Table of Contents

Title Page

Dedication

Foreword

Preface

Acknowledgement

Introduction
1. 0.1 Why Innovation?
2. 0.2 The Challenge of Wind
3. 0.3 The Specification of a Modern Wind Turbine
4. 0.4 The Variability of the Wind
5. 0.5 Early Electricity-Generating Wind Turbines
6. 0.6 Commercial Wind Technology
7. 0.7 Basis of Wind Technology Evaluation
8. 0.8 Competitive Status of Wind Technology
9. References

Part I: Design Background

Chapter 1: Rotor Aerodynamic Theory
1. 1.1 Introduction
2. 1.2 Aerodynamic Lift
3. 1.3 Power in the Wind
4. 1.4 The Actuator Disc Concept
5. 1.5 Open Flow Actuator Disc
6. 1.6 Why a Rotor?
7. 1.7 Actuator Disc in Augmented Flow and Ducted Rotor Systems
8. 1.8 Blade Element Momentum Theory
9. 1.9 Optimum Rotor Design
10. 1.10 Limitations of Actuator Disc and BEM Theory
11. References
Chapter 2: Rotor Aerodynamic Design
1. 2.1 Optimum Rotors and Solidity
2. 2.2 Rotor Solidity and Ideal Variable Speed Operation
3. 2.3 Solidity and Loads
4. 2.4 Aerofoil Design Development
5. 2.5 Sensitivity of Aerodynamic Performance to Planform Shape
6. 2.6 Aerofoil Design Specification
7. 2.7 Aerofoil Design for Large Rotors
8. References
Chapter 3: Rotor Structural Interactions
1. 3.1 Blade Design in General
2. 3.2 Basics of Blade Structure
3. 3.3 Simplified Cap Spar Analyses
4. 3.4 The Effective t/c Ratio of Aerofoil Sections
5. 3.5 Blade Design Studies: Example of a Parametric Analysis
6. 3.6 Industrial Blade Technology
7. References
Chapter 4: Upscaling of Wind Turbine Systems
1. 4.1 Introduction: Size and Size Limits
2. 4.2 The ‘Square-Cube’ Law
3. 4.3 Scaling Fundamentals
4. 4.4 Similarity Rules for Wind Turbine Systems
5. 4.5 Analysis of Commercial Data
6. 4.6 Upscaling of VAWTs
7. 4.7 Rated Tip Speed
8. 4.8 Upscaling of Loads
9. 4.9 Violating Similarity
10. 4.10 Cost Models
11. 4.11 Scaling Conclusions
12. References
Chapter 5: Wind Energy Conversion Concepts
1. References
Chapter 6: Drive-Train Design
1. 6.1 Introduction
2. 6.2 Definitions
3. 6.3 Objectives of Drive-Train Innovation
4. 6.4 Drive-Train Technology Maps
5. 6.5 Direct Drive
6. 6.6 Hybrid Systems
7. 6.7 Geared Systems – the Planetary Gearbox
8. 6.8 Drive Trains with Differential Drive
9. 6.9 Hydraulic Transmission
10. 6.10 Efficiency of Drive-Train Components
11. 6.11 Drive-Train Dynamics
12. 6.12 The Optimum Drive Train
13. 6.13 Innovative Concepts for Power Take-Off
14. References
Chapter 7: Offshore Wind Technology
1. 7.1 Design for Offshore
2. 7.2 High-Speed Rotor
3. 7.3 ‘Simpler’ Offshore Turbines
4. 7.4 Rating of Offshore Wind Turbines
5. 7.5 Foundation and Support Structure Design
6. 7.6 Electrical Systems of Offshore Wind Farms
7. 7.7 Operations and Maintenance (O&M)
8. 7.8 Offshore Floating Wind Turbines
9. References
Chapter 8: Future Wind Technology
1. 8.1 Evolution
2. 8.2 Present Trends – Consensus in Blade Number and Operational Concept
3. 8.3 Present Trends – Divergence in Drive-Train Concepts
4. 8.4 Future Wind Technology – Airborne
5. 8.5 Future Wind Technology – Energy Storage
6. 8.6 Innovative Energy Conversion Solutions
7. References

