tidal doc

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TIDAL ENERGY WHICH IS CLEAN, GREEN&SUSTAINABLE ENERGY

Abstract:

Energy can be extracted from tides by creating a reservoir or basin behind a

barrage and then passing tidal waters through turbines in the barrage to generate

electricity. Tidal energy is extremely site specific requires mean tidal differences

greater than 4 meters and also favorable topographical conditions, such as

estuaries or certain types of bays in order to bring down costs of dams etc.

Both tidal stream and wave power devices have suffered from stringent

economic assessments which have cut off R&D. The total tidal stream resource is

assessed as low (by the Carbon Trust) thus banishing it to the fringe, and tidal

lagoons get contrasting pro and anti-assessments while the Severn mega-barrage

gets optimistic treatment.

We find good reasons to distrust narrow economics, driven by interested

parties. However active engagement requires us to define and cover the range of

non-monetary issues - including learning and technology enhancement,

decentralized power, and wider environmental and socio-economic benefits.

The Sustainable Development Commission (SDC) currently has the task of

addressing the tidal power area, but has run restricted events dominated by an

in-group of official bodies and project promoters. With WWF and FOE arguing

different options, we on the fringe need to understand and discuss the issues in a

tidal context, and to make an input into the SDC process and the 2007 Energy

Review.

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INTRODUCTION:

Non-conventional energy sources can be replenished in a short period of

time. They are basically five types which include tide, wind, solar, bio-mass and

geo-thermal. Tide is nothing but the natural rise and fall of coastal waters caused

principally by the interaction of the gravitational fields of the sun and the moon.

This paper provides a review of tidal power development and global picture with

particular reference to the Indian scenario. Tidal energy is one of the renewable

energy sources that could be used without producing by-products that are

harmful to nature.

WHAT IS TIDAL ENERGY?

Tidal energy is the utilization of the sun and moon's gravitational forces - as

tides are formed by the gravitational pull of the sun and moon on the oceans of

the rotating earth. Tides can be found with varying degrees of strength on any

coastline, and sometimes even at sea, although these are better known as

currents. A flood tide is one that is coming in or rising and an ebb tide is one that

is going out. Tidal energy is one of the oldest forms of energy used as evidence of

tide mills from before 1100AD has been found along the coast of France, Spain

and the UK.

If there is one thing we can safely predict and be sure if on this planet, it is

the coming and going of the tide. This gives this form of renewable energy a

distinct advantage over other sources that are not as predictable and reliable,

such as wind or solar. The Department of Trade and Industry has stated that

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almost 10% of the United Kingdoms electricity needs could be met by tidal

power.

Why do the tides come and go? It is all to do with the gravitational force of

the Moon and Sun, and also the rotation of the Earth. This is displayed in the

following diagram

.

Figure 1 Gravitational effect of the Sun and the Moon on tidal range(Adapted

from Boyle, 1996)

Sourced: (ACRE) Australian CRC for Renewable Energy LTD

The diagram shows how the gravitational attraction of the moon and sun

affect the tides on Earth. The magnitude of this attraction depends on the mass of

the object and its distance away. The moon has the greater effect on earth

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despite having less mass than the sun because it is so much closer. The

gravitational force of the moon causes the oceans to bulge along an axis pointing

directly at the moon. The rotation of the earth causes the rise and fall of the tides.

When the sun and moon are in line their gravitational attraction on the earth

combine and cause a spring tide. When they are as positioned in the first

diagram above, 90 from each other, their gravitational attraction each pulls

water in different directions, causing a neap tide.

The rotational period of the moon is around 4 weeks, while one rotation of

the earth takes 24 hours; this results in a tidal cycle of around 12.5 hours. This

tidal behavior is easily predictable and this means that if harnessed, tidal energy

could generate power for defined periods of time. These periods of generation

could be used to offset generation from other forms such as fossil or nuclear

which have environmental consequences. Although this means that supply will

never match demand, offsetting harmful forms of generation is an important

starting point for renewable energy.

State of the art / Current Status

There are two options for getting energy from the tide, a tidal barrage or

utilizing tidal streams.

