89,99 €
Mehr erfahren.
- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
An updated and expanded new edition of this comprehensive guide to innovation in wind turbine design
Innovation in Wind Turbine Design, Second Edition comprehensively covers the fundamentals of design, explains the reasons behind design choices, and describes the methodology for evaluating innovative systems and components.
This second edition has been substantially expanded and generally updated. New content includes elementary actuator disc theory of the low induction rotor concept, much expanded discussion of offshore issues and of airborne wind energy systems, updated drive train information with basic theory of the epicyclic gears and differential drives, a clarified presentation of the basic theory of energy in the wind and fallacies about ducted rotor design related to theory, lab testing and field testing of the Katru and Wind Lens ducted rotor systems, a short review of LiDAR, latest developments of the multi-rotor concept including the Vestas 4 rotor system and a new chapter on the innovative DeepWind VAWT.
The bookis divided into four main sections covering design background, technology evaluation, design themes and innovative technology examples.
Key features:
- Expanded substantially with new content.
- Comprehensively covers the fundamentals of design, explains the reasons behind design choices, and describes the methodology for evaluating innovative systems and components.
- Includes innovative examples from working experiences for commercial clients.
- Updated to cover recent developments in the field.
The book is a must-have reference for professional wind engineers, power engineers and turbine designers, as well as consultants, researchers and graduate students.
Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 706
Veröffentlichungsjahr: 2018
Ähnliche
Table of Contents
Title Page
Copyright
Dedication
Foreword
Preface
Acknowledgement
Introduction
0.1 Why Innovation?
0.2 The Challenge of Wind
0.3 The Specification of a Modern Wind Turbine
0.4 The Variability of the Wind
0.5 Early Electricity-Generating Wind Turbines
0.6 Commercial Wind Technology
0.7 Basis of Wind Technology Evaluation
0.8 Competitive Status of Wind Technology
References
Part I: Design Background
Chapter 1: Rotor Aerodynamic Theory
1.1 Introduction
1.2 Aerodynamic Lift
1.3 Power in the Wind
1.4 The Actuator Disc Concept
1.5 Open Flow Actuator Disc
1.6 Why a Rotor?
1.7 Actuator Disc in Augmented Flow and Ducted Rotor Systems
1.8 Blade Element Momentum Theory
1.9 Optimum Rotor Design
1.10 Limitations of Actuator Disc and BEM Theory
References
Chapter 2: Rotor Aerodynamic Design
2.1 Optimum Rotors and Solidity
2.2 Rotor Solidity and Ideal Variable Speed Operation
2.3 Solidity and Loads
2.4 Aerofoil Design Development
2.5 Sensitivity of Aerodynamic Performance to Planform Shape
2.6 Aerofoil Design Specification
2.7 Aerofoil Design for Large Rotors
References
Chapter 3: Rotor Structural Interactions
3.1 Blade Design in General
3.2 Basics of Blade Structure
3.3 Simplified Cap Spar Analyses
3.4 The Effective
t/c
Ratio of Aerofoil Sections
3.5 Blade Design Studies: Example of a Parametric Analysis
3.6 Industrial Blade Technology
References
Chapter 4: Upscaling of Wind Turbine Systems
4.1 Introduction: Size and Size Limits
4.2 The ‘Square-Cube’ Law
4.3 Scaling Fundamentals
4.4 Similarity Rules for Wind Turbine Systems
4.5 Analysis of Commercial Data
4.6 Upscaling of VAWTs
4.7 Rated Tip Speed
4.8 Upscaling of Loads
4.9 Violating Similarity
4.10 Cost Models
4.11 Scaling Conclusions
References
Chapter 5: Wind Energy Conversion Concepts
References
Chapter 6: Drive-Train Design
6.1 Introduction
6.2 Definitions
6.3 Objectives of Drive-Train Innovation
6.4 Drive-Train Technology Maps
6.5 Direct Drive
6.6 Hybrid Systems
6.7 Geared Systems – the Planetary Gearbox
6.8 Drive Trains with Differential Drive
6.9 Hydraulic Transmission
6.10 Efficiency of Drive-Train Components
6.11 Drive-Train Dynamics
6.12 The Optimum Drive Train
6.13 Innovative Concepts for Power Take-Off
References