Part II: Technology Evaluation

Chapter 9: Cost of Energy
1. 9.1 The Approach to Cost of Energy
2. 9.2 Energy: the Power Curve
3. 9.3 Energy: Efficiency, Reliability, Availability
4. 9.4 Capital Costs
5. 9.5 Operation and Maintenance
6. 9.6 Overall Cost Split
7. 9.7 Scaling Impact on Cost
8. 9.8 Impact of Loads (Site Class)
9. References
Chapter 10: Evaluation Methodology
1. 10.1 Key Evaluation Issues
2. 10.2 Fatal Flaw Analysis
3. 10.3 Power Performance
4. 10.4 Structure and Essential Mass
5. 10.5 Drive-Train Torque
6. 10.6 Representative Baseline
7. 10.7 Design Loads Comparison
8. 10.8 Evaluation Example: Optimum Rated Power of a Wind Turbine
9. 10.9 Evaluation Example: the Carter Wind Turbine and Structural Flexibility
10. 10.10 Evaluation Example: Concept Design Optimisation Study
11. 10.11 Evaluation Example: Ducted Turbine Design Overview
12. References

Part III: Design Themes

Chapter 11: Optimum Blade Number
1. 11.1 Energy Capture Comparisons
2. 11.2 Blade Design Issues
3. 11.3 Operational and System Design Issues
4. 11.4 Multi-bladed Rotors
5. References
Chapter 12: Pitch versus Stall
1. 12.1 Stall Regulation
2. 12.2 Pitch Regulation
3. 12.3 Fatigue Loading Issues
4. 12.4 Power Quality and Network Demands
5. References
Chapter 13: HAWT or VAWT?
1. 13.1 Introduction
2. 13.2 VAWT Aerodynamics
3. 13.3 Power Performance and Energy Capture
4. 13.4 Drive-Train Torque
5. 13.5 Niche Applications for VAWTs
6. 13.6 Status of VAWT Design
7. References
Chapter 14: Free Yaw
1. 14.1 Yaw System COE Value
2. 14.2 Yaw Dynamics
3. 14.3 Yaw Damping
4. 14.4 Main Power Transmission
5. 14.5 Operational Experience of Free Yaw Wind Turbines
6. 14.6 Summary View
7. References
Chapter 15: Multi-rotor Systems (MRS)
1. 15.1 Introduction
2. 15.2 Standardisation Benefit and Concept Developments
3. 15.3 Operational Systems
4. 15.4 Scaling Economics
5. 15.5 History Overview
6. 15.6 Aerodynamic Performance of Multi-rotor Arrays
7. 15.7 Recent Multi-rotor Concepts
8. 15.8 MRS Design Based on VAWT Units
9. 15.9 MRS Design within the Innwind.EU Project
10. 15.10 Multi-rotor Conclusions
11. References
Chapter 16: Design Themes Summary

Part IV: Innovative Technology Examples

Chapter 17: Adaptable Rotor Concepts
1. 17.1 Rotor Operational Demands
2. 17.2 Management of Wind Turbine Loads
3. 17.3 Control of Wind Turbines
4. 17.4 LiDAR
5. 17.5 Adaptable Rotors
6. 17.6 The Coning Rotor
7. 17.7 Variable Diameter Rotor
8. References
Chapter 18: Ducted Rotors
1. 18.1 Introduction
2. 18.2 The Katru Shrouded Rotor System
3. 18.3 The Wind Lens Ducted Rotor
4. References
Chapter 19: The Gamesa G10X Drive Train
Chapter 20: DeepWind Innovative VAWT
1. 20.1 The Concept
2. 20.2 DeepWind Concept at 5 MW Scale
3. 20.3 Marine Operations Installation, Transportation and O&M
4. 20.4 Testing and Demonstration
5. 20.5 Cost Estimations
6. References
Chapter 21: Gyroscopic Torque Transmission
1. References
Chapter 22: The Norsetek Rotor Design
1. References
Chapter 23: Siemens Blade Technology
Chapter 24: Stall-Induced Vibrations
1. References
Chapter 25: Magnetic Gearing and Pseudo-Direct Drive
1. 25.1 Magnetic Gearing Technology
2. 25.2 Pseudo-Direct-Drive Technology
3. References
Chapter 26: Summary and Concluding Comments
Index

End User License Agreement

List of Illustrations

Introduction

Figure 0.1 Jill post mill at Clayton Sussex.
Figure 0.2 Blyth windmill commercial prototype.

