Wind Energy Handbook, 2nd Edition (2011, EBook)
ABOUT THE AUTHOR
Tony Burton, Wind Energy Consultant, Powys, UK
Nick Jenkins, Cardiff University, UK
David Sharpe, Wind Energy Consultant, Essex, UK
Ervin Bossanyi, GL Garrad Hassan, Bristol, UK
TABLE OF CONTENTS
About the Authors xvii
Preface to Second Edition xix
Acknowledgements for First Edition xxi
Acknowledgements for Second Edition xxiii
List of Symbols xxv
Figures C1 and C2 – Co-ordinate Systems xxxv
1 Introduction 1
1.1 Historical development 1
1.2 Modern wind turbines 4
1.3 Scope of the book 6
References 7
Further reading 8
2 The wind resource 9
2.1 The nature of the wind 9
2.2 Geographical variation in the wind resource 10
2.3 Long-term wind speed variations 11
2.4 Annual and seasonal variations 12
2.5 Synoptic and diurnal variations 14
2.6 Turbulence 14
2.7 Gust wind speeds 28
2.8 Extreme wind speeds 29
2.9 Wind speed prediction and forecasting 32
2.10 Turbulence in wakes and wind farms 33
2.11 Turbulence in complex terrain 36
References 36
3 Aerodynamics of horizontal axis wind turbines 39
3.1 Introduction 39
3.2 The actuator disc concept 40
3.3 Rotor disc theory 44
3.4 Vortex cylinder model of the actuator disc 49
3.5 Rotor blade theory (blade-element/momentum theory) 57
3.6 Breakdown of the momentum theory 64
3.7 Blade geometry 66
3.8 The effects of a discrete number of blades 75
3.9 Stall delay 92
3.10 Calculated results for an actual turbine 95
3.11 The performance curves 97
3.12 Constant rotational speed operation 101
3.13 Pitch regulation 105
3.14 Comparison of measured with theoretical performance 107
3.15 Variable speed operation 108
3.16 Estimation of energy capture 109
3.17 Wind turbine aerofoil design 114
References 119
Websites 120
Further reading 120
Appendix A3 lift and drag of aerofoils 120
A3.1 Definition of drag 121
A3.2 Drag coefficient 123
A3.3 The boundary layer 124
A3.4 Boundary layer separation 124
A3.5 Laminar and turbulent boundary layers 125
A3.6 Definition of lift and its relationship to circulation 127
A3.7 The stalled aerofoil 130
A3.8 The lift coefficient 131
A3.9 Aerofoil drag characteristics 131
A3.10 Cambered aerofoils 134
4 Further aerodynamic topics for wind turbines 137
4.1 Introduction 137
4.2 The aerodynamics of turbines in steady yaw 137
4.3 The method of acceleration potential 163
4.4 Unsteady flow 176
4.5 Quasi-steady aerofoil aerodynamics 183
4.6 Dynamic stall 189
4.7 Computational fluid dynamics 190
References 191
Further reading 192
5 Design loads for horizontal axis wind turbines 193
5.1 National and international standards 193
5.2 Basis for design loads 194
5.3 Turbulence and wakes 197
5.4 Extreme loads 199
5.5 Fatigue loading 205
5.6 Stationary blade loading 205
5.7 Blade loads during operation 213
5.8 Blade dynamic response 241
5.9 Blade fatigue stresses 267
5.10 Hub and low speed shaft loading 273
5.11 Nacelle loading 277
5.12 Tower loading 278
5.13 Wind turbine dynamic analysis codes 288
5.14 Extrapolation of extreme loads from simulations 294
References 306
Appendix 5: dynamic response of stationary blade in turbulent wind 308
A5.1 Introduction 308
A5.2 Frequency response function 309
A5.3 Resonant displacement response ignoring wind variations along the blade 310
A5.4 Effect of across-wind turbulence distribution on resonant displacement response 313
A5.5 Resonant root bending moment 316
A5.6 Root bending moment background response 318
A5.7 Peak response 319
A5.8 Bending moments at intermediate blade positions 322
References 323
6 Conceptual design of horizontal axis wind turbines 325
6.1 Introduction 325
6.2 Rotor diameter 325
6.3 Machine rating 332
6.4 Rotational speed 336
6.5 Number of blades 338
6.6 Teetering 346
6.7 Power control 349
6.8 Braking systems 356
6.9 Fixed speed, two speed or variable speed 358
6.10 Type of generator 365
6.11 Drive train mounting arrangement options 369
6.12 Drive train compliance 373
6.13 Rotor position with respect to tower 375
