3 ms·

Liquified hydrogen will anyway be the fuel of all future aviation. Enough will be stored in underground tanks at airports to fuel aircraft for a day. More will

by ncmncm 4y ago

Liquified hydrogen will anyway be the fuel of all future aviation. Enough will be stored in underground tanks at airports to fuel aircraft for a day. More will be made at need via transmission line and local electrolysis.

epistasis 4y ago
IMHO, hydrogen for aviation seems exceedingly unlikely, it will require redesign of all aircraft. And aircraft are fairly long lived capital. It seems far more likely that we will create synthetic kerosene (from hydrogen feedstocks).
- ncmncm 4y ago
  All aircraft age out. Anyplace where LH2 aircraft are in use, kerosene craft will be found to be completely unable to compete. Thus, starting on key routes, kerosene craft will be driven off to less profitable routes. Demand for LH2 craft will be driven by need to stay in the market at all. The earlier adopters will profit most, initially pocketing the huge difference between current prices and their own cost, and later by wholly owning the most profitable routes.
  - fomine3 4y ago
    Why unable to compete?
    - ncmncm 4y ago
      First, all of the extra weight left off because the fuel for a flight weighs much less is available for extra paying cargo. Second, because the hydrogen for a flight will cost less than kerosene, because it was made on-site rather than pumped, refined, and trucked in. Further, it was made at the time of day when grid power was cheapest. The result is that an LH2 operator can always undercut a kerosene operator, anytime they compete. The kerosene operator only gets flights the LH2 operator passes up. Thus, the LH2 operator also gets the most profitable routes, because those are where they choose to bid. Even after synthetic kerosene becomes available, it will necessarily cost more than hydrogen, and not anyway be made on-site, and still weigh too much.
      - deleted 4y ago
        [deleted]
      - epistasis 4y ago
        The gravimetric density of liquid hydrogen is pretty great, but the volumetric density is 4x lower, only 10GJ/m3 versus 38GJ/m3 for kerosene. I'm told this has really big impacts for aircraft design, which will put hydrogen aircraft at a big disadvantage compared to kerosene fueled vehicles. I could be wrong on this, and don't have any references handy, so I definitely welcome being corrected on this.
        ncmncm 4y ago
        Volume on aircraft is cheap. Weight is very, very expensive. In particular, increasing volume by a factor x means growing the skin by only x^1.5. Tankage is only a small fraction of aircraft volume. So, even though space in the wings, where fuel is put today, would go unused, the amount of extra weight for new tankage would be minimal. If, as I expect, tankage is slung under the wing alongside the engines, airframe design would not need to change, and existing aircraft could even be retrofitted. Lifting bodies are supposed to be more efficient and have lots more room inboard, but efficiency might get less important as fuel cost plummets. Ultimately we expect aircraft to move to electric-driven turbines, attached to fuel cells. Tankage and fuel cells could be anywhere convenient on board. It seems like there would be safety reasons to keep the tanks outboard, as the kerosene is, mostly, today.
regularfry 4y ago
I'm not convinced this adds up. The total commercial hydrogen production capacity in Europe for a day would power a grand total of 21 fully-fuelled 737's. You're talking about multiple hydrogen plants, as big as the current biggest, at every airport, just to satisfy the basic energy requirements. The energy in a full 737 is roughly equivalent to 85000m3 H2. To take a worst case look, there are about 1300 flights per day out of Heathrow. That means you need to generate or supply 110,000,000m3 H2 per day. Total production capacity per day, today, across all of Europe, looks about 42,000,000m3, across about 150 plants. The biggest of those makes 3,240,000m3 per day. So to supply Heathrow alone with enough H2 to supplant conventional fuels you need 34 of the biggest hydrogen plants we've currently got, and a power supply of at least 13.7GW. Storage is the least of the worries here. And to head off any criticisms about Heathrow being an outlier, I'm happy to talk about milliheathrows as a comparison unit for other airports; it doesn't make the overall picture much happier.
- ncmncm 4y ago
  You appear unaware of the magnitude of the system that now supplies kerosene to aircraft. To get current aircraft off mined kerosene would take a synthesis pipeline fully as large, but much more expensive than the hydrogen system. All of that kerosene is today moved -- shipped, trucked -- from refineries to airports, worldwide. On the up side, the mined kerosene infrastructure may be wound down as airport hydrogen infrastructure ramps up to serve the new, much more efficient aircraft. Getting electric power to airports will be an overwhelmingly smaller job than moving kerosene there. Generating the power to send to it will be an overwhelmingly smaller job than exploring, drilling, pumping, transporting, refining, transporting again, and distributing petroleum products. Producing and liquifying the needed hydrogen on site is done without any direct labor, from tap water already piped in. The equipment can be where the tanker trucks used to stop. Measuring future industry against current output before any of it is built gives you bad numbers.
  - regularfry 4y ago
    > You appear unaware of the magnitude of the system that now supplies kerosene to aircraft. Not at all. That system has a huge advantage over what you're proposing because a) it's distributed, and b) the energy doesn't have to be put into the kerosene by the infrastructure, it's already there. > Getting electric power to airports will be an overwhelmingly smaller job than moving kerosene there With the power requirements you're talking about, you're genuinely better off generating it onsite. The national grid won't cope. ~30 conventional nuclear reactors in the 500MW range ought to do it. Your wind option looks like tripling the UK's current onshore capacity, and solar means replacing Slough with a 14kmx14km square of photovoltaics (tempting), assuming it's always windy and/or sunny. > Generating the power to send to it will be an overwhelmingly smaller job than exploring, drilling, pumping, transporting, refining, transporting again, and distributing petroleum products Again, distributed vs concentrated. You've got to do that work all in one place. > The equipment can be where the tanker trucks used to stop. Problem of scale again. If you need a supply equivalent to 34 of the current biggest hydrogen-producing plant to generate the hydrogen, a fair guess says that you need at least a double-digit multiple of the land area of that plant to do so. "Where the tanker trucks used to stop" doesn't really work unless you mean "the west half of Hounslow". Besides which, if we're winding down kerosene infrastructure while hydrogen ramps up, they're both in use at the same time, so no, the equipment can't be where the tanker trucks used to stop because they're still there. Can't have it both ways. If you're generating on-site, the rate you need to be generating H2 is high enough that you absolutely can't be faffing about with underground caverns. You need to be piping it straight into buffer tanks that will supply one (1) plane then get refilled while the next plane taxis up. > Measuring future industry against current output before any of it is built gives you bad numbers. And planning without taking account of basic physics is worse. All I'm doing here is using a rough guess at the current energy requirements for the current activity and using that as a guide for future requirements according to your layout which, I think, is fair. If you think there are economic assumptions which break that, say so. If there are social changes you need to happen in order for this to make sense, say so. Otherwise you're arguing with thermodynamics. Efficiencies may come into the picture; I've assumed they're a wash between hydrogen generation tech, the on-site power generation, and present-day gas-turbine jets but even if that's not the case it's tweaking round the edges. This whole picture looks at least an order of magnitude out from anything practical in every respect.

