International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue5- May 2013
Best Non Conventional Way of Generating Electrical
Power by Using Tidal Energy
S.Bhargav reddy1, B Ashwini Kumar
2
1
2
ME, KLUNIVERSITY, INDIA
Asst. Professor, ME, KLUNIVERSITY, INDIA
Abstract— In the present world there is a lot of increase in
energy demand. It is time for us to come up with innovative
solutions as we are going short of our available resources.
Though the utilization of tidal energy is very less compared to
other available resources at present, it is going to double in
future. Although not yet widely used, tidal power has potential
for future electricity generation. Tides are more predictable than
wind energy and solar power. It describes tidal power and the
various methods of utilizing tidal power to generate electricity.
The paper also focuses on the potential this method of generating
electricity has and why this could be a common way of producing
electricity in the near future.
When a landmass is at 90 ͦ to the earth-moon system, the water
around it is at low tideThere are two high tides and two low
tides during each period of rotation of the earth.
Spring and Neap tides depend on the orientation of the sun,
moon, and the earth.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.Low neap tides occur when
the sun and moon line up at 90 ͦ to each other.
Flood Currents: currents moving in the direction of the
coast.Ebb Currents: the current receding from the coast
Keywords—.tidal power, tidal barrage, tidal current turbines
Different types of tidal plants
First generation, barrage-style tidal power plantsWorks by building
Barrage to contain water after high tide, then water has to pass
through a turbine to return to low tide
Sites in France (La Rance), Canada (Annapolis), and Russia
Future sites possibly on Severn River in England, San Francisco bay,
Passamaquoddy
I. INTRODUCTION
In the present world of increasing demand for energy
resources, it is crucial to come up with innovatory ideas to
reduce and conserve usage of energy. Tidal power also called
tidal energy is a form of hydro power that converts energy of
tides into electricity or other useful forms.Although not yet
widely used, tidal power has potential for future electricity
generation. Tides are more predictablethan wind energy and
solar power. Amongsources of renewable energy, tidal power
has traditionallysuffered from relatively high cost and limited
availabilityof sites with sufficiently high tidal ranges or flow
velocities,thus
constricting
its
total
availability.
However,many recent 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 maybe brought down to
competitive levels.
II What is tidal energy
Tidal energy comes from the gravitational forces of the Sun
and the Moon on the Earth’s bodies of water, creating periodic
shifts in these bodies of water .These shifts are called
tidesTidal power facilities harness the energy
from the
rise and fall of tides.
Ideal sites are located at narrow channels and experience high
variation in high and low tidesGravitational pull of the sun
and moon
and the pull of the centrifugal force of
rotation of the earth-moon system. When a landmass lines up
with the earth-moon system, the water around it is at high tide.
ISSN: 2231-5381
III How it works
Fig 1 Working of tides waves
1.Single basin system
a. Single ebb cycle system
b. Single tide cycle system
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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue5- May 2013
c. double cycle system
a.Ebb generation: During flood tide basin is filled and sluice
gates are closed , trapping water. Gates are kept closed until
the tide has ebbed sufficiently and thus turbines start spinning
and generating electricity.
b.Flood generation: The basin is filled through the turbine
which generate at flood tide.
c. double cycle system
Sluice gates and turbines are closed until near the end of the
flood tide when water is allowed to flow through the turbines
into the basin creating electricity.
At the point where the hydrostatic head is insufficient for
power generation the sluice gates are opened and kept open
until high tide when they are closed. When the tide outside the
barrage has dropped sufficiently water is allowed to flow out
of the basin through the turbines again creating electricity.
2.Double-basin system: There are two basins, but it operates
similar to en ebb generation, single-basin system. The only
difference is a proportion of the electricity is used to pump
water into the second basin allowing storage
force water through the generator, much like a traditional
hydropower dam.
1 Tidal Barrage
Utilize potential energy. Tidal barrages are typically dams built
across an estuary or bay consist of turbines, sluice gates,
embankments, and ship locks.
Fig 3 Tidal barrage
Facilities
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
2Tidal current turbines
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
Fig 4 Double basin system
IV Different Types of Tidal Plants
1. Tidal Barrages
These involve the creation of mammoth concrete dams with
sluices to create grander scale operations than the 12th century
tide mills.
2. Tidal Stream Generators
Very similar to the principles in wind power generation –
water flows across blades which turn a turbine much like how
wind turns blades for wind power turbines.
3. Dynamic Tidal Power
This is a technology that is not currently commercial viable,
but in which the UK, Korea, and China invested heavily to
research. It involves a partial dam which raises the tidal
height and several hydropower generators. The differences in
height between the head of the dam and the low tide coast
ISSN: 2231-5381
Fig 4 tidal current turbine
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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue5- May 2013
Facilities
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.
V Types of tidal stream generators
Since tidal stream generators are an immature technology,no
standard technology has yet emerged as the clear winner, but
large varieties of designs are being experimented with, some
very close to large scale deployment. Several prototypes have
shown promise with many companies making bold claims,
some of which are yet to be independently verified, but they
have not operated commercially for extended periods to
establish performances and rates of return on investments.
large scale tidal projects were considered. Today, sites
suitable for the utilization of tidal power exist in many places
around the world.
France
United Kingdom
Former Soviet Union
Canada
United States
The extraction of large quantities of tidal energy is
possible however, large scale tidal power operations are not
technologically or economically feasible at the present time.
Tidal sites are therefore limited to more modest developments.
VII The Future of Tidal Barrages
1 Energy calculations
Various turbine designs have varying efficiencies and
therefore varying power output. If the efficiency of the
turbine "p" is known the equation below can be used to
determine the power output of a turbine.
