handbook of power plant engineering pdf

Preface xxiii About the Author xxv1.1 Introduction to the sources of energy: conventional and non-conventional principle of power generation—1 1.1.1 Conventional energy sources —2 1.1.2

R K Hegde

Professor

Department of Mechanical Engineering

Srinivas Institute of Technology

Mangalore, Karnataka, India

Power Plant

EnginEEring

known as TutorVista Global Pvt Ltd, licensee of Pearson Education in South Asia.

No part of this eBook may be used or reproduced in any manner whatsoever without the publisher’s prior written consent

This eBook may or may not include all assets that were part of the print version The publisher reserves the right to remove any material in this eBook at any time

them to grow as responsible citizens.

Preface xxiii About the Author xxv

19 Instrumentation and Equipments in Power Station 837

Index 859

Preface xxiii About the Author xxv

1.1 Introduction to the sources of energy: conventional and non-conventional principle of power generation—1

1.1.1 Conventional energy sources —2 1.1.2 Non-conventional energy sources—5

1.2 Factors affecting selection of site—14

1.2.1 The factors to be considered for site selection

of steam power plants—14 1.2.2 Factors affecting selection of site for hydro-electric power plant—16 1.2.3 Factors affecting selection of site for a nuclear power plant—18

1.3 Principal types of power plants—181.4 Present status and future trends—191.5 Layout of steam, hydel, diesel, nuclear and gas turbine power plants—20

1.5.1 Layout of steam turbine plant—20 1.5.2 Layout of hydro-electric plant—22 1.5.3 Plant layout of diesel engine plant—23 1.5.4 Layout of a nuclear plant—23

1.5.5 Layout of gas turbine plant—24

1.6 Combined power cycles – comparison and selection—251.7 Merits of steam, gas, diesel, hydro and nuclear power plants—26

1.7.1 Advantages and disadvantages of the gas turbine plant—26 1.7.2 Advantages and disadvantages of the nuclear plant—30 1.7.3 Advantages and disadvantages of diesel plants—30 1.7.4 Advantages of hydro-electric power plants—32

1.8 Resources and development of power in India—33

1.8.1 Coal and lignite—33

1.9 Petroleum and natural gas—341.10 Present status of power generation in India—381.11 Role of private and government organization—391.12 State-level scenario, load shedding—41

1.13 Carbon credits—421.14 Questions—44

1.14.1 Objective questions—44 1.14.2 Review questions—45 1.14.3 References—45

2.1 Introduction—462.2 Classification of fuels and different types of fuels used for steam generation—46

2.2.1 Solid fuels—47 2.2.2 Liquid fuels—49 2.2.3 Gaseous fuels—50 2.2.4 Nuclear fuels—51

2.3 Calorific values of fuels—52

2.3.1 Higher calorific value and lower calorific value of fuels—52 2.3.2 Experimental procedure for determining Cv of fuels—54

2.4.8 Excess air supplied—70

2.5 Properties of coal, Indian coals—86

2.5.1 Analysis of coal—87 2.5.2 Indian coals—89

2.6 Selection of coal in thermal power station—90

2.6.1 Geological resources of coal in India—91 2.6.2 Status of coal resources in India during the past five years—92

2.7 Questions—93

2.7.1 Objective questions—93 2.7.2 Review questions—94

3.2 Choice of handling equipment—1003.3 Fuel burning—103

3.3.1 Overfeed and underfeed fuel bed stokers—103

3.4 Equipment for burning coal in lump form—106

3.4.1 Chain grate stoker—107 3.4.2 Travelling grate stoker—107 3.4.3 Spreader stoker—108 3.4.4 Retort stoker—110

3.5 Advantages and disadvantages of stoker firing over pulverized system of firing—1123.6 Preparation and burning of pulverized coal—113

3.6.1 Unit or direct system—113 3.6.2 Bin or central system—113 3.6.3 Advantages and disadvantages of pulverized coal burning—114

3.7 Pulverized fuel furnaces (burners)—1163.8 Pulverized mills—116

3.8.1 Causes for mill fires—121

3.9 Fuel-burning equipments—122

3.9.1 Coal burners—122 3.9.2 Oil burners—125 3.9.3 Gas burners—126

3.10 Flue gas analysis—126

3.10.1 Procedure—126

3.11 Ash handling system—128

3.11.1 Advantages and disadvantages

of wet and dry ash-handling systems—132

3.12 Dust collection—132

3.12.1 Mechanical dust collectors—133 3.12.2 Electrical dust collector (electrostatic precipitators)—135 3.12.3 Soot blowers—137

