The technology to harvest water vapor from the atmosphere has been in use commercially for decades now. Today, over 70 companies sell devices that harvest atmospheric water to drink, according to Chemistry World.
These devices are commonly deployed in drought-stricken areas, or in regions where fresh drinking water is either contaminated or limited. Most of them mimic the process of how dew from on vegetation in the early mornings and how air condenses on cool objects when pulled out from the fridge.
However, these dew-collecting foils require high energy input and only extract water at night because the sun heats the foil during the day, which prevents condensation to happen.
Self-Cooling Atmospheric Water Harvester
ETH Zurich researchers developed a new technology that harvests water 24 hours around the clock without using energy and even under the blazing sun.
SciTech Daily reported that the new atmospheric water harvester consists of a specially coated glass pane with polymer and silver layers that could reflect solar radiation and radiates away its heat through the atmosphere to outer space. Thus, cooling itself as much as 59 degrees Fahrenheit (15 degrees Celsius).
Meanwhile, the underside of the device turns water vapor into fresh drinking water that condenses from the air. This process can also be observed on poorly insulated windows during winter.
The special coating of the glass causes it to emit infrared radiation at a specific wavelength without absorbing nor reflecting it onto the pane. Also, its cone-shaped design serves as a shield to deflect heat radiation from the atmosphere and shields the pane from solar radiation but also allows radiate outward heat to passively self-cool.
New Atmospheric Water Harvester Produces Twice as Much Water than Others
Researchers tested their new device by putting it on the roof of one of ETH Zurich's buildings. Their findings suggest that it can produce twice the amount of water that other passive technologies can produce.
The small pilot atmospheric water harvester, with a pane diameter of 10 centimeters, produced 4.6 milliliters of water per day under real-world conditions, according to EurekAlert!
Under ideal conditions, the device was able to harvest 1.8 fluid ounces (0.53 deciliters) of water from the atmosphere per square meter of pane surface per hour. They said that this is close to the theoretical maximum amount that could be harvested which is 2.03 ounces (0.6 deciliters).
Ending Water Scarcity in Emerging Countries
The goal of the researchers of this project is to develop a technology for countries that are facing water scarcity problems, particularly for those emerging countries.
The team believes that other scientists could further develop their technology or combine other existing methods, like water desalination, to increase positive outcomes.
They said that coating the pane is relatively easy and possible, as well as building after condensers. Like solar cells that are used in many regions, atmospheric water harvesters could also be set next to each other and several water condensers could also be placed side by side to create a large-scale system.
Researchers published the full findings of their study, entitled "Exploiting radiative cooling for uninterrupted 24-hour water harvesting from the atmosphere," in the journal Science Advances.
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