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Is hydrogen gas dense enough to power an aircraft? I don't think battery technology will be dense enough to power aircraft in our lifetimes, but I feel like hyd

Is hydrogen gas dense enough to power an aircraft? I don't think battery technology will be dense enough to power aircraft in our lifetimes, but I feel like hydrogen could play a part

p_l 4y ago
Hydrogen has been tested, including in Soviet Union which considered it the future fuel for airliners, tested on Tu-154M modified for cryogenic hydrogen fuel.
stareatgoats 4y ago
Agree: https://newatlas.com/aircraft/hypoint-gtl-lightweight-liquid-hydrogen-tank https://newatlas.com/aircraft/hypoint-gtl-lightweight-liquid...
skykooler 4y ago
Hydrogen has an excellent energy-to-weight ratio, but in terms of energy-to-volume it's even worse than lithium-ion batteries as a gas. This is why proposals for hydrogen airliners usually need a complicated cryogenic setup to store it as liquid hydrogen instead.
- ncmncm 4y ago
  You don't need a "complicated" cryogenic setup. You just need insulated tankage. But it won't fit in the wings, so you need new airframes or fuel nacelles. We have a very great deal of experience with fuel nacelles already, because that is what a "drop tank" looks like; you just omit the "drop" complication. The advantages over inboard tankage are safety, possible retrofitting of existing fleets, and short plumbing runs. Once LH2 aircraft are used on any route, kerosene craft will be wholly unable to compete, even without carbon taxes. Carbon taxes could be spent on accelerating the transition.
  - hgomersall 4y ago
    Or a radically different airframe design. One that perhaps is much bigger and flies slower but is very low weight (by virtue of being mostly full of hydrogen).
    - ncmncm 4y ago
      A different airframe design would take a long time to field, and with inboard tankage arguably less safe.
NegativeLatency 4y ago
https://en.wikipedia.org/wiki/Lockheed_CL-400_Suntan https://en.wikipedia.org/wiki/Lockheed_CL-400_Suntan
marcosdumay 4y ago
Hydrogen looks like the perfect storage medium for aviation, except that every way people created to store it is either very dangerous or reduces its energy density enough that it becomes similar to batteries.
panick21_ 4y ago
Lithium Battery are already enough to power some airplanes. Airplanes now in development using current battery tech are already targeting many niches. They will not fly across oceans for a while but a lot of aviation is limited to one continent. And beyond that, the cheaper operational cost, can change how flights routes significantly and even open more markets. The problem with airplanes is partly that it takes a very long time to design a new one and the cost are significant. To create a longer range electric plane, you need to really start from the ground up, and rethink the airplane. Even with cars this took 10-15 years. For planes it will be even more difficult.
jillesvangurp 4y ago
There are a few flying prototypes of various sizes, so clearly there's a big flaw in your argument. In principle you can burn hydrogen in a jet or even in an internal combustion engine. Both have already been shown to work. Fuel cells are another possibility of course. As far as I understand it, most plane manufacturers are already designing planes with hyrdogen as a power source. Particularly for big Jets, the consensus seems to be that that is happening. The main challenge in the market is similar with what we've seen with existing car manufacturers. Changing technology disrupts them and threatens their profitability. So, you see companies that are talking the talk but not really committing to much beyond that. E.g. Airbus and Boeing have lots of fancy concept planes but not much in the line of actual planes being designed and marketed yet. As for battery, there are several battery powered planes flying and certified (or in the process of being certified). Most of the companies behind those are following up with longer range versions that they've already announced. Maybe aviation fuel goes a bit further but it is very expensive. Especially for general aviation, the value proposition might look pretty good a few years down the line with better ranges and charging speeds and lower cost. That does not even require that much in terms of breakthroughs in energy density either. Anything certified today is using battery tech that is several years old and was probably picked conservatively to speed up the process. That's just the nature of the certification process. What's flying legally today was the state of the art about half a decade ago in terms of batteries. Probably not that impressive compared to the latest electrical cars.
ggreer 4y ago
Hydrogen looks good on paper but has a lot of practical issues. - Currently, the most economically efficient method to obtain hydrogen is by methane steam reforming. This releases a lot of CO2. - If you want to get hydrogen without making CO2, you'll need to use electricity to split water. That's around 60-70% efficient. If you used the same electricity to charge a battery, it would be over 90% efficient. - Hydrogen embrittlement is a problem for tanks and pipes. This means you can't easily repurpose natural gas infrastructure. - Hydrogen has no odor, and adding an odorant can foul fuel cells. The most effective solution is to add hydrogen sensors everywhere, increasing costs. - Hydrogen burns with an invisible flame. It's also much more easily ignited than gasoline and will burn in a wider range of concentrations. (Though unlike gasoline, it won't pool up.) - Hydrogen is a small enough molecule that it will slowly permeate through a sealed tank. Newer tanks have coatings that reduce this, but research is ongoing. - Remember the ideal gas law? The pressure change involved in refilling a hydrogen tank causes the nozzle to get very cold. Even in southern California this can freeze the nozzle to the tank, limiting refill speeds. - Hydrogen is light, but tanks are heavy. The Toyota Mirai's tanks weigh 87.5kg but can only store 5kg of hydrogen. Considering all of these disadvantages, I don't think hydrogen aircraft are going to happen.
- lucb1e 4y ago
  > Remember the ideal gas law? For anyone else who doesn't: https://en.wikipedia.org/wiki/Ideal_gas_law https://en.wikipedia.org/wiki/Ideal_gas_law "also called the general gas equation [...] is a good approximation of the behavior of many gases under many conditions". It seems to relate how pressure, volume and temperature interact (combined with some constant and how much gas there is). (Bit of a weird name; 'general gas equation' makes more sense to me.) But okay so this reference is about "know how gas behaves?" and actually seems to mean "gas gets cold when it expands", if I understand the comment correctly (since I didn't have this in school). Not sure why the tank you're filling can't just have the same pressure if this is a problem (plunger on both ends, push the gas over, don't let the available space expand or shrink).
  - ggreer 4y ago
    To transfer gas into a tank, it has to go from higher pressure to lower pressure. If the pressure is equal, you won't transfer any gas. Also an empty tank is pretty much at atmospheric pressure. Gas has to expand to pressurize it. The easiest solution is probably to add heating coils around the parts that get cold. I haven't heard of any the hydrogen filling stations having such devices, but that's probably because hydrogen stations are only in California.
Kerrick 4y ago
There is already a type-certified electric aircraft. https://www.pipistrel-aircraft.com/aircraft/electric-flight/velis-electro-easa-tc/ https://www.pipistrel-aircraft.com/aircraft/electric-flight/...
zumu 4y ago
Lots of comments saying it's impractical but there are already several companies working on hydrogen (both gas and liquid) powered designs. Airbus/Delta and ZeroAvia/Alaska for example. https://www.airbus.com/en/innovation/zero-emission/hydrogen/zeroe https://www.airbus.com/en/innovation/zero-emission/hydrogen/... https://en.wikipedia.org/wiki/ZeroAvia https://en.wikipedia.org/wiki/ZeroAvia

