Most of a car's fuel energy is lost as waste heat through the radiator and whatnot. I just had the idle idea of using the 180+ degree water from the cooling system to run some kind of steam turbine, maybe the way they do with geothermal power.
In geothermal power the earth's heat usually boils another fluid, one that boils off at a really low temperature, like freon does. Or you could just run the engine at 225 to boil water to turn your turbine and spin a generator.
I'm imagining a sort of hybrid with maybe a tiny little alternator that almost never runs, and a BIG battery, but not that big. It seems like this would work best on long haul tractor trailers to remove the drag of powering all those lights and gadgets they have. Maybe if enough power can be snatched back from the cooling system you could have a Prius kinda thing without the Prius drivetrain, or at least eliminate alternator load on a normal car without eliminating the alternator altogether.
If my dumbass can come up with this idea, then I doubt that nobody else has, and so I'm wondering if anybody has heard about anything like this?
Still its a valid idea, using your exhaust to heat the fluid would be better than using your coolant IMO, since your exhaust runs much hotter.
Heat transfer would be more efficient from liquid vs air though. If you put you hand in 160F water, your skin would come off. Put your hand in 160F air, it will be really hot, but you won't have the same affects as the water.
"Combining the innovative assistance drive with a 1.8 litre BMW four-cylinder engine on the test rig reduced consumption by up to 15 percent and generated 10 kilowatts more power and 20 Nm more torque. This increased power and efficiency comes for, well, … nothing. The energy is extracted exclusively from the heat in the exhaust gases and cooling water so it is essentially a quantum leap in efficiency."
The only reasons not to do it are added complexity and cost.