scholarly journals Mooring Line Damping Estimation for a Floating Wind Turbine

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Dongsheng Qiao ◽  
Jinping Ou
Keyword(s):  
Wind Turbine ◽  
Estimation Method ◽  
Excitation Amplitude ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Scale Model ◽  
Mooring Line ◽  
Offshore Wind Turbine ◽  
Floating Wind Turbine ◽  
Excitation Period

The dynamic responses of mooring line serve important functions in the station keeping of a floating wind turbine (FWT). Mooring line damping significantly influences the global motions of a FWT. This study investigates the estimation of mooring line damping on the basis of the National Renewable Energy Laboratory 5 MW offshore wind turbine model that is mounted on the ITI Energy barge. A numerical estimation method is derived from the energy absorption of a mooring line resulting from FWT motion. The method is validated by performing a 1/80 scale model test. Different parameter changes are analyzed for mooring line damping induced by horizontal and vertical motions. These parameters include excitation amplitude, excitation period, and drag coefficient. Results suggest that mooring line damping must be carefully considered in the FWT design.

Parametric Study of Catenary Mooring System for a Semisubmersible Floating Wind Turbine in Intermediate Water Depth

2020 ◽  
Author(s):  
Jiawen Li ◽  
Qiang Zhang ◽  
Jiali Du ◽  
Yichen Jiang
Keyword(s):  
Wind Turbine ◽  
Water Depth ◽  
Offshore Wind ◽  
Design Parameters ◽  
Mooring Line ◽  
Offshore Wind Turbine ◽  
Reference Structure ◽  
Intermediate Water ◽  
Mooring System ◽  
Floating Wind Turbine

Abstract This paper presents a parametric design study of the mooring system for a floating offshore wind turbine. We selected the OC4 DeepCwind semisubmersible floating wind turbine as the reference structure. The design water depth was 50 m, which was the transition area between the shallow and deep waters. For the floating wind turbine working in this water area, the restoring forces and moments provided by the mooring lines were significantly affected by the heave motion amplitude of the platform. Thus, the mooring design for the wind turbine in this working depth was different from the deep-water catenary mooring system. In this study, the chosen design parameters were declination angle, fairlead position, mooring line length, environmental load direction, and mooring line number. We conducted fully coupled aero-hydro dynamic simulations of the floating wind turbine system in the time domain to investigate the influences of different mooring configurations on the platform motion and the mooring tension. We evaluated both survival and accidental conditions to analyze the mooring safety under typhoon and mooring fail conditions. On the basis of the simulation results, this study made several design recommendations for the mooring configuration for floating wind turbines in intermediate water depth applied in China.

scholarly journals Study of Floating Wind Turbine with Modified Tension Leg Platform Placed in Regular Waves

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 703 ◽  
Author(s):  
Juhun Song ◽  
Hee-Chang Lim
Keyword(s):  
Wind Turbine ◽  
Real Data ◽  
Offshore Wind ◽  
Scale Model ◽  
Offshore Wind Turbine ◽  
Wave Loads ◽  
Tension Leg Platform ◽  
Mooring Lines ◽  
Floating Wind Turbine ◽  
Wave Conditions

In this study, the typical ocean environment was simulated with the aim to investigate the dynamic response under various environmental conditions of a Tension Leg Platform (TLP) type floating offshore wind turbine system. By applying Froude scaling, a scale model with a scale of 1:200 was designed and model experiments were carried out in a lab-scale wave flume that generated regular periodic waves by means of a piston-type wave generator while a wave absorber dissipated wave energy on the other side of the channel. The model was designed and manufactured based on the standard prototype of the National Renewable Energy Laboratory (NREL) 5 MW offshore wind turbine. In the first half of the study, the motion and structural responses for operational wave conditions of the North Sea near Scotland were considered to investigate the performance of a traditional TLP floating wind turbine compared with that of a newly designed TLP with added mooring lines. The new mooring lines were attached with the objective of increasing the horizontal stiffness of the system and thereby reducing the dominant motion of the TLP platform (i.e., the surge motion). The results of surge translational motions were obtained both in the frequency domain, using the response amplitude operator (RAO), and in the time domain, using the omega arithmetic method for the relative velocity. The results obtained show that our suggested concept improves the stability of the platform and reduces the overall motion of the system in all degrees-of-freedom. Moreover, the modified design was verified to enable operation in extreme wave conditions based on real data for a 100-year return period of the Northern Sea of California. The loads applied by the waves on the structure were also measured experimentally using modified Morison equation—the formula most frequently used to estimate wave-induced forces on offshore floating structures. The corresponding results obtained show that the wave loads applied on the new design TLP had less amplitude than the initial model and confirmed the significant contribution of the mooring lines in improving the performance of the system.

