LiDAR Uncertainty Standard Review: Methodology review and recommendations

The OWA LiDAR Uncertainty Standard Review (LUSR) project publishes outcomes of a review of uncertainty estimation in wind resource and power performance assessments when using LIDARs.

Lidar uncertainty standard review cover

Overview

It is well established in the offshore wind industry that the effective application of remote sensing wind measurement technology, particularly using LIDARs (Light Detection And Ranging), could be improved by improving how the industry measures uncertainty. There is an established assessment procedure for power curve assessment using lidars that was originally drafted by IEC, however, industry generally agreed that this could be improved upon. 

This led to the Carbon Trust’s Offshore Wind Accelerator (OWA) to launch a project to review the uncertainty methodology embodied in the recently updated standard for wind turbine power performance measurement IEC 61400-12-1, specifically the new Annex L "The application of remote sensing technology". This report presents the results of this methodology review.

Published: June 2018

Key findings

Following the revised methodology proposed in this report, substantial reductions in wind speed uncertainty have been demonstrated. The case where this makes the largest impact is the offshore case using floating lidar data, where an overall reduction in estimated uncertainty of approximately 6% was demonstrated. The main contributors to this are:

  • A revised methodology, based on expected and realistic flow gradients across the site, to estimate uncertainty due to flow gradients between the floating lidar and the reference measurement during calibration.
  • A revised methodology for calibration uncertainty.
  • Careful selection of the implementation route for classification uncertainty; a detailed application of environmental variable sensitivity is preferred to the class number approach. Both are allowed in the standard; the class number approach is currently more likely to be applied as it is far simpler.
  • A revised methodology, based on expected and realistic flow gradients across the site and a model for the effects of induction, to estimate uncertainty due to flow gradients between the floating lidar and the turbine during the power performance test.
  • The assumption that uncertainty due to flow variation within the lidar’s control volume is negligible.

 

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