MARE-WINT Wiesław Ostachowicz Malcolm McGugan Jens-Uwe Schröder-Hinrichs Marcin Luczak Editors New Materials and Reliability in Offshore Wind Turbine Technology MARE-WINT Wiesław Ostachowicz • Malcolm McGugan • Jens-Uwe Schr R oder-Hinrichs • Marcin Luczak Editors MARE-WINT New Materials and Reliability in Offshore Wind Turbine Technology Editors Wiesław Ostachowicz Mechanics of Intelligent Structures Polish Academy of Sciences (IFFM) Gdansk, Poland Malcolm McGugan Department of Wind Energy Technical University of Denmark Roskilde, Denmark Jens-Uwe Schr R oder-Hinrichs Maritime Risk and System Safety (MaRiSa) World Maritime University Malm R o, Sweden Marcin Luczak Institute of Fluid-Flow Machinery Polish Academy of Sciences (IFFM) Gdansk, Poland ISBN 978-3-319-39094-9 ISBN 978-3-319-39095-6 (eBook) DOI 10.1007/978-3-319-39095-6 Library of Congress Control Number: 2016950528 © The Editor(s) (if applicable) and The Author(s) 2016. This book is published open access. 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Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. Printed on acid-free paper This Springer imprint is published by Springer Nature The registered company is Springer International Publishing AG Switzerland Acknowledgements The European Commission The editors would like to start by thanking the European Commission for their Marie Skłodowska-Curie actions (MSCA). The current research and publication was primarily made possible through funding under the MSCA project FP7-PEOPLE- 20120 ITN 309395 “MARE-WINT” (new MAterials and REliablity in offshore WINd Turbines technology). About MSCA The Marie Skłodowska-Curie actions (MSCA) provide grants at all stages of researchers’ careers, from doctoral candidates to highly experienced researchers, and encourage transnational, intersectoral and interdisciplinary mobility. For research institutions (universities, research centres and companies), MSCA offer the possibility to host talented foreign researchers and create strategic partnerships with leading institutions. The idea is to equip researchers with the necessary skills for a successful career, be it in the public or the private sector. The MSCA are open to all domains of research and innovation, from basic research up to market take-up and innovation services. Research and innovation fields are chosen freely by the applicants (individuals and/or organisations) in a fully bottom-up manner. International mobility is prerequisite under all Marie Skłodowska-Curie actions. There are no restrictions in terms of research field, nationality or age. Endowing researchers with new skills and a wider range of competencies, while offering them attractive working conditions, is a crucial aspect of the MSCA. In addition to mobility between countries, the MSCA also seek to break the real and perceived barriers between academic and other sectors, especially business. v vi Acknowledgements About ITN The doctoral training is covered under the action Innovative Training Networks (ITN). This high-quality joint research and doctoral training is delivered by interna- tional networks that bring together universities, research centres and non-academic organisations (companies, NGOs, charities, etc.) across Europe and beyond. ITN can take one of three forms: • European Training Networks (ETN): Joint research training, involving a mini- mum of three partners from in and outside academia (business, museum, NGO, etc.). • European Industrial Doctorates (EID): Joint doctoral training delivered by at least one academic partner entitled to award doctoral degrees and at least one partner from outside academia, primarily enterprise. Each participating researcher is enrolled in a doctoral programme and is jointly supervised by supervisors from the academic and non-academic sector, where they spend at least 50 % of their time. The aim is to broaden the career perspective of the PhD candidate upon completion of the training. • European Joint Doctorates (EJD): A minimum of three academic organisations form a network with the aim of delivering joint, double or multiple degrees. Joint supervision of the research fellow and a joint governance structure are mandatory. The participation of additional organisations from anywhere in the world, including from the non-academic sector, is encouraged. During their ITN training, researchers will develop key transferable skills common to all fields, such as entrepreneurship, management and financing of research activities and programmes, management of intellectual property rights, ethical aspects and communication. In all cases, the recruited researchers are fully funded by the Marie Skłodowska- Curie actions, with an attractive living and mobility allowance. The host organ- isations receive a contribution to the research and training costs of the recruited researcher