Storage of hydrogen fuel on aircraft
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Storage of hydrogen fuel on aircraft
I hope that this is the right forum - if not please move.
I have recently read a lot about the use of hydrogen to replace jet fuels. I suspect that bio fuels will be the way forward but to work the cost needs to reduce dramatically and if it doesn;t we may be stuck with hydrogen. There are basically three ways of storing hydrogen
- compression, which requires large and heavy tanks
- cryogenically
- interstitialy - the hydrogen reacts with another substance and can be released as required (in the same way that I believe butane can be dissolved in acetone but I'm certainly not an expert so may be wrong).
Can any experts here let me know which they think would be the most effective for long haul flights. I am particularly interested in cryogenic storage. This was famously used for the second and third stages of the Saturn V rocket. Fuelling them was a major task and a lot of hydrogen boiled off and was lost. You could see a lot of ice, formed by condensation, falling off the rocket on take off. This I would imagine would preclude its use in wing tanks so you would need tanks at the front and rear of the fuselage. I also read somewhere that a lot of hydrogen boiled off and that for this reason the third stage could only manage two and a half orbits (one more than was planned) before the trans lunar insertion had to be abandoned.
What are your thoughts on whether hydrogen can be used as a fuel?
As a matter of interest how was the hydrogen in the Apollo service module used for fuel cells stored and were there problems with losses en route?
I have recently read a lot about the use of hydrogen to replace jet fuels. I suspect that bio fuels will be the way forward but to work the cost needs to reduce dramatically and if it doesn;t we may be stuck with hydrogen. There are basically three ways of storing hydrogen
- compression, which requires large and heavy tanks
- cryogenically
- interstitialy - the hydrogen reacts with another substance and can be released as required (in the same way that I believe butane can be dissolved in acetone but I'm certainly not an expert so may be wrong).
Can any experts here let me know which they think would be the most effective for long haul flights. I am particularly interested in cryogenic storage. This was famously used for the second and third stages of the Saturn V rocket. Fuelling them was a major task and a lot of hydrogen boiled off and was lost. You could see a lot of ice, formed by condensation, falling off the rocket on take off. This I would imagine would preclude its use in wing tanks so you would need tanks at the front and rear of the fuselage. I also read somewhere that a lot of hydrogen boiled off and that for this reason the third stage could only manage two and a half orbits (one more than was planned) before the trans lunar insertion had to be abandoned.
What are your thoughts on whether hydrogen can be used as a fuel?
As a matter of interest how was the hydrogen in the Apollo service module used for fuel cells stored and were there problems with losses en route?
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Cryogenic hydrogen is probably out of the question for aviation. It works for rockets only because they continue topping up right up to the start and then it takes only a few minutes until they are out of most of the atmosphere. If there really is a requirement to use alternative fuels in widespread use, it probably has to be power to fuel conversion. Bio fuels are not practical either, as the amount of biomass that has to be used for biofuels would start to interfere with food production very fast.
Pressurized hydrogen could be possible, but requires quite a heavy structure and there will still be quite a bit of hydrogen leakage as it is a simply too small molecule. All in all hydrogen seems like an obvious choice, however, while it has the highest energy density per weight, it has one of the lowest per volume, which in the end is the problem in aviation.
Pressurized hydrogen could be possible, but requires quite a heavy structure and there will still be quite a bit of hydrogen leakage as it is a simply too small molecule. All in all hydrogen seems like an obvious choice, however, while it has the highest energy density per weight, it has one of the lowest per volume, which in the end is the problem in aviation.
Denti - hydrogen will always be problematic for long distance travel (at least for subsonic travel). The problem is density - it would take a massive volume of H2 to equal the energy of a thousand liters of Jet-A and either cryogenic or high pressure means spherical or cylindrical fuel tanks to be even remotely viable - you're not going to be storing it in the wing. So you're looking at devoting much of the fuselage to fuel - which of course makes it unavailable for payload (not to mention the issues with safely segregating the fuel from passengers). The equation changes rather dramatically when you start talking something like hypersonic - but that's going to require a major leap in technology before it becomes even remotely viable.
Don't be quick to dismiss biofuel - you're correct if biofuel was limited to things like turning corn or soybeans into jet fuel - but there are other options that look far better. One of the most promising is using algae - it takes a small fraction of the area per unit of fuel that land crops do, the downside being ti currently takes large amounts of fresh water. If they can come up with a variety of algae that produces a similar amount of fuel in salt water it could quickly become a viable option.
Don't be quick to dismiss biofuel - you're correct if biofuel was limited to things like turning corn or soybeans into jet fuel - but there are other options that look far better. One of the most promising is using algae - it takes a small fraction of the area per unit of fuel that land crops do, the downside being ti currently takes large amounts of fresh water. If they can come up with a variety of algae that produces a similar amount of fuel in salt water it could quickly become a viable option.
Hi Peter47,
It is actually acetylene which is absorbed in acetone. It has the nasty habit of exploding if left alone in a pressure vessel. A damn nuisance really. Don't ever lie the cylinders on their side lest you get a bubble which will announce itself with a nasty bang.
It is actually acetylene which is absorbed in acetone. It has the nasty habit of exploding if left alone in a pressure vessel. A damn nuisance really. Don't ever lie the cylinders on their side lest you get a bubble which will announce itself with a nasty bang.
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Denti - hydrogen will always be problematic for long distance travel (at least for subsonic travel). The problem is density - it would take a massive volume of H2 to equal the energy of a thousand liters of Jet-A and either cryogenic or high pressure means spherical or cylindrical fuel tanks to be even remotely viable - you're not going to be storing it in the wing. So you're looking at devoting much of the fuselage to fuel - which of course makes it unavailable for payload (not to mention the issues with safely segregating the fuel from passengers). The equation changes rather dramatically when you start talking something like hypersonic - but that's going to require a major leap in technology before it becomes even remotely viable.
Don't be quick to dismiss biofuel - you're correct if biofuel was limited to things like turning corn or soybeans into jet fuel - but there are other options that look far better. One of the most promising is using algae - it takes a small fraction of the area per unit of fuel that land crops do, the downside being ti currently takes large amounts of fresh water. If they can come up with a variety of algae that produces a similar amount of fuel in salt water it could quickly become a viable option.
Don't be quick to dismiss biofuel - you're correct if biofuel was limited to things like turning corn or soybeans into jet fuel - but there are other options that look far better. One of the most promising is using algae - it takes a small fraction of the area per unit of fuel that land crops do, the downside being ti currently takes large amounts of fresh water. If they can come up with a variety of algae that produces a similar amount of fuel in salt water it could quickly become a viable option.
I take your point about algae based fuels. Those could be a possibility, if and when they discover or engineer the correct kind of those to grow without too much of a downside. And i know, that P2F is currently in its infancy and very power hungry, basically it generates fuel out of power via hydrogen, using CO2 from the atmosphere to generate liquid fuels that can be easily engineered to be simply Jet-A1. However, it is extremely energy inefficient as of yet. Still could be a possibility.
In the end it could be a combination to generate the required amount of fuel.
