Download or read book Fully vs Sequentially Coupled Loads Analysis of Offshore Wind Turbines written by and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The design and analysis methods for offshore wind turbines must consider the aerodynamic and hydrodynamic loads and response of the entire system (turbine, tower, substructure, and foundation) coupled to the turbine control system dynamics. Whereas a fully coupled (turbine and support structure) modeling approach is more rigorous, intellectual property concerns can preclude this approach. In fact, turbine control system algorithms and turbine properties are strictly guarded and often not shared. In many cases, a partially coupled analysis using separate tools and an exchange of reduced sets of data via sequential coupling may be necessary. In the sequentially coupled approach, the turbine and substructure designers will independently determine and exchange an abridged model of their respective subsystems to be used in their partners' dynamic simulations. Although the ability to achieve design optimization is sacrificed to some degree with a sequentially coupled analysis method, the central question here is whether this approach can deliver the required safety and how the differences in the results from the fully coupled method could affect the design. This work summarizes the scope and preliminary results of a study conducted for the Bureau of Safety and Environmental Enforcement aimed at quantifying differences between these approaches through aero-hydro-servo-elastic simulations of two offshore wind turbines on a monopile and jacket substructure.

Download or read book A Comparison of Ultimate Loads from Fully and Sequentially Coupled Analyses written by and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This poster summarizes the scope and preliminary results of a study conducted for the Bureau of Safety and Environmental Enforcement aimed at quantifying differences between two modeling approaches (fully coupled and sequentially coupled) through aero-hydro-servo-elastic simulations of two offshore wind turbines on a monopile and jacket substructure.

Download or read book Loads Analysis of a Floating Offshore Wind Turbine Using Fully Coupled Simulation written by and published by . This book was released on 2007 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: The vast deepwater wind resource represents a potential to use floating offshore wind turbines to power much of the world with renewable energy. Comprehensive simulation tools that account for the coupled excitation and response of the complete system, including the influences of wind-inflow, aerodynamics, structural dynamics, controls, and, for offshore systems, waves, currents, and hydrodynamics, are used to design and analyze wind turbines. The application of such tools in the analysis of floating offshore wind turbines has previously been investigated to only a limited extent. There are numerous possible concepts for floating offshore wind turbine platforms, including a variety of configurations currently used in the offshore oil and gas industries. Coupled analyses are needed to determine their technical and economic feasibility. This paper presents the use of fully coupled aero-hydro-servo-elastic simulation tools to perform a preliminary loads analysis of a 5-MW offshore wind turbine supported by a barge with catenary moorings, which is one of the many promising floating platform concepts.

Download or read book Dynamics Modeling and Loads Analysis of an Offshore Floating Wind Turbine written by Jason Mark Jonkman and published by . This book was released on 2007 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objectives of the work described in this report are to develop a comprehensive simulation tool that can model the coupled dynamic response of offshore floating wind turbines, verify the simulation capability through model-to-model comparisons, and apply the simulation tool in an integrated loads analysis for one of the promising floating support platform concepts.

Download or read book Dynamics Modeling and Loads Analysis of an Offshore Floating Wind Turbine written by and published by . This book was released on 2007 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes the development, verification, and application of a comprehensive simulation tool for modeling coupled dynamic responses of offshore floating wind turbines.

Download or read book Fully Coupled Dynamic Analysis of a Floating Wind Turbine System written by Jon E. Withee and published by . This book was released on 2004 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of wind power is in a period of rapid growth worldwide and wind energy systems have emerged as a promising technology for utilizing offshore wind resources for the large scale generation of electricity Drawing upon the maturity of wind turbine and floater technologies developed by the wind energy and oil and gas industries, respectively, large offshore wind energy systems have been developed and are being proposed for operation in offshore areas where environmental restrictions are less restrictive, large wind resources exist, and open sea areas are available for wind farm development. A fully coupled dynamic analysis/technique was developed to predict the response of a floating wind turbine system in a stochastic wind and wave environment This technique incorporated both non-linear wave loading on the submerged floater and the aerodynamic loading on the wind turbine A tension leg spar buoy was designed to support the wind turbine This design was chosen due to its relatively small size and hence lower potential cost per wind turbine The system's tethers were attached to the ends of spokes which radiated out from the spar cylinder This arrangement of lines and spokes promised to be very stiff in the roll and pitch modes of motion.

