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{{short description|Technology to convert the energy from tides into useful forms of power}} | |||
], located in ], South Korea, is the world's largest tidal power installation, with a total power output capacity of 254 MW.]] | |||
], in ], northwestern France, was the first large-scale tidal power station (1966), with a total power output capacity of 240 MW]] | |||
{{Renewable energy sources}} | {{Renewable energy sources}} | ||
{{Sustainable energy}} | |||
{{portal|Energy}} | |||
'''Tidal Power''', sometimes called '''''tidal energy''''', is the power achieved by capturing the energy contained in moving water in ] and ]. There are two types of energy systems that can be used to extract energy: ], the moving water of rivers, tides and open ocean currents; and ] from the difference in height (or ''head'') between high and low tides. The former method - generating energy from tidal currents uses turbines in a similar way to underwater windmills - is gaining in popularity because of the lower ecological impact compared to potential systems that are similar to dams sometimes called barrages or tidal fences. Many coastal sites worldwide are being examined for the suitability to produce tidal (kinetic) energy. Sites that are suitable exhibit high water speeds which typically occur in channels such as the entrances to bays, rivers of between islands where water currents are concentrated. | |||
'''Tidal power''' or '''tidal energy''' is harnessed by converting energy from ]s into useful forms of power, mainly electricity using various methods. | |||
Tidal power is classified as a ] source, because ] are caused by the orbital mechanics of the ] (ocean currents are caused by the surface effect of winds) and are considered inexhaustible. The root source of the energy is the orbital kinetic energy of the earth-moon system, and also the earth-sun system. Tidal power has great potential for future ] and ] because of the essentially inexhaustible amount of energy contained in these rotational systems. However, there has been controversy over whether this is a ] because the moon does not lose energy just because energy is extracted from tides. In fact, even if all kinetic energy in the oceans were depleted until not a single molecule is moving (which is impossible), the moon will continue to orbit the earth. This is not only because the moon is extremely large and has a vast potential energy, but also that it can orbit a large mass (in this case the ]) forever, as long as there is no friction or change in the mass that it is orbiting. Tidal power is reliably predictable (unlike ] and ]). In Europe, ]s have been used for nearly a thousand years, mainly for grinding grains. | |||
Although not yet widely used, tidal energy has the potential for future ]. Tides are more predictable than ] and ]. Among sources of ], tidal energy has traditionally suffered from relatively high cost and limited availability of sites with sufficiently high tidal ranges or flow velocities, thus constricting its total availability. However many recent technological developments and improvements, both in design (e.g. ], ]) and turbine technology (e.g. new ], ]), indicate that the total availability of tidal power may be much higher than previously assumed and that economic and ]s may be brought down to competitive levels. | |||
The efficiency of tidal power generation in ocean dams largely depends on the amplitude (height of the rise and fall) of the tidal swell, which can be up to 10 m (33 ft) where the periodic tidal waves funnel into rivers and fjords and extreme water velocities can be 16 knots (Vancouver Island Canada). Amplitudes of up to 17 m (56 ft) occur for example in the ], where ] amplifies the tidal waves. | |||
Historically, ]s have been used both in Europe and on the Atlantic coast of North America. Incoming water was contained in large storage ponds, and as the tide goes out, it turns waterwheels that use the mechanical power to mill grain.<ref>{{cite web|author=Ocean Energy Council|title=Tidal Energy: Pros for Wave and Tidal Power|url=http://www.oceanenergycouncil.com/index.php/Tidal-Energy/Tidal-Energy.html|archive-url=https://web.archive.org/web/20080513175027/http://www.oceanenergycouncil.com/index.php/Tidal-Energy/Tidal-Energy.html|url-status=dead|archive-date=2008-05-13|date=2011}}</ref> The earliest occurrences date from the ], or even from ].<ref>{{cite web |url=http://www.kentarchaeology.ac/authors/005.pdf |title=Microsoft Word – RS01j.doc |access-date=2011-04-05 |url-status=live |archive-url=https://web.archive.org/web/20110517013738/http://www.kentarchaeology.ac/authors/005.pdf |archive-date=2011-05-17 }}</ref><ref>{{cite journal| author=Minchinton, W. E. | title=Early Tide Mills: Some Problems | journal=Technology and Culture | volume=20 | issue=4 |date=October 1979 | pages=777–786 | doi=10.2307/3103639| jstor=3103639| s2cid=112337062 }}</ref> The process of using falling water and spinning ]s to create electricity was introduced in the U.S. and Europe in the 19th century.<ref>{{cite book|last=Dorf|first=Richard|title=The Energy Factbook|url=https://archive.org/details/energyfactbook00dorf|url-access=registration|date=1981|publisher=McGraw-Hill|location=New York}}</ref> | |||
As with ], selection of location is critical for a tidal power ]. The ] contained in a volume of water is : | |||
:<math>E = xMg</math> | |||
where ''x'' is the height of the tide, ''M'' is the mass of water and ''g'' is the ]. Therefore, a tidal energy generator must be placed in a location with very high-amplitude tides. Suitable locations are found in the former USSR, USA, Canada, Australia, Korea, the UK and other countries (see below). | |||
Electricity generation from marine technologies increased an estimated 16% in 2018, and an estimated 13% in 2019.<ref>{{Cite web|title=Ocean power – Tracking Power 2020 – Analysis|url=https://www.iea.org/reports/tracking-power-2019/ocean-power|access-date=2020-08-25|website=IEA|language=en-GB|archive-date=2020-06-19|archive-url=https://web.archive.org/web/20200619154701/https://www.iea.org/reports/tracking-power-2019/ocean-power|url-status=dead}}</ref> Policies promoting R&D are needed to achieve further cost reductions and large-scale development. The world's first large-scale tidal power plant was France's ], which became operational in 1966. It was the largest tidal power station in terms of output until ] opened in South Korea in August 2011. The Sihwa station uses sea wall defense barriers complete with 10 turbines generating 254 MW.<ref>{{Cite book|title=Guinness world records 2014|last=Glenday|first=Craig|year=2013|publisher=Guinness World Records Limited |isbn=978-1-908843-15-9|url-access=registration|url=https://archive.org/details/guinnessworldrec0000unse_r3e7}}</ref> | |||
Several smaller tidal power plants have recently started generating electricity in Canada and ]. They all exploit the strong periodic tidal currents in narrow fjords using sub-surface ]s. | |||
== |
== Principle == | ||
] | |||
{{Main|Tide|Tidal acceleration}} | |||
Tidal energy is taken from the Earth's oceanic ]s. ]s result from periodic variations in gravitational attraction exerted by celestial bodies. These forces create corresponding motions or currents in the world's oceans. This results in periodic changes in sea levels, varying as the Earth rotates. These changes are highly regular and predictable, due to the consistent pattern of the Earth's rotation and the Moon's orbit around the Earth.<ref>{{cite book|last=DiCerto|first=JJ|title=The Electric Wishing Well: The Solution to the Energy Crisis|url=https://archive.org/details/electricwishingw0000dice|url-access=registration|date=1976|publisher=Macmillan|location=New York|isbn=9780025313200 }}</ref> The magnitude and variations of this motion reflect the changing positions of the Moon and Sun relative to the Earth, the ], and local ]. | |||
The largest amount of renewable energy available today is in the form of moving water in tides, rivers and open ocean currents. It is no surprise therefore that there is commercial interest in systems that harvest the kinetic energy in moving water using sub-surface ("underwater wind-mill") arrays. | |||
Tidal power is the only technology that draws on energy inherent in the orbital characteristics of the Earth–Moon system, and to a lesser extent in the Earth–Sun system. Other natural energies exploited by human technology originate directly or indirectly from the Sun, including ], ], ], ], ] and ]. ] makes use of Earth's mineral deposits of ] elements, while ] utilizes the Earth's ], which comes from a combination of residual heat from ] (about 20%) and heat produced through ] (80%).<ref name="turcotte">{{cite book| last=Turcotte| first=D. L.|author2=Schubert, G. | title=Geodynamics | publisher=Cambridge University Press| location=Cambridge, England, UK| date=2002 | edition=2nd| pages=136–137 | chapter=Chapter 4 | isbn=978-0-521-66624-4 }}</ref> | |||
These systems harness the flow in a naturally occurring tidal stream, river or open ocean current that occurs at the entrances to bays and rivers, around rocky points and headlands and between islands and the mainland to name a few. | |||
A tidal generator converts the energy of tidal flows into electricity. Greater tidal variation and higher tidal current velocities can dramatically increase the potential of a site for tidal electricity generation. On the other hand, tidal energy has high reliability, excellent energy density, and high durability.<ref>{{Cite journal |last1=Chowdhury |first1=M. S. |last2=Rahman |first2=Kazi Sajedur |last3=Selvanathan |first3=Vidhya |last4=Nuthammachot |first4=Narissara |last5=Suklueng |first5=Montri |last6=Mostafaeipour |first6=Ali |last7=Habib |first7=Asiful |last8=Akhtaruzzaman |first8=Md. |last9=Amin |first9=Nowshad |last10=Techato |first10=Kuaanan |date=2021-06-01 |title=Current trends and prospects of tidal energy technology |url=https://doi.org/10.1007/s10668-020-01013-4 |journal=Environment, Development and Sustainability |language=en |volume=23 |issue=6 |pages=8179–8194 |doi=10.1007/s10668-020-01013-4 |issn=1573-2975 |pmc=7538194 |pmid=33041645|bibcode=2021EDSus..23.8179C }}</ref> | |||
Moving water is a large renewable energy resource. It is 832 times more dense than air and more predictable than wind-turbines or solar panels. It is impossible to accurately predict if the wind will blow in the next 5 minutes or if the sun will shine tomorrow, but the predictability of moving water in tides and ocean currents makes water energy turbines systems attractive to commercialization. | |||
