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Pelamis Wave Energy Converter

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The 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.

Developed by the Scottish company Pelamis Wave Power (formerly Ocean Power Delivery), it was the world’s first commercial scale machine to generate electricity into the grid from offshore wave energy and the first to be used in a commercial wave farm project.[1] The first full scale prototype was successfully installed and generated electricity to the UK grid at the European Marine Energy Centre in Orkney, Scotland in August 2004.[2] The first wave farm consisting of three Pelamis machines and located off the coast of Portugal, was officially opened in September 2008.[3]




The Pelamis is an attenuating wave energy converter designed with survivability at the fore. The Pelamis’s long thin shape means it is almost invisible to hydrodynamic forces, namely inertia, drag, and slamming, which in large waves give rise to large loads. Its novel joint configuration is used to induce a tunable cross-coupled resonant response. Control of the restraint applied to the joints allows this resonant response to be ‘turned-up’ in small seas where capture efficiency must be maximised or ‘turned-down’ to limit loads and motions in survival conditions.[4]


The Pelamis device consists of a series of semi-submerged cylindrical sections linked by hinged joints. The wave-induced relative motion of these sections is resisted by hydraulic cylinders which pump high pressure oil through hydraulic motors via smoothing hydraulic accumulators. The hydraulic motors drive electrical generators to produce electricity. Power from all the joints is fed down a single umbilical cable to a junction on the sea bed. Several devices can be connected together and linked to shore through a single seabed cable.


1 of 3 Pelamis machines at the Aguçadoura Wave Park


The Portuguese minister of the economy officially opened the worlds first wave farm, consisting of three Pelamis wave energy converters, on 23 September 2008.[3] The farm is located at the Aguçadoura Wave Park near Póvoa de Varzim in Portugal. It has an installed capacity of 2.25MW, enough to meet the average electricity demand of more than 1,500 Portuguese homes.[5]

The first Pelamis machine was installed at the site in July 2008.[6] The installation followed the successful conclusion of work to replace a failed subsea buoyancy unit on the mooring system.[7] After work was completed to replace the buoyancy units on the remaining two mooring connection points all three machines were simultaneously connected to the grid in September.[8] The farm was successfully commissioned and operated during the summer and autumn of 2008, producing power into the Portuguese national grid.[9]

The project was originally conceived by the Portuguese renewable energy company, Enersis, which developed and financed the project and which was subsequently bought by the Australian infrastructure company Babcock & Brown for €490m in December 2005. Since the last quarter of 2008 Babcock & Brown had its shares suspended and has been in a managed process of selling its assets, including the Agucadoura project. In March 2009 Babcock & Brown went into voluntary administration.[10]

In November 2008 the Pelamis machines were brought back into harbor at Leixões due to a technical problem with some of the bearings for which a solution has been found. However the machines are likely to remain offline until a new partner is found to take over Babcock & Brown’s 77% share in the project.[9]

A second phase of the project was planned to increase the installed capacity from 2.25MW to 21MW using a further 25 Pelamis machines.[11]


Funding for Scotland’s first wave farm was announced by the Scottish Executive on 22 February 2007. It will have an installed capacity of 3 MW provided by four Pelamis machines. The farm will be located at the European Marine Test Centre off the coast of Orkney. The funding of just over £4 million is part of a £13 million funding package for marine power in Scotland.

Pelamis Wave Power announced an order from E.on for a P-2 machine, in February 2009.[12] The P-2 device is the next generation of Pelamis Wave Energy Converter and will be constructed at the company’s new facilities in Leith Docks, Edinburgh.[13]

In December 2009, Pelamis Wave Power announced a joint project with Vattenfall[14] to develop a large wave farm off the coast of Shetland.


Pelamis Wave Power has also expressed an interest in installing Pelamis devices at the Wave hub development off the north coast of Cornwall, in England and in the Pacific ocean off the coast of Tillamook, Oregon.


Pelamis platurus is a yellow-bellied sea snake that lives in tropical and subtropical waters. It prefers shallow inshore waters.


2 of 3 Pelamis machines in the harbour of Peniche, Portugal.

Pelamis on site at EMEC, the planned location for Scotland’s first wave farm.

