9 ms·

Electric motors are simpler, more reliable, smaller, lighter, almost perfectly efficient, and have better torque characteristics than ICE. You can't compare th

by phonon 6y ago

Electric motors are simpler, more reliable, smaller, lighter, almost perfectly efficient, and have better torque characteristics than ICE. You can't compare the energy storage density in isolation. Engines are heavy...Model S's motor generates 362 horsepower (according to the official specs), and only weighs 70 pounds...the equivalent ICE would be 500+ :-) (Yes, the inverter weighs something, but the transmission is much simpler as well for electric...overall you save a few hundred pounds easily...A Model 3 battery pack is between 600 and 1000 pounds--so pretty close to the crossover point.)

outworlder 6y ago
Forgot about that on my longer reply. EV engines are _tiny_ and incredibly efficient.
Shivetya 6y ago
However you are ignoring that while you can spin the blades more efficiently, however scaling an electric motor to that size may end up with even more weight, you also have to replace the turbojet portion of these motors. So you will need even more engine. That turbo jet is more efficient at speed while the fan is better at lower speed. In the end we would have slower planes but we will eventually reach a point where we can do it. Someone can probably explain it better and my understanding is rough and not current; jets were cool when I was kid
- hwillis 6y ago
  Your speculation about motors is incorrect; motors are actually more efficient the larger you build them. It's a property of the goodness factor: https://en.wikipedia.org/wiki/Goodness_factor https://en.wikipedia.org/wiki/Goodness_factor It is profoundly foolish to compare motors and heat engines on first principles like this, obviously. Still, here's a turbine that handles 30x the power of a jet engine, running a generator that is about the same size as a jet engine: https://www.ge.com/news/sites/default/files/Reports/uploads/2019/01/25132345/P1000089.jpg https://www.ge.com/news/sites/default/files/Reports/uploads/... generator is in the upper left. Obviously not at all optimized for size or weight- there aren't even any magnets in that thing.
rootusrootus 6y ago
> the equivalent ICE would be 500+ It's not quite that heavy. An LT1 makes 500 horsepower and weighs less than 500 pounds.
- samatman 6y ago
  Are you including the transmission? Teslas have a transmission, but it's not in the same league of complexity or weight.
- phonon 6y ago
  It definitely varies, though under 400 lbs would be tough to find....it takes a significant amount of effort to make a light, high power engine. Electric motors OTOH are well understood, and relatively easily engineered. The point still stands though. You're savings a few hundred pounds compared to an ICE, but you're losing more than in battery weight. An x2 (or maybe even x1.5) increase in battery density, and a (ground up) electric vehicle will almost always be lighter than a similar conventional car with a full tank of gas.
riffraff 6y ago
But the two aren't at odds, o e could use an electric engine and still burn gasoline to produce the electricity, sort of like ships do.
throwaway189262 6y ago
We're still not at the point where weight savings from motor offsets battery. Tesla cars are all extremely heavy for their size
- froh 6y ago
  The mass is a problem of you don't t recuperate braking energy. Tesla's do recuperate braking energy. A heavy ICE driven vehicle in contrast just loses braking energy as heat. Edit: typo
  - throwaway189262 6y ago
    Energy recovery from regen is minimal unless you're stuck in stop and go traffic. Usually less than 5%.
    - baybal2 6y ago
      It highly, highly depends on motor setup. Tesla low gearing induction motor is by far not the best here. Synchronous motors have much better regen capability.
      - throwaway189262 6y ago
        There's just not that much power available for regen. I've done a lot of dicking around with E-scooters. Even at their low speeds with lots of stop and go, regen is less than 10%. It's only used because dumping excess energy back to batteries is cheaper than including brake hardware. The math may work out the same for EV's. Regen just to decrease the cost of brakes rather than increase range significantly. In the e-scooter world, the cheap ones use regen and more expensive models have traditional disc brakes. Air resistance burns a ton of energy at any speeds over 20mph.
        baybal2 6y ago
        How much RPM were you getting at your scooter, and what was the vehicle mass? You say 5% at most... The difference in between, say, 5% and 10%, a bad and good regen is huge.
BoorishBears 6y ago
You're making the parent comment's point, ICE != ICE Mercedes is selling cars with an engine that weighs 354 lbs, with just 2 liters of volume. Now 354 lbs is still pretty heavy, but it's 354 lbs with fluids and accessories. Some (many even) of those accessories have equivalents on a Tesla that aren't included in saying it weighs 75lbs, like pumps for coolant and the AC compressor

by phonon 6y ago

outworlder 6y ago

Forgot about that on my longer reply. EV engines are _tiny_ and incredibly efficient.