VolturnUS 1:8: Conclusion of 18-Months of Operation of the First Grid-Connected Floating Wind Turbine Prototype in the Americas

2015 ◽  
Author(s):  
Anthony M. Viselli ◽  
Andrew J. Goupee ◽  
Habib J. Dagher ◽  
Christopher K. Allen
Keyword(s):  
Wind Turbine ◽  
Large Data ◽  
Full Scale ◽  
Offshore Wind ◽  
Mooring Line ◽  
Offshore Wind Turbine ◽  
Data Set ◽  
Floating Offshore Wind Turbine ◽  
The Past ◽  
Floating Wind Turbine

This paper presents an overview of the successful conclusion of 18 months of testing the first grid-connected floating offshore wind turbine prototype in the Americas. The prototype, called VolturnUS 1:8, was installed off Castine, Maine, USA. The prototype is a 1:8 scale prototype and serves to de-risk the deployment of a full-scale 6MW turbine. VolturnUS utilizes innovations in materials, construction, and deployment technologies such as a concrete semi-submersible hull and an advanced composite tower to reduce the costs of offshore wind. The prototype unit was designed following the American Bureau of Shipping (ABS) “Guide for Building and Classing Floating Offshore Wind Turbine Installations”. Froude scaling was used in designing the 1:8-scale VolturnUS prototype so that the motions of the prototype in the relatively protected site represent those of the full-scale unit in an open site farther offshore. During the past year, a comprehensive instrumentation package monitored key performance characteristics of the platform during operational, extreme, and survival storm conditions. Data collected include: wind speed, turbine power, rotor angular frequency, blade pitch, torque, acceleration; tower bending moment, 6 DOF accelerations at tower top and base, mooring line tensions, and wave elevation at the platform. During the past year the prototype has experienced many environments representative of scaled ABS design conditions including operational wind and sea-states, 50-year sea states and 500-year survival sea states. This large data set provides a unique view of a near full-scale floating wind turbine subjected to its prescribed environmental conditions. Inspections of the concrete hull following removal provided confirmation of material durability. Marine growth measurements provide data for future design efforts.

scholarly journals Dynamic Response for a Submerged Floating Offshore Wind Turbine with Different Mooring Configurations

2019 ◽  
Vol 7 (4) ◽  
pp. 115 ◽  
Author(s):  
Yane Li ◽  
Conghuan Le ◽  
Hongyan Ding ◽  
Puyang Zhang ◽  
Jian Zhang
Keyword(s):  
Dynamic Response ◽  
Wind Turbine ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Mooring Line ◽  
Offshore Wind Turbine ◽  
Intermediate Water ◽  
Mooring System ◽  
Mooring Lines ◽  
Floating Offshore Wind Turbine

The paper discusses the effects of mooring configurations on the dynamic response of a submerged floating offshore wind turbine (SFOWT) for intermediate water depths. A coupled dynamic model of a wind turbine-tower-floating platform-mooring system is established, and the dynamic response of the platform, tensions in mooring lines, and bending moment at the tower base and blade root under four different mooring configurations are checked. A well-stabilized configuration (i.e., four vertical lines and 12 diagonal lines with an inclination angle of 30°) is selected to study the coupled dynamic responses of SFOWT with broken mooring lines, and in order to keep the safety of SFOWT under extreme sea-states, the pretension of the vertical mooring line has to increase from 1800–2780 kN. Results show that the optimized mooring system can provide larger restoring force, and the SFOWT has a smaller movement response under extreme sea-states; when the mooring lines in the upwind wave direction are broken, an increased motion response of the platform will be caused. However, there is no slack in the remaining mooring lines, and the SFOWT still has enough stability.

