An MIT team has improved on existing systems to allow people in water-starved countries to harvest water from fog.
Like the Namib Beetle, which collects water droplets on its bumpy back, then lets them roll down into its mouth, the system works by attracting and channeling drops of water vapor via a fence-like mesh panel.
MIT’s Shreerang Chhatre says that his collector improves on the efficiency of previous versions. Using it, villagers could collect clean water near their homes, instead of spending hours carrying water from distant wells or streams.
“As a middle-class person, I think it’s terrible that the poor have to spend hours a day walking just to obtain a basic necessity,” he says. Nearly 900 million people worldwide live without safe drinking water, and it’s generally women and children that beat the burden of finding and transporting it.
To build larger fog harvesters, the researchers use mesh rather than a solid surface, because a completely impermeable object creates wind currents that drag water droplets away from it.
“We tried to replicate what the beetle has, but found this kind of open permeable surface is better,” Chhatre says. “The beetle only needs to drink a few micro-liters of water. We want to capture as large a quantity as possible.”
In some field tests, fog harvesters have captured a liter of water – about a quart – per square meter of mesh, per day. Chhatre and his colleagues are now conducting laboratory tests to improve this collection rate.
“About one-third of the planet’s water that is not saline happens to be in the air. Collecting water from thin air solves several problems, including transportation,” says Iqbal Z Quadir, director of the Legatum Center for Development and Entrepreneurship.
“If people do not spend time fetching water, they can be productively employed in other things which gives rise to an ability to pay. Thus, if this technology is sufficiently advanced and a meaningful amount of water can be captured, it could be commercially viable some day.”