Shivetya 6y ago

However you are ignoring that while you can spin the blades more efficiently, however scaling an electric motor to that size may end up with even more weight, you also have to replace the turbojet portion of these motors. So you will need even more engine. That turbo jet is more efficient at speed while the fan is better at lower speed. In the end we would have slower planes but we will eventually reach a point where we can do it. Someone can probably explain it better and my understanding is rough and not current; jets were cool when I was kid

hwillis 6y ago
Your speculation about motors is incorrect; motors are actually more efficient the larger you build them. It's a property of the goodness factor: https://en.wikipedia.org/wiki/Goodness_factor https://en.wikipedia.org/wiki/Goodness_factor It is profoundly foolish to compare motors and heat engines on first principles like this, obviously. Still, here's a turbine that handles 30x the power of a jet engine, running a generator that is about the same size as a jet engine: https://www.ge.com/news/sites/default/files/Reports/uploads/2019/01/25132345/P1000089.jpg https://www.ge.com/news/sites/default/files/Reports/uploads/... generator is in the upper left. Obviously not at all optimized for size or weight- there aren't even any magnets in that thing.

rootusrootus 6y ago

> the equivalent ICE would be 500+ It's not quite that heavy. An LT1 makes 500 horsepower and weighs less than 500 pounds.

samatman 6y ago
Are you including the transmission? Teslas have a transmission, but it's not in the same league of complexity or weight.
phonon 6y ago
It definitely varies, though under 400 lbs would be tough to find....it takes a significant amount of effort to make a light, high power engine. Electric motors OTOH are well understood, and relatively easily engineered. The point still stands though. You're savings a few hundred pounds compared to an ICE, but you're losing more than in battery weight. An x2 (or maybe even x1.5) increase in battery density, and a (ground up) electric vehicle will almost always be lighter than a similar conventional car with a full tank of gas.

riffraff 6y ago

But the two aren't at odds, o e could use an electric engine and still burn gasoline to produce the electricity, sort of like ships do.

throwaway189262 6y ago

We're still not at the point where weight savings from motor offsets battery. Tesla cars are all extremely heavy for their size

froh 6y ago
The mass is a problem of you don't t recuperate braking energy. Tesla's do recuperate braking energy. A heavy ICE driven vehicle in contrast just loses braking energy as heat. Edit: typo
- throwaway189262 6y ago
  Energy recovery from regen is minimal unless you're stuck in stop and go traffic. Usually less than 5%.
  - baybal2 6y ago
    It highly, highly depends on motor setup. Tesla low gearing induction motor is by far not the best here. Synchronous motors have much better regen capability.
    - throwaway189262 6y ago
      There's just not that much power available for regen. I've done a lot of dicking around with E-scooters. Even at their low speeds with lots of stop and go, regen is less than 10%. It's only used because dumping excess energy back to batteries is cheaper than including brake hardware. The math may work out the same for EV's. Regen just to decrease the cost of brakes rather than increase range significantly. In the e-scooter world, the cheap ones use regen and more expensive models have traditional disc brakes. Air resistance burns a ton of energy at any speeds over 20mph.
      - baybal2 6y ago
        How much RPM were you getting at your scooter, and what was the vehicle mass? You say 5% at most... The difference in between, say, 5% and 10%, a bad and good regen is huge.

BoorishBears 6y ago

You're making the parent comment's point, ICE != ICE Mercedes is selling cars with an engine that weighs 354 lbs, with just 2 liters of volume. Now 354 lbs is still pretty heavy, but it's 354 lbs with fluids and accessories. Some (many even) of those accessories have equivalents on a Tesla that aren't included in saying it weighs 75lbs, like pumps for coolant and the AC compressor