Efficient Multiline Anchor Systems for Floating Offshore Wind Turbines

2016 ◽  
Author(s):  
Casey M. Fontana ◽  
Sanjay R. Arwade ◽  
Don J. DeGroot ◽  
Andrew T. Myers ◽  
Melissa Landon ◽  
...  
Keyword(s):  
Dynamic Simulation ◽  
Wind Turbines ◽  
Wind Farm ◽  
Offshore Wind ◽  
Wave Loading ◽  
Peak Demand ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Anchor Systems ◽  
Floating Platforms

A mooring and anchoring concept for floating offshore wind turbines is introduced in which each anchor moors multiple floating platforms. Several possible geometries are identified and it is shown that the number of anchors for a wind farm can be reduced by factors of at least 3. Dynamic simulation of turbine dynamics for one of the candidate geometries and for two directions of wind and wave loading allows estimation of multiline anchor forces the preview the types of loads that a multiline anchor will need to resist. Preliminary findings indicate that the peak demand on the anchor may be reduced by as much as 30% but that anchors used in such a system will need to be able to resist multi-directional loading.

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.

scholarly journals On the Modeling of Spar-Type Floating Offshore Wind Turbines

2013 ◽  
Vol 569-570 ◽  
pp. 636-643 ◽  
Author(s):  
Van Nguyen Dinh ◽  
Biswajit Basu
Keyword(s):  
Wind Turbines ◽  
Operating Conditions ◽  
Offshore Wind ◽  
Wave Loads ◽  
Dynamic Coupling ◽  
Modeling Tools ◽  
Modeling And Analysis ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Floating Platforms

In this paper an overview about floating offshore wind turbines (FOWT) including operating conditions, property and applicability of the barge, tension-leg, and spar floating platforms is described. The spar-floating offshore wind turbines (S-FOWT) have advantages in deepwater and their preliminary design, numerical modeling tools and integrated modeling are reviewed. Important conclusions about the nacelle and blade motions, tower response, effects of wind and wave loads, overall vibration and power production of the S-FOWT are summarized. Computationally-simplified models with acceptable accuracy are necessary for feasibility and pre-engineering studies of the FOWT. The design needs modeling and analysis of aero-hydro-servo dynamic coupling of the entire FOWT. This paper also familiarizes authors with FOWT and its configurations and modeling approaches.

Fibre Spring Mooring Solution for Mooring Floating Offshore Wind Turbines in Shallow Water

2021 ◽  
Author(s):  
Paul McEvoy ◽  
Seojin Kim ◽  
Malak Haynes
Keyword(s):  
Shallow Water ◽  
Wind Turbines ◽  
Wind Farm ◽  
Significant Proportion ◽  
Wind Farms ◽  
Offshore Wind ◽  
Mooring Lines ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Electrical Cables

Abstract Mooring of Floating Offshore Wind Turbines (FOWT) in shallow water sites (30–80m) is challenging. These sites account for a significant proportion of the nearer to shore potential wind farm locations, and are desirable as they are closer to existing infrastructure and easier to access. Mooring large floating structures in very shallow waters however results in very long heavy mooring lines designed to minimize platform surge and protect the electrical cables. This paper presents an innovative Fibre Spring Mooring (FSM) solution which combines a high modulus, non-stretch, lightweight rope with a compliant nonlinear polymer spring offering a complete semi-taut mooring system which can be connected directly between the platform and the seabed. The paper will present Orcaflex simulation results of a 12MW barge type FOWT platform, moored using a semi-taut FSM mooring at three chosen North Sea locations close to existing wind farms, of 30m, 40m and 50m water depths. Different FSM configurations, with different line lengths, footprint, and ratio of fibre to spring are considered.

scholarly journals Digital twins of the mooring line tension for floating offshore wind turbines to improve monitoring, lifespan, and safety

2021 ◽  
Author(s):  
Jake Walker ◽  
Andrea Coraddu ◽  
Maurizio Collu ◽  
Luca Oneto
Keyword(s):  
Wind Turbines ◽  
Wind Farm ◽  
Mechanical Response ◽  
Offshore Wind ◽  
Mooring Line ◽  
Offshore Wind Turbines ◽  
Axial Tension ◽  
Floating Offshore Wind Turbines ◽  
Extreme Load ◽  
Operational Data

AbstractThe number of installed floating offshore wind turbines (FOWTs) has doubled since 2017, quadrupling the total installed capacity, and is expected to increase significantly over the next decade. Consequently, there is a growing consideration towards the main challenges for FOWT projects: monitoring the system’s integrity, extending the lifespan of the components, and maintaining FOWTs safely at scale. Effectively and efficiently addressing these challenges would unlock the wide-scale deployment of FOWTs. In this work, we focus on one of the most critical components of the FOWTs, the Mooring Lines (MoLs), which are responsible for fixing the structure to the seabed. The primary mechanical failure mechanisms in MoLs are extreme load and fatigue, both of which are functions of the axial tension. An effective solution to detect long-term drifts in the mechanical response of the MoLs is to develop a Digital Twin (DT) able to accurately predict the behaviour of the healthy system to compare with the actual one. Moreover, we will develop another DT able to accurately predict the near future axial tension as an effective tool to improve the lifespan of the MoLs and the safety of FOWT maintenance operations. In fact, by changing the FOWT operational settings, according to the DT prediction, operators can increase the lifespan of the MoLs by reducing the stress and, additionally, in the case where FOWT operational maintenance is in progress, the prediction from the DT can serve as early safety warning to operators. Authors will leverage operational data collected from the world’s first commercial floating-wind farm [the Hywind Pilot Park (https://www.equinor.com/en/what-we-do/floating-wind/hywind-scotland.html.)] in 2018, to investigate the effectiveness of DTs for the prediction of the MoL axial tension for the two scenarios depicted above. The DTs will be developed using state-of-the-art data-driven methods, and results based on real operational data will support our proposal.

