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Author: Mayank Chetan Publisher: ISBN: Category : Mechanical engineering Languages : en Pages : 0
Book Description
Wind energy over the years has positioned itself to become a primary source of renewable energy and this is attributed to the reduction in the Levelized Cost of Energy (LCOE). Historically, this is accomplished by an increase in tower heights which allow access to higher wind speeds, and also by increasing rotor diameters which allow for more power capture. However, there are significant challenges that come with these large turbines like aeroelastic instabilities of the blades due to their long and slender nature, and the need for more robust turbine components that can withstand the larger loads associated with large turbines. This has motivated the development of design strategies that incorporate different methods of load alleviation to achieve optimized wind turbine designs that can result in lower LCOE. This dissertation presents various methods of designing wind turbine rotors that take advantage of passive and active load reduction strategies. First, classical flutter is addressed for the design of large blades. Flutter is an aeroelastic instability that contributes to fatigue damage, or in the worst case can least to sudden catastrophic turbine failure. A comprehensive evaluation of flutter behavior including classical flutter, edgewise vibration, and flutter mode characteristics for two- and three-bladed wind turbine blade designs is carried out. Further, a study is performed to evaluate mitigation of flutter in the design process via structural redesign by evaluating the effect of leadingvi edge and trailing edge reinforcement on flutter speed and hence demonstrates the ability to increase the flutter speed and satisfy structural design requirements (such as fatigue) while maintaining or even reducing blade mass. This flutter structural mitigation study is conducted for two wind turbine designs, one a two-bladed rotor and the other a three-bladed rotor. Second, a new rotor design methodology is developed to integrate active load control in the form of controllable gurney flaps. A comprehensive sequential iterative design procedure is developed that integrates aerodynamics, structural, and baseline turbine control system design with advanced active load control into a design process. This procedure also takes into account the contribution of loads on all major components of the turbine. To realize the best LCOE reduction solution, new methods to evaluate blade structural properties are developed wherein, the reductions in damage equivalent loads (i.e.; fatigue loads) due to a generic active load control system are mapped to structural design improvements in terms of blade mass reduction, cost reduction in other major turbine components, and LCOE reductions that result from integration and redesign of the turbine with the active load control system. Third, using the design methodologies established, newer rotor designs with a larger rotor radius are explored to examine the impacts of the active load control system. These rotors take advantage of the fatigue load reductions due to the controllable gurney flaps integrated into the design. The effect of the controllable gurney flaps is evaluated for various blade and non-blade component loads on the turbine. This methodology results in larger rotors that have increased energy capture and reduced LCOE’s. For this study, two different turbine operating strategies are followed, one limits the turbine power to that of the baseline while the other allows the turbine to extract more power at higher wind speeds. Finally, a method is introduced to support the realization of new passive and active load mitigation strategies by improving prototype wind turbine development. A novel method of developing a multi-fidelity digital twin structural model of a wind turbine blade is presented. The digital twin model development methodology, presented herein, involves a novel calibration process to integrate a wide range of information including design specifications, manufacturing information, and structural testing data (modal and static) to produce a multi-fidelity digital twin structural model: a detailed high-fidelity model (i.e., 3D FEA) and consistent beam-type models for aeroelastic simulation. Digital twin models are useful to cost-effectively evaluate the performance of new technologies in the field like novel downwind rotors and controllable gurney flaps. Finally, the new methodology is demonstrated for an as-built two-bladed downwind prototype rotor resulting in a multi-fidelity digital twin model which has a 1% match in mass properties, 3.2% in blade frequencies, and 6% in deflection to the as-built blade. The rotor examined is the SUMR – Demonstrator (SUMR-D), which was installed on the Controls Advanced Research Testbed (CART-2) wind turbine at the National Wind Technology Center. The digital twin model developed here was utilized to design controllers to safely operate SUMR-D in field tests, which are providing additional data for further evaluation and development of the multi-fidelity digital twin structural model.
