Offshore Wind Power

Edited by John Twidell and Gaetano Gaudiosi
Publication date: April 2009 • ISBN 978-0906522-639 • xii + 358pp • £89


This is the most authoritative single volume on offshore wind power yet published. Distinguished experts, mainly from Europe’s leading universities, have contributed a collection of peer reviewed papers on the interfaces between wind power technology and marine engineering. The range of issues covered by the book include: wind as a resource; wind power generation; connection to the grid; the marine environment and engineering issues particular to it.

This book is essential for academic departments of mechanical engineering/energy engineering/ renewable energy. Offshore wind power generation will be the driver of the offshore industry for the foreseeable future: all organisations involved in offshore engineering should have this book.



John Twidell and Gaetano Gaudiosi

Ch 1 Offshore wind power: A review of progress
Poul Erik Morthorst, Jørgen Lemming and Niels-Erik Clausen
1. Introduction 2. Development and investment costs of offshore wind power 3. The cost of energy generated by offshore wind power 4. Offshore Windfarms under Construction and in planning stage
5. Future technological development 6. Scenarios for the future offshore development of wind power 7. Long-term cost perspectives for offshore turbines 8. New offshore concepts 9. Conclusions

Ch 2 Basics of wind turbines
John Twidell
1. Introduction 2. Wind power growth 3. How wind turbines function 4. Offshore or on land? 5. Environmental impact

Ch 3 Wind & waves in the Mediterranean Sea
Luigi Cavaleri and Corrado Ratto
1. The meteo-oceanographic characteristics of the Mediterranean Sea 2. The sources of wind and wave data in the Mediterranean Sea 3. Combining the different data into a consistent data set 4. Results

Ch 4 Climatology
Rebecca Barthelmie, S.C. Pryor and S.T. Frandsen
1. Introduction 2. Resource estimation 3. From resource to wind energy: impacts of wakes 4. Windfarm power output at short time scales: is offshore different? 5. Summary 6. Acknowledgements 7. References

Ch 5 Electrical aspects of wind turbines
Zhe Chen and Frede Blaabjerg
I. Introduction 2. Turbine power control 3. Generators for wind turbines 4. Modern power electronics and converter systems 5. Electrical power conversion systems of wind turbines 6. Control of wind turbines 7. Network topologies of windfarms 8. Integration of wind turbines into power systems 9. Improvement of wind turbine performance in power systems 10. Conclusion

Ch 6 Windfarm power connection
Thomas Ackermann
1. Introduction 2. The offshore collector system 3. Offshore substations 4. Transmission to shore 5. Reliability assessment 6. Economic evaluation of the transmission system 7. Conclusions

Ch 7 Grid Integration
Carlo Degli Esposti
1. Introduction 2. Regulation of renewable energy 3. Support schemes for electricity production 4. Integrating rese into the electricity market 5. System costs 6. Technical integration of renewables

Ch 8 Turbine dynamics and fatigue
Jan Van der Temple
1. Introduction 2. General terminology 3. Stochastic random processes 4. Waves and currents 5. Wind 6. The turbine 7. Dynamics of offshore wind turbines 8. Basic fatigue considerations
9. Foundations

Ch 9 Offshore floating turbines
Andrew Henderson
1. Introduction 2. History 3. Benefits of deepwater windfarms 4. Design drivers for concept design 5. Candidate concepts 6. Conclusion and final challenges

Ch 10 Access to windfarms
Goran Dalen and Mikael Jakobdsson
1. Introduction 2. Requirements for good access 3. Components of an access system 4. Experience and systems analysis 5. Further technology 6. Conclusion

Ch 11 Standards and Certification
Axel Andreä, Kimon Argyriadis, Peter Dalhoff, Christian Nath and Silke Schwartz
1. Introduction 2. Standards 3. Certification of wind turbines and windfarms 4. Risk evaluation 5. Summary and conclusions 6. References