HOW IT WORKS:

These work rather like a hydro-electric scheme, except that the dam is

much bigger. A huge dam (called a "barrage") is built across a river estuary. When

the tide goes in and out, the water flows through tunnels in the dam. The ebb and

flow of the tides can be used to turn a turbine, or it can be used to push air

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through a pipe, which then turns a turbine. Large lock gates, like the ones used on

canals, allow ships to pass. If one was built across the Severn Estuary, the tides at

Weston-super-Mare would not go out nearly as far -there'd be water to play in for

most of the time. But the Severn Estuary carries sewage and other wastes from

many places (e.g. Bristol & Gloucester) out to sea. A tidal barrage would mean

that this stuff would hang around Weston-super-Mare an awful lot longer! Also, if

you're a wading bird that feeds on the exposed mud flats when the tide goes out,

then you have a problem, because the tide won't be going out properly any more

Electricity is generated by water flowing both inwards and out of a bay.

There are periods of maximum generation every twelve hours, with no electricity

generation at the six-hour mark in between. The turbines may also be used as

pumps to pump extra water into the basin behind the dam at times when the

demand on electricity is low. This water can later be released when the demand

on the system is very high, thus allowing the tidal plant to function likepumped

storage" hydroelectricity.

THE TIDAL BARRAGE

Introduction

This is where a dam or barrage is built across an estuary or bay that

experiences an adequate tidal range. This tidal range has to be in excess of 5

meters for the barrage to be feasible. The purpose of this dam or barrage is to let

water flow through it into the basin as the tide comes in. The barrage has gates in

it that allow the water to pass through. The gates are closed when the tide has

stopped coming in, trapping the water within the basin or estuary and creating a

hydrostatic head. As the tide recedes out with the barrage, gates in the barrage

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that contain turbines are opened, the hydrostatic head causes the water to come

through these gates, driving the turbines and generating power. Power can be

generated in both directions through the barrage but this can affect efficiency and

the economics of the project.

This technology is similar to Hydropower, something that we have a lot of

experience with in Scotland. There is potential for a project of this kind in

Scotland, one place in particular which has been looked at is the Solway Firth in

south west Scotland, where there is a tidal range of 5.5 meters [1-The Open

University Renewable energy Pack T251].

The construction of a barrage requires a very long civil engineering project.

The barrage will have environmental and ecological impacts not only during

construction but will change the area affected forever. Just what these impacts

will be is very hard to measure as they are site specific, and each barrage is

different.

Current Technology

The following diagram is a simplified version of a tidal barrage.

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Figure 2 Ebb generating system with a bulb turbine (Adapted from Energy

Authority of NSW tidal Power Fact Sheet)


There are different types of turbines that are available for use in a tidal

barrage. A bulb turbine is one in which water flows around the turbine. If

maintenance is required then the water must be stopped which causes a problem

and is time consuming with possible loss of generation. When rim turbines are

used, the generator is mounted at right angles to the to the turbine blades,

making access easier. But this type of turbine is not suitable for pumping and it is

difficult to regulate its performance. Tubular turbines have been proposed for the

UKs most promising site, The Severn Estuary, the blades of this turbine are

connected to a long shaft and are orientated at an angle so that the generator is

sitting on top of the barrage. The environmental and ecological effects of tidal

barrages have halted any progress with this technology and there are only a few

commercially operating plants in the world, one of these is the La Rance barrage

in France, for more information see the La Rance Case Study.

Figure 3: Bulb Turbine
http://www.esru.strath.ac.uk/EandE/Web_sites/01-02/RE_info/tidal1.htmhttp://www.esru.strath.ac.uk/EandE/Web_sites/01-02/RE_info/tidal1.htm

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Figure 4: Rim Turbine


Figure 5: Tubular Turbine


Pumping

The turbines in the barrage can be used to pump extra water into the basin

at periods of low demand. This usually coincides with cheap electricity prices,

generally at night when demand is low. The company therefore buys the

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electricity to pump the extra water in, and then generates power at times of high

demand when prices are high so as to make a profit. This has been used in Hydro

Power, and in that context is known as pumped storage.

The power available from the turbine at any particular instant is given by:

Where,

Cd = Discharge Coefficient

A = Cross sectional area (m2)

G = gravity = 9.81

r = density (kg/m3)

The discharge coefficient accounts for the restrictive effect of the flow

passage within the barrage on the passing water.

The equation above illustrates how important the difference between the

water levels of the sea and the basin, (Z1-Z2), is when calculating the power

produced.

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Economics:

The capital required to start construction of a barrage has been the main

stumbling block to its deployment. It is not an attractive proposition to an

investor due to long payback periods. This problem could be solved by

government funding or large organizations getting involved with tidal power. In

terms of long term costs, once the construction of the barrage is complete, there

are very small maintenance and running costs and the turbines only need

replacing once around every 30 years. The life of the plant is indefinite and for its

entire life it will receive free fuel from the tide.

