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P R E S S E S I N T E R N A T I O N A L E S P O L Y T E C H N I K U M

Table of

Contents

Foreword v List of Figures xiii List of Tables xxiii

Chapter 1 Wind Energy 1.1 Wind Definition and Characteristics 1 1.2 Wind Turbines 1 1.3 Wind Energy Applications 5 1.4 Benefits and Obstacles in Wind Energy Development 6 1.5 Overview of Wind Energy Development 8 1.6 Wind Energy Development in the World 8 1.7 Cost of Wind Energy 10 1.8 Social Cost of Wind Energy 11 Conclusions 13 References 13

Chapter 2 State of the Art of Vertical-Axis Wind Turbines 2.1 The Madaras Rotor Concept 15 2.2 Savonius Rotor 16

2.2.1 Mathematical Model 17 2.2.2 Experimental Study 20

2.3 Drag-Driven Device 25 2.4 Lift-Driven Device 26 2.5 Giromill 28 2.6 Vortex Modeling Cross-Wind Axis Machine 32 2.7 Aerodynamic Characteristics 34 References 34

Chapter 3 The Darrieus Wind-Turbine Concept 3.1 Introduction 37 3.2 Geometry of the Darrieus Rotor 41 References 61

Chapter 4 Aerodynamic Performance Prediction Models 4.1 Single Streamtube Model 66

4.1.1 Aerodynamic Performance 70

viii Table of Contents

4.1.2 Comparison of Single Streamtube Model with Experiment 71 Conclusions 76

4.2 Multiple Streamtubes Model 77 4.3 Vortex Models 85

4.3.1 Free-Wake Vortex Model 86 4.3.2 Fixed-Wake Vortex Model 87 4.3.3 Comparisons between Vortex Models and Experiment 88

4.4 A High-Speed Lifting Line Model 90 4.4.1 Results and Discussion 94

4.5 Local-Circulation Model 97 References 98

Chapter 5 Unsteady Aerodynamics - CFD Models 5.1 Introduction 101

5.1.1 Dynamic-Stall Phenomenon 104 5.1.2 Numerical Simulation of Dynamic Stall 105

5.2 Numerical Procedure 106 5.2.1 Governing Equations 106 5.2.2 Boundary Conditions 108 5.2.3 Finite Element Discretization 109 5.2.4 Element Influence Matrices 110 5.2.5 Newton Linearization 112 5.2.6 Algorithm 113

5.3 Turbulence Modeling 114 5.3.1 Cebeci-Smith Model 114 5.3.2 Johnson-King Model 118

5.4 Results and Discussion 120 5.4.1 Test Cases 120 5.4.2 Darrieus Motion Airfoil 127 5.4.3 Flow Structure 130 5.4.4 Aerodynamic Characteristics 136 5.4.5 Discussion 139

5.5 Conclusions and Recommendations 141 References 141 Appendix to Chapter 5 144 A-5.1 Transformation of the Momentum Equation 144 A-5.2 Pressure Uniqueness Condition 145 A-5.3 Computation of the Aerodynamic Coefficients 146

Chapter 6 Double-Multiple Streamtube - A Practical Design Model 6.1 Double Actuator Disk Theory 147 6.2 Double Actuator Disk Momentum Theory 148 6.3 Blade Element Theory 153 6.4 Double-Multiple Streamtube Model for Studying Darrieus Turbine 156

Table of Contents ix

6.4.1 Aerodynamic Model 158 6.4.2 Influence of Secondary Effects on the Aerodynamics of the Darrieus Rotor .. 177 Conclusion 188 6.4.3 Streamtube Expansion Model 189 Conclusion 198

6.5 Aerodynamic Analysis of the Darrieus Wind Turbines Including Dynamic-Stall Effects 199 6.5.1 Introduction 200 6.5.2 Dynamic-Stall Models 201

6.6 Darrieus Rotor Aerodynamics in Turbulent Wind 226 6.6.1 Aerodynamic Analysis 228 6.6.2 Wind Model 230 Conclusion 236

6.7 Comparison with Other Computer Code Predictions 237 6.7.1 Aerodynamic Performance 237 6.7.2 Structural Dynamics in Connection with Momentum Models 238 Conclusion 240

6.8 Blade Tip and Finite Aspect Ratio Effects on the Darrieus Rotor 241 6.9 Performance Predictions of VAWTs with SNL Airfoil Blades 247

