![Sihwa Lake Tidal Power Station 01](https://upload.wikimedia.org/wikipedia/commons/9/95/Sihwa_Lake_Tidal_Power_Station_01.png)
Tidal power or tidal energy is harnessed by converting energy from
tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravity, gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another.
Tide t ...
s into useful forms of power, mainly electricity using various methods.
Although not yet widely used, tidal energy has the potential for future
electricity generation
Electricity generation is the process of generating electric power from sources of primary energy. For electric utility, utilities in the electric power industry, it is the stage prior to its Electricity delivery, delivery (Electric power transmi ...
. Tides are more predictable than
the wind and
the sun. Among sources of
renewable energy
Renewable energy is energy that is collected from renewable resources that are naturally replenished on a human timescale. It includes sources such as sunlight, wind, the movement of water, and geothermal heat. Although most 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
Dynamic tidal power or DTP is an untried but promising technology for tidal power generation. It would involve creating a long dam-like structure perpendicular to the coast, with the option for a coast-parallel barrier at the far end, forming a ...
,
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 cost
Environmental economics is a sub-field of economics concerned with environmental issues. It has become a widely studied subject due to growing environmental concerns in the twenty-first century. Environmental economics "undertakes theoretical or ...
s may be brought down to competitive levels.
Historically,
tide mill
A tide mill is a water mill driven by tidal rise and fall. A dam with a sluice is created across a suitable tidal inlet, or a section of river estuary is made into a reservoir. As the tide comes in, it enters the mill pond through a one-way gate ...
s have been used both in Europe and on the Atlantic coast of North America. The 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
In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire a ...
, or even from
Roman times
In modern historiography, ancient Rome refers to Roman civilisation from the founding of the city of Rome in the 8th century BC to the collapse of the Western Roman Empire in the 5th century AD. It encompasses the Roman Kingdom (753–509 BC ...
. The process of using falling water and spinning
turbine
A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating e ...
s 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
The Rance Tidal Power Station is a tidal power station located on the estuary of the Rance River in Brittany, France.
Opened in 1966 as the world's first tidal power station, it is currently operated by Électricité de France and was for 45 ye ...
, which became operational in 1966. It was the largest tidal power station in terms of output until
Sihwa Lake Tidal Power Station
Sihwa Lake Tidal Power Station is the world's largest tidal power installation, with a total power output capacity of 254 MW. When completed in 2011, it surpassed the 240 MW Rance Tidal Power Station which was the world's largest for 45 years. It ...
opened in South Korea in August 2011. The Sihwa station uses sea wall defense barriers complete with 10 turbines generating 254 MW.
Principle
![Tide type](https://upload.wikimedia.org/wikipedia/commons/d/da/Tide_type.svg)
Tidal energy is taken from the Earth's oceanic
tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravity, gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another.
Tide t ...
s.
Tidal force
The tidal force is a gravitational effect that stretches a body along the line towards the center of mass of another body due to a gradient (difference in strength) in gravitational field from the other body; it is responsible for diverse phenomen ...
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. 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
A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels m ...
,
conventional hydroelectric,
wind
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...
,
biofuel
Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels, such as oil. According to the United States Energy Information Administration (E ...
,
wave
In physics, mathematics, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Waves can be periodic, in which case those quantities oscillate repeatedly about an equilibrium (res ...
and
solar energy
Solar energy is radiant light and heat from the Sun that is harnessed using a range of technologies such as solar power to generate electricity, solar thermal energy (including solar water heating), and solar architecture. It is an essenti ...
.
Nuclear energy
Nuclear energy may refer to:
*Nuclear power, the use of sustained nuclear fission or nuclear fusion to generate heat and electricity
* Nuclear binding energy, the energy needed to fuse or split a nucleus of an atom
*Nuclear potential energy
...
makes use of Earth's mineral deposits of
fissionable
In nuclear engineering, fissile material is material capable of sustaining a nuclear fission chain reaction. By definition, fissile material can sustain a chain reaction with neutrons of thermal energy. The predominant neutron energy may be typi ...
elements, while
geothermal power
Geothermal power is electrical power generated from geothermal energy. Technologies in use include dry steam power stations, flash steam power stations and binary cycle power stations. Geothermal electricity generation is currently used in 2 ...
utilizes the Earth's
internal heat
{{Unreferenced, date=February 2012
Internal heat is the heat source from the interior of celestial objects, such as stars, brown dwarfs, planets, moons, dwarf planets, and (in the early history of the Solar System) even asteroids such as Vesta, r ...
