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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

#151

Post by pfdietz »

cyberax wrote: post #133
t0mas88 wrote: post #28

Earlier quoted context omitted.

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.

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.

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

#152

Post by pfdietz »

aeyes wrote: post #65
sp332 wrote: post #55

Earlier quoted context omitted.

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…

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…

Chile is cheaper, and in a solar-powered world energy intensive industries will move to such places. If (say) Sweden wants to try to preserve industries by building nuclear power plants, they'll find the expensive power from nukes competing against the dirt cheap power from Chilean (or Namibian, or Australian, or Saudi Arabian) solar.

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

#153

Post by avar »

tw061023 wrote: post #77
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…

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 electrica…

    > The very _complexity_ of it
    > somehow feels subtly wrong.
Why is in complex? Because it's not all square corners or a donut shape?

I understand that it was hard to build, but isn't that just because it's a one-off?

Any one part of the inside of it looks no more oddly shaped than the outside of any modern car, and we've managed to scale that.

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

#154

Post by DennisP »

MichaelZuo wrote: post #123
NateEag wrote: post #121

Earlier quoted context omitted.

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)

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 o…

Helion's fuel mix produces just 6% of its energy as neutron radiation, and if you harvest it you'll lose a third of that. As long as you have enough net energy, collecting that 4% might not make financial sense.

With fuel costs insignificant, your cost per kWh is mainly capital cost. Let's say it's all capital just to keep it simple. I don't know how much the input energy will be but if your choice is between, say, generating net energy of 50MW without a turbine or 54MW with a turbine, then you would skip the turbine if it adds more than 8% to the capital cost. I suspect Helion has done this calculation in detail.

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

#155

Post by skykooler »

fastneutron wrote: post #146
gus_massa wrote: post #134

Earlier quoted context omitted.

They plan to use 2D + 3He -> 4He + 1H, so no neutrons https://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.)

Nitpick: You’re always going to get some parasitic D+D reactions because it’s reaction cross section is appreciably higher than D + 3He below 50 keV, and non-negligible even after the crossover point.

Doesn't D+D just yield 4He (and no neutrons) though?

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

#156

Post by philipkglass »

skykooler wrote: post #155
fastneutron wrote: post #146

Earlier quoted context omitted.

Nitpick: You’re always going to get some parasitic D+D reactions because it’s reaction cross section is appreciably higher than D + 3He below 50 keV, and non-negligible even after the crossover point.

Doesn't D+D just yield 4He (and no neutrons) though?

It yields 3He plus a 2.45 MeV neutron at least part of the time.

See the diagram here: https://undsci.berkeley.edu/teach-resources/products-of-deut...

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

#157

Post by quickthrower2 »

tsimionescu wrote: post #59
karmajunkie wrote: post #30

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 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 is happening in a star to emit useful radiation? I feel I should know that, I probably did but forgot.

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

#158

Post by [deleted] »

snarkconjecture wrote: post #16
aidenn0 wrote: post #8

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...

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…

[deleted]

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

#159

Post by NovaDudely »

KyleBerezin wrote: post #90
Simon_O_Rourke wrote: post #72

Earlier quoted context omitted.

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?

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 fo…

First thing that comes to mind is like twisted pairing on cables. Distributes the external/internal forces more equally. Is it anything like this?

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

#160

Post by worik »

flotwig wrote: post #87
sdwr wrote: post #74

Earlier quoted context omitted.

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.

Please don't "move fast and break things" with nuclear fusion :-)

What is the worst that can happen?

Seriously, I think I might know (a fire) but I do not.

Is there any possibility these can go ban! and spread nasty stuff around the neighbourhood?

I doubt they can go thermonuclear bang! but I am not a physicist.

What is the worst than can happen?

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