That is to say, it needs no energy besides the sun, making it environmentally friendly and accessible to people in places with limited electricity. The results of the trials were published earlier this month in the journal Science Advances.
The team needs to conduct more trials on the current models to figure out which factors, such as device size and where the MOF is placed within the device, most affect how much water can be harvested. They also hope to learn more about how specific climate conditions affect water yield. The next trial is planned for late summer in Death Valley, where the nighttime humidity can be as low as 25 percent.
Yaghi has also developed a new aluminum-based MOF he says is 150 times cheaper and can capture twice as much water as the current MOFs. He and his team are designing a new water harvester that actively pulls air into the MOFs at high speed, thus delivering a much larger volume of water.
The team is now partnering with industry to test harvesters on an industrial scale. They also continue to search for newer, better and cheaper MOFs.
“I am very happy to see that more and more researchers around the world are joining our efforts in this regard,” Yaghi says.
The idea of sucking water out of the atmosphere is not new, says Eric Hoek, an engineering professor at the University of California, Los Angeles and editor of the journal npj Clean Water. It’s long been noted that when you run an air conditioner, water drips out—this is because the machine is cooling the air to the dew point, the temperature at which the air is saturated with water vapor and condensation occurs.
But creating water harvesters based on cooling technology is incredibly energy intense. In very dry climates, the dew point is below zero. Cooling the air to that temperature at any large scale is unfeasible.
“The real innovation [of Yaghi’s research] is a materials innovation,” Hoek says. “These materials [the MOFs] pull water out and more easily give it up.”