Evaluation of a Hybrid Representation to Model the Wind Turbine, Platform and Mooring Lines in the Analysis of Floating Offshore Wind Turbines

2020 ◽  
Author(s):  
Elói Daniel de Araújo Neto ◽  
William Steven Mendez Rodriguez ◽  
Fabricio Nogueira Correa ◽  
Beatriz de Souza Leite Pires de Lima ◽  
Breno Pinheiro Jacob ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Nonlinear Dynamic ◽  
Offshore Wind ◽  
Elastic Behavior ◽  
Coupled Analysis ◽  
Fe Model ◽  
Mooring Lines ◽  
Floating Offshore Wind Turbines ◽  
Hybrid Methodology ◽  
Platform Motions

Abstract This work presents and evaluates a hybrid methodology for the analysis of FOWT, taking advantage of the SITUA-Prosim code developed by LAMCSO/COPPE/UFRJ, and the NREL FAST code. SITUA-Prosim has been originally developed for the coupled analysis of floating platforms for oil production. It fully couples a validated hydrodynamic model, which represents the hull motions, with a full nonlinear dynamic Finite-Element based structural model, which represents mooring lines and risers. The first step of the methodology is to employ the FAST code to generate time-series of forces on the bottom of the tower. These forces are then applied as input for an analysis with the SITUA-Prosim code where the platform and mooring lines are fully coupled, the latter being represented by a full nonlinear dynamic FE model. This may be considered as a “hybrid” methodology since it uncouples the platform motion response from the forces from the wind turbine, but couples the platform motions with the nonlinear dynamic structural response of the mooring lines. The methodology is applied to analyze the OC4 DeepCwind semisubmersible, taking different wind velocities, and evaluating the influence of the elastic behavior of the blades on the global motion and line tension responses. The results are compared with a standard procedure where the whole system is analyzed entirely by the FAST program. Due to its simplification, this hybrid methodology can be employed for preliminary or intermediate design stages. The main goal of the studies presented here is to comprise an initial step toward a full integration between the Prosim and FAST programs. In future works a full coupling between the wind turbine forces and the platform motions will be implemented.

Coupled Dynamic Analysis for Multi-Unit Floating Offshore Wind Turbine in Maximum Operational and Survival Conditions

2015 ◽  
Author(s):  
H. K. Jang ◽  
H. C. Kim ◽  
M. H. Kim ◽  
K. H. Kim
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Time Domain ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Random Waves ◽  
Mooring Lines ◽  
Floating Offshore Wind Turbine ◽  
Coupled Dynamic Analysis ◽  
Floating Offshore Wind Turbines

Numerical tools for a single floating offshore wind turbine (FOWT) have been developed by a number of researchers, while the investigation of multi-unit floating offshore wind turbines (MUFOWT) has rarely been performed. Recently, a numerical simulator was developed by TAMU to analyze the coupled dynamics of MUFOWT including multi-rotor-floater-mooring coupled effects. In the present study, the behavior of MUFOWT in time domain is described through the comparison of two load cases in maximum operational and survival conditions. A semi-submersible floater with four 2MW wind turbines, moored by eight mooring lines is selected as an example. The combination of irregular random waves, steady currents and dynamic turbulent winds are applied as environmental loads. As a result, the global motion and kinetic responses of the system are assessed in time domain. Kane’s dynamic theory is employed to formulate the global coupled dynamic equation of the whole system. The coupling terms are carefully considered to address the interactions among multiple turbines. This newly developed tool will be helpful in the future to evaluate the performance of MUFOWT under diverse environmental scenarios. In the present study, the aerodynamic interactions among multiple turbines including wake/array effect are not considered due to the complexity and uncertainty.

scholarly journals Proposal and Performance Study of a Novel Mooring System with Six Mooring Lines for Spar-Type Offshore Wind Turbines

