Research Topics in Wind Energy – serie

This book presents numerical and experimental research in the field of wind energy exploitation in urban environments. It comprises a selection of the best papers from the international colloquium “Research and Innovation on Wind Energy Exploitation in Urban Environment” (TUrbWind), held in Riva del Garda, Italy in September 2018. The book includes contributions from different research fields in urban wind resources, wind energy conversion systems, and urban integration, mainly focusing on the following topics:·         turbine concepts for urban and sub-urban environment;·         measuring and modelling wind resource;·         rotor aerodynamics, wakes and noise;·         design, loads, and supporting structures;·         novel shapes and materials;·         building concepts for wind energy exploitation;·         planning approaches for wind exploitation in urban areas.It is a valuable resource for researchers and practitioners interested in the integration of wind energy systems and turbines in urban areas.

This book presents numerical and experimental research in the field of wind energy exploitation in urban environments. It comprises a selection of the best papers from the international colloquium “Research and Innovation on Wind Energy Exploitation in Urban Environment” (TUrbWind), held in Riva del Garda, Italy in September 2018. The book includes contributions from different research fields in urban wind resources, wind energy conversion systems, and urban integration, mainly focusing on the following topics:·         turbine concepts for urban and sub-urban environment;·         measuring and modelling wind resource;·         rotor aerodynamics, wakes and noise;·         design, loads, and supporting structures;·         novel shapes and materials;·         building concepts for wind energy exploitation;·         planning approaches for wind exploitation in urban areas.It is a valuable resource for researchers and practitioners interested in the integration of wind energy systems and turbines in urban areas.

This textbook provides a thorough exploration of wind effects on the built environment, serving as a valuable reference for students, researchers, and practicing engineers. Wind has always influenced the design and performance of structures, from early construction methods to today’s most advanced engineering achievements. In modern practice, the demand for taller buildings, longer-span bridges, and more resilient infrastructure has heightened the need for a deep understanding of wind–structure interaction.The book begins by introducing the fundamental principles that govern wind characteristics and wind-induced loads. It then progresses to specialized topics such as wind climate analysis, aerodynamics, and wind tunnel testing. Special attention is given to how structures—including bridges, towers, and vehicles—respond to wind, emphasizing the impact on their safety, serviceability, and overall performance. A distinctive feature of this textbook is its integration of theoretical foundations with real-world applications. Drawing on current research and case studies, it provides readers with the tools to approach practical design problems while maintaining a solid grasp of fundamental concepts. The work also presents recent advances in wind tunnel methodologies and numerical modelling of fluid–structure interaction, providing insights into ongoing developments in the field. Ultimately, this book empowers readers with both knowledge and a critical perspective, fostering a deeper understanding of wind engineering and its essential role in the sustainable and resilient development of the built environment.

This book presents recent advances in the physical, conceptual, and methodological foundations required for the reliable design, analysis, and operation of offshore megastructures. Modern offshore wind turbines are expected to make a significant contribution to the success of the energy transition. Future turbines are considerably larger than those in operation today, reaching total heights of more than 300 meters and featuring rotors with diameters exceeding 280 meters. At these scales, turbines are exposed to little-known influences and environmental conditions that develop at altitudes above 100 meters. Due to their dimensions and the delicate construction required, environmental effects and the interactions between individual components are becoming increasingly important. Established methods for the design and operation of wind turbines are no longer applicable to structures of this size. Therefore, new concepts are being developed worldwide to create an integrated design and operation methodology based on the concept of digital twins. This approach goes far beyond the sequential, state-of-the-art design process and calls for research into new physical, conceptual, and methodological foundations: The term offshore megastructures is often used to describe slender offshore wind turbines with rated powers exceeding 20 MW. These megastructures not only possess enormous dimensions and masses but also interact highly dynamically with their environment. According to this definition, the newest turbines developed by industry are already approaching the scale of megastructures. On one hand, this emphasizes that offshore megastructures become indispensable for future power generation. On the other hand, there is still no operational experience spanning 25 years or more for turbines of this scale. Hence, without entirely new design and operation methodologies, reliable long-term operation cannot be ensured. Integrating insights from various related fields, it highlights the paradigm shift essential for realizing the future of sustainable offshore wind energy.

