Response-Based Assessment of Operational Limits for Mating Blades on Monopile-Type Offshore Wind Turbines

Installation of wind-turbine blades on monopile-type offshore wind turbines is a demanding task. Typically, a jack-up crane vessel is used, and blades are individually lifted from the vessel deck and docked with the preinstalled hub. During the process of mating, large relative motions are developed between the hub and root due to combined effects of wind-generated blade-root responses and wave-generated monopile vibrations. This can cause impact loads at the blade root and induce severe damages at the blade-root connection. Such events are highly likely to cause the failure of the mating task, while affecting the subsequent activities, and thus require competent planning. The purpose of this paper is to present a probabilistic response-based methodology for estimating the allowable sea states for planning a wind-turbine blade-mating task, considering impact risks with the hub as the hazardous event. A case study is presented where the installation system consisting of blade-lift and monopile system are modelled using multibody formulations. Time-domain analyses are carried out for various sea states, and impact velocities between root and hub are analyzed. Finally, an extreme value analysis using the Gumbel fitting of response parameters is performed and limiting sea state curves are obtained by comparing characteristic extreme responses with allowable values. It is found that the limiting sea states for blade-root mating tasks are low for aligned wind–wave conditions, and further increase with increased wind–wave misalignment. The results of the study also show that the parameter T p is essential for estimating limiting sea states given that this parameter significantly influences monopile vibrations during the blade-root mating task. Overall, the findings of the study can be used for a safer and more cost-effective mating of wind-turbine blades.

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A Review of Recent Advancements in Offshore Wind Turbine Technology

Energies ◽

10.3390/en15020579 ◽

2022 ◽

Vol 15 (2) ◽

pp. 579

Author(s):

Taimoor Asim ◽

Sheikh Zahidul Islam ◽

Arman Hemmati ◽

Muhammad Saif Ullah Khalid

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Structural Integrity ◽

Turbine Blades ◽

Offshore Wind ◽

System Level ◽

Offshore Wind Turbine ◽

Component Level ◽

Foundation Design ◽

Offshore Wind Turbines

Offshore wind turbines are becoming increasingly popular due to their higher wind energy harnessing capabilities and lower visual pollution. Researchers around the globe have been reporting significant scientific advancements in offshore wind turbines technology, addressing key issues, such as aerodynamic characteristics of turbine blades, dynamic response of the turbine, structural integrity of the turbine foundation, design of the mooring cables, ground scouring and cost modelling for commercial viability. These investigations range from component-level design and analysis to system-level response and optimization using a multitude of analytical, empirical and numerical techniques. With such wide-ranging studies available in the public domain, there is a need to carry out an extensive yet critical literature review on the recent advancements in offshore wind turbine technology. Offshore wind turbine blades’ aerodynamics and the structural integrity of offshore wind turbines are of particular importance, which can lead towards system’s optimal design and operation, leading to reduced maintenance costs. Thus, in this study, our focus is to highlight key knowledge gaps in the scientific investigations on offshore wind turbines’ aerodynamic and structural response. It is envisaged that this study will pave the way for future concentrated efforts in better understanding the complex behavior of these machines.

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Wind/Wave Misalignment Effects on Mooring Line Tensions for a Spar Buoy Wind Turbine

Volume 1: Offshore Technology ◽

10.1115/omae2018-77586 ◽

2018 ◽

Cited By ~ 1

Author(s):

