The planned project would use solar power to evaporate salt water, generating cool air and pure water thereby allowing food to be grown
By Alok Jha, green technology correspondent guardian.co.uk, Tuesday 2 September 2008 15.50 BST
Vast greenhouses that use seawater to grow crops could be combined with solar power plants to provide food, fresh water and clean energy in deserts, under an ambitious proposal from a team of architects and engineers.
The Sahara Forest project would marry huge greenhouses with concentrated solar power (CSP), which uses mirrors to focus the sun's rays and generate heat and electricity. The installations would turn deserts into lush patches of vegetation, according to its designers, and without the need to dig wells for fresh water, which has depleted acquifers in many parts of the world.
The team includes one of the lead architects behind Cornwall's Eden project and demonstration plants are already running in Tenerife, Oman and the United Arab Emirates.
Plants cannot grow in deserts because of the extreme temperatures and lack of nutrients and water. Charlie Paton, one of the Sahara Forest team and the inventor of the seawater greenhouse concept, said his technology was a proven way to transform arid environments.
"Plants need light for growth but they don't like heat beyond a certain point," said Paton. Above a particular temperature, the amount of water lost through the holes in its leaves, called stomata, gets so large that a plant will shut down photosynthesis and cannot grow.
The greenhouses work by using the solar farm to power seawater evaporators and then pump the damp, cool air through the greenhouse. This reduces the temperature by about 15C compared to that outside. At the other end of the greenhouse from the evaporators, the water vapour is condensed. Some of this fresh water is used to water the crops, while the rest can be used for the essential task of cleaning the solar mirrors.
"So we've got conditions in the greenhouse of high humidity and lower temperature," said Paton. "The crops sitting in this slightly steamy, humid condition can grow fantastically well." …