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Progress toward fusion energy breakeven measured against Lawson criterion
- elevaet 4y agoCan someone explain in layman's terms what is the Lawson criterion, and Lawson parameter?
- 317070 4y agoFusion happens when hot enough hydrogen ions (=hydrogen atoms with the electron stripped so only the nucleus is left) are running into each other often enough. So you need a high enough density of those that stay hot enough for long enough (the triple product, vertical axis) at a high enough temperature (horizontal axis) for enough atoms to fuse. At the boundary, enough energy will start being released from fusion reactions to keep the reaction going. at Q=1 you have theoretical break-even. Somewhere between Q=5 and Q=10 you could extract more heat than you put in. The heat produced by the reactions should be enough to sustain the reaction. At Q=inf it just keeps burning like a fancy camp fire. Just throw in fuel, remove ashes and enjoy the heat. Commercial fusion can only start being viable probably somewhere between Q=10 and Q=20. Do note that the projected future in OP's gif should contain way more attempts from various companies to reach that limit. Just mentioning sparc is a bit selective.
- tifik 4y agoWould it be somewhat correct to say that the Sun (or generally stars of similar type) is approaching that Q=inf at this stage of its life?
- 317070 4y agoStars are at Q=inf, they don't have external heating. They are also on a weird place on this plot, considerably more to the top left side of the high Q's.
- tifik 4y agoHad to have a second look at the chart after reading your explanation to understand the variables. Thank you!
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- elevaet 4y agoThat's a great explanation, thank you. What does the black curve that intersects some of the Q curves represent?
- 317070 4y agoIt's the theoretical breakeven event (Q=1) when you use high power lasers rather than the magnetic confinement of a tokamak. The NIF is doing research on this inertial confinement fusion, where they shoot a lot of power with lasers on a tiny pellet with hydrogen. So you get extreme densities and temperatures, but not a lot of confinement time, i.e. the ions cool down _really_ fast. That shifts the curve a little bit. In my opinion, it is a bit misleading to add this to the plot, because for this laser-based fusion, the theoretical breakeven lies really far from the practical, commercial breakeven. But as shown there on the gif, the NIF did manage to cross the Q=1 for inertial confinement fusion last year!
- ncmncm 4y agoNIF is nothing other than dressed-up weapons research. But it is not more deceptive than other methods.
- sam 4y agoAuthor here. The black curve represents the hot-spot ignition condition for a laser inertial confinement fusion (ICF) experiment (like the NIF). This means that during the short period of inertial confinement, the self-heating exceeds all losses in the hot spot leading to an increase in temperature due to self heating. It only applies to the black 'x' points. The Q_sci^MCF contours correspond to scientific energy gain (ratio of fusion power to heating power crossing the vacuum vessel boundary) for a magnetic confinement experiment. For ICF we can't draw simillar Q_sci^ICF contours because the total fusion energy released depends on the degree to which the ignited hot-spot propagates a burn in the surrounding cold fuel. And this depends on other variables like the symmetry of the implosion which are not captured in this plot. If you're curious to read more about this check out Section III.F of the linked paper (pp.10-11).
- stavros 4y agoSo does eg Q=100 mean that it'll still go out on its own at some point? Ie is Q a measure of duration/total energy output for a given energy expenditure?
- 317070 4y agoYes, it means you will get out 100 times more energy than you put in, but at that point it does still go out if you don't keep supplying that external heat. At Q=infinity, you get out as much energy as you want compared to what you put in initially, but it keeps burning (as long as you add fuel and remove ashes, that is). At that point you pay an initial start-up cost and can fuse as much as you want.
- stavros 4y agoI see, thanks! So this doesn't take into account the hydrogen, just the external energy/heat you put in? I guess it must, otherwise Q=inf would be free energy.
- 317070 4y agoCorrect. The energy balance comes from the fuel mass that is converted to energy with E=mc^2.
- stavros 4y agoRight, thanks for the explanation!
- willis936 4y agoYou still have to run the cryogenic system for the superconductors and the pittance of power to keep the confinement coil power supplies. Q=inf means ignition: an entirely self-heated plasma. The collisions of the helium ash on the un-burnt fuel are enough to bring the fuel above the flash point. In this way it is like a campfire.