Chapter 7: Offshore Wind Technology
7.1 Design for Offshore
7.2 High-Speed Rotor
7.3 ‘Simpler’ Offshore Turbines
7.4 Rating of Offshore Wind Turbines
7.5 Foundation and Support Structure Design
7.6 Electrical Systems of Offshore Wind Farms
7.7 Operations and Maintenance (O&M)
7.8 Offshore Floating Wind Turbines
References
Chapter 8: Future Wind Technology
8.1 Evolution
8.2 Present Trends – Consensus in Blade Number and Operational Concept
8.3 Present Trends – Divergence in Drive-Train Concepts
8.4 Future Wind Technology – Airborne
8.5 Future Wind Technology – Energy Storage
8.6 Innovative Energy Conversion Solutions
References
Part II: Technology Evaluation
Chapter 9: Cost of Energy
9.1 The Approach to Cost of Energy
9.2 Energy: the Power Curve
9.3 Energy: Efficiency, Reliability, Availability
9.4 Capital Costs
9.5 Operation and Maintenance
9.6 Overall Cost Split
9.7 Scaling Impact on Cost
9.8 Impact of Loads (Site Class)
References
Chapter 10: Evaluation Methodology
10.1 Key Evaluation Issues
10.2 Fatal Flaw Analysis
10.3 Power Performance
10.4 Structure and Essential Mass
10.5 Drive-Train Torque
10.6 Representative Baseline
10.7 Design Loads Comparison
10.8 Evaluation Example: Optimum Rated Power of a Wind Turbine
10.9 Evaluation Example: the Carter Wind Turbine and Structural Flexibility
10.10 Evaluation Example: Concept Design Optimisation Study
10.11 Evaluation Example: Ducted Turbine Design Overview
References
Part III: Design Themes
Chapter 11: Optimum Blade Number
11.1 Energy Capture Comparisons
11.2 Blade Design Issues
11.3 Operational and System Design Issues
11.4 Multi-bladed Rotors
References
Chapter 12: Pitch versus Stall
12.1 Stall Regulation
12.2 Pitch Regulation
12.3 Fatigue Loading Issues
12.4 Power Quality and Network Demands
References
Chapter 13: HAWT or VAWT?
13.1 Introduction
13.2 VAWT Aerodynamics
13.3 Power Performance and Energy Capture
13.4 Drive-Train Torque
13.5 Niche Applications for VAWTs
13.6 Status of VAWT Design
References
Chapter 14: Free Yaw
14.1 Yaw System COE Value
14.2 Yaw Dynamics
14.3 Yaw Damping
14.4 Main Power Transmission
14.5 Operational Experience of Free Yaw Wind Turbines
14.6 Summary View
References
Chapter 15: Multi-rotor Systems (MRS)
15.1 Introduction
15.2 Standardisation Benefit and Concept Developments
15.3 Operational Systems
15.4 Scaling Economics
15.5 History Overview
15.6 Aerodynamic Performance of Multi-rotor Arrays
15.7 Recent Multi-rotor Concepts
15.8 MRS Design Based on VAWT Units
15.9 MRS Design within the Innwind.EU Project
15.10 Multi-rotor Conclusions
References
Chapter 16: Design Themes Summary
Part IV: Innovative Technology Examples
Chapter 17: Adaptable Rotor Concepts
17.1 Rotor Operational Demands
17.2 Management of Wind Turbine Loads
17.3 Control of Wind Turbines
17.4 LiDAR
17.5 Adaptable Rotors
17.6 The Coning Rotor
17.7 Variable Diameter Rotor
References
Chapter 18: Ducted Rotors
18.1 Introduction
18.2 The Katru Shrouded Rotor System
18.3 The Wind Lens Ducted Rotor
References
Chapter 19: The Gamesa G10X Drive Train
Chapter 20: DeepWind Innovative VAWT
20.1 The Concept
20.2 DeepWind Concept at 5 MW Scale
20.3 Marine Operations Installation, Transportation and O&M
20.4 Testing and Demonstration
20.5 Cost Estimations
References
Chapter 21: Gyroscopic Torque Transmission
References
Chapter 22: The Norsetek Rotor Design
References
Chapter 23: Siemens Blade Technology
Chapter 24: Stall-Induced Vibrations
References
Chapter 25: Magnetic Gearing and Pseudo-Direct Drive
25.1 Magnetic Gearing Technology
25.2 Pseudo-Direct-Drive Technology
References
Chapter 26: Summary and Concluding Comments
Index
End User License Agreement
Pages
c1
v
xv
xvii
xviii
xix
xx
ii
1
2
3
4
5
6
7
8
9
10
11
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
335
336
337
338
339
340
341
342
343
344
345
346
347
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
367
368
369
371
372
373
374
375
377
378
379
380
381
383
384
385
386
387
388
389
390
391
392
393
394
Guide
Table of Contents
Foreword
Preface
Begin Reading
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 SCDnezzy
2
.
