Lead Session Chair:
Stephan Barth, Managing Director, ForWind - Center for Wind Energy Research, Germany
Erik Brown (1) F P Andy Oldroyd (1)
(1) Oldbaum Services, Stirling, United Kingdom
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Presenter's biographyBiographies are supplied directly by presenters at OFFSHORE 2015 and are published here unedited
Erik Brown is an Senior Instrumentation Engineer at Oldbaum Services. Based in the UK, his principal focus is on providing measurement solutions to our worldwide customer base. Erik’s expertise in instrumentation and system integration has led to a number of successful offshore met mast projects including offshore remote sensing deployment and complete topside design. Erik’s work in Oldbaums UKAS accredited wind tunnel calibration service as well as his experience of offshore installation work is reflected in his focus on innovative solutions to the challenge of acquiring high quality wind data.
Yaw misalignment study for two neighbouring turbines using nacelle mounted lidar
Two nacelle LiDARs were installed on neighbouring wind turbines on an offshore wind farm in forward facing configuration. Using the wind direction measurements from each of the forward facing LiDARs we assess how well each turbine is yawing into the wind. Combining this with the turbine SCADA data we then further examine this performance for when the turbines are in the free-stream and also when the oncoming wind has been wake affected. The differences between the cases are quantified and the causes investigated.
This study has been carried out with in-situ measurements taken by two Wind IRIS systems located on neighboring turbines offshore. Comparison has been made with wind direction data taken from a nearby met mast, and also with yaw angle data recorded by turbine SCADA system. Thought has been given to appropriate filters, and to how the measurement geometry compares with that of the turbines rotor blades.
Main body of abstract
Two Wind IRIS nacelle mounted LiDARs have been installed on neighboring turbines offshore taking con-current measurements of oncoming wind speed and direction. The systems have been installed so that they are facing along the rotor axis. Studying the output from the two forward facing LiDARs, system we can investigate whether there is a systematic misalignment between the oncoming wind direction and yaw angle set by the control system. Additionally by using data from the SCADA system we can further examine the turbines behavior in the free-stream, and also when the wind coming onto the turbine is wake affected.
This paper presents the findings of this analysis: firstly it is shown that the turbines do both exhibit a systematic and significant yaw misalignment, this is then further quantified for the free-stream and wake affected cases. The differences between the cases are explored and possible reasons for this examined.
Nacelle mounted LiDAR are excellent tools for assessing turbine performance as, uniquely, they can measure the characteristics of the wind regime as they come onto the turbine. Amongst other possible tests, a turbines Yaw control may be tested and potentially optimized using this information thus allowing for power output to be maximised. Fine-tuning this approach further by accounting for sector-wise differences in the oncoming wind regime may also be useful and it is hoped that further work can be done on this in the future.
This paper aims to inform users on the uses of nacelle mounted LiDAR for testing and optimising turbine control systems. Also raised is the question of whether turbine control systems should be set to work differently depending on whether the incoming wind is coming from a free-stream sector, or one affected by turbine/building wakes or other areas where complex flow has been induced.