Download or read book Wind Wave Misalignment in the Loads Analysis of a Floating Offshore Wind Turbine Preprint written by and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wind resources far from the shore and in deeper seas have encouraged the offshore wind industry to look into floating platforms. The International Electrotechnical Commission (IEC) is developing a new technical specification for the design of floating offshore wind turbines that extends existing design standards for land-based and fixed-bottom offshore wind turbines. The work summarized in this paper supports the development of best practices and simulation requirements in the loads analysis of floating offshore wind turbines by examining the impact of wind/wave misalignment on the system loads under normal operation. Simulations of the OC3-Hywind floating offshore wind turbine system under a wide range of wind speeds, significant wave heights, peak-spectral periods and wind/wave misalignments have been carried out with the aero-servo-hydro-elastic tool FAST [4]. The extreme and fatigue loads have been calculated for all the simulations. The extreme and fatigue loading as a function of wind/wave misalignment have been represented as load roses and a directional binning sensitivity study has been carried out. This study focused on identifying the number and type of wind/wave misalignment simulations needed to accurately capture the extreme and fatigue loads of the system in all possible metocean conditions considered, and for a down-selected set identified as the generic US East Coast site. For this axisymmetric platform, perpendicular wind and waves play an important role in the support structure and including these cases in the design loads analysis canimprove the estimation of extreme and fatigue loads. However, most structural locations see their highest extreme and fatigue loads with aligned wind and waves. These results are specific to the spar type platform, but it is expected that the results presented here will be similar to other floating platforms.

Download or read book Wind Turbine Technology written by Muyiwa Adaramola and published by CRC Press. This book was released on 2014-02-24 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt: This title includes a number of Open Access chapters. This important book presents a selection of new research on wind turbine technology, including aerodynamics, generators and gear systems, towers and foundations, control systems, and environmental issues. This informative book: • Introduces the principles of wind turbine design • Presents methods for analysis of wind turbine performance • Discusses approaches for wind turbine improvement and optimization • Covers fault detection in wind turbines • Describes mediating the adverse effects of wind turbine use and installation

Download or read book Impact of Sea Ice Loads on Global Dynamics of Offshore Wind Turbines written by Wojciech Popko and published by Fraunhofer Verlag. This book was released on 2020-12-10 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: Support structures for offshore wind turbines (OWTs) are designed and certified site-specific based on the calculated load effects. These load effects originate from static, cyclic, stochastic, and transient loads from the met-ocean environment and rotating components of the wind turbine. The met-ocean environment of the Baltic Sea accounts for variable wind and marine conditions. Sea ice is part of marine conditions - which among others - should be included in the design process of OWT support structures. The load analysis and design of OWTs, including its components, rely on the time-domain based, coupled aero-hydro-servo-elastic simulation tools. Only this approach can provide an accurate prediction of the OWT dynamic response. Dynamic interaction between an OWT and external loads - including ice loads - cannot be disregarded as it may result in considerable loss of accuracy. A proper understanding of sea ice impact on the global dynamics of OWTs - involving the fully-integrated simulation approach - is necessary within the offshore wind research community, industry, and certification authorities.

Download or read book An Integrated Nonlinear Wind Waves Model for Offshore Wind Turbines written by Enzo Marino and published by Firenze University Press. This book was released on 2010 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents a numerical model capable of simulating offshore wind turbines exposed to extreme loading conditions. External condition-based extreme responses are reproduced by coupling a fully nonlinear wave kinematic solver with a hydro-aero-elastic simulator. First, a two-dimensional fully nonlinear wave simulator is developed. The transient nonlinear free surface problem is formulated assuming the potential theory and a high-order boundary element method is implemented to discretize Laplace's equation. For temporal evolution a second-order Taylor series expansion is used. The code, after validation with experimental data, is successfully adopted to simulate overturning plunging breakers which give rise to dangerous impact loads when they break against wind turbine substructures. Emphasis is then placed on the random nature of the waves. Indeed, through a domain decomposition technique a global simulation framework embedding the numerical wave simulator into a more general stochastic environment is developed. The proposed model is meant as a contribution to meet the more and more pressing demand for research in the offshore wind energy sector as it permits taking into account dangerous effects on the structural response so as to increase the global structural safety level.

