[HN Gopher] Wendelstein 7-X: Gigajoule energy turnover generated...
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Wendelstein 7-X: Gigajoule energy turnover generated for eight
minutes
Author : greesil
Score : 274 points
Date : 2023-08-11 18:36 UTC (4 hours ago)
(HTM) web link (www.ipp.mpg.de)
(TXT) w3m dump (www.ipp.mpg.de)
| YossarianFrPrez wrote:
| If I understand things correctly, the problem with magnetic
| confinement (e.g. Tokomaks, Stellarators) is that once you have
| heated a plasma such that it is "fusing," how do you get the
| power out with out cooling the very plasma you've just spent a
| lot of energy heating up?
|
| Helion, a fusion startup, claims to have solved this problem via
| capturing an induced current from colliding two hot plasmas
| together. I'd be curious if there is any way the Wendelstein can
| produce electricity.
| Tuna-Fish wrote:
| Most fusion power systems assume they are doing that as
| neutrons. D-T fusion conveniently has the proportion of energy
| that gets lost from the plasma as KE of neutrons be pretty
| close to the amount of energy that a conveniently sized fusion
| reactor can afford to remove from the plasma.
|
| Then you trap the neutrons with, for example, a lithium
| blanket, use them to breed more tritium, and produce energy
| with a turbine from the heating of the blanket.
| YossarianFrPrez wrote:
| Ah, got ya. Thanks for the information.
| karmajunkie wrote:
| This is perhaps an obvious question to some, but I'll ask it
| anyway: How is the power generated here converted into usable
| electricity?
|
| I know for conventional fission reactors the heat of fission is
| basically used to run a steam turbine. Given the extreme heat of
| the plasma, and that it must be magnetically suspended so that it
| doesn't even touch the sides of the containment, how is that heat
| transferred to some other medium to generate electricity?
| mdprock wrote:
| here there is no power generated as it's not working with
| deuterium-tritium. most of the heating will heat the plasma and
| a fraction of this will reach the cooling system. To make a
| comparison ITER is expected to have 50 MW heating for 400
| seconds approx. = 20 GJoule. Using a DT mix will result though
| in 500 MW Fusion Power
| peteradio wrote:
| You still get heat transfer from uncharged elements I guess.
| Etheryte wrote:
| I'm not sure if it's the case for this specific reactor, but
| the common answer to this question is that you need cooling in
| the surrounding walls and the coolant that runs through the
| walls transfers the heat out where it can be used to do useful
| work.
| WJW wrote:
| Given that the plasma is several million degrees, it will
| radiate a lot of energy and heat up the walls even if it does
| not directly touch them. Just cooling the walls can heat up the
| cooling fluid enough to later produce steam with. AFAIK the
| Wendelstein machine is not configured for electricity
| production though, so the cooling is just cooling atm.
| jeffbee wrote:
| > Given that the plasma is several million degrees, it will
| radiate a lot of energy
|
| That doesn't entirely follow. 2 particles whizzing past each
| other at relativistic speeds have extreme temperatures but
| don't offer much energy. Mass is in this equation.
| willis936 wrote:
| What if you have 10^20 particles? Each charged particle
| emits photons with energy/frequency proportional to their
| speed (Bremsstrahlung). This is mostly from electrons
| because they are much lighter and so are much
| hotter/faster. Plasmas are quasineutral though so you'll
| have those electrons present. There is a long line of
| research trying to get away from that constraint with
| little luck so far (but it should continue to be worked
| on!).
|
| Jumpjng back up the stack: photon radiation is mostly
| considered a loss since it transfers energy out of
| confinement and does not impart it on other fuel. You
| nominally extract your heat via neutrons: same as fission
| reactors. Some designs (Helion) aim for reactions with
| charged byproducts. The reaction produces a current that
| can be coupled by a surrounding coil, much like a
| transformer but powered by current induced by plasma rather
| than another copper wire.
| fizigura wrote:
| They currently run a bad-ass heatsink (which is one of the main
| challenges of this project, i.e., how to cool it), but
| eventually you will use that heat to convert it into
| electricity, yes.
|
| For the German-speaking crowd here, the Alternativlos podcast
| guys were there twice and had lengtly conversations with the
| researchers there. Like, between nerds. Really cool, if you
| understand the language.
|
| https://alternativlos.org/36/ (from 2016)
|
| https://alternativlos.org/51/ (most recent, from may 2023)
| drannex wrote:
| Omega Tau also visited and talked with some of the
| researchers and has a great podcast episode on it (and truth
| be told, all of their episodes are great).
|
| https://omegataupodcast.net/312-the-
| wendelstein-7-x-fusion-e... (from 2019, 3Hrs, English)
| tsimionescu wrote:
| Most of the answers are missing the actual (proposed)
| mechanism.
|
| The energy of the reaction is mostly carried away as high-
| energy neutrons. So, the way to get energy back is to "capture"
| those neutrons. Since neutrons are not electrically charged,
| you can't use them to directly create electricity, so all
| you're left with is using them for heat.
|
| Unfortunately, since they are electrically neutral, they're
| also relatively hard to catch. You need a dense material where
| they will have a good chance to hit some nucleus. The proposed
| designs are typically some kind of liquid metal blanket being
| circulated around the reactor and onto a place where it can
| boil water to produce steam to spin a turbine. Lithium is the
| metal most proposed for this, since it also has the advantage
| that it can produce tritium when bombarded with neutrons
| (tritium being the super rare half of the fuel that goes into
| the reaction).
| nerdponx wrote:
| It's always fascinating to me that, no matter how many
| interesting new ways to release lots of energy we develop, we
| are still stuck with the same method for converting it to
| electricity: release the energy as heat, use heat to make
| steam, use steam to drive generator.