2021 ◽  
Vol 11 (24) ◽  
pp. 11665
Author(s):  
Shi Liu ◽  
Yi Yang ◽  
Chao Wang ◽  
Yuangang Tu
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Offshore Wind Turbine ◽  
Mooring System ◽  
Mooring Lines ◽  
Included Angle ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

Spar-type floating offshore wind turbines commonly vibrate excessively when under the coupling impact of wind and wave. The wind turbine vibration can be controlled by developing its mooring system. Thus, this study proposes a novel mooring system for the spar-type floating offshore wind turbine. The proposed mooring system has six mooring lines, which are divided into three groups, with two mooring lines in the same group being connected to the same fairlead. Subsequently, the effects of the included angle between the two mooring lines on the mooring-system’s performance are investigated. Then, these six mooring lines are connected to six independent fairleads for comparison. FAST is utilized to calculate wind turbine dynamic response. Wind turbine surge, pitch, and yaw movements are presented and analyzed in time and frequency domains to quantitatively evaluate the performances of the proposed mooring systems. Compared with the mooring system with six fairleads, the mooring system with three fairleads performed better. When the included angle was 40°, surge, pitch, and yaw movement amplitudes of the wind turbine reduced by 39.51%, 6.8%, and 12.34%, respectively, when under regular waves; they reduced by 56.08%, 25.00%, and 47.5%, respectively, when under irregular waves. Thus, the mooring system with three fairleads and 40° included angle is recommended.

Dynamic Responses of a Spar Type Floating Offshore Wind Turbine With Failed Moorings

2020 ◽  
Author(s):  
Yajun Ren ◽  
Vengatesan Venugopal
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Mooring System ◽  
Floating Offshore Wind Turbine ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Platform Motions

Abstract The complex dynamic characteristics of Floating Offshore Wind Turbines (FOWTs) have raised wider consideration, as they are likely to experience harsher environments and higher instabilities than the bottom fixed offshore wind turbines. Safer design of a mooring system is critical for floating offshore wind turbine structures for station keeping. Failure of mooring lines may lead to further destruction, such as significant changes to the platform’s location and possible collisions with a neighbouring platform and eventually complete loss of the turbine structure may occur. The present study focuses on the dynamic responses of the National Renewable Energy Laboratory (NREL)’s OC3-Hywind spar type floating platform with a NREL offshore 5-MW baseline wind turbine under failed mooring conditions using the fully coupled numerical simulation tool FAST. The platform motions in surge, heave and pitch under multiple scenarios are calculated in time-domain. The results describing the FOWT motions in the form of response amplitude operators (RAOs) and spectral densities are presented and discussed in detail. The results indicate that the loss of the mooring system firstly leads to longdistance drift and changes in platform motions. The natural frequencies and the energy contents of the platform motion, the RAOs of the floating structures are affected by the mooring failure to different degrees.

Evaluation of a Hybrid Representation to Model the Wind Turbine, Platform and Mooring Lines in the Analysis of Floating Offshore Wind Turbines

2021 ◽  
Author(s):  
Eloi Daniel de Araujo Neto ◽  
William Rodriguez ◽  
Fabr\xedcio Nogueira Corr\xeaa ◽  
Beatriz De Souza Leite Pires De Lima ◽  
Breno Pinheiro Jacob ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Offshore Wind ◽  
Mooring Lines ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

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

2021 ◽  
Vol 10 (1) ◽  
pp. 37
Author(s):  
Vincenzo Piscopo ◽  
Antonio Scamardella ◽  
Giovanni Battista Rossi ◽  
Francesco Crenna ◽  
Marta Berardengo
Keyword(s):  
Spectral Analysis ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Time Domain ◽  
Offshore Wind ◽  
Stress Process ◽  
Mooring Lines ◽  
Offshore Wind Turbines ◽  
Analysis Methods ◽  
Floating Offshore Wind Turbines

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.

scholarly journals Prospects of Linear Model Predictive Control on a 10 MW Floating Wind Turbine