Because the Earth's tides are ultimately due to gravitational interaction with the Moon and Sun and the Earth's rotation, tidal power is practically inexhaustible, and is thus classified as a ] resource. Movement of tides causes a ] in the Earth-Moon system: this results from pumping of water through natural restrictions around coastlines and consequent ] dissipation at the ] and in ]. This loss of energy has caused the rotation of the Earth to slow in the 4.5 billion years since its formation. During the last 620 million years the period of rotation of the Earth (length of a day) has increased from 21.9 hours to 24 hours;<ref>{{cite journal | author=George E. Williams | bibcode=2000RvGeo..38...37W | title=Geological constraints on the Precambrian history of Earth's rotation and the Moon's orbit | journal=Reviews of Geophysics | volume=38 | issue=1 |date=2000 | pages=37–60 | doi=10.1029/1999RG900016 | citeseerx=10.1.1.597.6421 | s2cid=51948507 }}</ref> in this period the Earth-Moon system has lost 17% of its rotational energy. While tidal power will take additional energy from the system, the effect is negligible and would not be noticeable in the foreseeable future. | |||
The energy available from these kinetic systems can be expressed as, | |||
== Methods == | |||
Cp = 0.5.ρ.A.V<sup>3</sup> | |||
] – in ].<ref>{{Cite journal | |||
| doi = 10.1243/14750902JEME94 | |||
| volume = 222 | |||
| issue = 1 | |||
| pages = 1–12 | |||
| last1 = Douglas | |||
| first1 = C. A. | |||
| first2 = G. P. | |||
| last2 = Harrison | |||
| first3 = J. P. | |||
| last3 = Chick | |||
| title = Life cycle assessment of the Seagen marine current turbine | |||
| journal = Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment | |||
| date = 2008 | |||
| bibcode = 2008PIMEM.222....1D | |||
| s2cid = 111126521 | |||
| url = https://www.research.ed.ac.uk/portal/files/49243203/MCT_Seagen_Audit_Post_print.pdf | |||
| hdl = 20.500.11820/935cdfa5-aeed-423c-aa52-f51c5e5753ef | |||
| hdl-access = free | |||
}}</ref> The strong ] shows the power in the ].]] | |||
Tidal power can be classified into four generating methods: | |||
=== Tidal stream generator === | |||
Where Cp is the turbine coefficient of performance, | |||
{{Main|Tidal stream generator}} | |||
Tidal stream generators make use of the ] of moving water to power turbines, in a similar way to ]s that use the wind to power turbines. Some tidal generators can be built into the structures of existing bridges or are entirely submersed, thus avoiding concerns over aesthetics or visual impact. Land constrictions such as straits or inlets can create high velocities at specific sites, which can be captured using turbines. These turbines can be horizontal, vertical, open, or ducted.<ref name="Tethys">{{cite web|title=Tidal – Capturing tidal fluctuations with turbines, tidal barrages, or tidal lagoons|url=http://tethys.pnnl.gov/technology-type/tidal|website=Tidal / Tethys|publisher=] (PNNL)|access-date=2 February 2016|url-status=live|archive-url=https://web.archive.org/web/20160216190319/https://tethys.pnnl.gov/technology-type/tidal|archive-date=16 February 2016}}</ref> | |||
ρ = the density of the water (seawater is 1025 kg per cubic meter) | |||
=== Tidal barrage === | |||
A = the sweep area of the turbine | |||
{{Main|Tidal barrage}} | |||
Tidal barrages use ] in the difference in height (or ]) between high and low tides. When using tidal barrages to generate power, the potential energy from a tide is seized through the strategic placement of specialized dams. When the sea level rises and the tide begins to come in, the temporary increase in tidal power is channeled into a large basin behind the dam, holding a large amount of potential energy. With the receding tide, this energy is then converted into ] as the water is released through large turbines that create electrical power through the use of generators.<ref>{{cite book|last=Evans|first=Robert|title=Fueling Our Future: An Introduction to Sustainable Energy|url=https://archive.org/details/fuelingourfuture00evan_0|url-access=registration|date=2007|publisher=Cambridge University Press|location=New York}}</ref> Barrages are essentially ]s across the full width of a tidal estuary. | |||
V<sup>3</sup> = the velocity of the flow cubed (i.e. V x V x V) | |||
=== Tidal lagoon === | |||
Modern advance in turbine technology may eventually see large amounts of power generated from the oceans using this method. Arrayed in high velocity areas where natural flows are concentrated such 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 anywhere where there are entrances to bays and rivers, or between land masses where water currents are concentrated. | |||
A new tidal energy design option is to construct circular retaining walls embedded with turbines that can capture the potential energy of tides. The created reservoirs are similar to those of tidal barrages, except that the location is artificial and does not contain a pre-existing ecosystem.<ref name="Tethys" /> | |||
The lagoons can also be in double (or triple) format without pumping<ref>{{cite web |url=https://www.youtube.com/watch?v=lnHwb8BKJzU |title=Hydrological Changing Double Current-typed Tidal Power Generation |website=] |date=23 September 2012 |format=video |access-date=2015-04-15 |url-status=live |archive-url=https://web.archive.org/web/20151018074420/https://www.youtube.com/watch?v=lnHwb8BKJzU |archive-date=2015-10-18 }}</ref> or with pumping<ref>{{cite web |url=http://www.inference.phy.cam.ac.uk/sustainable/book/tex/Lagoons.pdf |title=Enhancing Electrical Supply by Pumped Storage in Tidal Lagoons |access-date=2014-03-13 |url-status=live |archive-url=https://web.archive.org/web/20150924034732/http://www.inference.phy.cam.ac.uk/sustainable/book/tex/Lagoons.pdf |archive-date=2015-09-24 }}</ref> that will flatten out the power output. The pumping power could be provided by excess to grid demand renewable energy from for example wind turbines or solar photovoltaic arrays. Excess renewable energy rather than being curtailed could be used and stored for a later period of time. Geographically dispersed tidal lagoons with a time delay between peak production would also flatten out peak production providing near baseload production at a higher cost than other alternatives such as district heating renewable energy storage. The cancelled ] in Wales, United Kingdom would have been the first tidal power station of this type once built.<ref>{{cite web|url=http://www.renewableenergyfocus.com/view/42607/green-light-for-worlds-first-tidal-lagoon/|title=Green light for world's first tidal lagoon|author=Elsevier Ltd, The Boulevard, Langford Lane, Kidlington, Oxford, OX5 1 GB, United Kingdom|website=renewableenergyfocus.com|access-date=26 July 2015|url-status=live|archive-url=https://web.archive.org/web/20150818213310/http://www.renewableenergyfocus.com/view/42607/green-light-for-worlds-first-tidal-lagoon/|archive-date=18 August 2015}}</ref> | |||
=== Dynamic tidal power === | |||
A factor in human settlement geography is water. Human settlements have often started around bays rivers and lakes. Future settlement may be concentrated around moving water, allowing communities to power themselves with non-polluting energy from moving water. | |||
{{Main|Dynamic tidal power}} | |||
] | |||
==Variable nature of power output== | |||
Dynamic tidal power (or DTP) is a theoretical technology that would exploit an interaction between potential and kinetic energies in tidal flows. It proposes that very long dams (for example: 30–50 km length) be built from coasts straight out into the sea or ocean, without enclosing an area. Tidal ]s are introduced across the dam, leading to a significant water-level differential in shallow coastal seas – featuring strong coast-parallel oscillating tidal currents such as found in the UK, China, and Korea. | |||
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 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), 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 with the demand cycle. | |||
== US and Canadian studies in the 20th century == | |||
==Barrage== | |||
The first study of large scale tidal power plants was by the US ] in 1924. If built, power plants would have been located in the northern border area of the US state of ] and the southeastern border area of the Canadian province of New Brunswick, with various dams, powerhouses, and ship locks enclosing the ] and ] (note: see map in reference). Nothing came of the study, and it is unknown whether Canada had been approached about the study by the US Federal Power Commission.<ref> {{webarchive|url=https://web.archive.org/web/20150321092258/http://books.google.com/books?id=zigDAAAAMBAJ&pg=PA29&dq=Popular+Science+1933+plane+%22Popular+Science%22&hl=en&ei=MIb5TZaFEajx0gGxtaHPAw&sa=X&oi=book_result&ct=result&resnum=4&ved=0CDUQ6AEwAzhQ |date=2015-03-21 }} May 1924 ''Popular Science Monthly''</ref> | |||
] | |||
In 1956, utility ] of ] commissioned a pair of studies into commercial tidal power development feasibility on the ] side of the Bay of Fundy. The two studies, by ] of ] and by ] of ], independently concluded that millions of horsepower (i.e. gigawatts) could be harnessed from Fundy but that development costs would be commercially prohibitive.<ref>Nova Scotia Light and Power Company, Limited, Annual Report, 1956</ref> | |||
The barrage method of extracting tidal energy involves building a ] and creating a tidal ]. 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 ] 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) | |||
There was also a report on the international commission in April 1961 entitled "Investigation of the International Passamaquoddy Tidal Power Project" produced by both the US and Canadian Federal Governments. According to benefit to costs ratios, the project was beneficial to the US but not to Canada. | |||
The basic elements of a barrage are ]s, embankments, ]s, ] 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. | |||
A study was commissioned by the Canadian & Nova Scotian and New Brunswick governments (Reassessment of Fundy Tidal Power) to determine the potential for tidal barrages at Chignecto Bay and Minas Basin – at the end of the Fundy Bay estuary. There were three sites determined to be financially feasible: Shepody Bay (1550 MW), Cumberland Basin (1085 MW), and Cobequid Bay (3800 MW). These were never built despite their apparent feasibility in 1977.<ref>{{Citation |first=Jen |last=Chang |title=Hydrodynamic Modeling and Feasibility Study of Harnessing Tidal Power at the Bay of Fundy |publisher=University of Southern California |location=Los Angeles |date=2008 |section=6.1 |type=PhD thesis |url=http://digitallibrary.usc.edu/assetserver/controller/item/etd-Chang-20080312.pdf |access-date=2011-09-27 |url-status=dead |archive-url=https://web.archive.org/web/20121122141719/http://digitallibrary.usc.edu/assetserver/controller/item/etd-Chang-20080312.pdf |archive-date=2012-11-22 |bibcode=2008PhDT.......107C }}</ref> | |||
