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Hydrogen fuel could revolutionize airlines - Los Angeles Times

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Hydrogen fuel could revolutionize airlines - Los Angeles Times

Old 28th Oct 2020, 19:07
  #21 (permalink)  
 
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Originally Posted by Deltasierra010 View Post
Hydrogen is not “energy dense” liquid hydrogen needs 5 times the volume to match jet fuel, moreover it needs to be compressed and refrigerated, less of a problem at 30,000 ft but critical on the ground, we are highly unlikely to see airliners fueled by hydrogen.
Yea, I laughed when I saw that little 'energy dense' tidbit in the article (apparently there is a reason we don't let reporters design aircraft). Yes it's light, but you need many times more volume. To be even remotely viable, the H2 tanks need to be spherical or cylindrical - so you're not going to be carrying it the wing. Worse, even though it's light relative to Jet A, you're still going to need a lot of it to go very far, so you need to store it near the aircraft CG to maintain acceptable trim as it burns off. So what you're going to end up with is a massive H2 tank in the middle of the fuselage - which needs to have fail-safe segregation from passengers and crew. So what you're apt to end up with is passenger/cargo space in the front and rear, with a massive fuel tank in between. At best, a complete re-think of aircraft design and layout.
Biofuel (probably based on algae) is a far more viable long-term solution than H2 - with the added advantage that it would work with today's aircraft...
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Old 28th Oct 2020, 20:06
  #22 (permalink)  
 
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Hydrogen fuels can be reformed into many different fuels, for Aviation weight and volume are critical, when land transport is fully non fossil fueled liquid fuels will still be used for Aviation, unless some yet unknown technology is discovered. Safety is a different matter, it is not possible to segregate passengers and compressed fuel in an airline, any fault would destroy the whole thing so either you accept that risk or forget it.

Limited range light aircraft have possibilities either Battery powered or Fuel Cell electric, wether that is within the price range of recreational pilots is another matter
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Old 29th Oct 2020, 05:08
  #23 (permalink)  
 
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@tdracer, "...with a massive fuel tank in between".

Could that not be two medium-sized tanks, or even four little 'uns? Granted that you waste space between the cylinders, and you face interchangeability problems.

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Old 29th Oct 2020, 10:03
  #24 (permalink)  
 
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Originally Posted by ericoides View Post
Whatever they come up with, as well as being carbon neutral, it must satisfy two criteria:
  1. No, or little, noise.
  2. No contrails, such as currently disfigure our skies like some sort of careless straight-line graffiti.
I can’t tell if this is serious or satire.
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Old 29th Oct 2020, 13:05
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By energy dense, I'm referring to the potential energy per kg compared to Jet A-1, this is not related to volume.

Relative energy densities
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Old 29th Oct 2020, 13:33
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Originally Posted by Momoe View Post
By energy dense, I'm referring to the potential energy per kg compared to Jet A-1, this is not related to volume.

Relative energy densities
The only density that matters is how much volume of fuel you need to travel a given distance, a heavy fuel like gasoline is 5 times more efficient than liquid hydrogen. In any moving vehicle that is important, if it’s a static installation, no problem you can pump it along a pipeline uncompressed.
But then there would be no point, you could have used the electricity directly, or store it in batteries, current technology is moving that way, not hydrogen. We need a quantum leap in technology for hydrogen to be more efficient.
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Old 29th Oct 2020, 14:09
  #27 (permalink)  
 
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We need a quantum leap in battery technology before any big commercial airplane can fly with electrical battery power. This view is undisputed within the industry and this is the reason why big manufacturers look elsewhere likte at hydrogen.
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Old 29th Oct 2020, 18:09
  #28 (permalink)  
 
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Battery power is out for large long range jets, it’s going to be hydrogen based that’s for sure but not compressed gas, the technology we have now has been around for many decades we need something new, that’s for batteries as well as hydrogen
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Old 29th Oct 2020, 18:13
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Originally Posted by tdracer View Post
So what you're going to end up with is a massive H2 tank in the middle of the fuselage - which needs to have fail-safe segregation from passengers and crew.
Or you could put strap a really big, uncompressed H2 tank on top. Would add massive drag, so speeds would be limited, but on the other hand it would provide lift. Might take longer to get from A to B but given the need for 14 days quarantine at B anyway, there may be les of a rush in future. Add emergency H2 (or Jet A1) tanks somewhere, say in the wings :-), and an ejection mechanism for the "tank" and you've got that fail-safe segregation.

