ME165-1_Week-6. Hydroelectric Power - Part 2_4831459

8/17/2019 ME165-1_Week-6. Hydroelectric Power - Part 2_4831459

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ME165-1

ALTERNATIVE ENERGY RESOURCES

Week-6 Hydroelectric Power (Part 2)2015-2016 / 3T


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AVAILABLE POWER CALCULATIONS

•

Hydraulic Power• The hydraulic power is a naturally available renewenergy source given by: P = ghQ

where:

P is the hydraulic power in watts,

is the density of water (~1000 kg/m3),

g is the acceleration due to gravity of 9.81 m

h is height of water or net head of water in m

Q is the flow rate or discharge in m3/s.


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• Other Formula• Volume flowrate, Q

• The volume flow rate of water is the product o

velocity and the cross sectional area of the pe

Q = vA

where:v is the velocity of water in the pe

m/s

A is the x-sectional area of the pen


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• Other Formula

• Gross head, hg• Gross head is the difference between head wa

and tail water elevation.

hg = hw - ht

where:hw is the head water elevation in m

ht is the tailwater elevation in m


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• Other Formula

• Friction Head Loss, h f • Friction head loss is the head lost by flow in a

conduit due to frictional disturbances

h f = fLV 2 /(2gd)

where: f-is the coefficient of friction,

L-is the penstock total length in m,

V -is the velocity of water in m/s,

G-is the pull of gravity, 9.81 m/s2,

D-inside diameter of penstock in m


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• Other Formula

• Net head or effective head, h

• Net head or effective head is the differen

between the gross head and the frictionhead loss.

h = hg - h f


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•

Other Formula• Penstock efficiency, e p

• Penstock efficiency is the ratio of the net head to the g

head

e p = h / hg


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• Calculating available power• A simple formula for approximating electric power pro

a hydroelectric plant is: P = ghQk where:

P is Power in watts,

is the density of water (~1000 kg/m3),

g is acceleration due to gravity of 9.8 m/s2,

h is height in meters,

Q is flow rate in cubic meters per second,

k is a coefficient of efficiency ranging from 0 to 1.Efficiency is often higher (that is, closer to 1) with larger and more modern turbin

Annual electric energy production depends on the available water supply. In som

installations the water flow rate can vary by a factor of 10:1 over the course of a


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• Example problem no.1:Calculate the available power for a turbine t

85% efficient, with water at 998 kg/cubic me

a flow rate of 79.3 cubic-meters/second, gra

9.80 meters per second squared and with a

of 146.3 m.



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•

Solution:P = g hQk = 998 kg/m3

h = 146.3 m

Q = 79.3 m3 /s

g = 9.80 m/s2

k = .85

P = 998 kg/m3 x 146.3 m x 79.3 m3 /s x 9.80 m/s2 x .85= 96.4 MW



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• Calculating available power

• The electrical energy produced in kWh can be wri

the form:

W = ghQkt

where:t is the operating time in hours (8

hrs/year)


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• Seat Works:

1. A hydraulic turbine receives water from a reserv

elevation of 120 m above it. What is the minimum

in kg/s to produce a steady water power of 55 MW

2. Water flows steadily with a velocity of 3.0 m/s in

long horizontal pipe having an inside diameter of 1

The inlet and outlet pressures of the pipe are 690 k

520 kPa, respectively. Find the friction in the pipe.


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CLASSIFICATION OF HYDROELECTRIC POWER PLANTS

• According to the Availability of Head

• High head power plants

•Medium head power plants

• Low head power plants


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• According to the Nature of Load

• Base load plants

• Peak load plants


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•

According to the Quantity of Water Available• Run-of-river-plant without pondage

• Run-of-river-plant with pondage

• Hydroelectric plants with storage reservoirs

• Pump storage plants

• Mini and micro hydroelectric plants


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CLASSIFICATION ACCORDING TO THE AVAILABILITY OF HEAD

• High head power plants

• These plants work under a head of 100 meter an• Water is stored in lakes or high mountains during

season or when snow melts.

• Surplus water is discharged by a spillway.

•

Tunnel through the mountain has a surge chambregulating valves at its exit.

• Pelton wheel is the common prime mover.

http://energie.edf.com/html/video/production/hydr

http://energie.edf.com/html/video/production/hydro/en/01/index.htmlhttp://energie.edf.com/html/video/production/hydro/en/01/index.html


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• High head power plants (cont’d.)


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• Medium head power plants• These plants operate under heads varying from 30m to

• Forebay before the penstock acts as the water reservoir

a surge tank.

• Francis turbine is the common prime mover.

http://energie.edf.com/html/video/production/hyd



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• Medium head power plants (cont’d.)


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•Low head power plants• A dam is constructed across a river and a sideway stre

from the river at the dam.

• Later this channel joins the river further downstream.

•

Francis turbine or Kaplan turbine is used for power ge

http://energie.edf.com/html/video/production/



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• Low head power plants (cont’d.)


