[Plasmoid]

We're actually not that far off.

Right now, liquid fuels have about 10x the energy density of batteries. Which absolutely kills it for anything outside of extreme short hop flights. But electric engines are about 3x more efficient than liquid fuel engines. So now we're only 3x-4x of a direct replacement.

That means we are not hugely far off. Boeing's next major plane won't run on batteries, but the one afterwards definitely will.

[WalterBright]

> So now we're only 3x-4x of a direct replacement.

The math leads out an important factor. As the liquid fuel burns, the airplane gets lighter. A lot lighter. Less weight => more range. More like 6x-8x.

Batteries don't get lighter when they discharge.

[Qwertious]

It's not that simple.

Batteries are inherently more aerodynamic, because they don't need to suck in oxygen for combustion, and because they need less cooling than an engine that heats itself up by constantly burning fuel. You can getvincredible gains just by improving motor efficiency - the difference between a 98%-efficient motor and a 99%-efficient motor is the latter requires half the cooling. That's more important than the ~1% increase in mileage.

Also, the batteries are static weight, which isn't as nightmarish as liquid fuel that wants to slosh around in the exact directions you want it not to. Static weight means that batteries can be potentially load-bearing structural parts (and in fact already are, in some EV cars).

The math leaves out a lot of important factors.

[WalterBright]

The fuel tanks are compartmentalized and have baffles to prevent sloshing. It's a solved problem.

Electric motors are not 98-99% efficient.

As you alluded to, battery weight is more than ICE weight. EVs are significantly heavier than ICEs.

I'm sure we can expect improvements along the lines you mentioned, but I seriously doubt it will be nearly enough.

[giobox]

Not to mention that jet planes routinely take off heavier than their max safe landing weight today too, relying on the weight reduction of consuming the fuel to return the plane to a safe landing weight again while enjoying the extra range afforded. This trick doesn't work well with batteries either.

[WalterBright]

There isn't any battery technology on the horizon that would lead to practical airliners.

[seanmcdirmid]

You could do it with a ground effect plane for inland sea jaunts, like Seattle to Victoria. If you can float, then you don’t technically need a huge reserve like is normally needed.

[breve]

> Boeing's next major plane won't run on batteries, but the one afterwards definitely will.

Jet engines work better. Boeing's next major plane will have jet engines, just like their previous major planes.

Synthetic, carbon neutral jet fuel will be the future for commercial jets.

[capitainenemo]

Well, there's also burning regular fuel in a fuel cell, a FCEV. That doubles the efficiencies over ICE, so I guess that bumps it back up to 8x away?

Given the great energy densities and stability in transport of hydrocarbons, there's already some plants out there synthesising them directly from green sources, so that could be a solution if we don't manage to increase battery densities by another order of magnitude.

[WalterBright]

> there's already some plants out there synthesising them directly from green sources

I didn't realize that a "green" carbon atom is different from a regular carbon atom. They both result in CO2 when burned.

[fc417fc802]

The problem isn't CO2 it's pulling carbon out of geological deposits. Thus the carbon atoms in synthetic fuel can be considered "green" provided an appropriate energy source was used.

[WalterBright]

I understand that, but it's a fallacious argument. It's still emitting the same amount of CO2 into the atmosphere.

You can also bury dead trees in a landfill.

[margalabargala]

You misunderstand the problem. The act of emitting CO2 into the atmosphere is not a problem.

Significantly increasing the CO2 concentration in the atmosphere is the problem. This happens when geological sources are used.

Unfortunately, burying dead trees in a landfill doesn't solve the problem because they decompose to methane which escapes. But you're right that geological CO2 production could be balanced by geologic CO2 sequestration, done properly.

[fc417fc802]

The point is that emitting CO2 into the atmosphere was never the problem. Adding geological carbon back into the carbon cycle is the root cause of the entire thing.

You can certainly bury dead trees. I'm not sure how deep you'd need to go to accomplish long term (ie geological timeframe) capture. I somehow doubt the economics work out since what is all the carbon capture research even about given that we could just be dumping bamboo chips into landfills?

[WalterBright]

> I'm not sure how deep you'd need to go to accomplish long term (ie geological timeframe) capture.

Coal mines are sequestered trees.

[vel0city]

But if the CO2 recently came from the atmosphere it's still a net zero impact though.

Like, take 5 units of carbon out of the atmosphere to create the fuel. Burn it and release 5 units of carbon to the atmosphere. What's the net increase again? (-5) + 5 = ?

FWIW I'm not saying these processes actually achieve this in reality. Just pointing out that it could be carbon neutral in the end.

[defrost]

> I didn't realize that a "green" carbon atom is different from a regular carbon atom.

Easy mistake to make, don't beat yourself up over it.

It's not the individual carbon atoms that carry the signature, it's the atoms in bulk that give the story ... eg: 6 x 10^23 carbon atoms

See: https://pmc.ncbi.nlm.nih.gov/articles/PMC7757245/

[jeffbee]

Its the time shift. Burning a plant releases CO2 and it is still considered to be carbon neutral.

[WalterBright]

Sorry, that's just verbal sleight of hand. There's no such thing as "green" CO2.

[shmeeed]

Yes there is. I used to fall for the same lie, but it's just not true. It's a question of system boundaries.

Green CO2 was recently (in geological terms) captured from the atmosphere into biomass, that's why its release is basically net zero.

Fossil CO2 hasn't been part of the atmosphere in eons (back in e.g. the Crustacean, the CO2 ratio was many times higher), so its release is additive.

[WalterBright]

So bury the trees. Or run them through the sawmill and build houses.

[jeffbee]

How do you justify exhaling then?

[Joker_vD]

Well, you don't. Everything you do has a carbon footprint, you know, haven't you heard? Everything.