Ch 12 Foundation design in deep waters
Franco Cesari
1. Introduction 2. Structural Solutions 3. Substructure design 4. Construction and transportation 5. Installation and dismantling 6. Weight and cost evaluation 7. Concluding remarks 8. References

Ch 13 Turbine materials
Lorenzo Battisti and Alessandra Brighenti
1. Introduction 2. Rotor component materials 3. Nacelle component materials 4. Supporting structure materials 5. Cold climate issues 6. Offshore wind turbines materials selection process 7. Conclusions


authors’ and editors’ biographies

John Twidell works independently as an academic consultant and writer in renewable energy and sustainability, and as Director of the AMSET Centre Ltd. He previously held the Chair in Renewable Energy at De Montfort University and was Director of the Energy Studies Unit of Strathclyde University. He has also held appointments at Universities in Africa and the South Pacific. He has served on the Boards of the British Wind Energy Association and the UK Solar Energy Society, on committees of the Institute of Physics and as an adviser to the UK Parliamentary Select Committee on Energy. Practical experience in wind power has included management of a 3 MW (60 m) wind turbine and other smaller wind turbines on Orkney, northern Scotland. He is a Board member of Westmill Windfarm Co-operative. Presently, he is Editor Emeritus of the academic journal ‘Wind Engineering’, having been General Editor from 1998 to 2007. He is a visiting lecturer at the Environmental Change Institute, University of Oxford (MSc in Environmental Change, Energy Module), and the School of Aeronautics and Engineering, City University, London (MSc in Energy, Environment, Economics and Technology). His co-authored textbook with A.D. Weir, ‘Renewable Energy Resources’ (second edition 2006, published by Taylor Francis) sells worldwide, mainly on postgraduate courses. He has written ~ 100 published papers on renewable and sustainable energy, and chapters in 9 other books.

Gaetano Gaudiosi graduated in Naval Engineering at Naples University in 1959, and now works independently as a consultant on offshore and onshore wind energy and other marine renewable energies. From its foundation in 2006, he has been president of the not-for-profit association OWEMES, emphasising the Mediterranean and Southern European seas. He is a Board member of ATENA (Associazione di Tecnica Navale) Rome Section and ANIV (Association Nazionale Ingegneria del Vento, 2001-2007). Previously he was an officer in the wind energy programs of ENEA (Project Manager 1980-1987 for MEDIT 300 KW and GAMMA 1.5 MW wind turbine; senior consultant and E.C. Italian project leader 1990-2001), Italian Member in the IEA Wind R& D Implement Agreement 1984-1990) and European Commission Expert for the evaluation of wind and ocean energy project proposals. From 1961 to 1980, he worked in nuclear energy, with experience in testing thermal critical phenomena in the reactor core (BWR and PWR) in Italy, USA and Sweden. From 1984, he has chaired the triennial European Seminar OWEMES in Italy (Rome 1994; La Maddalena 1997; Siracusa 2000; Napoli 2003; Civitavecchia 2006). He is author of papers on nuclear energy and wind energy, with particular attention to the offshore wind power applications presented in international conferences since 1992. He co-edited a special issue of the journal ‘Wind Engineering’, reviewing offshore wind energy. Teaching activity in Wind Energy has been carried out for many years in Italy and other countries, recently including the e-learning ENEA-UNESCO course on offshore wind energy.

