UV-Cured Robust and Transparent Double-Layer Membrane on Windows for Water Harvesting and Room Cooling

The increasing demand for energy in cooling systems due to global warming presents a significant challenge. Conventional air-conditioning methods exacerbate climate change by contributing to heightened carbon emissions. Glass facades, renowned in modern architecture for their versatility and aesthetic appeal, inadvertently trap solar radiation, resulting in heat buildup and the greenhouse effect. To tackle these issues, we utilized roll-to-flat and light-curing technology to develop a hydrogel coating on a glass substrate with the assistance of ultraviolet (UV) adhesive. This water-contained hydrogel selectively absorbs ultraviolet and infrared light while allowing visible light transmission, thereby maintaining glass transparency. Leveraging the absorption of partial ultraviolet and infrared as active cooling and the liquid-to-gaseous phase change enthalpy of water as passive cooling, the hydrogel significantly reduces room temperatures by up to 8.1 °C under 0.75 sun irradiation, corresponding to a total room cooling power of about 192.6 W m^-2. This study introduces a novel approach to transparent and energy-saving cooling in glass buildings, with the added potential for water resource recycling.