[antonvs]

Have you always had difficulty with abstraction?

[TheSpiceIsLife]

And, the two major byproducts of burning hydrocarbons are water and carbon dioxide.

Literally essential plant nutrients, essential for life.

Tangentially related, the 2022 Hunga Tonga–Hunga Haʻapai volcanic eruption ejected so much water vapour in to the upper atmosphere, it was estimated to have ongoing climate forcing effects for up to 10 years.

Water vapour is a stronger greenhouse gas than carbon dioxide.

And we heard precisely nothing about that in the media other than some science specific sources at the time and nothing on an ongoing basis.

From Wikipedia:

The underwater explosion also sent 146 million tons of water from the South Pacific Ocean into the stratosphere. The amount of water vapor ejected was 10 percent of the stratosphere's typical stock. It was enough to temporarily warm the surface of Earth. It is estimated that an excess of water vapour should remain for 5–10 years.

https://en.wikipedia.org/wiki/2022_Hunga_Tonga%E2%80%93Hunga...

[robertjpayne]

Please, the media didn't report on this because natural disasters affecting the climate is not controllable by humans and thus doesn't warrant a global effort to address unless it's so large as to be species ending.

Global warming is not fake, there's tons and tons of evidence it is real and the weather is getting more and more extreme as humans continue to burn petrol.

[jeffbee]

Also some time after that other guy copied and pasted his canned Hunga remark into his big spreadsheet of climate denial comments the international community of climate scientists concluded that Hunga cooled the atmosphere, on balance.

"As a consequence of the negative TOA RF, the Hunga eruption is estimated to have decreased global surface air temperature by about 0.05 K during 2022-2023; due to larger interannual variability, this temperature change cannot be observed."

https://juser.fz-juelich.de/record/1049154/files/Hunga_APARC...

[nandomrumber]

Thanks for linking that document, I’ll have a read.

[nandomrumber]

Yes, and it doesn’t fit the narrative.

We should be moving towards being able to terraform Earth not because of anthropogenic climate forcing, but because one volcano or one space rock could render our atmosphere overnight rather uncomfortable.

You won’t find the Swedish Doom Goblin saying anything about that.

> burn petrol.

Well yeah, so making electricity unreliable and expensive, and the end-user’s problem (residential roof-top solar) is somehow supposed help?

Let’s ship all our raw minerals and move all our manufacturing overseas to counties that care less about environmental impacts and have dirtier electricity, then ship the final products back, all using the dirties bunker fuel there is.

How is that supposed to help?

I mean, I used to work for The Wilderness Society in South Australia, now I live in Tasmania and am a card carrying One Nation member.

Because I’m not a complete fucking idiot.

Wait till you learn about the nepotism going on with the proposed Bell Bay Windfarm and Cimitiere Plains Solar projects.

I’m all for sensible energy project development, but there’s only so much corruption I’m willing to sit back and watch.

With the amount of gas, coal, and uraniam Australia has, it should be a manufacturing powerhouse, and host a huge itinerant worker population with pathways to residency / citizenship, drawn from the handful of countries that built this country. And citizens could receive a monthly stipend as their share of the enormous wealth the country should be generating.

Japan resells our LNG at a profit. Our government is an embarrassment.

[WalterBright]

Natural resources are not required to make a country an economic powerhouse. See Japan, for example. Hong Kong, Taiwan, S Korea.

What's needed are free markets. Any country that wants to become a powerhouse has it within their grasp. Free markets.

[rgmerk]

Hmmm. If we do simple extrapolation based on a battery density improvement rate of 5% a year, it takes about 30 years to get there. So it's not as crazy as it sounds - and it's also worth noting that there are incremental improvements in aerodynamics and materials so that gets you there faster...

However, as others have pointed out, the battery-powered plane doesn't get lighter as it burns fuel.

[crote]

If we do simple extrapolation, a cellphone-sized battery will reach the 80kWh needed to power a car in as little as 180 years.

Expecting a 5% / year growth rate sustained for 30 years is very optimistic. It is far more likely that we'll hit some kind of diminishing return well before that.

[TheSpiceIsLife]

More accurately, the calculation needs to factor in the fact that battery weight doesn’t decrease as charge is used.

Commercial aviation’s profitability hinges on being able to carry only as much fuel as strictly[1] required.

How can batteries compete with that constraint?

Also, commercial aviation aircraft aren’t time-restricted by refuelling requirements. How are batteries going to compete with that? Realistically, a busy airport would need something like a closely located gigawatt scale power plant with multi-gigawatt peaking capacity to recharge multiple 737 / A320 type aircraft simultaneously.

I don’t believe energy density parity with jet fuel is sufficient. My back of the neocortex estimate is that battery energy density would need to 10x jet fuel to be of much practical use in the case of narrow-body-and-up airliner usefulness.

[WalterBright]

You laid it out better than I. Thank you!

[TheSpiceIsLife]

Thanks Walter!

[abdullahkhalids]

An A320 can store 24k liters of fuel. Jet fuel stores 35 MJ/L. So, the plane carries 8.4E11 J of energy. If that was stored in a battery that had to be charged in an hour 0.23GW of electric power would be required.

So indeed, an airport serving dozens or hundreds of electric aircrafts a day will need obscene amounts of electric energy.

[vardump]

Jet engines are not 100% efficient.

Electric motors can be pretty close, 98% is realistic. Of course other parts of the system will lose energy, like conversion losses.

Of course that doesn't mean batteries are currently a viable replacement. One should still take efficiency into account in quick back of the envelope calculations.

[TheSpiceIsLife]

Halve it to 0.11G then.

It makes no difference, we’d still need gigawatt scale electricity production, with some multiple of that at peak, just for a fairly unremarkable airport.