Researchers at ETH Zurich have developed a water extraction device for arid countries. This is the first zero-energy solution for collecting water from the atmosphere in a 24-hour cycle. It is based on a self-cooling surface and special radiation shielding.
Fresh water is scarce in many parts of the world and it is not cheap to obtain it. Communities near the ocean can desalinate seawater, but this requires a lot of energy. Away from the coast, the only option is often to condense atmospheric humidity. However, these methods are costly.
The new device solves the problem.
Researchers at ETH Zurich have developed technology that, for the first time, allows them to collect water 24 hours a day without additional energy costs, even under the scorching sun. The new device consists of glass with a special coating that not only reflects solar radiation, but also radiates its own heat through the atmosphere into outer space. Thus, it is cooled to a temperature 15 ° C below the ambient temperature. On the underside of the panel, water vapor from the air is condensed into water. The process is the same as for poorly insulated windows in winter.
Scientists have coated the glass with specially designed polymer and silver layers. This special coating approach causes the glass to emit infrared radiation in a window at a specific wavelength into outer space without being absorbed by the atmosphere and reflected back onto the glass. Another key element of the device is the new conical radiation shielding. It deflects thermal radiation from the atmosphere and protects the glass from incoming solar radiation. In this way the device radiates the aforementioned heat to the outside and thus completely self-cooled passively.
Real-world testing of the new device on the roof of the ETH building in Zurich has shown that the technology produces at least twice as much water per floor area per day as the best current foil-based passive technologies. Thus, a pilot system with a glass diameter of 10 centimeters in real conditions condensed 4.6 milliliters of water per day.