The sluice gates applicable to tidal power are the flap gate, vertical rising gate, radial gate and rising sector. | |||
== US studies in the 21st century == | |||
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 ], a public utility district located primarily in Snohomish County, Washington State, began a tidal energy project in 2007.<ref>{{dead link|date=January 2019 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> In April 2009 the PUD selected OpenHydro,<ref>{{dead link|date=January 2019 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> a company based in Ireland, to develop turbines and equipment for eventual installation. The project as initially designed was to place generation equipment in areas of high tidal flow and operate that equipment for four to five years. After the trial period the equipment would be removed. The project was initially budgeted at a total cost of $10 million, with half of that funding provided by the PUD out of utility reserve funds, and half from grants, primarily from the US federal government. The PUD paid for part of this project from reserves and received a $900,000 grant in 2009 and a $3.5 million grant in 2010 in addition to using reserves to pay an estimated $4 million of costs. In 2010 the budget estimate was increased to $20 million, half to be paid by the utility, half by the federal government. The utility was unable to control costs on this project, and by October 2014, the costs had ballooned to an estimated $38 million and were projected to continue to increase. The PUD proposed that the federal government provide an additional $10 million towards this increased cost, citing a ].<ref> Everett Herald, Oct 2, 2014,</ref> When the federal government refused to pay this, the PUD cancelled the project after spending nearly $10 million from reserves and grants. The PUD abandoned all tidal energy exploration after this project was cancelled and does not own or operate any tidal energy sources. | |||
== Rance tidal power plant in France == | |||
===Modes of operation=== | |||
In 1966, ] opened the ], located on the ] of the ] in ]. It was the world's first<ref>{{cite web|title= Wyre Tidal Energy|url= http://www.wyretidalenergy.com/tidal-barrage/la-rance-barrage|url-status= dead|archive-url= https://web.archive.org/web/20150204062904/http://www.wyretidalenergy.com/tidal-barrage/la-rance-barrage|archive-date= 4 February 2015|df= dmy-all}}</ref> tidal power station. The plant was for 45 years the largest tidal power station in the world by installed capacity: Its 24 ] reach peak output at 240 ] (MW) and average 57 MW, a ] of approximately 24%. | |||
====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. | |||
== Tidal power development in the UK == | |||
====Flood generation==== | |||
The world's first marine energy test facility was established in 2003 to start the development of the wave and tidal energy industry in the UK. Based in Orkney, Scotland, the ] (EMEC) has supported the deployment of more wave and tidal energy devices than at any other single site in the world. EMEC provides a variety of test sites in real sea conditions. Its grid connected tidal test site is located at the ], off the island of ], in a narrow channel which concentrates the tide as it flows between the Atlantic Ocean and North Sea. This area has a very strong tidal current, which can travel up to {{cvt|4|m/s|mph kn km/h}} in spring tides. Tidal energy developers that have tested at the site include: Alstom (formerly Tidal Generation Ltd); ANDRITZ HYDRO Hammerfest; Atlantis Resources Corporation; Nautricity; OpenHydro; Scotrenewables Tidal Power; Voith.<ref>{{cite web|url=http://www.emec.org.uk/|title=EMEC: European Marine Energy Centre|website=emec.org.uk|url-status=live|archive-url=https://web.archive.org/web/20070127094922/http://www.emec.org.uk/|archive-date=2007-01-27}}</ref> The resource could be 4 TJ per year.<ref>{{cite journal | last1 = Lewis | first1 = M. | last2 = Neill | first2 = S.P. | last3 = Robins | first3 = P.E. | last4 = Hashemi | first4 = M.R. | year = 2015 | title = Resource assessment for future generations of tidal-stream energy arrays | doi = 10.1016/j.energy.2015.02.038 | journal = Energy | volume = 83 | pages = 403–415 | url = http://e.bangor.ac.uk/4613/1/32174..pdf | doi-access = free | bibcode = 2015Ene....83..403L }}{{Dead link|date=October 2022 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Elsewhere in the UK, annual energy of 50 TWh can be extracted if 25 GW capacity is installed with pivotable blades.<ref>{{cite web|url=http://www.tu.no/artikler/norske-oppfinneres-turbinteknologi-kan-bli-brukt-i-britisk-tidevannseventyr/367589|title=Norske oppfinneres turbinteknologi kan bli brukt i britisk tidevannseventyr|website=]|date=14 January 2017|access-date=15 January 2017|url-status=live|archive-url=https://web.archive.org/web/20170115165731/http://www.tu.no/artikler/norske-oppfinneres-turbinteknologi-kan-bli-brukt-i-britisk-tidevannseventyr/367589|archive-date=15 January 2017}}</ref><ref>{{cite web |url=https://hendryreview.files.wordpress.com/2016/08/hendry-review-final-report-english-version.pdf |title=Archived copy |access-date=2017-01-15 |url-status=live |archive-url=https://web.archive.org/web/20170118062135/https://hendryreview.files.wordpress.com/2016/08/hendry-review-final-report-english-version.pdf |archive-date=2017-01-18 }}</ref><ref>{{cite web|date=2017-01-12|title=Tidal Lagoon May Be Cheaper Than Hinkley, Government Report Says|url=https://www.bloomberg.com/news/articles/2017-01-12/swansea-tidal-lagoon-should-go-ahead-says-u-k-government-review|url-status=live|archive-url=https://web.archive.org/web/20170116181010/https://www.bloomberg.com/news/articles/2017-01-12/swansea-tidal-lagoon-should-go-ahead-says-u-k-government-review|archive-date=2017-01-16|access-date=2017-01-15|website=Bloomberg.com}}</ref> | |||
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. | |||
== Current and future tidal power schemes == | |||
====Pumping==== | |||
{{Main|List of tidal power stations}} | |||
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. | |||
] | |||
* The ] built over a period of six years from 1960 to 1966 at ], France.<ref> {{webarchive |url=https://web.archive.org/web/20050408052145/http://membres.lycos.fr/chezalex/projets/rance/sommaire_rance.htm |date=April 8, 2005 }}</ref> It has 240 MW installed capacity. | |||
* 254 MW ] in South Korea is the largest tidal power installation in the world. Construction was completed in 2011.<ref name=korea>{{cite web |url=http://www.newsworld.co.kr/cont/article2009/0909-52.htm |title=Hunt for African Projects |publisher=Newsworld.co.kr |access-date=2011-04-05 |url-status=dead |archive-url=https://web.archive.org/web/20110719135526/http://www.newsworld.co.kr/cont/article2009/0909-52.htm |archive-date=2011-07-19 }}</ref><ref>{{cite web|url=http://engsales.yonhapnews.co.kr/YNA/ContentsSales/EngSales/YISW_PopupPhotoPreview.aspx?CID=PYH20110411088100341|title=Tidal power plant nears completion|website=yonhapnews.co.kr|url-status=live|archive-url=https://web.archive.org/web/20120425235816/http://engsales.yonhapnews.co.kr/YNA/ContentsSales/EngSales/YISW_PopupPhotoPreview.aspx?CID=PYH20110411088100341|archive-date=2012-04-25}}</ref> | |||
* The ], south of ] in ] has been operational since 1985, with current installed capacity of 3.2 MW. More tidal power is planned near the mouth of the ].<ref>{{cite web |url=http://www.renewableenergyworld.com/rea/news/article/2004/11/china-endorses-300-mw-ocean-energy-project-17685 |title=China Endorses 300 MW Ocean Energy Project |date=2 November 2004 |publisher=Renewableenergyworld.com |access-date=2011-04-05 |url-status=live |archive-url=https://web.archive.org/web/20120715035036/http://www.renewableenergyworld.com/rea/news/article/2004/11/china-endorses-300-mw-ocean-energy-project-17685 |archive-date=2012-07-15 }}</ref> | |||
* The first in-stream tidal current generator in North America (]) was installed at ] on southern ] in September 2006.<ref>{{cite web |url=http://www.cleancurrent.com/technology/rrproject.htm |title=Race Rocks Demonstration Project |publisher=Cleancurrent.com |access-date=2011-04-05 |url-status=dead |archive-url=https://web.archive.org/web/20080705173021/http://www.cleancurrent.com/technology/rrproject.htm |archive-date=2008-07-05 }}</ref><ref>{{cite web |url=http://www.racerocks.com/racerock/energy/tidalenergy/tidalenergy2.htm |title=Tidal Energy, Ocean Energy |publisher=Racerocks.com |access-date=2011-04-05 |url-status=live |archive-url=https://web.archive.org/web/20110612142255/http://www.racerocks.com/racerock/energy/tidalenergy/tidalenergy2.htm |archive-date=2011-06-12 }}</ref> The Race Rocks project was shut down after operating for five years (2006–2011) because high operating costs produced electricity at a rate that was not economically feasible.<ref>{{Cite news|url=http://www.racerocks.ca/tidal-energy-turbine-removal/|title=Tidal Energy Turbine Removal|date=2011-09-18|work=Race Rocks Ecological Reserve- Marine mammals, seabirds|access-date=2018-09-09|language=en-CA}}</ref> The next phase in the development of this tidal current generator will be in Nova Scotia (Bay of Fundy).<ref>{{cite web |url=http://www.cleancurrent.com/media/index.htm |archive-url=https://web.archive.org/web/20070603100529/http://www.cleancurrent.com/media/index.htm |url-status=dead |archive-date=2007-06-03 |title=Information for media inquiries |publisher=Cleancurrent.com |date=2009-11-13 |access-date=2011-04-05 }}</ref> | |||
* A small project was built by the Soviet Union at ] on the ]. It has 0.4 MW installed capacity. In 2006 it was upgraded with a 1.2 MW experimental advanced orthogonal turbine. | |||
* ] in South Korea is a tidal stream generation scheme planned to be expanded progressively to 90 MW of capacity by 2013. The first 1 MW was installed in May 2009.<ref> {{dead link|date=June 2016|bot=medic}}{{cbignore|bot=medic}}</ref> | |||