The economics of a tidal barrage are very complicated. The optimum design

would be the one that produced the most power but also had the smallest

barrage possible.

Social Implications:

The building of a tidal barrage can have many social consequences on the

surrounding area. During the construction of the barrage, the amount of traffic

and people in the area will increase dramatically and will last for a number of

years. The La Rance tidal barrage in France took over 5 years to build. This will

also bring revenue to the area from the tourism and hospitality industry that will

accommodate all the different types of visitors that the barrage will bring. This

will give a boost to the local economy.

The barrage can be used as a road or rail link, providing a time saving

method of crossing the bay or estuary. There is also the possibility of

incorporating wind turbines into the barrage to generate extra power. The

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barrage would affect shipping and navigation and provision would have to be

made to allow ships to pass through.

The bay would become available for recreation; the waters would be calmer

not immediately after the barrage but further in towards the land. This would be

another tourist attraction and become a feature of the area.

Environmental Aspects

Perhaps the largest disadvantages of tidal barrages are the environmental

and ecological affects on the local area. This is very difficult to predict, each site is

different and there are not many projects that are available for comparison. The

change in water level and possible flooding would affect the vegetation around

the coast, having an impact on the aquatic and shoreline ecosystems. The quality

of the water in the basin or estuary would also be affected, the sediment levels

would change, affecting the turbidity of the water and therefore affecting the

animals that live in it and depend upon it such as fish and birds. Fish would

undoubtedly be affected unless provision was made for them to pass through the

barrage without being killed by turbines. All these changes would affect the types

of birds that are in the area, as they will migrate to other areas with more

favorable conditions for them.

These effects are not all bad, and may allow different species of plant and

creature to flourish in an area where they are not normally found. But these

issues are very delicate, and need to be independently assessed for the area in

question.

TIDAL STREAMS

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Introduction

Tidal streams are fast flowing volumes of water caused by the motion of the

tide. These usually occur in shallow a sea where a natural constriction exists

which forces the water to speed up. The technology involved is very similar to

wind energy, but there are some differences. Water is 800 times denser than air

and has a much slower flowrate; this means that the turbine experiences much

larger forces and moments. This results in turbines with much smaller diameters.

The turbines must either be able to generate power on both ebbs of the tide or

be able to withstand the structural strain. This technology is still in its infancy

despite the potential for a reliable and predictable source; therefore it has not

been included in the possible technologies discussed with relevance to the

Renewable Obligation for Scotland.

The experiences from the development of wind power can be applied to the

technology. Scotland has a definite potential for tidal stream energy to be

converted to electricity, one area of focus is the Pentland Firth off the north

coast.

Tidal stream technology has the advantage over tidal barrages when you

compare environmental and ecological issues. This technology is less intrusive

than on and offshore wind, and tidal barrages, any hazard to navigation or

shipping would be no more than that experienced by current offshore

installations. Tidal Stream systems often have to be installed in difficult coastal

waters and the installation and maintenance methods are often complicated, but

these hold they key for ensuring the success of the technology.

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Current Technology

Energy can be captured from tidal streams using two methods, tidal fences

and tidal turbines.

Tidal Fences

These are effectively another form of tidal barrage. They therefore share

some of the same environmental and social concerns, but also have the

advantage of being able to have the electrical generators and transformers above

the water. The flowing diagram shows an example of a tidal fence.

Tidal Turbines

This form of generation has many advantages over its other tidal energy

rivals. The turbines are submerged in the water and are therefore out of sight.

They dont pose a problem for navigation and shipping and require the use of

much less material in construction. They are also less harmful to the environment.

They function best in areas where the water velocity is 2 - 2.5 m/s [2-Fujita

Research]. Above this level the turbine experiences heavy structural loads and

below this not enough generation takes place. The following diagram, figures X!!!

is an impression of a tidal turbine farm.

One new technology that has been developed is the Stingray. This project

has definite potential and planning is underway for a trial in the North of

Scotland. For more information see the

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Impression of tidal Turbine Farm

Economics:

Tidal stream technology is still in its infancy and therefore there are no

comparable projects at the present time. The cost of utilising tidal streams will be

very site specific and depend on the technology used. The turbine or other

generating plant equipment can be considered to have a similar cost to wind.

Once installed, electricity will be produced with no fuel costs and will be

completely predictable. Maintenance costs will be the main costs during the life

of the project.

