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

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.

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

Volume 9: Ocean Renewable Energy ◽

10.1115/omae2015-42062 ◽

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 ◽

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.

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

Applied Sciences ◽

10.3390/app112411665 ◽

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 ◽

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.

Impact of Typhoons on Floating Offshore Wind Turbines: A Case Study of Typhoon Mangkhut

Journal of Marine Science and Engineering ◽

10.3390/jmse9050543 ◽

2021 ◽

Vol 9 (5) ◽

pp. 543

Author(s):

Jiawen Li ◽

Jingyu Bian ◽

Yuxiang Ma ◽

Yichen Jiang

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Safety Evaluation ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Motion Response ◽

Offshore Wind Turbines ◽

Coupling Motion

A typhoon is a restrictive factor in the development of floating wind power in China. However, the influences of multistage typhoon wind and waves on offshore wind turbines have not yet been studied. Based on Typhoon Mangkhut, in this study, the characteristics of the motion response and structural loads of an offshore wind turbine are investigated during the travel process. For this purpose, a framework is established and verified for investigating the typhoon-induced effects of offshore wind turbines, including a multistage typhoon wave field and a coupled dynamic model of offshore wind turbines. On this basis, the motion response and structural loads of different stages are calculated and analyzed systematically. The results show that the maximum response does not exactly correspond to the maximum wave or wind stage. Considering only the maximum wave height or wind speed may underestimate the motion response during the traveling process of the typhoon, which has problems in guiding the anti-typhoon design of offshore wind turbines. In addition, the coupling motion between the floating foundation and turbine should be considered in the safety evaluation of the floating offshore wind turbine under typhoon conditions.

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

Volume 5: Ocean Space Utilization; Ocean Renewable Energy ◽

10.1115/omae2011-50329 ◽

2011 ◽

Author(s):

Yougang Tang ◽

Jun Hu ◽

Liqin Liu

Keyword(s):

Wind Turbine ◽

Wind Farm ◽

Dynamic Responses ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Wave Load ◽

Mooring Lines ◽

Floating Foundation ◽

Wind Turbine System ◽

Sea Area

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.

Fatigue Life Analysis of Offshore Wind Turbine Support Structures in an Offshore Wind Farm

ASME 2018 1st International Offshore Wind Technical Conference ◽

10.1115/iowtc2018-1061 ◽

2018 ◽

Author(s):

Bryan Nelson ◽

Yann Quéméner

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Wind Farm ◽

The Body ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Analysis Tool ◽

Support Structures ◽

Offshore Wind Farm ◽

Actuator Disk

This study evaluated, by time-domain simulations, the fatigue lives of several jacket support structures for 4 MW wind turbines distributed throughout an offshore wind farm off Taiwan’s west coast. An in-house RANS-based wind farm analysis tool, WiFa3D, has been developed to determine the effects of the wind turbine wake behaviour on the flow fields through wind farm clusters. To reduce computational cost, WiFa3D employs actuator disk models to simulate the body forces imposed on the flow field by the target wind turbines, where the actuator disk is defined by the swept region of the rotor in space, and a body force distribution representing the aerodynamic characteristics of the rotor is assigned within this virtual disk. Simulations were performed for a range of environmental conditions, which were then combined with preliminary site survey metocean data to produce a long-term statistical environment. The short-term environmental loads on the wind turbine rotors were calculated by an unsteady blade element momentum (BEM) model of the target 4 MW wind turbines. The fatigue assessment of the jacket support structure was then conducted by applying the Rainflow Counting scheme on the hot spot stresses variations, as read-out from Finite Element results, and by employing appropriate SN curves. The fatigue lives of several wind turbine support structures taken at various locations in the wind farm showed significant variations with the preliminary design condition that assumed a single wind turbine without wake disturbance from other units.

Individual Blade Pitch Control for Alleviation of Vibratory Loads on Floating Offshore Wind Turbines

10.1115/omae2021-63316 ◽

2021 ◽

Author(s):

Luca Pustina ◽

Claudio Pasquali ◽

Jacopo Serafini ◽

Claudio Lugni ◽

Massimo Gennaretti

Keyword(s):

Renewable Energy ◽

Wind Turbine ◽

Bending Moment ◽

Offshore Wind ◽

Synthesis Process ◽

Control Synthesis ◽

Offshore Wind Turbine ◽

Floating Offshore Wind Turbine ◽

Blade Root ◽

Abstract Among the renewable energy technologies, offshore wind energy is expected to provide a significant contribution for the achievement of the European Renewable Energy (RE) targets for the next future. In this framework, the increase of generated power combined with the alleviation of vibratory loads achieved by application of suitable advanced control systems can lead to a beneficial LCOE (Levelized Cost Of Energy) reduction. This paper defines a control strategy for increasing floating offshore wind turbine lifetime through the reduction of vibratory blade and hub loads. To this purpose a Proportional-Integral (PI) controller based on measured blade-root bending moment feedback provides the blade cyclic pitch to be actuated. The proportional and integral gain matrices are determined by an optimization procedure whose objective is the alleviation of the vibratory loads due to a wind distributed linearly on the rotor disc. This control synthesis process relies on a linear, state-space, reduced-order model of the floating offshore wind turbine derived from aero-hydroelastic simulations provided by the open-source tool OpenFAST. In addition to the validation of the proposed controller, the numerical investigation based on OpenFAST predictions examines also the corresponding control effort, influence on platform dynamics and expected blade lifetime extension. The outcomes show that, as a by-product of the alleviation of the vibratory out-of-plane bending moment at the blade root, significant reductions of both cumulative blade lifetime damage and sway and roll platform motion are achieved, as well. The maximum required control power is less than 1% of the generated power.

