I think 2000 NM is the magical goldilock number for an entry of a widebody electric aircraft which would be very desirable for most airlines. Right now battery density is about 240w/kg on a cell level and 160w/kg on a battery pack level. There is this article that shows efficiency of Electric, Oil and Hydrogen https://cleantechnica.com/2020/06/10/th ... icles-win/ . With some basic calculations , it means A350-1000 size would need about 650w/kg energy density on a battery pack level which is four times today's level. But how do these other variables affect the range like takeoff , propulsion efficiency and no fuel burn during flight that really don't affect other vehicles? If A350K carries 124 Tonnes of fuel , how much of a battery pack in weight would be the maximum for it ?

Using what kind of propulsion?

One of the big issues is that batteries don't lose weight as they discharge. On the other hand as you burn fuel that weight disappears. This has a massive effect on range.

Also, an A350-1000 might carry a maximum of 124 tonnes of fuel, but not even the longest flights use that much. If nothing else you need reserves.

Hello Vladex,

Challenge accepted.
I take the following starting point: conventional airplanes burn approximately 1/30th of their current weight per hour - as an example an A320 would burn about 2.5t per hour at an assumed weight of 75t. Assuming an energy density of 12kWh per kg of kerosene, the aircraft would consume about 30MWh (equivalent) per hour.

Now, let's take into account that the thermodynamic efficiency of the engine is about half of the conversion efficiency of the electric motor, that would bring the energy consumption down to 15 MWh/h. For a 5h flight (2'000nm) this brings us to 75MWh of energy required for the flight - exactly 1kWh for each kg of airplane!.

So, if the energy content of the battery system exceeds 1kWh/kg, this type of flight becomes - at least a theoretical possibility. But given the fact that there is structural weight & payload to carry, this would end up being a very large and heavy aircraft. In practice, we will likely start flying electric with short range, highly efficient prop aircraft.

Hendric

hitower3 wrote:

Hello Vladex,

Challenge accepted.
I take the following starting point: conventional airplanes burn approximately 1/30th of their current weight per hour - as an example an A320 would burn about 2.5t per hour at an assumed weight of 75t. Assuming an energy density of 12kWh per kg of kerosene, the aircraft would consume about 30MWh (equivalent) per hour.

Now, let's take into account that the thermodynamic efficiency of the engine is about half of the conversion efficiency of the electric motor, that would bring the energy consumption down to 15 MWh/h. For a 5h flight (2'000nm) this brings us to 75MWh of energy required for the flight - exactly 1kWh for each kg of airplane!.

So, if the energy content of the battery system exceeds 1kWh/kg, this type of flight becomes - at least a theoretical possibility. But given the fact that there is structural weight & payload to carry, this would end up being a very large and heavy aircraft. In practice, we will likely start flying electric with short range, highly efficient prop aircraft.

Hendric

If we compare electric vs ICE cars the difference in efficiency is much bigger than double. It would make no sense to go electric without a huge efficiency advantage.
For example Tesla Model S uses 18.0 kWh/100KM and comparable ICE vehicle Audi A6 uses 10L/100KM
Assuming energy density of Gasoline at 12.9KWh/kg , the difference in efficiency is over 7 fold in favor of electric engine. The question is does it apply to aviation since aviation has its own characteristiscs ?
https://driving.ca/hyundai/kona-electri ... ving-range
https://www.guideautoweb.com/en/makes/a ... rogressiv/

Starlionblue wrote:

One of the big issues is that batteries don't lose weight as they discharge. On the other hand as you burn fuel that weight disappears. This has a massive effect on range.

Also, an A350-1000 might carry a maximum of 124 tonnes of fuel, but not even the longest flights use that much. If nothing else you need reserves.

Taken into context . I assume to use less battery weight than fuel , in the case of A350K , would 100 Tonnes of battery pack be reasonable?

Vladex wrote:

hitower3 wrote:

Hello Vladex,

Challenge accepted.
I take the following starting point: conventional airplanes burn approximately 1/30th of their current weight per hour - as an example an A320 would burn about 2.5t per hour at an assumed weight of 75t. Assuming an energy density of 12kWh per kg of kerosene, the aircraft would consume about 30MWh (equivalent) per hour.

