Oct 14 2008

Making the Desert Bloom

Posted by: Jonathan Marshall

German researchers, publishing in this month's issue of Nature Geoscience, are reporting evidence that the arid Sahara desert used to be a virtual Garden of Eden--not once but three times over the past 120,000 years. By studying marine sediments off the coast of Northwest Africa, they determined that grass and lakes covered what are now sandy wastelands, thanks to more favorable rainfall patterns in the past.

 The desert may yet turn green again if an initiative called the Sahara Forest Project gains any traction. A collaboration of inventor Charlie Paton, architect Michael Pawlyn, and engineer Bill Watts, the project marries concentrated solar power installations with a unique Seawater Greenhouse to produce electric power, fresh water and a cool, humid environment suitable for high-yield agriculture in dry coastal regions.

A first-generation greenhouse design, invented by Paton, was built in the Canary Islands; a lower-cost, second-generation model was erected in Abu Dhabi and a third was built recently in Oman. They use cold seawater to condense fresh water out of humid air.

The Sahara is an ideal place to site concentrated solar power plants, which could send electricity to Europe over high-voltage DC transmission lines. (Gordon Brown and Nicholas Sarkozy have reportedly both endorsed this concept.) In a clever feat of synergy, the power plants would also contribute waste heat to evaporate seawater for desalination. The greenhouses would use only about a quarter of the fresh water produced, leaving the rest to irrigate ground crops and trees or for use by the solar steam turbines.

The project has been called a "supremely elegant example of sustainable design."  And as another admirer said, it "could potentially produce enough energy for all of Africa and Europe while turning one of the world's most inhospitable regions into a flourishing oasis."

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