The potential of electric power generation from marine tidal currents is enormous. Tidal currents are being recognized as a resource to be exploited for the sustainable generation of electrical power. The high load factors resulting from the fluid properties and the predictable resource characteristics make marine currents particularly attractive for power generation and advantageous when compared to other renewable energies. Moreover, international treaties related to climate control have triggered resurgence in development of renewable ocean energy technology. Therefore, several demonstration projects in tidal power are scheduled to capture the tidal generated coastal currents. Regarding this emerging and promising area of research, this paper reviews marine tidal power fundamental concepts and main projects around the world. It also report issues regarding electrical generator topologies associated to tidal turbines. Moreover, attempts are made to highlight future issues so as to index some emerging technologies mainly according to relevant works that have been carried out on wind turbines and on ship propellers.

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Marine Tidal Current Electric Power Generation Technology: State of the Art and Current Status

This paper deals with the development of a Matlab-Simulink model of a marine current turbine system through the modeling of the resource and the rotor. The simulation model has two purposes: performances and dynamic loads evaluation in different operating conditions and control system development for turbine operation based on pitch and speed control. In this case, it is necessary to find a compromise between the simulation model accuracy and the control-loop computational speed. The blade element momentum (BEM) approach is then used for the turbine modeling. As the developed simulation model is intended to be used as a sizing and site evaluation tool for current turbine installations, it has been applied to evaluate the extractable power from the Raz de Sein (Brittany, France). Indeed, tidal current data from the Raz de Sein are used to run the simulation model over various flow regimes and yield the power capture with time.

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A Simulation Model for the Evaluation of the Electrical Power Potential Harnessed by a Marine Current Turbine

A hybrid ocean thermal energy conversion (OTEC) system, including an energy generation sub-system for receiving warm sea water, evaporating a working fluid at a natural depth of the received warm sea water to produce a working vapor, and generating energy from the working vapor and a pumping sub-system for pushing cold sea water up to a natural depth of the received warm sea water and condensing the working vapor with the cold sea water.

Ocean thermal energy conversion (otec) system

Design of a prototype ocean current turbine—Part I: mathematical modeling and dynamics simulation

Baseload The minimum amount of power that a utility must make available to its customers. Baseload plant An energy plant devoted to the production of baseload supply. Baseload plants typically run at all times through the year (24/7) except in the case of repairs or scheduled maintenance. CWP Cold water pipe, the pipe used to transport deep ocean water to the OTEC condenser. Draught (Draft) The depth of a ship’s keel below the water surface. Euphotic zone The upper layer of the ocean in which there is sufficient light for photosynthesis. Externalities The costs generated by the production of electricity that are not included in the price charged to consumers. These costs manifest themselves through changes in the environment and other societal costs. Gross power The electrical power generated by the turbine-generator. Net power The electrical power available for export from the OTEC plant. The difference between gross power and in-plant power consumption needed to run all sweater and working fluid pumps. Ocean thermal resource Defined by DT, the ocean temperature differences between water depths of 20 m (surface water) and 1,000 m. OTEC Ocean Thermal Energy Conversion, the process of converting the ocean thermal energy into electricity. OTEC transfer function The relationship between the thermal resource and the electricity generated. Plantship A ship designed to house an OTEC power plant. Re-entrainment The mixing of the water already used in the OTEC plant into the incoming warm (surface) water stream. WOA05 World Ocean Atlas 2005 version.

Ocean Thermal Energy Conversion

The history of ocean thermal energy conversion (OTEC), a process that employs the temperature difference between surface and deep ocean water to alternately evaporate and condense a working fluid, is reviewed. In the open-cycle OTEC configuration, the working fluid is seawater. In the closed-cycle configuration, a working fluid such as propane is used. OTEC is assessed for its practical merits for electric power generation. Because rather large amounts of seawater and working fluid are required, the energy requirements for pumping them may be greater than the energy recovered from the OTEC engine itself. The concept of net power production is discussed. The components of a typical OTEC plant are described with emphasis on the evaporator heat exchanger. Operation of an OTEC electric generating station is discussed, including transient operation. Recent experiments and efforts at the National Energy Laboratory-Hawaii (NELH) are summarized. Remarks are made on bottlenecks and the future of OTEC as an advanced electric generation methodology. >

G.T. Heydt

Papers

An assessment of ocean thermal energy conversion as an advanced electric generation methodology