Be aware that even if the theoretical poweryield from a lenz can be good,it's still a relative low rpm-machine,what means that if you want to extract all the power of your lenzrotor,you need a quite big,or even huge alternator or a gear.

Do some reading.Be studiing.This costs time.

In the ideal case you would be able to guestimate a powercurve.
What I mean by this is that you guess for some windspeeds the optimum rpm and poweryield.If you know the powercurve,you're nearly there.
Then you just ask the best alternator-guestimator of the web,named 'flux'(we're lucky he is living on this board)what you're alternator have to be like.
As long as you can't say anything about your rotor,even flux can't help you very much.