Energy: Renewable energy from evaporating water

Natural water evaporation represents a promising alternative source of renewable energy, reports a paper published online this week in Nature Communications. An evaluation of the amount of energy that can be harvested from this natural process reveals that natural water evaporation could provide power densities three times that of the wind power.

Nearly half of the solar energy absorbed at the Earth’s surface drives evaporation, which affects ecosystems, water resources, weather, and climate. Recent studies demonstrate the ability to convert evaporation energy into work, yet there is little understanding on the availability, reliability and potential of this resource.

Ozgur Sahin and colleagues develop a model to describe how an evaporation-driven engine affects the evaporation rate and provide predictions on how these energy harvesters could optimally perform in the natural environment. They estimate up to 325 gigawatts of power is potentially available from evaporation from existing lakes and reservoirs larger than 0.1 km2 (excluding the Great Lakes) in the United States, which is over 69% of the US electrical energy generation rate in 2015. The findings indicate the power available from this natural resource is comparable to wind and solar power, yet it does not suffer as much from varying weather conditions. Finally, the technology can cut the evaporative water losses by nearly half, which might favour the implementation of these energy harvesting systems in regions suffer from periods of water stress and scarcity.

These findings may motivate the improvement of materials and devices that convert energy from evaporation and provide a way to address the intermittency problem of renewable energy.