[HN Gopher] The Truth About Nuclear Fusion Q Factors
___________________________________________________________________
The Truth About Nuclear Fusion Q Factors
Author : terryf
Score : 84 points
Date : 2021-10-06 17:56 UTC (5 hours ago)
(HTM) web link (backreaction.blogspot.com)
(TXT) w3m dump (backreaction.blogspot.com)
| PicassoCTs wrote:
| I have a question, i ve read a book recommended on here, about
| fusion, called the "The Future of Fusion Energy". (It was very
| good, can recommend for a general topic overview and history of
| progress).
|
| But i do not understand the general approach to plasma-vessel
| construction, in particular, why it is so passive. Its either
| "bend" to orbital shape dicated by the plasma physics properties
| when constructing (Wendelstein, Stellerators etc.).
|
| Or increase the containment vessels magnetic field strength
| (scaling up the reactor, high-temperature-superconductors) until
| it is capable to hold all the chaotic increasing fluctuation
| inside no matter what.
|
| My Question: Is there not a more active, not brute force approach
| for containing the plasma? Sort of "Whack-The-mole" countering
| the escape-events as they happen in a Tokamak?
|
| If i understood correctly, the system adds to itself constantly
| energy (its a reactor after all) and any chaotic butterfly wing
| flapping on the plasma current can shape up to a tornado
| breaching the containment and ending fusion.
| hamburglar wrote:
| There is a fusion startup called CT Fusion that has an
| innovation in this vein: [warning: not a plasma physicist, this
| is just what I understand from talking to actual physics nerds
| who follow this] instead of using giant magnets for plasma
| confinement, they are using a continuously variable magnetic
| field that is provided by helical coils surrounding the plasma.
| By monitoring the shape of the surface of the plasma and
| varying the electrical input to the coils, playing whack-a-mole
| as you put it with the shape of the plasma.
| moogly wrote:
| ITER has/will have a multitude of different control systems
| to control the inherently unruly plasma too. As I understand
| it, any tokamak will have to do something like that.
|
| https://www.iter.org/newsline/-/3297
| vrm wrote:
| I'm a PhD student in robotics at Carnegie Mellon working on
| exactly this. It's extremely challenging for a few reasons:
|
| - the dataset is a mess. The experiments that have been
| conducted on the tokamak that we have access to were done for
| very many different reasons and under many different
| configurations of the machine so there is not a clear method
| for disambiguating what dynamical changes are due to
| differences in the system vs underlying dynamical truths
|
| - the simulators available are very slow and not that accurate
|
| - the physics is hard enough that it's not possible to develop
| a controller in closed form (obviously)
|
| This implies that we need a version of reinforcement learning
| or model-predictive control that is substantially more robust
| and sample-efficient than currently exists. We're working on
| that but obviously it's an open research problem.
| theptip wrote:
| Any papers you can link to on this? Sounds interesting.
| tinco wrote:
| I thought the design of the Wendelstein was actually to be able
| to control the plasma more completely by leveraging modern
| computing. Its design allows for a lot more input than a simple
| Tokamak would. But I only have a very superficial understanding
| of this.
|
| I don't understand why you're saying the Wendelstein follows
| the path of the plasma, it's not like plasma has a shape it
| wants to be in, you just sort of push it the way you want it to
| go, and wherever it goes you try and push it the other way
| again, to make it go in a circle.
|
| What other shape than the Stellerator would someone choose if
| they wanted to use even more fine control over the plasma?
| plutonorm wrote:
| This problem is clearly a fabulous use case for machine
| learning.
| vrm wrote:
| like I said above, we certainly hope so! It has been slow
| progress so far but applying modern ML / control techniques
| to tokamaks is one of the truly exciting applications of the
| current generation of AI in my opinion. Biased because this
| is literally what I do all day
| mrDmrTmrJ wrote:
| Do you have a website or any papers on your work I could
| read?
