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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, electricity generation, water desalination, or the pumping of water (into reservoirs). 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 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] In 2008, the first experimental wave farm was opened in Portugal, at the Aguçadoura Wave Park.^[2]

Physical concepts[link]

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.

Photograph of the water particle orbits under a – progressive and periodic – surface gravity wave in a wave flume. The wave conditions are: mean water depth d = 2.50 ft (0.76 m), wave height H = 0.339 ft (0.103 m), wavelength λ = 6.42 ft (1.96 m), period T = 1.12 s.^[3]

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, making the water to go into the 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).

Wave power formula[link]

In deep water where the water depth is larger than half the wavelength, the wave energy flux is^{[A 1]}

Failed to parse (Missing texvc executable; please see math/README to configure.): P = \frac{\rho g^2}{64\pi} H_{m0}^2 T \approx \left(0.5 \frac{\text{kW}}{\text{m}^3 \cdot \text{s}} \right) H_{m0}^2\; T,

with P the wave energy flux per unit of wave-crest length, H_m0 the significant wave height, T the wave period, ρ the water density and g the acceleration by gravity. 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 wavefront length.^[5][6][7]

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

Failed to parse (Missing texvc executable; please see math/README to configure.): P \approx 0.5 \frac{\text{kW}}{\text{m}^3 \cdot \text{s}} (3 \cdot \text{m})^2 (8 \cdot \text{s}) \approx 36 \frac{\text{kW}}{\text{m}},

meaning there are 36 kilowatts of power potential per meter of wave crest.

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[link]

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][8]

Failed to parse (Missing texvc executable; please see math/README to configure.): E=\frac{1}{16}\rho g H_{m0}^2,

[A 2][9]

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:^[10][4]

Failed to parse (Missing texvc executable; please see math/README to configure.): P = E\, c_g, \, \

with c_g 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][8]

Deep water characteristics and opportunities[link]

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.^[11]

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.^[12]

History[link]

The first known patent to utilize energy from ocean waves dates back to 1799 and was filed in Paris by Girard and his son.^[13] 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.^[14] It appears that this was the first Oscillating Water Column type of wave energy device.^[15] From 1855 to 1973 there were already 340 patents filed in the UK alone.^[13]

Modern scientific pursuit of wave energy was however pioneered by Yoshio Masuda's experiments in the 1940s.^[16] 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.^[17]

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.

Stephen Salters 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 giving 81% efficiency.^[18]

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.^[19]

Modern technology[link]

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,^[20] 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.^[21] 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.^[22] 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 File:Footprint. Protean Energy Wave Energy Converter prototype trial being conducted in the ocean off the coast of Western Australia in 2008.
SurgeDrive	AquaGen Technologies	Australia	Buoy	Offshore	Tension transfer	2007	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. This technology removes the more complex equipment of the system from the water.[23] With less equipment in the water, expensive subsea maintenance is reduced thus reducing the cost of the electricity produced.[24] The system also incorporates a storm survival system whereby the buoyancy units are automatically pulled under the water in a storm.
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.[25] 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.[26] PB150 PowerBuoy with peak-rated power output of 150 kW.
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.[27] Pelamis Wave Power first tested and grid connected a Pelamis machine in 2004 at the European Marine Energy Center.[28] 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.[29] Pelamis prototype machine at EMEC, Scotland in 2004.
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. Wave Dragon seen from reflector, prototype 1:4½
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 (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.[30][31]
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.[32][33][34][35]
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.[36][37][38]
SeaRaser	Alvin Smith (Dartmouth Wave Energy)	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.[39][40]
CETO Wave Power	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.[41][42] CETO Buoyant Actuator during the installation process
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.[43][44]
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 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	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.[45]
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.[46]
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.[47][48]
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.[12]
SDE Sea Waves Power Plant	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 100 MWh 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.[49][50]
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.[51]
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.[52][53][54] 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.
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.[55] A first generation full scale prototype for this solution was tested offshore in 2010,[56][57][58] and a second generation full scale prototype was tested offshore during 2011.[59] In 2012 the first units were sold to clients in various countries, for delivery within the year.[60][61] The first reduced scale prototypes were tested offshore during 2007, but the company decided to remain in a "stealth mode" until May 2010[62] and is now recognized as one of the technological innovators in the sector.[63] The company initially considered installing at Wave Hub in 2012,[64] 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.
bioWAVE[TM]	BioPower	Australia	ocean swell waves	depth of 30-45m	capture and conversion process	2011	The bioWAVETM is being developed for utility-scale power production from ocean waves. Its nature-inspired design (biomimicry) combines high conversion efficiency with the ability to avoid excessive wave forces, enabling supply of grid-connected electricity at a competitive price per MWh. The bioWAVETM is designed to operate in ocean swell waves, absorbing energy both at the surface and below. It is a bottom-mounted pitching device, which spans the full depth. The bioWAVETM prototype currently under development will operate at a depth of 30m, while the planned 1MW commercial model will operate where the depth is 40-45m. The energy capture and conversion process for bioWAVETM has been confirmed through peer reviewed scientific research, extensive device testing at model-scale, and by measured results from dry-tests on our full-scale grid-connected O-DriveTM test module. An ocean-based 250kW bioWAVETM demonstration project is currently under development at a grid-connected site with further plans in place to develop a 1MW demonstration, followed by multi-unit wave energy farms. [65] CETO Buoyant Actuator during the installation process

