merge WRG (2009-06-12)

[Old Forum Archivist]

How can I merge a WRG from several wind atlas (several masts on a large site)?

--------

Hello Cathy,

There are no easy ways to do this, but can you say whether the grids overlap each other?

--------

I can make the grids bigger enough to overlap, but those are large grid, in complex terrain, and the masts used to generate WRG can give noticeable difference on mean wind speed on the overlapping areas. My wind farm extension is 20 km wide minimum, with 3 masts (on a row for exemple) to make 3 differents WRG of about 7 km wide.

--------

Hi Cathy,



Sounds like you have two questions/problems. One is technical: how can I merge several resource grids? The other is scientific: is it OK to merge several grids in this case?



We don't have a tool that lets you merge the grids, but if this is something that you and others are needing to do quite often, then we could write something that does that (it could be a utility script). The question about overlap arises because if they do overlap (or have gaps, or have different resolutions) then a decision is needed about what to do when merging. If you have four square grids which together neatly form a larger grid, then merging is technically quite straightforward.



As for the scientific question, I'm not really qualified to advise. For what it's worth, though, I would say that if the different atlases are giving different results for the same location, you've got to work out why and what you want to do about it, before thinking about the technicalities of merging. It's probably more correct to handle the differences at the wind atlas level than at the site level: I think you should not average or interpolate the site results, but go back to the wind atlases and work out which is the right one to use for the overlap area. You could use the lib interpolator tool to interpolate new wind atlases from your original three, and use these to generate more grids until the edge overlap results look more similar.



Again, I offer these remarks as an unqualified WAsP user, not as a WAsP scientist. Perhaps others here have experienced this situation and can suggest some ways to handle it.

--------