The front of the Pelamis machine bursting through a wave at the Aguçadoura Wave Park

See also


  1. ^ “Pelamis Wave Power”. pelamiswave.com. http://www.pelamiswave.com/index.php. Retrieved 2008-08-06.
  2. ^ “Wave Site Activity”. European Marine Energy Centre. http://www.emec.org.uk/wave_site_activity.asp. Retrieved 2008-09-28.
  3. ^ a b “23 de Setembro de 2008”. Government of Portugal. http://www.portugal.gov.pt/portal/pt/comunicacao/agenda/20080923.htm. Retrieved 2008-09-24.
  4. ^ “P-750 Wave Energy Converter” (PDF). pelamiswave.com. http://www.pelamiswave.com/media/pelamisbrochure.pdf. Retrieved 2008-08-06.
  5. ^ “Wave energy contract goes abroad”. BBC Scotland. 2005-05-19. http://news.bbc.co.uk/1/hi/scotland/4563077.stm. Retrieved 2008-08-06.
  6. ^ “First Electricity Generation in Portugal”. http://www.pelamiswave.com/news_archive.php?offset=6. Retrieved 2008-07-15.
  7. ^ “Portugal Embraces Wave Power”. BBC News. 2008-09-24. http://news.bbc.co.uk/1/hi/programmes/working_lunch/7633597.stm. Retrieved 2008-10-24.
  8. ^ “Recession leaves Pelamis wave energy project struggling to stay afloat”. http://www.guardian.co.uk/environment/2009/mar/19/pelamis-wave-power-recession. Retrieved 2009-03-19.
  9. ^ a b “Statement on Agucadoura Project”. http://www.pelamiswave.com/news.php?id=32. Retrieved 2009-03-22.
  10. ^ “It’s game over foe investment bank Babcock & Brown”. http://www.theaustralian.news.com.au/business/story/0,28124,25183580-36418,00.html. Retrieved 2009-03-14.
  11. ^ Joao Lima. “Babcock, EDP and Efacec to Collaborate on Wave Energy Projects”. Bloomberg Television. http://www.bloomberg.com/apps/news?pid=20601081&sid=aSsaOB9qbiKE&refer=australia. Retrieved 2008-09-24.
  12. ^ [1] “Pelamis Wave Power-Latest News”]. http://www.pelamiswave.com/news.php?id=31]. Retrieved 2009-02-11.
  13. ^ [2] “New Energy Focus”]. http://www.newenergyfocus.com/do/ecco.py/view_item?listid=1&listcatid=107&listitemid=1902]. Retrieved 2009-02-11.
  14. ^ http://news.bbc.co.uk/1/hi/scotland/north_east/8414684.stm news.bbc.co.uk

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Wells turbine

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Wells turbine en.svg

The Wells turbine is a low-pressure air turbine that rotates continuously in one direction in spite of the direction of the air flow. Its blades feature a symmetrical airfoil with its plane of symmetry in the plane of rotation and perpendicular to the air stream.

It was developed for use in oscillating-water-column wave power plants, in which a rising and falling water surface moving in an air compression chamber produces an oscillating air current. The use of this bidirectional turbine avoids the need to rectify the air stream by delicate and expensive check valve systems.

Its efficiency is lower than that of a turbine with constant air stream direction and asymmetric airfoil. One reason for the lower efficiency is that symmetric airfoils have a higher drag coefficient than asymmetric ones, even under optimal conditions. Also, in the Wells turbine, the symmetric airfoil is used with a high angle of attack (i.e., low blade speed / air speed ratio), as it occurs during air velocity maxima in volatile flow. A high angle of attack causes a condition known as “stall” in which the airfoil loses lift. The efficiency of the Wells turbine in oscillating flow reaches values between 0.4 and 0.7.

This simple but ingenious device was developed by Prof. Alan Wells of Queen’s University Belfast in the late 1970s.


Another solution of the problem of stream direction independent turbine is the Darrieus wind turbine (Darrieus rotor).

See also

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Category:Energy from oceans and water

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Also called water power


This category has the following 2 subcategories, out of 2 total.



Pages in category “Energy from oceans and water”

The following 17 pages are in this category, out of 17 total. This list may not reflect recent changes (learn more).





O cont.







Suntory Mermaid II

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The Suntory Mermaid II is a catamaran, the first 9.5 meter, 3 tonne ship driven by wave power, featuring two fin tails which absorb wave energy and generate thrust by moving up and down with the motion of the boat. The ship was designed by Hiroshi Terao of Tokai University. On 18 March 2008, the boat and its sailor Kenichi Horie left Hawaii for its maiden voyage, currently en route to Japan. On April 17, Yomiuri Shimbun interviewed Horie through satellite phone , he responded the boat is running with speed of approx. 100 kilometre per day so far.

World record

July 4, 2008, Suntory Mermaid II reached the goal at offshore of Hinomisaki cape of Kii Peninsula, Wakayama Japan, without problem. Horie, 69, made the world’s longest solo voyage across the Western Pacific Ocean in a wave-powered boat, using green technology.[1] YachtPal and venerable sailing adventurer Horie ate mostly rice and curry, squid and flying fish he caught.[2]

