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Comment by pmcjones | Hacker News Reader

So diesel-electric cars.

More efficient than individual diesel cars.

Not really, especially not more efficient than hybrid diesel-electric cars. Why are there no diesel-electric hybrids on the market? There's diesel-electric trains and diesel-electric ships for a reason: diesel engines do really well in this type of constant-speed constant-load applications.

I'm not sure about that. I think an electric motor is more efficient than a diesel motor and a larger diesel motor is more efficient than a smaller one. Than charger multiple EVs from a single large diesel generator is more efficient than multiple individual diesel motors.

Single cylinder diesel engines meeting environmental standards don't seem to exist on the market. There are older designs but hard to source in the USA.

Why would a hybrid diesel be more efficient than an all electric car. The diesel motor would bring down the efficiency of the all electric.

I believe an electric motor converts about 60% of the power used into usable power. diesels are closer to 20%.

I did not claim that a hybrid diesel-electric car is more efficient than a battery EV so that question is off-base. Instead I questioned the premise of 'implicit diesel-electric cars' (i.e. battery EVs charged by means of diesel-powered fast charging stations) being more efficient than individual diesel cars or the proposed diesel-electric hybrid cars. There are losses involved in each phase, here starting with refined diesel since the energy losses from the oil well to the pump station are identical for both direct-drive diesel cars as well as battery EVs charged through diesel generators:

- the (modern) diesel engine itself has a thermal efficiency between ~43% (smaller direct injection engines as used in light cars) to > 50% (large truck engines, large generators), theoretical maximum thermal efficiency lies between 55% (achieved by the largest nautical diesel engines) and 60% (not yet available).

- for direct-drive diesel vehicles: transmission losses, commonly assumed to be around 15%

- for hybrid-drive diesel vehicles: generator losses + electrical motor losses + final drive losses

- for generator-charged battery EV vehicles: generator losses + electrical transmission losses + charger losses + battery charging losses + electrical motor losses + final drive losses

Average charging losses for battery EVs seem to lie around 15% with the lowest efficiency (75%, i.e. 25% of energy is lost) seen when using a single-phase AC charger and the highest efficiency (~90%, i.e. 10% of input energy is lost) using a HV DC fast charger. Using the latter does put an extra strain on the battery which shortens its lifetime and tends to be a lot more expensive than using a 3-phase home charger which ends up being the most cost efficient. The 'wire to wheel' efficiency of a typical EV is supposed to be around 77% (Natural Resources Canada (2022)), this includes charging losses. With drive train losses in direct-drive diesel vehicles being around 15% this leaves an 8% difference to the advantage of direct-drive diesel vehicles, some of which will be lost due to the lower efficiency of the small-bore high-speed diesel engines used in such vehicles compared to the larger-bore medium-speed engines used in larger generators. For relatively recent direct-drive diesel vehicles this comparison will probably end up showing them to be overall more efficient that the combination of a diesel-powered charging station and a recent EV.

https://www.adac.de/rund-ums-fahrzeug/elektromobilitaet/lade...

https://www.caranddriver.com/features/a36062942/evs-explaine...

https://insideevs.com/features/555906/tesla-charging-losses-...

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