Author: Mayank Chetan Publisher: ISBN: Category : Mechanical engineering Languages : en Pages : 0
Book Description
Wind energy over the years has positioned itself to become a primary source of renewable energy and this is attributed to the reduction in the Levelized Cost of Energy (LCOE). Historically, this is accomplished by an increase in tower heights which allow access to higher wind speeds, and also by increasing rotor diameters which allow for more power capture. However, there are significant challenges that come with these large turbines like aeroelastic instabilities of the blades due to their long and slender nature, and the need for more robust turbine components that can withstand the larger loads associated with large turbines. This has motivated the development of design strategies that incorporate different methods of load alleviation to achieve optimized wind turbine designs that can result in lower LCOE. This dissertation presents various methods of designing wind turbine rotors that take advantage of passive and active load reduction strategies. First, classical flutter is addressed for the design of large blades. Flutter is an aeroelastic instability that contributes to fatigue damage, or in the worst case can least to sudden catastrophic turbine failure. A comprehensive evaluation of flutter behavior including classical flutter, edgewise vibration, and flutter mode characteristics for two- and three-bladed wind turbine blade designs is carried out. Further, a study is performed to evaluate mitigation of flutter in the design process via structural redesign by evaluating the effect of leadingvi edge and trailing edge reinforcement on flutter speed and hence demonstrates the ability to increase the flutter speed and satisfy structural design requirements (such as fatigue) while maintaining or even reducing blade mass. This flutter structural mitigation study is conducted for two wind turbine designs, one a two-bladed rotor and the other a three-bladed rotor. Second, a new rotor design methodology is developed to integrate active load control in the form of controllable gurney flaps. A comprehensive sequential iterative design procedure is developed that integrates aerodynamics, structural, and baseline turbine control system design with advanced active load control into a design process. This procedure also takes into account the contribution of loads on all major components of the turbine. To realize the best LCOE reduction solution, new methods to evaluate blade structural properties are developed wherein, the reductions in damage equivalent loads (i.e.; fatigue loads) due to a generic active load control system are mapped to structural design improvements in terms of blade mass reduction, cost reduction in other major turbine components, and LCOE reductions that result from integration and redesign of the turbine with the active load control system. Third, using the design methodologies established, newer rotor designs with a larger rotor radius are explored to examine the impacts of the active load control system. These rotors take advantage of the fatigue load reductions due to the controllable gurney flaps integrated into the design. The effect of the controllable gurney flaps is evaluated for various blade and non-blade component loads on the turbine. This methodology results in larger rotors that have increased energy capture and reduced LCOE’s. For this study, two different turbine operating strategies are followed, one limits the turbine power to that of the baseline while the other allows the turbine to extract more power at higher wind speeds. Finally, a method is introduced to support the realization of new passive and active load mitigation strategies by improving prototype wind turbine development. A novel method of developing a multi-fidelity digital twin structural model of a wind turbine blade is presented. The digital twin model development methodology, presented herein, involves a novel calibration process to integrate a wide range of information including design specifications, manufacturing information, and structural testing data (modal and static) to produce a multi-fidelity digital twin structural model: a detailed high-fidelity model (i.e., 3D FEA) and consistent beam-type models for aeroelastic simulation. Digital twin models are useful to cost-effectively evaluate the performance of new technologies in the field like novel downwind rotors and controllable gurney flaps. Finally, the new methodology is demonstrated for an as-built two-bladed downwind prototype rotor resulting in a multi-fidelity digital twin model which has a 1% match in mass properties, 3.2% in blade frequencies, and 6% in deflection to the as-built blade. The rotor examined is the SUMR – Demonstrator (SUMR-D), which was installed on the Controls Advanced Research Testbed (CART-2) wind turbine at the National Wind Technology Center. The digital twin model developed here was utilized to design controllers to safely operate SUMR-D in field tests, which are providing additional data for further evaluation and development of the multi-fidelity digital twin structural model.
