Full Daytime Sub-ambient Radiative Cooling in Commercial-like Paints with High Figure of Merit. X. Li et al

Radiative cooling is a passive cooling technology by reflecting sunlight and emitting radiation in the sky window. Although highly desired, full daytime sub-ambient radiative cooling in commercial-like single-layer particle-matrix paints is yet to be achieved. Here we demonstrate full daytime sub-ambient radiative cooling in CaCO3-acrylic paint by utilizing the large bandgap CaCO3 fillers, a high particle concentration of 60% and a broad size distribution. Our paint shows high solar reflectance of 95.5% and high normal emissivity of 0.94 in the sky window. Field tests show cooling power exceeding 37W/m2 and surface temperature more than 1.7˚C below ambient at noon. A figure of merit RC is proposed to compare the cooling performance independent of weather conditions. The standard RC of our paint is 0.49, among the best radiative cooling performance while offering unprecedented benefits of the convenient paint form, low cost, and the compatibility with commercial paint fabrication process.辐射制冷是一种通过反射太阳光并在大气窗口波段发射辐射的被动制冷技术。尽管该技术极具应用价值，但类商用单层颗粒基体涂料尚未实现全时段日间低于环境温度的辐射制冷效果。本研究通过采用大带隙碳酸钙（CaCO₃）填料、60%的高颗粒浓度以及宽粒径分布，在碳酸钙-丙烯酸涂料中实现了全时段日间低于环境温度的辐射制冷。该涂料展现出95.5%的高太阳反射率，以及在大气窗口波段0.94的高法向发射率。现场测试结果表明，正午时段其制冷功率超过37W/m²，表面温度较环境温度低1.7℃以上。本研究提出了辐射制冷品质因数（Radiative Cooling, RC），以不受天气条件影响地对比不同材料的制冷性能。该涂料的标准RC值为0.49，其辐射制冷性能位居前列，同时具备涂料形式便捷、成本低廉以及与商用涂料制造工艺兼容等前所未有的优势。