Tidal Power

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  Handbook of Hydropower and Tidal Power

  • (Author)
  • 2014(Publication Date)
  • Academic Studio

    (Publisher)

  ____________________ WORLD TECHNOLOGIES ____________________ Chapter- 2 Tidal Power Tidal Power , also called tidal energy , 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. ____________________ WORLD TECHNOLOGIES ____________________ Generation of tidal energy Variation of tides over a day 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.

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  Geothermal Power & Hydropower

  • (Author)
  • 2014(Publication Date)
  • Academic Studio

    (Publisher)

  ____________________ WORLD TECHNOLOGIES ____________________ Chapter- 7 Tidal Power Tidal Power , also called tidal energy , 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. ____________________ WORLD TECHNOLOGIES ____________________ Generation of tidal energy Variation of tides over a day 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.

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  Power Engineering

  Advances and Challenges Part B: Electrical Power

  • Viorel Badescu, George Cristian Lazaroiu, Linda Barelli(Authors)
  • 2018(Publication Date)
  • CRC Press

    (Publisher)

  HAPTER 4 Tidal and Wave Power Systems

  Luca Castellini, Michele Martini and Giacomo Alessandri

  Umbragroup spa, Via Valter Baldaccini 1, 06034 Foligno (PG), Italy. Emails: [email protected] ; [email protected] ;[email protected]

  1.    Introduction

  Oceans, seas and rivers cover about 70% of the Earth’s surface. By definition, ocean energy includes resource associated to kinetic, potential, thermal and chemical energy of the seawater. Most often, such resources are used to generate electricity but there are other applications such as production of desalinated water, cooling systems and production of hydrogen through electrolysis. Other forms of energy, such as offshore wind and solar energy from marine structures, are not considered part of ocean energy as they do not belong intrinsically to seawater.

  Two forms of ocean energy are especially promising in terms of energy potential: -  Wave energy -  Tidal energy

  Waves are a renewable energy source, as they derive from solar energy. Indeed, sea waves are generated by a momentum exchange between the ocean surface and the winds, which in turn result from a non-uniform heating of air masses by the Sun. Storms generate local short-crested wind waves that can travel long distances before reaching the shore as long-crested swell waves. Waves move offshore almost without energy losses, and dissipate energy at low water depths due to bottom-friction effects and wave breaking phenomena. Wave energy consists of both kinetic and potential energy.

  Tides are the result of gravitational attraction of Earth, Sun and Moon that acts on the Earth’s oceans. This causes the slow motion of large masses of water. Tidal energy consists of both potential energy, related to vertical variations of the sea level, and kinetic energy, related to the horizontal motion of the water column.

  At first glance, power generation with wave and tidal energy has important advantages over other common renewable energy sources. First of all, they could allow powering coastal regions where 44% of the global population lives and where land availability for other renewable sources (wind, solar) is often scarce (United Nations 2016). Secondly, they are available throughout the day (unlike solar energy). Thirdly, they are highly predictable (2–3 days in advance for waves and weeks or months for tides, unlike wind energy). These points facilitate the delivery of electrical power to the grid, the integration with other sources of energy and the reduction of power cuts. In addition, the production of electricity from ocean energy is CO2

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  Introduction to Renewable Energy Conversions

  • Sergio Capareda, Sergio C. Capareda(Authors)
  • 2019(Publication Date)
  • CRC Press

    (Publisher)

  9

  Tidal Energy

  Learning Objectives

  Upon completion of this chapter, one should be able to:

  1. Describe the principles of harnessing tidal energy to generate useful power.
  2. Classify the various schemes of power generation from tidal energy.
  3. Describe the potential tidal energy available in the United States and worldwide.
  4. Compare the estimated cost of electrical energy produced from tidal energy from various countries.
  5. Relate the environmental and economic issues concerning tidal energy conversion.

  9.1 Introduction

  Tidal energy results from the forces of gravitational attraction between the earth, the sun, and the moon. The moon contributes to these gravitational forces and either creates additional tidal energy or subtracts from the sun's forces depending on its physical orientation. Because of gravity, the parts of the earth closest to the moon have higher tides, while those in the middle parts have the lowest. These “humps” occur twice every 24 hours and 50 minutes, which is also the time of the moon's apparent rotation around the earth. Tides due to the attraction of the moon, called semi-diurnal tides, occur every 12 hours and 25 minutes. Figure 9.1 shows the primary areas in the world with high potential for tidal energy. Figure 9.2 shows the variation of the height of the wave deviation as a function of time based on mean sea level. The way to take advantage of these tidal energies is to find a place on the shores of islands or continents where the tide elevations are at maximum. The energy derived comes from the potential and kinetic energy of water bodies similar to those used in hydro power plants.