| jessriedel wrote:
| The reason just that this is a simple process for which a
| steam turbine can achieves 90% of the thermodynamic
| optimum. To my knowledge, the only reason people consider
| alternatives is to reduce capital costs. You're still
| capped by thermodynamics though.
| sambapa wrote:
| It's because we're in local maximum - steam turbines are
| just so developed
| NateEag wrote:
| Helion is planning to use induction to generate electricity
| from the fusion reaction's generated magnetic field, IIUC:
|
| https://www.helionenergy.com/faq/
|
| (See "How does Helion generate electricity from fusion?"
| question)
| MichaelZuo wrote:
| Which doesn't make sense for power generation since there
| will always be some percentage of neutrons produced by
| any type of fusion reaction that can only be useful for
| generating steam.
|
| To entirely skip the steam cycle portion is to
| intentionally make a much less efficient design.
|
| For space-constrained, high-value, applications where
| economics don't matter that much, such as a submarine,
| that would make sense, but otherwise...
| jessriedel wrote:
| You could always add the liquid metal blanket if you want
| to eke out the extra 10% (or if you want to generate
| tritium). But it's not worth the complication in an early
| prototype.
| gus_massa wrote:
| They plan to use 2D + 3He -> 4He + 1H, so no neutrons htt
| ps://en.wikipedia.org/wiki/Aneutronic_fusion#Candidate_re
| ...
|
| (I'm still not convinced of their explanations, but a
| fast proton may be easy to catch by the magnetic field
| and create the effect they want.)
| 2-718-281-828 wrote:
| probably boiling water and the steam drives turbines whose
| coils and rotating magnets produce electricity.
| idiotsecant wrote:
| Yes, the boring and actually feasible answer is steam.
|
| But it sure is fun to dream!
|
| https://en.wikipedia.org/wiki/Direct_energy_conversion
| midasuni wrote:
| Isn't one of the problems with nuclear that it increases
| water temperature in rivers
| calfuris wrote:
| That's a problem associated with a particular cooling
| system design, so it's more of a thermal power problem than
| a nuclear power problem.
| jtriangle wrote:
| Same way most electricity is made, you use the energy created
| to heat up water into high pressure steam, high pressure steam
| turns a turbine(s) which turn gensets that produce 3 phase AC
| current.
|
| This one in particular isn't setup to do that, and as far as I
| know, none are yet. It's a pretty simple engineering problem,
| and, until we can maintain fusion for months at a time, it's
| not really something that needs to be built.
|
| There is, however, one fusion concept that shows some promise
| that doesn't require all that that helion energy is developing
| (helionenergy.com) they're yet to create net-power, but, their
| idea has some promise, and avoids the common problems with
| other forms of fusion power. I don't really see it as the be-
| all to end-all in the space, but from what I can tell they very
| well might be the stopgap that is needed between large scale
| stellerators and fission.
| mjfl wrote:
| The Stellarator is theoretically a superior design over the
| Tokamak, designed to neutralize the JxB force, where J is the
| current through the plasma and B is the magnetic field guiding
| the plasma around the device. By twisting the plasma into a shape
| where the curl of B (proportional to J) is parallel to B, i.e. a
| helix, the cross product is 0, and thus there are no net
| magnetohydrodynamic forces on the plasma.
| juujian wrote:
| 'Theoretically' is the right word for sure. iirc, the
| predecessor of the Wendelstein led to the bankruptcy of the
| engineering firms building the parts, because tolerances were
| so tight and they failed multiple times to land within the
| constraints.
| mjfl wrote:
| true. but on the other hand, the 'theoretical' is being
| turned into practice as evidenced by this 8 minute
| containment. the best a tokamak can do is half a second.
| moffkalast wrote:
| The last time it was in the news I think naysayers listed the
| main caveat with stellerators as something along the lines of
| very low plasma density compared to tokamaks, which makes them
| unable to get anywhere close to the energy break even point.
| expertentipp wrote:
| With gas cut off from pipeline terminated in Greifswald, how will
| they power now this bottomless energy pit? They still have some
| money, but a finite amount.
| TaylorAlexander wrote:
| Speaking of fusion does anyone know what is going on with SPARC
| at Commonwealth Fusion Systems? I have been very excited about
| their system but they are understandably in a deep development
| and construction cycle after a $2B investment, so all their news
| page has for the last year are updated business deals and awards.
| I would love to hear how reactor construction is going.
| cmplxconjugate wrote:
| My best friend works for them in diagnostic sub-systems
| development. The product is still a long way off delivery with
| many systems being actively designed and refined. Basically
| it's busy but will still be quite a while (3-5+ years at
| least).
| TaylorAlexander wrote:
| Makes sense. I would love to see a blog post with some
| progress pics, but I understand that building a fusion
| reactor is simply a slow process!
| [deleted]
| aidenn0 wrote:
| What is "energy turnover" in this usage?
|
| [edit]
|
| Found it: "Energy turnover is defined as the amount of heat
| multiplied by the duration of the discharge[1]." By "amount of
| heat" I assume they mean "heating power delivered to the plasma"
| b/c the the only way to multiply by time and get Joules is to
| start with power.
|
| 1:
| https://gigazine.net/gsc_news/en/20230227-wendelstein-7-x-en...
