Dew-harvesting 'web' conjures water out of thin air

Tom Simonite

      A portable dew-harvesting kit inspired by a spider's web is being developed by Israeli architects for use in areas where clean and safe water is scarce.

In February 2007, UK engineering firm Arup and charity WaterAid held a competition aimed at finding new technologies to help people gain access to clean water in areas where it is scarce. This is a problem for about 1 billion people worldwide.

The contest was won by Israeli architects Joseph Cory of company Geotectura and Eyal Malka of Malka Architects who suggested a dew-harvesting contraption.

Cory and Malka were inspired by seeing drops of water caught on desert spiders' webs first thing in the morning. Their design, called WatAir, consists of an inverted pyramid of sheet material, which collects dew and channels it into a collector and filtration unit in the centre.

The architects have now built and tested a prototype a 10 metre square canopy of canvas attached to trees by rope. In this, dew was channelled into a gravity-driven filter and collecting tank hanging from the centre. "In one day we collected more than 20 litres of water," says Cory. They are now developing an improved, portable version with a Dutch company.

The second prototype "will be a properly designed product," says Cory. Poles that snap together are used, so the whole thing can be packed inside the collection tank for carrying. "You can easily transport it that way, and then unpack everything and hang the tank below to start collecting," says Cory.

After winning the competition, Cory and Malka were approached by several companies offering to supply different types of sheet materials for WatAir. They will begin testing the dew-collecting ability of different materials soon.

Frank Lawson, a water engineer at Arup and part-time technical advisor for WaterAid, says fog harvesting has become popular in some mountainous parts of Chile, but dew is not currently harvested for water needs.

"This design has potential wherever the climate is right for a heavy dew fall the edge of deserts is one example," he says, adding that, to make the most of the idea, "selecting the right material for the canopy is important".

Balloon powerCory is developing another technology that could prove useful in the developing world large helium balloons with solar panels attached (see image bottom right). "Using photovoltaic panels requires a lot of surface area, and that can be limited in urban areas where you can only use rooftops," he says.

Along with aerospace engineer Pini Gurfil of the Technion technology institute in Haifa, Israel, Cory is attaching flexible solar panels, normally used to recharge camping equipment, to large helium balloons with a cable that runs back to the ground.

Currently, the 1 metre balloons can only provide 50 watts to power a light bulb, but in future they could do much more. "I imagine whole parks in cities covered with clusters of the balloons," says Cory. "As photovoltaics panels become more efficient this could be a useful way to deploy them."

15th Nov 2007