Lidar Turbulence Measurements for Wind Energy

Modeling of the systematic errors in the second-order moments of wind speeds measured by continuous-wave (ZephIR) and pulsed (WindCube) lidars is presented. These lidars use the velocity azimuth display technique to measure the velocity vector. The model is developed for the line-of-sight averaging and the full extent of conical scanning. The predictions are compared with the measurements from the ZephIR, WindCube and sonic anemometers at a flat terrain test site, under different atmospheric stability conditions. It is observed that the systematic errors are up to 90% for the vertical velocity variance, whereas they are up to 70% for the horizontal velocity variances. The systematic errors also vary with atmospheric stability, being lowest for the very unstable conditions. It is concluded that with the current measurement configuration, these lidars cannot be used to measure turbulence precisely.