Wave power is the transport of
energyIn physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
by
ocean surface waveIn fluid dynamics, wind waves or, more precisely, wind-generated waves are surface waves that occur on the free surface of oceans, seas, lakes, rivers, and canals or even on small puddles and ponds. They usually result from the wind blowing over a vast enough stretch of fluid surface. Waves in the...
s, and the capture of that energy to do useful
workIn physics, work is a scalar quantity that can be described as the product of a force times the distance through which it acts, and it is called the work of the force. Only the component of a force in the direction of the movement of its point of application does work...
— for example,
electricity generationElectricity generation is the process of generating electric energy from other forms of energy.The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday...
, water desalination, or the
pumpA pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...
ing of water (into
reservoirA reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...
s). Machinery able to exploit wave power is generally known as a wave energy converter (WEC).
Wave power is distinct from the diurnal flux of
tidal powerTidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into useful forms of power - mainly electricity....
and the steady gyre of ocean currents. Wave power generation is not currently a widely employed commercial technology although there have been attempts at using it since at least 1890. In 2008, the first experimental
wave farmA wave farm or wave power farm is a collection of machines in the same location and used for the generation of wave power electricity.-Portugal:...
was opened in Portugal, at the Aguçadoura Wave Park.
Physical concepts
- See Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
, PowerIn physics, power is the rate at which energy is transferred, used, or transformed. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts—the more wattage, the more power, or equivalently the more electrical energy is used per unit...
and WorkIn physics, work is a scalar quantity that can be described as the product of a force times the distance through which it acts, and it is called the work of the force. Only the component of a force in the direction of the movement of its point of application does work...
for more information on these important physical concepts. See Wind wave for more information on ocean waves.
Waves are generated by wind passing over the surface of the sea. As long as the waves propagate slower than the wind speed just above the waves, there is an energy transfer from the wind to the waves. Both air pressure differences between the upwind and the lee side of a wave
crestA crest is the point on a wave with the maximum value or upward displacement within a cycle. A trough is the opposite of a crest, so the minimum or lowest point in a cycle.-Interference:...
, as well as friction on the water surface by the wind, making the water to go into the
shear stressA shear stress, denoted \tau\, , is defined as the component of stress coplanar with a material cross section. Shear stress arises from the force vector component parallel to the cross section...
causes the growth of the waves.
Wave heightIn fluid dynamics, the wave height of a surface wave is the difference between the elevations of a crest and a neighbouring trough. Wave height is a term used by mariners, as well as in coastal, ocean and naval engineering....
is determined by wind speed, the duration of time the wind has been blowing, fetch (the distance over which the wind excites the waves) and by the depth and topography of the seafloor (which can focus or disperse the energy of the waves). A given wind speed has a matching practical limit over which time or distance will not produce larger waves. When this limit has been reached the sea is said to be "fully developed".
In general, larger waves are more powerful but wave power is also determined by wave speed,
wavelengthIn physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
, and water
densityThe mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
.
Oscillatory motion is highest at the surface and diminishes exponentially with depth. However, for standing waves (
clapotisIn hydrodynamics, the clapotis is a non-breaking standing wave pattern, caused for example, by the reflection of a traveling surface wave train from a near vertical shoreline like a breakwater, seawall or steep cliff....
) near a reflecting coast, wave energy is also present as pressure oscillations at great depth, producing
microseismIn seismology, a microseism is defined as a faint earth tremor caused by natural phenomena. The term is most commonly used to refer to the dominant background seismic noise signal on Earth, which are mostly composed of Rayleigh waves and caused by water waves in the oceans and lakes...
s. These pressure fluctuations at greater depth are too small to be interesting from the point of view of wave power.
The waves propagate on the ocean surface, and the wave energy is also transported horizontally with the
group velocityThe group velocity of a wave is the velocity with which the overall shape of the wave's amplitudes — known as the modulation or envelope of the wave — propagates through space....
. The mean transport rate of the wave energy through a vertical
planeIn mathematics, a plane is a flat, two-dimensional surface. A plane is the two dimensional analogue of a point , a line and a space...
of unit width, parallel to a wave crest, is called the wave energy
fluxIn the various subfields of physics, there exist two common usages of the term flux, both with rigorous mathematical frameworks.* In the study of transport phenomena , flux is defined as flow per unit area, where flow is the movement of some quantity per time...
(or wave power, which must not be confused with the actual power generated by a wave power device).
Wave power formula
In deep water where the water depth is larger than half the
wavelengthIn physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
, the wave
energy fluxEnergy flux is the rate of transfer of energy through a surface. The quantity is defined in two different ways, depending on the context:# Rate of energy transfer per unit area...
is
[The energy flux is ]
with 
the group velocity, see The group velocity is 
, see the collapsed table "Properties of gravity waves on the surface of deep water, shallow water and at intermediate depth, according to linear wave theory" in the section "Wave energy and wave energy flux" below.
with
P the wave energy flux per unit of wave-crest length,
Hm0 the
significant wave heightIn physical oceanography, the significant wave height is defined traditionally as the mean wave height of the highest third of the waves , but now usually defined as four times the standard deviation of the surface elevation...
