DenBommer wrote: ↑04 Jul 2024, 09:02
I don't know if anyone here knows about future/concept technologies. But I often think that the heat from a combustion engine also has the potential to be converted into electricity.
Imagine a naturally aspirated V8 without batteries (or with very small ones) that uses its heat to also power the electric motor(s).
And the higher the RPM, the hotter it gets, and the hotter it gets, the more energy is generated...
You're essentially just describing the MGU-H. The energy (heat) recovered by the MGU-H (energy that would otherwise be sent out of thee turbo wastegate) is really the only sufficiently energized heat source to make recovery worthwhile. Even then an MGU-H is only really worth it in super niche cases where cars regularly run at high enough boost to actually need to vent significant amounts of energy out of the wastegate. This is why the only road car to have one (that isn't running an F1 engine) is a 911 derivative. Other cars just don't rev high enough to make it worth it.
The extra weight and complexity of the MGU-H makes it useful for F1, but for any other application the weight and complexity and cost just isn't worth it, and the MGU-H may well make the car less efficient becuase it would be harvesting so little when you only really run the engine at 1200-3000 RPM on the road with any regularity that the weight penalty would cancel out any combustion efficiency.
Now with your example where you don't have a turbo, you would have no obvious spinning parts to harvest energy out of, like a turbo turbine. What you would need to do in that case is either just add a turbine in the exhaust, or perhaps use the radiator heat to produce pressure and spin one.
The former is essentially just all the disadvantages of a turbo (weight, complexity) with none of the advantages (forced induction and the subsequent power feedback loop). Yes, you would get some energy out of it, but said energy would be much better used to spin up a turbo because the increased combustion efficiency leads to several times power gain for the same (or less) extra weight. Basically converting exhaust heat to electrical power isn't worth it without a turbo, because a turbo is SIGNIFICANTLY more efficient, lighter and less complex than a generator. The generator is only good as an alternative to a wastegate.
The latter option is just so insanely inefficient that it just wouldn't be worth it. Yes, you could harvest that energy to some extent, but the amount of heat you would be able to harvest would probably be a low single digit percentage of the heat the ICE generates that isn't exhaust. It just isn't worth it for any application that has the goal of moving and turning (a car).
Or are you describing something else? If you have no battery you can't recover the heat unless you want to run a bunch of water over the engine and run a tiny steam turbine (or something) for extra power?
