Characterization of Wind Turbine Flows using Radar-Derived Fields and In-Situ Turbine Measurements

Wind farms pose a unique challenge and opportunity in the field of atmospheric measurements. As pressure mounts for renewably sourced energy around the globe, wind has proven itself a resource that can be harnessed responsibly, efficiently, and (increasingly) cost-effectively. That said, the performance of wind farms is directly tied not only to the environments in which they are placed, but also to an appropriate understanding and consideration of the flow within and around them and the effects turbines can have on it. Prior analyses of these environmental flow fields and concurrent wind farm power output have demonstrated that regions of decreased momentum downstream of wind turbines can severely diminish power generation, at times by up to 80%. As turbines extract inflow momentum, they trigger not only substantial speed deficits from the ambient flow but also appreciable intensifications in turbulence, in turn exerting uneven aerodynamic loads on wind turbines, increasing fatigue loading, and further fettering farm efficiency. Despite more than adequate knowledge of this problem, until recently most instrumentation had limited capacity to document flows at high spatial and temporal resolution while also covering a very large area, exactly the type of data a proper analysis of wind farm flow fields demands. The Texas Tech University Ka-band (TTUKa) radars were first used to address this shortcoming in 2012, and since then TTUKa-derived dual-Doppler (DD) synthesis has proven capable of covering large areas at high spatiotemporal resolution. This project seeks to investigate the behavior of turbine-modulated flows at the Sage Draw wind farm in West Texas, employing DD scanning strategies and advanced time-series analysis to assess inflow characteristics upstream of wind turbines and wake flow characteristics downstream of them as those characteristics pertain to turbine and wind plant power performance. Paired with these remotely-sensed radar measurements for a novel analysis are extensive in-situ data provided by the wind farm operator, measured at turbine hub height and featuring such variables of interest as individual blade pitch, turbine operation status and heading, rotor and generator speed, and instantaneous power output, in addition to wind speed. The comparison of these radar and turbine measurements can be used to assess the capabilities and limitations of remotely-sensed data, while relationships between turbine variables are helpful in analyzing the effectiveness of wind turbine and wind plant controls as well as their instrumentation.