Harvesting the clouds: how to make water out of fog

Image credit: Michele Lamberti

By Sandeep Ravindran 

Generally, when scientists look to nature for inspiration, they look to environments that mimic what they’re trying to build. In the case of collecting water from air, that meant desert plants and animals — seeing what special structures they might have to harvest fog water. So it was surprising when a fog collecting discovery came from a far wetter source: the beaks of shorebirds. And it could inspire a pretty radical redesign of fog collection devices.

Right now, most fog collection is done using mesh fabric. The Standard Fog Collector, used all over the world since Robert Schemenauer’s first paper on it in 1994, consists of a fabric mesh one square meter in size and faces the wind like little perforated sail. As the wind blows fog through the device, water droplets accumulate on the mesh and drop down into a trough, from which they flow down a tube into a container.

Daniel Fernandez, a fog researcher at California State University, Monterey Bay, has set up 20 standard fog collectors along the California coast. While most such fog collectors gather just a few liters a day, where they’re placed can make all the difference; Fernandez says he has collected almost 40 liters, or about 10 gallons, per square meter in a day from some parts of Big Sur.

“Fog has a really big impact on the world we live in, particularly in the coastal areas in California,” Fernandez says. On a summer day along the winding Northern California coast, the cool waters of the Pacific can cause the moisture in the air above to condense, forming low-lying clouds. As the breeze brings these clouds onto the shore and close to the ground, they form fog. It’s the same kind of fog that spreads into San Francisco, giving the city its iconic fog cover — and keeps temperatures along the California coast cool.

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