Jump to Content
OCS Alternative Energy and Alternate Use Programmatic EIS
Home About the EIS Getting Involved OCS Alternative Energy and Alternate Use Guide EIS Documents News Frequently Asked Questions Glossary E-mail Services

Search
Offshore Alternative Energy Guide
 The Outer Continental Shelf
 Ocean Energy Resources
 Ocean Wave Energy
 Ocean Current Energy
 Offshore Wind Energy
 Offshore Solar Energy
 Hydrogen Generation
 Platform Alternate Use
 Images
 Maps
 Links

Subscribe

Frequently Asked Questions

E-mail E-mail this page
Printer Print version

Ocean Wave Energy

Ocean wave energy is captured directly from surface waves or from pressure fluctuations below the surface.

wave
Waves are caused by the wind blowing over the surface of the ocean. In many areas of the world, the wind blows with enough consistency and force to provide continuous waves. There is tremendous energy in the ocean waves. Wave power devices extract energy directly from the surface motion of ocean waves or from pressure fluctuations below the surface.

Wave power varies considerably in different parts of the world, and wave energy can't be harnessed effectively everywhere. Wave-power rich areas of the world include the western coasts of Scotland, northern Canada, southern Africa, Australia, and the northwestern coasts of the United States.

Ocean Wave Energy Technologies

A variety of technologies have been proposed to capture the energy from waves. Some of the more promising designs are undergoing demonstration testing at commercial scales.

Wave technologies have been designed to be installed in nearshore, offshore, and far offshore locations. The OCS Alternative Energy Programmatic EIS is concerned primarily with offshore and far offshore wave technologies. Offshore systems are situated in deep water, typically of more than 40 meters (131 feet).

While all wave energy technologies are intended to be installed at or near the water's surface, they differ in their orientation to the waves with which they are interacting and in the manner in which they convert the energy of the waves into other energy forms, usually electricity. The following wave technologies have been the target of recent development.

Terminator devices extend perpendicular to the direction of wave travel and capture or reflect the power of the wave. These devices are typically onshore or nearshore; however, floating versions have been designed for offshore applications. The oscillating water column is a form of terminator in which water enters through a subsurface opening into a chamber with air trapped above it. The wave action causes the captured water column to move up and down like a piston to force the air though an opening connected to a turbine.

A point absorber is a floating structure with components that move relative to each other due to wave action (e.g., a floating buoy inside a fixed cylinder). The relative motion is used to drive electromechanical or hydraulic energy converters.

Rendition of a wave farm made up of Permanent Magnet Linear Generator Buoysclick to view larger image
Rendition of a Wave Farm Made Up of Permanent Magnet Linear Generator Buoys
Point absorber wave energy farmclick to view larger image
Point Absorber Wave Energy Farm
Animation of Point Absorber Operation
Animation of Point Absorber Operation
(Quicktime required)

Attenuator wave energy deviceclick to view larger image
Attenuator Wave Energy Device

Attenuators are long multisegment floating structures oriented parallel to the direction of the waves. The differing heights of waves along the length of the device causes flexing where the segments connect, and this flexing is connected to hydraulic pumps or other converters.

Animation of Attenuator Device Operation
(Macromedia Flash Player Required)

 

 

"Wave Dragon" Prototype Overtopping Deviceclick to view larger image
"Wave Dragon" Prototype Overtopping Device

Overtopping devices have reservoirs that are filled by incoming waves to levels above the average surrounding ocean. The water is then released, and gravity causes it to fall back toward the ocean surface. The energy of the falling water is used to turn hydro turbines. Specially built seagoing vessels can also capture the energy of offshore waves. These floating platforms create electricity by funneling waves through internal turbines and then back into the sea.

Environmental Considerations

Potential environmental considerations for the development of wave energy include the following:

  • Positive or negative impacts on marine habitat (depending on the nature of additional submerged surfaces, above-water platforms, and changes in the seafloor);
  • Toxic releases from leaks or accidental spills of liquids used in those systems with working hydraulic fluids;
  • Visual and noise impacts (device-specific, with considerable variability in visible freeboard height and noise generation above and below the water surface);
  • Conflict with other sea space users, such as commercial shipping and recreational boating;

      For More Information

      Download the wave technology white paper:

      PDF Technology White Paper on Wave Energy Potential on the U.S. Outer Continental Shelf. (450 KB)

      The following presentation from the National Renewable Energy Laboratory also provides information on ocean-based renewable energy technologies, including wave energy technology. This presentation was shown at scoping meetings for the OCS Alternative Energy Programmatic EIS.

      PDF NREL Scoping Meeting Presentation: Renewable Energy Technologies for Use on the Outer Continental Shelf (3 MB)

      Links to additional information on this topic are also available on the Links page.