2015 ◽  
Author(s):  
Frank Lemmer ◽  
Steffen Raach ◽  
David Schlipf ◽  
Po Wen Cheng
Keyword(s):  
Wind Turbine ◽  
Linear Model ◽  
Multiple Input Multiple Output ◽  
Simulation Models ◽  
Coupled System ◽  
Approximate Model ◽  
Offshore Wind ◽  
Design Stage ◽  
Mooring Lines ◽  
Floating Offshore Wind Turbines

The presented research has the objective of supporting the integrated conceptual design of floating offshore wind turbines (FOWT). The dynamics of the multidisciplinary coupled system with the aerodynamics, hydrodynamics, structural dynamics, the catenary mooring lines and the controller shall be represented in simulation models adapted to the current design stage. Here, a linear model-predictive controller (MPC) as an optimal multiple input-multiple output (MIMO) controller is designed for a novel concept of the floating foundation for a 10MW wind turbine. The performance of this controller is easily adjustable by a cost function with multiple objectives. Therefore, the MPC can be seen as a benchmark controller in the concept phase, based on a simplified coupled simulation model with only approximate model information. The linear model is verified against its nonlinear counterpart and the performance of the MPC compared to a SISO PI-controller, which is also designed in this work. The developed models show to be well suited and the linear MPC shows a reduction of the rotor speed overshoot and tower bending from a deterministic gust.

Development of a 10-MW Semisubmersible Type Floating Offshore Wind Turbine for the East Sea, Korea

2020 ◽  
Author(s):  
Hyeonjeong Ahn ◽  
Hyunkyoung Shin
Keyword(s):  
Renewable Energy ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Farm ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Mooring Lines ◽  
Floating Offshore Wind Turbines ◽  
Scale Ratio ◽  
The Stability

Abstract The area of renewable energy is expanding rapidly worldwide, with wind turbines being an example. In Korea, many researchers are conducting studies on floating offshore wind turbines (FOWTs) on areas with suitable wind resources. In particular, Ulsan, which is the site selected in this study, started research on the development of a 200-MW floating offshore wind farm. In this study, the references for upscaling are the 5-MW reference wind turbine of the National Renewable Energy Laboratory (NREL), and the OC4-DeepCwind semisubmersible type floating wind turbine. We upscaled the 5-MW wind turbine to a 10-MW FOWT by applying the appropriate scale ratio for each component of the turbine. We upscaled the specifications related to items such as the blades, hub, and nacelle using the power ratio. The mass of the blades was reduced by using carbon fiber-reinforced plastic (CFRP). We upscaled the specifications related to the tower using its deflection ratio, and the tower clearance criterion and the tower campbell diagram were used to confirm that the design is appropriate. We upscaled the specifications related to the platform using the upper structure mass ratio. The GZ curve of the platform was used to confirm the stability, and we used the air gap for safety. Three catenary type mooring lines were also designed. To understand the static response of the initial model of the 10-MW FOWT, a steady-state analysis was performed according to each wind speed. We followed the IEC and DNV standards, and we used NREL FAST in all simulations.

scholarly journals A Comparative Study on the Dynamic Response of Three Semisubmersible Floating Offshore Wind Turbines

2019 ◽  
Author(s):  
Wei Shi ◽  
Lixian Zhang ◽  
Dezhi Ning ◽  
Zhiyu Jiang ◽  
Constantine Michailides ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Wind Energy ◽  
Comparative Study ◽  
Wind Turbine ◽  
Offshore Wind ◽  
Offshore Wind Energy ◽  
Mooring Lines ◽  
Floating Offshore Wind Turbines ◽  
Floating System ◽  
Design Tradeoffs

Abstract Currently, there is a great interest to globally develop offshore wind energy due to the greenhouse effect and energy crisis. Great efforts have been devoted to develop reliable floating offshore wind energy technology to exploit the wind energy resources in deep seas. This paper presents a comparative study of the dynamic response of three different semisubmersible floating wind turbine structures. All the three platforms support the same 5MW wind turbine. The platforms examined are: a V-shaped Semi, an OC4-DeepCwind Semi and a Braceless Semi at 200 m water depth. A dynamic analysis is carried out in order to calculate and compare the performance of these platforms. The comparison is made on the rigid body motions of the semisubmersible platform and tensions of the mooring lines. The presented comparison is based on statistical values and spectra of the time series of the examined response quantities. Coupling effects are more significant for the V-shaped Semi platform. The V-shaped Semi and the Braceless Semi show a more rational motion response under the investigated load cases. The results of this analysis may help to resolve the fundamental design tradeoffs between among different floating system concepts.

