HYDRO POWER
Energy Conversion
1
INTRODUCTION
Flowing water referred to as hydro power is the most widely used renewable energy source in
the world, a renewable energy source based on the natural water cycle. Hydropower is the most
mature, reliable and cost-effective renewable power generation technology available.
Hydropower schemes often have significant flexibility in their design and can be designed to meet
base-load demands with relatively high capacity factors, or have higher installed capacities and a
lower capacity factor, but meet a much larger share of peak demand.
Contains moving water on a huge inventory of natural energy, whether the water is part of a
running river or waves in the ocean. Think about the destructive power of the river beyond its
banks and cause in the huge waves on the shores of a shallow , then you may wish to imagine
the amount of energy that exist.
This energy can be harnessed and converted into electricity that not lead to the emission of
greenhouse gases. Also is a source of renewable energy because the water is constantly
replenished thanks to the hydrological cycle of the earth. All he needs the system to generate
electricity from water is a constant source of running water as the table or the river. Unlike solar
or wind power, water can generate power continuously and continuously, at a rate of 24 hours a
day.
To generate electricity, water must be in motion. This is kinetic (moving) energy. When flowing
water turns blades in a turbine, the form is changed to mechanical (machine) energy. The turbine
turns the generator rotor which then converts this mechanical energy into another energy form
electricity. Since water is the initial source of energy, we call this hydroelectric power or
hydropower for short.
Hydropower is the cheapest way to generate electricity today. That's because once a dam has
been built and the equipment installed, the energy source flowing water is free. It's a clean fuel
source that is renewable yearly by snow and rainfall. It is also readily available; engineers can
control the flow of water through the turbines to produce electricity on demand. In addition,
reservoirs may offer recreational opportunities, such as swimming and boating.
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History
Hydropower has been used by humans since ancient times. Been using the energy of falling water
by the Greeks to turn the water wheels that the transfer of mechanical energy to the grinding
stone to turn wheat into flour before more than 2000 years. In the 1700s, was the use of water
power on a large scale for the mechanical milling and pumping. As the water mills were operated
textile mills in Britain and New England at the beginning of the 19th century. And has resulted in
the development of the steam turbine managed to make the water more energy efficient.
Triple Noria (Wooden Water Wheel)
Began the modern era in the development of hydroelectric power in the late 19th, in 1870 when
it was installed the first hydroelectric power plant in Cragside, England. Was the home of British
inventor Lord Ermsturng, the first house Works powered hydroelectri. And has begun commercial
use of hydroelectric power in 1880 in Grand Rapids, Michigan, where he was Dynamo (Aqueous
turbine generator Brash) led water turbines used to provide storage and theater lighting front.
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This was a small hydroelectric power stations in the early capabilities by today's standards, but a
pioneer in the development of modern industry, hydropower and built hydroelectric power plant
at Niagara Falls in 1879. In 1881, it was powered street lamps in the city of Niagara Falls by
hydropower. In 1882 began the first hydroelectric power plant in the world working in the United
States in Appleton, Wisconsin. The dam on the Fox River in Appleton, Wisconsin, site of the first
electric power plant in the world of water. Then grown hydropower quickly. In 1886 there were
45 plants in the United States. In 1889, he appeared 200 lab produce electricity using the water
for some or all forms of energy.
At the same time, set up hydro-electric power plants around the world. The built Italy's first plant
in 1885 on the River Tivoli, in the mountains outside Rome. The lab provides the luminance of
the neighboring town in the first place. But in 1892 built another plant in the same location and
it provides energy to Rome, and was the first transfer of power over a long distance in Italy.
After a short time the other countries, good conditions for the construction of hydroelectric
power plants. The Canada, and France, and Japan, and Russia are among the first states in this
area. And the increasing use of hydroelectric power quickly in the period between (1900 to 1950).
