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Power Plant Engineering

1.1Introduction

Power plant engineering deals with the study of energy, its sources and utilization of

energy for power generation. The power is generated by prime movers (example

Hydraulic turbines, steam turbines, diesel engines).arge amount of power is

generated using prime movers in a site or layout called power plants, where all the

e!uipment"s and machineries re!uired for power generation is located.

#nergy$ #nergy may be de%ned as the capacity to do wor&. #nergy exists in various

forms, such as 'echanical #nergy, thermal energy, electrical energy, solar energy

etc. #lectricity is the only form of energy, which is easy to produce, easy to

transport, easy to use and easy to control. #lectricity consumption per capita is the

index of the living standard people of a place or country i.e. the utilization of energyis an indication of the growth of the nation.

1.2 Power and Power Plant:

Power is primarily associated with mechanical wor& and electrical energy. Therefore,

power can be de%ned as the rate of ow of energy and can state that a power plant

is a unit built for production and delivery of a ow of mechanical or electrical

energy. n a common usage, a machine or assemblage of e!uipment that produces

and delivers a ow of mechanical or electrical energy is a power plant. Hence an

internal combustion engine is a power plant* a water wheel is a power plant, etc.

However, what we generally mean by the term power plant is that assemblage ofe!uipment, permanently located on some chosen site which receives raw energy in

the form of a substance capable of being operated on in such a way as to produce

electrical energy for deliver from the power plant.

1.3 Sources of energy

The basic sources of energy for power generation are coal, oil, nuclear fuels and

gas. These sources are &nown as +conventional sources of energy. These sources

of energy will one day be used up and are exhaustible. The most reassuring and

promising energy, which is abundant in supply and is inexhaustible is +-on

conventional sources of energy such as solar, wind, tidal, geothermal etc. #nergyresources can be broadly classi%ed as follows

Energy Resources

/onventional sources of energy -on conventional sources of energy (0r)or -on

renewable sources of energy 1enewable source of energy

#xamples$ 23uels li&e coal, oil, 4un, wind, waves, tides, energy -atural gas, nuclear

fuels etc. 3rom earth core, hydroelectric Power etc.

1.3.1 Non – renewable sources:

'ost of the energy we use are from source li&e coal, oil, natural gas and nuclear

fuels. These primary energy sources are called -on renewable sources because

once they have been used up, they cannot be replaced.

1.3.2 Renewable sources:



4ources of energy that can be used over and over again are called renewable

sources. These sources can be used to produce electricity. 4ome of the renewable

sources are$

5#nergy from the sun (Heat and light energy)

5#nergy from the wind (6inetic energy)

5#nergy from the waves and tides (6inetic energy)

5#nergy from earth"s core (7eothermal energy)

8.9 /lassi%cation of power plants

: power plant ma&es use of any one of the energy sources to produce power.

;epending on the type of energy source the power plants are classi%ed as

5Thermal power plant (t ma&es use of coal)

5nternal combustion engine plants (ma&es use of petrol or diesel)

57as turbine power plant (ma&es use of a permanent gas)

5-uclear power plant (ma&es use of nuclear fuels)

54olar power plant (ma&es use of the suns radiation heat)

5 Tidal power plant (ma&es use of the power of tides in the sea)

• Hydro electric power plant (ma&es use of the potential energy of water)

5<ind power (ma&es use of energy available in wind)

57eothermal power plant (ma&es use of heat energy available under the ground)

1.5 or!ing "rinci"le of Stea# "ower "lants

1.5.1 Introduction

4team power plant is also &nown as Thermal power plant. : steam power plant

converts the chemical energy of the fossil fuels (coal, oil, gas) into mechanical =

electrical energy. This is achieved by raising the steam in the boilers, expanding it

through the turbines and coupling the turbines to the generators which convertmechanical energy into electrical energy as shown in %g. 8.8.

$%e following two "ur"oses can be ser&ed by a stea# "ower "lant:

8. To produce electric power

>. To produce steam for industrial purposes besides producing electric power. The

steam may be used for varying purposes in the industries such as textiles, food

manufacture, paper mills, sugar mills and re%neries. 3ig. 8.8. Production of #lectric

energy by steam power plant



1.5.2 'lassi(cation of stea# "ower "lants

The steam power plants may be classi%ed as follows$

8./entral stations. The electrical energy available from these stations is meant for

general sale to the customers who wish to purchase it. 7enerally, these stations are

condensing type where the exhaust steam is discharged into a condenser instead of

into the atmosphere. n the condenser the pressure is maintained below the

atmospheric pressure and the exhaust steam is condensed.

>.ndustrial power stations or captive power stations. This type of power station is

run by a manufacturing company for its own use and its output is not available for

general sale. -ormally these plants are non2condensing because a large !uantity of

steam (low pressure) is re!uired for di?erent manufacturing operations

n the condensing steam power plants the following advantages accrue$

(i)The amount of energy extracted per &g of steam is increased (a given size of the

engine or turbine develops more power).

(ii)The steam, which has been condensed into water in the condenser, can be

recirculating to the boilers with the help of pumps.

n a non condensing steam power plants a continuous supply of fresh feed water is

re!uired which becomes a problem at places where there is a shortage of pure

water.

1.5.3. )ayout of #odern stea# "ower "lant

: steam power plant must have the following e!uipment"s$

5: furnace to burn the fuel.

54team generator or boiler containing water. Heat generated in the furnace is

utilized to convert water into steam.

5'ain power unit such as an engine or turbine to use the heat energy of steam and

perform wor&.

