I recently learned that train engines have been using electric motors powered by diesel generators since at least the 30’s, which surprised me. It made me wonder why cars or at least trucks and busses don’t do something similar, and why “parallel” hybrids are the only type of hybrid engine widely available.
I assume it has to do with the size difference, but what specifically? Needs to carry too much liquid fuel? Generator or electronics can’t be miniaturized? Or is it a purely economic problem and not a technological one?
In: Engineering
It used in car in combination will batteries.
The advantages of diesel-electric in the train are that you need to have high torque a low wheel speed. You need that in a train in a way that is not needed in a car. A car torque converter with automatic gearboxes or clutches with automatic works fine.
A diesel engine, generator, and electrical engine will weigh more than just direct drive in cars
Diesel eclectic is common in ships. There is space-saving if you have electric wires instead of long propeller shafts. You can put the engine in the middle of the ship for better weight distribution.
It also makes it possible to have multiple engine-generator where all is not used at the same time. You can have multiple diesel generators for low-speed operation. For high-speed operations, you can add a gas turbine generator. Gas turbines are efficient if you use all the power from the and small for the power they provide. So warships and cruise ships have them when they like to go fast. Some cruise ships put them up in the smokestacks.
So with multiple engines and lars space, they have advantages.
The result is that is it not efficient for cars to just have diesel-electric drive.
The idea can be used in cars if you combine them with batteries. You can then use the batteries to provide power when lost is needed like if you accelerate and store energy in them from regenerative braking. The batteries can also be charged from an outlet
The internal combustion engine only needs to be powerful enough to provide enough power when you drive at a constant speed. You can operate and the most efficient power level.
This is called a [Series_hybrid](https://en.wikipedia.org/wiki/Hybrid_vehicle_drivetrain#Series_hybrid) and a [Chevrolet_Volt](https://en.wikipedia.org/wiki/Chevrolet_Volt) or [Nissan E-power variants](https://en.wikipedia.org/wiki/Nissan_Note#2017_model_year_update_%E2%80%93_e-Power) is a common example.
There is a drawback with this designer. You need more components in them compared to just using electricity or just an internal combustion drive. A pure electric will be more efficient if you just drive the distance of its batteries to reach. Just internal combustion engines cost less.
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