| snarkconjecture wrote:
| Yes, it's a little buried but the article says
|
| > The energy turnover results from the coupled heating power
| multiplied by the duration of the discharge
|
| The numbers:
|
| > The energy turnover of 1.3 gigajoule was achieved with an
| average heating power of 2.7 megawatts, whereby the discharge
| lasted 480 seconds
|
| Also:
|
| > Within a few years, the plan is to increase the energy
| turnover at Wendelstein 7-X to 18 gigajoules, with the plasma
| then being kept stable for half an hour
|
| i.e. 10 megawatts for 30 minutes
| magicalhippo wrote:
| How long does it take to restart after losing stability?
|
| Ie, would it be feasible in a power plant scenario to settle
| for 30-60 minutes of stability, and just restart?
| amelius wrote:
| Isn't this similar to the monetary meaning of the word
| turnover? Like turnover : profit <==> energy turnover : net
| energy output?
| runako wrote:
| Possibly the poster is from a country like America where
| "turnover" is not a preferred term to refer to gross receipts
| of a business. (Americans typically use "revenue" instead.)
| aidenn0 wrote:
| I am indeed from the US and had never heard "turnover" to
| mean gross receipts.
| alkonaut wrote:
| So when this had a turnover of 1.3 GJ (361 kWh), was that
| with a net loss in the end? How much electricity did they put
| in?
| aidenn0 wrote:
| My layman's understanding:
|
| There has never been a net-positive-energy magnetic
| confinement fusion experiment. Inertial confinement fusion
| has had 2 events that were "more energy out of the fuel
| than delivered to the fuel." But is still about a factor of
| 100 away from what is needed for "more electricity in than
| out"
| [deleted]
| fefe23 wrote:
| FYI: This milestone was in February.
| ChuckMcM wrote:
| I love these guys, they are just knocking down the engineering
| challenges in their plan to completely characterize and control a
| fusion stream. Sometimes they feel like the Tortoise in the race
| to a working fusion power plant but they are answering questions
| (managing wall temps and hold fusion in streams[1]) that the
| Tokamak folks have yet to solve. My bias though is I'm way more
| on the "D" side of the R&D spectrum and following ITER often
| feels like pure "R."
|
| [1] https://www.iter.org/of-interest/1188
| aquafox wrote:
| Interesting fact: Nuclear fusion, even if we'll make it work,
| won't stop global warming, because the heat it creates heats up
| the earth enough to bring us outside the Paris agreement:
| https://twitter.com/rahmstorf/status/1605967891928596481
| RivieraKid wrote:
| One immediately apparent flaw of this argument is the
| assumption of energy use growing by 10x over a century. But in
| developed countries, energy use per capita has been roughly
| stable for decades. The 2 main drivers of energy growth will
| weaken over time (population growth + countries becoming
| developed).
|
| Also, if energy use does increase by 10x, the solution is
| simple, build giant refrigerators powered by fusion energy to
| cool the atmosphere. (joke)
| MichaelZuo wrote:
| I could see a plausible 10x growth if literally the entire
| world achieved within the ballpark of 2023 US levels of per
| capita wealth.
| andbberger wrote:
| this is a basic consequence of thermodynamics and true for all
| power generation. the only thing to be done to minimize waste
| heat is to to increase temperature of the hot side of the heat
| engine, with ie advanced fission reactors.
|
| and fusion never had any advantage over fission anyways, other
| than that people aren't scared of it yet.
| aquafox wrote:
| Why the down votes? What is factually wrong with that
| statement?
| constantcrying wrote:
| The threat of the earth heating up by 0.3 degrees due to
| energy production is irrelevant or at least absolutely worth
| it as a tradeoff for working fusion.
|
| The dangers of climate change is not that the earth heats up
| by some small amount, the earth can easily cope with that. It
| is that continued greenhouse gas emissons are causing a ever
| increasing heatup due to trapped solar energy.
|
| (It is also extremely strage that he argues for geothermal in
| his comments. Does he not realize what that is? Literally
| heating up the surface of the earth with energy from below.)
| coolspot wrote:
| Didn't downvote you, but having unlimited energy source is
| worth it and can allow us to remove heat from earth. Human-
| caused CO2 alone contributes 2.1W/sqm while all current human
| energy production is 0.04W/sqm . Removing extra CO2 alone
| would offset 50x energy production growth. Then you can do
| things like placing reflective satellites between earth and
| sun.
| pfdietz wrote:
| Because the argument involves unlimited future growth in
| energy use. Compared to the current energy use, fusion
| (assuming it could be made to work practically) would indeed
| solve global warming.
| EVa5I7bHFq9mnYK wrote:
| The burning of 1 kg of coal heats the earth in two ways:
|
| A) the energy that is produced immediately (about 24MJ)
|
| B) the excess energy absorbed from the Sun over many
| subsequent years, caused by CO2 emitted burning that coal.
|
| The B is much larger than A. The fusion only produces A, but
| not B.
| slashdev wrote:
| Assuming I trust the math, that's plotting exponential growth
| in energy usage out for 80 years, and assuming a fully nuclear
| grid. Neither of those is likely. Lastly the Paris accord is a
| pipe dream that will never happen. A target to aim for, and
| miss. Nothing more.
| lhoff wrote:
| Related recommendation for the german-speaking crowd here:
|
| The Podcast Alternativlos by Felix Von Leitner and Frank Rieger
| were twice in Greifswald to interview some of the people behind
| the Wendelstein. In the first episode
| (http://alternativlos.org/36 from 2016) they mainly focused on
| the development and build process and the history. The second one
| is from this year and they talk about the achievements and the
| future of Fusion (http://alternativlos.org/51/)
| anonuser123456 wrote:
| I don't get it; who cares? We know the equations to burn plasma;
| that's the easy part.
|
| The hard part is building a machine that can burn plasma and
| breed tritium at appreciable rates.