This book concerns the development of novel finite elements for the structural analysis of composite beams and blades. The introduction of material damping is also an important aspect of composite structures and it is presented here in terms of their static and dynamic behavior. The book thoroughly presents a new shear beam finite element, which entails new blade section mechanics, capable of predicting structural blade coupling due to composite coupling and/or internal section geometry. Theoretical background is further expanded towards the inclusion of nonlinear structural blade models and damping mechanics for composite structures. The models effectively include geometrically nonlinear terms due to large displacements and rotations, improve the modeling accuracy of very large flexible blades, and enable the modeling of rotational stiffening and buckling, as well as, nonlinear structural coupling. Validation simulations on specimen level study the geometric nonlinearities effect on the modal frequencies and damping values of composite strips of various angle-ply laminations under either tensile or buckling loading. A series of correlation cases between numerical predictions and experimental measurements give credence to the developed nonlinear beam finite element models and underline the essential role of new nonlinear damping and stiffness terms.

This book concerns the development of novel finite elements for the structural analysis of composite beams and blades. The introduction of material damping is also an important aspect of composite structures and it is presented here in terms of their static and dynamic behavior. The book thoroughly presents a new shear beam finite element, which entails new blade section mechanics, capable of predicting structural blade coupling due to composite coupling and/or internal section geometry. Theoretical background is further expanded towards the inclusion of nonlinear structural blade models and damping mechanics for composite structures. The models effectively include geometrically nonlinear terms due to large displacements and rotations, improve the modeling accuracy of very large flexible blades, and enable the modeling of rotational stiffening and buckling, as well as, nonlinear structural coupling. Validation simulations on specimen level study the geometric nonlinearities effect on the modal frequencies and damping values of composite strips of various angle-ply laminations under either tensile or buckling loading. A series of correlation cases between numerical predictions and experimental measurements give credence to the developed nonlinear beam finite element models and underline the essential role of new nonlinear damping and stiffness terms.

A smart rotor is a wind turbine rotor that, through a combination of sensors, control units and actuators actively reduces the variation of the aerodynamic loads it has to withstand. Smart rotors feature promising load alleviation potential and might provide the technological breakthrough required by the next generation of large wind turbine rotors.The book presents the aero-servo-elastic model of a smart rotor with Adaptive Trailing Edge Flaps for active load alleviation and provides an insight on the rotor aerodynamic, structural and control modeling. A novel model for the unsteady aerodynamics of an air foil section with flap is presented and coupled with a multi-body structural representation. A smart rotor configuration is proposed, where the Adaptive Trailing Edge Flaps extend along the outer 20 % of the blade span. Linear Quadratic and Model Predictive algorithms are formulated to control the flap deflection. The potential of the smart rotor is finally confirmed by simulations in a turbulent wind field. A significant reduction of the fatigue loads on the blades is reported: the flaps, which cover no more than 1.5 % of the blade surface, reduce the fatigue load by 15 %; a combination of flap and individual pitch control allows for fatigue reductions up to 30 %.

This book presents recent studies on the power electronics used for the next generation wind turbine system. Some criteria and tools for evaluating and improving the critical performances of the wind power converters have been proposed and established. The book addresses some emerging problems as well as possibilities for the wind power conversion, and may be useful as an inspiring reference for the researchers in this field.

This book reconsiders the basic approaches behind the BEM method and in particular assesses and validates the equations forming the general momentum theory. One part of the book concerns the validation, using numerical fluid mechanics (CFD), of the different terms in the equations forming the momentum theory. Other parts present new ideas for extending the theory and for enhancing the accuracy of the BEM approach. Besides a general introduction and explanation of the momentum theory, the book also deals with specialized topics, such as diffusor-augmented rotors, wind tunnel corrections, tip corrections, and combined momentum/vortex theory for design of wind turbine rotors. The book contains new as well as already published material, and the author has strived to put the material into a new and more consistent context than what usually is found in similar text books.The book is primarily intended for researchers and experienced students with a basic knowledge in fluid mechanics wishing to understand and expand their knowledge on wind turbine aerodynamics. The book is self-consistent, hence all necessary derivations are shown, and it should not be necessary to seek help in other literature to understand the contents of the book.

