92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Wednesday, 25 January 2012: 9:30 AM
Doppler Lidar Study of Wind Flow Characteristics in the Wake of Operating Wind Turbine
Room 345 (New Orleans Convention Center )
Yelena Pichugina, CIRES/Univ. of Colorado, Boulder, CO; and R. M. Banta, W. A. Brewer, J. K. Lundquist, N. D. Kelley, R. M. Hardesty, A. Clifton, R. J. Alvarez, M. L. Aitken, J. D. Mirocha, S. P. Sandberg, and A. Weickmann

Velocity deficits and enhanced turbulence generated by the blade rotation are two major wake effects that could extend to distances of several rotor diameters behind a wind turbine. Accounting for wakes is an important issue in the optimization of siting turbines in the wind farm, operational strategies to reduce wake effects, and improved design of wind turbines. We used NOAA's High-Resolution Doppler Lidar (HRDL) to obtain simultaneous measurements of vertical and horizontal wind flow features both upwind and downwind of a Siemens 2.3 MW research wind turbine during the Turbine Wake and Inflow Characterization Study (TWICS) at the NREL National Wind Technology Center in the spring of 2011. HRDL transmits a pulse of 2-Ám infrared radiation at a pulse repetition frequency of 200 Hz, velocity precision about 10 cm s-1, and range-gate resolution of 30 m. The ability of HRDL to sweep the atmosphere along both constant azimuth and elevation angles was used to develop a scanning strategy to provide a variety of high resolution boundary layer (BL) information. Velocity deficit, wake downwind extent and meandering were measured under different wind speed and BL stability conditions, but at wind directions possibly aligned along the direction of the flow from Eldorado Canyon, prevalent at the site. Results obtained from both vertical-slice scans, performed along the lidar-turbine centerline, and conical sector scans, performed in the narrow sector around wind turbine at four levels, show averaged velocity deficits of 6-8 m s-1 extending up to 10-15 rotor diameters downstream of the turbine. Profiles of wind speed, direction, and turbulence, obtained up to several km both above the ground and downstream of the turbine were used to estimate wind flow and its diurnal variations, to compute statistics and distributions of wind speed at several heights across the layer of the atmosphere swept by the turbine blades, and to monitor occurrences of the Low-Level Jet (LLJ) and other atmospheric features.

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