Kenichi left Honolulu March 16th and completed a 110-day solo voyage, reaching his destination in the channel between Honshu and Shikoku before midnight (1500 GMT Friday) after covering 7,000 kilometres (3,780 nautical miles) from Hawaii without a port call. His 9.5 metre (31-foot), 3-ton yacht used wave energy to move 2 fins at its bow and propel it forward, sailed at an average speed of 1.5 knots. It docked in Wakayama to return to his Nishinomiya home harbour. As environmentalist his mission is to use sailing boats powered by single solar battery or are made from recycled materials. He said: “Throughout history, mankind has used wind for power, but no one has appeared to be serious about wave power. I think I’m a lucky boy as this wave power system has remained virtually untouched.”[1][3]







by Jorge Chapa, 02/26/08


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GALLERY: The Suntory Mermaid II Wave-Powered Boat

suntory, wave power, mermaid, suntory mermaid II, kenichi horie, yutaka terao, tokai university, transportation, sailing, wave sailing, sailor

Wave power is looking like the next big thing in renewable energy, as evidenced by PG&E’s recent announcement about their California wave farm. And now Yutaka Terao from Tokai University in Japan, has engineered a way to put wave power to its most obvious use — to power boats! He has created a propulsion system that will power the Suntory Mermaid II’s trip from Hawaii to Japan using wave power, the expertise of eco-sailor Kenichi Horie, and a little bit of sun.

suntory, wave power, mermaid, suntory mermaid II, kenichi horie, yutaka terao, tokai university, transportation, sailing, wave sailing, sailorThe Suntory Mermaid II will be sailed by everyone’s favorite eco-sailor, Kenichi Horie. Horie will attempt the month’s long trip from Hawaii to Kii Channel in Japan. Although it is a first for the Suntory Mermaid, it’s not the first time that Horie has done this trip. In 1992 he pedaled all the way from Hawaii to Okinawa, made his way across the Pacific in a solar powered boat, and ventured in a catamaran made out of recycled beer barrels.

The propulsion system works by taking the usually-hindering power of waves to propel the boat forward. Two fins set at the front of the boat generate the power by moving up and down as the waves rock the boat. The fins act much like a dolphin’s tail, pushing the boat as the waves move past them. As if that wasn’t enough, the hull of the boat is made out of a super-thin recycled aluminum and solar power will be used for the ship’s interior electronics.

We applaud the eco-captain for putting wave power to use in its natural context. The Suntory Mermaid will set sail later this month.

+ Wave Runner @ Popular Mechanics
+ Go For it, Kenichi Horie

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Pacific Gas & Electric, PG&E, Finavera, AquaBuoy, wave power, wave park, renewable energy, California, Eureka, Humboldt County, ocean energy, kinetic energy, pge1.jpg

We’ve been following (and fascinated by) developments in wave power technology, from Portugal’s wave farm to Finavera’s AquaBuoy 2.0. And now we are thrilled to announce that San Francisco-based Pacific Gas & Electric Co (PG&E) has entered into a long-term commercial wave energy power purchasing agreement (PPA) to use this innovative technology. PG&E is the first US utility company to commit to wave power and expects to start delivering wave-powered electricity into the grid by 2010!

Pacific Gas & Electric, PG&E, Finavera, AquaBuoy, wave power, wave park, renewable energy, California, Eureka, Humboldt County, ocean energy, kinetic energy, pge2.jpg

The 15-year contract is with Vancouver-based Finavera Renewables, Inc, who will develop an AquaBuoy wave park about 2 1/2 miles off the coast of Northern California’s Humboldt County. The expected electricity generation will be a small part of California’s power needs, providing juice for under 2,000 homes, but the deal marks a milestone in the developing market.

While other promising techniques use below-surface motion and breaking waves, Finavera’s system uses offshore surface waves. The proposed wave park will contain eight AquaBuoys. The buoys will transfer the kinetic energy of the ocean into electricity by pumping water and turning a turbine which powers a generator. The electricity is then transferred to land through an underwater transmission cable.

While this is still an emerging technology, the PG&E commitment gives momentum to the potential of wave power as a viable source of renewable energy. As California utilities reach for 20% of their electricity from renewable sources by 2010, wave power offers a way to capture more energy in less space than other renewable energy technologies, like wind and solar.

+ Finavera Renewables
Via LA Times

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Wave power

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Large storm waves pose a challenge to wave power developers

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Wave power is the transport of energy by ocean surface waves, and the capture of that energy to do useful work — for example for electricity generation, water desalination, or the pumping of water (into reservoirs).

Wave power is distinct from the diurnal flux of tidal power 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.[1] The world’s first commercial wave farm is based in Portugal,[2] at the Aguçadoura Wave Park, which consists of three 750 kilowatt Pelamis devices.[3]



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[edit] Physical concepts

When an object bobs up and down on a ripple in a pond, it experiences an elliptical trajectory.

Motion of a particle in an ocean wave.
A = At deep water. The orbital motion of fluid particles decreases rapidly with increasing depth below the surface.
B = At shallow water (ocean floor is now at B). The elliptical movement of a fluid particle flattens with decreasing depth.
1 = Propagation direction.
2 = Wave crest.
3 = Wave trough.

