The utilization of cold, nutrient-rich deep ocean water
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In tropical and subtropical areas of the oceans, the warm surface waters constitute the world's largest storage of solar energy. The underlying cold deep water, less than 1000 m below the ocean's surface, constitutes a cold sink, making it possible to generate mechanical energy by inserting a suitable heat engine between the warm and cold waters. The energy required for pumping the deep water to the surface is typically 6.5% of the total energy produced by the plant. The nitrate, phosphate and other nutrients dissolved in the deep sea water constitute the raw materials for plant growth when brought into the light at the surface. Extrapolation of results from small-scale experiments conducted at the St. Croix (U.S. Virgin Islands) ‘Artificial Upwelling’ station, indicate that this system could produce 20 times more algal protein per hectare than alfalfa, the highest protein-producer per hectare in land-based agriculture. The algal protein can be converted into clam protein with better than 30% efficiency. It is recommended that a commercial feasibility test of a combined sea-thermal power plant and mariculture operation, utilizing deep-sea water and sunshine as major raw materials, be undertaken.
Presented at: Triennial International Exhibition on the Exploitation of the Oceans, Bordeaux, France