The VolturnUS 1:8 Floating Wind Turbine: Design, Construction, Deployment, Testing, Retrieval, and Inspection of the First Grid-Connected Offshore Wind Turbine in US

Offshore wind turbine is a novel approach in the field of wind energy technology. With the rapid development of coastal wind farms, it is the trend to move them outward to deep-water district. However, the cost of construction rises significantly with the increase in water depth. Floating wind turbine is one of the efficient methods to solve this problem. The early history, current status and cutting-edge improvements of overseas offshore floating wind turbine as well as the shortcomings shall be presented. The concept designs, international standards, fully coupled model simulations and hydrodynamic experiments will be illustrated and discussed together with the development of the theory and the related software modules. Thus a novel researching method and concept shall be presented to provide reference for future researches

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Mooring Line Damping Estimation for a Floating Wind Turbine

The Scientific World JOURNAL ◽

10.1155/2014/840283 ◽

2014 ◽

Vol 2014 ◽

pp. 1-10 ◽

Cited By ~ 1

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.

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

Volume 9: Ocean Renewable Energy ◽

10.1115/omae2020-18365 ◽

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.

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

Energies ◽

10.3390/en12040703 ◽

2019 ◽

Vol 12 (4) ◽

pp. 703 ◽

Cited By ~ 3

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.

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

Volume 9: Ocean Renewable Energy ◽

10.1115/omae2015-41065 ◽

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.

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Efficient preliminary floating offshore wind turbine design and testing methodologies and application to a concrete spar design

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2014.0350 ◽

2015 ◽

Vol 373 (2035) ◽

pp. 20140350 ◽

Cited By ~ 11

Author(s):

Denis Matha ◽

Frank Sandner ◽

Climent Molins ◽

Alexis Campos ◽

Po Wen Cheng

Keyword(s):

Wind Turbine ◽

Design Process ◽

Experimental Tests ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Floating Offshore Wind Turbine ◽

Testing Methodology ◽

Cost Of Energy ◽

Turbine Design ◽

Design And Testing

The current key challenge in the floating offshore wind turbine industry and research is on designing economic floating systems that can compete with fixed-bottom offshore turbines in terms of levelized cost of energy. The preliminary platform design, as well as early experimental design assessments, are critical elements in the overall design process. In this contribution, a brief review of current floating offshore wind turbine platform pre-design and scaled testing methodologies is provided, with a focus on their ability to accommodate the coupled dynamic behaviour of floating offshore wind systems. The exemplary design and testing methodology for a monolithic concrete spar platform as performed within the European KIC AFOSP project is presented. Results from the experimental tests compared to numerical simulations are presented and analysed and show very good agreement for relevant basic dynamic platform properties. Extreme and fatigue loads and cost analysis of the AFOSP system confirm the viability of the presented design process. In summary, the exemplary application of the reduced design and testing methodology for AFOSP confirms that it represents a viable procedure during pre-design of floating offshore wind turbine platforms.

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Modeling the TetraSpar Floating Offshore Wind Turbine Foundation as a Flexible Structure in OrcaFlex and OpenFAST

Energies ◽

10.3390/en14237866 ◽

2021 ◽

Vol 14 (23) ◽

pp. 7866

Author(s):

Jonas Bjerg Thomsen ◽

Roger Bergua ◽

Jason Jonkman ◽

Amy Robertson ◽

Nicole Mendoza ◽

...

Keyword(s):

Wind Turbine ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Entire Body ◽

Floating Offshore Wind Turbine ◽

Modeling Approaches ◽

Rigid Body Model ◽

Six Degree Of Freedom ◽

Turbine Design ◽

Floating Platforms

Floating offshore wind turbine technology has seen an increasing and continuous development in recent years. When designing the floating platforms, both experimental and numerical tools are applied, with the latter often using time-domain solvers based on hydro-load estimation from a Morison approach or a boundary element method. Commercial software packages such as OrcaFlex, or open-source software such as OpenFAST, are often used where the floater is modeled as a rigid six degree-of-freedom body with loads applied at the center of gravity. However, for final structural design, it is necessary to have information on the distribution of loads over the entire body and to know local internal loads in each component. This paper uses the TetraSpar floating offshore wind turbine design as a case study to examine new modeling approaches in OrcaFlex and OpenFAST that provide this information. The study proves the possibility of applying the approach and the extraction of internal loads, while also presenting an initial code-to-code verification between OrcaFlex and OpenFAST. As can be expected, comparing the flexible model to a rigid-body model proves how motion and loads are affected by the flexibility of the structure. OrcaFlex and OpenFAST generally agree, but there are some differences in results due to different modeling approaches. Since no experimental data are available in the study, this paper only forms a baseline for future studies but still proves and describes the possibilities of the approach and codes.

