Evapolectrics: Direct Harvesting of Electricity from Evaporation Using Thermoelectrics.

Abstract

Evaporation, a ubiquitous process driving Earth's water-energy cycle, has been largely untapped for energy harvesting. Here, we introduce "evapolectrics," a scalable strategy that directly converts evaporation enthalpy into electricity via thermoelectric generators (TEGs). By leveraging porous graphite coatings and optimizing wind speeds (2.8 m/s) and wet-bulb depression, a robust temperature gradient (ΔT) over 6 °C can be maintained across TEGs. This translates to a power density of 4.2 W/m², which exceeds other ambient energy harvesting technologies, such as triboelectric and hydrovoltaics. We also demonstrate the evapolectrics' ability to sustain a continuous power output of 2.72 mW over 30 min and scalability via a 7 × 7 device array. Unlike intermittent sources like solar or wind, evaporation's perennial nature offers reliable ambient energy harvesting. With global evaporation rates suggesting harvestable energy of ∼10⁵ TJ/year, evapotetics present a transformative approach to power self-sustaining devices, augmented by advances in thermoelectric materials.