Experimental Study for SPAR Type Floating Offshore Wind Turbine With Blade-Pitch Control

The experimental proof of the floating wind turbine has been started off Goto Islands in Japan. Furthermore, the project of floating wind farm is afoot off Fukushima Prof. in north eastern part of Japan. It is essential for realization of the floating wind farm to comprehend its safety, electric generating property and motion in waves and wind. The scale model experiments are effective to catch the characteristic of floating wind turbines. Authors have mainly carried out scale model experiments with wind turbine models on SPAR buoy type floaters. The wind turbine models have blade-pitch control mechanism and authors focused attention on the effect of blade-pitch control on both the motion of floater and fluctuation of rotor speed. In this paper, the results of scale model experiments are discussed from the aspect of motion of floater and the effect of blade-pitch control.

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Study on the Dynamic Response for Floating Foundation of Offshore Wind Turbine

Volume 5: Ocean Space Utilization; Ocean Renewable Energy ◽

10.1115/omae2011-50329 ◽

2011 ◽

Author(s):

Yougang Tang ◽

Jun Hu ◽

Liqin Liu

Keyword(s):

Wind Turbine ◽

Wind Farm ◽

Dynamic Responses ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Wave Load ◽

Mooring Lines ◽

Floating Foundation ◽

Wind Turbine System ◽

Sea Area

The wind resources for ocean power generation are mostly distributed in sea areas with the distance of 5–50km from coastline, whose water depth are generally over 20m. To improve ocean power output and economic benefit of offshore wind farm, it is necessary to choose floating foundation for offshore wind turbine. According to the basic data of a 600kW wind turbine with a horizontal shaft, the tower, semi-submersible foundation and mooring system are designed in the 60-meter-deep sea area. Precise finite element models of the floating wind turbine system are established, including mooring lines, floating foundation, tower and wind turbine. Dynamic responses for the floating foundation of offshore wind turbine are investigated under wave load in frequency domain.

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Fatigue Life Analysis of Offshore Wind Turbine Support Structures in an Offshore Wind Farm

ASME 2018 1st International Offshore Wind Technical Conference ◽

10.1115/iowtc2018-1061 ◽

2018 ◽

Author(s):

Bryan Nelson ◽

Yann Quéméner

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Wind Farm ◽

The Body ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Analysis Tool ◽

Support Structures ◽

Offshore Wind Farm ◽

Actuator Disk

This study evaluated, by time-domain simulations, the fatigue lives of several jacket support structures for 4 MW wind turbines distributed throughout an offshore wind farm off Taiwan’s west coast. An in-house RANS-based wind farm analysis tool, WiFa3D, has been developed to determine the effects of the wind turbine wake behaviour on the flow fields through wind farm clusters. To reduce computational cost, WiFa3D employs actuator disk models to simulate the body forces imposed on the flow field by the target wind turbines, where the actuator disk is defined by the swept region of the rotor in space, and a body force distribution representing the aerodynamic characteristics of the rotor is assigned within this virtual disk. Simulations were performed for a range of environmental conditions, which were then combined with preliminary site survey metocean data to produce a long-term statistical environment. The short-term environmental loads on the wind turbine rotors were calculated by an unsteady blade element momentum (BEM) model of the target 4 MW wind turbines. The fatigue assessment of the jacket support structure was then conducted by applying the Rainflow Counting scheme on the hot spot stresses variations, as read-out from Finite Element results, and by employing appropriate SN curves. The fatigue lives of several wind turbine support structures taken at various locations in the wind farm showed significant variations with the preliminary design condition that assumed a single wind turbine without wake disturbance from other units.

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Mooring Line Damping Estimation for a Floating Wind Turbine

The Scientific World JOURNAL ◽

10.1155/2014/840283 ◽

2014 ◽

Vol 2014 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Dongsheng Qiao ◽

Jinping Ou

Keyword(s):

Wind Turbine ◽

Estimation Method ◽

Excitation Amplitude ◽

Dynamic Responses ◽

Offshore Wind ◽

Scale Model ◽

Mooring Line ◽

Offshore Wind Turbine ◽

Floating Wind Turbine ◽

Excitation Period

The dynamic responses of mooring line serve important functions in the station keeping of a floating wind turbine (FWT). Mooring line damping significantly influences the global motions of a FWT. This study investigates the estimation of mooring line damping on the basis of the National Renewable Energy Laboratory 5 MW offshore wind turbine model that is mounted on the ITI Energy barge. A numerical estimation method is derived from the energy absorption of a mooring line resulting from FWT motion. The method is validated by performing a 1/80 scale model test. Different parameter changes are analyzed for mooring line damping induced by horizontal and vertical motions. These parameters include excitation amplitude, excitation period, and drag coefficient. Results suggest that mooring line damping must be carefully considered in the FWT design.

