Radiative Cooling Droplet-Electricity Generator for Energy-Saving Houses

Rising energy costs and depleting fossil fuel reserves necessitate integrating multiple energy-harvesting technologies in energy-saving houses to reduce carbon footprints. Unlike photovoltaics or wind generators, droplet-electricity generators (DEGs) can operate in rainy conditions, thereby complementing existing renewables in energy-saving houses. However, inadequate thermal management in traditional DEGs restricts their practical applicability. To overcome this limitation and enhance year-round energy efficiency, this work proposes a radiative cooling droplet-electricity generator (RC-DEG) combining raindrop energy harvesting with passive radiative cooling for efficient energy savings. This is achieved with a radiative triboelectric layer (RTL) comprising polydimethylsiloxane (PDMS)/titanium dioxide (TiO₂) composite and a porous polytetrafluoroethylene (PTFE) layer. As the DEG component, porous PTFE enhances triboelectric properties, while the PDMS/TiO₂ composite (dielectric constant 3.3) improves charge storage and electricity output performance during rainfall. For optimized radiative cooling parts, the binary TiO₂ particles (200 and 400 nm) in the PDMS matrix increase average reflectivity (92.9%) and also obtain high infrared emissivity (94.8%), yielding a temperature reduction of ≈6.8 °C below ambient temperature under solar irradiance (≈709 W m⁻²). This work introduces an effective synergistic energy solution operating under all-weather conditions in energy-saving houses, advancing both energy conversion and thermal management for sustainable technologies in future smart cities.