Thursday, September 4

Desalinated Seawater Greenhouse Cools Desert Agriculture

Seawater Greenhouse uses the sun, the sea and the atmosphere to produce fresh water and cool air where it is needed most: in the desert.

Greenhouses usually provide warm growing conditions in cooler climates. But why not use the idea in reverse to make growing crops possible in inhospitably hot climates. Thats the idea invented by Charlie Paton and engineered by Philip Davies in their Seawater Greenhouse Project.

The reverse greenhouse is designed to create an environment that is cool, humid and bright, a reverse of the warming effect of typical cold climate greenhouses. It is for use in desert climates adjacent to seawater. First, you have to find a desert next to the sea, which is not too difficult. Then, this is how this idea works:

1. Seawater cools inside the greenhouse

Facing the prevailing sea wind the entire front wall of the greenhouse is a honeycomb lattice that catches seawater and evaporates it. Seawater trickles down over the lattice, cooling and humidifying the air passing through into the planting area.

2. The heat of the sun is removed

Sunlight is filtered through a specially constructed roof that only allows visible light through to promote photosynthesis, but trapping the infrared heat in an isolated chamber.

3. Fresh water is created by condensation

Cool air passes through the planting area and then combines with the hot dry air contained in the roof cavity. The mixture passes through a second sea water evaporator creating extremely hot watersaturated air which then flows through a condenser cooled by deep seawater. The extreme temperature difference causes fresh water to condense.

4. Water is stored for irrigation

The freshwater is stored in a tank underneath the ground where it is kept cool and piped back up to irrigate the crops both inside and outside under a canopy.

Continued growth in demand for water and increasing supply shortages are two of the most certain and predictable scenarios of the 21st century. And the desert creeps towards ever more people. Agriculture, with its high demand for water, will be a major pressure point.

For Matternetwork