Download or read book Coupled Dynamic Analysis of Floating Offshore Wind Farms written by Sangyun Shim and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: During the past decade, the demand for clean renewable energy continues to rise drastically in Europe, the US, and other countries. Wind energy in the ocean can possibly be one of those future renewable clean energy sources as long it is economically feasible and technologically manageable. So far, most of the offshore wind farm research has been limited to fixed platforms in shallow-water areas. In the water depth deeper than 30m, however, floating-type wind farms tend to be more feasible. Then, the overall design and engineering becomes more complicated than fixed platforms including the coupled dynamics of platforms, mooring lines, and blades. In the present study, a numerical time-domain model has been developed for the fully coupled dynamic analysis of an offshore floating wind turbine system including blade-rotor dynamics and platform motions. As a test case, the TLP-type floater system with 3 blades of 70-m diameter designed by the National Renewable Energy Laboratory (NREL) is selected to analyze the dynamic coupling effects among floating system, mooring lines, and wind turbine. The performance of the selected system in a typical wind-wave-current condition has been simulated and analyzed. A similar study for the floater and rotor coupled dynamic analysis was conducted by MIT and NREL. However, in the present case, the dynamic coupling between platform and mooring lines are also considered in addition to the rotor-floater dynamic coupling. It is seen that the rotor-floater coupling effects increase with wind velocity and blade size. The increased coupling effects tend to increase the dynamic tension of TLP tethers. The developed technology and numerical tool are applicable to the new offshore floating wind farms planned in the future.

Download or read book Dynamics Modeling Simulation and Analysis of a Floating Offshore Wind Turbine written by Mohammed Khair Al-Solihat and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: " Floating Offshore Wind Turbines (FOWTs) are a promising technology to harness the abundant offshore wind energy resources in open ocean areas. A FOWT consists of a floating platform, the moorings, and the wind turbine structure (tower + Rotor-Nacelle Assembly (RNA)). The main focus of this thesis is to develop multibody dynamic models that integrate the structural dynamics, and hydrostatic, hydrodynamic, aerodynamic and mooring system loads. Special efforts are also devoted to characterize the mooring and hydrostatic loads as main sources of systems stiffness that shapes the dynamic behavior of the system. Two approaches for modeling the platform/tower dynamics are developed, a rigid multibody model and a coupled rigid-flexible multibody model. Both models treat the platform, nacelle and rotor as six-degrees-of-freedom (6-DOF) rigid bodies. However, modeling the wind turbine tower dynamics differs between these approaches. The rigid model considers the tower as a 6-DOF rigid body while the flexible model represents the tower as a three-dimensional (3D) tapered damped Euler-Bernoulli beam undergoing coupled general rigid body and elastic motions. In both approaches, the wind turbine drivetrain dynamics is also considered to capture the rotor spin response. The equations of motions of both models are derived symbolically using Lagrange's equations. The hydrostatic restoring loads are evaluated through development of a novel nonlinear hydrostatic approach. This approach allows evaluating the exact hydrostatic force and moment and position of the center of buoyancy as function of the platform displacement and finite rotation. New exact expressions for the water plane area restoring moments are developed. The hydrostatic stiffness matrix at an arbitrary position and orientation of the platform is subsequently derived. A quasi-static approach is then developed to determine the cable tensions of the single-segment and multi-segment mooring system configurations proposed to moor the platform to the seabed. The approach uses different governing equations, depending on whether the mooring lines partially rest on the seabed; are suspended; or fully taut. The exact mooring stiffness is subsequently derived and the influence of several mooring system parameters on the mooring system stiffness is investigated. As an alternative to the quasi-static cable model, a lumped mass cable model incorporating the cable-seabed contact effect is developed to integrate the cable dynamics into the FOWT system dynamics. The equations of motion of the mooring line nodes are assembled for the two mooring system configurations under consideration. A new methodology is also presented to calculate the equilibrium profile of the mooring line lying on a seabed as desirable initial conditions for solving the discretized cable equations of motion. Finally, the theoretical models are implemented through a large simulation tool to analyze the dynamic behavior of the spar FOWT system under study. A series of simulations under defined external loads (load cases) are performed to validate the dynamic models. The simulation results are compared with similar results obtained from well-known offshore wind design codes. The simulation results are found to be in very good agreement with the reported results. Numerical experiments are also performed to investigate the influence of the tower flexibility, mooring system configuration, tower twist and cable dynamics on the system dynamic behavior. The results show that the system responses obtained from the rigid body model under-predict the platform yaw response and exhibit less damping than those obtained from the flexible model. It is also found that the mooring system configuration choice does not influence the platform roll and pitch responses or tower elastic deflections." --

