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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.

Graham More SgurrEnergy Ltd, United Kingdom
Co-authors:
Gallacher Daniel (1) F P
(1) SgurrEnergy Ltd, Glasgow, United Kingdom

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2014 and are published here unedited

Graham More works within the analysis team at SgurrEnergy and specialises in analysis of measurements from remote sensing devices, in particular the Galion Lidar. Graham has been involved with ground breaking Lidar campaigns such as detailed measurements of wind turbine wakes onshore and offshore, allowing for accurate calculation of wake loss values for long term wind farm energy yield predictions. Beyond Galion analysis Graham has worked on pre-construction energy yields and optimisation of noise curtailment strategies for wind farm operation. Previous to working at SgurrEnergy, Graham graduated with a Bsc in Physics from the University of Strathclyde.

Abstract

Lidar measurements and visualisation of turbulence and wake decay length in an offshore wind farm

Introduction

A comparison of measured and modelled wake structures is important to inform the industry as to the accuracy of the commonly employed wake models. This in turn informs wind farm layout design and reduces the uncertainty associated with wake modelling at wind farms. Second generation scanning lidar allows the width and length of the wind turbine generator (WTG) wakes to be investigated and compared with model predictions.

Approach

Three second generation scanning Galion Lidars have been deployed on a WTG in an offshore wind farm. Two of these on the nacelle of the WTG. These two lidars measured the inflow and outflow conditions concurrently in order to compare the inflow conditions with the outflow and to measure the length and width of the WTG wake. The wake decay rate and wake width were measured for various inflow wind conditions to determine how the wakes recovered in various climatic conditions.

Main body of abstract

The width and length of a WTG wake are generally estimated using WTG wake models such as the Eddy-Viscosity (EV) and PARK models. These have been developed from a theoretical basis and validated using point anemometry measurements or by analysing operational wind farm production data. However, these validation techniques are limited by paucity of data, and significant associated uncertainty.
Second generation scanning lidar technology now allows wake structures to be measured and visualised directly, allowing wake models to be fully calibrated and validated for a single wake. The results of these validations should then allow wind farm layouts to be better optimised in terms of maximising energy yield and minimising WTG loading. In addition, more accurate energy yield predictions should also be realised. The visualisation of the wakes allows for the interaction of the wakes within the wind farm to be analysed to assess their effect on WTG performance.
Initial results indicate that in certain conditions the wake structures can propagate significantly further than predicted by existing models. Further analysis is ongoing to better understand the relationship between wake propagation and atmospheric parameters such as stability and turbulence.

Conclusion

This work presents a clear proof of concept for how advanced offshore wind resource measurements can be performed and used to calibrate and refine conventional wake models. In addition, it clearly presents an opportunity for new WTG wake models to be developed. Initial results from this study indicate that in certain conditions the wake structures can propagate significantly further than predicted by existing models.


Learning objectives
The technique has been developed which allows the use of second generation scanning lidar to study the effects of WTG wakes in an offshore wind farm. These measurements can compared to common wake models for validation and calibration. In addition, these measurements can be used to develop new, novel wake models.