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The age of electric flight is finally upon us

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Re: The age of electric flight is finally upon us

#61

Post by Yizahi »

bdamm wrote: post #46
Yizahi wrote: post #37

Simple electric wheel on aircrafts for taxiing (as compared to the electric powered flight) took almost 10 years from first demo tests and it still hasn't entered production on commercial airlines. And that thing is completely possible with modern tech. I highly doubt we will see electric powered aircrafts (bigger than small* experimental crafts) in our lifetimes. Way too much limitations existing today. But it would…

Electric wheel propulsion on aircraft seems like an entirely unnecessary feature. Airplanes have no difficulty using their primary form of propulsion - moving air - to move on the ground, and it takes very little energy to do it compared to the energy required to move through the air while off the ground.

I read years ago when it was first announced that price saving should be significant, also less machine hours for engines (longer maintenance intervals), less safety checks on the ground etc.

Re: The age of electric flight is finally upon us

#62

Post by rbanffy »

gambiting wrote: post #39
ginko wrote: post #2

I'm surprized hydrogen fueled flight isn't looked into more. Hydrogen can be produced using electrolysis and it's packs significantly more energy per weight even than kerosene. The main drawback is the low density which would require larger fuselages, but that should be offset by the significantly lower weight.

1kg of kerosone can be kept in a plastic tank that weighs nothing. 1kg of hydrogen has to be kept in a pressurized, pure-lead 70kg bottle, and even then hydrogen will diffuse through it in just few weeks. So to take 1kg of hydrogen with you you're taking a lot of weight in the tanks too.

The relative weight of the tank decreases with volume and the aircraft doesn't need to hold the fuel for more than the duration of the flight. The idea is not without merit.

Shape will be more interesting - storing the fuel within the wings is not a very bright idea in this case.

Re: The age of electric flight is finally upon us

#63

Post by Patrick_Devine »

iambateman wrote: post #10

From the article: conventional fuel for a 100 mile flight costs $400, while electric energy would cost $12. This seems like such a tremendous difference that the market would be in an arms race to make it a reality. Especially considering electric motors have fewer moving parts and so require less maintenance. Oh and it would be so quiet.

It's a game changer for airlines such as Harbour Air in British Columbia and Mokulele Airlines in Hawaii. These are small regional airlines which operate from the water or from small airports with flight times usually less than an hour, and most of their operational expenditures are in fuel costs. Typically for these airlines you show up 15 minutes before the flight and there is no security screening, so it's very hassle free.

Think of what it could do in other areas as well too though. Imagine a flight from the SF waterfront to Tahoe via seaplane in 45 minutes (instead of 4+ hours) with no TSA screening, or potentially even SF to LA in 90 minutes.

Re: The age of electric flight is finally upon us

#64

Post by gnode »

bdamm wrote: post #46
Yizahi wrote: post #37

Simple electric wheel on aircrafts for taxiing (as compared to the electric powered flight) took almost 10 years from first demo tests and it still hasn't entered production on commercial airlines. And that thing is completely possible with modern tech. I highly doubt we will see electric powered aircrafts (bigger than small* experimental crafts) in our lifetimes. Way too much limitations existing today. But it would…

Electric wheel propulsion on aircraft seems like an entirely unnecessary feature. Airplanes have no difficulty using their primary form of propulsion - moving air - to move on the ground, and it takes very little energy to do it compared to the energy required to move through the air while off the ground.

Propelling air to move on the ground is far less efficient than wheel propulsion. You have to give the air at least as much momentum as the vehicle, and without a very large propeller, this requires accelerating it to a high velocity, giving it much more kinetic energy than the vehicle itself. The energy use while taxiing can be substantial, and the range of electric planes is critical.

Wheel propulsion on the other hand can impart momentum at very high efficiency, as well as regeneratively brake.

Re: The age of electric flight is finally upon us

#65

Post by usrusr »

isostatic wrote: post #35
SeanBoocock wrote: post #16

Earlier quoted context omitted.

From the article: > Even assuming huge advances in battery technology, with batteries that are 30 times more efficient and "energy-dense" than they are today, it would only be possible to fly an A320 airliner for a fifth of its range with just half of its payload, says Airbus's chief technology officer Grazia Vittadini. > "Unless there is some radical, yet-to-be invented paradigm shift in energy storage, we are going…

A320 family range varies from 5500km to 8700km, so "a fifth of it's range" is around 1500km, which is 80% of the industry emissions. I'm not sure of that quote either -- a lithium ion battery is currently about 1MJ/kg and 1MJ/litre. Jet fuel is 43MJ/kg and 35MJ per litre (values from from wikipedia) So a battery that's 30 times more energy dense will be in the region of jet fuel, and thus would presumably be able to…

The 80% figure are flights longer than 1500 km. 1500 and less are the 20%.

