Saarblitz, Wind farm in HDR, flickr.com, creative commons by-nc-sa 2.0

AVATAR

The EU FP7 project AVATAR was started by an EERA (European Energy Research Alliance) consortium in November 2013. The project lasts 4 years and is carried out by the following consortim consisting of 11 research institutes and two industry partners:

  • Energy Research Centre of the Netherlands, ECN (The Netherlands, coordinator)
  • Delft University of Technology, TU Delft (The Netherlands)
  • Technical University of Denmark,  DTU (Denmark)
  • Fraunhofer IWES (Germany)
  • University of Oldenburg, Forwind (Germany)
  • University of Stuttgart (Germany)
  • National Renewable Energy Centre, CENER (Spain)
  • University of Liverpool (until September 2015) / University of Glasgow (as of September 2015) (United Kingdom)
  • Centre for Renewable Energy Sources and Saving, CRES (Greece)
  • National Technical University of Athens, NTUA (Greece)
  • Politecnico di Milano, Polimi (Italy)
  • General Electric, GE (Germany)
  • LM Wind Power (Denmark)

The aim of this project is to improve and validate aerodynamic models for such 10MW+ turbines. The project is needed because current aerodynamic modelling for such large blades violates assumptions on e.g. compressibility and Reynolds number effects, as well as assumptions on flow transition and separation effects. Moreover large blades are exposed to a much more complex flow-structure interaction than currently applied. Further complications enter by the possible implementation of active and/or passive flow devices which could be expected on such turbines in order to enhance power production or to reduce loads.

In the AVATAR project aerodynamic models are improved and calibrated for 10MW+ turbines with and without flow devices including an assessment of the aero-elastic consequences. Thereto a wide variety of aerodynamic models is considered, ranging from low complexity/computational efficient models (e.g. BEM) to high fidelity computational demanding models (e.g. CFD), with intermediate models (e.g. free vortex wake models) in between. In this respect it is important to recognize the crucial role of calculation time for wind energy design calculations by which, even in modern times, it is still imperative to use engineering aerodynamic models based on the Blade Element Momentum Theory (BEM theory) in industrial design. The wide variety of models in the project then enables a calibration from low complexity/fast tools with results from the high fidelity models.

The improvement and validation of aerodynamic models is also based on suitable experimental data but as 10 MW+ turbines do not exist today, experimental data are gained from a range of sub-model tests or tests at a smaller scale. Amongst others 2D airfoil measurements at high Reynolds numbers (up to 15 Million) were taken in the pressurized DNW HDG wind tunnel in Göttingen. In addition, the project partner LM provided airfoil measurements taken in their tunnel and Forwind provided wind tunnel data under controlled turbulent conditions. Several other wind tunnel measurement data sets for flow devices are available, either offered in-kind or obtained from the AVATAR project. .

 

The model assessment is carried out on two 10 MW reference turbines, one from the INNWIND.EU project and another one designed in AVATAR. The latter uses the INNWIND.EU reference turbine as an onset but is in the end more challenging in terms of aerodynamic modelling. Aspects like airfoil thicknesses, Reynolds and Mach numbers etc. are pushed toward the limits of what is conceivable for future commercial applications

AVATAR is organized in different Work Packages (WP’s). Apart from the Work Packages on dissemination and coordination there is a Work Package (WP2) that deals with the advanced aerodynamic modeling of all aspects which are expected to play a role in the design of large 10MW+ wind turbine blades. The modeling of flow devices is included in a separate Work Package (WP3). The modeling of aero-elastic effects on large and flexible rotor blades also needs a separate Work Package (WP4). Moreover a Work Package (WP1) is added which integrates and evaluates the results and which provides the reference turbines on which the modeling is tested.

As such there are four technical Work Packages:

  • WP1 Integration and Evaluation 10 MW Rotor  (WP1),
  • WP2 Advanced Aerodynamic Modelling(WP2),
  • WP3 Models for Flow Devices and Flow Control  (WP3),
  • WP4 Aeroelastic Analysis of Large and Flexible Blades (WP4).

Almost all results from the project are public and can be found on http://www.eera-avatar.eu/

The present site provides the relevant information for the benchmark cases which are provided within AVATAR.

At this moment (December 2015) benchmark cases from WP3 are provided. At a a later stage Benchmark cases from other Work Packages will be provided too.