8 ms·

Nuclear Fusion's New Idea: An Off-the-Shelf Stellarator

114 points by mfiguiere 2y ago

rgmerk 2y ago
Cool. But even if you have a working stellarator that's a very long way from an economically viable energy source. You've still got to a) figure out how to cheaply convert the released energy into electricity (and the baseline way of doing that in D-T fusion is...a steam turbine), and b) figure out materials that can survive the radiation bombardment for a sufficiently long time. In sunny places (and I fully acknowledge that's not all of the world) it's still going to be hard to beat sticking bits of special glass out in a field and connecting wires to it. But we should sure as heck keep tinkering away at it!
- tomxor 2y ago
  I don't think the point of this project is to be closer to economic viability, but to demonstrate an approach that would lead to faster economic viability due to allowing faster iteration and evaluation of small scale experimental designs. In HN terms they are demonstrating a significantly faster REPL by keeping the project small and minimising use of esoteric or highly bespoke components. It's the closest you can get to building your own stellarator by walking into radioshack. I think it's a pretty cool idea.
  - rgmerk 2y ago
    Yep, sure. And that's great.
- dexwiz 2y ago
  Newer solar panels don’t need full sun to function. It’s economically viable to place them further north and in cloudier climates now. So the area where these are alternatives are viable may be shrinking faster than you would expect.
  - rgmerk 2y ago
    Indeed, though in colder climates you do have the problem that peak electricity demand is precisely when you get minimum solar production. But in sunnier, warmer parts of the world (which notably includes India, Pakistan, Bangladesh, Indonesia, Nigeria, Egypt, Ethiopia, Iran, Mexico, and Brazil, amongst others), over the next few decades it's hard to see anything much competing against solar and batteries for the bulk of energy usage.
    - bkor 2y ago
      > But in sunnier, warmer parts of the world Though solar panels prefer if it isn't too hot. Still, any such inefficiencies are easily outweighed by their low cost. In Netherlands it is common to install practice (and advised) more Wp than the inverter can handle. Maybe also a solution if it gets too hot, make it up by having more panels.
    - thehappypm 2y ago
      That isn’t true yet, because most cold places don’t use electricity for heating; in Boston for example the norm is oil or gas furnaces. Europe typically uses gas for heating, as we all learned during the Ukraine war’s beginning. When I lived in the Boston area, our electricity use, peaked in the summer during air-conditioning season. That is, until we got a heat pump, then our electricity spiked like crazy in the winter. but we are long way from having the majority of homeowners using heat pumps for their primary heat source. (Also heat pumps are kinda awful compared to furnaces in my experience so we might never get there).
      - smolder 2y ago
        >heat pumps are kinda awful Heat pumps work great under the right circumstances. In cold climates like Boston and north of it, ideally you want ground source, which means digging deep (or wide) holes to flow water through instead of just pulling heat from outside air. Alternatively, (or additionally, ideally) they're best used in homes with very tight air envelopes, good insulation, and heat/energy recovery ventilation (HRV/ERV) systems. Installed in radiant heating systems in well-built houses, heat pumps are fantastic and you'll be comfortable all year for pennies on the dollar. The reality is that most (US) construction, especially older, is just terrible in terms of air seal and insulation. Couple that with a potentially undersized air-source heat pump, which gets inefficient as the outside temp gets near the low end of its operating range, and you will not have a great time. But even then they are a good way to supplement gas heating, so you can limit furnace use to the coldest weeks of the year and do the environment a favor, as well as cool in the summer.
- deleted 2y ago
  [deleted]
- fragmede 2y ago
  Not sure why steam engine is written like it's some crazy reveal. It's the accepted way of doing it in most other fossile fuel plants, to the point that there's a saying for it - someone, somewhere X is boiling water so you can boil water. There are other designs that have been proposed, but I'm not aware of anything in production that takes heat and turn it into electricity at powerplant scale. Eg RTGs exist, but only if you need a computer power supply's worth of power for decades.
  - ZeroGravitas 2y ago
    Perhaps because the steam part alone, even if powered by pixie dust and magic, can't compete on price with solar, and probably solar and batteries either (varies with latitude and time but the cost is going down and the latitude is getting wider). I think OpenAI is investing into a fusion design that avoids steam for exactly this reason, so it's not just an anti-nuclear talking point.