3.13 Questions—139

3.13.1 Objective questions—139 3.13.2 Review questions—140

4.1 Introduction—1414.2 General layout of modern thermal power plant—1424.3 Rankine and modified rankine cycles—147

4.3.1 Carnot cycle—147 4.3.2 Rankine cycle—148 4.3.3 Modified rankine cycle—159 4.3.4 Reheat cycle—160

4.3.5 Regenerative cycle—167

4.4 Working of different circuits—1764.5 Selection of site for steam power plants—1784.6 Questions—180

4.6.1 Objective questions—180 4.6.2 Review questions—182

5.2.6 Natural circulation and forced circulation boilers—185 5.2.7 Comparison of water tube boilers and fire tube boilers—186

5.3 Circulation in water tube boilers—187

5.4 Modern high-pressure water tube boilers—187

5.4.1 Generation of steam using forced circulation, high and supercritical pressures—188

5.4.2 A brief account of modern steam generators—190

5.5 Boiler performance calculations—196

5.5.1 Turbine efficiency—197 5.5.2 Rankine cycle efficiency ( h c )—198 5.5.3 Generator efficiency ( h g )—198 5.5.4 Overall turbo-alternator efficiency ( h ota )—198 5.5.5 Heat rate—199

5.5.6 Boiler performance—199

5.6 Accessories for the steam generator—200

5.6.1 Superheaters arrangement—202 5.6.2 Control of superheaters—203 5.6.3 Reheaters—207

5.6.4 Economizers—208 5.6.5 Air preheaters—210

5.7 Boiler mountings—212

5.7.1 Water-level indicator—212 5.7.2 Pressure gauge—213 5.7.3 Steam stop valve or junction valve—213 5.7.4 Feed check valve—213

5.7.5 Blow-down valve or blow-off-cock—214 5.7.6 Fusible plug—215

5.7.7 Safety valves—215

5.8 Questions—216

5.8.1 Objective questions—216 5.8.2 Review questions—220

6.1 Introduction to fluidized bed combustion—2216.2 Regimes of combustion—221

6.3 Fluidized bed boilers – classification—223

6.3.1 Atmospheric FBC system or bubbling FBC—223 6.3.2 Circulating FBC—226

6.3.3 Pressurized FBC system—227

6.4 Advantages of FBC system—228

6.5 Control of oxides of nitrogen—2286.6 Desulphurization technology—2296.7 Questions—229

6.7.1 Objective questions—229 6.7.2 Review questions—230 6.7.3 References—231

7.1 Introduction to draught system—2327.2 Air and supply systems (natural mechanical draught systems)—2327.3 Chimneys—235

7.4 Calculations involving height of chimney to produce a given draught—236

7.4.1 Chimney height and diameter—237 7.4.2 Condition for maximum discharge through a chimney—239 7.4.3 Chimney efficiency—242

7.5 Questions—247

7.5.1 Objective questions—247 7.5.2 Review questions—247

8.1 Feed water system – necessity—249

8.1.1 Feed water impurities—249

8.2 Feed water treatment—250

8.2.1 Mechanical methods—251 8.2.2 Thermal methods—252 8.2.3 Chemical methods—253

8.3 Questions—256

8.3.1 Objective questions—256 8.3.2 Review questions—257

9.1 Introduction—2589.2 Types of steam nozzles—2589.3 Flow of steam through nozzle—2599.4 Discharge through nozzle and critical pressure ratio—2619.5 Effect of friction and nozzle efficiency—265

9.6 Supersaturated flow—2669.7 Relation between area, velocity and pressure in nozzle flow—267

9.8 Characteristics of converging–diverging nozzle—2709.9 Steam injector—272

9.10 Questions—276

9.10.1 Objective questions—276 9.10.2 Review questions—280

10.3 Simple impulse turbines—283

10.3.1 Flow through turbine blades and velocity diagram—283 10.3.2 Compounding of steam turbines—283

10.3.3 Impulse turbine power and related calculations—287 10.3.4 Multistage impulse turbine—291

10.5 Losses in steam turbines—31610.6 Reheat factor and condition line—317

10.6.1 Stage efficiency per stage—317 10.6.2 Reheat factor—318

10.6.3 Internal turbine efficiency—318

10.7 Governing of turbines—31810.8 Questions—321

10.8.1 Objective questions—321 10.8.2 Review questions—326

11 Steam Condenser and Circulating

11.1 Introduction to condenser and its necessity—328

11.1.1 Function of a condenser—329 11.1.2 Elements of a condensing plant—329

11.2 Classification and types of condensers—330

11.2.1 Direct-contact condensers—330 11.2.2 Surface condensers—333 11.2.3 Evaporative condenser—335

11.3 Surface condenser performance—336

11.3.3 vacuum and vacuum efficiency—336

11.4 Cooling tower—341

11.4.1 Types—342 11.4.2 Principle of operation and performance—343 11.4.3 Location of cooling tower—348

11.5 Cooling ponds—349

11.5.1 Cooling pond—349 11.5.2 Types of cooling ponds—350

11.6 Corrosion in condensers and boilers—35211.7 Corrosion in boilers—352

11.7.1 Acidic corrosion—352 11.7.2 Galvanic corrosion—353 11.7.3 Steam blanketing—353 11.7.4 Oxygen attack—353 11.7.5 Carbon dioxide attack—354