Social Implications:

Tidal Streams are common in remote areas. This means that careful

consideration of the wishes of the local community is required to ensure the

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scheme can work to its potential. Being under water avoids aesthetic problems

and shipping and navigation should not be affected provided it is taken into

consideration when planning. The scheme can provide employment during

construction and operation, which will add to the local economic prosperity. Also,

these schemes are unique at present and would help to put the area on the map.

Environmental Aspects:

The environmental effects of utilising tidal streams are in no way as severe as

those for a tidal barrage. They will obviously affect the seabed where they are

positioned and this might have an effect on the aquatic life in the area. This is

again site specific and hard to predict; as long as proper environmental impact

assessments are done then this can be avoided or minimised.

Comparison of Tidal Barrage and Tidal Stream - different forms of Tidal Energy

Tidal range is the difference in height between high and low tide. Tidal

stream is the flow of water through channels or around coastlines as a result oftidal water movement. Some people talk of marine currents, as energy in the Gulf

Stream and other circulating currents could also be tapped.

Barrages to tap the tidal range are sited in upper estuaries, while tidal

stream turbines tap the currents in lower estuaries and straits. As a result the two

may not conflict. Tidal streams are tapped, in both ebb and flood directions, by

submerged turbines. These are much smaller than wind turbines because the

power density in water currents is much larger than in air currents. Though tidal

barrages have a long history, tidal stream generators are considered much more

feasible nowadays A major drawback with the Severn Barrage, and to a lesser

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extent Severn tidal lagoons, is the need for supporting power stations to fill in the

slack periods.

Tidal currents, on the other hand, deliver less discontinuous power than a

barrage and if Tidal current technology made use of several sites with a range of

Tidal timings it would give reasonably steady overall power.

A second drawback of barrages and lagoons is that they change the

sedimentation and erosion pattern. This is especially important in the Severn

because the strong currents make for very high loading in silt and sand. Note:

Spring tides contain about 4 times the energy of Neap tides, and about 10 times

the silt loading.

Major structures reduce currents, so the silt tends to deposit inside the

barrage or lagoon and in backwaters outside the structure. Scour may also be

enhanced outside the structure. For the former reasons, proposals for a major

barrage in the Bay of Fundy (Annapolis, Canada) have been dropped and, because

of shoreline erosion, a causeway is to be removed.

Each proposed barrage or lagoon would need specific studies - as far as a

scale hydrodynamic model, as done for the old Severn Barrage study - and even

then predictions would be uncertain.

Marine Current TurbinesLtd: (MCT) has come up with a tidal energy

turbine to generate carbon free electricity.The turbines are driven by tides or by

oceanic circulations. Now, MCT has successfully installed the worlds first

commercial scale tidal energy turbine in Northern Ireland. The tidal energy

turbine which looks like a submerged windmill, marks the completion of the first
http://www.marinebuzz.com/2007/12/20/california-goes-for-commercial-wave-power/http://www.marinebuzz.com/2007/12/20/california-goes-for-commercial-wave-power/http://www.marinebuzz.com/2007/12/20/california-goes-for-commercial-wave-power/http://www.marinebuzz.com/2007/12/20/california-goes-for-commercial-wave-power/

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installation phase of 1.2 MW SeaGen Tidal System. SeaGen is located

approximately 400 meters from the shoreline, 1 km south of the ferry route

between Stanford and Portaferry. The SeaGen tidal system is expected to be

operational later in the summer and has the following interesting features:

16 metre diameter blades

has twin rotors

will be turned by the water streaming in and out of Strangford Lough at up to 8

knots

Weighs 1000 tone

will operate for up to 18-20 hours per day

can power up 1000 homes

Here are some sketches of SeaGen Tidal System.
http://maps.google.com/maps?f=q&hl=en&geocode=&q=Strangford+,Northern+Ireland,&mrt=loc&ie=UTF8&ll=55.825973,-7.119141&spn=11.000557,40.737305&z=5http://maps.google.com/maps?f=q&hl=en&geocode=&q=Strangford+,Northern+Ireland,&mrt=loc&ie=UTF8&ll=55.825973,-7.119141&spn=11.000557,40.737305&z=5

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The Future of Tidal Power:

The high capital costs associated with tidal barrage systems are likely to

restrict development of this resource in the near future. The developments that

do proceed in the early 21st century will most likely be associated with road and
http://www.marineturbines.com/21/technology/24/technical_advantages/http://www.marineturbines.com/21/technology/http://www.marineturbines.com/21/technology/24/technical_advantages/http://www.marineturbines.com/21/technology/

