There is a lot of energy in evaporation, and there are technologies that theoretically could harvest it for human use.

About 50% of the solar energy absorbed at the Earth’s surface drives evaporation, fueling the water cycle that affects various renewable energy resources, such as wind and hydropower. Recent advances demonstrate our nascent ability to convert evaporation energy into work, yet there is little understanding about the potential of this resource. Here we study the energy available from natural evaporation to predict the potential of this ubiquitous resource. We find that natural evaporation from open water surfaces could provide power densities comparable to current wind and solar technologies while cutting evaporative water losses by nearly half. We estimate up to 325 GW of power is potentially available in the United States. Strikingly, water’s large heat capacity is sufficient to control power output by storing excess energy when demand is low, thus reducing intermittency and improving reliability. Our findings motivate the improvement of materials and devices that convert energy from evaporation.

This is interesting. Cutting evaporation losses in half could be a good thing in some situations, like reservoirs and swimming pools in arid regions. Cut too much evaporation elsewhere, and you could imagine a science fiction scenario where you have a full reservoir but nearby ecosystems or farmland turn into deserts. Or you end up pumping that reservoir and using it for irrigation using the energy you have harvested, in the end using technology to efficiently recreate the hydrologic cycle and ecosystem services nature used to provide for free.