NationMaster - Encyclopedia: Tidal power

Tidal power, sometimes called tidal energy, is a form of hydropower that converts the energy of tides into electricity or other useful forms of power. Renewable energy effectively utilizes natural resources such as sunlight, wind, tides and geothermal heat, which are naturally replenished. ... Bio-energy redirects here. ... For the use of the term in ecology, see Biomass (ecology). ... Krafla Geothermal Station in northeast Iceland Geothermal power (from the Greek words geo, meaning earth, and therme, meaning heat) is energy generated by heat stored beneath the Earths surface or the collection of absorbed heat in the atmosphere and oceans. ... Hydroelectricity is electricity produced by hydropower. ... The Solar Two 10 MW solar power facility, showing the power tower (left) surrounded by the sun-tracking mirrors. ... Wave power refers to the energy of ocean surface waves and the capture of that energy to do useful work - including electricity generation, desalination, and the pumping of water (into reservoirs). ... An example of a wind turbine. ... Undershot water wheels on the Orontes River in Hama, Syria Saint Anthony Falls Hydropower or hydraulic power is the force or energy of moving water. ... This article is about tides in the Earths oceans. ...

Although not yet widely used, tidal power has potential for future electricity generation. Tides are more predictable than wind energy and solar power. Historically, tide mills have been used, both in Europe and on the Atlantic coast of the USA, the earliest occurrences dating from the Middle Ages, or even from Roman times.^[1]^[2] World-wide electricity production for 1980 to 2005. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Solar power describes a number of methods of harnessing energy from the light of the sun. ... A tide mill is a specialist type of water mill driven by tidal rise and fall. ... The Middle Ages formed the middle period in a traditional schematic division of European history into three ages: the classical civilization of Antiquity, the Middle Ages, and modern times, beginning with the Renaissance. ... Ancient Rome was a civilization that grew from a small agricultural community founded on the Italian Peninsula circa the 9th century BC to a massive empire straddling the Mediterranean Sea. ...

Generation of tidal energy

Tidal power is the only form of energy which comes from the tidal forces produced by the relative motions of the Earth-Moon system. Other sources of energy originate directly or indirectly from the Sun, including fossil fuels, conventional hydroelectric, wind, biofuels, and solar. nuclear and geothermal come from radioactive material in the Earth. Image File history File links Size of this preview: 433 Ã— 600 pixel Image in higher resolution (621 Ã— 860 pixel, file size: 18 KB, MIME type: image/gif) page: OUR RESTLESS TIDES National Ocean Service NOAA http://co-ops. ... Image File history File links Size of this preview: 433 Ã— 600 pixel Image in higher resolution (621 Ã— 860 pixel, file size: 18 KB, MIME type: image/gif) page: OUR RESTLESS TIDES National Ocean Service NOAA http://co-ops. ... This article is about tides in the Earths oceans. ... It has been suggested that Tidal friction be merged into this article or section. ... Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiters tidal forces. ... Sol redirects here. ... Fossil fuels or mineral fuels are fossil source fuels, that is, hydrocarbons found within the top layer of the earthâ€™s crust. ... Hydroelectricity is electricity produced by hydropower. ... An example of a wind turbine. ... Biofuel is any fuel that derives from biomass _ recently living organisms or their metabolic byproducts, such as manure from cows. ... The Solar Two 10 MW solar power facility, showing the power tower (left) surrounded by the sun-tracking mirrors. ... This article is about applications of nuclear fission reactors as power sources. ... Krafla Geothermal Station in northeast Iceland Geothermal power (from the Greek words geo, meaning earth, and therme, meaning heat) is energy generated by heat stored beneath the Earths surface or the collection of absorbed heat in the atmosphere and oceans. ... Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. ...

Tidal energy is generated by the relative motion of the Earth, Sun and the Moon, which interact via gravitational forces. Periodic changes of water levels, and associated tidal currents, are due to the gravitational attraction by the Sun and Moon. The magnitude of the tide at a location is the result of the changing positions of the Moon and Sun relative to the Earth, the effects of Earth rotation, and the local shape of the sea floor and coastlines. Sol redirects here. ... This article is about Earths moon. ... Gravity redirects here. ... In the inertial frame of reference (upper part of the picture), the black object moves in a straight line. ... Bathymetry is the underwater equivalent to topography. ...

A tidal energy generator uses this phenomenon to generate energy. The stronger the tide, either in water level height or tidal current velocities, the greater the potential for tidal energy generation.