* A 1.2 MW ] system became operational in late 2008 on ] in ].<ref>{{cite news | url=http://news.bbc.co.uk/2/hi/uk_news/northern_ireland/7790494.stm | work=BBC News | title=Tidal energy system on full power | date=December 18, 2008 | access-date=March 26, 2010 | url-status=live | archive-url=https://web.archive.org/web/20100826022612/http://news.bbc.co.uk/2/hi/uk_news/northern_ireland/7790494.stm | archive-date=August 26, 2010 }}</ref> It was decommissioned and removed in 2016.<ref>{{Cite news |date=2016-01-27 |title=Strangford tidal energy turbine to be removed |url=https://www.bbc.co.uk/news/uk-northern-ireland-35416282 |access-date=2024-10-12 |work=BBC News |language=en-GB}}</ref> | |||
* The contract for an 812 MW tidal barrage near ] (South Korea) north-west of Incheon has been signed by Daewoo. Completion was planned for 2015<ref name=korea /> but project was retracted in 2013.<ref>{{Cite web|date=2011-06-29|title=Tidal Power in South Korea|url=https://saveinternational.org/saveinaction/tidal-power-in-south-korea/|access-date=2021-10-11|website=SAVE International|language=en}}</ref> | |||
* A 1,320 MW ] was proposed by the South Korean government in 2009, to be built around islands west of Incheon. The project halted since 2012 due to environmental concerns.<ref></ref> | |||
* The Scottish Government has approved plans for a 10 MW <nowiki>''Òran na Mara''</nowiki> array of tidal stream generators near ], Scotland, costing 40 million pounds, and consisting of 10 turbines – enough to power over 5,000 homes. The first turbine was expected to be in operation by 2013<ref>{{cite news |url=https://www.bbc.co.uk/news/uk-scotland-glasgow-west-12767211 |title=Islay to get major tidal power scheme |publisher=BBC |access-date=2011-03-19 |date=March 17, 2011 |url-status=live |archive-url=https://web.archive.org/web/20110318115244/http://www.bbc.co.uk/news/uk-scotland-glasgow-west-12767211 |archive-date=March 18, 2011 }}</ref> and then once again announced in 2021,<ref>{{Cite web |date=2021-02-22 |title=Islay project to produce Scotch whisky by tidal power |url=https://www.scottishconstructionnow.com/articles/islay-project-to-produce-scotch-whisky-by-tidal-power |access-date=2023-12-18 |website=Scottish Construction Now |language=en}}</ref> but as of 2023 none existed. | |||
* The Indian state of ] was planning to host South Asia's first commercial-scale tidal power station. The company Atlantis Resources planned to install a 50 MW tidal farm in the Gulf of Kutch on India's west coast, with construction planned to start 2012,<ref>{{cite news | url=https://www.bbc.co.uk/news/science-environment-12215065 | work=BBC News | title=India plans Asian tidal power first | date=January 18, 2011 | url-status=live | archive-url=https://web.archive.org/web/20110119045601/http://www.bbc.co.uk/news/science-environment-12215065 | archive-date=January 19, 2011 }}</ref> later withdrawn due to high costs.<ref>{{Cite web|date=2021-08-20|title=India's tidal power potential hampered by high costs and environmental risks|url=https://india.mongabay.com/2021/08/indias-tidal-power-potential-hampered-by-high-costs-and-environmental-risks/|access-date=2021-10-11|website=Mongabay-India|language=en-US}}</ref> | |||
* Ocean Renewable Power Corporation was the first company to deliver tidal power to the US grid in September 2012 when its pilot TidGen system was successfully deployed in ], near Eastport.<ref> {{webarchive |url=https://web.archive.org/web/20120916223233/http://www.cbsnews.com/8301-505245_162-57512964/1st-tidal-power-delivered-to-us-grid-off-maine/ |date=September 16, 2012 }}, CBS MoneyWatch, September 14, 2012</ref> | |||
* In New York City, Verdant Power successfully deployed and operated three tidal turbines in the East River near Roosevelt Island, on a single triangular base system, called a TriFrame. The Roosevelt Island Tidal Energy (RITE) Project generated over 300MWh of electricity to the local grid, an American marine energy record. The system's performance was independently confirmed by Scotland's European Marine Energy Centre (EMEC) under the new International Electrotechnical Commission (IEC) international standards. This is the first instance of a third-party verification of a tidal energy converter to an international standard.<ref>{{cite web|title=Turbines Off NYC East River Will Create Enough Energy to Power 9,500 Homes|url=http://energy.gov/articles/turbines-nyc-east-river-will-create-enough-energy-power-9500-homes|publisher=U.S. Department of Energy|access-date=13 February 2012|url-status=live|archive-url=https://web.archive.org/web/20120211073710/http://energy.gov/articles/turbines-nyc-east-river-will-create-enough-energy-power-9500-homes|archive-date=11 February 2012}}</ref> | |||
* The largest tidal energy project entitled ] (398 MW) is currently in construction in the ] in northern Scotland with 6 MW operational since 2018.<ref>{{cite news |url=https://www.ft.com/content/d197308a-7826-11e6-97ae-647294649b28 |title=Scotland unveils world's largest tidal stream power project |newspaper=Financial Times |date=12 September 2016 |access-date=2016-12-01 |url-status=live |archive-url=https://web.archive.org/web/20161202040709/https://www.ft.com/content/d197308a-7826-11e6-97ae-647294649b28 |archive-date=2016-12-02 }}</ref><ref>{{Cite web |title=MeyGen |url=http://saerenewables.com/tidal-stream/meygen/ |access-date=2023-12-18 |website=SAE Renewables |language=en-GB}}</ref> | |||
* Construction of a 320 MW tidal lagoon power plant outside the city of ] in the UK was granted planning permission in June 2015, however it was later rejected by the UK government in 2018. If built it would have been the world's first tidal power plant based on a constructed lagoon.<ref>{{cite news|url=https://www.bbc.co.uk/news/uk-wales-south-west-wales-44589083|title=£1.3bn Swansea Bay tidal lagoon project thrown out|date=25 June 2018|work=BBC News website|access-date=27 May 2022}}</ref> | |||
* Mersey Tidal Power, a proposed tidal range barrage within the channel of the ] with a capacity of up to 1 GW is undergoing local consultation by the ].<ref>{{Cite web |date=2024-09-25 |title=Mersey Tidal - Liverpool City Region Combined Authority - Citizen Space |url=https://lcrlistens.liverpoolcityregion-ca.gov.uk/merseytidal/ |url-status=live |archive-url=https://web.archive.org/web/20240925102134/https://lcrlistens.liverpoolcityregion-ca.gov.uk/merseytidal/ |archive-date=2024-09-25 |access-date=2024-09-25 |website=Liverpool City Region Combined Authority}}</ref> | |||
* Up to 240 MW of tidal stream generation is proposed at ], ] from multiple developers, with the first turbines expected to be installed in 2026. {{As of|2024|}}, a total of 38 MW of capacity has been awarded ] to supply power to the GB grid.<ref>{{Cite web |last=Maksumic |first=Zerina |date=2024-09-05 |title=Industry welcomes boost to tidal stream projects following latest UK renewables auction results |url=https://www.offshore-energy.biz/industry-welcomes-boost-to-tidal-stream-projects-following-latest-uk-renewables-auction-results/ |access-date=2024-10-12 |website=Offshore Energy |language=en-US}}</ref> | |||
== Issues and challenges == | |||
====Two-basin schemes==== | |||
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 concerns === | |||
==Mathematical modelling== | |||
Tidal power can affect marine life. The turbines' rotating blades can accidentally kill swimming sea life. Projects such as the one in Strangford include a safety mechanism that turns off the turbine when marine animals approach. However, this feature causes a major loss in energy because of the amount of marine life that passes through the turbines.<ref>{{cite web|title=Tidal Energy Technology Brief|url=http://www.irena.org/DocumentDownloads/Publications/Tidal_Energy_V4_WEB.pdf|publisher=International Renewable Energy Agency|access-date=16 October 2015|url-status=live|archive-url=https://web.archive.org/web/20151122225322/http://www.irena.org/documentdownloads/publications/tidal_energy_v4_web.pdf|archive-date=22 November 2015}}</ref> Some fish may avoid the area if threatened by a constantly rotating or noisy object. Marine life is a huge factor when siting tidal power ]s, and precautions are taken to ensure that as few ]s as possible are affected by it. In terms of ] (i.e. carbon footprint), the impact of tidal power generation technologies ranges between 15 and 37 gCO<sub>2</sub>-eq/kWhe, with a median value of 23.8 gCO<sub>2</sub>-eq/kWhe.<ref>{{cite journal |last1=Kaddoura |first1=Mohamad |last2=Tivander |first2=Johan |last3=Molander |first3=Sverker |title= life cycle assessment of electricity generation from an array of subsea tidal kite prototypes |journal=Energies |date=2020 |volume=13 |issue=2 |pages=456 |doi= 10.3390/en13020456 |doi-access=free }}</ref> This is in line with the impact of other renewables like wind and solar power, and significantly better than fossil-based technologies. The ] provides access to scientific literature and general information on the potential environmental effects of tidal energy.<ref>{{cite web|title=Tethys|url=https://tethys.pnnl.gov|website=Tethys |publisher=PNNL}}</ref> | |||
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. | |||
==== Tidal turbines ==== | |||
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. | |||
The main environmental concern with tidal energy is associated with blade strike and entanglement of marine organisms as high-speed water increases the risk of organisms being pushed near or through these devices. As with all offshore renewable energies, there is also a concern about how the creation of ]s and acoustic outputs may affect marine organisms. Because these devices are in the water, the acoustic output can be greater than those created with ]. Depending on the ] and ] of ] generated by the tidal energy devices, this acoustic output can have varying effects on marine mammals (particularly those who ] to communicate and navigate in the marine environment, such as ]s and ]s). Tidal energy removal can also cause environmental concerns such as degrading far-field ] and disrupting ] processes.<ref>{{Cite journal|last1=Li|first1=X.|last2=Li|first2=M.|last3=Amoudry|first3=L. O.|last4=Ramirez-Mendoza|first4=R.|last5=Thorne|first5=P. D.|last6=Song|first6=Q.|last7=Zheng|first7=P.|last8=Simmons|first8=S. M.|last9=Jordan|first9=L. -B.|last10=McLelland|first10=S. J.|date=2019-11-25|title=Three-dimensional modelling of suspended sediment transport in the far wake of tidal stream turbines|journal=Renewable Energy|volume=151|pages=956–965|doi=10.1016/j.renene.2019.11.096|doi-access=free|url=https://hull-repository.worktribe.com/preview/3474423/renene-2019-11-096.pdf}}</ref><ref>{{Cite journal|last1=Martin-Short|first1=R.|last2=Hill|first2=J.|last3=Kramer|first3=S. C.|last4=Avdis|first4=A.|last5=Allison|first5=P. A.|last6=Piggott|first6=M. D.|date=2015-04-01|title=Tidal resource extraction in the Pentland Firth, UK: Potential impacts on flow regime and sediment transport in the Inner Sound of Stroma|journal=Renewable Energy|volume=76|pages=596–607|doi=10.1016/j.renene.2014.11.079|doi-access=free|bibcode=2015REne...76..596M |hdl=10044/1/40674|hdl-access=free}}</ref> Depending on the size of the project, these effects can range from small traces of sediment building up near the tidal device to severely affecting nearshore ]s and processes.<ref name="tethys.pnnl.gov">{{cite web|title=Tethys|url=http://tethys.pnnl.gov/|url-status=live|archive-url=https://web.archive.org/web/20140525011534/http://tethys.pnnl.gov/|archive-date=2014-05-25}}</ref> | |||
