Generation Of
Electricity
Through
Tidal Energy
Group Members
• Asad Saleh Hayat
• Umad Zaib
• Azmat Ullah
• Halim Ullah
• Sibghat Ullah
Power Generation
1.
2.
3.
4.
5.
6.
7.
Tidal
Hydro
Wind
Solar
Nuclear
Fuel fossils
Geothermal
What are Tides?
• The alternate rising and falling of the sea, usually twice in each lunar
day at a particular place, due to the attraction of the moon and sun.
• Tides originate in the oceans and progress toward the coastlines
where they appear as the regular rise and fall of the sea surface.
• Tides are one of the most reliable phenomena in the world.
What Is Tidal Power???
• The objective of tidal power is to convert the kinetic energy
of the waves of water, flowing in the sea to electric energy
via Generator.
• Tidal 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 tides.
• Extracts kinetic energy from moving water generated by
tides.
Energy from the moon
• Tides generated by the combination of the moon and sun’s
gravitational forces.
• Greatest affect in spring when moon and sun combine forces
• Bays and inlets amplify the height of the tide.
• In order to be practical for energy production, the height difference
needs to be at least 5 meters.
• Only 40 sites around the world of this magnitude.
• Overall potential of 3000 gigawatts from movement of tides.
History of Wave Energy
• 1799: First patent of a device designed to use ocean
waves to generate power
• 1910: First oscillating water column was built by
Bochaux-Praceique to power his house
• 1940s: Yoshio Masuda experimented with many
concepts of wave power
• 2004: Wave power was delivered to an electrical grid
for the first time
How it works
• First generation, barrage-style tidal power plants
• Works 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
How it works: Tidal Barrages
Tidal Barrage:
A series of Water Turbine
Parts of TPS
• Barrage
• Turbines
• Hydro Generator
Barrage
• 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.
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.
•Two types:
• Single basin system
• Double-basin system
Wave Power
Some Turbine Types
Bulb Type
Rim Type
•In systems with a bulb turbine, water flows around
the turbine, making access for maintenance difficult,
as the water must be prevented from flowing past the
turbine.
Tubular Type
•Rim turbines reduce these problems as the generator
is mounted in the barrage, at right angles to the
turbine blades. Unfortunately, it is difficult to regulate
the performance of these turbines and it is unsuitable
for use in pumping.
•Tubular turbines have been proposed for use some
UK projects. In this configuration, the blades are
connected to a long shaft and orientated at an angle
so that the generator is sitting on top of the barrage.
Tidal Turbines (cont.)
• ‘SeaFlow,’ a 300 kW prototype turbine was the world’s first offshore tidal
turbine and was installed off Lynmouth, Devon in May 2003.
Cost £3.4 million and was funded by a
consortium of private companies and the
UK and German governments.
Tidal Multiple Turbines
Underwater turbines are
by definition out of sight
and it is believed that
their environmental
impact is negligible
thanks to their slow
rotation rates of just 1030 revolutions per
minute 10 times slower
than that of ships
propellers). In addition,
tidal turbines do not
affect navigation or
shipping and so there
are no hidden extra
costs to consider.
Different Generator Types
• Tidal Fences
• Tidal Lagoons
• Tidal Turbines
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 Fences (cont.)
• “A 2.2GW tidal fence using the Davis
turbine, was being planned for the San
Bernadino Strait in the Philippines to be
constructed by the Blue Energy
company. The project, estimated to cost
$US 2.8 Billion is unfortunately on hold
due to political instability”
according to Michael Maser a Blue
Energy spokesman.”
Davis Hydro Turbine
http://www.bluenergy.com/
Tidal Fences (cont.)
• Since they do not require flooding
of the basin, tidal fences have
much less impact on the
environment, and are significantly
cheaper to install.
• Unlike barrage generators, tidal
fences have the advantage of
being able to generate electricity
once the initial modules are
installed.
• Since a caisson structure is still
required, which can disrupt the
movement of large marine animals
and shipping, there are still
ecological concerns
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 hydroturbines.
• 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.
-Tidal Stream Generators• Very close in concept to traditional windmills
• Most popular prototype on the market
• Prototype sites include Norway, England, and New York.
• In 2007 8 prototype turbines where placed in the East River
between Queens and Roosevelt Island.
• It is the first major tidal power project in the USA.
Tidal Turbines
• 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 (cont.)
•
•
•
•
Tidal turbines offer significant
advantages over barrage and fence
tidal systems (and other renewable
energy sources):
High energy intensity: A 1MW tidal
turbine can access five to ten times as
much energy per square meter of rotor
than a 1MW wind turbine, resulting in a
smaller and potentially lower cost
machine.
Minimal environmental impact: tidal
turbines are visible enough to be
avoided by mariners but they have a
low visual impact on the seascape, they
produce no pollution or noise and their
slow moving rotors which turn at less
than one revolution in four seconds (15
rpm) are considered unlikely to harm
marine life.
High energy return on energy
invested: tidal turbines should offer
faster energy payback than most other
renewables.
-Comparison to Wind Energy• Tidal Stream generators draw energy in the same basic way wind
turbines do
• Higher density of water allows a single generator to provide
significantly more power
• Water speeds of nearly 1/10 the speed of wind can provide the
same energy output
• Current in water is much more reliable then wind in the air.
Environmental/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.
La Rance, France (240MW)
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.
240MW La Rance France
-SeaGen• 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
•http://www.energysavers. gov/renewable_energy/ocean/index.cfm/mytopic=50009
-Calculations: Tidal Stream Generators-
P = the power generated (in watts)
ξ = the turbine efficiency
ρ = 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
*Power equation is based on the kinetic energy of the moving water*
Future Expansion of Tidal Turbines
• Tidal Farms. Sets of up to hundreds
of tidal turbines working in
conjunction.
• Potential for giga-watts of power
• Marine Current Turbine (MCT)
created SeaFlow (300kW), is
following up with SeaGen (1MW),
which will expand to a 5 turbine tidal
farm that will provide 5MW.
• The Norwegian company,
Hammerfest Strom, believes that
they will have their first tidal farm of
over 20 second generation devices
operational before the end of 2008.
This would be the 3rd phase of their
'Blue Concept' project and would
result in a tidal farm that would
produce 10MW of renewable
electricity.
Advantages
• 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
Disadvantages
• 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
Pros and cons of both tidal power facilities
Tidal Barrages
•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
Tidal Current Turbines
•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.
Conclusions
• Tidal power is a renewable, potentially zero emission (during operation)
energy source.
• Tides have the advantage of being completely predictable, unlike solar and
wind power.
• Different types of Tidal Generators suit different areas and energy needs.
• There are environmental concerns that need to be addressed when
developing this technology further.