OTEC's subsurface discharges of Deep Ocean Water: Modelling Their Effects on the Primary Production

by Alain Menesguen, IFREMER-Cent de Brest, France,
Yves Monbet, IFREMER-Cent de Brest, France,
France Cousin, IFREMER-Cent de Brest, France,

Document Type: Proceeding Paper

Part of: Ocean Energy Recovery


The French project of a shore-based OTEC pilot plant (5 MW) at Tahiti gave the opportunity of simulating the ecological effects of a small, man-made upwelling in coastal-tropical oligotrophic waters. Based on the well-known nitrogen limitation, a very simple model was built, describing the pelagic nitrogen cycle by three state variables: inorganic nitrogen, phytoplanktonic nitrogen and detrital organic nitrogen. This biological model was first coupled with a vertical 10-boxes model, allowing the simulation of vertical exchanges due to eddy diffusion and sedimentation of particles. A rough simulation of the ecological effects of internal waves was attempted by a periodic, accordion-like deformation of this vertical box-model. The simulation fits adequately the observed profiles of inorganic nitrogen and chlorophyll. Depending on the depth of the outlet relatively to the local chlorophyll maximum depth, the thermal content of the effluent has to be adjusted following the proposed aim: sea surface fertilization or quick sinking in order to prevent any development of eutrophication processes.

Subject Headings: Water discharge | Thermal analysis | Nutrient pollution | Nitrogen | Thermal power | Thermal pollution | Ocean engineering

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