==== Tidal barrage ==== | |||
In these models, the basin is broken into large segments (1D), squares (2D) or cubes (3D). The complexity and accuracy increases with dimension. | |||
Installing a barrage may change the shoreline within the ] or ], affecting a large ecosystem that depends on ]s. Inhibiting the flow of water in and out of the bay, there may also be less flushing of the bay or estuary, causing additional ] (suspended solids) and less saltwater, which may result in the death of fish that act as a vital food source to birds and mammals. Migrating fish may also be unable to access breeding streams, and may attempt to pass through the turbines. The same acoustic concerns apply to tidal barrages. Decreasing shipping accessibility can become a socio-economic issue, though locks can be added to allow slow passage. However, the barrage may improve the local economy by increasing land access as a bridge. Calmer waters may also allow better recreation in the bay or estuary.<ref name="tethys.pnnl.gov" /> In August 2004, a ] swam through the open ] of the ] at slack tide, ending up trapped for several days before eventually finding its way out to the ].<ref>{{cite news|url=https://www.theglobeandmail.com/news/national/whale-still-drawing-crowds-at-ns-river/article1140088/|title=Whale still drawing crowds at N.S. river|website=The Globe and Mail|url-status=live|archive-url=https://web.archive.org/web/20160304134333/http://www.theglobeandmail.com/news/national/whale-still-drawing-crowds-at-ns-river/article1140088/|archive-date=2016-03-04}}</ref> | |||
==== Tidal lagoon ==== | |||
Mathematical modelling produces quantitative information for a range of parameters, including: | |||
Environmentally, the main concerns are blade strike on fish attempting to enter the ], the acoustic output from turbines, and changes in sedimentation processes. However, all these effects are localized and do not affect the entire estuary or bay.<ref name="tethys.pnnl.gov" /> | |||
* Water levels (during operation, construction, extreme conditions, etc.) | |||
* Currents | |||
* Waves | |||
* Power output | |||
* ] | |||
* ] | |||
* Sediment movements | |||
=== Corrosion === | |||
==Environmental impact== | |||
Saltwater causes corrosion in metal parts. It can be difficult to maintain tidal stream generators due to their size and depth in the water. The use of corrosion-resistant materials such as stainless steels, high-nickel alloys, copper-nickel alloys, nickel-copper alloys and titanium can greatly reduce, or eliminate corrosion damage. Composite materials could also be used, as composites do not corrode and could provide lightweight, durable structures for tidal power.<ref>{{Cite report |url=https://www.osti.gov/biblio/1641913 |title=Evaluation of composite materials for wave and current energy technologies. |last1=Hernandez-Sanchez |first1=Bernadette A. |last2=Nicholas |first2=James |last3=Gunawan |first3=Budi |last4=Miller |first4=David A. |last5=Bonheyo |first5=George T. |last6=Presuel-Moreno |first6=Francisco |last7=Hughes |first7=Scott |date=2019-09-01 |publisher=Sandia National Lab. (SNL-NM), Albuquerque, NM (United States) |issue=SAND2019–10368C |osti=1641913 |language=English}}</ref> Composite materials are being evaluated for tidal power.<ref>{{Cite journal |last1=Lusty |first1=Ariel F |last2=Murdy |first2=Paul |last3=Gionet-Gonzales |first3=Julia A |date=2024 |title=Submerged Fatigue Testing of Marine Energy Advanced Materials |url=https://rgdoi.net/10.13140/RG.2.2.34441.25445 |language=en |doi=10.13140/RG.2.2.34441.25445}}</ref> | |||
===Tidal Energy Efficiency=== | |||
Tidal energy has an efficiency of 80% in converting the potential energy of the water into electricity, which is efficient compared to other energy resources such as ]. | |||
There are not many effects on the environment, but it can damage some fish (reduce the population. | |||
Mechanical fluids, such as lubricants, can leak out, which may be harmful to the marine life nearby. Proper maintenance can minimize the number of harmful chemicals that may enter the environment. | |||
===Local environmental impact=== | |||
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 a much lower impact. | |||
=== |
=== Fouling === | ||
The biological events that happen when placing any structure in an area of high tidal currents and high biological productivity in the ocean will ensure that the structure becomes an ideal substrate for the growth of marine organisms. | |||
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 ]. The changes propagate up the ], causing a general change in the ]. | |||
=== |
=== Cost === | ||
Tidal energy has a high initial cost, which may be one of the reasons why it is not a popular source of ], although research has shown that the public is willing to pay for and support research and development of tidal energy devices.<ref>{{Cite journal |last1=Polis |first1=Hilary Jacqueline |last2=Dreyer |first2=Stacia Jeanne |last3=Jenkins |first3=Lekelia Danielle |date=2017-06-01 |title=Public Willingness to Pay and Policy Preferences for Tidal Energy Research and Development: A Study of Households in Washington State |journal=Ecological Economics |language=en |volume=136 |pages=213–225 |doi=10.1016/j.ecolecon.2017.01.024 |issn=0921-8009|doi-access=free |bibcode=2017EcoEc.136..213P |hdl=1773/35605 |hdl-access=free }}</ref><ref>{{Cite journal |last1=Dreyer |first1=Stacia J. |last2=Polis |first2=Hilary Jacqueline |last3=Jenkins |first3=Lekelia Danielle |date=July 2017 |title=Changing Tides: Acceptability, support, and perceptions of tidal energy in the United States |journal=Energy Research & Social Science |language=en |volume=29 |pages=72–83 |doi=10.1016/j.erss.2017.04.013|doi-access=free |bibcode=2017ERSS...29...72D }}</ref><ref>{{Cite journal |last1=Jenkins |first1=Lekelia Danielle |last2=Dreyer |first2=Stacia Jeanne |last3=Polis |first3=Hilary Jacqueline |last4=Beaver |first4=Ezra |last5=Kowalski |first5=Adam A. |last6=Linder |first6=Hannah L. |last7=McMillin |first7=Thomas Neal |last8=McTiernan |first8=Kaylie Laura |last9=Rogier |first9=Thea Thezin |last10=Wiesebron |first10=Lauren Eva |date=2018-12-01 |title=Human dimensions of tidal energy: A review of theories and frameworks |journal=Renewable and Sustainable Energy Reviews |language=en |volume=97 |pages=323–337 |doi=10.1016/j.rser.2018.08.036 |s2cid=117167506 |issn=1364-0321|doi-access=free |bibcode=2018RSERv..97..323J }}</ref> The methods of generating electricity from tidal energy are relatively new technology. Tidal energy is however still very early in the research process and it may be possible to reduce costs in future. The cost-effectiveness varies according to the site of the tidal generators. One indication of cost-effectiveness is the Gibrat ratio, which is the length of the barrage in metres divided by the annual energy production in ]s.<ref>{{Cite news|url=http://www.oceanenergycouncil.com/ocean-energy/tidal-energy/|title=Tidal Energy – Ocean Energy Council|work=Ocean Energy Council|access-date=2018-05-04|language=en-US}}</ref> | |||
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. | |||
As tidal energy is reliable, it can reasonably be predicted how long it will take to pay off the high up-front cost of these generators. Due to the success of a greatly simplified design, the orthogonal turbine offers considerable cost savings. As a result, the production period of each generating unit is reduced, lower metal consumption is needed and technical efficiency is greater.<ref>{{Cite web|url=http://www.ru.is/media/reyst/Niels-Sveinsson.pdf|title=Profitability Assessment for a Tidal Power Plant at the Mouth of Hvammsfjörður, Iceland|last=Sveinsson|first=Níels}}</ref> | |||
====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. | |||
A possible risk is rising sea levels due to climate change, which may alter the characteristics of the local tides reducing future power generation.<ref>{{cite news |last1=Johnson |first1=Doug |title=As Sea Levels Rise, Tidal Power Becomes a Moving Target |url=https://undark.org/2023/04/18/as-sea-levels-rise-tidal-power-becomes-a-moving-target/ |access-date=9 May 2023 |work=] |date=18 April 2023}}</ref><ref>{{cite journal |last1=Khojasteh |first1=Danial |last2=Chen |first2=Shengyang |last3=Felder |first3=Stefan |last4=Glamore |first4=William |last5=Hashemi |first5=M. Reza |last6=Iglesias |first6=Gregorio |title=Sea level rise changes estuarine tidal stream energy |journal=Energy |date=15 January 2022 |volume=239 |pages=122428 |doi=10.1016/j.energy.2021.122428 |bibcode=2022Ene...23922428K |s2cid=239908223|language=en |issn=0360-5442|hdl=10468/12300 |hdl-access=free }}</ref> | |||
With turbine generation, taking its power from the flow of the tidal stream, there will likely be a swirl of water down stream of the turbine. If this horizontal vortex touches the bottom, it will cause erosion. While the amount of sediment added to the tidal stream will likely be insignificant, this could, over time, erode the foundation of the turbine. Turbines held down with pilings would be largely immune to this problem but turbines held by heavy weights sitting on the bottom could eventually tip over. | |||
== Structural health monitoring == | |||
====Pollutants==== | |||
The high load factors resulting from the fact that water is around 800 times denser than air, and the predictable and reliable nature of tides compared with the wind, make tidal energy particularly attractive for electric power generation. Condition monitoring is the key for exploiting it cost-efficiently.<ref>{{cite web|title=Structural Health Monitoring in Composite Tidal energy converters|url=http://www.ndtwiki.com/index.php/SHM_of_Composite_in_tidal_energy_converters|url-status=live|archive-url=https://web.archive.org/web/20140325161507/http://www.ndtwiki.com/index.php/SHM_of_Composite_in_tidal_energy_converters|archive-date=2014-03-25}}</ref> | |||
