Renewable Energy

As I drove down the highway yesterday, I would catch occasional glances of the Yellowstone river and I started to think about the windmills that have been sprouting up on the western half of the state. It occurred to me that windmills generate energy by spinning in the wind, and once upon a time ago, wood mills used river power in much the same way, a wheel rotated in the current of the river or stream.

Why is it then, that a watermill could not be created to harness energy? By creating underwater wheels that constantly turn in the swift flowing current of rivers much energy could be produced. The wheels could even be attached to existing bridge structures to lessen the cost of engineering and manufacturing these energy producing wheels. Just a thought...