Exergy (eBook)

FRONT COVER 1
EXERGY: ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 4
COPYRIGHT PAGE 5
TABLE OF CONTENTS 10
PREFACE 6
ACKNOWLEDGMENTS 8
ABOUT THE AUTHORS 9
CHAPTER 1. THERMODYNAMIC FUNDAMENTALS 20
1.1. Introduction 20
1.2. Energy 20
1.2.1. Applications of energy 20
1.2.2. Concept of energy 21
1.2.3. Forms of energy 21
1.2.4. The first law of thermodynamics 22
1.2.5. Energy and the FLT 23
1.2.6. Economic aspects of energy 23
1.2.7. Energy audit methods 24
1.2.8. Energy management 24
1.3. Entropy 25
1.3.1. Order and disorder and reversibility and irreversibility 25
1.3.2. Characteristics of entropy 26
1.3.3. Significance of entropy 27
1.3.4. Carnot's contribution 28
1.3.5. The second law of thermodynamics 28
1.3.6. SLT statements 29
1.3.7. The Clausius inequality 29
1.3.8. Useful relationships 30
1.4. Exergy 30
1.4.1. The quantity exergy 30
1.4.2. Exergy analysis 30
1.4.3. Characteristics of exergy 31
1.4.4. The reference environment 31
1.4.5. Exergy vs. energy 32
1.4.6. Exergy efficiencies 33
1.4.7. Solar exergy and the earth 33
1.5. Illustrative examples 34
1.5.1. Illustrative example 1 34
1.5.2. Illustrative example 2 35
1.5.3. Illustrative example 3 36
1.5.4. Illustrative example 4 38
1.6. Closing remarks 40
Problems 40
CHAPTER 2. EXERGY AND ENERGY ANALYSES 42
2.1. Introduction 42
2.2. Why energy and exergy analyses? 42
2.3. Nomenclature 43
2.4. Balances for mass, energy and entropy 43
2.4.1. Conceptual balances 43
2.4.2. Detailed balances 43
2.5. Exergy of systems and flows 45
2.5.1. Exergy of a closed system 45
2.5.2. Exergy of flows 46
2.6. Exergy consumption 47
2.7. Exergy balance 47
2.8. Reference environment 48
2.8.1. Theoretical characteristics of the reference environment 48
2.8.2. Models for the reference environment 48
2.9. Efficiencies and other measures of merit 50
2.10. Procedure for energy and exergy analyses 51
2.11. Energy and exergy properties 51
2.12. Implications of results of exergy analyses 52
2.13. Closing remarks 53
Problems 53
CHAPTER 3. EXERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 55
3.1. Introduction 55
3.2. Exergy and environmental problems 56
3.2.1. Environmental concerns 56
3.2.2. Potential solutions to environmental problems 59
3.2.3. Energy and environmental impact 61
3.2.4. Thermodynamics and the environment 61
3.3. Exergy and sustainable development 64
3.3.1. Sustainable development 64
3.3.2. Sustainability and its need 64
3.3.3. Dimensions of sustainability 65
3.3.4. Environmental limits and geographic scope 66
3.3.5. Environmental, social and economic components of sustainability 66
3.3.6. Industrial ecology and resource conservation 66
3.3.7. Energy and sustainable development 68
3.3.8. Energy and environmental sustainability 68
3.3.9. Exergy and sustainability 68
3.3.10. Exergetic aspects of sustainable processes 70
3.3.11. Renewables and tools for sustainable development 70
3.3.12. Exergy as a common sustainability quantifier for process factors 74
3.4. Illustrative example 75
3.4.1. Implications regarding exergy and energy 76
3.4.2. Implications regarding exergy and the environment 77
3.4.3. Implications regarding exergy and sustainable development 77
3.5. Closing remarks 77
Problems 78
CHAPTER 4. APPLICATIONS OF EXERGY IN INDUSTRY 79
4.1. Introduction 79
4.2. Questions surrounding industry's use of exergy 80
4.3. Advantages and benefits of using exergy 80
4.3.1. Understanding thermodynamic efficiencies and losses through exergy 81
4.3.2. Efficiency 81
4.3.3. Loss 82
4.3.4. Examples 82
4.3.5. Discussion 83
4.4. Understanding energy conservation through exergy 83
4.4.1. What do we mean by energy conservation? 83
4.4.2. Exergy conservation 84
4.4.3. Examples 84
4.5. Disadvantages and drawbacks of using exergy 85
4.6. Possible measures to increase applications of exergy in industry 85
4.7. Closing remarks 86
Problems 86
CHAPTER 5. EXERGY IN POLICY DEVELOPMENT AND EDUCATION 87
5.1. Introduction 87
5.2. Exergy methods for analysis and design 87