and apply good employment practices in line with the European Charter for Researchers and the European Code of Conduct for the Recruitment of Researchers (European Commission 2016a). The Marie Skłodowska-Curie actions support PhD candidates by financing organisations which subsequently recruit candidates to the training programmes. Therefore PhD candidates do not apply to the commission for the funding of their posts. Instead, they apply directly on the European Researchers Mobility portal EURAXESS (European Commission 2016b). Acknowledgements vii The External Contributors In addition to the research conducted under MARE-WINT and MSCA, several fellows collaborated with other researchers, funded under different schemes. On behalf of all authors, the editors would like to thank these external collaborators; individual acknowledgements are present in the various chapters. The editors would also like to thank all external contributors who were not directly involved in MARE-WINT but contributed through workshops and subse- quent special chapters for the current book. Their knowledge, expertise and time were very greatly appreciated. In particular, the editors would like to thank: • Gregor Giebel and Charlotte Bay Hasager, who provided Chap. 19 • Johan Finsteen Gjødvad and Morten Dallov Ibsen, who authored Chap. 22 • Justine Beauson and Povl Brøndsted, who presented Chap. 23 The MARE-WINT Fellows and Project Partners The editors would especially like to thank all the fellows whose hard work led to the excellent research that is present in this book; the editors also extend their gratitude to the various supervisors and colleagues, who guided the fellows and helped them achieve their aims in the relevant research fields. References European Commission (2016a) The European Charter for Researchers. http://ec.europa.eu/ euraxess/index.cfm/rights/europeanCharter. Accessed 06 Apr 2016 European Commission (2016b) EURAXESS Researchers in Motion. http://ec.europa.eu/euraxess/ index.cfm/jobs/index. Accessed 06 Apr 2016 Contents 1 Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 1 Raza Ali Mehdi, Wiesław Ostachowicz, and Marcin Luczak Part I Wind Turbine Blades 2 Design of Wind Turbine Blades . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 13 Malcolm McGugan 3 Damage Sensing in Blades . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 25 Borja Hernandez Crespo 4 Fibre Bragg Grating as a Multi-Stage Structure Health Monitoring Sensor .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 53 Gilmar Ferreira Pereira 5 Analysis and Design of Bend-Twist Coupled Wind Turbine Blades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 67 Alexander R. Stäblein 6 Improvement of Wind Turbine Blade Performance by Means of Rod Vortex Generators . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 81 Javier Martinez, Pawel Flaszynski, Piotr Doerffer, and Oskar Szulc 7 Trailing and Leading Edge Flaps for Load Alleviation and Structure Control .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 103 Vladimir Leble and George N. Barakos Part II Enabling Technologies for Drivetrain and Gearbox Analysis 8 OWT Drivetrain & Gearbox Simulation and Testing . . . . . . . . . . . . . . . . . . 117 Simone Manzato and Bert Pluymers ix x Contents 9 Dynamic Behavior of Bearings on Offshore Wind Turbine Gearboxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 123 Rubén Cerdá, Bart Blockmans, Jakob Fiszer, Tommaso Tamarozzi, Bert Pluymers, and Wim Desmet 10 Experimental Characterization of Wind Turbine Gearbox in Operation .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 147 Emilio Di Lorenzo and Simone Manzato Part III Tower & Support Structure 11 An Overview of Analysis and Design of Offshore Wind Turbines . . . . 169 Torgeir Moan and Tomasz Bugalski 12 Dynamic Response Analysis of Floating Wind Turbines with Emphasis on Vertical Axis Rotors . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 173 Zhengshun Cheng, Torgeir Moan, and Zhen Gao 13 Bottom Fixed Substructure Analysis, Model Testing and Design for Harsh Environment . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 193 Duje Veic, Marek Kraskowski, and Tomasz Bugalski 14 Detection of Damage in Metallic Structures for Offshore Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 213 Rohan Soman, Paweł Malinowski, and Wiesław Ostachowicz Part IV Reliability & Preventive Maintenance of Offshore Wind Turbines 15 Reliability and Preventive Maintenance . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 235 Itamar Esdras Martínez García, Alejandro Sánchez Sánchez, and Stefano Barbati Part V CFD Analysis of a Complete Offshore Wind Turbine 16 An Overview of the CFD Analyses in the MARE-WINT Project . . . . . 