This document discusses underwater windmills, also known as tidal stream turbines, which harness the kinetic energy of moving underwater currents in a similar way that wind turbines use moving air. It provides background on the history and development of tidal stream turbines, including the first prototypes launched in the 1990s and 2000s in Scotland, England, and other locations. The document also describes the different types of underwater wind turbines, including horizontal axis and vertical axis designs, and discusses India's tidal energy potential, focused on locations in Gujarat and West Bengal. Initial tidal power project attempts and reports from the 1980s-2000s are also summarized.

1. REPORT ON
UNDER WATER WINDMILL
BY
Y B N

2. INDEX
CONTENTS
1. INTRODUCTION
2. LITRATURE SURVEY
3. HISTORY
4. TIDAL ENERGY
5. UNDERWATER WINDMIL
5.1 DEFINATION
5.2 PRINCIPLE
5.3 WORKING
6. TYPES OF UNDERWATER WIND TURBINES
6.1 HORIZONTAL AXIS TURBINE
6.2 VERTICAL AXIS TURBINE
7. INDIAN TIDAL ENERGY SCENARIO
7.1 TIDAL ENERGY POTENTIAL IN INDIA
8. TIDAL POWER PROJECTS IN INDIA
8.1 DEMONSTRATION PROJECT AT SUNDERBANS
8.2 TIDAL POWER PROJECTS IN GULF OF KUTCH, GUJARAT
9. MERITS AND DEMERITS OF UNDERWATER WINDMILL
9.1 MERITS
9.2 DEMERITS
10.MAINTENANCE OF UNDERWATER WINDMILL
11.CONCLUSION
12.REFERENCES

3. 1. INTRODUCTION
Tidal energy is one
of many forms of
hydropower generation.
It 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 tides. The tide
moves a huge amount of
water twice each day.
Tidal stream turbines are often described as underwater windmills. They are
driven by the kinetic energy of moving water in a similar way that wind turbines use
moving air. The generator is placed into a marine current that typically results when
water being moved by tidal forces comes up against, or moves around, an obstacle
or through a constriction such as a passage between two masses of land. There are
sufficient numbers of such fast-flowing underwater currents around the world to
make this form of marine renewable energy worth the UK‟s electricity supply by
2030.
Tidal currents are being recognized as a resource to be exploited for the
sustainable generation of electrical power. The high load factors resulting from the
fluid proper- ties and the predictable resource characteristics make marine currents
particularly attractive for power generation. These two factors makes electricity
generation from marine currents much more appealing when compared to other
renewables. Marine current turbine (MCT) installations could also provide base grid
power especially if two separate arrays had offset peak flow periods. This
characteristic dispels the myth that renewable energy generation is unsuitable on a
large scale.

4. 2. LITRATURE SURVEY
• Tidal Energy in Electric Power Systems by Shabana Sheth, and Mohammad
Shahidehpour, IEEE. This paper discusses the uses and advantages of tidal
energy in restructured power systems. The paper defines the resources as well
as the ways in which tidal energy is converted into electricity. The paper also
reviews a few tidal power projects around the world. It also shows the
working of hydro tidal power plant. A comparative review of renewable
energy sources is presented and conclusions are outlined.
• Reassessment of tidal energy potential in India and a decision-making tool for
tidal energy technology selection by K Murali and V Sundar, TIJOCS 2017,
From this article we got a detailed review of available tidal energy conversion
technologies and case studies, with specific focus on tidal power potential in
India.
• Tidal Energy: Technologies and Recent Developments, by Dr. Zhao Yong
and Dr. Su Xiaohui,, IEEE. In this pape several technological issues in the
design, analysis, testing and optimization of different types of tidal stream
turbines are discussed in detail.
• Tidal Energy: A Review by Vikas M, Subba Rao, Jaya Kumar Seelam,NITK
2016. In this paper, the tides at some locations across the world and along the
Indian coast, tidal power plants across the world, resource allocation of tidal
power plants, advantages and disadvantages of tidal power will be reviewed
from the literature