Tidal movement causes a continual loss of mechanical energy in the Earth-Moon system due to pumping of water through the natural restrictions around coastlines, and due to viscous dissipation at the seabed and in turbulence. This loss of energy has caused the period of rotation of the Earth to slow in the 4.5 billion years since formation. During the last 620 million years the period of rotation has reduced from 21.9 hours to the 24 hours ^[3] we see now; in this period the Earth has lost 17% of its rotational energy. Tidal power may take additional energy from the system, increasing the rate of slowing. It has been suggested that Tidal friction be merged into this article or section. ... For other uses, see Viscosity (disambiguation). ... The seabed (also sea floor, seafloor, or ocean floor) is the bottom of the ocean. ... In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic, stochastic property changes. ...

Categories of Tidal Power

Modern advances in turbine technology may eventually see large amounts of power generated from the ocean, especially tidal currents using the tidal stream designs. Tidal stream turbines may be arrayed in high-velocity areas where natural tidal current flows are concentrated such as the west and east coasts of Canada, the Strait of Gibraltar, the Bosporus, and numerous sites in south east Asia and Australia. Such flows occur almost anywhere where there are entrances to bays and rivers, or between land masses where water currents are concentrated. The cars of a roller coaster reach their maximum kinetic energy when at the bottom of their path. ... Potential energy can be thought of as energy stored within a physical system. ... It has been suggested that Hydraulic head (hydrology) and Head (hydraulic) be merged into this article or section. ... The Strait of Gibraltar as seen from space (on the left: Spain) A view across the Strait of Gibraltar taken from the hills over Tarifa, Spain The Strait of Gibraltar (Arabic: Ù…Ø¶ÙŠÙ‚ Ø¬Ø¨Ù„ Ø·Ø§Ø±Ù‚, Spanish: Estrecho de Gibraltar) is the strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Spain... I LOVE BORAT!!!!!!!!!!!!!!!Two bridges cross the Bosporus. ... Location of Southeast Asia Southeast Asia is a subregion of Asia. ...

Tidal stream generators

A relatively new technology, tidal stream generators draw energy from currents in much the same way as wind turbines. The higher density of water, 832 times the density of air, means that a single generator can provide significant power at low tidal flow velocities (compared with the wind speed). Image File history File links Question_book-3. ... Wind turbines near Aalborg, Denmark. ...

Similar to wind power, selection of location is important for the tidal turbine. 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: An example of a wind turbine. ...

The Pentland Firth, which is actually more of a strait than a firth, separates the Orkney Islands from Caithness, which is in the far north of the Highland area of Scotland. ... This article is about the country. ... This article is about the British dependencies. ... Pembrokeshire (Welsh: ) is a county in the southwest of Wales in the United Kingdom. ... A view from the summit of Mount Victoria, Wellington - Cook Strait stretches to the right (west). ... The Strait of Gibraltar as seen from space (on the left: Spain) A view across the Strait of Gibraltar taken from the hills over Tarifa, Spain The Strait of Gibraltar (Arabic: Ù…Ø¶ÙŠÙ‚ Ø¬Ø¨Ù„ Ø·Ø§Ø±Ù‚, Spanish: Estrecho de Gibraltar) is the strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Spain... I LOVE BORAT!!!!!!!!!!!!!!!Two bridges cross the Bosporus. ... Map of Australia with Bass Strait marked in light blue Bass Strait (IPA: ) is a sea strait separating Tasmania from the south of the Australian mainland (Victoria in particular). ... Torres Strait and islands The Torres Strait - Cape York Peninsula is at the bottom; several of the Torres Strait Islands can be seen strung out towards Papua New Guinea to the north. ... A close-up map showing the Strait of Malacca separating peninsular Malaysia and the Indonesian island of Sumatra. ... The Bay of Fundy (French: ) is a bay located on the Atlantic coast of North America, on the northeast end of the Gulf of Maine between the Canadian provinces of New Brunswick and Nova Scotia, with a small portion touching the U.S. state of Maine. ... New York City waterways: 1. ... New York, New York and NYC redirect here. ... Vancouver Island is separated from mainland British Columbia by the Strait of Georgia and the Queen Charlotte Strait, and from Washington by the Juan De Fuca Strait. ... A map of the Strait of Magellan The Strait of Magellan is a navigable sea route immediately south of mainland Chile, South America and north of Isla Grande de Tierra del Fuego. ... The Golden Gate The Golden Gate, looking south towards San Francisco. ... San Francisco Bay, San Pablo Bay, and the Golden Gate San Francisco Bay is a shallow, productive estuary through which water draining approximately forty percent of California, flowing in the Sacramento and San Joaquin rivers from the Sierra Nevada mountains, enters the Pacific Ocean. ... The Piscataqua River seen from downtown Portsmouth, New Hampshire The Piscataqua River, in the northeastern United States, is a 12 mi (19 km) long tidal estuary formed by the confluence of the Salmon Falls and Cocheco rivers. ... For other uses, see New Hampshire (disambiguation). ...