Luigia Riefolo ◽

Fernando del Jesus ◽

Raúl Guanche García ◽

Giuseppe Roberto Tomasicchio ◽

Daniela Pantusa

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Wind Wave ◽

Offshore Wind ◽

Mooring Line ◽

Ultimate Limit State ◽

International Electrotechnical Commission ◽

Wave Loads ◽

Offshore Wind Turbines ◽

Floating Offshore Wind Turbines

The design methodology for mooring systems for a spar buoy wind turbine considers the influence of extreme events and wind/wave misalignments occurring in its lifetime. Therefore, the variety of wind and wave directions affects over the seakeeping and as a result the evaluation of the maxima loads acting on the spar-buoy wind turbine. In the present paper, the importance of wind/wave misalignments on the dynamic response of spar-type floating wind turbine [1] is investigated. Based on standards, International Electrotechnical Commission IEC and Det Norske Veritas DNV the design of position moorings should be carried out under extreme wind/wave loads, taking into account their misalignments with respect to the structure. In particular, DNV standard, in ‘Position mooring’ recommendations, specifies in the load cases definition, if site specific data is not available, to consider non-collinear environment to have wave towards the unit’s bow (0°) and wind 30° relative to the waves. In IEC standards, the misalignment of the wind and wave directions shall be considered to design offshore wind turbines and calculate the loads acting on the support structure. Ultimate Limit State (ULS) analyses of the OC3-Hywind spar buoy wind turbine are conducted through FAST code, a certified nonlinear aero-hydro-servo-elastic simulation tool by the National Renewable Energy Laboratory’s (NREL’s). This software was developed for use in the International Energy Agency (IEA) Offshore Code Comparison Collaborative (OC3) project, and supports NREL’s offshore 5-MW baseline turbine. In order to assess the effects of misaligned wind and wave, different wind directions are chosen, maintaining the wave loads perpendicular to the structure. Stochastic, full-fields, turbulence simulator Turbsim is used to simulate the 1-h turbulent wind field. The scope of the work is to investigate the effects of wind/wave misalignments on the station-keeping system of spar buoy wind turbine. Results are presented in terms of global maxima determined through mean up-crossing with moving average, which, then, are modelled by a Weibull distribution. Finally, extreme values are estimated depending on global maxima and fitted on Gumbel distribution. The Most Probable Maximum value of mooring line tensions is found to be influenced by the wind/wave misalignments. The present paper is organized as follows. Section ‘Introduction’, based on a literature study, gives useful information on the previous studies conducted on the wind/wave misalignments effects of floating offshore wind turbines. Section ‘Methodology’ describes the applied methodology and presents the spar buoy wind turbine, the used numerical model and the selected environmental conditions. Results and the corresponding discussion are given in Section ‘Results and discussion’ for each load case corresponding to the codirectional and misaligned wind and wave loads. Results are presented and discussed in time and frequency domains. Finally, in Section ‘Conclusion’ some conclusions are drawn.

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A Fully Coupled Computational Fluid Dynamics Method for Analysis of Semi-Submersible Floating Offshore Wind Turbines Under Wind-Wave Excitation Conditions Based on OC5 Data

Applied Sciences ◽

10.3390/app8112314 ◽

2018 ◽

Vol 8 (11) ◽

pp. 2314 ◽

Cited By ~ 5

Author(s):

Yin Zhang ◽

Bumsuk Kim

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Wind Turbine ◽

Wind Turbines ◽

Wind Wave ◽

Offshore Wind ◽

Wave Excitation ◽

Offshore Wind Turbines ◽

Floating Offshore Wind Turbines ◽

Fully Coupled

Accurate prediction of the time-dependent system dynamic responses of floating offshore wind turbines (FOWTs) under aero-hydro-coupled conditions is a challenge. This paper presents a numerical modeling tool using commercial computational fluid dynamics software, STAR-CCM+(V12.02.010), to perform a fully coupled dynamic analysis of the DeepCwind semi-submersible floating platform with the National Renewable Engineering Lab (NREL) 5-MW baseline wind turbine model under combined wind–wave excitation environment conditions. Free-decay tests for rigid-body degrees of freedom (DOF) in still water and hydrodynamic tests for a regular wave are performed to validate the numerical model by inputting gross system parameters supported in the Offshore Code Comparison, Collaboration, Continued, with Correlations (OC5) project. A full-configuration FOWT simulation, with the simultaneous motion of the rotating blade due to 6-DOF platform dynamics, was performed. A relatively heavy load on the hub and blade was observed for the FOWT compared with the onshore wind turbine, leading to a 7.8% increase in the thrust curve; a 10% decrease in the power curve was also observed for the floating-type turbines, which could be attributed to the smaller project area and relative wind speed required for the rotor to receive wind power when the platform pitches. Finally, the tower-blade interference effects, blade-tip vortices, turbulent wakes, and shedding vortices in the fluid domain with relatively complex unsteady flow conditions were observed and investigated in detail.

