‘The Sahara Forest’ project is an ambitious proposal to turn areas of the dry arid desert into real-life oases. A team of architects and engineers are aiming to combine huge seawater greenhouses with solar power plants in the desert to provide food, fresh water and clean energy. They will use mirrors to focus the sun’s rays and generate heat and electricity, and eradicate the need to dig for fresh water creating lush areas of vegetation.
The vast majority of plants cannot grow in the desert due to the extreme temperature and lack of water, the seawater greenhouse can make these arid environments vegetation friendly. Charlie Paton is part of the Sahara team and the inventor of these greenhouses.
“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.”
Paton said that the greenhouse produces over five times required for watering the plants so after cleaning the mirrors, the excess can be released into the local environment, creating a local microclimate outside the greenhouses for hardier plants such as jatropha - an energy crop that can be turned into biofuel. The ability to create these microclimates has been shown by Paton’s demonstration greenhouse.
To purifying the seawater and cool the air of the greenhouse, solar energy is used to power the evaporators and then pump the damp, cool air through the greenhouse, reducing the temperature to 15c less than outside. At the other end of the greenhouse from the evaporators, the water vapour is condensed. This fresh water can be used to water the crops and clean the solar mirrors.
Demonstration plants are already running successfully in Tenerife, Oman and the United Arab Emirates, producing lettuces, peppers, cucumbers and tomatoes. The designers are confident that virtually any vegetables can be grown in the greenhouses depending on the climate maintained in them. The nutrients to grow the plants can be taken from seaweed or the seawater itself.
Both the CSP (solar power) and seawater greenhouses are proven technologies so the cost of this project should be relatively low. The designers estimate that building 20 hectares of greenhouses combined with a 10MW CSP scheme would cost around £65m. Groups in countries across the Middle East, including UAE, Oman, Bahrain, Qatar and Kuwait, have shown interest in funding demonstration projects.
These projects are useful due to the production of extra crops, but most importantly will benefit the environment. Hopefully these seawater greenhouses can be used instead of, or to counteract the environmental damage caused by greenhouses already built. In Algeria, southern Spain, more than 40,000 hectares of greenhouses have been built in this desert region over the past 20 years, taking water from the earth around five times faster than it comes in, so the water table drops and becomes more saline. To convert them all to the seawater greenhouses would make sustainable
“The beauty of the Sahara Forest scheme is that you can reverse that process and turn barren land into biologically-productive land.” Charlie Paton.
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