An Inter-Comparison Study of Multi- and DBS Lidar Measurements in Complex Terrain

Lukas Pauscher,Doron Callies,Martin Kühn,Julian Hieronimus,Nikola Vasiljevic,Jakob Mann,Tobias Klaas,Michael Courtney,Julia Gottschall,Guillaume Lea,Annedore Schwesig

doi:10.3390/rs8090782

Abstract

Wind measurements using classical profiling lidars suffer from systematic measurement errors in complex terrain. Moreover, their ability to measure turbulence quantities is unsatisfactory for wind-energy applications. This paper presents results from a measurement campaign during which multiple WindScanners were focused on one point next to a reference mast in complex terrain. This multi-lidar (ML) technique is also compared to a profiling lidar using the Doppler beam swinging (DBS) method. First- and second-order statistics of the radial wind velocities from the individual instruments and the horizontal wind components of several ML combinations are analysed in comparison to sonic anemometry and DBS measurements. The results for the wind speed show significantly reduced scatter and directional error for the ML method in comparison to the DBS lidar. The analysis of the second-order statistics also reveals a significantly better correlation for the ML technique than for the DBS lidar, when compared to the sonic. However, the probe volume averaging of the lidars leads to an attenuation of the turbulence at high wave numbers. Also the configuration (i.e., angles) of the WindScanners in the ML method seems to be more important for turbulence measurements. In summary, the results clearly show the advantages of the ML technique in complex terrain and indicate that it has the potential to achieve significantly higher accuracy in measuring turbulence quantities for wind-energy applications than classical profiling lidars.

Highlights

IntroductionLidar (light detection and ranging) technology has quickly penetrated wind-energy applications
Over recent years, lidar technology has quickly penetrated wind-energy applications
In Section 3.2., we turn to the wind statistics which are derived from the combination of multiple WindScanner devices

Summary

Introduction

Lidar (light detection and ranging) technology has quickly penetrated wind-energy applications. In resource assessment, Doppler lidars are widely used for wind measurements to predict the annual energy production of windfarms. In flat and homogeneous terrain, classical profiling lidars using the Doppler beam swinging (DBS) or velocity azimuth display (VAD) techniques achieve high accuracy [1]. In recent years, their use has been adopted into national and international standards and guidelines [2,3]. The application of Doppler lidars in complex terrain, remains difficult and is often associated with systematic errors in mean wind-speed estimations [4,5]. If the flow is complex, the homogeneity assumption underlying the DBS and VAD techniques is often violated

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Methods

Results

Conclusion