Prototypes

Several prototypes have shown promise with many companies making bold claims, some of which are yet to be independently verified, or operated commercially for extended periods to establish performances and rates of return on investments.

Trials in the Strait of Messina, Italy, started in 2001^[10] and Australian company Tidal Energy Pty Ltd undertook successful commercial trials of highly efficient shrouded turbines on the Gold Coast, Queensland in 2002. Tidal Energy Pty Ltd has commenced a rollout of their efficient shrouded turbine (the turbine resembles a jet turbine engine and is capable of converting 60% of the kinetic energy in the flow) for a remote Australian community in northern Australia where there exist some of the fasted flows ever recorded (11 m/s, 21 knots) – two small turbines will provided 3.5 MW. Another larger 5 meter diameter turbine, capable of 800kW in 4m/s of flow, is planned for deployment as a tidal powered desalination showcase near Brisbane Australia in October 2008. Satellite photo of the Strait of Messina with names. ... Gold Coast redirects here. ...

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.^[11] Image File history File links Metadata Size of this preview: 800 Ã— 483 pixelsFull resolution (2592 Ã— 1566 pixel, file size: 1. ... Image File history File links Metadata Size of this preview: 800 Ã— 483 pixelsFull resolution (2592 Ã— 1566 pixel, file size: 1. ... Harland and Wolff Heavy Industries is a diversified Heavy industrial company specialising in Shipbuilding, Ship breaking, Offshore construction, Modular construction, Civil, Marine engineering and Project management, located in Belfast, Northern Ireland. ... Strangford Lough from Portaferry, looking towards the narrows. ... Strangford Lough from Portaferry, looking towards the narrows. ... For other uses, see Devon (disambiguation). ... For other uses, see England (disambiguation). ... This article is about the country. ...

Although still a prototype, the world's first grid-connected turbine, generating 300 kW, started generation on November 13, 2003, in the Kvalsund, south of Hammerfest, Norway, with plans to install a further 19 turbines.^[12]^[13] 11kV/400V-230V transformer in an older suburb of Wellington, New Zealand Electricity distribution is the penultimate stage in the delivery (before retail) of electricity to end users. ... is the 317th day of the year (318th in leap years) in the Gregorian calendar. ... Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... County Finnmark District Municipality NO-2017 Administrative centre Kvalsund Mayor (2003) Ragnar Olsen (Ap) Official language form BokmÃ¥l Area - Total - Land - Percentage Ranked 37 1,844 kmÂ² 1,739 kmÂ² 0. ... County Finnmark District Municipality NO-2004 Administrative centre Hammerfest Mayor (2006) Kristine JÃ¸rstad Bock (Ap) Official language form Neutral Area - Total - Land - Percentage Ranked 129 849 kmÂ² 819 kmÂ² 0. ...

SeaGen, a commercial prototype has been installed by Marine Current Turbines Ltd in Strangford Lough in Northern Ireland in April 2008. The turbine is expected to generate 1.2MW and is being connected to the grid. It is the currently the only commercial scale device to have been installed anywhere in the world. ^[14] Strangford Lough from Portaferry, looking towards the narrows. ...

RWE's NPower announced that it is in partnership with Marine Current Turbines to build a tidal farm of SeaGen turbines off the coast of Anglesey in Wales, though strictly speaking this is not a prototype, but a commercial farm.^[15] RWE AG, until 1990 named Rheinisch-WestfÃ¤lisches ElektrizitÃ¤tswerk AG, is a German public utility and electric power company based in Essen. ... NPower is a national network of nonprofit technology assistance providers based in Seattle, WA, USA. // Mission ...to ensure all nonprofits can use technology to better serve their communities. ... Anglesey (historically Anglesea; Welsh: , pronounced (IPA)) is a predominantly Welsh-speaking island off the northwest coast of Wales. ... This article is about the country. ...

British Columbia Tidal Energy Corp. plans to deploy at least three 1.2-MW turbines in the Campbell River or in the surrounding coastline of British Columbia by 2009. ^[16] Categories: Stub | British Columbia communities | Coastal towns of Canada ...

In November 2007, British company Lunar Energy announced that, in conjunction with E.On, they would be building the world's first tidal energy farm off the coast of Pembrokshire in Wales. It will be the world's first deep-sea tidal-energy farm and will provide electricity for 5,000 homes. Eight underwater turbines, each 25 metres long and 15 metres high, are to be installed on the sea bottom off St David's peninsula. Construction is due to start in the summer of 2008 and the proposed tidal energy turbines, described as "a wind farm under the sea", should be operational by 2010.

