Wind power density vs. Energy yield

[windmueller]

Dear all,

Normally it is assumed that the energy yield (MWh/a) is more or less porportional to the wind power density (W/m²).

I now work on a project where I compare two sites and for one site the wind power density is 396W/m² the energy yield 6069MWh/a, whereas at the other site the value for the wind power density is 328W/m² and the energy yield is 6461MWh/a.

What could be the reason for that behaviour?

Thanks.

[Niels Gylling Mortensen]

This could be caused by the shape of the wind speed distribution, especially the Weibull k parameter. Distributions with a long tail will have high power density values, but the turbine can only utilise the wind speeds between, say, 4 and 25 m/s (and not the long tail part).

It does sound a bit odd though, so maybe you should also check your data again ;-)