| kryptn wrote:
| > Is there not a more active, not brute force approach for
| containing the plasma?
|
| I think General Fusion's approach is interesting, they're
| compressing the plasma with a liquid metal wall.
| Invictus0 wrote:
| I would be interested in reading a broader analysis of how
| scientists and other experts are misleading the public. I imagine
| there is enough on this subject to write a book. My layman's
| perspective is that it seems to follow from the belief that the
| public cannot understand the scientists' preferred decision, and
| that therefore the scientists must mislead the public "for their
| own good". The obvious example of course is the health
| authorities misleading the public on masks early on so that
| hospitals would be able to stockpile supplies, but I'd like to
| see even more places where the narrative is being twisted.
| beezle wrote:
| An honest assesment acknowledges that current fusion research,
| like string theory and even HEP, has become an employment
| program. You can tell this is the case when 1) no efforts are
| made to change course once it is clear the current dogma is
| impractical, unprovable or lends increasingly marginal gains in
| knowledge at extreme cost; and 2) any who question the accepted
| view are shouted down and pushed aside.
|
| That is not to say there should be no money spent on
| researching fusion or the standard model (or beyond). Just that
| the current system does a poor job of allocating limited funds
| by putting most of the monies in one basket until well after
| other ideas/technologies should be given time of day and ample
| funding.
| ufmace wrote:
| As I understand it, the bigger problem around fusion that we're
| still working towards fixing is being able to maintain an
| actively fusioning plasma. All of these Q measurements are around
| very short runs, sub-second I think. ITER seems to have a goal of
| 400-second runs, which sounds more like it. Once we have enough
| understanding of plasma physics and confining magnet behavior, it
| will hopefully be more straightforward to optimize the energy
| going into the plasma, and the energy going into the magnets and
| cooling system, etc to hopefully achieve a QTotal > 1. And maybe
| have enough heat being generated that it'll be necessary and
| reasonable to attach a boiler to it, hook it up to a steam
| turbine and generator, and make some electricity.
| zardo wrote:
| W7-X was supposed to demonstrate a 30-minute run in 2021, but
| that's been pushed back a year.
| mcwone wrote:
| Let not forget the total energy input it takes to construct the
| ITER project . We should not be wasting finite resources on this
| project.
| m0zg wrote:
| The relatively minuscule resources "wasted" on this project
| could eventually solve the "climate crisis" in one fell swoop
| via delivering nearly inexhaustible sources of clean energy. So
| inexhaustible, in fact, that we could reduce CO2 by entirely
| engineering-driven (rather than ineffectual policy) means. And
| fusion would do so while also _increasing_ not _reducing_
| everyone's standard of living. You could even use your gas
| guzzler still, by making gas from CO2 and water, and it'd be
| "carbon neutral" even if it belches a column of black smoke
| straight into the air. And this gas would be like 50 cents a
| gallon, too.
|
| I'd rather spend a trillion on fusion and get it done Manhattan
| project style than continue droning children in Afghanistan or
| funding $3.5T in pork barrel bullshit here at home. Just drown
| it in money completely until it's done. Put the very best
| people on it and let them have at it for real. We've done it
| before, several times, it worked. There's no reason why it
| wouldn't work this time. If there is any 21st century "Moon
| landing" type goal, this is it, and the United States is still
| best positioned to accomplish something of this magnitude. For
| how long that will be true I do not know, but it is true now.
| pfdietz wrote:
| ITER has zero chance of solving the climate crisis. Anything
| derived from it will be far too large, expensive, and late.