Author: Bernhard Stoevesandt Publisher: Springer Nature ISBN: 3030313077 Category : Technology & Engineering Languages : en Pages : 1495
Book Description
This handbook provides both a comprehensive overview and deep insights on the state-of-the-art methods used in wind turbine aerodynamics, as well as their advantages and limits. The focus of this work is specifically on wind turbines, where the aerodynamics are different from that of other fields due to the turbulent wind fields they face and the resultant differences in structural requirements. It gives a complete picture of research in the field, taking into account the different approaches which are applied. This book would be useful to professionals, academics, researchers and students working in the field.
Author: Katherine D. Van Ness Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Cost and reliability remain among the main barriers limiting widespread adoption ofriverine, estuarine, or ocean current turbine power generation. In particular, structural loads are significantly greater than for wind turbines with equivalent power output, which contributes to higher costs. Compounded with uncertainties about hydrodynamic loads, this can contribute to structural failure or excessive and expensive safety factors. Consequently, control strategies to mitigate structural loads and reduce cost are of considerable importance. Load reduction is of particular interest when currents exceed a certain threshold (i.e., theturbine-specific “rated speed”), and a control strategy is implemented to maintain a constant power output. Most fixed-pitch turbines will use a speed control strategy, increasing or decreasing the rotation rate to achieve the efficiency required for power regulation. However, these “overspeed” and “underspeed” control strategies correspond to large increases in thrust or torque, respectively, that require overdesigning the turbine blades or generator. Blade pitch control circumvents this trade-off, as decreased angles of attack simultaneously reduce thrust and torque. This does, however, require actuators to change blade pitch. While active pitch control is the conventional standard for wind turbines in these above-rated conditions, similar variable blade pitch mechanisms have not yet been uniformly adopted by marine current technology developers due to the higher cost of inspection, maintenance, and repairs relative to wind turbines. For this reason, passive adaptive blade pitch control, in which blades are designed to elastically deform under load without an actuator, sensor, or control logic, is conceptually attractive. Improved understanding of the loading associated with both speed and pitch control strategies is critical to optimizing a design for minimal cost and maximal reliability. Therefore, the overarching goal of this work is to experimentally investigate active and passive pitch control methods, characterize their potential for load reduction, and establish appropriate scaling relations for passive adaptive blades. The three underlying objectives supporting this goal are outlined below. The first objective is to demonstrate active blade pitch control in above-rated flow conditionsand compare the measured turbine loads to those observed with overspeed and underspeed control in order to develop our understanding of the trade-offs associated with each. To this end, we experimentally characterized power performance and turbine loading over a range of blade pitch settings and tip-speed ratios for a three-bladed axial-flow turbine. We then implemented a control strategy to maintain power output in time-varying currents using blade pitch control and compared the turbine performance under this control strategy to overspeed and underspeed control strategies for a fixed pitch turbine. The experiments were conducted with a laboratory-scale 0.45-m diameter turbine in an open channel flume with a 35% blockage ratio. During pitch characterization experiments, inflow velocity was maintained at 0.8 m/s with 4% turbulence intensity. During time-varying inflow experiments, currents varied from 0.7-0.8 m/s over a 20-minute period, while a proportional controller regulated either blade pitch or rotor speed, and we recorded turbine power output and turbine loads. In this velocity range, where turbine performance is independent of Reynolds number, we demonstrate that pitch control substantially reduces torque requirements relative to underspeed control and streamwise turbine loads relative to overspeed control. Additional tests were conducted for underspeed control and pitch control in a Reynolds-dependent regime with time-varying inflow between 0.4-0.5 m/s and 0.5-0.6 m/s. These cases suggest that blade pitch control could provide even greater benefits relative to speed control in small-scale applications. The second objective is to develop our understanding of passive adaptive blade fabricationand the effect of fiber orientation to inform a passive pitch control design. By tailoring the ply angle in a unidirectional carbon fiber blade, a desired twist can be induced in response to bending of the blade under load. In developing this form of passive adaptive control, a fundamental question is how to non-dimensionalize the fluid-structure interaction to make laboratory-scale experiments relevant to full-scale applications. To address these questions, we first