Electric Planes

[Gord_in_Toronto]

Yes, those sound very interesting, however, they don't promise any reduction in weight, and it's hard to see why there should be one. For ground vehicles, this could be great. For house batteries, too. For aircraft, only in that it may keep lithium affordable, as other applications phase it out. Of course, that is something, too.

Hans

If you don't like aluminum, how about sodium?

How Comparable Are Sodium-Ion Batteries to Lithium-Ion Counterparts?

Future research should focus on discovering advanced anode and cathode materials for Na-ion batteries with higher specific capacities and voltages so as to produce practical Na-ion batteries with specific energies approaching 200 Wh/kg. Efforts should also be made to develop advanced electrolytes that enable Na-ion battery performance at high charge–discharge rates over a wide temperature range while exhibiting the long cycle-life and shelf life required for large-scale energy storage applications. Research also should focus on gaining a deeper understanding of the crystal structure–ion transport property relationships in Na intercalation electrodes in order to acquire the ability to systematically design and develop high-capacity, reversible electrodes for Na-ion batteries. Research and development efforts should also continue on Na-ion battery prototypes with particular emphasis on evaluating their temperature- and rate-dependent performance and safety hazards.

 

[smartcooky]

Yes, those sound very interesting, however, they don't promise any reduction in weight, and it's hard to see why there should be one.

But weight alone is not the consideration, but weight v capacity. Say you had an aircraft that needed 50 batteries of Type A with a capacity of 100 each, and each battery weighs 10 and that gives you a range of about 300

_n = number of batteries to be carried
_c = capacity of each battery
_ct = total capacity of all batteries carried
_m = mass/weight of each battery
_mt = combined mass/weight of all batteries carried
All assuming _ct translates directly to range

Type A
50_n x 10_m = 500_mt
50_n x 100_c = 5,000_ct for range = 300

Then someone came up with a battery Type B that weighs 20% more (12) but has a 50% greater capacity (150). Then, to get range of at least 300


Type B
34_n x 12_m = 408_mt
34_n x 150_c = 5100_ct for range = 306

That would be a 20% reduction in weight for the same range, even though each individual battery was heavier. If the physical size was the same or similar, or even if not, if you had sufficient space to place the larger batteries, you could carry the same weight of batteries and get a longer range.

Type B
41_n x 12_m = 492_mt
41_n x 150_c = 6150_ct for range = 369

You have increased your range by 23% carrying the same weight (slightly less actually) of batteries.
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[jimbob]

Sounds Air flies the following routes (the blue ones are over water, so no land alternative.

Nelson <> Wellington 133KM
Nelson <> Paraparaumu 153 km
Blenheim <> Wellington 81 km
Blenheim <> Paraparaumu 111 km
Blenheim <> Christchurch 310 km
Wellington <> Westport 273 km
Wellington <> Taupo 307 km
Christchurch <> Wanaka 297 km


They fly the following aircraft

[qimg]https://www.dropbox.com/scl/fi/3p6ou7zeag0xhl3j2d42x/Cessna208.jpg?rlkey=7st69s5pojt0t1e0tps1gr34f&raw=1[/qimg]
Cessna 208 Caravan (12 seats) Max Cruise 277 kph

[qimg]https://www.dropbox.com/scl/fi/gbcoa06bk53am2oen7zy4/PilatusPC12.jpg?rlkey=gzownkn8x8g657q9hydth4kb0&raw=1[/qimg]
Pilatus PC12 (9) Max Cruise Speed 500 kph


IMO, the Eviation Alice would be fine to replace the aging Caravans (which are rarely full) and to supplement the operations of the Pilatus on the short distance over water runs.

Yes, there are quite a few places where such aircraft could be popular, even with the 200km range. Anywhere especially if there's there's both land and sea in the way between moderate sized locations.

So archipelagos, for example the Philippines, or Greece, or places with very indented coastlines, like Norway.

Or just where roads and rail go long routes to avoid terrain features, For example, places like the Highlands.

Yes there might only be demand for one flight a day or even less, but potentially a lot of places could get served. For example, there used to be a scheduled flight service between Plymouth and Cardiff.

 

[Roger Ramjets]

I sometimes wonder if all the investment in lithium might eventually prove to be misplaced.

That's silly. Do we lament all the investment in steam that 'eventually proved to be misplaced'? Lithium is producing useful results now when we need it. In the future other chemistries may take over, but what we have invested in lithium has already paid off and will continue to do so.

We should remember that to a large extent it's not the technology itself that matters, but how efficiently we can produce and use it. Electric cars have the required range now, but the batteries are expensive. So the big push is to make them cheaper. Sodium batteries have the potential to be much cheaper because they don't use 'rare' metals. But lithium might not be that rare after new deposits are exploited. It may be that sodium batteries only get used in 'budget' cars with low power requirements and short range, while 'premium' vehicles continue to use lithium.

