A Novel Concept for Floating Offshore Wind Turbines: Recent Developments in the Concept and Investigation on Fluid Interaction With the Rotating Foundation

2010 ◽  
Author(s):  
Luca Vita ◽  
Frederik Zhale ◽  
Uwe S. Paulsen ◽  
Troels F. Pedersen ◽  
Helge A. Madsen ◽  
...  
Keyword(s):  
Wind Turbines ◽  
Vertical Axis ◽  
Operating Conditions ◽  
Offshore Wind ◽  
Navier Stokes ◽  
Drag Forces ◽  
Floating Offshore Wind Turbines ◽  
Recent Developments ◽  
Lift And Drag ◽  
Novel Concept

This paper describes the recent developments regarding a new concept for deep sea offshore vertical axis wind turbines. The concept utilizes a cylindrical foundation rotating in the water. The 2D Navier-Stokes solver EllipSys2D has been used to investigate the interaction between the rotating foundation and a water flow stream passing the turbine. Lift and drag forces, and the friction moment on the rotating foundation of the turbine have been computed. The calculations are repeated for different operating conditions of the wind turbine on a range of rotational speeds. The Reynolds number, based on the diameter of the foundation, is 5×106.

Force Measurements of the Flow Around Arrays of Three and Four Columns With Different Geometry Sections, Spacing Ratios, and Incidence Angles

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Rodolfo Trentin Gonçalves ◽  
Shinichiro Hirabayashi ◽  
Guilherme Vaz ◽  
Hideyuki Suzuki
Keyword(s):  
Degrees Of Freedom ◽  
Incidence Angle ◽  
Offshore Structures ◽  
Offshore Wind ◽  
Cfd Validation ◽  
Numerical Work ◽  
Drag Forces ◽  
Floating Offshore Wind Turbines ◽  
Spacing Ratio ◽  
Lift And Drag

Abstract An experimental campaign for the flow around a stationary array of three and four columns with low aspect ratio, H/L = 1.5, piercing the water free surface, was carried out in a towing tank. These numbers of columns correspond to typical multi-column offshore systems, such as semi-submersibles (SS), tension leg platforms (TLPs), and floating offshore wind turbines (FOWTs). Three parameters were investigated: the spacing ratio between column centers (from two up to four characteristic lengths), current incidence angles, and column section geometries (circular, square, and diamond). The Reynolds number of the experiments was 100,000. Forces were measured in each column using a three degrees-of-freedom load cell, and results of lift and drag forces were presented for each column separately and the whole system. The results of mean and standard deviation of forces were assessed using a statistical uncertainty analysis procedure for finite length measurements’ signals. This methodology not only assesses the quality of the experimental data but also facilitates validation of numerical tools. The objectives of the current work were therefore manifold: to better understand the influence of the relative position, shape, and incidence angle on multi-column offshore structures; to create a reliable database for computational fluid dynamics (CFD) validation; and to prepare the path to flow-induced motions (FIMs) experimental and numerical work of free-moving multi-column offshore systems.

scholarly journals On the Modeling of Spar-Type Floating Offshore Wind Turbines

2013 ◽  
Vol 569-570 ◽  
pp. 636-643 ◽  
Author(s):  
Van Nguyen Dinh ◽  
Biswajit Basu
Keyword(s):  
Wind Turbines ◽  
Operating Conditions ◽  
Offshore Wind ◽  
Wave Loads ◽  
Dynamic Coupling ◽  
Modeling Tools ◽  
Modeling And Analysis ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Floating Platforms

In this paper an overview about floating offshore wind turbines (FOWT) including operating conditions, property and applicability of the barge, tension-leg, and spar floating platforms is described. The spar-floating offshore wind turbines (S-FOWT) have advantages in deepwater and their preliminary design, numerical modeling tools and integrated modeling are reviewed. Important conclusions about the nacelle and blade motions, tower response, effects of wind and wave loads, overall vibration and power production of the S-FOWT are summarized. Computationally-simplified models with acceptable accuracy are necessary for feasibility and pre-engineering studies of the FOWT. The design needs modeling and analysis of aero-hydro-servo dynamic coupling of the entire FOWT. This paper also familiarizes authors with FOWT and its configurations and modeling approaches.