, which comes from a combination of residual heat from
planetary accretion
In astrophysics, accretion is the accumulation of particles into a massive object by gravitationally attracting more matter, typically gaseous matter, in an accretion disk. Most astronomical objects, such as galaxies, stars, and planets, are forme ...
(about 20%) and heat produced through
radioactive decay
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...
(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
Renewable energy is energy that is collected from renewable resources that are naturally replenished on a human timescale. It includes sources such as sunlight, wind, the movement of water, and geothermal heat. Although most 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
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water.
Viscosity quantifies the inter ...
dissipation at the
seabed
The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'.
The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...
and in
turbulence
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between ...
. 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
![SeaGen installed](https://upload.wikimedia.org/wikipedia/commons/7/77/SeaGen_installed.jpg)
Tidal power can be classified into four generating methods:
Tidal stream generator
Tidal stream generators make use of the
kinetic energy
In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...
of moving water to power turbines, in a similar way to
wind turbine
A wind turbine is a device that converts the kinetic energy of wind into electrical energy. Hundreds of thousands of large turbines, in installations known as wind farms, now generate over 650 gigawatts of power, with 60 GW added each year. ...
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.
Tidal barrage
Tidal barrages use
potential energy
In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors.
Common types of potential energy include the gravitational potentia ...
in the difference in height (or
hydraulic head
Hydraulic head or piezometric head is a specific measurement of liquid pressure above a vertical datum., 410 pages. See pp. 43–44., 650 pages. See p. 22.
It is usually measured as a liquid surface elevation, expressed in units of length, ...
) 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
In Outline of physical science, physical sciences, mechanical energy is the sum of potential energy and kinetic energy. The principle of conservation of mechanical energy states that if an isolated system is subject only to conservative forces, t ...
as the water is released through large turbines that create electrical power through the use of generators. Barrages are essentially
dam
A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, a ...
s across the full width of a tidal estuary.
Dynamic tidal power
![DTP T dam top-down view](https://upload.wikimedia.org/wikipedia/commons/8/84/DTP_T_dam_top-down_view.jpg)
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
phase difference
In physics and mathematics, the phase of a periodic function F of some real variable t (such as time) is an angle-like quantity representing the fraction of the cycle covered up to t. It is denoted \phi(t) and expressed in such a scale that it v ...
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. Induced tides (TDP) could extend the geographic viability of a new hydro-atmospheric concept 'LPD' (lunar pulse drum) discovered by a Devon innovator in which a tidal 'water piston' pushes or pulls a metered jet of air to a rotary air-actuator & generator. The principle was demonstrated at London Bridge June 2019. Plans for a 30 m, 62.5kwh 'pilot' installation on a (Local Authority) tidal estuary shoreline in the Bristol Channel are underway.
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
Tidal Lagoon Swansea Bay was a proposed tidal lagoon power plant that was to be constructed in Swansea Bay off the south coast of Wales, United Kingdom. Development consent was granted by the UK government in June 2015, and in June 2018 the Wels ...
in Wales, United Kingdom would have been the first tidal power station of this type once built.
US and Canadian studies in the 20th century
The first study of large scale tidal power plants was by the US
Federal Power Commission
The Federal Power Commission (FPC) was an independent commission of the United States government, originally organized on June 23, 1930, with five members nominated by the president and confirmed by the Senate. The FPC was originally created in 1 ...
in 1924. If built, power plants would have been located in the northern border area of the US state of
Maine
Maine () is a state in the New England and Northeastern regions of the United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Canadian provinces of New Brunswick and Quebec to the northeast and north ...
and the southeastern border area of the Canadian province of New Brunswick, with various dams, powerhouses, and ship locks enclosing the
Bay of Fundy
The Bay of Fundy (french: Baie de Fundy) is a bay between the Canadian provinces of New Brunswick and Nova Scotia, with a small portion touching the U.S. state of Maine. It is an arm of the Gulf of Maine. Its extremely high tidal range is the hi ...
and
Passamaquoddy Bay
Passamaquoddy Bay (french: Baie de Passamaquoddy) is an inlet of the Bay of Fundy, between the U.S. state of Maine and the Canadian province of New Brunswick, at the mouth of the St. Croix River. Most of the bay lies within Canada, with its w ...