conducted an experimental investigation into the effect of fiber angle on blade performance and blade deformation during turbine operation. The composite blades were fabricated with 0°, 2.5°, 5°, and 10° fiber orientations, where a positive fiber orientation results in a reduced angle of attack as load increases (i.e., a “pitch-to-feather” control strategy). Blades were tested in a recirculating flume at 0.7 m/s (Rec = 5.3 · 104 − 2.0 · 105) while measuring force and torque on the rotor. Simultaneously, a high-speed camera observed in-situ deflection and twist at the blade tip. Results show a greater reduction in CP and CT for blades with larger fiber orientations relative to the neutral blade set, while even small fiber orientations were observed to limit thrust at high tip-speed ratios. To explore the correct non-dimensional scaling for this physical process, we performed a set of Cauchyscaled experiments using blades with identical bend-twist couplings but different bending stiffness. These results demonstrate that the Cauchy number is a meaningful parameter for scaling passive adaptive current turbine blades and to model steady-state hydrodynamic and hydroelastic behavior. The third and final objective is to implement passive pitch control to develop our understandingof the trade-offs between speed, active pitch, and passive pitch control methods. Two passive blade pitch control strategies for the same lab-scale turbine were developed and tested experimentally in a recirculating flume. The goal of the control is to regulate mechanical power, while minimizing rotor loads, when flow conditions exceed the rated condition. Both strategies used the 5° fiber blade set from the aforementioned study. One control strategy combined passive adaptive blades with overspeed control (actuating rotational speed above the tip-speed ratio corresponding to peak efficiency) while the other combined passive adaptive blades with active pitch control (actuating blade pitch using motors at the blade root). Both strategies were implemented in linearly increasing inflow from 0.7 m/s to 0.8 m/s and compared to control strategies using rigid, aluminum blades under the same flow conditions. The passive adaptive blades combined with active pitch control show no improvement in steady-state load reductions relative to rigid blades used with active pitch control. However, the passive adaptive blades combined with overspeed control show reduced torque and only a 12% increase in thrust relative to the rated flow condition. This indicates that passive adaptive blades combined with overspeed control can be an effective strategy in currents above the rated flow speed, removing the need for an active pitch mechanism in some applications. In addition to measuring turbine loads, deflection and twist of the passive adaptive blades during experimental testing were observed using a high-speed camera to support our understanding of the bend-twist behavior during turbine operation over a range of flow speeds, rotation rates, and preset pitch angles. Overall, active and passive pitch control strategies for Region III are shown to offer significantload reductions in thrust and torque relative to rigid blade speed control strategies. While controller selection is discussed primarily relative to their associated loads, we discuss additional considerations including blade design, channel blockage, range and frequency of flow variation, and Reynolds-number. These discussions underline the value of future investigations into active and passive pitch control for smoothing high-frequency loads and scaling between lab- and full-scale passive adaptive rotors, among other work.
Author: H. Söker Publisher: Elsevier Inc. Chapters ISBN: 012808913X Category : Technology & Engineering Languages : en Pages : 36
Book Description
This chapter deals with loads on wind turbine blades. It describes the load generating process, wind fields, and the concepts of stresses and strains. Aerodynamic loads, loads introduced by inertia, gravitation and gyroscopic effects, and actuation loads are discussed. The loading effects on the rotor blades and how they are interconnected with the dynamics of the turbine structure are highlighted. There is a discussion on how stochastic loads can be analysed and an outline of cycle counting methodology. The method of design verification testing is briefly described.
Author: Abdel Ghani Aissaoui Publisher: BoD – Books on Demand ISBN: 9535124951 Category : Technology & Engineering Languages : en Pages : 354
Book Description
Renewable energies constitute excellent solutions to both the increase of energy consumption and environment problems. Among these energies, wind energy is very interesting. Wind energy is the subject of advanced research. In the development of wind turbine, the design of its different structures is very important. It will ensure: the robustness of the system, the energy efficiency, the optimal cost and the high reliability. The use of advanced control technology and new technology products allows bringing the wind energy conversion system in its optimal operating mode. Different strategies of control can be applied on generators, systems relating to blades, etc. in order to extract maximal power from the wind. The goal of this book is to present recent works on design, control and applications in wind energy conversion systems.