275 George N. Barakos 17 CFD Investigation of a Complete Floating Offshore Wind Turbine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 277 Vladimir Leble and George N. Barakos 18 CFD Study of DTU 10 MW RWT Aeroelasticity and Rotor-Tower Interactions .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 309 Sergio González Horcas, François Debrabandere, Benoît Tartinville, Charles Hirsch, and Grégory Coussement Contents xi Part VI Offshore Wind Farm Design 19 An Overview of Offshore Wind Farm Design . . . . . . .. . . . . . . . . . . . . . . . . . . . 337 Gregor Giebel and Charlotte Bay Hasager 20 Large Eddy Simulation of Wind Farm Aerodynamics with Energy-Conserving Schemes . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 347 Dhruv Mehta 21 A Theoretical Risk Management Framework for Vessels Operating Near Offshore Wind Farms . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 359 Raza Ali Mehdi and Jens-Uwe Schröder-Hinrichs Part VII Offshore Wind Decommissioning 22 ODIN-WIND: An Overview of the Decommissioning Process for Offshore Wind Turbines . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 403 Johan Finsteen Gjødvad and Morten Dallov Ibsen 23 Wind Turbine Blades: An End of Life Perspective .. . . . . . . . . . . . . . . . . . . . 421 Justine Beauson and Povl Brøndsted Chapter 1 Introduction Raza Ali Mehdi, Wiesław Ostachowicz, and Marcin Luczak Abstract The current chapter provides an overview of the offshore wind industry, followed by an introduction to the MARE-WINT project. We discuss the important role that MARE-WINT has fulfilled in reducing the cost of offshore wind energy, by improving the reliability, and operation and maintenance strategies of various wind turbine components. Lastly, we present an overview of the current book for the readers. 1.1 The Emergent Offshore Wind Industry Wind is one of the most plentiful and widely available natural resources available on our planet. For centuries, mankind has harvested the power of the wind for applications such as maritime and agriculture. Most of the world was explored on the back of wind-powered ships, and it was truly wind that made globalisation and exploration possible. With society becoming increasingly mindful of the impacts of fossil fuels, renewable energy is on the rise, and the harvesting of wind to generate electricity is becoming increasingly common. To enable this to happen, wind turbines have been installed all over the globe. A vast majority of these wind turbines have been installed on land and are referred to as onshore wind turbines. Statistics by the Global Wind Energy Council (GWEC) indicate that only around 3 % of global electricity is currently generated by wind power—but this number is on the rise. R.A. Mehdi ( ) Maritime Risk and System Safety (MaRiSa) Research Group, World Maritime University, Fiskehamnsgatan 1, 21118 Malmö, Sweden e-mail: rm@wmu.se W. Ostachowicz Mechanics of Intelligent Structures Department, Institute of Fluid Flow Machinery, Polish Academy of Sciences, ul. Fiszera 14, 80-231 Gda ́ nsk, Poland e-mail: wieslaw@imp.gda.pl M. Luczak Aerodynamics Department, Institute of Fluid Flow Machinery, Polish Academy of Sciences (IFFM), ul. Fiszera 14, 80-231 Gda ́ nsk, Poland e-mail: marcin.luczak@imp.gda.pl © The Author(s) 2016 W. Ostachowicz et al. (eds.), MARE-WINT , DOI 10.1007/978-3-319-39095-6_1 1 2 R.A. Mehdi et al. The International Energy Agency (IEA) expects that by the year 2035, 25 % of the electricity generation will be fulfilled by renewable sources, and that wind energy will have a major role to play. 1.1.1 The Benefits of Wind Energy The popularity of wind energy arises from the simple fact that it is, by and large, cost effective, environmentally friendly and socially popular amongst a majority of the populace. A common method of assessing the cost-effectiveness of an energy source is through a parameter called Levelized Cost of Energy (LCOE), which is essentially a ratio between two parameters: the total lifetime costs and the total electricity produced over the lifetime . Siemens (2014) calculated the LCOE of various electricity generation sources to be as follows: As Table 1.1 shows, the LCOE of onshore wind is reasonably close to the LCOE of commonly used fossil fuels. However, the LCOE alone does not often provide the complete picture. A more comprehensive measure, as provided by Siemens (2014) is the so-called Society’s Cost of Energy (SCOE). The SCOE takes into consideration further factors such as number of jobs created by energy source, subsidies, transmission costs, variability costs, geopolitical risk impact, and environmental impact. The predicted SCOE in the year 2025 for various electricity generation sources is shown in Table 1.2. As shown in Table 1.2, it is expected that onshore and offshore wind will be the two most viable sources of energy in the near future. In fact, this phenomenon is already manifesting—statistics indicate the benefits from wind