| m0zg wrote:
| I'm not even talking about ITER here. Let them have their
| own nice European pork barrel boondoggle, though I'd point
| out that even if it fails miserably, it's still generating
| valuable science and technological capabilities that cannot
| be generated or sustained any other way, so it's not a
| "waste of resources". We're talking about these projects as
| if they'd offer marginal, rather than _radical_
| improvements in our situation, which is simply not true. If
| this is done this will completely upend the world and make
| it a better place - there's no doubt in my mind on this
| whatsoever. This is the _only_ environmental thing I
| wouldn't mind paying more taxes for, but I'd argue we don't
| even need that - we just need to look a little bit ahead
| and allocate existing resources towards longer term,
| riskier things benefits from which we _know_ will
| absolutely dwarf the investment. The reason why this is not
| happening is because we have trillions of dollars flowing
| into other troughs from which everyone involved is used to
| feeding. Until we disrupt those arrangements somehow our
| only chance of solving this is private sector investment,
| but private sector can't sustain things of this magnitude
| over an extended period of time. Not unless Musk gets
| involved.
| mdorazio wrote:
| Can anyone comment on the heat > electricity conversion ratio? My
| understanding has been that modern multi-stage steam turbines
| used in power plants are around 90% efficient, not 50%. I might
| be missing other energy losses along the way, though.
| phkahler wrote:
| >> Can anyone comment on the heat > electricity conversion
| ratio? My understanding has been that modern multi-stage steam
| turbines used in power plants are around 90% efficient, not
| 50%.
|
| They probably mean 90% of a theoretical maximum.
|
| For example, one of the results that stood out to me in
| thermodynamics class was that the maximum possible efficiency
| of an internal combustion engine (I forget which cycle) was a
| function of the compression ratio. In other words you could
| never reach 100% conversion of chemical energy to mechanical
| energy and the theoretical "efficiency" was a function that
| increased with compression ratio but could never reach 100
| percent. So lets assume an engine with a given compression
| ratio could have a theoretical efficiency of 50 percent, but a
| real-world design only achieved 45 percent. Someone might say
| 45/50 is 0.9 or 90 percent of the theoretical limit. That's a
| measure of how good the design was vs what's theoretically
| possible, but it has little to do with the actual efficiency of
| the energy conversion.
|
| IIRC the best heat-to-mechanical energy conversion devices are
| rockets with a theoretical efficiency of 50% but it's been half
| my life since I studied thermodynamics, so maybe I'm off on
| some of this.
| pfdietz wrote:
| The maximum theoretical efficiency of ideal rocket engines is
| much higher than 50%. At very high expansion ratio in vacuum
| the gas can become so cold it condenses, so almost all the
| internal energy of the initial hot gas will have been
| converted to jet kinetic energy.
| zardo wrote:
| I don't think so, checking Siemens they're touting a 65%
| efficient 600MW turbine. The higher number might be including
| some application for the waste heat.
| Robin_Message wrote:
| Carnot's law is what you want. Max efficiency is temperature
| differential divided by hot absolute temperature.
|
| So, with super heated steam of say 600 degrees C, I'd make that
| a maximum of about 66% theoretical, so 50% actual sounds pretty
| good.
|
| If you could build a plasma heat engine, you could get near
| 100% but I've no idea what that would technically look like.
| sb1752 wrote:
| Good documentary on Iter's claims by investigative journalist,
| Steve Krivit. https://www.youtube.com/watch?v=xnikAFWDhNw Shows
| that the public claims are not just an exaggeration but outright
| fraud for the purpose of getting more funding. It's one thing to
| say that the purpose is experimental research, it's another
| entirely to claim that it will produce net energy, which is not
| backed any evidence or even a reasonable scientific analysis.
| There's a long history of fraud in fusion research, it's really
| important the public is well educated on the history here.
| tuatoru wrote:
| This is what I like about scientists, they can change their minds
| based on the evidence. Well done, Sabine!
| anonporridge wrote:
| To be fair though, I don't believe Sabine is involved in any
| nuclear fusion research, so changing her mind on this doesn't
| necessarily put her own funding at risk. Changing your mind is
| easy when your next meal doesn't depend on continuing to
| believe something.
|
| In fact, she might even stand to gain if funding gets diverted
| from fusion research towards other projects.
