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