scholarly journals Dynamic Responses for WindFloat Floating Offshore Wind Turbine at Intermediate Water Depth Based on Local Conditions in China

2021 ◽  
Vol 9 (10) ◽  
pp. 1093
Author(s):  
Shan Gao ◽  
Lixian Zhang ◽  
Wei Shi ◽  
Bin Wang ◽  
Xin Li
Keyword(s):  
Wind Energy ◽  
Wind Turbine ◽  
Water Depth ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Mooring Line ◽  
Offshore Wind Turbine ◽  
Floating Offshore Wind Turbine ◽  
Coupled Method ◽  
Simplified Method

Offshore wind energy, a clean energy resource, is considered to be a possible alternative to fossil energy. Floating offshore wind technology is considered to be a proper concept to develop abundant wind energy in deep water. Considering the reality of offshore wind energy development in China, the floating offshore wind turbine concept is expected to be developed at moderate water depths. In this paper, a mooring system of the WindFloat semisubmersible floating offshore wind turbine (SFOWT) at a water depth of 60 m is designed. The dynamic responses of the WindFloat SFOWT under different wind–wave combination conditions are investigated using the coupled method and the simplified method, which do not include the effect of the tower top motion in the aerodynamic calculation. The results show that the dynamic responses of the WindFloat SFOWT, including the platform motions, tower loads, and mooring line tensions, perform fairly well at a moderate water depth. A comparison between the coupled method and simplified method shows that the calculated results are slightly different between the different conditions for the time domain results, response spectra results, and fatigue results. In addition, mooring line 1 (ML 1) suffers higher fatigue damage than ML2, which should be paid more attention.

scholarly journals Proposal of a Novel Semi-Submersible Floating Wind Turbine Platform Composed of Inclined Columns and Multi-Segmented Mooring Lines

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1809 ◽  
Author(s):  
Zhenqing Liu ◽  
Qingsong Zhou ◽  
Yuangang Tu ◽  
Wei Wang ◽  
Xugang Hua
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Mooring Line ◽  
Offshore Wind Turbine ◽  
Analysis Tool ◽  
Mooring Lines ◽  
Offshore Area ◽  
Floating Wind Turbine ◽  
Inclined Angle ◽  
Heave Motion

The semi-submersible floating offshore wind turbine has been studied in detail due to its good stability. However, the occurrence of typhoons are very frequent in China’s offshore area, putting forward a higher requirement for the stability of the floating wind turbine system. By changing the connection mode of the mooring line as well as the structural form of the platform based on the original OC4 model, two groups of models were examined by an in-house developed code named as the Analysis Tool of Floating Wind Turbine (AFWT). The influence of the arrangement of the mooring lines and the inclination angle of the upper columns on the motion response were clarified. It was found that the surge motion of the platform would be obviously decreased by decreasing the length of the upper segments of the mooring lines, while the heave motion of the platform would be significantly decreased as increasing the inclined angle of the columns. Therefore, a new model integrating the optimized multi-segmented mooring lines and the optimized inclined columns was proposed. The examinations showed that compared with the response motions of the original OC4 semi-submersible model, the proposed model could reduce both the surge and heave motions of the platform effectively.

scholarly journals Vibration Mitigation of the Barge-Type Offshore Wind Turbine with a Tuned Mass Damper on Floating Platform

2018 ◽  
Vol 36 (2) ◽  
pp. 238-245 ◽  
Author(s):  
Jiajia Yang ◽  
Erming He ◽  
Yaqi Hu
Keyword(s):  
Wind Turbine ◽  
Tuned Mass Damper ◽  
Equal Mass ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Platform ◽  
Vibration Mitigation ◽  
Floating Wind Turbine ◽  
Mass Damper

