Advantages of Pulsed Lidar technology

WindCube Offshore- 2023/09/08 WindCube Offshore Vertical Profiler Lidar

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Pulsed Lidars send Laser pulses at a very high frequency: tenths of thousand pulses are sent within 1s.

Light pulses are backscattered by aerosols and, from those received, Doppler shift is analyzed much before next Laser pulse is emitted. This avoids confusing time delays and distances. Therefore, probe distance, or height, only depends on the time it takes for a pulse to be received after it has been emitted.

Several technical advantages arise from Pulsed Lidar technology:

1. Multiple heights are measured simultaneously
  • A complete wind profile is measured within the same time in 1s: the shear profile is “frozen” and accurately captured.
  • More measurement heights does not impact the duration of measurement: a detailed wind profile is captured with no compromise on temporal resolution and thereby no decrease of accuracy nor data availability.
2. Spatial resolution is constant through the entire wind profile
  • Constant probe volume of atmosphere leads to constant accuracy at all heights.
  • Probe volume does not increase with measurement height: higher measurement ranges are possible.
3. Measurement is not affected by clouds, fog or high density of dust and sand particles, nor obstacles
  • For Pulsed Lidars, only atmospheric conditions at measurement heights matter: measurement accuracy is not affected by light backscattered from other atmospheric layers. At one measurement height, “door is closed” to atmospheric conditions of any other layer.
  • Measurement accuracy of Pulsed Lidars is therefore not sensitive to weather conditions or to varying density of aerosol layers. Pulsed Lidars maintain same accuracy under clear sky or presence of fog.
4. Pulsed Lidars directly measure accurately and unambiguously wind direction
  • Pulsed Lidars accurately measure direction of each wind speed over the full 0-360° range.
  • This ensures an accurate wind rose evaluation for a wind project, which is critical to design a wind farm and evaluate the project finance with the highest accuracy.
5. Pulsed Lidars can use a reasonable number of beams arranged within a flexible pattern
  • A vertical beam is possible.
  • Vertical beam provides a direct measurement of vertical wind speed, as well as serve advanced wind processing in complex terrain, or advanced techniques for Turbulence Intensity for instance.
6. Data recovery from Pulsed Lidars is not sensitive to wind conditions like shear and turbulence intensity
  • Although measurement availability is impacted by very low aerosol density (this is the case for all Lidar types), data recovery of Pulsed Lidars is however not sensitive to wind conditions like shear or turbulence intensity thanks to its large Doppler spectra.
  • Data recovery is therefore more stable and not sensitive to wind conditions which reduces the risk to bias the Energy Yield Assessment, and also easier to predict with simulation tools developed by Vaisala.