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Delegates are invited to meet and discuss with the poster presenters in this topic directly after the session 'The model chain: First steps towards tomorrow's technology' taking place on Thursday, 13 March 2014 at 09:00-10:30. The meet-the-authors will take place in the poster area.

Evangelia Maria Giannakopoulou EDF Energy R&D UK Centre , United Kingdom
Co-authors:
Evangelia Maria Giannakopoulou (1) F P Eric Dupont (2) Jerome Drevet (3)
(1) EDF Energy R&D UK Centre , London , United Kingdom (2) EDF R&D, Paris, France (3) CEREA, Paris, France

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2014 and are published here unedited

Dr. Giannakopoulou has been working in the wind sector for almost five years. She is currently a R&D Wind Resource Engineer at EDF Energy. She is working on wind flow modelling research activities with state-of-the-art tools and methodologies for offshore wind farms.
She has a degree in Mathematics. She did her MSc in Mathematical and Numerical Modelling of the Atmosphere and Oceans at the University of Reading and she holds a PhD in Atmospheric Physics from Imperial College. There, her research was focused on the land-boundary layer-sea interactions in the context of LLJ development.

Abstract

WRF Model Methodology for Offshore Wind Energy Applications as Part of the Model Chain

Introduction

Offshore wind energy has become a rapidly growing renewable energy resource worldwide, with several offshore wind projects in development. Despite of this, a better understanding of the interaction between the marine atmospheric boundary layer (MABL) and wind turbines is needed to ensure energy production and increase the lifetime of the projects. The MABL is less studied than the BL over land and one of the reasons/challenges is the scarcity and the costs of obtaining offshore observations. This study deals with these challenges by developing a mesoscale modelling method as part of a multi-scale approach for wind resource assessment (WRA).

Approach

We apply a multi-scale method which is an innovative approach of dynamically modelling the wind from a regional to a local scale. This approach is based on mesoscale modelling, clustering (selection of representative cases) and microscale modelling of selected cases for calculating the wake losses. This study mainly focuses on the mesoscale model and its ability to simulate with reasonable accuracy the MABL, including important atmospheric properties such as the stability conditions. However, the use of any mesoscale model for wind energy applications requires first a proper validation process to understand the accuracy and limitations of the model.

Main body of abstract

For this validation process, the Weather Research and Forecasting (WRF) model has been applied to simulate the wind and stability conditions at the North Sea and English Channel during 2004–2005. The main goals of the present study were:
• to investigate and show the capability of the WRF model to accurately simulate the wind flow and atmospheric stability occurring inland, in the coastal areas and over the MABL of the North Sea and English Channel,
• to achieve a better understanding of the offshore wind conditions and
• to develop a mesoscale modelling approach that could be used for more accurate WRA.
In order to achieve these goals, the sensitivity of the WRF model performance to the use of different PBL parameterisations, horizontal resolutions, initial and boundary conditions, and nesting options was examined. Comparison of the model results with high quality offshore and coastal observations showed that the different initial conditions and PBL schemes do have an impact on the model results. It was found that the ERA-Interim re-analysis data instead of the NCEP data allows reducing the bias between simulated and observed winds. It was also found that the wind and stability conditions in each region were best modelled using a different PBL scheme. For example, during 2004 the WRF model showed good performance following the pattern of the observed winds at the English Channel (with 0.08 m/s bias, 1.95 m/s standard deviation and correlation of 0.81) only when the Asymmetric-Convective-Model version2 (ACM2) PBL scheme was selected.


Conclusion

Deeper understanding of the MABL–turbine interactions is needed for an offshore wind farm development. To address this need and provide a better understanding of the MABL, we investigated and determined the wind and stability conditions in the North Sea and English Channel during 2004–2005 by using the WRF model. The WRF model appeared to be a valuable tool for the determination of the offshore wind conditions with small deviations from the observed wind speeds. We concluded that appropriate selection of the model configuration is needed for the accurate simulation of the winds and atmospheric stratification.


Learning objectives
In this study, a mesoscale method was developed considering important characteristics of the MABL. With this method we achieved a better understanding of the North Sea and English Channel wind and stability conditions and with our dynamical multi-scale approach, of which part is the mesoscale modelling, we expect to reduce the wind resource uncertainty compared to other simplified operational tools used until now in the offshore WRA (e.g. long-term corrections, horizontal and vertical extrapolation methods).