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Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

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Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#171

Post by cryptonector »

jmward01 wrote: post #9

This appears to ignore the new technology that electric brings in: Reduced maintenance, (for aircraft) reduced weight in other parts of an aircraft, new propulsion capabilities that increase efficiency of the energy used, new performance envelopes (like flying much higher because the physics are totally different), etc etc. Sure. Take an existing vehicle optimized for burning things and just swap that small part and…

Lithium cannot get much denser in energy storage, sorry. Even 10x denser than jet fuel is still way too heavy.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#172

Post by cryptonector »

jmward01 wrote: post #170
MegaButts wrote: post #50

Earlier quoted context omitted.

> reduced weight in other parts of an aircraft The bigger problem is that the overall weight increases. Rearranging the COG doesn't really matter when most of your energy is spent literally fighting gravity. This is the first thing that popped up in google when I wanted to compare gravimetric density between gasoline and lithium ion batteries. Gasoline is still approximately 30x denser. That is at least one revolutio…

The point was the other parts of the plane. No lines moving all that gas around and the pumps and the plumbing in and around the engine and the bleed air piping and the and the and the.... There are a lot of potential places to shave weight when you go electric. An aircraft optimized for electric will be massively different if done right.

The way jetliners scale shaving the weight of those things (and note that you're not counting the weight of electric cables that can carry hundreds of amps) is nothing. It might be something for tiny airplanes, but that's it.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#173

Post by cryptonector »

seb1204 wrote: post #68
MegaButts wrote: post #50

Earlier quoted context omitted.

> reduced weight in other parts of an aircraft The bigger problem is that the overall weight increases. Rearranging the COG doesn't really matter when most of your energy is spent literally fighting gravity. This is the first thing that popped up in google when I wanted to compare gravimetric density between gasoline and lithium ion batteries. Gasoline is still approximately 30x denser. That is at least one revolutio…

This is not correct for electric trucks. Replacing diesel motor and gearbox with battery pack and electric drive train is close to a zero sum game according to https://youtube.com/@electrictrucker?si=RjdWBQQXansebUyJ Definitely not a huge penalty.

Airplanes don't get to do regenerative braking except briefly upon landing, but you're not going to put generators in the wheels just for that, and you need active thrust reversers, so really there is simply no room for regenerating power in electric planes.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#174

Post by cryptonector »

hedora wrote: post #166
class3shock wrote: post #161

Earlier quoted context omitted.

"Additionally, that 60x claim is getting old by the minute. We are getting to 300+ with advancements coming in so fast they are hard to keep track of. That 60x could drop to 10x or lower in just a few years" What was a Tesla Model S power density 10 years ago? Today? Hardware moves slower than you think. All your points have some basis of consideration but the potential performance improvements they represent are tin…

Battery density doubled in the last ten years: https://www.westchestercleanenergy.com/post/lithium-battery-... Density is going up exponentially in the graph because it has been improving 18% for every doubling of the number shipped. Global EV market share is projected to cross 25% this year, so we should expect two more 18% improvements as it approaches 100%. That should improve density 39%. Then (ignoring batteries…

There are physical limits to Moore's-like laws for chip densities and chemical power densities. We can't be too far from those for lithium.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#175

Post by cryptonector »

zik wrote: post #91

His estimate the LCoE of an electric vehicle with lithium batteries is off by a factor of ten. My back-of-the-napkin calculations make it to be $0.22–0.25 per kWh. Let's compare two vehicles - an EV car vs an ICE car - in terms of their energy costs per mile, including energy storage. Using the above numbers the EV comes out to around $0.07 per mile including the lifetime costs of the battery, and the ICE comes out t…

> Let's compare two vehicles - an EV car vs an ICE car -

Ok, but TFA is about planes (and boats), not cars. That's a big caveat because neither planes nor boats can do regenerative braking, and planes need to be light. Boats can get big enough to float even if the power plant is heavy, though there is a maximum to what is reasonable.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#176

Post by svnt »

Retric wrote: post #136
svnt wrote: post #117

Earlier quoted context omitted.

