3 ms·

Just because the tank is light, doesn't mean that a completed fuel carriage will be much lighter than any other car.

aurizon 4y ago
A tanker that holds 80,000 pounds of kerosine will hold about 8000 pounds of LH2 in the same dimensionality. 0.07 = density of LH2, Density of water 1.0, kerosine 0.7 +/- varies with grade. So it take 10 times the cubeage plus Dewar grade insulation. At a permeant depot they will have a super refrigerator to condense boil off into LH2. They are trying to get a viable clathrate hydrate to hold a higher density form of bound but not reacted Hydrogen
- ncmncm 4y ago
  The measure of fuel you need to carry is not weight, but energy content. It takes a much smaller weight of LH2 to match the energy content of diesel. So, correspondingly less than 10x volume. It is this better "gravimetric energy density" that makes LH2 an attractive fuel in many cases. You end up needing only about 2-3x tankage space, including the insulation. Better gravimetric energy density doesn't make so much difference for a train, so its other advantages -- production on-site, zero emissions, carbon-neutral -- are more important. At the trainyard, the LH2 would be banked in an underground tank where insulation is easy. It is not necessary to refrigerate it after it is liquified. It will gradually boil off, so you just make more anytime the level goes down, whether from boil-off or pumping out to a locomotive tank.
  - aurizon 4y ago
    There is truth in that energy density. but it is still cheaper energetically to chill boil off to liquid back to the tank that to make new hot hydrogen you then chill to liquid back to the tank. The end game of clathrate storage will solve many of these problems.
    - ncmncm 4y ago
      True, keeping the LH2 below its boiling point is, energetically, strictly cheaper than producing as much new hydrogen as would have boiled off, and then chilling that... But, it incurs the added complexity cost of building refrigeration plumbing into the tank, and maintaining that. That could mean the tank has to be above ground, for easy access (which might be needed anyway). My expectation was that native electrical energy will be cheap enough that wasting some is better than complicating your system. Each tradeoff will be an engineering analysis. In this case it will all depend on how good your insulation is, which is of course better in an underground tank. Many old conventions will be overturned as the marginal cost of electrical power at peak times gets cheaper. Both will be tried, so we will see.
      - aurizon 4y ago
        Yes, flow batteries, gravity batteries and high water storage will all make their presence felt. Those ~~20-50 tonne bricks they haul and drop would be costly, but I expect them to make them as strong walled brick shapes, with a lower cost fill - be wise to add salt to limit freezing in cold weather.
        ncmncm 4y ago
        The bricks, anyway, will not happen. It's the dumbest idea I have run across.

A tanker that holds 80,000 pounds of kerosine will hold about 8000 pounds of LH2 in the same dimensionality. 0.07 = density of LH2, Density of water 1.0, kerosine 0.7 +/- varies with grade. So it take 10 times the cubeage plus Dewar grade insulation. At a permeant depot they will have a super refrigerator to condense boil off into LH2. They are trying to get a viable clathrate hydrate to hold a higher density form of bound but not reacted Hydrogen

ncmncm 4y ago
The measure of fuel you need to carry is not weight, but energy content. It takes a much smaller weight of LH2 to match the energy content of diesel. So, correspondingly less than 10x volume. It is this better "gravimetric energy density" that makes LH2 an attractive fuel in many cases. You end up needing only about 2-3x tankage space, including the insulation. Better gravimetric energy density doesn't make so much difference for a train, so its other advantages -- production on-site, zero emissions, carbon-neutral -- are more important. At the trainyard, the LH2 would be banked in an underground tank where insulation is easy. It is not necessary to refrigerate it after it is liquified. It will gradually boil off, so you just make more anytime the level goes down, whether from boil-off or pumping out to a locomotive tank.
- aurizon 4y ago
  There is truth in that energy density. but it is still cheaper energetically to chill boil off to liquid back to the tank that to make new hot hydrogen you then chill to liquid back to the tank. The end game of clathrate storage will solve many of these problems.
  - ncmncm 4y ago
    True, keeping the LH2 below its boiling point is, energetically, strictly cheaper than producing as much new hydrogen as would have boiled off, and then chilling that... But, it incurs the added complexity cost of building refrigeration plumbing into the tank, and maintaining that. That could mean the tank has to be above ground, for easy access (which might be needed anyway). My expectation was that native electrical energy will be cheap enough that wasting some is better than complicating your system. Each tradeoff will be an engineering analysis. In this case it will all depend on how good your insulation is, which is of course better in an underground tank. Many old conventions will be overturned as the marginal cost of electrical power at peak times gets cheaper. Both will be tried, so we will see.
    - aurizon 4y ago
      Yes, flow batteries, gravity batteries and high water storage will all make their presence felt. Those ~~20-50 tonne bricks they haul and drop would be costly, but I expect them to make them as strong walled brick shapes, with a lower cost fill - be wise to add salt to limit freezing in cold weather.
      - ncmncm 4y ago
        The bricks, anyway, will not happen. It's the dumbest idea I have run across.