Lidar in Complex Terrain

Research

Summary

Lack of experience in constrained the use of wind Lidars in complex terrain at the time of the study, despite its potential cost savings. While uncertainty of Lidars in flat terrain is well documented, there are few estimates of Lidar uncertainty in complex terrain.

Inhomogeneous flow across the swept measurement area of Lidars introduces measurement bias. CFD and other correction methods were developed to compensate for inhomogeneity caused by terrain effects. Uncertainty also relates to the deployment, processing and analysis of Lidar data by practitioners.

A primary purpose any measurement campaign is to reduce uncertainty in production estimates, but there is always a trade-off between uncertainty reduction and costs to achieve it.

Different configurations of masts and Lidars on a site could outperform a configuration of multiple measurement masts in terms of lowered uncertainty and costs. An additional possibility to increase cost savings is the implementation of horizontally scanning Lidars. These systems, able to scan in any desired configuration, expand the possibilities for conducting wind resource assessment in various new ways. Scanning horizontally (arc scanning) allows measuring multiple locations without moving the system. They can also be used to measure areas instead of point locations, allowing evaluation of spatial variation of shear, etc. A prerequisite, however, is that the uncertainty of Lidar measurements for these various scanning geometries is acceptable.

To address the above issues, we designed a measurement campaign with three different lidar types with the following goals:

  • Assess the uncertainty of Lidar measurements in complex terrain
  • Test the usefulness/accuracy of horizontally scanning Lidars with variable scanning geometries
  • Design the most cost-efficient combination of Lidar and masts for measurement campaigns

 

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Authors

Klaus Vogstad – Meventus AS
Anne H Simonsen – Meventus AS
Kyle J. Brennan – Meventus AS
John A. Lund – Meventus AS