(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
Nova Scotia Light and Power Company, Limited (NSLP) was an electric and gas utility company with its head office in Halifax, Nova Scotia, Halifax, Canada. The company still exists as a Shell corporation, shell but is no longer active; however, for ...
of
Halifax commissioned a pair of studies into commercial tidal power development feasibility on the
Nova Scotia
Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland".
Most of the population are native Eng ...
side of the Bay of Fundy. The two studies, by
Stone & Webster
Stone & Webster was an American engineering services company based in Stoughton, Massachusetts. It was founded as an electrical testing lab and consulting firm by electrical engineers Charles A. Stone and Edwin S. Webster in 1889. In the early ...
of
Boston
Boston (), officially the City of Boston, is the state capital and most populous city of the Commonwealth of Massachusetts, as well as the cultural and financial center of the New England region of the United States. It is the 24th- mo ...
and by
Montreal Engineering Company
Montreal Engineering Company, later Monenco was a Canadian engineering services company operating in the energy and infrastructure utilities area.
The company became an important player in North and Latin American, and elsewhere, such as the fea ...
of
Montreal
Montreal ( ; officially Montréal, ) is the List of the largest municipalities in Canada by population, second-most populous city in Canada and List of towns in Quebec, most populous city in the Provinces and territories of Canada, Canadian ...
, 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 highway system along the top of the dams was envisioned as well of
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
The Snohomish County Public Utility District is a public utility agency providing power to over 367,000 customers in Snohomish County and on Camano Island, Washington. It provides water service to about 23,000 customers in the northeast section ...
, 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
A gentlemen's agreement, or gentleman's agreement, is an informal and legally non-binding agreement between two or more parties. It is typically oral, but it may be written or simply understood as part of an unspoken agreement by convention or th ...
. 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
Électricité de France S.A. (literally ''Electricity of France''), commonly known as EDF, is a French multinational electric utility company, largely owned by the French state. Headquartered in Paris, with €71.2 billion in revenues in 2 ...
opened the
Rance Tidal Power Station
The Rance Tidal Power Station is a tidal power station located on the estuary of the Rance River in Brittany, France.
Opened in 1966 as the world's first tidal power station, it is currently operated by Électricité de France and was for 45 ye ...
, located on the
estuary
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...
of the
Rance River
The Rance (; br, Renk) is a river of northwestern France. It is long. It flows into the English Channel between Dinard and Saint-Malo.
Before reaching the Channel, its waters are barred by a 750 metre long dam forming the Rance tidal power plan ...
in
Brittany
Brittany (; french: link=no, Bretagne ; br, Breizh, or ; Gallo language, Gallo: ''Bertaèyn'' ) is a peninsula, Historical region, historical country and cultural area in the west of modern France, covering the western part of what was known ...
. 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
A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful Work (physics), work. The work produced by a turbine can be used ...
reach peak output at 240
megawatts
The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Watt ...
(MW) and average 57 MW, a
capacity factor
The net capacity factor is the unitless ratio of actual electrical energy output over a given period of time to the theoretical maximum electrical energy output over that period. The theoretical maximum energy output of a given installation is de ...
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
The European Marine Energy Centre (EMEC) Ltd is a UKAS accredited test and research center focusing on wave and tidal power development based in the Orkney Islands, UK. The centre provides developers with the opportunity to test full-scale grid ...
(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
Muckle Green Holm is an uninhabited island in the North Isles of the Orkney archipelago in Scotland. It is roughly in extent and rises to above sea level, the summit having a triangulation pillar.
Name
'Muckle' is Scots for 'big' or 'larg ...