5Piping system to convey steam and water. The general layout of the thermal power

plant consists of mainly 9circuits as shown in %g. 8.>. The four main circuits are$

8./oal and ash circuit >.:ir and gas circuit @.3eed water and steam ow circuit

9./ooling water circuit



/oal and ash circuit$ 2

This circuit consists of coal storage, ash storage, coal handling and ash handling

systems. The handling system consists of belt conveyors, screw conveyors etc. /oal

arrives at the storage yard and after necessary handling, passes on to the furnaces

through the fuel feeding device. :sh resulting from combustion of coal collects atthe bac& of the boiler and is removed to the ash storage yard through ash handling

e!uipment. The ndian coal contains @A to 9AB of ash and a power plant of 8AA'<

produces normally >A to >C tons of hot ash per hour

3ig.8.> ayout of 4team Power plant

:ir and gas circuit$ 2

This circuit consists of air %lter, air preheater, dust collector and chimney. :ir is

ta&en in from the atmosphere to the air preheater through the action of a forced or

induced draught fan or by using both. The dust from the air is removed by means of

using air %lter before supplying to the combustion chamber. The exhaust gasescarrying suDcient !uantity of heat and ash are passed through air preheater where

the exhaust heat of the gases is given to the air and then it is passed through dust

collectors where most of the dust is removed before exhausting the gases to the

atmosphere through chimney.

3eed water and steam ow circuit$ 2

This circuit consists of boiler feed pump, boiler, turbine and feed heaters. The steam

generated in the boiler is fed to the steam prime mover to develop the power. The

steam coming out of prime mover is condensed in the condenser and then fed to

the boiler with the help of pump. The condensate is heated in the feed heatersusing the steam tapped from di?erent points of the turbine. The feed heaters may

be of mixed type or indirect heating type. 4ome of the steam and water is lost

passing through di?erent components of the system* therefore, feed water is

supplied from external source to compensate this loss. The feed water supplied from

external source is passed through the purifying plant to reduce the dissolved salts

to an acceptable level. The puri%cation is necessary to avoid the scaling of the

boiler tubes.

/ooling water circuit$ 2

This circuit consists of circulating water pump, cooling water pumps and coolingtower. The !uantity of cooling water re!uired to condense the steam is considerably

large and it is ta&en from la&e, sea or river. The cooling water is ta&en from the

upper side of the river, it is passed through the condenser and heated water is

discharged to the lower side of the river. 4uch system of cooling water supply is

possible if ade!uate cooling water is available through the year. This system is

&nown as open system. <hen the ade!uate water is not available, then the water



coming out from the condenser is cooled either in cooling pond or cooling tower.

The cooling is e?ected by partly evaporating the water. This evaporative loss (this

includes evaporation and carryover) is nearly > to C Bof the cooling water circulated

in the system. To compensate the evaporative loss, the water from the river is

continuously supplied. <hen the cooling water coming out of the condenser is

cooled again and supplied to the condenser, then the system is &nown as closedsystem. <hen the water coming out from the condenser is discharged to river

downward side directly, the system is &nown as open system. 0pen system is

economical than closed system provided ade!uate water is available throughout the

year. The di?erent components, which are used in thermal power plants, are listed

below$ Eoiler, steam turbine, generator, condenser, cooling towers, circulating water

pump, boiler feed pump, induced=forced draught fans, ash precipitators etc.

1.5.* or!ing of t%e t%er#al "ower "lant

4team is generated in the boiler of the thermal power plant using the heat of the

fuel burned in the combustion chamber. The steam generated is passed through

steam turbine where part of its thermal energy is converted into mechanical energy,

which is further used for generating electric power. The steam coming out of the

steam turbine is condensed in the condenser and the condensate is supplied bac&

to the boiler with the help of the feed pump and the cycle is repeated. The function

of the boiler is to generate the steam. The function of condenser is to condensate

the steam coming out of steam turbine at low pressure. The function of the steam

turbine is to convert part of heat energy of steam into mechanical energy. The

function of the pump is to raise the pressure of the condensate from the condenser

pressure (A.A8C bar) to boiler pressure (>AA bar). The other components li&eeconomiser, super heater and steam feed heaters (steam from di?erent points of

turbine is fed to the heaters to heat the condensate to a higher temperature) are

used in the primary circuit to increase the overall eDciency of the thermal power

plant.

1.5. 5 '%aracteristics of stea# "ower "lant:

5Higher eDciency

5ower cost

5:bility to burn coal especially high ash content, inferior coals

51educed environmental impact in terms of air pollution

51educed water re!uirement

5Higher reliability and availability

8.C.F :dvantages (merits) of thermal power plant

8.The initial cost of construction of the plant is low compared to hydroelectric plant

>.The power plant may be located near the load centre, so that the cost oftransmission and the losses due to transmission are considerably reduced.

@.The !uantity of water in hydroelectric plant depends on nature, such as rain and

rivers. This is not so in the case of thermal power plants.



9.The construction and commissioning of thermal power plant ta&es lesser period

when compared to hydroelectric power plant.

1.5.+. ,isad&antages -de#erits of t%er#al "ower "lant

8.The fuel (coal or oil) used in thermal power plant will one day get exhausted since

it is a non2renewable source of energy that is used.

>.t cannot be used as pea& load plant, as its part load eDciency decreases very

rapidly with decreasing load.

@.The transportation of fuel is a maGor problem for power plants located away from

coal %elds.

9.The cost of power generation is considerably high compared to hydro2electric

power plant.

