I got in contact with EnBW, the operator of the new wind park in front of the coast of Germany. They donated me the exact positions of the generators, so now they are visible for Wikipedia and flight simulators, too :)
Comment from RM87 on 22 May 2011 at 08:56
Using Area around power generators is not a good idea. You can add all power generators to a relation and add tags to a relation (name, operator, source, wikipedia, power rating, etc.) Although I don't know what type to use for this kind of relation http://wiki.openstreetmap.org/wiki/Relation .
Comment from !i! on 22 May 2011 at 10:49
Yes, this was my opinion, too. But this was done by another mapper, and I doesn't think that it's that bad to delete it. So it's visible even on low zoom levels.