> After that, what about ICE's that run at optimal load/RPM for the highest possible efficiency to charge a smallish electrical system?
I've long wondered about that given so many trains and ships run that way using electrical transmission from the prime mover ("that's what "diesel-electric" is), I know little about the concerns so I must be missing some significant drawback on the scheme given so few hybrids are "series" and most manufacturers go for either parallel or split topologies.
Of note, an other potential advantage of a series hybrid is you can run alternative ICE topologies e.g. with high but very short efficiency bands.
A mechanical gear transmission is more efficient than a generator and motor. Can you make up that difference? For trains nobody has the ability to make the required parts of that size (this might be in part that you can't fit them in the space required - I think you could build the machine to make them if you wanted it)
It is only with the most recent emissions standards that the losses from non-optimal RPM is a significant factor and the generator/motor is better.
The big issue with trains is starting to move: that requires a slipping clutch, which is inefficient and maintenance-intensive. Also you tend to loose power while switching gears. Lower-power trains (e.g. around 300 kW per motor) are still available with mechanical coupling.
In ships, gears are used up into the multi-Megawatt range, but there you don't need a clutch and have a lot of space and mass available.
I've long wondered about that given so many trains and ships run that way using electrical transmission from the prime mover ("that's what "diesel-electric" is), I know little about the concerns so I must be missing some significant drawback on the scheme given so few hybrids are "series" and most manufacturers go for either parallel or split topologies.
Of note, an other potential advantage of a series hybrid is you can run alternative ICE topologies e.g. with high but very short efficiency bands.