,
T the wave period,
ρ the water
densityThe mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
and
g the
acceleration by gravityThe gravity of Earth, denoted g, refers to the acceleration that the Earth imparts to objects on or near its surface. In SI units this acceleration is measured in metres per second per second or equivalently in newtons per kilogram...
. The above formula states that wave power is proportional to the wave period and to the square of the wave height. When the significant wave height is given in meters, and the wave period in seconds, the result is the wave power in kilowatts (kW) per meter of
wavefrontIn physics, a wavefront is the locus of points having the same phase. Since infrared, optical, x-ray and gamma-ray frequencies are so high, the temporal component of electromagnetic waves is usually ignored at these wavelengths, and it is only the phase of the spatial oscillation that is described...
length.
Example: Consider moderate ocean swells, in deep water, a few kilometers off a coastline, with a wave height of 3 meters and a wave period of 8 seconds. Using the formula to solve for power, we get
meaning there are 36 kilowatts of power potential per meter of coastline.
In major storms, the largest waves offshore are about 15 meters high and have a period of about 15 seconds. According to the above formula, such waves carry about 1.7 MW of power across each meter of wavefront.
An effective wave power device captures as much as possible of the wave energy flux. As a result the waves will be of lower height in the region behind the wave power device.
Wave energy and wave energy flux
In a
sea stateIn oceanography, a sea state is the general condition of the free surface on a large body of water—with respect to wind waves and swell—at a certain location and moment. A sea state is characterized by statistics, including the wave height, period, and power spectrum. The sea state varies with...
, the average energy density per unit area of
gravity waveIn fluid dynamics, gravity waves are waves generated in a fluid medium or at the interface between two media which has the restoring force of gravity or buoyancy....
s on the water surface is proportional to the wave height squared, according to linear wave theory:
[For a small-amplitude sinusoidal wave ]
with wave amplitude 
the wave energy density per unit horizontal area is 
or 
using the wave height 
for sinusoidal waves. In terms of the variance of the surface elevation 
the energy density is 
. Turning to random waves, the last formulation of the wave energy equation in terms of 
is also valid (Holthuijsen, 2007, p. 40), due to Parseval's theoremIn mathematics, Parseval's theorem usually refers to the result that the Fourier transform is unitary; loosely, that the sum of the square of a function is equal to the sum of the square of its transform. It originates from a 1799 theorem about series by Marc-Antoine Parseval, which was later...
. Further, the significant wave heightIn physical oceanography, the significant wave height is defined traditionally as the mean wave height of the highest third of the waves , but now usually defined as four times the standard deviation of the surface elevation...
is defined as 
, leading to the factor in the wave energy density per unit horizontal area.
where
E is the mean wave energy density per unit horizontal area (J/m
2), the sum of
kineticThe kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...
and
potential energyIn physics, potential energy is the energy stored in a body or in a system due to its position in a force field or due to its configuration. The SI unit of measure for energy and work is the Joule...
density per unit horizontal area. The potential energy density is equal to the kinetic energy, both contributing half to the wave energy density
E, as can be expected from the equipartition theorem. In ocean waves, surface tension effects are negligible for wavelengths above a few
decimetreA decimetre is a unit of length in the metric system, equal to one tenth of a metre, the SI base unit of length. In simple words there are 10 cm in a decimetre....
s.
As the waves propagate, their energy is transported. The energy transport velocity is the
group velocityThe group velocity of a wave is the velocity with which the overall shape of the wave's amplitudes — known as the modulation or envelope of the wave — propagates through space....
. As a result, the wave energy
fluxIn the various subfields of physics, there exist two common usages of the term flux, both with rigorous mathematical frameworks.* In the study of transport phenomena , flux is defined as flow per unit area, where flow is the movement of some quantity per time...
, through a vertical plane of unit width perpendicular to the wave propagation direction, is equal to:
with
cg the group velocity (m/s).
Due to the
dispersion relationIn fluid dynamics, dispersion of water waves generally refers to frequency dispersion, which means that waves of different wavelengths travel at different phase speeds. Water waves, in this context, are waves propagating on the water surface, and forced by gravity and surface tension...
for water waves under the action of gravity, the group velocity depends on the wavelength
λ, or equivalently, on the wave period
T. Further, the dispersion relation is a function of the water depth
h. As a result, the group velocity behaves differently in the limits of deep and shallow water, and at intermediate depths:
Properties of gravity waves on the surface of deep water, shallow water and at intermediate depth, according to linear wave theoryIn fluid dynamics, Airy wave theory gives a linearised description of the propagation of gravity waves on the surface of a homogeneous fluid layer. The theory assumes that the fluid layer has a uniform mean depth, and that the fluid flow is inviscid, incompressible and irrotational...
|
| quantity |
symbol |
units |
deep water( h > ½ λ ) |
shallow water( h < 0.05 λ ) |
intermediate depth( all λ and h ) |
| phase velocity The phase velocity of a wave is the rate at which the phase of the wave propagates in space. This is the speed at which the phase of any one frequency component of the wave travels. For such a component, any given phase of the wave will appear to travel at the phase velocity...
|
 |
m / s |
 |
 |
 |
| group velocity The group velocity of a wave is the velocity with which the overall shape of the wave's amplitudes — known as the modulation or envelope of the wave — propagates through space....