A smart rotor is a wind turbine rotor that, through a combination of sensors, control units and actuators actively reduces the variation of the aerodynamic loads it has to withstand. Smart rotors feature promising load alleviation potential and might provide the technological breakthrough required by the next generation of large wind turbine rotors.The book presents the aero-servo-elastic model of a smart rotor with Adaptive Trailing Edge Flaps for active load alleviation and provides an insight on the rotor aerodynamic, structural and control modeling. A novel model for the unsteady aerodynamics of an air foil section with flap is presented and coupled with a multi-body structural representation. A smart rotor configuration is proposed, where the Adaptive Trailing Edge Flaps extend along the outer 20 % of the blade span. Linear Quadratic and Model Predictive algorithms are formulated to control the flap deflection. The potential of the smart rotor is finally confirmed by simulations in a turbulent wind field. A significant reduction of the fatigue loads on the blades is reported: the flaps, which cover no more than 1.5 % of the blade surface, reduce the fatigue load by 15 %; a combination of flap and individual pitch control allows for fatigue reductions up to 30 %.

This book reconsiders the basic approaches behind the BEM method and in particular assesses and validates the equations forming the general momentum theory. One part of the book concerns the validation, using numerical fluid mechanics (CFD), of the different terms in the equations forming the momentum theory. Other parts present new ideas for extending the theory and for enhancing the accuracy of the BEM approach. Besides a general introduction and explanation of the momentum theory, the book also deals with specialized topics, such as diffusor-augmented rotors, wind tunnel corrections, tip corrections, and combined momentum/vortex theory for design of wind turbine rotors. The book contains new as well as already published material, and the author has strived to put the material into a new and more consistent context than what usually is found in similar text books.The book is primarily intended for researchers and experienced students with a basic knowledge in fluid mechanics wishing to understand and expand their knowledge on wind turbine aerodynamics. The book is self-consistent, hence all necessary derivations are shown, and it should not be necessary to seek help in other literature to understand the contents of the book.

This book presents recent studies on the power electronics used for the next generation wind turbine system. Some criteria and tools for evaluating and improving the critical performances of the wind power converters have been proposed and established. The book addresses some emerging problems as well as possibilities for the wind power conversion, and may be useful as an inspiring reference for the researchers in this field.

This book presents the view of European wind energy experts on the long-term research challenges to be solved in order to develop wind energy beyond the applications of today and tomorrow. By this book, the European Academy of Wind Energy (eawe), representing universities and institutes with a significant windenergy programme in 14 countries, wants to:identify current technological and scientific barriers and to stimulate new creative ideas to overcome these barriersdefine priorities for future scientific researchrethink our scientific view of wind energystimulate the cooperation among researchers in fundamental and applied sciences towards wind energy researchThe eawe has discussed these long-term research with an explicit focus on a longer-term perspective, in contrast toresearch agendas addressing short- to medium-term research activities. In other words, this long-term research agenda is driven by problems and curiosity, addressing basic research and fundamental knowledge in 11 research areas, ranging from physics and design to environmental and societal aspects. Because of the very nature of this initiative, thisdocument does not intend to be permanent or complete. It shows the vision of the experts of the European Academy of Wind Energy, but other viewsmay be possible. The eawe sincerely hopes that it will spur an even more intensive discussion worldwide within thewind energy community.

