Scientific advances and innovation

  • Multidisciplinary approach to characterize the wave/wind/structure coupling for a floating wind turbine
  • Emulation of wind turbine floater motions in an atmospheric boundary layer wind tunnel
  • Experiments performed in controlled (atmospheric wind tunnel) and real (SEM-REV) conditions
  • Set-up of wake dynamic models for floating wind turbines

Expected technical and economic impact

FLOATEOLE project illustrates the objective of the research lab in Hydrodynamics, Energetics and Atmospheric Environment (LHEEA) to contribute, through a multidisciplinary approach, to the optimization of floating wind turbines operation by studying the consequences of the wave/wind/structure coupling on the performance and durability of the wind energy converters subjected to harsh and non-deterministic operating conditions.

The goal of the project is to combine wind tunnel and full-scale offshore experiments in order to characterize the wave influence on the aerodynamic behavior of the floating wind turbines and on their wake development. Indeed, wake interactions, particularly strong in offshore conditions, are responsible of power production loss and structural fatigue increase. The wave effects will be emulated in wind tunnel by applying a controlled motion to the wind turbine models. The motion scenarios will be representative of idealized sea states, and then of more realistic ones. The unsteady behavior of the wind turbine wakes will be captured and some unsteady wake models adapted to floating systems will be proposed. This work will be completed by full scale measurements with a scanning LiDAR system of the local environment of the floating wind turbine prototype FLOATGEN; the wind resource as well as the wind turbine wake will therefore be captured in real sea state conditions.

FLOATEOLE project highlights the positioning of the Region Pays de Loire in the landscape of the offshore wind energy research and development. This major objective contributes to the overall optimization of the marine renewable energies and so, to tackle the energetic, climatic and socio-economic challenges levied by the energy transition.

Key project milestones

  • November 2017 - Project Kick-off
  • October 2019 - Emulation of 1DoF floater motions in an atmospheric boundary layer wind tunnel
  • Winter 2021 - Emulation of 3DoF floater motions in an atmospheric boundary layer wind tunnel
  • Fall 2021 - Wind resource Measurements in the surrounding of the prototype FLOATGEN in SEM-REV
  • November 2021 - Wake dynamic models for floating wind turbines

Demonstrator

Emulator of wind turbine floater motions in an atmospheric boundary layer wind tunnel

Results

The first year has been dedicated to the preparation of the wind tunnel experimental aspects related to FLOATEOLE project (atmospheric wind tunnel conditioning and validation, Choice of the motion emulator). During a 5-month internship, an engineering student has been involved on the technical specifications of the electromechanical system that will be used to emulate the floater motion in the wind tunnel. He has also designed the experimental-set-up to reproduce a typical offshore boundary layer on the atmospheric wind tunnel of the LHEEA lab. He has been performed the preliminary validation measurements. These first tasks enable the PhD student recruited in October 2018 to start his work in optimal conditions.

The second year was dedicated to the refinement of the modelled marine atmospheric boundary layer in the wind tunnel at the geometric scale of 1:500 and to the characterization of the wind turbine porosity-based model wake. The development of a 1DDL motion system able to reproduce floater motions had been performed. A parametrical study on the surge motion magnitude and period had been carried out and it was shown that the turbulence level, measured within the wake at four diameters downstream of the porous disc, was reduced. These preliminary results need to be completed and further interpreted.

Vertical profiles of mean velocity downstream of a floating wind turbine model versus the frequency of the imposed surge motion

Vertical profiles of mean velocity downstream of a floating wind turbine model versus the frequency of the imposed surge motion

The third year was dedicated to a finer characterization of the impact of the periodic surge and sway motions on the FOWT wake recovery. Some stereo-PIV measurements were performed to capture the wake evolution several diameters downstream of the FOWT model. Additional data processing is still needed to determine the physical phenomena responsible of the FOWT wake modifications.

The specifications and the selection of a 3DoF motion system were also performed during this third year. Two motion systems were purchased in 2020 thanks to the present project and to the WEAMEC project 3D4FLOATEOLE.

Example of mean velocity fields measured with a stereo-PIV system downstream of a floating wind turbine model

Example of mean velocity fields measured with a stereo-PIV system downstream of a floating wind turbine model

Publications and papers published

Oral communications
Publication

Prospects

The European project H2020-MSCA-ITN FLOAWER (FLOAting Wind Energy netwoRk) started on November 2019.It is composed of 10 beneficiaries and 11 academic and industrial associate partners. Centrale Nantes coordinates the project. FLOAWER will provide 13 Early Stage Researchers (ESR) with an interdisciplinary training with the aim to design better performing, economically viable floating wind turbines. FLOAWER website: www.floawer-h2020.eu

The present project enabled us to collaborate with the German consortium involved in VAMOS project (Univ Stuttgart, TU Hamburg, DNV-GL and UL, DEWI et Sowento). This project started in July 2019, for three years. It will enable the set-up of a joint experiment on Floatgen prototype and a collaboration on the measurement exploitation and on the wake models.