UC Berkeley researchers discover how to use solar power to harvest water in the desert

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UC Berkeley Media Relations/Courtesy

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A team of UC Berkeley researchers successfully tested a solar-powered water harvester that collected water from the air in the Arizona desert in October 2017.

Omar Yaghi, the James and Neeltje Tretter chair professor of chemistry, invented the technology that the harvester was based on. According to Yaghi, the water harvester is essentially a “simple box” that uses no energy inputs other than sunlight.

Yaghi added that the technology behind the harvester was deemed one of the top-10 emerging technologies at the 2017 World Economic Forum.

“For the first time, we are demonstrating that you can harvest drinkable amount of pure water from the dry desert air every day,” Yaghi said in an email.

The water harvester could be useful for people living in areas where access to water is difficult to obtain, such as desert regions, according to UC Berkeley researcher Jingjing Yang, who says he developed a cheaper version of the water harvester that is partly made of aluminum and collects more water. He added that normally, heavy energy expenditures are needed to obtain water in these places.

Yaghi said in an email that his goal is to achieve “personalized water,” where everyone in water-deficient areas can have a solar powered water harvester for basic needs.

The inspiration for the project came from studying the trapping of carbon dioxide using a box called a metal-organic framework, or MOF, containing a special absorptive porous material, Yaghi said in the email. He added that the research team realized the gases they were trapping included water, as well as carbon dioxide, and further testing revealed that some MOFs could collect water in dry climates.

According to Yaghi, the key discovery was that specific types of MOFs had high water affinity because of how these MOFs allowed water molecules to bond to each other — similar to how ice is formed. He added that to release water trapped in the pores of the MOF material, the MOF’s temperature simply had to be raised to 45 degrees Celsius (113 degrees Fahrenheit) to create enough energy to break bonds between water molecules.

“Water molecule presents a challenge since it competes with carbon dioxide for the adsorptive sites in the pores of MOFs,” Yaghi said in the email. “Thus, we were studying water uptake into MOFs to understand the behavior of MOFs in the post combustion environment.”

Yang noted in an email that, in April 2017, the team created the machine that managed to collect water, but the amount collected was not enough for a “drinkable amount.” According to Yang, two of the largest challenges were trying to maximize solar capture and the need to use better, cheaper material to increase water uptake.

“This is one real step to a practical water harvester as the prototype was developed and can produce a drinkable amount of water,” Yang said.

Yao Huang covers research and ideas. Contact him at [email protected] and follow him on Twitter at @Yhoneplus.