Friday, March 19, 2010

Harvesting Water from the Sky

In many places around the world, getting fresh water is not as simple as turning on the faucet. In fact, in rural areas around the world, limited access to fresh water supplies force inhabitants to walk miles to fetch water. This hike not only entails long walks and the carrying of heavy water-laden receptacles, but in many rural developing countries, the groundwater may also be contaminated or in short supply. However, in areas where fog or low-lying cloud cover is frequent enough, there is a low-tech solution that could provide clean drinking water to communities. A recent installation in Venda, South Africa - part of the fog harvesting research project by The University of South Africa, has proven the technology successful by supplying approximately 300 litres of water per day on average to the community of Tshanowa. The system is relatively simple. According to Professor Jana Oliver of UNISA School of Agriculture and Environmental Sciences:
"Each collection system consists of three six-meter-high (twenty feet) wooden poles, mounted nine meters (thirty feet) apart. Steel cables stretch horizontally between the poles and anchor the structure. A double layer of 30 percent shade cloth is then draped over the cables and fixed to the poles on each side. This forms a fog collection screen of about 70 square meters (750 square feet), with a gutter attached to its lower end. The technology behind fog collection is extremely simple, during foggy conditions, the tiny fog particles are blown against the screen and deposited on it. As the drops become larger, they trickle downwards and drop into the gutter. From there, the water is channeled through a filter to a pipe that leads to a water collection tank."
Due to the simplicity of construction and also the technology behind the concept, this seems to be a solution that would work very well in areas with little access to suitable or existing infrastructure.
A similar project by Imke Hoehler called Dropnet also uses the same technology as the UNISA but has redesigned the system to be smaller and more portable. Whereas the UNISA project is a built-in-place installation, the Dropnet can function as a re-deployable system.

UNISA project seen on NatGeo News Watch and The University of South Africa.
Dropnet project found on Designboom.

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