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I have mostly questions... Are we at the theoretical limit of energy density in current batteries? How much more progress can we make, in theory? Could it be t

I have mostly questions... Are we at the theoretical limit of energy density in current batteries? How much more progress can we make, in theory? Could it be that in 20 years we find drastically better materials for batteries? Materials which would make electrical flight feasible. Assuming high energy-density batteries are coming, shouldn't you start now with developing electrical airplanes to be one step ahead of competition?

jareklupinski 5y ago
jumping on with one more question: would there be an advantage to lining the wings/flat surfaces with solar cells and patching them into the powertrain, helping drive even higher efficiency gains during optimal weather?
- dsign 5y ago
  I did the math for that one, though not exactly for an airplane, but for a boring land vehicle (think Ford Traffic). I assumed futuristic photovoltaics with 40% efficiency, a factor of 0.7 to account for angle-of-incidence inefficiencies, pretty much all of of the van covered in panels, for an area of about 16 square meters, similar to the wing area of a glider Schleicher ASW 22 (I couldn't find the wing area of a Cessna 172). The result I get is somewhere from 3 to 8 kilowatts. A quick search in the Internet shows that a typical car has engine power starting at 130 horsepowers, which is 95 kilowatts. A van the size of a Ford traffic probably uses twice as much, and the Cessna uses 132 kilowatts. So, no, I don't think we are getting aviation as it exists today with solar panels and batteries, but one hour twenty minutes in good weather will be enough for some recreational pursuits. I also did the math for sailplanes with solar panels. That looks better, if all you are looking for is activating the propeller for a small fraction of the total flight time, or having an aircraft that can go very slow (that, in fact, has been done). I'm just an amateur, but my opinion is that, without solving the energy density issue, about 98% of the aviation we enjoy today will be gone.
- davedx 5y ago
  I spreadsheeted this out a few months back for a plane. It is absolutely not worth it.
evandijk70 5y ago
Assuming that higher energy-density batteries are possible is an extremely big ask. Yet somehow, plane companies are valued as if there is a commercial business case. I think long-range (over 2000 km), big airplanes are as far away as fusion power plants. Maybe even further, as fusion does not require any theoretical breakthroughs. You don't see big valuations for companies purporting fusion power generators, but for some reason, you do for electric planes..
- kwhitefoot 5y ago
  > plane companies are valued as if there is a commercial business case. I Perhaps that is because there is a large number of passengers who wish to fly shorter distances than 2000 km. In most countries all internal flights are considerably shorter than that.
  - Ekaros 5y ago
    I wonder if culturally we need to change if we even need to travel. After all it is very recent phenomenon outside migrations. After all most of the history vast majority of population stayed or travelled very little.
    - kwhitefoot 5y ago
      > After all most of the history vast majority of population stayed or travelled very little. That doesn't make it inherently desirable.
tuatoru 5y ago
> Are we at the theoretical limit of energy density in current batteries? Yes and no. Using air for the "ox" part of the redox reaction makes it possible to dramatically increase energy density (gravimetric and volumetric both). The tricky part of that is making the battery rechargeable. Lots of research attention is focused on it. If you want your battery totally enclosed (e.g. for use in vacuum or corrosive environments), than we are closer to the limits. Probably within a factor of 5, maybe within a factor of 2. > Could it be that in 20 years we find drastically better materials for batteries? No, the periodic table is fixed.[1] Maybe, if you are prepared to consider using nuclear "batteries". 1. https://en.wikipedia.org/wiki/Reduction_potential https://en.wikipedia.org/wiki/Reduction_potential
Gibbon1 5y ago
I think a lithium ion battery is only about 6-7% lithium by weight. So primary physics isn't blocking. If you could double that you'd be able to increase flight time from current roughly 90 minutes to 3 hours.
davedx 5y ago
No we're not. The next step forwards in energy density for Lithium Ion batteries is likely to be 100% silicon anode Li-Ion. This is a very difficult manufacturing/engineering challenge but significant progress has been made (look up e.g. Sila Nano and Enovix). These give us a significant step forward in energy density. Then there are solid state batteries. These are more difficult. But again multiple companies with lots of funding are attacking this from all sorts of angles. The OP making this claim as if it's a law of physics is simply wrong.

