Like a Spider, Researchers Snag Fresh Water with Vapor Capture System

The water capture system at work.

Abolfazl Sadeghpour/UCLA

“The growing global concern over the scarcity of fresh water has motivated the development of economically feasible ways to capture water vapor,” said Sungtaek Ju, professor of mechanical and aerospace engineering at the UCLA Samueli School of Engineering and the principal investigator of the study. “This idea of imitating the natural rain cycle to produce clean water, called ‘the humidification-dehumidification process,’ has been around for quite some time. However, making such a system that’s inexpensive to build and operate has been a major challenge. Our system is inexpensive, lightweight and energy-efficient. These factors can potentially help overcome challenges for its adoption.”

Some proposed water vapor capture methods have used chilled metal to make water vapor condense on a surface. But limited surface areas, as well as weight, material and manufacturing costs, have slowed their adoption. Similarly, methods using spray nozzles or electric fields use too much electricity to be viable.

A key element in the UCLA team’s system is its ability to consistently generate water droplets of the same size and constant flowing speed. These water beads enable the system to effectively capture water vapor, without causing significant pressure drop, and hence fan power consumption.

“The liquid beads form highly curved surfaces that enhance the rate at which water vapor diffuses through the air,” said Abolfazl Sadeghpour, a UCLA mechanical engineering graduate student and a co-lead author of the study. “Simply said, this is analogous to a snowball rolling downhill. The beads are picking up water vapor as they travel down. And while a drop may seem small, think of an entire array of threads working constantly. The water vapor harvested could add up to quite a bit.”

The study’s other co-lead author is recent mechanical engineering doctoral graduate Zezhi Zeng. Other authors are postdoctoral scholar Hangjie Ji of mathematics, UCLA graduate student Navid Dehdari Ebrahimi of mechanical and aerospace engineering, and Andrea Bertozzi, a distinguished professor of mathematics and mechanical and aerospace engineering and UCLA’s Besty Wood Knapp Professor for Innovation and Creativity.

The research was supported by the National Science Foundation and the Simons Foundation.

Contacts and sources:
Amy Akmal

UCLA – University of California Los Angeles