See Energy, Power and 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 crest, as well as friction on the water surface by the wind shear stress causes the growth of the waves.[4]

Wave height 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, wavelength, and water density.

Oscillatory motion is highest at the surface and diminishes exponentially with depth. However, for standing waves (clapotis) near a reflecting coast, wave energy is also present as pressure oscillations at great depth, producing microseisms.[4] 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 velocity. The mean transport rate of the wave energy through a vertical plane of unit width, parallel to a wave crest, is called the wave energy flux (or wave power, which must not be confused with the actual power generated by a wave power device).

[edit] Wave energy and wave energy flux

In a sea state, the average energy density per unit area of gravity waves on the water surface is proportional to the wave height squared, according to linear wave theory:[4][5]

E=\frac{1}{16}\rho g H_{m0}^2, [A 1][6]

where E is the mean wave energy density per unit horizontal area (J/m2), the sum of kinetic and potential energy density per unit horizontal area. The potential energy density is equal to the kinetic energy,[4] 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 decimetres.

As the waves propagate, their energy is transported. The energy transport velocity is the group velocity. As a result, the wave energy flux, through a vertical plane of unit width perpendicular to the wave propagation direction, is equal to:[7][4]

P = E\, c_g, \, \

with cg the group velocity (m/s). Due to the dispersion relation 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:[4][5]

[show]Properties of gravity waves on the surface of deep water, shallow water and at intermediate depth, according to linear wave theory
quantity symbol units deep water
( h > ½ λ )
shallow water
( h < 0.05 λ )
intermediate depth
( all λ and h )
phase velocity \displaystyle c_p=\frac{\lambda}{T}=\frac{\omega}{k} m / s \frac{g}{2\pi} T \sqrt{g h} \sqrt{\frac{g\lambda}{2\pi}\tanh\left(\frac{2\pi h}{\lambda}\right)}
group velocity[A 2] \displaystyle c_g= c_p^2 \frac{\partial\left(\lambda/c_p\right)}{\partial\lambda}=\frac{\partial\omega}{\partial k} m / s \frac{g}{4\pi} T \sqrt{g h} \frac{1}{2} c_p \left( 1 + \frac{4\pi h}{\lambda}\frac{1}{\sinh\left(\displaystyle \frac{4\pi h}{\lambda}\right)} \right)
ratio  \displaystyle \frac{c_g}{c_p} \displaystyle\frac{1}{2} \displaystyle 1 \frac{1}{2} \left( 1 + \frac{4\pi h}{\lambda}\frac{1}{\sinh\left(\displaystyle \frac{4\pi h}{\lambda}\right)} \right)
wavelength \displaystyle\lambda m \frac{g}{2\pi} T^2 T \sqrt{g h} for given period T, the solution of:

\displaystyle     \left(\frac{2\pi}{T}\right)^2=\frac{2\pi g}{\lambda}\tanh\left(\frac{2\pi h}{\lambda}\right)

wave energy density \displaystyle E J / m2 \frac{1}{16} \rho g H_{m0}^2
wave energy flux \displaystyle P W / m \displaystyle E\;c_g
angular frequency \displaystyle \omega rad / s \frac{2\pi}{T}
wavenumber \displaystyle k rad / m \frac{2\pi}{\lambda}

[edit] 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 velocity. In shallow water, 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.[8]

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.[9]

[edit] History

The first known patent to utilise energy from ocean waves dates back to 1799 and was filed in Paris by Girard and his son[10]. An early application of wave power was a device constructed around 1910 by Bochaux-Praceique to light and power his house at Royan, near Bordeaux in France[11]. It appears that this was the first Oscillating Water Column type of wave energy device[12]. From 1855 to 1973 there were already 340 patents filed in the UK alone[10].

Modern scientific pursuit of wave energy was however pioneered by Yoshio Masuda‘s experiments in the 1940s[13]. 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[14].

A renewed interest in wave energy was motivated by the oil crisis in 1973. A number of university researchers reexamined the potential of generating energy from ocean waves, among whom notably were Stephen Salter from the University of Edinburgh, Kjell Budal and Johannes Falnes from Norwegian Institute of Technology (now merged into Norwegian University of Science and Technology), Michael E. McCormick from U. S. Naval Academy, David Evans from Bristol University, Michael French from University of Lancaster, John Newman and Chiang C. Mei from MIT.

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[15].