Biofuel (probably based on algae) is a far more viable long-term solution than H2 - with the added advantage that it would work with today's aircraft...
Or synthetic fuel produced from carbon capture by chemical process. Definitely the easier way to go, utilising all existing infrastructure, if such a process (or algae) can be found and scaled up. That is the bet that is being hedged with H2 R&D.
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Old 30th Oct 2020, 10:07
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One major advantage that hydrogen has over batteries is that you are not carrying the full weight of the reactants around with you. You carry the hydrogen (which gets consumed throughout the flight) but you don’t need to carry the oxygen as it is in the air through which you fly. A battery must carry all reactants throughout the flight and what’s more, will weigh just as much on landing.

Over a decade ago I was lectured on the exciting possibility of storing hydrogen in a “carbon sponge” which went some way to alleviating the fears of explosion of hydrogen tanks in a car accident. I haven’t since heard much on this technology!
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Old 30th Oct 2020, 10:11
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With a battery aircraft every landing is overweight.
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Old 30th Oct 2020, 10:45
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Not if you take off from a hilltop aerodrome using a ground-based battery-powered catapult, and release used batteries along the way, which then self-glide to collection points.
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Old 30th Oct 2020, 11:09
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Originally Posted by jolihokistix View Post
Not if you take off from a hilltop aerodrome using a ground-based battery-powered catapult, and release used batteries along the way, which then self-glide to collection points.
The Electron Rocket does this very cool 'hot battery swap' with it's second stage. The turbo pumps are electrically driven, powered by Li-Po batteries. When the first two batteries are exhausted, it automatically switches to the third battery and jettisons the first two. At the moment they burn up on reentry but recovery and re-use is not impossible.
About 33 minutes into this video.

https://m.youtube.com/watch?v=_6SxcO-fHEU
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Old 30th Oct 2020, 15:06
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Originally Posted by TURIN View Post
The turbo pumps are electrically driven
​​​​​​In other words, "the pumps"
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Old 30th Oct 2020, 21:55
  #35 (permalink)  
 
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Originally Posted by flypaddy View Post
Over a decade ago I was lectured on the exciting possibility of storing hydrogen in a “carbon sponge” which went some way to alleviating the fears of explosion of hydrogen tanks in a car accident. I haven’t since heard much on this technology!
The problem with the 'sponge' technology that absorbs H2, then releases it slowly is that it's heavy - even for an automotive application. The one I looked at (many years ago) - a 'sponge' that could hold enough H2 to equate to a ~20 gallon fuel tank weighed nearly two tons. Troublesome for an auto - non-starter for an aircraft.

Something I didn't mention previously - liquid H2 has another problem: The cryogenic temperatures involved are very hard on the materials used. This means a massive maintenance burden to keep the system working properly and safely. Rocket engines and the associated hardware (pumps, etc.) only operate for minutes, then are either discarded or rebuilt before they are used again - not a practical solution for an aircraft that is expected to operate eight or more hours a day, every day, for years...
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Old 31st Oct 2020, 04:07
  #36 (permalink)  
 
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So if you put AI and hydrogen together, which revolutionizes which?
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Old 1st Nov 2020, 16:45
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Originally Posted by TURIN View Post
Pretty sure combusting methane creates CO2
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Old 1st Nov 2020, 18:37
  #38 (permalink)  
 
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Originally Posted by Ex Cargo Clown View Post
Pretty sure combusting methane creates CO2
However if you manufacture the methane using CO2 from the atmosphere, it can be carbon neutral (depending on the source of the energy used in the process). Same basic theory as biofuels.

Being 'carbon neutral' doesn't have to mean moving away from hydrocarbon fuels - it just means you need to re-think how you source them.
Given the inefficiencies inherent in using H2 as fuel, I remain far from convinced it's a better solution than 'manufacturing' hydrocarbon fuels.
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Old 8th Nov 2020, 08:42
  #39 (permalink)  
 
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Whatever the fuel of the future for air transport is it wont be liquid hydrogen, far too dangerous, technically difficult and expensive. Maybe Ethanol or some other liquid synthetic fuel but that is way in the future, as land transport moves to electric there will be ample fossil fuel for aviation for at least 50 yrs and probably way into the next century.
Until there is a quantum leap in hydrogen technology it will remain the holy grail of energy.
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Old 8th Nov 2020, 19:27
  #40 (permalink)  
 
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They may have to take out the chemtrails tanks to fit the H2 tanks.
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