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LARGE HYDROELECTRIC Suvagata Chakraborty Suvagata Chakraborty

Large Hydroelectric

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Large Hydroelectric. Suvagata Chakraborty. Types of Hydro projects. 1) Large Hydro 2) Small Hydro. Difference. Principals of Hydroelectric Power Stations. - PowerPoint PPT Presentation

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Page 1: Large Hydroelectric

LARGE HYDROELECTRIC

Suvagata ChakrabortySuvagata Chakraborty

Page 2: Large Hydroelectric

TYPES OF HYDRO PROJECTS

1) Large Hydro 2) Small Hydro

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DIFFERENCECategory Large

hydroSmall hydro

Generation Few hundred MW-More than 10GW

General 25MW(max)USA and Canada(35-50 MW)

Construction Large Dams Low or no Dams

Applications Grid Connected Off-grid systems

Investment and Maintenance

$60,000-100,000High maintenance cost

$6000-20,000Low maintenance cost

Environmental Impact

High Low

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PRINCIPALS OF HYDROELECTRIC POWER STATIONS

To harness the power of water flowing down from a high level, where huge generators convert the potential energy of falling or fast moving water into electrical energy (known as Hydroelectricity or hydroelectric power)

It is the most widely used form of renewable energy. to calculate the amount of available hydro power. The two vital factors to consider are the flow and

the head of the stream or river. The flow is the volume of water which can be captured and re-directed to turn the turbine generator, and the head is the distance the water will fall on its way to the generator. The larger the flow - i.e. the more water there is, and the higher the head - i.e. the higher the distance the water falls - the more energy is available for conversion to electricity.

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• Power = Flow x Head x Efficiency

x Gravity where power is measured in Watts, head in

meters, flow in liters per second, and acceleration due to gravity in meters per second per second.

• A low head site has a head of below 10 meters. In this case we need to have a good volume of water flow if we are to generate much electricity. A high head site has a head of above 20 meters. In this case you can get away with not having a large flow of water, because gravity will give what we have an energy boost.

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PLANT COMPONENTS

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DAMS

Dams are structures built over rivers to stop the water flow and form a reservoir.

The reservoir stores the water .

The dams should be water-tight and should be able to withstand the pressure exerted by the water on it.

Typically a large dam is classified as being higher than 50-65 feet (15-20 meters) while major dams are those over 492-820 feet (150-250 meters).•Around 5,300 (11%) of the world’s 48,000 large dams were built solely for hydropower. Further 13,300 (28%) were built for more than one function. Many of these multipurpose dams, especially the larger ones, have a hydropower function

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DAMSThe various types of dams (by structure)are: 

1)Gravity Dams

Gravity dams are huge dams that are constructed to hold back water using only their own weight. To do this, they are constructed using extensive amounts of concrete, making them difficult and expensive to build. The Grand Coulee Dam in the U.S. state of Washington is a gravity dam.

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DAMS

2) Arch Dam

One of the most common types of major dams is the arch dam. These masonry or concrete dams are ideal for narrow and/or rocky locations because their curved shape easily holds back water via gravity without the need for a lot of construction materials. Arch dams can have one large single arch or they can have multiple small arches separated by concrete buttresses. The Hoover Dam which is on the border of the U.S. states of Arizona and Nevada is an arch dam.

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DAMS

3) Buttress dam•Another type of dam is the buttress dam. These can have multiple arches, but unlike a traditional arch dam, they can be flat as well. Normally buttress dams are made of concrete and feature a series braces called buttresses along the downstream side of the dam to prevent the natural flow of water. The Daniel-Johnson Dam in Quebec, Canada is a multiple arch buttress dam.

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DAMS

4) Embankment dam•In the U.S., the most common type of dam is the embankment dam. These are large dams made out of soil and rock which use their weight to hold back water. To prevent water from moving through them, embankment dams also have a thick waterproof core. The Tarbela Dam in Pakistan is the world’s largest embankment dam.

