Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

ipp.mpg.de

Post reply on HN
Print view View original

121–130 of 322 posts

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

#121

Post by NateEag »

nerdponx wrote: post #105
tsimionescu wrote: post #59

Earlier quoted context omitted.

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…

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.

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)

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

#122

Post by moffkalast »

pfdietz wrote: post #99

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.

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?

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

#123

Post by MichaelZuo »

NateEag wrote: post #121
nerdponx wrote: post #105

Earlier quoted context omitted.

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.

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 otherwise...

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

#124

Post by ChuckMcM »

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

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

#125

Post by calfuris »

midasuni wrote: post #70
idiotsecant wrote: post #45

Earlier quoted context omitted.

Yes, the boring and actually feasible answer is steam. But it sure is fun to dream! https://en.wikipedia.org/wiki/Direct_energy_conversion

Isn’t one of the problems with nuclear that it increases water temperature in rivers

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.

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

#126

Post by MichaelZuo »

RivieraKid wrote: post #113
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 ene…

I could see a plausible 10x growth if literally the entire world achieved within the ballpark of 2023 US levels of per capita wealth.

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

#127

Post by bmicraft »

fizigura wrote: post #46
KyleBerezin wrote: post #18

Earlier quoted context omitted.

Yea, but compare the financial burden of that compared to a solar farm of the same output. Not to mention the technical risk.

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.

No, solar farms in the desert with a HVDC lines obviously.

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

#128

Post by jessriedel »

nerdponx wrote: post #105
tsimionescu wrote: post #59

Earlier quoted context omitted.

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…

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.

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.

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

#129

Post by sambapa »

nerdponx wrote: post #105
tsimionescu wrote: post #59

Earlier quoted context omitted.

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…

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.

It's because we're in local maximum - steam turbines are just so developed

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

#130

Post by jessriedel »

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…

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.
Post reply on HN