11.8 Questions—354

11.8.1 Objective questions—354 11.8.2 Review questions—356

12.1 Introduction—358

12.1.1 Joule or brayton cycle—359

12.2 Classification of gas turbines—371

12.2.1 Principle of working of open- and closed-cycle

gas turbines—371 12.2.2 Comparison of open and closed-cycle turbines—374

12.3 Construction and plant layout with auxiliaries—375

12.3.1 Components of a gas turbine—375 12.3.2 Centrifugal compressor—376 12.3.3 Main parts of a centrifugal compressor—377 12.3.4 Impeller and diffuser—377

12.3.5 Diffuser—379 12.3.6 Axial centrifugal compressor—380

12.3.7 Stage velocity triangles—382 12.3.8 Work input to compressor—382 12.3.9 Work done factor—383 12.3.10 Degree of reaction—383

12.4.1 Natural gas—385 12.4.2 Liquefied natural gas—385 12.4.3 Liquid fuels—385

12.6.1 Advantages and disadvantages of gas turbine plant—390

12.7.1 Reheating—391 12.7.2 Regeneration—393 12.7.3 Intercooling—396

12.9 1 Combined cycle principles of operation—418 12.9.2 Coupled cycle – GT–ST plant operation—419 12.9.3 Thermodynamic analysis of a simple

combined cycle GT–ST plant—423

12.10 Layout of gas turbine plant—42612.11 Questions—426

12.11.1 Objective questions —426 12.11.2 Review questions—428 12.11.3 References—429

13.1 Introduction to diesel engine plant—430

13.1.1 IC engine nomenclature—430 13.1.2 Standard terminology—432 13.1.3 Four-stroke diesel engine—433 13.1.4 Two-stroke diesel engine—435

13.2 Types of diesel plants and components—43613.3 Selection of engine type and engine size—43713.4 Plant layout with auxiliaries—438

13.5 Fuel supply system—439

13.5.1 Fuel injection system—442 13.5.2 Types of fuel injection systems—443

13.6 Super charging—44513.7 Method of starting diesel engines—44613.8 Cooling and lubrication system for the diesel engine—449

13.8.1 Engine cooling system—449 13.8.2 Lubrication system—451 13.8.3 Filters, centrifuges and oil heaters—454

13.9 Intake and exhaust systems—456

13.9.1 Intake system—456 13.9.2 Exhaust system—457

13.10 Application of diesel power plant, advantages and disadvantages—458

13.10.1 Comparison with stream power plants—460

13.11 Layout of diesel plant—46013.12 Diesel engine performance and operation—46213.13 Questions—485

13.13.1 Review questions—485

14.1 Recent developments in methods of power generation—487

14.1.1 Conventional energy sources—487 14.1.2 Non-conventional energy sources—489

14.2 Utilization of solar energy—493

14.2.1 Solar radiation—493 14.2.2 Solar radiation at earth’s surface—494 14.2.3 Basic definitions of solar angles—495 14.2.4 Solar constant and intensity of solar radiation—499 14.2.5 Average solar radiation or monthly average

daily global radiation—500 14.2.6 Solar radiation on tilted surfaces—504 14.2.7 Solar energy collectors—507

14.2.8 Photovoltaic power system—512 14.2.9 Solar central receiver system—515

14.3 Wind energy—518

14.3.1 Generation of wind energy—519 14.3.2 Wind turbine operation—521 14.3.3 Components of a wind generator—522 14.3.4 velocity and power from wind—525 14.3.5 Wind turbine operation—532 14.3.6 Horizontal and vertical axis (HAWT, vAWT) wind mills—533

14.3.7 Aerodynamic considerations of wind mill design—540 14.3.8 Coefficient of performance of wind mill rotor—545 14.3.9 Availability of wind energy in India—547

14.3.10 Wind power by country—549

14.4 Tidal energy—551

14.4.1 The simple single pool tidal system—552 14.4.2 The modulated single pool tidal system—555 14.4.3 The two-pool tidal system—555

14.5 Ocean thermal energy conversion—556

14.5.1 Principle of working—556 14.5.2 Ocean temperature differences—556 14.5.3 The open or claude cycle—557 14.5.4 The closed or anderson OTEC cycle—559

14.6 Wave energy—560

14.6.1 Energy and power from waves—560 14.6.2 Wave energy conversion by floats—562 14.6.3 High-pressure accumulator wave machines—563

14.7 Fuel cells—564

14.7.1 Working principle—564 14.7.2 Types of fuel cells—566

14.8 Thermoelectric and thermionic power—570

14.8.1 Thermoelectric power—570 14.8.2 Thermionic converter—572

14.9 MhD generation—573 14.10 Geothermal energy—574

14.10.1 A typical geothermal field—574 14.10.2 Hydrothermal systems—574 14.10.3 Petro thermal systems—578 14.10.4 Hybrid geothermal fossil systems—579 14.10.5 Problems associated with geothermal conversion—581