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SPILLWAY AND FLOOD GATE• Spillway

A spillway could be called as a way for spilling of water from dams. It is  used to provide for the release of flood water from a dam. It is used to prevent over toping of the dams which could result in damage or failure of  dams. Spillways could be controlled type or uncontrolled type. The uncontrolled types start releasing water upon water rising above a particular level. But in case of the controlled type, regulation of flow is possible.

• Floodgates are devices that are designed to allow for the controlled flow of water from various types of water systems. The floodgate is a common component in all sorts of systems ranging from reservoirs, dams, and spillways. Essentially, any human constructed system that is used to control the level and flow of water in a river, lake, or stream will be equipped with some type of floodgate.

Page 13: Large Hydroelectric

PENSTOCK AND SURGE TANK

• Penstock and TunnelPenstocks are pipes which carry water from the reservoir to the turbines inside power station. They are usually made of  steel and are equipped with gate systems. Water under high pressure flows through the penstock. A tunnel serves the same purpose as a penstock. It is used when an obstruction is present between the dam and power station such as a mountain. 

• Surge TankSurge tanks are tanks connected to the water conductor system. It serves the purpose of reducing water hammering in pipes which can cause damage to pipes. The sudden surges of water in penstock is taken by the surge tank, and when the water requirements increase, it supplies the collected water thereby regulating water flow and pressure inside the penstock.

Page 14: Large Hydroelectric

POWER STATION/HOUSE

Power StationPower station contains a turbine coupled to a generator. The water brought to the power station rotates the vanes of the turbine producing  torque and rotation of turbine shaft. This rotational torque is transferred to the generator and is converted into electricity. The used water is released through the tail race.

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TURBINES

• As water sources vary, water turbines have been designed to suit different locations. The design used is determined largely by the head and quantity of water available at the particular site.

• The three main types are: Pelton wheels, Francis turbines, and Kaplan or propeller type turbines 

Page 16: Large Hydroelectric

THE PELTON WHEEL• The Pelton wheel

is used where a small flow of water is available with a ‘large head’. The Pelton wheel has small ‘buckets’ all around its rim. Water from the dam is fed through nozzles at very high speed hitting the buckets, pushing the wheel around.

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THE FRANCIS TURBINE• The Francis turbine is

used where a large flow and a high or medium head of water is involved. This wheel is called a ‘runner’. A circle of guide vanes surround the runner and control the amount of water driving it. Water is fed to the runner from all sides by these vanes causing it to spin.

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PROPELLER OR KAPLAN TURBINES • Propeller type turbines

are designed to operate where a small head of water is involved. These turbines resemble ship’s propellers. However, with the Kaplan turbines the angle (or pitch) of the blades can be altered to suit the water flow. The variable pitch feature permits the machine to operate efficiently over a range of heads, to allow for the seasonal variation of water levels in a dam.

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HYDROELECTRIC GENERATOR It is a low-speed synchronous

generator driven by water turbines. Hydro generators may have a horizontal or vertical shaft. The horizontal units are usually small with speeds of 300–1200 revolutions per minute (rpm). The vertical units are usually larger(<100 rpm) and more easily adapted to small hydraulic heads. The rotor diameters range from 2 to 62 ft (0.6 to 19 m) and capacities from 50 to 900,000 kVA. The generators are rated in kVA (kilovolts times amperes). The kilowatt output is the product of kVA and power factor. For large generators a rating of 0.9–0.95 is common with the machines able to operate up to 1.0 when the load requires. The generators may also supply reactive power.

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How a Hydro power station works

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ADVANTAGES

• FlexibilityHydro is a flexible source of electricity since plants can be ramped up and down very quickly to adapt to changing energy demands like peak demands, maintain the system voltage levels, and quickly re-establish supply after a blackout. Energy generated by hydroelectric installations can be injected into the electricity system faster than that of any other energy source. The capacity of hydroelectric systems to reach maximum production from zero in a rapid and foreseeable manner makes them exceptionally appropriate for addressing alterations in the consumption and providing ancillary services to the electricity system, thus maintaining the balance between the electricity supply and demand.