- ncmncm 4y ago
- ncmncm 4y agoCommercial fusion will not be competitively viable at any Q. Even unlimited free heat is not valuable if it costs too much to make power from it. A volcano, earthquake, or hurricane releases many TWh of energy, but not usefully so, for reasons. Once you start to get enough neutron kinetic energy out, those neutrons have to be captured and their kinetic energy degraded to heat in thousands of tons of molten lithium pumped in big pipes snaking around inside your magnets, which you must then use to boil water and drive a turbine. The cost of operating such a plant would be at least 10x the equivalent fission plant. But fission is already not competitive, and gets less so every day. Part of operation would need to be purifying grams of tritium, daily, out of those thousands of tons of radioactive molten lithium, for the fuel needed to continue operating. That might not be possible. No one is even trying it yet. The power density of your D-T plasma would be much less than fissioning uranium (Th, Pu, etc.), which means you need a great deal of it, and a huge plant. If superconducting magnets squeeze it smaller, you have the problem that all this neutron flux has to come through a wall of limited area, destroying it in short order. Magnets so strong would need thousands of tons of steel to hold them in place, which would weaken rapidly under heavy hot neutron bombardment. So, the D-T fusion chased is a series of fascinatingly hard technical problems, but there is no plausible prospect of ever getting any commercially valuable power out. And, they are not even safer than a regular nuke; the thousand tons of molten radioactive lithium is hugely inflammable, even explosive, and the smoke turns into radioactive drain opener on contact with anything damp, e.g. lungs.
- jhrmnn 4y agoAre you suggesting that all those people doing fusion research don’t know about this, or that they make false promises to the public to fund their research?
- ncmncm 4y agoAt least many know and do not care. Many deceive themselves, as often seen here. Others don't think about it, considering it Somebody Else's Problem. Promises of commercial power are naked lies they will never be called to account for.
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- xt00 4y agoFor SPARC the big innovation sounds like it is being able to use some special superconducting electromagnets to generate the massive magnetic field in the tokamak -- since that part is such a critical part, it would seem like in the next say 5-10 years that it takes to get SPARC up and running there should be a parallel group just trying to improve that magnet design by say 2X, which would likely have a massive impact.. seems like a smart thing for National science foundation or darpa or whatever to be funding that.. (maybe already happening) but it would be a bummer to be talking about this in 2030 and them saying, ok now we just need to design a more powerful magnet..
- TaylorAlexander 4y agoWell SPARC and the planned successor ARC can successfully generate power without needing more powerful magnets. Assuming all goes to plan (lol) ARC will be commercially viable with existing magnet tech. They have said that as you go towards higher field strengths, the physical forces pushing and pulling between magnets gets so extreme that it is difficult to build a machine that doesn't tear itself apart. So stronger magnets are only useful in conjunction with an entire machine design that can handle them. It looks to me like a good path is to get commercially viable machines with existing magnets, and then iterate on the entire machine once they have learned the basics of operating commercial fusion. But I am just a robotics engineer who has watched a lot of the SPARC lectures, so I have no domain expertise here.
- jacquesm 4y agoThis goes for permanent magnets as well. I've had a ceramic magnet and a neo explode on me and to say that I was surprised at the incredible forces unleashed would be an understatement. I'm a sucker for working with proper safety gear and if not for wearing very good safety glasses I'd have been in serious trouble, multiple magnet fragments sat embedded in the glasses and a couple in my skin where it wasn't covered by the glasses (easily removed with another magnet :) ).
- dTal 4y agoHow large of a magnet are we talking, and what were you doing with it? So I know what to be terrified of, for future reference.
- alfiedotwtf 4y agoIs there an inverse of the Kardashev Scale i.e for energy production rather than energy consumption? If so, what Level would we be now vs the projected?
- willis936 4y agoSome context on why progress slowed: From the 60s to the 80s we got pretty good at tokamaks (stellarators have been catching up since we got computers) but Magnetic Confinement Fusion (MCF) triple product performance scales with major radius ^ 1.3 and confinement field strength ^ 3. Power density scales linearly with major radius and with the magnetic field strength ^ 4. At some point increasing the major radius becomes extremely expensive, so pushing past the barrier of Q=1 has been a long, political process. At the same time a real burning plasma (Q>1) machine has a lot of added cost to operate a nuclear facility (tritium handling and neutron radiation). So there has never been a physics barrier to Q>1, but an economic one. What's changed in the past year is that REBCO manufacturing and working matured to the point that confinement fields are now twice as strong as they used to be. Suddenly building a burning plasma machine isn't a 40 year international venture and economically viable MCF plants are in the crosshairs.