Verdant Power^[17] is running a prototype project in the East River between Queens and Roosevelt Island in New York City. Verdant Power is a maker and installer of tidal power and hydroelectric systems. ... New York City waterways: 1. ... This article is about the borough of New York City. ... This article is about the island in New York City. ... New York, New York and NYC redirect here. ...

OpenHydro an Irish based company, exploiting the Open-Centre Turbine turbine developed in the US, has a prototype being tested at the European Marine Energy Centre (EMEC), in Orkney, Scotland. Nova Scotia Power has selected their turbine for a tidal energy demonstration project in the Bay of Fundy, Nova Scotia, Canada and Alderney Renewable Energy Ltd for the supply of tidal turbines in the Channel Islands. Open Hydro

Shrouded tidal energy turbines

An emerging tidal stream technology is the shrouded tidal turbine enclosed in a Venturi shaped shroud or duct producing a sub atmosphere of low pressure behind the turbine, allowing the turbine to operate at higher efficiency (than the Betz Limit ^[18] of 59.3%) in one case nearly 4 times higher power output ^[19] than the same minus the shroud. A Venturi meter is shown in a diagram, the pressure in 1 conditions is higher than 2, and the relationship between the fluid speed in 2 and 1 respectively, is the same as for pressure. ... // The aerodynamics of a horizontal axis wind turbine are not straight forward. ...

Considerable commercial interest has been shown in shrouded tidal stream turbines due to the increased power output. They can operate in shallower slower moving water with a smaller turbine at sites where large turbines are restricted. Arrayed across a seaway or in fast flowing rivers, shrouded turbines are cabled to shore for connection to a grid or a community. Alternatively the property of the shroud that produces an accelerated flow velocity across the turbine allows tidal flows formerly too slow for commercial use to be used for energy production. Categories: Canada geography stubs ...

While the shroud may not be practical in wind, as the next generation of tidal stream turbine design it is gaining more popularity and commercial use. Tidal Energy Pty Ltd^[20]in Australia make use of the design and Lunar Energy (http://www.lunarenergy.co.uk/duct.htm) use a double ended shroud. The Tidal Energy Pty Ltd tidal turbine is multi directional able to face up-stream in any direction and the Lunar Energy turbine bi directional. All tidal stream turbines constantly need to face at the correct angle to the water stream in order to operate. The Tidal Energy Pty Ltd is a unique case with a pivoting base. Lunar Energy use a wide angle diffuser to capture incoming flow that may not be inline with the long axis of the turbine. A shroud can also be built into a tidal fence or barrage increasing the performance of turbines.

Types of shroud

Not all shrouded turbines are the same - the performance of a shrouded turbine varies with the design of the shroud. Not all shrouded turbines have undergone independent scrutiny of claimed performances, as companies closely guard their respective technologies, so quoted performance figures need to be closely scrutinised. Claims vary from a 15%-25% [4] to a 384% [5] improvement over the same turbine without the shroud. Shrouded turbines do not operate at maximum efficiency when the shroud does not intercept the current flow at the correct angle, which can occur as currents eddy and swirl, resulting in reduced operational efficiency. At lower turbine efficiencies the extra cost of the shroud must be justified, while at higher efficiencies the extra cost of the shroud has less impact on commercial returns. Similarly the added cost of the supporting structure for the shroud has to be balanced against the performance gained. Yawing (pivoting) the shroud and turbine at the correct angle, so it always faces upstream like a wind sock, can increase turbine performance but may need expensive active devices to turn the shroud into the flow. Passive designs can be incorporated, such as floating the shrouded turbine under a pontoon on a swing mooring, or flying the turbine like a kite under water. [6] One design yaws the shrouded turbine using a turntable [7].

Advantages

Disadvantages

For other uses, see Fish (disambiguation). ... A Humpback whale (Megaptera novaeangliae), a member of Order Cetacea A Leopard seal (Hydrurga leptonyx), a member of infrafamily Pinnipedia A West Indian Manatee (Trichechus manatus), a member of Order Sirenia A pair of Sea Otters (Enhydra lutris), a member of family Mustelidae A Polar bear (Ursus maritimus), a member... A Venturi meter is shown in a diagram, the pressure in 1 conditions is higher than 2, and the relationship between the fluid speed in 2 and 1 respectively, is the same as for pressure. ...

Energy calculations

Various turbine designs have varying efficiencies and therefore varying power output. If the efficiency of the turbine "Cp" is known the equation below can be used to determine the power output.

