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New records on Wendelstein 7-X

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Re: New records on Wendelstein 7-X

#71

Post by colechristensen »

tgtweak wrote: post #26

This article has zero quantifiable information in it aside from the duration... which has no context. Who's recordkeeping this stuff? What are the other results so far? What is the tipping point where it is net positive? how long does it need to sustain a net positive fusion reaction to produce sufficient power for grid consumption? Are there other losses (thermal generation inefficiencies) that make the target even…

>What is the tipping point where it is net positive?

There are several interesting net positive tipping points depending on where you draw the boundary that energy in and energy out cross. We're still in the earlier stages of net positive where the boundary is quite small and little consideration is being given to the part of the process where electrons get pushed around in a power grid.

Re: New records on Wendelstein 7-X

#72

Post by thinkcontext »

sheepscreek wrote: post #51

TL;DR - Looks dangerous, but is it? (open question) Can we quantify it or at least make it more tangible? God, this contraption appears to be the kind of thing I wouldn’t trust my life with. Every time I look at a fusion reactor, it seems far more dangerous than my hobby lab, failing to inspire any confidence. The numerous moving parts create an equal number of potential points of failure. In contrast, a nuclear reac…

That fusion reactions are so difficult to get started makes the reactors very safe because failure makes them stop. So, if you lose magnetic confinement the reaction stops. The reactor may be damaged but that's it.

This is unlike fission reactors, where a failure causes reactivity to increase. That causes meltdown and the possibility of explosion and all the nasty radioactive contamination.

Re: New records on Wendelstein 7-X

#73

Post by vilhelm_s »

empath75 wrote: post #23
apples_oranges wrote: post #3

Looking at the picture, I wonder if complexity of these devices will significantly be reduced once it finally works. I assume a lot of the bells and whistles are needed to find the way, but once it's found..

The real problem with fusion power is that even if they figure it out, it still won't be cost competitive with solar and wind. Economically all the cost of building a "boil some water and turn some turbines" plant is _already_ in the "boiling some water and turning some turbines" part of the generation, and even if the heat part of it was _free_, the rest of it would be too expensive to bother building a plant for it…

Batteries are nowhere near that cheap.

Currently the cheapest non-intermittent energy source is gas; solar costs about half as much, and nuclear costs 50% more than gas [0]. Battery storage is currently competitive with gas for storing around 4 hours of electricity [1].

If we would want to replace the baseload with solar + batteries we would need to store 12 hours instead, during the dark half of the day, so it would cost 3x as much, 200% more than gas.

Maybe we can hope for battery prices to drop, but extrapolating from a Wright's law curve, for them to become cheaper by a factor of 3 we need to produce 32 times as many of them [1, again], it won't happen in the near future.

[0] https://www.eia.gov/outlooks/aeo/electricity_generation/pdf/... [1] https://www.lesswrong.com/posts/mnaEgW9JgiochnES2/2024-was-t...

Re: New records on Wendelstein 7-X

#74

Post by jeffbee »

LeifCarrotson wrote: post #21
apples_oranges wrote: post #3

Looking at the picture, I wonder if complexity of these devices will significantly be reduced once it finally works. I assume a lot of the bells and whistles are needed to find the way, but once it's found..

In my experience doing plumbing/hydraulics/pneumatics for industrial equipment, the first generation of a new product always looks way more complex than later versions. But I'm not sure they're actually more complex, they're often using a smaller variety of more flexible "industrial Lego" rather than custom, unique parts that are harder to extend or modify. Yeah, a single welded tube of the right diameter that necks…

W7-X looks insane because its configuration was discovered by a computer pursuing a numerical optimization. We don't have any sound reasons to believe the next one will be simpler.

Re: New records on Wendelstein 7-X

#75

Post by pengaru »

StevenWaterman wrote: post #7
apples_oranges wrote: post #3

Looking at the picture, I wonder if complexity of these devices will significantly be reduced once it finally works. I assume a lot of the bells and whistles are needed to find the way, but once it's found..

Your question reminds me of the image showing how SpaceX raptor motors evolved https://imgur.com/a/4w3q3lS

Is that an actual honest photo? The first two seem fully equipped including what seems to be shielded wiring harnesses. #3 looks totally devoid of any electronics.

disclaimer: I don't follow this stuff at all. It just looks like a b.s. photo deliberately exaggerating how simplified #3 is vs. the others to this grease monkey.

