‘Fog harp’ makes water out of thin air

In some of the most arid regions of the world, from the Sahara to the Andes, special nets have long been used to catch moisture from the air, turning fog into drinking water.

These fog harvesters are put up against wind streams to catch microscopic droplets which gather and merge on a fine mesh until they have enough weight to travel down into a water tank, cnn.com wrote.

They provide essential access to water too many communities, and the technology behind them has evolved over the years to offer a higher yield, resistance to the elements and a reduced need for maintenance.

Now, researchers at Virginia Tech University have developed a new design that they say has three times the efficiency of regular fog nets.

They call it a ‘harp’, because its vertical pattern of wires makes it resemble the string instrument.

Jonathan Boreyko, one of the authors of the study at Virginia Tech, said, “Our long-term goal is that the fog harp can completely replace the classical net design, resulting in cheaper fog harvesters that end up collecting substantially more water.”

Improved design

The problem with the classical design, according to Boreyko, is that the fog droplets end up getting stuck in the holes of the net, because the horizontal wires obstruct their path on the way down into the reservoir.

The net then becomes heavily clogged with water, which makes it impermeable to the wind.

As a result, the foggy wind simply flows around the net, instead of through it, which reduces the amount of fog that can be collected.

The fog harp consists instead of an array of vertical wires held under tension within a frame, without any intersecting wires, so that droplets can easily slide down at very small sizes.

Boreyko said, “This solves the clogging issue to ensure that the wind can continuously flow through the harp for efficient fog capture.”

The new design takes inspiration from plants that use fog harvesting to supplement their water intake, such as redwood trees on the California coast.

Boreyko said, “Most trees and plants have arrays of branches and leaves that run parallel to each other.

“Our harp design is therefore, in many ways, analogous to what nature is already doing to efficiently manage water. The classical net structure, on the other hand, is an inefficient design that nature has learned to avoid.”