4 ms·

I don't believe that this is entirely mis-stated. We already know that fusion power plants are going to operate by igniting plasma in short bursts -- a few sec

by SamBam 5y ago

I don't believe that this is entirely mis-stated. We already know that fusion power plants are going to operate by igniting plasma in short bursts -- a few seconds, maybe 10s at most -- and generating a huge amount of power during that single burst. You then ignite it again and again. The question is how much total energy you can extract from each of those bursts. By that metric, the total energy is what's important, not the power. Producing 10 quadrillion watts of power isn't that useful if it's only for 100 trillionths of a second. (Both numbers pulled from an actual recent result last August. [1]) "59 megajoules of sustained fusion energy" means a single burst produced that much. That's significantly more than the paltry 1.3MJ from that other result I just linked to. Yes, of course you could get that much from a wall socket over the course of hours, but we know we haven't been able to sustain a fusion reaction for a few seconds, so that's the timeframe we're talking about for a single burst. 1. https://www.livescience.com/fusion-experiment-record-breaking-energy.html https://www.livescience.com/fusion-experiment-record-breakin... EDIT: And, at the bottom of the article it says that the reaction ran at 11MW, so plugging that in it sounds like, indeed, it ran for 5 seconds.

robbomacrae 5y ago
Your description made me wonder if it would be possible to make an ICE to extract the power. I then found a paper called Fusion Internal Combustion Engine from 2010 [0]. Does anyone know if there was any merit to this idea and if anything else has come of it since? 0: https://www.researchgate.net/publication/215544178_Fusion_Internal_Combustion_Engine https://www.researchgate.net/publication/215544178_Fusion_In...
- lisper 5y ago
  A few elementary calculations reveal how feasible this might be. A typical ICE produces a few hundred horsepower using 4-8 cylinders rotating at a few thousand RPM. 1 HP = 745 watts. Figure out how much energy is released per cylinder on each cycle, and compare that to the energy released in a typical fusion ignition. Also note the cycle time of an ICE rotating at a few thousand RPMs, and compare that to the cycle time of a current state-of-the-art fusion reactor. (Hint: the former is measured in milliseconds, the latter currently in months if not years.)
  - robbomacrae 5y ago
    I'm a layman and so its possible I am missing some limiting factors but I do feel as though this rebuttal does not take into account the possible ranges of values that can be configured when tweaking things like scale and operating speed. For example the Wärtsilä-Sulzer RTA96-C operates at 15-102 RPM generating 100,000 HP (or 74.5 megawatts for your comparison) [0]. Nor does it take into account the difference between a prototype investigation being constantly modified for experimentation and analysis and a production system built to purpose. 0: https://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA96-C https://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA9...
    - lisper 5y ago
      Yes, I probably should have used numbers from a large diesel rather than an automobile engine. Wow, the Wärtsilä-Sulzer RTA96-C operates at speeds as low as 15 RPM! That is just mind-boggling. I found this video: https://www.youtube.com/watch?v=jXHvY-zY9hA https://www.youtube.com/watch?v=jXHvY-zY9hA Still, I think you will find that even this doesn't help all that much. A cycle time measured in seconds rather than milliseconds is still orders of magnitude away from what can presently be achieved. > the difference between a prototype investigation being constantly modified for experimentation and analysis and a production system built to purpose. AFAICT, no one has ever built an ICE that is within even an order of magnitude of realistic operating parameters of a fusion ICE. It's a whole 'nuther level of engineering challenge beyond just getting the fusion itself to work. I'm not saying it's impossible, but I'll give you long odds against seeing it happen in any of our lifetimes.
lisper 5y ago
> "59 megajoules of sustained fusion energy" means a single burst produced that much. In what sense is that "sustained"? A typical power plant produces that much energy in less than a second on a continuous (i.e. sustained) basis. Producing 59 megajoules once is basically a joke. It is analogous to detonating a pipe bomb (at a cost of several billion dollars) and claiming that as significant progress towards an internal combustion engine.
- rat9988 5y ago
  > A typical power plant Fusion power plant aren't typical though
  - lisper 5y ago
    Yes, that is exactly the problem. If they are ever going to be commercially viable they need to become typical. 59MJ per cycle isn't going to do you a lot of good if a cycle time is measured in months as is currently the case. You have to get that cycle time down to fractions of a second at this energy level before you even have a chance at commercial viability. 59 MJ is a tiny amount of energy by the standards of commercial power generation.
    - exitheone 5y ago
      I hope you realize that these are research reactors that are not designed to give you a low interval between cycles or produce power. They are meant so clarify some of the open research questions for the likes of ITER/DEMO that will integrate these findings into things that are actually designed to produce a lot more power quicker.
      - lisper 5y ago
        Yes, of course I realize that. I hope you realize that even if they get these research reactors to work (which is far from given) that there will still be a shit ton of work to be done before this technology can be used to produce commercially viable power.