Is hydrogen gas dense enough to power an aircraft? I don't think battery technology will be dense enough to power aircraft in our lifetimes, but I feel like hydrogen could play a part

p_l 4y ago

Hydrogen has been tested, including in Soviet Union which considered it the future fuel for airliners, tested on Tu-154M modified for cryogenic hydrogen fuel.

stareatgoats 4y ago

Agree: https://newatlas.com/aircraft/hypoint-gtl-lightweight-liquid-hydrogen-tank https://newatlas.com/aircraft/hypoint-gtl-lightweight-liquid...

skykooler 4y ago

Hydrogen has an excellent energy-to-weight ratio, but in terms of energy-to-volume it's even worse than lithium-ion batteries as a gas. This is why proposals for hydrogen airliners usually need a complicated cryogenic setup to store it as liquid hydrogen instead.

ncmncm 4y ago
You don't need a "complicated" cryogenic setup. You just need insulated tankage. But it won't fit in the wings, so you need new airframes or fuel nacelles. We have a very great deal of experience with fuel nacelles already, because that is what a "drop tank" looks like; you just omit the "drop" complication. The advantages over inboard tankage are safety, possible retrofitting of existing fleets, and short plumbing runs. Once LH2 aircraft are used on any route, kerosene craft will be wholly unable to compete, even without carbon taxes. Carbon taxes could be spent on accelerating the transition.
- hgomersall 4y ago
  Or a radically different airframe design. One that perhaps is much bigger and flies slower but is very low weight (by virtue of being mostly full of hydrogen).
  - ncmncm 4y ago
    A different airframe design would take a long time to field, and with inboard tankage arguably less safe.

