Turning Air Humidity Into Water

Scientists at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart have found a way of converting air humidity into drinkable water. The developed method could prove extremely useful in desolate areas such as deserts, where dry soil prevents the seeding of plants and very low precipitation limits human habitat.

Although deserts are known for their dryness, researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, in collaboration with the German company “Logos Innovationen”, have found a way of obtaining drinking water in the desert by utilizing air humidity. The developed system, say the scientists, is based completely on renewable energy and is therefore ecologic.

In the Negev desert in Israel, for example, relative annual average air humidity is 64 percent, which means that each cubic meter of air contains about 11.5 milliliters of water. Now, thanks to the novel technique, this air humidity can be harnessed to allow desert-filled countries to expand their habitat areas. IGB department head Siegfried Egner said: “The process we have developed is based exclusively on renewable energy sources such as thermal solar collectors and photovoltaic cells, which makes this method completely energy-autonomous. It will therefore function in regions where there is no electrical infrastructure.”

Egner explained how the process works; hygroscopic brine – a saline solution that absorbs moisture – runs down a tower-shaped unit and absorbs water from the air. It is then sucked into a tank a few meters off the ground in which a vacuum prevails. Energy from solar collectors heats up the brine, which is diluted by the water it has absorbed. Because of the vacuum, the boiling point of the liquid is lower than what it would be under normal atmospheric pressure (a similar effect can be observed in the mountains, where water boils at temperatures distinctly below 100 degrees Celsius). The evaporated, non-saline water is condensed and runs down through a completely filled tube in a controlled manner. Thanks to the gravity of this water column the vacuum is produced, thus eliminating the need for a vacuum pump. In the last stage, the re-concentrated brine runs down the tower surface once more, in order to absorb moisture from the air.

“The concept is suitable for various sizes of installation. Single-person units and plants supplying water to entire hotels are conceivable,” says Egner. According to the Fraunhofer Institute, prototypes have already been built for both system components – air moisture absorption and vacuum evaporation. However, the research is yet to be completed. While the scientists have already tested their interplay on a laboratory scale, the next and more crucial phase will be the development of a full scale demonstration facility.

TFOT has previously covered the AquaMaker, an innovative water-generating machine that uses similar principles to enhance water availability, as well as the development of a new way to produce water from such unlikely materials as alcohols, discovered by scientists at the University of Illinois. Another related TFOT story covers the Aquaduct, a pedal-powered water transportation and filtration vehicle designed to aid families in developing countries.

For more information about the conversion of air humidity into water, please visit the Institute’s official website.

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