Relative to an open turbine in free stream, shrouded turbines are capable of efficiencies as much as 3 to 4 times the power of the same turbine in open flow. ^[25]

Price calculations

Prices paid for electricity varies around the globe. The kilowatt price can be 10-15 British Pence in the UK, or 30-40 US cents or more in remote areas.^{[citation needed]} Image File history File links Question_book-3. ...

The following equation can be used to calculate the revenue from a tidal stream turbine.^{[citation needed]} By substituting variables such as the efficiency, size of the turbine, flow velocity and price into the equation it is possible to accurately predict an annual return.

Keeping in mind this equation does not include the cost of civil infrastructure which would vary with manufacturer and from site to site.

In order to calculate the revenue that a tidal stream generator would return the following equation can be used as a guide only. Assuming 1000 meters of cabling then the following would be a close approximation.

Annual Revenue = Cp x 0.5 x ρ x A x V³ x Hr x LL x GGL x $ x Y (x 3 for shrouded turbines)

Where:
Cp = the turbine coefficient of performance (say 20% for free stream turbine - up to 60% for a shrouded turbine)
ρ = the density of the water (seawater is 1025 kg/m³ or 998 kg/m³ for fresh water)
A = the sweep area of the turbine (in m²)
V³ = the velocity of the flow cubed (i.e. V x V x V)
Hr = the number of hours per day that the turbine would operate at maximum efficiency (12-22 hours for tidal and 24 for run of river)
LL* = x .95 line losses (multiply by .95 )assuming a 5% loss in a cable run of 1000 meters. This may vary by manufacturer.
Gearbox and Generator Losses* = x .95 (multiply by .95) assuming 5% for gearbox and generator losses
$ = the price per kilowatt hour that would be paid (prices vary with location)
Year = 350 days (allowing 15 days per year for maintenance if necessary)

Shrouded turbines can produce 3 to 4 times as much revenue as a free stream turbine.^{[citation needed]}

For example, a tidal stream turbine with a sweep area of 1m² at a site with a 3 m/s flow velocity, operating at maximum output for 12 hours, and earning 10 cents per kilowatthour would earn

Annual Revenue = 0.20 x 0.5 x 1025 x 27 x 12 x 0.95 x 0.95 x 0.10/1000 x 350

Keeping in mind this is only a 1m² sized turbine, in 3m/s flow velocity for only 12 hours per day. Many commercial turbines are 20-30 times or greater in size, in faster flow velocity, at 20 or more hours per day. A run of river turbine would operate for as long as the river flows, which is obviously 24 hours per day. For example a commercial sized turbine with a 100m² sweep area would therefore return $1,049,022.00 per annum (or $3,147,062.00 for a shrouded turbine with 60% efficiency)

From the above equation it can be demonstrated that the predictability of tidal power holds very great potential and interest for renewable investment dollars. Wind and solar are unpredictable by nature, but tidal stream can be predicted years in advance, allowing businesses to plan years in advance.

As the flow velocity doubles, the revenue increases by 8 times (as power is a function of the velocity cubed). The same commercial turbine given in the example above, if installed in a 6 m/s velocity flow, would return $8,392,000 (or $25,176,000 for a shrouded turbine) for every square meter of sweep area of the turbine. It's not hard to see the commercial attraction of tidal stream turbines.

Source of the energy

Because the Earth's tides are caused by the tidal forces due to gravitational interaction with the Moon and Sun, and the Earth's rotation, tidal power is practically inexhaustible and classified as a renewable energy source. This article is about tides in the Earths oceans. ... Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiters tidal forces. ... Gravity redirects here. ... This article is about Earths moon. ... Sol redirects here. ... This article is about rotation as a movement of a physical body. ... Renewable energy effectively utilizes natural resources such as sunlight, wind, tides and geothermal heat, which are naturally replenished. ...

