Design of Foundations for Offshore Wind Turbines

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.

Autorentext

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.

Inhalt
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 (34) 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

2.11.2.3 Method 3: Intelligent Scaling or Code Specified Spectrum Compatible Motion 91

2.11.3 Site Response Analysis (SRA) 93

2.11.4 Liquefaction 94

2.11.5 Analysis of the Foundation 95

2.12 Chapter Summary and Learning Points 101

3 Considerations for Foundation Design and the Necessary Calculations 103

3.1 Introduction 103

3.2 Modes of Vibrations of Wind Turbine Structures 104

3.2.1 Sway-Bending Modes of Vibration 105 3.2.1.1 Example Numerical Application of Modes of Vibration of Jacket Syst...