TIDAL & WAVE POWER

University of CanberraUniversity of CanberraJuly 2007July 2007

bybyAshuriAshuriGunoroGunoro

Presented in Professional Management ProgramPresented in Professional Management Program

1. Tidal Power1. Tidal Power Tidal powerTidal power, sometimes called , sometimes called tidal energytidal energy, is a form of , is a form of hydropowerhydropower that that exploits the rise and fall in sea levels due to the exploits the rise and fall in sea levels due to the tidestides, or the movement of , or the movement of water caused by the tidal flow. Because the water caused by the tidal flow. Because the tidal forcestidal forces are caused by are caused by interaction between the interaction between the gravitygravity of the of the EarthEarth, , MoonMoon and and SunSun, tidal power is , tidal power is essentially inexhaustible and classified as a essentially inexhaustible and classified as a renewable energyrenewable energy source. source.

Although not yet widely used, tidal power has great potential for future Although not yet widely used, tidal power has great potential for future electricity generationelectricity generation and is more predictable than and is more predictable than wind energywind energy and and solar powersolar power. In Europe, . In Europe, tide millstide mills have been used for nearly a thousand have been used for nearly a thousand years, mainly for grinding grains. years, mainly for grinding grains.

Tidal power can be classified into two types. Tidal stream systems make Tidal power can be classified into two types. Tidal stream systems make use of the use of the kinetic energykinetic energy from the moving water currents to power turbines, from the moving water currents to power turbines, in a similar way to underwater in a similar way to underwater wind turbineswind turbines. This method is gaining in . This method is gaining in popularity because of the lower ecological impact compared to the second popularity because of the lower ecological impact compared to the second type of system, the barrage. Barrages make use of the type of system, the barrage. Barrages make use of the potential energypotential energy from the difference in height (or from the difference in height (or headhead) between high and low tides, and ) between high and low tides, and their use is better established.their use is better established.

Modern advance in turbine technology may eventually see large amounts Modern advance in turbine technology may eventually see large amounts of power generated from the oceans using the tidal stream designs. of power generated from the oceans using the tidal stream designs. Arrayed in high velocity areas where natural flows are concentrated such Arrayed in high velocity areas where natural flows are concentrated such as the west coast of Canada, the Strait of Gibraltar, the Bosporus, and as the west coast of Canada, the Strait of Gibraltar, the Bosporus, and numerous sites in south east Asia and Australia. Such flows occur almost numerous sites in south east Asia and Australia. Such flows occur almost anywhere where there are entrances to bays and rivers, or between land anywhere where there are entrances to bays and rivers, or between land masses where water currents are concentrated. masses where water currents are concentrated.

A factor in human settlement geography is water. Human settlements have A factor in human settlement geography is water. Human settlements have often started around bays rivers and lakes. Future settlement may be often started around bays rivers and lakes. Future settlement may be concentrated around moving water, allowing communities to power concentrated around moving water, allowing communities to power themselves with non-polluting energy from moving water. themselves with non-polluting energy from moving water.

A relatively new technology tidal stream generators draw energy from currents in much the same way as wind turbines. The higher density of water, some 832 times the density of air, means that a single generator can provide significant power.Even more so than with wind power, selection of location is critical for a tidal stream power generator. Tidal stream systems need to be located in areas with fast currents where natural flows are concentrated between obstructions, for example at the entrances to bays and rivers, around rocky points, headlands, or between islands or other land masses. The following potential sites have been suggested:

1.1 Tidal stream power1.1 Tidal stream power

• The Pentland Firth in Scotland • The Channel Islands in the United Kingdom • The Cook Straits in New Zealand • The Strait of Gibraltar • The Bosporus in Turkey • The Bass Strait in Australia • The Torres Strait in Australia • The Strait of Malacca between Indonesia and Singapore • The Bay of Fundy in Canada.

