Evapolectrics: Direct Harvesting of Electricity from Evaporation

Abstract Evaporation is a key to global water and energy cycle. It drives climate dynamics, and regulates human body temperature. It has a perennial nature rarely observed in other energy sources, including sunlight. Despite this, evaporation has hardly ever been exploited for energy harvesting.1 The few limited efforts to-date mainly focused on indirect approaches, via mechanical or biochemical means, yielding only minuscule amount of power.2-4 Herein, we demonstrate scalable and continuous direct-harvesting of electricity from evaporation (evapolectrics), which leverages on wet-bulb depression to maintain robust temperature gradient (ΔT) across thermoelectric generators. The power density of 4.2 W/m2 from evapolectrics is comparable to those of indoor photovoltaics, triboelectrics, and radiative cooling power harvesting.5 Our demonstration suggests a compelling development of ambient-energy harvesting technologies in powering small electronics.