[edit] Modern technology

Wave power devices are generally categorized by the method used to capture the energy of the waves. They can also be categorized by location and power take-off system. Method types are point absorber or buoy; surfacing following or attenuator; terminator, lining perpendicular to wave propagation; oscillating water column; and overtopping. Locations are shoreline, nearshore and offshore. Types of power take-off include: hydraulic ram, elastomeric hose pump, pump-to-shore, hydroelectric turbine, air turbine,[16] and linear electrical generator. Some of these designs incorporate parabolic reflectors 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.[17]

These are descriptions of some wave power systems:

The front of the Pelamis machine bursting through a wave at the Agucadoura Wave Park

Wave Dragon seen from reflector, prototype 1:4½

  • In the United States, the Pacific Northwest Generating Cooperative is funding the building of a commercial wave-power park at Reedsport, Oregon.[18] The project will utilize the PowerBuoy technology Ocean Power Technologies which consists of modular, ocean-going buoys. The rising and falling of the waves moves the buoy-like structure creating mechanical energy which is converted into electricity and transmitted to shore over a submerged transmission line. A 40 kW buoy has a diameter of 12 feet (4 m) and is 52 feet (16 m) long, with approximately 13 feet of the unit rising above the ocean surface. Using the 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.
  • An example of a surface following device is the Pelamis Wave Energy Converter. The sections of the device articulate with the movement of the waves, each resisting motion between it and the next section, creating pressurized oil to drive a hydraulic ram which drives a hydraulic motor.[19] The machine is long and narrow (snake-like) and points into the waves; it attenuates the waves, gathering more energy than its narrow profile suggests. Its articulating sections drive internal hydraulic generators (through the use of pumps and accumulators).
  • With the Wave Dragon wave energy converter large “arms” focus waves up a ramp into an offshore reservoir. The water returns to the ocean by the force of gravity via hydroelectric generators.
  • The Anaconda Wave Energy Converter is in the early stages of development by UK company Checkmate SeaEnergy.[20] The concept is a 200 metre 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[21].
  • The AquaBuOY is made by Finavera Renewables Inc. Energy transfer takes place by converting the vertical component of wave kinetic energy into pressurized seawater by means of two-stroke hose pumps. Pressurized seawater is directed into a conversion system consisting of a turbine driving an electrical generator. The power is transmitted to shore by means of a secure, undersea transmission line. A commercial wave power production facility utilizing the AquaBuOY technology is beginning initial construction in Portugal.[22] The company has 250 MW of projects planned or under development on the west coast of North America.[23]
  • The SeaRaser, built by Alvin Smith, uses an entirely new technique (pumping) for gathering the wave energy.[24]
  • A device called CETO, currently being tested off Fremantle, Western Australia,[25] consists of a single piston pump attached to the sea floor, with a float 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.[26]
  • Another type of wave buoys, using special polymeres, is being developed by SRI [27]
  • Wavebob is an Irish Company who have conducted some ocean trials .
  • The Oyster wave energy converter is a hydro-electric wave energy device currently being developed by Aquamarine Power. The wave energy device captures the energy found in nearshore waves and converts it into clean usable 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.[28]
  • Ocean Energy have developed the OE bouy which has completed (September 2009) a 2-year sea trial in one quarter scale form. The OE bouy has only one moving part.[29]
  • The Lysekil Project is based on a concept with a 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.[30][31]
  • An Australian firm, Oceanlinx, is developing a 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 companies much smaller first-generation prototype unit, in operation since 2006, is now being disassembled.[9]

[edit] Challenges

These are some of the challenges to deploying wave power devices:

  • The device needs to capture a reasonable fraction of the wave energy in irregular waves, in a wide range of sea states.
  • There is an extremely large fluctuation of power in the waves. The peak absorption capacity needs to be much (more than 10 times) larger than the mean power. For wind power the ratio is typically 4.
  • The device has to efficiently convert wave motion into electricity. Generally speaking, wave power is available at low speed and high force, and the motion of forces is not in a single direction. Most readily-available electric generators operate at higher speeds, and most readily-available turbines require a constant, steady flow.
  • The device has to be able to survive storm damage and saltwater corrosion. Likely sources of failure include seized bearings, broken welds, and snapped mooring lines. Hence, designers may create prototypes that are so overbuilt that materials costs prohibit affordable production.
  • The total cost of electricity is high. Wave power will be competitive only when the total cost of generation is reduced (or the total cost of power generated from other sources increases). The total cost includes the primary converter, the power take-off system, the mooring system, installation & maintenance cost, and electricity delivery costs.
  • 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.[32]
  • 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.[33]
  • In the US, development of wave farms is currently hindered by a maze of state and federal regulatory hurdles and limited R&D funding.
  • Waves generate about 2,700 gigawatts of power. Of that 2,700 gigawatts, only about 500 gigawatts can be captured with the current technology.[17]

[edit] Wave farms

Main article: Wave farm

The world’s first commercial wave farm opened in 2008 at the Aguçadora Wave Park near Póvoa de Varzim in Portugal. It uses three Pelamis P-750 machines with a total installed capacity of 2.25MW.[3][34] However, in November the units were removed from the water, and in March 2009 the project was suspended indefinitely.[35] A second phase of the project planned to increase the installed capacity to 21MW using a further 25 Pelamis machines[36] is in doubt following Babcock’s withdrawal from the project.

