Abstract
Air conditioning systems consume a significant amount of energy used in buildings while the refrigerants used in air conditioners leads to ozone layer depletion, causing global warming. Recently, to mitigate this issue, passive radiative cooling has attracted great interest. By reflecting the solar irradiance and selectively emitting mid-infrared thermal radiation, net cooling can be realized by passive radiative cooling without any power input. However, practically, a cooling effect is not desired all year round. To solve this problem, in this study, we propose a thermal-controllable passive radiative cooling coating (TPRCC) consisting of a hierarchically porous structured polymer embedded with thermochromic core-shell microparticles, which can automatically regulate the solar reflectivity by the ambient temperature. This study aims to develop a simple method to fabricate the proposed TPRCC with several common colors (i.e. grey, green, yellow, and red) as well as to investigate its cooling power modulation ability numerically. Based on the results of the study, among those colors, the green-TPRCC achieves the best radiative cooling and cooling power modulation ability, which shows the adjustable solar reflectivity between 68.64% to 92.60% under medium concentrations of thermochromic dyes with estimated 265 W/m2 cooling power modulation ability. Overall, the proposed TPRCC shows tremendous potential to be applied on exterior walls of smart-green buildings, and thus save a large amount of energy consumed by air conditioning systems thanks to its functionality and adjustable appearance.