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• Low power costsNo cost of fuel. Hydroelectric plants have long economic lives, 50–100 years. Operating labor cost is also usually low, as plants are automated and have few personnel on site during normal operation. So construction costs will be covered after 5 to 8 years of full generation.

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COST COMPARISON WITH OTHER RENEWABLE SOURCES

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COST EFFECT

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Page 26: Large Hydroelectric

The Three Gorges Dam is the world's largest power station in terms of installed capacity (22,500 MW), over  Yangtze River 

Itaipu Dam, capacity(14,000 MW), located at Paraná River on the border section between Brazil and Paraguay

Page 27: Large Hydroelectric

• Its resources are widely spread around the world. Potential exists in about 150 countries, and about 70 per cent of the economically feasible potential remains to be developed. This is mostly in developing countries.

• It is a proven and well advanced technology (more than a century of experience), with modern power plants providing the most efficient energy conversion process (> 90 per cent), which is also an important environmental benefit.

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• Hydroelectricity helps fight climate changes.The hydroelectric life cycle produces very small amounts of greenhouse gases (GHG). In emitting less GHG than power plants driven by gas, coal or oil, hydroelectricity can help retard global warming. Although only 33% of the available hydroelectric potential has been developed, today hydroelectricity prevents the emission of GHG corresponding to the burning of 4.4 million barrels of petroleum per day worldwide.

Page 34: Large Hydroelectric

• Hydroelectricity contributes to the storage of drinking water.

Hydroelectric power plant reservoirs collect rainwater, which can then be used for consumption or for irrigation. In storing water, they protect the water tables against depletion and reduce our vulnerability to floods and droughts.

Page 35: Large Hydroelectric

DISADVANTAGES

• Disturbance of habitatThe formation of large and huge dams destroys

the living beings around them. Local life is disturbed as human can’t live in such a flooded area and plants are destroyed. People living nearby have to relocate.

Page 36: Large Hydroelectric

• Emission of methane and carbon dioxideThe reservoir of water for hydroelectric power

releases a large amount of carbon dioxide and methane. The area around the dam is filled with water. The plants and trees in them start rotting and decompose by other method without the use of oxygen . So this type of decomposition dumps a great amount of methane and carbon dioxide which increase pollution.

Page 37: Large Hydroelectric

• Limited useAs the hydroelectric power is produced by the water

which depend on the yearly rain falls so only those areas can use this method which receives a good amount of rainfall water because this method needs a huge reservoir of water.

• Installation costsAlthough the effective cost is zero but the

manufacturing and building a dam and installation of the turbines is very costly due to which many countries do not employ this alternative source of energy

Page 38: Large Hydroelectric

• Effects on agricultureMaking dams on rivers affect the amount, quality

and temperature of water that flow in streams which has drastic effects on agriculture and drinking water.

• Fish killingThe water while flowing through the dam collects

nitrogen which can damage and also kills fish. They can also damage the reproduction of fishes thus eliminating the whole species of fishes.

Page 39: Large Hydroelectric

INCLUDING LARGE HYDRO IN RENEWABLES INITIATIVES WOULD CROWD OUT FUNDS FOR NEW RENEWABLES

Large hydro plants are among the most expensive infrastructure projects on the planet, with major projects costing in the billions and even tens of billions of dollars. Including subsidies for large hydro in renewables schemes could thus consume the lion’s share of funds available to promote renewables.