NegativeLatency 4y ago

https://en.wikipedia.org/wiki/Lockheed_CL-400_Suntan https://en.wikipedia.org/wiki/Lockheed_CL-400_Suntan

marcosdumay 4y ago

Hydrogen looks like the perfect storage medium for aviation, except that every way people created to store it is either very dangerous or reduces its energy density enough that it becomes similar to batteries.

panick21_ 4y ago

Lithium Battery are already enough to power some airplanes. Airplanes now in development using current battery tech are already targeting many niches. They will not fly across oceans for a while but a lot of aviation is limited to one continent. And beyond that, the cheaper operational cost, can change how flights routes significantly and even open more markets. The problem with airplanes is partly that it takes a very long time to design a new one and the cost are significant. To create a longer range electric plane, you need to really start from the ground up, and rethink the airplane. Even with cars this took 10-15 years. For planes it will be even more difficult.

jillesvangurp 4y ago

There are a few flying prototypes of various sizes, so clearly there's a big flaw in your argument. In principle you can burn hydrogen in a jet or even in an internal combustion engine. Both have already been shown to work. Fuel cells are another possibility of course. As far as I understand it, most plane manufacturers are already designing planes with hyrdogen as a power source. Particularly for big Jets, the consensus seems to be that that is happening. The main challenge in the market is similar with what we've seen with existing car manufacturers. Changing technology disrupts them and threatens their profitability. So, you see companies that are talking the talk but not really committing to much beyond that. E.g. Airbus and Boeing have lots of fancy concept planes but not much in the line of actual planes being designed and marketed yet. As for battery, there are several battery powered planes flying and certified (or in the process of being certified). Most of the companies behind those are following up with longer range versions that they've already announced. Maybe aviation fuel goes a bit further but it is very expensive. Especially for general aviation, the value proposition might look pretty good a few years down the line with better ranges and charging speeds and lower cost. That does not even require that much in terms of breakthroughs in energy density either. Anything certified today is using battery tech that is several years old and was probably picked conservatively to speed up the process. That's just the nature of the certification process. What's flying legally today was the state of the art about half a decade ago in terms of batteries. Probably not that impressive compared to the latest electrical cars.

ggreer 4y ago

Hydrogen looks good on paper but has a lot of practical issues. - Currently, the most economically efficient method to obtain hydrogen is by methane steam reforming. This releases a lot of CO2. - If you want to get hydrogen without making CO2, you'll need to use electricity to split water. That's around 60-70% efficient. If you used the same electricity to charge a battery, it would be over 90% efficient. - Hydrogen embrittlement is a problem for tanks and pipes. This means you can't easily repurpose natural gas infrastructure. - Hydrogen has no odor, and adding an odorant can foul fuel cells. The most effective solution is to add hydrogen sensors everywhere, increasing costs. - Hydrogen burns with an invisible flame. It's also much more easily ignited than gasoline and will burn in a wider range of concentrations. (Though unlike gasoline, it won't pool up.) - Hydrogen is a small enough molecule that it will slowly permeate through a sealed tank. Newer tanks have coatings that reduce this, but research is ongoing. - Remember the ideal gas law? The pressure change involved in refilling a hydrogen tank causes the nozzle to get very cold. Even in southern California this can freeze the nozzle to the tank, limiting refill speeds. - Hydrogen is light, but tanks are heavy. The Toyota Mirai's tanks weigh 87.5kg but can only store 5kg of hydrogen. Considering all of these disadvantages, I don't think hydrogen aircraft are going to happen.

lucb1e 4y ago
> Remember the ideal gas law? For anyone else who doesn't: https://en.wikipedia.org/wiki/Ideal_gas_law https://en.wikipedia.org/wiki/Ideal_gas_law "also called the general gas equation [...] is a good approximation of the behavior of many gases under many conditions". It seems to relate how pressure, volume and temperature interact (combined with some constant and how much gas there is). (Bit of a weird name; 'general gas equation' makes more sense to me.) But okay so this reference is about "know how gas behaves?" and actually seems to mean "gas gets cold when it expands", if I understand the comment correctly (since I didn't have this in school). Not sure why the tank you're filling can't just have the same pressure if this is a problem (plunger on both ends, push the gas over, don't let the available space expand or shrink).
- ggreer 4y ago
  To transfer gas into a tank, it has to go from higher pressure to lower pressure. If the pressure is equal, you won't transfer any gas. Also an empty tank is pretty much at atmospheric pressure. Gas has to expand to pressurize it. The easiest solution is probably to add heating coils around the parts that get cold. I haven't heard of any the hydrogen filling stations having such devices, but that's probably because hydrogen stations are only in California.

Kerrick 4y ago

There is already a type-certified electric aircraft. https://www.pipistrel-aircraft.com/aircraft/electric-flight/velis-electro-easa-tc/ https://www.pipistrel-aircraft.com/aircraft/electric-flight/...

zumu 4y ago

Lots of comments saying it's impractical but there are already several companies working on hydrogen (both gas and liquid) powered designs. Airbus/Delta and ZeroAvia/Alaska for example. https://www.airbus.com/en/innovation/zero-emission/hydrogen/zeroe https://www.airbus.com/en/innovation/zero-emission/hydrogen/... https://en.wikipedia.org/wiki/ZeroAvia https://en.wikipedia.org/wiki/ZeroAvia