Electrostatic field-enabled ultra-efficient evaporative cooling.

Abstract

In the global sustainability drive, the role of water in the water-energy nexus is increasingly prominent due to the potential of passive evaporative cooling. However, the feasibility of evaporative cooling as a sustainable cooling alternative is currently limited by a lack of energy-efficient enhancement methods. Meanwhile, though electrostatic field-enhanced water evaporation has been widely documented, its underlying mechanism and impact on evaporative cooling remain unclear. Herein, we present experimental evidence establishing causality between electrostatic fields and evaporative cooling enhancement. We reveal two dominant factors at play, i.e., generation of ionic wind and tuning of vaporization enthalpy. The efficiency of the cooling enhancement method, when operating around the corona onset voltage, far exceeds that of conventional evaporative coolers. Similar cooling enhancements were also demonstrated on solid water within a hydrogel, showcasing its potential for practical applications. In addition, the electrostatic field reduces the vaporization enthalpy of solid water by altering the surface molecular arrangement, a finding corroborated through Raman spectroscopy. Besides elucidating cooling enhancement mechanisms, this study expands the toolkit for passive cooling solutions.