Boosting photovoltaic efficiency via efficient passive cooling from all-natural hydrogels with robust interfacial adhesion

The operational temperature rise of photovoltaic (PV) panels reduces their power generation efficiency and shortens their lifespan. Hygroscopic hydrogel-based evaporative cooling technology provides a promising solution for PV cooling due to high-enthalpy water evaporation. However, current hydrogels remain plagued by cooling interface mismatch and environmental concerns, which limit their practical implementation. Herein, a “green” and self-adhesive hygroscopic hydrogel consisting only of cheap lotus root powder and LiCl is designed, which can form robust interfacial adhesion with PV panels for efficient and durable cooling. Leveraging its compelling hygroscopicity, the hydrogel is able to rapidly capture moisture to recover cooling capacity, thus achieving self-sustained cooling. Besides, the “salting-in” effect brought by LiCl endows the hydrogel with notable softness and self-adhesiveness, which enables it to tightly combine with PV panels to optimize heat conduction and improve cooling efficiency. As a result, under 1.0 kW m−2 illumination, a PV temperature drop of 18.2 °C and a cooling power of 358 W m−2 were delivered by attaching the hydrogel to the rear of the PV panel, accompanied by a 7.7 % improvement in energy efficiency. Overall, this self-sustained passive cooling strategy, activated by the all-natural hydrogel, sheds light on the development of PV thermal management.