energy to be Table 1.1 LCOE in 2013 for various electricity generation sources Source of electricity generation LCOE ( A C/MWh) Nuclear 79 Coal 63 Gas 60 Photovoltaics 145 Onshore wind 81 Offshore wind 140 Source: Siemens (2014) Table 1.2 SCOE in 2025 for various electricity generation sources Source of electricity generation SCOE ( A C/MWh) Nuclear 107 Coal 110 Gas 89 Photovoltaics 78 Onshore wind 60 Offshore wind 61 Source: Siemens (2014) 1 Introduction 3 significant. As an example of the social benefits of wind energy, GWEC estimates that more than 600,000 people are employed by the wind industry—a number that is likely to rise to more than 2,000,000 by 2030. In terms of a positive environmental impact, wind energy helped to avoid more than 608 million tonnes of carbon dioxide emissions in 2014 alone. GWEC also estimate that wind farms generate between 17 and 39 times more power than they consume—compared to 16 times for nuclear and 11 times for coal plants (GWEC 2016). 1.1.2 The Challenges of Going Offshore The continued increase in wind energy is not without its challenges. Offshore wind, in particular, still has some way to go before it can meet the LCOE and SCOE cost expectations. This raises the question—why go offshore at all? The growth of offshore wind is primarily due to better, more consistent wind resource available on open seas. Combined with limited land space, and the fact that onshore turbines may be less socially acceptable, this makes offshore wind very appealing. On the other hand, going offshore presents novel challenges—currently, there are limitations in deep-water installation technology, and the harsher environment is not ideal for the reliability, maintainability and availability of offshore wind turbines. Furthermore, offshore wind farms (OWFs) need to be situated in locations where simultaneously, the wind resource and the transmission-to-shore options are optimum. Often times, these locations may be in conflict with national, regional or international marine spatial plans, and other sectors such as fisheries and shipping may take precedence in these areas. There is, thus, a clear need to improve the viability and feasibility of OWFs, and to make offshore turbines closely competitive to their onshore counterparts—and indeed other sources of energy. To fulfil this gap, organizations like the European Commission have encouraged and funded research projects such as MARE-WINT. 1.2 An Introduction to the MARE-WINT Project The aim of the MARE-WINT (new MAterials & REliability in offshore WInd Turbine Technology) project was to reduce cost of energy, and increase the energy output, by improving reliability of wind turbines and their components and optimizing operation and maintenance (O&M) strategies. Thus, the project contributed towards making wind energy more competitive. The outcomes of the project are particularly evident and relevant for the offshore sector, where O&M represents a high percentage of total costs. An offshore wind turbine (OWT) is a complex energy conversion fluid flow machine with coupled hydro-aero-mechanical issues. To design, build, and operate 4 R.A. Mehdi et al. a reliable OWT, knowledge from disciplines like mechanical engineering, material science, metrology, fluid mechanics, condition monitoring, and computer simulation needs to be combined. The MARE-WINT network bought together specific part- ners’ capabilities and know-how to realize tailored training trajectories, focusing on an increased reliability OWT design. MARE-WINT achieved the overall aim by providing training in the context of doctoral programmes for 15 researchers, in multi-disciplinary areas related to future generations of Offshore Wind Turbines (OWT). An emphasis was placed on issues that may have a major impact on the mechanical loading of OWT and which were not sufficiently addressed at the initiation of the project. One of the strengths of MARE-WINT has been the validation of various numerical, analytical and empirical models through experimental data. This has allowed novel concepts such as floating 10 MW wind turbines to be thoroughly investigated, to better prepare the industry for the challenges of tomorrow. 1.3 An Overview of the Current Research To get a better insight of the outstanding work done by the fellows in the MARE- WINT project—as presented in this book—it is firstly important to understand the components, design process and operation of a typical wind turbine. 1.3.1 The Components of a Wind Turbine Wind turbines are aero-mechanical devices that convert the rotational movement of a rotor into electrical energy. In order for wind turbines to function, there needs to be wind flowing past them. Wind on Earth is created as a result of the uneven heating of our atmosphere, the irregularities of the Earth’s surface, and the actual rotation of our plant. As wind flows past a turbine, it generates a lifting force on the blades of a wind turbine—which are connected to a rotor. The lifting force on the blades creates a rotational movement on the rotor. This rotational movement is transferred, via a shaft and gearbox, to a generator where it is converted into electrical energy. The components of a turbine are shown in Fig. 1.1. 