[For determining the group velocity the angular frequency ω is considered as a function of the wavenumber k, or equivalently, the period T as a function of the wavelength λ.] |
 |
m / s |
 |
 |
 |
| ratio |
 |
- |
 |
 |
 |
| wavelength |
 |
m |
 |
 |
for given period T, the solution of:  |
| general |
| wave energy density |
 |
J / m2 |
 |
wave energy fluxIn the various subfields of physics, there exist two common usages of the term flux, both with rigorous mathematical frameworks.* In the study of transport phenomena , flux is defined as flow per unit area, where flow is the movement of some quantity per time...
|
 |
W / m |
 |
angular frequencyFrequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
|
 |
rad Radian is the ratio between the length of an arc and its radius. The radian is the standard unit of angular measure, used in many areas of mathematics. The unit was formerly a SI supplementary unit, but this category was abolished in 1995 and the radian is now considered a SI derived unit...
/ s |
 |
| wavenumber In the physical sciences, the wavenumber is a property of a wave, its spatial frequency, that is proportional to the reciprocal of the wavelength. It is also the magnitude of the wave vector...
|
 |
rad / m |
 |
Deep water characteristics and opportunities
Deep water corresponds with a water depth larger than half the wavelength, which is the common situation in the sea and ocean. In deep water, longer period waves propagate faster and transport their energy faster. The deep-water group velocity is half the
phase velocityThe phase velocity of a wave is the rate at which the phase of the wave propagates in space. This is the speed at which the phase of any one frequency component of the wave travels. For such a component, any given phase of the wave will appear to travel at the phase velocity...
. In
shallow waterWhen waves travel into areas of shallow water, they begin to be affected by the ocean bottom. The free orbital motion of the water is disrupted, and water particles in orbital motion no longer return to their original position. As the water becomes shallower, the swell becomes higher and steeper,...
, for wavelengths larger than twenty times the water depth, as found quite often near the coast, the group velocity is equal to the phase velocity.
The regularity of deep-water ocean swells, where "easy-to-predict long-wavelength oscillations" are typically seen, offers the opportunity for the development of energy harvesting technologies that are potentially less subject to physical damage by near-shore cresting waves.
History
The first known patent to utilize energy from ocean waves dates back to 1799 and was filed in Paris by Girard and his son. An early application of wave power was a device constructed around 1910 by Bochaux-Praceique to light and power his house at
RoyanRoyan is a commune in the Charente-Maritime department, along the Atlantic Ocean, in southwestern France.A seaside resort, Royan is in the heart of an urban area estimated at 38,638 inhabitants, which makes it the fourth-largest conurbation in the department, after La Rochelle, Rochefort and Saintes...
, near
BordeauxBordeaux is a port city on the Garonne River in the Gironde department in southwestern France.The Bordeaux-Arcachon-Libourne metropolitan area, has a population of 1,010,000 and constitutes the sixth-largest urban area in France. It is the capital of the Aquitaine region, as well as the prefecture...
in France. It appears that this was the first Oscillating Water Column type of wave energy device. From 1855 to 1973 there were already 340 patents filed in the UK alone.
Modern scientific pursuit of wave energy was however pioneered by
Yoshio MasudaYoshio Masuda was a former Japanese naval commander, regarded as the father of modern wave energy technology. Among other devices, the now used principle of Oscillating Water Column is regarded as his invention. It was initially used for small-scale navigation buoys.-References:...
's experiments in the 1940s. He has tested various concepts of wave energy devices at sea, with several hundred units used to power navigation lights. Among these was the concept of extracting power from the angular motion at the joints of an articulated raft, which was proposed in the 1950s by Masuda.
A renewed interest in wave energy was motivated by the
oil crisis in 1973The 1973 oil crisis started in October 1973, when the members of Organization of Arab Petroleum Exporting Countries or the OAPEC proclaimed an oil embargo. This was "in response to the U.S. decision to re-supply the Israeli military" during the Yom Kippur war. It lasted until March 1974. With the...
. A number of university researchers reexamined the potential of generating energy from ocean waves, among whom notably were
Stephen SalterStephen Hugh Salter is Emeritus Professor of Engineering Design at the University of Edinburgh and inventor of the eponymous Salter duck wave energy device...
from the
University of EdinburghThe University of Edinburgh, founded in 1583, is a public research university located in Edinburgh, the capital of Scotland, and a UNESCO World Heritage Site. The university is deeply embedded in the fabric of the city, with many of the buildings in the historic Old Town belonging to the university...