Now, let's take into account that the thermodynamic efficiency of the engine is about half of the conversion efficiency of the electric motor, that would bring the energy consumption down to 15 MWh/h. For a 5h flight (2'000nm) this brings us to 75MWh of energy required for the flight - exactly 1kWh for each kg of airplane!.

So, if the energy content of the battery system exceeds 1kWh/kg, this type of flight becomes - at least a theoretical possibility. But given the fact that there is structural weight & payload to carry, this would end up being a very large and heavy aircraft. In practice, we will likely start flying electric with short range, highly efficient prop aircraft.

Hendric

If we compare electric vs ICE cars the difference in efficiency is much bigger than double. It would make no sense to go electric without a huge efficiency advantage.
For example Tesla Model S uses 18.0 kWh/100KM and comparable ICE vehicle Audi A6 uses 10L/100KM
Assuming energy density of Gasoline at 12.9KWh/kg , the difference in efficiency is over 7 fold in favor of electric engine. The question is does it apply to aviation since aviation has its own characteristiscs ?
https://driving.ca/hyundai/kona-electri ... ving-range
https://www.guideautoweb.com/en/makes/a ... rogressiv/

My self edit: 10L of Gasoline is actually 7.37KG and then X12.9kwh/kg which gives 95Kwh/100KM which translates overall to an electric car being 5.3 more efficient on the powertrain and engine efficiency.

Vladex wrote:

hitower3 wrote:

Hello Vladex,

Challenge accepted.
I take the following starting point: conventional airplanes burn approximately 1/30th of their current weight per hour - as an example an A320 would burn about 2.5t per hour at an assumed weight of 75t. Assuming an energy density of 12kWh per kg of kerosene, the aircraft would consume about 30MWh (equivalent) per hour.

Now, let's take into account that the thermodynamic efficiency of the engine is about half of the conversion efficiency of the electric motor, that would bring the energy consumption down to 15 MWh/h. For a 5h flight (2'000nm) this brings us to 75MWh of energy required for the flight - exactly 1kWh for each kg of airplane!.

So, if the energy content of the battery system exceeds 1kWh/kg, this type of flight becomes - at least a theoretical possibility. But given the fact that there is structural weight & payload to carry, this would end up being a very large and heavy aircraft. In practice, we will likely start flying electric with short range, highly efficient prop aircraft.

Hendric

If we compare electric vs ICE cars the difference in efficiency is much bigger than double. It would make no sense to go electric without a huge efficiency advantage.
For example Tesla Model S uses 18.0 kWh/100KM and comparable ICE vehicle Audi A6 uses 10L/100KM
Assuming energy density of Gasoline at 12.9KWh/kg , the difference in efficiency is over 7 fold in favor of electric engine. The question is does it apply to aviation since aviation has its own characteristiscs ?
https://driving.ca/hyundai/kona-electri ... ving-range
https://www.guideautoweb.com/en/makes/a ... rogressiv/

There will be no such change for airplanes. As of right now, total propulsion efficiency for modern airplanes is approaching 40%. Even if electric offers lower losses in the cycle, propulsive losses would still be there. So 2x improvement is already an optimistic value.

kalvado wrote:

Vladex wrote:

hitower3 wrote:

Hello Vladex,

Challenge accepted.
I take the following starting point: conventional airplanes burn approximately 1/30th of their current weight per hour - as an example an A320 would burn about 2.5t per hour at an assumed weight of 75t. Assuming an energy density of 12kWh per kg of kerosene, the aircraft would consume about 30MWh (equivalent) per hour.

Now, let's take into account that the thermodynamic efficiency of the engine is about half of the conversion efficiency of the electric motor, that would bring the energy consumption down to 15 MWh/h. For a 5h flight (2'000nm) this brings us to 75MWh of energy required for the flight - exactly 1kWh for each kg of airplane!.

So, if the energy content of the battery system exceeds 1kWh/kg, this type of flight becomes - at least a theoretical possibility. But given the fact that there is structural weight & payload to carry, this would end up being a very large and heavy aircraft. In practice, we will likely start flying electric with short range, highly efficient prop aircraft.

