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General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.
Users may download and print one copy of any publication from the public portal for the purpose of private study or research.
You may not further distribute the material or use it for any profit-making activity or commercial gain
You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Downloaded from orbit.dtu.dk on: Aug 19, 2021
Nacelle lidar calibration – how we do it at DTU Wind Energy
Borraccino, Antoine
Publication date:2017
Document VersionPublisher's PDF, also known as Version of record
Link back to DTU Orbit
Citation (APA):Borraccino, A. (Author). (2017). Nacelle lidar calibration – how we do it at DTU Wind Energy. Sound/Visualproduction (digital)
• White-box–calibration of all the inputs of the Wind Field ReconstructionPROS Low sensititivity to WFR assumptions Genericity Uncertainties on any wind characteristics (WFC)
CONS Longer process Need expert knowledge
DTU Wind Energy, Technical University of Denmark
Generic calibration methodology2) calibration of LOS velocity
D=262m
ZDM 5B-demo
5
• Measurement setup, in Høvsøre (DK)
DTU Wind Energy, Technical University of Denmark
Generic calibration methodology2) calibration of LOS velocity
6
• Measurement setup, in Høvsøre (DK) - zoom
260m
ZDM
5B-demo
DTU Wind Energy, Technical University of Denmark7
Linear regressions on 10-min data
2) Calibration of LOS velocityResults (1/2)
LOS 0 Bottom LOS5B-demo ZDM
DTU Wind Energy, Technical University of Denmark8
Linear regressions on binned data
the calibration relation is obtained!
5B-demo ZDMLOS 0 Bottom LOS
2) Calibration of LOS velocityResults (2/2)
DTU Wind Energy, Technical University of Denmark9
Uncertainty of LOS velocityResults
• Expanded uncertainties (k=2) vs. 𝑽𝑽𝒍𝒍𝒍𝒍𝒍𝒍: in m/s and in %𝑈𝑈𝑒𝑒𝑒𝑒𝑒𝑒 increases linearly (m/s)
∼ 3% at 4m/s∼ 2% at 10 m/s
5B-demo ZDMLOS 0 Bottom LOS
almost same as cup anemometer
DTU Wind Energy, Technical University of Denmark10
𝒖𝒖𝒂𝒂
𝒖𝒖𝒄𝒄,𝒚𝒚
𝒖𝒖𝝋𝝋
𝒖𝒖𝜽𝜽
𝒖𝒖𝒄𝒄,𝜽𝜽𝒓𝒓
𝒖𝒖𝜽𝜽𝒍𝒍𝒍𝒍𝒍𝒍
𝒖𝒖𝒄𝒄,𝑽𝑽𝒓𝒓𝒓𝒓𝒓𝒓
𝒖𝒖𝒄𝒄,𝑽𝑽𝒉𝒉𝒍𝒍𝒓𝒓
𝒖𝒖𝒄𝒄𝒂𝒂𝒍𝒍 𝒖𝒖𝒍𝒍𝒐𝒐𝒓𝒓 𝒖𝒖𝒎𝒎𝒂𝒂𝒍𝒍𝒎𝒎 𝒖𝒖𝒐𝒐𝒍𝒍𝒍𝒍 𝒖𝒖𝒊𝒊𝒊𝒊𝒄𝒄
~0%8% 92%
6% 94%40% 30% 24% 5% 1%
99%1%
Uncertainty of LOS velocityPrevailing sources
• Conclusions: the lidar 𝐕𝐕𝐥𝐥𝐥𝐥𝐥𝐥 uncertainty is almost entirely inherited from the cup need to improve uncertainty assessment of cup anemometersOR need for new reference sensors
DTU Wind Energy, Technical University of Denmark11
Take-aways• Calibration of nacelle lidars at DTU
–the white-box methodology is now• a well-proven method• the preferred technique by industry
–Procedures available for different types of commercial systems
• The barriers, what we need:1. better reference anemometers: move away from cups? (their
uncertainty prevail massively)2. shorter calibration procedures: especially true for pulsed syst.3. unify methods and improve measurement setups4. work on the propagation of lidar V_los uncertainty to
reconstructed wind field characteristics5. And… maybe dig into what’s upstream V_los !
(estimators, ranging, time stability of optics, etc)
DTU Wind Energy, Technical University of Denmark20
2) Calibration of LOS velocityData analysis (1/2)
• LOS direction evaluation (part 1)– Cosine / rectified cosine fitting to wind direction response– The lidar LOS is normalised by the horizontal speed Gives a first good estimation of LOS direction in sonic CS
ZDM5B-demoLOS 0 Bottom LOS
Presenter
Presentation Notes
The reference quantity is the projection of the wind vector onto the lidar LOS
DTU Wind Energy, Technical University of Denmark21
2) Calibration of LOS velocityData analysis (1/2) – RSS process
• LOS direction evaluation (part 2)– Projection angle range: ±1°to cosine fitted LOS_dir– Linear reg. each 0.1°
– LOS dir = min parabola
ZDM5B-demoLOS 0 Bottom LOS
Presenter
Presentation Notes
Slides 13-14 = 1min (cumul = 8min)
DTU Wind Energy, Technical University of Denmark
Calibration results
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• Summary:– lidar-measured LOS velocity: error of ∼0.5 − 0.9%– excellent agreement with the reference quantity 𝑉𝑉𝑟𝑟𝑒𝑒𝑟𝑟: 𝑅𝑅2 > 0.9998– LOS direction method provides robust results (±0.05°)
Presenter
Presentation Notes
Slides 18-19 = 1min (cumul = 12min)
DTU Wind Energy, Technical University of Denmark
Uncertainty assessment: how to combinecomponents?
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• GUM methodology: analytic method1) Define measurement model: 𝑦𝑦𝑚𝑚 = 𝑓𝑓 𝑥𝑥1, 𝑥𝑥2, … , 𝑥𝑥𝑛𝑛2) Law of propagation of uncertainties: