I don't think that "installing" windmills on top of the hill would be really feasible, unfortunately. Windmills that generate electricity are usually tens of meters tall and such. As for conversion of wind energy to electrical energy, it's a propeller connected to a magnet, so Maxwell's equations would be what to use. I don't think this can be charted, since it depends on the windmill, the elevation (less air at high altitude), the strength of the magnet, the resistance of your power grid, etc.

I'm sorry, I can't answer your question, but I'm thinking you may need a permit for something like this. You can't go installing large structures on public land without first getting permission. Most of these regulations exist for a good reason. If you're trying to generate power, and someone attempts to dismantle or move or otherwise touches your set up, you would not want them to get hurt. Ditto if the set up falls down the hill and hits a hiker. Windmills are potential hazards to wildlife as well.