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German Scientists Use Solar Power to Produce Drinking Water


Science Technology News
January 14, 2008


Freiburg, Germany - Clean water with free energy is the
goal of German scientists who are using the sun's rays
to power small water treatment plants for developing
countries. The system is designed for arid areas of
Africa and Asia where a lack of electricity makes it
impossible to use large industrial plants for the
desalination of seawater, like those in the Middle East.

"The regions have a very poor infrastructure. Quite
often there is no electricity grid, so conventional
desalination plants are out of the question," says
Joachim Koschikowski.

The engineer and his team at the Fraunhofer Institute
for Solar Energy Systems (ISE) have developed small
decentralized units with their own solar power supplies
that can transform salt water or brackish water into
pure drinking water.

"Our plants work on the principle of membrane
distillation," says Koschikowski, comparing the
technology to that used in breathable, waterproof
fabrics, where the membrane prevents rainwater from
penetrating through to the skin, while allowing water
vapour to pass through to the outside.

"In our plant, the salty water is heated up and guided
along a micro-porous, water-repellent membrane. Cold
drinking water flows along the other side of the
membrane," he says.

The steam pressure gradient resulting from the
temperature difference causes part of the salt water to
evaporate and pass through the membrane.

"The salt is left behind, and the water vapour condenses
as it cools on the other side. It leaves us with clean,
germ-free water," says Koschikowski.

The German researchers have so far built two different
systems, both with their own energy supply.

"Our compact system for about 120 litres of fresh water
per day consists of six square metres of thermal solar
collectors, a small photovoltaic module to power a pump,
and the desalination module itself," says Koschikowski.
In the dual-circuit system, on the other hand, several
desalination modules are connected in parallel, enabling
several cubic metres of water to be treated every day.

One cubic metre of drinking water, the equivalent of
1,000 litres, will cost about 10 euros (14.50 dollars).
"When you think how much the inhabitants currently have
to pay for the same amount of bottled water or soft
drinks, the plant will pay off very quickly," says
Koschikowski.

His institute has been successfully operating pilot
projects on the Spanish island of Gran Canaria and in Jordan.

The researchers are planning to market the plants
through a spin-off company known as SolarSpring from the
middle of 2008.

 

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