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• Pelton wheel

• The Pelton wheel is a water

impulse turbine.

• It was invented by Lester Allan

Pelton in the 1870s.

• The Pelton wheel extracts energy

from the impulse of moving water,

as opposed to its weight like

traditional overshot water wheel.

http://www.youtube.com/watch?v=qbyL--6q7_4

http://www.youtube.com/watch?v=qbyL--6q7_4http://www.youtube.com/watch?v=qbyL--6q7_4


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• Francis turbine• Francis turbines are the most common water

turbine in use today. It was developed by James B.Francis in Lowell, Massachusetts.

• It is an inward-flow reaction turbine that combines

radial and axial flow concepts.

• Guide vanes around the outside of the turbine's

rotating runner adjust the water flow rate through

the turbine for different water flow rates and powerproduction rates.

• Francis turbines are almost always mounted with

the shaft vertical to keep water away from the

attached generator and to facilitate installation and

maintenance access to it and the turbine.

http://www.youtub

http://www.youtube.com/wat

http://www.youtube.com/watch?v=3BCiFeykRzohttp://www.youtube.com/watch?v=JD4VkzHk6rkhttp://www.youtube.com/watch?v=JD4VkzHk6rkhttp://www.youtube.com/watch?v=3BCiFeykRzo


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CLASSIFICATION ACCORDING TO THE NATURE OF LOAD

• Base load plants

• These plants are required to supply constant

the grid.

• They run continuously without any interrupti

mostly remote controlled.


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CLASSIFICATION ACCORDING TO THE NATURE OF LOAD

• Peak load plants• They only work during certain hours of a day wh

load is more than the average.

• Thermal stations work with hydel plants in tande

meet the base load and peak load during variou

seasons.

CLASSIFICATION ACCORDING TO THE QUANTITY


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OF WATER AVAILABLE

•

Run-of-river-plant without pondage• As the name indicates, it does not store water

the water as it comes.

• Such plants can be built at a considerably low c

the head available and the amount of power geare usually very low.

• During the high flow periods such plants can be

employed to supply a substantial portion of ba



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OF WATER AVAILABLE

• Run-of-river-plant with pondage• Run-off river power plants with pondage have increased

because of pondage which usually refers to the collectio

behind a dam at the plant and increases the firm capacit

short-period; say a week or more depending on the size

• Such power plants are comparatively more reliable and

generating capacity is less dependent on available rate owater.

• Such power plants can serve as base load or peak load p

depending on the flow of stream (during high flow perio

load plants and during low flow periods –as peak load p



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OF WATER AVAILABLE

• Hydroelectric plants with storage reservoirs

• Reservoir power plants are with reservoirs of sufficiently

permit carry-over storage form the wet season to the dry

and thus to supply firm flow substantially more than the

natural flow.

• Such plants can be used as base load plants or peak loadper requirement.

• Most of the hydro-electric power plants everywhere in th

of this type.



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OF WATER AVAILABLE

• Pumped storage plants (PSP)

• Although the losses of the pumping process makes the

consumer of energy overall, the system increases reven

more electricity during periods of peak demand, when

prices are highest.• The method stores energy in the form of potential ener

pumped from a lower elevation reservoir to a higher ele



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OF WATER AVAILABLE

• Pumped storage plants (PSP) (cont’d.)

•

Low-cost off-peak electric power is used to run the pumpperiods of high electrical demand, the stored water is rel

through turbines to produce electric power.

• Pumped storage is the largest-capacity form of grid energ

available, and, as of March 2012, the Electric Power Rese

Institute (EPRI) reports that PSP accounts for more than 9storage capacity worldwide, representing around 127,000

• PSP reported energy efficiency varies in practice between

80%, with some claiming up to 87%.



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OF WATER AVAILABLE

• Pumped storage plants (cont’d.)



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OF WATER AVAILABLE

• Mini and micro hydroelectric plants

• More emphasis is now being given on such plants.

• The natural water source in hilly terrain can be

utilized for power generation with low-head

standardized turbo-generator units.

• Its adverse affect on ecology is minimal.

• The mini-plants operate with 5m-20m head

producing about 100 kW – 500 kW of power, while

micro-plants are still smaller and work under a

head of less than 5m and generate electricity up

to 100 kW.


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SELECTION OF SITE FOR A HYDROELECTRIC PLANT

• Factors to be considered in selecting the site fo

hydroelectric power plant:

• Availability of water

• Water storage capacity

•

Available water head• Accessability of the site

• Distance from the load center

• Type of land site



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• Factors to be considered….

• Availability of water

• The design and capacity of the hydro-plant greatly dethe amount of water available at the site.

• The run-off data along with precipitation at the propo

with maximum and minimum quantity of water availa

year should be made available

a) decide the capacity of the plant.b) set up the peak load plant such as a steam, diesel or

plant.

c) provide adequate spillways or gate relief during flood



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•

Factors to be considered….• Water storage capacity

• Since there is a wide variation in rainfall all arou

year, it is always necessary to store the water fo

continuous generation of power.

