Self-sustaining fan

I was thinking about the comic and the idea of making a very small windmill. If you connected the windmill/dynamo to a chargable battery that was supplying power to your wind fan, and aimed the windfan back in the general direction of the mill, you would still circulate cool air through the room, but the fan would essentially power itself. Even if you just had the fan on rotation, meaning that the windmill only spun every now and then, it would help charge the battery powering the fan, and save energy. I'm not entirely sure how much energy a small windmill/dynamo would actually generate, but I would think about enough to power a fan.

Living in a hot country, those who are lucky enough to have fans use them almost all day every day. So if a self sustaining fan were perfected, and if it replaced the conventional fans, a notable amount of in-house electricity could be saved. I'll see if I can get the necessary materials from friends and see if I can get help designing and building it.