5.3. The role and place for exergy in energy-related education and awareness policies 89
5.3.1. Public understanding and awareness of energy 89
5.3.2. Public understanding and awareness of exergy 89
5.3.3. Extending the public's need to understand and be aware of exergy to government and the media 90
5.4. The role and place for exergy in education policies 90
5.4.1. Education about exergy 90
5.4.2. The need for exergy literacy in scientists and engineers 91
5.4.3. Understanding the second law through exergy 91
5.4.4. Exergy's place in a curriculum 92
5.5. Closing remarks 93
Problems 94
CHAPTER 6. EXERGY ANALYSIS OF PSYCHROMETRIC PROCESSES 95
6.1. Basic psychrometric concepts 95
6.2. Balance equations for air-conditioning processes 97
6.3. Case study: exergy analysis of an open-cycle desiccant cooling system 101
6.3.1. Introduction 101
6.3.2. Operation and design of experimental system 101
6.3.3. Energy analysis 103
6.3.4. Exergy analysis 103
6.3.5. Results and discussion 106
6.4. Closing remarks 108
Problems 108
CHAPTER 7. EXERGY ANALYSIS OF HEAT PUMP SYSTEMS 110
7.1. Introduction 110
7.2. System description 112
7.3. General analysis 113
7.4. System exergy analysis 114
7.5. Results and discussion 117
7.6. Concluding remarks 117
Problems 121
CHAPTER 8. EXERGY ANALYSIS OF DRYING PROCESSES AND SYSTEMS 122
8.1. Introduction 122
8.2. Exergy losses associated with drying 123
8.3. Analysis 124
8.3.1. Balances 124
8.3.2. Exergy efficiency 125
8.4. Importance of matching supply and end-use heat for drying 126
8.5. Illustrative example 126
8.5.1. Approach 126
8.5.2. Results 126
8.5.3. Discussion 129
8.6. Energy analysis of fluidized bed drying of moist particles 131
8.6.1. Fluidized bed drying 131
8.6.2. Thermodynamic model and balances 133
8.6.3. Efficiencies for fluidized bed drying 135
8.6.4. Effects of varying process parameters 136
8.6.5. Example 136
8.7. Concluding remarks 145
Problems 145
CHAPTER 9. EXERGY ANALYSIS OF THERMAL ENERGY STORAGE SYSTEMS 146
9.1. Introduction 146
9.2. Principal thermodynamic considerations in TES 147
9.3. Exergy evaluation of a closed TES system 148
9.3.1. Analysis of the overall processes 148
9.3.2. Analysis of subprocesses 150
9.3.3. Implications for subprocesses and overall process 152
9.4. Relations between temperature and efficiency for sensible TES 153
9.4.1. Model and analysis 153
9.4.2. Efficiencies and their dependence on temperature 154
9.5. Exergy analysis of thermally stratified storages 156
9.5.1. General stratified TES energy and exergy expressions 156
9.5.2. Temperature-distribution models and relevant expressions 158
9.5.3. Increasing TES exergy storage capacity using stratification 161
9.6. Energy and exergy analyses of cold TES systems 164
9.6.1. Energy balances 165
9.6.2. Exergy balances 167
9.6.3. Efficiencies 167
9.7. Exergy analysis of aquifer TES systems 168
9.7.1. ATES model 168
9.7.2. Energy and exergy analyses 169
9.8. Examples and case studies 171
9.8.1. Inappropriateness of energy efficiency for TES evaluation 171
9.8.2. Comparing thermal storages 171
9.8.3. Thermally stratified TES 174
9.8.4. Cold TES 175
9.8.5. Aquifer TES 178
9.9. Concluding remarks 181
Problems 181
CHAPTER 10. EXERGY ANALYSIS OF RENEWABLE ENERGY SYSTEMS 182
10.1. Exergy analysis of solar photovoltaic systems 182
10.1.1. PV performance and efficiencies 183
10.1.2. Physical exergy 183
10.1.3. Chemical exergy 184
10.1.4. Illustrative example 186
10.1.5. Closure 186
10.2. Exergy analysis of solar ponds 186
10.2.1. Solar ponds 188
10.2.2. Experimental data for a solar pond 189
10.2.3. Energy analysis 191
10.2.4. Exergy analysis 199
10.2.5. Closure 204
10.3. Exergy analysis of wind energy systems 206
10.3.1. Wind energy systems 207
10.3.2. Energy and exergy analyses of wind energy aspects 208
10.3.3. Case study 211
10.3.4. Spatio-temporal wind exergy maps 215
10.3.5. Closure 223
10.4. Exergy analysis of geothermal energy systems 224
10.4.1. Case study 1: energy and exergy analyses of a geothermal district heating system 226
