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OBSERVATIONS OF EXTREME SPEED AND DIRECTIONAL WIND SHEAR IN THE US GREAT PLAINS

OBSERVATIONS OF EXTREME SPEED AND DIRECTIONAL WIND SHEAR IN THE US GREAT PLAINS. Kevin Walter Christopher C. Weiss Andrew H.P. Swift and Jamie Chapman Texas Tech University Wind Science and Engineering Research Center. Neil D. Kelley

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OBSERVATIONS OF EXTREME SPEED AND DIRECTIONAL WIND SHEAR IN THE US GREAT PLAINS

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  1. OBSERVATIONS OF EXTREME SPEED AND DIRECTIONAL WIND SHEAR IN THE US GREAT PLAINS Kevin Walter Christopher C. Weiss Andrew H.P. Swift and Jamie Chapman Texas Tech University Wind Science and Engineering Research Center Neil D. Kelley National Renewable Energy Laboratory, National Wind Test Center presented at the European Wind Energy Conference, 7-10 May 2007, Milan, Italy

  2. Overview Data acquisition & definition of atmospheric stability Speed shear observations (10m & 116m levels) and correlation with static stability Joint-probability of speed and direction shear observations (10m & 116m levels)

  3. Tower Location

  4. - Using UVW anemometers at 10m & 116m • - Data Analysis Period: Feb. 16, 2005 to Feb. 15, 2007 • 30 Hz collection 1 hour averages • Additional quality-control and validation • Observations where 10m wind speed < 3 m/s are omitted and not replaced

  5. Static atmospheric stability metric: Virtual Potential Temperature Temperature, Barometric Pressure, Relative Humidity

  6. Speed Shear

  7. Power Law Shear Exponent Static Stability Correlation of diurnal averages = 1.00

  8. Joint Probabilities Speed shear, direction shear, wind speed

  9. Hub height wind speed > 8 m/s

  10. Hub height wind speed > 8 m/s

  11. Conclusions • Significant speed and direction shear coexist in the boundary layer over relatively long averaging times at relatively high hub-height wind speeds. • The long-term average magnitude of speed shear is highly correlated with static atmospheric stability. • The link between shear and static stability is not location-specific. • Speed and direction shears gain importance as turbine rotor size increases.

  12. Acknowledgements • National Science Foundation IGERT Program, NSF Grant No. 0221668 • State of Texas • United States Department of Energy for travel funding • National Renewable Energy Labs (NREL / NWTC)

  13. Questions/Discussion

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