Dynamic Response Analysis Of Floating Offshore Wind Turbines With Failed Moorings
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Dynamic Response Analysis Of Floating Offshore Wind Turbines With Failed Moorings
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Author : Yajun Ren
language : en
Publisher:
Release Date : 2022
Dynamic Response Analysis Of Floating Offshore Wind Turbines With Failed Moorings written by Yajun Ren and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with categories.
Dynamic Response Of Spar Type Offshore Floating Wind Turbines
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Author : Roberts Proskovics
language : en
Publisher:
Release Date : 2015
Dynamic Response Of Spar Type Offshore Floating Wind Turbines written by Roberts Proskovics and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
In recent years there has been a significant increase in the interest in floating offshore wind turbines from the wind energy industry, governments and academia. Partially driven by the recent nuclear disaster in Japan, but also by the lack or complete absence of shallow waters in various countries around the globe (making fixed offshore wind turbines infeasible), multiple different topology floating offshore wind turbines have been proposed and, in some cases, prototypes built and installed offshore. The most well-known of these is Hywind by Statoil, which has been operational off the coast of Norway since the end of 2009. While small scale prototypes had been installed even before Hywind, for example Blue-H in 2007, no guidelines have yet emerged that would give recommendations and guiding principles in designing new floating offshore wind turbines. The aim of this thesis is to provide some knowledge base for future design of floating offshore wind turbines by looking at what simplifications could be made and what effect these would have on the preliminary designs of new floating offshore wind turbines. This thesis starts by comparing different topology floating offshore wind turbines and choosing one, deemed the most promising, as the base case scenario for use in the subsequent analysis and calculations. This thesis also looks at the importance of unsteady representations of the aerodynamics compared with quasi-steady when designing a new floating offshore wind turbine, by comparing quasi-steady aerodynamic loads first with fully-attached unsteady loads and later with fully-unsteady (fully-attached, separated and dynamic stall). A chapter is allocated to identifying which degree-of-freedom of loading is the most damaging to the system, as floating offshore wind turbines operate in very harsh and unstable environments. Once identified, this knowledge can be used to further improve floating offshore wind turbines, hence making them even more feasible. Finally, the wind turbine previously chosen as a base case has its floating support shortened and four different draft designs proposed that would allow it to be deployed in medium-to-deep waters, in which fixed supports for wind turbines are not economical.
Dynamic Response Analysis Of An Offshore Wind Turbine Supported By A Moored Semi Submersible Platform
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Author : Mohit Soni
language : en
Publisher:
Release Date : 2014
Dynamic Response Analysis Of An Offshore Wind Turbine Supported By A Moored Semi Submersible Platform written by Mohit Soni and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
Wind energy, the fastest growing source of renewable energy, is a promising resource for power generation. Offshore wind energy, in particular,offers favorable conditions for power generation--high winds with low turbulence, minimal visual impacts and high generation capacities. Offshore wind turbines mounted on floating platforms are the most economical and viable solution for deep water sites. A semi-submersible platform is an appropriate floating platform for a deep water site, providing stability through high water-plane area. In the wind energy industry, there has been continuing interest in developing larger turbines. At Sandia National Laboratories (SNL), efforts have led to the development of a 13.2 MW wind turbine model with blades 100 meters in length, significantly larger than commercially available blades at present. Such a large wind turbine needs to be carefully analyzed and studied before it can be considered suitable for commercial purposes. The dynamic analysis of the SNL 13.2 MW wind turbine mounted on a moored semi-submersible platform is the subject of this study. This integrated 13.2 MW wind turbine system has been developed and its various physical properties have been studied in this and another associated study. The semi-submersible platform is developed using various modeling tools. For the wind turbine-platform system model developed, dynamic analyses are performed using simulation tools to understand the coupled behavior of the wind turbine and the platform. A reference site is chosen to define the environmental conditions, based on which the short-term extreme response of the offshore wind turbine is estimated. The system is loaded with selected combinations of winds and waves to assess controlling combinations of wind speeds and wave heights that influence the response. The influence of changes in model parameters on overall response is also studied.
