Hybrid Vehicles/powering hybrids
I heard that of the energy used by the combustion engine roughly 30% is used as useful mechanical work, 30% is lost to friction and 30% is lost as heat. I have looked into some household generators at compared them to the energy requirements of some hybrids and the numbers don't seem too far off. Well I have an idea for a hybrid to use a home generator like configuration to get electric power and use a sterling motor to convert the exhaust heat back to electric energy. It seems that this would help to cut down some friction and recycle some of the heat. Do you think that this is a valid way to convert more calories in one gallon of gasoline into useful work?
Actually, the classic rule of thumb for a gasoline engine is 25% out the shaft, 25% out the radiator, and 50% out the exhaust as heat. These numbers vary widely under different operating conditions. 10% out the shaft is not unusual when a big engine is loafing. Car diesels can get up to 40%, and ship diesels are pushing 60%.
Doing something with that exhaust heat is an old challenge. BMW recently tried it to run a steam engine. The Napier Nomad, which held the efficiency prize in aircraft for decades, basically used the piston engine to feed a gas turbine. Stirlings are another obvious possibility. As fuel becomes relatively more expensive, and complex machinery cheaper, it may become a popular combination.
One inhibiting factor is that most of the time, car engines are not working hard, and have a fairly cool exhaust. An intake turbine to replace the throttle plate would probably run the accessories pretty well, but cut out on acceleration.