5. 3. HISTORY
Two British consultants have developed an underwater pump that can irrigate
riverside fields without using fuel or causing pollution. The prize-winning turbine
is easy to construct and can work continuously. Originally designed to harness the
energy of the Nile to irrigate the desert areas of Sudan, the pump has a three-blade
rotor that utilizes the energy of moving water, just as a windmill uses wind. The
underwater pump can be operated by a single person with little training.
Researchers launched the first offshore tidal energy turbine on Monday. The
rotor on the English coast uses the power of the tides to generate electricity. Just the
beginning: The first "farm" of tidal turbines could spring up off the English coast
within years.
Imagine taking a windmill, turning it
on its side and sinking it in the ocean. That
in effect is what engineers have done in the
Bristol Channel in England. The aim is to
harness the energy the tide produces day in,
day out. In 1994 the world's first Prototype
tidal energy turbine was launched in Loch
Linnhe, off the west coast of scotland. In
May 2003 the "Sea flow" installation was
built into the seabed about one and a half
kilometers (one mile) off the Devon coast,
England. Above the surface, only a white
and red-striped tower is visible.
Beneath, 20 meters down, the single 11-meter long rotor turns up to 17 and a
half times a minute at a maximum speed of 12 meters per second, drawing energy
from the water's current. The €6 million ($7 million) project's supporters which
include the British and German governments and the European Union hope that tidal
turbines may one day be a further source of energy. Unlike sun and wind energy,
tidal energy is reliable, since it's not affected by the weather.
Sea flow can generate around 300 kilowatts, while rotors developed in the
future should be able to produce a megawatt. The new facility is pegged to be linked
to Britain's national grid in August, and a second rotor is to be added by the end of
2004. Marine Current Turbines (MCT), which operates Sea flow, estimates that 20
to 30 percent of British electricity needs could be provided by the new technology.

6. 4. TIDAL ENERGY
Tidal power is a consequence of Sun's and Moon's gravity forces. For now,
there is no major commercial exploitation of this energy, despite of its big potential.
This energy can be gained in places where sea changes are extremely emphasized
(for instance some places have difference between high tide and low tide bigger
then10 meters). The principle is quite simple and very similar to the one of the water
power plant. On the entrance to some gulf, escarpment is built and when the level
of the water rises, water leaks across the turbine in to a gulf. When gulf is filled with
the water escarpment is sealed and after the level of the water falls the same principle
is being used to direct water out of the gulf. In more simple case water leaks through
turbines in only one direction, and in this case turbines are less complicated
(unilateral, not bilateral).
La Rance Tidal Power station Delta river
The biggest problems of this use of energy are vicissitude of tidal power (wait
the sufficient level of the water to rise enough, or to fall enough) and small number
of places suitable for using this energy source. The most famous power plant is the
one on the river Rance delta in France (picture) built in 1960 and still functional.
Russia has build small power plant near city of Murmansk, Canada in gulf Fundy,
China small number of them, but neither of this countries has made any significant
progress. Alternative method of use relates to the location of power plants in sea
ravines where to canalizing tidal energy its energy increases, and underwater
turbines similar as the ones of the wind power plants would be used as the generator
machinery. Energy of the sea currents is also planned to be used in the same way,
but this technology is still in very early phase.

7. 5. UNDERWATER WINDMILL
5.1 DEFINITION
Tidal stream turbines
are often described as
underwater windmills. They
are driven by the kinetic
energy of moving water in a
similar way that wind
turbines use moving air. The
generator is placed into a
marine current that typically
results when water being
moved by tidal forces comes
up against, or moves around,
an obstacle or through a
constriction such as a
passage between two masses
of land. There are sufficient
numbers of such fast -
flowing underwater currents
around the world to make this form of marine renewable energy worth pursuing.
It can also be defined as, Energy derived from the moon that now helps to
power a small arctic village. An Underwater windmill-like device gets power from
the tides. The gravitational pull of the moon produces a swift tidal current, which
courses through the channel and spins the long blades of the turbine.

