Electric planes

[Kandiru]

Don't kill me but the next revolution in commercial air and maritime transport is hydrogen based, for the simple reason that it contains x3 the energy of fossil fuels per weight, though requiring larger volume for the same energy density. The dirty truth is current batteries are still very heavy.

Airbus looks to the future with hydrogen planes

Hydrogen 'can power virtually all container ships crossing the Pacific' | Recharge

Now we need more nuclear power plants to manufacture it, but alas the world is going apexxxx with regional wars as global warming leads to famines and floods, and the time of lifetime superpower dictators is upon us, just like before the last two world wars. What a mess!

 

[Etna]

Don't kill me but the next revolution in commercial air and maritime transport is hydrogen based, for the simple reason that it contains x3 the energy of fossil fuels per weight, though requiring larger volume for the same energy density. The dirty truth is current batteries are still very heavy.

Another dirty truth is that pressurized hydrogen is also extremely heavy. For example an aircraft the size of a 39 seat Dash-8 requires only about 1000 lb of hydrogen to cover 600 nm, but with today's cutting edge technologies (e.g. Fiber Patch Placement) results in a tank weight of 10000 lb, and a volume of approximately 400 ft3 at 700 bar. This is equivalent to the entire baggage bay and one quarter of the takeoff weight.

This gives you about two or three times the range of batteries for now, but batteries are improving every year while hydrogen storage does not. And it is also several times more expensive, not counting an entire complex infrastructure to set up.

Liquid hydrogen storage is much lighter and smaller, but that is going to be even more expensive to operate. At that point, synthetic fuels will look like a bargain.

Airbus big hydrogen splash recently was, IMHO, nothing else than a PR stunt to yield to political pressure.

 

[ItsNotAboutTheMoney]

Another dirty truth is that pressurized hydrogen is also extremely heavy. For example an aircraft the size of a 39 seat Dash-8 requires only about 1000 lb of hydrogen to cover 600 nm, but with today's cutting edge technologies (e.g. Fiber Patch Placement) results in a tank weight of 10000 lb, and a volume of approximately 400 ft3 at 700 bar. This is equivalent to the entire baggage bay and one quarter of the takeoff weight.

This gives you about two or three times the range of batteries for now, but batteries are improving every year while hydrogen storage does not. And it is also several times more expensive, not counting an entire complex infrastructure to set up.

Liquid hydrogen storage is much lighter and smaller, but that is going to be even more expensive to operate. At that point, synthetic fuels will look like a bargain.

Airbus big hydrogen splash recently was, IMHO, nothing else than a PR stunt to yield to political pressure.

Refueling speed.
Fuel reserve.
Heat.

While the release was for PR, I'm sure they're thinking seriously about it.

 

[daniel]

It does create the economic forcing function which allows for increased R&D as there is now a market for an electric plane where incremental improvements will be valued.

True. Which is why I'm happy to see it. It's just important to point out that this plane is just the first baby step, and we have no way of knowing if batteries will ever become light enough or cheap enough for large-scale commercial aviation. Synthetic fuels are feasible now. We just need more green electric capacity. Synthetic fuel is a less efficient use of our present limited green electricity so won't become the choice for aviation until we have excess.

Another dirty truth is that pressurized hydrogen is also extremely heavy. For example an aircraft the size of a 39 seat Dash-8 requires only about 1000 lb of hydrogen to cover 600 nm, but with today's cutting edge technologies (e.g. Fiber Patch Placement) results in a tank weight of 10000 lb, and a volume of approximately 400 ft3 at 700 bar. This is equivalent to the entire baggage bay and one quarter of the takeoff weight.

This gives you about two or three times the range of batteries for now, but batteries are improving every year while hydrogen storage does not. And it is also several times more expensive, not counting an entire complex infrastructure to set up.

Liquid hydrogen storage is much lighter and smaller, but that is going to be even more expensive to operate. At that point, synthetic fuels will look like a bargain.

