Self-Adaptive Evaporative Cooling with Hygroscopic Materials.

Abstract

Evaporative cooling dissipates heat through the large latent heat of water evaporation and thus provides a high cooling capacity. However, conventional evaporative cooling systems continuously consume water, which limites their sustainable operation. Self-adaptive evaporative cooling addresses this limitation by coupling evaporation with atmospheric water sorption, where hygroscopic materials exchange water with the surrounding air and dynamically regulate sorption and evaporation in response to ambient vapor pressure. The environment-responsive interaction enables sustainable water replenishment, closed-loop operation, and simplified system architecture. This Mini-Review analyzes the thermodynamic evaporation-sorption cycle and examines cooling capacity from the perspective of coupled heat and mass transport. Cyclic stability is further evaluated based on the kinetic imbalance between evaporation and sorption. Representive hygroscopic materials are summarized and compared by using the saturated vapor pressure at different water contents, highlighting the amount of evaporable water per unit volume. Finally, challenges and future perspectives related to applicability, environmental constraints, system configurations, and costs are outlined for their practical implementation.