| aaronblohowiak wrote:
| ITER isnt meant to have Q-total > 1 though, it is meant as an
| experimental platform not energy generation. I wonder if the
| author has similar thoughts on promise for smaller reactors that
| take advantage of HTSC magnets.. should they have an easier time
| achieving breakeven Q-total?
| jeffreyrogers wrote:
| Her point is that almost all coverage of fusion elides the
| difference between Q-total and Q-plasma. I didn't know how big
| the difference was until reading her article and I'm guessing
| almost no one else does either.
| beezle wrote:
| Her point is that the "Q" that has been used to sell ITER leads
| the public and policy makers to believe it is Q-Total, not
| Q-Plasma.
| ben_w wrote:
| > should they have an easier time achieving breakeven Q-total?
|
| I believe that's why they're being made: Q being a function of
| both physical size and magnetic field strength, and the new
| superconductors being useful for increasing the latter so the
| former can be reduced.
|
| But I have no idea if any of them are _currently_ attempting
| Q_total > 1 or not: too much hopeful PR for me to know what
| stage they're really at.
| hamburglar wrote:
| How could they possibly be attempting Q-total > 1 when they
| aren't even near Q-plasma = 1 yet?
|
| If the gain of the system overall is greater than Q-plasma,
| you've invented some other energy source in there somewhere
| and should throw away your reactor and focus on that thing.
| :D
| ben_w wrote:
| I'm not sure what you're arguing against here. The new
| fusion startups claim the tech now exists to make compact
| useful Tokamaks. I'm not a physicist of any kind, so I
| don't know what they think their MVPs are. I don't know,
| and am not claiming to know, if they're jumping straight to
| {Q_total, Q_plasma} > 1 or if they're going to make a mere
| Q_plasma > 1, Q_total < 1 "fund-raising only" demo reactor
| first.
| hamburglar wrote:
| I'm responding to "but I have no idea if any of them are
| currently attempting Q_total > 1 or not." My point is
| that literally nobody is going to set their target on
| Q-total > 1 without first setting a target of Q-plasma >
| 1. It would be like wondering if a rocket company was
| setting their sights on landing on the moon straight away
| or if they were going to attempt to escape earth's
| atmosphere first.
|
| Edit: one might think Q-plasma > 1 is just an internal
| milestone, not a public goal, but it's not. Fusion
| startups are all going to be forced to make a public fuss
| over Q-plasma > 1 because the amount of funding you need
| to get from there to Q-total > 1 is MASSIVE and that
| milestone will be an investor aphrodisiac.
| hobscoop wrote:
| No currently operating device is 'attempting' to achieve
| Q_total; they are all physics experiments, not simply
| searching for a magic combination of knobs that will ignite
| the plasma.
|
| The Europeans are doing quite a bit of preliminary design
| scoping and engineering for DEMO, a 'demonstration' reactor
| which is supposed to come after ITER and generate net
| electricity, but there's not been a site selected, for
| example. Similarly, Chinese researchers are working on their
| CFETR, 'Chinese Fusion Engineering Test Reactor'.
| AshamedCaptain wrote:
| I feel like if this was the 2000s all over again, with ITER
| making headlines alongside some dubious claims of fusion being
| around the corner.
| SubiculumCode wrote:
| Fusion research is fundamentally good research to pursue, and
| vigorously. But in terms of energy for the world, we just happen
| to have an already made fusion plant some 92 million miles away.
| Its just an engineering problem of how to get more of it's wasted
| energy onto the earth using space solar arrays (Only one one-
| billionth of the Sun's total energy output actually reaches the
| Earth, now, per a google search...which seems too high,
| honestly).
| tsimionescu wrote:
| Space solar arrays would be the perfect solution if we needed
| the energy in space. Since we need it on Earth, and since the
| sun is already sending exactly that energy to Earth, they are
| almost entirely pointless.
