Solar-Powered Moisture Harvesting Could Solve the Water Crisis


SEATTLE — In recent years, scientists around the world have made major breakthroughs in the water collection method of moisture harvesting. Today, one in 10 people in developing countries lack access to clean, safe drinking water. About half of the people drinking water from unprotected sources live in sub-Saharan Africa; 80 percent of those live in rural areas.

Many developing countries are near large bodies of water, but desalination is an expensive solution the countries cannot afford. Other countries are in arid regions and can’t use mesh systems to harvest fog due to low humidity levels. Researchers at University of California, Berkeley and MIT developed a solar-powered moisture harvesting system that could provide clean water for millions in developing, arid areas.

The 8.5 million residents of Lima, Peru, a city that sits at 90 percent humidity for the majority of the year, receive less than an inch of rain each year and face devastating water shortages. Scientists developed a billboard that converts the moisture in the air to clean drinking water by reverse osmosis. Three months after the project’s installment, the billboard had produced around 2,600 gallons of potable water.

American architecture students recently developed a moisture harvesting concept for the Atacama Desert in Chile. Their design, the Mist Tree Tower Concept, uses circular mesh openings on the humid, western side of the Andes to harvest fog from the Pacific Ocean. The mesh gathers condensation like a spider web and acts like the cross-section of a tree root, sending water underground to trees and plants on the arid, eastern side of the Andes.

While moisture harvesting has been effective in humid areas, rural, desert areas are still in need of a solution. That’s why Omar Yaghi, professor of chemistry at UC Berkeley and Evelyn Wang of MIT developed a solar-powered moisture harvesting system that, like the projects in Peru and Chile, draws water out of the air. But unlike the projects in Peru and Chile, the modified dehumidifier traps moisture in areas with humidity levels as low as 20 percent — levels common in deserts around the world.

The device pulls 2.8 liters of water from the air in 12 hours. Yaghi and Wang developed the solar-powered moisture harvesting system to meet the water needs of off-grid households in developing communities.

The system is made of highly porous materials known as “metal-organic framework,” a system Yaghi invented that links metal clusters using organic molecules. Yaghi’s framework uses a combination of water-attracting zirconium and water-repelling organic molecules to harvest the humidity in the air. Then the sun’s hot temperature releases the water droplets for collection. Even better, the dehumidifier is inexpensive to make.

Yaghi’s system isn’t on the market yet. To ready it for commercialization, he is developing ways for the device to hold more water, while Wang is improving its efficiency and output.

— Rachel Cooper

Photo: Flickr


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