Seems like a cool idea to be more self sufficient with power, and the price of entry is low.
Like others though, I question the practicality of it. Unless you're differnet than most, people generally (us included) try to get out of the wind when camping.
Didn't think about mounting on the camper roof. Would definitely work going down the highway, not sure how the cheap ones would handle 60-100mph winds though. (Think, doing 55-70mph into a headwind = 100mph pretty easy on the right day.)
Interested to hear what you come up with and how well it works though.