Incremental improvements in lithium batteries combined with bringing down production cost may result in them dominating the market even though other chemistries might be theoretically better. CATLs 'condensed' battery appears to just be conventional lithium technology fine tuned to aviation use. If they do manage to get 500 Wh/kg out of them at reasonable cost it truly will be a 'game-changer' for aviation.

 

[MRC_Hans]

But weight alone is not the consideration, but weight v capacity. Say you had an aircraft that needed 50 batteries of Type A with a capacity of 100 each, and each battery weighs 10 and that gives you a range of about 300

_n = number of batteries to be carried
_c = capacity of each battery
_ct = total capacity of all batteries carried
_m = mass/weight of each battery
_mt = combined mass/weight of all batteries carried
All assuming _ct translates directly to range

Type A
50_n x 10_m = 500_mt
50_n x 100_c = 5,000_ct for range = 300

Then someone came up with a battery Type B that weighs 20% more (12) but has a 50% greater capacity (150). Then, to get range of at least 300


Type B
34_n x 12_m = 408_mt
34_n x 150_c = 5100_ct for range = 306

That would be a 20% reduction in weight for the same range, even though each individual battery was heavier. If the physical size was the same or similar, or even if not, if you had sufficient space to place the larger batteries, you could carry the same weight of batteries and get a longer range.

Type B
41_n x 12_m = 492_mt
41_n x 150_c = 6150_ct for range = 369

You have increased your range by 23% carrying the same weight (slightly less actually) of batteries.
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Yes, thank you, I can do simple math. Since detailed information on aluminium- (or sodium-) based batteries is not yet available, however, that is so far a futile exercise. My point was that of all the announced potential virtues of the new battery type, low weight was not mentioned, so I posit that it would be naive to assume any major break-through in that area.

I am sure, as I have also pointed out in an earlier post, that once electrical aircraft become commercially interesting, we shall see improvements in the weight/capacity of energy storage devices, but it is too early to even guess on a winner.

In the meantime, it is encouraging that the technology is researched and that all the other engineerig aspects are investigated.

Hans

 

[Lplus]

God help the passengers on the first flight to suffer an inflight Lithium battery fire - because no one else will be able to.

 

[Ranb]

Do you think that a battery fire on an airliner is going to be more likely than a fuel tank fire on a jet powered airliner? Who will help them? https://sma.nasa.gov/docs/default-s...9-twa800inflightbreakup.pdf?sfvrsn=6fae1ef8_4

 

[Lplus]

Do you think that a battery fire on an airliner is going to be more likely than a fuel tank fire on a jet powered airliner? Who will help them? https://sma.nasa.gov/docs/default-s...9-twa800inflightbreakup.pdf?sfvrsn=6fae1ef8_4

Yes, considering the number of flights by jet fuelled aircraft up to now and the incredibly low number of fuel tank fires. Note the the particular fire/explosion you point out was itself most probably started by an electrical fault in the fuel level sender system. Do you have any more to show?

Lithium Ion batteries do self discharge without warning and cannot be put out. It may be extremely rare, but I think it will happen more than once as more and more short range electric aircraft are put into service.

 

[3point14]

This has been intriguing me for a while.

If it's viable, who knows?

https://en.wikipedia.org/wiki/XTI_TriFan_600

 

[MRC_Hans]

God help the passengers on the first flight to suffer an inflight Lithium battery fire - because no one else will be able to.

Well, actually one advantage of e-planes will likely be improved safety. Catastrophic failures of electric engines will be far less likely than for jet engines. Likewise fuel fires from ruptured tanks during crash-landings.

So there is battery fires. I assume a lot of things can be done to reduce the risk of those. It's not like they are actually frequent in electrical vehicles.

Hans

 

[Gord_in_Toronto]

That's silly. Do we lament all the investment in steam that 'eventually proved to be misplaced'? Lithium is producing useful results now when we need it. In the future other chemistries may take over, but what we have invested in lithium has already paid off and will continue to do so.

We should remember that to a large extent it's not the technology itself that matters, but how efficiently we can produce and use it. Electric cars have the required range now, but the batteries are expensive. So the big push is to make them cheaper. Sodium batteries have the potential to be much cheaper because they don't use 'rare' metals. But lithium might not be that rare after new deposits are exploited. It may be that sodium batteries only get used in 'budget' cars with low power requirements and short range, while 'premium' vehicles continue to use lithium.