Several prototypes have shown promise. Trials in the Strait of Messina, Italy, started in 2001[1] and an Australian company <http://tidalenergy.net.au/> undertook successful commercial trials of highly efficient shrouded turbines on the Gold Coast, Queensland in 2002 that was followed by successful joint venture commercial trials by Canada by Quantum Hydro Power in 2005-2006 using the Gorlov Helical Turbine on the Canadian West Coast where water speeds have been measured up to 16 knots. These small 2-4 meter diameter highly efficient shrouded turbines, considered to be the next generation in design, are capable of 100 kW - 200kW in 6 - 10 knots of water speed commonly available in many of the Western Canadian regions waterways.

PrototypesPrototypes

One of the Sea Generators awaiting installation in Strangford Lough

During 2003 a 300 kW Periodflow marine current propeller type turbine was tested off the coast of Devon, England, and a 150 kW oscillating hydroplane device, the Stingray, was tested off the Scottish coast. Another British device, the Hydro Venturi, is to be tested in San Francisco Bay.[citation needed]Although still a prototype, the world's first grid-connected turbine, generating 300 kW, started generation November 13, 2003, in the Kvalsund, south of Hammerfest, Norway, with plans to install a further 19 turbines.[2][3]The world's first commercial prototype will be installed by Marine Current Turbines Ltd in Strangford Lough in Northern Ireland in September 2007. The turbine will generate 1.2MW and be connected to the grid.

Tidal systems do not interfere with fish migration at times of spawning, since the water remains open. As water current turbines typically turn very slowly at around 20-30 r.p.m., fish are able to safely navigate either past or through the turbines, drastically reducing or eliminating fish kills compared to barrage systems.

Environmental impactEnvironmental impact

The energy available from these kinetic systems can be expressed as:The energy available from these kinetic systems can be expressed as:P = Cp x 0.5 x ρ x A x V3 P = Cp x 0.5 x ρ x A x V3 Where:Where:Cp is the turbine coefficient of performanceCp is the turbine coefficient of performanceP = the power generated (in kW)P = the power generated (in kW)ρ = the density of the water (seawater is 1025 kg per cubic meter)ρ = the density of the water (seawater is 1025 kg per cubic meter)A = the sweep area of the turbine (in m2)A = the sweep area of the turbine (in m2)V3 = the velocity of the flow cubed (i.e. V x V x V)V3 = the velocity of the flow cubed (i.e. V x V x V)Relative to an open turbine in free stream. Shrouded turbines are Relative to an open turbine in free stream. Shrouded turbines are capable of higher efficiencies as much as 4 times the power of the same capable of higher efficiencies as much as 4 times the power of the same turbine in open flow.turbine in open flow.

Energy calculationsEnergy calculations

The barrage method of extracting tidal energy involves building a barrage and creating a tidal lagoon. The barrage traps a water level inside a basin. Head (a height of water pressure) is created when the water level outside of the basin or lagoon changes relative to the water level inside. The head is used to drive turbines. The largest such installation has been working on the Rance river, France, since 1967 with an installed (peak) power of 240 MW, and an annual production of 600 GWh (about 68 MW average power)

1.2 Barrage tidal power1.2 Barrage tidal power

• An artistic impression of a tidal barrage, including embankments, a ship lock and caissons housing a sluice and two turbines.

Artist's impression of the Artist's impression of the Severn BarrageSevern Barrage and road link proposed in 1989. and road link proposed in 1989. The scheme would have generated 6% of the The scheme would have generated 6% of the UK'sUK's electricity supplyelectricity supply

The basic elements of a barrage are caissons, embankments, sluices, turbines and ship locks. Sluices, turbines and ship locks are housed in caisson (very large concrete blocks). Embankments seal a basin where it is not sealed by caissons.

The sluice gates applicable to tidal power are the flap gate, vertical rising gate, radial gate and rising sector.

Barrage systems are sometimes affected by problems of high civil infrastructure costs associated with what is in effect a dam being placed across two estuarine systems, and the environmental problems associated with changing a large ecosystem.