• The storage capacity can be estimated with the

mass curve.


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• Factors to be considered….• Available water head

• In order generate the desired quantity of pow

necessary that a large quantity of water at a s

head should be available.• An increase in effective head, for a given outp

reduces the quantity of water required to be

to the turbines.



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•

Factors to be considered….• Accessability of the site

• The site should be easily accessible by rail and road

• An inaccessible terrain will jeopardize the moveme

and material.• Distance from the load center

• If the site is close to the load center, the cost of tran

lines and the transmission losses will be reduced.


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• Factors to be considered….

• Type of land site

• The land of the site should be cheap and rocky.

• The dam constructed at the site should have lar

catchment area to store water at high head.• The foundation rocks of the masonry dam shou

strong enough to withstand the stresses in the

and the thrust of water when the reservoir is fu

ENVIRONMENTAL IMPACT


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• Air Emissions

• A few recent studies of large reservoirs created behind hy

have suggested that decaying vegetation, submerged by f

may give off quantities of greenhouse gases equivalent to

other sources of electricity.

• If this turns out to be true, hydroelectric facilities such as

Bay project in Quebec that flood large areas of land mighsignificant contributors to global warming.

• Run of the river hydro plants without dams and reservoir

be a source of these greenhouse gases (e.g. methane – a

greenhouse gas).



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• Land Resource Use• The most obvious impact of hydroelectric dams is the floo

areas of land, much of it previously forested or used for ag• The size of reservoirs created can be extremely large. The

project in the James Bay region of Quebec has already sub

10000 square kilometres of land; and if future plans are c

the eventual area of flooding in northern Quebec will be l

the country of Switzerland.• Reservoirs can be used for ensuring adequate water supp

irrigation, and recreation; but in several cases they have f

homelands of native peoples, whose way of life has then

destroyed. Many rare ecosystems are also threatened by

development.



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• Natural river system, fish and wildlife• Large dams and reservoirs can have other impac

watershed. Damming a river can alter the amounquality of water in the river downstream of the d

well as preventing fish from migrating upstream

• These impacts can be reduced by requiring mini

downstream of a dam, and by creating fish laddeallow fish to move upstream past the dam.

• Silt, normally carried downstream to the lower r

river, is trapped by a dam and deposited on the

reservoir.



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• Natural river system, fish and wildlife

• This silt can slowly fill up a reservoir, decreasing t

amount of water, which can be stored and used fo

electrical generation.

• The river downstream of the dam is also deprived

which fertilizes the river's flood plain during high

periods.


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• Water Resource Use• Bacteria present in decaying vegetation can also change m

present in rocks underlying a reservoir, into a form, which

in water.

• The mercury accumulates in the bodies of fish and poses

hazard to those who depend on these fish for food.

• The water quality of many reservoirs also poses a health h

to new forms of bacteria, which grow in many of the hydr

• Therefore, run of the river type hydro plants generally ha

impact on the environment.

REFERENCES


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REFERENCES

• Textbooks

• Renewable Energy Technologies, Jean-Claude Sabonnadiere, 2009

•

Energy Conversion, D. Yogi Goswami, Frank Kreith, 2008• Power Plant Engineering, 3rd Edition, PK Nag, 2008, Tata McGraw Hill

• Web

• http://www.renewableenergyworld.com/rea/tech/home

• http://en.wikipedia.org/wiki/Renewable_energy

• http://www.waterwideweb.org/hydroelectricity.html

•

http://en.wikipedia.org/wiki/Hydroelectricity

• http://www.groept.be/www/dam/HYDROpower.htm#H4

• http://www.epa.gov/cleanenergy/energy-and-you/affect/hydro.html
http://www.renewableenergyworld.com/rea/tech/homehttp://www.renewableenergyworld.com/rea/tech/homehttp://en.wikipedia.org/wiki/Renewable_energyhttp://en.wikipedia.org/wiki/Renewable_energyhttp://www.waterwideweb.org/hydroelectricity.htmlhttp://www.waterwideweb.org/hydroelectricity.htmlhttp://en.wikipedia.org/wiki/Hydroelectricityhttp://en.wikipedia.org/wiki/Hydroelectricityhttp://www.groept.be/www/dam/HYDROpower.htmhttp://www.groept.be/www/dam/HYDROpower.htmhttp://www.epa.gov/cleanenergy/energy-and-you/affect/hydro.htmlhttp://www.epa.gov/cleanenergy/energy-and-you/affect/hydro.htmlhttp://www.epa.gov/cleanenergy/energy-and-you/affect/hydro.htmlhttp://www.groept.be/www/dam/HYDROpower.htmhttp://en.wikipedia.org/wiki/Hydroelectricityhttp://www.waterwideweb.org/hydroelectricity.htmlhttp://en.wikipedia.org/wiki/Renewable_energyhttp://www.renewableenergyworld.com/rea/tech/home

ME165-1_Week-6. Hydroelectric Power - Part 2_4831459

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