Design of foundations for offshore wind turbines /
Subhamoy Bhattacharya, University of Surrey.
- 1 online resource.
ABOUT THE AUTHOR SUBHAMOY BHATTACHARYA, PHD, is a Professor and Chair in Geomechanics at the University of Surrey. He is also a visiting fellow at the University of Bristol. His main research interest is the design for offshore wind turbines. He has also worked as a consultant in the in the civil and offshore engineering industry.
Includes bibliographical references and index.
TABLE OF CONTENTS Preface xi
About the Companion Website xv
1 Overview of a Wind Farm and Wind Turbine Structure 1
1.1 Harvesting Wind Energy 1
1.2 Current Scenario 2
1.2.1 Case Study: Fukushima Nuclear Plant and Near-Shore Wind Farms during the 2011 Tohoku Earthquake 5
1.2.2 Why Did the Wind Farms Survive? 6
1.3 Components of Wind Turbine Installation 8
1.3.1 Betz Law: A Note on Cp 11
1.4 Control Actions of Wind Turbine and Other Details 11
1.4.1 Power Curves for a Turbine 14
1.4.2 What Are the Requirements of a Foundation Engineer from the Turbine Specification? 15
1.4.3 Classification of Turbines 15
1.5 Foundation Types 16
1.5.1 Gravity-Based Foundation System 18
1.5.1.1 Suction Caissons or Suction Buckets 19
1.5.1.2 Case Study: Use of Bucket Foundation in the Qidong Sea (Jiangsu Province, China) 22
1.5.1.3 Dogger Bank Met Mast Supported on Suction Caisson 22
1.5.2 Pile Foundations 22
1.5.3 Seabed Frame or Jacket Supported on Pile or Caissons 23
1.5.4 Floating Turbine System 25
1.6 Foundations in the Future 27
1.6.1 Scaled Model Tests 33
1.6.2 Case Study of a Model Tests for Initial TRL Level (3–4) 34
1.7 On the Choice of Foundations for a Site 35
1.8 General Arrangement of a Wind Farm 36
1.8.1 Site Layout, Spacing of Turbines, and Geology of the Site 37
1.8.2 Economy of Scales for Foundation 40
1.9 General Consideration for Site Selection 42
1.10 Development of Wind Farms and the Input Required for Designing Foundations 44
1.11 Rochdale Envelope Approach to Foundation Design (United Kingdom Approach) 46
1.12 Offshore Oil and Gas Fixed Platform and Offshore Wind Turbine Structure 48
1.13 Chapter Summary and Learning Points 50
2 Loads on the Foundations 51
2.1 Dynamic Sensitivity of Offshore Wind Turbine Structures 51
2.2 Target Natural Frequency of a Wind Turbine Structure 53
2.3 Construction of Wind Spectrum 58
2.3.1 Kaimal Spectrum 60
2.4 Construction of Wave Spectrum 61
2.4.1 Method to Estimate Fetch 63
2.4.2 Sea Characteristics for Walney Site 63
2.4.3 Walney 1Wind Farm Example 63
2.5 Load Transfer from Superstructure to the Foundation 64
2.6 Estimation of Loads on a Monopile-Supported Wind Turbine Structure 66
2.6.1 Load Cases for Foundation Design 67
2.6.2 Wind Load 70
2.6.2.1 Comparisons with Measured Data 72
2.6.2.2 Spectral Density of Mudline Bending Moment 76
2.6.3 Wave Load 76
2.6.4 1P Loading 79
2.6.5 Blade Passage Loads (2P/3P) 80
2.6.6 Vertical (Deadweight) Load 81
2.7 Order of Magnitude Calculations of Loads 81
2.7.1 Application of Estimations of 1P Loading 82
2.7.2 Calculation for 3P Loading 82
2.7.3 Typical Moment on a Monopile Foundation for Different-Rated Power Turbines 84
2.8 Target Natural Frequency for Heavier and Higher-Rated Turbines 85
2.9 Current Loads 86
2.10 Other Loads 87
2.11 Earthquake Loads 87
2.11.1 Seismic Hazard Analysis (SHA) 90
2.11.2 Criteria for Selection of Earthquake Records 91
