scholarly journals Deformation Analysis of Large Diameter Monopiles of Offshore Wind Turbines under Scour

2020 ◽  
Vol 10 (21) ◽  
pp. 7579
Author(s):  
Zhaoyao Wang ◽  
Ruigeng Hu ◽  
Hao Leng ◽  
Hongjun Liu ◽  
Yifan Bai ◽  
...  
Keyword(s):  
Wind Turbines ◽  
Wind Farm ◽  
Large Diameter ◽  
Horizontal Displacement ◽  
Local Scour ◽  
Offshore Wind ◽  
Deformation Analysis ◽  
Pile Head ◽  
Offshore Wind Turbines ◽  
Test Conditions

The displacement of monopile supporting offshore wind turbines needs to be strictly controlled, and the influence of local scour can not be ignored. Using p–y curves to simulate the pile–soil interaction and the finite difference method to calculate iteratively, a numerical frame for analysis of lateral loaded pile was discussed and then verified. On the basis of the field data from Dafeng Offshore Wind Farm in Jiangsu Province, the local scour characteristics of large diameter monopile were concluded, and a new method of considering scour effect applicable to large diameter monopile was put forward. The results show that, for scour of large diameter monopiles, there was no obvious scour pit, but local erosion and deposition. Under the test conditions, the displacement errors between the proposed and traditional method were 46.4%. By the proposed method, the p–y curves of monopile considering the scour effect were obtained through ABAQUS, and the deformation of large diameter monopile under scour was analyzed by the proposed frame. The results show that, with the increase of scour depth, the horizontal displacement of the pile head increases nonlinearly, the depth of rotation point moves downward, and both of the changes are related to the load level. Under the test conditions, the horizontal displacement of the pile head after scour could reach 1.4~3.6 times of that before scour. Finally, for different pile parameters, the pile head displacement was compared, and further, the susceptibility to scour was quantified by a proposed concept of scour sensitivity. The analysis indicates that increasing pile length is a more reasonable way than pile diameter and wall thickness to limit the scour effect on the displacement of large diameter pile.

scholarly journals Maintenance Planning of Offshore Wind Turbine Using Condition Monitoring Information

2009 ◽  
Author(s):  
Jose´ G. Rangel-Rami´rez ◽  
John D. So̸rensen
Keyword(s):  
Condition Monitoring ◽  
Wind Turbines ◽  
Wind Farm ◽  
Offshore Structures ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Maintenance Planning ◽  
Offshore Wind Turbines ◽  
Inspection And Maintenance ◽  
Monitoring Information

Deterioration processes such as fatigue and corrosion are typically affecting offshore structures. To “control” this deterioration, inspection and maintenance activities are developed. Probabilistic methodologies represent an important tool to identify the suitable strategy to inspect and control the deterioration in structures such as offshore wind turbines (OWT). Besides these methods, the integration of condition monitoring information (CMI) can optimize the mitigation activities as an updating tool. In this paper, a framework for risk-based inspection and maintenance planning (RBI) is applied for OWT incorporating CMI, addressing this analysis to fatigue prone details in welded steel joints at jacket or tripod steel support structures for offshore wind turbines. The increase of turbulence in wind farms is taken into account by using a code-based turbulence model. Further, additional modes t integrate CMI in the RBI approach for optimal planning of inspection and maintenance. As part of the results, the life cycle reliabilities and inspection times are calculated, showing that earlier inspections are needed at in-wind farm sites. This is expected due to the wake turbulence increasing the wind load. With the integration of CMI by means Bayesian inference, a slightly change of first inspection times are coming up, influenced by the reduction of the uncertainty and harsher or milder external agents.

scholarly journals Dynamic Impedances of Offshore Rock-Socketed Monopiles

2019 ◽  
Vol 7 (5) ◽  
pp. 134 ◽  
Author(s):  
Rui He ◽  
Ji Ji ◽  
Jisheng Zhang ◽  
Wei Peng ◽  
Zufeng Sun ◽  
...  
Keyword(s):  
Numerical Model ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Dynamic Stiffness ◽  
Large Diameter ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Thin Walled ◽  
Rock Parameters ◽  
Radiative Damping