- slightwinder 2y ago
  > In sunny places (and I fully acknowledge that's not all of the world) it's still going to be hard to beat sticking bits of special glass out in a field and connecting wires to it. Why not both? Can't we utilize the special glass to fetch energy from a man-made fusion reactor, in similar ways as we use it to fetch energy from the natural fusion reactor in space?
  - pyrale 2y ago
    Treating this as a serious question: because the big reactor in the sky has a built-in gravity well and a very big sphere of vacuum that works as a free containment system while still letting just enough energy out to be useful. Also we don’t need to refill it or handle the spent fuel.
  - nine_k 2y ago
    No. D + T or D + D fusion reaction produces neutrons and hard gamma radiation. The special glass cannot capture the energy of these directly. The natural fusion reactor has a blanket that is literally thousands of kilometers thick. It effectively converts much of this into longer-wavelength electromagnetic radiation, from ultraviolet to infrared, with quite some visible light. That's what the special glass can make use of. Also, the highly radioactive blanket is kept hundreds of millions km away from consumers, which helps alleviate the problem of disposing of radioactive waste. With a planet-based fusion reactor, we'd have to think where to put thousands and thousands of tons of slightly radioactive concrete which would realistically serve as a blanket.
  - thehappypm 2y ago
    In theory, yes. Those are called radiovoltaics and are being researched.
- lupusreal 2y ago
  Steam turbines are very good at what they do, so I don't think that's the problem. Turbines are well understood technology so they're they're the major impediment to economic viability then everything else must be working amazing. I do think economic viability will be a major problem though. The fusion hype crowd focus on Q>1 being their major milestone but that's still a long way away from it being profitable to operate a fusion plant.
  - nine_k 2y ago
    IIRC, a cascade of turbines, going from high-temperature water steam to basically room-temperature ammonia, can reach a total efficiency exceeding 50%. Of course, ammonia is chemically active, and water at 700K is also chemically active, so the turbines, as usual, require special metallurgy and regular maintenance.
    - rgmerk 2y ago
      Sure, but your cascade of turbines isn't free. The capital cost of just the turbines is enough to make it hard to compete with solar and batteries in many situations.
  - rgmerk 2y ago
    Turbines are indeed very well understood and mature technology, and even where the fuel is almost free and the reactor (a coal burner) is cheap, steam turbines are too expensive to compete with solar electricity in most places now.
- johnea 2y ago
  That's all just good money after bad. How many more trillion $$$ are going to be pissed away on this? I'd say, shelve the idea for 50 to 75 years and then look at it again. In the mean time, I think we could make major headway on a global elecrtic grid, that connects whatever part of the planet is sunny with all the rest. Add to this some major storage capacity, and I think we could resolve almost all of our energy problems with the money that would be wasted on further fusion efforts.
King-Aaron 2y ago
I admittedly don't know much about fusion reactors, but I do love that the thing which you create a star within is called a "Stellarator".
credit_guy 2y ago
People don't understand the fundamental problem of fusion. It's a problem of energy loss. Of enormous energy losses. Roughly speaking energy can be mechanical, for particles or radiative, for photons. The first one is proportional to the temperature (the famous NRT) and the second is proportional to the fourth power of the temperature. The constant of proportionality is very small, and at regular temperatures we generally don't think of it that much. But at millions of degrees Kelvin, it starts to dominate all considerations. The heat always moves form hot to cold. In the case of particles the heat flow is proportional to the difference in temperature, and in the case of radiation with the difference in temperature to the power 4. But heat also travels from particles to photons and vice-versa. It doesn't matter how. The problem with fusion is now this. Suppose that you have a super-duper device, let's call it brompillator. It brings an amount of deuterium-tritium mix at the required temperature, let's say 10 million Kelvin. Now that volume of plasma is surrounded by cold stuff. You can imagine that you have some mirrors, or magnetic fields, or some magic stuff, but the cold hard stuff is that that plasma will want to radiate to the exterior and the flow of heat would be proportional to the surface area times the fourth power of the difference in temperature. Since for all practical purposes the outer temperature is zero, we are talking about the fourth power of 10 million Kelvin. Now that constant of porportionality is very small, it is called the