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 ram, elastomeric hose pump, pump-to-shore, hydroelectric turbine, air turbine, 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. 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 transmission power cables. The table contains descriptions of some wave power systems:
| Device | Proponent | Country of origin | Capture method | Location | Power take off | Year build | Notes |
|---|---|---|---|---|---|---|---|
| Anaconda Wave Energy Converter | Checkmate SeaEnergy. | UK | Surface-following attenuator | Offshore | Hydroelectric turbine | 2008 | In the early stages of development, the device is a 200 metres (660 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. 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. |
| AWS-iii | AWS Ocean Energy | UK (Scotland) | Surface-following attenuator? | Offshore | Air turbine | 2010 | The AWS-III is a floating toroidal vessel. It has rubber membranes on the outer faces which deform as waves pass, moving air inside chambers which in turn drive air-turbines to generate electricity. AWS Ocean tested a 1/9 scale model in Loch Ness in 2010, and are now working on a full sized version which will be 60m across and should generate 2.5MW. It is envisage these will be installed in offshore farms moored in around 100m depth of water. |
| CETO Wave Power | Carnegie | Australia | Buoy | Offshore | Pump-to-shore | 1999 | As of 2008, the device is being tested off Fremantle, Western Australia, 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. |
| 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. It works by means of a cable that due to the bobbing effect of the buoy, generates electricity. |
| Islay LIMPET | Islay LIMPET | Scotland | oscillating water column | Onshore | air turbine | 1991 | Islay LIMPET is a 500 kW shoreline device uses an oscillating water column to drive air in and out of a pressure chamber through a Wells turbine. The chamber of the LIMPET is an inclined concrete tube with its opening below the water level. As external wave action causes the water level in the chamber to oscillate, the variation in water level alternately compresses and decompresses the trapped air above, causing air to flow backwards and forwards through a pair of contra-rotating turbines. |
| Lysekil Project | Uppsala University | 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 | 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.
In May 2010, the wave energy generator snapped from its mooring lines and wrecked on Port Kembla's eastern breakwater. |
| OE buoy | 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. |
| Oyster wave energy converter | 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. |
| Pelamis Wave Energy Converter | Pelamis Wave Power | 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 of the 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. 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.ON. |
| 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 a rack and pinion 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. |
| R38/50 kW, R115/150 kW | 40South Energy | UK | Underwater attenuator | Offshore | Electrical conversion | 2010 | These machines work by extracting energy from the relative motion between one Upper Member and one Lower Member, following an innovative method which earned the company one UKTI Research & Development Award in 2011. A first generation full scale prototype for this solution was tested offshore in 2010, and a second generation full scale prototype was tested offshore during 2011. In 2012 the first units were sold to clients in various countries, for delivery within the year. The first reduced scale prototypes were tested offshore during 2007, but the company decided to remain in a "stealth mode" until May 2010 and is now recognized as one of the technological innovators in the sector. The company initially considered installing at Wave Hub in 2012, but that project is on hold for now. The R38/50 kW is rated at 50 kW while the R115/150 kW is rated at 150 kW. |
| SDE Sea Waves Power Plant | SDE Energy Ltd. | Israel | Buoy | Inshore | Hydroelectric turbine | 2010 | 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 100 MWh power plants in the islands of Zanzibar and Kosrae, Micronesia. |
| SeaRaser | Alvin Smith (Dartmouth Wave Energy)\Ecotricity | UK | Buoy | Nearshore | Hydraulic ram | 2008 | Consisting of a piston pump(s) 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 resoviors onshore which then drive hydraulic generators. |
| 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 | Ireland | Buoy | Offshore | Direct Drive Power Take off | 1999 | Wavebob have conducted some ocean trials, as well as extensive tank tests. It is an ocean-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") |
| Wave Dragon | 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. |
| WaveRoller | AW-Energy Oy | Finland | Oscillating wave surge converter | Nearshore | Hydraulic | 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. |
| Wave Star | Wave Star A/S | Denmark | Multi-point absorber | Offshore | Hydroelectric turbine | 2000 | The Wavestar machine draws energy from wave power with floats that rise and fall with the up and down motion of waves. The floats are attached by arms to a platform that stands on legs secured to the sea floor. The motion of the floats is transferred via hydraulics into the rotation of a generator, producing electricity. Wave Star have been testing a 1:10 machine since 2005 in Nissum Bredning, Denmark, it was taken out of duty in November 2011. A 1:2 Wave Star machine is place in Hanstholm which has produced electricity to the grid since September 2009. |
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