[Daox]

Interesting idea, not unlike something we here on EM have come up with.

Even Better Gas Mileage For Plug-In Hybrids? Look To Heat Recovery

The system passes the hot exhaust gasses over pipes containing Pentafluropropane--a hydroflurocarbon refrigerant known as R-245fa--transferring thermal energy from the exhaust into the refrigerant.

Because it has a lower boiling point than water, the refrigerant expands, turning into a vapor that can power a turbine to generate electricity.

After passing through the turbine, the refrigerant is then condensed back into its liquid form before recirculation.

...

Already, the researchers say they have recovered up to 10 percent of engine waste heat under highway driving conditions using a prototype plug-in hybrid designed by Ohio State University.

That translates to a potential 1.9 kilowatts of electrical power, or a 7 percent improvement in gas mileage.