Potential[link]

The realistically usable worldwide resource has been estimated to be greater than 2 TW.^[66][67] 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.

Challenges[link]

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.^[6] Other biophysical impacts (flora and fauna, sediment regimes and water column structure and flows) of scaling up the technology is being studied.^[68] 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.^[69] Waves generate about 2,700 gigawatts of power. Of those 2,700 gigawatts, only about 500 gigawatts can be captured with the current technology.^[21]

Wave farms[link]

The Aguçadoura Wave Farm was the world's first wave farm. It was located 5 km (3 mi) offshore near Póvoa de Varzim north of Oporto in Portugal. The farm was designed to use three Pelamis wave energy converters to convert the motion of the ocean surface waves into electricity, totalling to 2.25 MW in total installed capacity. The farm first generated electricity in July 2008^[70] and was officially opened on the 23rd of September 2008, by the Portuguese Minister of Economy.^[71][72] 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.^[73] A second phase of the project planned to increase the installed capacity to 21 MW using a further 25 Pelamis machines^[74] is in doubt following Babcock's financial collapse.

Funding for a 3 MW 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 first of 66 machines was launched in May 2010.^[75]

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 20 MW of capacity to be connected, with potential expansion to 40 MW. Four device manufacturers have so far expressed interest in connecting to the Wave hub.^[76][77]

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.^[78]

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] [79][80]}

Patents[link]

• U.S. Patent 3,928,967 — 1974 Apparatus and method of extracting wave energy - The original "Salter's Duck" patent
• U.S. Patent 4,134,023 — 1977 Apparatus for use in the extraction of energy from waves on water - Salter's method for improving "duck" efficiency
• U.S. Patent 6,194,815 — 1999 Piezoelectric rotary electrical energy generator
• US application 20,040,217,597  — 2004 Wave energy converters utilizing pressure differences (src)

See also[link]

• CETO Wave Power
• Ocean thermal energy conversion
• World energy resources and consumption

Notes[link]

1. ^ The energy flux is Failed to parse (Missing texvc executable; please see math/README to configure.): P = \tfrac{1}{16} \rho g H_{m0}^2 c_g, with Failed to parse (Missing texvc executable; please see math/README to configure.): c_g the group velocity, see Herbich, John B. (2000). Handbook of coastal engineering. McGraw-Hill Professional. p. A.117, Eq. (12). ISBN 978-0-07-134402-9.  The group velocity is Failed to parse (Missing texvc executable; please see math/README to configure.): c_g=\tfrac{g}{4\pi}T , 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.
2. ^ For a small-amplitude sinusoidal wave Failed to parse (Missing texvc executable; please see math/README to configure.): \scriptstyle \eta=a\,\cos\, 2\pi\left(\frac{x}{\lambda}-\frac{t}{T}\right) with wave amplitude Failed to parse (Missing texvc executable; please see math/README to configure.): \scriptstyle a,\, the wave energy density per unit horizontal area is Failed to parse (Missing texvc executable; please see math/README to configure.): \scriptstyle E=\frac{1}{2}\rho g a^2, or Failed to parse (Missing texvc executable; please see math/README to configure.): \scriptstyle E=\frac{1}{8}\rho g H^2 using the wave height Failed to parse (Missing texvc executable; please see math/README to configure.): \scriptstyle H\,=\,2\,a\, for sinusoidal waves. In terms of the variance of the surface elevation Failed to parse (Missing texvc executable; please see math/README to configure.): \scriptstyle m_0=\sigma_\eta^2=\overline{(\eta-\bar\eta)^2}=\frac{1}{2}a^2, the energy density is Failed to parse (Missing texvc executable; please see math/README to configure.): \scriptstyle E=\rho g m_0\, . Turning to random waves, the last formulation of the wave energy equation in terms of Failed to parse (Missing texvc executable; please see math/README to configure.): \scriptstyle m_0\, is also valid (Holthuijsen, 2007, p. 40), due to Parseval's theorem. Further, the significant wave height is defined as Failed to parse (Missing texvc executable; please see math/README to configure.): \scriptstyle H_{m0}=4\sqrt{m_0} , leading to the factor ¹⁄₁₆ in the wave energy density per unit horizontal area.
   