Chapter 1: Rotor Aerodynamic Theory

Figure 1.1 Power in the air.
Figure 1.2 Open flow.
Figure 1.3 Constrained flow example (diffuser).
Figure 1.4 Open flow actuator disc model.
Figure 1.6 Power balance for ideal actuator disc (no wake rotation).
Figure 1.5 Axisymmetric control volumes for an actuator disc at plane 1.
Figure 1.7 Power balance in reference frames of Cases A and B.
Figure 1.8 Area ratio fallacy.
Figure 1.11 Seven shapes of line duct analysed as in inviscid flow.
Figure 1.13 Source area and energy gain with flow augmentation.
Figure 1.9 General flow diagram.
Figure 1.10 The reference plane in relation to disc loading.
Figure 1.12 Comparison of cases with equal source flow areas.
Figure 1.14 Performance characteristics of ducts.
Figure 1.15 Actuator annulus.
Figure 1.16 Local flow geometry at a blade element.
Figure 1.17 C_p max versus tip speed ratio for various lift-to-drag ratios.
Figure 1.18 Influence of blade number and lift-to-drag ratio on maximum C_p.
Figure 1.19 Out-of-plane bending moment shape functions.
Figure 1.20 Design parameters related to axial induction.
Figure 1.21 GE Wind experimental hub flow system on a 1.7 MW wind turbine. Reproduced with permission of General Electric.

Chapter 2: Rotor Aerodynamic Design

Figure 2.1 Variable speed operation.
Figure 2.2 Lift characteristics of a ‘D’ section.
Figure 2.3 Overview of DU aerofoils.
Figure 2.4 Lift-to-drag ratio comparisons.
Figure 2.5 Planform envelopes based on the NACA 634xx aerofoils.
Figure 2.6 Performance (L/D) of the 18% low-lift 10–90 airfoil for transitional and fully turbulent flow conditions. Fixed transition locations were taken from XFOIL using the e^N model with N = 4.

Chapter 3: Rotor Structural Interactions

Figure 3.1 Rotor blades manufactured by Vestas Blades in transportation.
Figure 3.2 Blade structure zones.
Figure 3.3 Blade power distribution.
Figure 3.4 Cap spar parameters.
Figure 3.5 Typical spanwise distribution of thickness-to-chord ratio.
Figure 3.6 Effective t/c of a typical aerofoil section (NACA 63-221). Reproduced with permission of Airfoil Tools.
Figure 3.7 S818 aerofoil. Reproduced with permission of Airfoil Tools.
Figure 3.8 Relative mass of blades.
Figure 3.9 Blade design for minimum cost.
Figure 3.10 Blade mass related to design tip speed ratio.
Figure 3.11 Rotor blade finite element mesh.

Chapter 4: Upscaling of Wind Turbine Systems

Figure 4.1 Blade hinge mechanism of the Smith–Putnam wind turbine.
Figure 4.2 Growth in size of wind turbines.
Figure 4.3 Growth pattern in the aircraft industry.
Figure 4.4 Blade mass trends based on blade manufacturers' data.
Figure 4.5 Blade mass scaling related to blade technologies.
Figure 4.6 Blade mass trends.
Figure 4.7 Enercon rotor shafts.
Figure 4.8 Nacelle mass trends.
Figure 4.9 Torque trend.
Figure 4.10 Nacelle mass versus torque.
Figure 4.11 Tower top mass.
Figure 4.12 Hub height trends.
Figure 4.13 Tower mass trends.
Figure 4.14 Normalised tower mass trends.
Figure 4.15 Verification of normalisation exponent.
Figure 4.16 Gearbox mass trends.
Figure 4.17 Tip speed trends.
Figure 4.18 Extreme blade root out-of-plane bending moment.
Figure 4.19 Extreme blade root in-plane bending moment.
Figure 4.20 Upscaling loads to 20 MW.

Chapter 5: Wind Energy Conversion Concepts

Figure 5.1 Wind energy converter concepts.

