Tidal power
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Tidal power, is a form of hydropower that converts the energy of tides into electricity or other useful forms of power. The first large-scale tidal power plant (the Rance Tidal Power Station) started operation in 1966.
Although not yet widely used, tidal power has potential for future electricity generation. Tides are more predictable than wind energy and solar power. Among sources of renewable energy, tidal power 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, crossflow 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. The earliest occurrences date from the Middle Ages, or even from Roman times.[1][2]
Generation of tidal energy
Tidal power is the only form of energy which derives directly from the relative motions of the Earth–Moon system, and to a lesser extent from the Earth–Sun system. Tidal forces produced by the Moon and Sun, in combination with Earth's rotation, are responsible for the generation of the tides. Other sources of energy originate directly or indirectly from the Sun, including fossil fuels, conventional hydroelectric, wind, biofuels, wave power and solar. Nuclear energy makes use of Earth's mineral deposits of fissile elements, while geothermal power uses 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%).[3]
Tidal energy is extracted from the relative motion of large bodies of water. Periodic changes of water levels, and associated tidal currents, are due to the gravitational attraction of the Sun and Moon. Magnitude of the tide at a location is the result of the changing positions of the Moon and Sun relative to the Earth, the effects of Earth rotation, and the local geography of the sea floor and coastlines.
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 classified as a renewable energy resource.
A tidal generator uses this phenomenon to generate electricity. Greater tidal variation or tidal current velocities can dramatically increase the potential for tidal electricity generation.
The movement of the tides causes a continual loss of mechanical energy in the Earth–Moon system due to pumping of water through the 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 formation. During the last 620 million years the period of rotation has increased from 21.9 hours to the 24 hours[4] we see now; in this period the Earth has lost 17% of its rotational energy. While tidal power may take additional energy from the system, increasing the rate of slowdown, the effect would be noticeable over millions of years only, thus being negligible.
Generating methods
Template:Fix bunching Tidal power can be classified into three generating methods:
Tidal stream generator
Tidal stream generators (or TSGs) make use of the kinetic energy of moving water to power turbines, in a similar way to wind turbines that use moving air. This method is gaining in popularity because of the lower cost and lower ecological impact compared to tidal barrages.
Tidal barrage
Tidal barrages make use of the potential energy in the difference in height (or head) between high and low tides. Barrages are essentially dams across the full width of a tidal estuary, and suffer from very high civil infrastructure costs, a worldwide shortage of viable sites and environmental issues.
Dynamic tidal power
Dynamic tidal power (or DTP) is a theoretical generation 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 by the dam, leading to a significant water level differential (at least 2–3 meters) in shallow coastal seas featuring strong coast-parallel oscillating tidal currents such as found in the UK, China and Korea. Each dam would generate power at a scale of 6 - 15 GW.
Current and future tidal power schemes
- The first tidal power station was the Rance tidal power plant built over a period of 6 years from 1960 to 1966 at La Rance, France.[6] It has 240 MW installed capacity.
- The first tidal power site in North America is the Annapolis Royal Generating Station, Annapolis Royal, Nova Scotia, which opened in 1984 on an inlet of the Bay of Fundy.[7] It has 20 MW installed capacity.
- 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.[8]
- 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.[9][10] The next phase in the development of this tidal current generator will be in Nova Scotia.[11]
- 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 1.2MW 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.[12]
- A 1.2 MW SeaGen system became operational in late 2008 on Strangford Lough in Northern Ireland.[13]
- 254 MW Sihwa Lake Tidal Power Plant in South Korea is under construction and planned to be completed by the end of 2010.[14]
- The contract for an 812 MW tidal barrage near Ganghwa Island north-west of Incheon has been signed by Daewoo. Completion is planned for 2015.[14]
- A 1,320 MW barrage built around islands west of Incheon is proposed by the Korean government, with projected construction start in 2017.[15]
- Other South Korean projects include barrages planned for Garorim Bay, Ansanman, and Swaseongho, and tidal generation associated with the Saemangeum reclamation project. The barrages are all in the multiple-hundred megawatts range.[16]
- The Indian state of Gujarat is planning to host South Asia's first commercial-scale tidal power station. The company Atlantis Resources is to install a 50MW tidal farm in the Gulf of Kutch on India's west coast, with construction starting early in 2012.[17]
- Estimates for new tidal barrages in England give the potential generation at 5.6GW mean power.[18]
| Country | Place | Mean tidal range (m) | Area of basin (km²) | Maximum capacity (MW) | Ref |
|---|---|---|---|---|---|
 United Kingdom |
River Severn | 7.8 | 450 | 8,640 | |
 Russia |
Penzhinskaya Bay | 6.0 | 20,500 | 87,000 | [19][20][21] |
See also
Notes
- 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, [Online], v81, n3, pp 419–433. Available from: IEEE/IEEE Xplore. [July 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.
References
- ^ Spain, Rob: "A possible Roman Tide Mill", Paper submitted to the Kent Archaeological Society
- ^ Minchinton, W. E. (1979). "Early Tide Mills: Some Problems". Technology and Culture. 20 (4). Society for the History of Technology: 777–786. doi:10.2307/3103639.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ Turcotte, D. L. (2002). "4". Geodynamics (2 ed.). Cambridge, England, UK: Cambridge University Press. pp. 136–137. ISBN 978-0-521-66624-4.
{{cite book}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ George E. Williams (2000). "Geological constraints on the Precambrian history of Earth's rotation and the Moon's orbit". Reviews of Geophysics. 38: 37–60. doi:10.1029/1999RG900016.
- ^ Douglas, C. A.; Harrison, G. P.; Chick, J. P. (2008). "Life cycle assessment of the Seagen marine current turbine". Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment. 222 (1): 1–12. doi:10.1243/14750902JEME94.
- ^ L'Usine marémotrice de la Rance
- ^ Nova Scotia Power - Environment - Green Power- Tidal
- ^ China Endorses 300 MW Ocean Energy Project
- ^ Race Rocks Demonstration Project
- ^ Tidal Energy, Ocean Energy
- ^ Information for media inquiries
- ^ Korea's first tidal power plant built in Uldolmok, Jindo
- ^ "Tidal energy system on full power". BBC News. December 18, 2008. Retrieved March 26, 2010.
- ^ a b Hunt for African Projects
- ^ $ 3-B tidal power plant proposed near Korean islands
- ^ Sihwa Tidal Power Plant Project
- ^ [1]
- ^ Smith, Andrew (2009-08-20). "Tidal Barrage power generation potential in England". Claverton Energy Group. Retrieved 2010-07-21.
- ^ http://www.elektropages.ru/article/4_2006_ELEKTRO.html
- ^ Russian power plants soon to utilize tidal energy :: Russia-InfoCentre
- ^ http://www.severnestuary.net/sep/pdfs/managingtidalchangeprojectreport-phase1final.pdf
External links
- Enhanced tidal lagoon with pumped storage and constant output as proposed by David J.C. MacKay, Cavendish Laboratory, University of Cambridge, UK.
- Marine and Hydrokinetic Technology Database The 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.
- Severn Estuary Partnership: Tidal Power Resource Page
- Location of Potential Tidal Stream Power sites in the UK
- 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
- Sustainable Development Commission - Report looking at 'Tidal Power in the UK', including proposals for a Severn barrage
- World Energy Council - Report on Tidal Energy
