A radiative cooling-based technology was engineered at Wuhan University of Technology in China to reduce fossil fuel consumption for heating and cooling of buildings. The zero-energy switchable radiative cooler (ZESRC) offers an efficient thermal management solution for improving sustainable building operations.

The ZESRC operates on a morphology-driven approach using materials with varying thermal expansion coefficients to enable a dynamic response to temperature changes. This design allows for a seamless transition between cooling and heating modes to minimize energy use while maintaining desired indoor conditions.

A radiative cooling layer composed of zirconium dioxide nanoparticles, poly(methyl methacrylate) and dimethylacetamide is combined with a copper-based solar heating layer and a temperature-sensitive actuator layer composed of copper foil-backed polyethylene film.

With an increase in temperature, the deformation of polyethylene exceeds that of the thermally inert copper foil. The thermal mismatch caused by the difference in expansion forces the driving layer to curl the initially flat solar heating layer toward the fixed end, maximizing exposure of the radiative cooling layer beneath and enabling a shift from heating to cooling mode. As the temperature decreases, the solar heating layer uncoils and extends to cover the radiative cooling layer, leading to a transition from cooling to heating mode.

Field tests conducted in China demonstrated the ZESRC delivered temperature reductions of up to 7.1° C in summer and increases of up to 7.5° C in winter compared to outdoor conditions. Analyses conducted for different climates and reported in the Journal of Photonics for Energy indicate that the system can reduce building heating/cooling energy consumption by 14.3% compared to other devices that only use solar heating or cooling.

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