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
= 0.1
D
.
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
a
0
.
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’
Innovation in Wind Turbine Design
Second Edition
Peter Jamieson
Strathclyde University, UK
This edition first published 2018
© 2018 John Wiley & Sons Ltd
Edition History
John Wiley & Sons Ltd (1e, 2011)
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions.
The right of Peter Jamieson to be identified as the author of this work has been asserted in accordance with law.
Registered Offices
John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA
John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK
Editorial Office
The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK
For details of our global editorial offices, customer services, and more information about Wiley products visit us at www.wiley.com.
Wiley also publishes its books in a variety of electronic formats and by print-on-demand. Some content that appears in standard print versions of this book may not be available in other formats.
Limit of Liability/Disclaimer of Warranty
While the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.
Library of Congress Cataloging-in-Publication Data applied for
Hardback ISBN- 9781119137900
Cover design by Wiley
Cover image: © Mischa Keijser/Gettyimages
To Adele and Rose
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
Introduction
0.1 Why Innovation?
Fuel crises, concerns about global environmental threats and the urgent needs for energy in expanding new economies of the former third world have all contributed to an ever-increasing growth of renewable energy technologies. Presently, wind energy is the most mature and cost-effective of these.
While other more diverse applications are discussed, this book keeps the main focus on wind energy converters that produce electricity. This is primarily because the greater part of the author's experience is with such systems. However, in a more objective defence of that stance, it may be observed that by far the largest impact of wind technology on the world's energy supply presently comes from systems generating into electrical networks.
Innovation is about new ideas, and some quite unusual designs are evaluated in this book. Why give attention to such designs which may not be in the mainstream? Exploring alternative concepts not only deepens understanding of why the mainstream options are preferred but also suggests where they should be challenged by alternatives that have significant promise. In any case, ideas are grist to the mill of technological progress and those which fail in one embodiment may well later be adapted and successfully reincarnated.
As is discussed shortly, the generation of power from the wind presents unique challenges. Unlike cars and houses, for example, energy is a commodity which has utilitarian value only. No one prefers a particular petrol because it has a nicer colour. The wealthy may indulge in gold or gold-plated bathroom taps, but no one can purchase gold-plated electricity. Energy must meet generally stringent specifications of quality in order to be useful (voltage and frequency levels particularly in the case of electricity). Once it does, the main requirement is that it is dependably available and as cheap as possible.
The end purpose of innovation in wind turbine design is to improve the technology. Usually, this means reducing the cost of energy and this is the general basis of evaluating innovation in this book. However, even this simply stated goal is not always the final criterion. In some instances, for example, the objective is to maximise energy return from an available area of land. Sometimes capital cost has a predominant influence. The bottom line is that any technology must be tailored accurately to an engineering design specification that may include environmental, market, cost and performance issues.
The detailed design of a wind turbine system is not a minor or inexpensive task. By the time an innovative design is the subject of a detailed design study, although it may yet be some way from market, it has already received significant investment and has passed preliminary tests as to the potential worth of the new concepts.
Thus, there is an intermediate stage between first exposure of a concept up to the stage of securing investment in a prototype when the concepts are examined and various levels of design are undertaken. Usually, a search for fatal flaws or obvious major shortcomings is the first stage. The design may be feasible but will have much more engineering content than its competitors and it is therefore unlikely to be cost-effective. More typically, there is no clear initial basis for rejecting the new concepts and a second level of appraisal is required. A systematic method is needed to review qualitatively, and where possible quantitatively, how the design compares to existing technology and for what reason(s) it may have merit. At this stage, detailed, expensive and time-consuming analyses are precluded, but there is a great need for parametric evaluations and simplified analyses that can shed light on the potential of the new concepts.