, off the island of
Eday
Eday (, sco, Aidee) is one of the islands of Orkney, which are located to the north of the Scottish mainland. One of the North Isles, Eday is about from the Orkney Mainland. With an area of , it is the ninth-largest island of the archipelago. ...
, 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 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
![VerdantPower 22Oct2020 RooseveltIsland](https://upload.wikimedia.org/wikipedia/commons/1/1c/VerdantPower_22Oct2020_RooseveltIsland.jpg)
* The
Rance tidal power plant
The Rance Tidal Power Station is a tidal power station located on the estuary of the Rance River in Brittany, France.
Opened in 1966 as the world's first tidal power station, it is currently operated by Électricité de France and was for 45 ye ...
built over a period of 6 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
The Jiangxia Tidal Power Station (江厦潮汐电站) is the fourth largest tidal power station in the world, located in Wuyantou, Wenling City, Zhejiang Province, China. Although the proposed design for the facility was 3,000 kW, the cur ...
, south of
Hangzhou
Hangzhou ( or , ; , , Standard Mandarin pronunciation: ), also romanized as Hangchow, is the capital and most populous city of Zhejiang, China. It is located in the northwestern part of the province, sitting at the head of Hangzhou Bay, whi ...
in
China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
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 Yalu River, known by Koreans as the Amrok River or Amnok River, is a river on the border between North Korea and China. Together with the Tumen River to its east, and a small portion of Paektu Mountain, the Yalu forms the border between ...
.
* The first in-stream tidal current generator in North America (
Race Rocks Tidal Power Demonstration Project
The Race Rocks Tidal Power Demonstration Project (official name: Pearson College - EnCana - Clean Current Tidal Power Demonstration Project at Race Rocks) was a joint project of the Lester B. Pearson College, EnCana Corporation and Clean Current Po ...
) was installed at
Race Rocks
Race Rocks Ecological Reserve is a BC Parks ecological reserve off the southern tip of Vancouver Island in the Strait of Juan de Fuca in Metchosin, British Columbia, Canada.
Description
Located at a narrow part of the Strait, the area covers o ...
on southern
Vancouver Island
Vancouver Island is an island in the northeastern Pacific Ocean and part of the Canadian Provinces and territories of Canada, province of British Columbia. The island is in length, in width at its widest point, and in total area, while are o ...
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
Kislaya Guba (meaning ''sour bay'' in Russian) is a fjord on the Kola Peninsula near Murmansk, Russia. The fjord is connected to the Barents Sea to the north and is primarily known as the site of the experimental tidal power project, Kislaya Guba T ...
on the
Barents Sea
The Barents Sea ( , also ; no, Barentshavet, ; russian: Баренцево море, Barentsevo More) is a marginal sea of the Arctic Ocean, located off the northern coasts of Norway and Russia and divided between Norwegian and Russian territo ...
. 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
SeaGen was the world's first large scale commercial tidal stream generator.
It was four times more powerful than any other tidal stream generator in the world at the time of installation.
It was successfully decommissioned by SIMEC Atlant ...
system became operational in late 2008 on
Strangford Lough
Strangford Lough (from Old Norse ''Strangr Fjörðr'', meaning "strong sea-inlet"[PlaceNames N ...](_blank)
in
Northern Ireland
Northern Ireland ( ga, Tuaisceart Éireann ; sco, label= Ulster-Scots, Norlin Airlann) is a part of the United Kingdom, situated in the north-east of the island of Ireland, that is variously described as a country, province or region. Nort ...
.
* The contract for an 812 MW tidal barrage near
Ganghwa Island
Ganghwa Island (Hangul ; Hanja ), also known by its native name Ganghwado, is a South Korean island in the estuary of the Han River. It is in the Yellow Sea, off Korea's west coast. The island is separated from Gimpo (on the South Korean mainla ...
(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 built around islands west of Incheon was proposed by the South Korean government in 2009. Project halted since 2012 due to environmental concerns.