1.3.2 Designing a Wind Turbine Within the MARE-WINT project, several researchers worked in the context of the 10 MW reference turbine developed by the Technical University of Denmark (DTU), and described by Bak et al. (2013); the parameters are shown in Table 1.3. 1 Introduction 5 Fig. 1.1 Wind turbine components. Source : wind.energy.gov; copyright: public domain Table 1.3 Properties of the 10 MW DTU reference wind turbine Parameter Value Rating 10 MW Rotor orientation, configuration Upwind, three blades Control Variable speed, collective pitch Drivetrain Medium speed, multiple stage gearbox Rotor, hub diameter 178.3 m, 5.6 m Cut-in, rated, cut-out wind speed 4 m/s, 11.4 m/s, 25 m/s Cut-in, rated rotor speed 6 RPM, 9.6 RPM Rated tip speed 90 m/s Overhang, shaft tilt, pre-cone 7.07 m, 5 ı , 2.5 ı Pre-bend 3 m Rotor mass 229 tons (each blade 41 tons) Nacelle mass 446 tons Tower mass 605 tons Source: Bak et al. (2013) To design and develop this 10 MW reference turbine, the Bak et al. (2013) applied the method shown in Fig. 1.2. Figure 1.2 has a heavy emphasis on aerodynamics and structural mechanic and is, in fact, only a simplified version of a much more sophisticated process. Typically, as shown in Fig. 1.2, the starting point for a wind turbine concept is the design of the blades. The size (primarily, the length) of the blades directly determines the capacity 6 R.A. Mehdi et al. Fig. 1.2 Method for developing the 10 MW reference wind turbine. Adapted from Bak et al. (2013) of the turbine. As a rule of thumb, the larger the diameter, the greater the power output of the turbine. Of course, principals of aerodynamics govern the efficiency of the wind turbine. On a very basic level, the Betz law means that theoretically only around 59.3 % (16/27) of the kinetic energy from wind can actually be captured— no matter how large the rotor size is; furthermore, being a mechanical device, there are further inefficiencies in the system, which means that only around 75–80 % of the 59.3 % theoretical cap is actually achieved. In order to make wind turbines more reliable and efficient, these inefficiencies need to be minimized as much as possible. Therefore, the design of blades is crucial. Blades must be aerodynamically efficient, whilst at the same time being structurally sound enough to bear all the mechanical and aerodynamic loads. Balancing the aerodynamic and structural parameters is becoming increasingly challenging as wind turbines get larger and more sophisticated. The blades are connected to a rotor, which in turn is connected to a shaft, which goes through a gearbox into the generator. The shaft and gearbox must be able to 1 Introduction 7 tolerate the mechanical loads in an often harsh environment, and be able to transmit the rotational movement as efficiently as possible. If the drivetrain and gearbox are unable to handle the loads from the blade and rotor, the blades design may have to be changed; alternatively, the gearbox and drivetrain would be updated. The research in this area, too, is critical as offshore turbines get more complex. The blade and the nacelle (housing the gearbox and generator, amongst other components) assembly must be supported on an adequate tower structure, which in turn needs to be mounted or tethered on the sea-bed through an appropriate sub- structure. Depending on the design requirements and factors such as the turbine location, optimizing the tower and sub-structure can be a substantial task. The tower and sub-structure must not only cope with aerodynamic and mechanical loading (particularly from the blades, rotor and nacelle), but also bear its own load and various hydrodynamic loads. As with the research conducted for the blades and the gearbox, optimizing the tower and support structure for larger, more complex turbines is a unique challenge. Once all the components are in place and assembled, the overall reliability of the turbine and all its sub-systems must be assessed. Furthermore, maintenance strategies must be optimized in order to reduce the costs associated with offshore wind. If it is unfeasible to maintain a wind farm in a cost effective manner, the design or maintenance strategy may have to be adapted. To ensure that a turbine is reliable and efficient, it is also important to analyse the complete system. This is generally done using combined fluid and structural analysis methods, to ensure that the components complement each other, and are able to tolerate