The Seawater Greenhouse is a process which provides water for agriculture in arid coastal regions.
The Seawater Greenhouse uses seawater to cool and humidify the air that ventilates the greenhouse and sunlight to distill fresh water from seawater. This enables the year round cultivation of high value crops that would otherwise be difficult or impossible to grow in hot, arid regions.
The entire front wall of the greenhouse is a seawater evaporator. It consists of a honeycomb lattice that faces the prevailing wind. Seawater trickles down over the lattice, cooling and humidifying the air passing through into the planting area.
Sunlight is filtered through a specially constructed roof. The roof traps infrared heat, while allowing visible light through to promote photosynthesis. This creates optimum growing conditions – cool and humid with high light intensity.
Cool air passes through the planting area and then combines with hot dry air from the roof cavity. The mixture passes through a second sea water evaporator creating hot saturated air which then flows through a condenser. The condenser is cooled by incoming seawater. The temperature difference causes fresh water to condense out of the air stream. The water is pure distilled water, produced without chemical treatment. The quantity produced depends on the climate – the hotter and sunnier, the more water.
The Seawater Greenhouse project dates back to 1991 when the concept was first researched and developed by Light Works Ltd. The first pilot project commenced in 1992 with a test site on the Canary Island of Tenerife. In Tenerife, a barren area ‘turned green’ as seepage from irrigation reversed saline intrusion and enabled new plant growth.
The original pilot design has now evolved into a more elegant yet lower cost solution using a light but strong steel structure similar to a multi-span polytunnel. This design has been tested and validated through a second Seawater Greenhouse that was constructed on Al-Aryam Island, Abu Dhabi, United Arab Emirates in 2000. In both cases, crop production in terms of quality and quantity has been outstanding, with the Greenhouse supplying in excess of the water required for irrigation.
The Seawater Greenhouse project is currently seeking partners to develop further projects in appropriate regions, including Australia.