- prox 4y agoI don’t know a whole lot about fusions latest and greatest. Thanks for putting it into context. So could we have had a working fusion machine with infinite money and political will? Also what is your prognosis of the next 5 or 10 years?
- willis936 4y agoInfinite money is a weird concept. It doesn't matter how much money humans print, what matters is what humans can accomplish. If we eliminated the concept of money we still would not be able to power mankind on 100 meter tall machines because we don't have the resources to build them quickly. There are sound practical and theoretical reasons for keeping "minimize the levelized cost of electricity" be the first goal of any alternate power source. My prognosis is that CFS is on a good track and that their state goals are achievable. There's going to be some big headlines in a few years. If other startups also hit their goals we'll likely see a race with private investment. Public interest and government funding will likely lag the private progress by a few years.
- ianai 4y ago
- willis936 4y agoThese authors put out a paper last December that really kicks ass. It's linked in the tweet. It's worth flipping through. https://aip.scitation.org/doi/10.1063/5.0083990 https://aip.scitation.org/doi/10.1063/5.0083990
- sam 4y agoThanks. We published a number of prepublication versions over the past year on arXiv to gather feedback from the physics community before submitting to Physics of Plasmas last December. The version linked to above (and in the tweet) is the peer reviewed version which was published yesterday.
- willis936 4y agoMy mistake! Last December was submission but publication was yesterday. Congrats and thanks for making it public access!
- burlesona 4y agoSerious question, since this is being done by a US company: is high-end engineering like this done in metric - as surely all the science is done in metric - or is the machinery built in customary units? I wonder the same about SpaceX and the other rocket companies… does US manufacturing mean you really have no choice but to operate in obsolete units, or are these things so “custom” that they get to be done in metric anyway?
- jccooper 4y agoIt varies. Automotive is basically all metric now. Aviation is typically in customary units. SpaceX is doing their new vehicle in metric, but the Falcon 9 is in the old style. Manufacturing is varied.
- woodruffw 4y agoMy understanding is that there isn't a consistent standard (or enforcement) for metric versus imperial units in engineering. The US military uses a mash of the two, but prefers metric in many instances due to NATO. NASA uses metric internally (I believe), but famously lost the Mars Climate Orbiter[1] because a defense contractor used imperial units instead. [1]: https://en.wikipedia.org/wiki/Mars_Climate_Orbiter https://en.wikipedia.org/wiki/Mars_Climate_Orbiter
- gs17 4y ago> because a defense contractor used [US customary] units That is a common but very limited evaluation of what happened. The contractor ignored the specifications, no proper testing was done to make sure their component would do what it was supposed to before launch, and when someone noticed the issue in-flight they were ignored due to the bureaucratic process until it was too late. The exact same issue would have happened entirely in metric units if one side used CGS and the other used MKS.
- tinco 4y agoI like this image even more than the one in the tweet: https://aip.scitation.org/na101/home/literatum/publisher/aip/journals/content/php/2022/php.2022.29.issue-6/5.0083990/20220608/images/large/5.0083990.figures.online.f3.jpeg https://aip.scitation.org/na101/home/literatum/publisher/aip... It helps my layman's eyes clearly relate the trajectories of the various developmental processes of each approach. I wonder why SPARC and ITER are the only projected ones. Do the other reactors being built not have estimated yields? My favourite has long been the wendelstein, because of they way it looks and how it feels like its pathway to success might be software based. I like the way Tokamak Energy markets itself, and would have loved to see the ST25 and the ST40 in that image, but maybe they're not complete enough projects to be on there?
- sam 4y agoWe only included projected values of SPARC and ITER because they're the only ones whose physics basis has been published in the peer-reviewed literature. We would certainly like to include other devices - hopefully this will encourage more teams to publish results in the literature from which we can extract the required parameters.
- willis936 4y agoIf anyone wants to see how triple product performance relates to Q for DT MCF machines: https://twitter.com/jb_fusion/status/1506964692627034118 https://twitter.com/jb_fusion/status/1506964692627034118