Wednesday, 3 February 2010
Coastal Desert Greenhouses: Water and Food
The Seawater Greenhouse uses the sun, the sea and the atmosphere to produce fresh water and cool air to assist in the growing of crops. The process recreates the natural hydrological cycle within a controlled environment. The entire front wall of the building is a seawater evaporator. It consists of a honeycomb lattice and faces the prevailing wind. Fans may need to assist and control air movement in very hot locations. Seawater trickles down over the lattice, passively 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 volume of fresh water is determined by air temperature, relative humidity, solar radiation and the airflow rate. These conditions can be replicated in the thermodynamic model and, with appropriate meteorological information, the detailed design and performance of the Seawater Greenhouse can be optimised for every suitable location and environment.