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The Seawater Greenhouse is an established technology with the potential to create surplus fresh water from seawater, using a novel form of greenhouse that also provides suitable food-growing conditions in arid regions. Three such units have been built so far. The technique is applicable to only a very limited number of world sites due to the topographic elements essential to the process. The technology won the Tech Museum Award for a 2006 project in Oman, and was a finalist in the 2007 St Andrews Prize for the Environment.

Proposals for the Seawater Greenhouse include the Sahara Forest Project , a scheme that aims to provide fresh water, food and renewable energy in hot arid regions as well as re-vegetating areas of uninhabited desert. This ambitious proposal combines the Seawater Greenhouse and concentrating solar power (CSP) to achieve highly efficient synergies. CSP is increasingly seen as a promising form of renewable energy, producing electricity from sunlight at a fraction of the cost of photovoltaics. By combining these technologies there is huge commercial potential to create a sustainable source of energy, food and water.

The scheme is proposed at a significant scale such that very large quantities of seawater can be evaporated. By using a location that lies below sea level, this can be achieved without pumping and there is an opportunity to capture some of the substantial volumes of residual humidity that leave the greenhouses. A 20,000 hectare area of Seawater Greenhouses will evaporate a million tonnes of seawater per day. If the scheme were located upwind of higher terrain then the air carrying this ‘lost’ humidity would rise and contribute to forming mist, cloud and dew. It would then be possible to harvest this precipitate using fog-nets that can supply tree saplings with water and thereby reverse the process of desertification, returning barren land to forest.

The scheme was first publicly proposed to a group of energy specialists at the third Claverton Energy GroupConference held at the Headquarters of Wessex Water Plc on April 13 2008 updated