The basin is filled through the sluices until high tide. Then the sluice The basin is filled through the sluices until high tide. Then the sluice gates are closed. (At this stage there may be "Pumping" to raise the level gates are closed. (At this stage there may be "Pumping" to raise the level further). The turbine gates are kept closed until the sea level falls to further). The turbine gates are kept closed until the sea level falls to create sufficient head across the barrage, and then are opened so that create sufficient head across the barrage, and then are opened so that the turbines generate until the head is again low. Then the sluices are the turbines generate until the head is again low. Then the sluices are opened, turbines disconnected and the basin is filled again. The cycle opened, turbines disconnected and the basin is filled again. The cycle repeats itself. Ebb generation (also known as outflow generation) takes repeats itself. Ebb generation (also known as outflow generation) takes its name because generation occurs as the tide ebbs. its name because generation occurs as the tide ebbs.

Modes of operationModes of operation Ebb generationEbb generation

The basin is filled through the turbines, which generate at tide flood. This The basin is filled through the turbines, which generate at tide flood. This is generally much less efficient than ebb generation, because the volume is generally much less efficient than ebb generation, because the volume contained in the upper half of the basin (which is where ebb generation contained in the upper half of the basin (which is where ebb generation operates) is greater than the volume of the lower half (and making the operates) is greater than the volume of the lower half (and making the difference in levels between the basin side and the sea side of the difference in levels between the basin side and the sea side of the barrage), (and therefore the available potential energy) less than it would barrage), (and therefore the available potential energy) less than it would otherwise be. This is not a problem with the "lagoon" model; the reason otherwise be. This is not a problem with the "lagoon" model; the reason being that there is no current from a river to slow the flooding current being that there is no current from a river to slow the flooding current from the sea. from the sea.

Flood generationFlood generation

Turbines are able to be powered in reverse by excess energy in the grid Turbines are able to be powered in reverse by excess energy in the grid to increase the water level in the basin at high tide (for ebb generation). to increase the water level in the basin at high tide (for ebb generation). This energy is more than returned during generation, because power This energy is more than returned during generation, because power output is strongly related to the head. output is strongly related to the head.

PumpingPumping

With two basins, one is filled at high tide and the other is emptied at low With two basins, one is filled at high tide and the other is emptied at low tide. Turbines are placed between the basins. Two-basin schemes offer tide. Turbines are placed between the basins. Two-basin schemes offer advantages over normal schemes in that generation time can be advantages over normal schemes in that generation time can be adjusted with high flexibility and it is also possible to generate almost adjusted with high flexibility and it is also possible to generate almost continuously. In normal estuarine situations, however, two-basin continuously. In normal estuarine situations, however, two-basin schemes are very expensive to construct due to the cost of the extra schemes are very expensive to construct due to the cost of the extra length of barrage. There are some favourable geographies, however, length of barrage. There are some favourable geographies, however, which are well suited to this type of scheme. which are well suited to this type of scheme.

Two-basin schemes Two-basin schemes

The placement of a barrage into an estuary has a considerable effect on The placement of a barrage into an estuary has a considerable effect on the water inside the basin and on the fish. A tidal current turbine will have the water inside the basin and on the fish. A tidal current turbine will have a much lower impact.a much lower impact.[

Environmental impactEnvironmental impact

Turbidity (the amount of matter in suspension in the water) decreases as Turbidity (the amount of matter in suspension in the water) decreases as a result of smaller volume of water being exchanged between the basin a result of smaller volume of water being exchanged between the basin and the sea. This lets light from the Sun to penetrate the water further, and the sea. This lets light from the Sun to penetrate the water further, improving conditions for the improving conditions for the phytoplankton. The changes propagate up . The changes propagate up the the food chain, causing a general change in the , causing a general change in the ecosystem..

TurbidityTurbidity

As a result of less water exchange with the sea, the average salinity As a result of less water exchange with the sea, the average salinity inside the basin decreases, also affecting the ecosystem. "Tidal inside the basin decreases, also affecting the ecosystem. "Tidal Lagoons" do not suffer from this problem. Lagoons" do not suffer from this problem.

