> The energy turnover of 1.3 gigajoule was achieved with an average heating power of 2.7 megawatts, whereby the discharge lasted 480 seconds.
Can a physicist/thermal engineer explain what this means?
Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes
181–190 of 322 posts
Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes
#182Earlier quoted context omitted.
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…
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, ...)
Yes I was referring to odd. But I've been reading some papers and I think even 4-fold had the mobius effect. I'll comment here again tomorrow when I have learned a bit more on the topic.
Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes
#183This 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 oth…
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 relative…
What eventually happens to the excess neutron “waste”? Surely there’s some negative consequence to producing an enormous number of neutrons, no?
Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes
#184Earlier quoted context omitted.
You'll freeze to death in winter, but that's a minor thing. Living is overrated.
Not with a properly design energy system. The conclusion of 100% RE research is that such a system will have costs similar to fossil fuels.
No. Right now there is no reasonable way to have a 100% renewable and reliable grid in Northern Europe, excepting classic hydro.
I specifically studied the German grid, and it needs about a MONTH of storage to compensate for a once-in-a-century Dunkelflaute (a period with little wind, no sun, and cold temperatures).
Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes
#185Earlier quoted context omitted.
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…
great comment, thanks - this is why I read HN
I’m going to assume the name “waterheater” is from a prosaic way of naming a nuclear reactor.
Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes
#186This is an incredible achievement but there are strong reasons to suspect that stellarators are not and will never be plausible candidates for energy generation. For some more experimental or perhaps military tasks, it's viable.
Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes
#187This is an incredible achievement but there are strong reasons to suspect that stellarators are not and will never be plausible candidates for energy generation. For some more experimental or perhaps military tasks, it's viable.
Why do you think this? Also, suggesting only the military should use it suggests it is stellarators are well suited for energy weapons versus powering homes/industry, which is also curious, as energy weapons need huge impulse amounts of power, not power that is constantly available and ramps slowly by comparison.
Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes
#188Earlier 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?
The 1.3 GJ is how much electricity they put in. There is no fusion reaction or energy production, it's just an experimental device to study plasma containment.
Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes
#189Ahh, 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…
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?
It's actually really easy to explain.
Draw a torus and then draw rectangular "bands" across it, they will represent the containment magnets.
Due to pure geometry, the area closer to the center will have a smaller distance between bars. This means that the magnetic field will be stronger near the center.
This in turn means that particles will separate (depending on charge) and drift to the sides. It seriously interferes with the containment.
You can fix that by changing the torus into something resembling "8", so that particles move to one side when they fly through the upper part, but then they'll move back as they fly through the lower part.
Of course, you can't just do that in 2D because the part in the middle of "8" will have no magnetic field. You need something without self-intersections. You can try to move one side up and another down. But that doesn't quite work either because you will get another set of preferred directions.
So instead you go with the gentle twisting, resulting in the Möbius-looking shape.
Re: Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes
#190Speaking 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.
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).
Thanks for the update. I was taking no news as good news and didn't expect to hear anything until 2025 anyway.