‘Fog Harp’ could make sweet music for thirsty Capetonians

28 March 2018 - 14:36 By Jacqueline Flynn
Study co-author Josh Tulkoff constructs a large prototype of the fog harp, which consists of a vertical array of 700 wires and is based on initial experimental results. Tulkoff was part of an interdisciplinary research team at Virginia Tech that discovered parallel wire arrays could increase the water collection capacity of fog nets by threefold.
Study co-author Josh Tulkoff constructs a large prototype of the fog harp, which consists of a vertical array of 700 wires and is based on initial experimental results. Tulkoff was part of an interdisciplinary research team at Virginia Tech that discovered parallel wire arrays could increase the water collection capacity of fog nets by threefold.
Image: Virginia Tech

The fog rolling over Table Mountain could go right into your tap.

The makers of the “fog harp”‚ designed to trap water from vapour‚ say their invention could help in drought and water-scarce areas.

The fog-harvester of 700 wires on a 1m x 1m frame is still in development but the team says the principle is well tested: In areas where the technology is applied at a large scale‚ harvesting projects can collect as much as 6‚000 litres a day‚ depending on weather conditions.

Capturing water in this way is normally achieved with a wire mesh net that collects microscopic droplets until they are heavy enough to roll into a collection basin.

The mesh design has been used since the 1980s‚ but the “harp” structure is new and promises a greater yield.

The problem with the net‚ scientists have found‚ was that the size of the mesh holes had to be precise. If they were too big‚ the fog passed through; too small and water clogged them.

The new prototype‚ from a research team at Virginia Tech in the US‚ might have solved this problem. It will collect more water with less clogging.

“From a design point of view‚ I’ve always found it somewhat magical that you can essentially use something that looks like screen door mesh to translate fog into drinking water‚” said Brook Kennedy‚ one of the designers of the device and a co-author of a paper on the invention published in ACS Applied Materials & Interfaces.

Part of the design inspiration came from looking at the Californian sequoia trees‚ whose water supply collects on their needles.

“We found that the smaller the wires‚ the more efficient the water collection was‚” said another member of the team‚ Jonathan Boreyko. “These vertical arrays kept catching more and more fog‚ but the clogging never happened.”

The team hopes its design will make a difference in water-scarce areas. Researchers estimate that two thirds of the world’s population is affected by scarcity at least one month of every year.

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