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Wind Energy Science The interactive open-access journal of the European Academy of Wind Energy
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Discussion papers
https://doi.org/10.5194/wes-2018-78
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/wes-2018-78
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research articles 16 Jan 2019

Research articles | 16 Jan 2019

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Wind Energy Science (WES).

Detection of wakes in the inflow of turbines using nacelle lidars

Dominique P. Held1,2 and Jakob Mann1 Dominique P. Held and Jakob Mann
  • 1Department of Wind Energy, Technical University of Denmark (DTU), Frederiksborgvej 399, 4000 Roskilde, Denmark
  • 2Windar Photonics A/S, Helgeshøj Alle 16–18, 2630 Taastrup, Denmark

Abstract. Nacelle-mounted lidar systems offer the possibility of remotely sensing the inflow of wind turbines. Due to the limitation of line-of-sight measurements and the limited number of focus positions, assumptions are necessary to derive useful inflow characteristics. Typically, horizontally homogeneous inflow is assumed which is well satisfied in flat, homogeneous terrain and over sufficiently large time averages. However, it is violated if a wake impinges the field of view of one of the beams. In such situations, the turbine yaw misalignment measurements show large biases which require the detection and correction of these observations. Here, a detection algorithm is proposed based on the spectral broadening of the Doppler spectrum due to turbulence within the probe volume. The small-scale turbulence generated within wake flows will typically lead to a significantly larger broadening than in the ambient flow. Thus, by comparing the spectral widths at several locations, situations, where a wake is impinging the field of view of one or more beams can be identified. The correction method is based on an empirical relationship between the difference in turbulence levels at distinct beams and the difference in wind direction derived from the lidar and the real wind direction. The performance of the algorithm is evaluated in a field experiment identifying all wake situations, and thus, correcting the lidar derived wind direction.

Dominique P. Held and Jakob Mann
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Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Dominique P. Held and Jakob Mann
Dominique P. Held and Jakob Mann
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Latest update: 26 Apr 2019
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Short summary
In this study the capabilities of detecting wakes in the inflow of turbine by nacelle-mounted lidars is investigated. It is shown that higher turbulence levels can be measured within a wake by estimating the Doppler spectrum width. In an experimental setup all half- and full-wake situations have been identified. A correction method for the influence of the wake on the lidar system has also been proposed.
In this study the capabilities of detecting wakes in the inflow of turbine by nacelle-mounted...
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