[Piwoslaw]

The alternator sucks up lots of engine power, producing more electricity than the car needs. The reason it produces so much is because it doubles as a high power motor for getting the engine started in less than a second. If the alternator could be less powerful, it would be less of a power drain while driving.
So would it be possible to start the engine with some kind of powerful spiral spring, which would be wound by the alternator? The alternator could be less powerful since it would take its sweet time winding the spring, say 5-15 seconds. The spring could also be wound when braking. The spring could be slightly more powerful than a regular alternator, making it ideal for stop-and-start at traffic lights. Also, if your battery dies, the spring might still be wound up making starting possible. Or if it isn't, it could be wound up by a good old-fashioned hand crank. Just take the handle out of the trunk, pop it in a hole in your bumper, turn it 20-50 times and that's that.
I haven't fooled around with springs enough to know whether they can handle the load needed to start an engine, or how large/heavy they would have to be. Any comments?