By harnessing the basic processes of the hydrological cycle, the Sea Water Greenhouse is able to use seawater and sunlight to nourish plants and create a cool, humid atmosphere for a wide variety of growth. The incoming seawater is drawn up from the ground and through a series of evaporators and condensers, which are all run by self-sufficient solar energy. This water is then released slowly over the crops. Much like other greenhouses, the roof traps infrared heat while still allowing visible light through to promote photosynthesis. In using the natural resources already available at any seaside location, the Sea Water Greenhouse is able to greatly improve energy efficiency while lessening the negative environmental impact of large-scale agriculture. Since the seawater is going through an extensive desalination process, the Sea Water Greenhouse can also double as a desalination plant for a small community. Costs for the DIY structure greatly depend upon the size and scale of the project, however, the suggested infrastructure of polythene-clad steel is a relatively common construction material. Fully functional greenhouses have already been implemented in such semi-arid agricultural powerhouses as Oman and Gran Canaria. Let's hope the rest of the industrial world will catch on.
— Christopher Miller

Sea Water Greenhouse, via Tree Hugger