Scientists around the world have been working to secure access to drinkable water as pollution, population growth, and persistent drought caused by global warming make it a luxury for many — currently, as many as 2.1 billion people lack access to safe drinking water at home, according to the World Health Organization and UNICEF.
This year, Evelyn Wang’s engineering prowess was central to that mission.
In April, Wang, an associate professor of mechanical engineering at the Massachusetts Institute of Technology, hit on a bold approach that could provide fresh water in the dry, hot climates not served by previous generations of water-harvesting technologies. In collaboration with researchers at the University of California, Berkeley, Wang and her team proved out a model for a solar-powered device that can pull water from thin air even in the driest desert climates — an inexpensive harvester that can be powered entirely by the sun or a small organic heat source. The breakthrough, announced in a paper Wang co-authored in the journal Science, immediately created a buzz in the scientific community and was featured by CNN, NPR, Forbes, and the Washington Post.
“We think, ‘Oh yeah, of course water is very important,’” Wang says. But when it comes to government support and funding for climate change research, water loses out to things like renewable energy. “I think now people are starting to see the importance of water,” she continues, “but we’re already very late in the game.”
Harvesting water isn’t a new idea. For decades, there have been two primary technologies available for extracting it out of air, Wang said. One is fog harvesting, which requires around 100 percent relative humidity in order to work. The second, called dewing, uses condensers to pull vapor from the air and turn it into water. But this method requires a significant amount of energy to keep its condensers at the correct temperature, an obvious hindrance in places where power outages are frequent or electricity is in short supply.
The key to Wang’s innovation is a compound known as a metal-organic framework, a porous, crystalline material that links metal ions with organic molecules. In 2014, researchers at Berkeley developed a metal-organic framework that was particularly good at absorbing water, and they reached out to Wang to build a structure that would allow the material to condense water by pressing those tiny crystals into a thin sheet of porous copper metal where water molecules can stick to their interior surfaces.
Wang has been focused on water and solar power-related issues for a decade. After graduating in 2000 from MIT — the school where her parents met and were married, and from which both of her brothers hold degrees — Wang returned to California to work on her Ph.D. at Stanford University. But in 2007, she was pulled back east to teach at MIT, where her work took off. She says this year’s advance proves that it is possible to harvest water in a viable way without draining a lot of energy. She notes that the new device is “pretty much passive, just requiring a renewable energy source or a low-grade heat source.”
While the system isn’t yet available for production, and the combined Berkeley/MIT research team is only producing several liters of water at a time in its proof-of-concept phase, Wang says the goal is to build a system the size of a carry-on suitcase that can produce 15 liters of water a day.
“What we’re trying to do now is think about a larger-scale unit that could supply enough water for a family of four — that’s our goal right now,” she says. It might take a couple of years to develop, Wang thinks, but getting to that point where they can do more “realistic testing to provide enough water for a family” isn’t that far off.
Wang’s palpable sense of urgency traces back to her childhood in Santa Monica, California. She remembers Southern California’s strict water usage rules during the increasingly frequent droughts in the 1980s. Those experiences impressed on her that, while taken for granted, water is “the one resource humans need to survive.”
Paul McLeary is a staff writer at Foreign Policy.
Wang grew up playing violin and piano; she says her musical training gave her the discipline to be a successful scientist.