When first built laboratories for hydropower, electricity was sent directly. This led to a limited
travel distance for electricity. Therefore, it was within the power plants provide about 2.6 square
kilometers from the dam. Can integrate the power of several separate laboratories in order to
serve the largest cities. The small towns are fortunate enough to be able to build a coefficient of
electrical system of its own. With the development of the current change in the late 1880s, it
became possible to move electricity over longer distances. I've become separate systems that
serve the cities is a huge one system. As has become laboratories in remote locations distant
cities provide energy - such as, Hoover Dam southwestern United States (built in 1936). Also
contributed hydraulic turbines best in this progress. However, after 1940, became cheap fossil
fuels is the primary source of electricity generation. We have continued to provide hydro-electric
power some of the world's electricity, but the use of oil and natural gas and coal outweigh the
use of water power.
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Hydropower
Hydroelectricity is the term referring to electricity generated by hydropower; the production of
electrical power through the use of the gravitational force of falling or flowing water. It is the
most widely used form of renewable energy, accounting for 16 percent of global electricity
generation, and is expected to increase about 3.1% each year for the next 25 years.
Large hydropower systems tend to be connected to centralised grids in order to ensure that there
is enough demand to meet their generation capacity. Small hydropower plants can be, and often
are, used in isolated areas off-grid or in mini-grids. In isolated grid systems, if large reservoirs are
not possible, natural seasonal flow variations might require that hydropower plants be combined
with other generation sources in order to ensure continuous supply during dry periods.
Hydropower is produced in 150 countries, with the Asia-Pacific region generating 32 percent of
global hydropower in 2010. China is the largest hydroelectricity producer, with 721 terawatthours of production in 2010, representing around 17 percent of domestic electricity use. There
are now three hydroelectricity plants larger than 10 GW: the Three Gorges Dam in China, Itaipu
Dam across the Brazil/Paraguay border, and Guri Dam in Venezuela.
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The cost of hydroelectricity is relatively low, making it a competitive source of renewable
electricity. Hydro is also a flexible source of electricity since plants can be ramped up and down
very quickly to adapt to changing energy demands. However, damming interrupts the flow of
rivers and can harm local ecosystems, and building large dams and reservoirs often involves
displacing people and wildlife. Once a hydroelectric complex is constructed, the project produces
no direct waste, and has a considerably lower output level of the greenhouse gas carbon dioxide
(CO2) than fossil fuel powered energy plants.
Efforts to ensure the safety of dams and the use of newly available computer technologies to
optimize operations have provided additional opportunities to improve the environment. Yet,
many unanswered questions remain about how best to maintain the economic viability of
hydropower in the face of increased demands to protect fish and other environmental resources.
Most hydroelectric power comes from the potential energy of dammed water driving a water
turbine and generator. The power extracted from the water depends on the volume and on the
difference in height between the source and the water's outflow. This height difference is called
the head. The amount of potential energy in water is proportional to the head. A large pipe
delivers water to the turbine.
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A typical hydro plant is a system with three parts: an electric plant where the electricity is
produced; a dam that can be opened or closed to control water flow; and a reservoir where water
can be stored. The water behind the dam flows through an intake and pushes against blades in a
turbine, causing them to turn. The turbine spins a generator to produce electricity. The amount
of electricity that can be generated depends on how far the water drops and how much water
moves through the system. The electricity can be transported over long-distance electric lines to
homes, factories, and businesses.
Hydropower is also readily available; engineers can control the flow of water through the
turbines to produce electricity on demand. In addition, reservoirs may offer recreational
opportunities, such as swimming and boating. But damming rivers may destroy or disrupt wildlife
and other natural resources. Some fish, like salmon, may be prevented from swimming upstream
to spawn. Technologies like fish ladders help salmon go up over dams and enter upstream
spawning areas, but the presence of hydroelectric dams changes their migration patterns and
hurts fish populations. Hydropower plants can also cause low dissolved oxygen levels in the
water, which is harmful to river habitats.
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Hydropower capacity factors
The capacity factor achieved by hydropower projects needs to be looked at somewhat differently
than for other renewable projects. For a given set of inflows into a catchment area, a hydropower
scheme has considerable flexibility in the design process. One option is to have a high installed
capacity and low capacity factor to provide electricity predominantly to meet peak demands and
provide ancillary grid services. Alternatively, the installed capacity chosen can be lower and
capacity factors higher, with potentially less flexibility in generation to meet peak demands and
provide ancillary services.
