Many people still lack access to a reliable supply of clean water. The solar-powered moisture harvester may provide a solution to the problem of water shortages, even in areas without a nearby body of water or source of groundwater.
A research team at The University of Texas at Austin (UT) came up with the breakthrough technology in water recovery and purification. They used hydrogels, hybrid materials that combined the properties of gels and polymers.
Hydrogels acted like highly efficient sponges. They quickly absorbed and stored considerable amounts of water.
UT researcher Guihua Yu and his team put together hydrogels that also released the absorbed water when they got hot enough. Their trials showed that the combination worked in both dry and humid weather conditions.
The combined hydrogels made it possible to collect water moisture from the air and turn it into clean and safe drinking water.
The UT researchers believed that their invention may be deployed to disaster scenarios, water shortages, impoverished areas, and developing nations.
The atmosphere holds around 50,000 cubic kilometers of water. Those reserves may become accessible through the moisture harvester and similar technologies.
Future development of the technology may produce small, inexpensive, and portable water filtration systems. (Related: Green and clean: Energy-efficient water purification system developed by scientists.)
Moisture harvester taps the atmosphere for clean drinking water
“We have developed a completely passive system where all you need to do is leave the hydrogel outside and it will collect water,” explained UT researcher Fei Zhao, who co-authored the study along with Yu. “The collected water will remain stored in the hydrogel until you expose it to sunlight.”
It took just five minutes of exposure to natural sunlight before the water got released.
To create their new moisture harvester, Yu and Zhao drew from their earlier work on solar-powered water purification. Back in 2018, they invented hydrogels that used solar energy to purify water samples taken from any source.
The UT researchers took that breakthrough to the next step by tapping the water vapor already present in the atmosphere. They used the same techniques from their earlier work, where they successfully combined two different materials with both hygroscopic properties and thermal-responsive hydrophilicity.
Hygroscopic refers to a material's ability to absorb water. Thermal-responsive hydrophilicity, on the other hand, lets a material release water once it got heated.
“The new material is designed to both harvest moisture from the air and produce clean water under sunlight, avoiding intensive energy consumption,“ explained Yu.
Sunlight powers hydrogel-based water purification process
There are existing technologies and techniques for harvesting water from moisture. Refrigerators rely on vapor condensation to cool their contents.
But these processes are not energy-efficient. A refrigerator consumes a lot of electricity to achieve the desired temperature.
Yu and Zhao's hydrogel-based approach needed much less energy than a fridge. Sunlight sufficed to power the water purification process.
Also, their moisture harvester was smaller and lighter than a refrigerator. Despite its compact size, it produced enough drinking water to satisfy a typical household. Trials showed that a kilogram of the hydrogel in the harvester produced up to 50 liters of potable water every day.
The solar-powered water purification system presented a new approach to harvesting water from the atmosphere. It might replace central parts in earlier moisture harvesting systems as well as other moisture-absorbing systems.
Yu and Zhao published the details on their moisture harvester in the science journal Advanced Materials. They already filed a patent on their water-purifying hydrogels.
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