Dynamics Modeling Simulation And Analysis Of A Floating Offshore Wind Turbine
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Author : Mohammed Khair Al-Solihat
language : en
Publisher:
Release Date : 2018
Dynamics Modeling Simulation And Analysis Of A Floating Offshore Wind Turbine written by Mohammed Khair Al-Solihat and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
" 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." --
Dynamic Analysis Of A Spar Type Offshore Floating Wind Turbine And Its Mooring System
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Author : Xue Xu
language : en
Publisher:
Release Date : 2020
Dynamic Analysis Of A Spar Type Offshore Floating Wind Turbine And Its Mooring System written by Xue Xu and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020 with categories.
The demand for developing sustainable and renewable energy is increasing due to the greenhouse gas effect and the reducing availability of fossil fuels. Wind energy is one of the cleanest and most sustainable renewable resources. People mainly use two types of wind turbines - onshore and offshore, to harvest the wind energy. Compared with onshore wind, offshore wind resources allow more reliable generation of electricity. In shallow water, bottom-fixed turbines may be used. However, as water depths increase it becomes increasingly difficult to build suitable fixed foundations, and floating offshore wind turbines become attractive. The OC3-Hywind is an offshore floating wind turbine (OFWT) supported by a spar platform and held in place with three mooring lines. It is important to study the dynamic responses of the floating platform and the mooring system behaviour so that the OFWT can be designed and constructed safely and economically and generate electricity with reliability. However, there are not many studies which have validated the numerical simulation results for floating offshore wind turbines with physical experiments while published studies rarely show the details of the mooring line motion behaviour for OFWTs. This thesis investigates the dynamic behaviour of a spar-type OFWT including its mooring systems, analysed under various environmental loads both by using state-of-the-art numerical software and conducting an experiment campaign at the Kelvin Hydrodynamics Laboratory. The free decay test has been carried out first to get the spar platform's motions natural frequencies and damping characteristics. A range of regular and irregular waves has been applied to the platform (both with and without realistic mooring lines) to obtain the platform motion RAO (response amplitude operator) - which can be used to predict the platform dynamic responses under other wave conditions - and to examine the reliability of the numerical predictions under realistic sea conditions. For the mooring line tensions and motion, the software shows its limitations in the calculation. A non-linear snatching phenomenon has been observed at the tank for some wave frequencies, which has rarely been discussed in published research. It is very important to study this non-linear behaviour as it is shown that snatching leads to the high instantaneous mooring line loads and platform accelerations, which could cause the failure of the mooring lines in the real structure.
Dynamic Response And Reliability Analysis Of An Offshore Wind Turbine Supported By A Semi Submersible Platform
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Author : Edwin Thomas
language : en
Publisher:
Release Date : 2015
Dynamic Response And Reliability Analysis Of An Offshore Wind Turbine Supported By A Semi Submersible Platform written by Edwin Thomas and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
Wind Energy is the fastest growing renewable energy source in the world. The trend is expected to continue with falling costs of technology, energy security concerns and the need to address environmental issues. Offshore wind turbines have a few important advantages over land-based turbines; offshore sites experience stronger and less turbulent winds, there are fewer negative aesthetic impacts in an offshore location, there is greater ease in the transport of wind turbine components over sea than on land, etc. Large offshore wind turbines mounted atop floating platforms offer a viable solution for deepwater sites. Of the various floating platform concepts that are being considered, a moored semi-submersible platform is considered in this study. The dynamic response and reliability analysis of a 13.2~MW offshore wind turbine supported by a moored semi-submersible platform is the subject of this study. A model for this integrated system has been developed and its various physical, geometric, and dynamic properties have been studied in this and another associated study. Loads data for the extreme and fatigue analysis of such systems are generally attained by running time-domain simulations for a range of sea states that are representative of the expected site-specific metocean conditions. The selected site of interest in the North Sea has a water depth of 200 m. The Environmental Contour (EC) method is used to identify sea states of interest that are associated with a target return period (50 years). These sea states are considered in short-term (1-hour) simulations of the integrated turbine-platform-mooring system. The dynamic behavior of the integrated wind turbine system is studied. Critical sea states for the various response loads are identified and the sensitivity of the system to the metocean conditions is discussed. Estimation of 50-year response levels (for turbine loads, platform motions, and the mooring line tension at the fairlead) associated with the target probability is subsequently carried out using 2D and 3D Inverse First-Order Reliability Method (FORM) approaches.
