[spodek]

They talk about regional flight. Does anyone have any sign that battery-powered planes carrying a hundred people will cross the Atlantic, Pacific, or the U.S.?

The physics in Tom Murphy's textbook https://dothemath.ucsd.edu/2021/03/textbook-debut suggests it's impossible. I've talked to people at electric plane companies who have offered no hope.

I originally thought since we engineered from the Wright brothers to 747s, aren't we just at the Wright brothers stage now, but am starting to conclude it's not possible.

[choeger]

I don't have such a sign, but 100 passengers is still smaller than what current jets do, so it might be possible.

It would be a radically more efficient design than what we currently have, though.

Before we can even think of long-range flights, let's consider mid-range:

A 737-300 has a range of ca. 4000km from 20,000l of fuel. But that's not flying with full tanks all the time. It has a payload capacity of 17t (on top of passengers, I think) and carries up to 149 passengers.

If we cut the payload to 10t and passengers to 100, our "comparable" electric plane has 10t free payload for batteries (3t for the 50 passengers and 7t from the reduced payload). If we, generously, assume that we can add another 10t as "structural batteries" (basically, building the airframe out of batteries, because, why not, but also smaller and lighter engines), we end up with maybe a total capacity of 40t for our batteries (assuming 1kg/l for the jet fuel). We need the energy for a mid-range flight, say 1000km. That would be about 5000l of kerosene, in a 737 (not completely true due to weight loss during the flight). Fortunately, our electric propulsion is probably much more efficient (thermally) than a turbojet, so we might only need about 2/3 of the same energy. That puts us, very roughly, to the equivalent of 3.333l of kerosene, or about 86GJ. Hence our battery would have to offer 3.6MJ/kg.

This is inside the theoretical realm of a zinc-air battery. So with this very rough calculation it does not seem to be impossible to achieve mid-range battery electric flight. And this usually means it is going to happen whenever it is economically sensible.

For long-range flight, though, we would need even better batteries. Like, at least 4 times better. This is not on the horizon, currently.

[busterarm]

Unless the energy density of batteries suddenly goes up 50x to meet avgas, then no it's extremely unlikely.

Even with road vehicles, electric is only viable right now to the weight and load of your average 4-door sedan.

[SonicScrub]

The Youtuber Real-Engineering (aerospace engineering background) has a good video discussing the viability of electric aircraft. Barring some dramatic revolution in battery energy density, electric aircraft beyond a certain range are simply not-feasible. They are very feasible for short-range routes though.

https://www.youtube.com/watch?v=VNvzZfsC13o

[topkai22]

I think the caveat here is "battery powered electric aircraft." Fuel cells have much higher energy density IIRC.

It's not inconceivable that fuel cell electric planes could become a thing as well, especially if these early BEV show other benefits around maintainability, noise reduction, etc. I think its a long shot though, as jet fuel + carbon capture will probably be price competitive before fuel cell airliners become a thing.

[benhurmarcel]

Fuel cell aircraft are very much a thing, and are being researched by the biggest companies in the industry.

But they’d be called hydrogen aircraft rather than electric by most people.

[macksd]

As others have mentioned, the energy density is a big deal because those planes' fuel accounts for A LOT of their take-off weight. To both illustrate this and point out another potential problem: when a fully fueled heavy, long-haul / high-capacity airliner needs to make an emergency landing shortly after take-off, one of the first things they do is start dumping fuel to reduce the weight (make it more maneuverable) and reduce the fire risk of a crash. Not sure what a comparable procedure for batteries might look like.

[FabHK]

An A380 at MTOM has about 15% payload (pax, cargo) and about 40% airplane, so a full 45% fuel. And kerosene has about 30 to 90x the specific energy (energy per mass) as current batteries, so for an electric airplane the numbers would be much worse. (Plus the Airbus doesn't have to carry the fuel it has burned, while an electric plane does have to carry the empty batteries.)

TLDR: Long range air travel with batteries is a long time off.