Following global climatic change and the progression of arid areas, there is a dire need for liquid water in water-scarce areas. These areas are very vulnerable, and the upcoming decades are expected to worsen their condition. Technologies that can source water from alternative resources are of urgent importance.
While desalination offers a solution to water scarcity, it is not applicable in arid areas. Therefore, the atmospheric water harvesting (AWH) technology is an emerging set of reliable approaches.
Engineers at the University of Nevada, Las Vegas, have proposed a new approach to converting water vapor in the air into usable form. Unlike the existing water harvesting approaches, which harvest at 30% or more humidity, the proposed technology is effective down to 10% humidity.
“This paper really establishes that you can capture water at a very fast rate. We can start to forecast how big of a system we would need to produce a set amount of water. If I have one square meter, which is around three feet by three feet, we can generate about a gallon of water per day in Las Vegas, and up to three times more in humid environments,” says the lead author H. Jeremy Cho.
The new approach relies on the passive vapor-condensation category, including a hydrogel membrane. This hydrogel, inspired by frog skin and plant cuticle, facilitates the transport of water from the air into a liquid desiccant for storage. This desiccant/sorbent is a saturated lithium bromide (LiBr) salt solution.
Water remains inaccessible until it’s released, and the release requires substantial thermal energy. Researchers have demonstrated that atmospheric water harvesting can be solar-powered, and sunlight can be used to reduce the eventual cost of generating water.
(Jeff Scheid for UNLV)
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The researchers performed 12 independent indoor storage and outdoor tests in Las Vegas and noted that water capture was recorded even though the humidity dipped below 10%. This exhibited the water capture at the lowest relative humidities so far.
“Both lab and outdoor test results confirm that, through our bioinspired design, water can be captured and stored in liquid salt solution at relative humidities as low as 10% and at rates that are close to the solar limit of water release at higher humidities. Faster rates can be achieved at higher humidities,” mentions the study.
The research has already been used practically at WAVR Technologies, Inc. The lead author Jeremy Cho co-founded this startup and aims to capture water vapors for commercial and individual use.
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Journal Reference
- Gao, Y., Eason, A., Ricoy, S., Cobb, A., Phung, R., Kashani, A., Mata, M. R., Sahm, A., Ortiz, N., Rao, S., & Cho, H. J. (2024). High-yield atmospheric water capture via bioinspired material segregation. Proceedings of the National Academy of Sciences, 121(44), e2321429121. DOI: 10.1073/pnas.2321429121