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REFERENCES• http://www.see.murdoch.edu.au/resources/info/

Tech/hydro/large.html• http://en.wikipedia.org/wiki/List_of_largest_hydroe

lectric_power_stations• http://www.conserve-energy-future.com/Disadvan

tages_HydroPower.php• http://energyfuture.wikidot.com/hydropower-reso

urces• http://www.energytoolbox.org/gcre/mod_4/gcre_h

ydropower.pdf• http://ga.water.usgs.gov/edu/hydroadvantages.ht

ml• http://

geography.about.com/od/waterandice/a/damsreservoirs.html

Page 41: Large Hydroelectric

SMALL HYDROELECTRIC

Md Rakib Ur Rahman

Page 42: Large Hydroelectric

SMALL HYDROELECTRIC

Small hydroelectric generation is a renewable and decentralized source of electricity, which is typically employed with very minimal environmental impact.

Unlike large hydroelectric projects requiring the damming of rivers, small hydro projects simply divert a portion of a river or creek’s flow or are constructed on pre-existing diversions, such as raw water distribution systems

Page 43: Large Hydroelectric

SMALL HYDROELECTRIC Small hydropower

facilities can produce 100 – 30,000 kilowatts (kW) of electricity.

Small hydropower facilities may involve a small dam, or be a diversion of the main stream, or be a run-of-the-river system

Page 44: Large Hydroelectric

WHAT DO SMALL HYDRO SYSTEMS PROVIDE? Electricity for

Central grids

Isolated-grids

Remote power supplies

Beyond their ability to provide electricity they have number of attributes that make Small Hydro more attractive:

Reliability

Very low operating cost

Reduced exposure to energy price volatility

Page 45: Large Hydroelectric

SMALL HYDRO SYSTEM DESCRIPTION

Head (m)Head (m)

Flow (m3/s)

Power in kW 7 x Head x Flow

Page 46: Large Hydroelectric
Page 47: Large Hydroelectric

“SMALL” HYDRO PROJECTS

“Small” is not universally defined

Size of project related not just to electrical capacity but also to whether low or high head.

Typical Power

RETScreen®

FlowRETScreen®

Runner Diameter

Micro < 100 kW < 0.4 m3/s < 0.3 m

Mini 100 to 1,000 kW 0.4 to 12.8 m3/s 0.3 to 0.8 m

Small 1 to 50 MW > 12.8 m3/s > 0.8 m

Page 48: Large Hydroelectric

CLASSIFICATION DEPENDING ON THE HEADThe objective of a hydropower scheme is to convert the potential energy of a mass of water, flowing in a stream with a certain fall to the turbine (termed the "head"), into electric energy at the lower end of the scheme, where the powerhouse is located. The power output from the scheme is proportional to the flow and to the head. Schemes are generally classified according to the “Head”:• High head: 100-m and above • Medium head: 30 - 100 m • Low head: 2 - 30 m These ranges are not rigid but are merely means of categorizing sites. Schemes can also be defined as: • Run-of-river schemes • Schemes with the powerhouse located at the base of a dam • Schemes integrated on a canal or in a water supply pipe

Page 49: Large Hydroelectric

TYPES OF SMALL HYDRO PROJECTS Type of grid

Central-grid Isolated-grid or off-grid

Type of civil works Run-of-river

No water storage Power varies with flow

available from river: lower firm capacity

Reservoir Higher firm capacity year-

round Significant damming

usually required

Page 50: Large Hydroelectric

COMPONENTS: CIVIL WORKS

Typically account for 60% of plant initial costs

Diversion dam or weir Low dam of simple construction for run-of-river

Concrete, wood, masonry

Cost of dam alone can render project unviable

Water passage Intake with trashrack and gate; tailrace at exit

Excavated canal, underground tunnel and/or penstock

Valves/gates at turbine entrance/exit, for maintenance

Power house Houses turbine, mechanical, and electrical equipment

Page 51: Large Hydroelectric

COMPONENTS: TURBINE

Scaled-down versions of large-hydro turbines

Efficiency of 90% possible

In run-of-river, flow rate is quite variable Turbine should function well over a range of flow rates

or multiple turbines should be used

Reaction: Francis, fixed pitch propeller, Kaplan For low to medium head applications

