18 Mar 2021
18 Mar 2021
The COTUR project: Remote sensing of offshore turbulence for wind energy application
- 1Geophysical Institute and Bergen Offshore Wind Centre, University of Bergen, Allegaten 70, N-5007 Bergen, Norway
- 2NORCE Norwegian Research Centre AS, P.O. box 22 Nygårdsgaten 112, 5838 Bergen, Norway
- 3Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, N-4036 Stavanger, Norway
- 4Equinor ASA, Postboks 7200, 5020 Bergen, Norway
- 5Institute of Atmospheric Physics, German Aerospace Center (DLR), Oberpfaffenhofen, 82234 Wessling, Germany
- 1Geophysical Institute and Bergen Offshore Wind Centre, University of Bergen, Allegaten 70, N-5007 Bergen, Norway
- 2NORCE Norwegian Research Centre AS, P.O. box 22 Nygårdsgaten 112, 5838 Bergen, Norway
- 3Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, N-4036 Stavanger, Norway
- 4Equinor ASA, Postboks 7200, 5020 Bergen, Norway
- 5Institute of Atmospheric Physics, German Aerospace Center (DLR), Oberpfaffenhofen, 82234 Wessling, Germany
Abstract. The paper presents the measurement strategy and dataset collected during the COTUR (COherence of TURbulence with lidars) campaign. This field experiment took place from February 2019 to April 2020 on the southwestern coast of Norway. The coherence quantifies the spatial correlation of eddies and is little known in the marine atmospheric boundary layer. The study was motivated by the need to better characterize the lateral coherence, which partly governs the dynamic wind load on multi-megawatt offshore wind turbines. During the COTUR campaign, the coherence was studied using land-based remote sensing technology. The instrument setup consisted of three long-range scanning Doppler wind lidars, one Doppler wind lidar profiler and one passive microwave radiometer. Both the WindScanner software and Lidar Planner software were used jointly to simultaneously orient the three scanner heads into the mean wind direction, which was provided by the lidar wind profiler. The radiometer instrument complemented these measurements by providing temperature and humidity profiles in the atmospheric boundary layer. The preliminary results show an undocumented variation of the lateral coherence with the distance from the coast. The scanning beams were pointed slightly upwards to record turbulence characteristics both within and above the surface layer, providing further insight on the applicability of surface-layer scaling to model the turbulent wind load on offshore wind turbines.
Etienne Cheynet et al.
Status: open (until 13 May 2021)
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RC1: 'Comment on amt-2020-511', Anonymous Referee #3, 15 Apr 2021
reply
This article gives an overview of a unique measurement campaign that uses cutting-edge instrumentation with the intent of answering difficult and important questions for wind engineering. The dataset seems promising and the authors seem to have put a lot of thought into instrument choice, placement, analysis, etc. I have specific comments on the attached PDF. An overview of key comments is below:
Technical -- I would like to request a little more on (i) coastal internal boundary layers, including previous work/measurements where appropriate; (ii) the validity of assuming v_r==wind speed; (iii) acknowledgment of other coherence models in addition to davenport; (iv) can these data potentially be used to improve the way we model coherence rather than rely on axisting model for coherence for their very analysis?; (v) if/how/when can any of these data be shared with other groups for collaborative research; (vi) a discussion on where we need to go in instrumentation development so you could get more and better data next time (your dataset is great in comparison to past efforts but obviously we have a long way to go); (vii) how do you anticipate modeling studies being able to complement this dataset?; (viii) at the end, please provide some big-picture take-aways of how far this dataset can take us -- for technology development in the context of wind plants, offshore turbine design and operation, coastal infrastructure, etc; (ix) why wasn't the lidar data validated against the sonics at the beginning, just at the end?
Other minor -- while the article is well written and relatively easy to follow, it could benefit substantially from editing by a professional communications specialist (several sentences are a bit strange or have small mistakes); clean up on nomenclature, variable definition, figure improvements, etc are noted in the pdf.
Etienne Cheynet et al.
Etienne Cheynet et al.
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