8 ms·

Airbus pioneers a superconducting powertrain cooled by liquid hydrogen

44 points by sahin 6y ago

intrepidhero 6y ago
This makes no sense to me. Don't you also need cryogenic systems to keep the H2 cold? Wouldn't those use waaaaay more energy than what you save with superconducting motors? Maybe they are talking about short haul flights where the H2 is ground cooled and then used as a cold sink but then in order to keep your electronics cold you're carrying lots more fuel than you need. TFA was too thin to pass the sniff test.
- XorNot 6y ago
  Motors are solid 3D structures. The more power you put in not superconducting, the more heat you have to extract. Superconductors mean you only need to keep your refrigerant cool, and that's a product of insulation effectiveness, not power output.
  - ethbr0 6y ago
    This is the difference between electric and combustion powertrains, no? In electric, heat is the enemy and inefficient. In combustion, heat is a key component of the thermodynamic efficiency, unavoidable, and effectively only limited by material tolerances. (I didn't major in physics, so someone keep me honest on the ceiling / floor efficiency equations for combustion engines?)
    - XorNot 6y ago
      You still have to cool a combustion engine - hence why car's have radiators. Combustion engine's are also limited by Carnot cycle engine efficiency - about 64% theoretically, no more then 50% in the real world. So you're still going to wind up having to dump progressively more heat from a fixed surface area.
      - ethbr0 6y ago
        (Post coffee) Cars have radiators to cool the operating structure (e.g. engine block), but that cooling's ancillary to power produced, no? Carnot cycle was what I was grasping for. Original point being that in a thermal engine, increasing your temperature gradient by increasing your high-temperature side (while holding exhaust constant) leads to more potential power. Or IOW, a thermal engine that doesn't burn hot somewhere isn't going to produce much power. (Electric being a completely different ball of wax)
- ginko 6y ago
  I think the idea is to use the H2 both as fuel and refrigerant.
  - Valgrim 6y ago
    So you recover the boiloff and use it to power a generator which powers a drivetrain cooled by the liquid hydrogen. This seems like a good idea.
- ncmncm 6y ago
  The idea is that a large-scale LH2 flow into the system is being consumed, and perforce heated, and may be used as refrigerant on the way there. It makes perfect sense. Rockets do this today, as indeed they have done from the earliest days, sending liquified gases through channels in the engine bell and combustion chamber before burning, keeping them both from vaporizing. Here, the very high efficiency of electric-driven turbines is offset by the lower efficiency of fuel-cell generation, for what is expected to be a substantial net gain over burning H2 in internal combustion turbines. The latter are the obvious first stage of deployment, taking advantage of LH2's extreme energy-to-weight ratio for reducing the takeoff fuel load by as much as 5:1. This form will probably be fielded in existing airframes, displacing some cargo space with in-hull LH2 tanks.
  - ethbr0 6y ago
    Aka regenerative cooling: https://en.m.wikipedia.org/wiki/Regenerative_cooling_(rocketry) https://en.m.wikipedia.org/wiki/Regenerative_cooling_(rocket...
- Tuna-Fish 6y ago
  This is effectively regenerative cooling, like what rockets are commonly using. There are no cryogenic systems onboard, but all the fuel is loaded as very cold, and you can use the fuel as a coolant just before you burn it.
  - candiodari 6y ago
    They will, however, be using kerosene, not liquid Hydrogen. It cannot provide cryogenic temperatures.
    - Tuna-Fish 6y ago
      Did you read the article? It was specifically about future liquid hydrogen-powered aircraft.
- upofadown 6y ago
  The H2 keeps itself cold by boiling away. You just need some insulation to slow down the rate to something manageable. Insulation normally uses a gas such as air to block the heat flow and as a result tends to be very light.
- petertodd 6y ago
