Research and development about the mechanisms of a single point mooring system for 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.

Download Full-text

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

Volume 9: Ocean Renewable Energy ◽

10.1115/omae2020-18353 ◽

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.

Download Full-text

Demonstration of the Intelligent Mooring System for Floating Offshore Wind Turbines

ASME 2019 2nd International Offshore Wind Technical Conference ◽

10.1115/iowtc2019-7544 ◽

2019 ◽

Cited By ~ 1

Author(s):

Magnus J. Harrold ◽

Philipp R. Thies ◽

Peter Halswell ◽

Lars Johanning ◽

David Newsam ◽

...

Keyword(s):

Wind Turbines ◽

Oil And Gas ◽

Oil And Gas Industry ◽

Offshore Wind ◽

Mooring System ◽

Gas Industry ◽

Offshore Wind Turbines ◽

Floating Offshore Wind Turbines ◽

Physical Testing ◽

Line Loads

Abstract Existing mooring systems for floating offshore wind turbines are largely based on designs from the oil and gas industry. Even though these can ensure the safe station keeping of the floating wind platform, the design of the mooring system is currently largely conservative, leading to additional expense in an industry striving to achieve cost reduction. Recent interest in the usage of mooring materials with non-linear stiffness has shown that they have the potential to reduce peak line loads, ultimately reducing cost. This paper reports on the combined physical testing and numerical modeling of a hydraulic-based mooring component with these characteristics. The results suggest that the inclusion of the component as part of the OC4 semi-submersible platform can reduce the peak line loads by 10%. The paper also discusses a number of challenges associated with modeling and testing dynamic mooring materials.

Download Full-text

Offshore Wind Turbines – Research and Development

Journal of Maritime & Transportation Science ◽

10.18048/2018-00.59 ◽

2018 ◽

Vol 2 (Special edition 2) ◽

pp. 59-70

Author(s):

Neven Hadžić ◽

Ivan Ćatipović ◽

Marko Tomić ◽

Nikola Vladimir ◽

Hrvoje Kozmar

Keyword(s):

Research And Development ◽

Wind Turbines ◽

Offshore Wind ◽

Response Analysis ◽

Energy Potential ◽

Analysis And Design ◽

Offshore Wind Turbines ◽

Design Procedures ◽

Sea Current ◽

Current Loading

The purpose of the present study is to review the state-of-the-art in research and development of offshore wind turbines in order to address the latest findings and trends in structural design and response analysis. This could enhance a development of sophisticated offshore wind turbines. To complete such a task, a detailed review of offshore wind renewable energy potential, wind, wave and sea current loading as well as structural analysis and design procedures and experimental work are presented.

Download Full-text

Fault Detection of the Mooring system in Floating Offshore Wind Turbines based on the Wave-excited Linear Model

Journal of Physics Conference Series ◽

10.1088/1742-6596/1618/2/022049 ◽

2020 ◽

Vol 1618 ◽

pp. 022049

Author(s):

Yichao Liu ◽

Alessandro Fontanella ◽

Ping Wu ◽

Riccardo M.G. Ferrari ◽

Jan-Willem van Wingerden

Keyword(s):

Fault Detection ◽

Linear Model ◽

Wind Turbines ◽

Offshore Wind ◽

Mooring System ◽

Offshore Wind Turbines ◽

Floating Offshore Wind Turbines

Download Full-text

Investigation of Hydrodynamic Forces for Floating Offshore Wind Turbines on Spar Buoys and Tension Leg Platforms with the Mooring Systems in Waves

Applied Sciences ◽

10.3390/app9030608 ◽

2019 ◽

Vol 9 (3) ◽

pp. 608 ◽

Cited By ~ 1

Author(s):

Yu-Hsien Lin ◽

Shin-Hung Kao ◽

Cheng-Hao Yang

Keyword(s):

Wind Turbines ◽

Time Domain ◽

Simulation System ◽

Offshore Wind ◽

Modular System ◽

Mooring System ◽

Mooring Lines ◽

Offshore Wind Turbines ◽

Motion Responses ◽

Floating Offshore Wind Turbines

This study aims to develop a modularized simulation system to estimate dynamic responses of floating Offshore Wind Turbines (OWTs) based on the concepts of spar buoy and Tension Leg Platform (TLP) corresponding with two typical mooring lines. The modular system consists of the hydrodynamic simulator based the Cummins time domain equation, the Boundary Element Method (BEM) solver based on the 3D source distribution method, and an open-source visualization software ParaView to analyze the interaction between floating OWTs and waves. In order to realize the effects of mooring loads on the floating OWTs, the stiffness and damping matrices are applied to the quasi-static mooring system. The Response Amplitude Operators (RAOs) are compared between our predicted results and other published data to verify the modularized simulation system and understand the influence of mooring load on the motion responses in regular or irregular waves. It is also demonstrated that the quasi-static mooring system is applicable to different types of mooring lines as well as determining real-time motion responses. Eventually, wave load components at the resonance frequencies of different motion modes for selected floating OWTs would be present in the time domain.

Download Full-text

Concept Design and Analysis of Wind-Tracing Floating Offshore Wind Turbines

ASME 2019 2nd International Offshore Wind Technical Conference ◽

10.1115/iowtc2019-7580 ◽

2019 ◽

Cited By ~ 1

Author(s):

Shuijin Li ◽

Azin Lamei ◽

Masoud Hayatdavoodi ◽

Carlos Wong

Keyword(s):

Wind Turbines ◽

Single Point ◽

Offshore Wind ◽

Concept Design ◽

Floating Platform ◽

Floating Structure ◽

Element Analysis ◽

Offshore Wind Turbines ◽

Cost Of Energy ◽

Floating Offshore Wind Turbines

Abstract Most of the existing floating offshore wind turbines (FOWT), whether in concept or built, host a single turbine. Structures that can host multiple turbines have received attention in recent years, mainly with the aim of reducing the overall cost of energy production and maintenance. A concept challenge of placing multiple wind turbines on a single floating platform is that under variable wind directions, the leading turbines may block the wind against the trailing turbines. In this work, concept design of a wind-tracing floating structure accommodating three wind turbines is presented. The triangular-shapefloating platform is made of pre-stressed concrete, and the turbines are located on the corners. The floating structure uses a single-point mooring system which allows for the entire structure to rotate in response to the change of wind direction. Due to the particular configuration of the floating structure, it is essential to consider the wind, wave and current loads, along with the response of the structure, simultaneously. Response of the FOWT to simultaneous environmental loads from different directions is studied by use of the constant panel approach of the Green function method, subject to constant wind loads on the turbines and linear mooring loads. We also consider the elasticity of the structure by use of finite element analysis, coupled with the hydro- and aero-dynamic loads and responses.

Download Full-text