Stefan-Boltzman constant and has a value of about 10^7 W m^-2 K^-4. Let's say the surface area is 1 square meter. So the heat loss happens at a rate of 10^-7 times (10^7)^4 = 10^21 Watts. That is 10^12 GigaWatts. One GW is the output of a decent sized nuclear power plant. Of course, you can try to shield that plasma, but that shield has to be 99.99999....9% effective, where the number of 9s needs to be about 15 or so. That is the immensity of the challenge that nobody is willing to tell you about. How was this overcome in the case of the thermonuclear bomb? People imagine that once you have a fission bomb, you just put some deuterium-tritium mix next to it, and voila, you have a fusion bomb. No. The world's greatest minds have worked at this issue for about 5 years. The solution was something like this: if you first compress significantly the volume of fusion fuel, then the heat losses are much smaller (remember they are proportional to the area, and that's proportional to the square of the radius). They will still be tremendous, but you don't even aim to keep the reaction going for a long time. The duration of the fusion reaction in a thermonuclear bomb is still classified information, but public sources put it at the order of 1 microsecond. The heat losses are still tremendous, but for a short moment the heat gains from the fusion reaction are even greater, so ignition is achieved. In the NIF experiment that achieved more than breakeven 2 years ago, the fusion lasted less than 10 nanoseconds [1]. If someone thinks the brompillator will achieve fusion and that will run for years, or even hours, or seconds, they don't understand the fundamental problem. Unfortunately, nobody is willing to ask hard questions about this, not even Sabine Hossenfelder. [1] https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.132.065102 https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.132.065...
BenFranklin100 2y ago
“PPPL researchers say their simpler machine demonstrates a way to build stellarators far more cheaply and quickly, allowing researchers to easily test new concepts for future fusion power plants.” This quote reminded of the SpaceX’s approach to engineering and why they have leapfrogged past Boeing. Instead of spending 10-20 years and billions into a single design, SpaceX iterates.
- deleted 2y ago
  [deleted]
jayyhu 2y ago
The actual paper describing the construction of the MUSE Stellarator: https://www.cambridge.org/core/journals/journal-of-plasma-physics/article/design-and-construction-of-the-muse-permanent-magnet-stellarator/3028EBD0A22067E0ECE1EF22D9725BFF https://www.cambridge.org/core/journals/journal-of-plasma-ph...
deleted 2y ago
[deleted]
timoth3y 2y ago
I'm having trouble understanding what's actually been accomplished here. The article provides a good overview of Tokamak vs Stellarator, but seems to jump back and forth between proclaiming this as an innovative breakthrough and saying it's just a framework to test ideas. > In terms of its ability to confine particles, Muse is two orders of magnitude better than any stellarator previously built Is it? It doesn't seem as if they have reached first plasma or have plans to do so anytime soon. Using electromagnets to not only confine but also to control the the plasma is a big selling point of the stellarator design, and they don't seem to address this. This seems really cool, and I love the idea of lower-cost fusion. (Or even just functional fusion.) There are about a dozen companies making real progress in fusion, but I can't quite figure out what this team has actually accomplished. What am I missing?
- klysm 2y ago
  The struggle for funding can explain a lot of things
- ElevenLathe 2y ago
  Seems like the premise is that building these small experimental stellarators is a major cost in doing fusion research and therefore if we can bring the cost of these down from billions to less than a million, more teams can do more research faster, even if this specific design never generates any economic power. I have no idea if this premise is true or not -- I'm just a layman who read the article.
doricksnri 2y ago
I want to like this but at break even temperatures these things just melt. How about making ship stones from nuclear waste? You could make car engine sized batteries that would effectively last for years if properly shielded and which would provide essentially free power to run a dozen homes.
trhway 2y ago
how one can estimate a progress of a given design? For example on the photo there are no walls protecting the people in the lab from neutrons. Even the fusor 60 years ago running at 100KV already generated neutron flux requiring such walls.
- pbmonster 2y ago
  There's absolutely no way to get fusion with permanent magnets and copper coils. This is a plasma test stand, and because it is so simple, you can potentially quickly iterate through different field configurations. This is at least a little bit useful, because a full Stellerator is extremely complicated to take apart, so you can't just change the coils around if you want to change something.