Airbus big hydrogen splash recently was, IMHO, nothing else than a PR stunt to yield to political pressure.

Batteries keep improving, but it seems doubtful they'll ever be as light as liquid hydrocarbon fuels. By their very nature, batteries use "stuff" to hold an electric charge, and that stuff has weight, and will probably always have significant weight. Chemical fuels hold their energy in the chemical bonds, and furthermore are consumed, so that weight decreases with flying time. And they can be contained in very lightweight tanks. I don't see batteries ever matching the energy of hydrocarbons. And unlike cars, airplanes are very sensitive to weight.

H2 for aviation will flop as badly as for cars, and for the same reasons: There's no infrastructure, it's dangerous, containers are heavy, and at present it all comes from natural gas.

Batteries work for cars because they don't have to lift their weight off the ground. And they can recover some of the energy on the downhills that they expend on the uphills, though they're still a lot less efficient in hilly terrain than flat.

 

[SmartElectric]

Refueling speed

liquid or pressurized fuel is zero advantage in refueling.

It takes 2 hours parked to deplane, clean, prep and load up again, plenty of time for a full charge.

 

[SmartElectric]

By their very nature, batteries use "stuff" to hold an electric charge, and that stuff has weight, and will probably always have significant weight. Chemical fuels hold their energy in the chemical bonds, and furthermore are consumed, so that weight decreases with flying time

You excluded the weight, complexity and cost of the jet engines that power planes. Electric motors are smaller, lighter, cheaper, longer lasting and better aerodynamically than jet engines.

Battery cells can be formed into the structure of the aircraft given an optimal first principles design. Wings are fuel tanks, they can just as well be formed from from battery cells structurally placed together, forget the "battery pack" as dead weight, think about "battery wing structure" or "battery fuselage structure".

 

[tga]

liquid or pressurized fuel is zero advantage in refueling.

It takes 2 hours parked to deplane, clean, prep and load up again, plenty of time for a full charge.

2 hours? I'm guessing you don't fly much. I've been on plenty of flights where the plane arrives late and the airline is pushing hard to get the next flight out on time, with maybe a 30 min layover.

 

[daniel]

You excluded the weight, complexity and cost of the jet engines that power planes. Electric motors are smaller, lighter, cheaper, longer lasting and better aerodynamically than jet engines.

Battery cells can be formed into the structure of the aircraft given an optimal first principles design. Wings are fuel tanks, they can just as well be formed from from battery cells structurally placed together, forget the "battery pack" as dead weight, think about "battery wing structure" or "battery fuselage structure".

And yet 60% of the entire weight of the airplane featured above is batteries. Even if they double the energy density of batteries, that's still a third of the total weight of the plane. My Model 3 is HEAVY. That's fine for a car. Not so much for an airplane.

And the batteries have to be protected from possible puncture. That adds a lot of weight since the volume of batteries is a large part of the volume of the plane. Batteries can be embedded in the structure of the plane, but batteries themselves don't have sufficient structural strength. Giving them that strength adds weight.

For electric planes to move beyond these small private and micro-commercial models, batteries have to get much lighter and oil has to become a lot more expensive. But a jet engine can burn synthetic fuel produced with electricity from sun and wind.

 

[ThomasD]

In an emergency planes can dump fuel to make the plane lighter. You can't make the plane lighter with batteries The average fuel capacity of a 787 is 266,720 pounds. If batteries were to replace the fuel how much would the batteries weigh?

 

[SmartElectric]

Yes. 2 hours layover. Very standard time for this based on my local airport in Toronto.

No need to dump anything for an electric airplane. Take off and land with identical weight.

747’s dump fuel to emergency land early for very long haul flights but that’s no common for the mid to short routes that electric planes will take over first.

The reason to over-fuel is due to air traffic control throttling planes at an overloaded airport. Clearly electric planes won’t have a lot of excess range to loiter, that’s an issue, dumping fuel isn’t.

 

[Etna]

Yes. 2 hours layover. Very standard time for this based on my local airport in Toronto.

