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Delegates are invited to meet and discuss with the poster presenters in this topic directly after the session 'Remote sensing: From toys to tools?' taking place on Wednesday, 12 March 2014 at 14:15-15:45. The meet-the-authors will take place in the poster area.

John Medley ZephIR lidar, United Kingdom
Co-authors:

(1) ZephIR lidar, Ledbury, United Kingdom (2) Z, ,

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Abstract

Lidar turbulence measurements for wind turbine selection studies: design turbulence

Introduction

The use of lidar wind speed measurements in wind energy project methodologies has been demonstrated to provide advantages over traditional mast anemometry in terms of cost, logistics and accuracy. To optimize these advantages it is important that the ancillary data collected by these instruments is also suitable for use in such methodologies. In this paper the suitability of lidar turbulence measurements is established in the context of an industry standard turbine selection methodology and also in terms of the turbulence spectra that are of relevance in this application.

Approach

In selecting a turbine for a wind farm, turbulence measurements and modelled wake added turbulence are combined to assess the design turbulence levels at the turbine locations against manufacturer specifications. The turbulence measurements used are restricted to the neutral climatic conditions that predominantly occur during higher wind speed periods. This has implications in terms of the length-scales of turbulence that are relevant in turbulence measurements used to inform the selection of wind turbines. In this study the suitability of lidar turbulence measurements for this application is investigated at the ten minute mean level and also at the spectral level.

Main body of abstract

Comparison of turbulence measurements made by a ZephIR 300 VAD scanning wind lidar and a 91m IEC compliant anemometer mast are used to inform the analysis of the suitability of lidar measurements of turbulence for use in wind turbine selection studies following IEC 61400-1 and the Frandsen method. The deviation in turbulence measurements observed between the lidar and mast recorded over a full calendar year in the wind speed ranges applicable is used to determine bounds on deviation in the site classification results for a typical eight turbine wind farm layout in non-complex terrain. Deviation in the design equivalent turbulence levels assessed at each turbine location for the range of deviation observed in mean turbulence measured by the lidar is shown to be minimal with respect to the turbulence bands used in the turbine classification. The turbulence spectrum measured by the lidar in neutral conditions is shown to match that of relevance in the turbine selection methodology particularly where the spatial filtering of the turbine rotor is taken into consideration.

Conclusion

Lidar is increasingly being used as the sole source of site measured wind data. Where this measurement strategy is applied it is important that the wind parameters measured by the lidar are of a suitable nature and quality to fulfill all of the analysis requirements of the wind project. Establishing the suitability of lidar turbulence measurements for use in turbine selection studies lends support to the use of lidar as a sole data source in wind energy projects demonstrating that the benefits afforded by lidar can be attained without compromising accuracy.


Learning objectives
Delegates will gain an understanding of the relative performance of lidars and high quality anemometer masts in determining design equivalent turbulence for turbine selection studies. They will gain confidence in the use of lidar turbulence measurements in such studies enabling them to incorporate lidar data into their wind energy project methodologies accruing benefits in terms of cost and flexibility.