3. ^ 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.

References[link]

Further reading[link]

• Cruz, Joao (2008). Ocean Wave Energy - Current Status and Future Prospects. Springer. ISBN 3-540-74894-6. , 431 pp.
• Falnes, Johannes (2002). Ocean Waves and Oscillating Systems. Cambridge University Press. ISBN 0-521-01749-1. , 288 pp.
• McCormick, Michael (2007). Ocean Wave Energy Conversion. Dover. ISBN 0-486-46245-5. , 256 pp.
• Twidell, John; Weir, Anthony D.; Weir, Tony (2006). Renewable Energy Resources. Taylor & Francis. ISBN 0-419-25330-0. , 601 pp.

External links[link]

Wikimedia Commons has media related to: Wave power

Wikimedia Commons has media related to: Renewable energy

• "Ocean waves - our new electricity supplier" Archived 7 January 2010 at the Wayback Machine (Uppsala university 2010)
• Kate Galbraith (September 22, 2008). "Power From the Restless Sea Stirs the Imagination". New York Times. http://www.nytimes.com/2008/09/23/business/23tidal.html?em. Retrieved 2008-10-09. 
• "Wave Power: The Coming Wave" from the Economist, June 5, 2008
• "The untimely death of Salter's Duck"
• "Ocean Power Fights Current Thinking"
• "Wave energy in New Zealand"
• Wave technologies: types of devices (LORC Knowledge 2011)
• "How it works: Wave power station"

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Terry Bogard (テリー・ボガード, Terī Bogādo^?) is a video game character created by SNK Playmore (previously SNK), and is the main character of the Fatal Fury series. In the series, he is an American fighter who enters the worldwide tournaments called The King of Fighters to kill Geese Howard, a criminal who killed Terry's father. Terry becomes a formidable fighter, earning the title of "Legendary Hungry Wolf". In the fourth tournament he participates, Terry nearly kills Geese, but recants from doing so. Geese responds to this by apparently committing suicide. Terry then decides to become the guardian of Geese's son, Rock Howard.

In addition to video game, Terry has appeared in anime films based on his adventures from the Fatal Fury series, as well as soundtracks and manga serialized to Japanese monthly manga magazine Comic Bom Bom. He is also a regular character in the crossover video game series The King of Fighters, in which he continues participating in tournaments. Dating back to the first Fatal Fury, Terry is one of SNK's first fighting game characters and has appeared as a playable character in every Fatal Fury and main King of Fighters game to date.^[7][8] The character has been well received by video games players; he is ranked high in several popularity polls developed by SNK and video games magazines. Publications have praised the character and how he was developed from Fatal Fury to The King of Fighters. He is prominently featured on merchandise from SNK and their crossover series, becoming an icon for them.

Character design[link]

In most of the Fatal Fury and King of Fighters games, Terry wears a red, short-sleeved jacket with a white star on the back worn over a short-sleeved white t-shirt; occasionally, the shirt is sleeveless and occasionally has tattered sleeves.^[9][10] In the original Fatal Fury, however, Terry wears a red leather jacket that features rolled-up sleeves.^[11] He also wears fingerless gloves, blue jeans, a pair of red Chuck Taylor All Star shoes, and a red-and-white baseball/trucker cap. The character has long, blonde hair, but keeps it tied in a ponytail with bangs around his forehead/cheeks.^[9][10]

In Mark of the Wolves and other recent games, Terry's design consists of a brown bomber jacket with a white star on the back with the words "Running Wild" below it, as well as a white shirt, blue jeans, and brown boots. His hair, while still notably long, is considerably shorter than his former ponytail, and flows freely instead of braiding it.^[12] All of the main King of Fighters games up until 2002 feature Terry in his Fatal Fury 2 outfit. The King of Fighters 2003 and XI feature the Mark of the Wolves depiction.^[13][14] In The King of Fighters XII, Terry was given his Fatal Fury 2 outfit once again because the staff wanted to "use the most macho, stand-out, original Terry" as well as to keep in line with the "original clashing of fists."^[15]

Attributes[link]