Again, as a result of reduced volume, the pollutants accumulating in the basin may be less efficiently dispersed, so their concentrations may increase. For ] pollutants, such as sewage, an increase in concentration is likely to lead to increased bacteria growth in the basin, having impacts on the health of the human community and the ecosystem. | |||
== |
== See also == | ||
{{Portal|Renewable energy|Oceans|Energy|Water}} | |||
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% (from pressure drop, contact with blades, ], etc.). This can be acceptable for a ], but is devastating for local fish who pass in and out of the basin on a daily basis. Alternative passage technologies (]s, 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. | |||
* ] | |||
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* ] | |||
* ] | |||
* ] | |||
* ] | |||
* ] | |||
* ] | |||
* ] | |||
* ] | |||
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== References == | |||
Using tidal stream systems that do not close off rivers and streams would allow fish migration at times of spawning. These water current turbines typically turn very slowly at around 20-30 ], allowing fish to safely navigate either past or through the turning impellor drastically reducing or eliminating fish kills. | |||
{{Reflist|30em}} | |||
== Further reading == | |||
===Global environmental impact=== | |||
* Baker, A. C. 1991, ''Tidal power'', Peter Peregrinus Ltd., London. | |||
A tidal power scheme is a long-term source of electricity. A proposal for the ], if built, has been projected to save 18 million tons of coal per year of operation. This decreases the output of greenhouse gases into the atmosphere. More importantly, as the fossil fuel resource is likely to be eliminated by the end of the twenty-first century, tidal power is one of the alternative source of energy that will need to be developed to satisfy the human demand for energy. | |||
* Baker, G. C., Wilson E. M., Miller, H., Gibson, R. A. & Ball, M., 1980. "The Annapolis tidal power pilot project", in ''Waterpower '79 Proceedings'', ed. Anon, U.S. Government Printing Office, Washington, pp 550–559. | |||
* Hammons, T. J. 1993, "Tidal power", ''Proceedings of the IEEE'', , v81, n3, pp 419–433. Available from: IEEE/IEEE Xplore. . | |||
* Lecomber, R. 1979, "The evaluation of tidal power projects", in ''Tidal Power and Estuary Management'', eds. Severn, R. T., Dineley, D. L. & Hawker, L. E., Henry Ling Ltd., Dorchester, pp 31–39. | |||
* Jubilo, A., 2019, "Renewable Tidal Energy Potential: Basis for Technology Development in Eastern Mindanao", 80th PIChE National Convention; Crowne Plaza Galleria, Ortigas Center, Quezon City, Philippines. | |||
* . BBC News. Published 22 October 2023. | |||
* . David J.C. MacKay, Cavendish Laboratory, University of Cambridge, UK. Published 3 May 2007. | |||
* – Report by Sustainable Development Commission. Published October 2007. | |||
* – Report by Global Energy Survey. Published 2007. | |||
== External links == | |||
==Economic considerations== | |||
{{Commons category|Tidal power}} | |||
* A network of databases providing broad access to marine energy information. | |||
* Basic information about current energy. | |||
* A database that provides up-to-date information on marine energy deployments in the U.S. and around the world. | |||
* A database of information on potential environmental effects of marine energy and offshore wind energy development. | |||
* A database of information on technical design and engineering of marine energy devices. | |||
* A database for all data collected by marine energy research and development projects funded by the U.S. Department of Energy. | |||
* | |||
* —Detailed analysis of marine energy resource, current energy capture technology appraisal and environmental impact outline | |||
* | |||
* – Listing of Tidal Energy Developers -retrieved 1 July 2011 (link updated 31 January 2014) | |||
* | |||
* {{Webarchive|url=https://web.archive.org/web/20140325161507/http://www.ndtwiki.com/index.php/SHM_of_Composite_in_tidal_energy_converters |date=2014-03-25 }} | |||
* | |||
* | |||
{{Energy footer}} | |||
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 years, and investors are thus 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 ] (see for example key principles 4 and 6 within Planning Policy Statement 22) 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 its goals forward. | |||
{{Ocean energy}} | |||
{{Physical oceanography}} | |||
{{Natural resources}} | |||
{{Authority control}} | |||
] | |||
==Resource around the world== | |||
] | |||
===Operating tidal power schemes=== | |||
] | |||
* The first tidal power station was the ] built over a period of 6 years from 1960 to 1966 at ], France (). It has 240MW installed capacity. | |||
] | |||
* The first (and only) tidal power site in North America is the ], ], ], which opened in ] on an inlet of the ]. It has 20MW installed capacity. | |||
* A small project was built by the Soviet Union at ] on the ]. 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 ] | |||
) | |||
*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. | |||
*South African energy parastatal ] is investigating using the ] to generate power off the coast of ]. 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 considered=== | |||
In the table, '-' indicates missing information, '?' indicates information which has not been decided | |||
<table class="wikitable"> | |||
<tr> | |||
<td>'''Country'''</td> | |||
<td>'''Place'''</td> | |||
<td>'''Mean tidal range (m)'''</td> | |||
<td>'''Area of basin (km²)'''</td> | |||
<td>'''Maximum capacity (MW)'''</td> | |||
</tr> | |||
<tr> | |||
<td>]</td> | |||
<td>]<!--] is a disambiguation page. A more specific article should be linked to.--></td> | |||
<td>5.9</td> | |||
<td>-</td> | |||
<td>6800</td> | |||
</tr> | |||
<tr> | |||
<td>]</td> | |||
<td>]</td> | |||
<td>10.9</td> | |||
<td>-</td> | |||
<td>?</td> | |||
</tr> | |||
<tr> | |||
<td rowspan="3">]</td> | |||
<td>]</td> | |||
<td>12.4</td> | |||
<td>240</td> | |||
<td>5338</td> | |||
</tr> | |||
<tr> | |||
<td>]</td> | |||
<td>10.9</td> | |||
<td>90</td> | |||
<td>1400</td> | |||
</tr> | |||
<tr> | |||
<td>]</td> | |||
<td>10.0</td> | |||
<td>115</td> | |||
<td>1800</td> | |||
</tr> | |||
<tr> | |||
<td rowspan="2">]</td> | |||
<td>]</td> | |||
<td>5.3</td> | |||
<td>170</td> | |||
<td>900</td> | |||
</tr> | |||
<tr> | |||
<td>]</td> | |||
<td>6.8</td> | |||
<td>1970</td> | |||
<td>7000</td> | |||
</tr> | |||
<tr> | |||
<td rowspan="2">]</td> | |||
<td>]</td> | |||
<td>4.7</td> | |||
<td>100</td> | |||
<td>480</td> | |||
</tr> | |||
<tr> | |||
<td>]</td> | |||
<td>4.5</td> | |||
<td>-</td> | |||
<td>-</td> | |||
</tr> | |||
<tr> | |||
<td rowspan="2">]</td> | |||
<td>]</td> | |||
<td>6-7</td> | |||
<td>-</td> | |||
<td>?</td> | |||
</tr> | |||
<tr> | |||
<td>]</td> | |||
<td>-</td> | |||
<td>-</td> | |||
<td>?</td> | |||
</tr> | |||
<tr> | |||
<td rowspan="4">]</td> | |||
<td>]</td> | |||
<td>7.8</td> | |||
<td>450</td> | |||
<td>]</td> | |||
</tr> | |||
<tr> | |||
<td>]</td> | |||
<td>6.5</td> | |||
<td>61</td> | |||
<td>700</td> | |||
</tr> | |||
<tr> | |||
<td>]</td> | |||
<td>-</td> | |||
<td>-</td> | |||
<td>-</td> | |||
</tr> | |||
<tr> | |||
<td>]</td> | |||
<td>5.2</td> | |||
<td>5.5</td> | |||
<td>33</td> | |||
</tr> | |||
<tr> | |||
<td rowspan="3">]</td> | |||
<td>]</td> | |||
<td>5.5</td> | |||
<td>-</td> | |||
<td>?</td> | |||
</tr> | |||
<tr> | |||
<td>]</td> | |||
<td>7.5</td> | |||
<td>-</td> | |||
<td>2900</td> | |||
</tr> | |||
<tr> | |||
<td>]</td> | |||
<td>7.5</td> | |||
<td>-</td> | |||
<td>6501</td> | |||
</tr> | |||
<tr> | |||
<td rowspan="3">]</td> | |||
<td>]</td> | |||
<td>9.1</td> | |||
<td>2300</td> | |||
<td>19200</td> | |||
</tr> | |||
<tr> | |||
<td>]</td> | |||
<td>-</td> | |||
<td>-</td> | |||
<td>8000</td> | |||
</tr> | |||
<tr> | |||
<td>]</td> | |||
<td>6.0</td> | |||
<td>-</td> | |||
<td>87000</td> | |||
</tr> | |||
<tr> | |||
<td rowspan="3">]</td> | |||
<td>]</td> | |||
<td>?</td> | |||
<td>?</td> | |||
<td>?</td> | |||
</tr> | |||
</table> | |||
==See also== | |||
* ] | |||
* ] | |||
==External links== | |||
* -- Article about new tidal power technology | |||
* -- Summary of tidal and marine current generators | |||
* -- Detailed analysis of marine energy resource, current energy capture technology appraisal and environmental impact outline | |||
* -- Articles about tidal power generation. | |||
* | |||
* | |||
==Sources== | |||
* Baker, A. C. 1991, Tidal power, Peter Peregrinus Ltd., London. | |||
* Baker, G. C., Wilson E. M., Miller, H., Gibson, R. A. & Ball, M., 1980. 'The Annapolis tidal power pilot project', in Waterpower `79 Proceedings, ed. Anon, U.S. Government Printing Office, Washington, pp 550-559. | |||
* Hammons, T. J. 1993, 'Tidal power', Proceedings of the IEEE, , v81, n3, pp 419-433. Available from: IEEE/IEEE Xplore. . | |||
* Lecomber, R. 1979, 'The evaluation of tidal power projects', in Tidal Power and Estuary Management, eds. Severn, R. T., Dineley, D. L. & Hawker, L. E., Henry Ling Ltd., Dorchester, pp 31-39. | |||
==Patents== | |||
* {{US patent|6,982,498}}, Tharp, January 3, 2006, Hydro-electric farms | |||
* {{US patent|6,995,479}}, Tharp, February 7, 2006, Hydro-electric farms | |||
* {{US patent|6,998,730}}, Tharp, February 14, 2006, Hydro-electric farms | |||
{{Energy Conversion}} | |||
{{Sustainability and energy development group}} | |||
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Latest revision as of 09:20, 29 December 2024
Technology to convert the energy from tides into useful forms of powerPart of a series on |
Renewable energy |
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Tidal power or tidal energy is harnessed by converting energy from tides into useful forms of power, mainly electricity using various methods.
Although not yet widely used, tidal energy has the potential for future electricity generation. Tides are more predictable than the wind and the sun. Among sources of renewable energy, tidal energy has traditionally suffered from relatively high cost and limited availability of sites with sufficiently high tidal ranges or flow velocities, thus constricting its total availability. However many recent technological developments and improvements, both in design (e.g. dynamic tidal power, tidal lagoons) and turbine technology (e.g. new axial turbines, cross flow turbines), indicate that the total availability of tidal power may be much higher than previously assumed and that economic and environmental costs may be brought down to competitive levels.