10.4.2. Case study 2: exergy analysis of a dual-level binary geothermal power plant 236
10.5. Closing remarks 245
Problems 246
CHAPTER 11. EXERGY ANALYSIS OF STEAM POWER PLANTS 248
11.1. Introduction 248
11.2. Analysis 249
11.2.1. Balances 249
11.2.2. Overall efficiencies 250
11.2.3. Material energy and exergy values 250
11.3. Spreadsheet calculation approaches 252
11.4. Example: analysis of a coal steam power plant 254
11.5. Example: impact on power plant efficiencies of varying boiler temperature and pressure 254
11.6. Case study: energy and exergy analyses of coal-fired and nuclear steam power plants 257
11.6.1. Process descriptions 258
11.6.2. Approach 264
11.6.3. Analysis 264
11.6.4. Results 265
11.6.5. Discussion 267
11.7. Improving steam power plant efficiency 271
11.7.1. Exergy-related techniques 271
11.7.2. Computer-aided design, analysis and optimization 272
11.7.3. Maintenance and control 272
11.7.4. Steam generator improvements 272
11.7.5. Condenser improvements 273
11.7.6. Reheating improvements 273
11.7.7. Regenerative feedwater heating improvements 274
11.7.8. Improving other plant components 274
11.8. Closing remarks 275
Problems 275
CHAPTER 12. EXERGY ANALYSIS OF COGENERATION AND DISTRICT ENERGY SYSTEMS 276
12.1. Introduction 276
12.2. Cogeneration 277
12.3. District energy 278
12.4. Integrated systems for cogeneration and district energy 279
12.5. Simplified illustrations of the benefits of cogeneration 280
12.5.1. Energy impacts 280
12.5.2. Energy and exergy efficiencies 282
12.5.3. Impact of cogeneration on environmental emissions 283
12.5.4. Further discussion 284
12.6. Case study for cogeneration-based district energy 284
12.6.1. System description 284
12.6.2. Approach and data 286
12.6.3. Preliminary analysis 286
12.6.4. Analysis of components 287
12.6.5. Analysis of overall system 291
12.6.6. Effect of inefficiencies in thermal transport 291
12.6.7. Analyses of multi-component subsystems 291
12.6.8. Results 291
12.6.9. Discussion 293
12.7. Closing remarks 294
Problems 295
CHAPTER 13. EXERGY ANALYSIS OF CRYOGENIC SYSTEMS 296
13.1. Introduction 296
13.2. Energy and exergy analyses of gas liquefaction systems 296
13.3. Exergy analysis of a multistage cascade refrigeration cycle for natural gas liquefaction 300
13.3.1. Background 300
13.3.2. Description of the cycle 300
13.3.3. Exergy analysis 301
13.3.4. Minimum work for the liquefaction process 304
13.3.5. Discussion 307
13.4. Closing remarks 307
Problems 307
CHAPTER 14. EXERGY ANALYSIS OF CRUDE OIL DISTILLATION SYSTEMS 309
14.1. Introduction 309
14.2. Analysis approach and assumptions 310
14.3. Description of crude oil distillation system analyzed 310
14.3.1. Overall system 310
14.3.2. System components 311
14.4. System simulation 313
14.5. Energy and exergy analyses 313
14.5.1. Crude heating furnace 313
14.5.2. Atmospheric distillation unit 314
14.5.3. Overall exergy efficiency 315
14.6. Results and discussion 315
14.6.1. Simulation results 315
14.6.2. Energy and exergy results 315
14.6.3. Impact of operating parameter variations 317
14.6.4. Result limitations 319
14.7. Closing remarks 320
Problems 321
CHAPTER 15. EXERGY ANALYSIS OF FUEL CELL SYSTEMS 322
15.1. Introduction 322
15.2. Background 323
15.2.1. PEM fuel cells 323
15.2.2. Solid oxide fuel cells 323
15.3. Exergy analysis of a PEM fuel cell power system 324
15.3.1. System description 324
15.3.2. PEM fuel cell performance model 325
15.3.3. Analysis 326
15.3.4. Results and discussion 327
15.3.5. Closure 331
15.4. Energy and exergy analyses of combined SOFC–gas turbine systems 332
15.4.1. Description of systems 332
15.4.2. Analysis 334
15.4.3. Thermodynamic model of the SOFC stack 337
15.4.4. Exergy balances for the overall systems 338
15.4.5. Results and discussion 339
15.4.6. Closure 342
15.5. Closing remarks 342
Problems 342
CHAPTER 16. EXERGY ANALYSIS OF AIRCRAFT FLIGHT SYSTEMS 344
16.1. Introduction 344
16.2. Exergy analysis of a turbojet 345
16.2.1. Exergy flows through a turbojet 345
16.2.2. Exergy efficiencies for a turbojet 347
