Sector-wise Weibull parameters calculation method

[Ecoingenieros]

What method (such as Least Sqaures, Maximum Likelihood, Method of Moments, etc) does Wasp use to estimate the Weibull parameters for each direction sector as shown in the "Turbine Site" window ? Thanks !

[Morten]

WAsP is fitting Weibull distributions to data by matching two types of statistics:


1) The mean of the cube of the wind speed
=
2) The probability of winds above the observed mean wind speed
P_model(u>u1) = P_obs(u>u1) where u1 =


This procedure does not guarantee a match of the mean wind speed and the fit is generally less accurate at low wind speeds than at high wind speeds. The focus on the high wind-speed range is intentional, since this is where turbines are operating.


Cheers,
Morten

[Ecoingenieros]

Thanks for your answer. What is the method used for fitting Weibull parameters to the observed Wind Climate (e.g. *.tab tables) ?

[Morten]

The main principle is first to compute the two types of statistics mentioned above based on the observations and then to select the A and k parameters which give the same statistics when calculated by the Weibull probability model. This is done for every wind sector. The situations with calm weather need special treatment, since we cannot trust the wind direction sensor when the wind speed is close to zero. Calm data are therefore distributed proportionally over the wind sectors using the frequency of occurrence determined by winds above the calm threshold.