C.The smo&e produced by the burning fuel when exhausted into the atmospherecauses air pollution.

F.The life of thermal power plant according to the #lectricity supply act is>C years

and that of hydroelectric plant is @C years. The eDciency decreases to less than

8AB after its life period. Hydroelectric power plant can have a life of even 8AA to

8>C years.

.The turbines in thermal power plants run at a speed of @AAA to 9AAArpm and they

re!uire special material and rigid construction as compared to hydroelectric plant

which has a low running speed of @AAto 9AA rpm.

1./ 0as $urbine Power "lant

: gas turbine power plant may be de%ned as one +in which the principal prime

mover is of the turbine type and the wor&ing medium is a permanent gas

: simple gas turbine plant consists of the following$

8.compressor

>.ntercooler

@.1egenerator

9./ombustion chamber

C.7as turbine

F.1eheating unit

8. /ompressor$

n gas turbine plant, the axial and centrifugal ow compressors are used. n most of

the gas turbine power plant, two compressors are used. 0ne is low pressure

compressor and the other is high pressure compressor. n low pressure compressor,

the atmospheric air is drawn into the compressor through the %lter. The maGor part

of the power developed by the turbine (about FFB) is used to run the compressor.

This low pressure air goes to the high pressure compressor through the intercooler.

Then the high pressure air goes into the regenerator.

>.The intercooler is used to reduce the wor& of the compressor and it is placed in

between the high pressure and low pressure compressor. ntercoolers are generally



used when the pressure ratio is very high. The energy re!uired to compress the air

is proportional to the air temperature at inlet. The cooling of compressed air in

intercooler is generally done by water.

@. 1egenerator$

1egenerators are used to preheat the air which is entering into the combustion

chamber to reduce the fuel consumption and to increase the eDciency. His is done

by the heat of the hot exhaust gases coming out of the turbine

9. /ombustion chambers

Hot air from regenerator ows to the combustion chambers and the fuel li&e coal,

natural gas or &erosene are inGected into the combustion chamber. :fter the fuel

inGection, the combustion ta&es place. This high pressure, high temperature

products of combustion are passed through the turbine.

3ig.8.@ ayout of 7as turbine power plant

C. 7as turbine

Two types of gas turbines are used in gas turbine plant.

8.High pressure turbine >.ow pressure turbine

8. High Pressure turbine

n the beginning, the starting motor runs the compressor shaft. The burnt gases

(product of combustion) expand through the high pressure turbine. t is important to

note that when the turbine shaft rotates it in fact drives the compressor shaft which

is couples to it. -ow, the high pressure turbine runs the compressor and the starting

motor is stopped. :bout FFB of the power developed by the turbine is used to run

the compressor and only@9B of the power developed is used to generate electric

power.

>. ow pressure turbine

The purpose of the low pressure turbine is to produce electric power. The shaft of

the PT is coupled with the generator. The burnt fuel (gases) after leaving the HPT is

again sent to a combustion chamber where it further undergoes combustion. #ven if

there is any left out unburnt fuel from the previous turbine it gets fully burnt in the



combustion chamber. The burnt gases run the low pressure turbine (PT). The shaft

of the turbine is directly coupled with the generator for producing electricity. The

exhaust hot gases after leaving the PT passes through there generator before

exhausted through the chimney into the atmosphere. The heat from the hot gases is

used to preheat the air leaving the HP/ before it enters the combustion chamber.

This preheating of the air improves the eDciency of the combustion chamber.

F. 1eheating unit

n this unit, the additional fuel is added to the exhaust gases coming out from the

high pressure turbine, and the reheated combustion products goes into the low

pressure turbine.

1./.1 or!ing of 0as $urbine Power "lant

The wor&ing of gas turbine plant is shown in %g.8.@.

The atmosphere air is drawn into the low pressure compressor through the air %lterand it is compressed. The compressed low pressure air goes into the high pressure

compressor through the intercooler. Here, the heat of the compressed air is

removed. Then the high pressure compressed air goes into the combustion chamber

through the regenerator. n the combustion chamber, the fuel is added to the

compressed air and the combustion of the fuel ta&es place.

The product of the combustion goes into the high pressure turbine. The exhaust of

the high pressure turbine goes to another combustion chamber and the additional

fuel is added and it goes to the low pressure turbine. :fter the expansion in the low

pressure turbine, the exhaust is used to heat the high pressure air coming to the

combustion chamber through there generator. :fter that, the exhaust goes to the

atmosphere.

1./.2..d&antages of 0as turbine "ower "lant

8.3or a gas turbine plant, -atural gas is a very suitable fuel. t would be ideal to

install gas turbine plants near the site where natural gas is readily available.

>.7as turbine plants can wor& economically for short running hours.

@.4torage of fuel re!uires less area and handling is easy.

9.7as turbine plant is small and compact in size as compared to steam power

plants.

C.t can be started !uic&ly and can be put on load in a very short time.

F.The cost of maintenance is less.

.t is simple in construction. There is no need for boiler, condenser and other

accessories as in the case of steam power plants.

I.The gas turbine can operate at high speed since there are no reciprocating parts

J./heaper fuel such as &erosene, paraDn, benzene and powdered coal(cheaper

than petrol and diesel) can be used.

8A.7as turbine plants can be used in water scarcity areas

88.ess pollution and less water is re!uired.

1./.3 ,isad&antages of gas turbine "ower "lant



8.FFB of the power developed is used to drive the compressor* the gas turbine unit

has a low thermal eDciency

>. The running speed of the gas turbine is in the range of (9A, AAA to 8,AA,AAA rpm)

and the operating temperature is as high as >AAAA /, for this reason special metals

and alloys have to be used for the various parts of the turbine.