  The sun has an understandably strong effect on the variations of these tides. During a full moon or new moon, the sun's attractive forces add to the pull of the tidal “humps,” and this makes the tidal heights higher than normal (see illustrations in Figure 9.1

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  Ten Technologies to Save the Planet

  Energy Options for a Low-Carbon Future

  • Chris Goodall(Author)
  • 2010(Publication Date)
  • Greystone Books

    (Publisher)

  This dismissive attitude to the usefulness of tidal energy was widely shared until recently. The total amount of energy in the tides across the world is not enormous, at least when compared with solar or wind power, or indeed the energy in waves. However, it is still far more than the total power needed by today’s electricity grids. The energy contained in the global tides at any one moment is probably about 3,800 gigawatts, or almost twice today’s worldwide electricity consumption. Most tidal energy is impossible to extract; it is found in deep oceans far from coastlines. But at a small number of places, such as the Pentland Firth or the Bay of Fundy, huge resources of energy are concentrated into narrow funnels.

  Of course, tidal-stream turbines are not the only way to capture energy from the seas. Barrages are another option. These large dams harness their energy from the “range” of the tide, or the difference between its high and its low points. The barrage is built across a tidal river or estuary, and the incoming tide is allowed in through sluices. When the tide reverses, the sluices are opened, and the force of outgoing tide turns electricity turbines. We know that tidal barrages will work, as there are already commercial plants in France, Canada, and Russia.

  There are also at least three marine-energy technologies that don’t rely on either the range or the current of the tides. First, turbines could be positioned to collect the energy of the main ocean currents, such as the Gulf Stream. Second, wave power collectors can use the up-and-down motion of the sea as the waves pass. Finally, heat pumps can use differences between the temperature of the sea surface and the deep ocean to drive an engine, usually to generate electricity.

  All of these technologies are commercially interesting, but, as this chapter shows, the power from tidal currents and ocean waves looks like the easiest to exploit and offers us the biggest potential for generating electricity.

  THE POTENTIAL FOR ENERGY FROM THE SEAS

  Although both the vigor and the regularity of marine energy have been obvious since humans started to sail the oceans, we have been slow to exploit their potential. Even now, only a dozen or so sites around the globe successfully generate electricity from the oceans. France built a large barrage across the River Rance to collect energy from the tides on the northern coast of Brittany over forty years ago, and a small number of other places with large ranges between the high and low tides have installed similar dams. A prototype power station in Hawaii has occasionally generated electricity from ocean temperature variations. But the general picture is of hesitant and slow progress. Only in the last few years has the pace of installation started to pick up. The first two commercial-scale turbines that capture the flow of the tide on the ocean floor have been connected to the U.K. electricity grid, and a small wave power farm has been installed off the coast of Portugal. Vancouver-based Clean Current’s prototype tidal stream turbine has been successfully tested at Race Rocks off the coast of British Columbia, and a few other developers have put working machines in the water.

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  Sustainable Energy, SI Edition

  • Richard Dunlap(Author)
  • 2018(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 432 CHAPTER 13: Tidal Energy Milford Haven St Govan’s Head Lundy Hartland Point England Wales Cardiff Bristol Dover Portsmouth Southampton Plymouth Falmouth Felixstowe Mouth of the Severn Haverfordwest Carmarthen Newport Bristol Taunton Barnstaple LONDON Ilfracombe Bath Swansea Cardiff Porthcawl Weston-super-mare Bridgwater B r i s t o l C h a n n e l Figure 13.28: Location and geography of the Mouth of Severn in England. Combination of CIA World Factbook map and Demis Map Server (http://www2.demis.nl/mapserver/mapper.asp) data with additional annotations and modifications by ChrisO. may be more serious than for horizontal-axis water turbines, either isolated or in Tidal Power farms, and careful consideration of any possible adverse environmental impacts is necessary. If properly implemented, Tidal Power can be a renewable resource with low envi-ronmental impact. Although the tidal energy in the oceans is substantial, the number of locations where it can be utilized as a viable energy source is somewhat limited. However, new, developing technologies have met with success and may lead the way to further implementation of this energy source. 13.5 Summary The tides in the earth’s oceans are the result of the combined gravitational forces from the sun and the moon. This chapter has reviewed the properties of tidal energy and has discussed the possible approaches to harnessing this energy. Although the tidal ampli-tude in most locations on earth is relatively small, the tidal range becomes amplified in certain enclosed basins as a result of resonance effects.