|
| Why even bother with these machines that can never be built
| economically?
| constantcrying wrote:
| >Why even bother with these machines that can never be built
| economically?
|
| If you can not build a research reactor which functions well,
| then "building a machine that can burn plasma and breed tritium
| at appreciable rates." is more than impossible.
| fizigura wrote:
| We know the equations for flight. Why didn't they just build a
| 787 in the 40s already?
|
| Oh, is it because the technology didn't exist and first had to
| be developed, in incremental refinements? Initial airplanes
| didn't even fly and half the people trying them died? Oh...
| munchler wrote:
| Maintaining a controlled fusion reaction for eight freaking
| minutes seems like a pretty worthwhile accomplishment in and of
| itself. The only other place this is known to occur is in the
| center of a star. Doing it here on Earth is pretty mind-blowing
| IMHO.
| foolfoolz wrote:
| i've been following this project for 10 years. it's been
| successful. but how do projects like these move faster? the
| wendelstein 7x is never going to generate usable electricity.
| it's supposed to be the pre cursor to the producing reactor
| barbazoo wrote:
| > the wendelstein 7x is never going to generate usable
| electricity
|
| What's the reason for that?
| AnimalMuppet wrote:
| It's a research reactor, not a production reactor. Generating
| useful electricity was never the design goal. The goal was to
| learn _how_ to build a reactor that could generate useful
| electricity.
| ethbr0 wrote:
| tl;dr - Output nuclear fusion power, plasma volume, and
| magnetic field strength scale differently with reactor size
| increases
|
| In detail, I'll let someone smarter than me in nuclear
| physics explain: https://physics.stackexchange.com/questions/
| 175830/nuclear-f...
| KyleBerezin wrote:
| We are researching fusion technology. It would take a reactor
| many times larger to get more energy out of the facility than
| you put in. The technology still needs to mature before a
| reactor that size would be financially responsible.
| aeyes wrote:
| In the German Alternativlos podcast the Wendelstein team
| (Prof. Dr. Thomas Klinger, Dr. Adrian von Stechow) recently
| stated that it is already feasible, they estimate a cost of
| ~EUR20B and a 5 year construction time for a commercial
| fusion power plant if we started now.
|
| https://alternativlos.org/51/
| KyleBerezin wrote:
| Yea, but compare the financial burden of that compared to
| a solar farm of the same output. Not to mention the
| technical risk.
| fizigura wrote:
| Solar farms on farmland? That won't scale to the energy
| needs of 8bn+ people if we still want to keep feeding
| them. Especially a non-vegetarian diet.
| KyleBerezin wrote:
| I'm just saying the money doesn't back the idea yet. I'm
| not anti-fusion.
| bmicraft wrote:
| No, solar farms in the desert with a HVDC lines
| obviously.
| t0mas88 wrote:
| For less than 15 billion euro you could buy enough solar
| to power a country the size of the Netherlands. With 5
| billion to spend on batteries you might even make it
| through night time usage.
|
| Or in other words: Fusion is too expensive at this point
| to be useful.
| jahnu wrote:
| That seems amazingly cheap! Are we really down to that
| low level of cost?
| sp332 wrote:
| Grid-scale solar is $33/MWh (+)
| https://emp.lbl.gov/publications/utility-scale-
| solar-2022-ed... and the Netherlands uses 1,000,000,000
| MWh/year
| https://ourworldindata.org/energy/country/netherlands so
| it's only off by a factor of ~2.
|
| (+) These numbers are for the USA. I found a mention of a
| cheaper project in Chile
| https://about.bnef.com/blog/cost-of-new-renewables-
| temporari... but I don't know what the situation is in
| Europe. And wind might be even lower.
| aeyes wrote:
| Chile is an outlier, the plants are in remote locations
| in the Atacama desert where you have two compelling
| reasons to build solar plants: There is a lot of space
| where nobody lives and the sun is always shining. There
| are mountains but there are also lots of places which are
| flat for as far as the eye can see, an example would be
| the Cerro Dominador plant which probably didn't require
| any ground preparation.
|
| On http://generadoras.cl/tipos-energia/energia-solar
| scroll down to "Capacidad por region", Antofagasta and
| Atacama are the desert regions in the with over 90% of
| installed capacity.
|
| In Germany or the Netherlands it is a bit harder to find
| space for large solar plants.
| bbarnett wrote:
| The first plant is going to be more expensive, and the
| next gens after that will benefit from things learned.
|
| The first TVs were for the very rich, and had 4" bw
| screens. Now they're 80", thin, and insanely cheap.
| peteradio wrote:
| How exactly is that calculated?
| fizigura wrote:
| The same was said 20 years ago about solar power.
|
| Then some countries stepped up the subsidies game and
| booom, prices fell dramatically since suddenly everybody
| wanted a piece of the cake. And competition drove this
| all down.
|
| All you need is for somebody to start. Or we just keep
| telling ourselves that it's too expensive, shrug, and
| move on.
|
| Also note how the goal posts changed. Until recently,
| everybody made fun of fusion by basically saying it's too
| hard, it's too far in the future. Now it's not too hard
| anymore, it's just too expensive. What's next? Too loud?
| Too big? Induces headaches with the esoterically minded?
| cyberax wrote:
| You'll freeze to death in winter, but that's a minor
| thing. Living is overrated.
| jasonwatkinspdx wrote:
| You can't jump from idea to production power plant in one
| step. This is research about the fundamental science
| involved. What they're doing is incredibly difficult and
| complex. They have a plasma at millions of degrees mere
| centimeters from superconductors at near absolute zero. The
| field geometry and interactions are so complex it brings even
| current supercomputers to their knees. The device wasn't even
| possible to simulate until the late 90s using the biggest
| machines in the world.