8. 5.2 PRINCIPLE
Underwater turbines operate on the same principles that wind turbines. These
turbines use a flow of fluid moves a set of blades creating mechanical energy which
is then converted to electrical energy. They are equally troublesome for
environmentalists, as wind turbines interrupt bird flights just as water turbines
can disturb underwater life. One advantage water turbines enjoy over other sources
of renewable energy is a predictable tide table.
MCT's ocean energy
device works on the same
principles as a windmill,
where large underwater rotors,
shaped like propellers, are
driven by the huge mass of
flowing water to be found at
certain places in the sea. The
technology consists of rotors
mounted on steel piles (tubular
steel columns) set into a socket
drilled in the seabed. The
rotors are driven by the flow of water in much the same way that windmill rotors are
driven by the wind, the main difference being that water is more than 800 times as
dense as air, so quite slow
velocities in water will generate
significant amounts of power.
The energy generated, being
derived from tides has the added
significant advantage of being
predictable.
Tower can be higher as
energy distributed by cable
rather than a shaft (energy in the
wind is proportional to the cube of it's speed) for water pumping the tower does not
have to be directly over the source - easier to be lowered for maintenance or when
wind speeds may get too high.

9. 5.3 WORKING
Underwater turbines rely on tides to push water against angled blades, causing
them to spin. These turbines can be placed in natural bodies of water, such as harbors
and lagoons that naturally feature fast-moving flows of water. These turbines must
be able to swivel 180 degrees to accommodate the ebb and flow of tides, as
demonstrated by the SeaGen prototype turbine in Ireland. As the blades spin, a
gearbox turns an induction generator, which produces an electric current. Other
devices can be tethered and attached to a float, such as the Evopod in England. This
design allows the face of the turbine to always face the direction of the current, much
like a moored boat does.
Many wave power machines are
designed to capture the energy of the
wave's motions through a bobbing buoy-
like device. Another approach is a
Pelamis wave generator, now being
tested in Scotland and in Portugal, which
transfers the motion of surface waves to a
hydraulic pump connected to a generator.
Tidal power typically uses underwater spinning blades to turn a generator,
similar to how a wind turbine works. Because water is far more dense than air,
spinning blades can potentially be more productive than off-shore wind turbines for
the same amount of space
There are only a few
underwater turbines in operation
today and they all operate like
underwater windmills, with their
blades turning at right angles to
the flow of the water. In contrast,
the Oxford team's device is built
around a cylindrical rotor, which
rolls around its long axis as the
tide ebbs and flows. As a result, it
can use more of the incoming
water than a standard underwater
windmill.

10. The first commercial-scale tidal stream energy system has achieved a new
milestone of 5 gigawatt-hours (GWh) of tidal power generation since starting
operation at Strangford Lough in Northern Ireland. That equals the annual power
consumption of 1,500 British households. The Siemens-owned system is one of the
largest tidal stream power projects today.
6. TYPES OF UNDERWATER WIND TURBINES
6.1 HORIZONTAL AXIS TURBINE
The Marine Current Turbine (MCT)
project: Figure shows hybrid
illustrations of the Sea flow turbine. It
has a single 11 m diameter rotor, with
full span pitch control, and is installed
in a mean depth of seawater of 25 m
approximately. It has exceeded its 300
kW rated power under favourable flow
conditions with a 15 rpm rotor speed.
A key feature is that it is mounted on a
steel tubular pile, 2.1 m in diameter,
set in a hole drilled in the seabed and
tall enough to always project above the surface of the sea. The entire rotor and power
system can be physically raised up the pile above the surface to facilitate
maintenance or repairs from a boat. MCT Second project was Seagen. The Seagen
turbine has its rotors mounted at the outer ends of a pair of streamlined wing-like
arms projecting either side of the supporting pile. Each rotor drives a power-train
consisting of a gearbox and generator each rated at around 500 kW. The total rated
power is approximately 1 MW. Essentially the Seagen turbine produces three times
the power of Sea flow. The Seagen project will be followed by an array of similar
systems (farm) to be installed in an open sea location. Three turbines will be added
to provide a total capacity up to 5 MW.