Download or read book Offshore Wind Turbine Loads Under the Coupled Influences of Wind Waves and Currents During Hurricanes written by Eungsoo Kim and published by . This book was released on 2015 with total page 600 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the United States, potential offshore wind plant sites have been identified along the Atlantic seaboard and in the Gulf of Mexico. At such sites, it is imperative that we consider load cases for and define external conditions associated with hurricanes and severe winter storms for which wind turbines may need to be designed. We select two hurricanes, Ike (2008) and Sandy (2012), and investigate what effect these tropical storms would have on bottom-supported offshore wind turbines that were hypothetically in or close to their path as they made landfall. For realistic turbine loads assessment, it is important that the coupled influences of the changing wind, wave, and current fields are simulated throughout the evolution of the hurricanes. We employ a coupled model—specifically, the University of Miami Coupled Model (UMCM)—that integrates atmospheric, wave, and ocean components to produce needed wind, wave, and current data. The wind data are used to generate appropriate vertical wind profiles and full wind velocity fields including turbulence; the current field over the water column is obtained by interpolated discrete output current data; and short-crested irregular second-order waves are simulated using output directional wave spectra from the coupled model. Two monopile-supported offshore wind turbines sited in 20 meters of water in the Gulf of Mexico are studied so as to estimate loads during Hurricane Ike; a jacket space-frame platform-supported offshore wind turbine sited in 50 meters of water in the mid-Atlantic region is studied so as to estimate loads during Hurricane Sandy. We discuss in detail how the simulated hurricane wind, wave, and current output data are used in turbine loads studies. We discuss important characteristics of the external conditions including the relative importance of swell versus wind seas, of aerodynamic versus hydrodynamic forces, of current velocity effects, of yaw control options for the turbine, of hydrodynamic drag versus inertia forces, and of soil-structure interaction effects. A detailed framework is presented that explains how coupled inputs can be included in turbine loads studies during a hurricane; this can aid in future efforts aimed at developing offshore wind turbine design criteria and load cases related to hurricanes.

Download or read book Model Development and Loads Analysis of a Wind Turbine on a Floating Offshore Tension Leg Platform written by and published by . This book was released on 2010 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents results of the analysis of a 5-MW wind turbine located on a floating offshore tension leg platform (TLP) that was conducted using the fully coupled time-domain aero-hydro-servo-elastic design code FAST with AeroDyn and HydroDyn. Models in this code are of greater fidelity than most of the models that have been used to analyze floating turbines in the past--which have neglected important hydrodynamic and mooring system effects. The report provides a description of the development process of a TLP model, which is a modified version of a Massachusetts Institute of Technology design derived from a parametric linear frequency-domain optimization process. An extensive loads and stability analysis for ultimate and fatigue loads according to the procedure of the International Electrotechnical Commission offshore wind turbine design standard was performed with the verified TLP model. Response statistics, extreme event tables, fatigue lifetimes, and selected time histories of design-driving extreme events are analyzed and presented. Loads for the wind turbine on the TLP are compared to those of an equivalent land-based turbine in terms of load ratios. Major instabilities for the TLP are identified and described.

Download or read book Development of Fully Coupled Aeroelastic and Hydrodynamic Models for Offshore Wind Turbines written by and published by . This book was released on 2006 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aeroelastic simulation tools are routinely used to design and analyze onshore wind turbines, in order to obtain cost effective machines that achieve favorable performance while maintaining structural integrity. These tools employ sophisticated models of wind-inflow; aerodynamic, gravitational, and inertial loading of the rotor, nacelle, and tower; elastic effects within and between components; and mechanical actuation and electrical responses of the generator and of control and protection systems. For offshore wind turbines, additional models of the hydrodynamic loading in regular and irregular seas, the dynamic coupling between the support platform motions and wind turbine motions, and the dynamic characterization of mooring systems for compliant floating platforms are also important. Hydrodynamic loading includes contributions from hydrostatics, wave radiation, and wave scattering, including free surface memory effects. The integration of all of these models into comprehensive simulation tools, capable of modeling the fully coupled aeroelastic and hydrodynamic responses of floating offshore wind turbines, is presented.

