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Greening the Nullabor
THE need to adapt to climate change is not only driving new technologies. It is also bringing forward new combinations of well tried ideas - like the concept pictured above that aims to mix known technologies to "green the desserts".
In this case the combination is solar energy and a unique form of greenhouse desalination. The result, say the proponents, will be large amounts of renewable energy, food, fresh water, and the recovery of extensive areas of unproductive land.
The UK companies behind the idea (Seawater Greenhouse Ltd, Exploration Architecture, and Max Fordham & Partners LLP) are promoting it under the rather audacious title "The Sahara Forest Project". Nonetheless, according to one of its designers, architect Michael Pawlyn, there is no technical reason why it could not be applied to other places, like for example - WA’s Nullarbor Dessert.
"A quick look at data on the Nullarbor Desert suggests that it would be ideal as it is very hot and dry," Mr Pawlyn told TransScan. "The absence of any significant depressions would not be a problem as the scheme still works if the seawater has to be pumped. In terms of cost, 80 million Euros for a 20 hectare /10Megawatt scheme is a reasonable ballpark estimate."
It is the seawater and the specially designed greenhouses that convert the seawater into pure water that is the key to the concept. In the picture above, the greenhouses are shown snaking their way across the Sahara. According to Mr Pawlyn individual seawater greenhouses of a similar kind are already operating successfully in Tenerife, Oman and the United Arab Emirates.
These three schemes essentially mimic the hydrological cycle in miniature. As a project background paper explains it: "Seawater is evaporated from cardboard grills at the front end of the greenhouse to create cool humid conditions within the greenhouse and is then condensed as distilled water at the back."
In the Sahara Forest Project the idea is to combine seawater greenhouses with Concentrated Solar Power (CSP) - the technology that involves concentrating the sun’s heat to create steam to drive conventional turbines.
"CSP and the seawater greenhouse work extremely well in hot desert conditions," says the statement. "While the former produces large quantities of surplus heat, the latter can make use of this to evaporate more seawater. The seawater greenhouse produces large quantities of pure de-ionised water which Concentrated Solar Power plants need for the turbines and cleaning the mirrors to maintain maximum efficiency."
It says on a large scale, the project would be able to distribute electrical energy to local users as well as fresh water. In fact the greenhouses would be producing five times as much fresh water as they would need for the plants inside. Much of that additional fresh water would allow crops to be grown outside the greenhouses.
The growth beyond the greenhouses would steadily reverse desertification. That process itself would be assisted by the fact that the greenhouses will be evaporating much more water than they will be condensing into fresh water. Depending on local geography, the evaporation could mean extra rain.
"I am aware of some of the water problems in Australia and the proposed solutions such as building enormous desalination plants," Mr Pawlyn said.
"Our proposal would produce large quantities of surplus fresh water and renewable energy without the huge environmental impact of fossil fuel based desalination. And as the cost of oil increases, the economics will only improve."