11. 6.2 VERTICAL AXIS TURBINE
Turbines Vertical axis turbines that
operate in marine currents are based on the
same principles as the land based Darrieus
turbine. The Darrieus turbine is a cross flow
machine, whose axis of rotation meets the
flow of the working fluid at right angles. The
vertical axis design permits the harnessing of
tidal flow from any direction, facilitating the
extraction of energy not only in two
directions, the incoming and outgoing tide,
but making use of the full tidal ellipse of the
flow. In this kind of turbines as in the horizontal axis ones the rotation speed is very
low (around 15 rpm).
7. INDIAN TIDAL ENERGY SCENARIO
Tidal Energy is one of the new and emerging technologies, which is
commercially not viable and still in Research & Development (R&D) stage. India
has a long coastline with the estuaries and gulfs where tides are strong enough to
move turbines for electrical power generation.
The Gulf of Cambay and the Gulf of Kutch in Gujarat on the west coast have
the maximum tidal range of 11m and 8m with average tidal range of 6.77m and
5.23m respectively. The Ganges Delta in the Sundarbans is approximately 5m with
an average tidal range of 2.97m.
No tidal power generation plant has been installed in India due to its high cost
of generation of electricity and lack of techno economic viability.

12. 7.1 TIDAL ENERGY POTENTIAL IN INDIA
In 1975, studies were carried out by the erstwhile Central Water and Power
Commission (CWPC). As per the studies, the Gulf of Kutch and Gulf of Cambay in
Gujarat and Sunderbans area in West Bengal are the only potential sites in India for
the development of Tidal Energy Projects.
In eighties, Central Electricity Authority (CEA) undertook a study for the
assessment of tidal energy potential in India. According to the study, the identified
economic power potential is of the order of 8000 MW with about 7000 MW in the
Gulf of Cambay, about 1200 MW in the Gulf of Kachchh in the State of Gujarat and
about 100 MW in the Gangetic Delta in the Sunderbans region in the State of West
Bengal.
Tidal Energy Potential in India
Region State Tidal Potential (MW)
Gulf of Cambay (Khambhat) Gujarat 7000
Gulf of Kutch Gujarat 1200
Gangetic Delta, Sunderbans West Bengal 100
8. TIDAL POWER PROJECTS IN INDIA
Initial attempts to
establish tidal power plants in
India were made in 1980s.
Project reports on tidal power in
Panchapada River in Balasour
District of Odisha and in the
Andaman & Nicobar Islands
were prepared in the years 1983
and 1992 respectively. A
detailed Project Report for a 3
MW Tidal Power Plant at
Durgaduani creek in Sundarbans
area was also prepared

13. 8.1 DEMONSTRATION PROJECT AT SUNDERBANS
The West Bengal Renewable Energy Development Agency (WBREDA)
submitted a Detailed Project Report (DPR) in 2001 for setting up a 3.65 MW
capacity tidal power project at Durgaduani Creek in Sundarbans Island of West
Bengal. This report was examined by an Expert Group and WBREDA was advised
to obtain required statutory clearances and revise the cost estimates. These details
were submitted to the Ministry in June, 2006. The revised estimated cost submitted
for the project was INR 40.15 crores.
Also, WBREDA entered into a MoU with the National Hydroelectric Power
Corporation Limited (NHPC), Faridabad for updating of the DPR (Detailed Project
Report) and its execution. The updated DPR prepared by NHPC was received by the
Ministry in November, 2007.
As per this DPR, the project capacity was raised to 3.75 MW (earlier it was
3.65 MW) with cost projections of INR 53.98 crores and project completion period
of 33 months from the date of sanction. The Ministry has agreed to it in principle.
In February 2008, under the Tidal Energy Programme, the Ministry of New &
Renewable Energy (MNRE) sanctioned a demonstration project for setting up a 3.75
MW tidal power plant at Durgaduani Creek in Sunderbans, West Bengal.
The NHPC Limited was given responsibility to execute the project. The total
estimated project cost was INR 48 crores, out of which 90% (INR 43.20 crores) was
to be shared by the MNRE and the remaining 10% (INR 4.80 crores) by the
Government of West Bengal.
However, the project has been discontinued due to very high tender cost
amounting to INR 238 crores against originally estimated cost of INR 48 crores.
8.2 TIDAL POWER PROJECTS IN GULF OF KUTCH, GUJARAT
Tidal Power Project (900 MW) in Kutch
A committee was constituted under the Central Electricity Authority (CEA)
on the 900 MW Kutch Tidal Power Project for estimating the cost of the project. A
techno-economic feasibility study was carried out by the CEA in 1988 for a 900
MW Tidal Power Project. A revised estimate of INR 6184 crores was worked out
for the execution of this project in 1993.

