Table Of ContentRenewable Energy Series 13
Offshore Wind Turbines
Reliability, availability and maintenance
RO
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liaff
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The development of offshore wind power has become a Peter Tavner is Emeritus Professor of ilith
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pressing modern energy issue in which the UK is taking a major New and Renewable Energy at the School ,
part, driven by the need to find new electrical power sources, of Engineering and Computing Sciences avre
avoiding the use of fossil fuels, in the knowledge of the extensive at Durham University. He has received a
wind resource available around our islands and the fact that the an MA from Cambridge (1969), a PhD ila W
from Southampton (1978) and a DSc b
environmental impact of offshore wind farms is likely to be low. from Durham (2012) Universities. He has ilitin
However, there are major problems to solve if offshore wind held senior positions in the manufacturing y
power is to be realised and these problems revolve around the industry, including Group Technical Director ad
need to capture energy at a cost per kWh which is competitive of FKI Energy Technology, an international nd T
with other sources. This depends upon the longevity of the wind business manufacturing wind turbines, mu
turbines which make up offshore wind farms. Their availability, electrical machines and drives in Europe.
He has also been Principal Investigator of ar
reliability and the efficacy and cost-effectiveness of the the EPSRC Supergen Wind Consortium inb
maintenance, needed to achieve that availability, are essential and Sino-British Future Renewable Energy tein
to improve offshore wind life-cycle costs and the future of this n
emerging industry. Nis eat wFeolrlko wSy sotfe tmhes (InFsRtEituNtSio)n C oofn Esnogrtiinueme.r iHnge ane
This book intends to address these issues head-on and and Technology, President of the European ces
demonstrate clearly to manufacturers, developers and operators Academy of Wind Energy and a Non-
Executive Director of Wind Technologies, a
the facts and figures of wind turbine operation and maintenance
Cambridge University spin-out company.
in the inclement offshore environment, recommending how
He is a winner of the Institution Premium
maintenance should be done to achieve low life-cycle costs.
of the IET.
Offshore Wind Turbines
Reliability, availability and maintenance
T Peter Tavner
a
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e
r
The Institution of Engineering and Technology
www.theiet.org
978-1-84919-229-3
Offshore Wind Turbines.indd 1 19/07/2012 16:03:09
IET RENEWABLEENERGYSERIES 13
Offshore Wind
Turbines
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Offshore Wind
Turbines
Reliability, availability and
maintenance
Peter Tavner
The Institution ofEngineeringand Technology
PublishedbyTheInstitutionofEngineeringandTechnology,London,UnitedKingdom
The Institution of Engineering and Technology is registered as a Charity in England &
Wales(no.211014)andScotland(no.SC038698).
†2012TheInstitutionofEngineeringandTechnology
Firstpublished2012
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Convention.Allrightsreserved.Apartfromanyfairdealingforthepurposesofresearch
orprivatestudy,orcriticismorreview,aspermittedundertheCopyright,Designsand
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ISBN978-1-84919-229-3(hardback)
ISBN978-1-84919-230-9(PDF)
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This book is dedicated to
Sarah and Charles.
Behold, the sea itself
And on its limitless, heaving breast, the ships;
See where their white sails, bellying in the wind,
Speckle the green and blue sea.
Walt Whitman, put to music in the Sea Symphony
by Ralph Vaughan Williams.
