Regenerative braking is touted as one of the energy-saving advantages of hybrid/electric vehicles. Without going into the merits of that claim, I'd like to ask if there might be any way for the regenerative braking idea to work for regular combustion-powered vehicles (without resorting to flywheels).
In other words, is there any way for energy recuperated from braking to be used to regenerate chemical fuel in a reasonably efficient way?