3 simple rules of thermodynamics:
You can't get something for nothing
You can't win
You have to lose.
The power demand for an electric motor that can actually move enough air to make a difference would require an alternator that would create as much parasitic drag as a supercharger if not more or would require you to drag around 4 extra batteries worth of weight.
heard many orror stories, and have seen it happen. its basicly a little fan, but i've seen the fan peices brake and end up getting sucked into your intake many.. hmm your engine loves tht