Chapter 1. Poul Erik Morthorst, Jørgen Lemming and Niels-Erik Clausen,
Poul Erik Morthorst is a Professor at Risø National Laboratory for Sustainable Energy, the Technical University of Denmark. He has worked in the Department for Systems Analyses at Risø for more than 30 years. His main activities cover the assessment of the economics of renewable energy technologies; especially wind power, evaluation of policy instruments for regulating energy and environment and development of long-term scenarios for energy, technology and environmental systems. He has participated in a large number of projects within these fields and has extensive experience in international collaboration. He has taken part in several national and international committees. He is member of the board of the Danish TSO,, and appointed to the Danish Research Councils on Sustainable Energy and Environment and on Transport. Recently he was appointed member of the Danish Commission on Climate Change set up by the Danish Government. The main task of this commission is to analyse national and international proposals of how to reduce significantly emissions of greenhouse gases.
Jørgen Lemming is Chief Consultant at Risø National Laboratory for Sustainable Energy, the Technical University of Denmark. Dr Lemming joined the Department for Wind Energy at Risø in 2005, after many years in the Danish Energy Authority as an expert on wind power. He has extensive experience in national and international collaboration within the wind energy field and is much involved in the IEA annexes on wind energy.
Niels-Erik Clausen is Senior Adviser at Risø National Laboratory for Sustainable Energy, the Technical University of Denmark. Dr. Clausen joined Risø DTU in 2000, where he has worked with research as well as consultancy for private and institutional clients within application of wind energy. Research areas include Climate Change and renewable energy potential; design of wind turbines in areas with tropical cyclones; development of wind energy projects; environmental impact assessment of wind power projects. Presently he is responsible for a course on planning and development of windfarms at DTU’s MSc degree programme in wind energy.

Chapter 2. John Twidell
see above.

Chapter 3 Luigi Cavaleri
Luigi Cavaleri received his Degree of Mechanical Engineer from the University of Padua, Italy, in 1965 and his Master of Aeronautics from the California Institute of Technology, Cal, USA, in 1969. Since then he worked for the Institute of Marine Science, CNR, In Venice Italy, firstly in 1969 as a researcher, then in 1992 as Director of Research, and finally in 2006 Director. Presently retired, but continuing as a Senior Scientist at the same institute. His main professional interest have always been wind waves, with connected activities in wind modelling and air-sea interaction processes. Author of almost 100 refereed papers and 3 books.

Chapter 4 Rebecca Barthelmie
Rebecca Barthelmie holds the Ewart Farvis Chair of Energy System at the University of Edinburgh and Professor of Atmospheric Science and Sustainability at Indiana University. Prior to this, she worked as a consultant and researcher in offshore wind energy at Risø National Laboratory, Denmark. She is a workpackage leader in two European Union funded projects; ’Flow’ in UPwind and ’Wakes’ in POWWOW. She is author/co-author of more than 80 international journal articles and more than 200 conference papers. She is an elected member of the European Union Technology Platform on Wind Energy and an editor of the journal Wind Energy.

Chapter 5 Zhe Chen and Frede Blaabjerg
Zhe Chen received the B.Eng. and M.Sc. degrees from Northeast China Institute of Electric Power Engineering, Jilin City, China, and the Ph.D. degree from University of Durham, U.K. He was a Lecturer and then a Senior Lecturer with De Montfort University, U.K. In 2002, he became a Research Professor and is now a Professor with the Institute of Energy Technology, Aalborg University, Denmark, where he is the coordinator of the Wind Power System Research program. His background areas are power systems, power electronics and electric machines; and his main current research areas are wind energy and modern power systems. He has more than 170 publications in his technical field. He is an Associate Editor (Renewable Energy) of the IEEE Transactions on Power Electronics, a Member of the Institution of Engineering and Technology (London, U.K.), and a Chartered Engineer in the U.K
Frede Blaabjerg received the M.Sc.EE. from Aalborg University, Denmark in 1987, and the PhD. degree from the Institute of Energy Technology, Aalborg University, in 1995. He was employed at ABB-Scandia, Randers, from 1987-1988. During 1988-1992 he was a PhD. student at Aalborg University. There he became an Assistant Professor in 1992, in 1996 Associate Professor and in 1998 Full Professor in power electronics and drives. He research expertise is especially in power electronics, static power converters, ac drives, switched reluctance drives, modelling, characterization of power semiconductor devices and simulation, wind turbines and green power inverter. He is the author or co-author of more than 300 publications in his research fields, including the book ‘Control in Power Electronics’ (series editors. M.P. Kazmierkowski, R. Krishnan, F. Blaabjerg) 2002, Academic Press.