, Kjell Budal and
Johannes FalnesJohannes Falnes is a Professor Emeritus of Experimental Physics at the Department of Physics of the Norwegian University of Science and Technology noted for his contributions to wave energy research...
from
Norwegian Institute of TechnologyThe Norwegian Institute of Technology, known by its Norwegian abbrevation NTH was a science institute in Trondheim, Norway. It was established in 1910, and existed as an independent technical university for 85 years, after which it was merged into the University of Trondheim as an independent...
(now merged into
Norwegian University of Science and TechnologyThe Norwegian University of Science and Technology , commonly known as NTNU, is located in Trondheim. NTNU is the second largest of the eight universities in Norway, and, as its name suggests, has the main national responsibility for higher education in engineering and technology...
),
Michael E. McCormickMichael E. McCormick is Corbin A. McNeill Professor Emeirtus of the Department of Naval Architecture and Ocean Engineering at the U. S. Naval Academy. He is one of the pioneers of modern wave energy research....
from U. S. Naval Academy,
David EvansDavid V. Evans is a British applied mathematician noted for his contributions to water waves and acoustics. Together with John Nicholas Newman, he initiated the International Workshop on Water Waves and Floating Bodies. He is also known for the Bristol cylinder, a wave energy converter...
from Bristol University, Michael French from University of Lancaster,
John NewmanJohn Nicholas Newman is an American applied mathematician noted for his contributions to marine hydrodynamics. Together with David Evans, he initiated the International Workshop on Water Waves and Floating Bodies. He is also known for his contribution in the development of the wave-structure...
and
Chiang C. MeiChiang Chung "CC" Mei is Ford Professor of Engineering, Emeritus, at the Department of Civil and Environmental Engineering of Massachusetts Institute of Technology, known for his contributions in fluid mechanics with applications to civil, environmental, and coastal engineering.He has been an...
from MIT.
Stephen Salters
1974 inventionThe year 1974 in science and technology involved some significant events, listed below.-Astronomy and space exploration:* February 8 - After 84 days in space, the last crew of the temporary American space station Skylab return to Earth....
became known as
Salter's DuckSalter's duck, also known as the nodding duck or by its official name the Edinburgh duck, is a device that converts wave power into electricity. The wave impact induces rotation of gyroscopes located inside a pear-shaped "duck", and an electrical generator converts this rotation into electricity...
or Nodding Duck, although it was officially referred to as the Edinburgh Duck. In small scale controlled tests, the Duck's curved cam-like body can stop 90% of wave motion and can convert 90% of that to electricity giving 81% efficiency.
In the 1980s, as the oil price went down, wave-energy funding was drastically reduced. Nevertheless, a few first-generation prototypes were tested at sea. More recently, following the issue of climate change, there is again a growing interest worldwide for renewable energy, including wave energy.
Modern technology
Wave power devices are generally categorized by the
method used to capture the energy of the waves, by
location and by the
power take-off system. Method types are point absorber or buoy; surfacing following or attenuator oriented parallel to the direction of wave propagation; terminator, oriented perpendicular to the direction of wave propagation; oscillating water column; and overtopping. Locations are shoreline, nearshore and offshore. Types of power take-off include:
hydraulic ramA hydraulic ram, or hydram, is a cyclic water pump powered by hydropower. It functions as a hydraulic transformer that takes in water at one "hydraulic head" and flow-rate, and outputs water at a higher hydraulic-head and lower flow-rate...
,
elastomeric hose pumpA peristaltic pump, or roller pump, is a type of positive displacement pump used for pumping a variety of fluids. The fluid is contained within a flexible tube fitted inside a circular pump casing . A rotor with a number of "rollers", "shoes" or "wipers" attached to the external circumference...
, pump-to-shore,
hydroelectric turbineHydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...
, air turbine, and
linear electrical generatorA linear motor is an electric motor that has had its stator and rotor "unrolled" so that instead of producing a torque it produces a linear force along its length...
. Some of these designs incorporate
parabolic reflectorA parabolic reflector is a reflective device used to collect or project energy such as light, sound, or radio waves. Its shape is that of a circular paraboloid, that is, the surface generated by a parabola revolving around its axis...
s as a means of increasing the wave energy at the point of capture. These capture systems use the rise and fall motion of waves to capture energy. Once the wave energy is captured at a wave source, power must be carried to the point of use or to a connection to the electrical grid by
transmissionElectric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...
power cablesSubmarine power cables are major transmission cables for carrying electric power below the surface of the water. These are called "submarine" because they usually carry electric power beneath salt water but it is also possible to use submarine power cables beneath fresh water...