So even if all those flights were switched to magic zero emission electricity, the aggregate improvement over the whole industry would barely beat the relative improvement between a 737 NG and a MAX. (yes, this is an apples to orchards comparison)

Re: The age of electric flight is finally upon us

#66

Post by ac29 »

bdamm wrote: post #46
Yizahi wrote: post #37

Simple electric wheel on aircrafts for taxiing (as compared to the electric powered flight) took almost 10 years from first demo tests and it still hasn't entered production on commercial airlines. And that thing is completely possible with modern tech. I highly doubt we will see electric powered aircrafts (bigger than small* experimental crafts) in our lifetimes. Way too much limitations existing today. But it would…

Electric wheel propulsion on aircraft seems like an entirely unnecessary feature. Airplanes have no difficulty using their primary form of propulsion - moving air - to move on the ground, and it takes very little energy to do it compared to the energy required to move through the air while off the ground.

No, that's exactly backwards -- jet engines are far less efficient at low speed than at cruise speed. Various numbers I found say 100-300 kg of fuel used taxiing for single aisle planes like 737 [0][1] all the way up to two tons of fuel for large aircraft like 747 at large airports like JFK [0].

This can be extremely relevant for shorter flights: "[taxiing] aircraft fuel burn which is estimated to be as high as 27% of total fuel burn for a 90-minute flight where waiting in queue adds to the time on the ground" [2]

[0] https://www.airliners.net/forum/viewtopic.php?t=747735

[1] https://www.aviationtoday.com/2019/05/01/electric-taxiing-sy...

[2] https://en.wikipedia.org/wiki/Taxiing

Re: The age of electric flight is finally upon us

#67

Post by gnode »

CraftThatBlock wrote: post #25
taf2 wrote: post #22

I wonder if with electric we can fly higher like much higher maybe 80k to 90k since we don’t have to worry about the engine stalling. Could this also make the flight times comparable or faster? For sure less turbulence. As someone who lives on a flight path I’m eager for the change in noise pollution too- though I’m worried the transition will take decades...

Higher means lower air density, meaning less lift, meaning higher power usage, which is even more critical with electric

Although electric motors are capable of very high power density. If the flight is substantially shorter than the full range, flying at a faster speed, or higher altitude may be practical.

Re: The age of electric flight is finally upon us

#68

Post by aphextron »

Yizahi wrote: post #56
aphextron wrote: post #49

Earlier quoted context omitted.

>I highly doubt we will see electric powered aircrafts (bigger than small* experimental crafts) in our lifetimes. The whole point of electrifying flight is that it makes small aircraft economical for airlines. The future of inter-city transport will be light aircraft with less than 20 passengers flying out of of small regional airports. Driving to LAX and waiting in security to get on a huge jet and fly for 90 minute…

The answer is - railway ;) . I doubt that small craft (any prop type) will ever be so quick overall - they are aircrafts and require all aircraft related checks and control, safety for passengers, safety from passengers etc. And about price I don't know, maybe it will be slightly cheaper than jets. So you'll have slightly cheaper businessjet prices, which are still astronomical.

Rail is an option in less developed countries, or places like Europe and Japan where the easements have existed for centuries. But building a new high-speed rail line in the US is basically a nonstarter at this point.

Electrified aviation will be more than 10x cheaper vs turbine based. Practically the entire cost of aviation is in the engine, with its' associated fuel logistics, maintenance requirements, and pilot training.

Re: The age of electric flight is finally upon us

#69

Post by isostatic »

usrusr wrote: post #65
isostatic wrote: post #35

Earlier quoted context omitted.

A320 family range varies from 5500km to 8700km, so "a fifth of it's range" is around 1500km, which is 80% of the industry emissions. I'm not sure of that quote either -- a lithium ion battery is currently about 1MJ/kg and 1MJ/litre. Jet fuel is 43MJ/kg and 35MJ per litre (values from from wikipedia) So a battery that's 30 times more energy dense will be in the region of jet fuel, and thus would presumably be able to…

The 80% figure are flights longer than 1500 km. 1500 and less are the 20%. So even if all those flights were switched to magic zero emission electricity, the aggregate improvement over the whole industry would barely beat the relative improvement between a 737 NG and a MAX. (yes, this is an apples to orchards comparison)

So they do, that'll teach me for not reading twice
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