This book is very much about these preliminary evaluation stages, how simple insightful methods can provide guidance at a point where the value of the innovation is too uncertain to justify immediate substantial investment or detailed design.
0.2 The Challenge of Wind
According to Murray [1], the earliest written reference to windmills is of the fifth century BC. Windmills (although probably only then existing as children's toys) are listed, among other things, as something a devout Buddhist would have nothing to do with! The aerodynamic rotor concept is evidently ancient.
To generate electricity (by no means the only use for a wind turbine but certainly a major one under present consideration), requires the connection of such a rotor to an electric generator. Electric motor/generator technology began in Faraday's discoveries in the mid-nineteenth century. About 70 years ago and preceding the modern wind industry, the average household in the United States contained about 40 electric motors. The electric motor/generator is therefore not ancient but has been in mass production for a long time in recent history. What then is difficult about the marriage of rotor and generator into successful and economic power generating systems? The challenge of modern wind technology lies in two areas, the specification of an electricity-generating wind turbine and the variability of the wind.
0.3 The Specification of a Modern Wind Turbine
Traditional ‘Dutch’ windmills (Figure 0.1) have proliferated to the extent of 100 000 over Europe in their heyday. Some have survived 400–600 years, the oldest still operating in the United Kingdom being the post mill at Outwood, Surrey built in 1628. A short account of the history of early traditional wind technology in Eggleston and Stoddard [2] shows that they exhibit considerable practical engineering skill and empirical aerodynamic knowledge in their design and interesting innovations such as variable solidity blades (spilling the air through slats that can open or close) that have not surfaced in modern wind turbine design. However, these machines were always attended, were controlled manually for the most part, were integrated parts of the community and were designed for frequent replacement of certain components, and efficiency was of little consequence.
Figure 0.1 Jill post mill at Clayton Sussex.
Reproduced with permission of Paul Barber.
In contrast, to generate electricity cost-effectively is the specification of a modern power-generating wind turbine. To meet economic targets, it is unthinkable for the wind turbine to be permanently attended, and unacceptable for it to be much maintained. Yet, each unit is a self-contained mini-power station, requiring to output electricity of standard frequency and voltage into a grid system. Cost-effectiveness is overriding, but the efficiency of individual units cannot be sacrificed lightly. Energy is a prime value; whereas the lifetime costs comprise many components, each one of which has a lesser impact on cost of energy. Also, the total land area requirements per unit output will increase as efficiency drops.
It should be clear that wind technology embraces what is loosely called ‘high-tech’ and ‘low-tech’ engineering. The microprocessor plays a vital role in achieving self-monitoring unmanned installations. There is in fact nothing particularly simple about any kind of system for generating quality electricity. Diesel generators are familiar but not simple, and have a long history of development.
Thus, it is by no means enough to build something ‘simple and rugged’ that will survive any storm. Instead, the wind turbine must be value engineered very carefully to generate cheap electricity with adequate reliability. This is the first reason why the technology is challenging.
0.4 The Variability of the Wind
The greatest gust on record was on 12 April 1934 at the peak of Mount Washington in the Northern Appalachians [3]. ‘On record’ is a revealing phrase as anemometers have usually failed in the most extreme conditions. At 103 m/s, a person exposing 0.5 m2 of frontal area would have experienced a force equivalent to about 1/3 of a tonne weight. In terms of annual mean wind speed, the windiest place in the world [3] is on the edge of Antarctica, on a mountain margin of East Adelie land. At 18 m/s annual mean wind speed, the available wind energy is about 200 times that of a typical European wind site. These are of course extreme examples and there are no plans to erect wind turbines on either site.
Nevertheless, it underlines that there is enormous variation in wind conditions. This applies both on a worldwide basis but also in very local terms. In the rolling hills of the Altamont Pass area of California, where many wind farms were sited in the 1980s, there are large differences in wind resource (100%, say, in energy terms) between locations no more than a few hundred metres apart. Wind turbines are situated right at the bottom of the earth's boundary layer. Their aerofoils generally travel much more slowly than aircraft or helicopter rotors, and the effect of wind turbulence is much more consequential for design. The crux of this is that it is hard to refine a design for such potentially variable conditions, and yet uneconomic to design a wind turbine fit to survive anywhere. Standardisation is much desired to cheapen production, but is in conflict with best economics at specific local sites. Designs often need to have adaptive features to accommodate larger rotors, uprated generators or additional structural reinforcement as necessary.