@.4pecial cooling methods are re!uired for cooling the turbine blades.

9.t is diDcult to start a gas turbine as compared to a diesel engine in a diesel

power plantC.The life of a gas turbine plant is up to 8A years, after which its

eDciency decreases to less than 8A per cent.

1./.* ""lications of gas turbine "ower "lant

5To drive generators and supply loads in steam, diesel or hydro plants

5 To wor& as combination plants with conventional steam boilers

5 Thermal process industries

5Petro chemical industries

5Power generation (used for pea& load and as stand by unit)

5:ircraft and ships for their propulsion. They are not suitable for automobiles

because of their very high speeds.

1./.5 'lassi(cation of 0as $urbine

7as turbines may be broadly classi%ed as$(i)0pen cycle gas turbine (ii)/losed cycle

gas turbine

0pen cycle gas turbine

n the open cycle gas turbine, %g.8.9, air is drawn into the compressor from the

atmosphere. The compressed air is heated by directly burning the fuel in the air at

constant pressure inside the combustion chamber. The high pressure hot gases from

the combustion chamber drive the turbine and the power is developed when the

turbine shaft rotates. 7as turbines are not self2starting. 4tarting motor drives the

compressor till fuel is inGected inside the combustion chamber, once the turbine

starts gaining speed the starting motor is disengaged. Part of the power developed

by the gas turbine (about FAB) is used to drive the compressor and the remaining is

used to drive a generator or other machinery



/losed cycle gas turbine

n this the compressed air from the atmosphere is heated in air heater (heat

exchanger). Heat is added to the air heater from some external source (oil or coal)

at constant pressure. High pressure wor&ing uid expands through the turbine and

power is developed. The exhaust wor&ing uid is cooled in a pre2cooler before thesame uid is sent into the compressor again.

n a closed cycle gas turbine the same wor&ing uid is continuously circulated. The

fuel re!uired for adding heat from an external source can be any fuel ranging from

&erosene, to heavy oil and even peat and coal slurry without reducing the eDciency.

1.+ ,iesel "ower "lant

1.+.1 Introduction

This is a fossil fuel plant since diesel is a fossil fuel. ;iesel engine power plants areinstalled where supply of coal and water is not available insuDcient !uantity.

(i)These plants produce the power in the range of > to CA '<.(ii)They are used as

standby sets for continuity of supply such as hospitals, telephone exchanges, radio

stations, cinema theatres and industries.(iii)They are suitable for mobile power

generation and widely used in railways and ships.(iv)They are reliable compared to

other plants.(v);iesel power plants are becoming more popular because of

diDculties experienced in construction of new diesel plants and thermal plants.

8..> ayout of ;iesel Power plant

The essential components of diesel power plant are

;iesel engine

5:ir %lter and super charger

5#ngine starting system

53uel system

5ubrication system

5/ooling system

57overning system

5#xhaust system

;iesel engine$



This is the main component of a diesel power plant. The engines are classi%ed as

two stro&e engine and four stro&e engines. #ngines are generally directly coupled to

the generator for developing power. n diesel engines, air admitted into the cylinder

is compressed. :t the end of compression stro&e, fuel is inGected. The fuel is burned

and the burning gases expand and do wor& on the piston. The shaft of the engine is

directly coupled to the generator. :fter the combustion, the burned gases areexhausted to the atmosphere.

:ir %lter and supercharger

The air %lter is used to remove the dust from the air which is ta&en by the engine.

:ir %lters may be of dry type, which is made up of felt, wool or cloth. n oil bath type

of %lters, the air is swept over a bath of oil so that dust particles get coated. The

function of the supercharger is to increase the pressure of the air supplied to the

engine and thereby the power of the engine is increased.

#ngine starting system

;iesel engine used in diesel power plants is not self2starting. #ngine starting system

includes air compressor and starting air tan&. This is used to start the engine in cold

conditions by supplying the air.

3uel system

t includes the storage tan&, fuel pump, fuel transfer pump, strainers and heaters.

Pump draws diesel from the storage tan& and supplies it to the small day tan&

through the %lter. ;ay tan& supplies the daily fuel need for the engine. The day tan&is usually placed high so that diesel ows to engine under gravity. ;iesel is again

%ltered before being inGected into the engine by the fuel inGection pump. The fuel

inGection system performs the following functions.

53ilter the fuel

5'eter the correct !uantity of the fuel to be inGected

5 Time the inGection process

51egulate the fuel supply

54ecure %ne atomization of fuel oil

5;istribute the atomized fuel properly in the combustion* chamber

The fuel is supplied to the engine according to the load on the plant.

ubrication system

t includes oil pumps, oil tan&s, coolers and pipes. t is used to reduce the friction of

moving parts and reduce wear and tear of the engine parts such as cylinder walls

and piston. ubrication oil which gets heated due to the friction of the moving parts

is cooled before recirculation. n the lubrication system the oil is pumped from the

lubricating oil tan& through the oil cooler where the oil is cooled by the cold water

entering the engine. The hot oil after cooling the moving parts return to the

lubricating oil tan&.



/ooling system

The temperature of the burning fuel inside the engine cylinder is in the order of

8CAA / to >AAA /. n order to lower this temperature, water is circulated around the

engine. The water envelopes (water Gac&et) the engine, the heat from the cylinder,

piston, combustion chamber etc., is carried by the circulating water. The hot waterleaving the Gac&et is passed through the heat exchanger. The heat from the heat

exchanger is carried away by the raw water circulated through the heat exchanger

and is cooled in the cooling tower.

