Rising global temperatures and a growing world population have made fresh water a precious resource. But there’s moisture in the air all around us, even in arid regions of the world. Harvesting this atmospheric water is a promising solution to provide drinking water. And if it can be done without using electricity, it would be a boon for remote areas.
Researchers at the King Abdullah University of Science and Technology (KAUST) have now designed a cooling technology that extracts water from the air using only gravity and no electricity.
Scientists estimate that the atmosphere contains six times more water than all the fresh water in rivers. Scientists have devised many ways to capture this moisture. They have used nets, artificial spider silk, spongy gels, and other innovative materials.
The KAUST team’s water-harvesting technology is based on the concept of radiative cooling. The idea is to radiate infrared heat waves from a surface into the night sky. This cools the surface enough to condense vapor onto it the way dew drops form. Beetles that live in the Namib desert survive this way, using their bodies as a cooling surface to capture moisture from air. Humans have also been using radiative condensation for dew collection.
But traditional radiative condensers do not produce enough cooling per unit area. So water droplets remain pinned on the surface, and require active collection, write KAUST materials scientist and engineer Qiaoqiang Gan and his colleagues in a paper they published in the journal Advanced Materials.
To overcome this issue, the researchers added a simple twist to the condenser surface. They coated it with a rubber polymer layer lubricated with silicone oil, and incorporated it in a vertical double-sided architecture that cools and condenses on both sides. This doubles the cooling power of the condenser surface, and the lubricating layer keeps water droplets from sticking so that the water droplets easily roll down for collection.
The researchers tested a 30 cm × 30 cm (about 1 square foot) panel in an outdoor location six times over the year, so it faced different humidity levels and wind speeds during the tests. In one test, the material collected about 7 grams of water per hour, double the rate of water collection using alternative atmospheric water harvesting technology that relies on water-repelling surfaces.
In addition to keeping electronic devices and other technologies cool, the researchers say water collected using this technology could be used for irrigation, cooling buildings, and other applications.
Source: Shakeel Ahmad et al, Lubricated Surface in a Vertical Double‐Sided Architecture for Radiative Cooling and Atmospheric Water Harvesting, Advanced Materials, 2024.
Image: Envato/megafilm
