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Friday, 20 November 2015
09:30 - 11:00 LiDARs replacing meteorological masts
Resource assessment  
Onshore      Offshore    


Room: Montparnasse

Over the last five years the on and offshore wind industries have seen an increase in both acceptance of LiDAR measurements and commercial applications for LiDAR. It is through sharing the results of validation studies that uncertainties can be reduced and the full commercial value of this technology and its wide number of applications can be realized.

Learning objectives

  • Delegates will be able to describe the value of validation of floating against fixed LiDARs and defend why this practice is a suitable alternative to validation against meteorological masts
  • Delegates will be able to explain why LiDAR measurements are at least as good as meteorological mast measurements
  • Delegates will be able to identify two different approaches to using commercial LiDARs to measure turbulence intensity
  • Delegates will be able to explain why different measurement devices have different uncertainties levels
Lead Session Chair:
Breanne Gellatly, Axys, Italy
Jan Willem Wagenaar ECN, The Netherlands
Co-authors:
Wagenaar Jan Willem (1) F Verhoef Hans (1) Wouters Dennis (1)
(1) ECN, Petten, The Netherlands

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Presenter's biography

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

Dr Jan Willem Wagenaar currently is project manager and researcher at ECN Wind Energy. He obtained his master of science at the University of Groningen and his PhD at the University of Nijmegen both in physics. In 2009 he joined ECN and his work focusses on measurements regarding power performance, wind resource assessment and LiDAR in national and international projects. He is coordinator of the MEASNET power performance expert group and within ECN R&D coordinator for facilities and experiments.

Abstract

Ring analysis floating LiDAR, static LiDAR and offshore meteorological mast

Introduction

The business case for offshore wind farms relies on accurate wind resource assessments. Wind data for such assessments may stem from various sources. Today, the most accurate wind data are generated using offshore meteorological masts, being very expensive. Floating LiDAR technology provides a much cheaper solution and builds upon the ground based LiDAR technology, accepted by industry for flat terrain. To make sure floating LiDARs provide reliable data in harsh marine and moving conditions validation studies are a necessity. To aid the development of floating LiDAR the Offshore Wind Accelerator (OWA) has published a roadmap towards the commercial application of floating LiDAR.

In this study a ring analysis is performed on a floating LiDAR, a static LiDAR and an IEC compliant meteorological mast. The uniqueness of this work is that not only the floating LiDAR is validated, but also due to the presence of the static LiDAR deviations between the floating LiDAR and the meteorological mast are categorized in terms of atmospheric conditions, metocean conditions and technology (mast vs LiDAR). In addition, this work shows a floating LiDAR to calibrated static LiDAR validation case as a possible alternative to meteorological mast validation.




Approach

A Fugro Seawatch floating LiDAR, equipped with a Zephir LiDAR, was placed near offshore meteorological mast IJmuiden for the period January 2014 until November 2014. The meteorological mast, located 75km from shore, has wind measurements at 26m, 58m, 85m and 91m. For these heights wind speed and wind direction measurements from the floating LiDAR are gathered as well. A static Zephir LiDAR, present inside the mast, has wind speed and wind direction at 92m and onwards. For the indicated period these data are gathered together with the wave and current measurements from the triaxys buoy.

Main body of abstract

With the gathered data a validation analysis is performed of the Floating LiDAR against the meteorological mast as much as possible according to the Offshore Wind Accelerator roadmap KPI’s and CD2 IEC 61400-12-1 Annex L. This analysis provides an answer on the maturity of the system with respect to commercial application.

Because of the presence of the static LiDAR the floating LiDAR is also validated against this static LiDAR and the static LiDAR itself is validated against the meteorological mast. Both, as much as possible according to the same guidelines. In other words a ring analysis is performed and shows whether deviations with the masts measurements are technology driven or caused by sea motions. This cannot be investigated using a floating LiDAR and offshore meteorological mast, only.

Last but not least a sensitivity analysis is performed on the floating LiDAR as well as on the static LiDAR validation. Here, the identified possible influencers are atmospheric conditions as turbulence intensity, vertical wind shear, wind veer etc. and marine wave conditions.


Conclusion

Conclusion are drawn on the commercial maturity of the Fugro Seawatch floating LiDAR system with respect to the OWA roadmap.

In addition, conclusions are drawn on whether deviations of the floating LiDAR with the meteorological mast are technology driven or stem from atmospheric and/or metocean conditions.

Last, but not least conclusions are drawn on to what extent static LiDAR can be used for floating LiDAR validation.



Learning objectives
The learning objectives of this study are summarized as follows:
• The commercial maturity of the floating LiDAR system.
• Identification of main validation influencers and categorization of them in terms of atmospheric conditions, metocean conditions or technology.
• Static LiDAR as floating LiDAR reference.