|
| What they've already demonstrated is a tremendous
| accomplishment. But apparently if it doesn't go from idea to
| an option in door dash in 6 months flat that's not good
| enough for people here.
| constantcrying wrote:
| >What's the reason for that?
|
| It is about research. It generating usable electricity is
| absolutely irrelevant.
|
| You need research projects to figure out what works and what
| doesn't. The goal isn't to build a practical reactor.
| Eji1700 wrote:
| Mostly, they don't?
|
| There should be more funding in this area, but at some point
| you've got to build it, and that takes a ton of time.
| Regulations/bureaucracy could be better but at the end of the
| day you're not going to cut off a ton of time safely.
|
| Once you have a working model iteration gets much much faster,
| but we've simply been hitting walls for decades.
| hedora wrote:
| Is there a minimum viable size for a fusion reactor? If it
| scaled down ennough, they could just launch prototypes into
| space, and see if they explode.
| adhesive_wombat wrote:
| Fusion reactors are pretty non-explodey. Really all they
| can do is spring a leak, then fill with air and extinguish
| the plasma. Maybe if you quench the magnets hard enough you
| might get something dramatic like leaking a gram of
| tritium.
| b3orn wrote:
| I'm no expert on this, but a minimum viable size exists and
| it's much larger than what you could just launch into
| space. I watched a video on this years ago, I don't recall
| the exact relation to size but if I'm not remembering this
| completely wrong there's a minimum size you need for a
| fusion reactor to "ignite", ITER is huge for a reason.
| willis936 wrote:
| ITER is huge because it uses weak magnets.
| Eji1700 wrote:
| I'm honestly not sure if you're joking but in case you're
| not, the "minimum viable size" is hardly the largest issue
| with what you're proposing and it sounds like you're not
| getting what the key issues are.
|
| You're talking about taking a technology that's so finicky
| we've barely gotten it to work after almost 100 years and
| rocketing it into space? We're no where near good enough at
| this to get a test that would work after the extreme
| violence of an escape velocity launch.
|
| Further fusion reactors aren't like fission. "exploding"
| really isn't a problem . Keeping the reaction going in an
| efficient manner is.
|
| IF exploding was a problem, space is probably the worst
| place for it? Putting it way underground would be vastly
| easier and a hell of a lot safer because you won't have
| material possible falling back to earth/hitting satellites
| in orbit.
| sdwr wrote:
| That was not a real question, it was a subconscious plea
| for elon musk to take over and make it work.
|
| "Shooting it into space" is a reference to how SpaceX
| disrupted the rocket industry through a "fail fast"
| mentality, aggressive goals, and sheer force of will.
| flotwig wrote:
| Please don't "move fast and break things" with nuclear
| fusion :-)
| Eji1700 wrote:
| This take is even more baffling to me than the original
| question.
| ladams wrote:
| Stellarators in particular suffer from very long development
| cycles. It takes years and years of research to develop the
| algorithms used to optimize the coil geometries, and then the
| production of the coils and assembly of the vacuum vessel
| within the coils is much more challenging than for a tokamak.
| The coils are hard to produce because they have highly
| irregular shapes, and tight tolerances. Assembling the vacuum
| vessel is hard because the coils cover much more of the
| "toroidal-ish" surface area than in a tokamak.
|
| The is a lot of interesting work going on in stellarator design
| optimization now, but it will likely be many years before that
| research is realized in another actual reactor.
| fizigura wrote:
| For a few billion USD you could build a real power plant of
| this type. Sounds expensive, but consider how much money
| nuclear fission did cost initially, and how much money we
| burn on other stuff, then it's not unthinkable to have
| somebody rich chip in and make it happen. (Germany just gave
| $10bn subsidies for a domestic Intel factory.)
| Guvante wrote:
| They managed to handle what a fission reactor outputs every
| second in this experiment.
|
| I don't think that points to a commercial reactor whenever
| someone spends a few billions.
| willis936 wrote:
| HSX beat them to the punch by over a decade. Small is easy.
| Unfortunately no machine worth making (power generator
| relevant) is small. Practice helps.
| stjohnswarts wrote:
| Can someone tell me why this won't produce commercial level
| fusion for 30 years so I can shut down my eternally optimistic
| "physics kid" portion of my brain for a while?
| bmicraft wrote:
| It will cost too much
| Dulat_Akan wrote:
| I am thinking why companies making so huge reactors, everything
| should be simple just for test to get energy
| sp332 wrote:
| It's a been a long time, but in a talk at Google, I think
| Bussard said that power output scales with the 5th power of the
| radius of the device. There's really no point making a small
| one.
| pfdietz wrote:
| Bussard's last reactor concept, polywell, didn't work.
| sp332 wrote:
| Oh right, I had WB-7 confused with Wendelstein 7.
| pfdietz wrote:
| I greet W7-X with a huge yawn. A reactor based on stellarators
| will still be very large and have very low volumetric power
| density. The beta is not good, so these would only work with DT,
| and suffer from the generic problems of all DT schemes.
| moffkalast wrote:
| What makes tokamaks so much better at power density? After all
| it's the exact same setup, just shaped differently and without
| the center coil?
| pfdietz wrote:
| I didn't say that. Both tokamaks and stellarators on DT will
| have lousy volumetric power density. Indeed, any DT scheme
| will suffer in that respect.
| KyleBerezin wrote:
| Ahh, Wendelstein is that stellerator reactor. The stellerator is
| really cool, and an alternative to a tokamak reactor. Tokamak is
| the doughnut shaped reactor, and it has a problem where the
| plasma near the outer circumference has less magnetic
| confinement. The stellerator is similar, but confines the plasma
| to a ribbon and folds it over on itself in a mobius-like
| arrangement.
