4 ms·

Took me a while to find an estimate of the actual average efficiency of ICE cars, and the number I found was “about 20%”. Some places claim the most fuel effic

by wredue 2y ago

Took me a while to find an estimate of the actual average efficiency of ICE cars, and the number I found was “about 20%”. Some places claim the most fuel efficient vehicles are about 40% (again, on a good day in testing conditions). EVs on the other hand are up around 87% or higher.

KennyBlanken 2y ago
They're very high especially if power is coming from solar panels on your roof or excess power from neighbors because there are virtually no transmission losses. Also, most power plants aren't that much better than car engines. Coal plants are about 33% efficient and natural gas plants are about 45%.
- akoboldfrying 2y ago
  Commercially available solar panels are below 30% in efficiency. If the energy going into the EV battery instead came from a gas turbine, the efficiency drop would be similar, I expect. If you want to say that this factor doesn't count: In what sense should the oft-quoted factor in the final step count? (That is, the loss in converting from petrol to rotational motion in an ICE, or from electric potential to rotational motion in an EV.) I think the only real utility that number has is in estimating the total amount of stored energy in a typical car of each type -- this could be used to estimate the amount of damage that would be caused by the vehicle catching on fire. Other claims strike me as meaningless.
  - 698969 2y ago
    It's fair game to compare if you include the conversion efficiency of the organisms that made the fossil fuels :P We care about the efficiency of converting resources we have a limited amount of, sunlight is unlimited on humanity's scale, so is wind, but how much solar or wind power we can extract from them and transmit has constraints and that is the step where we should start caring about efficiency
    - akoboldfrying 2y ago
      This is indeed a good argument to burn our limited petrol supplies for heat (closer to 100% efficient) instead of using it in today's inefficient ICE cars.
malfist 2y ago
Those 40% numbers, if you actually read how they got that, it's almost always that they were running the engine in a fixed point operation with a constant RPM. You can make it a bit more efficient by optimizing an engine for a specific singular output, sometimes up to 50% I think is what nissan claims. One automaker, I forget who, was researching doing a hybrid drive train like the volt had, but where the engine could run in that one single speed and charge a battery. Seems a lot more complicated than just electrifying the system, but I'm not a auto researcher. Nissan's PR about it: https://www.nissan-global.com/EN/INNOVATION/TECHNOLOGY/ARCHIVE/E_POWER50/ https://www.nissan-global.com/EN/INNOVATION/TECHNOLOGY/ARCHI...
- AdrianB1 2y ago
  I think this is how some Diesel-electric locomotives are built, with Diesel engines creating electricity for electric motors, running the ICE at constant speed and minimum transmission (not sure a reduction is needed, probably not). Looks like solid engineering for the cases when electrification is not possible for various reasons.
  - whaleofatw2022 2y ago
    Diesel electrics can be big enough and with long enough expected lifetimes to go 'all out', I think in some ways they can get closer to CCGT as far as efficiency. Where the challenge comes for smaller vehicles, is the more power you are trying to give, the more you have to build everything up; not just the engine but whatever that engine is inputting into, also trains have somewhat more predictable speed profiles over a trip vs a car. This is why some manufacturers have vehicles that are PHEVS but really BEVs with an 'oh crap' extender that can struggle to keep up a good grade. I gotta give TRD/Toyota/Ford credit, the HSD style drive train does work around a lot of this stuff for PHEVS; in lockup mode you have a 1:1 ratio with minimal losses and at that point it's up to the ability of the engine to adjust profile. Works very well in practice, and far simpler than the setups of others.
  - Animats 2y ago
    Diesel-electric locomotives were the first vehicles to get really good motor control. In what are called "AC" locomotives, the wheel motors are 3 phase variable-frequency AC motors. The power train is Diesel engine -> generator -> really big MOSFETs -> synchronous 3-phase motors. Each motor is separately controlled and they are run as synchronized servomotors, to prevent wheel slip. When multiple locomotives are coupled together, they synchronize at the wheel level. The effect is almost 2x more traction than older technology, which means fewer locomotives per train. Automotive motor controllers now use similar technology, but the locomotives had it first.

