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With very-high-temperature reactors (one of potential paths for Generation IV reactors) you can produce hydrogen using reactor heat directly, bypassing the elec

• 7952 5y ago
  Oh I absolutely agree that nuclear is a brilliant choice for hydrogen production. And presumably it would allow nuclear to adjust electricity output whilst maintaining high utilisation and profitability. But still I think there is a mistake in assuming that everything needs to be tightly coupled. The benefit of an electricity grid and storable fuels is that you have flexibility.
  • pfdietz 5y ago
    How is nuclear a brilliant choice for hydrogen production? Hydrogen provides inherent storage, so energy sources will (aside from cost of electrolysers) be competing based on levelized cost -- and levelized cost of new nuclear sucks. High temperature electrolysis doesn't change this: it reduces the electrical power needed by maybe 25%, at the cost of a nuclear reactor that has to operate at 1000 C with all the material problems that implies (there's a reason LWRs won and HTGC reactors did not.)
    • 7952 5y ago
      I don't have the expertise to answer that at a technical level. I think it could be a good choice because it would help balance out intermittent sources like wind and solar. And give alternative revenue streams for nuclear power.
      • pfdietz 5y ago
        If it balances out renewables, it also then pushes new nuclear entirely out of the picture.
        • 7952 5y ago
          I don't see why. Currently you would subsidise a nuclear power station because it provides reliable capacity that you may not need. The customer is created artificially by the market. But if you can link nuclear with hydrogen production the customer is not artificial anymore. You could provide guarantees about future hydrogen prices instead and still get the capacity. You then get a product that helps to decarbonise other parts of the economy.
          • pfdietz 5y ago
            It pushes out new nuclear because the levelized cost of new nuclear is much higher than the levelized cost of wind/solar. And with highly dispatchable demand, levelized cost is what matters. Why should someone who wants hydrogen buy expensive nuclear electricity when they can use much cheaper renewable electricity?
• taubek 5y ago
  Is then hydrogen liquefied? I remember reading somewhere that hydrogen requires pretty heavy/thick containers for storage. Does it need to be kept at low temperatures?
  • fuoqi 5y ago
    The Haber-Bosch process used in ammonia production is done at high temperatures (400-500 °C), so you can use "hot" hydrogen to power it (i.e. to heat input nitrogen) and maybe even extract some of leftover energy in produced ammonia heat to generate electricity. Same with steel production, you don't need to cool hydrogen before using it, on the contrary, high temperatures are useful in such cases. Using "hot" hydrogen would mean that you have to build ammonia and steel plants right near nuclear reactors, which can be somewhat difficult, but potential efficiency benefits could be big enough to offset it.
    • pfdietz 5y ago
      HB consumes energy in its compressors, but releases that energy as heat on the catalyst. Hot hydrogen doesn't compress well, so you'd cool it beforehand.
      • fuoqi 5y ago
        For HB you need pressure of 250-350 bars, while existing PWRs routinely work with 150 bars of coolant pressure. I assume it's possible to produce hydrogen with the necessary pressure using VHTRs, i.e. you would get hydrogen already pressurized and hot. You would still need to run compressors on input water, but it's much easier than working with hydrogen later.
        • pfdietz 5y ago
          Producing hydrogen at pressure doesn't eliminate the energy needed, it just forces the electrolyser to act as the compressor (the voltage goes up).
          • 5y ago