Researchers at ETH Zurich have developed a technology that allows them to harvest water around the clock, with no energy input, even under the blazing sun, reports Tech Xplore. The new device consists of a coated glass pane, which reflects solar radiation and radiates away its own heat through the atmosphere to outer space. It thus cools itself to as much as 15 degrees Celsius below the ambient temperature. On the underside of this pane, water vapour from the air condenses into water. The process is the same as can be observed on poorly insulated windows in winter.
The scientists coated the glass with polymer and silver layers. This coating approach causes the pane to emit infrared radiation at a specific wavelength with no absorption by the atmosphere nor reflection back onto the pane. Another key element of the device is a cone-shaped radiation shield. It largely deflects heat radiation from the atmosphere and shields the pane from incoming solar radiation, while allowing the device to radiate the heat outward to self-cool, fully passively. The new technology can produce at least twice as much water per area per day as the best current passive technologies based on foils: the small pilot system with a pane diameter of 10 centimetres delivered 4.6 millilitres of water per day under real-world conditions. The researchers’ goal was to develop a technology for countries with water scarcity and, in particular, for developing and emerging countries.