The book introduces the fundamentals of fluid-mechanics, momentum theories, vortex theories and vortex methods necessary for the study of rotors aerodynamics and wind-turbines aerodynamics in particular. Rotor theories are presented in a great level of details at the beginning of the book. These theories include: the blade element theory, the Kutta-Joukowski theory, the momentum theory and the blade element momentum method. A part of the book is dedicated to the description and implementation of vortex methods. The remaining of the book focuses on the study of wind turbine aerodynamics using vortex-theory analyses or vortex-methods. Examples of vortex-theory applications are: optimal rotor design, tip-loss corrections, yaw-models and dynamic inflow models. Historical derivations and recent extensions of the models are presented. The cylindrical vortex model is another example of a simple analytical vortex model presented in this book. This model leads to the development of differentBEM models and it is also used to provide the analytical velocity field upstream of a turbine or a wind farm under aligned or yawed conditions. Different applications of numerical vortex methods are presented. Numerical methods are used for instance to investigate the influence of a wind turbine on the incoming turbulence. Sheared inflows and aero-elastic simulations are investigated using vortex methods for the first time. Many analytical flows are derived in details: vortex rings, vortex cylinders, Hill's vortex, vortex blobs etc. They are used throughout the book to devise simple rotor models or to validate the implementation of numerical methods. Several Matlab programs are provided to ease some of the most complex implementations.

This book presents the view of European wind energy experts on the long-term research challenges to be solved in order to develop wind energy beyond the applications of today and tomorrow. By this book, the European Academy of Wind Energy (eawe), representing universities and institutes with a significant windenergy programme in 14 countries, wants to:identify current technological and scientific barriers and to stimulate new creative ideas to overcome these barriersdefine priorities for future scientific researchrethink our scientific view of wind energystimulate the cooperation among researchers in fundamental and applied sciences towards wind energy researchThe eawe has discussed these long-term research with an explicit focus on a longer-term perspective, in contrast toresearch agendas addressing short- to medium-term research activities. In other words, this long-term research agenda is driven by problems and curiosity, addressing basic research and fundamental knowledge in 11 research areas, ranging from physics and design to environmental and societal aspects. Because of the very nature of this initiative, thisdocument does not intend to be permanent or complete. It shows the vision of the experts of the European Academy of Wind Energy, but other viewsmay be possible. The eawe sincerely hopes that it will spur an even more intensive discussion worldwide within thewind energy community.

The book introduces the fundamentals of fluid-mechanics, momentum theories, vortex theories and vortex methods necessary for the study of rotors aerodynamics and wind-turbines aerodynamics in particular. Rotor theories are presented in a great level of details at the beginning of the book. These theories include: the blade element theory, the Kutta-Joukowski theory, the momentum theory and the blade element momentum method. A part of the book is dedicated to the description and implementation of vortex methods. The remaining of the book focuses on the study of wind turbine aerodynamics using vortex-theory analyses or vortex-methods. Examples of vortex-theory applications are: optimal rotor design, tip-loss corrections, yaw-models and dynamic inflow models. Historical derivations and recent extensions of the models are presented. The cylindrical vortex model is another example of a simple analytical vortex model presented in this book. This model leads to the development of differentBEM models and it is also used to provide the analytical velocity field upstream of a turbine or a wind farm under aligned or yawed conditions. Different applications of numerical vortex methods are presented. Numerical methods are used for instance to investigate the influence of a wind turbine on the incoming turbulence. Sheared inflows and aero-elastic simulations are investigated using vortex methods for the first time. Many analytical flows are derived in details: vortex rings, vortex cylinders, Hill's vortex, vortex blobs etc. They are used throughout the book to devise simple rotor models or to validate the implementation of numerical methods. Several Matlab programs are provided to ease some of the most complex implementations.

This book presents the results of the seminar “Wind Energy and the Impact of Turbulence on the Conversion Process” which was supported from three societies, namely the EUROMech, EAWE and ERCOFATC and took place in Oldenburg, Germany in spring 2012.The seminar was one of the first scientific meetings devoted to the common topic of wind energy and basic turbulence. The established community of researchers working on the challenging puzzle of turbulence for decades met the quite young community of researchers, who face the upcoming challenges in the fast growing field of wind energy applications.From the fluid mechanical point of view, wind turbines are large machines operating in the fully turbulent atmospheric boundary layer. In particular they are facing small-scale turbulent inflow conditions. It is one of the central puzzles in basic turbulence research to achieve a fundamental understanding of the peculiarities of small-scale turbulence. This book helps to better understand the resulting aerodynamics around the wind turbine’s blades and the forces transmitted into the machinery in this context of puzzling inflow conditions. This is a big challenge due to the multi-scale properties of the incoming wind field ranging from local flow conditions on the profile up to the interaction of wake flows in wind farms.