this post was submitted on 06 Feb 2024
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[–] [email protected] 263 points 9 months ago (40 children)

Excluding all the ancillary services, including the lasers that maintained the plasma, which was the principle part of this latest test.

Factoring everything in, they're at about 15% return.

This is still very good for this stage, but the publications are grossly misleading.

[–] [email protected] 9 points 9 months ago (11 children)

That's what I came to the comments to find. Thank you. Would have been much bigger news if it was net energy positive.

[–] [email protected] 8 points 9 months ago (10 children)

15% return is still net energy positive isn't it? Or is that not 15% above the input?

[–] [email protected] 3 points 9 months ago* (last edited 9 months ago) (2 children)

I can't read the full article (paywalled for me) but it references the National Ignition Facility so the way it goes is super lasers blast a tiny hydrogen thing and that creates a tiny bit of fusion that releases the energy. The energy of the laser blast is what's being called the input and the fusion energy released the output. What is misleading is that a greater amount of energy was used create the laser blast than the laser blast itself outputs. If you consider the energy that went into creating the laser blast the input (rather than the laser blast itself), then it's usually not a net positive energy release.

[–] [email protected] 2 points 9 months ago
[–] [email protected] 2 points 9 months ago (2 children)

What other energy are you referring to? Like warming up the laser?

[–] [email protected] 2 points 9 months ago (1 children)

[email protected] got it, but basically lasers are pretty inefficient. The article I just found said (in a different run of this facility) they put 400MJ into the laser to get 2.5MJ out of it. So that makes the whole firing system what, 0.6% efficient? Your fusion reaction would have to give more than 400MJ to truly be in the positive for this particular setup/method, but again this facility is a research one and not meant to generate power - there isn't even a way to harness/collect it here.

[–] [email protected] 2 points 9 months ago

Oh so the laser's generating mostly heat and a little coherent radiation, and they're only referring to the coherent radiation as the "energy input" to the process.

Hmm. Kinda sketch.

Especially because that's not trivial. If we have no way of obtaining laser light other than that process, and the laser is the only way to feed the fusion reactor, then that's 100% on the balance books of this process.

[–] [email protected] 3 points 9 months ago

Remember when incandescent light bulbs were the norm? They worked by sending full line voltage through a tiny tungsten wire that would get so hot that it glows, making some light, but 95% of the energy that gets consumed is frittered away as heat? The high-power lasers needed to make fusion happen are a lot like that.

I believe all this article is saying is that 15% more energy than what came out of the lasers as useful laser light was liberated in the reaction.This completely ignores the energy it took to power those massively inefficient lasers.

I think it also ignores the fact that the 15% more energy liberated wasn't actually, like, harnessed by a generator. I believe (and I may be wrong) this was testing only the reaction itself. Actually hooking that up to a turbine and using it to create energy that is cost competitive with contemporary sources is still a completely unsolved problem.

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