Bio-inspired Dual-Mode Cooling Hydrogel Composite for Passive Heat Dissipation of Photovoltaic Panels

Photovoltaic (PV) panels experience pronounced efficiency loss and reliability degradation at elevated operating temperatures, creating an urgent demand for efficient thermal management. Conventional active cooling approaches, however, are constrained by high energy consumption and system complexity, restricting their applicability. Inspired by the thermoregulation strategy of the land snail Theba pisana, this work reports a dual-mode cooling hydrogel composite that integrates evaporative and radiative cooling in one material system, enabling passive thermal management of PV panels. The hydrogel composite, composed of sodium polyacrylate (PAAS), anhydrous calcium chloride (CaCl2), and hexagonal boron nitride (h-BN), enables sustained moisture sorption and release, while maintaining high solar reflectance and broadband mid-infrared emissivity. When integrated with the backside of a PV panel, the composite enables coupled evaporative-radiative heat dissipation, while its high solar reflectance can further reduce backside solar heat gain. Under direct sunlight, the composite achieves a temperature reduction of 17.8 °C on a simulated heat-generating device. When applied to a commercial PV panel, it lowers the operating temperature by up to 17.9 °C and increases the maximum output power by 7.1%. The hydrogel composite also exhibits intrinsic self-adhesion, flame retardancy, and stability during prolonged outdoor exposure, underscoring its potential for reliable and scalable PV thermal management. This work demonstrates a multifunctional biomimetic materials strategy for passive thermal management.