Photovoltaic efficiency improved by self-adaptive water uptake hydrogel evaporative cooling

The integration of evaporative cooling and self-adsorption desorption behavior is becoming increasingly crucial for achieving freshwater-electricity cogeneration in desert off-grid applications. In this paper, an adaptive photovoltaic cooling system was demonstrated utilizing self-adaptive water uptake hydrogel for evaporative cooling across various climate conditions. Both numerical simulations and experimental studies were conducted to assess the evaporation cooling and solar-thermal-electrical conversion capabilities of the system. The self-adaptive water uptake hydrogel was fabricated through a chemical crosslinking process. This design can facilitate rapid evaporation of water upon heating, effectively dissipating the heat generated. The influence of temperature and humidity on the adsorption and desorption performances was elucidated. The water vapor transport rate and the equilibrium time required were investigated during both the desorption and adsorption cycles. A solar-thermal-electrical model for integrated systems was developed, and the mechanism of energy transmission and conversion was clarified. The influences of the hydrogel thickness on the temperature and the solar-electrical efficiency of the photovoltaic cell were evaluated. The evaporative cooling of the pure hydrogel could lower the temperature of a photovoltaic cell by 21.9 °C in laboratory conditions under one sun, and enhance solar-electricity efficiency from 15.8 % to 16.9 %. Meanwhile, the evaporation rate reaches 0.88 kg·m⁻²·h⁻¹. The evaporative cooling performance of the PV-LiCl-Hydrogel system was measured across various climate conditions, and its renewable cycle performance was demonstrated. This integrated system offers a strategy in the current photovoltaic industry to enhance the energy transfer efficiency of both existing and future photovoltaic plants under all climate conditions.