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I disagree with your statement about hydrogen. Hydrogen's killer app is usage for huge vehicles, basically ships, trains and mining trucks. The main issue with

I disagree with your statement about hydrogen. Hydrogen's killer app is usage for huge vehicles, basically ships, trains and mining trucks. The main issue with hydrogen is not the volumetric density compared to hydrocarbons: hydrocarbons produce emissions and hydrogen doesn't. The main issue is storage, and for that the square-cube law helps. If your application can make use of huge tanks, then the cost of storage becomes negligible. Nuclear-powered shipping is and will remain a non-starter for the simple reason that pirates exist and will continue to exist. Even if pirates didn't exist, rogue states, like the Houthis, or Iran, or North Korea do exist. You'd basically need to escort each nuclear powered ship with a warship, and the cost would be too high.

Manuel_D 3y ago
Liquid hydrogen is less than 1/3 the energy density of diesel by volume: https://upload.wikimedia.org/wikipedia/commons/thumb/c/c6/Energy_density.svg/1920px-Energy_density.svg.png https://upload.wikimedia.org/wikipedia/commons/thumb/c/c6/En... Liquid hydrogen also has difficulties in terms of converting that energy into work. It burns really hot, and produces nitrous oxides (which are greenhouse gases) in combustion engines. It can produce electricity via a fuel cell, but doing that at large scale has never been done. Nuclear powered ships are probably expensive enough that arming them is not super expensive. North Korea already has nukes, and pirates are usually just equipped with small arms. Again nuclear powered shipping has already existed for decades. The better part of a century, in fact. Piracy and rogue states have not been a problem.
- credit_guy 3y ago
  > Liquid hydrogen is less than 1/3 the energy density of diesel by volume Yes, but in a ship volume is not a concern. > Liquid hydrogen also has difficulties in terms of converting that energy into work Check [1] out. Current diesel engines can be retrofitted to burn a mix of diesel and hydrogen that reduces emissions by 86%. “If you just put hydrogen into the engine and let it all mix together you will get a lot of nitrogen oxide (NOx) emissions, which is a significant cause of air pollution and acid rain,” Prof. Kook says. “But we have shown in our system if you make it stratified – that is in some areas there is more hydrogen and in others there is less hydrogen – then we can reduce the NOx emissions below that of a purely diesel engine.” > Again nuclear powered shipping has already existed for decades. The better part of a century, in fact. Piracy and rogue states have not been a problem. Nuclear powered warships have existed for decades. Civilian nuclear power ships were a rarity. Most were Russian icebreakers, operating in the arctic, where pirates are quite hard to find. The idea you are proposing is to start putting nuclear reactors on thousands of ships that would criss-cross the world's oceans on a daily basis. It's just not going to happen. And if you want to put them only on a handful, why bother? They won't make a dent in the emissions. [1] https://newsroom.unsw.edu.au/news/science-tech/new-system-retrofits-diesel-engines-run-90-cent-hydrogen https://newsroom.unsw.edu.au/news/science-tech/new-system-re...
  - elzbardico 3y ago
    Russia still operates and builds nuclear icebreakers.
  - _aavaa_ 3y ago
    > Current diesel engines can be retrofitted to burn a mix of diesel and hydrogen that reduces emissions by 86%. There is a large gulf between something that has worked in a research lab once and something that is ready to be commercialized and ready to be implemented in a working ship. Further, unless they have a way of producing carbon-free hydrogen at all the ports that this ship would have to dock at, then it won't be saving us CO2 emissions.
    - credit_guy 3y ago
      > There is a large gulf between something that has worked in a research lab once and something that is ready to be commercialized and ready to be implemented in a working ship. Your point is correct generally speaking. But here we are comparing modifying a combustion engine to make it burn hydrogen, versus modifying a ship to make it run on nuclear power. Which gap do you think is wider?
      - _aavaa_ 3y ago
        Given that there already exist many military ships running on nuclear reactors, the gap for one is smaller than you imply.
- baybal2 3y ago
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Manuel_D 3y ago

Liquid hydrogen is less than 1/3 the energy density of diesel by volume: https://upload.wikimedia.org/wikipedia/commons/thumb/c/c6/Energy_density.svg/1920px-Energy_density.svg.png https://upload.wikimedia.org/wikipedia/commons/thumb/c/c6/En... Liquid hydrogen also has difficulties in terms of converting that energy into work. It burns really hot, and produces nitrous oxides (which are greenhouse gases) in combustion engines. It can produce electricity via a fuel cell, but doing that at large scale has never been done. Nuclear powered ships are probably expensive enough that arming them is not super expensive. North Korea already has nukes, and pirates are usually just equipped with small arms. Again nuclear powered shipping has already existed for decades. The better part of a century, in fact. Piracy and rogue states have not been a problem.

credit_guy 3y ago
> Liquid hydrogen is less than 1/3 the energy density of diesel by volume Yes, but in a ship volume is not a concern. > Liquid hydrogen also has difficulties in terms of converting that energy into work Check [1] out. Current diesel engines can be retrofitted to burn a mix of diesel and hydrogen that reduces emissions by 86%. “If you just put hydrogen into the engine and let it all mix together you will get a lot of nitrogen oxide (NOx) emissions, which is a significant cause of air pollution and acid rain,” Prof. Kook says. “But we have shown in our system if you make it stratified – that is in some areas there is more hydrogen and in others there is less hydrogen – then we can reduce the NOx emissions below that of a purely diesel engine.” > Again nuclear powered shipping has already existed for decades. The better part of a century, in fact. Piracy and rogue states have not been a problem. Nuclear powered warships have existed for decades. Civilian nuclear power ships were a rarity. Most were Russian icebreakers, operating in the arctic, where pirates are quite hard to find. The idea you are proposing is to start putting nuclear reactors on thousands of ships that would criss-cross the world's oceans on a daily basis. It's just not going to happen. And if you want to put them only on a handful, why bother? They won't make a dent in the emissions. [1] https://newsroom.unsw.edu.au/news/science-tech/new-system-retrofits-diesel-engines-run-90-cent-hydrogen https://newsroom.unsw.edu.au/news/science-tech/new-system-re...
- elzbardico 3y ago
  Russia still operates and builds nuclear icebreakers.
- _aavaa_ 3y ago
  > Current diesel engines can be retrofitted to burn a mix of diesel and hydrogen that reduces emissions by 86%. There is a large gulf between something that has worked in a research lab once and something that is ready to be commercialized and ready to be implemented in a working ship. Further, unless they have a way of producing carbon-free hydrogen at all the ports that this ship would have to dock at, then it won't be saving us CO2 emissions.
  - credit_guy 3y ago
    > There is a large gulf between something that has worked in a research lab once and something that is ready to be commercialized and ready to be implemented in a working ship. Your point is correct generally speaking. But here we are comparing modifying a combustion engine to make it burn hydrogen, versus modifying a ship to make it run on nuclear power. Which gap do you think is wider?
    - _aavaa_ 3y ago
      Given that there already exist many military ships running on nuclear reactors, the gap for one is smaller than you imply.
baybal2 3y ago
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