Barrage tidal power

With only three operating plants globally Rance River, Bay of Fundy and Kislaya Guba the barrage method of extracting tidal energy involves building a barrage as in the case of the Rance River in France. The barrage turbines generate as water flows in and out the estuary bay or river. These systems are similar to a hydro dam that produces Static Head or pressure head (a height of water pressure). When the water level outside of the basin or lagoon changes relative to the water level inside, the turbines are able to produce power. The largest such installation has been working on the Rance river, France, since 1966 with an installed (peak) power of 240 MW, and an annual production of 600 GWh (about 68 MW average power).^{[citation needed]} Image File history File links Question_book-3. ... Image File history File linksMetadata Download high-resolution version (1600x1200, 216 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Rance tidal power plant Metadata This file contains additional information, probably added from the digital camera or scanner... Image File history File linksMetadata Download high-resolution version (1600x1200, 216 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Rance tidal power plant Metadata This file contains additional information, probably added from the digital camera or scanner... Rance tidal power plant Other view Scale model of the tidal power plant The Rance tidal power plant is the worlds first electrical generating station powered by tidal energy. ... I created this image myself using Blender. ... I created this image myself using Blender. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Barrage locations considered over the years The Severn Barrage is the name of a number of ideas for building a barrage from the English coast to the Welsh coast over the Severn tidal estuary. ... For Government policy, see Energy policy of the United Kingdom Energy use and conservation in the United Kingdom has been receiving increased attention over recent years. ... The Rance is a river of northwestern France. ... The Bay of Fundy (French: ) is a bay located on the Atlantic coast of North America, on the northeast end of the Gulf of Maine between the Canadian provinces of New Brunswick and Nova Scotia, with a small portion touching the U.S. state of Maine. ... Kislaya Guba map Kislaya Guba is a fjord on the Kola Peninsula near Murmansk, Russia. ... The bridge and weir mechanism at Sturminster Newton on the River Stour, Dorset. ... The Rance is a river of northwestern France. ... Fluid pressure is the pressure at some point within a fluid, such as water or air. ... Rance tidal power plant Other view Scale model of the tidal power plant The Rance tidal power plant is the worlds first electrical generating station powered by tidal energy. ... The Rance is a river of northwestern France. ...

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. In geotechnical engineering, a caisson is a retaining, watertight structure used, for example, to work on the foundations of a bridge pier, for the construction of a concrete dam, or for the repair of ships. ... Sluice gates near Henley, on the River Thames A small wooden sluice in Magome, Japan, used to power a waterwheel. ... Kaplan turbine and electrical generator cut-away view. ...

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

Barrage systems are affected by problems of high civil infrastructure costs associated with what is in effect a dam being placed across estuarine systems, and the environmental problems associated with changing a large ecosystem.^{[citation needed]}

Ebb generation

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 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 the turbines generate until the head is again low. Then the sluices are opened, turbines disconnected and the basin is filled again. The cycle repeats itself. Ebb generation (also known as outflow generation) takes its name because generation occurs as the tide ebbs.

Flood generation

The basin is filled through the turbines, which generate at tide flood. This is generally much less efficient than ebb generation, because the volume 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 difference in levels between the basin side and the sea side of the barrage), (and therefore the available potential energy) less than it would 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 from the sea.

Pumping

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). This energy is more than returned during generation, because power output is strongly related to the head. If water is raised 2 ft (61 cm) by pumping on a high tide of 10 ft (3 m), this will have been raised by 12 ft (3.7 m) at low tide. The cost of a 2 ft rise is returned by the benefits of a 12 ft rise.

Two-basin schemes

Another form of energy barrage configuration is that of the dual basin type. 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 advantages over normal schemes in that generation time can be adjusted with high flexibility and it is also possible to generate almost continuously. In normal estuarine situations, however, two-basin schemes are very expensive to construct due to the cost of the extra length of barrage. There are some favourable geographies, however, which are well suited to this type of scheme.

Environmental impact

The placement of a barrage into an estuary has a considerable effect on the water inside the basin and on the ecosystem. Many governments have been reluctant in recent times to grant approval for tidal barrages.

Turbidity

Turbidity (the amount of matter in suspension in the water) decreases as 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, improving conditions for the phytoplankton. The changes propagate up the food chain, causing a general change in the ecosystem. Diagrams of some typical phytoplankton Phytoplankton are the autotrophic component of plankton. ... Food chains, food webs and/or food networks describe the feeding relationships between species to another within an ecosystem. ... A coral reef near the Hawaiian islands is an example of a complex marine ecosystem. ...

Salinity

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

Sediment movements

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

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 be unable to escape the water speed near a turbine and will be sucked through. Even with the most fish-friendly turbine design, fish mortality per pass is approximately 15%^{[citation needed]} (from pressure drop, contact with blades, cavitation, etc.). Alternative passage technologies (fish ladders, fish lifts, etc.) have so far failed to solve this problem for tidal barrages, either offering extremely expensive solutions, or ones which are used by a small fraction of fish only. Research in sonic guidance of fish is ongoing^{[citation needed]}. The Open-Centre turbine reduces this problem allowing fish to pass through the open centre of the turbine. Recently a run of the river type turbine has been developed in France. This basically is a very large slow rotating Kaplan type turbine mounted on an angle. Testing for fish mortality has indicated much lower mortality figures, less than 5%. This concept seems very suitable for adaption to marine current/tidal turbines also VLH TURBINE Cavitating propeller model in a water tunnel experiment High speed jet of fluid impact on a fixed surface. ... Pool-and-weir fish ladder at Bonneville Dam on the Columbia River Fishways, most commonly referred to as fish ladders but also known as fish passes, are structures placed on or around man-made barriers (such as dams and weirs) to assist the natural migration of diadromous fishes. ...