Chapter 6: Drive-Train Design

Figure 6.1 Top-level drive-train technology map.
Figure 6.2 System-level drive-train technology map.
Figure 6.3 (a,b) Motion in a planetary gearbox.
Figure 6.4 Forces in a planetary gearbox.
Figure 6.5 SET DSgen-set®.
Figure 6.6 Hydraulic pump of Artemis Intelligent Power.
Figure 6.7 Schematic of the Artemis 1.6 MW transmission.
Figure 6.8 Artemis – MHI 1.6 MW drive-train test rig.
Figure 6.9 Seven megawatt ring-cam pump in MHI factory.
Figure 6.10 The 7 MW wind turbine of MHI at Hunterston, with the Fukushima floating system inset.
Figure 6.11 Comparison of drive-train efficiency.
Figure 6.12 Wind speed and energy distributions. (a) 6 m/s AMWS and (b) 8.5 m/s AMWS.
Figure 6.13 Gearbox efficiency characteristics.
Figure 6.14 Generator efficiency comparisons.
Figure 6.15 Efficiency comparison of generator types.
Figure 6.16 Efficiency of IGBT-based converter.
Figure 6.17 Transformer efficiency.
Figure 6.18 Spectrum of generator speed.
Figure 6.19 Drive-train optimisation.
Figure 6.20 Gravity torque reaction concept.
Figure 6.21 Secondary rotor concept.

Chapter 7: Offshore Wind Technology

Figure 7.1 Rotor blade tip and tower clearance.
Figure 7.2 Blade fatigue loads comparison at mid span (m = 10).
Figure 7.3 Extreme load reductions of a high-speed rotor.
Figure 7.4 Gearbox torque – influence of tower shadow.
Figure 7.5 Power density characteristics of large modern wind turbines.
Figure 7.6 (a) Gravity foundation, (b) tripod and (c) jacket.
Figure 7.7 Effect of load reduction on support structure cost of a 7 MW wind turbine.
Figure 7.8 (a,b) Radial and single-side ring design of a collector network.
Figure 7.9 (a,b) Single return with single hub design and double-side ring design.
Figure 7.10 (a,b) Star design and single return with multi-hub design.
Figure 7.11 HVAC connection for wind farm integration.
Figure 7.12 Configuration of LCC-HVDC for connecting offshore wind farm.
Figure 7.13 Schematic of a typical VSC-HVDC system.
Figure 7.14 Optimising O&M cost.
Figure 7.15 Hywind floating wind turbine system.
Figure 7.16 Floating power plant.
Figure 7.17 Aerodyn 3 MW SCDnezzy.
Figure 7.18 Aerodyn 15 MW SCDnezzy².
Figure 7.19 SWAY offshore floating wind turbine system.

Chapter 8: Future Wind Technology

Figure 8.1 Consensus.
Figure 8.2 Divergence.
Figure 8.3 Institutions involved in airborne wind energy (2015).
Figure 8.4 Kite motion in earth's reference frame.
Figure 8.5 Kite in its own reference frame as an actuator disc.
Figure 8.6 Kite as a blade element aerofoil section.
Figure 8.7 Asymmetric kite of Kite Power Solutions and aerodynamic modelling (inset).
Figure 8.8 The Daisy Kite of Windswept and Interesting Ltd.
Figure 8.9 EWICON concept – charged particle flow simulation.
Figure 8.10 Electro hydrodynamic wind energy system.

Chapter 9: Cost of Energy

Figure 9.2 Typical power curves of stall- and pitch-regulated wind turbines.
Figure 9.3 Variation of rated power with diameter.
Figure 9.4 Effect of wind turbulence on power performance.
Figure 9.5 Effect of wind turbulence at rated power.
Figure 9.6 Effect of mean wind speed and wind turbulence on deviation from expected power.
Figure 9.7 Steady-state rotor thrust of a 100-m-diameter 3 MW wind turbine.
Figure 9.8 Typical load regimes.

Chapter 10: Evaluation Methodology

Figure 10.1 Prototype wind turbine of Arter Technology.
Figure 10.2 Thrust limiting strategy.
Figure 10.3 Power curves of a 65 m diameter rotor at power ratings from 1 to 5 MW.
Figure 10.4 Power curves in a selected region below rated wind speed.
Figure 10.5 Energy and cost of energy.
Figure 10.6 Power density.
Figure 10.7 Cost of energy evaluation.
Figure 10.8 Comparison of ducted and bare turbine systems.