14.11 Electricity from city refuge—581 14.12 Questions—583

14.12.1 Objective questions—583 14.12.2 Review questions—586

15.1 Introduction to water power—588 15.2 hydrological cycle—589

15.3 Rainfall and its measurement—590

15.3.1 Intensity of rainfall—591 15.3.2 Measurement of rainfall—592 15.3.3 Location of rain gauge—593 15.3.4 Average or mean depth of rainfall—593 15.3.5 Run-off and its measurement—597

15.4 hydrographs—601

15.4.1 The unit hydrograph—603

15.5.1 Flow duration curve—605 15.5.2 Mass curve and storage—609

15.6.1 Site selection for hydel power plants—656 15.6.2 General arrangement of hydroelectric power plant—657 15.6.3 Plant layout—659

15.6.4 Penstock and water hammer—659 15.6.5 Specific speed and capacity calculations—660

15.10 Classification of dams and spillways—67115.11 Brief description of some of the important hydel installations in India—675

15.12 Water turbines—679

15.12.1 Selection of turbines—679 15.12.2 Classification and types of water turbines—680 15.12.3 Governing of turbines—700

15.13 Micro hydel developments—70215.14 Project cost of hydroelectric plant—70415.15 Advantages of hydro-power plant—70915.16 Questions—711

15.16.1 Review questions—711

16 Nuclear Power Plants 714

16.1 Introduction to nuclear engineering—714

16.1.1 Atomic structure—715 16.1.2 Some definitions—716

16.2 Radioactive decay, half life—717

16.2.1 Radioactive decay—717 16.2.2 Half-life—719

16.3 Principles of release of nuclear energy—721

16.3.1 Fusion and fission reactions—721 16.3.2 Breeding and fertile materials—724 16.3.3 Nuclear fuels used in the reactors—724 16.3.4 Multiplication and thermal utilization factors—725 16.3.5 Life cycle of a neutron—727

16.4 Nuclear reactor components—728 16.5 Classification of nuclear reactors—730 16.6 Thermal fission reactors and power plant and their location—733

16.6.1 Pressurized water reactor—734 16.6.2 Boiling water reactor (BWR)—736 16.6.3 CANDU heavy water reactor—739 16.6.4 Gas-cooled reactor—742

16.6.5 Fast breeder reactors—743 16.6.6 Organic substance cooled reactor—747

16.7 Reactor control—750 16.8 Radiation hazards—751

16.8.1 Handling of nuclear waste and safety measures—751 16.8.2 Radioactive waste disposal—753

16.9 Nuclear power generation in India—758 16.10 Questions—760

16.10.1 Objective questions—760 16.10.2 Review questions—765 16.10.3 Reference—766

17.1 Introduction and basic definitions—767 17.2 Types of loads—768

17.2.1 Load curves—769 17.2.2 Drawing load duration curve—774

17.2.3 Effect of variable load on power

plant design and operation—775 17.2.4 Methods to meet variable load—776 17.2.5 Prediction of future loads—777

17.4.1 Depreciation—801

17.5.1 Different types of tariffs—804

17.6.1 Steam power plants—810 17.6.2 Diesel engine plants—810 17.6.3 Gas turbine power plant—810 17.6.4 Hydro-electric power plant—810

and distribution of power—812

17.10 Power achievement, target v/s achieved—813 17.11 Questions—814

17.11.1 Objective questions—814 17.11.2 Review questions—816

18.5.1 Radiation from nuclear power plant effluents—824 18.5.2 Pollution standards—827

18.5.3 Methods of pollution control—829

18.6 Environmental impact of power plant: social

and economical issues of the power plants—833

18.6.1 Land and air space—834 18.6.2 Water—834

18.6.3 Solid waste—834 18.6.4 Construction and operation—834 18.6.5 Noise—834

18.6.6 Economical aspects—835

18.7.1 Objective questions—835 18.7.2 Review questions—836 18.7.3 References—836

19 Instrumentation and Equipments

19.1.1 Process control system—837 19.1.2 Operational monitoring system—838 19.1.3 Automatic generation control system—838 19.1.4 Load frequency control system—838 19.1.5 Power plant maintenance—838 19.1.6 Plant monitoring system—838

19.2.1 Drum water-level control—838

19.3.1 Super heat temperature control—840

19.4.1 The elementary AC generator—842 19.4.2 Development of the sine wave—843 19.4.3 Types of generators—845

19.4.4 Generator parts and function—846 19.4.5 The exciter—846

19.9.1 Control room instrumentation—851

19.10 Switch gear for power station auxiliaries—852

19.11 Testing of power plants and heat balance—852

19.11.1 British standards, BS845: 1987—853 19.11.2 ASME standard: PTC-4-1 power test code

for steam generating units—853 19.11.3 IS 8753: Indian standard for boiler efficiency testing—854