Submerged turbine uses water pressure and kinetic energy

Impulse: Pelton, Turgo, crossflow For high head applications

Uses kinetic energy of a high speed jet of water

Page 52: Large Hydroelectric

COMPONENTS:ELECTRICAL AND OTHER EQUIPMENT

Generator Induction

Must be tied to other generators

Use to feed electricity onto large grid

Synchronous Can function in isolation from other generators

For stand-alone and isolated-grid applications

Other equipment Speed increaser to match turbine to generator

Valves, electronic controls, protection devices

Transformer

Page 53: Large Hydroelectric

WORLD HYDRO RESOURCE

More rain falls on continents than evaporates from them

For equilibrium, rain must flow to the oceans in rivers

Technical Potential (TWh/year)

% Developed

Africa 1,150 3

South Asia and Middle East 2,280 8

China 1,920 6

Former Soviet Union 3,830 6

North America 970 55

South America 3,190 11

Central America 350 9

Europe 1,070 45

Australasia 200 19

Page 54: Large Hydroelectric

SMALL HYDRO SYSTEM COSTS

75% of costs are site specific

High initial costs

But civil works and equipment can last >50 years

Very low operating and maintenance costs

One part-time operator is usually sufficient

Periodic maintenance of major equipment requires

outside contractor

High head developments tend to be less costly

Typical range: $1,200 to $6,000 per installed kW

Page 55: Large Hydroelectric

RUN-OF-THE-RIVER HYDROPOWER SYSTEM A run-of-the-river system uses the river’s natural flow

and requires little or no impoundment. It may involve a diversion of a portion of the stream through a canal or penstock, or it may involve placement of a turbine right in the stream channel. Run-of-the-river systems are often low-head.

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RUN OF THE RIVER PROJECT

http://www.youtube.com/watch?v=rQNfkg7DfUI

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KEY BENEFITS : GENERATING COST

Fig: Generating Cost of Small Hydro( source http://www.panamhydro.com/i/pdf/PAH-Small-Hydro-101.pdf

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TECHNOLOGY RISK AND MATURITY

Fig: Technology Risk & Maturity of Small Hydro( source http://www.panamhydro.com/i/pdf/PAH-Small-Hydro-101.pdf

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CAPITAL COSTS

Fig: Capital Costs of Small Hydro( source http://www.panamhydro.com/i/pdf/PAH-Small-Hydro-101.pdf

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ENVIRONMENTAL FOOTPRINT

Fig: Environmental Footprint of Small Hydro( source http://www.panamhydro.com/i/pdf/PAH-Small-Hydro-101.pdf

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CAPACITY UTILIZATION

Fig: Capacity Utilization of Small Hydro( source http://www.panamhydro.com/i/pdf/PAH-Small-Hydro-101.pdf

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MAINTENANCE & OPERATING COSTS

Fig Operating and Maintenance cost of Small Hydro

( source http://www.panamhydro.com/i/pdf/PAH-Small-Hydro-101.pdf  )

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SMALL HYDROENVIRONMENTAL CONSIDERATIONS

Small hydro development can change

Fish habitat

Site aesthetics

Recreational/navigational uses

Impacts and environmental assessment requirements depend on site & type of project:

Run-of-river at existing dam: relatively minor

Run-of-river at undeveloped site: dam/weir/diversion construction

Water storage developments: larger impacts that increase with scale of project

Page 64: Large Hydroelectric

CURRENT STATUS OF SMALL HYDRO

Fig : Small Hydroelectric projects in USA ( source : www.intellectualtakeout.org )

Page 65: Large Hydroelectric

Fig : Statistical data of California ISO ( source http://www.energyalmanac.ca.gov/renewables/hydro/

http://cdec.water.ca.gov/)

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REFERENCES

http://www.energyalmanac.ca.gov/renewables/hydro/

http://www.energy.ca.gov/hydroelectric/hydro_forecast_links.html

http://cdec.water.ca.gov/ www.ilsr.org  http://www.nrel.gov/docs/fy01osti/29065.pdf www.intellectualtakeout.org