Incremental improvements in lithium batteries combined with bringing down production cost may result in them dominating the market even though other chemistries might be theoretically better. CATLs 'condensed' battery appears to just be conventional lithium technology fine tuned to aviation use. If they do manage to get 500 Wh/kg out of them at reasonable cost it truly will be a 'game-changer' for aviation.

Not so silly. I obviously meant the huge investment in the future of lithium -- there are people and governments who are developing mines and battery plants, anticipating later usage and profits. If something better than lithium comes along these will turn into astronomical lases.

Do I expect this to happen? No. I only "sometimes wonder", but it cannot be ruled out.

 

[Delvo]

The most batterified plane that's routinely flying right now is the 787, and it had some battery fires about a decade ago: https://en.wikipedia.org/wiki/2013_Boeing_787_Dreamliner_grounding

 

[Lplus]

Well, actually one advantage of e-planes will likely be improved safety. Catastrophic failures of electric engines will be far less likely than for jet engines. Likewise fuel fires from ruptured tanks during crash-landings.

So there is battery fires. I assume a lot of things can be done to reduce the risk of those. It's not like they are actually frequent in electrical vehicles.

Hans

One of the most likely scenarios for runaway lithium ion battery fires is if they are damaged, and they can't be put out, even by airport foam equipment. Sure electric engines themselves might well be more reliable, but engine failure is not the only reason aircraft crash by any means.

 

[Ziggurat]

Well, actually one advantage of e-planes will likely be improved safety. Catastrophic failures of electric engines will be far less likely than for jet engines.

That's probably true.

Likewise fuel fires from ruptured tanks during crash-landings.

That's not really a common occurrence. And fuel can be dumped during flight, batteries can't be.

So there is battery fires. I assume a lot of things can be done to reduce the risk of those. It's not like they are actually frequent in electrical vehicles.

They are frequent enough to be a concern. I can't really gauge the risk vs. fuel fires, I don't have comparative data. But it's not negligible. And it's also a different risk profile. A stationary plane that's turned off doing nothing is at basically zero risk of a fire, because there's no ignition source. A stationary electric vehicle is not at zero risk of fire. Battery fires don't need an ignition source, they can self-ignite. Sometimes with devastating consequences. This risk doesn't necessarily preclude electric flight (and a fire on the ground may be preferable to a fire in the air), but it is an issue that needs consideration. I don't think we know how to totally eliminate battery fire risk. I'm not sure we even can while maintaining high energy densities.

 

[MRC_Hans]

That's probably true.



That's not really a common occurrence. And fuel can be dumped during flight, batteries can't be.

Just nit-picking: In principle, they could. Probably not a good idea , but .....

OK, carry on ...

 

[macdoc]

Yes, those sound very interesting, however, they don't promise any reduction in weight,

Weight is not a major factor except on takeoff - drag is. Additional weight stores kinetic energy as any performance sail plane pilot will tell you.

I always thought the natural solution to the high energy cost of getting a plane in the air is a less violent version of the catapult system in aircraft carriers. Use ground based power to get the plane to rotation speed.

 

[theprestige]

I dunno. Jet engines have gotten pretty reliable. I think at this point, jet engines would have to be seen as incredibly risky, in order to justify moving to electric engines. Trading away significant efficiency for marginal safety gains is probably a non-starter for the commercial air travel industry.

 

[Ziggurat]

Weight is not a major factor except on takeoff - drag is.

Except weight affects drag, because lift and drag go hand in hand.

Additional weight stores kinetic energy as any performance sail plane pilot will tell you.

I don't think these are really equivalent flight scenarios.

I always thought the natural solution to the high energy cost of getting a plane in the air is a less violent version of the catapult system in aircraft carriers. Use ground based power to get the plane to rotation speed.

That's really not going to get you much. The takeoff speed of a 787 is about 161 mph, but the cruising speed is about 652 mph, about 4 times as fast. So the kinetic energy on liftoff is only about 1/16th of the cruising kinetic energy, which doesn't account for the potential energy gain getting to altitude or the losses from drag. The overall effect on energy savings is probably trivial. Add in the capital and maintenance issues of implementing such a system, I don't think an assisted liftoff is going to be worth doing if you've got the runway to do without.

 

[macdoc]

They are not hand in hand...

Boeing says the wing design alone could produce a fuel savings of as much as 10%. And when combined with additional advances in propulsion systems, materials and systems architecture, a single-aisle TTBW airplane could reduce fuel consumption and emissions by as much as 30%, Boeing says.

https://www.theverge.com/2023/1/18/23561233/nasa-boeing-airplane-design-fuel-efficient-climate

 

[The Great Zaganza]

I'm not sure about the wing design.

the reason why it is usually under the fuselage is because when the wings are closer to the ground you need less thrust for liftoff and therefore and make do with shorter runways.