Impact of a Wind Turbine Blade Pitch Rate on a Floating Wind Turbine During an Emergency Shutdown Operation

2020 ◽  
Author(s):  
Pauline Louazel ◽  
Daewoong Son ◽  
Bingbin Yu
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Floating Platform ◽  
Floating Structure ◽  
Rapid Variation ◽  
Emergency Shutdown ◽  
Floating Wind Turbine ◽  
Time Period ◽  
Wave Induced ◽  
Loss Of Thrust

Abstract During the shutdown of a wind turbine, the turbine blades rotate from their typical operating angle to their typical idling angle (approximately 90 degrees) at a specific speed, called the blade pitch rate. This operation leads to rapid loss of thrust force on the turbine resulting in a corresponding heel response of the floating structure. This rapid variation of loads at the turbine also leads to large nacelle accelerations which are transferred to the bottom of the tower and consequently to the floating structure, making the turbine shutdowns, and specifically emergency shutdowns, of significance in the design and certification of the turbine, tower and floating structure. In case of an emergency shutdown (for instance due to a grid loss), the blades typically pitch from 0 degree to 90 degrees in approximately 20–35 seconds, whereas this time period can be more than 100 seconds in the case of a normal shutdown [6]. For fixed-bottom wind turbines, increasing the blade pitch rate leads to an increase of instantaneous loads at the nacelle and tower, leading to the emergency shutdown pitch rate being usually chosen to be as low as possible. In the case of a floating wind turbine, however, water/platform interaction effects such as wave induced damping on the floating platform, challenge this approach. Indeed, increasing the blade pitch rate can increase the effect of wave-induced damping on the floater and therefore reduce the loads on the overall structure. On the other hand, reducing the blade pitch rate during an emergency shutdown can reduce this damping effect and increase those loads, meaning that an optimal blade pitch rate for a fixed bottom turbine is not necessarily optimal for a floating wind turbine. This paper will examine the behavior of a floating offshore semi-submersible platform, the WindFloat, during turbine shutdown operations, with an emphasis on the blade pitch rate during an emergency shutdown.

Experimental Validation of a Wave Elevation Observer on a Floating Wind Turbine Model

2021 ◽  
Author(s):  
Simone Di Carlo ◽  
Alessandro Fontanella ◽  
Alan Facchinetti ◽  
Sara Muggiasca ◽  
Federico Taruffi ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Experimental Validation ◽  
Control Strategies ◽  
Estimation Procedure ◽  
Floating Platform ◽  
Experimental Campaign ◽  
Wave Elevation ◽  
Floating Wind Turbine ◽  
Wave Basin ◽  
Turbine Model

Abstract The scope of this work is to investigate if and how it is possible to estimate the incident wave elevation on a floating wind turbine, with the purpose of improved control strategies. A Kalman based algorithm is proposed, which receives as input the rigid motions of the floater and estimates the wave elevation hitting the floating platform. The structure of the observer is described and the estimator is tested numerically on the OC3-Hywind platform coupled with the 5-MW reference wind turbine from NREL. Limitations to the estimation procedure are discussed. Finally the algorithm is tested on experimental data coming from a wave basin experimental campaign on a floating wind turbine model. The algorithm still needs improvements, but results are encouraging in the development of this technology.

Progressive Drifting of Floating Wind Turbines in a Wind Farm

2009 ◽  
Author(s):  
Hideyuki Suzuki ◽  
Masaru Kurimoto ◽  
Yu Kitahara ◽  
Yukinari Fukumoto
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Farm ◽  
Wind Farms ◽  
Floating Platform ◽  
Allowable Limit ◽  
Main Research ◽  
Analysis And Design ◽  
Floating Wind Turbine ◽  
Wide Range

