Power curve and thrust co efficient

[HARIHARAN B R]

I have used Tools --> wind turbine editor and edited the existing turbines power curve by keeping thrust coefficient unchanged. I wanted to know is this correct way to go? If not is there any correlation between the thrust coefficient and wind speed in power curve?

[Morten]

Alternative power curves could reflects different ambient conditions, like air density, and modes of turbine operation, like reduced tip-speed as a means for noise reduction. The changes are made by the wind turbine controller managing tip speed and blade pitch angle, so yes, you are right, this should both affect power curve and thrust-coefficient curve. However, we normally don’t know the exact strategy of the control system or the detailed rotor aerodynamics, so it is difficult to predict changes in the thrust just from changes in the power.


Some manufactures supply sets of power- and thrust-coefficient curves for different conditions, and then you type both curves into the WAsP turbine editor. However, I have also noticed manufactures who supply the same thrust-coefficient curve for different power curves. I think the argument is that the power curve is the most important one, as it influences the AEP more directly. The usually wake loss is only 5-10%, so a modified thrust-coefficient curve will not have as significant an effect on the AEP as a modified power curve.


Cheers,
Morten