Paul A. Lynn 
Onshore and Offshore Wind Energy 
An Introduction

A highly accessible and authoritative account of wind
energy’s scientific background, current technology, and
international status, with an emphasis on large turbines and wind
farms, both onshore and offshore

Topics covered include:

* a brief history of wind energy

* the nature of the wind

* turbine aerodynamics, mechanics, and electrics

* wind farms

* offshore opportunities and challenges

* grid integration of wind energy

* economic and environmental aspects

Whilst intellectually rigorous, this is not an academic
treatise. Key equations are fully discussed, providing essential
theoretical background. The text is supported by copious
illustrations and about 50 inspiring full-colour photographs from
around the world.

This book is aimed at a wide readership including professionals,
policy makers and employees in the energy sector in need of a basic
appreciation of the underlying principles of wind energy or a quick
update. Its style and level will also appeal to second and third
year undergraduate and postgraduate students of renewable and wind
energy, energy systems and electrical/electronic engineering. It
also gives a concise account of the technology for the large and
growing number of people who are interested in onshore and offshore
wind farms and the contribution they are making to carbon-free
electricity generation in the 21st century.

Table of Content

Preface ix

Acknowledgements xi

1. Introduction 1

1.1 Wind energy and Planet Earth 1

1.2 Winds of the world 5

1.3 From windmills to wind turbines 9

1.4 Power, energy and performance 17

1.5 Coming up to date 24

References 29

2. Capturing the wind 31

2.1 Wind speed and power 31

2.2 Wild wind 37

2.2.1 Introductory 37

2.2.2 Wind statistics 40

2.2.3 Mapping and forecasting 49

2.3 Predicting turbine output 57

References 61

3. Wind turbines 63

3.1 Turbine types and sizes 63

3.2 Aerodynamics 69

3.2.1 Rotor effi ciency and the Betz Limit 69

3.2.2 Lift and drag 72

3.2.3 Rotor speed 80

3.2.4 Rotor blades 87

3.2.4.1 Choosing airfoils 87

3.2.4.2 Stall and pitch control 90

3.3 Mechanics 94

3.3.1 Gearboxes 94

3.3.2 Towers 97

3.3.3 Vibration and fatigue 98

3.4 Electrics 107

3.4.1 AC electricity 107

3.4.2 Generators 116

3.4.2.1 Introductory 116

3.4.2.2 Synchronous generators 122

3.4.2.3 Asynchronous generators 128

3.4.2.3.1 Squirrel-cage and wound-rotor induction machines
128

3.4.2.3.2 Doubly-fed induction generators 133

3.5 Turbine control 138

3.6 Onshore wind farms 143

3.6.1 Introductory 143

3.6.2 Siting and spacing 146

3.6.3 Monitoring and control 150

References 152

4. Moving offshore 153

4.1 Introductory 153

4.2 Wind and waves 157

4.3 Turbines and foundations 161

4.4 Offshore wind farms 166

4.4.1 Case study: Horns Rev 2 166

4.4.2 Case study: London Array 170

4.5 Bringing the power ashore 173

References 177

5. Grid integration 179

5.1 Setting the scene 179

5.2 Connecting to the grid 182

5.2.1 Grid strength and fault levels 182

5.2.2 Electrical quality 186

5.3 Large-scale wind power 190

5.3.1 Introductory 190

5.3.2 Intermittency and variability 191

5.3.3 Capacity credit and backup generation 194

References 198

6. Economics and the environment 199

6.1 Wind energy economics 199

6.1.1 Capital and installation costs 199

6.1.2 Operation, maintenance and cash fl ow 202

6.2 Environmental aspects 204

6.2.1 Introductory 204

6.2.2 Landscape and amenity 207

6.2.3 Birds, bats and farming 211

6.2.4 Seabirds, fi sh and marine conservation 216

References 218

Index 219

About the author

PAUL A. LYNN obtained his B.Sc.(Eng) and Ph.D. degrees from Imperial College London, UK. After several years in the electrical/electronics industry, he lectured at Imperial College and the University of Bristol. As a retired academic, Dr. Lynn’s long-term interest in renewable energy has led to a trilogy of Wiley books (including this one), and three solar-powered boats. He is the author of ten other books and numerous technical papers and articles.