Janus film for passive radiative cooling and solar heating for year-round thermal regulation

The energy demand for heating and cooling buildings constitutes approximately 30% of the global energy consumption, underscoring the imperative for sustainable temperature regulation solutions. This research introduces an approach for building thermal management, employing a Janus film that integrates advanced photonic metamaterials with spectrally selective solar absorber and radiative cooler. This configuration enables a dynamic adjustment of solar absorption properties, crucial for adapting to seasonal and climatic variations. During winter, the aluminum nanoparticles embedded within polyethylene film show high solar absorptance and low thermal emittance that facilitates solar heating during the daytime while preserving heat during the nighttime. Concurrently, in the summer scenario, the PDMS thin film atop of aluminum thin layer demonstrates high solar reflectance and high thermal emittance, activating the radiative cooling capability and dissipating heat through the atmospheric transparent window. Simulation results confirm the film’s efficacy, indicating a potential for a 8.2°C reduction in ambient temperature during peak summer conditions and maintaining a near-ambient temperature during winter daylight hours which is 7.2°C above the regular black absorber. Energy-saving simulation shows that is projected to decrease energy saving 57 GJ per year for San Francisco. This dual-functional technology heralds a significant advancement in passive thermal regulation, offering a versatile and energy-efficient solution for buildings, vehicles, and agricultural greenhouses across diverse geographical locations.