16.2.3. Impact of environment on turbojet assessment 347
16.3. Flight characteristics 348
16.4. Cumulative rational efficiency 348
16.4.1. Variable reference environment 348
16.4.2. Constant reference environment 350
16.5. Cumulative exergy loss 351
16.6. Contribution of exhaust gas emission to cumulative exergy loss 351
16.6.1. Variable reference environment 351
16.6.2. Constant reference environment 352
16.7. Closing remarks 353
Problems 353
CHAPTER 17. EXERGOECONOMIC ANALYSIS OF THERMAL SYSTEMS 354
17.1. Introduction 354
17.2. Economic aspects of exergy 355
17.2.1. Exergy and economics 355
17.2.2. Energy and exergy prices 356
17.3. Modeling and analysis 357
17.3.1. Fundamental relationships 357
17.3.2. Definition of key terms 359
17.3.3. Ratio of thermodynamic loss rate to capital cost 360
17.4. Key difference between economic and thermodynamic balances 360
17.5. Example: coal-fired electricity generation 361
17.5.1. Plant description and data 362
17.5.2. Data categorization 364
17.5.3. Results and discussion 366
17.6. Case study: electricity generation from various sources 368
17.6.1. Results and discussion 369
17.6.2. Relations for devices in a single generating station 369
17.6.3. Generalization of results 375
17.7. Exergoeconomics extended: EXCEM analysis 376
17.7.1. The EXCEM analysis concept 376
17.7.2. Development of a code for EXCEM analysis 376
17.7.3. Illustrative examples of EXCEM analysis 377
17.7.4. Exergy loss and cost generation 378
17.8. Closing remarks 380
Problems 380
CHAPTER 18. EXERGY ANALYSIS OF COUNTRIES, REGIONS AND ECONOMIC SECTORS 382
18.1. Introduction 382
18.2. Background and benefits 383
18.3. Applying exergy to macrosystems 383
18.3.1. Energy and exergy values for commodities in macrosystems 383
18.3.2. The reference environment for macrosystems 384
18.3.3. Efficiencies for devices in macrosystems 385
18.4. Case study: energy and exergy utilization in Saudi Arabia 386
18.4.1. Analysis of the residential sector 387
18.4.2. Analysis of the public and private sector 390
18.4.3. Analysis of the industrial sector 396
18.4.4. Analysis of the transportation sector 399
18.4.5. Analysis of the agricultural sector 405
18.4.6. Analysis of the utility sector 407
18.4.7. Energy and exergy efficiencies and flows for the sectors and country 409
18.4.8. Discussion 412
18.4.9. Summary of key findings 413
18.5. Comparison of different countries 413
18.6. Closing remarks 413
Problems 414
CHAPTER 19. EXERGETIC LIFE CYCLE ASSESSMENT 416
19.1. Introduction 416
19.2. Life cycle assessment 416
19.3. Exergetic LCA 417
19.4. Case study: exergetic life cycle analysis 418
19.4.1. Natural gas and crude oil transport 419
19.4.2. Natural gas reforming and crude oil distillation 419
19.4.3. Hydrogen production from renewable energy 421
19.4.4. Hydrogen compression 422
19.4.5. Hydrogen and gasoline distribution 423
19.4.6. Life cycle exergy efficiencies 424
19.5. Economic implications of ExLCA 425
19.6. LCA and environmental impact 426
19.6.1. Power generation and transportation 426
19.6.2. Environmental-impact reduction by substitution of renewables for fossil fuels 428
19.6.3. Main findings and extensions 434
19.7. Closing remarks 434
Problems 434
CHAPTER 20. EXERGY AND INDUSTRIAL ECOLOGY 436
20.1. Introduction 436
20.2. Industrial ecology 436
20.3. Linkage between exergy and industrial ecology 437
20.3.1. Depletion number 437
20.3.2. Integrated systems 437
20.4. Illustrative example 438
20.4.1. The considered gas-turbine combined cycle with hydrogen generation 438
20.4.2. Exergy analysis of the gas-turbine combined cycle with hydrogen generation 440
20.4.3. Results 440
20.5. Closing remarks 442
Problems 442
CHAPTER 21. CLOSING REMARKS AND FUTURE EXPECTATIONS 443
NOMENCLATURE 445
REFERENCES 448
APPENDIX A: GLOSSARY OF SELECTED TERMINOLOGY 459
APPENDIX B: CONVERSION FACTORS 462
APPENDIX C: THERMOPHYSICAL PROPERTIES 464
INDEX 470
A 470
B 470
C 470
D 470
E 471
F 471
G 471
H 471
I 471
K 471
L 471
M 472
N 472
O 472
P 472
Q 472
R 472
S 472
T 472
U 473
V 473
W 473