| tuatoru wrote:
| In fact, space sunshades would be _much_ more useful to us at
| this point than space PV.
| sbierwagen wrote:
| Space solar is now something of a fossil idea from the 70s. At
| the time it was thought that solar panels would be
| comparatively expensive, and spacelaunch/space manufacturing
| would be comparatively cheap. But the economics changed out
| from under its feet: solar panels became a hundred times
| cheaper
| http://costofsolar.com/management/uploads/2013/06/price-of-s...
| but space stuff remained the same price. Now the most
| economical option is to put solar arrays on the Earth's
| surface, but build ten times more of them than you need.
|
| Specifically, one of the killer engineering problems of space
| based solar is getting the power back to Earth. Tom Murphy
| wrote the canonical post on this:
| https://dothemath.ucsd.edu/2012/03/space-based-solar-power/
| Depending on what frequency you're using and how big the
| orbital antenna is, the receiving rectenna array is going to be
| a couple kilometers across. If you use a beam power density
| that isn't going to cook birds flying across the antenna, then
| you're not receiving too much more power than regular solar
| irradiation. The atmosphere eats some of the power, the
| receiving antenna eats some power, and then the rectified power
| has to be converted to AC, losing a few percent more power.
| Maybe 50% total transmission loss. For the cost of putting a
| million tons into orbit, you might want to just build more
| ground solar.
| pfdietz wrote:
| Space solar was an idea from when PV was expensive. Put those
| expensive PV up in space with cheap launchers so they're more
| effective, that was the idea. But now PV is very cheap, so
| there's no need to put it in 24/7 sunlight. And with storage
| improving transmitting the power in time will be cheaper than
| transmitting it in space.
| SubiculumCode wrote:
| Yes, this IS the problem. Could not a space tether system
| help with that? Although, space elevators are quite a
| daunting challenge too.
| goodpoint wrote:
| Besides, there is no need for space solar. The amount of
| solar radiation hitting deserts around the planet is way more
| than enough to generate electricity for the whole human
| society.
| orthecreedence wrote:
| And soon we'll all live in a desert, so it will finally
| make sense to generate our power with solar.
| tuatoru wrote:
| Its advantage is continuity of supply - ground based PV in a
| single location is only available for about a third of a day.
|
| Building transcontinental and transoceanic UHV power
| transmission lines circling the northern hemisphere,
| providing the same function is _probably_ cheaper, but may be
| more politically difficult.
|
| But that's moot. We have a cornucopia of viable storage
| methods in active development--viable meaning capable of
| being scaled up to global scale in 20 years or so.
| roughly wrote:
| > We have a cornucopia of viable storage methods in active
| development--viable meaning capable of being scaled up to
| global scale in 20 years or so.
|
| Do you have more info on this? I'm skeptical of any claims
| of scaling to global scale that quickly.
| tuatoru wrote:
| Form Energy's iron-air battery, for instance - good at
| the two days to two weeks duration, needed as backup for
| wind during prolonged calms. We already mine a great deal
| of iron; the extra needed globally wouldn't really be
| noticed. Others are working on iron-air also.
|
| At least a couple of teams are quite far along with hot
| rock energy storage. Good for the one week to one month
| timescale.
|
| Various other battery technologies for sub-day timescales
| - lithium for grid frequency stabilisation, flow
| batteries.
|
| I don't know of any active trials of ammonia energy
| storage, one of the most scalable candidates for seasonal
| storage, but ammonia engineering is very old and very
| widespread, so there don't appear to be roadblocks to
| scaling up rapidly once required.
|
| The YouTube channels "Just Have a Think"[1] and
| "Undecided with Matt Ferrell"[2] focus on this stuff, and
| do some research.
|
| Edit: you should be sceptical; well done! Scaling really
| does take forever. That's why the only viable
| technologies are those already lying around all over the
| place, being used for other things.