19.11.4 The indirect method testing—855 19.11.5 Energy balance sheet—856

19.12 Questions—856

19.12.1 Objective questions—856 19.12.2 Review questions—857 19.12.3 References—858 Index 859

Energy, or power as it is often referred to, is critical, directly or indirectly, in the entire process

of evolution, growth and survival of all living beings It plays a vital role in the socio-economic

development and human welfare of a country

Power is a ‘strategic commodity’ Any uncertainty about its supply can threaten the

functioning of an economy, particularly in developing countries Since the demand for power

is growing consistently, an emphasis is given to generate power by utilizing various sources

of environment-friendly energy In this context, acquiring the fundamental aspects of power

generation is a must for everyone

The book discusses about the intricacies of power generation using both renewable and

non-renewable resources throughout its nineteen chapters Conventional method of power

generation and the system details have been covered in the first fourteen chapters while the

non-conventional methods of power generation have been explained in chapters 15 and 16

The chapters cover issues like thermal power plant, steam power plant, diesel engine

power plant, gas turbine plant, hydro-electric plant, and nuclear power plant, power from

non-conventional sources and power plant economics and Instrumentation All chapters are

supplemented by neat sketches and illustrations while SI units have also been used throughout

the book which makes it a good reference for engineering students and teachers alike

Key Features

Salient features of the book are:

1 Thermal, hydro and nuclear power generations

2 Solar and wind energy conversion systems

3 Ocean, geothermal and biomass energy systems

4 Fluidized bed combustion technology

5 Power from non-conventional sources

6 Illustrations, sketches and supplementary photographs

7 Environmental aspect of power generation

8 Power plant economics

Acknowledgements

I would like to dedicate this book to my father late N R Hegde, who was a humble teacher

and had been a role model for me I thank my mother Savitri Hegde, who is a constant source

of guidance and encouragement for me My thanks are due to the publishing team of Pearson,

in particular Dheepika, for her timely response and utmost care taken during the manuscript

preparation stage I would also like to thank Sandhya Jayadev for her inputs I would like to

thank my family members, namely, my wife Sathyabhama and lovely daughters Divya and

Disha for their support and sacrifice while writing this book

My special thanks to CA Raghavendra Rao, President, Srinivas Group of Institutions,

Mangalore and Srinivas Rao, Vice-President, Srinivas Group of Institutions, Mangalore for

their whole hearted support in bringing out this book

My heartfelt thanks to Shrinivasa Mayya, Principal, Srinivas Institute of Technology for his

encouragement and motivation Finally, I would like to thank one and all who have been directly

or indirectly involved during the process of writing this book

R K Hegde

R K Hegde obtained his Ph.D in nanofluid heat transfer from

National Institute of Technology, Karnataka The author has more

than 20 years of rich industrial and academic experience Earlier he

was involved in power plant operation and maintenance, handling

high pressure FBC boilers, Babcock–Wilcox boilers, turbines

and pumps He worked in a power plant in maintenance and is

also an authorized boiler operation engineer He is also a member

of I.S.T.E His area of interest includes nanofluids, compact heat

exchangers, and CFD He has more than 30 papers published

in reputed international journals and also presented 15 papers in

international/national conferences He is also an active reviewer for

reputed international journals

Introduction to

Power Plants

1.1 introduction to the sources of energy:

conventional and non-conventional principle of power generation

1.2 Factors affecting selection of site

1.3 Principal types of power plants

1.4 Present status and future trends

1.5 Layout of steam, hydel, diesel, nuclear

and gas turbine power plants 1.6 Combined power cycles – comparison

1.11 Role of private and government organization

1.12 State-level scenario, load shedding 1.13 Carbon credits

1.1 INTRODUCTION TO THE SOURCES OF ENERGY:

CONVENTIONAL AND NON-CONVENTIONAL PRINCIPLE

OF POWER GENERATION

A variety of energy sources are available to supply to expanding needs in each country around the world These sources are broadly classified as commercial or conventional energy sources and noncommercial or nonconventional energy sources Most of the developed countries are highly dependent on conventional form of energy, whereas developing countries such as India

is dependent on both the forms of energy sources

Energy sources may be mainly classified into two categories: renewable and non-renewable energy sources

1. Renewable energy sources

These are produced by nature and are inexhaustible Renewable energy sources include both direct solar radiation utilized by solar collectors and cells and indirect solar energy in the form

of wind, hydropower, ocean energy and sustainable biomass resources

Contents

2. Non-renewable energy sources

These are either available in nature or produced by man artificially They are exhaustible and

non-renewable Conventional energy sources such as nuclear power and fossil fuels are nonnon-renewable

Advantages and disadvantages of renewable energy sources are as follows:

