Posters

Abstract

To measure the wind, lidars rely on backscatter from aerosols. In very clear air the backscattered energy drops. This can result in a decrease in lidar data measurement availability. The impact of this can be particularly significant for some applications, such as lidar assisted control (LAC), where a turbine’s operation uses the output of a nacelle mounted lidar as one of the primary inputs to the turbine control system. However, other applications, such as turbine performance measurement, can also be badly affected, resulting in longer than expected, or even failed, measurement campaigns. This paper reports on the clean air performance of continuous wave circular scan lidars, a popular choice for many nacelle mounted deployments. One of the advantages of this type of lidar is its excellent sensitivity, a consequence of a lens being used to focus the laser beam down to a diffraction limited probe volume. Interestingly, sensitivity is independent of range. Measurement performance from several campaigns are compared and contrasted. These include some particularly challenging clear air conditions in deserts, as well as cold, high altitude test sites. Excellent measurement data availability is reported, down to backscatter coefficients b as low as 10-9 m-1sr-1.