Hydropower Classification by type:
Run of river technologies
In run of river (ROR) hydropower systems (and reservoir systems), electricity production is
driven by the natural flow and elevation drop of a river. Run of river schemes have little or no
storage, although even run of river schemes without storage will sometimes have a dam.12 Run
of river hydropower plants with storage are said to have “pond age”. This allows very shortterm water storage (hourly or daily). Plants with pond age can regulate water flows to some
extent and shift generation a few hours or more over the day to when it is most needed. A
plant without pond age has no storage and therefore cannot schedule its production. The
timing of generation from these schemes will depend on river flows. Where a dam is not used,
a portion of the river water might be diverted to a channel or pipeline (penstock) to convey the
water to the turbine.
Run of river schemes are often found downstream of reservoir projects as one reservoir can
regulate the generation of one or many downstream run of river plant. The major advantage of
this approach is that it can be less expensive than a series of reservoir dams because of the
lower construction costs. However, in other cases, systems will be constrained to be run of river
because a large reservoir at the site is not feasible.
The operation regime of run of river plants, with and without pond age, depends heavily on
hydro inflows. Although it is difficult to generalize, some systems will have relatively stable
inflows while others will experience wide variations in inflows. A drawback of these systems is
that when inflows are high and the storage available is full, water will have to be “spilled”. This
represents a lost opportunity for generation and the plant design will have to trade off capacity
size to take advantage of high inflows, with the average amount of time these high inflows
occur in a normal year. The value of the electricity produced will determine what the trade-off
between capacity and spilled water will be and this will be taken into account when the scheme
is being designed.
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Hydropower schemes with reservoirs for storage
Hydropower schemes with large reservoirs behind dams can store significant quantities of
water and effectively act as an electricity storage system. As with other hydropower systems,
the amount of electricity that is generated is determined by the volume of water flow and the
amount of hydraulic head available.
The advantage of hydropower plants with storage is that generation can be decoupled from the
timing of rainfall or glacial melt. For instance, in areas where snow melt provides the bulk of
inflows, these can be stored through spring and summer to meet the higher electricity demand
of winter in cold climate countries, or until summer to meet peak electricity demands for
cooling. Hydropower schemes with large-scale reservoirs thus offer unparalleled flexibility to an
electricity system.
The design of the hydropower plant and the type and size of reservoir that can be built are very
much dependent on opportunities offered by the topography and are defined by the landscape
of the plant site. However, improvements in civil engineering techniques that reduce costs
mean that what is economic is not fixed. Reduced costs for tunneling or canals can open up
increased opportunities to generate electricity.
Hydropower can facilitate the low-cost integration of variable renewables into the grid, as it is
able to respond almost instantaneously to changes in the amount of electricity running through
the grid and to effectively store electricity generated by wind and solar by holding inflows in the
reservoir rather than generating. This water can then be released when the sun is not shining or
the wind not blowing.
Pumped Storage
pumped storage is a method of keeping water in reserve for peak period power demands.
Pumped storage is water pumped to a storage pool above the power plant at a time when
customer demand for energy is low, such as during the middle of the night. The water is then
allowed to flow back through the turbine-generators at times when demand is high and a heavy
load is place on the system.
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The reservoir acts much like a battery, storing power in the form of water when demands are low
and producing maximum power during daily and seasonal peak periods. An advantage of
pumped storage is that hydroelectric generating units are able to start up quickly and make rapid
adjustments in output. They operate efficiently when used for one hour or several hours.
Because pumped storage reservoirs are relatively small, construction costs are generally low
compared with conventional hydropower facilities.
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Biggest hydroelectric power plants in world
Three Gorges Dam, China
The Three Gorges Dam that spans the Yangtze River in Hubei province, China, is the world's largest
power station in terms of installed capacity (22,500 MW). Made of concrete and steel, the dam is 2,335
meters long and 181 meters tall. More than 102.6 million cubic meters of earth was moved to make
way for 27.2 million cubic meters of concrete and 463,000 tonnes of steel, enough to build 63 Eiffel
Towers. It cost the state US$ 22.5 billion to build the dam.
When the water level is at its maximum of 175 meters above sea level, which is 110 meters higher
than the river level downstream, the dam reservoir is on average about 660 kilometers in length and
1.12 kilometers in width, giving it an effective capacity of 39.3 km3 and 1,045 square kilometers of
surface area.
