Hybrid hydrovoltaic electricity generation driven by water evaporation

Water evaporation is a ubiquitous natural process exploiting thermal energy from ambient environment. Hydrovoltaic technologies emerged in recent years offer one prospective route to generate electricity from water evaporation, which has long been overlooked. Herein, we developed a hybrid hydrovoltaic generator driven by natural water evaporation, integrating an “evaporation motor” with an evaporation-electricity device and a droplet-electricity device. A rotary motion of the “evaporation motor” relies on phase change of ethanol driven by water-evaporation induced temperature gradient. This motion enables the evaporation-electricity device to work under a beneficial water-film operation mode to produce output of ~4 V and ~0.2 μA, as well as propels the droplet-electricity device to convert mechanical energy into pulsed output of ~100 V and ~0.2 mA. As different types of hydrovoltaic devices require distinctive stimuli, it was challenging to make them work simultaneously, especially under one single driving force. We here for the first time empower two types of hydrovoltaic devices solely by omnipresent water evaporation. Therefore, this work presents a new pathway to exploiting water evaporation-associated ambient thermal energy and provides insights on developing hybrid hydrovoltaic generators.