SalinitySalinity

Estuaries often have high volume of sediments moving through them, Estuaries often have high volume of sediments moving through them, from the rivers to the sea. The introduction of a barrage into an estuary from the rivers to the sea. The introduction of a barrage into an estuary may result in sediment accumulation within the barrage, affecting the may result in sediment accumulation within the barrage, affecting the ecosystem and also the operation of the barrage.ecosystem and also the operation of the barrage.

Sediment movementsSediment movements

Again, as a result of reduced volume, the pollutants accumulating in the Again, as a result of reduced volume, the pollutants accumulating in the basin may be less efficiently dispersed, so their concentrations may basin may be less efficiently dispersed, so their concentrations may increase. For increase. For biodegradable pollutants, such as pollutants, such as sewage, an increase in , an increase in concentration is likely to lead to increased bacteria growth in the basin, concentration is likely to lead to increased bacteria growth in the basin, having impacts on the health of the human community and the having impacts on the health of the human community and the ecosystem.ecosystem.

PollutantsPollutants

Fish may move through sluices safely, but when these are closed, fish Fish may move through sluices safely, but when these are closed, fish will seek out turbines and attempt to swim through them. Also, some fish will seek out turbines and attempt to swim through them. Also, some fish will be unable to escape the water speed near a turbine and will be will be unable to escape the water speed near a turbine and will be sucked through. Even with the most fish-friendly turbine design, fish sucked through. Even with the most fish-friendly turbine design, fish mortality per pass is approximately 15% (from pressure drop, contact mortality per pass is approximately 15% (from pressure drop, contact with blades, with blades, cavitation, etc.). This can be acceptable for a , etc.). This can be acceptable for a spawning run, , but is devastating for local fish who pass in and out of the basin on a but is devastating for local fish who pass in and out of the basin on a daily basis. Alternative passage technologies (daily basis. Alternative passage technologies (fish ladders, fish lifts, etc.) , fish lifts, etc.) have so far failed to solve this problem for tidal barrages, either offering have so far failed to solve this problem for tidal barrages, either offering extremely expensive solutions, or ones which are used by a small extremely expensive solutions, or ones which are used by a small fraction of fish only. Research in sonic guidance of fish is ongoing.fraction of fish only. Research in sonic guidance of fish is ongoing.

FishFish

The energy available from barrage is dependant on the volume of water. The energy available from barrage is dependant on the volume of water. The The potential energy contained in a volume of water is : contained in a volume of water is :

Energy calculationsEnergy calculations

A barrage is therefore best placed in a location with very high-amplitude A barrage is therefore best placed in a location with very high-amplitude tides. Suitable locations are found in tides. Suitable locations are found in Russia, , USA, , Canada, , Australia, , Korea, the , the UK and elsewhere. Amplitudes of up to 17 m (56 ft) occur for and elsewhere. Amplitudes of up to 17 m (56 ft) occur for example in the example in the Bay of Fundy, where , where tidal resonance amplifies the tidal amplifies the tidal waves. waves.

where:x : is the height of the tideM : is the mass of waterg : is the acceleration due to gravity at the Earth's surface.

xMgE

Tidal barrage power schemes have a high capital cost and a very low Tidal barrage power schemes have a high capital cost and a very low running cost. As a result, a tidal power scheme may not produce returns running cost. As a result, a tidal power scheme may not produce returns for years, and investors are thus reluctant to participate in such projects. for years, and investors are thus reluctant to participate in such projects. Governments may be able to finance tidal barrage power, but many are Governments may be able to finance tidal barrage power, but many are unwilling to do so also due to the lag time before investment return and unwilling to do so also due to the lag time before investment return and the high irreversible commitment. For example the the high irreversible commitment. For example the energy policy of the United Kingdom[4] recognizes the role of tidal energy recognizes the role of tidal energy and expresses the need for local councils to understand the broader and expresses the need for local councils to understand the broader national goals of renewable energy in approving tidal projects. The UK national goals of renewable energy in approving tidal projects. The UK government itself appreciates the technical viability and sitting options government itself appreciates the technical viability and sitting options available, but has failed to provide meaningful incentives to move its available, but has failed to provide meaningful incentives to move its goals forward.goals forward.