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A Coupled CFD/Multibody Dynamics Analysis Tool for Offshore Wind Turbines With Aeroelastic Blades

Volume 10: Ocean Renewable Energy ◽

10.1115/omae2017-61062 ◽

2017 ◽

Cited By ~ 1

Author(s):

Yuanchuan Liu ◽

Qing Xiao ◽

Atilla Incecik

Keyword(s):

Wind Turbine ◽

Multibody Dynamics ◽

Wind Turbines ◽

Large Scale ◽

Turbine Blades ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Analysis Tool ◽

Dynamics Analysis ◽

Offshore Wind Turbines

Aero-elasticity is an important issue for modern large scale offshore wind turbines with long slender blades. The behaviour of deformable turbine blades influences the structure stress and thus the sustainability of blades under large unsteady wind loads. In this paper, we present a fully coupled CFD/MultiBody Dynamics analysis tool to examine this problem. The fluid flow around the turbine is solved using a high-fidelity CFD method while the structural dynamics of flexible blades is predicted using an open source code MBDyn, in which the flexible blades are modelled via a series of beam elements. Firstly, a flexible cantilever beam is simulated to verify the developed tool. The NREL 5 MW offshore wind turbine is then studied with both rigid and flexible blades to analyse the aero-elastic influence on the wind turbine structural response and aerodynamic performance. Comparison is also made against the publicly available data.

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Structural damping sensitivity affecting the flutter performance of a 10-MW offshore wind turbine

Advances in Structural Engineering ◽

10.1177/1369433220927260 ◽

2020 ◽

Vol 23 (14) ◽

pp. 3037-3047

Author(s):

Xugang Hua ◽

Qingshen Meng ◽

Bei Chen ◽

Zili Zhang

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Turbine Blades ◽

Three Dimensional ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Delay Model ◽

Structural Damping ◽

Torsional Mode ◽

Offshore Wind Turbines

Classical flutter of wind turbine blades is one of the most destructive instability phenomena of wind turbines especially for several-MW-scale turbines. In the present work, flutter performance of the DTU 10-MW offshore wind turbine is investigated using a 907-degree-of-freedom aero-hydro-servo-elastic wind turbine model. This model involves the couplings between tower, blades and drivetrain vibrations. Furthermore, the three-dimensional aerodynamic effects on wind turbine blade tip have also been considered through the blade element momentum theory with Bak’s stall delay model and Shen’s tip loss correction model. Numerical simulations have been carried out using data calibrated to the referential DTU 10-MW offshore wind turbine. Comparison of the aeroelastic responses between the onshore and offshore wind turbines is made. Effect of structural damping on the flutter speed of this 10-MW offshore wind turbine is investigated. Results show that the damping in the torsional mode has predominant impact on the flutter limits in comparison with that in the bending mode. Furthermore, for shallow water offshore wind turbines, hydrodynamic loads have small effects on its aeroelastic response.

