Abstract: With the acceleration of industrialization and global warming, the demand for cooling has surged. Traditional cooling technologies face severe challenges due to high energy consumption, carbon emissions, or excessive water consumption. Although radiative cooling and evaporative cooling are zero-energy passive strategies, the former is limited by cooling power and weather sensitivity, while the latter relies on continuous water replenishment and complex systems. This study proposes a renewable radiative-evaporative (RRE) cooling film that synergizes dual mechanisms to achieve high-efficiency daytime passive cooling and photovoltaic (PV) thermal management. The RRE cooling film is composed of polyvinyl alcohol hydrogel, boron nitride nanosheets, and lithium bromide (LiBr). The RRE cooling film achieves a solar reflectance of 0.9 and a mid-infrared emissivity of 0.93. By optimizing the LiBr content to 40 %, the RRE cooling film maintains an evaporation enthalpy of 1.29 kJ g^-1 while achieving rapid regeneration speed (0.74 g^-1 h^-1). Experimental results demonstrate that under 906 W m^-2 solar irradiance on clear days, the RRE cooling film achieves a temperature reduction of 9.37 °C with a cooling power of 273 W m^-2, tripling the performance of radiative cooling films. Even under cloudy conditions, it realizes a sub-ambient cooling performance of 3.87 °C, overcoming the weather dependency of radiative cooling. Furthermore, when applied to PV cells, the RRE cooling film reduces the surface temperature by 22.1 °C and increases the output power by 20.3 W m^-2. The exceptional performance of the RRE cooling film offers a zero-energy and sustainable solution for building energy conservation and electronic thermal management.

Key words: Radiative cooling, Evaporative cooling, Hydrogel, Photovoltaic cell, Thermal management