Chapter 11: Optimum Blade Number

Figure 11.1 Optimum rotor performance at lift-to-drag ratio of 120.
Figure 11.2 Parking strategies of a one-bladed rotor.
Figure 11.3 ADES single-bladed pendular wind turbine.
Figure 11.4 Nordic N 1000 two-bladed wind turbine (Paraje Ojos de Agua, Uruguay).
Figure 11.5 Teetered rotor dynamics.

Chapter 12: Pitch versus Stall

Figure 12.1 Power versus rotor speed characteristics.
Figure 12.2 Howden 26 MW wind farm in the Altamont Pass, California.
Figure 12.3 Rotor thrust of pitch- and stall-regulated designs.

Chapter 13: HAWT or VAWT?

Figure 13.1 Modern VAWT designs.
Figure 13.2 VAWT aerodynamics.
Figure 13.3 Actuator cylinder model for a VAWT.
Figure 13.4 Swept area and maximum C_p.
Figure 13.5 Effect of drag on VAWT performance.
Figure 13.6 Optimum solidity and tip speed ratio of a VAWT.
Figure 13.7 Power curve comparisons of HAWT designs with the FloWind 19 m.
Figure 13.8 Comparison of aerofoils for VAWT design.

Chapter 14: Free Yaw

Figure 14.1 Transformation of blade harmonics.

Chapter 15: Multi-rotor Systems (MRS)

Figure 15.1
Figure 15.2 Basic scaling characteristics.
Figure 15.5 The Vestas four-rotor MRS.
Figure 15.3 Normalised axial velocity contours (TSR = 9) for a 45-rotor MRS. (a) Rotor plane x = 0 and (b) downstream position x = 0.1D.
Figure 15.4 MRS at Kyushu University.
Figure 15.6 OWES 16-rotor multi-rotor array.
Figure 15.7 Coriolis multi-rotor concept.
Figure 15.8 Comparison of system centre thrust forces.
Figure 15.9 Yaw bearing concepts for a 20 MW, 45-rotor MRS.
Figure 15.10 Sensitivity of cost components in the 20 MW MRS design.

Chapter 17: Adaptable Rotor Concepts

Figure 17.1 Power coefficient characteristic for selected pitch angles.
Figure 17.2 Limiting tip speed ratio.
Figure 17.3 Typical steady-state pitch schedule.
Figure 17.4 Wind vectors measured with converging beams.
Figure 17.5 Pitch linkage system of the MS2 wind turbine.
Figure 17.6 Capability of smart blade devices to change lift coefficient.
Figure 17.7 Operation of a coning rotor.
Figure 17.8 Rotor power and energy comparison of coned rotor with baseline.
Figure 17.9 Blade of a variable diameter rotor. Extracted from Patent Document US 6,972,498 B2.
Figure 17.10 Power curve of a variable diameter rotor.

Chapter 18: Ducted Rotors

Figure 18.1 Rimmed rotor design – Swift 1.5 kW.
Figure 18.2 (a,b) Implux shrouded rotor system of Katru Eco-Inventions.
Figure 18.3 Velocity field (m/s) in operation on top of a building.
Figure 18.4 Test vehicle schematic image.
Figure 18.5 Theoretical power coefficient characteristics for various values of a₀.
Figure 18.6 (a) Wind Lens 100 kW turbines at Kyushu University, Ito Campus. (b) An irrigation-greenery plant using wind energy (5 kW Wind Lens turbine farm) in a desert area of northwest China.
Figure 18.7 (a) Three kilowatt Wind Lens turbines in Hakata bay. (b) Wind Lens MRS at Kyushu University.
Figure 18.8 CFD dynamic simulation (2D) of Wind Lens flow field.
Figure 18.9 Maximum power coefficient for various duct geometries of cycloidal section.

Chapter 19: The Gamesa G10X Drive Train

Figure 19.1 The G10X gearbox assembly.
Figure 19.2 The G10X generator (a) and wind turbine system (b).