Energy calculations

The energy available from barrage is dependent on the volume of water. The potential energy contained in a volume of water is : Potential energy can be thought of as energy stored within a physical system. ...

Mathematical demonstration of a sample Tidal power generation

Mass of the water = volume of water * specific gravity A foot (plural: feet or foot;[1] symbol or abbreviation: ft or, sometimes, â€² â€“ a prime) is a unit of length, in a number of different systems, including English units, Imperial units, and United States customary units. ... This article is about the unit of length. ...

Therefore the total energy generation potential per day = Energy for a single tide * 4

Therefore, the power generation potential = Energy generation potential / time in 1 day

Since we have assumed the power conversion efficiency to be 30%, The power generated = 419 MW * 30%

A barrage is therefore best placed in a location with very high-amplitude tides. Suitable locations are found in Russia, USA, Canada, Australia, Korea, the UK. Amplitudes of up to 17 m (56 ft) occur for example in the Bay of Fundy, where tidal resonance amplifies the tidal range. Motto: (traditional) In God We Trust (official, 1956â€“present) Anthem: The Star-Spangled Banner Capital Washington, D.C. Largest city New York City Official language(s) None at the federal level; English de facto Government Federal Republic - President George W. Bush (R) - Vice President Dick Cheney (R) Independence - Declared - Recognized... This article is about the Korean civilization. ... The Bay of Fundy (French: ) is a bay located on the Atlantic coast of North America, on the northeast end of the Gulf of Maine between the Canadian provinces of New Brunswick and Nova Scotia, with a small portion touching the U.S. state of Maine. ... In oceanography, tidal resonance is a phenomenon perhaps best exemplified in the Bay of Fundy. ...

Economics

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 for many years, and investors may be reluctant to participate in such projects.

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 the high irreversible commitment. For example the energy policy of the United Kingdom^[26] recognizes the role of tidal energy and expresses the need for local councils to understand the broader national goals of renewable energy in approving tidal projects. The UK government itself appreciates the technical viability and siting options available, but has failed to provide meaningful incentives to move these goals forward. For energy use in practice, see Energy use and conservation in the United Kingdom The Energy policy of the United Kingdom is a set of official publications and activities directed at the present and future production, transmission and use of various power technologies within the UK. Historically a country emphasizing...

Mathematical modelling of tidal schemes

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. Every step, neighbouring segments influence each other and variables are updated.

The simplest type of model is the flat estuary model, in which the whole basin is represented by one segment. The surface of the basin is assumed to be flat, hence the name. This model gives rough results and is used to compare many designs at the start of the design process.

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

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

Turbidity standards of 5, 50, and 500 NTU Turbidity is a cloudiness or haziness of a fluid, or of air, caused by individual particles (suspended solids) that are generally invisible to the naked eye, similar to smoke in air. ... Annual mean sea surface salinity for the World Ocean. ...

Energy efficiency

Tidal energy has an efficiency of 80% in converting the potential energy of the water into electricity,^{[citation needed]} which is efficient compared to other energy resources such as solar power or fossil fuel power plants. Solar power describes a number of methods of harnessing energy from the light of the sun. ... Mohave Generating Station, a 1,580 MW coal power plant near Laughlin, Nevada A fossil fuel power plant is an energy conversion center that burns fossil fuels to produce electricity, designed on a large scale for continuous operation. ...

Global environmental impact

A tidal power scheme is a long-term source of electricity. A proposal for the Severn Barrage, if built, has been projected to save 18 million tonnes of coal per year of operation. This decreases the output of greenhouse gases into the atmosphere. Barrage locations considered over the years The Severn Barrage is the name of a number of ideas for building a barrage from the English coast to the Welsh coast over the Severn tidal estuary. ... Coal Example chemical structure of coal Coal is a fossil fuel formed in ecosystems where plant remains were saved by water and mud from oxidization and biodegradation. ... Top: Increasing atmospheric levels as measured in the atmosphere and ice cores. ...

If fossil fuel resource is likely to decline during the 21st century, as predicted by Hubbert peak theory, tidal power is one of the alternative source of energy that will need to be developed to satisfy the human demand for energy. The Hubbert peak theory posits that for any given geographical area, from an individual oil field to the planet as a whole, the rate of petroleum production tends to follow a bell-shaped curve. ...