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  Water for Energy and Fuel Production

  • Yatish T. Shah(Author)
  • 2014(Publication Date)
  • CRC Press

    (Publisher)

  The extraction of only 15 % of the energy in coastal waves would generate as much electricity as we currently produce in con-ventional hydroelectric dams [36–40] (Bertsch, 2012, pers. comm.; Dixon et al., 2008, pers. comm.). ¶ Much of this wave potential is found along our Pacific coast, near big cities and towns. Besides waves, ocean tides hold promise as an energy resource. Each change in the tide creates a current, called tidal stream. Regular tidal streams have the potential to provide a reliable new source of electricity without building dams and barrages. Ocean currents, such as Gulf stream, also offer hydrokinetic energy. These result from winds and equatorial solar heating. Free flowing rivers (without dams) and constructed waterways such as irrigation canals also allow the use of hydrokinetic * Bertsch, D.J., Juris Doctoral candidate, The University of South Dakota School of Law, 2011; Congress defined hydrokinetic energy as “electrical energy from waves, tides, and currents in oceans, estuar-ies, and tidal areas; free flowing water in rivers, lakes, and streams, or man-made channels; and dif-ferentials in ocean temperature (ocean thermal energy conversion),” The Energy Independence and Security Act of 2007, 42 USC §17211 (2006). † Ibid. ‡ Hydrokinetic energy was included as an eligible renewable energy resource by the Energy Policy Act of 2005. Various funding authorizations for research and development were also included in this Act as well as the Energy Independence and Security Act of 2007. § Bertsch, D.J., Juris Doctoral candidate, The University of South Dakota School of Law, 2011; Congress defined hydrokinetic energy as “electrical energy from waves, tides, and currents in oceans, estuar-ies, and tidal areas; free flowing water in rivers, lakes, and streams, or man-made channels; and dif-ferentials in ocean temperature (ocean thermal energy conversion),” The Energy Independence and Security Act of 2007, 42 USC §17211 (2006).

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  Electricity Production from Renewable Energies

  • Benoît Robyns, Arnaud Davigny, Bruno François, Antoine Henneton, Jonathan Sprooten(Authors)
  • 2012(Publication Date)
  • Wiley-ISTE

    (Publisher)

  equation [4.17] ).

  4.2.3.4. Potential

  The tidal range of a tide has the advantage of being specifically predictable, because the motion of the Moon and the Sun can be determined over several centuries. We consider a site that is exploitable from a tidal range higher than 5 m. The global exploitable resource is estimated at 380 TWh/year for a peak power of 160 GW. The potential in the United Kingdom is estimated at 6 GW and at 2 GW in France [ADE 09].

  The observed tidal ranges around the world are very variable according to the typology of the seas. In deep waters, the tidal range is generally low or even nonexistent, of about a few dozen centimeters at a maximum. On the coasts, the values are much higher, up to several meters (Figure 4.28 ). The most significant tidal range is found in the Bay of Fundy, on the Atlantic Coast of Canada: it reaches 16 m.

  Figure 4.28.

  Amplitudes in meters of the average spring tides around the world [GIB 55]

  The French resource is mainly located on the Brittany coast, where tidal ranges can reach 14 m, as in Mont Saint-Michel bay (Figure 4.29 ). The French Tidal Power production is located in La Rance estuary and is about 500 TWh/year.

  Figure 4.29.

  Amplitudes in meters of the average spring tides on the coasts of France and Great-Britain [GIB 55]

  The resource related to the tidal current is studied similarly to that of the tidal range and can also be represented as an atlas with propagation speeds expressed in m/s. The French coast potential is greater than 6 GW, with favorable zones on the coasts of Brittany and Normandy (Figure 4.30

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  Tidal Energy Systems

  Design, Optimization and Control

  • Vikas Khare, Cheshta Khare, Savita Nema, Prashant Baredar(Authors)
  • 2018(Publication Date)
  • Elsevier

    (Publisher)