Economics Economics

Tidal power schemes do not produce energy all day. A conventional Tidal power schemes do not produce energy all day. A conventional design, in any mode of operation, would produce power for 6 to 12 hours design, in any mode of operation, would produce power for 6 to 12 hours in every 24 and will not produce power at other times. As the tidal cycle is in every 24 and will not produce power at other times. As the tidal cycle is based on the rotation of the Earth with respect to the moon (24.8 hours), based on the rotation of the Earth with respect to the moon (24.8 hours), and the demand for electricity is based on the period of rotation of the and the demand for electricity is based on the period of rotation of the earth (24 hours), the energy production cycle will not always be in phase earth (24 hours), the energy production cycle will not always be in phase with the demand cycle. with the demand cycle.

Variable nature of power outputVariable nature of power output

Mathematical modelling of tidal schemesMathematical modelling of tidal schemes

In mathematical modelling of a scheme design, the basin is broken into In mathematical modelling of a scheme design, the basin is broken into segments, each maintaining its own set of variables. Time is advanced in steps. segments, each maintaining its own set of variables. Time is advanced in steps. Every step, neighbouring segments influence each other and variables are Every step, neighbouring segments influence each other and variables are updated.updated.

In these models, the basin is broken into large segments (1D), squares (2D) or In these models, the basin is broken into large segments (1D), squares (2D) or cubes (3D). The complexity and accuracy increases with dimension.cubes (3D). The complexity and accuracy increases with dimension.

Mathematical modelling produces quantitative information for a range of Mathematical modelling produces quantitative information for a range of parameters, including:parameters, including:

• Water levels (during operation, construction, extreme conditions, etc.) Water levels (during operation, construction, extreme conditions, etc.) • Currents Currents • Waves Waves • Power output Power output • Turbidity • Salinity • Sediment movementsSediment movements

Tidal energy has an efficiency of 80% in converting the potential energy Tidal energy has an efficiency of 80% in converting the potential energy of the water into electricity,of the water into electricity,[citation needed] which is efficient compared which is efficient compared to other energy resources such as to other energy resources such as solar power or or fossil fuel power plants. .

Energy efficiencyEnergy efficiency

A tidal power scheme is a long-term source of electricity. A proposal for A tidal power scheme is a long-term source of electricity. A proposal for the the Severn Barrage, if built, has been projected to save 18 million tons of , if built, has been projected to save 18 million tons of coal per year of operation. This decreases the output of per year of operation. This decreases the output of greenhouse gases into the atmosphere. into the atmosphere.

Global environmental impactGlobal environmental impact

If fossil fuel resource is likely to decline during the 21st, as predicted by If fossil fuel resource is likely to decline during the 21st, as predicted by Hubbert peak theory, tidal power is one of the alternative source of , tidal power is one of the alternative source of energy that will need to be developed to satisfy the human demand for energy that will need to be developed to satisfy the human demand for energy. energy.

Operating tidal power schemesOperating tidal power schemes

Resource around the worldResource around the world

• The first tidal power station was the Rance tidal power plant built over a period of 6 years from 1960 to 1966 at La Rance, France.[5] It has 240MW installed capacity.

• The first (and only) tidal power site in North America is the Annapolis Royal Generating Station, Annapolis Royal, Nova Scotia, which opened in 1984 on an inlet of the Bay of Fundy.[6] It has 20MW installed capacity.

• A small project was built by the Soviet Union at Kislaya Guba on the Barents Sea. It has 0.5MW installed capacity.

• China has apparently developed several small tidal power projects and one large facility in Jiangxia.