. The table contains descriptions of some wave power systems:
| Device |
Proponent |
Country of Origin |
Capture Method Category |
Location Category |
Power take off Category |
Year Announced |
Notes |
| ProteanTM Energy Wave Energy Converter |
Protean Energy Ltd |
Australia |
Point-absorber wave-buoy device |
Offshore |
Direct drive energy conversion |
2004 |
The Protean™ WEC technology is a unique type of wave buoy or point absorber. When deployed, it sits on the ocean surface where the energy density is the highest. The Protean™ WEC technology works on a buoy and tethering system. The buoy converts relative movement between the static ocean floor and the floating buoy into energy. The innovative tension mooring system uses a combination of cables running from an ocean floor mounted clump weight to the WEC buoy on the ocean surface. The Protean™ technology has no exposed turbines or moving parts that are dangerous to marine life and each unit has a small environmental footprint.
|
| PowerBuoy |
Ocean Power Technologies |
US |
Buoy |
Offshore |
Hydroelectric turbine |
1997 |
In the United States, the Pacific Northwest Generating Cooperative is funding construction of a commercial wave-power park at Reedsport, Oregon that will utilize this technology which consists of modular, ocean-going buoys. The rise and fall of the waves moves hydraulic fluid within the buoy and spins a generator. The electricity is transmitted to shore over a submerged transmission line. A 150 kW buoy has a diameter of 36 feet (11 m) and is 145 feet (44 m) tall, with approximately 30 feet of the unit rising above the ocean surface. Using a three-point mooring system, they are designed to be installed one to five miles (8 km) offshore in water 100 to 200 feet (60 m) deep. |
Pelamis Wave Energy ConverterThe Pelamis Wave Energy Converter is a technology that uses the motion of ocean surface waves to create electricity. The machine is made up of connected sections which flex and bend as waves pass; it is this motion which is used to generate electricity....
|
Pelamis Wave Power Pelamis Wave Power designs and manufactures the Pelamis Wave Energy Converter–a technology that uses the motion of ocean surface waves to create electricity...
|
UK (Scottish) |
Surface-following attenuator |
Offshore |
Hydraulic |
1998 |
The Pelamis machine consists of a series of semi-submerged cylindrical sections linked by hinged joints. As waves pass along the length of the machine, the sections move relative to one another. The wave-induced motion In physics, motion is a change in position of an object with respect to time. Change in action is the result of an unbalanced force. Motion is typically described in terms of velocity, acceleration, displacement and time . An object's velocity cannot change unless it is acted upon by a force, as...
of the sections is resisted by hydraulic cylinderA Hydraulic cylinder is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in engineering vehicles.- Operation :...
s which pump high pressure oil through hydraulic motorsHydraulic machines are machinery and tools that use liquid fluid power to do simple work. Heavy equipment is a common example.In this type of machine, hydraulic fluid is transmitted throughout the machine to various hydraulic motors and hydraulic cylinders and which becomes pressurised according to...
via smoothing hydraulic accumulators. The hydraulic motors drive electrical generatorIn electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...
s to produce electricity. Pelamis Wave Power first tested and grid connected a Pelamis machine in 2004 at the European Marine Energy Center. The first of a second generation of machines, the P2 started grid connected tests off Orkney in 2010, the machine is owned by E.ONE.ON AG, marketed with an interpunct as E•ON, is the holding company of the world's largest investor-owned energy service provider based in Düsseldorf, Germany. The name comes from the Greek word aeon which means eternity....
..
|
| Poseidon |
Floating Power Plant |
Denmark |
Surface-following attenuator and wind turbine |
Offshore |
Hydroelectric turbine and wind turbine |
1998 |
The Poseidon, aka. Floating Power Plant, combines wave and wind energy forms. It's base is a semi-submerged platform (three quarters submerged) with the wave absorbers aligned in a row perpendicular to the wave direction. Three wind turbines are mounted on the platform. The platform is secured with a turret mooring system, known from FPSO vessels A floating production, storage and offloading unit is a floating vessel used by the offshore industry for the processing of hydrocarbons and for storage of oil. A FPSO vessel is designed to receive hydrocarbons produced from nearby platforms or subsea template, process them, and store oil until it...
. The platform will always turns against the wave front. The device has a rated power production of 177kWe, where 140kWe origins from the wave floaters and 33kWe from the three wind turbines. The device can be built up to six times larger with a rated power production of 11-12MWe.
|
| SurgeDrive |
AquaGen Technologies |
Australia |
Buoy |
Offshore |
Tension transfer |
? |
This technology captures wave energy from point absorber buoyancy units and transfers the pure wave forces out of the water via tension transfer elements. The ‘out-of-water’ Energy Conversion Module then converts the wave forces into electricity or desalinated water. The advantage of this technology is that by removing the more complex equipment of the system from the water, the maintenance and hence generating costs are significantly reduced whilst the storm survivability of the system is greatly enhanced. |
| WaveDragon |
Erik Friis-Madsen |
Denmark |
Surface-following attenuator |
Offshore |
Hydroelectric turbine |
2003 |
With the Wave Dragon wave energy converter large wing reflectors focus waves up a ramp into an offshore reservoir. The water returns to the ocean by the force of gravity via hydroelectric generators.