Anemometry studies, both to determine suitable sites and for the micro-siting of machines within a chosen area, are not academic exercises. Because of the sensitivity of wind energy to wind speed and wind speed to short- and longer term climatic patterns, the developer who is casual about wind resource estimates is playing a game of roulette on profit margins. Thus, the variability of the wind is the second major reason wind turbine design is challenging.
0.5 Early Electricity-Generating Wind Turbines
Rather presciently, from a twenty-first century viewpoint, Sir William Thomson (later to become Lord Kelvin) suggested in his address to the British Association meeting in York in 1881 that, as fossil fuel resources were consumed and become more expensive, wind power might be used to generate electricity. Professor James Blyth, of Anderson's college, Glasgow (later to become Strathclyde University) was thus inspired to build and test in 1887 the first windmill to be used for electricity generation. Power stored in a battery was used to light up to 10, 8 candlepower, 25 V, incandescent lamps in Blyth's cottage.
There is no photographic record of Blyth's first electricity-generating wind turbine of 1887, a horizontal-axis, American-style multi-bladed rotor. A little later in 1891, he developed a vertical-axis wind turbine which provided lighting for his holiday home at Marykirk, a small village in Scotland about 45 km from the city of Dundee. The diameter was about 10 m and the ‘blades’, 8 semi-cylindrical boxes, as Blyth called them, are each about 1.8 m wide and 1.8 m high. Soon afterwards he had this design engineered more professionally (Figure 0.2) and sold a small number of these, the first ‘commercial’ electricity generating wind turbines in the world.
Figure 0.2 Blyth windmill commercial prototype.
Reproduced with permission of the Andersonian Library, University of Strathclyde.
Blyth was succeeded by the American, Charles Brush who in 1888 used a large multi-bladed windmill to illuminate his Cleveland mansion. The rotor had 144 blades and a diameter of 17 m and with the tower weighed about 36 tonnes. At full load, the dynamo would then turn at 500 rpm and give an output of 12 kW. The early stand-alone electricity-generating windmills had significant problems with highly variable input, affecting the reliability of the accumulators. The Dane, Poul la Cour built his first windmill at Askov (in Jutland, about 40 km east of Esbjerg) in 1891 with a diameter of 11.6 m and four sails each 2 m wide. In 1891, la Cour invented the ‘kratostata’ to smooth out the power fluctuations that result from the turbulence in the wind. This was a mechanical device allowing some slip in a belt transmission alleviating rapid changes in load from turbulent wind variations, and it appreciably helped the problems with batteries. However, at the end of the nineteenth century, there was neither sufficient technology development nor a suitable market context for wind-generated electricity to progress further and become cost-effective.
0.6 Commercial Wind Technology
In the twentieth century, wind technology headed towards mainstream power generation beyond the water pumping and milling applications that had been exploited for several thousand years. The Gedser wind turbine is often credited as the seminal design of the modern wind industry. With assistance from Marshall Plan post war funding, a 200 kW, 24 m diameter, three-bladed wind turbine was installed during 1956–1957 on the island of Gedser in the south east of Denmark. This machine operated from 1958 to 1967 with about 20% capacity factor.1
In the early 1960s, Professor Ulrich Hütter developed high tip speed designs, which had a significant influence on wind turbine research in Germany and the United States.
In the early 1980s, many issues of rotor blade technology were investigated. Steel rotors were tried but rejected as too heavy, and aluminium as too uncertain in the context of fatigue endurance. Wood was a logical natural material designed by evolution for high fatigue bending strength-to-weight ratio. The problem of moisture stabilisation of wood was resolved in the wood-epoxy system developed by Gougeon Brothers in the United States. This system has since been employed in a number of small and large wind turbines (e.g. the former NEG-Micon NM82). Wood-epoxy blade technology was much further developed in the United Kingdom, latterly by Taywood Aerolaminates who were assimilated by NEG-Micon and then in turn by Vestas. The blade manufacturing industry was, however, dominated by fibreglass polyester construction which evolved from a boat building background, became thoroughly consolidated in Denmark in the 1980s and has since evolved into more sophisticated glass composite technologies using higher quality fibres (sometimes with carbon reinforcement), and more advanced manufacturing methods such as resin infusion.
