Wake detection in the turbine inflow using nacelle lidars

In this study we present the ability to detect wakes in the inflow of turbines using nacelle-mounted continuous-wave lidar systems. Wake flows generate small-scale turbulence, which has significantly smaller length-scales than ambient turbulence. Due to the lidars large probe volume this turbulence is attenuated and will not be visible in the lidar's measurements. One approach to retrieve information about small-scale turbulence is by measuring the lidar Doppler spectrum width. Here we present an wake detection algorithm based on these measurements at two distinct locations in front of the turbine. By comparing the line-of-sight turbulence intensity and considering the instantaneous misalignment it is possible to detect half-and full-wakes. This has been tested during a 4.5 month long experiment and results show that situations where the wake affects the lidar measurements can be removed.