Ok I was thinking about this the other day. Of course you can get an alternator to run like a motor but what's the longevity of doing that? Would it wear out right away?
You would normally drive a 14 V RMS motor with DC of about 14 * 1.414 = 20 VDC; you get the factor of 2 by using a push-pull circuit. You could probably use a 24 V battery for this, and maybe overvoltage the alternator a little (if it overheats, just don't use the full voltage available). By using a 6 transistor circuit (you need three drivers, one for each phase), you can regen into the battery without changing the battery configuration (leave it as 24 V).... for running in motor mode it needs 36 Volts power supply.
14 x sqrt(2) x 2 = 39.6 Volts, 36 Volts is not equal but it approaches good enough.