During the 1980s, some megawatt-scale prototypes had appeared and this history is well documented by Spera [4] and Hau [5]. In general, these wind turbines had short lives and, in some cases, fatal flaws in design or manufacture. Valuable research information was gained; yet, in many respects, these designs followed technology routes rather disconnected from the emerging commercial wind turbine market. In contrast to this, in Denmark during the 1970s and 1980s, a gradual development of wind technology had occurred. This was a result of public pressures to develop renewables and to avoid nuclear energy combined with a lack of indigenous conventional energy sources. Wind turbine design development proceeded with incremental improvement of designs which were being maintained in commercial use and with gradual increase in scale into ratings of a few 100 kW. And, a much more successful technology resulted.
Just as the first-generation commercial Danish designs were emerging in the early 1980s, a combination of state and federal, energy and investment tax credits had stimulated a rapidly expanding market for wind in California. Over the period 1980–1995, about 1700 MW of wind capacity was installed, more than half after 1985 when the tax credits had reduced to about 15%.
Tax credits fuelled the indiscriminate overpopulation of various areas of California (San Gorgonio, Tehachapi and Altamont Pass) with wind turbines many of which were ill-designed and functioned poorly. It was the birthplace and graveyard of much more or less casual innovation. This created a poor image for the wind industry, which took time to remedy. However, the tax credits created a major export market for European, especially Danish, wind turbine manufacturers who had relatively cost-effective, tried and tested hardware available. The technically successful operation of the later, better designed wind turbines in California did much to establish the foundation on which the modern wind industry has been built.2
0.7 Basis of Wind Technology Evaluation
A summary of some of the key issues in the evaluation of new wind technology is presented here. These topics are addressed in more detail in Chapters 9 and 10.
0.7.1 Standard Design as Baseline
The most straightforward way to evaluate new technology is to set it alongside existing state-of-the-art technology and conduct a side-by-side comparison. This is particularly effective in the case of isolated components which are innovative and different in themselves from the standard solution but have little direct impact on the rest of the system. It is then reasonable to assume that all other components in the system have the same costs as in the standard design and conduct a cost of energy analysis in which only the new component is differentiated. Other innovations may be much more challenging. For example, a new rotor concept can have wide-ranging implications for system loads. In that case, one approach is to tailor certain key loads to be within the same level as the standard design and therefore to have no impact on the components designed by those loads. Another more challenging route is to develop analyses where the impact of loads on component cost is considered. The development of a baseline standard, state-of-the-art design will be seen as a key element in most of the evaluations of innovative technology.
0.7.2 Basis of Technological Advantage
If an innovative system is feasible in principle, the next obvious question is why is it better than anything that precedes it? Does it offer performance gains or cost reduction, does it enhance reliability? In the first instance, it is not a matter of assessing the level of merit or the realism of the claim so much as confirming that there is a core reason being offered why the system may have merit.
0.7.3 Security of Claimed Power Performance
Especially with radically new system designs, there may be a question mark over the likely level of performance. The evaluation of this is clearly critical for the system economics and a number of evaluations go no further than consideration of whether the proposed system has a sufficiently good power performance coefficient. This is particularly the case in systems that sacrifice performance for simplicity. Sometimes the illusion of a very simple and cheap system will persuade an uncritical inventor that an idea is very promising when, in fact, the system in its essential concepts sacrifices so much energy that the considerable capital cost savings that it may achieve are not enough to justify the concept and the cost of energy is high.
0.7.4 Impact of Proposed Innovation
Where can successful innovation make the greatest impact?
This is addressed by looking at the relative costs of components in a wind turbine system and any impacts they have on system productivity through efficiency or reliability. Innovation is disruptive and needs to offer sufficient benefit to be worth the trouble. The capital cost of a yaw system of a large horizontal axis wind turbine is typically around 3% or 4% of total wind turbine capital cost. About half to two-thirds of this cost is in the yaw bearing. This major component is generally not dispensable and so it is clear that no yaw system solution, however innovative, can make large capital cost savings in relation to wind turbine capital cost. On the other hand, if a new yaw system has improved reliability, its total value in terms of impact in cost of energy is enhanced.
