Posters

Abstract

In recent years, ground-based lidars have become an alternative to me masts (MM) for wind resource assessment and power curve testing due to their easy installation and lower maintenance cost. Despite their advantages, ground-based lidars have not replaced traditional anemometry, and their use is only advised in non-complex sites. Ground-based lidars measure over a volume and the reconstruction of the wind speed components is based upon the assumption that there is flow homogeneity over the scanning trajectory. Consequently, in complex terrain the uncertainty of the wind measurements increases significantly. To account for this, CFD corrections are often applied to transform the measurements into outputs comparable to those of an anemometer. While not being recommended, lidars can be the only option in complex terrain, as available wind sites are getting more complex, and the MM deployment is very expensive. The impact of the lidar measurement principle on the wind speed in complex terrain is accounted as an uncertainty due to non-homogenous flow within the measurement volume, due to terrain complexity and flow variation across the site in the IEC 61400-12-1 ed.2 standard for power curve testing. This is reviewed in detail in the OWA Report 2017-001, where it is recommended to combine those terms into a flow gradient uncertainty. In this work we first analyse the mean wind speed deviations observed between different ground-based lidars co-located with MMs in complex sites. The mean deviations are obtained by performing on-site verification tests following the IEC 61400-12-1 ed. 2. The nature of those deviations is investigated by assessing the terrain complexity. Moreover, the impact of applying different flow corrections to the lidar data is evaluated in terms of wind speed and AEP errors. Finally, the uncertainty in the corrections is derived by calibrating the lidar data with the mean deviations.