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Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes

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Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes

#111

Post by aidenn0 »

alkonaut wrote: post #58
amelius wrote: post #24

Earlier quoted context omitted.

Isn't this similar to the monetary meaning of the word turnover? Like turnover : profit energy turnover : net energy output?

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?

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"

Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes

#112

Post by mjfl »

juujian wrote: post #110
mjfl wrote: post #67

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.

'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.

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.

Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes

#113

Post by RivieraKid »

aquafox wrote: post #56

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

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)

Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes

#114

Post by KyleBerezin »

themagician wrote: post #63
KyleBerezin wrote: post #3

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, b…

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 understandi…

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.

Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes

#115

Post by adhesive_wombat »

hedora wrote: post #38
Eji1700 wrote: post #6

Earlier quoted context omitted.

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.

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.

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.

Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes

#116

Post by constantcrying »

aquafox wrote: post #60
aquafox wrote: post #56

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

Why the down votes? What is factually wrong with that statement?

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.)

Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes

#117

Post by lhoff »

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/)

Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes

#118

Post by KyleBerezin »

waterheater wrote: post #108
KyleBerezin wrote: post #101

Earlier quoted context omitted.

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?

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 yo…

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.

Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes

#119

Post by waldothedog »

eternityforest wrote: post #76
themagician wrote: post #63

Earlier quoted context omitted.

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 understandi…

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 ther…

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 :)

Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes

#120

Post by moffkalast »

mjfl wrote: post #67

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.

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.
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