0.8 Competitive Status of Wind Technology
After many years of battling to reduce costs, assailed by critics about the extent to which wind was subsidised, as if other energy supplies had not been, a breakthrough picture is emerging. The following article [6] by Paul Gardner, Global Segment Leader, Energy Storage at DNV GL, summarises the situation very well:
In November, the UK Government published an updated version of its Electricity Generation Costs analysis. This is a rigorous assessment of Levelised Cost of Energy (LCOE) for a very wide range of generation options … a major benefit of this kind of study is that it compares competing technologies on the same basis, or at least on mutually consistent assumptions.
…—the report has a section specifically highlighting… enormous reductions from the costs forecast in the previous issue (2013), for large-scale PV, onshore wind, and offshore wind.
For projects commissioning in 2020, the cheapest options available at significant scale all have similar costs: H-class combined cycle gas turbines (CCGTs) at 78 EUR/MWh, onshore wind (projects larger than 5 MW) at 74 EUR/MWh, and large-scale ground-mounted solar at 79 EUR/MWh. By 2025, wind and PV are the clear winners at 72 and 74 EUR/MWh; CCGT costs increase to 96 EUR/MWh due to higher assumed gas and carbon costs.
A good result for renewables. In fact, by 2025 even large hydro, small building-mounted PV, and near-shore wind will be competitive with large CCGTs. However, on closer inspection of the figures there's a more important and perhaps surprising conclusion. A common criticism of costings of the variable renewables (wind, PV, and others) is that they don't include the costs for ‘backup’ generation to cover demand when needed. In the UK the worst case is an extended period of anticyclonic weather in winter, resulting in days or weeks of very low winds, low temperatures, and high electricity demand. This criticism is justified, though the assumption that every wind or PV project should be ‘charged’ the capital cost of fossil generation of the same capacity is overly simplistic. However, the UK figures show that even with this overly simplistic assumption, wind and PV still win.
How? Well, the cost forecasts include fixed and variable costs. For CCGTs in 2025, the fuel, carbon, and variable O&M costs alone total 86 EUR/MWh. This is significantly more expensive than the total costs for wind and PV. So, wind and PV projects could indeed afford to pay for the costs of CCGTs, to be treated as ‘firm’, and would still be the cheapest generation option available at scale. Or in other words, a CCGT operating in 2025 as ‘baseload’ will find it cheaper to buy the output of wind or PV projects, whenever available, in preference to buying and burning gas.
This marks the next stage in cost-competitiveness of renewables. First there is ‘retail parity’, where behind-the-meter wind or PV beats the retail price of electricity to residential, commercial or industrial consumers. Then there is ‘wholesale parity’, where renewable costs compete on wholesale or spot markets. And now on the horizon we can see ‘fuel parity’, where renewables become cheaper than just the fuel (and carbon) costs of fossil generation.
In fact, the ‘horizon’ is not that far off: interpolating the UK figures for 2020 and 2025 shows that fuel parity is forecast for 2023. That is only 6 years from now. Companies currently developing potential new CCGT projects will no doubt be factoring this into their calculations.
References
1 Murray, H.J.R.A. (1913)
A History of Chess
, Oxford University Press, London; (1985) Benjamin Press, Northampton, MA. ISBN: 0-936317-01-9.
2 Eggleston, D.M. and Stoddard, F.S. (1987)
Wind Turbine Engineering Design
, Kluwer Academic Publishers. ISBN: 13: 9780442221959.
3 Watson, L. (1984)
Heavens Breath: A Natural History of the Wind
, Hodder General Publishing Division. ISBN: 0340430982 (0-340-43098-2).
4 Spera, D.A. (ed.) (2009)
Wind Turbine Technology: Fundamental Concepts in Wind Turbine Engineering
, 2nd edn, ASME Press, New York.
5 Hau, E. (2006)
Wind Turbines: Fundamentals, Technologies, Application, Economics
, Springer-Verlag. ISBN: 13 978-3-540-24240-6
6 Gardner, P.
https://www.linkedin.com/pulse/renewables-track-beat-fuel-parity-combined-cycle-gas-turbines-paul?trk=v-feed&lipi=urn%3Ali%3Apage%3Ad_flagship3_feed%3BsXZmYFRfaHIrsHuo%2FxkBiQ%3D%3D
(viewed February 2017).
1
A historical review of wind technology (also written by the author) similar to the text up to this point may be found in the EWEA publication,
Wind Energy the Facts
.
2