We are talking short range regional aviation here, and their turnaround time is typically 30 minutes. Some cases like Hawaiian Airlines, which is the operational yardstick I am using for the electric regional aircraft I am working on, you get no more than 18 minutes charging time for the batteries.

This is still feasible, using the same charging infrastructure currently in development for electric trucks. And the new cells that allow core cooling, such as the latest one announced by Tesla, can charge a lot faster.

In an emergency planes can dump fuel to make the plane lighter. You can't make the plane lighter with batteries The average fuel capacity of a 787 is 266,720 pounds. If batteries were to replace the fuel how much would the batteries weigh?

Unlike long haul airplanes, regional aircraft often land near their maximum takeoff weight. For example the ATR42-600 has a max takeoff weight of 41005 lb and maximum landing weight of 40344 lb. Beefing up the structure to handle the extra 661 lb requires only 32 lb (I am not making that number up). So... noise levels and a red herring.

If you were to replace the 266,720 pounds of fuel by batteries, according to my calculations you would end up with... 266,720 pounds of batteries. You just wouldn't go as far.

You may still use the aircraft for ultra-short haul markets. Likely a limited market for 250 seats, aircraft seating no more than 75 seats would work better for short ranges that are within reach of electric propulsion.

 

[daniel]

In an emergency planes can dump fuel to make the plane lighter. You can't make the plane lighter with batteries The average fuel capacity of a 787 is 266,720 pounds. If batteries were to replace the fuel how much would the batteries weigh?

It's more that this, because long-haul planes often don't load fuel to full capacity. (I was once on a flight that was delayed because they had loaded too much fuel and had to pump some of it out.) They load only what they'll need plus a safety margin. An electric plane always carries its full weight of batteries, which in the case of the plane featured above is 1/3 the weight of the plane.

As noted above, however, small short-haul aircraft are not comparable to long-haul aircraft. But they still have to deal with the economics of the cost and weight of batteries. And they represent a small segment of the aviation market so they are not a large part of the solution to global warming.

Don't get me wrong, though: I think the development of electric airplanes is a great thing, and if I were a private pilot I'd want an electric plane. But it will be a very long time before they make a dent in commercial aviation. Cost and weight.

 

[ggr]

2 hours? I'm guessing you don't fly much. I've been on plenty of flights where the plane arrives late and the airline is pushing hard to get the next flight out on time, with maybe a 30 min layover.

Yeah, but quick turnaround flights don't refuel. Part of the reason for this is the requirement to know exactly the weight and balance of the fuel load, which they can't know until after it is finished refuelling. But recharging a battery doesn't change its weight (actually this is not true, but the difference is E=Mc^2, which is micrograms).

 

[GlmnAlyAirCar]

Yeah, but quick turnaround flights don't refuel. Part of the reason for this is the requirement to know exactly the weight and balance of the fuel load, which they can't know until after it is finished refuelling. But recharging a battery doesn't change its weight (actually this is not true, but the difference is E=Mc^2, which is micrograms).

I flew for regional airlines for years. It was extremely rare not to refuel.

 

[bxr140]

If you were to replace the 266,720 pounds of fuel by batteries, according to my calculations you would end up with... 266,720 pounds of batteries.

I can confirm: The math checks out.

 

[bxr140]

Random thought regarding turnaround time: Gut feel says some or perhaps many regional legs could incrementally extend ground time without too much total impact, if required to facilitate charging. Its primarily a cost/benefit analysis of daily and lifetime seat-miles (or some similar metric) and if the e-plane is inherently more financially efficient than the gasser, it doesn't necessarily need to fly as much to break even that analysis.

Obviously there's plenty of elements to juggle (connecting flights, fleet size, route size, maintenance/downtime, curfews, etc,), but It really does seem like there's a path forward even if charge time drives turnaround time.

 

[Solor]

Battery cells can be formed into the structure of the aircraft given an optimal first principles design. Wings are fuel tanks, they can just as well be formed from from battery cells structurally placed together, forget the "battery pack" as dead weight, think about "battery wing structure" or "battery fuselage structure".

