Biomimetic Thermo-Responsive Hydrogel Coating for Passive Photovoltaic Cooling via Self-Adaptive Water Management

Currently, evaporative cooling stands out as a promising technology tailored for mitigating minor temperature spikes and enhancing both the power generation efficiency and longevity of photovoltaic (PV) panels. However, the intricate balance between water sorption and desorption poses significant challenges, impeding further advancements in its cooling capabilities. Drawing inspiration from the exceptional water absorption and expansion mechanisms of the reticulated carpet shark, the research has culminated in the development of a sophisticated thermo-responsive hydrogel coating, meticulously crafted with renewable biomasses (hydroxypropyl cellulose and sodium alginate) and hygroscopic salt (calcium chloride, CaCl₂). This innovative coating harnesses self-adaptive water management in response to temperature variation, facilitating highly efficient water sorption and evaporation processes. By leveraging the potent hygroscopic properties of CaCl₂, the coating achieves an impressive water uptake of 216.4% at a relative humidity (RH) of 70% and reaches a peak cooling power of 379.49 W∙m^{- 2} under 1000 W∙m^{- 2}. This approach results in a remarkable temperature reduction of 19.2 °C on the PV panel surface. Furthermore, outdoor experiments have efficiently validated the practical viability and long-term durability of the method. This study introduces a competitive PV cooling solution, eliminating external power dependency and integrating high performance with practical applications.