Tidal Energy

KAUTILYA INSTITUTE OF TECHNOLOGY & ENGINEERING,JAIPUR

Session 2008-12 Seminar Report ON (TIDAL ENERGY) Presented on DATE-31March,2012

Submitted ToProf.B.K.GRAG (Dean Mechanical Depatment)

Submmited ByPUSHPENDRA SINGH Roll No.08EKTME044

MECHANICAL ENGINEERING DEPARTMENT KAUTILYA INSTITUTE OF TECHNOLOGY & ENGINEERING SITAPURA INDUSTRIAL AREA ,JAIPUR Website:

www.kautilya.net

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PREFACE

This seminar report has been prepared as per the requirement of the syllabus of Mechanical engineering course structure under which the students are required to prepare seminar for final year. My job during the preparation of this project report was to get knowledge about “TIDAL ENERGY” and its various generating methods. It was a great experience for me that to get exposed to the professional set up. During seminar, we had very knowledgably experience. We found in this project that we gain a lot of knowledge in Mechanical field. Now we take opportunity to present report and sincerely hope that it will be as much knowledge enhancing to the readers as it was to use during the field work of project and compilation of the report.

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ACKNOWLEDGMENT

I am deeply indebted to many people for the successful completion of this report. I would like to take this opportunity and go on record to thank them for their help and support. I am deeply indebted to the Kautilya Institute Of Technology & Engg. for all the pains and trouble they have gone through on my behalf and all the support they continue to provide me with. I express my deep sense of gratitude and sincere feelings of obligation to my guide faculty Prof. R.K. Agarwal (KITE) who helped in overcoming difficulties and who imparted me the necessary conceptual knowledge. I would also like to thanks Prof. B.K Grag (Dean of Mechanical) who have directly or indirectly extend their kind co-operation and support by guiding me systematically and methodically in completion of the report. I wish to express my greatness to all my friends and teachers for their helpful input, insightful comments, steadfast love and support. Thank You for being there for me every time.

Pushpendra Singh Shekhawat (4th year B. Tech., VIII sem)

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CERTIFICATE

This is to certify that Pushpendra Singh Shekhawat

(4th year B. Tech.

Mechanical, VIII Sem.), is a student of Kautilya Institute of Technology and Engineering, Jaipur (2008-12) batch. He has done his seminar on “TIDAL ENERGY” under my guidance Prof. B.K.Garg (Dean of Mechanical Department). The work is only for academic purpose. I am fully satisfied with his work and recommend its acceptance in the partial fulfilment of the requirement for the award of KITE course.

(Prof. B. K. Garg Sir) (Dean of Mechanical Department) Place: Jaipur (Raj.)

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INDEX

 Tidal Energy  Generation of tidal energy  Generating methods 1. Tidal stream generator 2. Tidal barrage 3. Dynamic tidal power  Advantages  Disadvantages

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Tidal Energy Gravitational forces between the moon and, the sun and earth cause the rhythmic rising and lowering of ocean waters around the world that result in tide waves.Tidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into useful forms of power - mainly electricity.

Fig1. Spring and Neap tide 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 6

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. The earliest occurrences date from the Middle Ages, or even from Roman times.[1][2]The world's first large-scale tidal power plant (the Rance Tidal Power Station) became operational in 1966.

Generation of tidal energy Tidal power is extracted from the Earth's oceanic tides; tidal forces are periodic variations in gravitational attraction exerted by celestial bodies. These forces create corresponding motions or currents in the world's oceans..

Fig2. Variation of tide over a day

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The magnitude and character of this motion reflects the changing positions of the Moon and Sun relative to the Earth, the effects of Earth's rotation, and local geography of the sea floor 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 with 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 taps 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%).

Fig3. Turbine under the water

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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. 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. Movement of tides causes a loss of mechanical energy in the Earth–Moon system: this is a result of 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;[4] in this period the Earth has lost 17% of its rotational energy. While tidal power may take additional energy from the system, the effect is negligible and would only be noticed over millions of years.

Generating methods  Tidal stream generator  Tidal barrage  Dynamic tidal power Tidal stream generator A tidal stream generator, often referred to as a tidal energy converter (TEC) is a machine that extracts energy from moving masses of water, in particular tides, although the term is often used in reference to machines designed to extract energy

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from run of river or tidal estuarine sites. Certain types of these machines function