Advantages

(i) They are produced by nature and considered as inexhaustible

(ii) They are pollution free, and hence eco-friendly

(iii) If utilized properly in developing countries, they can save a lot of foreign exchange and

generate employment opportunities

(iv) Deployment is easy and rapid due to flexibility in their utilization

(v) They are economical when considered over a longer period of time

Disadvantages

(i) Their availability is intermittent (e.g solar, wind, tidal, hydro, etc.) and hence need the

assistance of nonrenewable energy

(ii) Complete commercialization is difficult on a larger scale

(iii) Initial cost is high due to the newer technologies used, which are still at preliminary stages

(iv) Sources are not evenly spread across the globe

In sections that follow, both conventional and nonconventional energy sources are discussed

in detail

1.1.1 Conventional Energy Sources

These are commercial forms of energy available They include the following:

(i) Fossil fuel that may be in solid, liquid or gaseous forms

(ii) Water power or energy stored in water

(iii) Nuclear energy

Worldwide consumption of total energy is as shown in the Table 1.1

Table 1.1 Worldwide Consumption of Total Energy

Source of energy

Contribution (%)

Overall contribution (%)

Source of energy

Contribution (%)

Overall contribution (%)

Figure 1.1 shows a thermal power plant using steam as a working fluid It consists of a steam generator, a condensing turbine coupled to a generator, a condenser with a condensate extrac-

tion pump and a feed water tank with a feed pump

High-pressure steam

Bled steam

Feed tank

Power transmission tower

Turbine

Generator

Condensate pump Feed pump

Fig 1.1 A Typical Thermal Power Plant

In a coal-fired thermal power plant, coal is burnt in a boiler furnace The heat generated

is utilized to convert water, which is the working fluid, into superheated steam in the boiler

or steam generator The high-pressure steam is used to run the prime mover (steam turbine) The prime mover rotates along with an electrical generator coupled to it Thus, mechanical energy is converted into electrical energy that is supplied to various points using power feeders The steam that expands in the turbine is condensed into water in a surface condenser The condensate water is pumped back to the feed tank The feed water in the feed tank is heated by bleeding some amount of steam from the turbine The hot feed water is pumped to the boiler using a feed pump

Table 1.1 (Continued )

According to estimates, coal reserves are sufficient enough to last for 200 years However, coal reserves have lower calorific value, and their transportation is uneconomical When burnt, they

2. Oil

Almost 40 per cent of energy needs is met by oil alone With present consumption and a resource

of 250,000 million tons of oil, it is estimated to last for only 100 years, unless more oil is

dis-covered Major chunk of oil comes from petroleum

3. Gas

Due to the non-availability of ready market gas is not completely and effectively utilized and

is burnt in huge quantities Its transportation cost is much higher than oil Large reserves are estimated to be located in inaccessible areas Gaseous fuels are classified as follows:

(i) Gases of fixed composition such as acetylene, ethylene, methane, etc

(ii) Industrial gases such as producer gas, coke oven gas, blast furnace gas, water gas, etc

4 Agricultural and organic wastes

These include saw dust, bagasse, garbage, animal dung, paddy husk, corn stem, etc., accounting for a major energy consumption

5. Water

It is one of the potential sources of energy meant exclusively for hydro-electric power

genera-tion Potential energy of water is utilized to convert it into mechanical energy by using prime movers known as hydraulic turbines The operating cost of the plant is cheaper as compared to other types of power plants It is the only renewable non-depleting source of energy that does not contribute to pollution

Figure 1.2 shows a hydraulic power plant designed for high head In a hydro-electric power plant, water is stored behind a dam that forms a reservoir Water is taken from the reservoir

through tunnels from where it is distributed to penstocks A penstock is a large diameter pipe

that carries water to the turbine Trash racks are fitted at the inlet of tunnels to prevent any

for-eign matter from entering into the tunnels A surge tank built before the valve house prevents sudden pressure rise in the penstock when the load on the turbine decreases or when the inlet valves to the turbine suddenly get closed The flow of water in the penstocks is controlled in the valve house that is electrically driven Thus, potential energy of water is utilized to run the prime mover (hydraulic turbine) coupled to an electric generator in the power house After doing work, the water is discharged to the tail race

6. Nuclear power

Any matter consists of atoms held together by means of binding energy Controlled fission of

This is possible only by utilizing small amount of nuclear fuels It may be noted that the energy

4,500 kg of coal This factor makes the nuclear energy more attractive The energy generated during nuclear fission reaction is used to produce steam in heat exchangers, which is utilized to run the turbo-generators

For nuclear power generation, three systems are considered The first is based on natural

ura-nium yielding power and plutoura-nium The second is by using plutoura-nium and depleted uraura-nium in

a fast breeder reactor The third system is by using thorium and converting it into uranium in a

that is a meager 1 per cent of its current energy requirements

1.1.2 Non-Conventional Energy Sources

1. Solar energy

Solar energy has the greatest potential of all the sources of renewable energy that comes to the earth from sun This energy keeps the temperature of the earth above that in colder space, causes wind currents in the ocean and the atmosphere, causes water cycle and generates photosynthe-

energy than our requirement Even if we use 5 per cent of this energy, it is more than 50 times out