Model-Inversion Feedforward Control for Wave Load Reduction in Floating Wind Turbines

2021 ◽  
Author(s):  
Alessandro Fontanella ◽  
Marco Belloli
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Control Strategy ◽  
Feedforward Control ◽  
Operating Conditions ◽  
Offshore Wind ◽  
Linear Wave ◽  
Wave Load ◽  
Floating Wind Turbine ◽  
Floating Offshore Wind Turbines

Abstract This paper develops a novel feedforward control strategy for reducing structural loads caused by waves in floating offshore wind turbines. The proposed control strategy is based on the inversion of a linear model of the floating wind turbine, and a real-time forecast of the wave obtained from an upstream measurement is utilized to compute a collective pitch control action. Two feedforward controllers are considered: one is designed to cancel the rotor speed oscillations and one to lower the towertop fore-aft shear force. The feedforward control strategies are implemented in a 10MW floating wind turbine, complementing the standard feedback controller for generator speed regulation. Numerical simulations are carried out in FAST, in four operating conditions with realistic wind and waves, proving the proposed feedforward controller effectively mitigates the structural loads caused by waves. In detail, the feedforward action reduces the loads spectra in the frequency range where linear wave is active. The best performance is realized higher winds (the FA force is reduced up to 25% in 22 m/s wind), where the wave excitation is the strongest.

scholarly journals Load Mitigation on Floating Offshore Wind Turbines With Advanced Controls and Tuned Mass Dampers

2018 ◽  
Author(s):  
John Cross-Whiter ◽  
Benjamin B. Ackers ◽  
Dhiraj Arora ◽  
Alan Wright ◽  
Paul Fleming ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
Wind Turbines ◽  
Water Depth ◽  
Operating Conditions ◽  
Offshore Wind ◽  
Tuned Mass Dampers ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Advanced Controls ◽  
Load State

General Electric, the National Renewable Energy Laboratory (NREL), the University of Massachusetts Amherst (UMass), and Glosten have recently completed a US Department of Energy (DOE)-funded research program to study technologies for mitigating loads on floating offshore wind turbines through the use of advanced turbine controls and tuned mass dampers (TMDs). The analysis was based upon the Glosten PelaStar tension leg platform (TLP) with GE Haliade 150 turbine, a system developed in a previous front end engineering design (FEED) study funded by the Energy Technology Institute (ETI) in the UK. The platform was designed for the WaveHub wave energy research site, with a mean water depth of 59-m. Loads were analyzed by running time-domain simulations in four 50-year return period (50-YRP) ultimate load state (ULS) conditions and 77 fatigue load state (FLS) environmental conditions. In 50-YRP conditions advanced controls are not active. The influence of TMDs on ULS loads have been reported previously (Park et al. [2]). In FLS conditions advanced controls and TMDs afford dramatic reductions in fatigue damage, offering the potential of significant savings in tower structural requirements. Simulations in turbine idling conditions were run in OrcaFlex, and simulations in operating conditions were run in FAST. Simulations were run with a baseline turbine controller, representative of the current state of the art, and an advanced controller developed by NREL to use collective and individual blade pitch control to maintain rotor speed and reduce tower loads. UMass developed a number of TMD types, with varying system configurations, including passive nonlinear dampers and semi-actively controlled dampers with an inverse velocity groundhook control algorithm. Loads and accelerations in FLS conditions were evaluated on the basis of damage equivalent loads (DELs), and fatigue damage was computed by Miner’s summations of stress cycles at the tower base. To study sensitivity to water depth, loads were analyzed at both the 59-m WaveHub depth and a more commercially realistic depth of 100 m. TMDs reduce fatigue damage at the tower-column interface flange by up to 52% in 59-m water depth and up to 28% in 100 m water depth. Advanced controls reduce fatigue damage at the tower-column flange by up to 22% in 59-m water depth and up to 40% in 100 m water depth. The most effective load-mitigation strategy is combining advanced controls with TMDs. This strategy affords a 71% reduction in fatigue damage in both 59-m and 100-m water depths.

scholarly journals General Methodology for the Identification of Reduced Dynamic Models of Barge-Type Floating Wind Turbines

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3902
Author(s):  
Daniel Villoslada ◽  
Matilde Santos ◽  
María Tomás-Rodríguez
Keyword(s):  
Wind Turbines ◽  
Structural Control ◽  
Dynamic Models ◽  
Operating Conditions ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Data Set ◽  
General Methodology ◽  
Floating Offshore Wind Turbines ◽  
Reduced Dynamic

