Vertical Axis Wind Turbine - What is the best airfoil?
I've always been interested in windmills. The vertical axis wind turbine (VAWT) seem really cool. I discovered there is a company that (under contract) assembles them right here in my state of Michigan. So, on our summer vacation last year I diverted the family unit over to the assembly plant to see what's new, and exciting. Well, guess what, the plant is closed on weekend. Who knew. Well, for one, Momma thought I should have. Oh well, we got to see their demo unit Windspire up close anyway. It was just whipping.
Anyway, to my question, if I wanted to build a really efficient VAWT, what would be the best shape for the airfoil?
I've attached an old patent I found that has a drawing (Patent 4247252). I copied the drawing into Inkscape and redrew the airfoil using bezel curves.
But, is this the best shape to start with?
I'm hoping some aeronautical engineer out there can comment.