Method of calculation of weibull parameters A and k

[Arya]

Hello Team,

I was not able to find anywhere which method is used to calculate the weibull parameters A and k. Can anyone confirm the method of weibull estimation used and whether there are any special approaches taken by WASP in the estimation? 

[Rogier]

It is probably easiest to check this code for the calculation:

https://docs.wasp.dk/windkit/_modules/windkit/weibull.html#_fit_wasp_m1_m3_fgtm

[Arya]

Thank you so much.

I was specifically looking for the calculation of weib_A_combined and weib_k_combined values which is obtained from downloading the wind data from Microscale API https://wps.neweuropeanwindatlas.eu/api/microscale-atlas/v1/get-data-bbox. 

Do they use https://docs.wasp.dk/windkit/_modules/windkit/weibull.html#_fit_wasp_m1_m3_fgtm as well for the calculation of weib_A_combined and weib_k_combined ?

[Rogier]

Yes that calculation is similar except you don't need the fgtm (frequency greater than mean) variable, because the inputs for NEWA microscale are sectorwise A and k's, the fgtm is only required when you have a wind speed histogram as input. The first and third moments are calculated from the wind direction frequency weighted first and third moments and then you can use `_fit_wasp_m1_m3` to find the combined A and k from those.

[Arya]

Thanks that was helpful.
How is sectorwise A and k's, first and third moments calculated by NEWA

[Rogier]

You can see that in this code:

https://docs.wasp.dk/windkit/_modules/windkit/weibull_wind_climate.html#weibull_combined

It is getting the sector weighted first and third moments and does the weibull fitting with the method `_fit_k_sumlogm`

[Arya]

Thank you so much for the update. Your response was very helful to us.

My understanding is weibull_combined function in https://docs.wasp.dk/windkit/_modules/windkit/weibull_wind_climate.html#weibull_combined gives us the sector combined shape and scale values along with that it calculates the 1st and 3rd moments. These are calculated by taking the sectowise A and k and sectowise wind frequency. 

I have few questions. I hope you would be kind enough to answer them.
1. What is in resource file? Is sectorwise A, k and wdfreq already present in resource file ? From where do we get the resource file ?
2. How is sectorwise A and k and sectorwise wind frequency calculated ? Is it provided by meterological stations directly? Do they have any software to calculate this?
I tried to understand how this is calculated by referring to "European wind atlas" but was not able to get a clear picture of it. 

 

Thanks,
Arya