Historically, tide mills have been used both in Europe and on the Atlantic coast of North America. Incoming water was contained in large storage ponds, and as the tide goes out, it turns waterwheels that use the mechanical power to mill grain. The earliest occurrences date from the Middle Ages, or even from Roman times. The process of using falling water and spinning turbines to create electricity was introduced in the U.S. and Europe in the 19th century.
Electricity generation from marine technologies increased an estimated 16% in 2018, and an estimated 13% in 2019. Policies promoting R&D are needed to achieve further cost reductions and large-scale development. The world's first large-scale tidal power plant was France's Rance Tidal Power Station, which became operational in 1966. It was the largest tidal power station in terms of output until Sihwa Lake Tidal Power Station opened in South Korea in August 2011. The Sihwa station uses sea wall defense barriers complete with 10 turbines generating 254 MW.
Principle
Main articles: Tide and Tidal accelerationTidal energy is taken from the Earth's oceanic tides. Tidal forces result from periodic variations in gravitational attraction exerted by celestial bodies. These forces create corresponding motions or currents in the world's oceans. This results in periodic changes in sea levels, varying as the Earth rotates. These changes are highly regular and predictable, due to the consistent pattern of the Earth's rotation and the Moon's orbit around the Earth. The magnitude and variations of this motion reflect the changing positions of the Moon and Sun relative to the Earth, the effects of Earth's rotation, and local geography of the seafloor and coastlines.
Tidal power is the only technology that draws on energy inherent in the orbital characteristics of the Earth–Moon system, and to a lesser extent in the Earth–Sun system. Other natural energies exploited by human technology originate directly or indirectly from the Sun, including fossil fuel, conventional hydroelectric, wind, biofuel, wave and solar energy. Nuclear energy makes use of Earth's mineral deposits of fissionable elements, while geothermal power utilizes the Earth's internal heat, which comes from a combination of residual heat from planetary accretion (about 20%) and heat produced through radioactive decay (80%).
A tidal generator converts the energy of tidal flows into electricity. Greater tidal variation and higher tidal current velocities can dramatically increase the potential of a site for tidal electricity generation. On the other hand, tidal energy has high reliability, excellent energy density, and high durability.
Because the Earth's tides are ultimately due to gravitational interaction with the Moon and Sun and the Earth's rotation, tidal power is practically inexhaustible, and is thus classified as a renewable energy resource. Movement of tides causes a loss of mechanical energy in the Earth-Moon system: this results from pumping of water through natural restrictions around coastlines and consequent viscous dissipation at the seabed and in turbulence. This loss of energy has caused the rotation of the Earth to slow in the 4.5 billion years since its formation. During the last 620 million years the period of rotation of the Earth (length of a day) has increased from 21.9 hours to 24 hours; in this period the Earth-Moon system has lost 17% of its rotational energy. While tidal power will take additional energy from the system, the effect is negligible and would not be noticeable in the foreseeable future.
Methods
Tidal power can be classified into four generating methods:
Tidal stream generator
Main article: Tidal stream generatorTidal stream generators make use of the kinetic energy of moving water to power turbines, in a similar way to wind turbines that use the wind to power turbines. Some tidal generators can be built into the structures of existing bridges or are entirely submersed, thus avoiding concerns over aesthetics or visual impact. Land constrictions such as straits or inlets can create high velocities at specific sites, which can be captured using turbines. These turbines can be horizontal, vertical, open, or ducted.
Tidal barrage
Main article: Tidal barrageTidal barrages use potential energy in the difference in height (or hydraulic head) between high and low tides. When using tidal barrages to generate power, the potential energy from a tide is seized through the strategic placement of specialized dams. When the sea level rises and the tide begins to come in, the temporary increase in tidal power is channeled into a large basin behind the dam, holding a large amount of potential energy. With the receding tide, this energy is then converted into mechanical energy as the water is released through large turbines that create electrical power through the use of generators. Barrages are essentially dams across the full width of a tidal estuary.
Tidal lagoon
A new tidal energy design option is to construct circular retaining walls embedded with turbines that can capture the potential energy of tides. The created reservoirs are similar to those of tidal barrages, except that the location is artificial and does not contain a pre-existing ecosystem. The lagoons can also be in double (or triple) format without pumping or with pumping that will flatten out the power output. The pumping power could be provided by excess to grid demand renewable energy from for example wind turbines or solar photovoltaic arrays. Excess renewable energy rather than being curtailed could be used and stored for a later period of time. Geographically dispersed tidal lagoons with a time delay between peak production would also flatten out peak production providing near baseload production at a higher cost than other alternatives such as district heating renewable energy storage. The cancelled Tidal Lagoon Swansea Bay in Wales, United Kingdom would have been the first tidal power station of this type once built.
Dynamic tidal power
Main article: Dynamic tidal powerDynamic tidal power (or DTP) is a theoretical technology that would exploit an interaction between potential and kinetic energies in tidal flows. It proposes that very long dams (for example: 30–50 km length) be built from coasts straight out into the sea or ocean, without enclosing an area. Tidal phase differences are introduced across the dam, leading to a significant water-level differential in shallow coastal seas – featuring strong coast-parallel oscillating tidal currents such as found in the UK, China, and Korea.
US and Canadian studies in the 20th century
The first study of large scale tidal power plants was by the US Federal Power Commission in 1924. If built, power plants would have been located in the northern border area of the US state of Maine and the southeastern border area of the Canadian province of New Brunswick, with various dams, powerhouses, and ship locks enclosing the Bay of Fundy and Passamaquoddy Bay (note: see map in reference). Nothing came of the study, and it is unknown whether Canada had been approached about the study by the US Federal Power Commission.
In 1956, utility Nova Scotia Light and Power of Halifax commissioned a pair of studies into commercial tidal power development feasibility on the Nova Scotia side of the Bay of Fundy. The two studies, by Stone & Webster of Boston and by Montreal Engineering Company of Montreal, independently concluded that millions of horsepower (i.e. gigawatts) could be harnessed from Fundy but that development costs would be commercially prohibitive.
There was also a report on the international commission in April 1961 entitled "Investigation of the International Passamaquoddy Tidal Power Project" produced by both the US and Canadian Federal Governments. According to benefit to costs ratios, the project was beneficial to the US but not to Canada.
A study was commissioned by the Canadian & Nova Scotian and New Brunswick governments (Reassessment of Fundy Tidal Power) to determine the potential for tidal barrages at Chignecto Bay and Minas Basin – at the end of the Fundy Bay estuary. There were three sites determined to be financially feasible: Shepody Bay (1550 MW), Cumberland Basin (1085 MW), and Cobequid Bay (3800 MW). These were never built despite their apparent feasibility in 1977.
US studies in the 21st century
The Snohomish PUD, a public utility district located primarily in Snohomish County, Washington State, began a tidal energy project in 2007. In April 2009 the PUD selected OpenHydro, a company based in Ireland, to develop turbines and equipment for eventual installation. The project as initially designed was to place generation equipment in areas of high tidal flow and operate that equipment for four to five years. After the trial period the equipment would be removed. The project was initially budgeted at a total cost of $10 million, with half of that funding provided by the PUD out of utility reserve funds, and half from grants, primarily from the US federal government. The PUD paid for part of this project from reserves and received a $900,000 grant in 2009 and a $3.5 million grant in 2010 in addition to using reserves to pay an estimated $4 million of costs. In 2010 the budget estimate was increased to $20 million, half to be paid by the utility, half by the federal government. The utility was unable to control costs on this project, and by October 2014, the costs had ballooned to an estimated $38 million and were projected to continue to increase. The PUD proposed that the federal government provide an additional $10 million towards this increased cost, citing a gentlemen's agreement. When the federal government refused to pay this, the PUD cancelled the project after spending nearly $10 million from reserves and grants. The PUD abandoned all tidal energy exploration after this project was cancelled and does not own or operate any tidal energy sources.
Rance tidal power plant in France
In 1966, Électricité de France opened the Rance Tidal Power Station, located on the estuary of the Rance River in Brittany. It was the world's first tidal power station. The plant was for 45 years the largest tidal power station in the world by installed capacity: Its 24 turbines reach peak output at 240 megawatts (MW) and average 57 MW, a capacity factor of approximately 24%.
Tidal power development in the UK
The world's first marine energy test facility was established in 2003 to start the development of the wave and tidal energy industry in the UK. Based in Orkney, Scotland, the European Marine Energy Centre (EMEC) has supported the deployment of more wave and tidal energy devices than at any other single site in the world. EMEC provides a variety of test sites in real sea conditions. Its grid connected tidal test site is located at the Fall of Warness, off the island of Eday, in a narrow channel which concentrates the tide as it flows between the Atlantic Ocean and North Sea. This area has a very strong tidal current, which can travel up to 4 m/s (8.9 mph; 7.8 kn; 14 km/h) in spring tides. Tidal energy developers that have tested at the site include: Alstom (formerly Tidal Generation Ltd); ANDRITZ HYDRO Hammerfest; Atlantis Resources Corporation; Nautricity; OpenHydro; Scotrenewables Tidal Power; Voith. The resource could be 4 TJ per year. Elsewhere in the UK, annual energy of 50 TWh can be extracted if 25 GW capacity is installed with pivotable blades.
Current and future tidal power schemes
Main article: List of tidal power stations- The Rance tidal power plant built over a period of six years from 1960 to 1966 at La Rance, France. It has 240 MW installed capacity.
- 254 MW Sihwa Lake Tidal Power Plant in South Korea is the largest tidal power installation in the world. Construction was completed in 2011.
- The Jiangxia Tidal Power Station, south of Hangzhou in China has been operational since 1985, with current installed capacity of 3.2 MW. More tidal power is planned near the mouth of the Yalu River.
- The first in-stream tidal current generator in North America (Race Rocks Tidal Power Demonstration Project) was installed at Race Rocks on southern Vancouver Island in September 2006. The Race Rocks project was shut down after operating for five years (2006–2011) because high operating costs produced electricity at a rate that was not economically feasible. The next phase in the development of this tidal current generator will be in Nova Scotia (Bay of Fundy).
- A small project was built by the Soviet Union at Kislaya Guba on the Barents Sea. It has 0.4 MW installed capacity. In 2006 it was upgraded with a 1.2 MW experimental advanced orthogonal turbine.