design loads without failures occurring. A wind turbine on its own is often not the end goal—it needs to be integrated into a wind farm. In order to do so, one must analyse the aerodynamic effects of wake turbulence from each individual turbine over the entire proposed wind farm area. This helps to determine the efficiency of various turbines in different layouts. The layout of a wind farm is not only driven by aerodynamic factors; factors such as seabed conditions, grid connection locations, hydrography and bathymetry must also be taken into account. Furthermore, wind resource in an area must be considered. Equally important is the consideration of potential ‘conflict’ or ‘overlap’ areas—which may be reserved for marine, environmental, or other purposes. The layout of any wind farm can also have an impact on the navigational safety of passing vessels; in turn, vessel accidents in the area may damage wind turbines, or cause a wind farm shutdown, leading to reduced reliability. Wind turbine towers may have to be designed to be ‘collision-friendly’ to ships (BSH 2015). A potential conflict with other marine and maritime activities may cause a wind farm application to be denied, or at the very least, the layout may have to be changed. Wind turbines are designed to last around 25 years. Once their lifetime has been fulfilled, the turbines need to be decommissioned. This is a fairly novel research area, as most offshore turbines are just now entering their end-of-life cycle. Despite this, the decommissioning is an important phase to consider when assessing LCOE, as it can have a significant impact on the parameter. It may even be the case that a wind farm is approved or denied permission based on its decommissioning plan. 8 R.A. Mehdi et al. 1.3.3 MARE-WINT’s Contribution to the Offshore Wind Industry In the MARE-WINT project, the focus was not solely on the design of a wind tur- bine; rather, the fellows also focused on developing tools to analyse and improve the reliability and efficiency of various wind turbine components. The best way to high- light the contributions of the MARE-WINT project is by summarizing the content of the present book, which more or less covers the topic areas identified in Sect. 1.3.2: • Part I of this book focuses on blade design, and tools to improve analysis and reliability of wind turbine blades. This research ranges from damage sensing to the analysis of bend-twist coupling of blades—and even a study into rod-vortex generators to minimize aerodynamic noise on the blade. Part I also describes the ‘Smart-Blade’ strategy used in the current work. • Part II focuses on analysing and improving the reliability of these components. The research described in this part of the book can allow turbine engineers to assess the adequacy of the drivetrain and gearbox sub-systems. • Part III presents tools that can be used to study, analyse and improve the reliability and design of the tower and substructure. Researchers performed a thorough fluid–structure interaction analysis of different wind turbine concepts— floating, horizontal axis, and vertical axis, and determined the feasibility and viability of each, compared to the others. Researchers also conducted numerical and experimental studies focusing on hydrodynamic loads on various sub- structures and towers. Lastly, a tool for structural health monitoring, to provide an improved method of assessing turbine tower damage is also presented. • Part IV discusses tools, methods strategies which can be used to analyse and improve reliability and preventive maintenance of offshore wind turbines. • Part V of the current book presents novel research in this area of complete offshore wind turbine analysis. It describes relevant tools and models to assess the fluid–structure interactions in a complex system like an offshore turbine. • Part VI covers the crucial area of wind farm design. Topics including aerody- namic simulations over wind farms, maritime risk assessment are covered. The EERA-DTOC tool for designing wind farm clusters is also presented. • Part VII of this book covers original decommissioning tools and strategies, both from an industry and research perspective. Several topics are not explicitly covered in this book, as they have been sufficiently addressed in other published works. The spatial planning and approval of wind farms, for instance, has been the focus of the SEANERGY project (EWEA et al. 2012). Similarly, the environmental impacts of wind farms have been covered by Koeller et al. (2006). The installation process of OWFs is also not explicitly covered in this current work, although it is briefly discussed in Chap. 22, in the context of the decommissioning phase of offshore turbines. Aside from these aforementioned areas, the book comprehensively covers all topics from design to decommissioning of OWFs.