POWER PRODUCTION

FROM

TIDAL ENERGY

WHAT IS A TIDE ? THE CONTINUOUS RISE

AND FALL OF WATER LEVEL IN ANY EARTH’S

WATER BODY IS CALLED A TIDE.

FORMATION OF TIDES IN OCEANS AND SEAS HAS IT’S ORIGIN FROM THE GRAVITATIONAL AT FORCE BINDING SUN ,MOON ,EARTH.

o When a landmass lines up with the earth-moon system, the water around it is at high tide.

o When a landmass is at 90 to the earth-moon ͦsystem, the water around it is at low tide.

o There are two high tides and two low tides during each period of rotation of the earth.

o Spring and Neap tides depend on the orientation of the sun, moon, and the earth.o High spring tides occur

when the sun and moon line up with the earth. This occurs whether they are either on same or opposite side.

o Low neap tides occur when the sun and moon line up at 90 ͦ to each other.

TIDAL FORCE IS THE VECTORIAL DIFFERENCE BETWEEN THE GRAVITATIONAL FORCE OF EARTH AND GRAVITATIONAL FORCE OF MOON.

THE DIFFERENCE IN THE HEIGHTS OF HIGH TIBE AND LOW TIDE IS CALLED TIDAL RANGE.

TIDAL FORCE AND TIDAL RANGE

ONE OF THE MOST RENEWABLE SOURCES OF ENERGY.

75% OF EARTH’S SURFACE IS COVERED WITH WATER.

UNTIL SUN AND MOON EXIST IN THEIR POSITIONS, TIDAL ENERGY IS INEXHAUSTABLE.

PROVIDES MECHANICAL ENERGY WHICH NEEDS TO BE CONVERTED INTO ELECTRICAL ENERGY.

IT IS PREDICTABLE.

TIDAL ENERGY- SOURCE OF ELECTRICITY

TIDAL POWER BUILDINGS WERE BUILT AS EARLY AS THE 9TH CENTURY THROUGHOUT EUROPE.THIS BUILDING WAS BUILT IN OHALO ,PORTUGAL CIRCA 1280.

787: Simple technique of a waterwheel by the Spanish, French, and British1966: “La Rance” tidal power plant went in operation.2001: British Parliament states “the world can no longer neglect the massive potential of wave and tidal energy”2002-present: Large investments in research and prototypes spark proposals in Turkey, China, and United States; among others

HISTORY OF HARNESSING TIDAL ENERGY

PREREQUISITS FOR INSTALLING A TIDAL POWER PLANT

ANY WATER BODY WITH CONSISTENT TIDE SUPPLY IS NEEDED.

SEVERAL ‘BAY’S ARE BEST SUITED AREAS.

SEVERAL ESTUARIES ALSO SERVE THE PURPOSE

WORLDWIDE - WAVE POWER RESOURCES

World Energy Council 2001 Survey stated the "potential exploitable wave energy" resources worldwide to be 2 TW. For European waters the resource was estimated to be able to cover more than 50% of the total power consumption.

The wave market is estimated at $32 billion in the United Kingdom and $800 billion worldwide.

The United States has exhibited weak effort compared to overseas projects in Norway, Denmark, Japan and the United Kingdom.

As of 1995, 685 kilowatts (kW) of grid-connected wave generating capacity was operating worldwide. This capacity comes from eight demonstration plants ranging in size from 350 kW to 20 kW.

Until recently the commercial use of wave power has been limited to small systems of tens to hundreds of watts aboard generate power

TIDAL ENERGY RESUORCES DISTRIBUTIONS

TYPES OF TIDAL POWER PLANTS

TIDAL BARRAGE SYSTEM TIDAL STREAM SYATEM

TIDAL BARRAGE

1.PRINCIPLE2.CONSTRUCTION

3.LA RANCE TIDAL POWER

PLANT

The basin is filled through the sluices and freewheeling turbines until high tide. Then the sluice gates and turbine gates are closed.

They are kept closed until the sea level falls to create sufficient head across the barrage and the turbines generate until the head is again low. Then the sluices are opened, turbines disconnected and the basin is filled again.

The cycle repeats itself.

PRINCIPLE

COSTRUCTION

HISTORY The first commercial tidal power plant in the world since the middle ages is the

La Rance Tidal Barrage in France.

The barrage was constructed in 1960 and consists of a 330m long dam with a 22km2 basin. The effective tidal range is 8m.