Impact Of Aerodynamics And Mooring System On Dynamic Response Of Floating Wind Turbines
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Author : Denis Matha
language : en
Publisher:
Release Date : 2017
Impact Of Aerodynamics And Mooring System On Dynamic Response Of Floating Wind Turbines written by Denis Matha and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
Loads Analysis Of Several Offshore Floating Wind Turbine Concepts
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Author :
language : en
Publisher:
Release Date : 2011
Loads Analysis Of Several Offshore Floating Wind Turbine Concepts written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
This paper presents a comprehensive dynamic-response analysis of six offshore floating wind turbine concepts.
Dynamic Response Analysis Of Spar Buoy Floating Wind Turbine Systems
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Author : Sungho Lee (Ph. D.)
language : en
Publisher:
Release Date : 2008
Dynamic Response Analysis Of Spar Buoy Floating Wind Turbine Systems written by Sungho Lee (Ph. D.) and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.
The importance of alternative energy development has been dramatically increased by the dwindling supplies of oil and gas, and our growing efforts to protect our environment. A variety of meaningful steps have been taken in order to come up with cleaner, healthier and more affordable energy alternatives. Wind energy is one of the most reliable energy alternatives for countries that have sufficiently large wind sources. Due to the presence of steady and strong winds, and the distance from coastline residential, the offshore wind farm has become highly attractive as an ideal energy crisis solution. Floating wind turbine systems are being considered as a key solution to make the offshore wind farm feasible from an economic viewpoint, and viable as an energy resource. This paper presents the design of a synthetic mooring system for spar buoy floating wind turbines functioning in shallow water depths. Nacelle acceleration, static and dynamic tensions on catenaries, the maximum tension acting on the anchors are considered as design performances, and a stochastic analysis method has been used to evaluate those quantities based on sea state spectral density functions. The performance at a 100-year hurricane condition is being defined as a limiting case, and a linear wave theory has been the most fundamental theory applied for the present analysis.
Coupled Dynamic Analysis Of Multiple Unit Floating Offshore Wind Turbine
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Author : Yoon Hyeok Bae
language : en
Publisher:
Release Date : 2013
Coupled Dynamic Analysis Of Multiple Unit Floating Offshore Wind Turbine written by Yoon Hyeok Bae and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
In the present study, a numerical simulation tool has been developed for the rotor-floater-tether coupled dynamic analysis of Multiple Unit Floating Offshore Wind Turbine (MUFOWT) in the time domain including aero-blade-tower dynamics and control, mooring dynamics and platform motion. In particular, the numerical tool developed in this study is based on the single turbine analysis tool FAST, which was developed by National Renewable Energy Laboratory (NREL). For linear or nonlinear hydrodynamics of floating platform and generalized-coordinate-based FEM mooring line dynamics, CHARM3D program, hull-riser-mooring coupled dynamics program developed by Prof. M.H. Kim's research group during the past two decades, is incorporated. So, the entire dynamic behavior of floating offshore wind turbine can be obtained by coupled FAST-CHARM3D in the time domain. During the coupling procedure, FAST calculates all the dynamics and control of tower and wind turbine including the platform itself, and CHARM3D feeds all the relevant forces on the platform into FAST. Then FAST computes the whole dynamics of wind turbine using the forces from CHARM3D and return the updated displacements and velocities of the platform to CHARM3D. To analyze the dynamics of MUFOWT, the coupled FAST-CHARM3D is expanded more and re-designed. The global matrix that includes one floating platform and a number of turbines is built at each time step of the simulation, and solved to obtain the entire degrees of freedom of the system. The developed MUFOWT analysis tool is able to compute any type of floating platform with various kinds of horizontal axis wind turbines (HAWT). Individual control of each turbine is also available and the different structural properties of tower and blades can be applied. The coupled dynamic analysis for the three-turbine MUFOWT and five-turbine MUFOWT are carried out and the performances of each turbine and floating platform in normal operational condition are assessed. To investigate the coupling effect between platform and each turbine, one turbine failure event is simulated and checked. The analysis shows that some of the mal-function of one turbine in MUFOWT may induce significant changes in the performance of other turbines or floating platform. The present approach can directly be applied to the development of the remote structural health monitoring system of MUFOWT in detecting partial turbine failure by measuring tower or platform responses in the future. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/149465