A wide range of platform types have been investigated for a floating wind turbine. Most of the research projects on a floating wind turbine assume that a land based wind turbine is to be installed on a platform with minimum modification to reduce the overall cost. For this reason, allowable limit of a motion of wind turbine is limited to lower value, for example, five degrees for static inclination and one to two degrees for pitching motion. So far analysis and design of motion characteristics of the platform have been main research concern. One key research area less focused is floating platform related risk. If the wind energy would be one of the major sources of power supply, wind farms which are comprised of large number of floating wind turbines must be deployed in the ocean. Wind turbines will be closely spaced in a wind farm so that installation cost should be minimized. In such an arrangement, a wind turbine accidentally started drifting has some possibility to collide or contact with the moorings of neighboring wind turbines and might cause progressive drifting of wind turbines. This paper present investigation of scenario of progressive drifting of floating wind turbines and evaluate risk of the scenario. Quantitative risk of several arrangements of wind farms is estimated. Effect of arrangement of wind turbines in a wind farm and safety factor used in design moorings is discussed.

Short and Long Term Extreme Reliability Analysis Applied to Floating Wind Turbine Design

2011 ◽  
Author(s):  
Timothe´e Perdrizet ◽  
Daniel Averbuch
Keyword(s):  
Wind Turbine ◽  
International Energy Agency ◽  
Energy Agency ◽  
Floating Wind Turbine ◽  
Extreme Response ◽  
Short And Long Term ◽  
Turbine Design ◽  
Wave Induced

This paper describes and exemplifies an efficient methodology to assess, jointly and in a single calculation, the short and long terms failure probabilities associated to the extreme response of a floating wind turbine, subjected to wind and wave induced loads. This method is applied to the realistic case study OC3-Hywind used in phase IV of the IEA (International Energy Agency) Annex XXIII Offshore Code Comparison Collaboration. The key point of the procedure, derived from the outcrossing approach, consists in computing the mean of the outcrossing rate of the floating wind turbine response in the failure domain over both the short term variables and the ergodic variables defining long term parameters.

Modelling the Aerodynamics of a Floating Wind Turbine Model Using a CFD-Based Actuator Disc Method

2019 ◽  
Author(s):  
Ryan Bezzina ◽  
Tonio Sant ◽  
Daniel Micallef
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Speed Ratio ◽  
Offshore Wind Turbine ◽  
Floating Platform ◽  
Blade Element Theory ◽  
Floating Wind Turbine ◽  
Actuator Disc ◽  
Turbine Wake ◽  
Blade Element

Abstract Significant research in the field of Floating Offshore Wind Turbine (FOWT) rotor aerodynamics has been documented in literature, including validated aerodynamic models based on Blade Element Momentum (BEM) and vortex methods, amongst others. However, the effects of platform induced motions on the turbine wake development downstream of the rotor plane or any research related to such areas is rather limited. The aims of this paper are two-fold. Initially, results from a CFD-based Actuator Disc (AD) code for a fixed (non-surging) rotor are compared with those obtained from a Blade Element Momentum (BEM) theory, as well as previously conducted experimental work. Furthermore, the paper also emphasises the effect of tip speed ratio (TSR) on the rotor efficiency. This is followed by the analysis of floating wind turbines specifically in relation to surge displacement, through an AD technique implemented in CFD software, ANSYS Fluent®. The approach couples the Blade Element Theory (BET) for estimating rotating blade loads with a Navier Stokes solver to simulate the turbine wake. With regards to the floating wind turbine cases, the code was slightly altered such that BET was done in a transient manner i.e. following sinusoidal behaviour of waves. The AD simulations were performed for several conditions of TSRs and surge frequencies, at a constant amplitude. Similar to the fixed rotor analysis, significant parameters including thrust and power coefficients, amongst others, were studied against time and surge position. The floating platform data extracted from the AD approach was compared to the non-surging turbine data obtained, to display platform motion effects clearly. Data from hot wire near wake measurements and other simulation methods were also consulted.

