Posters

Abstract

Wind profiling lidars are largely used in the wind energy sector to determine wind conditions e.g., for wind resource assessment purposes. This is mainly due to their flexibility, mobility, and ability to measure at high altitudes in contrast to traditional meteorological masts that were used before. Commercial wind profiling lidars typically use the velocity-azimuth display (VAD) scanning technique to determine the velocity components. The measurement points are located along an azimuthal orbit and the radial velocity is measured at these points. The horizontal wind speed can then be reconstructed from the measured radial wind speeds. The distance between the individual measuring points increases according to the altitude and depends on the aperture angle used. Therefore, the distance between individual measurement points can be up to several hundred meters.In flat terrain with homogeneous flow conditions, this circumstance is usually negligible for the determination of the 10-minute mean wind speed and wind direction, but at sites with complex flow, this can result in deviations or errors in the reconstruction of the wind speed. The determination of this systematic measurement error remains crucial for the use of wind profiling measurements for site characterization of complex terrain. Within the research project "Lidar data correction for sites in complex terrain" (LoTar FKZ:03EE3052) funded by the Federal German Ministry for Economic Affairs and Climate Action (BMWK) the lidar measurement error from two separate measurement campaigns in complex terrain was therefore examined. Both measurement campaigns were carried out at topographically different locations. Wind profiling lidars were set up neighboring met masts with top heights of 100 m and 120 m, respectively. The measurement periods range from 1.5 to 3.5 months for both locations. Typically, wind site characterization in complex terrain is made with the help of computational flow simulations, therefore a test framework (a round-robin test conducted by the association FGW e.V.) was set up to compare different estimates for this measurement error. Within the round-robin test results from 15 participants were analyzed, comparing their estimated correction parameters for different heights based on these two specific locations. All participants calculated the correction parameters with their preferred model setup based on geodata (topographic model and land use data) and atmospheric stability. For an estimate of atmospheric stability, the lidar measurement data could be used and analyzed. Mostly computational fluid dynamic (CFD) wind flow models were used, but there were also some other simulations applied (e.g., WAsP). The comparison to the error estimates from a round-robin test showed that there are still significant deviations and differences in the various types of application for wind site characterization in complex terrain. Additional measurement campaigns in complex terrains and their comparison to further wind flow model simulations are needed for further investigation. By carrying out the extensive measurement campaigns such as the ones mentioned above, we hope to generate a deeper understanding in the industry and research community of the applicability of lidar profilers in complex terrain.