Chapter 6 Thomas Ackermann.
Thomas Ackermann has the degree of a Diplom Wirtschaftsingenieur (M.Sc. in Mechanical Engineering combined with an MBA) from the Technical University Berlin/ Germany, an M.Sc. in Physics from Dunedin University/ New Zealand and a Ph.D. from the Royal University of Technology in Stockholm/ Sweden. He is the editor of the book “Wind Power in Power Systems”. In addition to wind power, his main interests are related to the concept of distributed power generation and the impact of market regulations on the development of distributed generation in deregulated markets. He has worked in the wind energy industry in Germany, Sweden, China, USA, New Zealand, Australia and India. He is CEO of ‘energynautics’, a research and consulting company in the area of sustainable energy supply and lecturer at the Royal University of Technology (KTH) in Stockholm, Sweden.

Chapter 7 Carlo Degli Esposti
Carlo Degli Esposti received the M.S. degree in electrical engineering in 1999 from the University of Bologna. He is presently a Project Manager and Technical & Economical Adviser for ETSO, the European Transmission Systems Organisation.

Chapter 8, Jan van der Tempel
Jan van der Tempel received his MSc in Civil Engineering, section Offshore, in 2000 at the Delft University of Technology. Worked at Royal Boskalis Westminster after graduating, focusing on installation methods for Horns Rev and sub-sea cable installation and protection. Went back to DUT for a PhD on design of support structures for offshore wind turbines, defining a frequency domain fatigue calculation method (April 2006). He designed the Ampelmann, a system for safe access to offshore structures, even in high wave conditions. Currently working as project manager and assistant professor at the DUT teaching offshore wind energy courses and CEO of the spin-out Ampelmann Company.

Chapter 9 Andrew Henderson
Andrew Henderson is an Offshore Wind Engineer at Garrad Hassan, responsible for Offshore Wind Technical Due Diligence. Previously Andrew worked for Spanish offshore wind farm developers, leading technical development in shallow and deep waters. He held the position of Assistant Professor in Offshore Wind Energy at the Technical University of Delft, where he was involved in major European and Dutch research projects including “Design Methods for Offshore Wind Turbines at Exposed Sites” and the “CA-Offshore Wind Energy” information dissemination project. As a Research Fellow at the University College of London, he undertook the research project on “The Development of Research Tools for Offshore Wind Farms Implementation” including detailed modelling of the performance of offshore wind turbines and the floating support structures.

Chapter 10, Göran Dalén
Göran Dalén received his M.Sc degree in Naval Architecture and Marine Engineering at Chalmers University of Technology in Gothenburg, Sweden in 1978. He has worked with Wind Energy for many years for the manufacturing industry as well as for developers and utilities such as Vattenfall and E.ON. He has also been involved in various EU projects including the coordination of the R&D part of the Downvind project. He has also been the Swedish head delegate in IEC TC 88 and representative in different steering committees for the Swedish Energy Board as well as for different working groups within the European commission such as the Technology Platform for Offshore Wind Energy. He is currently working for wpd Scandinavia as a project manager developing offshore projects in Germany and other European countries.