by SamBam 5y ago

robbomacrae 5y ago

Your description made me wonder if it would be possible to make an ICE to extract the power. I then found a paper called Fusion Internal Combustion Engine from 2010 [0]. Does anyone know if there was any merit to this idea and if anything else has come of it since? 0: https://www.researchgate.net/publication/215544178_Fusion_Internal_Combustion_Engine https://www.researchgate.net/publication/215544178_Fusion_In...

lisper 5y ago
A few elementary calculations reveal how feasible this might be. A typical ICE produces a few hundred horsepower using 4-8 cylinders rotating at a few thousand RPM. 1 HP = 745 watts. Figure out how much energy is released per cylinder on each cycle, and compare that to the energy released in a typical fusion ignition. Also note the cycle time of an ICE rotating at a few thousand RPMs, and compare that to the cycle time of a current state-of-the-art fusion reactor. (Hint: the former is measured in milliseconds, the latter currently in months if not years.)
- robbomacrae 5y ago
  I'm a layman and so its possible I am missing some limiting factors but I do feel as though this rebuttal does not take into account the possible ranges of values that can be configured when tweaking things like scale and operating speed. For example the Wärtsilä-Sulzer RTA96-C operates at 15-102 RPM generating 100,000 HP (or 74.5 megawatts for your comparison) [0]. Nor does it take into account the difference between a prototype investigation being constantly modified for experimentation and analysis and a production system built to purpose. 0: https://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA96-C https://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA9...
  - lisper 5y ago
    Yes, I probably should have used numbers from a large diesel rather than an automobile engine. Wow, the Wärtsilä-Sulzer RTA96-C operates at speeds as low as 15 RPM! That is just mind-boggling. I found this video: https://www.youtube.com/watch?v=jXHvY-zY9hA https://www.youtube.com/watch?v=jXHvY-zY9hA Still, I think you will find that even this doesn't help all that much. A cycle time measured in seconds rather than milliseconds is still orders of magnitude away from what can presently be achieved. > the difference between a prototype investigation being constantly modified for experimentation and analysis and a production system built to purpose. AFAICT, no one has ever built an ICE that is within even an order of magnitude of realistic operating parameters of a fusion ICE. It's a whole 'nuther level of engineering challenge beyond just getting the fusion itself to work. I'm not saying it's impossible, but I'll give you long odds against seeing it happen in any of our lifetimes.

lisper 5y ago

> "59 megajoules of sustained fusion energy" means a single burst produced that much. In what sense is that "sustained"? A typical power plant produces that much energy in less than a second on a continuous (i.e. sustained) basis. Producing 59 megajoules once is basically a joke. It is analogous to detonating a pipe bomb (at a cost of several billion dollars) and claiming that as significant progress towards an internal combustion engine.

rat9988 5y ago
> A typical power plant Fusion power plant aren't typical though
- lisper 5y ago
  Yes, that is exactly the problem. If they are ever going to be commercially viable they need to become typical. 59MJ per cycle isn't going to do you a lot of good if a cycle time is measured in months as is currently the case. You have to get that cycle time down to fractions of a second at this energy level before you even have a chance at commercial viability. 59 MJ is a tiny amount of energy by the standards of commercial power generation.
  - exitheone 5y ago
    I hope you realize that these are research reactors that are not designed to give you a low interval between cycles or produce power. They are meant so clarify some of the open research questions for the likes of ITER/DEMO that will integrate these findings into things that are actually designed to produce a lot more power quicker.
    - lisper 5y ago
      Yes, of course I realize that. I hope you realize that even if they get these research reactors to work (which is far from given) that there will still be a shit ton of work to be done before this technology can be used to produce commercially viable power.