by wredue 2y ago

KennyBlanken 2y ago

They're very high especially if power is coming from solar panels on your roof or excess power from neighbors because there are virtually no transmission losses. Also, most power plants aren't that much better than car engines. Coal plants are about 33% efficient and natural gas plants are about 45%.

akoboldfrying 2y ago
Commercially available solar panels are below 30% in efficiency. If the energy going into the EV battery instead came from a gas turbine, the efficiency drop would be similar, I expect. If you want to say that this factor doesn't count: In what sense should the oft-quoted factor in the final step count? (That is, the loss in converting from petrol to rotational motion in an ICE, or from electric potential to rotational motion in an EV.) I think the only real utility that number has is in estimating the total amount of stored energy in a typical car of each type -- this could be used to estimate the amount of damage that would be caused by the vehicle catching on fire. Other claims strike me as meaningless.
- 698969 2y ago
  It's fair game to compare if you include the conversion efficiency of the organisms that made the fossil fuels :P We care about the efficiency of converting resources we have a limited amount of, sunlight is unlimited on humanity's scale, so is wind, but how much solar or wind power we can extract from them and transmit has constraints and that is the step where we should start caring about efficiency
  - akoboldfrying 2y ago
    This is indeed a good argument to burn our limited petrol supplies for heat (closer to 100% efficient) instead of using it in today's inefficient ICE cars.

malfist 2y ago

Those 40% numbers, if you actually read how they got that, it's almost always that they were running the engine in a fixed point operation with a constant RPM. You can make it a bit more efficient by optimizing an engine for a specific singular output, sometimes up to 50% I think is what nissan claims. One automaker, I forget who, was researching doing a hybrid drive train like the volt had, but where the engine could run in that one single speed and charge a battery. Seems a lot more complicated than just electrifying the system, but I'm not a auto researcher. Nissan's PR about it: https://www.nissan-global.com/EN/INNOVATION/TECHNOLOGY/ARCHIVE/E_POWER50/ https://www.nissan-global.com/EN/INNOVATION/TECHNOLOGY/ARCHI...

AdrianB1 2y ago
I think this is how some Diesel-electric locomotives are built, with Diesel engines creating electricity for electric motors, running the ICE at constant speed and minimum transmission (not sure a reduction is needed, probably not). Looks like solid engineering for the cases when electrification is not possible for various reasons.
- whaleofatw2022 2y ago
  Diesel electrics can be big enough and with long enough expected lifetimes to go 'all out', I think in some ways they can get closer to CCGT as far as efficiency. Where the challenge comes for smaller vehicles, is the more power you are trying to give, the more you have to build everything up; not just the engine but whatever that engine is inputting into, also trains have somewhat more predictable speed profiles over a trip vs a car. This is why some manufacturers have vehicles that are PHEVS but really BEVs with an 'oh crap' extender that can struggle to keep up a good grade. I gotta give TRD/Toyota/Ford credit, the HSD style drive train does work around a lot of this stuff for PHEVS; in lockup mode you have a 1:1 ratio with minimal losses and at that point it's up to the ability of the engine to adjust profile. Works very well in practice, and far simpler than the setups of others.
- Animats 2y ago
  Diesel-electric locomotives were the first vehicles to get really good motor control. In what are called "AC" locomotives, the wheel motors are 3 phase variable-frequency AC motors. The power train is Diesel engine -> generator -> really big MOSFETs -> synchronous 3-phase motors. Each motor is separately controlled and they are run as synchronized servomotors, to prevent wheel slip. When multiple locomotives are coupled together, they synchronize at the wheel level. The effect is almost 2x more traction than older technology, which means fewer locomotives per train. Automotive motor controllers now use similar technology, but the locomotives had it first.