  The gravitational effects of the sun or the moon on the world's oceans causes huge amounts of sea water to be directed toward the nearest coastline. The result of this movement of water is a rise in the sea level. In the open ocean, this rise is very small as there is a large surface area with deeper depths for it to flow into. However, as the ocean water moves nearer the coastline, the sea level rises steeply, especially around inlets and estuaries because of the upward sloping gradient of the sea bed. The effect of this sloping gradient is to funnel the water into the estuaries, lagoons, river inlets, and other such tidal “bottlenecks” along the coastline. This increase in the sea level can create a tidal range of > 10 m in height in some estuaries and locations that can be exploited to generate electricity. The tidal range is the vertical difference between the high tide sea level and the low tide sea level. The tidal energy extracted from these tides is potential energy as the tide moves in a vertical up-down direction between a low and high tide and back to a low, creating a height or head differential. A tidal barrage generation scheme exploits this head differential to generate electricity by creating a difference in the water levels on either side of a dam and then passing this water difference through the turbines.

  2.3.3 Single-Basin System

  In a single-basin system, there is only one interface with the tidal energy generation process. There are two system seas and tidal basins separated by a dam and in this situation, water flows between through sluice valves so that only one basin is connected with the sea water. In this case, power can be generated at regular intervals of time at different tidal ranges and tidal currents. The power house, which consists of an electrical system, is installed inside the dam. The single-basin system also interacts with turbine and generator because the turbine converts kinetic energy into mechanical energy. Further, the generator converts mechanical energy into electrical energy. During high tide, when the water level increases, the tidal turbine valves are opened and the sea stream flows into the basin through the turbine, generating power. The necessary condition of generated power is the level of the sea water and the basin are equal. If water is pass into the basin, until the level reaches its maximum position and at this point find out the maximum power through tidal energy system. During low tide, the altitude of the basin is more than the altitude of sea water. Fig. 2.14 shows the operating cycle of single barrage Tidal Power plants. After attaining sufficient head, the turbine valves are opened and water flows from the basin to the sea through the turbine, generating power. Single-basin Tidal Power plants normally use reversible water turbines because, in this case power is generated in both directions. Figs. 2.15 and 2.16 show schematic diagrams of single-basin tidal energy systems. Fig. 2.17

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  Future Energy

  Improved, Sustainable and Clean Options for our Planet

  • Trevor Letcher, Trevor M. Letcher(Authors)
  • 2008(Publication Date)
  • Elsevier Science

    (Publisher)

  The exploitation of tidal current power is too attractive to ignore, and the UK has an abundance of resource in this field, but a much more coherent effort is required to make it realistically possible. References 1. Weaver , M. A. (1976). The Tide Mill Woodbridge , p. 4. Friends of Woodbridge Tide Mill, April. 2. Pickard, G. L. and W. J. Emery (1995). Descriptive Physical Oceanography , 5th edn, pp. 180–181. Butterworth-Heinemann, Oxford. 3. Boon, J. D. (2004). Secrets of the Tide , p. 39. Horwood, Chichester . 4. Darwin, G. H. D. (1911). The Tides and Kindred Phenomena , 3rd edn, p. 89. John Murray , London. 5. Pugh, D. T. (2004). Changing Sea Levels , p. 118. Cambridge University Press, Cambridge. 6. Couch, S. J. and I. Bryden (2004). The Impact of Energy Extraction on Tidal Flow Development. 3rd IMarEST International Conference on Marine Renewable Energy . 128 A. Owen 7. Roy, A. E. (1982). Orbital Motion , 2nd edn. Institute of Physics, Bristol. 8. Wright, J., A. Colling and D. Park (2002). Waves, Tides and Shallow Water Processes , 2nd edn, p. 22. Butterworth-Heinemann, Oxford and Open University . 9. Patel, M. H. (1989). Dynamics of Offshore Structures , p. 121. Butterworths, London. 10. Patel, M. H. (1989). Dynamics of Offshore Structures , p. 188. Butterworths, London. 11. http://www.geo.ed.ac.uk/scotgaz/features/featurehistory6716.html. 12. http://engb.com/downloads/M0200301.pdf. 13. Salter, S. H. (2005). Theta-Islands for Flow Velocity Enhancement for Vertical Axis Generators at Morecambe Bay. World Renewable Energy Conference , Aberdeen. 14. Fraenkel, P. L. (2004). Marine Current Turbines: An Emerging Technology . Paper for Scottish Hydraulics Study Group seminar, Glasgow, p. 5. 19 March. 15. Supergen Marine Phase 1, Homepage on the internet, University of Edinburgh, c. 2003–2007, accessed 20/04/2008. Available from: http//www.supergen-marine.org.uk. 16. Niet, T. and G. McLean (2001). Race Rocks Sustainable Energy System Development.

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