Prediction of Extreme Tensions in Mooring Lines of a Floating Offshore Wind Turbine in a 100-Year Storm

2015 ◽  
Author(s):  
Wei-ting Hsu ◽  
Krish P. Thiagarajan ◽  
Michael MacNicoll ◽  
Richard Akers
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Wind Turbine ◽  
Test Data ◽  
Green Energy ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Mooring System ◽  
Mooring Lines ◽  
Floating Offshore Wind Turbines

Floating offshore wind turbines (FOWTs) contribute to an emerging green energy technology, by exploiting higher and consistent wind speeds above the ocean. There are several challenges facing the design of mooring system of FOWTs, including installation costs, stability of light-weight minimalistic platforms, and shallow depths (50–300m). The extreme tension in mooring lines of a light displacement platform in shallow-water is dominated by snap loads. This is because light pre-tension requirements in the line may be insufficient to prevent the mooring lines from being exposed to wave motion induced slack and shock events. In this paper, we present a comparative analysis of a semi-submersible based FOWT exposed to a 100-year storm condition, based on model test data and numerical simulations of well-known industry standard software. The data was obtained from a 1/50th-scale FOWT with the wind turbine modeled after the NREL 5MW wind turbine. The software, OrcaFlex, was used for numerical simulations of the mooring system. NREL’s FAST software was coupled to OrcaFlex to obtain aerodynamic loads along with hydrodynamic load for FOWT analyses. The numerical simulation of the moored FOWT in a 3-hour storm was executed in both the frequency-domain and the time-domain to determine the dynamic behavior of the platform and mooring system, respectively. Snap–type impact events were observed in both test data and numerical simulation. Tension maxima were fitted into extreme value distributions and comparisons are made between simulated and measured data. It is seen that snap events follow a different exceedance probability distribution compared to the cycle-to-cycle tension maxima.

scholarly journals Effect of Roughness of Mussels on Cylinder Forces from a Realistic Shape Modelling

2021 ◽  
Vol 9 (6) ◽  
pp. 598
Author(s):  
Antoine Marty ◽  
Franck Schoefs ◽  
Thomas Soulard ◽  
Christian Berhault ◽  
Jean-Valery Facq ◽  
...  
Keyword(s):  
Marine Species ◽  
Offshore Structures ◽  
Offshore Wind ◽  
Mooring Lines ◽  
Shape Modelling ◽  
Offshore Wind Turbines ◽  
Specific Effects ◽  
Hydrodynamic Loading ◽  
Floating Offshore Wind Turbines ◽  
Realistic Shape

After a few weeks, underwater components of offshore structures are colonized by marine species and after few years this marine growth can be significant. It has been shown that it affects the hydrodynamic loading of cylinder components such as legs and braces for jackets, risers and mooring lines for floating units. Over a decade, the development of Floating Offshore Wind Turbines highlighted specific effects due to the smaller size of their components. The effect of the roughness of hard marine growth on cylinders with smaller diameter increased and the shape should be representative of a real pattern. This paper first describes the two realistic shapes of a mature colonization by mussels and then presents the tests of these roughnesses in a hydrodynamic tank where three conditions are analyzed: current, wave and current with wave. Results are compared to the literature with a similar roughness and other shapes. The results highlight the fact that, for these realistic roughnesses, the behavior of the rough cylinders is mainly governed by the flow and not by their motions.

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