6.14 Tower stiffness 376
6.15 Personnel safety and access issues 379
References 381
7 Component design 383
7.1 Blades 383
7.2 Pitch bearings 419
7.3 Rotor hub 422
7.4 Gearbox 425
7.5 Generator 437
7.6 Mechanical brake 446
7.7 Nacelle bedplate 453
7.8 Yaw drive 453
7.9 Tower 456
7.10 Foundations 467
References 471
8 The controller 475
8.1 Functions of the wind turbine controller 476
8.2 Closed loop control: issues and objectives 478
8.3 Closed loop control: general techniques 484
8.4 Closed loop control: analytical design methods 506
8.5 Pitch actuators (see also, Chapter 6 Section 6.7.2) 518
8.6 Control system implementation 519
References 522
9 Wind turbine installations and wind farms 525
9.1 Project development 526
9.2 Landscape and visual impact assessment 533
9.3 Noise 542
9.4 Electromagnetic Interference 551
9.5 Ecological assessment 558
References 562
10 Wind energy and the electric power system 565
10.1 Introduction 565
10.2 Wind farm power collection systems 569
10.3 Earthing (grounding) of wind farms 572
10.4 Lightning protection 575
10.5 Connection of wind generation to distribution networks 578
10.6 Power system studies 581
10.7 Power quality 582
10.8 Electrical protection 590
10.9 Distributed generation and the Grid Codes 598
10.10 Wind energy and the generation system 602
References 607
Appendix A10 Simple calculations for the connection of wind turbines 609
A10.1 The Per-unit system 609
A10.2 Power flows, slow voltage variations and network losses 609
11 Offshore wind turbines and wind farms 613
11.1 Development of offshore wind energy 613
11.2 The offshore wind resource 616
11.3 Design loads 620
11.4 Machine size optimisation 661
11.5 Reliability of offshore wind turbines 663
11.6 Support structures 667
11.7 Environmental assessment of offshore wind farms 704
11.8 Offshore power collection and transmission 707
11.9 Operation and access 717
References 719
Appendix A11 723
References for table A11.1 723
Index 729
Tony Burton, Wind Energy Consultant, Powys, UK
Nick Jenkins, Cardiff University, UK
David Sharpe, Wind Energy Consultant, Essex, UK
Ervin Bossanyi, GL Garrad Hassan, Bristol, UK
TABLE OF CONTENTS
About the Authors xvii
Preface to Second Edition xix
Acknowledgements for First Edition xxi
Acknowledgements for Second Edition xxiii
List of Symbols xxv
Figures C1 and C2 – Co-ordinate Systems xxxv
1 Introduction 1
1.1 Historical development 1
1.2 Modern wind turbines 4
1.3 Scope of the book 6
References 7
Further reading 8
2 The wind resource 9
2.1 The nature of the wind 9
2.2 Geographical variation in the wind resource 10
2.3 Long-term wind speed variations 11
2.4 Annual and seasonal variations 12
2.5 Synoptic and diurnal variations 14
2.6 Turbulence 14
2.7 Gust wind speeds 28
2.8 Extreme wind speeds 29
2.9 Wind speed prediction and forecasting 32
2.10 Turbulence in wakes and wind farms 33
2.11 Turbulence in complex terrain 36
References 36
3 Aerodynamics of horizontal axis wind turbines 39
3.1 Introduction 39
3.2 The actuator disc concept 40
3.3 Rotor disc theory 44
3.4 Vortex cylinder model of the actuator disc 49
3.5 Rotor blade theory (blade-element/momentum theory) 57
3.6 Breakdown of the momentum theory 64
3.7 Blade geometry 66
3.8 The effects of a discrete number of blades 75
3.9 Stall delay 92
3.10 Calculated results for an actual turbine 95
3.11 The performance curves 97
3.12 Constant rotational speed operation 101
3.13 Pitch regulation 105
3.14 Comparison of measured with theoretical performance 107
3.15 Variable speed operation 108
3.16 Estimation of energy capture 109
3.17 Wind turbine aerofoil design 114
References 119
Websites 120
Further reading 120
Appendix A3 lift and drag of aerofoils 120
A3.1 Definition of drag 121
A3.2 Drag coefficient 123
A3.3 The boundary layer 124
A3.4 Boundary layer separation 124
A3.5 Laminar and turbulent boundary layers 125
A3.6 Definition of lift and its relationship to circulation 127