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rail crossings to maximize the economic benefit. There is, however, more interest

in entrainment systems now than at any time in the past 20 years and it is

increasingly likely that new barrage and lagoon developments will be seen,

especially in those locations which offer combination with transport

infrastructure. In a future in which energy costs are likely to rise and assuming

that low-cost nuclear fusion or other long-term alternatives do not make an

unexpectedly early arrival, then tidal barrage schemes could prove to be a major

provider of strategic energy in the late 21st century and beyond. The technology

for tidal barrage systems is already available and there is no doubt, given the

experience at La Rance, that the resource is substantial and available.

Full-scale prototype tidal-current systems are now being deployed. If these

schemes continue to prove successful, then the first truly commercial

developments will appear in the first decade of the 21st century. Tidal-current

systems may not yet have the strategic potential of barrage systems but, in the

short term at least, they do offer opportunities for supplying energy in rural,

coastal and island communities. In the longer term, massive sites such as the

Pentland Firth could become strategically important.

INDIAN SCENARIO:

Since India is surrounded by sea on three sides, its potential to hamess tidal

energy has been recognized by the Government of India. Potential sites for tidal

power development have already been located. The most attractive locations are

the Gulf of Cambay and the Culf of Kachchh on the west coast where the

maximum tidal range is 11 m and 8 m with average tidal range of 6.77 m and 5.23

m respectively. The Ganges Delta in the Sunderbans in West Bengal also has good

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locations for small scale tidal power development. The maximum tidal range in

Sunderbans is approximately 5 m with an average tidal range of 2.97 m. The

identified economic tidal power potential in India is of the order of 8000-9000

MW with about 7000 MW in the Gulf of Cambay about 1200 MW in the Gulf of

Kachchh and less than 100 MW in Sundarbans. The Kachchh Tidal Power Project

with an installed capacity of about 900 MW is estimated to cost about Rs. 1460/-

crore generating electricity at about 90 paise per unit. The techno-economic

feasibility report is now being examined.

ADVANTAGES OF TIDAL ENERGY:

The most important advantage of tidal energy is its economical benefits, as

tidal energy does not require any fuel. Tides rise and fall every day in a very

consistent pattern. The economic life of a tidal plant is very high. A plant is

expected to be in production for 75 to 100 years, in comparison with the 35 years

of a conventional fossil fuel plant. Besides the economical factors, tidal energy is

clean and renewable, unlike fossil fuels. Tidal energy offers a lot of potential to be

a substitute for hydrocarbon and fossil fuels. A very important feature of tidal

energy is that it is non-polluting. A tidal barrage can prevent approximately one

million tons of CO2 per TWH generated. A barrage can also safeguard coastlines

from storms.

DISADVANTAGES OF TIDAL ENERGY:

The altering of the ecosystem at the bay is the biggest drawback of tidal

power. Damages like reduced flushing, winter icing and erosion can change the

vegetation of the area and disrupt the balance. The alteration of tidal currents

affects the habitat of the seabirds and the fish. Similar to other ocean energies,

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tidal energy has several prerequisites that make it only available in a small

number of regions. For a tidal power plant to produce electricity effectively

(about 85% efficiency), it requires a basin or a gulf that has a mean tidal

amplitude (the differences between spring and neap tide) of 7 meters or above. It

is also desirable to have semi-diurnal tides where there are two high and low

tides every day. Tides out in the ocean have maximum amplitude of about one

meter. As you move closer to shore, this can increase to as high as 12 or more.

This can depend on local features such as shelving or funneling meaning the tidal

range can vary considerably along any given coastline. This can mean that a lot of

places just aren't suitable. When planning the location major consideration has to

be given to see whether the tides are high enough and if there is a suitable place

for building the site.

The Severn Mega-Barrage:

The ebb-tide generating scheme as drawn up by the Severn Tidal Power Group

(STPG) could deliver 17 terawatt hours per year (TWh/yr). A revised report was

published in 2002 for the DTI (STPG 2002). The scheme would deliver about 5% of

current England and Wales electricity consumption of 350 TWh/yr and cut 18

million tones CO2 per yr (from the UK's ~600 Mt CO2 per yr total).

Diurnal fluctuations could be smoothed out by a two-basin design, whereby

off-demand power is used to pump water into a higher second basin.

