The air contains 6x more water than all the world’s rivers. Here’s how to harvest it.

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Image from Antrhopocene magazine: Schematic of the concept to capture oceanic water vapor. Courtesy of Praveen Kumar and Scientific Reports.

Researchers designed a cooling technology that extracts water from the air using only gravity and no electricity.

By Anthropocene Team
October 3, 2024

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.

 

A massive supply of fresh water exists as vapor above oceans. Scientists have an idea to tap it.

Desalinating the oceans is energy-hungry business, so why not economically and sustainably capture the water vapor floating above the oceans with cruise ship-sized structures?
By Prachi Patel
December 8, 2022

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The air above oceans is usually heavy with moisture rising up from the waters below as the sun warms their surface. In a new study, researchers propose a way to tap into this boundless source of freshwater.

Collecting oceanic water vapor using appropriately engineered structures could provide the needs of several large population centers across the globe, they report in the journal Scientific Reports. And it would be sustainable under a warming climate as potable water needs increase for the world’s increasing population.

Over one billion people already lack access to safe drinking water around the world, and climate change will keep increasing this shortage. Removing salt from seawater is one option to produce drinking water. But desalination is energy-intensive and expensive, so it has been relegated mostly to richer countries. Plus, the concentrated brine it produces causes environmental damage and is costly to dispose.

Praveen Kumar, a civil and environmental engineering professor at the University of Illinois Urbana Champaign and his colleagues wanted to develop an approach to “tap into the oceanic sources of water in an economically viable and environmentally friendly manner.”

They propose capturing oceanic moisture via towering structures a few kilometers offshore, and piping it onshore where it is condensed to give freshwater. The concept mimics the natural water cycle. In the natural version, moisture rises to form clouds which are driven by air currents to land, where they shed the water vapor as rain. “The difference is that we can guide where the evaporated water from the ocean goes,” said Francina Dominguez, a co-author of the paper, in a press release.

Schematic of the concept to capture oceanic water vapor.

Schematic of the concept to capture oceanic water vapor. Courtesy of Praveen Kumar and Scientific Reports.

 

To test if the concept would provide enough atmospheric moisture to be practical, the team analyzed the amount of moisture available at 14 different locations around the globe. They used data over a 30-year period from the year 1990 to 2019.

Then they assessed how structures that are about 210 meters wide and 100 meters tall, roughly the size of a large cruise ship, would fare at these locations. Their calculations show that the concept would extract enough moisture to meet the daily needs of around 500,000 people on average.

Several water-stressed regions around the world could benefit from trapping water vapor above the oceans, they concluded. As a bonus, the maximum amount of water is available during the warmer periods of the year when human water demand is also the highest.

Source: Rahman, A., Kumar, P. & Dominguez, F. Increasing freshwater supply to sustainably address global water security at scale. Sci Rep, 2022.

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