- Jindo Uldolmok Tidal Power Plant in South Korea is a tidal stream generation scheme planned to be expanded progressively to 90 MW of capacity by 2013. The first 1 MW was installed in May 2009.
- A 1.2 MW SeaGen system became operational in late 2008 on Strangford Lough in Northern Ireland. It was decommissioned and removed in 2016.
- The contract for an 812 MW tidal barrage near Ganghwa Island (South Korea) north-west of Incheon has been signed by Daewoo. Completion was planned for 2015 but project was retracted in 2013.
- A 1,320 MW barrage was proposed by the South Korean government in 2009, to be built around islands west of Incheon. The project halted since 2012 due to environmental concerns.
- The Scottish Government has approved plans for a 10 MW ''Òran na Mara'' array of tidal stream generators near Islay, Scotland, costing 40 million pounds, and consisting of 10 turbines – enough to power over 5,000 homes. The first turbine was expected to be in operation by 2013 and then once again announced in 2021, but as of 2023 none existed.
- The Indian state of Gujarat was planning to host South Asia's first commercial-scale tidal power station. The company Atlantis Resources planned to install a 50 MW tidal farm in the Gulf of Kutch on India's west coast, with construction planned to start 2012, later withdrawn due to high costs.
- Ocean Renewable Power Corporation was the first company to deliver tidal power to the US grid in September 2012 when its pilot TidGen system was successfully deployed in Cobscook Bay, near Eastport.
- In New York City, Verdant Power successfully deployed and operated three tidal turbines in the East River near Roosevelt Island, on a single triangular base system, called a TriFrame. The Roosevelt Island Tidal Energy (RITE) Project generated over 300MWh of electricity to the local grid, an American marine energy record. The system's performance was independently confirmed by Scotland's European Marine Energy Centre (EMEC) under the new International Electrotechnical Commission (IEC) international standards. This is the first instance of a third-party verification of a tidal energy converter to an international standard.
- The largest tidal energy project entitled MeyGen (398 MW) is currently in construction in the Pentland Firth in northern Scotland with 6 MW operational since 2018.
- Construction of a 320 MW tidal lagoon power plant outside the city of Swansea in the UK was granted planning permission in June 2015, however it was later rejected by the UK government in 2018. If built it would have been the world's first tidal power plant based on a constructed lagoon.
- Mersey Tidal Power, a proposed tidal range barrage within the channel of the Mersey Estuary with a capacity of up to 1 GW is undergoing local consultation by the Liverpool City Region Combined Authority.
- Up to 240 MW of tidal stream generation is proposed at Morlais, Anglesey from multiple developers, with the first turbines expected to be installed in 2026. As of 2024, a total of 38 MW of capacity has been awarded Contracts for Difference to supply power to the GB grid.
Issues and challenges
Environmental concerns
Tidal power can affect marine life. The turbines' rotating blades can accidentally kill swimming sea life. Projects such as the one in Strangford include a safety mechanism that turns off the turbine when marine animals approach. However, this feature causes a major loss in energy because of the amount of marine life that passes through the turbines. Some fish may avoid the area if threatened by a constantly rotating or noisy object. Marine life is a huge factor when siting tidal power energy generators, and precautions are taken to ensure that as few marine animals as possible are affected by it. In terms of global warming potential (i.e. carbon footprint), the impact of tidal power generation technologies ranges between 15 and 37 gCO2-eq/kWhe, with a median value of 23.8 gCO2-eq/kWhe. This is in line with the impact of other renewables like wind and solar power, and significantly better than fossil-based technologies. The Tethys database provides access to scientific literature and general information on the potential environmental effects of tidal energy.
Tidal turbines
The main environmental concern with tidal energy is associated with blade strike and entanglement of marine organisms as high-speed water increases the risk of organisms being pushed near or through these devices. As with all offshore renewable energies, there is also a concern about how the creation of electromagnetic fields and acoustic outputs may affect marine organisms. Because these devices are in the water, the acoustic output can be greater than those created with offshore wind energy. Depending on the frequency and amplitude of sound generated by the tidal energy devices, this acoustic output can have varying effects on marine mammals (particularly those who echolocate to communicate and navigate in the marine environment, such as dolphins and whales). Tidal energy removal can also cause environmental concerns such as degrading far-field water quality and disrupting sediment processes. Depending on the size of the project, these effects can range from small traces of sediment building up near the tidal device to severely affecting nearshore ecosystems and processes.
Tidal barrage
Installing a barrage may change the shoreline within the bay or estuary, affecting a large ecosystem that depends on tidal flats. Inhibiting the flow of water in and out of the bay, there may also be less flushing of the bay or estuary, causing additional turbidity (suspended solids) and less saltwater, which may result in the death of fish that act as a vital food source to birds and mammals. Migrating fish may also be unable to access breeding streams, and may attempt to pass through the turbines. The same acoustic concerns apply to tidal barrages. Decreasing shipping accessibility can become a socio-economic issue, though locks can be added to allow slow passage. However, the barrage may improve the local economy by increasing land access as a bridge. Calmer waters may also allow better recreation in the bay or estuary. In August 2004, a humpback whale swam through the open sluice gate of the Annapolis Royal Generating Station at slack tide, ending up trapped for several days before eventually finding its way out to the Annapolis Basin.
Tidal lagoon
Environmentally, the main concerns are blade strike on fish attempting to enter the lagoon, the acoustic output from turbines, and changes in sedimentation processes. However, all these effects are localized and do not affect the entire estuary or bay.
Corrosion
Saltwater causes corrosion in metal parts. It can be difficult to maintain tidal stream generators due to their size and depth in the water. The use of corrosion-resistant materials such as stainless steels, high-nickel alloys, copper-nickel alloys, nickel-copper alloys and titanium can greatly reduce, or eliminate corrosion damage. Composite materials could also be used, as composites do not corrode and could provide lightweight, durable structures for tidal power. Composite materials are being evaluated for tidal power.
Mechanical fluids, such as lubricants, can leak out, which may be harmful to the marine life nearby. Proper maintenance can minimize the number of harmful chemicals that may enter the environment.
Fouling
The biological events that happen when placing any structure in an area of high tidal currents and high biological productivity in the ocean will ensure that the structure becomes an ideal substrate for the growth of marine organisms.
Cost
Tidal energy has a high initial cost, which may be one of the reasons why it is not a popular source of renewable energy, although research has shown that the public is willing to pay for and support research and development of tidal energy devices. The methods of generating electricity from tidal energy are relatively new technology. Tidal energy is however still very early in the research process and it may be possible to reduce costs in future. The cost-effectiveness varies according to the site of the tidal generators. One indication of cost-effectiveness is the Gibrat ratio, which is the length of the barrage in metres divided by the annual energy production in kilowatt hours.
As tidal energy is reliable, it can reasonably be predicted how long it will take to pay off the high up-front cost of these generators. Due to the success of a greatly simplified design, the orthogonal turbine offers considerable cost savings. As a result, the production period of each generating unit is reduced, lower metal consumption is needed and technical efficiency is greater.
A possible risk is rising sea levels due to climate change, which may alter the characteristics of the local tides reducing future power generation.
Structural health monitoring
The high load factors resulting from the fact that water is around 800 times denser than air, and the predictable and reliable nature of tides compared with the wind, make tidal energy particularly attractive for electric power generation. Condition monitoring is the key for exploiting it cost-efficiently.
See also
- Hydroelectricity
- Hydropower
- List of tidal power stations
- Run-of-the-river hydroelectricity
- Structural health monitoring
- Tidal barrage
- Tidal farm
- Tidal power in Canada
- Tidal power in New Zealand
- Tidal power in Scotland
- Tidal stream generator
- Marine energy
- Marine current power
- Wave power
- Ocean thermal energy conversion
- Osmotic power
- World energy consumption
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Further reading
- Baker, A. C. 1991, Tidal power, Peter Peregrinus Ltd., London.
- Baker, G. C., Wilson E. M., Miller, H., Gibson, R. A. & Ball, M., 1980. "The Annapolis tidal power pilot project", in Waterpower '79 Proceedings, ed. Anon, U.S. Government Printing Office, Washington, pp 550–559.
- Hammons, T. J. 1993, "Tidal power", Proceedings of the IEEE, , v81, n3, pp 419–433. Available from: IEEE/IEEE Xplore. .
- Lecomber, R. 1979, "The evaluation of tidal power projects", in Tidal Power and Estuary Management, eds. Severn, R. T., Dineley, D. L. & Hawker, L. E., Henry Ling Ltd., Dorchester, pp 31–39.
- Jubilo, A., 2019, "Renewable Tidal Energy Potential: Basis for Technology Development in Eastern Mindanao", 80th PIChE National Convention; Crowne Plaza Galleria, Ortigas Center, Quezon City, Philippines.
- Could the UK's tides help wean us off fossil fuels?. BBC News. Published 22 October 2023.
- Enhancing Electrical Supply by Pumped Storage in Tidal Lagoons. David J.C. MacKay, Cavendish Laboratory, University of Cambridge, UK. Published 3 May 2007.
- Turning the Tide: Tidal Power in the UK – Report by Sustainable Development Commission. Published October 2007.
- 2007 – Report by Global Energy Survey. Published 2007.
External links
- Portal and Repository for Information on Marine Renewable Energy A network of databases providing broad access to marine energy information.
- Marine Energy Basics: Current Energy Basic information about current energy.
- Marine Energy Projects Database A database that provides up-to-date information on marine energy deployments in the U.S. and around the world.
- Tethys Database A database of information on potential environmental effects of marine energy and offshore wind energy development.
- Tethys Engineering Database A database of information on technical design and engineering of marine energy devices.
- Marine and Hydrokinetic Data Repository A database for all data collected by marine energy research and development projects funded by the U.S. Department of Energy.
- Severn Estuary Partnership: Tidal Power Resource Page
- University of Strathclyde ESRU—Detailed analysis of marine energy resource, current energy capture technology appraisal and environmental impact outline
- Coastal Research – Foreland Point Tidal Turbine and warnings on proposed Severn Barrage
- European Marine Energy Centre – Listing of Tidal Energy Developers -retrieved 1 July 2011 (link updated 31 January 2014)
- Resources on Tidal Energy
- Structural Health Monitoring of composite tidal energy converters Archived 2014-03-25 at the Wayback Machine
- Tidal Power: A New Source of Energy (1959)
- Tidal projects funded by the Australian Renewable Energy Agency
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