Pareto-Optimal Evaluation of Ultimate Limit States in Offshore Wind Turbine Structural Analysis

Abstract This paper summarizes the results of the implementation and verification of a hydro-aero-servo-elastic load simulation model for a self-aligning floating offshore wind turbine (FOWT) combined with a structural analysis methodology of this FOWT structure. The main focus is a comparison of a rigid and a flexible support structure representation in the load simulation. This investigation is part of the multiparty project for the ‘Hydrodynamic and Structural Optimization of a Semi-submersible Offshore Wind Turbine’ (HyStOH), joining partners from science and industry and financially supported by the German Ministry of Economics Affairs and Energy, BMWi (Bundesministerium für Wirtschaft und Energie).

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Scour Protections for Offshore Foundations of Marine Energy Harvesting Technologies: A Review

Journal of Marine Science and Engineering ◽

10.3390/jmse9030297 ◽

2021 ◽

Vol 9 (3) ◽

pp. 297

Author(s):

Tiago Fazeres-Ferradosa ◽

João Chambel ◽

Francisco Taveira-Pinto ◽

Paulo Rosa-Santos ◽

Francisco V. C. Taveira Pinto ◽

...

Keyword(s):

Renewable Energy ◽

Wind Turbine ◽

Marine Environment ◽

Professional Community ◽

Tidal Energy ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Limit States ◽

Commercial Development ◽

Marine Renewable Energy

The offshore wind is the sector of marine renewable energy with the highest commercial development at present. The margin to optimise offshore wind foundations is considerable, thus attracting both the scientific and the industrial community. Due to the complexity of the marine environment, the foundation of an offshore wind turbine represents a considerable portion of the overall investment. An important part of the foundation’s costs relates to the scour protections, which prevent scour effects that can lead the structure to reach the ultimate and service limit states. Presently, the advances in scour protections design and its optimisation for marine environments face many challenges, and the latest findings are often bounded by stakeholder’s strict confidential policies. Therefore, this paper provides a broad overview of the latest improvements acquired on this topic, which would otherwise be difficult to obtain by the scientific and general professional community. In addition, this paper summarises the key challenges and recent advances related to offshore wind turbine scour protections. Knowledge gaps, recent findings and prospective research goals are critically analysed, including the study of potential synergies with other marine renewable energy technologies, as wave and tidal energy. This research shows that scour protections are a field of study quite challenging and still with numerous questions to be answered. Thus, optimisation of scour protections in the marine environment represents a meaningful opportunity to further increase the competitiveness of marine renewable energies.

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Ultimate Limit State Risk Assessment of Penta Pod Suction Bucket Support Structures for Offshore Wind Turbine due to Scour

Journal of Korean Society of Coastal and Ocean Engineers ◽

10.9765/kscoe.2021.33.6.374 ◽

2021 ◽

Vol 33 (6) ◽

pp. 374-382

Author(s):

Young Jin Kim ◽

Ngo Duc Vu ◽

Dong Hyawn Kim

Keyword(s):

Risk Assessment ◽

Wind Turbine ◽

Limit State ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Ultimate Limit State ◽

Support Structures ◽

Significant Wave ◽

Scour Hazard ◽

Ultimate Limit

The scour risk assessment was conducted for ultimate limit state of newly developed penta pod suction bucket support structures for a 5.5 MW offshore wind turbine. The hazard was found by using an empirical formula for scour depth suitable for considering marine environmental conditions such as significant wave height, significant wave period, and current velocity. The scour fragility curve was calculated by using allowable bearing capacity criteria of suction foundation. The scour risk was assessed by combining the scour hazard and the scour fragility.

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A Comprehensive Aero-Hydro-Structural Analysis of a 5-MW Offshore Wind Turbine System: Towards Cost-Effective Deployment of Offshore Wind Turbines in Maryland

34th Wind Energy Symposium ◽

10.2514/6.2016-1993 ◽

2016 ◽

Cited By ~ 1

Author(s):

Scott Smith ◽

Abdul-Bari Syed ◽

Daming Chen ◽

Meilin Yu ◽

Weidong Zhu ◽

...