Effect of Nacelle Drag on the Performance of a Floating Wind Turbine Platform

2019 ◽  
Author(s):  
Daewoong Son ◽  
Pauline Louazel ◽  
Bingbin Yu
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Simulation Tool ◽  
Floating Structure ◽  
Drag Forces ◽  
Floating Wind Turbine

Abstract Wind forces acting on an offshore wind turbine are transferred to the bottom of the tower and consequently to the floating structure. Thus, drag forces acting on each component of the wind turbine such as the blades, the nacelle, and the tower must be accounted for properly in order to evaluate the performance of the supporting platform. In the aero-elastic wind turbine simulation tool FAST v.7, the nacelle drag component, however, has not been implemented, which means that only the drag forces on the tower and on the blades are represented. In this work, the front and side nacelle drag forces are modelled in FAST v.7 via different drag contributions. This paper will examine the behavior of a floating offshore semisubmersible platform, the WindFloat, for different Rotor-Nacelle-Assembly (RNA) yaw-misalignments with emphasis on the nacelle drag component.

Coupled Aerodynamic and Hydroelastic Analysis of an Offshore Floating Wind Turbine System Under Wind and Wave Loads

2010 ◽  
Author(s):  
Kazuhiro Iijima ◽  
Junghyun Kim ◽  
Masahiko Fujikubo
Keyword(s):  
Wind Turbine ◽  
Time Domain ◽  
Response Analysis ◽  
Wave Loads ◽  
Structural System ◽  
Floating Structure ◽  
Floating Wind Turbine ◽  
Wind Turbine System ◽  
Offshore Floating Wind Turbine ◽  
The Impact

A numerical procedure for the fully coupled aerodynamic and hydroelastic time-domain analysis of an offshore floating wind turbine system including rotor blade dynamics, dynamic motions and flexible deflections of the structural system is illustrated. For the aerodynamic analysis of wind turbine system, a design code FAST developed by National Renewable Energy Laboratory (NREL) is employed. It is combined with a time-domain hydroelasticity response analysis code ‘Shell-Stress Oriented Dynamic Analysis Code (SSODAC)’ which has been developed by one of the authors. Then, the dynamic coupling between the rotating blades and the structural system under wind and wave loads is taken into account. By using this method, a series of analysis for the hydroelastic response of an offshore large floating structure with two rotors under combined wave and wind loads is performed. The results are compared with those under the waves and those under the winds, respectively, to investigate the coupled effects in terms of stress as well as motions. The coupling effects between the rotor-blades and the motions are observed in some cases. The impact on the structural design of the floating structure, tower and blade is addressed.

The unsteady aerodynamics of floating wind turbine under platform pitch motion

2018 ◽  
Vol 232 (8) ◽  
pp. 1019-1036 ◽  
Author(s):  
Xin Shen ◽  
Ping Hu ◽  
Jinge Chen ◽  
Xiaocheng Zhu ◽  
Zhaohui Du
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Degrees Of Freedom ◽  
Unsteady Aerodynamics ◽  
Aerodynamic Performance ◽  
Floating Platform ◽  
Pitch Motion ◽  
Floating Wind Turbine ◽  
Fixed Base ◽  
Turbine Rotors

The aerodynamic performance of floating platform wind turbines is much more complex than fixed-base wind turbines because of the flexibility of the floating platform. Due to the extra six degrees-of-freedom of the floating platform, the inflow of the wind turbine rotors is highly influenced by the motions of the floating platform. It is therefore of interest to study the unsteady aerodynamics of the wind turbine rotors involved with the interaction of the floating platform induced motions. In the present work, a lifting surface method with a free wake model is developed for analysis of the unsteady aerodynamics of wind turbines. The aerodynamic performance of the NREL 5 MW floating wind turbine under the prescribed floating platform pitch motion is studied. The unsteady aerodynamic loads, the transient of wind turbine states, and the instability of the wind turbine wakes are discussed in detail.

scholarly journals On Tower Top Axial Acceleration and Drivetrain Responses in a Spar-Type Floating Wind Turbine

2017 ◽  
Author(s):  
Amir Rasekhi Nejad ◽  
Erin E. Bachynski ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Global Analysis ◽  
Correlation Study ◽  
Analysis Tool ◽  
Maximum Acceleration ◽  
Peak Period ◽  
Floating Wind Turbine ◽  
Axial Acceleration ◽  
Northern North Sea ◽  
Wave Induced