Funding for a 3MW wave farm in Scotland was announced on 20 February 2007 by the Scottish Executive, at a cost of over 4 million pounds, as part of a £13 million funding package for marine power in Scotland. The farm will be the world’s largest, with a capacity of 3MW generated by four Pelamis machines.[37]

Funding has also been announced for the development of a Wave hub 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.[38][39]

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.[40]

A CETO 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.[citation needed] see http://www.ceto.com.au/home.php

[edit] Discussion of Salter’s Duck

In response to the Oil Crisis, a number of researchers reexamined the potential of generating energy from ocean waves, among whom is Professor Stephen Salter of the University of Edinburgh, Scotland. His 1974 invention became known as Salter’s Duck 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.[41] The machine has never gone to sea.[citation needed]

According to sworn testimony before the House of Parliament, The UK Wave Energy program was shut down on 1982-03-19, in a closed meeting,[42] the details of which remain secret.

An analysis of Salter’s Duck resulted in a miscalculation of the estimated cost of energy production by a factor of 10,[43] an error which was only recently identified. Some wave power advocates believe that this error, combined with a general lack of enthusiasm for renewable energy in the 1980s (after oil prices fell), hindered the advancement of wave power technology.[44]

[edit] Potential

Deep water wave power resources are truly enormous, between 1 TW and 10 TW, but it is not practical to capture all of this.[45] The useful worldwide resource has been estimated to be greater than 2 TW.[46][47] 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 westerlies in these zones blow strongest in winter. Waves are very predictable. The waves that are caused by winds can be predicted five days in advance. Tidal currents, caused by lunar positions, are known 100 years in advance. Water has a power density that is 832 times greater than air’s power density. That means that large amounts of energy can be obtained from relatively small devices. For example, it would require a wind turbine three times its size to generate the same amount of power as a regular-sized underwater turbine.[48]

Tidal currents in the seas affect the wave heights. This translates to greater energy captured by a wave motor. Studies by the Journal of Coastal Research show that the maximum wave height occurs 50-60 min after the tidal current flooding. These tidal currents have a speed of 0.7 m/s.[49]

The UK has an estimated recoverable resource of between 50–90TWh of electricity a year, this is roughly 15–25% of the current UK electricity demand.[50]

[edit] Patents

[edit] See also

[edit] Notes

  1. ^ For a small-amplitude sinusoidal wave \scriptstyle \eta=a\,\cos\, 2\pi\left(\frac{x}{\lambda}-\frac{t}{T}\right) with wave amplitude \scriptstyle a,\, the wave energy density per unit horizontal area is \scriptstyle E=\frac{1}{2}\rho g a^2, or \scriptstyle E=\frac{1}{8}\rho g H^2 using the wave height \scriptstyle H\,=\,2\,a\, for sinusoidal waves. In terms of the variance of the surface elevation \scriptstyle m_0=\sigma_\eta^2=\overline{(\eta-\bar\eta)^2}=\frac{1}{2}a^2, the energy density is \scriptstyle E=\rho g m_0\,. Turning to random waves, the last formulation of the wave energy equation in terms of \scriptstyle m_0\, is also valid (Holthuijsen, 2007, p. 40), due to Parseval’s theorem. Further, the significant wave height is defined as \scriptstyle H_{m0}=4\sqrt{m_0}, leading to the factor 116 in the wave energy density per unit horizontal area.
  2. ^ 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.