Keyword(s):

Structural Analysis ◽

Wind Turbine ◽

Wind Turbines ◽

Cost Effective ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Offshore Wind Turbines ◽

Wind Turbine System

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A Comprehensive Aero-Hydro-Structural Analysis of a 5 MW Offshore Wind Turbine System

Journal of Solar Energy Engineering ◽

10.1115/1.4043514 ◽

2019 ◽

Vol 141 (6) ◽

Author(s):

Scott Smith ◽

Abdul-Bari Syed ◽

Kan Liu ◽

Meilin Yu ◽

Weidong Zhu ◽

...

Keyword(s):

Structural Analysis ◽

Stress Field ◽

Wind Turbine ◽

Turbine Rotor ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Foundation Design ◽

Structural Dynamic ◽

Wind Turbine System ◽

Analysis Strategy

A comprehensive aero-hydro-structural analysis is conducted for a 5 MW offshore wind turbine system in this study. Soil–structure interaction under complex aero-hydro loading is analyzed to provide a suitable foundation design with high safety. With consideration of the wind turbine size and water depth, the monopile foundation design by the National Renewable Energy Laboratory (NREL) is selected in the current study. Both aerodynamic loading for the 5 MW wind turbine rotor defined by NREL and hydrodynamic loading on the foundation are simulated under different flow conditions using high-fidelity computational fluid dynamics methods. Structural dynamic analysis is then carried out to estimate the stress field in the foundation and soil. Results from the comprehensive analysis indicate that the Morison equation is conservative when looking at the stress field in the monopile foundation and underestimates the stress field in soil. A similar analysis strategy can be applied to other types of foundations such as jacket foundations and lead to more economical and reliable designs of foundations.

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The Influence of Foundation Modeling Assumptions on Long-Term Load Prediction for Offshore Wind Turbines

Volume 6: Nick Newman Symposium on Marine Hydrodynamics; Yoshida and Maeda Special Symposium on Ocean Space Utilization; Special Symposium on Offshore Renewable Energy ◽

10.1115/omae2008-57893 ◽

2008 ◽

Author(s):

Erica Bush ◽

Puneet Agarwal ◽

Lance Manuel

Keyword(s):

Wind Turbine ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Load Prediction ◽

Offshore Wind Turbines ◽

Extreme Loads ◽

Foundation Model ◽

Flexible Foundation ◽

Ultimate Limit

In evaluating ultimate limit states for design, time-domain aeroelastic response simulations are typically carried out to establish extreme loads on offshore wind turbines. Accurate load prediction depends on proper modeling of the wind turbulence and the wave stochastic processes as well as of the turbine, the support structure, and the foundation. One method for modeling the support structure is to rigidly connect it to the seabed; such a foundation model is appropriate only when the sea floor is firm (as is the case for rock). To obtain realistic turbine response dynamics for softer soils, it is important that a flexible foundation is modeled. While a single discrete spring for coupled lateral/rotational motion or several distributed springs along the length of the monopile may be employed, a tractable alternative is to employ a fictitious fixed-based pile modeled as an “equivalent” cantilever beam, where the length of this fictitious pile is determined using conventional pile lateral load analysis in combination with knowledge of the soil profile. The objective of this study is to investigate the influence of modeling flexible pile foundations on offshore wind turbine loads such as the fore-aft tower bending moment at the mudline. We employ a utility-scale 5MW offshore wind turbine model with a 90-meter hub height in simulations; the turbine is assumed to be sited in 20 meters of water. For a critical wind-wave combination known to control long-term design loads, we study time histories, power spectra, response statistics, and probability distributions of extreme loads for fixed-base and flexible foundation models with the intention of assessing the importance of foundation model selection. Load distributions are found to be sensitive to foundation modeling assumptions. Extrapolation to rare return periods may be expected to lead to differences in derived nominal loads needed in ultimate limit state design; this justifies the use of flexible foundation models in simulation studies.

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