlayer based on a spectral-selectivity porous polymer membrane (PM) and a thermochromic top layer based on a thermochromic microcapsule hybrid coating (TMHC) was designed and fabricated in this study. The color of the TMHC can change with ambient temperature, and the solar reflectance of the coating can be adjusted independently. The results showed that the TMHC became transparent at high temperatures, and the overall solar reflectance of PM/TMHC was 91.25%, while the TMHC became rose red at low temperatures and absorbed visible light, which could reduce the solar reflectance of PM/TMHC to 72.71%. In summer, when PM/TMHC is exposed to direct sunlight with an intensity of 900 W/m2, the backside temperature of the coating is 7.1 °C lower than that of traditional colored coatings and is also lower than that of TARCC with commercial white thermal insulation coating (CC/TMHC). In winter, when the solar intensity drops below 500 W/m2, PM/TMHC maintains its color, and its temperature is 6 °C higher than that of the PM, achieving all-season thermal regulation. Moreover, the light fatigue resistance of the coating was significantly improved using a light stabilizer. This study provides a new method for developing intelligent building coatings, with great development prospects.