|
| 1. https://www.youtube.com/c/JustHaveaThink/videos
|
| 2. https://www.youtube.com/c/UndecidedMF/videos
| causi wrote:
| _Its just an engineering problem of how to get more of it 's
| wasted energy onto the earth using space solar arrays_
|
| Considering even the best solar panels have under 50%
| efficiency, increasing the total solar radiation to earth would
| be very bad for the climate.
| SubiculumCode wrote:
| This is a silly comment. First, its not any different that
| creating your land-based fusion energy. Yes you are adding
| more energy into the system, thus more heat. In any case,
| space solar arrays that inefficiently convert electricity
| while in space would not be heating the earth directly. Just
| the inefficiencies in how that energy is used later.
| HPsquared wrote:
| It also applies to fossil fuels: the energy would otherwise
| be locked up underground.
|
| It'd be interesting to compare the energy directly released
| as usable heat from burning hydrocarbons, to the indirect
| increase in energy absorption over the life of the released
| greenhouse gases.
|
| Not sure, but I reckon the cumulative greenhouse effect
| would be massively more than the usable energy released
| during combustion.
| cinntaile wrote:
| > increasing the total solar radiation to earth would be very
| bad for the climate.
|
| Citation needed.
|
| The radiation to earth varies already, sometimes we're
| farther away from the sun and the output of the sun isn't
| constant either. The earth seems to handle that just fine.
| knodi123 wrote:
| > The radiation to earth varies already, sometimes we're
| farther away from the sun and the output of the sun isn't
| constant either. The earth seems to handle that just fine.
|
| That sounds remarkably similar to "how can there be global
| warming if we still have a cold season and a hot season".
|
| I don't say space-based solar arrays are necessarily a
| problem, but arguing that earth handles variations, as if
| the net total doesn't matter, is a little blinkered.
| goodpoint wrote:
| Actually it's true that increasing the overall input of
| energy in the planet atmosphere is bad.
|
| Yet, this also happens with nuclear, coal, gas, oil...
|
| The only solution is to capture the energy that is already
| being received from the sun in order to prevent it from
| heating up the atmosphere on site.
|
| E.g. solar panels on the desert and wind turbines
| orthecreedence wrote:
| > The only solution is to capture the energy that is
| already being received from the sun.
|
| Or stop screwing with it entirely (it worked fine without
| our help for quite a while) and build nuclear reactors
| everywhere, which scale wonderfully and work even when it's
| dark, cloudy, or shrouded in smoke.
| Galaxeblaffer wrote:
| And also works in space..
| goodpoint wrote:
| missing the point much?
| gene-h wrote:
| The problem with space based solar power is RF interference.
| The transmitter will interfere with RF comms on the same band
| thousands of kilometers from the receiver. And I mean
| thousands. Figures 55 and 56 show how much RF power is incident
| a given distance from the center of the receiver for 2.4 GHz
| and 5.8 GHz.[0]
|
| 2.4 GHz is one of the best frequencies to use because losses
| through storms and what not are quite low. However, we now have
| bluetooth and wifi devices which operate at this frequency now.
| 1000 km from the receiver, the incident power is stronger than
| the minimum sensitivity of a bluetooth receiver.
|
| [0]https://www.researchgate.net/publication/348442155_Microwave
| ...
| cyberpsybin wrote:
| Why will nuclear fusion scientists bother with anything other
| than Qplasma. Heat to electricity is separate problem.
| AlbertCory wrote:
| Because Qplasma >> 1 _might_ mean there 's enough energy to
| make Qtotal > 1 as well.
| MobiusHorizons wrote:
| I can imagine it would be reasonable for fusion scientists to
| not spend effort on the Heat -> electricity part. What I think
| the article is highlighting is that they are currently totally
| ignoring all the energy that goes into anything other than
| plasma, (ie the power to run magnets, vacuum pumps, or lasers),
| which from the examples given is on the order of 10s-100s of
| times the power delivered to the plasma.
