7 ms·

What about CFS is fishy to you? Those are the guys I'd put my money on, but I'm curious why you'd think otherwise.

by Mizza 5y ago

Retric 5y ago
For me it’s the “seemingly” crazy unrealistic deadlines, which are achievable if they don’t actually try and hit net energy gain. Use 20MW of energy to add 10MW into plasma, get 20MW of fusion, convert 30MW of heat into 10MW of electricity and they have reached their stated goal without actually achieving anything useful. And that’s assuming steady state operation rather than a fraction of a second pulse that briefly reaches their goals. It’s exactly the same thing as a startup selling dollars for pennies and saying yea we’re going to make it up in volume.
- DennisP 5y ago
  ARC will be about the size of JET, and JET was built in four years, with most of that being just for the buildings. The test reactor, SPARC, will be about half that size. Tokamak scaling is very well established. The output scales with the square of plasma volume, and the fourth power of magnetic field strength. Stronger magnetic fields also make the plasma more stable. JET already demonstrated a five-second plasma, which they only had to shut down because they have copper coils that would melt if operated longer than that. Because of all this, many independent fusion researchers think SPARC will succeed in getting 10X gain in 2025. After that, the larger ARC should easily reach commercial levels. Of all the commercial fusion companies, CFS is the most conservative one. Tokamak Energy is a close second, with a very similar approach. The other fusion startups are attempting approaches that have more physics risk, though many of them would have fewer engineering and economic difficulties if the physics does work out.
  - Retric 5y ago
    Simply scaling SPAR or ITER doesn’t result in commercial operation. First you need fuel, global Tritium supplies are tiny and DD fusion is much harder. Next stability is an open question, no Tokamak has ever operated near maximum capacity for even 1 hour. Add to that serious material science questions, etc etc and even Q>100 alone just doesn’t actually mean much. Now let’s just assume all of that is solved, you still need to actually ensure your design is economically viable. Simply producing energy from fusion alone isn’t enough which means you need to cheaply solve not only all the above but do so cheaply.
    - akomtu 5y ago
      Doesn't Moon have immense supplies of tritium? I bet Musk, with his landing rockets, has bigger plans than just launching a bunch of sats.
      - DennisP 5y ago
        Tritium has only a 12-year half-life, and decays to He3. The Moon has large supplies of He3, which could be fuel for more advanced fusion reactors. He3 barely exists on Earth. However, pure deuterium fusion is easier than He3 fusion, and its waste is half He3, half tritium.
        pfdietz 5y ago
        3He on the moon occurs in regolith at a concentration of maybe 10 ppb. At that concentration, simply heating the regolith to drive out the 3He uses more energy than the 3He would produce in fusion, unless extreme heat recycling can be achieved (and good luck transferring heat into/out of powders in vacuum.) Even if it could be recovered, all the 3He on the entire moon might power the world for maybe 100 years.
        DennisP 5y ago
        Thanks, didn't realize the energy balance was so bad. That strengthens the point I was trying to get at, which was that there's no reason to go to the moon for He3 when, if we can get net power from He3, we can just make it in a D-D reactor and gain energy in the process.
        pfdietz 5y ago
        My favorite 3He source would be "Planet X", if it exists and is an Earth (or perhaps even Mars) size planet out far enough that the temperature at the exobase is low enough to retain 3He in its atmosphere. Sure, getting there would be difficult, but this scenario assumes we have D3He fusion, which we can handwave would get the miners out there in a reasonable amount of time.
- nimish 5y ago
  I don't think they'll have SPARC by 2025 but the physics work out. It's basically a bog-standard tokamak with superconducting magnets but with much more current capacity and therefore magnetic field strength from newer HTS. It's the fabrication of the magnets at scale that's totally new engineering and manufacturing; as we saw with Tesla that's quite hard. Plus the supply chains of HTS tapes aren't exactly mature. I think both Tokamak and CFS have roughly the same strategy of using bigger magnetic fields. Given the scalings here https://royalsocietypublishing.org/doi/10.1098/rsta.2017.0437 https://royalsocietypublishing.org/doi/10.1098/rsta.2017.043... + JET working well it's a lot less risk than whatever most others are doing. Make a JET sized tokamak but have 5x the magnetic field strength gives a 625x gain in power, ideally.
  - Retric 5y ago
    I agree with what your saying, but that’s doesn’t mean the end result is even close to an economically viable fusion reactor. Look back in 1990 people could have spend a lot of money building a truly monumental reactor and hitting Q>100 briefly. Nobody suggested that was a good idea because all the other unsolved problems which is why ITER was being built in the first place. The point wasn’t simply to scale it was to test blanket materials etc in an environment very close to a working reactor. SPARK is undoubtedly a more efficient design but it’s not a solution for any of the major outstanding problems.
    - nimish 5y ago
      Of course. They are basically a privately funded research group at this point. No one has any idea how to operate a profitable fusion plant.
- apendleton 5y ago
  By those kinds of metrics, Tokamak Energy haven't "achiev[ed] anything useful" either. Note that both companies are aiming to build a tokamak using high-temperature superconducting coils, which will facilitate energy gain in a small, high-field tokamak. CFS has built the coils, but no tokamak yet. Tokamak Energy has built a tokamak, but it doesn't use HTS coils yet, it uses standard/super-inefficient copper ones (they're developing the HTS coils as a separate project and expect to marry them in a future prototype). This prototype has the same "make it up on volume" problem, it's just lossy in a different way. Both have made important advances that demonstrate critical components that will be necessary to do the full thing, but different ones, and neither of them has demonstrated everything. If anything, CFS's piece is arguably more important, because other copper-magnet high-field tokamaks have been built before (e.g., Alcator C-Mod at MIT, essentially the predecessor to CFS's prototype), but nobody has built a full-sized HTS coil before.
  - Retric 5y ago
    I am all for fusion research, in the context of research. But CFS’s short term goals comes off as a publicity stunt which rubs me the wrong way. Like IBM’s Watson playing Jeopardy etc, where what’s achieved seems like a breakthrough for non exports. It’s possible they could succeed long term, but I don’t think it’s particularly likely.
    - apendleton 5y ago
      Sure, I think that's valid. I just don't think Tokamak Energy's announcement is less of a stunt. They've both made progress on a well-defined but ultimately not-that-big piece of a big pie. Just different pieces. If the act of making big press pronouncements around incremental progress is a stunt, they all do it.
    - willis936 5y ago
      I hardly view "build a machine to understanding burning plasmas and steady-state tokamak operation" as a publicity stunt. These are hard machines to build in the best of conditions. The design of any power plant must be informed of results from machines like SPARC.