A3.7 The stalled aerofoil 130
A3.8 The lift coefficient 131
A3.9 Aerofoil drag characteristics 131
A3.10 Cambered aerofoils 134
4 Further aerodynamic topics for wind turbines 137
4.1 Introduction 137
4.2 The aerodynamics of turbines in steady yaw 137
4.3 The method of acceleration potential 163
4.4 Unsteady flow 176
4.5 Quasi-steady aerofoil aerodynamics 183
4.6 Dynamic stall 189
4.7 Computational fluid dynamics 190
References 191
Further reading 192
5 Design loads for horizontal axis wind turbines 193
5.1 National and international standards 193
5.2 Basis for design loads 194
5.3 Turbulence and wakes 197
5.4 Extreme loads 199
5.5 Fatigue loading 205
5.6 Stationary blade loading 205
5.7 Blade loads during operation 213
5.8 Blade dynamic response 241
5.9 Blade fatigue stresses 267
5.10 Hub and low speed shaft loading 273
5.11 Nacelle loading 277
5.12 Tower loading 278
5.13 Wind turbine dynamic analysis codes 288
5.14 Extrapolation of extreme loads from simulations 294
References 306
Appendix 5: dynamic response of stationary blade in turbulent wind 308
A5.1 Introduction 308
A5.2 Frequency response function 309
A5.3 Resonant displacement response ignoring wind variations along the blade 310
A5.4 Effect of across-wind turbulence distribution on resonant displacement response 313
A5.5 Resonant root bending moment 316
A5.6 Root bending moment background response 318
A5.7 Peak response 319
A5.8 Bending moments at intermediate blade positions 322
References 323
6 Conceptual design of horizontal axis wind turbines 325
6.1 Introduction 325
6.2 Rotor diameter 325
6.3 Machine rating 332
6.4 Rotational speed 336
6.5 Number of blades 338
6.6 Teetering 346
6.7 Power control 349
6.8 Braking systems 356
6.9 Fixed speed, two speed or variable speed 358
6.10 Type of generator 365
6.11 Drive train mounting arrangement options 369
6.12 Drive train compliance 373
6.13 Rotor position with respect to tower 375
6.14 Tower stiffness 376
6.15 Personnel safety and access issues 379
References 381
7 Component design 383
7.1 Blades 383
7.2 Pitch bearings 419
7.3 Rotor hub 422
7.4 Gearbox 425
7.5 Generator 437
7.6 Mechanical brake 446
7.7 Nacelle bedplate 453
7.8 Yaw drive 453
7.9 Tower 456
7.10 Foundations 467
References 471
8 The controller 475
8.1 Functions of the wind turbine controller 476
8.2 Closed loop control: issues and objectives 478
8.3 Closed loop control: general techniques 484
8.4 Closed loop control: analytical design methods 506
8.5 Pitch actuators (see also, Chapter 6 Section 6.7.2) 518
8.6 Control system implementation 519
References 522
9 Wind turbine installations and wind farms 525
9.1 Project development 526
9.2 Landscape and visual impact assessment 533
9.3 Noise 542
9.4 Electromagnetic Interference 551
9.5 Ecological assessment 558
References 562
10 Wind energy and the electric power system 565
10.1 Introduction 565
10.2 Wind farm power collection systems 569
10.3 Earthing (grounding) of wind farms 572
10.4 Lightning protection 575
10.5 Connection of wind generation to distribution networks 578
10.6 Power system studies 581
10.7 Power quality 582
10.8 Electrical protection 590
10.9 Distributed generation and the Grid Codes 598
10.10 Wind energy and the generation system 602
References 607
Appendix A10 Simple calculations for the connection of wind turbines 609
A10.1 The Per-unit system 609
A10.2 Power flows, slow voltage variations and network losses 609
11 Offshore wind turbines and wind farms 613
11.1 Development of offshore wind energy 613
11.2 The offshore wind resource 616
11.3 Design loads 620
11.4 Machine size optimisation 661
11.5 Reliability of offshore wind turbines 663
11.6 Support structures 667
11.7 Environmental assessment of offshore wind farms 704
11.8 Offshore power collection and transmission 707
11.9 Operation and access 717
References 719
Appendix A11 723
References for table A11.1 723
Index 729
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