Integration of Radiative Cooling and Solar Heating in Thermal Management Films for Year-Round Energy Savings

The application of zero-emission passive radiative coolers is a crucial step toward global carbon neutrality. However, a single radiative cooling function cannot meet the thermal requirements under various weather conditions. We present a dual-mode thermal management film that integrates passive radiative cooling and heating functions through its porous polymer surface for cooling and a light-to-heat conversion surface enabled by graphene and carbon nanotubes for heating. The surfaces of the dual-mode film were physically flipped, positioning the corresponding surface toward solar radiation to obtain the desired functionality. In the cooling surface, the film achieves sub-ambient cooling of ≈13.3 °C under 853.88 W m^–2 of sunlight, thanks to its high solar reflectance (0.92) and mid-infrared emissivity (0.95). In the heating surface, it uses high solar absorption (0.90) to increase the temperature by 11.4 °C and generates Joule heating at various voltage levels. According to EnergyPlus software estimates, buildings with roofs covered in the film could reduce CO₂ emissions by 1.109 billion metric tons, equivalent to 3% of current global CO₂ emissions. This study offers a promising solution to climate challenges and holds great potential for energy savings and carbon reduction.