The global dynamic positioning of a floating OTEC plant with an attached cold water pipe is considered, using the momentum flux associated with the warm surface seawater intake. The present work exploits the idea that, under normal OTEC operating conditions, a floating body could be kept in a global position, within a given radius, without the need for mooring lines or thrusters if the momentum flux from the surface seawater intake or the effluent discharge is adequately distributed around the hull. This problem is studied In the presence of steady external forces that act on the platform-pipe system in regular seas, and a positioning model is developed. The model is then applied to a sample OTEC plant to determine the technical feasibility of the solution in particular cases. The proposed positioning model can be used to determine the distribution and amount of momentum flux necessary to keep the plant in position.
In an OTEC process, warm seawater is fed to the plant from the surface of the ocean, while cold seawater is pumped from the deep ocean by means of a long cold-water pipe (CWP). The mixed effluent discharge pipes can be moderate in length, extending to a depth sufficient not to interfere with the warm-water intake. When warm seawater flows through lateral openings slightly above the keel of the platform, momentum is generated. The rate of this momentum can be used to balance, either partially or totally, the external forces exerted on the platform and attached pipes, to achieve positioning without the need for additional power for thrusters. Nihous and Vega (1991) presented the designs of several floating OTEC plants that show possible locations of the warm-water intake pipes, as" well as the mixed effluent discharge pipes.
