Anemometer installed whitin an existing Wind farm

[Marco C.]

I have to use wind data of an anemometer installed within an existing wind farm. Therefore the wind data are affected by wake affect of the surrounding wind turbine.

How can I simulate this in order to take in account the wake affect? I think that is not a good way simulate the wind turbine as obstacle. Is there a solution?

Thanks and Regards
Marco

[Ole Rathmann]

Hi Marco - you are posing a tricky question!
It is in fact possible to use WAsP to get an estimate of the speed-reduction due to the wake from the wind farm in dependence of wind direction, but it is a somewhat cumbersome.
You would need, in a special WAsP-project, to set up the wind farm, using the actual power curve of the turbines; and then add an additional "virtual" turbine to represent the met-mast, i.e. with the location of the met-mast and the hub-height=met-mast measuring height. However, this virtual turbine should have its own, very special power-curve object (WTG): the Ct-should be = 0 for all wind speeds, and the power curve should be a "fake" one: it should be completely linear over a large speed-span, e.g. (0 for 0 m/s), (50 for 50 m/s). You could use any OWC to define the generalized wind climate of the "special" WAsP project, as long as it is well-behaved in all sectors: having a non-zero frequency and a histogram with a decent mean wind speed, e.g. 8 m/s.
The resulting wake effect for the virtual turbine, in dependence of wind direction, would then give the average speed-reduction due to the wake effect from the true turbines. I have written "average" since the wake effect will in fact be speed dependent since the Ct-coefficient for the true turbines depends on the speed.
This way you should have numbers for the speed reduction at your met-mast site.

Now, in your true Wasp project, you should then apply these speed reductions as negative user corrections for the met-mast: if in sector 1 the speed reduction (due to wakes) was found to be 5% you should then specify a user-correction of -5 for sector 1. Same thing for the remaining directions.

Good luck!

Ole Rathmann.