What is pitch angle in wind turbines?

Wind turbine blade pitch angle can have a significant impact on the power curve and production of the turbine. But what is pitch angle and how do you measure it?

How to measure pitch angle?

Pitch angles (measured from the theoretical 0° position) can have a significant impact on the power curve and the production of the turbine. Today’s methods used to calibrate the angle at the commissioning stage are not always reliable and it is not uncommon to see several degrees of variations. Therefore, a pitch angle measurement can be calculated during the operational phase of your wind assets.

The mechanical power generated in a wind turbine is calculated as below:

The only difference between two wind turbines on the same wind farm is the wind speed (u) and the blade angle (θ): the power coefficient.

The coefficient is very sensitive at low wind speed, meaning any small deviation in the blade angle will have a significant impact on the production of usually mean wind speed (5-7 m/s).

Hence the pitch control system is in charge of moving the pitch blade angle θ in order to get the maximum Cp for each wind speed.

One way to evaluate a park is to compare the CP of the best and worst performing turbines:

Once you have done this, you can then calculate the potential production increase using the best WTG CP:

What to do with a pitch angle measurement?

After the detailed analysis of the wind farm data, and having calculated the wind power curves of all the wind turbines, a ranking of the wind turbines has been done. This takes into account the power production generated by these power curves with the average wind of the farm. The worst turbines will be recalibrated by comparing the pitch angle of the best in class turbine.

The result of this calibration method is an angle adjustment of the pitch of the blades that have a deviation of more than +-0.15º of the settings of the best in class in the same position of the blade.

How can Greensolver help?

Greensolver strongly advise to perform this kind of study on wind farms with potential power curve issues if the regular checks for this type of problem (anemometer, north alignment, slope offset parameters, etc…) did not reveal anything.

To find out more about how our studies can help you, contact us now!