* The Scottish Government has approved plans for a 10 MW array of tidal stream generators near
Islay
Islay ( ; gd, Ìle, sco, Ila) is the southernmost island of the Inner Hebrides of Scotland. Known as "The Queen of the Hebrides", it lies in Argyll just south west of Jura, Scotland, Jura and around north of the Northern Irish coast. The isl ...
,
Scotland
Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...
, 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 but as of 2021 was not operational.
* The Indian state of
Gujarat
Gujarat (, ) is a state along the western coast of India. Its coastline of about is the longest in the country, most of which lies on the Kathiawar peninsula. Gujarat is the fifth-largest Indian state by area, covering some ; and the ninth ...
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
Cobscook Bay is located in Washington County in the state of Maine. It opens into Passamaquoddy Bay, within the Bay of Fundy. Cobscook Bay is immediately south of the island city of Eastport, the main island of which (Moose Island) straddles the ...
, 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. .
* A turbine project is being installed in
Ramsey Sound in 2014.
* The largest tidal energy project entitled
MeyGen
MeyGen (full name MeyGen tidal energy project) will be the world's largest tidal power, tidal energy plant, which is currently in construction. The first phase of the project uses four 1.5MW turbines with rotor diameter turbines submerged on the ...
(398 MW) is currently in construction in the
Pentland Firth
The Pentland Firth ( gd, An Caol Arcach, meaning the Orcadian Strait) is a strait which separates the Orkney Islands from Caithness in the north of Scotland. Despite the name, it is not a firth.
Etymology
The name is presumed to be a corruption ...
in northern Scotland
* Construction of a 320 MW tidal lagoon power plant outside the city of
Swansea
Swansea (; cy, Abertawe ) is a coastal city and the second-largest city of Wales. It forms a principal area, officially known as the City and County of Swansea ( cy, links=no, Dinas a Sir Abertawe).
The city is the twenty-fifth largest in ...
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.
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 animal
Marine life, sea life, or ocean life is the plants, animals and other organisms that live in the salt water of seas or oceans, or the brackish water of coastal estuaries. At a fundamental level, marine life affects the nature of the planet. M ...
s as possible are affected by it. The
Tethys database provides access to scientific literature and general information on the potential environmental effects of tidal energy. In terms of global warming potential (i.e. carbon footprint), the impact of tidal power generation technologies ranges between 15 and 37 gCO
2-eq/kWhe, with a median value of 23.8 gCO
2-eq/kWhe. This is in line with the impact of other renewables like wind and solar power, and significantly better than fossil-based technologies.
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 field
An electromagnetic field (also EM field or EMF) is a classical (i.e. non-quantum) field produced by (stationary or moving) electric charges. It is the field described by classical electrodynamics (a classical field theory) and is the classical c ...
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
offshore wind energy
Offshore wind power or offshore wind energy is the generation of electricity through wind farms in bodies of water, usually at sea. There are higher wind speeds offshore than on land, so offshore farms generate more electricity per amount of c ...
. Depending on the
frequency
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
and
amplitude
The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of amplit ...
of
sound
In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid.
In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...
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
dolphin
A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the ...
s and
whale
Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...
s). Tidal energy removal can also cause environmental concerns such as degrading far-field
water quality
Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through tr ...
and disrupting
sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...
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
ecosystem
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
s and processes.
Tidal barrage
Installing a barrage may change the shoreline within the
bay
A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a Gulf (geography), gulf, sea, sound (geography), sound, or bight (geogra ...
or
estuary
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...
, affecting a large ecosystem that depends on
tidal flat
Mudflats or mud flats, also known as tidal flats or, in Ireland, slob or slobs, are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers. A global analysis published in 2019 suggested that tidal fl ...
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
turbidity
Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality.
Fluids can ...
(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
The humpback whale (''Megaptera novaeangliae'') is a species of baleen whale. It is a rorqual (a member of the family Balaenopteridae) and is the only species in the genus ''Megaptera''. Adults range in length from and weigh up to . The hump ...
swam through the open
sluice gate
Sluice ( ) is a word for a channel controlled at its head by a movable gate which is called a sluice gate. A sluice gate is traditionally a wood or metal barrier sliding in grooves that are set in the sides of the waterway and can be considered ...
of the
Annapolis Royal Generating Station
The Annapolis Royal Generating Station was a tidal power generating station in the Bay of Fundy in Nova Scotia, Canada. When operational, it was the only tidal generating station in North America and was one of the few in the world. Located ups ...
at slack tide, ending up trapped for several days before eventually finding its way out to the
Annapolis Basin
The Annapolis Basin is a sub-basin of the Bay of Fundy, located on the bay's southeastern shores, along the northwestern shore of Nova Scotia and at the western end of the Annapolis Valley.
