Ocean Wave Energy
Ocean wave energy is captured directly from surface
waves or from pressure fluctuations below the surface.
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
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
Animation of Point Absorber
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.
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.
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:
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
Links to additional information on this topic are also available
on the Links