|
| This energy should be considered by fusion scientists, because
| it may end up invalidating certain topologies that can achieve
| a Qplasma > 1, but can't achieve a Qtotal > 1. For instance
| from the article, it seems like pulsed lasers are relatively
| inefficient at turning input energy into laser energy, which
| might mean they would need a QPlasma > 100 before QTotal
| aproaches 1. I don't know which of those inefficiencies are
| deemed to be fundamental and which are potentially improveable,
| but it could suggest the whole line of research is not worth
| perusing.
| beezle wrote:
| Because the ultimate goal is a power plant, not just a paper
| saying that Q-Plasma of 1 (or 10) has been reached.
| zardo wrote:
| What's the significance of reaching the Qplasma = 1 milestone?
|
| They get to uncork some champagne, but they still need to get Q
| up to ~10 before handing it off to the powerplant engineers.
| TheDudeMan wrote:
| They can bother with whatever they want. But stop misleading
| the public and the media.
| jkelleyrtp wrote:
| Things like the NIF also have power losses in feeding the
| ignition. The NIF lasers are maybe .1% efficient, or less,
| meaning that even if energy delivered by the lasers is less
| than created by the reaction, it must deliver a 1000x power
| output just for lasers to be break-even.
| anonymousiam wrote:
| It's a valid point that ITER will not produce net power, but it's
| still a big step forward.
|
| Years ago I worked for a brilliant physicist who believed
| (usually correctly) that any factor less than an order of
| magnitude was just an "engineering problem".
| Invictus0 wrote:
| Did you read TFA? The author is not arguing that it's not
| worthwhile to fund fusion research; she's arguing against the
| misleading discourse surrounding it. "But it's still a step
| forward" is exactly the reason that science is misleading the
| public.
| anonymousiam wrote:
| Yes. I RTFA and saw that. I was not disagreeing with her.
| pfdietz wrote:
| Unfortunately for that viewpoint, the power density of a DT
| fusion reactor is at least an order of magnitude worse than
| commercial fission reactors. PWR reactor vessel = 20 MW/m^3,
| ITER = 0.05 MW/m^3, ARC = 0.5 MW/m^3.
| AlbertCory wrote:
| If you haven't read Sabine Hossenfelder, you should check out her
| other work. She is pretty acerbic about the politics of Big
| Physics.
| 2OEH8eoCRo0 wrote:
| Commonwealth Fusion expects to start commercialization in 2025.
| They say it will put power onto the grid.
| knodi123 wrote:
| Fusion as a power source has been several years away for
| several decades.
| tuatoru wrote:
| Theranos Fusion.
|
| Edit: There has been Edison, and there has been Musk. If you're
| not either of them, and you claim other people are doing their
| engineering wrong ... consider that you might be mistaken.
|
| Make a big song and dance about it, you look like a charlatan.
| vjaswal wrote:
| I think this take is too skeptical to apply to all the
| startups. For all the talks from CFS I've seen, they've been
| very measured and sober about the viability of near-term
| fusion.
|
| The game changer here is not very new reactor designs, but
| cheap high performance high-temperature superconductors that
| enable very high field and therefore much smaller size.
|
| Other fusion work, like ICF or the LLNL laser fusion or
| Lockheed or General Fusion all seem to be built on designs
| that are far less understood and less Q performance so far.
| pfdietz wrote:
| The high-Tc superconductors are nice, but they are not a
| panacea. They move fusion from "absurdly" to just
| "desperately" uncompetitive.
| vjaswal wrote:
| I've seen various youtube videos from their employees and CEO.
| From what I remember, Dennis Whyte (head of the fusion lab at
| MIT and CFS cofounder) says you need about Q>5 at least, to
| make fusion economically viable. So that must mean Qplasma > 5.
| SPARC is working towards that by 2025.