• China is also developing a tidal lagoon near the mouth of the Yalu.[7] • Scotland has committed to having 18% of its power from green sources by 2010,

including 10% from a tidal generator. The British government says this will replace one huge fossil fueled power station.[8]

• South African energy parastatal Eskom is investigating using the Mozambique Current to generate power off the coast of KwaZulu Natal. Because the continental shelf is near to land it may be possible to generate electricity by tapping into the fast flowing Mozambique current.

Tidal power schemes being consideredTidal power schemes being considered

In the table,

'-' indicates missing information,

'?' indicates information which has not been decided

Country Place Mean tidal range (m)

Area of basin (km²)

Maximum capacity (MW)

Argentina San Jose 5.9 - 6800

Australia Secure Bay 10.9 - ?

Canada

Cobequid 12.4 240 5338

Cumberland 10.9 90 1400

Shepody 10.0 115 1800

Passamaquoddy 5.5 - ?

IndiaKutch 5.3 170 900

Cambay 6.8 1970 7000

KoreaGarolim 4.7 100 480

Cheonsu 4.5 - -

MexicoRio Colorado 6 -7 - ?

Tiburon - - ?

United Kingdom

Severn 7.8 450 8640

Mersey 6.5 61 700

Strangford Lough - - -

Conwy 5.2 5.5 33

United States

Passamaquoddy 5.5 - ?

Knik Arm 7.5 - 2900

Turnagain Arm 7.5 - 6501

Russia

Mezen 9.1 2300 19200

Tugur - - 8000

Penzhinskaya Bay 6.0 - 87000

South Africa Mozambique Channel ? ? ?

Introduction

The tide moves a huge amount of water twice each day, and harnessing it could provide a great deal of energy - around 20% of Britain's needs. Although the energy supply is reliable and plentiful, converting it into useful electrical power is not easy.

There are eight main sites around Britain where tidal power stations could usefully be built, including the Severn, Dee, Solway and Humber estuaries.

Only around 20 sites in the world have been identified as possible tidal power stations.

How it works: Tidal Barrages

These work rather like a hydro-electric scheme, except that the dam is much bigger.

A huge dam (called a "barrage") is built across a river estuary. When the tide goes in and out, the water flows through tunnels in the dam.

The ebb and flow of the tides can be used to turn a turbine, or it can be used to push air through a pipe, which then turns a turbine. Large lock gates, like the ones used on canals, allow ships to pass.

More details

The largest tidal power station in the world (and the only one in Europe) is in the Rance estuary in northern France. It was built in 1966.

A major drawback of tidal power stations is that they can only generate when the tide is flowing in or out - in other words, only for 10 hours each day. However, tides are totally predictable, so we can plan to have other power stations generating at those times when the tidal station is out of action.

There have been plans for a "Severn Barrage" from Brean Down in Somerset to Lavernock Point in Wales. Every now and again the idea gets proposed, but nothing has been built yet.

It may have over 200 large turbines, and provide over 8,000 Megawatts of power (that's over 12 nuclear power station's worth). It would take 7 years to build, and could provide 7% of the energy needs for England and Wales.

There would be a number of benefits, including protecting a large stretch of coastline against damage from high storm tides, and providing a ready-made road bridge. However, the drastic changes to the currents in the estuary could have huge effects on the ecosystem.

offshore turbines

Another option is to use offshore turbines rather like an underwater wind farm.

This has the advantage of being much cheaper to build, and does not have the environmental problems that a tidal barrage would bring.

There are also many more suitable sites.

Find out more about the world's first offshore tidal power station at

The University of Wales Swansea and partners are also researching techniques to extract electrical energy from flowing water.

The "Swanturbines" design is different to other devices in a number of ways. The most significant is that it is direct drive, where the blades are connected directly to the electrical generator without a gearbox between. This is more efficient and there is no gearbox to go wrong. Another difference is that it uses a "gravity base", a large concrete block to hold it to the seabed, rather than drilling into the seabed. Finally, the blades are fixed pitch, rather than actively controlled, this is again to design out components that could be unreliable.

vertical-axis turbines

2. Wave Power2. Wave Power

2.1 Introduction2.1 IntroductionOcean waves are caused by the wind as Ocean waves are caused by the wind as it blows across the sea. Waves are a it blows across the sea. Waves are a powerful source of energy.powerful source of energy. The problem is that it's not easy to The problem is that it's not easy to harness this energy and convert it into harness this energy and convert it into electricity in large amounts. Thus, wave electricity in large amounts. Thus, wave power stations are rare.power stations are rare.

