Wind feedin ts contains values greater than nominal power

wind-python / windpowerlib

The windpowerlib is a library to model the output of wind turbines and farms.

https://oemof.org/

MIT License

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Wind feedin ts contains values greater than nominal power #44

Open nesnoj opened 5 years ago

nesnoj commented 5 years ago

@SabineHaas As mentioned before, I tested the windpowerlib to find out whether the feedin exceeds the nominal power of a turbine. I used the following script: https://gist.github.com/nesnoj/b275925d829cd03fce871e2e9d825490

The max. output is 5,8% larger than nominal power in this case
I used your example weather data weather.csv from the repo but I encountered the same behaviour with a different dataset
Similar results with different turbines (I tested E82/3000)

Is this due to an incorrect cp curve?

Original issue: https://github.com/reegis/reegis/issues/9

nesnoj commented 5 years ago

When using power_curve instead of power_coefficient_curve the output exceedance drops to 2,18% which exactly matches the ratio of max. power (2350.25) to the nominal power (2300).

So it seems to be a cp-related issue..

SabineHaas commented 5 years ago

Thank you for reporting and for the example!

Concerning the power curves it would be interesting how manufacturers set the nominal power of a wind turbine: obviously it's not necessarily the maximum output of the power curve
I recalculated the cp-curve of your turbine to a power curve using standard air density (see the script here):

As you can see the values originating from the cp curve are highly fluctuating around the highest power value in the power curve.

Thus, I'd like to recommend you to calculated with power curves for now. However, lets keep up the discussion about the cp curves!

nesnoj commented 5 years ago

Thanks for your quick reply and the plot! That's quite some fluctuation.. I'll use the power curve for now until we have better data. Cheers

uvchik commented 4 years ago

Does this problem persist or did you solve it by using the power curve.

We could add something like a "force_to_max" method that will force the output to the nominal output if the wind_speed is above a specific value. But this is only needed if there is a power coefficient curve but no power curve. Actually everybody is already free to do this in a post processing.

I cannot gauge the importance of this problem.