The Chinese government takes huge pride in the project, in its state-of-the-art large turbines, and its
move toward limiting greenhouse gas emissions, even though it displaced some 1.3 million people,
causing significant ecological changes as well as controversy both domestically and abroad.
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Itaipu Dam, Brazil and Paraguay
The Itaipu Dam is located on the Paraná River on the border between Brazil and Paraguay. Although
the dam has a capacity of 14,000 MW, lower than that of the Three Gorges Dam, it has a higher annual
yield generating an average of 91 ~ 95 TWh in comparison to 80 TWh by the latter. The plant supplies
90% of the electricity consumed by Paraguay and 19% of that consumed by Brazil.
The Itaipu Dam is actually four dams joined together from the far left, an earth fill dam, a rock fill dam,
a concrete buttress main dam, and a concrete wing dam to the right, giving it a total length of 7235
meters. To build this massive structure, the course of the seventh biggest river in the world had to be
altered, and 50 million tons of earth and rock had to moved. To give you an idea, the amount of
concrete used to build the Itaipu Power Plant would be enough to build 210 football stadiums; the iron
and steel used would allow for the construction of 380 Eiffel Towers and the volume of excavation of
earth and rock in Itaipu is 8.5 times greater than that of the Channel Tunnel.
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ADVANTAGES:
1. Once a dam is constructed, electricity can be produced at a constant rate.
2. If electricity is not needed, the sluice gates can be shut, stopping electricity generation. The water can
be saved for use another time when electricity demand is high.
3. Dams are designed to last many decades and so can contribute to the generation of electricity for many
years / decades.
4. The lake that forms behind the dam can be used for water sports and leisure / pleasure activities. Often
large dams become tourist attractions in their own right.
5. The lake's water can be used for irrigation purposes.
6. The build up of water in the lake means that energy can be stored until needed, when the water is
released to produce electricity.
7. When in use, electricity produced by dam systems do not produce green house gases. They do not
pollute the atmosphere.
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DISADVANATGES:
1. Dams are extremely expensive to build and must be built to a very high standard.
2. The high cost of dam construction means that they must operate for many decades to become
profitable.
3. The flooding of large areas of land means that the natural environment is destroyed.
4. People living in villages and towns that are in the valley to be flooded, must move out. This means that
they lose their farms and businesses. In some countries, people are forcibly removed so that hydro-power
schemes can go ahead.
5. The building of large dams can cause serious geological damage. For example, the building of the Hoover
Dam in the USA triggered a number of earth quakes and has depressed the earth’s surface at its location.
6. Although modern planning and design of dams is good, in the past old dams have been known to be
breached (the dam gives under the weight of water in the lake). This has led to deaths and flooding.
7. Dams built blocking the progress of a river in one country usually means that the water supply from the
same river in the following country is out of their control. This can lead to serious problems between
neighbouring countries.
8. Building a large dam alters the natural water table level. For example, the building of the Aswan Dam
in Egypt has altered the level of the water table. This is slowly leading to damage of many of its ancient
monuments as salts and destructive minerals are deposited in the stone work from ‘rising damp’ caused
by the changing water table level.
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Hydraulic Turbine
A hydraulic turbine converts the energy of flowing water into mechanical energy. A hydroelectric
generator converts this mechanical energy into electricity. The operation of a generator is based
on the principles discovered by Faraday. He found that when a magnet is moved past a
conductor, it causes electricity to flow. In a large generator, electromagnets are made by
circulating direct current through loops of wire wound around stacks of magnetic steel
laminations. These are called field poles, and are mounted on the perimeter of the rotor. The
rotor is attached to the turbine shaft, and rotates at a fixed speed. When the rotor turns, it causes
the field poles (the electromagnets) to move past the conductors mounted in the stator. This, in
turn, causes electricity to flow and a voltage to develop at the generator output terminals.
The generator consists of a large metal shaft in the center. At the bottom end of the shaft are a
series of blades, sort of like a giant propeller. The water from the dam is directed into those
blades through a group of slots called wicket gates. The wicket gates are designed so that the
greatest amount of water will strike the turbine blades without creating too much turbulence.