  > Don't you also need cryogenic systems to keep the H2 cold? Wouldn't those use waaaaay more energy than what you save with superconducting motors? Probably not. Cryogenic liquids like liquid H2 are typically stored in dewers, which use a vacuum as the primary insulation, along with silvered surfaces and layers of mylar film to reduce radiation losses. We've been able to make dewers with boil off rates of 1% per day or better for decades. That's more than low enough that you don't need any refrigeration at all for an aircraft application where the flight just lasts a few hours anyway. Most likely they'll actually use less effective insulation to save weight. Fortunately for them, cryogenic liquids are commonly used in rockets, so there's already lots of know-how and technology out there for making lightweight cryogenic insulation.
- Gravityloss 6y ago
  You use the boiloff hydrogen in the power source, I assume a fuel cell in this case. This is regularly done by LNG tanker ships. Evaporating LNG is simply routed to the engines.
throwaway0a5e 6y ago
While there might be something to the underlying tech the current two most promising paths to carbon neutral airlines are synthetic fuel generated with green energy and better batteries. It's highly unlikely that exotic, barely developed hydrogen tech that's not even made it to the "tech demonstrator prototype" phase is going to work exactly the way they're hoping in the end. A few % here and there from unexpected circumstances tends to make a big difference in viability, especially in situations where engineering margins or economic margins are thin (both apply to commercial flight).
- ncmncm 6y ago
  [superseded]
  - throwaway0a5e 6y ago
    Yeah, people don't like being told they fell for exactly what the editor who chose the title wanted them to fall for.
    - ncmncm 6y ago
      No, ignorant editorial bloviating is specifically forbidden in the ToS.
      - throwaway0a5e 6y ago
        The article is clearly greenwashed with respect to the potential impact of the tech (it's at such an early stage lord knows where if any applications in which it will be used). This is corporate press release SOP. Calling it out as wasted words to be ignored or disregarded isn't "editorial bloviating". And they're guidelines, not a ToS.
ncmncm 6y ago
I have estimated that an Airbus A320 generates something on the order of 80 MW during takeoff. A hydrogen-powered aircraft, for the same freight load, will have benefit of efficiencies not available to an A320, so the needed power will be less, but I don't know how much less. The 0.5 MW system described looks like a good first step, but should be scaled up quickly. Results will be immediately useful for co-generation and energy storage on terrestrial power systems. For at least the next decade, that will be its only benefit, which may come to overshadow its aviation application, particularly if the latter encounters snags.
- Tuna-Fish 6y ago
  If I understand correctly, this makes use of a hydrogen fuel cell for electric power, and then has that turn electric fans. In general, a modern fuel cell is ~60% efficient at turning chemical energy into electricity, and an electric fan is ~4x as efficient at turning electricity into thrust when compared to a turbofan engine turning chemical energy into thrust. So ignoring transmissions losses (which would probably be really low anyway if ran on superconductors...) you'd need about 40% of the power of a modern jet to do the same work. There is clearly a lot of scaling work needed, and I don't see a fuel cell/electric aircraft beating existing ones anytime soon if you ignore the emissions, but at least this clearly shows that there is a future for mass commercial aviation once burning carbohydrates is no longer acceptable.
userbinator 6y ago
The failure modes are going to be interesting, to say the least...
- upofadown 6y ago
  Yeah, It would be great if any fires were to burn clean and had a strong tendency to rise away from the aircraft, particularly for ground fires. H2 is also nice in that it doesn't create a lot of infrared energy while it burns. You might be able to save the weight of any fire suppression systems.
  - coolspot 6y ago
    I think OP meant that electric motor losing superconductivity in-flight will cause irreversible run-away heating of the motor. Which must be mitigated by having more motors than nominally needed, all with independent power supply and cryogenic contours.
    - Valgrim 6y ago
