Nacelle-based lidar measurements of wind farm turbulence and validation with a fleet of multicopter drones

Kurzfassung

Measuring atmospheric turbulence in spatially heterogeneous environments, such as wind farms, presents a significant observational challenge. This study aims to enable and validate turbulence measurements derived from a nacelle-based Doppler Wind Lidar (DWL). We present a refined measurement methodology and validate it against simultaneous in situ reference data collected by a fleet of ten drones and sonic anemometers mounted on meteorological masts at the WiValdi research park.

A comparative analysis of a multi-hour case study under moderately non-stationary conditions - including the onset of wind turbine wakes - yields deviations between the remote sensing and in situ systems that are on the order of the drone fleet’s measurement uncertainty. This demonstrates the high potential of the lidar-based approach. We observe that in wake flow conditions, distinctions between geodetically fixed and turbine-fixed reference frames can lead to divergences in measurement comparisons. Despite these challenges, the lidar estimates prove robust. The resulting spatial maps successfully resolve variations in turbulence intensity across different regions, specifically enabling accurate turbulence estimation within waked wind farm flows.