Floating offshore wind turbines (FOWT) are designed to overcome some of the limitations of offshore bottom-fixed ones. The development of computational models to simulate the behavior of the structure and the turbine is key to understanding the wind energy system and demonstrating its feasibility. In this work, a general methodology for the identification of reduced dynamic models of barge-type FOWTs is presented. The method is described together with an example of the development of a dynamic model of a 5 MW floating offshore wind turbine. The novelty of the proposed identification methodology lies in the iterative loop relationship between the identification and validation processes. Diversified data sets are used to select the best-fitting identified parameters by cross evaluation of every set among all validating conditions. The data set is generated for different initial FOWT operating conditions. Indeed, an optimal initial condition for platform pitch was found to be far enough from the system at rest to allow the dynamics to be well characterized but not so far that the unmodeled system nonlinearities were so large that they affected significantly the accuracy of the model. The model has been successfully applied to structural control research to reduce fatigue on a barge-type FOWT.

A Comparison of Two Coupled Model of Dynamics for Offshore Floating Vertical Axis Wind Turbines (VAWT)

2014 ◽  
Author(s):  
Michael Borg ◽  
Kai Wang ◽  
Maurizio Collu ◽  
Torgeir Moan
Keyword(s):  
Wind Turbines ◽  
Coupled Model ◽  
Vertical Axis ◽  
Offshore Wind ◽  
Design Codes ◽  
Vertical Axis Wind Turbines ◽  
Complex Simulation ◽  
Floating Offshore Wind Turbines ◽  
Horizontal Axis Wind Turbines ◽  
Engineering Models

As part of the deployment of floating offshore wind turbines (FOWTs) in deep sea, robust coupled dynamic design codes based on engineering models are being developed to investigate the behaviour of FOWTs in the offshore environment. The recent re-emerging interest in vertical axis wind turbines (VAWTs) for floating foundation applications has resulted in a number of design codes being developed concurrently by different researchers. In this study, two such design codes for floating VAWTs developed at Cranfield University and the Norwegian University of Science and Technology are compared through a series of increasingly complex simulation load cases. A floating VAWT design was specified to be used in this study. The rotor is based on the Darrieus Troposkein shape and is the same used within the DeepWind VAWT spar concept, with a 5MW rated capacity. The floating support structure is a semi-submersible that is being used in the Offshore Code Collaboration Continuation (OC4) Phase II project for floating horizontal axis wind turbines. A series of load cases were set out to assess and compare the two different design codes. A comparison of the performance of the two design tools is presented, illustrating their level of maturity and areas of improvement.

Design and Dynamic Analysis of a Compact 10 MW Medium Speed Gearbox for Offshore Wind Turbines

2019 ◽  
Author(s):  
Shuaishuai Wang ◽  
Amir R. Nejad ◽  
Torgeir Moan
Keyword(s):  
Wind Turbines ◽  
Power Distribution ◽  
Operating Conditions ◽  
International Standards ◽  
Offshore Wind ◽  
Resonance Phenomenon ◽  
Offshore Wind Turbine ◽  
Power Splitting ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

Abstract This paper presents the design of a compact gearbox for the DTU 10 MW reference offshore wind turbine. An innovative gearbox concept consisting of a fixed planetary stage with a differential compound epicyclic stage is proposed. Power splitting and compound epicyclic transmission technologies are employed, which could effectively reduce the gearbox’ size. Power transmission principle of the gearbox is described, and power distribution on two transfer paths is derived by the geometrical and mechanical relationships among the components. The gearbox is designed based on the design loads and criteria with reference to the relevant international standards, and all of the critical components, gears and bearings, are designed by performing fatigue limit state (FLS) check. A high fidelity drivetrain dynamic model, consisting of the compact gearbox and one four-point support drivetrain configuration, is established by means of multi-body system (MBS) approach. Then, validation of the power distribution is conducted by the comparison of the simulation results and design values. Resonance analysis of the drivetrain model is conducted by employing Campbell diagram, energy distribtuion of components and time domain simulation approach, and the results show that no resonance phenomenon appears in this drivetrain model during the normal operating conditions. In addition, load sharing performance of the MBS model is assessed, indicating the a favorable dynamic operating behavior of the gearbox. It is believed that such compact design could be good alternative for floating offshore wind turbines.

Pitch Angle Control of Floating Offshore Wind Turbines by H∞ Control

2014 ◽  
Vol 134 (8) ◽  
pp. 1096-1103 ◽  
Author(s):  
Sho Tsujimoto ◽  
Ségolène Dessort ◽  
Naoyuki Hara ◽  
Keiji Konishi
Keyword(s):  
Wind Turbines ◽  
Pitch Angle ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

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

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 ◽  
Floating 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.

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