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Modelling the Aerodynamics of a Floating Wind Turbine Model Using a CFD-Based Actuator Disc Method

ASME 2019 2nd International Offshore Wind Technical Conference ◽

10.1115/iowtc2019-7526 ◽

2019 ◽

Author(s):

Ryan Bezzina ◽

Tonio Sant ◽

Daniel Micallef

Keyword(s):

Wind Turbine ◽

Offshore Wind ◽

Speed Ratio ◽

Offshore Wind Turbine ◽

Floating Platform ◽

Blade Element Theory ◽

Floating Wind Turbine ◽

Actuator Disc ◽

Turbine Wake ◽

Blade Element

Abstract Significant research in the field of Floating Offshore Wind Turbine (FOWT) rotor aerodynamics has been documented in literature, including validated aerodynamic models based on Blade Element Momentum (BEM) and vortex methods, amongst others. However, the effects of platform induced motions on the turbine wake development downstream of the rotor plane or any research related to such areas is rather limited. The aims of this paper are two-fold. Initially, results from a CFD-based Actuator Disc (AD) code for a fixed (non-surging) rotor are compared with those obtained from a Blade Element Momentum (BEM) theory, as well as previously conducted experimental work. Furthermore, the paper also emphasises the effect of tip speed ratio (TSR) on the rotor efficiency. This is followed by the analysis of floating wind turbines specifically in relation to surge displacement, through an AD technique implemented in CFD software, ANSYS Fluent®. The approach couples the Blade Element Theory (BET) for estimating rotating blade loads with a Navier Stokes solver to simulate the turbine wake. With regards to the floating wind turbine cases, the code was slightly altered such that BET was done in a transient manner i.e. following sinusoidal behaviour of waves. The AD simulations were performed for several conditions of TSRs and surge frequencies, at a constant amplitude. Similar to the fixed rotor analysis, significant parameters including thrust and power coefficients, amongst others, were studied against time and surge position. The floating platform data extracted from the AD approach was compared to the non-surging turbine data obtained, to display platform motion effects clearly. Data from hot wire near wake measurements and other simulation methods were also consulted.

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Effect of Nacelle Drag on the Performance of a Floating Wind Turbine Platform

ASME 2019 2nd International Offshore Wind Technical Conference ◽

10.1115/iowtc2019-7595 ◽

2019 ◽

Author(s):

Daewoong Son ◽

Pauline Louazel ◽

Bingbin Yu

Keyword(s):

Wind Turbine ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Simulation Tool ◽

Floating Structure ◽

Drag Forces ◽

Floating Wind Turbine

Abstract Wind forces acting on an offshore wind turbine are transferred to the bottom of the tower and consequently to the floating structure. Thus, drag forces acting on each component of the wind turbine such as the blades, the nacelle, and the tower must be accounted for properly in order to evaluate the performance of the supporting platform. In the aero-elastic wind turbine simulation tool FAST v.7, the nacelle drag component, however, has not been implemented, which means that only the drag forces on the tower and on the blades are represented. In this work, the front and side nacelle drag forces are modelled in FAST v.7 via different drag contributions. This paper will examine the behavior of a floating offshore semisubmersible platform, the WindFloat, for different Rotor-Nacelle-Assembly (RNA) yaw-misalignments with emphasis on the nacelle drag component.

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Assessing the Impact of Integrating Energy Storage on the Dynamic Response of a Spar-Type Floating Wind Turbine

ASME 2019 2nd International Offshore Wind Technical Conference ◽

10.1115/iowtc2019-7577 ◽

2019 ◽

Author(s):

Charise Cutajar ◽

Tonio Sant ◽

Robert N. Farrugia ◽

Daniel Buhagiar

Keyword(s):

Energy Storage ◽

Dynamic Response ◽

Wind Turbine ◽

Energy Demand ◽

Large Scale ◽

Preliminary Investigation ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Floating Wind Turbine ◽

The Impact

Abstract Offshore wind technology is at the forefront of exploiting renewable energy at sea. The latest innovations in the field comprise floating wind turbines deployed in deep waters that are capable of intercepting the stronger, less turbulent winds farther away from the landmass. Despite being able to augment the power harnessed, wind resources remain intermittent in nature, and so unable to satisfy the energy demand at all times. Energy storage systems (ESS) are therefore being considered a key component to smoothen out the supply-demand mismatch when wind penetration into electricity grids increases. Yet, multiple issues pertaining to the integration of ESSs on large-scale projects arise, including economic, environmental and safety considerations. This paper presents a novel concept for integrating a hydro-pneumatic energy storage (HPES) system within a spar-type floating offshore wind turbine (FOWT) platform. It aims to assess the technical feasibility of integrating the storage unit within the floater. A preliminary investigation on the influence of integrated storage on the static stability and hydrostatic response of a conventional ballast-stabilised FOWT is conducted, followed by numerical simulations for the dynamic response using ANSYS® AQWA™. Based on the results presented, several conclusions are drawn on the implications of integrating energy storage with floating wind turbine structures. Finally, a preliminary assessment of the thermal efficiency of the storage system based on this specific embodiment is also presented and discussed.

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