Figure 1.3 shows a concentrating type solar collector used to trap solar energy

2. Wind energy

Wind energy can be economically used for the generation of electrical energy Winds are caused

by two main factors:

(i) Heating and cooling of the atmosphere which generates convection currents Heating is

caused by the absorption of solar energy on the earth’s surface and in the atmosphere

(ii) The rotation of the earth with respect to atmosphere and its motion around sun

Dam

Tunnel

Surge tank Valve house

Penstock

Power house

Tail race Head race

Fig 1.2 A Hydraulic Power Plant

(Absorber tube with concentric glass cover)

Pivoting receiver support Receiver

Water out Support

Water in

Cylindrical parabolic concentrator

Fig 1.3 A Concentrating-Type Solar Collector

which is almost the same as the present-day energy consumption Wind energy can be utilized

to run windmill that in turn is used to drive to generators India has a potential of 20,000 MW

of wind power

which is almost the same as the present-day energy consumption Wind energy can be utilized

to run windmill that in turn is used to drive the generators India has a potential of 20,000 MW

of wind power

Due to pressure differential existing between any two places on earth, air moves at high speed This pressure differential is caused due to earth’s rotation and by uneven heating of the earth by sun The kinetic energy of air can be utilized to generate electric power The kinetic energy per unit volume of moving air is given by the following equation:

2

12

E = r V

Figure 1.4 shows a typical windmill where water can be pumped out for irrigation and

drink-ing purpose Here the rotational motion of the wheel can be either translated into rotary motion (to generate electricity) or reciprocating motion (to drive the pump)

3 Energy from biomass and biogas

Bio-mass means organic matter that is produced in nature through photosynthesis In the

to 469 kJ/mole

Water tank

Fig 1.4 A Typical Windmill

It is possible to produce large amount of carbohydrate by growing plants such as algae in plastic tubes or ponds The algae could be harvested, dried and burned for production of heat that could

be converted into electricity by conventional methods The biomass can be either used directly

by burning or can be processed further to produce more convenient liquid or gaseous fuels

Three different categories of bio-mass resources are as follows:

burnt directly to get energy

methanol that are used as liquid fuels in engines

Various resources of bio-mass are as follows:

(i) Concentrated waste – municipal solids, sewage wood products, industrial waste and manure of large lots

(ii) Dispersed waster residue – crop residue, legging residue and disposed manure

(iii) Harvested biomass, stand by bio-mass and bio-mass energy plantation

4. Energy from oceans

A large amount of solar energy is collected and stored in oceans The surface of water acts

as a collector for solar heat, while the upper layer of the sea constitutes infinite heat storage

reservoir The heat contained in the oceans could be converted into electricity due to the

tem-perature difference (20–25 K) between the warm surface water of the tropical oceans and the colder waters in the depths This is the basic idea of OTEC systems The surface water that is at higher temperature could be used to heat some low-boiling-point organic fluid, the vapours of which would run a heat engine The amount of energy available from OTEC is enormous, and

Boiler

Pump

Cool deep water

Generator

Surface water discharge

Fig 1.5 An OTEC Plant

Disadvantages

(i) Efficiency is extremely low, and hence the system needs extremely large power plant heat

exchangers and components

(ii) Even though there is no fuel cost, the capital cost is very high, and hence the unit power

The tides are rhythmic but not constant Their occurrence is due to a balance of forces, mainly gravitational force of the moon and sun to some extent, balancing the centrifugal force

on water due to earth rotation This results in rhythmic rise and fall of water The moon rotates

around the earth every 24 hr 50 min During this period, tide rises and falls twice, resulting in

a tidal cycle lasting for 12 hr 25 min Thus, the tidal range R is given by the following relation;

This range is maximum during new and full moons and is known as spring tide and neap tide

To harness tides, a dam is built across the mouth of the bay with large gates and low head hydraulic reversible turbines (Figure 1.6) A tidal basin formed thus gets separated from the sea, by dam There always exists a difference between the water levels on either side of the dam during low tide and high tide Thus, the reversible water turbine runs continuously producing power by using the generator connected to it

High tide level

Ocean at low tide

Reversible turbines and gates Pool

Fig 1.6 A Tidal Energy Harnessing Plant

6. Wave energy conversion

Waves are caused by wind that in turn is caused by the uneven solar heating and subsequent cooling of the earth’s crust and the rotation of the earth When at its most active stage, wave energy produces more power than incident solar energy at its peak