The work was completed in 1967 when 24 5.4m diameter bulb turbines, rated at 10MW each, were connected to the French power network with a 225kV transmission line.

Contains 24 reversible 10 MW bulb turbines generating a capacity of 240 MW and a net power output of 480 GWh per year

LA RANCE POWER PLANT

IMAGES OF LA RANCE TIDAL POWER PLANT

ENVIRONMENT OR ECOLOGICAL CONCERNS Tidal power generation can offer significant

advantages, including improved transportation due to the development of traffic or rail bridges across estuaries and reduced greenhouse gas emissions by utilizing tidal power in place of fossil fuels.

However there are also some significant environmental disadvantages which make tidal power, particularly barrage systems less attractive than other forms of renewable energy.

TIDAL CHANGES

The construction of a tidal barrage in an estuary will change the tidal level in the basin. This change is difficult to predict, and can result in a lowering or raising of the tidal level. This change will also have a marked effect on the sedimentation and purity of the water within the basin. In addition, navigation and recreation can be affected as a result of a sea depth change due to increased sedimentation within the basin. A raising of the tidal level could result in the flooding of the shoreline, which could have an effect on the local marine food chain.

ECOLOGICAL CHANGES

Potentially the largest disadvantage of tidal power is the effect a tidal station has on the plants and animals which live within the estuary. As very few tidal barrages have been built, very little is understood about the full impact of tidal power systems on the local environment. What has been concluded is that the effect due to a tidal barrage is highly dependent upon the local geography and marine ecosystem.

Wales have been caught in tidal generators. Fish may move through sluices safely, but when these are

closed, fish will seek out turbines and attempt to swim through them. Also, some fish will be unable to escape the water speed near a turbine and will be sucked through

SOCIAL IMPLICATIONS

During the construction of the barrage, human activity in the area will increase dramatically and continue to be high till completion. The La Rance tidal barrage in France took over 5 years to construct. The 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. The inundation would cause displacement of people, especially fishermen

TOTAL TIDAL BARRAGES

Site Mean Tidal Range (m)

Basin (sq-km)

Installed Capacity (MW)

Approx Output (GWh/yr)

In service (year)

La Rance (France)

8 17 240 540 1966

Kislaya Guba (Russia)

2.4 2 0.4 - 1968

Jingxia (China) 7.1 2 3.2 11 1980-86

Annapolis Royal (Canada)

6 6 17.8 30 1984

TTIDAL STREAM GENERATORS

1.PRINCIPLE

2.CONSTRUCTION

3.SEA GEN POWER PLANT

PRINCIPLE Extracts kinetic energy from

moving water generated by tides.

Operate during flood and ebb tides.

Consists of a rotor, gearbox, and a generator. These three parts are mounted onto a support structure. There are three main types: Gravity structure Piled structure Floating structure

CONSTRUCTION

TYPES OF TIDAL STREAM GENERATORS

TIDAL FENCES TIDAL TURBINES TIDAL LAGOONS

TIDAL FENCES

Tidal fences are composed of individual, vertical axis turbines which are mounted within the fence structure, known as a caisson.

Kind of like giant turn styles which completely block a channel, forcing all of the water through them.

Unlike barrage tidal power stations, tidal fences can also be used in unconfined basins, such as in the channel between the mainland and a nearby off shore island, or between two islands

TIDAL LAGOONS

Tidal lagoons are an adaptation of the barrage system. Similar to standard barrage models, tidal lagoons retain a head pond and generate power via conventional hydro-turbines.

The difference is that the conventional barrage designs exploit the natural coast line to minimize barrage length. However, this entails blocking the estuary regardless of how deep it is. This raise the costs considerably.

However, a lagoon, for a low cost can pretty much be built anywhere that there is a high tidal range.

The lagoon has relatively little visual impact, as it is below the high water tide mark and appears like a normal sea wall at low tide.

Proposed shortly after the oil crisis of the 1970s, tidal turbines have only become reality in the last decade, when a 10-15kW 'proof of concept' turbine was operated on Loch Linnhe. Resembling a wind turbine, tidal turbines offer significant advantages over barrage and fence tidal systems, including reduced environmental effects.

Tidal turbines utilize tidal currents that are moving with velocities of between 2 and 3 m/s (4 to 6 knots) to generate between 4 and 13 kW/m2. Fast moving current (>3 m/s) can cause undue stress on the blades in a similar way that very strong gale force winds can damage traditional wind turbine generators, whilst lower velocities are uneconomic.