[edit] References

  1. ^ Christine Miller (August 2004). “Wave and Tidal Energy Experiments in San Francisco and Santa Cruz”. http://www.outsidelands.org/wave-tidal3.php. Retrieved 2008-08-16.
  2. ^ Emily Ford. “Wave power scientist enthused by green energy”. London: The Times. http://www.timesonline.co.uk/tol/life_and_style/career_and_jobs/careers_in/careers_in_science/article4111684.ece. Retrieved 2008-10-15.
  3. ^ a b Alok Jha (25 September 2008). “Making waves: UK firm harnesses power of the sea … in Portugal”. The Guardian. http://www.guardian.co.uk/technology/2008/sep/25/greentech.alternativeenergy. Retrieved 2008-10-09.
  4. ^ a b c d e f Phillips, O.M. (1977). The dynamics of the upper ocean (2nd edition ed.). Cambridge University Press. ISBN 0 521 29801 6.
  5. ^ a b Goda, Y. (2000). Random Seas and Design of Maritime Structures. World Scientific. ISBN 978 981 02 3256 6.
  6. ^ Holthuijsen, Leo H. (2007). Waves in oceanic and coastal waters. Cambridge: Cambridge University Press. ISBN 0521860288.
  7. ^ Reynolds, O. (1877). “On the rate of progression of groups of waves and the rate at which energy is transmitted by waves”. Nature 16: 343–44.
    Lord Rayleigh (J. W. Strutt) (1877). “On progressive waves”. Proceedings of the London Mathematical Society 9: 21–26. doi:10.1112/plms/s1-9.1.21.  Reprinted as Appendix in: Theory of Sound 1, MacMillan, 2nd revised edition, 1894.
  8. ^ R. G. Dean and R. A. Dalrymple (1991). Water wave mechanics for engineers and scientists. Advanced Series on Ocean Engineering. 2. World Scientific, Singapore. ISBN 978-9810204204.  See page 64–65.
  9. ^ a b Adee, Sally (2009-10-21). “This Renewable Energy Source Is Swell”. IEEE Spectrum Inside Technology. http://spectrum.ieee.org/energy/renewables/this-renewable-energy-source-is-swell. Retrieved 2009-10-22.
  10. ^ a b Clément et al. (2002). “Wave energy in Europe: current status and perspectives”. Renewable and Sustainable Energy Reviews 6: 405–431.
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  12. ^ Morris-Thomas et al. (2007). “An Investigation Into the Hydrodynamic Efficiency of an Oscillating Water Column”. Journal of Offshore Mechanics and Arctic Engineering 129: 273–278.
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  14. ^ Farley, F. J. M. and Rainey, R. C. T. (2006). “Radical design options for wave-profiling wave energy converters”. International Workshop on Water Waves and Floating Bodies. Loughborough. http://www.iwwwfb.org/Abstracts/iwwwfb21/iwwwfb21_15.pdf. Retrieved 2009-12-18.
  15. ^ Falnes, J. (2007). “A review of wave-energy extraction”. Marine Structures 20: 185–201.
  16. ^ Embedded Shoreline Devices and Uses as Power Generation Sources Kimball, Kelly, November 2003
  17. ^ a b McCormick, Michael E., and R. Cengiz Ertekin. Mechanical Engineering-CIME 131.5 (2009): 36. Expanded Academic ASAP. Web. 5 Oct. 2009.
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  19. ^ Jenny Haworth (24 September 2008). “If Portugal can rule the waves, why not Scotland?”. The Scotsman. http://news.scotsman.com/opinion/If-Portugal-can-rule-the.4520629.jp. Retrieved 2008-10-09.
  20. ^ Anaconda WEC
  21. ^ Article about Anaconda on physics.org
  22. ^ Wave Energy: Figueira da Foz, Portugal Finavera Renewables
  23. ^ Wave Energy Device Deployed
  24. ^ SeaRaser
  25. ^ Stephen Cauchi (October 5, 2008). “New wave of power in renewable energy market”. The Age. http://www.theage.com.au/national/new-wave-of-power-in-renewable-energy-market-20081004-4tyd.html. Retrieved 2008-10-10.
  26. ^ “CETO Overview”. carnegiecorp.com.au. http://www.carnegiecorp.com.au/index.php?url=/ceto/ceto-overview. Retrieved 2008-11-03.
  27. ^ SRI Demonstrates Ocean Wave-Powered Generator off California Coast, SRI International, 08.12.2008
  28. ^ http://www.aquamarinepower.com
  29. ^ http://www.oceanenergy.ie/oe-technology/platform.html
  30. ^ Leijon, Mats et. al (9 April 2008). “Wave Energy from the North Sea: Experiences from the lysekil Research site”. http://www.springerlink.com/content/8634116882r00t13/fulltext.pdf. Retrieved 24 June 2009.
  31. ^ Leijon, Mats et. al (January/February 2009). “Catch the Wave to Electricity”. IEEE power energy magazine: 50–54. 10.1109/MPE.2008.930658. http://ieeexplore.ieee.org/search/searchresult.jsp?SortField=Score&SortOrder=desc&ResultCount=25&maxdoc=100&coll1=ieeejrns&coll2=ieejrns&coll3=ieeecnfs&coll4=ieecnfs&coll5=ieeestds&coll6=preprint&coll7=books&coll8=modules&coll9=aip&srchres=0&history=yes&queryText=((Catch+the+wave+to+electricity)%3CIN%3Emetadata)&oldqrytext=((the+conversion+of+wave+motions+to+electricity)%3Cin%3Emetadata)&imageField.x=0&imageField.y=0&imageField=((the+conversion+of+wave+motions+to+electricity)%3Cin%3Emetadata)&radiobutton=cit. Retrieved 29 June 2009.
