I am trying to estimate wind speeds at a proposed wind farm site using the method described in this paper: Modeling of Ethiopian Wind Power Production Using ERA5 Reanalysis Data. The approach is summarized in figure 2 of the paper.
Short Summary, you get ERA5 reanalysis data, then you scale it relative to wind speed figures calculated in a microscale model (Global Wind Atlas) using a bunch of formulas.
What I've done
- I have downloaded 12 months of historic hourly ERA5 reanalysis data.
- I've taken hourly 100m wind speed readings from the 4 neighboring grid points near my site
- I've used bilinear interpolation to estimate wind speed at site.
- I've used wind_stats (hyperlink here to get the site specific Generalized Wind Climate (gwc) file from the Global Wind Atlas. to use for statistical downscaling purposes.
But this is where I get stuck
What I've having trouble with
I am having two issues with the gwc file that I am unsure on how to resolve.
- The gwc file provides the Weibull A & K parameters at a sector level (i.e. in 30 degree increments up to 360 degree, sort of in a wind rose format). Do I aggregate the sector figures up (if so, how?) or do I do I transform my ERA5 data into sectors then apply the downscaling formulas at that level?
- The gwc file doesn't give me a site specific roughness figure, instead it gives me 5 different values. how do I know which roughness figure to use? Do I need a different source of data to first determine what site roughness is?
Does anyone have any experience with the gwc file format? Any assistance be greatly appreciated.