Chapter 20: DeepWind Innovative VAWT

Figure 20.1 (a) HYWIND concept, [Statoil]. (b) DTU DeepWind concept. (c) DeepWind spar-buoy schematic with underwater generator compartment.
Figure 20.2 Schematic diagram of the pultrusion process.
Figure 20.3 (a–e) Generator configurations and torque reaction drag device.
Figure 20.4 Schematic illustration of the 5 MW concept.
Figure 20.5 One kilowatt DeepWind turbine for testing (demonstrator) in different rotor configurations.

Chapter 21: Gyroscopic Torque Transmission

Figure 21.1 Single GVT unit.
Figure 21.2 GVT system layout.
Figure 21.3 Mechanical and electrical power output.
Figure 21.4 Low speed shaft torque history – typical 1 MW wind turbine.
Figure 21.5 Typical low speed shaft speed history of a 1 MW wind turbine.
Figure 21.6 Generator torque from the GVT system at 1 MW rated output.

Chapter 22: The Norsetek Rotor Design

Figure 22.1 The Norsetek braced rotor concept.

Chapter 23: Siemens Blade Technology

Figure 23.1 One-piece blade technology developed by Stiesdal and Winther-Jensen for Siemens.

Chapter 24: Stall-Induced Vibrations

Figure 24.1 Asymmetric edgewise vibration mode.
Figure 24.2 Simple and compound pendula.

Chapter 25: Magnetic Gearing and Pseudo-Direct Drive

Figure 25.1 Early magnetic gear design.
Figure 25.2 High-torque magnetic gear, with p_i = 4, p_o = 23 and n_p = 27.
Figure 25.3 (a) Flux density, (b) spatial harmonic spectrum of (a). Field due to the inner magnets only, in air gap adjacent to outer magnets, with modulating rotor absent.
Figure 25.4 (a) Flux density, (b) spatial harmonic spectrum of (a). Field due to the inner magnets only, in air gap adjacent to outer magnets with modulating rotor present.
Figure 25.5 Cross section of a pseudo-direct drive.
Figure 25.6 (a) Components in PDD® which are part of the magnetic gear element and (b) components which form the PMG.
Figure 25.7 Magnomatics 300 kW PDD under test.

List of Tables

Chapter 1: Rotor Aerodynamic Theory

Table 1.1 Conservation laws
Table 1.2 Power concentrations in a 1.5 MW wind turbine
Table 1.3 Limiting performance of ducts
Table 1.4 Summary results comparing open and constrained flow

Chapter 2: Rotor Aerodynamic Design

Table 2.1 Design lift characteristics
Table 2.2 Overview of HAWT aerofoils
Table 2.3 Tolerance of aerofoil types to percentage solidity variation
Table 2.4 Aerofoil design specification

Chapter 3: Rotor Structural Interactions

Table 3.1 Blade technologies

Chapter 4: Upscaling of Wind Turbine Systems

Table 4.1 Curve fit exponents of blade mass versus diameter
Table 4.2 Mass trends of Darrieus-type VAWTs
Table 4.3 Tip speed/torque/power trends

Chapter 6: Drive-Train Design

Table 6.2 Hybrid drive trains
Table 6.1 Direct-drive wind turbines

Chapter 7: Offshore Wind Technology

Table 7.1 Distribution of total O&M cost

Chapter 8: Future Wind Technology

Table 8.1 Airborne wind power developments

Chapter 9: Cost of Energy

Table 9.1 Representative cost split
Table 9.2 Comparison of Equation 9.3 with simulation results
Table 9.3 Cost of energy fractions
Table 9.4 Offshore lifetime project cost split
Table 9.5 Site class wind conditions

Chapter 10: Evaluation Methodology

Table 10.1 Design comparison
Table 10.2 Parameter ranges

Chapter 11: Optimum Blade Number

Table 11.1 Rotor mass comparison

Chapter 13: HAWT or VAWT?

