Selective Regulation of Mid-Infrared Emissivity for Passive Cooling and Air Source Heating

The “atmospheric window” functions as a channel for radiative heat exchange between radiators on the Earth's surface and the cold background of space. Passive radiative heating and cooling can be achieved by regulating the heat exchange of radiators with the atmosphere and space through customized mid-infrared spectral properties, particularly within the “atmospheric window” band. Given that single-function passive cooling or heating is constrained by dynamic thermal demand variations, materials with tunable spectral properties are attracting increasing attention. A vanadium dioxide (VO₂) -based temperature-adaptive emissivity structure is designed to enable passive cooling and heating. At high temperatures, this structure exhibits a high emissivity of 0.81 within the “atmospheric window” (8–13 µm), enabling passive radiative heat dissipation through this spectral band. Conversely, at low temperatures, the structure exhibits a low emissivity (0.11) within the “atmospheric window” and a high emissivity (0.6) in other spectral regions (5–8 µm and 13–20 µm), which can suppresses radiative heat dissipation while facilitating heat absorption from atmospheric radiation, thereby achieving passive radiative heating through thermal exchange with the atmospheric environment. Then, the dynamic radiative cooling potential is evaluated through numerical calculations.