scholarly journals Numerical and Physical Modeling of a Tension-Leg Platform for Offshore Wind Turbines

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3554
Author(s):  
Daniel Walia ◽  
Paul Schünemann ◽  
Hauke Hartmann ◽  
Frank Adam ◽  
Jochen Großmann
Keyword(s):  
Numerical Model ◽  
Wind Turbines ◽  
Model Testing ◽  
Offshore Wind ◽  
Scaled Model ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Cost Efficient ◽  
Decay Tests ◽  
Floating Platforms

In order to tap the world wide offshore wind resources above deep waters, cost efficient floating platforms are inevitable. Tension-Leg Platforms (TLPs) could enable that crucial cost reduction in floating wind due to their smaller size and lighter weight compared to spars and semi-submersibles. The continuous development of the GICON®-TLP is driven by computer-aided engineering. So-called aero-hydro-servo-elastic coupled simulations are state-of-the-art for predicting loads and simulating the global system behavior for floating offshore wind turbines. Considering the complexity of such simulations, it is good scientific praxis to validate these numerical calculations by use of scaled model testing. This paper addresses the setup of the scaled model testing as carried out at the offshore basin of the École Centrale de Nantes, as well as the numerical model for the GICON®-TLP. The results of dedicated decay tests of the scaled model are used to validate the computational model at the first stage and to determine the natural frequencies of the system. Besides different challenges to the scaled model during the survey, it was possible to take these difficulties into account when updating the numerical model. The results show good agreements for the tank tests and the numerical model.

The Effect of Yaw Error on the Mooring Systems of Floating Offshore Wind Turbines in Extreme Weather Conditions

2018 ◽  
Author(s):  
Evelyn R. Hunsberger ◽  
Spencer T. Hallowell ◽  
Casey M. Fontana ◽  
Sanjay R. Arwade
Keyword(s):  
Wind Speed ◽  
Wind Turbines ◽  
Wind Farm ◽  
Turbine Blades ◽  
Wind Farms ◽  
Offshore Wind ◽  
Single Line ◽  
Direct Result ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

As floating offshore wind turbines (FOWTs) become the most viable option for wind farms in deeper waters, it is important to investigate their dynamic response in inclement conditions when failures, such as yaw misalignment, are more likely to occur. This research uses hour-long simulations in FAST, software developed by The National Renewable Energy Lab (NREL), to analyze the effect of yaw error on anchor tensions and platform displacements in both a traditional single-line wind farm geometry, where each anchor is connected to one turbine, and an optimum multiline anchor geometry, where each anchor is connected to three turbines. NREL’s 5 MW reference turbine on a semi-submersible base is analyzed using six realizations of each combination of co-directional wind and waves, wind speed and yaw error; resulting in 2,484 simulations in total. The variability in platform displacements and mooring forces increases as wind speed increases, and as yaw errors approach critical values. The angle of incidence of the co-directional wind and waves dictates which anchor experiences the most tension for both the single-line and multiline concepts. In the multiline geometry, the greatest increases in anchor tension occurs when the downwind turbine has yaw error. Yaw error increases the maximum anchor tension by up to 43% in the single-line geometry and up to 37% in the multiline geometry. In the multiline geometry, yaw error causes the direction of the resultant anchor force to vary by up to 20°. These changes in anchor tension magnitudes and directions are governed by the platform displacements, and are a direct result of the differences in the tangential and normal coefficients of drag of the turbine blades. When designing floating offshore wind farms, the influence of yaw error on loading magnitudes and directions are to be considered when determining the necessary capacities and calculating the corresponding reliabilities for wind turbine components.

Spatial coherence of ocean waves in multiline anchor systems for floating offshore wind turbines

2019 ◽  
Vol 184 ◽  
pp. 59-73 ◽  
Author(s):  
Casey M. Fontana ◽  
Spencer T. Hallowell ◽  
Sanjay R. Arwade ◽  
Don J. DeGroot ◽  
Melissa E. Landon ◽  
...  
Keyword(s):  
Wind Turbines ◽  
Spatial Coherence ◽  
Ocean Waves ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Anchor Systems

Pitch Angle Control of Floating Offshore Wind Turbines by H∞ Control

2014 ◽  
Vol 134 (8) ◽  
pp. 1096-1103 ◽  
Author(s):  
Sho Tsujimoto ◽  
Ségolène Dessort ◽  
Naoyuki Hara ◽  
Keiji Konishi
Keyword(s):  
Wind Turbines ◽  
Pitch Angle ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

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.

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