114 points by mfiguiere 2y ago

Cool. But even if you have a working stellarator that's a very long way from an economically viable energy source. You've still got to a) figure out how to cheaply convert the released energy into electricity (and the baseline way of doing that in D-T fusion is...a steam turbine), and b) figure out materials that can survive the radiation bombardment for a sufficiently long time. In sunny places (and I fully acknowledge that's not all of the world) it's still going to be hard to beat sticking bits of special glass out in a field and connecting wires to it. But we should sure as heck keep tinkering away at it!

tomxor 2y ago
I don't think the point of this project is to be closer to economic viability, but to demonstrate an approach that would lead to faster economic viability due to allowing faster iteration and evaluation of small scale experimental designs. In HN terms they are demonstrating a significantly faster REPL by keeping the project small and minimising use of esoteric or highly bespoke components. It's the closest you can get to building your own stellarator by walking into radioshack. I think it's a pretty cool idea.
- rgmerk 2y ago
  Yep, sure. And that's great.
dexwiz 2y ago
Newer solar panels don’t need full sun to function. It’s economically viable to place them further north and in cloudier climates now. So the area where these are alternatives are viable may be shrinking faster than you would expect.
- rgmerk 2y ago
  Indeed, though in colder climates you do have the problem that peak electricity demand is precisely when you get minimum solar production. But in sunnier, warmer parts of the world (which notably includes India, Pakistan, Bangladesh, Indonesia, Nigeria, Egypt, Ethiopia, Iran, Mexico, and Brazil, amongst others), over the next few decades it's hard to see anything much competing against solar and batteries for the bulk of energy usage.
  - bkor 2y ago
    > But in sunnier, warmer parts of the world Though solar panels prefer if it isn't too hot. Still, any such inefficiencies are easily outweighed by their low cost. In Netherlands it is common to install practice (and advised) more Wp than the inverter can handle. Maybe also a solution if it gets too hot, make it up by having more panels.
  - thehappypm 2y ago
    That isn’t true yet, because most cold places don’t use electricity for heating; in Boston for example the norm is oil or gas furnaces. Europe typically uses gas for heating, as we all learned during the Ukraine war’s beginning. When I lived in the Boston area, our electricity use, peaked in the summer during air-conditioning season. That is, until we got a heat pump, then our electricity spiked like crazy in the winter. but we are long way from having the majority of homeowners using heat pumps for their primary heat source. (Also heat pumps are kinda awful compared to furnaces in my experience so we might never get there).
    - smolder 2y ago
      >heat pumps are kinda awful Heat pumps work great under the right circumstances. In cold climates like Boston and north of it, ideally you want ground source, which means digging deep (or wide) holes to flow water through instead of just pulling heat from outside air. Alternatively, (or additionally, ideally) they're best used in homes with very tight air envelopes, good insulation, and heat/energy recovery ventilation (HRV/ERV) systems. Installed in radiant heating systems in well-built houses, heat pumps are fantastic and you'll be comfortable all year for pennies on the dollar. The reality is that most (US) construction, especially older, is just terrible in terms of air seal and insulation. Couple that with a potentially undersized air-source heat pump, which gets inefficient as the outside temp gets near the low end of its operating range, and you will not have a great time. But even then they are a good way to supplement gas heating, so you can limit furnace use to the coldest weeks of the year and do the environment a favor, as well as cool in the summer.
deleted 2y ago
[deleted]
fragmede 2y ago