The DTI recommended this for further study. Operating the pair of basins to

meet the demand cycle gives electricity of much greater value. The timing issue

has been largely ignored for renewable, but will have to be taken into account for

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any large tidal scheme. If back-up power stations or storage systems are needed,

economic assessment will need to compare total system costs with a two-basin

design.

The Barrage proposed would stretch 10 miles from Lavernock Point, east of

Barry, to near Brean Down in Somerset, impounding an area of 185 square miles.

The scheme's embankment would pass between the two islands (Steep Holm and

Flat Holm) between which there is a deep channel. The Barrage would

incorporate locks to allow shipping and smaller craft to access the port at Bristol,

other docks and the river Severn. The proposed generating capacity (maximum

output) is 8.6 gigawatts (GW). To balance slack periods, it needs operating

together with our largest power station (Drax) cycling up and down (at the

maximum output from spring tides, it would require two such power stations to

cover the slack times).

The Shoots barrage scheme sited upstream of Bristol is sized at 1 GW, to

generate 2.75 TWh/yr (one sixth the mega-barrage). The capital cost is an eighth

and construction time a half of the mega-barrage. Other advantages claimed for it

by promoters PB Power (of Parsons Brinkerhoff Ltd.) are - no impacts on the

major ports (only on Sharpness), sufficient grid capacity (the mega-barrage

requires ~ 1.5 bn to reinforce the electricity grid), and suitable to carry a high-

speed rail link. The sedimentation problem is severe, but considered manageable

via a design with high turbines and limiting intake at storm times and spring tides.

The mega-barrage as a development project:

Protection against sea-level rise - the DTI assessment argues for multi-bn

benefits in terms of coastal protection. The Shoots Barrage would secure part of

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these benefits. However, present policy is for coastal retreat ('realignment') and

spending of ~600M on defences, so the Environment Agency has challenged the

DTI claims.

The mega-barrage is inevitably a large development project. As well as the

construction sites at each end, electrical substations with new National Grid lines

and a new road link are envisaged. Marinas and executive housing islands linked

to the barrage structure are also proposed. Prof. Brian Morgan (ex-Wales

Development Agency) promotes the concept of a seven side urban metropolis.

Some, if not all, of the CO2 saving would be absorbed in energy -hungrydevelopment and on-going activity.

Environmental studies so far indicate that tidal energy does not result in the

emission of gases responsible for global warming or acid rain associated with

fossil fuel generated electricity. Use of tidal energy could also decrease the need

for nuclear power, with its associated radiation risks. One concern is that the tidal

flows caused by damming a bay or estuary could, result in negative impacts on

the immediate environment. This is still unclear as very little is understood about

how altering the tides can affect incredibly complex aquatic and shoreline

ecosystems. However each specific site is different and the impacts depend

greatly upon local geography. Local tides changed only slightly due to the La

Rance dam, and the environmental impact has been negligible. It has been

estimated that in the Bay of Fundy, tidal power plants could decrease local tides

by 15 cm.

The negative environmental impacts of tidal barrages are probably much

smaller than those of other sources of electricity. Tidal energy has the power to

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generate significant amounts of electricity at suitable sites around the world. But

the potential is yet to be fully explored.

USES AND ECONOMY

The friction of the bulging oceans acting on the spinning earth results in a very

gradual slowing down of the earth's rotation but this is not expected to impact us

for billions of years. Therefore, for practical purposes, tidal energy can be

considered a sustainable and renewable source of energy. It can prove to be a

valuable source of renewable energy to an electrical system. The demand of

electricity from a grid varies with the time of the day. Tidal power, although

variable, is reliable and predictable and can make a valuable contribution to an

electrical system, which has a variety of sources. Tidal electricity provides a good

alternative to conventional methods of generating electricity, which would

otherwise be generated by fossil fuel (coal, oil, natural gas) etc, thus reducing

emissions of greenhouse and acid gases.

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Conclusion:

Tidal energy should be focused on for next generative fuel source, it is renewable

energy source with many potential benefits. There are many sites worldwide that

can use barrage open water turbine process. Tidal power has a potential to one-

day account for one fifth is our total consumption, so they never solve or current

energy dilemma. They could provide assistance, but never more than that-we

could not totally rely on this technology.

BIBILOGRAPHY:

Sites referred:

1] www.worldcollegs.info

2] www.darvill.clara.net

3] www.google.com
http://www.darvill.clara.net/http://www.darvill.clara.net/

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SEMINAR REPORT

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