Bahir Dar University , Institute of Technology

School of Computing and Electrical Engineering

Copyright ,TassT , 2009 2010 Tad

AppliedEnergyConversion Eeng 428 AppliedEnergyConversion 4/10/2010

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Hydro-Electric Power PlantsIntroduction I t d tiWater flowing from higher level to lower level has kinetic energy which can be converted to mechanical energy and then electrical energy. The hydro-energy in flowing water is a function of weight of water and the head through which the water falls. Hydro-energy is an easily storable, conventional renewable energy. The question is how much water can be stored for channelizing through penstocks and hydro turbines, economically and conveniently, The t t d the Th water stored iin th upper reservoir/ llake/ pond constitutes th primary energy. i/ k / d tit t the i The water flows through the pressure pipe line and through the hydro- turbine and draft tube to the tail race.Bahir Dar Universi Faculty of Engine ity, eering

School of Computing and Elect C trical Engineering

The hydro-turbines d i th generators and th water iis di h Th h d t bi drive the t d the t discharged th d through t il h tail-race. The potential energy is stored water in the reservoir at high head is converted into kinetic energy in the flowing water. The flowing t Th fl i water converts th energy iinto mechanicall rotary energy iin th h d t bi t the t h i t the hydro turbine. Hydro-turbine drives the rotor of hydro- electric generator.4/10/2010 2

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Hydro-Electric Power PlantsTypical Hydro-Electric Power Plants T i l H d El t i P Pl tHydro Electric Schemes have a reservoir or a pool on one side of the darn and turbine generator units on the other side at lower level. The Head of water results in the flow. Energy is proportional to total weight of upper level water than can flow through turbine multiplied by the Head of fall. The head of water and flow rate have decisive influence on the choice of the turbine. The types of Hydro Plants are: 1. High Head 3. Low Head. 2. Medium Head 4. Underground high head.

Bahir Dar Universi Faculty of Engine ity, eering

School of Computing and Elect C trical Engineering

Reservoir is created in a valley by building a dam across a river flowing through the valley at reasonably high level. Copyright 2009, Ta assTad

The power plant is built on the downstream side of the dam. Water from the reservoir may be taken through pressure pipe, tunnel, penstock etc. up to turbine. The plant rating range covers a few hundred kW to a few thousand MW.4/10/2010 3

Hydro-Electric Power PlantsThe figures. below illustrate typical conventional H d R Th fi b l ill t t t i l ti l Hydro Reservoir Schemes. i S h

School of Computing and Elect C trical Engineering

High Head Hydro-Electric Power Plant.

Bahir Dar Universi Faculty of Engine ity, eering

High Head Scheme has a large reservoir on higher level and water from high level reservoir flows through pressure pipe to the turbine and is finally discharged into the tail race race. The upper reservoir is usually formed by constructing a dam on a river valley at high level. The excess water from the reservoir is discharged through the gates in the dam.4/10/2010 The tail race water usually meets the river along the down-stream. 4

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Hydro-Electric Power PlantsMedium Head Hydro Electric Power Plants. Medium-HeadSchool of Computing and Elect C trical Engineering

Medium Head Scheme has usually a darn on a river forming the reservoir on the river side and a hydro-electric power plant on the y p p lower level. The tail race water is discharged into the river.

Low-head Run-of-River Scheme (Small Hydro). The low head schemes are generally small hydro schemes rated up to 15 MW. Low Head Scheme is usually with a barrage* on a fl i b * flowing river and t bi i d turbinegenerator units mounted' within the nozzle shaped tubular passage through the barrage. Low Head Schemes are generally Run-ofRiver schemes with a low high barrage or weir g g across a river or a canal. The bulb type or tube type turbine-generator is installed axially within the passage of water through the draft tube.4/10/2010 * river barrier: an artificial barrier built across a river or canal to provide water or prevent flooding. 5

Bahir Dar Universi Faculty of Engine ity, eering

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Hydro-Electric Power PlantsTurbine and Pump at Storage type hydropower plantSchool of Computing and Elect C trical Engineering

Turbine T bi

Pump P

Turbines:Bahir Dar Universi Faculty of Engine ity, eering

,. ,.-- ; ; . , l Pumps:n (rpm) P/QH loss Centrifugal g Mixed flow Axial flow n (rpm) 10-80 HH&SD 70-180 MH&MD 150-320 LH&LD Q QH/Pi loss

Pelton Francis Kaplan Copyright 2009, Ta assTad

10-40 10 40 HH&SD 35-400 MH&MD 300-1000 LH&LD

4/10/2010

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Hydro-Electric Power PlantsUnderground Hydro Electric Power Plant. Hydro-ElectricSchool of Computing and Elect C trical Engineering Bahir Dar Universi Faculty of Engine ity, eering

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Underground Hydro Electric Power Plants are built at lower level and inside a cave. The tail race water is discharged through a tunnel into the downstream path of the river.

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Hydro-Electric Power Plants

School of Computing and Elect C trical Engineering

The small hydro power plants are considered as nonconventional. Hydro-Electric Projects rated up to and including 15 MW, are called Small Hydro Projects. Projects rated up to and including 1 MW rating are called Mini Hydro Projects. Projects t d P j t rated up to 100 kW are called Mi t ll d Micro Hydro Projects. Th t H d P j t The terms are somewhat h t arbitrary and not exact. Conventional Hydro Projects are generally in the range of 100 MW and above. The economics of Small/Mini/Micro Hydro Projects is different from that of Conventional y j Hydro Projects. The Mini/Micro/Small Hydro Projects are further classified as Low Head/Medium Head/ High head Projects:.

Bahir Dar Universi Faculty of Engine ity, eering

Classification of small hydro power plants by their ratings and head.Large Medium Copyright 2009, Ta assTad

> 100 MW > 15 MW