Not sure why steam engine is written like it's some crazy reveal. It's the accepted way of doing it in most other fossile fuel plants, to the point that there's a saying for it - someone, somewhere X is boiling water so you can boil water. There are other designs that have been proposed, but I'm not aware of anything in production that takes heat and turn it into electricity at powerplant scale. Eg RTGs exist, but only if you need a computer power supply's worth of power for decades.
- ZeroGravitas 2y ago
  Perhaps because the steam part alone, even if powered by pixie dust and magic, can't compete on price with solar, and probably solar and batteries either (varies with latitude and time but the cost is going down and the latitude is getting wider). I think OpenAI is investing into a fusion design that avoids steam for exactly this reason, so it's not just an anti-nuclear talking point.
slightwinder 2y ago
> In sunny places (and I fully acknowledge that's not all of the world) it's still going to be hard to beat sticking bits of special glass out in a field and connecting wires to it. Why not both? Can't we utilize the special glass to fetch energy from a man-made fusion reactor, in similar ways as we use it to fetch energy from the natural fusion reactor in space?
- pyrale 2y ago
  Treating this as a serious question: because the big reactor in the sky has a built-in gravity well and a very big sphere of vacuum that works as a free containment system while still letting just enough energy out to be useful. Also we don’t need to refill it or handle the spent fuel.
- nine_k 2y ago
  No. D + T or D + D fusion reaction produces neutrons and hard gamma radiation. The special glass cannot capture the energy of these directly. The natural fusion reactor has a blanket that is literally thousands of kilometers thick. It effectively converts much of this into longer-wavelength electromagnetic radiation, from ultraviolet to infrared, with quite some visible light. That's what the special glass can make use of. Also, the highly radioactive blanket is kept hundreds of millions km away from consumers, which helps alleviate the problem of disposing of radioactive waste. With a planet-based fusion reactor, we'd have to think where to put thousands and thousands of tons of slightly radioactive concrete which would realistically serve as a blanket.
- thehappypm 2y ago
  In theory, yes. Those are called radiovoltaics and are being researched.
lupusreal 2y ago
Steam turbines are very good at what they do, so I don't think that's the problem. Turbines are well understood technology so they're they're the major impediment to economic viability then everything else must be working amazing. I do think economic viability will be a major problem though. The fusion hype crowd focus on Q>1 being their major milestone but that's still a long way away from it being profitable to operate a fusion plant.
- nine_k 2y ago
  IIRC, a cascade of turbines, going from high-temperature water steam to basically room-temperature ammonia, can reach a total efficiency exceeding 50%. Of course, ammonia is chemically active, and water at 700K is also chemically active, so the turbines, as usual, require special metallurgy and regular maintenance.
  - rgmerk 2y ago
    Sure, but your cascade of turbines isn't free. The capital cost of just the turbines is enough to make it hard to compete with solar and batteries in many situations.
- rgmerk 2y ago
  Turbines are indeed very well understood and mature technology, and even where the fuel is almost free and the reactor (a coal burner) is cheap, steam turbines are too expensive to compete with solar electricity in most places now.
johnea 2y ago
That's all just good money after bad. How many more trillion $$$ are going to be pissed away on this? I'd say, shelve the idea for 50 to 75 years and then look at it again. In the mean time, I think we could make major headway on a global elecrtic grid, that connects whatever part of the planet is sunny with all the rest. Add to this some major storage capacity, and I think we could resolve almost all of our energy problems with the money that would be wasted on further fusion efforts.

