Ocean Energy: Technology Overview

Ocean Tidal Energy

The generation of electrical power from ocean tides is very similar to traditional hydroelectric generation.  A tidal power plant consists of a tidal pond created by a dam, a powerhouse in the dam containing a turbo generator, and a sluice gate in the dam to allow the tidal flow to enter and leave.  By opening the sluice gate in the dam, the rising tidal waters are allowed to fill the tidal basin.  At high tide these gates are closed and the tidal basin behind the dam is filled to capacity.  After the ocean waters have receded, the tidal basin is released through a turbo-generator in the dam.  Power may be generated during ebb tide, flood tide, or both.  The capacity factor of such a facility may be expected to be up to 25 percent.  Commercial tidal plants have been developed; a 240 MW plant in France and an 18 MW plant in Canada are the two largest plants in the world.

Times and amplitudes of high and low tide are predictable, although these characteristics will vary considerably from region to region.  Economic studies suggest that tidal power will be most economical at sites where mean tidal range exceeds about 16 feet.

Utilization of tidal energy for power generation has the environmental advantage of a zero emission technology.  However, the environmental and aesthetic impact that the facility has on the coastline must be carefully evaluated. The main barriers to the increased use of tidal energy are the high cost and long period for the construction of the tidal generating system and concerns about impacts on sensitive estuarine ecosystems.  As noted previously, the economic viability of this option is highly dependent on the location chosen for application. 

Ocean Wave Energy

Ocean wave energy systems convert the kinetic and potential energy contained in the natural oscillations of ocean waves into electricity.  A variety of proposed mechanisms for the utilization of this energy source exist, most of which are still in the demonstration or prototype testing stage.  Surge devices and oscillating water column devices are the primary technologies for converting wave energy to electricity.

Wave energy research was intensive in 1970s and 1980s.  Research funding has slowed and wave energy applications are not likely to be competitive in the near future. The optimal regions for wave power applications typically occur between 40 and 60 degrees latitude, although seas that consistently experience trade winds can also produce sufficient wave energy for power applications. The potential for offshore/deep wave plants is large, but the technical barriers and associated costs are also considerably high.

The technical problems of dealing with adverse sea conditions, complexity and difficulty of electricity interconnection and transmission, and low reliability have kept wave energy systems from being developed commercially.  Furthermore, the high capital costs of such systems have deterred the implementation of wave energy systems.