With the development of offshore wind energy in China, more and more offshore wind turbines are being constructed in rock-based sea areas. However, the large diameter and thin-walled steel rock-socketed monopiles are very scarce at present, and both the construction and design are very difficult. For the design, the dynamic safety during the whole lifetime of the wind turbine is difficult to guarantee. Dynamic safety of a turbine is mostly controlled by the dynamic impedances of the rock-socketed monopile, which are still not well understood. How to choose the appropriate impedances of the socketed monopiles so that the wind turbines will neither resonant nor be too conservative is the main problem. Based on a numerical model in this study, the accurate impedances are obtained for different frequencies of excitation, different soil and rock parameters, and different rock-socketed lengths. The dynamic stiffness of monopile increases, while the radiative damping decreases as rock-socketed depth increases. When the weathering degree of rock increases, the dynamic stiffness of the monopile decreases, while the radiative damping increases.

scholarly journals Floating Performance of a Composite Bucket Foundation with an Offshore Wind Tower during Transportation

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 882 ◽  
Author(s):  
Hongyan Ding ◽  
Zuntao Feng ◽  
Puyang Zhang ◽  
Conghuan Le ◽  
Yaohua Guo
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Farm ◽  
Wind Farms ◽  
Interaction Force ◽  
Offshore Wind ◽  
Construction Technique ◽  
Bucket Foundation ◽  
Offshore Wind Turbines ◽  
One Step

The composite bucket foundation (CBF) for offshore wind turbines is the basis for a one-step integrated transportation and installation technique, which can be adapted to the construction and development needs of offshore wind farms due to its special structural form. To transport and install bucket foundations together with the upper portion of offshore wind turbines, a non-self-propelled integrated transportation and installation vessel was designed. In this paper, as the first stage of applying the proposed one-step integrated construction technique, the floating behavior during the transportation of CBF with a wind turbine tower for the Xiangshui wind farm in the Jiangsu province was monitored. The influences of speed, wave height, and wind on the floating behavior of the structure were studied. The results show that the roll and pitch angles remain close to level during the process of lifting and towing the wind turbine structure. In addition, the safety of the aircushion structure of the CBF was verified by analyzing the measurement results for the interaction force and the depth of the liquid within the bucket. The results of the three-DOF (degree of freedom) acceleration monitoring on the top of the test tower indicate that the wind turbine could meet the specified acceleration value limits during towing.

Condition Monitoring of Wind Turbine Drivetrain Bearings

2019 ◽  
Author(s):  
Konstantinos Gryllias ◽  
Junyu Qi ◽  
Alexandre Mauricio ◽  
Chenyu Liu
Keyword(s):  
Wind Energy ◽  
Condition Monitoring ◽  
Wind Turbines ◽  
Wind Farm ◽  
The Other ◽  
Offshore Wind ◽  
Center Frequency ◽  
Classical Statistic ◽  
Offshore Wind Turbines ◽  
Other Hand