|
| I used to be really interested in this, but forgot it existed
| over the years. Glad to see it works!
|
| https://en.wikipedia.org/wiki/Stellarator
| lostlogin wrote:
| Are you able to say more about what you do? Judging by your
| comments, you have some idea what you are talking about.
| Simon_O_Rourke wrote:
| Just curious as to why a Mobius strip type arrangement is
| better than a toroid? Is it anything to do with the turbulence
| in the plasma flow being easier to control?
| KyleBerezin wrote:
| These are great questions for someone more knowledgable, but
| as I understand it, If you follow a single point on the
| surface all the way around the loop, it will spend as much
| time in high confinement as it does in low confinement.
|
| That explains why folding is important, as for the mobius, I
| oversimplified a bit. The Wendelstein has 5 folds, making it
| a mobius, but I think I read about one in Spain that had only
| 4 folds. That would mean the mobius isn't imperitive, but I'm
| sure there is a good reason for it.
|
| Really a stellerator doesn't need 'folding' at all, they can
| be as simple as a twisted torroid. I didn't want to go into
| excruciating detail though, the more in detail I go the more
| likely I am to say something that is wrong lol.
|
| Edit: I looked it up, the one in spain is called "TJ-II"
| Bjartr wrote:
| I think it's about ensuring the plasma heat/energy
| distribution is more uniform so you get fewer outlier
| particles with high enough energy to escape confinement and
| damage the interior of the reactor. Or something like that.
| extrapickles wrote:
| It primarily has to do with the physical construction of the
| magnets, in a toroid the inside of the toroid effectively has
| more windings per meter of circumference than the outside
| causing uneven containment.
|
| With mobius strip you regularly flip between inside and
| outside, so the plasma particles get more even force applied.
| tw061023 wrote:
| What's interesting is that stellarator actually is not just an
| alternative, but a wholly parallel branch of evolution - it's
| not like one was invented strictly after another, and the
| authors of both designs never knew about the other's work
| before they completed theirs.
|
| What's even more interesting is that the fusor - the simplest
| possible design for a thermonuclear reactor, so simple that
| anyone skilled in electrical engineering and having access to
| proper civilan equipment can build one with ease - seems to be
| invented _after_ both stellarator and tokamak.
|
| That said, I never particularly liked stellarator design. The
| very _complexity_ of it somehow feels subtly wrong, like
| doubling down in the wrong direction.
|
| However, this is one of the cases where I would absolutely love
| to be proven wrong. We are far past due big breakthroughs in
| the field.
| jcheng wrote:
| > The very _complexity_ of it somehow feels subtly wrong,
| like doubling down in the wrong direction.
|
| This made me think of modern jet fighters being designed to
| be aerodynamically unstable, making them all but impossible
| for human pilots to operate without flight computers.
| Apparently the maneuverability benefits make the added
| complexity more than worth it.
|
| https://en.wikipedia.org/wiki/General_Dynamics_F-16_Fighting.
| ..
| waterheater wrote:
| Compared to a tokamak, the stellarator bring engineering
| efficiency while matching performance. Though ideas for the
| tokamak and the stellarator may have emerged together, the
| main reason tokamaks were built first is because they COULD
| be built. Without computer-assisted magnet design,
| stellarators simply couldn't be properly built; the magnetic
| geometries are just too complex.
|
| In the long run, it's not known stellarators will be the
| eventual winner in the long race for a viable fusion reactor.
| The attributes in a winner will be net-positive operational
| efficiency and superior energy harvesting abilities. Perhaps
| multiple approaches will be viable.
| tw061023 wrote:
| I understand the theory. I just hope I will live long
| enough to see a winner in this race.
|
| To be honest, I've been interested in the domain for quite
| a time and I still want to build a fusor or a polywell at
| some point just to see it glow. Probably won't happen
| though.
| white_dragon88 wrote:
| You know enough to say more. Say more!
| waterheater wrote:
| I'm not that guy, but I can speak to what you're asking. I've
| followed Wendelstein 7-X for almost a decade.
|
| Nuclear fusion occurs at extremely-high temperatures. As you
| heat your fusion fuel to sufficiently-high temperatures to
| allow fusion, the matter transitions into a plasma, which is
| great: plasmas react to electromagnetic fields. As such, a
| major challenge with achieving viable nuclear fusion is
| making a vessel capable of holding the fusion reaction.
| Because we can't create on-demand gravity wells, the next
| best option for confinement is using electromagnetic fields
| to hold the plasma in the air.
|
| So, you now have an "electromagnetic bottle" capable of
| suspending a fusion reaction above the reactor's walls. Now,
| you have another issue: how do you ensure the fuel will
| sufficiently mix to sustain a fusion reaction? One approach
| is to move the plasma in a loop. The topologically-simplest
| method to accomplish this loop is the torus. Such a plasma-
| confinement device is called a tokamak. A tokamak uses two
| magnetic fields, torodial and polodial, to accomplish its
| task. The torodial field is driven through the plasma to push
| it forward, while the polodial field pulls the plasma in
| toward the center. Proper balance of these fields will allow
| the plasma to circuit the vessel following a helical path,
| achieving confinement.
|
| However, driving two separate magnetic fields is energy-
| intensive, and a successful fusion reactor will want to
| minimize its own power consumption to maximize the amount
| available for external usage. Enter the stellarator. The
| stellarator also drives the plasma around in a circle, it but
| uses a single magnetic field. How? It "tricks" the plasma
| into "thinking" there's only one magnetic field by using
| computer-optimized magnets with highly-complex geometries.