|
| Anaconda Wave Energy Converter |
Checkmate SeaEnergy.[25] |
UK |
Surface-following attenuator |
Offshore |
Hydroelectric turbine |
2008 |
In the early stages of development, the device is a 200 metres (656.2 ft) long rubber tube which is tethered underwater. Passing waves will instigate a wave inside the tube, which will then propagates down its walls, driving a turbine at the far end. |
| AquaBuOY |
Finavera Wind Energy, later SSE Renewables Limited |
Ireland-Canada-Scotland |
Buoy |
Offshore |
xxx |
2003 |
In 2009 Finavera Renewables surrendered its wave energy permits from FERC.[27] In July 2010 Finavera announced that it had entered into a definitive agreement to sell all assets and intellectual property related to the AquaBuOY wave energy technology. |
| FlanSea (Flanders Electricity from the Sea) |
FlanSea |
Belgium |
Buoy |
Offshore |
Hydroelectric turbine |
2010 |
A point absorber buoy developed for use in the southern North Sea conditions.[31][32][33] It works by means of a cable that due to the bobbing effect of the buoy, generates electricity. |
| SeaRaser |
Alvin Smith (Dartmouth Wave Energy) |
UK |
Buoy |
Nearshore |
Hydraulic ram |
2008 |
Uses pumping technique to gather wave energy. |
| CETO Wave Power CETO is a wave energy technology that converts ocean swells into renewable power and desalinated freshwater. It was developed by Carnegie Wave Energy Limited, an Australian ASX-listed inventor and owner of the patented device...
|
Carnegie |
Australia |
Buoy |
Offshore |
Pump-to-shore |
1999 |
Currently being tested off Fremantle, Western Australia,[35] the device consists of a single piston pump attached to the sea floor with a float (buoy) tethered to the piston. Waves cause the float to rise and fall, generating pressurized water, which is piped to an onshore facility to drive hydraulic generators or run reverse osmosis water desalination.
|
| Unnamed Ocean Wave-Powered Generator |
SRI International |
US |
Buoy |
Offshore |
Electroactive polymer artificial muscle |
2004 |
A type of wave buoys, built using special polymers, is being developed by Stanford Research Institute. |
| Wavebob Wavebob is a wave energy converter which has been in development since 1999. In 2006 it commenced the first of a number of sea trials in Galway Bay in Ireland during which it was tested its a 1/4 scale device for short periods at the SEAI 1/4 Scale Wave Power Testing facility which is located in...
|
Wavebob |
Ireland |
Buoy |
Offshore |
Direct Drive Power Take off |
1999 |
Wavebob have conducted some ocean trials, as well as extensive tank tests. It is an ccean-going heaving buoy, with a submerged tank which captures additional mass of seawater for added power and tunability, and as a safety feature (Tank "Venting") |
|
| Oyster wave energy converter The Oyster is a hydro-electric wave energy device that uses the motion of ocean waves to generate electricity. It is made up of a Power Connector Frame , which is bolted to the seabed, and a Power Capture Unit . The PCU is a hinged buoyant flap that moves back and forth with movement of the waves...
|
Aquamarine Power |
UK (Scots-Irish) |
Oscillating wave surge converter |
Nearshore |
Pump-to-shore (hydro-electric turbine) |
2005 |
The wave energy device captures the energy found in nearshore waves and converts it into electricity. The systems consists of a hinged mechanical flap connected to the seabed at around 10m depth. Each passing wave moves the flap which drives hydraulic pistons to deliver high pressure water via a pipeline to an onshore turbine which generates electricity. In November 2009, the first full-scale demonstrator Oyster began producing power when it was launched at the European Marine Energy Centre (EMEC) on Orkney. |
| OE buoy An OE Buoy or Ocean Energy Buoy is a wave power device that was deployed in half-scale test mode in Spiddal near Galway in Ireland for over two years between 2007 and 2009...
|
Ocean Energy |
Ireland |
Buoy |
Offshore |
xxx |
2006 |
In September 2009 completed a 2-year sea trial in one quarter scale form. The OE buoy has only one moving part. |
| Lysekil Project The Lysekil project is an ongoing wave power project which is run by the Centre for Renewable Electric Energy Conversion at Uppsala University in Sweden.-Introduction:...
|
Uppsala UniversityUppsala University is a research university in Uppsala, Sweden, and is the oldest university in Scandinavia, founded in 1477. It consistently ranks among the best universities in Northern Europe in international rankings and is generally considered one of the most prestigious institutions of...