Abstract The current pace of renewable energy development around the world is unprecedented, with offshore wind in particular proving to be an extremely valuable and reliable energy source. The global installed capacity of offshore wind turbines by the end of 2022 is expected to reach the 46.4 GW, among which 33.9 GW in Europe. Costs are critical for the future success of the offshore wind sector. The industry is pushing hard to make cost reductions to show that offshore wind is economically comparable to conventional fossil fuels. Efficiencies in Operations and Maintenance (O&M) offer potential to achieve significant cost savings as it accounts for around 20%–30% of overall offshore wind farm costs. One of the most critical and rather complex assembly of onshore, offshore and floating wind turbines is the gearbox. Gearboxes are designed to last till the end of the lifetime of the asset, according to the IEC 61400-4 standards. On the other hand, a recent study over approximately 350 offshore wind turbines indicate that gearboxes might have to be replaced as early as 6.5 years. Therefore sensing and condition monitoring systems for onshore, offshore and floating wind turbines are needed in order to obtain reliable information on the state and condition of different critical parts, focusing towards the detection and/or prediction of damage before it reaches a critical stage. The development and use of such technologies will allow companies to schedule actions at the right time, and thus will help reducing the costs of operation and maintenance, resulting in an increase of wind energy at a competitive price and thus strengthening productivity of the wind energy sector. At the academic level a plethora of methodologies have been proposed during the last decades for the analysis of vibration signatures focusing towards early and accurate fault detection with limited false alarms and missed detections. Among others, Envelope Analysis is one of the most important methodologies, where an envelope of the vibration signal is estimated, usually after filtering around a selected frequency band excited by impacts due to the faults. Different tools, such as Kurtogram, have been proposed in order to accurately select the optimum filter parameters (center frequency and bandwidth). Cyclostationary Analysis and corresponding methodologies, i.e. the Cyclic Spectral Correlation and the Cyclic Spectral Coherence, have been proved as powerful tools for condition monitoring. On the other hand the application, test and evaluation of such tools on general industrial cases is still rather limited. Therefore the main aim of this paper is the application and evaluation of advanced diagnostic techniques and diagnostic indicators, including the Enhanced Envelope Spectrum and the Spectral Flatness on real world vibration data collected from vibration sensors on gearboxes in multiple wind turbines over an extended period of time of nearly four years. The diagnostic indicators are compared with classical statistic time and frequency indicators, i.e. Kurtosis, Crest Factor etc. and their effectiveness is evaluated based on the successful detection of two failure events.

scholarly journals Turbulence in a coastal environment: the case of Vindeby

2021 ◽  
Author(s):  
Rieska Mawarni Putri ◽  
Etienne Cheynet ◽  
Charlotte Obhrai ◽  
Jasna Bogunovic Jakobsen
Keyword(s):  
Wind Turbines ◽  
Wind Farm ◽  
Similarity Theory ◽  
Spectral Characteristics ◽  
Measurement Data ◽  
Offshore Wind ◽  
Wind Component ◽  
Neutral Atmosphere ◽  
Strong Wind ◽  
Offshore Wind Turbines

Abstract. Turbulence spectral characteristics for various atmospheric stratifications are studied using the observations from an offshore mast at Vindeby wind farm. Measurement data at 6 m, 18 m and 45 m above the mean sea level are considered. At the lowest height, the normalized power spectral densities of the velocity components show deviations from Monin-Obukhov similarity theory (MOST). A significant co-coherence at the wave spectral peak frequency between the vertical velocity component and the velocity of the sea surface is observed, but only when the significant wave heights exceed 0.9 m. The turbulence spectra at 18 m generally follow MOST and are consistent with the empirical spectra established on the FINO1 offshore platform from an earlier study. The data at 45 m is associated with a high-frequency measurement noise which limits its analysis to strong wind conditions only. The estimated co-coherence of the along-wind component under near-neutral atmosphere matches remarkably well with those at FINO1. The turbulence characteristics estimated from the present dataset are valuable to better understand the structure of turbulence in the marine atmospheric boundary layer and are relevant for load estimations of offshore wind turbines. Yet, a direct application of the results to other offshore or coastal sites should be exercised with caution, since the dataset is collected in shallow waters and at heights lower than the hub height of the current and the future state-of-the-art offshore wind turbines.

Progress on the Development of a Holistic Coupled Model of Dynamics for Offshore Wind Farms: Phase I — Aero-Hydro-Servo-Elastic Model, With Drive Train Model, for a Single Wind Turbine

2018 ◽  
Author(s):  
Z. Lin ◽  
D. Cevasco ◽  
M. Collu
Keyword(s):  
Wind Turbine ◽  
Failure Mode ◽  
Wind Turbines ◽  
Wind Farm ◽  
Failure Modes ◽  
Coupled Model ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Elastic Model ◽  
Offshore Wind Turbines