This is unfortunately not true because of the dynamics of diesel engines: there is by design surplus energy relative to requirements from running them at efficient operating points. Otherwise the ship is not a good ship.

You can always scale design to fit reduced demand. Also, loss of efficiency is more than made up for with vastly lower energy demand. “Lowering speed reduces fuel consumption because the force of drag imparted by a fluid increases quadratically with increase in speed. Thus traveling twice as fast requires four times as much energy and therefore fuel for a given distance.” https://en.wikipedia.org/wiki/Slow_steaming “…

Sure, but what does this have to do with what I said? You need design and operating margin, and the engine is always running.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#177

Post by ViewTrick1002 »

Animats wrote: post #165
londons_explore wrote: post #156

Earlier quoted context omitted.

> few applications need the speed. Speed is key to profitability for most usecases. If you are transporting people from A to B, and you can do it in half the time, then you can make twice as many trips per day, doubling revenue (or, if there isn't enough demand, you can buy a smaller boat and reduce your capital costs whilst maintaining the same revenue). And thats before you consider that by going faster you might w…

Not in shipping. See "Slow Steaming".[1] Most container ships could go much faster than they normally do. Sadly, the S.S. United States, the fastest transatlantic liner ever, is about to be disposed of by sinking.[2] 35 knot top speed. Southampton to New York in 3.5 days. No market for that once air travel crossed the Atlantic. [1] https://en.wikipedia.org/wiki/Slow_steaming [2] https://6abc.com/post/what-are-doing-s…

The difference is for short distance passenger transport, I.e. commuting.

A route that used to take 1 hour suddenly becomes 30 minutes and suddenly your daily commute becomes bearable.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#178

Post by perilunar »

cryptonector wrote: post #173
seb1204 wrote: post #68

Earlier quoted context omitted.

This is not correct for electric trucks. Replacing diesel motor and gearbox with battery pack and electric drive train is close to a zero sum game according to https://youtube.com/@electrictrucker?si=RjdWBQQXansebUyJ Definitely not a huge penalty.

Airplanes don't get to do regenerative braking except briefly upon landing, but you're not going to put generators in the wheels just for that, and you need active thrust reversers, so really there is simply no room for regenerating power in electric planes.

There’s no reason why you couldn’t do regen when descending with an electric-powered prop plane. It would give a steeper descent than normal, and may not be more efficient overall than cutting power earlier and descending more gradually, but it could be done.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#179

Post by mariusor »

kjkjadksj wrote: post #154
MostlyStable wrote: post #25

Just going off the tweet about electric scooters being a scam: Nothing in that tweet is convincing. Let's just take at face value the assertion that a KWh of energy in an electric scooter costs $5 (as an EV owner: I'm skeptical). I'm going to use Lime (an SF based scooter rental company, chosen at random) as an example. I tried finding exact battery specs, and couldn't, but based on the range and some general scooter…

Driving it full speed is how you drive these things. They are safer when the speed delta is minimal between you and the rest of the traffic and you are charged by the minute so the incentive is full speed short of obligatory stopping for traffic lights or stops (really blown through) or slight slowing for turns. Battery estimates fwiw are very optimistic on the app in my experience. Assume error of 1/3 in range to be…

> Driving it full speed is how you drive these things

Except for the parts where you have to accelerate and brake because, of course, you're obeying the rules of the road and you are in a city.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#180

Post by dmoy »

hedora wrote: post #167
dmoy wrote: post #70

Earlier quoted context omitted.

Fair, but the context here is planes (and boats I guess though that seems less difficult than planes)

Container boats are ridiculously carbon efficient because they move unimaginable amounts of weight (amortizing any fixed costs like keeping the engine running) slowly (low drag) over a perfectly level surface (no loss from going up hill). Almost any carbon reduction scheme that involves doing anything other than using them doesn’t work. For instance, the embodied carbon of an apple that goes from China to the US, the…

Right and it's precisely because they can have unimaginable amounts of weight that it's a more tractable thing to solve compared to electric planes.

I don't think the article is debating cargo ship vs car carbon footprint here, it's just the feasibility of electric cargo ship vs bunker fuel cargo ship. (And planes, which seems way harder)

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