Hendric

If we compare electric vs ICE cars the difference in efficiency is much bigger than double. It would make no sense to go electric without a huge efficiency advantage.
For example Tesla Model S uses 18.0 kWh/100KM and comparable ICE vehicle Audi A6 uses 10L/100KM
Assuming energy density of Gasoline at 12.9KWh/kg , the difference in efficiency is over 7 fold in favor of electric engine. The question is does it apply to aviation since aviation has its own characteristiscs ?
https://driving.ca/hyundai/kona-electri ... ving-range
https://www.guideautoweb.com/en/makes/a ... rogressiv/

There will be no such change for airplanes. As of right now, total propulsion efficiency for modern airplanes is approaching 40%. Even if electric offers lower losses in the cycle, propulsive losses would still be there. So 2x improvement is already an optimistic value.

Are you talking only about thermal efficiency? Even cars are approaching 50% efficiency in thermal but there are other losses associated with ICE engines and so many moving parts.
https://www.sae.org/news/2019/04/high-e ... dci-engine
https://www.fueleconomy.gov/feg/atv.shtml

Vladex wrote:

Starlionblue wrote:

One of the big issues is that batteries don't lose weight as they discharge. On the other hand as you burn fuel that weight disappears. This has a massive effect on range.

Also, an A350-1000 might carry a maximum of 124 tonnes of fuel, but not even the longest flights use that much. If nothing else you need reserves.

Taken into context . I assume to use less battery weight than fuel , in the case of A350K , would 100 Tonnes of battery pack be reasonable?

You might start a flight with 100 tonnes of fuel, but you'll land with maybe 7 tonnes. If you use a 100 tonne battery pack, you land with a 100 tonne battery pack. The total energy requirement would thus be much higher since the weight is higher for the entire flight except right at takeoff.

Also keep in mind that you rarely need 100 tonnes of fuel.

The battery pack would have to more like 40 tonnes (figure plucked out of the air), with the same energy content as 100 tonnes of fuel.

Vladex wrote:

kalvado wrote:

Vladex wrote:

If we compare electric vs ICE cars the difference in efficiency is much bigger than double. It would make no sense to go electric without a huge efficiency advantage.
For example Tesla Model S uses 18.0 kWh/100KM and comparable ICE vehicle Audi A6 uses 10L/100KM
Assuming energy density of Gasoline at 12.9KWh/kg , the difference in efficiency is over 7 fold in favor of electric engine. The question is does it apply to aviation since aviation has its own characteristiscs ?
https://driving.ca/hyundai/kona-electri ... ving-range
https://www.guideautoweb.com/en/makes/a ... rogressiv/

There will be no such change for airplanes. As of right now, total propulsion efficiency for modern airplanes is approaching 40%. Even if electric offers lower losses in the cycle, propulsive losses would still be there. So 2x improvement is already an optimistic value.

Are you talking only about thermal efficiency? Even cars are approaching 50% efficiency in thermal but there are other losses associated with ICE engines and so many moving parts.
https://www.sae.org/news/2019/04/high-e ... dci-engine
https://www.fueleconomy.gov/feg/atv.shtml

I am talking about 70% propulsion and 60% thermal, for a total of 40 or so.

kalvado wrote:

I am talking about 70% propulsion and 60% thermal, for a total of 40 or so.

In a car? Phew. I do remember quite a buzz when Scania did an engine to achieve over 50%, some years ago. Generally, the thermal efficiency would be between 8-10% (naturally aspirated, old gas guzzlers) and 40+ % (diesels with turbine and exhaust energy recovery), depending on configuration.

See the https://www.sciencedirect.com/topics/en ... efficiency for details

Cheers, Adam

Vladex wrote:

kalvado wrote:

Vladex wrote:

If we compare electric vs ICE cars the difference in efficiency is much bigger than double. It would make no sense to go electric without a huge efficiency advantage.
For example Tesla Model S uses 18.0 kWh/100KM and comparable ICE vehicle Audi A6 uses 10L/100KM
Assuming energy density of Gasoline at 12.9KWh/kg , the difference in efficiency is over 7 fold in favor of electric engine. The question is does it apply to aviation since aviation has its own characteristiscs ?
https://driving.ca/hyundai/kona-electri ... ving-range
https://www.guideautoweb.com/en/makes/a ... rogressiv/

There will be no such change for airplanes. As of right now, total propulsion efficiency for modern airplanes is approaching 40%. Even if electric offers lower losses in the cycle, propulsive losses would still be there. So 2x improvement is already an optimistic value.

