Overseas, Honda is looking at different ways to generate power for hybrid engines. The latest technique involves a Rankine cycle-co-generation unit, which can be used to produce energy from the heat produced from an engine. In tests, a Honda Stream outfitted with a Rankine unit generated three times as much electricity using the engine heat than just the regenerative braking system alone.

A Rankine unit basically turns your engine into a sustainable steam engine. The engine heats compressed water, therefore producing steam that turns a generator. See? Simple. If only the Doc and Marty had had a Rankine system in Back to the Future III... [Green Car Congress]