      The way I see it, losing superconductivity instantly shuts down the motor by tripping the circuit breaker, and causes it to transfer it's momentum energy into the surrounding liquid hydrogen. Some hydrogen might boil off, but it's nothing a safety valve can't handle. The plane can then glide to the closest airport or switch to a non-superconducting mode.
      - userbinator 6y ago
        If anything, losing superconductivity will cause less current to flow, since the resistance will increase greatly, and a massive amount of heat will be created.
redis_mlc 6y ago
The aviation industry is exploring alternative fuels in case of draconian regulation, including sustainable aviation fuel (SFA) and hydrogen. But the problems with hydrogen as an aviation fuel are many: - hydrogen embrittlement of containers - volatility (compared to Jet A). Since hydrogen is the smallest molecule, it can escape any container. - distribution (world-wide locations and airport safety) - containment weight and condensation - containment integrity at low temperatures (airplanes flex and fuselage fasteners fail around 33,000 cycles.) And ffs, the Hindenburg: https://en.wikipedia.org/wiki/Hindenburg_disaster https://en.wikipedia.org/wiki/Hindenburg_disaster https://www.avweb.com/ownership/fuel-news/williams-international-tests-saf-on-fj44/ https://www.avweb.com/ownership/fuel-news/williams-internati...
nickserv 6y ago
Cool idea. I would be more enthused if it came from another company though. It seems like all the "green" projects Airbus does are aborted. Remember their last electric plane? Canceled before the first flight. Meanwhile a couple startups are successfully retrofitting electric propulsion on light aircraft.
peter_d_sherman 6y ago
>"Liquid H2's key drawcard to aircraft designers is its impressive energy density by weight, but Airbus believes there are serious opportunities to be explored in another of its properties: temperature. To keep it liquid, it needs to be stored cryogenically at -253.15 °C (-423.7 °F), and Airbus figures that if you've got a monster cold source like that on board your aircraft, you might as well make use of it. The theory is that the liquid hydrogen can supercool the entire electric powertrain down to superconducting temperatures, at which point resistance virtually disappears from the system, and efficiency skyrockets. A powertrain designed to take full advantage of this effect, reasons Airbus, could get the same job done at less than half the weight, half the electrical losses and reduced voltages. So it's building one. The Ascend system will be a ground-based proof of concept developed over the next three years. It'll be a 500-kW (670-hp) powertrain , with cables, controllers, electronics and motors that are cryogenically cooled by liquid hydrogen pumped around in a circuit from the fuel tanks." PDS: Seems like this could have electric antigravity ("electrogravitic") applications -- but as of this point in time, the theory of exactly how to do that seems lacking... Still, the immense power (500-kW) and superconductivity aspect of things, seems to be there -- perhaps what's needed is for someone or some group to do some electric anti-gravity experimentation with this infrastructure... Can they get weight loss electrically -- even as little as an ounce -- using all of that electricity and superconducting apparatus -- in some new, novel fashion? ?
- Valgrim 6y ago
  Electrogravitics is pure pseudo-science, anti-gravity bullshit, not supported in any way by our current understanding of physics or any experiment. However, superconductivity (and using liquid hydrogen both as energy source and coolant) may be useful for ion thrusters; see: -https://www.researchgate.net/publication/245438424_Superconducting_Materials_Applied_to_Electric_Propulsion_Systems https://www.researchgate.net/publication/245438424_Supercond... -https://www.nasa.gov/directorates/spacetech/strg/vitucci.html#:~:text=The%20Helicon%20Thruster%20is%20a,mechanism%20for%20forming%20the%20plasma https://www.nasa.gov/directorates/spacetech/strg/vitucci.htm....
  - peter_d_sherman 6y ago
schainks 6y ago
Liquid hydrogen can do cool things, but how do you reliably stop leaks of the smallest atoms in the universe, even if they are supercooled?
- civildude 6y ago
  making it stick to itself