Are you talking only about thermal efficiency? Even cars are approaching 50% efficiency in thermal but there are other losses associated with ICE engines and so many moving parts.
https://www.sae.org/news/2019/04/high-e ... dci-engine
https://www.fueleconomy.gov/feg/atv.shtml

Cars are approaching 50% thermal efficiency at their optimum operating point, which car engines essentially never work at. Aircraft engines in cruise are at or close to that point. Compare that A6 and Model S at 200kph at it already changes a lot. My Passat TDI is just a hair width below 10L/100km@200kph, with the Model S going through 40KWh/100km...... https://www.youtube.com/watch?v=3aIcuH_ ... eeringGmbH
And just like that 7x becomes only ~2.5x.

There is also no equivalent to recuperation on an aircraft. Aircraft also have a pretty good power to propulsion ratio compared to cars with a lot of mechanical gear between engine and road.

best regards
Thomas

Thinking about it... there are 3 energy components required to reach the top of descent.
There is energy required to climb to a flight level, say 10 km for simplicity. E=mgh, that is 28 Wh/kg of gross weight
There is energy required to accelerate to cruise speed, say 250 m/s (486 knots). E=mv^2/2=8.8 Wh/kg of gross weight
There is energy required to maintain aircraft airborne via aerodynamic lift. That is thrust * distance traveled. And the thrust has to be at least weight/(lift/drag ratio). L/D is about 20 for modern airliners, so E=mg * d / (L*D) For the distance of 4000 km (slightly more than 2000 nm, though) that is 20x climb energy, 560 Wh/kg
So a total of 600 Wh/kg of gross weight is the barest minimum. Not that different from 1 kWh/kg mentioned above as there is no efficiency or parasitic drag in my calculations.

tommy1808 wrote:

Vladex wrote:

kalvado wrote:

There will be no such change for airplanes. As of right now, total propulsion efficiency for modern airplanes is approaching 40%. Even if electric offers lower losses in the cycle, propulsive losses would still be there. So 2x improvement is already an optimistic value.

Are you talking only about thermal efficiency? Even cars are approaching 50% efficiency in thermal but there are other losses associated with ICE engines and so many moving parts.
https://www.sae.org/news/2019/04/high-e ... dci-engine
https://www.fueleconomy.gov/feg/atv.shtml

Cars are approaching 50% thermal efficiency at their optimum operating point, which car engines essentially never work at. Aircraft engines in cruise are at or close to that point. Compare that A6 and Model S at 200kph at it already changes a lot. My Passat TDI is just a hair width below 10L/100km@200kph, with the Model S going through 40KWh/100km...... https://www.youtube.com/watch?v=3aIcuH_ ... eeringGmbH
And just like that 7x becomes only ~2.5x.

There is also no equivalent to recuperation on an aircraft. Aircraft also have a pretty good power to propulsion ratio compared to cars with a lot of mechanical gear between engine and road.

best regards
Thomas

Good point but that inefficiency at high speed is all about air and road resistance which is a big equalizer on land but is not a factor at 40000 feet . I think there is four times less air density at 40 000 so acceleration would be still efficient at cruise. What I am wondering about is about the instant torque from the electric motor . Would it require less takeoff distance and would the takeoff be quicker?

Vladex wrote:

tommy1808 wrote:

Vladex wrote:

Are you talking only about thermal efficiency? Even cars are approaching 50% efficiency in thermal but there are other losses associated with ICE engines and so many moving parts.
https://www.sae.org/news/2019/04/high-e ... dci-engine
https://www.fueleconomy.gov/feg/atv.shtml

Cars are approaching 50% thermal efficiency at their optimum operating point, which car engines essentially never work at. Aircraft engines in cruise are at or close to that point. Compare that A6 and Model S at 200kph at it already changes a lot. My Passat TDI is just a hair width below 10L/100km@200kph, with the Model S going through 40KWh/100km...... https://www.youtube.com/watch?v=3aIcuH_ ... eeringGmbH
And just like that 7x becomes only ~2.5x.

There is also no equivalent to recuperation on an aircraft. Aircraft also have a pretty good power to propulsion ratio compared to cars with a lot of mechanical gear between engine and road.

best regards
Thomas

Good point but that inefficiency at high speed is all about air and road resistance which is a big equalizer on land but is not a factor at 40000 feet .

Nope, its the ICE closing in its Optimum operating point, while the electric car does not have such effects. Engines on planes operate near their optimum point for most of the trip.
Air and road resistance also effects both types of cars exactly the same.