At the top end of the generator shaft is the rotor assembly which is a series of wire coils. As the
shaft turns the wires through a magnetic field an electrical current is created.
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Impulse Turbines and Reaction Turbines
A) Impulse Turbines:
In an impulse turbine, a fast moving fluid is fired through a narrow nozzle at the turbine
blades to make them spin around. The blades of an impulse turbine are usually bucket
shaped so they catch the fluid and direct it off at an angle or sometimes even back the
way it came (because that gives the most efficient transfer of energy from the fluid to the
turbine). In an impulse turbine, the fluid is forced to hit the turbine at high speed. Imagine
trying to make a wheel like this turn around by kicking soccer balls into its paddles. You'd
need the balls to hit hard and bounce back well to get the wheel spinning and those
constant energy impulses are the key to how it works. Water turbines are often based
around an impulse turbine (though some do work using reaction turbines), works as
follows:
a.
b.
c.
d.
It runs by impulse of water.
Nozzle directs the water on the curved blades, which causes them to rotate.
The blades are in the shape of buckets.
The energy to rotate an impulse turbine is derived from the kinetic energy of the
water flowing through the nozzle.
e. The potential energy is converted into kinetic energy when it passes through the
nozzle.
f. The velocity of water is reduced when it passes over the blades.
B) Reaction turbines:
In a reaction turbine the runners are fully immersed in water and are enclosed in a
pressure casing. The runner blades are angled so that pressure differences across them
create lift forces, like those on aircraft wings, and the lift forces cause the runner to
rotate).
It has no nozzle, Two rows of moveable blades are separated by one row of fixed blades,
Fixed blades are attached to the casing and act as nozzles, Blades are like the wings of a
plane, Velocity of steam is increased when it passes through the fixed blades, The
enthalpy drop in moving blades is called degree of reaction, A common arrangement can
have 50% of enthalpy drop in moving blades, it is said to have 50% reaction, If all enthalpy
drops in moving blades then it is said to be 100% reaction.
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Difference between impulse and reaction turbine:
Types of turbines
1. Pelton Turbines:
The Pelton Turbine has a circular disk mounted on the rotating shaft or rotor. This circular disk
has cup shaped blades, called as buckets, placed at equal spacing around its circumference.
Nozzles are arranged around the wheel such that the water jet emerging from a nozzle is
tangential to the circumference of the wheel of Pelton Turbine. The high speed water jets
emerging form the nozzles strike the buckets at splitters, placed at the middle of a bucket, from
where jets are divided into two equal streams. These stream flow along the inner curve of the
bucket and leave it in the direction opposite to that of incoming jet. The change in momentum
(direction as well as speed) of water stream produces an impulse on the blades of the wheel of
Pelton Turbine. This impulse generates the torque and rotation in the shaft of Pelton Turbine.
2. Turgo Turbines:
A Turgo turbine is an impulse type of turbine in which a jet of water strikes the turbine blades.
The structure of a Turgo wheel is much like that of airplane turbine in which the hub is
surrounded by a series of curved vanes. These vanes catch the water as it flows through the
turbine causing the hub and shaft to turn. Turgo turbines are designed for higher speeds than
Pelton turbines and usually have smaller diameters.
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3. Francis Turbines:
The Francis turbine is a reaction turbine, which means that the working fluid changes pressure as
it moves through the turbine, giving up its energy. A casement is needed to contain the water
flow. The turbine is located between the high pressure water source and the low pressure water
exit, usually at the base of a dam.
The inlet is spiral shaped. Guide vanes direct the water tangentially to the turbine wheel, known
as a runner. This radial flow acts on the runner's vanes, causing the runner to spin. The guide
vanes (or wicket gate) may be adjustable to allow efficient turbine operation for a range of water
flow conditions.
As the water moves through the runner its spinning radius decreases, further acting on the
runner. For an analogy, imagine swinging a ball on a string around in a circle; if the string is pulled
short, the ball spins faster due to the conservation of angular momentum. This property, in
addition to the water's pressure, helps Francis and other inward-flow turbines harness water
energy efficiently.
At the exit, water acts on cup shaped runner features, leaving with no swirl and very little kinetic
or potential energy. The turbine's exit tube is shaped to help decelerate the water flow and
recover the pressure.
