OEWC vs REWC

[jorgezz]

Dear all,

My question is:

What is the difference between OEWC and REWC?

I'm calculating turbulence. What is the file (OEWC or REWC) that I need to use for this?

Thank you in Advance for your replies

[Morten]

An observed extreme wind climate (OEWC) represents wind conditions at the site of observation. You can use it as input to WEng and predict extreme wind climates at turbine sites within the same flow model domain as the reference site.

An OEWC may be transformed to a regional extreme wind climate (REWC), which applies to a standard height of 10 m above ideal flat terrain with a uniform surface roughness of 5 cm. Site-specific effects are removed from the REWC and we are left with conditions representative for a larger region. The extend of that region could be something like 100x100 km as long as you are sure that the overall wind climate is the same as at the site of observation. The REWC is typically saved on file and may be used in other WEng projects modelling wind conditions far from the site of observation. A REWC is equivalent to a WAsP wind atlas (LIB file) and the conversion to and from the REWC also relies on the wind atlas method.

OEWC and REWC files does not contain turbulence information, but some of the WEng scripts calculating turbulence for several directions applies these files as input, mainly as a way to iterate over different winds. In most projects the WEng turbulence intensity is independent of wind speed, because WEng only predict turbulence for neutral atmospheric stability. The exception is offshore projects where wariable surface roughness over water induces a wind-speed dependence.