  32. ^ “Wave Energy Potential on the U.S. Outer Continental Shelf” (PDF). United States Department of the Interior. http://www.ocsenergy.anl.gov/documents/docs/OCS_EIS_WhitePaper_Wave.pdf. Retrieved 2008-10-17.
  33. ^ Steven Hackett. “Economic and Social Considerations for Wave Energy Development in California. In P. Nelson and L. Engeman (eds.), Developing Wave Energy in Coastal California: Socio-Economic and Environmental Effects. Report CEC-500-2008-083”. California Energy Commission. http://www.energy.ca.gov/2008publications/CEC-500-2008-083/CEC-500-2008-083.PDF. Retrieved 2008-12-14.
  34. ^ “Portugal Goverenment”. http://www.portugal.gov.pt/portal/pt/comunicacao/agenda/20080923.htm. Retrieved 2008-09-24.
  35. ^ “Pelamis sinks Portugal wave-power project”. cleantech. 2009. http://cleantech.com/news/4276/pelamis-sinks-portugal-wave-power-p.
  36. ^ Joao Lima. “Babcock, EDP and Efacec to Collaborate on Wave Energy Projects”. Bloomberg Television. http://www.bloomberg.com/apps/news?pid=20601081&sid=aSsaOB9qbiKE&refer=australia. Retrieved 2008-09-24.
  37. ^ “Orkney to get ‘biggest’ wave farm”. BBC News. http://news.bbc.co.uk/2/hi/uk_news/scotland/6377423.stm. Retrieved 2008-10-22.
  38. ^ James Sturcke (26 April 2007). “Wave farm wins £21.5m grant”. The Guardian. http://www.guardian.co.uk/environment/2007/apr/26/energy.uknews. Retrieved 2009-04-08.
  39. ^ “Tender problems delaying Wave Hub”. BBC News. 2 April 2008. http://news.bbc.co.uk/2/hi/uk_news/england/cornwall/7326971.stm. Retrieved 2009-04-08.
  40. ^ “Go-ahead for £28m Cornish wave farm”. The Guardian. http://www.guardian.co.uk/environment/2007/sep/17/renewableenergy.uknews. Retrieved 2008-10-12.
  41. ^ “Edinburgh Wave Energy Project” (PDF). University of Edinburgh. http://www.mech.ed.ac.uk/research/wavepower/EWPP%20archive/duck%20efficiency%20&%20survival%20notes.pdf. Retrieved 2008-10-22.
  42. ^ “Memorandum submitted by Professor S H Salter, Department of Mechanical Engineering, University of Edinburgh”. Parliament of the United Kingdom. http://www.parliament.the-stationery-office.co.uk/pa/cm200001/cmselect/cmsctech/291/1031409.htm. Retrieved 2008-10-22.
  43. ^ “Water Power Devices”. Earth Science Australia. http://www.earthsci.org/mineral/energy/wavpwr/wavepwr.html. Retrieved 2008-10-22.
  44. ^ “The untimely death of Salter’s Duck”. Green Left Weekly. http://www.greenleft.org.au/1992/64/2832. Retrieved 2008-10-22.
  45. ^ Engineering Committee on Oceanic Resources — Working Group on Wave Energy Conversion (2003), John Brooke, ed., Wave Energy Conversion, Elsevier, pp. 7, ISBN 0080442129, http://books.google.com/books?id=UGAXRwoLZY4C&dq=John+Brooke,+ed.,+Wave+Energy+Conversion&source=gbs_summary_s&cad=0
  46. ^ Tom Thorpe. “An Overview of Wave Energy Technologies: Status, Performance and Costs” (PDF). wave-energy.net. http://www.wave-energy.net/Library/An%20Overview%20of%20Wave%20Energy.pdf. Retrieved 2008-10-13.
  47. ^ Cruz J.; Gunnar M., Barstow S., Mollison D. (2008), Joao Cruz, ed., Green Energy and Technology, Ocean Wave Energy, Springer Science+Business Media, pp. 93, ISBN 978-3-540-74894-6
  48. ^ “Stormy Seas: Ocean Power Promoters Struggle to Overcome a Stiff Current of Challenges.” Curlik, Larissa. “Stormy Seas: Ocean Power Promoters Struggle to Overcome a Stiff Current of Challenges.” Earth Island Journal 24.1 (2009): 51(5). Expanded Academic ASAP. Web. 5 Oct. 2009.
  49. ^ “Tidal modulation of incident wave heights: fact or fiction?.” Davidson, M. A., T. J. O’Hare, and K. J. George. “Tidal Modulation of Incident Wave Heights: Fact or Fiction.” Journal of Costal Research 24.2 (2008): S151. Expanded Academic ASAP. Web. 5 Oct. 2009.
  50. ^ “Pelamis Wave Power”. pelamiswave.com. http://www.pelamiswave.com/index.php. Retrieved 2008-10-13.

[edit] Further reading

  • Cruz, Joao (2008), Ocean Wave Energy – Current Status and Future Prospects, Springer, ISBN 3540748946 , 431 pp.
  • Falnes, Johannes (2002), Ocean Waves and Oscillating Systems, Cambridge University Press, ISBN 0521017491 , 288 pp.
  • McCormick, Michael (2007), Ocean Wave Energy Conversion, Dover, ISBN 0486462455 , 256 pp.
  • Twidell, John; Weir, Anthony D.; Weir, Tony (2006), Renewable Energy Resources, Taylor & Francis, ISBN 0419253300 , 601 pp.

[edit] External links

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