Half a billion people around the world live in areas where water is constantly scarce. A huge reservoir of fresh water is the atmosphere that, in principle, can quench the thirst of the whole world. Researchers are now offering a way to tap into the tank in areas with high levels of humidity.
The heart of the project is a pane of glass on which water vapor condenses in the form of droplets. Thanks to a special coating, these water droplets roll on the surface and fall into the collecting trough. team report it Ewan Hechler From ETH Zurich in the trade magazine “Advance of Science”. Using a small experimental system on the roof of an ETH building, the researchers demonstrated that under ideal conditions — high humidity, little wind, and little sun — about half a deciliter of water could be obtained per square meter of baseboard area per hour.
For water vapor to condense, the slate must be cooler than the air—as when drops fall under ice-cold windows in winter. The team achieved a cooling effect by building a sheet of glass like a sandwich out of specific minerals and polymers. This sandwich has the property that it radiates heat absorbed through the atmosphere into space. In addition, the researchers protected the glass pane with a cone-shaped shield from heat radiation in the atmosphere and the sun. This allowed it to cool down to 15 degrees below ambient temperature without any action.
To get more water from the atmosphere, larger and more pans of glass will be needed next to each other. The only limitation here, Hächler said, is the space required for this production: “There is no need for expensive or scarce raw materials.”
Especially in areas close to the sea, green technology will defuse water scarcity, for example in India, Saudi Arabia or Israel. Seawater desalination technologies can also be combined here. However, in sub-Saharan African countries, the humidity is so low that harvesting water from the air using this technology is not self-sufficient.
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