Total energy of waves is the sum of potential and kinetic energies The potential energy arises from the elevation of the water above the mean sea level The kinetic energy of the wave is that

of the liquid between two vertical planes perpendicular to the direction of wave propagation x

and placed one wavelength apart

Figure 1.7 shows a typical wave energy conversion system It consists of a square float that moves up and down with the water guided by four vertical manifolds The platform is stabilized within the water by four large underwater floatation tanks supported by buoyancy forces that restrict the vertical or horizontal displacement of the platform due to wave action Damping fins may be used so that the platform is stationary in space even in heavy seas

A piston attached to the float moves up and down the cylinder The cylinder is attached to the platform, and hence is stationary The piston–cylinder arrangement acts as a reciprocating air compressor The downward motion of the piston draws air into the cylinder via an inlet check valve The upward motion compresses the air and sends it through an outlet check valve to the four underwater floatation tanks via the four manifolds The four floatation tanks serve the dual purpose of buoyancy and air storage, and the four vertical manifolds serve the dual purpose of manifolds and float guides The compressed air in the buoyancy-storage tanks is in turn used to drive an air turbine that drives an electrical generator The electric current is transmitted to the shore via an underground cable

Inlet check valve

Outlet check valve Cylinder

Piston Square float

Buoyancy and air storage tanks

Platform Manifold

Fig 1.7 A Typical Wave Energy Conversion System

7. Geothermal energy

This is the energy that comes from within the earth’s crust In some locations of the earth, the steam and hot water comes naturally to the surface For large-scale use, bore holes are normally sunk with depth up to 1,000 m releasing steam and water at temperatures 200–300°C and pressure

Method I

In this method, the heat energy is transferred to a working fluid that operates the power cycle It

is found that molten interior mass of earth vents to the surface through fissures at temperatures ranging between 450 and 550°C

Method II

In this method, the hot geothermal water and/or steam is used to operate the turbines directly From the well head, steam is transmitted by using pipes of 1 m diameter over distances up to 3,000 m to the power plant In this system, water separators are used to separate moisture and solid particles from steam

8. Hydrogen energy

Hydrogen as an energy is another alternative for conventional fuels It can be easily produced from water that is available abundantly in nature It has the highest energy content per unit of mass of any chemical fuel and is a better substitute for hydrocarbons, with increased combus-

tion efficiency It is non-polluting and can be used in fuel cells to produce both electricity and useful heat However, it has technical problems such as production, storage and transportation

Igneous rock

Permeable reservoir

Solid rock (impermeable)

A B

B

G

E

F D

These are electrochemical devices that are used for the continuous conversion of the portion

of the free energy change in a chemical reaction to electrical energy It operates with

contin-uous replenishment of the fuel, and the oxidant at active electrode area and does not require recharging

Main components of a cell are (i) a fuel electrode, (ii) an oxidant or an air electrode, and

Figure 1.9 shows a typical hydrogen–oxygen cell popularly known as a hydrox cell It

consists of two porous or permeable electrodes made up of either carbon or nickel immersed

in an electrolyte of KOH solution Since the electrochemical reaction at the porous electrode where gas, electrolyte and electrode in contact are slow, a catalyst (finely divided platinum or platinum such as material) is embedded in the electrodes The concentration of KOH solution is maintained at about 30–40 per cent, since it has higher thermal conductivity and less corrosive compared to acids.

A single hydrogen–oxygen cell can produce an electromagnetic force (emf) of 1.23 V at

atmos-pheric pressure and at a temperature of 298 K By combining the cells in series, it is possible to generate power ranging between a few kilo-watts to mega-watts

Advantages

(i) Since power conversion is a direct process, the conversion efficiency is as high as 70 per cent

(ii) It is pollution free when operated using hydrogen and operates with minimum noise

(iii) It is compact in size and lighter in weight

(iv) Maintenance cost is less due to lesser mechanical components

Disadvantages

(i) It involves higher initial cost

(ii) It has lower voltage

(iii) It has lower service life

10. MHD generators

MHD generators are used for direct conversion of thermal energy into electrical energy (Figure  1.10) They work on Faraday principle When an electric conductor moves across a magnetic field, a voltage is induced in it, which produces an electric current In MHD gener-

ators, the solid conductors are replaced by a fluid that is electrically conducting The working fluid may be either an ionized gas or liquid metal The hot, partially ionized and compressed gas is expanded in a duct, and forced through a strong magnetic field, electrical potential is

generated in the gas Electrodes placed on the side of the duct pick-up potential generated in the gas The direct current thus obtained can be converted into AC using an inverter.

The system is simple with large power and temperature-handling capacity without any moving parts It is highly reliable and can be brought to full load within 45 sec Power output can be changed from no load to full load in fraction of a second

Electrons that are emitted by heating cathode are migrated to cooler anode collector and flow through outer circuit to develop electric power Low-work function materials such as bar-

ium and strontium oxides are used for anodes, whereas high-work function materials such as Tungsten impregnated with barium is used for cathodes

RL Vacuum

Magnet

Fig 1.10 Principle of MHD Power Generation