7overning system

t is used to regulate the speed of the engine. This is done by varying the fuel

supply according to the engine load.

#xhaust system

The exhaust gases coming out of the engine is very noisy. n order to reduce the

noise a silencer (muKer) is used.

8..@ <or&ing of ;iesel Power Plant

The air and fuel mixture act as a wor&ing medium in diesel engine power plant. The

atmosphere air enters inside the combustion chamber during the suction stro&e and

the fuel is inGected through the inGection pump. The air and fuel is mixed inside the

engine and the charge is ignited due to high compression inside the engine cylinder.

The basic principle in diesel engine is that, the thermal energy is converted into

mechanical energy and this mechanical energy is converted into electrical energy to

produce the power by using generator or alternator.

8..9 :pplications of ;iesel #ngines in Power 3ield

The diesel electric power plants are chiey used in the following %eld.



(a) Pea& load plant$ ;iesel plants can be used in combination with thermal or hydro2

plants as pea& load units. They can be easily started or stopped at a short notice to

meet the pea& demand.

(b) 'obile plant$ ;iesel plants mounted on trailers can be used for temporary or

emergency purposes such as for supplying power to large civil engineering wor&s.

(c) 4tandby unit$ f the main unit fails or cannot cope up with the demand, a diesel

plant can supply the necessary power. 3or example, if water available in a hydro2

plant is not ade!uately available due to less rainfall, the diesel station can operate

in parallel to generate the short fall in power.

(d) #mergency plant$ ;uring power interruption in a vital unit li&e a &ey industrial

plant or a hospital, a diesel electric plant can be used to generate the needed

power.

(e) -ursery station$ n the absence of main grid, a diesel plant can be installed to

supply power in a small town. n course of time, when electricity from the main grid

becomes available in the town, the diesel unit can be shifted to some other area

which needs power on a small scale. 4uch a diesel plant is called a Lnursery

stationL.

(f) 4tarting stations$ ;iesel units can be used to run the auxiliaries (li&e 3; and ;

fans, E3P, etc.) for starting a large steam power plant

(g) /entral stations $;iesel electric plants can be used as central station where the

capacity re!uired is small

8..C :dvantages and disadvantages of diesel power plant

3ollowing are the advantages of diesel electric stations.

8.t is easy to design and install these electric stations.

>. They are easily available in standard capacities.

@.They can respond to load changes without much diDculty.

9. There are less standby losses.

C.They occupy less space.F.They can be started and stopped !uic&ly.

. They re!uire less cooling water.I./apital cost is less.

J.ess operating and supervising sta? re!uired.

8A.High eDciency of energy conversion from fuel to electricity.

88.#Dciency at part loads is also higher.

8>.ess of civil engineering wor& is re!uired.

8@. They can be located near the load centre.

89. There is no ash handling problem.

8C.#asier lubrication system.

8..F ;isadvantages in installing diesel units for power generation.

8.High operating cost.



>.High maintenance and lubrication cost.

@./apacity is restricted. /annot be of very big size.9.-oise problem.

C./annot supply overload.

F.Mnhygienic emissions.

.The life of the diesel power plant is less ( to 8A years) as compared to that of a

steam power plant which has a life span of >C to 9C years. The eDciency of the

diesel plant decreases to less than 8AB after its life period.

1. ydroelectric "ower "lant

8.I.8 <or&ing principle

Hydroelectric power plant (Hydro plant) utilizes the potential energy of water stored

in a dam built across the river. The potential energy of the stored water is converted

into &inetic energy by %rst passing it through the penstoc& pipe. The &inetic energy

of water is then converted into mechanical energy in a water turbine. The turbine is

coupled to the electric generator. The mechanical energy available at the shaft of

the turbine is converted into electrical energy by means of the generator. Eecause

gravity provides the force which ma&es the water fall, the energy stored in the

water is called gravitational potential energy.

8.I.> ayout of Hydroelectric power plant

3ig.8. shows the schematic representation of a Hydroelectric power plant. The

main components are

5<ater reservoir

5;am

54pillway

57ate

5Pressure tunnel

54urge tan&

5Penstoc&



5<ater turbine

5;raft tube

5 Tail race level

5Power house

<ater reservoir$ n a reservoir the water collected from the catchment area during

rainy season is stored behind a dam. /atchment area gets its water from rains and

streams. /ontinuous availability of water is a basic necessity for a hydroelectric

power plant. The level of water surface in the reservoir is called Head water level.

The water head available for power generation depends on the reservoir height.

;am$ the purpose of the dam is to store the water and to regulate the outgoing ow

of water. The dam helps to store all the incoming water. t also helps to increase the

head of the water. n order to generate a re!uired !uantity of power, it is necessary

that a suDcient head is available.

4pillway$ #xcess accumulation of water endangers the stability of dam construction.

:lso in order to avoid the overow of water out of the dam especially during rainy

seasons spillways are provided. This prevents the rise of water level in the dam.

4pillways are passages which allow the excess water to ow to a di?erent storage

area away from the dam.

7ate$ : gate is used to regulate or control the ow of water from the dam.

Pressure tunnel$ t is a passage that carries water from the reservoir to the surge

tan&.

4urge tan&$ : surge tan& is a small reservoir or tan& in which the water level rises or

falls due to sudden changes in pressure. There may sudden increase of pressure in

the penstoc& pipe due to sudden bac&ow of water, as load on the turbine is

reduced. This sudden rise of pressure in the penstoc& pipe is &nown as water

hammer.

