Sea water to ‘green’ deserts
Vast greenhouses that use sea water for crop cultivation 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.
Demonstration projects
The Sahara Forest Project, which is already running demonstration plants in Tenerife, Oman and the United Arab Emirates, envisages huge greenhouses with concentrated solar power (CSP), a technology that uses mirrors to focus the sun’s rays, creating steam to drive turbines to generate electricity.
The installations would turn deserts into lush patches of vegetation, according to its designers, and do away with the need to dig wells for fresh water, an activity that has depleted aquifers across the world.
Charlie Paton, a member of the team, and the inventor of the Seawater Greenhouse, said the scheme was a proven way to transform arid environments. “Plants need light for growth but they don’t like heat beyonda certain point,” he said.
Above certain temperatures the amount of water lost rises so much plants stop their photosynthesis and do not grow.
The solar farm planned by the project runs seawater evaporators, pumping damp, cool air through the greenhouses. This reduces the warmth inside by about15 degrees C, compared with the temperature outside.
Ideal conditions
At the other end of the greenhouse from the evaporators water vapour is condensed. Some of this fresh water is used to water the crops, some for 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.” The designers said that virtually any vegetables could be grown in the greenhouses. The nutrients to grow the plants could come from local seaweed or be extracted from the seawater. Michael Pawlyn, of Exploration Architecture, based in London, worked onthe Eden Project for seven years and is now part of the Sahara Forest team.
He said that the Seawater Greenhouse and CSP provided substantial synergies for each other. He said the Greenhouses could reverse the environmental damage done by the glasshouses already built in places such as the desert region of Almeria, southern Spain.
Paton said: “They take water out of the ground something like five times faster than it comes in, so the water table drops and becomes more saline. The whole of Spain is being sucked dry. If one were to convert them all to the Seawater Greenhouse concept it would turn an unsustainable solution into a more sustainable one.
— Guardian Newspapers Limited 2008
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