Hello and welcome. In this video series, we will talk about the power curve of wind turbines and how we can calculate the energy yield of a wind turbine at a given site. But first, we discuss the power curve of the wind turbine, and more or less we could say now we can forget about everything we have learned so far, because the complete behavior of the turbine, starting from the wind speed coming to the world, wind turbine to the power output, the electrical power output in kilowatt is displayed in this power curve.
That means here we do not consider any more aerodynamic behavior of the gearbox or the generator itself for the power electronics. Everything is here aggregated in one curve. So what we see here is the wind velocity on the horizontal line and on the vertical axis we have the power in kilowatt.
The curve we see here, that is just the power in the wind that we have this typical velocity to the free behavior and then we have a real power curve of a real wind turbine in the there. We also see this at least in the beginning, this behavior of the velocity to the free depending power before we reached a nominal power and it is constant. What we also have drawn here is the line for the pets limit and there we see that is very fair ethical limit.
Almost modern wind turbines get very close to this very theoretical limit and therefore that is already good. It is not any more close at the nominal power operation because here we have much more power in the wind than we can use by our generator that is installed there. Then we have a certain number of indicators that is typical for the power curve, and the first is the so-called cut in wind speed and everything left of the cut in wind speed.
The at the power output is zero. That means we have a certain wind speed needed before the wind turbine generates electrical power. And then we have this behavior to the velocity, to the free until we obtain the nominal power and the corresponding wind speed is then the so-called nominal wind velocity.
From there on we have the nominal power output and then we always have a certain wind speeds where we have the cut off wind velocity. That means here the power is then decreasing to zero because we switched a wind turbine off that we do not need to construct it for very strong winds there. The expenditure is just too high.
And then we also need to say that there is a kind of hysteresis for switching the wind turbine on again. And that is the reason when we have the wind velocity that is close to the cut of wind velocity, we want to avoid that. The wind turbine is switching on and off and on and off all the time.
That would mean mechanical air to the turbine and that we would like to avoid. And that's the reason why we have this hysteresis that we switched a turbine on at a at a little less wind velocity. Again, modern wind turbines use the positioning of the rotor blades and organize to cut off wind speed more in the way we see here that we go down more, move the line and not have a rapid switching off and switching on.
And that is smooth smoothening to complete behavior, especially with very high wind speeds much more. And in the next video, we then will have a look how we can calculate the energy yield 50 help of the power curve for a given wind site. Thank you very much.