Not exactly. To certify the aircraft the batteries will need to be in a fire proof/explosion proof containment vessel with a vent to outside the aircraft. Not easy to scatter batteries all over the aircraft and meet this criteria. I actually only see them in a few locations on the aircraft.

 

[daniel]

The idea of electric airplanes is great. The fact that a private pilot can now buy one for pleasure and short trips is marvelous. The electric-take-off gliders look like so much fun that I wish I was a pilot and could have one. (In Spokane there's a club called Quiet Flyers who fly electric R/C airplanes, which are mostly electric take-off gliders, as well as some catapult-launched gliders. Really fun to watch.)

But the cost, and especially the weight of batteries and the low energy density compared to liquid fuels means that they are not going to replace a significant percentage of commercial passenger-miles in the foreseeable future, if ever. The future of aviation is in synthetic liquid fuels produced from renewable, sustainable, green energy sources and atmospheric carbon for a zero-net-carbon footprint. Either that or we continue on our present path until it's too late and the whole thing comes crashing down on our heads.

According to a quick google search, gasoline has 2.2*10^7 joules per pound. And the Tesla Model 3 battery pack is 2.6*10^5 joules per pound. This doesn't account for the greater simplicity of electric motors or the cost of gasoline vs. electricity, but in an airplane weight is so critical that two orders of magnitude difference is a nearly unsurmountable obstacle. It can be done, but at what cost? Most of us here on TMC are willing to pay the additional cost for electric, but the general public won't. When the cost of petroleum gets so high that people can no longer afford to fly, we're more likely to see a return to trains and steamships than large-scale use of electric jumbo jets. That, or synthetic fuels.

 

[Thekiwi]

The idea of electric airplanes is great. The fact that a private pilot can now buy one for pleasure and short trips is marvelous. The electric-take-off gliders look like so much fun that I wish I was a pilot and could have one. (In Spokane there's a club called Quiet Flyers who fly electric R/C airplanes, which are mostly electric take-off gliders, as well as some catapult-launched gliders. Really fun to watch.)

But the cost, and especially the weight of batteries and the low energy density compared to liquid fuels means that they are not going to replace a significant percentage of commercial passenger-miles in the foreseeable future, if ever. The future of aviation is in synthetic liquid fuels produced from renewable, sustainable, green energy sources and atmospheric carbon for a zero-net-carbon footprint. Either that or we continue on our present path until it's too late and the whole thing comes crashing down on our heads.

According to a quick google search, gasoline has 2.2*10^7 joules per pound. And the Tesla Model 3 battery pack is 2.6*10^5 joules per pound. This doesn't account for the greater simplicity of electric motors or the cost of gasoline vs. electricity, but in an airplane weight is so critical that two orders of magnitude difference is a nearly unsurmountable obstacle. It can be done, but at what cost? Most of us here on TMC are willing to pay the additional cost for electric, but the general public won't. When the cost of petroleum gets so high that people can no longer afford to fly, we're more likely to see a return to trains and steamships than large-scale use of electric jumbo jets. That, or synthetic fuels.

I think you might need to re-read this thread, there are already numerous designs in various stages of development for feasible short haul electric aircraft of various sizes that are using current battery technology. They will increasingly become even more efficient as battery tach improves.

most commercial flights are short haul, so that is the initial target. Yes long haul flights will take a long time to replace with a zero carbon solution, but that’s not where the focus is.

 

[Etna]

@daniel says that electric aircraft are not going to replace a significant percentage of commercial passenger-miles in the foreseeable future, and I complete agree with that statement. All those electric aircraft projects will cover about 2% of the marketspace with current battery tech.

The bulk of commercial flights, and emissions, is above 400 nautical miles range. That is out or reach of electric propulsion with current battery tech, unrealistic claims from startups notwithstanding.

However it is still worth chasing that sub-200 miles market, as small as it is.