What about CFS is fishy to you? Those are the guys I'd put my money on, but I'm curious why you'd think otherwise.

by Mizza 5y ago

What about CFS is fishy to you? Those are the guys I'd put my money on, but I'm curious why you'd think otherwise.

For me it’s the “seemingly” crazy unrealistic deadlines, which are achievable if they don’t actually try and hit net energy gain. Use 20MW of energy to add 10MW into plasma, get 20MW of fusion, convert 30MW of heat into 10MW of electricity and they have reached their stated goal without actually achieving anything useful. And that’s assuming steady state operation rather than a fraction of a second pulse that briefly reaches their goals. It’s exactly the same thing as a startup selling dollars for pennies and saying yea we’re going to make it up in volume.

DennisP 5y ago
ARC will be about the size of JET, and JET was built in four years, with most of that being just for the buildings. The test reactor, SPARC, will be about half that size. Tokamak scaling is very well established. The output scales with the square of plasma volume, and the fourth power of magnetic field strength. Stronger magnetic fields also make the plasma more stable. JET already demonstrated a five-second plasma, which they only had to shut down because they have copper coils that would melt if operated longer than that. Because of all this, many independent fusion researchers think SPARC will succeed in getting 10X gain in 2025. After that, the larger ARC should easily reach commercial levels. Of all the commercial fusion companies, CFS is the most conservative one. Tokamak Energy is a close second, with a very similar approach. The other fusion startups are attempting approaches that have more physics risk, though many of them would have fewer engineering and economic difficulties if the physics does work out.
- Retric 5y ago
  Simply scaling SPAR or ITER doesn’t result in commercial operation. First you need fuel, global Tritium supplies are tiny and DD fusion is much harder. Next stability is an open question, no Tokamak has ever operated near maximum capacity for even 1 hour. Add to that serious material science questions, etc etc and even Q>100 alone just doesn’t actually mean much. Now let’s just assume all of that is solved, you still need to actually ensure your design is economically viable. Simply producing energy from fusion alone isn’t enough which means you need to cheaply solve not only all the above but do so cheaply.
  - akomtu 5y ago
    Doesn't Moon have immense supplies of tritium? I bet Musk, with his landing rockets, has bigger plans than just launching a bunch of sats.
    - DennisP 5y ago
      Tritium has only a 12-year half-life, and decays to He3. The Moon has large supplies of He3, which could be fuel for more advanced fusion reactors. He3 barely exists on Earth. However, pure deuterium fusion is easier than He3 fusion, and its waste is half He3, half tritium.
      - pfdietz 5y ago
        3He on the moon occurs in regolith at a concentration of maybe 10 ppb. At that concentration, simply heating the regolith to drive out the 3He uses more energy than the 3He would produce in fusion, unless extreme heat recycling can be achieved (and good luck transferring heat into/out of powders in vacuum.) Even if it could be recovered, all the 3He on the entire moon might power the world for maybe 100 years.
        DennisP 5y ago
        Thanks, didn't realize the energy balance was so bad. That strengthens the point I was trying to get at, which was that there's no reason to go to the moon for He3 when, if we can get net power from He3, we can just make it in a D-D reactor and gain energy in the process.
        pfdietz 5y ago