|
Sweden |
Buoy |
Offshore |
Linear generator |
2002 |
Direct driven linear generator placed on the seabed. The generator is connected to a buoy at the surface via a line. The movements of the buoy will drive the translator in the generator. The advantage of this setup is a less complex mechanical system with potentially a smaller need for maintenance. One drawback is a more complicated electrical system. |
| Oceanlinx Oceanlinx is a leading international company which has created Wave Energy Converter technology. The company has developed proprietary technology for extracting energy from ocean waves and converting it into either electricity or desalinated sea water. Known as Energetech until 2007, Oceanlinx has...
|
Oceanlinx |
Australia |
Buoy |
Offshore |
Hydroelectric turbine |
1997 |
An Australian firm is developing this deep-water technology to generate electricity from, ostensibly, easy-to-predict long-wavelength ocean swell oscillations. Oceanlinx recently began installation of a third and final demonstration-scale, grid-connected unit near Port Kembla, near Sydney, Australia, a 2.5 MWe system that is expected to go online in early 2010, when its power will be connected to the Australian grid. The company's much smaller first-generation prototype unit, in operation since 2006, was since disassembled. |
| SDE Sea Waves Power Plant The SDE Sea Wave Power Plant is a type of renewable energy power plant utilizing sea wave energy for the production of electricity.-Description:...
|
SDE Energy Ltd. |
Israel |
Buoy |
Inshore |
Hydroelectric turbine |
xxx |
A breakwater-based wave energy converter, this device is built close to the shore and utilizes the vertical motion of buoys for creating hydraulic pressure which in turn operates the system's generators. In 2010 it began construction of a new 250 kWh model in the port of Jaffa, Tel Aviv and preparing to construct its standing orders for a 100mWh power plants in the islands of Zanzibar and Kosrae, Micronesia. |
| WaveRoller |
AW-Energy Oy |
Finland |
Surface-following attenuator |
Offshore |
Pump-to-shore |
1994 |
The WaveRoller is a plate anchored on the sea bottom by its lower part. The back and forth movement of surge moves the plate. The kinetic energy transferred to this plate is collected by a piston pump. Full-scale demonstration project built off Portugal in 2009. |
| Cycloidal Wave Energy Converter |
Atargis Energy Inc. |
US |
submerged wave-cancelling turbine |
Offshore |
Hydroelectric turbine |
2011 |
Atargis Energy Inc. is developing a long ocean wave-cancelling device that simulations and small-scale tests show can capture more than 95% of the energy of long ocean waves. Using a submerged cycloidal turbine to convert wave power into lift, the turbine converts waves to rotational energy, a rotating shaft generating electrical energy. The initial concept came from the so-called Voith Schneider propeller which is used to power tugboats. Atargis Energy is commercializing the concept with the support of the US Department of Energy. |
| Dexawave |
Dexawave A/S |
Denmark |
Surface-following attenuator |
Offshore |
Hydraulic ram/
Hydroelectric turbine |
2008 |
The Dexawave concept consists of two rigid pontoons, connected through a patented hinge system.
The one pontoon can pivot relative to the other. A hydraulic power take-off system on top of the converter will generate up to 250 kW.
By November 2011, following extensive laboratory tests, 1:8 and 1:5 concept demonstrators have been at sea off the coasts of HanstholmHanstholm is a small town and a former island, now elevated area in Thisted municipality of Region Nordjylland, located in the northern part of Denmark. Coordinates:...
, DenmarkDenmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
and
MaltaMalta , officially known as the Republic of Malta , is a Southern European country consisting of an archipelago situated in the centre of the Mediterranean, south of Sicily, east of Tunisia and north of Libya, with Gibraltar to the west and Alexandria to the east.Malta covers just over in...
, Republic of Malta. |
Potential
The realistically usable worldwide resource has been estimated to be greater than 2 TW.
Locations with the most potential for wave power include the western seaboard of Europe, the northern coast of the UK, and the Pacific coastlines of North and South America, Southern Africa, Australia, and New Zealand. The north and south temperate zones have the best sites for capturing wave power. The prevailing
westerliesThe Westerlies, anti-trades, or Prevailing Westerlies, are the prevailing winds in the middle latitudes between 30 and 60 degrees latitude, blowing from the high pressure area in the horse latitudes towards the poles. These prevailing winds blow from the west to the east, and steer extratropical...
in these zones blow strongest in winter. Waves are very predictable; waves that are caused by winds can be predicted five days in advance.
Challenges
There is a potential impact on the marine environment. Noise pollution, for example, could have negative impact if not monitored, although the noise and visible impact of each design varies greatly.. Other biophysical impacts (flora and fauna, sediment regimes and water column structure and flows) of scaling up the technology is being studied. In terms of socio-economic challenges, wave farms can result in the displacement of commercial and recreational fishermen from productive fishing grounds, can change the pattern of beach sand nourishment, and may represent hazards to safe navigation. Waves generate about 2,700 gigawatts of power. Of those 2,700 gigawatts, only about 500 gigawatts can be captured with the current technology.
