WaterSeer, developed by VICI-Labs with UC Berkeley and the National Peace Corps Association, is designed to harvest drinking water from the air without electricity. A small wind turbine drives fan blades that push air down a pipe into a chamber buried about two metres underground. The surrounding soil keeps the chamber cooler than the air, so water vapour condenses on its walls and collects in a reservoir.
Its makers estimated a yield of 11 to 14 gallons a day, but field trials of half- and quarter-scale models in Berkeley collected about 300 millilitres in roughly three hours. A thermodynamicist interviewed by Popular Science explained that the device only works while the ground is colder than the air, which at that depth is true for only about half the day, and that very dry air has too low a dew point to condense much water. It may be more useful in humid regions where clean water is scarce because of poor infrastructure.
via This device may pull water out of thin air, but not as well as we hoped | Popular Science