This competition is a very good idea, beware that they might retain the good ones and make a lot of money from it ;^)
In discussions within researcher fellows, we have noticed that the actual windmills that we see around Lancaster and the Lake District (UK) are all made with old fashion...
Strirling engine
I would suggest you to use a Stirling engine instead.
This engine is built on a close circuit where you do not loose the fluid at each stroke.
Lets be green all the way and loose nothing.
LHR