Re: New records on Wendelstein 7-X

#77

Post by rnhmjoj »

smallerize wrote: post #49
Analemma_ wrote: post #42

Earlier quoted context omitted.

I thought the expectation was that actually-operating fusion plants would operate in pulses rather than continuously, but I could be misremembering.

Toroidal reactors have to operate in pulses. Stellarators can be operated in steady-state (although sometimes they are pulsed to achieve higher energy).

Tokamaks can also be operated in steady-state, at least theoretically. The reason a tokamak is pulsed is due to the fact the toroidal current is driven inductively, so there is a limit to how long you can keep increasing the current in the central solenoid. However there are other methods, for example, neutral beam injection and electron cyclotron current drive. You can even exploit the bootstrap current (self-generated by collisional processes in the plasma) to obtain a near 100% non-inductive toroidal plasma (this is called "advanced tokamak" regime).

Anyway, the older generation of devices was pulsed for engineering reasons (like non-superconducting coils getting too hot). The current generation of device is solving most of these and is limited by MHD instabilities alone (neoclassical tearing modes, mostly), if we can get active control mechanism working, then will be finally approach the long-pulse or steady-state regime.

Re: New records on Wendelstein 7-X

#78

Post by jcims »

pengaru wrote: post #75
StevenWaterman wrote: post #7

Earlier quoted context omitted.

Your question reminds me of the image showing how SpaceX raptor motors evolved https://imgur.com/a/4w3q3lS

Is that an actual honest photo? The first two seem fully equipped including what seems to be shielded wiring harnesses. #3 looks totally devoid of any electronics. disclaimer: I don't follow this stuff at all. It just looks like a b.s. photo deliberately exaggerating how simplified #3 is vs. the others to this grease monkey.

Ready to rock(et)

https://x.com/gwynne_shotwell/status/1821674726885924923?s=4...

Re: New records on Wendelstein 7-X

#79

Post by johannes1234321 »

i_am_proteus wrote: post #58
tgtweak wrote: post #43

Earlier quoted context omitted.

Here is an actual article with some context - and a reality check that other experimental reactors in the past have sustained similar triple product for longer durations... https://www.ipp.mpg.de/5532945/w7x

>The fact that W7-X results are on a par with JET is remarkable because JET had three times the plasma volume of Wendelstein 7-X. What's important here is that W 7-X is a stellarator , a different type of fusion reactor from almost all prior reactors (they are tokamaks), with a smaller volume than the co-record holder. That a stellarator gets these results with a much smaller fusion volume is promising for the perfor…

> from almost all prior reactors (they are tokamaks)

Tokamak and Stllerator are about equally old, 1953 vs 1954, while both types where for a period developed in secrecy behind either side of the iron curtain till end of the 1960ies where collaboration started.

IPP was founded in 1960 (by, among others, my dad) and focussed on Stllerator since then (while collaborating in JET and ITER around their tokamak projects)

Re: New records on Wendelstein 7-X

#80

Post by Tuna-Fish »

riffraff wrote: post #62
smallerize wrote: post #49

Earlier quoted context omitted.

Toroidal reactors have to operate in pulses. Stellarators can be operated in steady-state (although sometimes they are pulsed to achieve higher energy).

But don't you need to "refuel" now and then?

Refueling is not why tokamaks are pulsed.

A smooth toroidal magnetic field cannot confine plasma. The field at the outer side (further away from axis) are spread more widely and weaker than in the inner side. In a very short time, this will cause ions to drift out of confinement at the outer side. The solution is to produce a twisted, helical field, where the field lines go in circles in both directions of the toroid simultaneously, like the stripes of a candy cane in the bend.

Different reactor designs have different solutions to this. Tokamaks use a solenoid to drive a strong toroidal current in the plasma. This, in turn, causes a poloidal magnetic field, which provides the second half of the field needed for confinement. But this only works when magnetic field of the solenoid coil is varying smoothly over time in a single direction. Eventually, you hit some limit in your ability to do that, at which point you lose your ability to confine the plasma and the pulse ends.

Stellarators do not have this issue. They get the full field geometry needed from their primary field, by twisting it around the toroid in a very complex path. The downside is that they are much more difficult to design and build.

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