Contents
Preface xiv
Acknowledgements xvi
Nomenclature xvii
List of abbreviations xix
1 Overview of offshore winddevelopment 1
1.1 Development of wind power 1
1.2 Large wind farms 4
1.3 Firstoffshore developments 6
1.4 Offshore wind in Northern Europe 7
1.4.1 Overview 7
1.4.2 Baltic Sea 8
1.4.3 UKwaters 8
1.5 Offshore wind rest of the world 12
1.5.1 The United States 12
1.5.2 Asia 12
1.6 Offshore wind power terminologyand economics 12
1.6.1 Terminology 12
1.6.2 Cost of installation 15
1.6.3 Cost of energy 16
1.6.4 O&Mcosts 18
1.6.5 Effect of reliability, availability and maintenance
oncost of energy 20
1.6.6 Previous work 20
1.7 Roles 20
1.7.1 General 20
1.7.2 Regulator 20
1.7.3 Investors 20
1.7.4 Certifiers and insurers 21
1.7.5 Developers 21
1.7.6 Original equipment manufacturers 21
1.7.7 Operators and asset managers 22
1.7.8 Maintainers 22
1.8 Summary 23
1.9 References 23
viii Offshore wind turbines: reliability, availability and maintenance
2 Reliability theory relevant to offshorewindturbines 25
2.1 Introduction 25
2.2 Basic definitions 25
2.3 Random and continuous variables 26
2.4 Reliabilitytheory 28
2.4.1 Reliabilityfunctions 28
2.4.2 Reliabilityfunctions example 29
2.4.3 Reliabilityanalysisassuming constant failure rate 30
2.4.4 Point processes 32
2.4.5 Non-homogeneous Poissonprocess 33
2.4.6 Power law process 34
2.4.7 Total time on test 34
2.5 Reliabilityblock diagrams 36
2.5.1 General 36
2.5.2 Series systems 36
2.5.3 Parallel systems 37
2.6 Summary 38
2.7 References 38
3 Practical windturbine reliability 39
3.1 Introduction 39
3.2 Typical wind turbine structure showingmain assemblies 40
3.3 Reliabilitydata collection 40
3.4 Wind turbine taxonomies 41
3.5 Failure location, failure mode, root cause and
failure mechanism 41
3.6 Reliabilityfield data 42
3.7 Comparative analysis of that data 43
3.8 Current reliability knowledge 46
3.9 Current failure mode knowledge 47
3.10 Linkage between failure mode and root cause 47
3.11 Summary 49
3.12 References 50
4 Effects of windturbine configuration onreliability 51
4.1 Modern wind turbine configurations 51
4.2 WT configuration taxonomy 52
4.2.1 General 52
4.2.2 Conceptsand configurations 54
4.2.3 Sub-assemblies 55
4.2.4 Populationsand operating experience 55
4.2.5 Industrial reliability data for sub-assemblies 56
4.3 Reliabilityanalysisassuming constant failure rate 56
4.4 Analysis of turbine concepts 59
Contents ix
4.4.1 Comparison of concepts 59
4.4.2 Reliability of sub-assemblies 59
4.4.2.1 General 59
4.4.2.2 Generators 60
4.4.2.3 Gearboxes 63
4.4.2.4 Converters 63
4.5 Evaluation of current different WT configurations 68
4.6 Innovative WT configurations 70
4.7 Summary 71
4.8 References 72
5 Design andtesting for windturbine availability 75
5.1 Introduction 75
5.2 Methods to improve reliability 75
5.2.1 Reliability results and future turbines 75
5.2.2 Design 76
5.2.3 Testing 77
5.2.4 Monitoring and O&M 78
5.3 Design techniques 78
5.3.1 Wind turbine designconcepts 78
5.3.2 Wind farm design and configuration 79
5.3.3 Design review 80
5.3.4 FMEAand FMECA 82
5.3.5 Integrating design techniques 86
5.4 Testing techniques 86
5.4.1 Introduction 86
5.4.2 Accelerated life testing 87
5.4.3 Sub-assembly testing 90
5.4.4 Prototype and drive train testing 90
5.4.5 Offshore environmental testing 92
5.4.6 Production testing 93
5.4.7 Commissioning 93
5.5 Fromhighreliability to high availability 94
5.5.1 Relation of reliability to availability 94
5.5.2 Offshore environment 95
5.5.3 Detection and interpretation 95
5.5.4 Preventive and corrective maintenance 96
5.5.5 Asset management throughlife 96
5.6 Summary 96
5.7 References 97
6 Effect of reliability onoffshore availability 99
6.1 Early Europeanoffshore wind farm experience 99
6.1.1 HornsRev I wind farm, Denmark 99
6.1.2 Round 1wind farms, the United Kingdom 100
