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Comment by ilyt | Hacker News Reader

> - electric cars are still burning fossil fuels cause powerplants burn fossil fuels (yeah, but electric cars go ~2 times further on 1 liter of fuel even if all our power came from fossil fuels which it doesn't)

So do hybrids. Burning fuel at power station isn't 2x as efficient as burning it in ICE engine; most of the savings come from not wasting power while braking

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Burning fuel at a single power station that is reasonably distant from populated areas is far better from a health perspective than tens of thousands of small, poorly-regulated engines burning fuel within 10 yards of people's homes. I would take electric over ICE even if it were 1-to-1 on fuel consumption, just to feel like I can safely breath outside again.

As long as they're still cars, you should keep holding your breath. Tires and breaks still give off the polluting dust, not to mention the noise

Noise from electric cars is practically non-existent compared to cars (particularly trucks, SUVs, and motorcycles). I'm sure the pollution from tires and brakes isn't great, but that's like saying that if we cured cancer people would still die. Duh, but we should still cure cancer.

I agree with the general point, but the answer for livable cities still has to be fewer cars. Lower speed limits help a lot: there's a point around 30mph where the greatest source of noise goes from being the engine to the tires, so we have a lot of room to make cities better by getting people onto e-bikes or into smaller low-speed vehicles which use orders of magnitude less energy.

Regenerative breaking significantly decreases break pads use.

One correction - a typical coal burning power plant is approximately 33% efficient at converting fuel to energy [https://www.energy.gov/fecm/transformative-power-systems], and combined cycled natural gas power plants are 45-57% efficient. [https://www.sciencedirect.com/topics/engineering/natural-gas...]

Direct ICE vehicles are between 11-27% efficient. [https://sciendo.com/pdf/10.2478/rtuect-2020-0041]

So even a inefficient coal plant is about 50% more efficient than a very efficient normal ICE car, and combined cycle natural gas IS 2x more efficient than a very efficient normal ICE car - and about 5x more efficient than a non-efficient ICE car.

Lots of cross comparisons can be made, but on overage, even with transmission losses, charging losses, etc. it would be very unusual for an EV + power plant combo to be less efficient end to end than directly fueling a traditional ICE vehicle. If it was, it would likely just be a few percent.

CapEx is a real concern here of course, and logistics.

But opex and energy efficiency are solidly in the EV camp.

That's why I talked about hybrids - ICEs have slim efficiency area, add breaking lossess and you get to that number. But put it in a hybrid and you can run it at near-max efficiency most of the time and don't waste that much in breaking.

Hell, Formula engines get to 50% but those don't exactly need to care about emission equipment

> So do hybrids

No they don't. All the energy in a hybrid comes from an internal combustion engine which is generally less than 40%. Hybrids help by running the the ICE only when it would be efficient to do so but they can't help in constant speed highway driving.

> All the energy in a hybrid comes from an internal combustion engine which is generally less than 40%.

Only if you define hybrid to exclude plug-in hybrids. Almost all my driving is on charge, with only longer trips 2 or 3 times a month relying on the ICE in my hybrid.

You are one of a small minority of people who plug their plug in hybrid in. Car leasing companies here in Norway lease a lot of plug in hybrids because the count as electric and so are cheaper to buy. They have statistics about the charging and say that hardly anyone does it, the use chose it simply because it was a cheaper vehicle.

Partially true. You can get away with a more efficient thermodynamic cycle on the ICE due to the more uniform load on the engine so they can be more efficient.

> Burning fuel at power station isn't 2x as efficient as burning it in ICE engine

ICE engines are under 30% efficient (not counting the losses to accelerating/breaking and standing on idle in traffic jams), multi-stage turbines at powerplants are 50-60% efficient (but the 60% ones are rare).

I love my Prius, but over my years of driving it my suspicion is that the regen braking contributes VERY little power to the battery, and I try to brake using regen as much as possible. I would guess that most Prius drivers (who drive the car like a normal car, which is even what Toyota says to do) get back a truly trivial amount of energy out of regen braking.

It wouldn't surprise me if full EV regen braking is much more efficient and useful, though.

It's optimal to coast if you can avoid regeneration, but if you must brake then you want as much of that to be regenerative as possible.

On both EVs and on hybrids.

EVs have more regenerative braking power and capacity though; my Prius fills up rapidly when descending a mountain.

My EV reports 18 kWh/100km for driving and 4 kWh/100km gained from recuperation. That is significant.

Fwiw, my truck has an electric motor and battery, for extra torque only, not for any hybrid ability, but due to its regenerative braking ability I’m still on its original brake pads at 50k miles.

I seem to recall estimates on various EV conversion forums that regen braking saves 5-10% range at best, and the more efficiently you drive normally, the less difference it makes.

> most of the savings come from not wasting power while braking

That doesn't check out for me. ICE engines are inefficient because much of the energy from the fuel is converted into heat rather than kinetic energy. Every ICE engine has a radiator whose sole purpose is to vent off waste heat from the engine. ICE engines don't even need a distinct heating element to keep the cabin warm, the waste heat from the engine is more heat than the cabin will ever need.

I don't know that much about how power stations work, but surely it is not this inefficient.

EDIT: Did a bit of reading on gas/coal power plants and it sounds like they are indeed very inefficient: as bad as 20 percent, as good as 60 percent: https://www.energy.gov/fecm/how-gas-turbine-power-plants-wor...

That is mildly horrifying.

Look up the Carnot cycle and its efficiency. This is theorized to be the best possible efficiency for a heat engine. All heat engines work by rejecting a large fraction of their input heat to an output heat sink. I've heard efficiencies in the 30-50% range for big coal and nuclear plants, much lower for smaller plants.

For specifity, ICE engines will look more like an Otto cycle https://en.m.wikipedia.org/wiki/Otto_cycle

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