Currently, around 1500 offshore wind turbines are operating in the UK, for a total of 5.4GW, with further 3GW under construction, and 13GW consented. Until now, the focus of the research on offshore wind turbines has been mainly on how to minimise the CAPEX, but Operation and maintenance (O&M) can represent up to 39% of the lifetime costs of an offshore wind farm, due mainly to the high cost of the assets and the harsh environment, limiting the access to these assets in a safe mode. The present work is a part of a larger project, called HOME Offshore (www.homeoffshore.org), and it has as aim an advanced interpretation of the fault mechanisms through a holistic multiphysics modelling of the wind farm. The first step (presented here) toward achieving this aim consists of two main tasks: first of all, to identify and rank the most relevant failure modes within a wind farm, identifying the component, its mode of failure, and the relative environmental conditions. Then, to assess (for each failure mode) how the full-order, nonlinear model of dynamics used to represent the dynamics of the wind turbine can be reduced in order, such that is less computationally expensive (and therefore more suitable to be scaled up to represent multiple wind turbines), but still able to capture and represent the relevant dynamics linked with the inception of the chosen failure mode. A methodology to rank the failure modes is presented, followed by an approach to reduce the order of the Aero-Hydro-Servo-Elastic (AHSE) model of dynamics adopted. The results of the proposed reduced-order models are discussed, comparing it against the full-order coupled model, and taking as case study a fixed offshore wind turbine (monopile) in gearbox failure condition.

Harmonizing the Mooring System Reliability of Multiline Anchor Wind Farms

2021 ◽  
Vol 7 (4) ◽  
Author(s):  
Spencer T. Hallowell ◽  
Sanjay R. Arwade ◽  
Brian D. Diaz ◽  
Charles P. Aubeny ◽  
Casey M. Fontana ◽  
...  
Keyword(s):  
Wind Turbines ◽  
System Reliability ◽  
Wind Farm ◽  
Wind Farms ◽  
Offshore Wind ◽  
Line System ◽  
Offshore Wind Turbines ◽  
Anchor System ◽  
Floating Offshore Wind Turbines ◽  
Additional Safety

Abstract One of many barriers to the deployment of floating offshore wind turbines is the high cost of vessel time needed for soil investigations and anchor installation. A multiline anchor system is proposed in which multiple floating offshore wind turbines (FOWTs) are connected to a single caisson. The connection of multiple FOWTs to a single anchor introduces interconnectedness throughout the wind farm. Previous work by the authors has shown that this interconnectedness reduces the reliability of the FOWT below an acceptable level when exposed to survival loading conditions. To combat the reduction in system reliability an overstrength factor (OSF) is applied to the anchors functioning as an additional safety factor. For a 100 turbine wind farm, single-line system reliabilities can be achieved using the multiline system with an OSF of 1.10, a 10% increase in multiline anchor safety factors for all anchors in a farm.

WindFloat: A Floating Foundation for Offshore Wind Turbines—Part I: Design Basis and Qualification Process

2009 ◽  
Author(s):  
Dominique Roddier ◽  
Christian Cermelli ◽  
Alla Weinstein
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Oil And Gas ◽  
Large Diameter ◽  
Offshore Wind ◽  
Site Location ◽  
Offshore Wind Turbines ◽  
Design Basis ◽  
Floating Foundation ◽  
Visual Impacts

This paper and the corresponding hydrodynamic and structural study paper (also in these proceedings) summarize the feasibility study conducted for the WindFloat technology. The WindFloat is a 3-legged floating foundation for very large offshore wind turbines. It is designed to accommodate a wind turbine, 5 MW or larger, on one of the columns of the hull with minimal modifications to the tower, nacelle and turbine. Technologies for floating foundations for offshore wind turbines are evolving. It is agreed by most experts that the offshore wind industry will see a significant increase in activity in the near future. Fixed offshore turbines are limited in water depth to approximately 30∼50m. Market transition to deeper waters is inevitable, provided suitable technologies can be developed. Despite the increase in complexity, a floating foundation offers distinct advantages: • Flexibility in site location. • Access to superior wind resources further offshore. • Ability to locate in coastal regions with limited shallow continental shelf. • Ability to locate further offshore to eliminate visual impacts. • An integrated structure, without a need to redesign the mast foundation connection for every project. • Simplified offshore installation procedures. Anchors are significantly cheaper to install than fixed foundations and large diameter towers. This paper focuses on the design basis for wind turbine floating foundations, and explores the requirements that must be addressed by design teams in this new field. It shows that the design of the hull for a large wind turbine must draw on the synergies with oil and gas offshore platform technology, while accounting for the different design requirements and functionality of the wind turbine.

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