Study on the Dynamic Response for Floating Foundation of Offshore Wind Turbine

Author(s):  
Yougang Tang ◽  
Jun Hu ◽  
Liqin Liu

The wind resources for ocean power generation are mostly distributed in sea areas with the distance of 5–50km from coastline, whose water depth are generally over 20m. To improve ocean power output and economic benefit of offshore wind farm, it is necessary to choose floating foundation for offshore wind turbine. According to the basic data of a 600kW wind turbine with a horizontal shaft, the tower, semi-submersible foundation and mooring system are designed in the 60-meter-deep sea area. Precise finite element models of the floating wind turbine system are established, including mooring lines, floating foundation, tower and wind turbine. Dynamic responses for the floating foundation of offshore wind turbine are investigated under wave load in frequency domain.

2013 ◽  
Vol 275-277 ◽  
pp. 852-855 ◽  
Author(s):  
Zhuang Le Yao ◽  
Chao He Chen ◽  
Yuan Ming Chen

In this paper, the overall finite element model is established, to analyze the small-sized floating foundation of a tri-floater and to make a local optimization on the stress concentration area. The transfer functions and the response spectrums of wave load and motion of floating wind turbine system are calculated by AQWA. Besides the concept of the floating foundation group is put forward in this paper. It is small in structure, easy to assemble, and it can be developed for any power of wind field.This concept has a certain reference value for the development of offshore wind industry in China.


2012 ◽  
Vol 170-173 ◽  
pp. 2316-2321
Author(s):  
Ruo Yu Zhang ◽  
Chao He Chen ◽  
You Gang Tang

In this paper, the dynamic behaviors are studied for Spar type floating foundation of a 3kW in the 10m deep water considering the coupled wind turbine-tower-floating foundation and mooring lines and ocean environment load effects. The paper focus on the key issues of design of floating foundation, such as coupling dynamic analysis model and calculating method. The finite element models are established and dynamic responses of floating wind turbine system under different combinations of turbulent wind, constant current and irregular wave are calculated in frequency and time domain with SESAM software. The motion performance and lines’ tension are investigated, and some valuable conclusions are drawn. The results show that the Spar type floating foundation and mooring system can work in the ocean environment which significant wave height less than 2m, the designed large water-entrapment plate can minimized the motion of floating foundation obviously.


2020 ◽  
Vol 217 ◽  
pp. 108155
Author(s):  
Guangwei Cao ◽  
Zhixiong Chen ◽  
Chenglong Wang ◽  
Xuanming Ding

2019 ◽  
Vol 7 (4) ◽  
pp. 115 ◽  
Author(s):  
Yane Li ◽  
Conghuan Le ◽  
Hongyan Ding ◽  
Puyang Zhang ◽  
Jian Zhang

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.


Author(s):  
Hyungjun Kim ◽  
Joonmo Choung ◽  
Gi-Young Jeon

This paper presents a mooring design procedure of a floating offshore wind turbine. The offshore environment data of Jeju south sea collected from Korea Hydrographic and Oceanographic Administration (KHOA) are used as environmental conditions for hydrodynamic analysis. A semi-submersible floating wind turbine system is considered based on Offshore Code Comparison Collaborative Continuation (OC4) DeepCWind platform and the National Renewable Energy Laboratory (NREL) 5MW class wind turbine. Catenary mooring with studless chain is chosen as the mooring system. Important design decisions such as how large the nominal sizes are, how long the mooring lines are, how far the anchor points are located, are demonstrated in detail. Considering ultimate limit state and fatigue limit state based on 100-year return period and 50 year design life, respectively, long-term predictions of breaking strength and fatigue are performed.


Author(s):  
Hyeonjeong Ahn ◽  
Hyunkyoung Shin

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.


Author(s):  
Wei Gong

Renewable energy provides a solution for complex current and future social and environmental problems whereas offshore industry has a large potential for providing renewable energy for future. Currently, offshore technology making use of wind for energy generation purpose becomes a hot spot with highly advanced research and development going on on one side and complex and critical problems present and difficult to solve on the other. This paper is trying to study problems related to the quantification of the hydrodynamic and aerodynamic loads for the design of offshore wind turbine support structures in the offshore wind farm. Both the hydrodynamic and aerodynamic conditions in the offshore site are extremely complex resulting in the difficulty of reasonable determination for the external loads on the wind turbine support structures. However, due to the increasing global demands for future energy solution, the design, analysis and optimization of offshore wind turbine is nevertheless an important issue. The paper first gives an introduction of the offshore wind farm and the complexity of the offshore environment. Wave load is explored with introduction of existing wave load models, comparison of their characteristics while the focus is placed on the nonlinear wave load by means of the Stokes higher order wave theory. Properties of a single regular wave based on methods of linear wave theory and Stokes higher order wave theory are compared which lead to differences in the results of wave load models when these two different methods are used. Wind load model is introduced briefly, followed by the introduction of current methods for determination or approximation of combined wave and wind load and also recommendations for practice. Park effect of the wind load and wave load is also introduced at limited depth in the latter stage as a direction for future research. Conclusion and recommendations based on all the above are therefore given at the last section of the paper.


Author(s):  
Motohiko Murai ◽  
Kensaku Takahashi

The progress of the global warming is one of our key issue should be overcome in the 21st century. We should balance the energy consumption and reduction of exhausting greenhouse effect gas. The wind energy is expected as one of the key technology for utilizing renewable energy. It is said that as for the efficiency of the electric generation, it is better the wider wind farm with larger wind mill. But, as the land space for the extensive wind farm is quite limited, it will be a candidate how to use the vast ocean space for human activity. So, the construction of an offshore wind farm is one of the solution now. To extend the wind farm widely in the ocean the floating wind turbine system becomes an essential technology. Under such background, there are many researches on the floating wind turbine in waves and in wind. And hydrodynamic response of them in waves is one of the major topics. Many of the researches on the hydrodynamic response, however, deal with the motion of a single floating wind turbine. This report deals with the hydrodynamic response of a wind farm which is consisted of semi-submersible wind turbines. In addition, the investigation of how does the arrangement of the array impact on the hydrodynamic response including the motion of the nacelle is also reported. In the last the example of the change of the expected efficiency of the generator by change of the array arrangement in each sea area around Japan are shown.


Author(s):  
Toshiki Chujo ◽  
Yoshimasa Minami ◽  
Tadashi Nimura ◽  
Shigesuke Ishida

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.


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