Chapter 11 Christian Nath, Axel Andraea, Kimon Argyriadis, Peter Dalhoff, Silke Schwartz,
Christian Nath received his degree as a Diplom-Ingenieur for Naval Architecture from the Technical University of Hannover in Germany in 1976. Upon his graduation, he received a research fellowship for a year at the University of California in Berkeley, where he worked as a Visiting Scholar in nonlinear Finite Element Analysis. After his return, he worked for Germanischer Lloyd in the structural analysis group. The time at GL was interrupted by a two-year research project with employment at the University of Hamburg. In the early eighties, he worked in the approval of wind energy as a structural engineer. From 1989-1992 he was project manager of a project of the Federal Research Ministry to install a test site for wind turbines in China. Since 1993 he was been responsible for wind energy at Germanischer Lloyd. He is now Global Head of Practice for Certification and Inspection within the Renewables Segment. Also from 1993, he has been chair of the German Wind Turbine Standardisation Committee and was member in several Working Groups of the IEC. He has contributed to several national and international research projects and is currently a member of the Executive Committee of the European Technology Platform TP Wind. His first offshore wind involvement was in the “Study on Offshore Wind Energy in the EG” carried out by Germanischer Lloyd and Garrad Hassan.
Axel Andreä received his degree as a Dipl.-Ing. from the University of Applied Sciences in Hamburg in 1989. He worked in the field of measurements at Windtest-Kaiser-Wilhelm-Koog GmbH for two years. After that he was engaged at aerodyn Energiesysteme GmbH and worked in load analysis, component and tower design. In 1995, he joined Germanischer Lloyd’s Wind Energy Department where he stayed until 2008. The time at GL was interrupted by a one-year-leave for REpower Systems AG. At GL he held the position of the Head of the Department for Load Assumptions. He left GL in 2008 to work for support projects in developing countries in Southern America.
Kimon Argyriadis has a Naval Architect Degree (Dipl. Ing.) from Hamburg University. After a period in marine engineering consultancy, he joined Germanischer Lloyd (GL) in 1994. His field of activities covers load analysis for onshore and offshore wind turbines, and he is responsible for ocean-energy device certification. He is Expert-in-Charge for load assumptions and is involved in software and guideline development. He participates in national and international standardisation and is member of IEC Technical Committee 114 “marine energy”, and Working Group 3, developing offshore wind turbine standard IEC61400-3. He has contributed to several national and international research projects and is currently a member of the European Technology Platform TP Wind.and the International Ship and Offshore Structures Congress (ISSC) specialist committee “Ocean wave and wind energy utilisation”.
Peter Dalhoff is Head of the Projects Department, Business Segment Wind Energy, at Germanischer Lloyd. His involvement in wind energy began as a mechanical engineer in 1996 with GL. He performed design reviews and on-site inspections on wind turbines focusing on machinery and drive trains. As a project manager Peter Dalhoff was responsible for certification projects of different turbine manufacturers and wind farm developers. Since 2000, he has been engaged in Offshore Wind Energy and has led several offshore wind related projects, including project certifications, development and maintenance of offshore wind standards and participation in international research projects. He has been a team member in a number of technical due diligence processes as a technical advisor on behalf of banks and investors. He has organised wind related seminars and is a funding member of the Hamburg Offshore Wind conference (HOW), being responsible for its organisation.
Silke Schwartz has a degree in Naval Architecture from the technical University in Hamburg. Her engineering experience with Germanischer Lloyd had earned her a position as Expert-in-Charge for load assumptions for onshore and offshore wind turbines from January 2001, and Deputy Head of the load assumption department from 2004. She has worked with developing guidelines for load assumptions, research of ocean energy concepts and supervision of final thesis and performance of research concerning offshore loads. Since 2006, she has worked in Australia for Hydro Tasmania Consulting, a leading consultancy in the renewable energy sector.

Chapter 13 Lorenzo Battisti.
Lorenzo Battisti is currently Fluid-Machinery Associate Professor by the Mechanical and Structural Engineering Department, University of Trento, Italy and Head of the Turbomachinery Laboratory. He graduated in Mechanical Engineering in 1988 and post-graduated- at the von Karman Institute of Bruxelles- Belgium following the 40th (AGARD-NATO) Postgraduate Diploma – option Turbomachnery. The scientific activity is focussed on heat transfer in gas turbine and wind energy conversion, where a wide experimental and numerical activity on high temperature heat-transfer mechanism in gas turbine components and anti-icing de-icing systems for wind turbines has been carried out. He was member of the Technical Option Committee – Refrigeration, AC and Heat Pumps of United Nations Environmental Programme (UNEP) and co author of the 1998 Protocol, and member 2005-2007 of the IEA – XIX ANNEX “Wind Energy in Cold Climate”. Former member of the ETN (European Turbine Network). Lorenzo Battisti is author of many papers and international patents on gas turbine cooling and anti-icing systems. (The kind assistance of Alessandra Brighenti is acknowledged in the final preparation of the text).


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authors’ and editors’ biographies