3ig. 8. ayout of Hydroelectric Power plant



: surge tan& is introduced between the dam and the turbine and serves the

following purposes$8.To reduce the distance between the free water surface in the

dam and the turbine, thereby reducing the water hammer e?ect. 0therwise,

penstoc& will be damages by the water e?ect.>.To serve as a supply tan& to the

turbine when the water in the pipe is accelerated during increased load conditions

and as a storage tan& when the water is decelerating during reduced loadconditions.

Penstoc&$ Penstoc& pipe is used to bring water from the dam to the hydraulic

turbine. Penstoc& pipes are made up of steel or reinforced concrete. The turbine is

installed at a lower level from the dam. Penstoc& is provided with a gate valve at

the inlet to completely close the water supply. t has a control valve to control the

water ow rate into the turbine.

<ater turbine or hydraulic turbine (Prime mover)$ The hydraulic turbine converts the

energy of water into mechanical energy. The mechanical energy (rotation) available

on the turbine shaft is coupled to the shaft of an electric generator and electricity isproduced. The water after performing the wor& on turbine blade is discharged

through the draft tube. The prime movers which are in common use are Pelton

wheel, 6aplan turbine, 3rancis turbine.

;raft tube$ ;raft tube is connected to the outlet of the turbine. t converts the

&inetic energy available in the water into pressure energy in the diverging portion.

Thus, it maintains a pressure of Gust above the above the atmospheric at the end of

the draft tube to move the water into a tail race. <ater from the tail race is released

for irrigation purposes.

Tail race level$ Tail race is a water path to lead the water discharged from theturbine to the river or canal. The water held in the tail race is called Tailrace water

level.

Power House$ The power house accommodates the water turbine, generator, and

transformer and control room. :s the water rushes through the turbine, it spins the

turbine shaft, which is coupled to the electric generator. The generator has a

rotating electromagnet called a rotor and a stationary part called a stator. The rotor

creates a magnetic %eld that produces an electric charge in the stator. The charge is

transmitted as electricity. The step up transformer increases the voltage of the

current coming from the stator. The electricity is distributed through power lines.

8.I.@ /lassi%cation of Hydroelectric power plant

Hydroelectric power plants are usually classi%ed according to the available of head

of water

5High head power plants

5'edium head power plants

5ow head power plants

High head power plants$ <hen the operating head of water exceeds Ameters, theplant is &nown as High head power plant. Pelton wheel turbine is the prime mover

used.

'edium head power plants$ <hen the water ranges from 8C to Ameters, then the

power plant is &nown as 'edium head power plant. t uses 3rancis Turbine.



ow head power plants$ <hen the head is less than 8C meters, the plant is named

as ow head power plant. t uses 3rancis or 6aplan turbine as prime mover.

8.I.9 :dvantages of hydroelectric power plant

8.<ater source is perennially available. -o fuel is re!uired to be burnt to generate

electricity. t is aptly termed as Nthe white coalN. <ater passes through turbines to

produce wor& and downstream its utility remains undiminished for irrigation of

farms and !uenching the thirst of people in the vicinity.

>.The running costs of hydropower installations are very low as compared to

thermal or nuclear power stations. 8n thermal stations, besides the cost of fuel, one

has to ta&e into account the transportation cost of the fuel also.

@.There is no problem with regards to the disposal of ash as in a thermal station.

The problem of emission of polluting gases and particulates to the atmosphere also

does not exist. Hydropower does not produce any greenhouse e?ect, cause the

pernicious acid rain and emit obnoxious -0.

9.The hydraulic turbine can be switched on and o? in a very short time. n a thermal

or nuclear power plant the steam turbine is put on turning gear for about two days

during start2up and shut2down.

C.The hydraulic power plant is relatively simple in concept and self2contained in

operation. ts system reliability is much greater than that of other power plants.

F.'odern hydropower e!uipment has a greater life expectancy and can easily last

CA years or more. This can be compared with the e?ective life of about @A years of

a thermal or nuclear station.

.;ue to its great ease of ta&ing up and throwing o? the load, the hydro2power can

be used as the ideal spinning reserve in a system mix of thermal, hydro and nuclear

power stations.

I.'odern hydro2generators give high eDciency over a considerable range of load.

This helps in improving the system eDciency.

J.Hydro2plants provide ancillary bene%ts li&e irrigation, ood control, a?orestation,

navigation and a!ua2culture.

8A.Eeing simple in design and operation, the hydro2plants do not re!uire highly

s&illed wor&ers. 'anpower re!uirement is also low.

8.I.C ;isadvantages of <ater Power

8.Hydro2power proGects are capital2intensive with a low rate of return. The annual

interest of this capital cost is a large part of the annual cost of hydropower

installations.

>.The gestation period of hydro proGects is !uite large. The gap between the

foundation and completion of a proGect may extend from ten to %fteen years.

@.Power generation is dependent on the !uantity of water available, which may vary

from season to season and year to year. f the rainfall is in time and ade!uate, then

only the satisfactory operation of the plant can be expected.

9.4uch plants are often far away from the load centre and re!uire long transmission

lines to deliver power. Thus the cost of transmission lines and losses in them are

more.



C.arge hydro2plants disturb the ecology of the area, by way of deforestation,

destroying vegetation and uprooting people. 4trong public opinion against erection

of such plants is a deterrent factor. The emphasis is now more on small, mini and

micro hydro stations.