Wave energy from the wind on the seaWave energy from the wind on the sea

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

WAVE ENERGY MACHINEWAVE ENERGY MACHINE

DESIGN VARIATIONSDESIGN VARIATIONS

Wrist Pin & Roller GearWrist Pin & Roller Gear

General Assembly Gear & FlywheelGeneral Assembly Gear & Flywheel

"Spinner Drive" & Flywheel"Spinner Drive" & Flywheel

Simple Bilge PumpSimple Bilge Pump

Neo-AeroDynamicNeo-AeroDynamic

Oscillating or Assisted Water Columns (OWC), buoys and pontoons (the Oscillating or Assisted Water Columns (OWC), buoys and pontoons (the Hosepump), flaps and tapered channels (the Pendulor and TAPCHAN) still Hosepump), flaps and tapered channels (the Pendulor and TAPCHAN) still existor continue to be developedexistor continue to be developed

How it worksHow it works

• There are several methods of getting energy from waves, but one of the most effective works like a swimming pool wave machine in reverse.

• At a swimming pool, air is blown in and out of a chamber beside the pool, which makes the water outside bob up and down, causing waves.

• At a wave power station, the waves arriving cause the water in the chamber to rise and fall, which means that air is forced in and out of the hole in the top of the chamber.

We place a turbine in this holeWe place a turbine in this hole

We place a turbine in this holeWe place a turbine in this hole

• which is turned by the air rushing in and out. The turbine turns a generator.

• A problem with this design is that the rushing air can be very noisy, unless a silencer is fitted to the turbine. The noise is not a huge problem anyway, as the waves make quite a bit of noise themselves.

More detailsMore details

• Once you've built it, the energy is free, needs no fuel and produces no waste or pollution.

• One big problem is that of building and anchoring something that can withstand the roughest conditions at sea, yet can generate a reasonable amount of power from small waves. It's not much use if it only works during storms!

LimpetLimpet

A company called Wavegen now operate a commercial wave power station called "Limpet" on the Scottish island of Islay.

LimpetLimpet (Land-Installed Marine-Powered Energy Transformer)(Land-Installed Marine-Powered Energy Transformer)

View a SimulationView a Simulation

PelamisPelamis

A company called Ocean Power Delivery are developing a method of offshore wave energy collection, using a floating tube called "Pelamis".

Pelamis in ExperimentPelamis in Experiment

The pelamisThe pelamis(named after a sea-snake)(named after a sea-snake)

PelamisPelamis – prototype (Ocean Power Delivery Ltd.)– prototype (Ocean Power Delivery Ltd.)

Pelamis Ready to InstallPelamis Ready to Install

PELAMISPELAMISabout the size of 5 railway carriagesabout the size of 5 railway carriages

PELAMISPELAMISbobs up and down in the waves, as the hinges bend they bobs up and down in the waves, as the hinges bend they pump hydraulic fluid which drives generators.pump hydraulic fluid which drives generators.

The first prototype was installed at the European The first prototype was installed at the European

Marine Energy Centre at Orkney.Marine Energy Centre at Orkney.

The Pelamis on site at the EMEC The Pelamis on site at the EMEC centre, Orkney  centre, Orkney 

Pelamis WavefarmPelamis Wavefarm

DisadvantagesDisadvantages

• Depends on the waves - sometimes you'll get loads of energy, sometimes nothing.

• Needs a suitable site, where waves are consistently strong.

• Some designs are noisy.

• Must be able to withstand very rough weather.

Is it renewable?Is it renewable?• Wave power is renewable.• Don’t Forget to Remember it !!!!

Thank youThank you

Have an any question ?