Net Energy Gain from Fusion! What?!

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classical_Liberal
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Net Energy Gain from Fusion! What?!

Post by classical_Liberal »

I'm not a physicist, but I know big news when I see it. Net Energy Gain fusion has evidently been accomplished and will be officially announced in short order. I have confirmed this report through at least a half dozen reputable news sources. The linked is just my favorite source, feel free to use the search engine of your favorite source to find the information.

The potential of 20% return on energy in a controlled fusion reaction seems to me one of the most important headlines in the past century. If repeatable, and scalable, this is literally the type of thing that makes a post scarcity future possible.

BUT, like I stated, I'm not a physicist. This forum has it's fair share of scientists. Is there a reason this is not as exciting as it seems to a novice first glance? Or is this actually score one for the techno-optimists?

Thanks.

Edit to add: Sorry that was not pay-walled when I posted the link, now it is.
Last edited by classical_Liberal on Mon Dec 12, 2022 6:28 pm, edited 1 time in total.

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Ego
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Re: Net Energy Gain from Fusion! What?!

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jacob
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Re: Net Energy Gain from Fusion! What?!

Post by jacob »

I am a physicist and I used to work about half a mile away from the National Ignition Facility where it happened including touring the facility and a workshop on ideas for how to spend all this tax payer money.

The NIF is somewhat different from the typical magnetic confinement setup that dominates most fusion research. Instead of a bunch of superconducting magnets, you have 192 giant lasers (the laser bay is the size of a football field) where the beams are directed onto a small pellet (pinhead sized IIRC) in a reaction chamber (the size of a bathroom) from all sides to compress the pellet enough to maintain "a sufficient density for a sufficient time"(*) to achieve fusion (the nucleons in the pellet must be close enough for long enough to react).

The 1.2 (20%) refers to the energy from this fusion (numerator) divided by the impacting laser energy (denominator).

What the denominator doesn't include, but should include if fusion is to be used as a power source rather than just an experimental research facility for plasma physics, is the energy required to drive these lasers (lasers are nowhere near 100% efficient---it costs much more than 1W to drive a 1W laser beam), and the energy losses from using the heat from the fusion to drive a turbine to generate the electricity to drive the lasers. That's just the physics part of it. Turning this into a power plant at scale is a much bigger problem.

"Controlled" is also a bit ... misleading. This is a one-shot reaction. It's as controlled as firing a gun, that is, you can control the size of the "bang", but in order use this as a power plant, you'd want more of a burn than a bang ... or at least regularly repeating bangs.

(*) This is THE problem with fusion. It's hard to have both at the same time since it involves ginormous pressures. Pressures that are generally only found at stellar densities ... which is why my work was tangentially relevant.

I'm not as excited about this as I was/am about the tokamaks being able to sustain fusion for a few seconds at this point. Give it another 30 years ... as usual.

PS: To be fair, I'm not easily excited. I'd rank this on par with the "scientists take first picture of a black hole" with my reaction being "Well, that's not exactly... but okay, that's cool."

classical_Liberal
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Re: Net Energy Gain from Fusion! What?!

Post by classical_Liberal »

@jacob
Ahh, so the energy gain is P/S rather than P/E. Are you going to follow this story as the details are released? I'd be curious to read your opinion of more specifics if you are willing to post them.

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Re: Net Energy Gain from Fusion! What?!

Post by Sclass »

It sounds a little unfair not to include the laser power.

I had a number of friends working on that rig. Some are dead now. It has been close for years.

I don’t hold my breath when somebody from that tribe says “we are really close.”

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Re: Net Energy Gain from Fusion! What?!

Post by figmenter »

For a comprehensive overview of the difficulties with fusion, read the summary of articles over at https://energyskeptic.com/2021/why-fusi ... ears-away/

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Re: Net Energy Gain from Fusion! What?!

Post by Sclass »

Good article. Some of that stuff like the scalability issue of the tritium capsules is depressing.

