Photovoltaic passive cooling via water vapor sorption-evaporation by hydrogel

Photovoltaic (PV) power generation, which converts sunlight into electricity, stands as a pivotal mode of solar energy utilization. The thermal effect poses a significant challenge for all types of PV panels under real operating conditions, as it diminishes both the photovoltaic conversion efficiency and the lifespan of the PV panels. This paper presents a novel passive cooling approach for silicon-based photovoltaic panels, employing night-time hygroscopic hydrogel adsorption, daytime desorption, and subsequent water evaporation for cooling. Both laboratory and outdoor experiments were conducted to validate this strategy. Experimental results reveal that under simulated laboratory light of 1 kW m−2, the hydrogel cooling layer delivers an average cooling power of 288.2 W m−2. It lowers the PV panel temperature by 9.9 °C and enhances both the maximum power and efficiency at equilibrium by 5.92% and 5.93%, respectively. Outdoor experiments in Beijing, China, during summer demonstrated that this method reduced the average daytime temperature of the PV plate by 7.1 °C and increased the average maximum power by 5.21%. The hydrogel layer's high hygroscopicity enables it to support passive cooling effectively all day. Passive cooling strategies for PV panels, leveraging the atmospheric water harvesting cycle, face fewer application constraints. They offer the potential to increase power generation and reduce CO2 emissions from PV plants both now and in the future.