by ncmncm 4y ago

epistasis 4y ago

IMHO, hydrogen for aviation seems exceedingly unlikely, it will require redesign of all aircraft. And aircraft are fairly long lived capital. It seems far more likely that we will create synthetic kerosene (from hydrogen feedstocks).

ncmncm 4y ago
All aircraft age out. Anyplace where LH2 aircraft are in use, kerosene craft will be found to be completely unable to compete. Thus, starting on key routes, kerosene craft will be driven off to less profitable routes. Demand for LH2 craft will be driven by need to stay in the market at all. The earlier adopters will profit most, initially pocketing the huge difference between current prices and their own cost, and later by wholly owning the most profitable routes.
- fomine3 4y ago
  Why unable to compete?
  - ncmncm 4y ago
    First, all of the extra weight left off because the fuel for a flight weighs much less is available for extra paying cargo. Second, because the hydrogen for a flight will cost less than kerosene, because it was made on-site rather than pumped, refined, and trucked in. Further, it was made at the time of day when grid power was cheapest. The result is that an LH2 operator can always undercut a kerosene operator, anytime they compete. The kerosene operator only gets flights the LH2 operator passes up. Thus, the LH2 operator also gets the most profitable routes, because those are where they choose to bid. Even after synthetic kerosene becomes available, it will necessarily cost more than hydrogen, and not anyway be made on-site, and still weigh too much.
    - deleted 4y ago
      [deleted]
    - epistasis 4y ago
      The gravimetric density of liquid hydrogen is pretty great, but the volumetric density is 4x lower, only 10GJ/m3 versus 38GJ/m3 for kerosene. I'm told this has really big impacts for aircraft design, which will put hydrogen aircraft at a big disadvantage compared to kerosene fueled vehicles. I could be wrong on this, and don't have any references handy, so I definitely welcome being corrected on this.
      - ncmncm 4y ago
        Volume on aircraft is cheap. Weight is very, very expensive. In particular, increasing volume by a factor x means growing the skin by only x^1.5. Tankage is only a small fraction of aircraft volume. So, even though space in the wings, where fuel is put today, would go unused, the amount of extra weight for new tankage would be minimal. If, as I expect, tankage is slung under the wing alongside the engines, airframe design would not need to change, and existing aircraft could even be retrofitted. Lifting bodies are supposed to be more efficient and have lots more room inboard, but efficiency might get less important as fuel cost plummets. Ultimately we expect aircraft to move to electric-driven turbines, attached to fuel cells. Tankage and fuel cells could be anywhere convenient on board. It seems like there would be safety reasons to keep the tanks outboard, as the kerosene is, mostly, today.