14. A feasibility study for setting up this power project in Kutch district of Gujarat
was conducted by National Hydro Power Corporation Ltd. (NHPC) in the early
nineties. However, the project was not found to be commercially viable due to high
capital cost as well as high cost of generation of electricity.
Mandavi Tidal Power Project (250 MW) in Kutch
In January 2011, Government of Gujarat signed a Memorandum of
Understanding (MoU) for establishing a 250 MW tidal power project in Gulf of
Kutch with Gujarat Power Corporation Ltd. (GPCL) Vadodara, Atlantis Resource
Corporation, United Kingdom and Perfect Mining Energy Solutions (PMES),
Singapore.
A Special Purpose Vehicle was incorporated in May, 2011 and GPCL has
taken up a 50 MW tidal power project at Mandavi in district Kutch in the first phase.
GPCL has made a request for grant of INR 1035 crores for the tidal power plant to
Ministry of New and Renewable Energy (MNRE).
9. MERITS AND DEMERITS OF UNDERWATER WINDMILL
9.1 MERITS
• Tidal and ocean current is completely renewable.
• Tidal and ocean current produces no emissions.
• Hidden beneath the water.
• Have lesser impact on the environment
• Low running cost
• Long lifetime with little maintenance
• Reduces the dependence upon fossil fuels
9.2 DEMERITS
• The initial cost is too high
• Very difficult to install
• The blade must be coated to avoid corrosion
• Damages habitat up to 500km away

15. 10. MAINTENANCE OF UNDERWATER WINDMILL
Maintenance of the device
while it is submerged in fast
currents would be exceptionally
challenging and expensive, so a
key patented feature of the
technology is that the rotor and
drive train (i.e. gearbox and
generator) can be raised
completely above the surface.
Once raised, any maintenance or
repairs can readily be carried out
from the structure Attended by a
surface vessel.
The world's largest tidal
power project, Meygen in Pentland
Strait in northern Scotland, has
gained green light. In February, the
construction of the power plant
will begin, which will be the
world's first of its kind
11.CONCLUSION
Tides play a very important role in the formation of global climate as well as
the ecosystem for ocean habitants .At the same time tides are substantial sources of
clean renewable energy for the future human generation. Depilating oil reserves, the
emission of greenhouse gases by burning coal, oil and other fossil fuels as well as
the accumulation of nuclear waste from nuclear reaction will inevitably force people
to replace energy in the future. Tidal energy is one of the best candidates for this
approaching revolution.

16. 12.REFERENCES
1. Tidal Energy in Electric Power Systems IEEE Research paper
2. Reassessment of tidal energy potential in India and a decision-making tool for
tidal energy technology selection by K Murali and V Sundar, TIJOCS 2017
3. International Research Journal of Engineering and Technology (IRJET)
4. Tidal Energy: Technologies and Recent Developments, by Dr. Zhao Yong
and Dr. Su Xiaohui,, IEEE.
5. Tidal Energy: A Review by Vikas M, Subba Rao, Jaya Kumar Seelam,NITK
2016