Turbulence and Heterogeneous Wind Conditions in the Field of Wind Energy

Turbulence and Heterogeneous Wind Conditions in the Field of Wind Energy: Quantification of Heterogeneity Effect on Lidar Measurements and Turbulence Normalisation on Wind Turbine Power Curves

Keus, R.

Bierbooms, W.A.A.M. (mentor)

Aerospace Engineering

Aerodynamics, Wind Energy & Propulsion

Wind Energy

2017-05-17

Monitoring and optimising turbine performance are important tasks of a wind energy operator. However, monitoring activities are expensive and the current state-of-the-art in this field could be improved. A newly developed Avent five-beam Lidar was tested and the impact of heterogeneity on Lidar measurements was analysed. Also, the effect of turbulence on turbine performance was investigated. The Avent five-beam Lidar measurements were compared to several measurement devices: an IEC-compliant met-mast, a ZephIR Lidar and a ROMO Wind spinner anemometer. The Avent five-beam Lidar proved to be an accurate measurement device compared to the met-mast in measuring wind speed and yaw misalignment. However, the thresholds for its availability seemed to be too conservative. The Avent Lidar underestimated the power curve and consequently measured up to 3.5\% difference in AEP. Furthermore, by including a meteorological station at hub height, a more accurate PCV can be performed. The IEC presented a methodology to normalise power curves in order to determine the effects of turbulence on power curves. It was expected that the scatter would be improved and that power curve uncertainty would be reduced. Simulations showed the effects on the power curves and a lower scatter was obtained after normalising the power curves to one turbulence intensity. The theoretical results were validated with measurements from two measurement campaigns, however the circumstances were different due to varying conditions next to turbulence intensity during the measurement campaign. The effects of turbulence on the power curves were clearly observed whereas no improvement in the scatter around the power curves was perceived. Therefore, it could be valuable to investigate the turbulence normalisation by isolating the effects of turbulence. Simulations were performed to approach heterogeneous wind conditions. Also, a five-beam Lidar was simulated to analyse its ability to correct for heterogeneity. Measurements from the met-mast and Avent five-beam Lidar were used to validate the simulations in order to examine the magnitude and possible effect on Lidar measurements. It was found that the effect of heterogeneity depended on the magnitude. A linear correction could be applied, but was insufficient in wind fields with large heterogeneity. In case of low heterogeneity, a correction is not needed. Finally, it is recommended to investigate heterogeneity further by measuring with a Lidar continuously looking into the direction of a met-mast.

Windenergy

http://resolver.tudelft.nl/uuid:ea6e801c-a72d-418f-ac54-a526cc44f7bd

Student theses

master thesis

(c) 2017 Keus, R.