Extracting drinking water from humidity

An energy-autonomous process for capturing air humidity for drinking water has been developed by scientists at the Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB; Stuttgart; www.fraunhofer.de) and Logos-Innovationen GmbH (Bodnegg, both Germany; www.logos-innovationen.com). The concept is suitable for supplying water to single households or hotels in regions where there is no electricity infrastructure.

In the process, water from the atmosphere is absorbed by hygroscopic brine, which runs down a tower-shaped unit. The brine is then sucked up to an elevated tank, which is under vacuum, and heated by solar collectors thereby evaporating the water. Water vapor is then condensed and runs through a completely filled column, creating the vacuum needed for the brine tank. Reconcentrated brine then repeats the cycle. Prototypes for both system components — absorption and vacuum evaporation — have been built, and the combination tested on a laboratory scale. A demonstration facility is the next step.