| This provides stellarators with a major engineering advantage
| over tokamaks and is a primary reason Wendelstein 7-X would
| have chosen it.
|
| With the confinement vessel topology largely identified, the
| next main step is to figure out how to build a vessel able to
| contain a sustained fusion reaction. For context, fusion
| experiments traditionally only operate on timescales of
| milliseconds to maybe a second. The reason? Fusion occurs at
| millions of degrees, and keeping the reaction vessel cool,
| ensuring a continuous supply of fuel, and dealing with
| reaction "exhaust" (e.g., alpha particles) and stray high-
| energy neutrons from the common deuterium-tritium reaction
| (which irradiate your reactor walls because neutrons don't
| react with electomagnetic fields) is a major, major
| engineering challenge. Any operational, net-positive fusion
| reactor must be able to operate for days, weeks, and months
| on end.
|
| What Wendelstein 7-X has been attempting to do for years is
| demonstrate that building such a vessel is even possible.
| Their overall goal is to sustain a fusion reaction for about
| 30 minutes. Such a timescale will show a proof-of-concept
| system which enables sustained fusion reactions to occur.
|
| Currently, the preferred fuel is deuterium-tritium because
| the fuel is generally available and has an attainable fusion
| temperature. The stray neutron issue can be mitigated by
| lining reactor walls with lithium to breed tritium fuel. Even
| better is to use the helium3-helium3 reaction, which
| completely annihilate to produce pure energy as the output
| (welcome to e=mc^2, enjoy your stay). The main holdups are:
| (1) the reaction occurs at much higher temperatures than
| deuterium-tritium, and (2) he(lium)3 is quite scarce on
| Earth. Once Wendelstein 7-X shows how to engineer a proper
| confinement vessel at a "lower" temperature, you can then
| work on the higher temperature levels required for he3-he3.
| Also, he3 is plentiful on the surface of the moon, so mining
| the surface of the moon will be performed to obtain the
| required fuel, which is the fundamental premise of the movie
| "Moon".
|
| Someone asked for information on electromagnetic plasma
| containment folding. I recommend reading up on
| magnetohydrodynamics (MHD). It's the mathematical and
| physical foundation of your interest.
| KyleBerezin wrote:
| One guy asked why the mobius aspect is needed and I
| couldn't answer. I know a lot of stellarators aren't odd-
| period like Wendelstein, and the old designs didn't do
| folding at all. Do you know what improvements the mobius
| design has over something like TJ-II?
| waterheater wrote:
| The helical path creates a twist in the plasma which
| cancels out the drift forces. This is what I meant by
| "tricking" the plasma. User mjfl gives an even more
| technical explanation:
|
| > By twisting the plasma into a shape where the curl of B
| (proportional to J) is parallel to B, i.e. a helix, the
| cross product is 0, and thus there are no net
| magnetohydrodynamic forces on the plasma.
|
| Hope all that's a good answer for you.
|
| > Mobius aspect
|
| You might avoid using the word "Mobius" and instead use
| "helical." A Mobius strip is important because it has two
| faces which form a single surface. The surface aspect
| isn't relevant in this context, so a term which refers to
| the shape would likely dispel confusion in a reader.
|
| As far as I'm aware, each section of a stellarator is
| periodic in its own right, which means the end and start
| points of each section are the same. Though I'm not
| certain, the choice of four versus five is more likely an
| engineering factor rather than one of physics, whereas
| the distinction between a tokamak and stellarator is of
| physics and not just engineering.
| golem14 wrote:
| I suppose that any number of twists would be OK, but the
| more twists, the less efficient ?
|
| Is that what you are saying ? Or are there other
| constraints on the number of twists (e.g. must be odd,
| ...)
| KyleBerezin wrote:
| If a 'particle' (I don't know a better word) finds itself
| near one of the top divertors, at the same point in the
| next orbit it will find itself near the bottom divertor.
| That is a product of the "mobius-like" shape, so although
| it isn't really a 'ribbon' and isn't really a mobius, it
| helps explain the concept concisely. I just don't know
| WHY that shape helps lol. Maybe it doesn't and it was
| just a practical design change like you said.
|
| edit: changed language about the divertors.
| gabereiser wrote:
| Seconded. This is fascinating stuff and reminds me of some
| crazy rant some guy was telling me about anti-gravity and how
| electromagnetic "ribbons" could propel you. Obviously the guy
| _was_ nuts, right? How would one go about learning more about
| electromagnetic plasma containment folding?
| KyleBerezin wrote:
| Haha, no I am just some random guy who reads too many
| Wikipedia articles. "Electromagnetic plasma containment
| folding" does sound like something a crazy person at a bus
| station would rant about.
|
| My explanation was definitely over simplified, but I'm not
| knowledgable enough to go into detail on the topic. I can't
| even point you towards something to read on the topic since
| everything I read about it is like 15 years old at this
| point.
| tootie wrote:
| If a Hollywood screenwriter were naming a crazy science
| device, they would come up with something like
| Wendelstien 7-X
| tboughen wrote:
| My favourite fact about it comes from
| https://phys.org/news/2016-02-plasma-physicist-discusses-
| wen...
|
| "...the supporting structure can only withstand the
| forces if the interfaces between the ten individual
| segments of the central rings, which weighs several
| tonnes, are built with a level of precision of less than
| 100 millionths of a metre..." - and they found a small
| family business in the north of Italy capable of doing
| this!
| dale_glass wrote:
| Odd units.
|
| 1 meter = 100 cm = 1000mm.