Author: Leonardo Bergami Publisher: Springer ISBN: 3319073656 Category : Technology & Engineering Languages : en Pages : 161
Book Description
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 %.
Author: Povl Brondsted Publisher: Elsevier ISBN: 0857097288 Category : Technology & Engineering Languages : en Pages : 485
Book Description
Wind energy is gaining critical ground in the area of renewable energy, with wind energy being predicted to provide up to 8% of the world’s consumption of electricity by 2021. Advances in wind turbine blade design and materials reviews the design and functionality of wind turbine rotor blades as well as the requirements and challenges for composite materials used in both current and future designs of wind turbine blades. Part one outlines the challenges and developments in wind turbine blade design, including aerodynamic and aeroelastic design features, fatigue loads on wind turbine blades, and characteristics of wind turbine blade airfoils. Part two discusses the fatigue behavior of composite wind turbine blades, including the micromechanical modelling and fatigue life prediction of wind turbine blade composite materials, and the effects of resin and reinforcement variations on the fatigue resistance of wind turbine blades. The final part of the book describes advances in wind turbine blade materials, development and testing, including biobased composites, surface protection and coatings, structural performance testing and the design, manufacture and testing of small wind turbine blades. Advances in wind turbine blade design and materials offers a comprehensive review of the recent advances and challenges encountered in wind turbine blade materials and design, and will provide an invaluable reference for researchers and innovators in the field of wind energy production, including materials scientists and engineers, wind turbine blade manufacturers and maintenance technicians, scientists, researchers and academics. Reviews the design and functionality of wind turbine rotor blades Examines the requirements and challenges for composite materials used in both current and future designs of wind turbine blades Provides an invaluable reference for researchers and innovators in the field of wind energy production
Author: Martin O. L. Hansen Publisher: Earthscan ISBN: 9781902916064 Category : Science Languages : en Pages : 156
Book Description
Wind power is an increasingly significant renewable energy resource, producing no environmentally damaging CO2 emissions. The efficient production of electricity by wind turbines relies on aerodynamics: Aerodynamics of Wind Turbines provides the fundamental solutions to efficient wind turbine design. Following a historical introduction, Part 1 of Aerodynamics of Wind Turbines is concerned with basic rotor aerodynamics, while Part 2 deals with structural aspects of the wind turbine and calculation of the loads on it. Topics covered include increasing mass flow through the turbine, performance at low and high wind speeds, assessment of the extreme conditions under which the turbine will perform and the theory for calculating the lifetime of the turbine. The classical Blade Element Momentum method is also covered, as are eigenmodes and the dynamic behavior of a turbine. Aerodynamics of Wind Turbines is an essential reference for both engineering students and others with a professional or academic interest in the physics and technologies behind horizontal axis wind turbines. It will provide a sound understanding of the mechanisms behind the generation of forces on a wind turbine.
Author: Committee on Assessment of Research Needs for Wind Turbine Rotor Materials Technology Publisher: National Academies Press ISBN: 0309583187 Category : Technology & Engineering Languages : en Pages : 119
Book Description
Wind-driven power systems represent a renewable energy technology. Arrays of interconnected wind turbines can convert power carried by the wind into electricity. This book defines a research and development agenda for the U.S. Department of Energy's wind energy program in hopes of improving the performance of this emerging technology.
Author: Emmanuel Branlard Publisher: Springer ISBN: 3319551647 Category : Technology & Engineering Languages : en Pages : 632
Book Description
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 different BEM 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.
Author: Mayank Chetan
Author: Mayank Chetan
Author: Bernhard Stoevesandt
Author: Katherine D. Van Ness
Author: H. Söker
Author: Abdel Ghani Aissaoui
Author: Leonardo Bergami
Author: Povl Brondsted
Author: Martin O. L. Hansen
Author: Committee on Assessment of Research Needs for Wind Turbine Rotor Materials Technology
Author: Emmanuel Branlard