Would it require less takeoff distance and would the takeoff be quicker?

Gas turbines have a lot of torque too, and since electric planes also just accelerate by the same means as conventional ones. Throwing out air.

Best regards
Thomas

Basically this gets into semantics about what a "battery" even is. A battery is a whole bunch of hazardous chemicals that contain energy. Hydrogen is an example of a substance that can be converted into electricity. The power density would need to be 50% as good as Jet-A to accomplish what you want to do. Which is quite high.

Consider this page.
https://en.wikipedia.org/wiki/Energy_density

It tells us that Jet fuel contains 42 MJ/kg energy density (by mass).
Wood contains 18 MJ/kg (coal is roughly the same by weight, just more densely packed).
Lithium ion batteries are apparently 0.4-0.9 MJ/kg.

Keep in mind (I think) the thermal efficiency of combustion engines is only 40%, versus electronic products 90+% or so, so take half off the fossil fuels. They are still at least a factor of 10 more energy dense than iPhone batteries.

Change the definition of "battery" to mean "hydrogen tank," then maybe it might work, but it would have to be kept at immense pressure. Much more research into battery tech is being done every day, but we are in the infancy of that.

LCDFlight wrote:

Basically this gets into semantics about what a "battery" even is. A battery is a whole bunch of hazardous chemicals that contain energy. Hydrogen is an example of a substance that can be converted into electricity. The power density would need to be 50% as good as Jet-A to accomplish what you want to do. Which is quite high.

Consider this page.
https://en.wikipedia.org/wiki/Energy_density

It tells us that Jet fuel contains 42 MJ/kg energy density (by mass).
Wood contains 18 MJ/kg (coal is roughly the same by weight, just more densely packed).
Lithium ion batteries are apparently 0.4-0.9 MJ/kg.

Keep in mind (I think) the thermal efficiency of combustion engines is only 40%, versus electronic products 90+% or so, so take half off the fossil fuels. They are still at least a factor of 10 more energy dense than iPhone batteries.

Change the definition of "battery" to mean "hydrogen tank," then maybe it might work, but it would have to be kept at immense pressure. Much more research into battery tech is being done every day, but we are in the infancy of that.

It doesn't even need to be hazardous materials. Water reservoirs are used for energy storage.

But I digress.

Starlionblue wrote:

LCDFlight wrote:

Basically this gets into semantics about what a "battery" even is. A battery is a whole bunch of hazardous chemicals that contain energy. Hydrogen is an example of a substance that can be converted into electricity. The power density would need to be 50% as good as Jet-A to accomplish what you want to do. Which is quite high.

Consider this page.
https://en.wikipedia.org/wiki/Energy_density

It tells us that Jet fuel contains 42 MJ/kg energy density (by mass).
Wood contains 18 MJ/kg (coal is roughly the same by weight, just more densely packed).
Lithium ion batteries are apparently 0.4-0.9 MJ/kg.

Keep in mind (I think) the thermal efficiency of combustion engines is only 40%, versus electronic products 90+% or so, so take half off the fossil fuels. They are still at least a factor of 10 more energy dense than iPhone batteries.

Change the definition of "battery" to mean "hydrogen tank," then maybe it might work, but it would have to be kept at immense pressure. Much more research into battery tech is being done every day, but we are in the infancy of that.

It doesn't even need to be hazardous materials. Water reservoirs are used for energy storage.

But I digress.

For any energy storage system, unintended release of stored energy is a hazard, and the more energy is stored, the bigger the hazard. If storage is via molecular chemical energy, material will be flammable, explosive, combustible or something else. Mitigation strategies can be used to keep hazard in check.
If storage is in a nuclear form, Radioactive is the name of the game. Again, precautions
In case of mechanical energy, it is not the material, but setup itself which is hazardous. Broken levies or spinning wheels are no better than burning tanks. Fan blades are not storing energy per se, but act in a similar way.

kalvado wrote:

Starlionblue wrote:

LCDFlight wrote:

Basically this gets into semantics about what a "battery" even is. A battery is a whole bunch of hazardous chemicals that contain energy. Hydrogen is an example of a substance that can be converted into electricity. The power density would need to be 50% as good as Jet-A to accomplish what you want to do. Which is quite high.

