Printable, Emissivity-Adaptive and Albedo-Optimized Radiative Covering for Dynamic Radiative Thermal Management

Radiative cooling technology utilizes thermal emission to cool buildings and uses outer space as a natural heat sink. Traditional radiative cooling materials focus on static, cooling-optimized material properties to maximize the cooling power, but the constant strong cooling causes overcooling in cold climates, which increases energy budget in the HVAC system. Recently, advances in temperature-adaptive structures have been made to solve the overcooling issue. However, great challenges remain in their fabrication feasibility, and their unoptimized solar heating that may override the radiative cooling benefit.<br/>In this work, we develop a printable, emissivity-adaptive and albedo-optimized covering (PEAC) based on recyclable materials with roll-to-roll fabrication. With a metastructure embedded with the phase change material vanadium dioxide, PEAC automatically switches its sky-window emissivity from 0.25 to 0.85 when the surface temperature exceeds a preset transition temperature, whereas delivering an albedo that is optimized for maximal year-round energy saving or thermal comfort in a given climate. Numerical simulations and outdoor experiments show that PEAC outperforms radiative cool roofs in terms of annual energy saving in most climates, especially those with substantial seasonal variations. PEAC can also be applied to objects in addition to building roofs and walls, such as space objects, tents, and vehicles.