Design and comparative analysis of alternative mooring systems for floating wind turbines in shallow water with emphasis on ultimate limit state design

Xu, Kun; Larsen, Kjell; Shao, Yanlin; Zhang, Min; Gao, Zhen; Moan, Torgeir

doi:10.1016/j.oceaneng.2020.108377

Cited by 74 publications

(25 citation statements)

References 12 publications

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“…Xu et al [94] have reported a comparative analysis of different mooring designs for shallow water (50 m) 5 MW floating offshore wind turbines with a view to find the optimal mooring design based on structural integrity and costs involved. Different catenary (chain) and taut (synthetic fiber rope) mooring cables, components (clump weight and buoy) and anchors (drag embedment and suction) have been considered for analysis.…”

Section: Design Parameter Stability Criteriamentioning

confidence: 99%

A Review of Recent Advancements in Offshore Wind Turbine Technology

et al. 2022

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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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Section: Design Parameter Stability Criteriamentioning

confidence: 99%

A Review of Recent Advancements in Offshore Wind Turbine Technology

et al. 2022

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“…where ρ a is the standard air density; A is the structural element projected area normal to the wind direction; C d,w is the drag coefficient; h wind is the wind direction vector and v w is the wind relative velocity, consisting of both steady and turbulent components, the latter generated according to the Norwegian Petroleum Directorate wind spectrum [36]. A similar approach was followed to assess the force exerted by the wind turbine, after replacing the drag coefficient C d by the relevant thrust coefficient C t , depending on the wind speed at hub height [37].…”

Section: Qmentioning

confidence: 99%

“…The benchmark study, carried out in Section 6, was performed based on the reference environmental conditions recently investigated by Xu et al [36] and listed in Table 3. They are representative of both power production and parked wind turbine situations.…”

Section: Selection Of Reference Conditionsmentioning

confidence: 99%

“…They are representative of both power production and parked wind turbine situations. The sea state condition is described by the JONSWAP spectrum [39], with a significant wave height, H s , ranging from 1.96 to 9.77 m and a wave peak period ranging from 9.72 to 12.95 s. The wind climate was described by the 10 min wind speed at hub height, combined with the Norwegian Petroleum Directorate wind spectrum [36], which is representative of the turbulent component. Wave and wind loads were assumed to be codirectional, with heading angle equal to 0 • , to exert the highest loads in the mooring line #1.…”

Section: Selection Of Reference Conditionsmentioning

confidence: 99%

“…Before carrying out the benchmark study, a preliminary analysis was performed to test the effectiveness and robustness of the hydrodynamic model developed in MATLAB. Figures 4 and 5 provide the mean values, µ, and the standard deviations, σ, of the stress process in the mooring line #1, obtained by the numerical model, currently developed in MATLAB, and by the numerical simulations performed by Xu et al [36] by the commercial code SIMA [55]. The SIMA software, currently licensed and supported by the Det Norske Veritas, is a complete tool for the simulation of marine operations from modelling to results, which include lifting of topsides and modules, offshore wind turbine installation, offshore crane operations, subsea installations, transportation and installation of TLPs and towing operations, among others.…”

Section: Preliminary Analysismentioning

confidence: 99%

See 2 more Smart Citations

Fatigue Assessment of Moorings for Floating Offshore Wind Turbines by Advanced Spectral Analysis Methods

Piscopo

Scamardella

Rossi

et al. 2021

JMSE

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The fatigue assessment of mooring lines for floating offshore wind turbines represents a challenging issue not only for the reliable design of the stationkeeping system but also for the economic impact on the installation and maintenance costs over the entire lifetime of the offshore wind farm. After a brief review about the state-of-art, the nonlinear time-domain hydrodynamic model of floating offshore wind turbines moored by chain cables is discussed. Subsequently, the assessment of the fatigue damage in the mooring lines is outlined, focusing on the combined-spectrum approach. The relevant fatigue parameters, due to the low- and wave-frequency components of the stress process, are estimated by two different methods. The former is based on the time-domain analysis of the filtered stress process time history. The latter, instead, is based on the spectral analysis of the stress process by two advanced methods, namely the Welch and Thomson ones. Subsequently, a benchmark study is performed, assuming as reference floating offshore wind turbine the OC4-DeepCWind semisubmersible platform, equipped with the 5 MW NREL wind turbine. The cumulative fatigue damage is determined for eight load conditions, including both power production and parked wind turbine situations. A comparative analysis between time-domain and spectral analysis methods is also performed. Current results clearly show that the endorsement of advanced spectral analysis methods can be helpful to improve the reliability of the fatigue life assessment of mooring lines.

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Numerical analysis of a tethered‐buoy mooring system for a prototype floating wind farm

Liang,

Wickmann Hanssen,

Otto Merz

et al. 2024

Wind Energy

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Conventional mooring systems contribute significantly to the cost of floating wind projects, and innovative solutions with cost‐saving potentials are desired. In the present paper, we investigate the fundamental dynamic behavior of an innovative tethered‐buoy mooring system for a prototype wind farm in which two spar floating offshore wind turbines (FOWTs) are moored to five submerged tethered buoys. Numerical decay tests are used to characterize the fundamental frequencies and oscillatory modes of the system. The influence of net buoyancy is established through a parametric study. Finally, the dynamic response of the tethered‐buoy mooring system is compared against two alternative shared mooring configurations with catenary mooring lines. Time‐domain simulations are carried out for one accidental scenario with a parked and an operational FOWT, and one extreme scenario with two parked FOWTs. The results show that net buoyancy has a significant influence on platform motions and mooring loads. Compared to alternative configurations with catenary mooring lines, the tethered‐buoy mooring system exhibits substantially lower mooring tension loads and practically eliminates the threat of snap events. The reduction in the maximum characteristic fairlead tension is up to 85%. The mean positional offset of the wind turbines in the loading direction is larger, up to 36% of the water depth, however, the relative motions are comparable. The mean distance between the FOWTs is even smaller for the tethered‐buoy system. With the application of dynamic inter‐array cables, the proposed tethered‐buoy system can be a promising mooring solution for floating offshore wind farms.

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Design and comparative analysis of alternative mooring systems for floating wind turbines in shallow water with emphasis on ultimate limit state design

Cited by 74 publications

References 12 publications

A Review of Recent Advancements in Offshore Wind Turbine Technology

A Review of Recent Advancements in Offshore Wind Turbine Technology

Fatigue Assessment of Moorings for Floating Offshore Wind Turbines by Advanced Spectral Analysis Methods

Numerical analysis of a tethered‐buoy mooring system for a prototype floating wind farm

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