Analysis of Wind Speed Measurements using Continuous Wave LIDAR for Wind Turbine Control ∗† Eric Simley ‡ Lucy Y. Pao § Rod Frehlich ¶ Bonnie Jonkman ‖ Neil Kelley ∗∗ Light Detection and Ranging (LIDAR) systems are able to measure the speed of incom- ing wind before it interacts with a wind turbine rotor. These preview wind measurements can be used in feedforward control systems designed to reduce turbine loads. However, the degree to which such preview-based control techniques can reduce loads by reacting to turbulence depends on how accurate the incoming wind field can be measured. This study examines the accuracy of different measurement scenarios that rely on coherent continuous- wave Doppler LIDAR systems to determine their applicability to feedforward control. In particular, the impacts of measurement range and angular offset from the wind direction are studied for various wind conditions. A realistic case involving a scanning LIDAR unit mounted in the spinner of a wind turbine is studied in depth, with emphasis on choices for scan radius and preview distance. The effects of turbulence parameters on measurement accuracy are studied as well. Nomenclature d measurement preview distance F focal distance k wind velocity wavenumber (m −1 ) r scan radius for spinning LIDAR RMS root mean square σ u standard deviation of u component of wind velocity TI turbulence intensity θ LIDAR measurement angle ¯ u mean u wind speed u ∗ friction velocity U ∗ D average friction velocity over rotor disk φ angle between laser and wind velocity vector ψ angle in the rotor plane ω rotational rate of spinning LIDAR ∗ This work was supported in part by the US National Renewable Energy Laboratory. Additional industrial support is also greatly appreciated. The authors also thank Alan Wright, Fiona Dunne, and Jason Laks for discussions on desired characteristics of wind speed measurement devices that can enable preview-based control methods for wind turbines. † Employees of the Midwest Research Institute under Contract No. DE-AC36-99GO10337 with the U.S. Dept. of Energy have authored this work. The United States Government retains, and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for the United States Government purposes. ‡ Graduate Student, Dept. of Electrical, Computer, and Energy Engineering, University of Colorado, Boulder, CO, Student Member AIAA. § Richard and Joy Dorf Professor, Dept. of Electrical, Computer, and Energy Engineering, University of Colorado, Boulder, CO, Member AIAA. ¶ Senior Research Associate, Cooperative Institute for Research in Environmental Sciences, Boulder, CO 80309. ‖ Senior Scientist, National Wind Technology Center, NREL, Golden, CO 80401, AIAA Member. ∗∗ Principal Scientist, National Wind Technology Center, NREL, Golden, CO 80401, AIAA Member. 1 of 16 American Institute of Aeronautics and Astronautics 49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 4 - 7 January 2011, Orlando, Florida AIAA 2011-263 Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc. Under the copyright claimed herein, the U.S. Government has a royalty-free license to exercise all rights for Go