jareklupinski 5y ago

jumping on with one more question: would there be an advantage to lining the wings/flat surfaces with solar cells and patching them into the powertrain, helping drive even higher efficiency gains during optimal weather?

dsign 5y ago
I did the math for that one, though not exactly for an airplane, but for a boring land vehicle (think Ford Traffic). I assumed futuristic photovoltaics with 40% efficiency, a factor of 0.7 to account for angle-of-incidence inefficiencies, pretty much all of of the van covered in panels, for an area of about 16 square meters, similar to the wing area of a glider Schleicher ASW 22 (I couldn't find the wing area of a Cessna 172). The result I get is somewhere from 3 to 8 kilowatts. A quick search in the Internet shows that a typical car has engine power starting at 130 horsepowers, which is 95 kilowatts. A van the size of a Ford traffic probably uses twice as much, and the Cessna uses 132 kilowatts. So, no, I don't think we are getting aviation as it exists today with solar panels and batteries, but one hour twenty minutes in good weather will be enough for some recreational pursuits. I also did the math for sailplanes with solar panels. That looks better, if all you are looking for is activating the propeller for a small fraction of the total flight time, or having an aircraft that can go very slow (that, in fact, has been done). I'm just an amateur, but my opinion is that, without solving the energy density issue, about 98% of the aviation we enjoy today will be gone.
davedx 5y ago
I spreadsheeted this out a few months back for a plane. It is absolutely not worth it.

evandijk70 5y ago

Assuming that higher energy-density batteries are possible is an extremely big ask. Yet somehow, plane companies are valued as if there is a commercial business case. I think long-range (over 2000 km), big airplanes are as far away as fusion power plants. Maybe even further, as fusion does not require any theoretical breakthroughs. You don't see big valuations for companies purporting fusion power generators, but for some reason, you do for electric planes..

kwhitefoot 5y ago
> plane companies are valued as if there is a commercial business case. I Perhaps that is because there is a large number of passengers who wish to fly shorter distances than 2000 km. In most countries all internal flights are considerably shorter than that.
- Ekaros 5y ago
  I wonder if culturally we need to change if we even need to travel. After all it is very recent phenomenon outside migrations. After all most of the history vast majority of population stayed or travelled very little.
  - kwhitefoot 5y ago
    > After all most of the history vast majority of population stayed or travelled very little. That doesn't make it inherently desirable.

tuatoru 5y ago

> Are we at the theoretical limit of energy density in current batteries? Yes and no. Using air for the "ox" part of the redox reaction makes it possible to dramatically increase energy density (gravimetric and volumetric both). The tricky part of that is making the battery rechargeable. Lots of research attention is focused on it. If you want your battery totally enclosed (e.g. for use in vacuum or corrosive environments), than we are closer to the limits. Probably within a factor of 5, maybe within a factor of 2. > Could it be that in 20 years we find drastically better materials for batteries? No, the periodic table is fixed.[1] Maybe, if you are prepared to consider using nuclear "batteries". 1. https://en.wikipedia.org/wiki/Reduction_potential https://en.wikipedia.org/wiki/Reduction_potential

Gibbon1 5y ago

I think a lithium ion battery is only about 6-7% lithium by weight. So primary physics isn't blocking. If you could double that you'd be able to increase flight time from current roughly 90 minutes to 3 hours.

davedx 5y ago

No we're not. The next step forwards in energy density for Lithium Ion batteries is likely to be 100% silicon anode Li-Ion. This is a very difficult manufacturing/engineering challenge but significant progress has been made (look up e.g. Sila Nano and Enovix). These give us a significant step forward in energy density. Then there are solid state batteries. These are more difficult. But again multiple companies with lots of funding are attacking this from all sorts of angles. The OP making this claim as if it's a law of physics is simply wrong.