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Delegates are invited to meet and discuss with the poster presenters during the poster presentation sessions between 10:30-11:30 and 16:00-17:00 on Thursday, 19 November 2015.

Lead Session Chair:
Stephan Barth, ForWind - Center for Wind Energy Research, Germany
Michael Courtney Denmarks Technical University, Wind Energy Department, Denmark
Co-authors:
Michael Courtney (1) F Ginka Yordanova (1)
(1) Denmarks Technical University, 4000, Denmark

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2015 and are published here unedited

Mike Courtney has been working in wind energy for over 30 years, primarily in the field of wind measurement. He has been at DTU Wind Energy, formerly Risø National Laboratory, for a total of 24 years. Currently he holds the position of Senior Researcher and is team leader for the Applied Measurement Technology group in the Test and Measurements Section. Mike has experience with many types of measurement technology but in recent years, beside his managerial duties, has specialized in developing calibration procedures for remote sensing devices.


Poster

Poster Download poster (12.75 MB)

Abstract

Lidar to Lidar calibration

Introduction

Wind lidar calibration is currently carried out by comparing wind speeds measured by the test lidar with simultaneous wind speeds obtained from calibrated reference instruments on a co-located mast. Due to the sensitivities of both the test and reference instruments to temperature, turbulence and wind shear, the results obtained are not completely repeatable. The current procedure requires high quality mast measurements at a very flat test site. Due to the necessary restrictions in acceptable wind directions, the calibration can take a considerable amount of time. As an alternative, we are proposing a lidar to lidar calibration procedure that will be more repeatable, can be performed at most operational sites and will be faster and cheaper.

Approach

Instead of using a mast-mounted cup anemometer as the calibration reference, we propose to use a lidar of the same type. This reference or ‘golden’ lidar has itself been calibrated against a mast using the best available procedure over a fairly length period, in order to have the best possible understanding of the various instrument sensitivities. In the lidar to lidar calibration, the sensitivities of the two lidars to both environmental parameters (e.g. shear and turbulence) and to flow inhomogeneity due to terrain irregularities, will be essentially identical. This will give more repeatable results and allow lidar to lidar testing even at moderately complex sites. Since generally most or all wind directions will be acceptable (no mast shadow), the calibration duration will be considerably shorter.

Main body of abstract

To test the new concept, three measurement campaigns were carried out – the same two lidars were deployed at three different sites of varying terrain complexity - in Høvsøre (flat), Orsay (sub-urban) and Kassel (complex). By using one of the lidars as a reference, the other one was calibrated at each of the sites. The data analysis showed the new methodology can yield consistent regression results, only a small increase in uncertainty compared to a mast calibration and, due to the larger available sector – a much shorter measurement period.

Conclusion

The new lidar to lidar calibration procedure produces more repeatable results over a much shorter time and requires neither a very flat site nor a measuring mast. Only a very small penalty in terms of a marginally increased uncertainty has to be paid even though the procedure will be significantly cheaper in monetary terms.


Learning objectives
Delegates will learn about lidar calibrations, in particular that lidars can be usefully calibrated from other lidars with better repeatability and lower cost.