Download or read book Verification of the New FAST V8 Capabilities for the Modeling of Fixed Bottom Offshore Wind Turbines written by and published by . This book was released on 2014 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coupled dynamic analysis has an important role in the design of offshore wind turbines because the systems are subject to complex operating conditions from the combined action of waves and wind. The aero-hydro-servo-elastic tool FAST v8 is framed in a novel modularization scheme that facilitates such analysis. Here, we present the verification of new capabilities of FAST v8 to model fixed-bottom offshore wind turbines. We analyze a series of load cases with both wind and wave loads and compare the results against those from the previous international code comparison projects-the International Energy Agency (IEA) Wind Task 23 Subtask 2 Offshore Code Comparison Collaboration (OC3) and the IEA Wind Task 30 OC3 Continued (OC4) projects. The verification is performed using the NREL 5-MW reference turbine supported by monopile, tripod, and jacket substructures. The substructure structural-dynamics models are built within the new SubDyn module of FAST v8, which uses a linear finite-element beam model with Craig-Bampton dynamic system reduction. This allows the modal properties of the substructure to be synthesized and coupled to hydrodynamic loads and tower dynamics. The hydrodynamic loads are calculated using a new strip theory approach for multimember substructures in the updated HydroDyn module of FAST v8. These modules are linked to the rest of FAST through the new coupling scheme involving mapping between module-independent spatial discretizations and a numerically rigorous implicit solver. The results show that the new structural dynamics, hydrodynamics, and coupled solutions compare well to the results from the previous code comparison projects.

Download or read book Coupled Dynamic Modeling of Floating Wind Turbine Systems written by and published by . This book was released on 2006 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: This article presents a collaborative research program that the Massachusetts Institute of Technology (MIT) and the National Renewable Energy Laboratory (NREL) have undertaken to develop innovative and cost-effective floating and mooring systems for offshore wind turbines in water depths of 10-200 m. Methods for the coupled structural, hydrodynamic, and aerodynamic analysis of floating wind turbine systems are presented in the frequency domain. This analysis was conducted by coupling the aerodynamics and structural dynamics code FAST [4] developed at NREL with the wave load and response simulation code WAMIT (Wave Analysis at MIT) [15] developed at MIT. Analysis tools were developed to consider coupled interactions between the wind turbine and the floating system. These include the gyroscopic loads of the wind turbine rotor on the tower and floater, the aerodynamic damping introduced by the wind turbine rotor, the hydrodynamic damping introduced by wave-body interactions, and the hydrodynamic forces caused by wave excitation. Analyses were conducted for two floater concepts coupled with the NREL 5-MW Offshore Baseline wind turbine in water depths of 10-200 m: the MIT/NREL Shallow Drafted Barge (SDB) and the MIT/NREL Tension Leg Platform (TLP). These concepts were chosen to represent two different methods of achieving stability to identify differences in performance and cost of the different stability methods. The static and dynamic analyses of these structures evaluate the systems' responses to wave excitation at a range of frequencies, the systems' natural frequencies, and the standard deviations of the systems' motions in each degree of freedom in various wind and wave environments. This article in various wind and wave environments. This article explores the effects of coupling the wind turbine with the floating platform, the effects of water depth, and the effects of wind speed on the systems' performance. An economic feasibility analysis of the two concepts was also performed. Key cost components included the material and construction costs of the buoy; material and installation costs of the tethers, mooring lines, and anchor technologies; costs of transporting and installing the system at the chosen site; and the cost of mounting the wind turbine to the platform. The two systems were evaluated based on their static and dynamic performance and the total system installed cost. Both systems demonstrated acceptable motions, and have estimated costs of $1.4-$1.8 million, not including the cost of the wind turbine, the power electronics, or the electrical transmission.