The basin takes its name from the Annapolis River, which ...
.
Tidal lagoon
Environmentally, the main concerns are blade strike on fish attempting to enter the
lagoon
A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') a ...
, 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.
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. In th
references of the Tidal Current Projecta
Race Rocksin British Columbia, this is documented.
Also se
and
Several structural materials and coatings were tested by th
to assist Clean Current in reducing fouling on the turbine and other underwater infrastructure.
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
Renewable energy is energy that is collected from renewable resources that are naturally replenished on a human timescale. It includes sources such as sunlight, wind, the movement of water, and geothermal heat. Although most 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 hour
A kilowatt-hour (unit symbol: kW⋅h or kW h; commonly written as kWh) is a unit of energy: one kilowatt of power for one hour. In terms of SI derived units with special names, it equals 3.6 megajoules (MJ). Kilowatt-hours are a common bil ...
s.
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.
Structural health monitoring
The high load factors resulting from the fact that water is 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
*
List of tidal power stations
This article lists most power stations that run on tidal power. Since tidal stream generators are an immature technology, no technology has yet emerged as the clear standard. A large variety of designs are being experimented with, with some very ...
*
Marine energy
Marine energy or marine power (also sometimes referred to as ocean energy, ocean power, or marine and hydrokinetic energy) refers to the energy carried by ocean waves, tides, salinity, and ocean thermal energy, ocean temperature differences. The ...
*
Penzhin Tidal Power Plant Project
The Penzhin Tidal Power Plant Project is a set of proposals for construction of a tidal power plant in the Penzhin Bay, which is an upper right arm of Shelikhov Bay in the north-east corner of the Sea of Okhotsk. Because Penzhin Bay has one of the ...
*
Structural health monitoring
Structural health monitoring (SHM) involves the observation and analysis of a system over time using periodically sampled response measurements to monitor changes to the material and geometric properties of engineering structures such as bridges an ...
*
Tidal power in Canada
*
Tidal power in New Zealand
*
Tidal power in Scotland
*
World energy consumption
World energy supply and consumption is global production and preparation of fuel, generation of electricity, energy transport, and energy consumption. It is a basic part of economic activity. It includes heat, but not energy from food.
This art ...
References
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'',
nline v81, n3, pp 419–433. Available from: IEEE/IEEE Xplore.
uly 26, 2004
* 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.
External links
Enhanced tidal lagoon with pumped storage and constant outputas proposed by David J.C. MacKay, Cavendish Laboratory, University of Cambridge, UK.
Marine and Hydrokinetic Technology DatabaseThe U.S. Department of Energy's Marine and Hydrokinetic Technology Database provides up-to-date information on marine and hydrokinetic renewable energy, both in the U.S. and around the world.
Tethys DatabaseA database of information on potential environmental effects of marine and hydrokinetic and offshore wind energy development.
Location of Potential Tidal Stream Power sites in the UKDetailed analysis of marine energy resource, current energy capture technology appraisal and environmental impact outline
*
ttps://web.archive.org/web/20090904021113/http://www.sd-commission.org.uk/publications.php?id=607 Sustainable Development Commission– Report looking at 'Tidal Power in the UK', including proposals for a Severn barrage
World Energy Council– Report on Tidal Energy
European Marine Energy Centre– Listing of Tidal Energy Developers -retrieved 1 July 2011 (link updated 31 January 2014)
Resources on Tidal EnergyStructural Health Monitoring of composite tidal energy convertersTidal Power: A New Source of Energy (1959)Tidal projects funded by the Australian Renewable Energy Agency
{{Authority control
Bright green environmentalism
Coastal construction
Tides
Renewable energy