Table 13.1 Performance of VAWT UK designs
Table 13.2 Torque rating of FloWind 19 m compared to HAWTs

Chapter 15: Multi-rotor Systems (MRS)

Table 15.1 Comparison of designs for yawing and fixed base
Table 15.2 Levelised cost of energy comparisons

Chapter 17: Adaptable Rotor Concepts

Table 17.1 Comparison of critical bending moments (kNm) Cone 450 and Baseline 450 kW

Chapter 18: Ducted Rotors

Table 18.1 Key parameters of various duct geometries

Chapter 20: DeepWind Innovative VAWT

Table 20.1 Baseline 5 MW rotor design

Chapter 21: Gyroscopic Torque Transmission

Table 21.1 Properties of a gyro ‘black box’

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Foreword

Those of us who have been active in the wind energy industry for the past few decades have been lucky. We have been involved in an industry that is technically fascinating, commercially exciting and thoroughly worthwhile. We have seen turbines increase in diameter from 10 to 120 m and in power from 10 to 10 000 kW – what a fantastic journey!

The size of the turbines is the most obvious characteristic because it can be so clearly seen – wind turbines are now by far the biggest rotating machines in the world. Less visible is the ingenuity of the designs. Looking back a couple of decades, there were many ‘whacky’ ideas that were seriously contemplated and even offered commercially and some of those whacky ideas have become conventional. Superficially, the latest generation of turbines may all look the same, but underneath the nacelle and inside the blades there are many fascinating differences. For a long time, the mantra of the wind turbine industry has been ‘bigger and bigger’, but now it has moved to ‘better and better’ and this change marks a change in the areas of innovation.

Peter Jamieson is one of the clearest thinkers in the industry and I am delighted and honoured to have worked with him for almost 20 years. He is a real blue sky thinker unimpeded by convention and driven by a strong sense of rigour. Innovation in wind turbine design is what Peter has been doing for the past 30 years and it is about time he wrote a book about it. I fully supported Peter's idea that he should put his professional thoughts on record and now he has done so.

Anyone interested in the technical aspects of both the past developments and the exciting future of wind turbines should read this book carefully and be inspired. This is no arid technical text or history – this is real intellectual capital and, of course, innovation.

Andrew Garrad

Preface

This book is about innovation in wind turbine design – more specifically about the evaluation of innovation – assessing whether a new concept or system will lead to improved design-enhancing performance or reducing cost. In the course of a working life in wind energy that began in 1980, the author's work has increasingly been, at the request of commercial clients and sometimes public authorities, to evaluate innovative systems providing reports which may or may not encourage further investment or development. In some cases, the clients are private inventors with a cherished idea. Other cases include small companies strategically developing innovative technologies, major industrial companies looking for an entry to the wind turbine market or major established wind turbine companies looking to their next-generation technology.

There is substantial conservatism in the wind industry as in most others and largely for the best possible reasons. Products need to be thoroughly proved and sound, whereas change is generally risky and expensive even when there is significant promise of future benefit. To some extent, change has been enforced by the demands year by year for larger wind turbines and components. There has been convergence in the preferred mainstream design routes but, as new players and new nations enter the wind business, there is also a proliferation of wind technology ideas and demand for new designs. The expansion of wind energy worldwide has such impetus that this book could be filled with nothing but a catalogue of different innovative designs and components.

It may initially seem strange that as much of the book is devoted to technology background as to discussion of specific innovative concepts. However, innovation is not a matter of generating whacky concepts as an entertainment for bored engineers. The core justification for innovation is that it improves technology, solving problems rather than creating them. To achieve that, it is crucial that the underlying requirements of the technology are well understood and that innovation is directed in areas where it will produce most reward. Hence is the emphasis on general technology background. Within that background some long-established theory is revisited (actuator disc and blade element momentum) but with some new equations developed.

Among much else, this second edition contains predictable updates regarding new larger turbines and new systems plus expanded sections on the ever-growing offshore applications and the developing interest in airborne wind power. There is also new content relating to presentation of basic theory, a fuller evaluation of many issues concerning ducted rotors, various new top-level analyses of the low-induction rotor concept, flow relativity (relating to driving rotors through still air as a means of performance measurement) and kite performance, for example.

Innovative ideas by definition break the mould. They often require new analytical tools or new developments of existing ones and, in general, fresh thinking. They do not lend themselves to a systematised, routine approach in evaluation. Evaluating innovation is an active process like design itself, always in evolution with no final methodology. On the other hand, there are basic principles and some degree of structure can be introduced to the evaluation process.