regularfry 4y ago

I'm not convinced this adds up. The total commercial hydrogen production capacity in Europe for a day would power a grand total of 21 fully-fuelled 737's. You're talking about multiple hydrogen plants, as big as the current biggest, at every airport, just to satisfy the basic energy requirements. The energy in a full 737 is roughly equivalent to 85000m3 H2. To take a worst case look, there are about 1300 flights per day out of Heathrow. That means you need to generate or supply 110,000,000m3 H2 per day. Total production capacity per day, today, across all of Europe, looks about 42,000,000m3, across about 150 plants. The biggest of those makes 3,240,000m3 per day. So to supply Heathrow alone with enough H2 to supplant conventional fuels you need 34 of the biggest hydrogen plants we've currently got, and a power supply of at least 13.7GW. Storage is the least of the worries here. And to head off any criticisms about Heathrow being an outlier, I'm happy to talk about milliheathrows as a comparison unit for other airports; it doesn't make the overall picture much happier.

ncmncm 4y ago
You appear unaware of the magnitude of the system that now supplies kerosene to aircraft. To get current aircraft off mined kerosene would take a synthesis pipeline fully as large, but much more expensive than the hydrogen system. All of that kerosene is today moved -- shipped, trucked -- from refineries to airports, worldwide. On the up side, the mined kerosene infrastructure may be wound down as airport hydrogen infrastructure ramps up to serve the new, much more efficient aircraft. Getting electric power to airports will be an overwhelmingly smaller job than moving kerosene there. Generating the power to send to it will be an overwhelmingly smaller job than exploring, drilling, pumping, transporting, refining, transporting again, and distributing petroleum products. Producing and liquifying the needed hydrogen on site is done without any direct labor, from tap water already piped in. The equipment can be where the tanker trucks used to stop. Measuring future industry against current output before any of it is built gives you bad numbers.
- regularfry 4y ago
  > You appear unaware of the magnitude of the system that now supplies kerosene to aircraft. Not at all. That system has a huge advantage over what you're proposing because a) it's distributed, and b) the energy doesn't have to be put into the kerosene by the infrastructure, it's already there. > Getting electric power to airports will be an overwhelmingly smaller job than moving kerosene there With the power requirements you're talking about, you're genuinely better off generating it onsite. The national grid won't cope. ~30 conventional nuclear reactors in the 500MW range ought to do it. Your wind option looks like tripling the UK's current onshore capacity, and solar means replacing Slough with a 14kmx14km square of photovoltaics (tempting), assuming it's always windy and/or sunny. > Generating the power to send to it will be an overwhelmingly smaller job than exploring, drilling, pumping, transporting, refining, transporting again, and distributing petroleum products Again, distributed vs concentrated. You've got to do that work all in one place. > The equipment can be where the tanker trucks used to stop. Problem of scale again. If you need a supply equivalent to 34 of the current biggest hydrogen-producing plant to generate the hydrogen, a fair guess says that you need at least a double-digit multiple of the land area of that plant to do so. "Where the tanker trucks used to stop" doesn't really work unless you mean "the west half of Hounslow". Besides which, if we're winding down kerosene infrastructure while hydrogen ramps up, they're both in use at the same time, so no, the equipment can't be where the tanker trucks used to stop because they're still there. Can't have it both ways. If you're generating on-site, the rate you need to be generating H2 is high enough that you absolutely can't be faffing about with underground caverns. You need to be piping it straight into buffer tanks that will supply one (1) plane then get refilled while the next plane taxis up. > Measuring future industry against current output before any of it is built gives you bad numbers. And planning without taking account of basic physics is worse. All I'm doing here is using a rough guess at the current energy requirements for the current activity and using that as a guide for future requirements according to your layout which, I think, is fair. If you think there are economic assumptions which break that, say so. If there are social changes you need to happen in order for this to make sense, say so. Otherwise you're arguing with thermodynamics. Efficiencies may come into the picture; I've assumed they're a wash between hydrogen generation tech, the on-site power generation, and present-day gas-turbine jets but even if that's not the case it's tweaking round the edges. This whole picture looks at least an order of magnitude out from anything practical in every respect.