Wave farms
The Aguçadoura Wave Farm was the world's first
wave farmA wave farm or wave power farm is a collection of machines in the same location and used for the generation of wave power electricity.-Portugal:...
. It was located 5 km (3 mi) offshore near
Póvoa de VarzimPóvoa de Varzim is a Portuguese city in the Norte Region and sub-region of Greater Porto, with a 2011 estimated population of 63,364. According to the 2001 census, there were 63,470 inhabitants with 42,396 living in the city proper. The urban area expanded, southwards, to Vila do Conde, and there...
north of Oporto in
PortugalPortugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
. The farm was designed to use three
PelamisThe Pelamis Wave Energy Converter is a technology that uses the motion of ocean surface waves to create electricity. The machine is made up of connected sections which flex and bend as waves pass; it is this motion which is used to generate electricity....
wave energy converters to convert the motion of the
ocean surface waveIn fluid dynamics, wind waves or, more precisely, wind-generated waves are surface waves that occur on the free surface of oceans, seas, lakes, rivers, and canals or even on small puddles and ponds. They usually result from the wind blowing over a vast enough stretch of fluid surface. Waves in the...
s into electricity, totalling to 2.25MW in total installed capacity. The farm first generated electricity in July 2008 and was officially opened on the 23rd of September 2008, by the Portuguese Minister of Economy. The wave farm was shut down two months after the official opening in November 2008 as a result of the financial collapse of Babcock & Brown due to the global economic crisis. The machines were off-site at this time due to technical problems, and although resolved have not returned to site and were subsequently scrapped in 2011 as the technology had moved on to the P2 variant as supplied to Eon and Scottish Power Renewables. A second phase of the project planned to increase the installed capacity to 21MW using a further 25 Pelamis machines is in doubt following Babcock's financial collapse.
Funding for a 3MW wave farm in Scotland was announced on 20 February 2007 by the
Scottish ExecutiveThe Scottish Government is the executive arm of the devolved government of Scotland. It was established in 1999 as the Scottish Executive, from the extant Scottish Office, and the term Scottish Executive remains its legal name under the Scotland Act 1998...
, at a cost of over 4 million
poundsThe pound sterling , commonly called the pound, is the official currency of the United Kingdom, its Crown Dependencies and the British Overseas Territories of South Georgia and the South Sandwich Islands, British Antarctic Territory and Tristan da Cunha. It is subdivided into 100 pence...
, as part of a £13 million funding package for marine power in Scotland. The first of 66 machines was launched in May 2010.
Funding has also been announced for the development of a
Wave hubThe Wave Hub is a wave power research project. The project is developed approximately off Hayle, on the north coast of Cornwall, United Kingdom. The hub is a 'socket' sitting on the seabed for wave energy converters to be plugged into; it will have connections to it from arrays of four kinds of...
off the north coast of Cornwall, England. The Wave hub will act as giant extension cable, allowing arrays of wave energy generating devices to be connected to the electricity grid. The Wave hub will initially allow 20MW of capacity to be connected, with potential expansion to 40MW. Four device manufacturers have so far expressed interest in connecting to the Wave hub.
The scientists have calculated that wave energy gathered at Wave Hub will be enough to power up to 7,500 households. Savings that the Cornwall wave power generator will bring are significant: about 300,000 tons of carbon dioxide in the next 25 years.
A
CETOCETO is a wave energy technology that converts ocean swells into renewable power and desalinated freshwater. It was developed by Carnegie Wave Energy Limited, an Australian ASX-listed inventor and owner of the patented device...
wave farm off the coast of Western Australia has been operating to prove commercial viability and, after preliminary environmental approval, is poised for further development.
Patents
—
Apparatus and method of extracting wave energy - The original "Salter's Duck" patent —
Apparatus for use in the extraction of energy from waves on water - Salter's method for improving "duck" efficiency —
Piezoelectric rotary electrical energy generator —
Wave energy converters utilizing pressure differences
See also
- CETO Wave Power
CETO is a wave energy technology that converts ocean swells into renewable power and desalinated freshwater. It was developed by Carnegie Wave Energy Limited, an Australian ASX-listed inventor and owner of the patented device...
- Index of wave articles
- Ocean thermal energy conversion
Ocean Thermal Energy Conversion uses the difference between cooler deep and warmer shallow or surface ocean waters to run a heat engine and produce useful work, usually in the form of electricity....
- O. H. Hinsdale Wave Research Laboratory
O. H. Hinsdale Wave Research Laboratory is a research facility in Corvallis, Oregon, United States. Operated by Oregon State University’s Coastal & Ocean Engineering Program within the Department of Civil, Construction, and Environmental Engineering. Built in 1972, the laboratory was designated as...
- World energy resources and consumption
]World energy consumption in 2010: over 5% growthEnergy markets have combined crisis recovery and strong industry dynamism. Energy consumption in the G20 soared by more than 5% in 2010, after the slight decrease of 2009. This strong increase is the result of two converging trends...
External links