Presentations

Abstract

The IEA Task 52 deals with Large-Scale Deployment of Wind LiDAR. Wind LiDARs are an important measurement technology in the wind industry and are used in applications such as energy yield assessments, power performance measurements, or as a permanent wind measurement on operational sites. Therefore a reliable measurement operation of the LiDAR is essential all year round. Doppler Wind LiDARs operate by transmitting a laser signal and measuring the light scattered by particles carried by the wind. This Doppler shift provides the wind velocity along the line-of-sight. The intensity of this backscattered light is a function of the intensity of the incident light and scatterer density. Doppler wind LiDAR performance can vary under different environmental conditions. Specifically in extremely low aerosol atmospheres such as in clear-air locations with low-backscatter conditions and/or high latitudes and high altitudes data availability drops at times drastically. During periods of heavy fog, atmospheric conditions can prevent eye-safe Doppler Wind LiDAR from measuring at the intended heights as the laser beam gets extinct in the cloud. These two conditions are rather frequent in winter time compared to summer and therefore pose a challenge. The objective of the working group 'LiDAR in cold climate' of Task 52 is to first of all identify the reasons for low data availability in winter time and then try to mitigate the barrier and increase the LiDAR's performance. The LiDAR manufacturer Vaisala has developed a method to overcome the data loss caused by fog and clear-air. This method is tested with data sets from several locations in Switzerland where a Windcube V2 or Windcube V2.1 is installed next to a 100m met mast.