4. Kaplan Turbines:
Kaplan Turbine has propeller like blades but works just reverse. Instead of displacing the water
axially using shaft power and creating axial thrust, the axial force of water acts on the blades of
Kaplan Turbine and generating shaft power.
Most of the turbines developed earlier were suitable for large heads of water. With increasing
demand of power need was felt to harness power from sources of low head water, such as, rivers
flowing at low heights. For such low head applications Viktor Kaplan designed a turbine similar
to the propellers of ships. Its working is just reverse to that of propellers. The Kaplan Turbine is
also called as Propeller Turbine.
5. Cross-Flow Turbines:
A cross-flow turbine, also sometimes called a Michell-Banki turbine (from the name of the
manufacturer) is a turbine that uses a drum shaped runner much like the wheel on an old paddle
wheel steamboat. A vertical rectangular nozzle is used with this type of turbine to drive a jet of
water along the full length of the runner. One advantage of this type of turbine is that it can be
used in situations where you have significant flow but not enough head pressure to use a high
head turbine.
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6. Propeller Turbine:
A propeller turbine is just what its name implies. It uses a runner shaped just like a boat propeller
to turn the generator. The propeller usually has six vanes. A variation of the propeller turbine is
the Kaplan turbine in which the pitch of the propeller blades is adjustable. This type of turbine is
often used in large hydroelectric plants. An advantage of propeller type of turbines is that they
can be used in very low head conditions provided there is enough flow.
Pelton turbine
Francis turbine
Kaplan turbine
Turgo turbine
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CONCLUSION
Reclamation is helping to meet the needs of our country, and one of the most pressing needs is the
growing demand for electric power. Reclamation power plants annually generate more than 42 billion
kWh of hydroelectric energy, which is enough to meet the annual residential needs of 14 million people
or the energy equivalent of more than 80 million barrels of crude oil.
The deregulation of wholesale electricity sales and the imposition of requirements for open
transmission access are resulting in dramatic changes in the business of electric power production in
the United States. This restructuring increases the importance of clean, reliable energy sources such
as hydropower.
Hydropower is important from an operational standpoint as it needs no "ramp-up" time, as many
combustion technologies do. Hydropower can increase or decrease the amount of power it is supplying
to the system almost instantly to meet shifting demand. With this important load-following capability,
peaking capacity and voltage stability attributes, hydropower plays a significant part in ensuring
reliable electricity service and in meeting customer needs in a market driven industry. In addition,
hydroelectric pumped storage facilities are the only significant way currently available to store
electricity.
Hydro powers ability to provide peaking power, load following, and frequency control helps protect
against system failures that could lead to the damage of equipment and even brown or blackouts.
Hydropower, besides being emissions-free and renewable has the above operating benefits that
provide enhanced value to the electric system in the form of efficiency, security, and most important,
reliability. The electric benefits provided by hydroelectric resources are of vital importance to the
success of our National experiment to deregulate the electric industry.
Water is one of our most valuable resources, and hydropower makes use of this renewable treasure.
As a National leader in managing hydropower, Reclamation is helping the Nation meet its present and
future energy needs in a manner that protects the environment by improving hydropower projects and
operating them more effectively.
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References:
http://www.amusingplanet.com - Ambitious Hydroelectric Power Projects.
http://www.alstom.com – power - renewables - hydro turbines.
http://www.hydroquebec.com - learning - hydro electricite - types-turbines.
http://environment.nationalgeographic.com - environment - global-warming – hydropower.
http://ga.water.usgs.gov - Hydroelectric power: How it works.
http://www.slideshare.net - hydraulic-energy.
http://www.technologystudent.com - PUMP STORAGE SYSTEMS.
http://en.wikipedia.org - hydropower.
http://www.slideshare.net – Hydroelectricity.
https://www.google.ps – Hydropower.
RENEWABLE ENERGY TECHNOLOGIES: COST ANALYSIS SERIES – Hydropower.
Reclamation – Managing Water in the West – Hydroelectric Power.
Voith Hydro Holding GmbH & Co. KG Alexanderstrasse 11.
Renewable Energy Essentials: Hydropower.
Energy Hydropower & Dams
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