Wasp Discrepancy

[m.sinesi-wpd]

I have a wind calculation in the wind pro Meteo object equal to 6,07m/s at the turbine hub. But in the simulation with wasp in Park object, if I put a turbine at the same position of the Met site the wind become 6.5 m/s. The site is a very complex site. I have changed the roughness but it doesn’t affect the wind just in a small amount, let’s say 6,47m/s. I make more frequent the contour line from 10 to 2 m. Nothing. The RIX in any case is not more than 3%. What do you suggest?

[Morten]

The wind distribution in WAsP is modelled by a statistical model based on 2-parameter Weibull distributions for each wind sector. You can fit Weibull distributions by many methods matching different properties. The WAsP fitting method matches two properties

1) the mean of the cube of the wind speed
2) the probability of winds higher than the empirical mean wind.

If you compare with histograms for individual sectors, you will often see a very good fit to the upper part of the distribution and some deviation at low wind speeds. This is intentional as accuracy is most critical in the range of turbine operation. The mean is however not always accurately reproduced if the observed data does not follow an exact Weibull distribution. This may not be a problem but you should check whether you have measured long enough or whether there is an unusual wind phenomenon at your site which could significantly disturb the Weibull fits (in the range of turbine operation).

Read more about this at these two pages:
www.wasp.dk/Support/FAQ/WindDistributions.html
www.wasp.dk/Support/FAQ/EmergentExample.html