Wind Farm Wake: The Horns Rev Photo Case

Charlotte Hasager,Leif Rasmussen,Leo Jensen,Alfredo Peña,Pierre-Elouan Réthoré

doi:10.3390/en6020696

Charlotte Hasager, Leif Rasmussen + Show 3 more

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https://doi.org/10.3390/en6020696

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Journal: Energies	Publication Date: Feb 5, 2013
Citations: 71	License type: CC BY 4.0

Affiliation: Technical University of Denmark

Abstract

The aim of the paper is to examine the nowadays well-known wind farm wake photographs taken on 12 February 2008 at the offshore Horns Rev 1 wind farm. The meteorological conditions are described from observations from several satellite sensors quantifying clouds, surface wind vectors and sea surface temperature as well as ground-based information at and near the wind farm, including Supervisory Control and Data Acquisition (SCADA) data. The SCADA data reveal that the case of fog formation occurred 12 February 2008 on the 10:10 UTC. The fog formation is due to very special atmospheric conditions where a layer of cold humid air above a warmer sea surface re-condensates to fog in the wake of the turbines. The process is fed by warm humid air up-drafted from below in the counter-rotating swirl generated by the clock-wise rotating rotors. The condensation appears to take place primarily in the wake regions with relatively high axial velocities and high turbulent kinetic energy. The wind speed is near cut-in and most turbines produce very little power. The rotational pattern of spiraling bands produces the large-scale structure of the wake fog.

Highlights

IntroductionThe Horns Rev 1 wind farm is located in the North Sea at about 14 to 20 km offshore from the Danish coastline (Figure 1)
The Horns Rev 1 wind farm is located in the North Sea at about 14 to 20 km offshore from the Danish coastline (Figure 1).The wake photographs taken at the offshore wind farm at Horns Rev 1 are well known in the wind energy community
The distance in the turbine wakes at which the first condensation takes place is around 50 to 100 m downstream centered at the nacelle position (Figure 2)

Summary

Introduction

The Horns Rev 1 wind farm is located in the North Sea at about 14 to 20 km offshore from the Danish coastline (Figure 1). The wake photographs taken at the offshore wind farm at Horns Rev 1 are well known in the wind energy community. They illustrate the wind turbine shadow effect in an attractive manner. The two photographs were taken by the pilot from the window of the helicopter on its way out to the oil rigs in the North Sea at an altitude around 1 to 3 km on 12 February 2008 at around 10:10 UTC. Advanced wake modeling with Computational Fluid Dynamics (CFD) using

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