A Case Study on Using a Nacelle Lidar for Power Performance Testing in Complex Terrain. Megan Quick December 11, 2013

Transcription

1 A Case Study on Using a Nacelle Lidar for Power Performance Testing in Complex Terrain Megan Quick December 11, 2013

2 Introduction Can a nacelle lidar be used for site calibration? Can nacelle lidar be used for power performance testing in complex terrain? Previous investigation for uses in simple terrain was done by DTU New draft standard includes provisions for ground based lidar Case study of available data Opportunistic approach at existing test site 2

3 Nacelle Lidar Avent Wind Iris Avent Wind Iris Two-beam, pulsed laser 10 measurements between 80 m and 440 m upwind Lidar availability is mainly limited by blade pass 3

4 Terrain profile looking North & uphill Site Layout Moderately sloping complex hillside terrain Wind Iris mounted on top of 80-m hub height (HH) wind turbine (WTG) First class anemometer mounted at 80-m HH Height of lidar measurement varies with terrain 200 m measurement circle Terrain profile looking East & across hill 4

5 Wind Iris Wind Speed (WS) and Turbulence Intensity (TI) Measurements Original scalar lidar output: poor agreement with met mast Post processed vector lidar output: lidar WS & TI have better agreement 5

6 Verification Verified as per Annex L of Draft IEC 12-1 Ed.2 Wind speed is binned per 0.5 m/s wind speed bins Deviation = (V Met V Lidar )/V Met Deviations should be < 1% Deviations are large for WS < 7 m/s Blades block measurement Filters to adjust: Availability Rotor RPM Filters improve correlation Filters: turbine ON, no curtailment, lidar availability > 20%, valid sector

7 Verification with Elevation Difference Removed data with low rotor RPM Only used data with lidar facing uphill Met wind speed 2.5% higher than lidar Indicates the decreased measurement height Filters: turbine ON, no curtailment, lidar availability > 20%, valid sector

8 Site Calibration Can site calibration be replaced by a nacelle lidar? Calculated lidar-based site calibration correction factors Met with SC IEC Met Met with SC lidar Does not consider wind evolution between 80 m upwind and the turbine rotor WTG must be OFF IEC met site cal Met tur Met ref SC IECmet = Met tur Met ref lidar 80 lidar 200 Proposed lidar site cal SC lidar = lidar 80 lidar 200 8

9 Results Correction Factors Flat Sector Lidar correction factor Limited data due to WTG Availability Site Calibration without turbine mast SC IECmet - SC lidar < 0.1 m/s across WS range IEC Compliant Site Calibration Lidar 200 m 80m Site Calibration 9

10 Results Correction Factors Power Curve Lidar only used to develop the correction factor Applied to Met Wind speed 8 m/s Rayleigh distribution annual energy production (AEP) lidar site calibration is 0.56% lower than AEP Well within the uncertainty for each measurement. Power Curves with Corrections sector Filters: turbine ON, no curtailment, lidar availability > 20%, valid sector

11 Results Correction Factors Sector North & Uphill WTG Site calibration factors for 3 sectors Two flattest sectors match IEC site calibration 65 sector has significant deviation from IEC site calibration Low data counts introduces extra uncertainty 10 Sector Center ( ) Measurement Height (m) SC IECmet - SC lidar 4m/s (m/s) 8m/s (m/s) 12m/s (m/s)

12 Results Correction Factors Power Curve With a 8 m/s Rayleigh distribution AEP is 0.6% higher with the site calibration factors calculated from the Lidar Well within the uncertainty for each measurement. AEP difference between only using the sector and is about 1% Power Curves with Corrections Filters: turbine ON, no curtailment, lidar availability > 20%, valid sector

13 Results Power Curves Three scenarios for comparison IEC Compliant Test with met mast and site calibration Nacelle Anemometer comparison without any adjustment 200m Lidar with lidar correction factor applied calibration The difference in %AEP for an 8 m/s Rayleigh wind distribution is: (AEP IEC AEP Lidar200 )/ AEP IEC = 0.1% (AEP IEC AEP NacAne )/ AEP IEC = 0.1% Filters: turbine ON, no curtailment, lidar availability > 20%, valid sector

14 Conclusions Results are encouraging and nacelle lidar may have uses in complex terrain Not yet suitable to replace IEC compliant site calibration and power curve measurements but promising for locations with little elevation change within 2D Upcoming IEC update only includes ground-based lidar operational assessment Further studies at other sites are needed to prove the results Additional shear measurement points would allow for REWS evaluation Results Summary: Updated vector calculation shows better correlation with met mast Verification shows good correlation at high wind speeds and filters were found that correlate at low wind Calibration factors with Lidar and IEC method were similar Resulting power curves were very similar No significant conclusions could be made due to lack of data Different measurement methods were compared significant differences were seen in the power curves but the AEP results were similar. Favorable AEP results may be due to the flat terrain 14

15 Question Slide Place holder When will lidar overtake met masts for power performance testing? A. 5 years B. 10 years C. Never 15

16 Thank you! References: Wagner, R: Courtney, M; Gottschall, Antoniou, I; Møller, R; Pederson, Sm; Velociter, T; Bardon, M; Le, N; Mouritzen, AS; 2012 Power performance measurement using a nacelle lidar 16