The energy available from these kinetic systems can be
expressed as:
Where:
= the turbine efficiency
P = the power generated (in watts)
= the density of the water (seawater is 1025 kg/m³)
A = the sweep area of the turbine (in m²)
V = the velocity of the flow
P=AV3/2
Relative to an open turbine in free stream, depending
on the geometry of the shroud shrouded turbines are capable
of as much as 3 to 4 times the power of the same
turbine rotor in open flow.
2 Resource assessment
While initial assessments of the available energy in a
Channel have focus on calculations using the kinetic energy
Flux model, the limitations of tidal power generation Are
significantly more complicated. For example, the maximum
physical possible energy extraction from a strait connecting
two large basins is given to within 10% by
P=0.22g
Hmax
Qmax
Where
 = the density of the water (seawater is 1025 kg/m³),
g =gravitational acceleration (9.81 m/s2), Hmax = maximum
differential water surface elevation across the channel,
Qmax= maximum volumetric flow rate though the channel.
VI Present use of Tidal Energy
Tidal power has on a small scale been used through out the
history of mankind. It was not until the twentieth century that
ISSN: 2231-5381
The Transverse Horizontal Axis Water Turbine (THAWT) has
been proposed as a tidal device which can be easily scaled and
requires fewer foundations, bearings seals and generators than
a more conventional axial-flow device. The THAWT device is
a horizontally deployed variant of the Darrieus cross-flow
turbine, in which the blades can be oriented into a truss
configuration to produce long, stiff multi-bay rotors. A fluid
particle passing through a Darrieus cross-flow turbine
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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue5- May 2013
encounters two sets of blades. One on the front side of the
turbine as the fluid enters, and again on the rear side as it
leaves. This increased stiffness and strength allows longer
units to be constructed, and reduces the overall costs of
foundations, bearings, seals and generators. A full scale
device might have a diameter of 10 – 20 m and would operate
in a flow depth of 20 – 50 m.The THAWT device employs a
truss design of blades, which is intended to increase the
rigidity of the structure, so that it can be stretched across a
channel without significant increases in blade stresses. The
Thawt device is mechanically far less complicated than
anything available today, meaning it would cost less to build
and maintain. "The manufacturing costs are about 60% lower,
the maintenance costs are about 40% lower”. The size of
thawt is not limited by the depth of water in which it is
situated, and the need to intersect the largest possible area of
current has been incorporated into the design. Power
generation of up to 100mw could be achieved by an array of
only 10 thawt devices. For comparison, if that devices were
extended across the same area of current as axial flow devices,
thawt would require:



Less generators,
Less primary seals, and
Less foundations
I would like to conclude that from the above discussion that
tidal power is renewable ,doesn’t cause pollution, and doesn’t
need any fuel. A tidal barrage is very expensive to build and
effects large area is the only disadvantage and there is very
few places that you could sensibly built a tidal barrage Iit
works when tide is going in or out .Under water turbine may
be better than barrage ,they are cheaper and wont have huge
environmental impact
[1]TIDALENERGYUPDATE2009
APPLIED ENERGY, VOLUME 87, ISSUE 2 , FEBRUARY 2010, PAGES 398-409
FERGAL O ROURKE, FERGAL BOYLE, ANTHONY REYNOLDS
Lower capital costs
Lower maintenance costs, and
Lower operational costs
VIII Example calculation of tidal power generation
Assumptions:
Let us assume that the tidal range of tide at a particular
place is 32 feet = 10m (approx)
The surface of the tidal energy harnessing plant is
4km² (2 km × 2 km) = 2000 m × 2000 m =4 × 10^6 m2
Density of sea water = 1025.18 kg/m3
Mass of the sea water = volume of sea water × density
of sea water
= (area × tidal range) of water × mass density
= (4 × 106m2 × 10 m) × 1025.18 kg/m3
= 41 × 109 kg (approx)
Potential energy content of the water in the basin at high
tide =½ × area × density × gravitational acceleration × tidal
range squared= ½ × 4 × 106m2 × 1025 kg/m3 × 9.81 m/s2 ×(10
m)2=2 × 1012 J (approx)
Now we have 2 high tides and 2 low tides every day. At
low tide the potential energy is zero.
Therefore the total energy potential per day = Energy
for a single high tide × 2
= 2 × 1012 J × 2
= 4 × 1012 J
Therefore, the mean power generation potential =
Energy generation potential / time in 1 day
= 4 × 1012 J / 86400 s
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IX. CONCLUSION
References
and consequently that would incur:



= 46 MW
Assuming the power conversion efficiency to be 30%:
The daily-average power generated = 46 MW * 30% /
100%
= 14 MW (approx)
Because the available power varies with the square of
the tidal range, a barrage is best placed in a location with
very high-amplitude tides. Suitable locations are found in
Russia, USA, Canada, Australia, Korea, and the UK. Amplitudes
of up to 17 m (56 ft) occur for example in the Bay
of Fundy, where tidal resonance amplifies the tidal range.
[2]http://www.travelandtransitions.com/stories_photos/evangeline_trail.htm
[3]http://www.emec.org.uk/
[4] Ocean Energy: Tide and Tidal Power by Roger H. Charlier
[5] Ocean Wave Energy: Current Status and Future Prespectives
(Green Energy and Technology) by Joao Cruz
[6] Ocean Wave Energy Conversion by Michael E. McCormick
[7] The Analysis of Tidal Stream Power by Jack Hardisty
[8] Developments in Tidal Energy: Proceedings of the Third Conference
on Tidal Power, Institution Of Civil Engineers (Contributor)
[9] Ocean, Tidal, and Wave Energy: Power from the Sea (Energy
Revolution) by Lynne Peppas
Acknowledgement
I would like to thank B Ashwini Kumar(asst professor) for for
his support, encouragement & valuable suggestions We would
like to thank him for motivating us to work on tidal power
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