All-Ceramic, compressible and scalable nanofibrous aerogels for subambient daytime radiative cooling

Radiative cooling is a passive cooling technology that radiates heat directly to outer space without any additional energy input and is therefore of great significance in reducing the consumption of energy. However, the radiative cooling in subambient daytime is difficult to implement and usually requires complicated structural designs, such as photonic crystals and metamaterials, which are neither cost-effective nor scalable. Here, we demonstrate that silica-alumina nanofibrous aerogels (SAFAs) synthesized by electrospinning can provide a high solar reflectance of ∼95 % and a high atmospheric window emissivity of ∼93 %, owing to the scattering reflection and selective emission of the fiber network in aerogel. During field tests, the SAFAs remain more than 5 °C below the ambient temperature, theoretically yielding a radiative cooling power of ∼133.1 W m−2. Through scalable manufacturing routes, the SAFAs exhibit high compression fatigue resistance, robust fire resistance and excellent thermal insulation. The low cost and high performance of these SAFAs present great potential for large-scale passive radiative cooling applications.