|
| So 1 millionth of a meter = 1/1000th of 1mm.
|
| thus, 100 millionths of a meter = 0.1mm, or ~4 thou in
| American units. Easily achievable by hobbyists, let alone
| by serious, professional equipment.
|
| Sure, that is a pretty exacting specification for what I
| suppose is a big machine, but I'm pretty sure very normal
| things like say, car engines get made to far tighter
| tolerances.
| Retric wrote:
| You messed up at your last step 1 millionth = 1mm, 10
| millionth = 0.1mm, 100 millionth = 0.01mm
|
| 0.01mm is very difficult when you're talking large custom
| objects with complex shapes.
| dale_glass wrote:
| Oh, English fail on my part then. I had assumed that 100
| millionths of a metre == 100 * 1/1000000.
| eis wrote:
| The german site of the source speaks of 0.1mm so you were
| correct > bei Toleranzen von teilweise
| nur 0,1 Millimeter
|
| https://www.ipp.mpg.de/de/aktuelles/presse/pi/2020/01_20
| starkrights wrote:
| I think the original commenter is right- correct me if I
| missed what you're getting at.
|
| Keeping it all in the same units until the end here:
|
| 1 millionth of 1 meter = (1 / 1,000,000)m = (1e-6m)
|
| 1 millionth * 100 = 100 millionths => (1e-6m) * 100 =
| (1e-4m) = 100 millionths
|
| (1e-4m) = .0001m | 1m = 1000mm => .0001m*1000 = .1mm
| [deleted]
| Retric wrote:
| Ops, 100 ( 1 millionths of a meter) is a much more
| reasonable tolerance than 1 / 100 millionths of a meter.
|
| I am to used to people saying 100 millionth of a meter to
| mean 10 nm.
| dekhn wrote:
| millionths of a meter are known as micron so most people
| would call this '100 micron' (or '100 micrometers') which
| is indeed close to 4 thou, as you calculated, and is the
| level of accuracy of my ~$500 3d printer.
|
| 1 thou was achievable in routine shops in the 1940s and a
| tenth of a thou (2.54 micron) is a common accuracy to
| target these days. Obviously it depends on the context
| and the size of the object, at some point you move away
| from cutting to using grinding and lapping to achieve
| your results, which is ultra-timeconsuming.
| StackOverlord wrote:
| > Dr. Ning Li of Huntsville, AL passed peacefully away on
| July 27, 2021. She was 79 years old. One of the world's
| leading scientists in super-conductivity anti-gravity. Dr.
| Li had constructed first 12" HTSD of the world in late 90s.
|
| https://www.berryhillfh.com/obituary/ning-
| li?lud=4CF765EE88E...
| themagician wrote:
| I find the geometry of things like this fascinating. We
| typically think in such simple shapes. I feel like my brain can
| do triangle, rectangle and maybe hexagons and that's about it.
| I remember when I finally understood radians enough to really
| understand circles and waveforms--I felt so enlightened. Like I
| actually remember the moment when it clicked. For years I was
| just "doing the work" without actually understanding what I was
| doing, but once I was able to understand it... it's like
| something changed in my brain.
|
| I want to be able to think in mobius, but my brain is currently
| like, "No thanks."
| sdwr wrote:
| I'll argue that "thinking in mobius" is simpler than thinking
| in circles, and more true to life than thinking in basic
| shapes.
|
| The core concepts in mobius-land are local curvature and
| global cumulative field.
| stjohnswarts wrote:
| Sorry those just aren't the way the average joe on the
| street thinks about things.
| KyleBerezin wrote:
| Yea they are kinda confusing, especially when you get into
| the 3D ones like klien bottles and roman surfaces. I also
| recently learned that if you make a mobius shaped
| transmission line (like a ladder line) and you send a pulse
| down it, that pulse will continue looping until it dissipates
| (or forever if it is a superconductor).
|
| https://www.microwavejournal.com/articles/21001-printed-
| reso...
|
| I have no idea if there are any advantages over a simple
| planar circular loop though.
| colordrops wrote:
| Are real life superconductors ideal, i.e. they truly would
| store a charge forever (at least until the material
| disintegrated)? Or is there some sort of loss, albeit much
| less than typical resistance?
| dekhn wrote:
| I can't really think in (visualize) 3d shapes, so I depend a
| lot on 3D geometry programs when I design things like for my
| microscope. A fair number of people I've talked to can
| visualize complex shapes in their head, rotate them around,
| do interference checking, etc.
| willis936 wrote:
| They're actually quite simple geometries in the right
| (unintuitive and warped) coordinate system.
| eternityforest wrote:
| Doing CAD design is really interesting. A lot of stuff is
| just 2.5D, extrusions of 2D sketches sitting on other 2D
| sketches.
|
| Then you accidentally make something truly 3D by intersecting
| things and realize you have no idea what you're looking at,
| couldn't imagine it if you closed your eyes, couldn't
| replicate it if you had a picture of the result and didn't
| know the 2D inputs that made it... and then you realize there
| are probably people out there who can see that entire design
| in their head.
|
| To me it's like unicycling on a tightrope or skateboarding or
| realistic oil painting or playing piano well. I have no real
| concept or reference point for what that experience must be
| like.
| p1mrx wrote:
| Just drawing a 3D slanted plane to match the front of my
| printer made my head hurt:
| https://www.printables.com/model/526981-ender-3-s1-quad-z-
| br...
| waldothedog wrote:
| Interesting. With a very strong reference for the
| experience of skateboarding, reading your sentence made me
| think about how hard it is to explain! I suppose when it's
| going well, it feels like body/mind flow, when it's going
| poorly it feels like physics :)
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