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A Comparison of Time Domain Seismic Analysis Methods for Offshore Wind Turbine Structures: Using a Superelement Approach

ASME 2019 2nd International Offshore Wind Technical Conference ◽

10.1115/iowtc2019-7562 ◽

2019 ◽

Author(s):

Laurens Alblas ◽

Corine de Winter

Keyword(s):

Rigid Body ◽

Wind Turbine ◽

Time Domain ◽

Wind Farm ◽

Assessment Tool ◽

Seismic Analysis ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Rigid Body Motions ◽

Seismic Accelerations

Abstract Recently, wind farm development has gained more traction in Asian countries such as Taiwan, which are seismically active. Compared to Europe, the offshore wind structures need to be designed for these additional extreme environmental conditions. For monopiles, these calculations can typically be performed in an integrated way in the wind turbine load calculation, but for jackets the superelement (SE) approach remains preferred. At the time of writing different approaches are being applied in the industry to apply the SE approach for seismic time domain analysis. This work explains and compares three different methods, based on calculations performed in offshore strength assessment tool Sesam and aeroelastic tool BHawC. When including additional interface nodes at the foundation model bottom into the SE to which the seismic accelerations can be applied in BHawC similarly as in the re-tracking run in Sesam, the results between BHawC and Sesam are nearidentical. Using a normal SE, which only includes an interface node for the connection to the wind turbine tower bottom, and including the response due to seismic displacements into the SE load file gives a match between BHawC and Sesam, and closely matches the results of the case with additional interface nodes. Doing the same but only including the dynamic response of the interface point relative to a frame of reference moving with the rigid body motions as caused by the seismic accelerations into the SE load file, significant differences occur. This is due to the lack of the loading effect of rigid body motions. The same conclusions on how these methods compare can be drawn when using different wind and wave cases. The presented results give insights into the differences between the methods and how the choice of method may influence the results.

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Machine Learning Control for Floating Offshore Wind Turbine Individual Blade Pitch Control

2020 American Control Conference (ACC) ◽

10.23919/acc45564.2020.9147912 ◽

2020 ◽

Author(s):

Michael B. Kane

Keyword(s):

Machine Learning ◽

Wind Turbine ◽

Learning Control ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Floating Offshore Wind Turbine ◽

Pitch Control

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Study of Floating Wind Turbine with Modified Tension Leg Platform Placed in Regular Waves

Energies ◽

10.3390/en12040703 ◽

2019 ◽

Vol 12 (4) ◽

pp. 703 ◽

Cited By ~ 3

Author(s):

Juhun Song ◽

Hee-Chang Lim

Keyword(s):

Wind Turbine ◽

Real Data ◽

Offshore Wind ◽

Scale Model ◽

Offshore Wind Turbine ◽

Wave Loads ◽

Tension Leg Platform ◽

Mooring Lines ◽

Floating Wind Turbine ◽

Wave Conditions

In this study, the typical ocean environment was simulated with the aim to investigate the dynamic response under various environmental conditions of a Tension Leg Platform (TLP) type floating offshore wind turbine system. By applying Froude scaling, a scale model with a scale of 1:200 was designed and model experiments were carried out in a lab-scale wave flume that generated regular periodic waves by means of a piston-type wave generator while a wave absorber dissipated wave energy on the other side of the channel. The model was designed and manufactured based on the standard prototype of the National Renewable Energy Laboratory (NREL) 5 MW offshore wind turbine. In the first half of the study, the motion and structural responses for operational wave conditions of the North Sea near Scotland were considered to investigate the performance of a traditional TLP floating wind turbine compared with that of a newly designed TLP with added mooring lines. The new mooring lines were attached with the objective of increasing the horizontal stiffness of the system and thereby reducing the dominant motion of the TLP platform (i.e., the surge motion). The results of surge translational motions were obtained both in the frequency domain, using the response amplitude operator (RAO), and in the time domain, using the omega arithmetic method for the relative velocity. The results obtained show that our suggested concept improves the stability of the platform and reduces the overall motion of the system in all degrees-of-freedom. Moreover, the modified design was verified to enable operation in extreme wave conditions based on real data for a 100-year return period of the Northern Sea of California. The loads applied by the waves on the structure were also measured experimentally using modified Morison equation—the formula most frequently used to estimate wave-induced forces on offshore floating structures. The corresponding results obtained show that the wave loads applied on the new design TLP had less amplitude than the initial model and confirmed the significant contribution of the mooring lines in improving the performance of the system.

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Estimation of Risk of Progressive Drifts in a Wind Farm Caused by Collision of Drift Ship

Volume 6: Ocean Space Utilization ◽

10.1115/omae2015-41473 ◽

2015 ◽

Author(s):

Eiji Hirokawa ◽

Hideyuki Suzuki ◽

Shinichiro Hirabayashi ◽

Minon Muratake

Keyword(s):

Wind Turbine ◽

Wind Farm ◽

Offshore Wind ◽

Mooring Line ◽

Offshore Wind Turbine ◽

Mooring System ◽

Environmental Load ◽

Collision Process ◽

Tank Experiment ◽

Estimation Of Risk

In off-shore wind turbine, it is difficult to determine the risk of accident caused by the mooring destruction through experiment. In this paper, the authors discuss the risk, with the case of a drifting ship wanders into the wind farm. In the design of a floating offshore wind turbine (FOWT), drift of a FOWT is considered as a serious failure mode and the mooring system must be designed to avoid the failure. The failure of mooring line is not initiated just by extreme environmental load but can be initiated by collision with a drifting ship, which enters the wind farm. This phenomenon is difficult to investigate by a tank experiment. So far, little knowledge exists about the phenomenon. In this research, a simulator to reproduce the collision process of a FOWT and a drift ship and a progressive drift of FOWTs in a wind farm was developed. Using this simulator and statistics of drift incidents of a ship, a procedure to evaluate risk of progressive drifts in a wind farm was established. In that case, second accident that a wind turbine which has started drifting caused by the drifting ship collides with one another wind turbine is expected. As a result, the risk mainly depends on the risk of drifting caused by a large displaced ship. In addition, the risk partly depends on the arrangement of wind farm.

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