This paper evaluates the application of a passive control technique with a tuned mass damper on platform for the barge-type offshore wind turbine. First of all, the three degrees of freedom mathematical model for the floating wind turbine is established based on Lagrange's equations, and the Levenberg-Marquardt algorithm is adopted to estimate the parameters of the wind turbine. Then, the method of frequency tuning which is utilized in engineering projects and genetic algorithm are employed respectively to simulate the optimum parameters of the tuned mass damper. The vibration mechanism about the phase-angle difference between tuned mass damper and floating platform is analyzed. Finally, the dynamic responses of floating wind turbine with/without tuned mass damper are calculated under five typical wind and wave load cases, and the vibration mitigation effects are researched in marine environment. Partial ballast is substituted by the equal mass of tuned mass damper due to the mass of floating platform with tuned mass damper would increase obviously, which would change the design of the wind turbine, and the vibration mitigation is also simulated in five typical load cases. The results show that the suppression rate of standard deviation of platform pitch is up to 47.95%, after substituting the partial mass of ballast, the suppression rate is 50%. Therefore, the dynamic responses of the barge-type floating wind turbine would be reduced significantly when the ballast is replaced by the equal mass of the tuned mass damper on floating platform.

Experimental Study for SPAR Type Floating Offshore Wind Turbine With Blade-Pitch Control

2013 ◽  
Author(s):  
Toshiki Chujo ◽  
Yoshimasa Minami ◽  
Tadashi Nimura ◽  
Shigesuke Ishida
Keyword(s):  
Wind Turbine ◽  
Wind Farm ◽  
Offshore Wind ◽  
Scale Model ◽  
Offshore Wind Turbine ◽  
Experimental Proof ◽  
Pitch Control ◽  
Model Experiments ◽  
North Eastern ◽  
North Eastern Part

The experimental proof of the floating wind turbine has been started off Goto Islands in Japan. Furthermore, the project of floating wind farm is afoot off Fukushima Prof. in north eastern part of Japan. It is essential for realization of the floating wind farm to comprehend its safety, electric generating property and motion in waves and wind. The scale model experiments are effective to catch the characteristic of floating wind turbines. Authors have mainly carried out scale model experiments with wind turbine models on SPAR buoy type floaters. The wind turbine models have blade-pitch control mechanism and authors focused attention on the effect of blade-pitch control on both the motion of floater and fluctuation of rotor speed. In this paper, the results of scale model experiments are discussed from the aspect of motion of floater and the effect of blade-pitch control.

Model Test and Numerical Analysis of an Offshore Bottom Fixed Pentapod Wind Turbine Under Seismic Loads

2016 ◽  
Author(s):  
Wenhua Wang ◽  
Zhen Gao ◽  
Xin Li ◽  
Torgeir Moan ◽  
Bin Wang
Keyword(s):  
Wind Turbine ◽  
Wind Wave ◽  
Seismic Analysis ◽  
Wind Farms ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Test Model ◽  
Structural Dynamic ◽  
Load Conditions

In the last decade the wind energy industry has developed rapidly in China, especially offshore. For a water depth less than 20m, monopile and multi-pile substructures (tripod, pentapod) are applied widely in offshore wind farms. Some wind farms in China are located in high seismicity regions, thus, the earthquake load may become the dominant load for offshore wind turbines. This paper deals with the seismic behavior of an offshore wind turbine (OWT) consisting of the NREL 5MW baseline wind turbine, a pentapod substructure and a pile foundation of a real offshore wind turbine in China. A test model of the OWT is designed based on the hydro-elastic similarity. Test cases of different load combinations are performed with the environmental conditions generated by the Joint Earthquake, Wave and Current Simulation System and the Simple Wind Field Generation System at Dalian University of Technology, China, in order to investigate the structural dynamic responses under different load conditions. In the tests, a circular disk is used to model the rotor-nacelle system, and a force gauge is fixed at the center of the disk to measure the wind forces during the tests. A series of accelerometers are arranged along the model tower and the pentapod piles, and strain gauges glued on the substructure members are intended to measure the structural dynamic responses. A finite element model of the complete wind turbine is also established in order to compare the theoretical results with the test data. The hydro-elastic similarity is validated based on the comparison of the measured dynamic characteristics and the results of the prototype modal analysis. The numerical results agree well with the experimental data. Based on the comparisons of the results, the effect of the wind and sea loads on the structural responses subjected to seismic is demonstrated, especially the influence on the global response of the structure. It is seen that the effect of the combined seismic, wind, wave and current load conditions can not be simply superimposed. Hence the interaction effect in the seismic analysis should be considered when the wind, wave and current loads have a non-negligible effect.

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