8.I.F Hydroelectric power plant in ndia

4risailam Hydro power plant :P A '< Mpper sileru Hydroelectric proGect :P 2

8>A6odayar hydroelectric power plant T- 8AA '< ddi&i hydro proGect 6erala

IAA '<

1.4 Nuclear "ower "lant

8.J.8. ntroduction

:s large amounts of coal and petroleum are being used to produce energy, time

may come when their reserves may not be able to meet the energy re!uirements.

Thus there is tendency to see& alternative sources of energy. The discovery thatenergy can be liberated by the nuclear %ssion of materials li&e uranium (M),

Plutonium (Pu), has opened up a new source of power of great importance. The heat

produced due to %ssion of M and Pu is used to heat water to generate steam which

is used for running turbo generator. t has been found that one &ilogram of M can

produce as much energy as can be produced by burning 9CAA tonnes of high grade

coal. This shows that nuclear energy can be successfully employed for producing

low cost energy in abundance as re!uired by the expanding and industrializing

population of future.

4ome of the factors which go in favour of nuclear energy are as follows$

8.Hydroelectric power is of storage type and is largely dependent of monsoons. The

systems getting power from such plants have to shedload during the period of low

rainfall.

>.0il is mainly needed for transport, fertilizers and petrochemicals and thus cannot

be used in large !uantities for power generation.

@./oal is available only in some parts of the country and transportation of coals

re!uires big investments.

9.-uclear power is partially independent of geographical factors, the only

re!uirement being there should be reasonably good supply of water. 3uel

transportation networ&s and larger storage facilities are not needed and nuclear

power plant is a clean source of power which does not pollute the air if radioactive

hazards are e?ectively prevented.

C.arge !uantity of energy is released with consumption of only a small amount of

fuel.

8.J.> -uclear %ssion

The fuel inside the reactor is metal called uranium. Mranium exists as an isotope in

the form of M>@C, M>@9 and M>@I. 0ut of these isotopes M>@Cis more unstable.

<hen a neutron is captured by a nucleus of an atom of M>@C, it splits up roughly

into two e!ual fragments and about >.C neutrons are released and a large amount

of energy (nearly >AA million electron volts 'eO) is produced. This is called %ssion

process. The neutrons so produced are very moving neutrons and can be made to



%ssion other nuclei of M>@C thus enabling a chain reaction to ta&e place. <hen a

large number of %ssion occurs, enormous amount of heat is produced. The following

%g.8.I.showsthe chain reaction

The %g.8.J shows how the reactor is put on and o? 3ig. 8.I -uclear

3ission

t may be observed from the %g.8.I that >.C neutrons are released in %ssion of each

nucleus of M>@C, out of these one neutron is used to sustain the chain reaction, A.Jneutrons is absorbed by M>@I and becomes Pu>@J. The remaining A.F neutrons

escape from the reactor. 'oderators are provided to slow down the neutrons from

the high velocities but not to absorb them. The moderators which are commonly

used are ordinary water and Heavy water.

/ontrol rods limit the number of fuel atoms that can split. They are made up of a

material that absorbs neutrons. To turn on the reactor some rods are pulled out. The

rods are made of boron or cadmium.

8.J.@ 'ain components of a nuclear power plant

The main components of a nuclear power plant are

5-uclear fuel

5-uclear reactor

54team generator



5'oderator

5/ontrol rods

51eector

5 Turbine

5/ondenser

54hielding

-uclear 3uel$ 3uel of a nuclear reactor should be %ssionable material which can be

de%ned as an element or isotope whose nuclei can be caused to undergo nuclear

%ssion by nuclear bombardment and to produce a %ssion chain reaction. t can be

one or all of the following M>@C, M>@@ and Pu>@J

-uclear reactor$ : nuclear reactor may be regarded as a substitute for the boiler

furnace of a steam power plant. Heat is produced in the reactor due to nuclear

%ssion of the fuel. ;uring the %ssion process, the large amount of heat is liberated.

This large amount of heat is absorbed by the coolant and itis circulated through the

core. The various types of reactors used in nuclear power plant is

8.Eoiling water reactor >.Pressurised water reactor @.3ast breeder reactor

4team generator$ The heat liberated in the reactor is ta&en up by the coolant

circulating through the core. The purpose of the coolant is to transfer the heat

generated in the reactor core and use it for steam generation. 0rdinary water or

heavy water is a common coolant.

'oderator$ t is used to reduce the &inetic energy of fast neutrons into slow

neutrons and to increase the probability of chain reaction. 7raphite, heavy water

and beryllium are generally used as moderator. : moderator should possess the

following properties$8.t should have high thermal conductivity>.t should be

available in large !uantities in pure [email protected] should have high melting point in case

of solid moderators and low melting point in case of li!uid moderators. 4olid

moderators should also possess good strength and machinability.9.t should provide

good resistance to corrosionC.t should be stable under heat and radiationF.t should

be able to slow down neutrons

/ontrol rods$ They regulate the rate of a chain reaction. They are made of boron,

cadmium or other elements which absorb neutrons. /ontrol rods should possess the

following properties$8.They should have ade!uate heat transfer properties>.They

should be stable under heat and [email protected] should be corrosion

resistant9.They should be suDcient strong and should be able to shut down the

reactor almost instantly under all conditions.C.They should have suDcient cross

sectional area for the absorption.