Terry Bogard is typically a cheerful and friendly fellow to everyone around him. He seems to bear no ill will towards anyone other than Geese Howard, the killer of his adoptive father. He and his younger brother Andy Bogard were orphans adopted by Jeff Bogard, who was killed by Geese Howard when Terry and Andy were children. Wishing to take revenge, Terry trained alone in the streets until he developed a unique fighting style which combines boxing, kung fu, kickboxing and street fighting moves.^[16] He became strong enough to enter The King of Fighters tournament, in which he is often referred to as the Legendary Hungry Wolf (from Legend of the Hungry Wolf (餓狼伝説, Garou Densetsu^?), the Japanese title of his first appearance) for his remarkable skills. Although Terry manages to defeat Geese, he tries to save him when Geese is about to fall from a tower. Geese refuses this help, and seemingly falls to his death, though he's since returned in numerous games.^[17] Some time after that, Terry met Geese's son, Rock Howard, and started taking care of him. He treats Rock as his son, but gives him some freedom of choice.^[18] Terry appears to fit many Japanese stereotypes for an American character in appearance, personality and speech (his in-game vocabulary is usually limited to American colloquialisms, such as "Okay!" and "Hey, c'mon, c'mon."). He has a pet monkey named Ukee (ウッキー^?) which commonly appears around him in some games. Terry is also streetsmart as his knowledge of what goes on in the streets and slang is vast.^[19] During the Fatal Fury series, Terry meets Blue Mary, with whom he appears to have a longtime relationship.^[20]

Appearances[link]

In video games[link]

Terry has served as the lead character of the Fatal Fury series since his debut in the first game. The original Fatal Fury centers around Terry and his younger brother Andy, who enter the King of Fighters tournament to avenge their father's death, who was murdered a decade ago by the tournament's sponsor, Geese Howard.^[16] Along with their friend Joe Higashi, they manage to defeat Geese who dies falling from a tower after fighting one of the three main characters.^[21]

The numerous Fatal Fury sequels released afterward feature Terry and his friends competing in new tournaments. The initial sequel, Fatal Fury 2, introduced a new antagonist for Terry to defeat named Wolfgang Krauser, who tries to conquer Southtown.^[22] By Fatal Fury 3: Road to the Final Victory, Terry continues his fight against Geese who survived his apparent death and now seek revenge against Terry and other rivals.^[23] Real Bout Fatal Fury concludes the Bogard and Howard rivalry by killing off Geese at the end of the game.^[17] Two subsequent Real Bout sequels were produced, Real Bout Fatal Fury Special and Real Bout Fatal Fury 2: The Newcomers, featuring Terry although neither game contains any storyline.^[24][25] A 3D fighting game version of the series, Fatal Fury: Wild Ambition was produced as well, which retells the plot of the first game.^[26] Terry Bogard's character would be reinvented for Garou: Mark of the Wolves, which features an older Terry as the mentor of Geese Howard's son, Rock Howard. During this time, Terry and Rock enter a new King of Fighters tournament dubbed Maximum Mayhem.^[27]

After the release of Fatal Fury 2, Terry appeared in The King of Fighters '94, where he serves as the leader of the game's "Fatal Fury" team alongside his younger brother Andy and Joe. The King of Fighters series, which was originally conceived as a crossover of SNK's previous video game franchises, eventually established their own self-contained continuity set apart from the previous Fatal Fury series and Terry became a staple in both franchises.^[28] While the Fatal Fury Team's members change various times across the series, Terry remains as the team's leader.^[29][30][31] The King of Fighters XII and The King of Fighters XIII bring back the character in his Fatal Fury 2 outfit.^[32]

The Fatal Fury Team remains as in the first KOF in the games without storyline: these games include The King of Fighters '98, The King of Fighters 2002 and Neowave.^[33][34][35] In The King of Fighters: Kyo, a RPG centered on Kyo Kusanagi, Terry appears when Kyo goes to South Town, and helps him to fight Geese Howard.^[36] In the two games for the Game Boy Advance titled EX: Neo Blood and EX2, the Fatal Fury also participates in the new tournaments.^[37][38] Terry also appears in the KOF: Maximum Impact sub-series in both his Fatal Fury 2 and Mark of the Wolves outfits, with the latter being labelled as "Wild Wolf" (ワイルドウルフ^?).^[39] He is also playable in the shooter game Sky Stage.^[40] Terry also stars in the crossover video games NeoGeo Battle Coliseum and SNK vs. Capcom series; in the former in his Mark of the Wolves outfit, and the latter in his Fatal Fury 2 outfit.^[41][42]

In other media[link]

