Measuring offshore winds from onshore one lidar or two?

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1 Downloaded from orbit.dtu.dk on: Dec 21, 2017 Measuring offshore winds from onshore one lidar or two? Vasiljevic, Nikola; Courtney, Michael; Pena Diaz, Alfredo; Lea, Guillaume; Vignaroli, Andrea Publication date: 2015 Link back to DTU Orbit Citation (APA): Vasiljevic, N., Courtney, M., Peña, A., Lea, G., & Vignaroli, A. (2015). Measuring offshore winds from onshore one lidar or two? European Wind Energy Association (EWEA). [Sound/Visual production (digital)]. EWEA Offshore 2015 Conference, Copenhagen, Denmark, 10/03/2015 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.

2 Measuring offshore winds from onshore one lidar or two? Nikola Vasiljević, Michael Courtney, Alfredo Peña, Guillaume Lea and Andrea Vignaroli 11/03/2015 EWEA Offshore 2015, Copenhagen

3 Estimation of near-shore wind resource Land Sea Area of future wind farm Technique Pros Cons Mesoscale models Cheap Uncertainty of prediction up to 10% 2

4 Estimation of near-shore wind resource Land Sea Area of future wind farm Measurements Technique Pros Cons Mesoscale models Cheap Uncertainty of prediction up to 10% 3 DTU Wind Energy, Technical Mesoscale University models + of Denmark local measurements

5 Estimation of near-shore wind resource Land Sea Area of future wind farm Technique Pros Cons Mesoscale models Cheap Uncertainty of prediction up to 10% 4 DTU Wind Energy, Technical Mesoscale University models + of Denmark local measurements Uncertainty reduced to 3%

6 Options for local measurements Land Sea Scanning lidar Area of future wind farm Scanning lidar Lidar Floating lidar Met mast Met mast Scanning lidar Technique Pros Cons Mesoscale models Cheap Uncertainty of prediction up to 10% 5 DTU Wind Energy, Technical Mesoscale University models + of Denmark local measurements Uncertainty reduced to 3%

7 Which measurement solution is most cost-effective (cost vs. accuracy)? Land Sea Scanning lidar Area of future wind farm Scanning lidar Lidar Floating lidar Met mast Met mast Scanning lidar Technique Pros Cons Mesoscale models Cheap Uncertainty of prediction up to 10% 6 DTU Wind Energy, Technical Mesoscale University models + of Denmark local measurements Uncertainty reduced to 3% EWEA OFFSHORE $$$? 2015

8 Which measurement solution is most cost-effective? The RUNE project is designed to investigate cost-effective measurement solutions for improving wind resource modeling of coastal areas. Comparison with mast mounted cup anemometer and wind vane Offshore mast Floating lidar Onshore lidar Onshore scanning lidar(s) 7

9 First attempt to answer the question: One or two lidars? Land Sea Scanning lidar Area of future wind farm Scanning lidar Met mast Scanning lidar 8

10 Lidar measurement background Wind V wind V wind Lidar A lidar can only measure a portion of the wind vector!!! 9

11 Dual-Doppler V wind Two independent LOS measurements Low elevation angles => neglect vertical component With two lidars it is possible to measure: - Horizontal wind speed - Wind direction 10

12 Conical scan Sector scan V wind Flow horizontally homogenous Conical scan (VAD) => estimate wind vector φ 11

13 Sector scan V wind θ 1 θ n θ 1 θ 2 θ 2 φ Flow horizontally homogenous Vertical component low Neglect vertical component Low elevation angle Sector scan => estimate horizontal wind speed and wind direction 12

14 Pre-RUNE experiment, April-May 2014 W N E Long-range WindScanners S Høvsøre D e n m a r k Risø EWEA 1000 m A detailed description of the long-range WindScanners: Master computer Nikola Vasiljevic. A time-space synchronization of coherent Doppler scanning lidars for 3D measurements of wind fields. PhD thesis, Technical University of Denmark (DTU), PhD-0027 Link: 13

15 Experimental layout N W E S 250 m WindScanner 1 WindScanner 3 WindScanner m Configuration 110 m WindScanner 1 WindScanner 2 Fixed line-of-sight (LOS) 2.5 Hz measurement rate Probe length 60 m (FWHM) Dual-Doppler Fixed line-of-sight (LOS) 2.5 Hz measurement rate Probe length 60 m (FWHM) Dual-Doppler 5.85 WindScanner 3 60 sector scan 2.5 Hz measurement rate WindScanner Probe length 1 60 m (FWHM) 12 s per complete scan LOS per scan Backward/Forward Mast 60

16 Data processing 165 h Horizontal wind speeds from 4 to 25 m/s 143 h Wake free sector ( ) 47 h 62% Device specific filters Hard target removal 37 h Run at least 10 min Signal quality (-27dB <CNR<-8dB) All LOS per sector scan 75% of samples per LOS All three WS working Wind condition and site specific filters 23 h 22% 10 min averaging 140 samples 15

17 Horizontal wind speed Cup anemometer Two lidars (Dual-Doppler) One lidar (Sector Scan 60 ) 16

18 Horizontal wind speed One lidar (Sector Scan 60 ) Two lidars (Dual-Doppler) dif dif Cup One lidar Two lidars Number of samples Mean wind speed [m/s] R 2 / Difference [m/s] / Difference [ %] / <1 <1 Standard deviation of the difference [m/s] /

19 Wind direction Wind vane Two lidars (Dual-Doppler) One lidar (Sector Scan 60 ) 18

20 Wind direction One lidar (Sector Scan 60 ) Two lidars (Dual-Doppler) dif dif Cup One lidar Two lidars Number of samples Mean wind direction [ ] R 2 / Difference [ ] / Difference [ %] / Standard deviation of the difference [ ] /

21 One lidar or two? One lidar will provide necessary local measurements If you have sufficient funds there are merits of using two lidars: - Higher measurement rate - Small portion of area sampled - More measurement points - If the flow is not horizontally homogeneous Be careful with the installation! A high pointing accuracy is crucial in achieving reliable measurements!!! 20

22 Future work Derive a parameter that indicates if the estimated values of the horizontal wind speed and direction from the sector scan are trustworthy Relating the theoretical calculation of the minimum sector scan to the experimental results Perform a similar experiment in real offshore conditions while going for a longer range and adding: - floating lidar - onshore lidar - Test pointing accuracy 21

23 For a live demonstration of the long-range WindScanner system visit the DTU WIND ENERGY stand in front of the Bella Center!

24 Thank you!