Common industrial practice for designing floating wind turbines is to set an operational limit for the tower-top axial acceleration, normally in the range of 0.2–0.3g, which is typically understood to be related to the safety of turbine components. This paper investigates the rationality of the tower-top acceleration limit by evaluating the correlation between acceleration and drivetrain responses. A 5 MW reference drivetrain is selected and modelled on a spar-type floating wind turbine in 320 m water depth. A range of environmental conditions are selected based on the long-term distribution of wind speed, significant wave height, and peak period from hindcast data for the Northern North Sea. For each condition, global analysis using an aero-hydro-servo-elastic tool is carried out for six one-hour realizations. The global analysis results provide useful information on their own — regarding the correlation between environmental condition and tower top acceleration, and correlation between tower top acceleration and other responses of interest — which are used as input in a decoupled analysis approach. The load effects and motions from the global analysis are applied on a detailed drivetrain model in a multi-body system (MBS) analysis tool. The local responses on bearings are then obtained from MBS analysis and post-processed for the correlation study. Although the maximum acceleration provides a good indication of the wave-induced loads, it is not seen to be a good predictor for significant fatigue damage on the main bearings in this case.

VolturnUS 1:8-Scale FRP Floating Wind Turbine Tower: Analysis, Design, Testing and Performance

2014 ◽  
Author(s):  
Andrew C. Young ◽  
Steve Hettick ◽  
Habib J. Dagher ◽  
Anthony M. Viselli ◽  
Andrew J. Goupee
Keyword(s):  
Wind Turbine ◽  
The United States ◽  
Pilot Scale ◽  
Full Scale ◽  
Lessons Learned ◽  
Offshore Wind ◽  
Floating Platform ◽  
Floating Wind Turbine ◽  
Wind Turbine Tower ◽  
Analysis Design

In May of 2013 the VolturnUS 1:8 floating semi-submersible wind turbine was successfully deployed off the coast of Castine, Maine, making the unit the first grid connected offshore turbine in the United States. The VolturnUS 1:8 structure features a 20 kW turbine, a post-tensioned and reinforced concrete semi-submersible base and a fiber reinforced plastic (FRP) tower (E-glass and polyester resin). The VolturnUS 1:8 structure is a geometrically 1:8-scale of a 6 MW floating turbine design and is used to demonstrate the feasibility of both the concrete base and FRP tower and validate the performance of the structure in a scaled environment. Data collected from the deployed 1:8-scale structure will be used for modeling and simulating the behavior of the system at full-scale. The effort was led by the University of Maine’s Advanced Structures and Composites Center (UMaine) and a consortium of industry partners, including FRP manufacturer Ershigs, Inc. An overview of the process and methodology used in the analysis, design and testing of the 1:8 scale FRP floating wind turbine tower is presented. The use of an FRP tower on a floating wind turbine platform offers the benefits of reduced tower mass and maintenance requirements and has the potential to further reduce hull mass by lowering the global center of gravity of the structure. An FRP tower for use on the UMaine semi-submersible concrete VolturnUS 1:8 platform was developed that meets all strength and serviceability criteria and is robust enough to withstand the loading from both wind and waves. An overview of the tower loads analysis and FAST modeling, tower structural design, structural proof testing and preliminary analysis of performance are presented. The VolturnUS 1:8 wind turbine tower is the first time FRP materials have been used in an offshore wind tower application. Further, the methodologies and procedures that were developed in the design of the pilot-scale tower are directly applicable to the design and analysis of composite wind turbine towers at the full-scale level. These “lessons learned” are already in use as Ershigs and UMaine work to design a full-scale composite tower over 80 meters tall for use on the VolturnUS platform with a 6MW wind turbine. The results of the 1:8-scale program demonstrate the successful use of an FRP wind turbine tower on a floating platform and highlights the potential for the use of an FRP tower at the full-scale (6 MW) level.

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