44 points by sahin 6y ago

This makes no sense to me. Don't you also need cryogenic systems to keep the H2 cold? Wouldn't those use waaaaay more energy than what you save with superconducting motors? Maybe they are talking about short haul flights where the H2 is ground cooled and then used as a cold sink but then in order to keep your electronics cold you're carrying lots more fuel than you need. TFA was too thin to pass the sniff test.

XorNot 6y ago
Motors are solid 3D structures. The more power you put in not superconducting, the more heat you have to extract. Superconductors mean you only need to keep your refrigerant cool, and that's a product of insulation effectiveness, not power output.
- ethbr0 6y ago
  This is the difference between electric and combustion powertrains, no? In electric, heat is the enemy and inefficient. In combustion, heat is a key component of the thermodynamic efficiency, unavoidable, and effectively only limited by material tolerances. (I didn't major in physics, so someone keep me honest on the ceiling / floor efficiency equations for combustion engines?)
  - XorNot 6y ago
    You still have to cool a combustion engine - hence why car's have radiators. Combustion engine's are also limited by Carnot cycle engine efficiency - about 64% theoretically, no more then 50% in the real world. So you're still going to wind up having to dump progressively more heat from a fixed surface area.
    - ethbr0 6y ago
      (Post coffee) Cars have radiators to cool the operating structure (e.g. engine block), but that cooling's ancillary to power produced, no? Carnot cycle was what I was grasping for. Original point being that in a thermal engine, increasing your temperature gradient by increasing your high-temperature side (while holding exhaust constant) leads to more potential power. Or IOW, a thermal engine that doesn't burn hot somewhere isn't going to produce much power. (Electric being a completely different ball of wax)
ginko 6y ago
I think the idea is to use the H2 both as fuel and refrigerant.
- Valgrim 6y ago
  So you recover the boiloff and use it to power a generator which powers a drivetrain cooled by the liquid hydrogen. This seems like a good idea.
ncmncm 6y ago
The idea is that a large-scale LH2 flow into the system is being consumed, and perforce heated, and may be used as refrigerant on the way there. It makes perfect sense. Rockets do this today, as indeed they have done from the earliest days, sending liquified gases through channels in the engine bell and combustion chamber before burning, keeping them both from vaporizing. Here, the very high efficiency of electric-driven turbines is offset by the lower efficiency of fuel-cell generation, for what is expected to be a substantial net gain over burning H2 in internal combustion turbines. The latter are the obvious first stage of deployment, taking advantage of LH2's extreme energy-to-weight ratio for reducing the takeoff fuel load by as much as 5:1. This form will probably be fielded in existing airframes, displacing some cargo space with in-hull LH2 tanks.
- ethbr0 6y ago
  Aka regenerative cooling: https://en.m.wikipedia.org/wiki/Regenerative_cooling_(rocketry) https://en.m.wikipedia.org/wiki/Regenerative_cooling_(rocket...
Tuna-Fish 6y ago
This is effectively regenerative cooling, like what rockets are commonly using. There are no cryogenic systems onboard, but all the fuel is loaded as very cold, and you can use the fuel as a coolant just before you burn it.
- candiodari 6y ago
  They will, however, be using kerosene, not liquid Hydrogen. It cannot provide cryogenic temperatures.
  - Tuna-Fish 6y ago
    Did you read the article? It was specifically about future liquid hydrogen-powered aircraft.
upofadown 6y ago
The H2 keeps itself cold by boiling away. You just need some insulation to slow down the rate to something manageable. Insulation normally uses a gas such as air to block the heat flow and as a result tends to be very light.
petertodd 6y ago
> Don't you also need cryogenic systems to keep the H2 cold? Wouldn't those use waaaaay more energy than what you save with superconducting motors? Probably not. Cryogenic liquids like liquid H2 are typically stored in dewers, which use a vacuum as the primary insulation, along with silvered surfaces and layers of mylar film to reduce radiation losses. We've been able to make dewers with boil off rates of 1% per day or better for decades. That's more than low enough that you don't need any refrigeration at all for an aircraft application where the flight just lasts a few hours anyway. Most likely they'll actually use less effective insulation to save weight. Fortunately for them, cryogenic liquids are commonly used in rockets, so there's already lots of know-how and technology out there for making lightweight cryogenic insulation.
Gravityloss 6y ago
You use the boiloff hydrogen in the power source, I assume a fuel cell in this case. This is regularly done by LNG tanker ships. Evaporating LNG is simply routed to the engines.

throwaway0a5e 6y ago

While there might be something to the underlying tech the current two most promising paths to carbon neutral airlines are synthetic fuel generated with green energy and better batteries. It's highly unlikely that exotic, barely developed hydrogen tech that's not even made it to the "tech demonstrator prototype" phase is going to work exactly the way they're hoping in the end. A few % here and there from unexpected circumstances tends to make a big difference in viability, especially in situations where engineering margins or economic margins are thin (both apply to commercial flight).

ncmncm 6y ago
[superseded]
- throwaway0a5e 6y ago
  Yeah, people don't like being told they fell for exactly what the editor who chose the title wanted them to fall for.
  - ncmncm 6y ago
    No, ignorant editorial bloviating is specifically forbidden in the ToS.
    - throwaway0a5e 6y ago
      The article is clearly greenwashed with respect to the potential impact of the tech (it's at such an early stage lord knows where if any applications in which it will be used). This is corporate press release SOP. Calling it out as wasted words to be ignored or disregarded isn't "editorial bloviating". And they're guidelines, not a ToS.

ncmncm 6y ago

I have estimated that an Airbus A320 generates something on the order of 80 MW during takeoff. A hydrogen-powered aircraft, for the same freight load, will have benefit of efficiencies not available to an A320, so the needed power will be less, but I don't know how much less. The 0.5 MW system described looks like a good first step, but should be scaled up quickly. Results will be immediately useful for co-generation and energy storage on terrestrial power systems. For at least the next decade, that will be its only benefit, which may come to overshadow its aviation application, particularly if the latter encounters snags.