TIDAL TURBINES

SEA GEN

World’s first large scale commercial tidal stream generator.

First one was installed in the Strangford Narrows (Ireland)

Generates 1.2MW between 18-20 hours a day

Blades span 16 meters in diameter

THUS THE LATTER ONE IS MORE PREFERRED

TIDAL BARRAGES TIDAL STREAM GENERATORS

Mature technology that has been around for nearly 50 years.

Reliable energy source. BUT High costs of construction Environmental impacts on

marine life Low power output in comparison

to other energy source like coal and nuclear power plants

Able to utilize both ebb and flood tides.

Tidal current turbines are not large massive dam structure.

BUT Tidal current turbine

technology is young in its development.

Installation and maintenance challenges.

Environmental impacts are still being tested.

COMPARISION OF BOTH THE TIDAL POWER PLANTS

Prospective sites for tidal energy projects

Country Country Mean tidal range (m)

Basin area (km2)

Installed capacity

(MW)

Approximate annual output

(TWh/year)

Annual plant load factor (%)

Argentina San José 5.8 778 5 040 9.4 21  Santa Cruz 7.5 222 2 420 6.1 29Australia Secure Bay 7.0 140 1 480 2.9 22  Walcott

Inlet7.0 260 2 800 5.4 22

Canada Cobequid 12.4 240 5 338 14.0 30  Cumberlan

d10.9 90 1 400 3.4 28

  Shepody 10.0 115 1 800 4.8 30India Gulf of

Kutch5.0 170 900 1.6 22

  Gulf of Khambat

7.0 1 970 7 000 15.0 24

UK Severn 7.0 520 8 640 17.0 23  Mersey 6.5 61 700 1.4 23USA Pasamaquo

ddy5.5        

  Knik Arm 7.5   2 900 7.4 29  Turnagain

Arm7.5   6 500 16.6 29

Russian Fed.

Mezen 6.7 2 640 15 000 45 34

  Tugur 6.8 1 080 7 800 16.2 24  Penzhinsk 11.4 20 530 87 400 190 25

POTENTIAL IN INDIA

Two estuaries on the west coast : Gulf of Cambay & Gulf of Kutch in Gujarat

Gulf of Kutch potential estimated to be 900 MW; annual output of 1.6 TWh

Potential of Gulf of Cambay : 7000 MW, basin area of 1970 sq-km, annual output of 15 TWh

Along east coast : Sunderbans in West Bengal

20 MW power estimated in regions of Dungaduani, Belladonna Creek & Pitts Creek

o Tidal Stream generators draw energy in the same basic way wind turbines do

o Higher density of water allows a single generator to provide significantly more power

o Water speeds of nearly 1/10 the speed of wind can provide the same energy output

o Current in water is much more reliable then wind in the air.

COMPARISION OF TIDAL ENERGY TO

WIND ENERGY

The cost of building a Tidal Power plant can have a high capital cost.

UK: $15 Billion8000MW

Philippines: $3 Billion2200MW

Operating costs are low and usually come from maintenance

ECONOMICS OF TIDAL POWER PLANT

ECONOMICS OF TIDAL POWER PLANT

Characterized by high capital costs per MW of installed capacity High payback period Annual operation & maintenance costs are typically less than 0.5 %

of initial capital Possible consumption of power locally & shorter construction times

for small schemes make them more economic compared to large ones

High capital costs & long construction time make tidal energy sensitive to discount rates

Non-energy benefits should be taken into account in assessing potential schemes

ADVANTAGES DISADVANTAGES No pollution Renewable resource More efficient than wind

because of the density of water

Predictable source of energy vs. wind and solar

Second generation has very few disadvantages Does not affect wildlife Does not affect silt deposits Less costly – both in building

and maintenance

Presently costly Expensive to build and maintain A 1085MW facility could cost as much

as 1.2 billion dollars to construct and run

Connection to the grid Technology is not fully developed Barrage style only produces

energy for about 10 hours out of the day

Barrage style has environmental affects

Such as fish and plant migration Silt deposits Local tides change- affects still under

study

CONCLUSION

Tidal energy is predictableTidal Energy is technologically developed Environmental impacts are lesserEconomics are difficult to get around These projects are capital intensiveAre people really willing to pay?