The Effect of the Second-Order Wave Loads on Drift Motion of a Semi-Submersible Floating Offshore Wind Turbine

Journal of Marine Science and Engineering ◽

10.3390/jmse8110859 ◽

2020 ◽

Vol 8 (11) ◽

pp. 859

Author(s):

Thanh-Dam Pham ◽

Hyunkyoung Shin

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Second Order ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Wave Loads ◽

Hydrodynamic Loads ◽

Drift Motion ◽

Offshore Wind Turbines ◽

Floating offshore wind turbines (FOWTs) have been installed in Europe and Japan with relatively modern technology. The installation of floating wind farms in deep water is recommended because the wind speed is stronger and more stable. The design of the FOWT must ensure it is able to withstand complex environmental conditions including wind, wave, current, and performance of the wind turbine. It needs simulation tools with fully integrated hydrodynamic-servo-elastic modeling capabilities for the floating offshore wind turbines. Most of the numerical simulation approaches consider only first-order hydrodynamic loads; however, the second-order hydrodynamic loads have an effect on a floating platform which is moored by a catenary mooring system. At the difference-frequencies of the incident wave components, the drift motion of a FOWT system is able to have large oscillation around its natural frequency. This paper presents the effects of second-order wave loads to the drift motion of a semi-submersible type. This work also aimed to validate the hydrodynamic model of Ulsan University (UOU) in-house codes through numerical simulations and model tests. The NREL FAST code was used for the fully coupled simulation, and in-house codes of UOU generates hydrodynamic coefficients as the input for the FAST code. The model test was performed in the water tank of UOU.

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 ◽

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.

Design Requirements for Floating Offshore Wind Turbines

Volume 8: Ocean Renewable Energy ◽

10.1115/omae2013-11365 ◽

2013 ◽

Author(s):

Xiaohong Chen ◽

Qing Yu

Keyword(s):

Wind Turbine ◽

Case Studies ◽

Wind Turbines ◽

Offshore Wind ◽

Design Parameters ◽

Offshore Wind Turbine ◽

Support Structure ◽

Offshore Wind Turbines ◽

Design Requirements

This paper presents the research in support of the development of design requirements for floating offshore wind turbines (FOWTs). An overview of technical challenges in the design of FOWTs is discussed, followed by a summary of the case studies using representative FOWT concepts. Three design concepts, including a Spar-type, a TLP-type and a Semisubmersible-type floating support structure carrying a 5-MW offshore wind turbine, are selected for the case studies. Both operational and extreme storm conditions on the US Outer Continental Shelf (OCS) are considered. A state-of-the-art simulation technique is employed to perform fully coupled aero-hydro-servo-elastic analysis using the integrated FOWT model. This technique can take into account dynamic interactions among the turbine Rotor-Nacelle Assembly (RNA), turbine control system, floating support structure and stationkeeping system. The relative importance of various design parameters and their impact on the development of design criteria are evaluated through parametric analyses. The paper also introduces the design requirements put forward in the recently published ABS Guide for Building and Classing Floating Offshore Wind Turbine Installations (ABS, 2013).

Progress on the Development of a Holistic Coupled Model of Dynamics for Offshore Wind Farms: Phase I — Aero-Hydro-Servo-Elastic Model, With Drive Train Model, for a Single Wind Turbine

Volume 10: Ocean Renewable Energy ◽

10.1115/omae2018-77886 ◽

2018 ◽

Cited By ~ 1

Author(s):

Z. Lin ◽

D. Cevasco ◽

M. Collu

Keyword(s):

Wind Turbine ◽

Failure Mode ◽

Wind Turbines ◽

Wind Farm ◽

Failure Modes ◽

Coupled Model ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Elastic Model ◽

Offshore Wind Turbines

Currently, around 1500 offshore wind turbines are operating in the UK, for a total of 5.4GW, with further 3GW under construction, and 13GW consented. Until now, the focus of the research on offshore wind turbines has been mainly on how to minimise the CAPEX, but Operation and maintenance (O&M) can represent up to 39% of the lifetime costs of an offshore wind farm, due mainly to the high cost of the assets and the harsh environment, limiting the access to these assets in a safe mode. The present work is a part of a larger project, called HOME Offshore (www.homeoffshore.org), and it has as aim an advanced interpretation of the fault mechanisms through a holistic multiphysics modelling of the wind farm. The first step (presented here) toward achieving this aim consists of two main tasks: first of all, to identify and rank the most relevant failure modes within a wind farm, identifying the component, its mode of failure, and the relative environmental conditions. Then, to assess (for each failure mode) how the full-order, nonlinear model of dynamics used to represent the dynamics of the wind turbine can be reduced in order, such that is less computationally expensive (and therefore more suitable to be scaled up to represent multiple wind turbines), but still able to capture and represent the relevant dynamics linked with the inception of the chosen failure mode. A methodology to rank the failure modes is presented, followed by an approach to reduce the order of the Aero-Hydro-Servo-Elastic (AHSE) model of dynamics adopted. The results of the proposed reduced-order models are discussed, comparing it against the full-order coupled model, and taking as case study a fixed offshore wind turbine (monopile) in gearbox failure condition.