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Delegates are invited to meet and discuss with the poster presenters in this topic directly after the session 'Optimising measurement strategies to maximise project value: Is the industry making false economies at the expense of project value?' taking place on Tuesday, 11 March 2014 at 11:15-12:45. The meet-the-authors will take place in the poster area.

Bárbara Jiménez Douglas DEWI GmbH, Germany
Co-authors:
Bárbara Jiménez Douglas (1) F P Danny Rimpl (1) Kai Moennich (1)
(1) DEWI GmbH, Oldenburg, Germany

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Abstract

Validation and comparison of wind resource models in highly complex terrain

Introduction

The Annual Energy Production (AEP) estimation for a wind farm is a crucial step in the planning phase of new wind farm projects. More and more wind farms are built in highly complex terrain for which the traditional tools for flow field calculations, like the industry standard WAsP (4) developed by DTU (Risø), are beyond their application limits. It is well known that such linear flow models cannot resolve flow detachment and recirculation, which become increasingly important in complex terrain analysis and evident in the Bolund blind comparison results (7).

Approach

The ability of the Computational Fluid Dynamics (CFD) model to capture non-linear flow effects allows being more representative than the linear flow model at all locations across a complex site.
Therefore, more attention is given to these models in the wind energy community and new software packages or CFD extensions with improved calculation cores are available on the market.



Main body of abstract

But how much do these new models really improve the reliability of the flow modelling, and therefore the determination of the energy yields to be expected?
A validation of CFD wind field modelling versus field measurement data is essential in order to improve simulation accuracy for long-term AEP estimations.
For this presentation several sites with multiple measurement masts in different countries have been simulated with CFD model and the results have been compared. The CFD calculations have been performed using the O.F.Wind software package based on OpenFoam (2)(3), with Phoenics software (7), and with the WAsP-CFD model (4).
The comparison of measured and numerically modelled data has been done in terms of mean wind speed and vertical wind profile, as well as, wind resource files for long-term AEP predictions have been generated. The long-term AEP on each wind turbine position results were also compared to the linear flow model WAsP output.


Conclusion

In our presentation we will shortly introduce the different models and the sites, and then focus on the validation of the models with the measurement masts and on the crosswise comparison. Furthermore, we will show the major pitfalls one can step in during a CFD calculation, such as the importance of the quality of the measurements and their position on the terrain in order to get good model performance.



Learning objectives
How much do these new CFD models really improve the reliability of the flow modelling?
Validation of CFD models with the measurement masts and on the crosswise comparison.
Major pitfalls one can step in during a CFD calculation.