Consider this page.
https://en.wikipedia.org/wiki/Energy_density

It tells us that Jet fuel contains 42 MJ/kg energy density (by mass).
Wood contains 18 MJ/kg (coal is roughly the same by weight, just more densely packed).
Lithium ion batteries are apparently 0.4-0.9 MJ/kg.

Keep in mind (I think) the thermal efficiency of combustion engines is only 40%, versus electronic products 90+% or so, so take half off the fossil fuels. They are still at least a factor of 10 more energy dense than iPhone batteries.

Change the definition of "battery" to mean "hydrogen tank," then maybe it might work, but it would have to be kept at immense pressure. Much more research into battery tech is being done every day, but we are in the infancy of that.

It doesn't even need to be hazardous materials. Water reservoirs are used for energy storage.

But I digress.

For any energy storage system, unintended release of stored energy is a hazard, and the more energy is stored, the bigger the hazard. If storage is via molecular chemical energy, material will be flammable, explosive, combustible or something else. Mitigation strategies can be used to keep hazard in check.
If storage is in a nuclear form, Radioactive is the name of the game. Again, precautions
In case of mechanical energy, it is not the material, but setup itself which is hazardous. Broken levies or spinning wheels are no better than burning tanks. Fan blades are not storing energy per se, but act in a similar way.

Exactly, a "nuclear battery" can be a feasible way to power airplanes today. It's dangerous, but it can be done with existing know-how. IIRC it can have a 1 million mile range, too.

Anyhow, isn't it more likely that we can develop renewable-generated propane, or something like this?

"There is a process by which a liquid hydrocarbon fuel – a so-called e-fuel – can be made, which takes carbon dioxide from the atmosphere, and combines it with artificially-made hydrogen to form a hydrocarbon – the building block of a fuel. Such e-fuels have hit the headlines recently as the likes of Porsche, Siemens and Mazda have all invested in projects that seek to mass-produce such fuels.
Porsche has plans to start making e-fuels in bulk next year, but the German sports car maker – which already has one all-electric model, the Taycan, on sale – says it’s not backing away from electric investment. “Electromobility is a top priority at Porsche,” said its chief executive, Oliver Blume."

https://www.irishtimes.com/life-and-sty ... -1.4544790
https://newatlas.com/generating-isobuta ... ity/22005/
https://www.en-former.com/en/efuels-power-to-liquid/

LCDFlight wrote:

kalvado wrote:

Starlionblue wrote:

It doesn't even need to be hazardous materials. Water reservoirs are used for energy storage.

But I digress.

For any energy storage system, unintended release of stored energy is a hazard, and the more energy is stored, the bigger the hazard. If storage is via molecular chemical energy, material will be flammable, explosive, combustible or something else. Mitigation strategies can be used to keep hazard in check.
If storage is in a nuclear form, Radioactive is the name of the game. Again, precautions
In case of mechanical energy, it is not the material, but setup itself which is hazardous. Broken levies or spinning wheels are no better than burning tanks. Fan blades are not storing energy per se, but act in a similar way.

Exactly, a "nuclear battery" can be a feasible way to power airplanes today. It's dangerous, but it can be done with existing know-how. IIRC it can have a 1 million mile range, too.

Anyhow, isn't it more likely that we can develop renewable-generated propane, or something like this?

"There is a process by which a liquid hydrocarbon fuel – a so-called e-fuel – can be made, which takes carbon dioxide from the atmosphere, and combines it with artificially-made hydrogen to form a hydrocarbon – the building block of a fuel. Such e-fuels have hit the headlines recently as the likes of Porsche, Siemens and Mazda have all invested in projects that seek to mass-produce such fuels.
Porsche has plans to start making e-fuels in bulk next year, but the German sports car maker – which already has one all-electric model, the Taycan, on sale – says it’s not backing away from electric investment. “Electromobility is a top priority at Porsche,” said its chief executive, Oliver Blume."

https://www.irishtimes.com/life-and-sty ... -1.4544790
https://newatlas.com/generating-isobuta ... ity/22005/
https://www.en-former.com/en/efuels-power-to-liquid/

Well, all the biofuel- oils, algae, bacterial, methane from composting whatnot - are just, renewables. Problem is that bio things tend to contain oxygen atoms, reducing energy density.
Things could be more interesting if not for highly political view of issue and "zis iz sayens!" mobs

Electric propulsion in aviation is likely to only be in the 9 seat and smaller market. Caravans and down. Biofuels are what will power transport category aircraft into the future.