Terry Bogard is the central character of a trilogy of Japanese animated Fatal Fury films, where his character is voiced by Shōnentai lead singer Nishikori Kazukiyo in the Japanese originals and Mark Hildreth in the English dubs. The first two movies, 1992's Fatal Fury: Legend of the Hungry Wolf and 1993's Fatal Fury 2: The New Battle, loosely follows the storylines of their respective games, while the third film, 1994's Fatal Fury: The Motion Picture, features an original storyline. The first film introduces a new love interest for Terry Bogard named Lily McGwire, an orphaned girl raised by Geese Howard. Lily is killed by Geese during the first film, but she appears in both sequels as a spirit who guides Terry.^[43][44] The third film introduced a new love interest for Terry named Sulia, the younger sister of antagonist Laocorn Gaudeamus, who sacrifices herself in the end of the film to help Terry defeat her brother.^[1]

Terry also plays a supporting role in the 2006 original net animation The King of Fighters: Another Day. Terry appears in the episode "Accede", where he is voiced in the Japanese version by Satoshi Hashimoto, his voice actor from the video games, and Tony Carroll in the English dub.^[45] Satoshi Hashimoto also voiced Terry in Memories of Stray Wolves a twenty-minute featurette which serves as a retrospective of the Fatal Fury series, with Terry narrating the events of the games to Rock.^[46] Terry is also featured in the volume 3 from the soundtracks series SNK Character Sounds Collection released by Pony Canyon. The CD features several songs based on his character.^[47] He is appears in several mawhua, including the Fatal Fury series, The King of Fighters and SNK Vs. Capcom: SVC Chaos which retell the stories from its respective games.^[48][49] The first seven chapters from the manhua The King of Fighters 2003 by Wing Yen features a short chapter from Garou: Mark of the Wolves that tell Rock's training with Terry.^[50] His character is also part of a social action program created by SNK Playmore named "Nakoruru & Terry Club". The organization supports children to guide them to a better future.^[51] David Leitch portrays Terry in the 2010The King Of Fighters movie.^[52]

Reception[link]

Terry is frequently used to symbolize the company in crossover games, merchandise and publicity.^[53] During the KOF Year-End Party in 2005, a fan event made by SNK, the character's cap was given to every fan in attendance.^[54] His character has been well-received by fans, appearing in several video games popularity polls. In Gamest's 1997 Heroes Collection, Terry was voted as the staff's eighth favorite character.^[55] In a popularity poll by SNK for the release of Garou: Mark of the Wolves, Terry ranked 2nd with a SNK staff commenting that "Terry's the eternal hero".^[56] A character popularity poll on the website Neo Geo Freak journal resulted in Terry as the fourth favorite character from the series with a total of 2,479 votes.^[57] He was voted as the number one fan favorite character with a total of 10,014 votes in a 2005 poll made by SNK-Playmore USA.^[58] For the special endings in The King of Fighters '97, three video games publications, Gamest, Famitsu and Neo Geo Freak, had to create a team composed of three characters from the game so that they would be featured in an image after passing the arcade mode. The Gamest's team created a team composed of Terry, Blue Mary and Joe Higashi. The special ending only appears in Japanese versions of the game.^[59]

The character has received praise and criticism from several media publications. GameSpot reviewer Frank Provo commented that one of Fatal Fury's biggest accomplishments is the creation of Terry Bogard and for making him appear in later sequels.^[60] Damien McFerran praised Terry's design, saying that he is "emanating so much coolness it’s little wonder that SNK otaku can always be seen wearing his trademark red cap".^[61] Dale Nardozzi from Reviews Teambox also praised Terry's distinct appearance. He further commented that his clothes is one of the most common cosplays at every convention with video game importance.^[62] Andrew Sztein from GamingExcellence commented that Terry was one of his favourite characters from the series. He mentioned that he liked his design because as "he should be working at Petro Canada part time" and added that his mispronunciation of English quotes are quite funny.^[63] IGN reviewer Ryan Clements also found preference over Terry from all the other characters in the Fatal Fury series, commenting he liked how the character played in each game.^[64] Dan Whitehead from Eurogamer praised each part of Terry's appearance that makes him look cool. He also commented that Terry is one of the most popular characters from Fatal Fury although he is "rather bland".^[65] UGO.com listed Terry's baseball cap thirteenth on their list of "The Coolest Helmets and Headgear in Video Games", calling it "completely badass" despite its reading of "Fatal Fury."^[66] Den of Geek listed Terry 3rd in their "best fighting game characters" list with editor Harry Slater commenting "Bogard is a stark reminder of the glory days of the two dimensional fighter".^[67]

References[link]