6.9.1 Performance of Conventional and SNL Blades 251 Conclusion 253

6.10 CARDAAV Software 253 6.10.1 Rotor Geometry 255 6.10.2 Operational Conditions 256 6.10.3 Control Parameters 256 6.10.4 Results 257 Conclusion 259

References 259

Chapter 7 Aerodynamic Loads and Performance Tests 7.1 Water Channel Experiments 266

7.1.1 Texas Tech University Tests 266 7.1.2 Water Channel Experiments of Dynamic Stall on Darrieus Rotor 277

7.2 Wind Tunnel Experiments 288 7.2.1 National Research Council of Canada Wind Tunnel Tests 288 7.2.2 Sandia Research Turbines 291 7.2.3 Predicted and Experimental Aerodynamic Forces on the Darrieus Rotor 296

7.3 Field Test of Darrieus Wind Turbines 303 7.3.1 Sandia 5 Meter Research Turbine 303 7.3.2 NRC/Hydro-Quebec Magdalen Islands 24 Meter Research Turbine 304 7.3.3 NRC/DAF 6.1 Meter Research Turbine 305 7.3.4 Lavalin Eole (64-m) Research Turbine, (Cap-Chat, Quebec) 306 7.3.5 Pionier I (15 Meter) Cantilevered Rotor Research Turbine (Netherlands) 308 7.3.6 Sandia 17 Meter Research Turbine 308

x Table of Contents

7.4 Commercial Prototype Wind Turbines 312 7.4.1 DOE 100 kW (17-m) Darrieus Wind Turbine 312 7.4.2 FloWind 17-m and 19-m Commercial Turbines 312 7.4.3 Indal Technologies 50 kW (11.2-m) and 6400/500 kW (24-m) 314

7.5 Measurements and Prediction of Aerodynamic Torques for a Darrieus Wind Turbine 315 7.5.1 Introduction 315 7.5.2 Measurements and Data Reduction 317 7.5.3 Prediction of Aerodynamic Torque 321 7.5.4 Measured and Predicted Aerodynamic Torque 322

References 326

Chapter 8 Innovative Aerodynamic Devices for Darrieus Rotor 8.1 Natural Laminar Flow (NLF) Airfoils and Tapered Blades 329 8.2 Aerobrakes 340

8.2.1 Spoilers 341 8.3 Vortex Generators 342 8.4 Pumped Spoiling 345 8.5 Toe-in-Angle Effects 346 8.6 Blade Camber 349 8.7 Blade Roughness (Soiling), Blade Icing and Parasite Drag Effects 351 References 355

Chapter 9 Future Trends Design of Darrieus Wind Turbine 9.1 Wind Turbine Design Parameters 359

9.1.1 Swept Area 359 9.1.2 Rotor Aspect Ratio 362 9.1.3 Blade Airfoil 364 9.1.4 Rotor Speed 365 9.1.5 Rotor Solidity 365 9.1.6 Blade Material and Construction 366 9.1.7 Central Column of Darrieus Rotor 367 9.1.8 Horizontal Struts 368 9.1.9 Guy Cables 368 9.1.10 Cantilever Darrieus Rotor 370 9.1.11 Type and Location of Brakes 370 9.1.12 Gearbox 371 9.1.13 Drive Train 372 9.1.14 Motor/Generator 373 9.1.15 Variable Speed 374

9.2 Darrieus Wind Turbine Design 374 9.2.1 Darrieus Design Issues 374 9.2.2 Future Design Alternatives 375

9.3 Comparison Between Horizontal-Axis and Vertical-Axis Wind Turbines 377

Table of Contents xi

9.3.1 HAWTs vs VAWTs Technical Aspects 377 9.3.2 Taking VAWTs to Viability 381

References 382

Chapter 10 Acceptability Environmental and Social Aspects of Wind Energy

10.1 Introduction 387 10.2 Environmental Aspects 388

10.2.1 Human Environment Aspects 389 10.2.2 Natural Environment Aspects 391 10.2.3 Environmental Effects of Wind Turbine Operation 393

10.3 Gas Emissions: Wind and Other Energy Sources 394 10.4 Public Attitudes in Various Countries 396 10.5 Social Impact 398 10.6 Wind Power and Traditional Power Sources 398 Conclusions 401 References 401

Appendix A Aerodynamic Characteristics of Symmetrical Airfoils 405 Appendix В Canada and Worldwide Wind Energy Production 417 Appendix С Wind Energy on the Worldwide Web 425

Index 427