Operating tidal power schemes

Rance tidal power plant Other view Scale model of the tidal power plant The Rance tidal power plant is the worlds first electrical generating station powered by tidal energy. ... The Rance is a river of northwestern France. ... The Annapolis Royal Generating Station is an 18-MW tidal power plant located on the Annapolis River immediately upstream from the town of Annapolis Royal, Nova Scotia, Canada. ... Website: http://www. ... Motto: Munit Haec et Altera Vincit (Latin: One defends and the other conquers) Capital Halifax Largest city Halifax Regional Municipality Official languages English (de facto) Government Lieutenant-Governor Mayann E. Francis Premier Rodney MacDonald (PC) Federal representation in Canadian Parliament House seats 11 Senate seats 10 Confederation July 1, 1867... The Bay of Fundy (French: ) is a bay located on the Atlantic coast of North America, on the northeast end of the Gulf of Maine between the Canadian provinces of New Brunswick and Nova Scotia, with a small portion touching the U.S. state of Maine. ... Kislaya Guba map Kislaya Guba is a fjord on the Kola Peninsula near Murmansk, Russia. ... Location of the Barents Sea. ... Kislaya Guba map Kislaya Guba is a fjord on the Kola Peninsula near Murmansk, Russia. ... The Yalu (Amnok) River is a river on the border between China and North Korea. ... Eskom is a South African electricity public utility company. ... The Mozambique Current is an ocean current in the Indian Ocean, usually defined as warm surface waters flowing south between the African east coast in the vicinity of Mozambique and the island of Madagascar. ... KwaZulu-Natal, often referred to as KZN, is a province of South Africa. ...

Tidal power schemes being considered

In the table, "-" indicates missing information, "?" indicates information which has not been decided Image File history File links Question_book-3. ...

San JosÃ© (also called Villa San JosÃ©) is a city in the center-east of the province of Entre RÃos, Argentina, located some 10 km northwest from ColÃ³n, near the Uruguay River. ... Cobequid Bay is an inlet of the Bay of Fundy and the easternmost part of the Minas Basin, located in the Canadian province of Nova Scotia. ... Passamaquoddy Bay is an inlet of the Bay of Fundy, between the U.S. state of Maine and the Canadian province of New Brunswick, at the mouth of the St. ... Kutch (Kuchchh) District, State of Gujarat Kutch (also spelled Cutch, Kachh, Kachch and even Kachchh) is a district of Gujarat state in western India. ... Cambay, also known as Khambhat, is a town in Gujarat state, India. ... Colorado River can refer to one of the following rivers: The Colorado River in the western United States and Mexico that passes through the Grand Canyon. ... Tiburon is a town located in Marin County, California. ... The Severn is the name of a river in the United Kingdom. ... Barrage locations considered over the years The Severn Barrage is the name of a number of ideas for building a barrage from the English coast to the Welsh coast over the Severn tidal estuary. ... The River Mersey is a river in the north west of England. ... Strangford Lough from Portaferry, looking towards the narrows. ... This article is about the town. ... Passamaquoddy Bay is an inlet of the Bay of Fundy, between the U.S. state of Maine and the Canadian province of New Brunswick, at the mouth of the St. ... Cook Inlet, showing Knik and Turnagain Arms The Cook Inlet or Nuti Inlet is a large inlet of the Gulf of Alaska in south-central Alaska. ... Cook Inlet, showing Knik and Turnagain Arms The Cook Inlet or Nuti Inlet is a large inlet of the Gulf of Alaska in south-central Alaska. ... The Golden Gate The Golden Gate, looking south towards San Francisco. ... Mezen (ÐœÐµÐ·ÐµÐ½ÑŒ) is a town in Russia, Arkhangelsk Oblast. ... Penzhinskaya Bay is a large bay off the northwestern coast of Kamchatka, Russia. ... Location of Mozambique Channel The Mozambique Channel is a portion of the Indian Ocean between the island of Madagascar and southeast Africa, namely Mozambique. ...

Contents

Generation of tidal energy

Categories of Tidal Power

Tidal stream generators

Prototypes

Shrouded tidal energy turbines

Types of shroud

Advantages

Disadvantages

Energy calculations

Price calculations

Source of the energy

Barrage tidal power

Ebb generation

Flood generation

Pumping

Two-basin schemes

Environmental impact

Turbidity

Salinity

Sediment movements

Fish

Energy calculations

Mathematical demonstration of a sample Tidal power generation

Economics

Mathematical modelling of tidal schemes

Energy efficiency

Global environmental impact

Operating tidal power schemes

Tidal power schemes being considered

See also

Patents

References

Notes

External links