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Wednesday, 12 March 2014
14:15 - 15:45 Remote sensing: From toys to tools?
Resource Assessment  


Room: Tramuntana
Session description

The use of remote sensing within the wind industry has developed significantly since these techniques were first adopted. The new opportunities to make measurements that have been made available have themselves influenced the aims and objectives of the measurements, as it has become possible to consider assessing aspects of wind that were previously overlooked due to an inability to acquire data with more limited instruments. This has led to an industry-wide learning process, as new applications have emerged in response to the measurement opportunities made available by remote sensing, and more effective methods for meeting existing requirements of measurement campaigns have been identified. This session provides an opportunity both to review industry progress in making the most of remote sensing and to look ahead to the possiblities that are now emerging.

Lead Session Chair:
Peter Clive, SgurrEnergy Ltd, United Kingdom
Markos Asimakopoulos SgurrEnergy, United Kingdom
Co-authors:
Markos Asimakopoulos (1) F P Graham More (1) Peter Clive (1) Richard Bodington (1)
(1) SgurrEnergy, Glasgow, United Kingdom

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Presenter's biography

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

Markos Asimakopoulos has been working in the wind industry for 2 years as a Mechanical Engineer within SgurrEnergy. He completed an MSc in Sustainable Energy Futures at Imperial College London which followed his B.Eng in Mechanical Engineering at the University of Edinburgh.
During his time with SgurrEnergy Markos has been a key contributor to the following:
• Mechanical input to the design, specification and fit-out of two offshore meteorological platforms;
• Carbon trust , offshore wind accelerator study;
• Onshore and offshore wind turbine technology assessments;
• Onshore and offshore Wind due diligence assignment; and
• Offshore wind Lidar analysis.

Abstract

Offshore compression zones: measurement and visualisation

Introduction

Power curve tests make use of meteorological (met) masts installed at a distance of between 2-4 rotor diameters (RD) from a wind turbine generator (WTG). This assumes that the compression zone effects have dissipated and are negligible at this distance. However, if this were not the case, then the met mast would record wind speeds that were lower than the true wind speed, leading to a power curve shift to the left (overstating the power curve). If this holds true, power curve testing procedures would need to be amended to better account for the effects of the compression zone.

Approach

SgurrEnergy installed three Galion Lidar units on a single offshore WTG at the Alpha Ventus wind farm. This allowed a comprehensive wind measurement campaign to be performed, including measurement of the wind flow into the rotor at a range of distances in front of the rotor. This included direct measurement of the compression zone in front of the WTG rotor. These measurements have been reviewed to determine the extent of the compression zone in front of a WTG rotor.

Main body of abstract

Traditionally, WTG power curve tests use meteorological masts which are installed between 2-4 RD from a WTG. This methodolgy assumes that the compression zone resulting from the WTG rotor is negligible at this distance. However, if this is not the case, then the met mast would record wind speeds that are lower than the true “free stream” wind speed for any given power output, leading to a power curve shift to the left which in turn suggests that a wind turbine generates more power at low wind speeds.
As a result of this, SgurrEnergy is performing a bespoke measurement campaign on an offshore WTG. This measurement campaign is helping identify the extent of a compression zone, how it compares to a WTG’s rotor diameter and current industry standard power curve testing practices. These specific measurements are conducted with a second generation Galion Lidar unit which allows SgurrEnergy to perform Plan Position Indicator (PPI) scans and hence visualise the full wind profile of the compression zone. The extent of the compression has been measured directly under a range of different climatic conditions.


Conclusion

Preliminary results from this analysis suggest that compression zone effects may be present up to a distance approximately 3-4 rotor diameters in front of the rotor. If this is confirmed, the wind industry may be required to update standard power curve testing methodologies to account for the effect of compression zones on wind speed measurements upon which WTG power curve test are based.



Learning objectives
The key learning objective of this assessment is to identify whether WTG rotor compression zones are affecting the outcome of power curve tests and, if so, what impact this may have on the results of these tests and subsequent assessments.