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The use of wind turbines and the problem of icing

Wind Engineering ◽

10.1177/0309524x21998270 ◽

2021 ◽

pp. 0309524X2199827

Author(s):

Cevahir Tarhan ◽

Mehmet Ali Çil

Keyword(s):

Wind Energy ◽

Wind Turbines ◽

Energy Demand ◽

Power Plants ◽

Turbine Blades ◽

Offshore Wind ◽

Wind Turbine Blades ◽

Offshore Wind Turbines ◽

Wind Power Plants ◽

The World

The world’s energy demand is increasing. Wind energy plays an important role in meeting this demand. Investments in wind energy have been increasing in recent years. It can be said that the source of wind energy will be unlimited since there will be wind as long as there is sun. Most governments meet a large energy need by generating electricity from wind. At the end of 2019, the total amount of electricity generated from wind was 650 GW. Wind energy capacity is increasing with offshore wind pairs. Offshore wind turbines are a new field and research studies are ongoing. Wind turbines have the capacity to be installed anywhere in the world, and each government will have its own energy source. There is a problem of icing in wind power plants installed in cold climates. With this problem, efficiency in wind turbines decreases. Many methods have been found and developed in studies on icing problems. In this article, wind turbines were investigated, states’ perspectives on wind energy, developments and investments in wind energy, and the problem of icing were examined. Many articles in the literature have been reviewed and a solution to the icing problem of wind turbine blades has been sought.

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A Summary of the Recent Work at NTNU on Marine Operations Related to Installation of Offshore Wind Turbines

Volume 11A: Honoring Symposium for Professor Carlos Guedes Soares on Marine Technology and Ocean Engineering ◽

10.1115/omae2018-78334 ◽

2018 ◽

Author(s):

Zhen Gao ◽

Amrit Verma ◽

Yuna Zhao ◽

Zhiyu Jiang ◽

Zhengru Ren

Keyword(s):

Wind Turbine ◽

Recent Work ◽

Wind Turbines ◽

Turbine Blades ◽

Dynamic Responses ◽

Offshore Wind ◽

Structural Safety ◽

Offshore Wind Turbines ◽

Global Dynamic ◽

Contact Impact

In this paper, a summary of the recent work at NTNU on the installation of offshore wind turbines using jack-up and floating vessels will be reported. The wind turbine components considered here are the monopile foundations and the blades. The detailed discussions are given to the crane operations for installing wind turbine blades as well as novel installation methods for pre-assembled rotor-nacelle-tower. It includes numerical modelling and analysis for global dynamic responses of the installation system (installation vessels plus wind turbines) and for local structural responses of the blades in case of contact/impact. In particular, the stochastic nature of the environmental conditions (mainly wind and waves) and their influence on the global dynamic responses of the installation system will be assessed based on time-domain simulations. In addition, tugger line tension control is introduced for the final connection to the hub in order to reduce the motions of the blade and therefore the potential damages to the blades. It is then followed by a discussion about nonlinear structural analysis of the blade in contact with tower or surrounding structures using ABAQUS. Damages in the composite plies and sandwich core materials of the blade due to contact/impact for a given initial velocity are then estimated. The obtained damage distribution formulates the basis for a probabilistic assessment of structural safety during installation. Novel installation methods in which the rotor-nacelle-tower structure is pre-assembled onshore and installed on top of the foundation offshore, and the corresponding installation vessels are discussed at the end of the paper. Finally, the main conclusions and the recommendations for future work are drawn.

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Improving the Strategy of Maintaining Offshore Wind Turbines through Petri Net Modelling

Applied Sciences ◽

10.3390/app11020574 ◽

2021 ◽

Vol 11 (2) ◽

pp. 574

Author(s):

Rundong Yan ◽

Sarah Dunnett

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Petri Net ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Maintenance Costs ◽