|
| And so far, the company, CFS, has been achieving their
| milestones for the performance of their magnets. The HTS
| magnets and coils is the main ingredient that the startup is
| optimizing for. Sometime in the last year, they implied that
| their Qplasma was much better than they minimally hoped for. I
| think they achieved Qplasma > 10, but Dennis was keeping the
| details proprietary.
|
| From all the talks I remember, they are targeting power on the
| grid with the ARC reactor by 2035.
|
| Edit:
|
| This is the best recent video I've seen, about SPARC and ARC.
| Jumped to 2:25 for Dennis Whyte.
|
| https://www.youtube.com/watch?v=bHJyoqDO0zw
|
| It's targeted to MechE students and gives a lot of details
| about other aspects of a potential ARC reactor design, e.g. how
| to get the heat out.
| 2OEH8eoCRo0 wrote:
| Yes. They _start_ commercialization. Not that a commercial
| reactor will be ready in 2025 but where they work to
| commercialize SPARC - > ARC.
|
| https://cfs.energy/technology
| vjaswal wrote:
| Ah, yes, I understand what you meant with your wording.
| Proof-of-concept by 2025, and commercialization after that.
| pfdietz wrote:
| They plan in 2025 to be where fission was in 1942. Only a
| small matter of engineering after that that can't take
| very long, right?
| vjaswal wrote:
| I added a link above to a good talk from Dennis Whyte. I
| think it will help address your question about the
| additional engineering issues in a commercial reactor
| based on ARC.
|
| In short, from my basic understanding, there are quite a
| few additional major challenges involved with fusion
| power generation. e.g. After creating net-positive
| fusion, the heat must be efficiently extracted without
| stopping the reaction. Also tritium must be continually
| extracted from the FLiBe (fluorine-lithium-beryllium)
| bath that stops and collects neutrons and extracts the
| heat.
|
| Since I'm a total novice in all this, I don't know if
| these require incremental innovations or major advances.
| But from the video, the problems mentioned seem to be
| more tractable than achieving fusion ignition or Q>10.
| hamburglar wrote:
| What I've heard is that they will have a _demonstration_ of
| "net energy" by 2025. This is still a long way from solving the
| engineering problem of putting energy on the grid. And if that
| "net energy" definitions is actually Q-plasma as this video
| claims, it's a lot farther still.
| hobscoop wrote:
| SPARC is aiming for Q_plasma of about 10 in 2025, but not to
| generate energy at all: it doesn't have any of the required
| 'blanket' system for breeding tritium. SPARC is a physics
| test, to make sure our theories of burning plasma are correct
| and to test the stability of these high field tokamaks.
|
| ITER is (among other things) supposed to be a physics test,
| but won't come until 2035. So SPARC's goal is to 'leapfrog'
| that by 10 years.
|
| You're right that there's a lot of work to be done between
| Q_plasma = 10 and generating energy. A lot of this work on
| the materials side, to engineer materials that can last for
| years in a fusion reactor environment.
| dr_orpheus wrote:
| "This HTS magnet technology will next be used in SPARC, which
| is under construction in Devens, Massachusetts and on track to
| demonstrate net energy from fusion by 2025. SPARC will pave the
| way for the first commercially viable fusion power plant called
| ARC." [0]
|
| But this does not say that they are going to put power on the
| grid in 2025. They say net energy from fusion by 2025 which may
| just mean Q-plasma > 1, it does not say (which kind of proves
| the point of the article). They don't have any estimates of an
| on the grid fusion plant.
|
| https://cfs.energy/news-and-media/cfs-commercial-fusion-powe...
| gene-h wrote:
| SPARC will not generate electricity[0]. It's intended to show
| that the ARC concept, which should be able to generate net
| electricity[1], is viable. If SPARC works, ARC might be built
| as early as 2030. 'As early as' being the keywords here.
| Showing that the difficult physics work is important to do
| before moving on to the difficult engineering.
|
| [0]https://www.psfc.mit.edu/sparc/faq
| [1]https://arxiv.org/pdf/1409.3540.pdf
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