Abstract
Traditionally met masts are used for power and load verifications. They are normally placed 2-4 rotor diameters ahead of the turbine. However in complex terrain this can lead to complex analysis of the effect of the terrain on the flow field. A nacelle mounted lidar can provide a better tool for wind field measurements in all terrains. Provided that the measurement is close enough to the rotor disc, the uncertainty in the flow field measurement can be reduced significantly. Therefore any complex terrain calibration and changes in the wind direction can be avoided. However, close distance lidar measurements are affected by the presence of the wind turbine, due to its induction zone. In this work, the dynamic coupling between changes in the wind turbine operating point and the velocities inside the induction zone is studied. Reynolds-Averaged Navier-Stokes (RANS) simulations are used to investigate this interaction. Thereafter, system identification is used to fit first order dynamic models to the simulation results. The parameters of the model are given for the turbine induction zone. These results possibly reduce the uncertainty in lidar measurements, arising from wind turbine blockage.
Highlights
Lidar sensors prove to be very helpful in the wind energy industry for different reasons
In this work we address the problem with close range measurements where the lidar measurements are close enough to be affected by the induction of the rotor
In order to illustrate the effect a change in the gain and time constant have on the transfer function, Figure 3 compares the response of the function with the following parameters:
Summary
Lidar sensors prove to be very helpful in the wind energy industry for different reasons. In [14] the authors have used SOWFA [1] for Large Eddy Simulations (LES) of a wind turbine model in a wind field in order to investigate the effect of the induction zone on lidar measurements. The authors have compared the simulation measurements in terms of mean wind velocity and turbulence intensity in the steady state conditions. Another investigation of the induction zone effect is presented in [13] where the wind field in the induction zone of a Vestas V27 is investigated. Published under licence by IOP Publishing Ltd results of this work can be used to reduce the uncertainty in the wind speed measurements close to the rotor disc.
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