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MA9001 - Introduction to Energy

5. Hydroelectric Energy Part I Asst/Prof Qin Xiaosheng School of Civil & Environmental Engineering Tel : 67905288 Email : [email protected]

Introduction  Hydropower is extracted from the natural potential of usable water resources  Flowing water contains energy  can be captured and turned into electricity  Hydroelectric  Wave  Tidal

 Hydroelectric power currently the largest and cheapest source of renewable electricity chinatravelplanner.com

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History  First use of water power 250 BC  First electricity generation with water in 1882  using a waterwheel on Fox river in Wisconsin

(www.cairns.com.au)

 Niagara Falls 1893  One of the first hydroelectric power plants (2.2 MW)

 20th century  Most new hydro-electric development focus on larger hydro dams  environmental problems

(www.dailycognition.com)

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Sources of Electric Power - US

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Renewable Energy Sources - US

Wisconsin Valley Improvement Company, http://www.wvic.com/hydro-facts.htm

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World hydroelectricity consumption  Worldwide hydroelectricity installed capacity reached 816 GW in 2005  750 GW of large plants, and 66 GW of small hydro installations

(EnergyInsight.net, 2007)

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Fossil fuel reserves

Location of the World's Main Fossil Fuel Reserves (2010 World Coal Institute)

 oil & gas will last another 50-100 years  coal will last over 200 years  A shift towards renewable energy sources 7

Hydrologic cycle

r po a v

r e ne rg y

off n u R

Evaporation

Ru no ff

Hydrostatic head

S o la

ter a W

Condensation and precipitation

(Wikipedia, 2010)

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Hydroelectric power generator  Water falls down from a high altitude and passes through a turbine  The turbine drives a generator  The generator produces electricity  Power generation depends on fall height and flow rate

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how hydroelectric power is created Potential Energy Electrical Energy

Kinetic Energy

Mechanical Energy

/www.ncgreenpower.org

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Components of the system a. Dam: The structure that creates the reservoir as well as maintains the head pond at a certain level of water b. Head water: the water upstream of the dam whereas tail water is at the downstream of dam c. Tail water: water below a dam or waterpower development

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Components of the system d. Forebay: a pool of water in front of a larger body of water e. Afterbay: the tail race of a hydroelectric power plant at the outlet of the turbines f. Penstock: a tunnel carries the water from the forebay into the power house

(Taylor & Francis, 2007)

Penstocks at the Ohakuri Dam, New Zealand (Wikpedia, 2010)

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Components of the system g. Turbine: a rotary engine that extracts energy from water flow and converts it into useful work. h. Generator: an electrical machine coupled to the turbine shaft. Rotor: an assembly of electromagnets (poles) which rotates Stator: a system of conductors (armature windings)

(Photos.com, 2010)

(Monster Guide, 2008)

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Types of Hydroelectric Installation • Head – Water must fall from a higher elevation to a lower one to release its stored energy. – The difference between these elevations (the water levels in the forebay and the afterbay) is called head • Dams: three categories – high-head (250 or more m) – medium-head (50 to 250 m) – low-head (less than 50 m)

Boyle, Renewable Energy, 2nd edition, Oxford University Press, 2003

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Turbine technologies  Selection of turbines  based on particular application and effective head  Larger turbines have higher efficiencies but cost more  Runner  turning part of the turbine  Types: Impulse turbines and Reaction turbines

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Impulse turbines  Use water jets to hit bucket on the runner  Use the velocity of the water to move the runner, converting the potential energy to high velocity kinetic energy  As water discharges under atmospheric pressure  no pressure drop across turbines  Relatively low flow applications  Types: Pelton, turgo, cross-flow

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Pelton turbine  One or more jets of water spins the wheel  Resembles a waterwheel  Used for medium to highhead sites (100~1000 m), flow: 1-50 m3/s  Unit capacity: up to 200 MW  Efficiency: up to 92%

http://re.emsd.gov.hk

http://ucmr.com

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Turgo Turbine  A modification of the Pelton wheel  the runner (wheel) of a Turgo turbine is like a Pelton wheel sliced in half  The incoming jet of water strikes the plane of the runner on one side – usually at an angle of about 20°  Used for medium to medium head sites (50 - 250 m), flow: 1-10 m3/s  Efficiency: 87%-90%

© Copyright 2008 VARSPEED Hydro Ltd

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Cross-flow turbine  Water passes through a drumtype turbine transversely  go through runner twice  Used for low- to medium head condition (5-100 m), low flow condition (1- 10 m3/s)  Low price & good regulation  micro hydropower  Efficiency: 84% - 87% (flat efficiency curve)

(Wikipedia, 2010)

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Reaction turbines  The reaction turbine is turned by reactive force rather than by a direct push or impulse.  The runner is fully immersed in water and is enclosed in a pressure casing.  Power is derived from pressure drop  Higher flow rates and wider range of heads compared with impulse turbines  Types: Francis, Kaplan

(Wikipedia, 2010)

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Francis turbine  Most common water turbine  has a runner with fixed vanes  Combines radial and axial flow  Operational range  10-800 m head  Up to 800 MW unit size  Flow: up to 1000 m3/s

 Efficiency  over 90%

(Wikipedia, 2010)

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Kaplan turbine  A propeller-type water turbine  adjustable blade pitch  Operational range  1 to 100 m head (low to medium)  up to 1000 m3/s flow  Up to 100 MW unit size

 Kaplan turbine efficiencies are typically over 90% (Wikipedia, 2010)

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Types of Hydropower Turbines Boyle, Renewable Energy, 2nd edition, Oxford University Press, 2003

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Turbine selection

Chart for selecting turbines of hydropower plant (Tridentes Energy, 2009)

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