Further info for you and your German friends on our own built and modified Hugh Piggott design.
http://www.bryanhorology.com/wind-turbines.php
I do have a full and completed chapter on our wind turbines from my 21 years of Sustainability Project book, yea still writing the thing hahaha. Its in PDF form but too big a file size to openly post here.
A few pages/images here for you, yes all my publications have lots of photos, as English is not always the readers first language.