King-Aaron 2y ago

I admittedly don't know much about fusion reactors, but I do love that the thing which you create a star within is called a "Stellarator".

credit_guy 2y ago

People don't understand the fundamental problem of fusion. It's a problem of energy loss. Of enormous energy losses. Roughly speaking energy can be mechanical, for particles or radiative, for photons. The first one is proportional to the temperature (the famous NRT) and the second is proportional to the fourth power of the temperature. The constant of proportionality is very small, and at regular temperatures we generally don't think of it that much. But at millions of degrees Kelvin, it starts to dominate all considerations. The heat always moves form hot to cold. In the case of particles the heat flow is proportional to the difference in temperature, and in the case of radiation with the difference in temperature to the power 4. But heat also travels from particles to photons and vice-versa. It doesn't matter how. The problem with fusion is now this. Suppose that you have a super-duper device, let's call it brompillator. It brings an amount of deuterium-tritium mix at the required temperature, let's say 10 million Kelvin. Now that volume of plasma is surrounded by cold stuff. You can imagine that you have some mirrors, or magnetic fields, or some magic stuff, but the cold hard stuff is that that plasma will want to radiate to the exterior and the flow of heat would be proportional to the surface area times the fourth power of the difference in temperature. Since for all practical purposes the outer temperature is zero, we are talking about the fourth power of 10 million Kelvin. Now that constant of porportionality is very small, it is called the Stefan-Boltzman constant and has a value of about 10^7 W m^-2 K^-4. Let's say the surface area is 1 square meter. So the heat loss happens at a rate of 10^-7 times (10^7)^4 = 10^21 Watts. That is 10^12 GigaWatts. One GW is the output of a decent sized nuclear power plant. Of course, you can try to shield that plasma, but that shield has to be 99.99999....9% effective, where the number of 9s needs to be about 15 or so. That is the immensity of the challenge that nobody is willing to tell you about. How was this overcome in the case of the thermonuclear bomb? People imagine that once you have a fission bomb, you just put some deuterium-tritium mix next to it, and voila, you have a fusion bomb. No. The world's greatest minds have worked at this issue for about 5 years. The solution was something like this: if you first compress significantly the volume of fusion fuel, then the heat losses are much smaller (remember they are proportional to the area, and that's proportional to the square of the radius). They will still be tremendous, but you don't even aim to keep the reaction going for a long time. The duration of the fusion reaction in a thermonuclear bomb is still classified information, but public sources put it at the order of 1 microsecond. The heat losses are still tremendous, but for a short moment the heat gains from the fusion reaction are even greater, so ignition is achieved. In the NIF experiment that achieved more than breakeven 2 years ago, the fusion lasted less than 10 nanoseconds [1]. If someone thinks the brompillator will achieve fusion and that will run for years, or even hours, or seconds, they don't understand the fundamental problem. Unfortunately, nobody is willing to ask hard questions about this, not even Sabine Hossenfelder. [1] https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.132.065102 https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.132.065...

BenFranklin100 2y ago

“PPPL researchers say their simpler machine demonstrates a way to build stellarators far more cheaply and quickly, allowing researchers to easily test new concepts for future fusion power plants.” This quote reminded of the SpaceX’s approach to engineering and why they have leapfrogged past Boeing. Instead of spending 10-20 years and billions into a single design, SpaceX iterates.

deleted 2y ago
[deleted]

jayyhu 2y ago

The actual paper describing the construction of the MUSE Stellarator: https://www.cambridge.org/core/journals/journal-of-plasma-physics/article/design-and-construction-of-the-muse-permanent-magnet-stellarator/3028EBD0A22067E0ECE1EF22D9725BFF https://www.cambridge.org/core/journals/journal-of-plasma-ph...

deleted 2y ago

[deleted]

timoth3y 2y ago

I'm having trouble understanding what's actually been accomplished here. The article provides a good overview of Tokamak vs Stellarator, but seems to jump back and forth between proclaiming this as an innovative breakthrough and saying it's just a framework to test ideas. > In terms of its ability to confine particles, Muse is two orders of magnitude better than any stellarator previously built Is it? It doesn't seem as if they have reached first plasma or have plans to do so anytime soon. Using electromagnets to not only confine but also to control the the plasma is a big selling point of the stellarator design, and they don't seem to address this. This seems really cool, and I love the idea of lower-cost fusion. (Or even just functional fusion.) There are about a dozen companies making real progress in fusion, but I can't quite figure out what this team has actually accomplished. What am I missing?

klysm 2y ago
The struggle for funding can explain a lot of things
ElevenLathe 2y ago
Seems like the premise is that building these small experimental stellarators is a major cost in doing fusion research and therefore if we can bring the cost of these down from billions to less than a million, more teams can do more research faster, even if this specific design never generates any economic power. I have no idea if this premise is true or not -- I'm just a layman who read the article.

doricksnri 2y ago

I want to like this but at break even temperatures these things just melt. How about making ship stones from nuclear waste? You could make car engine sized batteries that would effectively last for years if properly shielded and which would provide essentially free power to run a dozen homes.

trhway 2y ago

how one can estimate a progress of a given design? For example on the photo there are no walls protecting the people in the lab from neutrons. Even the fusor 60 years ago running at 100KV already generated neutron flux requiring such walls.

pbmonster 2y ago
There's absolutely no way to get fusion with permanent magnets and copper coils. This is a plasma test stand, and because it is so simple, you can potentially quickly iterate through different field configurations. This is at least a little bit useful, because a full Stellerator is extremely complicated to take apart, so you can't just change the coils around if you want to change something.