Offshore Wind Turbines ◽

Major Repair ◽

Wind Turbine System ◽

Periodic Maintenance

In order to improve the operation and maintenance (O&M) of offshore wind turbines, a new Petri net (PN)-based offshore wind turbine maintenance model is developed in this paper to simulate the O&M activities in an offshore wind farm. With the aid of the PN model developed, three new potential wind turbine maintenance strategies are studied. They are (1) carrying out periodic maintenance of the wind turbine components at different frequencies according to their specific reliability features; (2) conducting a full inspection of the entire wind turbine system following a major repair; and (3) equipping the wind turbine with a condition monitoring system (CMS) that has powerful fault detection capability. From the research results, it is found that periodic maintenance is essential, but in order to ensure that the turbine is operated economically, this maintenance needs to be carried out at an optimal frequency. Conducting a full inspection of the entire wind turbine system following a major repair enables efficient utilisation of the maintenance resources. If periodic maintenance is performed infrequently, this measure leads to less unexpected shutdowns, lower downtime, and lower maintenance costs. It has been shown that to install the wind turbine with a CMS is helpful to relieve the burden of periodic maintenance. Moreover, the higher the quality of the CMS, the more the downtime and maintenance costs can be reduced. However, the cost of the CMS needs to be considered, as a high cost may make the operation of the offshore wind turbine uneconomical.

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Novel Application and Validation of a Method to Assess Visual Impacts of Rotating Wind Turbine Blades Within Woodland Areas

PFG – Journal of Photogrammetry Remote Sensing and Geoinformation Science ◽

10.1007/s41064-021-00141-4 ◽

2021 ◽

Vol 89 (1) ◽

pp. 1-14

Author(s):

U. Nopp-Mayr ◽

F. Kunz ◽

F. Suppan ◽

E. Schöll ◽

J. Coppes

Keyword(s):

Environmental Impact ◽

Wind Turbine ◽

Wind Turbines ◽

Power Plants ◽

Laser Scanning ◽

Forest Canopy ◽

Turbine Blades ◽

Wind Turbine Blades ◽

Environmental Impact Assessments ◽

Independent Field

AbstractIncreasing numbers of wind power plants (WPP) are constructed across the globe to reduce the anthropogenic contribution to global warming. There are, however, concerns on the effects of WPP on human health as well as related effects on wildlife. To address potential effects of WPP in environmental impact assessments, existing models accounting for shadow flickering and noise are widely applied. However, a standardized, yet simple and widely applicable proxy for the visibility of rotating wind turbines in woodland areas was largely lacking up to date. We combined land cover information of forest canopy extracted from orthophotos and airborne laser scanning (LiDAR) data to represent the visibility of rotating wind turbines in five woodland study sites with a high spatial resolution. Performing an in-situ validation in five study areas across Europe which resulted in a unique sample of 1738 independent field observations, we show that our approach adequately predicts from where rotating wind turbine blades are visible within woodlands or not. We thus provide strong evidence, that our approach yields a valuable proxy of the visibility of moving rotor blades with high resolution which in turn can be applied in environmental impact assessments of WPP within woodlands worldwide.

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Impact of Typhoons on Floating Offshore Wind Turbines: A Case Study of Typhoon Mangkhut

Journal of Marine Science and Engineering ◽

10.3390/jmse9050543 ◽

2021 ◽

Vol 9 (5) ◽

pp. 543

Author(s):

Jiawen Li ◽

Jingyu Bian ◽

Yuxiang Ma ◽

Yichen Jiang

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Safety Evaluation ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Motion Response ◽

Offshore Wind Turbines ◽

Floating Offshore Wind Turbines ◽

Coupling Motion

A typhoon is a restrictive factor in the development of floating wind power in China. However, the influences of multistage typhoon wind and waves on offshore wind turbines have not yet been studied. Based on Typhoon Mangkhut, in this study, the characteristics of the motion response and structural loads of an offshore wind turbine are investigated during the travel process. For this purpose, a framework is established and verified for investigating the typhoon-induced effects of offshore wind turbines, including a multistage typhoon wave field and a coupled dynamic model of offshore wind turbines. On this basis, the motion response and structural loads of different stages are calculated and analyzed systematically. The results show that the maximum response does not exactly correspond to the maximum wave or wind stage. Considering only the maximum wave height or wind speed may underestimate the motion response during the traveling process of the typhoon, which has problems in guiding the anti-typhoon design of offshore wind turbines. In addition, the coupling motion between the floating foundation and turbine should be considered in the safety evaluation of the floating offshore wind turbine under typhoon conditions.

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