1eector$ The neutrons produced during the %ssion process will be partly absorbed

by the fuel rods* moderator, coolant or structural material etc. -eutrons left

unabsorbed will try to leave the reactor core and will be lost. 4uch loss is minimized

by surrounding the reactor core by a material called reector which will send the

neutrons bac& into the core. The returned neutrons can then cause more %ssion and

improve the neutrons economy of the reactor. 7enerally the reector is made up of

graphite and beryl

Turbine$ The steam produced in the steam generator is passed to the turbine. <or&

is done by the expansion of stem in the turbine.



/ondenser$ The exhaust steam from the turbine ows to the condenser where

cooling water is circulated. The exhaust steam is condensed to water in the

condenser by cooling. The condensate is pumped again into the steam generator by

the feed pump.

4hielding$ The reactor is a source of intense radioactivity. These radiations are veryharmful and shielding is provided to absorb the radioactive rays. : thic& concrete

shielding and a pressure vessel are provided to prevent the radiations escaped to

atmosphere.

8.J.9 <or&ing of a -uclear Power plant

The reactor of a nuclear power plant is similar to the furnace of steam power plant.

The heat liberated in the reactor due to the nuclear %ssion of the fuel is ta&en up by

the coolant circulating through the reactor core. Hot coolant leaves the reactor at

top and then ows through the tubes of steam generator (boiler) and passes on its

heat to the feed water. The steam produced is passed through the turbine and after

wor& has been done by expansion of steam in the turbine, steam leaves the turbine

and ows to condenser. Pumps are provided to maintain the ow of coolant,

condensate and feed water.

8.J.C Eoiling water reactor (E<1)

n this reactor, enriched uranium (enriched uranium contains more %ssionable

isotope M>@Cthan the naturally occurring percentage A.B as nuclear fuel and

water is used as coolant. <ater enters the reactor at the bottom. t ta&es up the

heat generated due to the %ssion of fuel and gas converted into steam. 4team

leaves the reactor at the top and ows into the turbine. <ater also serves as

moderator. ndia"s %rst nuclear power plant at Tarapur has two reactors (each of >AA

'< capacity) of boiling water reactor type

8. J.F Pressurised <ater reactor (P<1)



: pressurised water nuclear plant is shown in %g. t uses enriched uranium as fuel.

<ater is used as coolant and moderator. <ater passes through the reactor core and

ta&es up the heat liberated due to nuclear %ssion of the fuel. n order that water

may not boil (due to its low boiling point >8> 3 at atmospheric conditions) and

remain in li!uid state, it is &ept under a pressure of about 8>AA p.s.i.g in the

pressuriser. This enables water to ta&e up more heat from the reactor. 3rom the

pressuriser, water ows to the steam generator where it passes on its heat to the

feed water which in turn gets converted into steam.

8.J. 3ast breeder reactor (3E1)

n this reactor the core containing M>@C is surrounded by a blan&et (a layer of fertile

material placed outside the core) or fertile material M>@I. n this reactor no

moderator is used. The fast moving neutrons liberated due to %ssion of M>@Care

absorbed by M>@I which gets converted into %ssionable material Pu>@J, Pu>@Jis

capable of sustaining chain reaction. Thus the reactor is important because it

breeds %ssionable material from fertile material M>@I available in large !uantities.

This reactor uses two li!uid metal coolant circuits. i!uid sodium is used as primary

coolant when circulated through the tubes of intermediate heat exchanger transfer

its heat to secondary coolant sodium potassium alloy. The secondary coolant whileowing through the tubes of steam generator, transfer its heat to feed water. 3ast

breeder reactors are better than conventional reactor both from the point of view of

safety and thermal eDciency. 3or ndia which already is fast advancing towards self2

reliance in the %eld of nuclear power technology, the fast breeder reactor becomes

inescapable in view of the massive reserves of thorium and the %nite limits of its

uranium resources.

8.J.I :dvantages of nuclear power plant

8.The fuel used in nuclear power plant is uranium* it does not release chemical or

solid pollutants into the air during use.

>.4pace re!uired is less when compared with other power plants.

@.3uel consumption is very less.

9.3uel transportation cost is low and no large storage area for fuel is re!uired.



C.The plant is not a?ected by weather conditions. The plant can function throughout

the year (Hydro power plants depends on monsoon)

F.Ey using nuclear fuel we can conserve the fossil fuels li&e coal, oil, gas etc. for

other purposes. 3or example coal can be used to power steam engines, oil can be

used for running vehicles, and gas be used for coo&ing.

.-umber of wor&ers re!uired is less.I.-uclear power plant is the only source which

can meet the increasing demand of electricity.J.: nuclear power plant uses much

less fuel than a fossil fuel plant

8 metric ton of uranium fuel @ million metric tons of coal 8> million barrels of oil

8.J.J ;isadvantages of nuclear power plant

8.-uclear plants cost more to build than thermal or hydroelectric power plants of

the same capacity.>.1adioactive wastes must be disposed carefully, otherwise it will

adversely a?ect the health of wor&ers and the environment asawhole.@.'aintenance cost of the plant is high.9.-ot suitable for varying load

conditionsC.<ell trained persons are re!uired to operate the plant.

8.J.8A -uclear power stations in ndia

5 Tarapur -uclear power station (Eombay) Eoiling water reactor >AA '<

51ana Pratap 4agar -uclear power station (6ota in 1aGasthan) Two>AA '<

56alpa&&am -uclear power station Two >@C '< Pressurised water reactor

5-arora -uclear power station (Mttar Pradesh) Two >@C '< /:-;M reactor

56a&arpur -uclear power plant (7uGarat) 9 >@C '< /:-;M type reactor

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