        My favorite 3He source would be "Planet X", if it exists and is an Earth (or perhaps even Mars) size planet out far enough that the temperature at the exobase is low enough to retain 3He in its atmosphere. Sure, getting there would be difficult, but this scenario assumes we have D3He fusion, which we can handwave would get the miners out there in a reasonable amount of time.
nimish 5y ago
I don't think they'll have SPARC by 2025 but the physics work out. It's basically a bog-standard tokamak with superconducting magnets but with much more current capacity and therefore magnetic field strength from newer HTS. It's the fabrication of the magnets at scale that's totally new engineering and manufacturing; as we saw with Tesla that's quite hard. Plus the supply chains of HTS tapes aren't exactly mature. I think both Tokamak and CFS have roughly the same strategy of using bigger magnetic fields. Given the scalings here https://royalsocietypublishing.org/doi/10.1098/rsta.2017.0437 https://royalsocietypublishing.org/doi/10.1098/rsta.2017.043... + JET working well it's a lot less risk than whatever most others are doing. Make a JET sized tokamak but have 5x the magnetic field strength gives a 625x gain in power, ideally.
- Retric 5y ago
  I agree with what your saying, but that’s doesn’t mean the end result is even close to an economically viable fusion reactor. Look back in 1990 people could have spend a lot of money building a truly monumental reactor and hitting Q>100 briefly. Nobody suggested that was a good idea because all the other unsolved problems which is why ITER was being built in the first place. The point wasn’t simply to scale it was to test blanket materials etc in an environment very close to a working reactor. SPARK is undoubtedly a more efficient design but it’s not a solution for any of the major outstanding problems.
  - nimish 5y ago
    Of course. They are basically a privately funded research group at this point. No one has any idea how to operate a profitable fusion plant.
apendleton 5y ago
By those kinds of metrics, Tokamak Energy haven't "achiev[ed] anything useful" either. Note that both companies are aiming to build a tokamak using high-temperature superconducting coils, which will facilitate energy gain in a small, high-field tokamak. CFS has built the coils, but no tokamak yet. Tokamak Energy has built a tokamak, but it doesn't use HTS coils yet, it uses standard/super-inefficient copper ones (they're developing the HTS coils as a separate project and expect to marry them in a future prototype). This prototype has the same "make it up on volume" problem, it's just lossy in a different way. Both have made important advances that demonstrate critical components that will be necessary to do the full thing, but different ones, and neither of them has demonstrated everything. If anything, CFS's piece is arguably more important, because other copper-magnet high-field tokamaks have been built before (e.g., Alcator C-Mod at MIT, essentially the predecessor to CFS's prototype), but nobody has built a full-sized HTS coil before.
- Retric 5y ago
  I am all for fusion research, in the context of research. But CFS’s short term goals comes off as a publicity stunt which rubs me the wrong way. Like IBM’s Watson playing Jeopardy etc, where what’s achieved seems like a breakthrough for non exports. It’s possible they could succeed long term, but I don’t think it’s particularly likely.
  - apendleton 5y ago
    Sure, I think that's valid. I just don't think Tokamak Energy's announcement is less of a stunt. They've both made progress on a well-defined but ultimately not-that-big piece of a big pie. Just different pieces. If the act of making big press pronouncements around incremental progress is a stunt, they all do it.
  - willis936 5y ago
    I hardly view "build a machine to understanding burning plasmas and steady-state tokamak operation" as a publicity stunt. These are hard machines to build in the best of conditions. The design of any power plant must be informed of results from machines like SPARC.