Tidal Energy

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basic of tidal energy

Text of Tidal Energy

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4/14/2015Footer text here TIDAL ENERGY4/14/2015Footer text hereAdvantages of Tidal Energy1) It is an inexhaustible source of energy.2) Tidal energy is environment friendly energy and doesn't produce greenhouse gases.3) As 71% of Earths surface is covered by water, there is scope to generate this energy on large scale.4) We can predict the rise and fall of tides as they follow cyclic fashion.5) Efficiency of tidal power is far greater as compared to coal, solar or wind energy. Its efficiency is around 80%.6) Although cost of construction of tidal power is high but maintenance costs are relatively low.7) Tidal Energy doesnt require any kind of fuel to run.8) The life of tidal energy power plant is very long.9) The energy density of tidal energy is relatively higher than other renewable energy sources.

4/14/2015Footer text hereDisadvantages of Tidal Energy1) Cost of construction of tidal power plant is high.2) There are very few ideal locations for construction of plant and they too are localized to coastal regions only.3) Intensity of sea waves is unpredictable and there can be damage to power generation units.4) Influences aquatic life adversely and can disrupt migration of fish.5) The actual generation is for a short period of time. The tides only happen twice a day so electricity can be produced only for that time.6) Frozen sea, low or weak tides, straight shorelines, low tidal rise or fall are some of the obstructions.7) Usually the places where tidal energy is produced are far away from the places where it is consumed. This transmission is expensive and difficult.

Origin and nature of tidal energy

The Low Tide

The High Tide


First tidal Power Plant was built by General De-Gaulle at La Rance in 1966.

Generates 240MW.

The average tidal range is 8.4m .

The maximum range is 13.5m.It is located in North-West France and it is the worlds largest tidal power plant till date.9Basic Principle of Tidal Power

During high tide, water will flow from sea to tidal basin through turbine, thus producing electricity. During low tide, water will flow from tidal basin to sea through turbine producing electricity.10Components of Tidal Power PlantThere are Three main Components:1.The Power House.2.The Dam or Barrage.3.Sluice-ways from the basin to the sea and Vice VersaThe Power House

The power house contains main equipment's like turbines and electric generators.12DAM or BARRAGE

The function of dam to form a barrier between the sea and the basin or between one basin and the other in case of multiple basins.13Sluice-ways

The sluice ways are used either to fill the basin during the high tide or empty the basin during the low tide, as per operational requirements.14Operation methods of utilization of Tidal Energy1.Single Basin arrangement2.Double Basin arrangementThe operational methods are classified in to types they are:-15Simple single Basin Tidal System

Here the power generation is intermittent and it is the simplest way to generate tidal power .16Single ebb-cycle system

When the high tide comes in, sluice gates are opened to permit sea-water to enter the basin , while the turbine sets are shut.17Single tide cycle system

18Double Cycle System

4/14/2015Footer text hereSingle Basin Scheme: This scheme has one barrage and one water storage basin, one way system, the incoming tide is allowed to fill the basin through sluice ways during the tide and the impounded water is used to generate electricity by letting the water flow from basin to the sea through the turbines during single basin schemes is intermittent generation power.

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4/14/2015Footer text hereTIDAL POWERTidal power works 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. Only around 20 sites in the world have been identified as possible tidal power stations.

4/14/2015Footer text hereTidal Energy

Tidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into useful forms of power - mainly electricity.

Tides are the waves caused due to the gravitational pull of the moon and also sun(though its pull is very low).

During high tide, the water flows into the dam and during low tide, water flows out which result in turning the turbine.

4/14/2015Footer text hereOcean tides are the periodic rise and fall of ocean water level occurs twice in each lunar day.

During one lunar day (24.83 H) the ocean water level rises twiceand fall twice.

Time interval between a consecutive low tide and high tide is 6.207 hrs.

Tidal range is the difference between the consecutive high tide and low tide.4/14/2015Footer text here

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Double Basin Scheme: In the double basin scheme, there are two basins on the landward side with the powerhouse located at the interconnecting waterway between the two basins4/14/2015Footer text hereTHE TIDAL BARRAGE Its a huge dam built across a river estuary. When the tide goes in and out, the water flows through tunnels in the dam.

4/14/2015Footer text here Tidal range has to be in excess of 5 meters for tidal power 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. As the tide recedes, gates in the barrage 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 Components of barrage- Turbines4/14/2015Footer text hereTypes of TURBINESBulb turbine

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.

4/14/2015Footer text here2. Rim turbinesWhen rim turbines are used, the generator is mounted at right angles 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.

4/14/2015Footer text hereThe 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. There are only a few commercially operating plants in the world, one of these is the La Rance barrage in France 3. Tubular turbines

4/14/2015Footer text herePOTENTIAL Total tidal energy potential worldwide estimated 500 1000 TWh/year

Only a fraction is exploitable owing to economics & other constraints Represents 3 7 % of total energy dissipated by tides

Has potential to contribute up to 10 12 % of the total energy obtained from renewable sources worldwide4/14/2015Footer text hereWORLD AT A GLANCE..

The darkened regions shows the potential sites4/14/2015Footer text herePOTENTIAL IN INDIATwo 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

4/14/2015Footer text herePLANT LOCATIONTidal mills built on inlets branching off tidal estuaries

Average Tidal range : the higher, the better

Feasibility of plant construction & basin closure

Environmental consequences 4/14/2015Footer text hereECONOMICSCharacterized 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

4/14/2015Footer text hereEnvironmental impact Local Impact


Volume of water exchanged between the basin and the sea is lesser, turbidity decreases Light from the Sun penetrates the water deeper


Again as a result of less water exchange with the sea, the average salinity inside the basin decreases, also affecting the ecosystem. Sediment movements

High volume of sediments moving through estuaries rivers to sea Barrage in estuary may result in sediment accumulation within the barrage4/14/2015Footer text here Pollutants

Reduced water volume - pollutants in basin are less efficiently dispersed. Increased bacteria content affects human life

Fish Fish will seek out turbines and attempt to swim through them. Fish mortality per pass is approximately 15% (from pressure drop, contact with blades, cavitation, etc.). Research in sonic guidance of fish is ongoing.

Global environmental impact A tidal power scheme is a long-term source of electricity. Severn Barrage is projected to save a million tons of coal per year of operation Decreases the output of greenhouse gases.

4/14/2015Footer text hereSOCIAL 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 t