2.11.2.1 Method 1: Direct Use of Strong Motion Record 91
2.11.2.2 Method 2: Scaling of Strong Motion Record to Expected Peak Bedrock Acceleration 91
5.6.1.2 Sub-step 2. Calculate the Corresponding Range of Wave Periods 257
5.6.1.3 Sub-step 3. Calculate the Number of Waves in a Three-Hour Period 257
5.6.1.4 Sub-step 4. Calculate the Ratio of the Maximum Wave Height to the Significant Wave Height 257
5.6.1.5 Sub-step 5. Calculate the Range of Wave Periods Corresponding to the Maximum Wave Height 257
5.7 Methodologies for Long-Term Rotation Estimation 258
5.7.1 Simple Power Law Expression Proposed by Little and Briaud (1988) 259
5.7.2 Degradation Calculation Method Proposed by Long and Vanneste (1994) 260
5.7.3 Logarithmic Method Proposed by Lin and Liao (1999) 260
5.7.4 Stiffness Degradation Method Proposed by Achmus et al. (2009) 261
5.7.5 Accumulated Rotation Method Proposed by Leblanc et al. (2010) 261
5.7.6 Load Case Scenarios Conducted by Cuéllar (2011) 262
5.8 Theory for Estimating Natural Frequency of the Whole System 262
5.8.1 Model of the Rotor-Nacelle Assembly 263
5.8.2 Modelling the Tower 263
5.8.3 Euler-Bernoulli Beam – Equation of Motion and Boundary Conditions 264
5.8.4 Timoshenko Beam Formulation 264
5.8.5 Natural Frequency versus Foundation Stiffness Curves 266
5.8.6 Understanding Micromechanics of SSI 268
6 Simplified Hand Calculations 273
6.1 Flow Chart of a Typical Design Process 273
6.2 Target Frequency Estimation 274
6.3 Stiffness of a Monopile and Its Application 276
6.3.1 Comparison with SAP 2000 Analysis 287
6.4 Stiffness of a Mono-Suction Caisson 287
6.5 Mudline Moment Spectra for Monopile Supported Wind Turbine 291
6.6 Example for Monopile Design 299
Appendix A Natural Frequency of a Cantilever Beam with Variable Cross Section 333
Appendix B Euler-Bernoulli Beam Equation 337
Appendix C Tower Idealisation 341
Appendix D Guidance on Estimating the Vertical Stiffness of Foundations 345
Appendix E Lateral Stiffness KL of Piles 347
Appendix F Lateral Stiffness KL of Suction Caissons 349
Bibliography 351
Index 369
Comprehensive reference covering the design of foundations for offshore wind turbines
As the demand for “green” energy increases the offshore wind power industry is expanding at a rapid pace around the world.
Design of Foundations for Offshore Wind Turbines is a comprehensive reference which covers the design of foundations for offshore wind turbines, and includes examples and case studies. It provides an overview of a wind farm and a wind turbine structure, and examines the different types of loads on the offshore wind turbine structure. Foundation design considerations and the necessary calculations are also covered. The geotechnical site investigation and soil behavior/soil structure interaction are discussed, and the final chapter takes a case study of a wind turbine and demonstrates how to carry out step by step calculations.
Key features:
New, important subject to the industry. Includes calculations and case studies. Accompanied by a website hosting software and data files. Design of Foundations for Offshore Wind Turbines is a must have reference for engineers within the renewable energy industry and is also a useful guide for graduate students in this area.
9781119128151 (Adobe PDF) 9781119128144 (ePub)
2018047955
Offshore wind power plants--Design and construction. Offshore structures--Foundations.