Fig4.Tidal stream generator very much like underwater wind turbines, and are thus often referred to as tidal turbines. They were first conceived in the 1970s during the oil crisis. Tidal stream generators are the cheapest and the least ecologically damaging among the three main forms of tidal power generation. Similarity to wind turbines Tidal stream generators draw energy from water currents in much the same way as wind turbines draw energy from air currents. However, the potential for power generation by an individual tidal turbine can be greater than that of similarly rated wind energy turbine. The higher density of water relative to air (water is about 800 times the density of air) means that a single generator can provide significant power at low tidal flow velocities compared with similar wind speed. Given that power varies with the density of medium and the cube of velocity, it is simple to 10

see that water speeds of nearly one-tenth of the speed of wind provide the same power for the same size of turbine system; however this limits the application in practice to places where the tide moves at speeds of at least 2 knots (1 m/s) even close to neap tides. Furthermore, at higher speeds in a flow between 2 to 3 metres per second in seawater a tidal turbine can typically access four times as much energy per rotor swept area as a similarly rated power wind turbine. Tidal barrage A tidal barrage is a dam-like structure used to capture the energy from masses of water moving in and out of a bay or river due to tidal forces. Instead of damming water on one side like a conventional dam, a tidal barrage first allows water to flow into a bay or river during high tide, and releasing the water back during low tide. This is done by measuring the tidal flow and controlling the sluice gates at key times of the tidal cycle. Turbines are then placed at these sluices to capture the energy as the water flows in and out.

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Fig.5 The Rance Tidal Power Station, a tidal barrage in France. 11

Tidal barrages are among the oldest methods of tidal power generation, with projects being developed as early as the 1960s, such as the 1.7 megawatt Kislaya Guba Tidal Power Station in Kislaya Guba, Russia. Dynamic tidal power Dynamic tidal power or DTP is a new and untested method of tidal power generation. It would involve creating large dam-like structure extending from the coast straight to the ocean, with a perpendicular barrier at the far end, forming a large 'T' shape. This long T-dam would interfere with coast-parallel oscillating tidal waves which run along the coasts of continental shelves, containing powerful hydraulic currents (common in e.g. China, Korea, and the UK). The concept was invented and patented in 1997 by Dutch coastal engineers Kees Hulsbergen and Rob Steijn.

Fig.6 Top-down view of a DTP dam. Blue and dark red colors indicate low and high tides, respectively. 12

A DTP dam is a long dam of 30 to 60 km which is built perpendicular to the coast, running straight out into the ocean, without enclosing an area. The horizontal acceleration of the tides is blocked by the dam. In many coastal areas the main tidal movement runs parallel to the coast: the entire mass of the ocean water accelerates in one direction, and later in the day back the other way. A DTP dam is long enough to exert an influence on the horizontal tidal movement, which generates a water level differential (head) over both sides of the dam. The head can be converted into power using a long series of conventional low-head turbines installed in the dam. Benefits A single dam can accommodate over 1 GW (1000 MW) of installed capacity, with a capacity factor of about 30%, for an estimated annual power production of each dam of about 4.6 TWh .To put this number in perspective, an average European person consumes about 6800 kWh per year, so one DTP dam could supply energy for about 6.76 hundred thousand Europeans. If two dams are installed at the right distance from one another (about 200 km apart), they can complement one another to level the output (one dam is at full output when the other is not generating power). Dynamic tidal power doesn't require a very high natural tidal range, so more sites are available and the total availability of power is very high in countries with suitable conditions, such as Korea, China, and the UK (the total amount of available power in China is estimated at 80 - 150 GW).

Advantages  It reduces the dependence upon fossil fuels  Tidal and wave energy is free, renewable, and clean source of energy

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 It produces clean electricity, with no production of greenhouse gas or pollution.  Tidal and wave energy generation and consumption creates no liquid or solid pollution  Highly efficient resource (compared with coal and oil at 30%, tidal power efficiency is about 80%)  Energy capturing and conversion mechanism may help protect the shoreline  Energy capturing and conversion mechanism has little visual impact  About 60 billion watts of energy from tides can be used for electricity generation  Tides are active 24 hours a day, 365 days a year  Tidal power is a renewable source of energy.  It produces energy for free, once the initial costs are recovered.

Disadvantages  It is not cost effective because fossil-fuel power stations do not pay for the cost of their carbon emissions to the planet. This will change as fossil fuel is valued at its real price.  It leads to the displacement of wild life habitats.  It can only be used where there is suitable tidal flow or wave motion. So it can not be used inland.  It only produces electricity during tidal surges.  Barrage systems require salt resistant parts and lots of maintenance.  The frames of the turbines can disrupt the movement of large marine animals and ships through the channels on which the barrage is built.

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 The barrage systems have the disadvantages of disrupting fish migration and killing fish passing through the turbines, therefore, there is also the risk of destruction of ecosystem that rely on the coming and going of tides.  The ecosystem is disrupted during the construction of building the tidal fence. this affects the fishes and also the fishermen who depends their life on it.  Fossil fuels can be moved to just about anyplace to create energy on the spot. This is what allows a car to work while moving.

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