In tackling these issues, a gap was apparent – between broad concepts and detailed design. This is territory where brainstorming and then parametric analyses are needed, when pure judgement is too limited but when heavyweight calculation is time consuming, expensive and cannot be focused on with any certainty in the right direction. This why ‘detailed design’ is not much addressed. It is the subject of another book. This one concerns building bridges and developing tools to evaluate innovative concepts to the point where investment in detailed design can be justified. Innovation in wind energy expresses the idealism of the designer to further a sustainable technology that is kind to the planet.

Peter Jamieson

Acknowledgement

My professional life in wind technology began in 1980 in the employment of James Howden and Company of Glasgow and I very much appreciate many colleagues who shared these early days of discovery. Howden regrettably withdrew from turbine manufacture in 1988, but by then my addiction to wind was beyond remedy.

In those days I much admired a growing wind energy consultancy, Garrad Hassan and Partners. I was delighted to join them in 1991 and, as it happened, founded their Scottish office. I felt that it would be great to have a working environment among such talented people and that I would have a continuing challenge to be worthy of them.

In particular, I would very much like to thank Andrew Garrad and Dave Quarton for encouragement, practical support and great tolerance over 4 years in the preparation of the first edition. At the end of 2013 I retired from Garrad Hassan, by then part of DNV GL. Commencing in 2009, I was employed part time in the Centre for Doctoral Training in Wind Energy in the University of Strathclyde and enjoy working with great teams of staff and students who, now numbering over 40, are studying wind and marine topics at PhD level. I am much indebted to Bill Leithead, director of the centre, especially for many valuable brainstorming sessions on wind technology over the years.

I have to say special thanks to the late Woody Stoddard, who was an inspiring friend and enormously supportive, especially considering the few times we met.

Considering the very many times I have imposed on his good nature, I have equally to thank Mike Graham for his freely given help in so many projects and as an excellent, unofficial aerodynamics tutor. Much thanks also to Henrik Stiesdal, who, as an extremely busy man at the technical helm of a large wind turbine manufacturing company, found time to contribute a chapter to this book.

My warm thanks also go to very many other work colleagues and associates who, knowingly or otherwise, have made valuable contributions to this book. Among them are:

Albert Su, Alena Bach, Alexander Ovchinnikov, Andrew Latham, Anne Telfer, Ben Hendriks, Bob Thresher, Carlos Simao Ferreira, Chai Toren, Charles Gamble, Chris Hornzee-Jones, Chris Kirby, Christine Sams, David Banks, David Milborrow, David Sharpe, Ed Spooner, Emil Moroz, Ervin Bossanyi, Fabio Spinato, Fatma Murray, Iain Dinwoodie, Jan Rens, Geir Moe, Georg Böhmeke, Gerard van Bussel, Herman Snel, Irina Dyukova, Jamie Taylor, Jega Jegatheeson, Jim Platts, John Armstrong, Kamila Nieradzinska, Kerri Hart, Leong Teh, Lindert Blonk, Lois Connell, Lutz Witthohn, Magnus Kristbergsson, Marcia Heronemus, Mark Hancock, Martin Hansen, Masaaki Shibata, Mauro Villanueva-Monzón, Mike Anderson, Mike Smith, Nathalie Rousseau, Nick Jenkins, Nils Gislason, Patrick Rainey, Paul Gardner, Paul Gipe, Paul Newton, Paul Veers, Peter Dalhoff, Peter Musgrove, Peter Stuart, Rob Rawlinson-Smith, Roger Haines, Roland Schmehl, Roland Stoer, Ross Walker, Ross Wilson, Ruud van Rooij, Sandy Butterfield, Seamus Garvey, Stephen Salter, Steve Gilkes, Stuart Calverley, Tim Camp, Takis Chaviaropoulos, Theo Holtom, Tomas Blodau, Trevor Nash, Uli Goeltenbott, Unsal Hassan, Uwe Paulsen, Varan Sureshan, Vidar Holmöy, Win Rampen, Wouter Haans, Yuji Ohya.

Peter Jamieson

Innovation in Wind Turbine Design

Second Edition

Foreword

Preface

Acknowledgement