Tuna-Fish 6y ago
If I understand correctly, this makes use of a hydrogen fuel cell for electric power, and then has that turn electric fans. In general, a modern fuel cell is ~60% efficient at turning chemical energy into electricity, and an electric fan is ~4x as efficient at turning electricity into thrust when compared to a turbofan engine turning chemical energy into thrust. So ignoring transmissions losses (which would probably be really low anyway if ran on superconductors...) you'd need about 40% of the power of a modern jet to do the same work. There is clearly a lot of scaling work needed, and I don't see a fuel cell/electric aircraft beating existing ones anytime soon if you ignore the emissions, but at least this clearly shows that there is a future for mass commercial aviation once burning carbohydrates is no longer acceptable.

userbinator 6y ago

The failure modes are going to be interesting, to say the least...

upofadown 6y ago
Yeah, It would be great if any fires were to burn clean and had a strong tendency to rise away from the aircraft, particularly for ground fires. H2 is also nice in that it doesn't create a lot of infrared energy while it burns. You might be able to save the weight of any fire suppression systems.
- coolspot 6y ago
  I think OP meant that electric motor losing superconductivity in-flight will cause irreversible run-away heating of the motor. Which must be mitigated by having more motors than nominally needed, all with independent power supply and cryogenic contours.
  - Valgrim 6y ago
    The way I see it, losing superconductivity instantly shuts down the motor by tripping the circuit breaker, and causes it to transfer it's momentum energy into the surrounding liquid hydrogen. Some hydrogen might boil off, but it's nothing a safety valve can't handle. The plane can then glide to the closest airport or switch to a non-superconducting mode.
    - userbinator 6y ago
      If anything, losing superconductivity will cause less current to flow, since the resistance will increase greatly, and a massive amount of heat will be created.

redis_mlc 6y ago

The aviation industry is exploring alternative fuels in case of draconian regulation, including sustainable aviation fuel (SFA) and hydrogen. But the problems with hydrogen as an aviation fuel are many: - hydrogen embrittlement of containers - volatility (compared to Jet A). Since hydrogen is the smallest molecule, it can escape any container. - distribution (world-wide locations and airport safety) - containment weight and condensation - containment integrity at low temperatures (airplanes flex and fuselage fasteners fail around 33,000 cycles.) And ffs, the Hindenburg: https://en.wikipedia.org/wiki/Hindenburg_disaster https://en.wikipedia.org/wiki/Hindenburg_disaster https://www.avweb.com/ownership/fuel-news/williams-international-tests-saf-on-fj44/ https://www.avweb.com/ownership/fuel-news/williams-internati...

nickserv 6y ago

Cool idea. I would be more enthused if it came from another company though. It seems like all the "green" projects Airbus does are aborted. Remember their last electric plane? Canceled before the first flight. Meanwhile a couple startups are successfully retrofitting electric propulsion on light aircraft.

peter_d_sherman 6y ago

>"Liquid H2's key drawcard to aircraft designers is its impressive energy density by weight, but Airbus believes there are serious opportunities to be explored in another of its properties: temperature. To keep it liquid, it needs to be stored cryogenically at -253.15 °C (-423.7 °F), and Airbus figures that if you've got a monster cold source like that on board your aircraft, you might as well make use of it. The theory is that the liquid hydrogen can supercool the entire electric powertrain down to superconducting temperatures, at which point resistance virtually disappears from the system, and efficiency skyrockets. A powertrain designed to take full advantage of this effect, reasons Airbus, could get the same job done at less than half the weight, half the electrical losses and reduced voltages. So it's building one. The Ascend system will be a ground-based proof of concept developed over the next three years. It'll be a 500-kW (670-hp) powertrain , with cables, controllers, electronics and motors that are cryogenically cooled by liquid hydrogen pumped around in a circuit from the fuel tanks." PDS: Seems like this could have electric antigravity ("electrogravitic") applications -- but as of this point in time, the theory of exactly how to do that seems lacking... Still, the immense power (500-kW) and superconductivity aspect of things, seems to be there -- perhaps what's needed is for someone or some group to do some electric anti-gravity experimentation with this infrastructure... Can they get weight loss electrically -- even as little as an ounce -- using all of that electricity and superconducting apparatus -- in some new, novel fashion? ?

Valgrim 6y ago
Electrogravitics is pure pseudo-science, anti-gravity bullshit, not supported in any way by our current understanding of physics or any experiment. However, superconductivity (and using liquid hydrogen both as energy source and coolant) may be useful for ion thrusters; see: -https://www.researchgate.net/publication/245438424_Superconducting_Materials_Applied_to_Electric_Propulsion_Systems https://www.researchgate.net/publication/245438424_Supercond... -https://www.nasa.gov/directorates/spacetech/strg/vitucci.html#:~:text=The%20Helicon%20Thruster%20is%20a,mechanism%20for%20forming%20the%20plasma https://www.nasa.gov/directorates/spacetech/strg/vitucci.htm....
- peter_d_sherman 6y ago

schainks 6y ago

Liquid hydrogen can do cool things, but how do you reliably stop leaks of the smallest atoms in the universe, even if they are supercooled?

civildude 6y ago
making it stick to itself