I wanted to mention when I first read @jacob’s post about the accounting of laser power I read it too fast and thought he meant they don’t account for the power of the lasers. After watching the interview with the DOE secretary online I realized what he means is they aren’t considering the electrical energy going into the laser when getting their output ratio > 1. They do count the optical power, but if their laser was only 1% efficient at converting electricity to light their number would be 100x lower.

In the NIF’s defense I’d say it’s an issue of accounting. Laser efficiency has increased over the last 60 years since people conceived this experiment. It may be fair to separate the electrical conversion efficiency from the laser or else it muddies things up. It’s analogous to discussing total solar energy generation and leaving out the revolution in solar cell efficiency that’s occurred in a decade. Lasers have really increased in efficiency over the years so this may be something that should be taken out of the final figure.

Maybe it’s like arguing CPU power consumption and trying to incorporate the revolution in PC power supply efficiency at the same time. It muddies things up to mash it all together.

I completely uniformed on this fusion project. But my takeaway is they’ve shown that the laser containment trick is works. That’s a big deal. It may not be scalable but just knowing something is possible totally changes the trajectory of R&D. We used to have a saying at HP Labs, “don’t even tell our competitors about our smallest achievement because once they know something is actually possible they will work a hundred times harder on the same thing.”

Back in my undergrad (Berkeley/Livermore academic incest family) I had a couple of physics professors working on this machine in some way or another. They were really committed to it and swore it was the better hope at engineering controllable fusion (as opposed to tokamaks). They’re dead now and never got to see this. I think it’s a very big deal.

There are still the question in my mind whether this is the right approach if you want scalability. The science may be like the relentless pursuit of removing amyloid tangles from Alzheimer’s patients which may have steered us away from a cure to the real cause of Alzheimer’s disease. That is just because their laser experiment worked maybe it’s still a useless way to achieve fusion on a scale suited for power grid supplies.

Just my thoughts this morning. Hats off to the people who gave their lives to this project.

ETA - my naive recollection was fusion was to provide limitless free electricity once you got it going. Perhaps worrying about electrical efficiency of a laser is less of a worry if you have all the electricity you want from your fusion? I suspect that is the story the fusion people have been selling us for decades…maybe I’m just drinking their grant koolaid.

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Re: Net Energy Gain from Fusion! What?!

Post by jacob »

To be more explicit, the 20% number they're talking about is the Q factor of the reaction itself. They've verified experimentally what was already known theoretically. It may be easier to explain in more concrete terms. See https://en.wikipedia.org/wiki/Hohlraum# ... ent_fusion and https://en.wikipedia.org/wiki/Fusion_energy_gain_factor for more details.

NIF is basically a bay of 192 lasers the size of small ship that concentrate their light in an instant burst on a hollow pellet (the size of a BB) made out of depleted uranium. Inside that pellet is the actual target made out of the fusion materials, the size of a pinhead. When the photons from the lasers hit the outside of the pellet, they explosively evaporate the surface causing a shockwave to travel outwards. Due to Newton's third law, this action causes an opposite and equal reaction with a shockwave traveling symmetrically inwards towards the center of the pinhead. If the shockwave symmetry is perfect (so there's no way for the plasma to "squeeze out"---this is what the magnetic field does in tokamaks) the pressure (density * temperature) will reach stellar core densities and cause the fusion process to happen. The Q factor how much heat (and light) came out of the fusion process divided by either the energy in the 192 laser beams or the inbound shockwave (I'm not sure, the difference would be a factor 2).

Note, we're used to thinking of lasers as a continuous beam. These lasers fire a very short burst.

The total energy released by the fusion was 3.15MJ. The total energy going in was 2.6MJ.

3.15MJ is enough to turn about 1.2kg of water into steam. It's also the energy released by burning 191 grams of pine wood.

So basically what happened here was that a torch made out of 160g of wood was used to set fire to a stack of 2x4s and burn 191g of them. That's not counting the energy to ignite the torch, carry the torch to the fire, etc.

It was more a proof of concept that a torch can actually burn a slightly bigger amount of wood.

We can also compare it to a nuclear power plant. A standard size is about 1GW. The boilers are 70% efficient (just to pull a number out of my ...), so the fission reaction is delivering 1.43GW. To create a similarly sized fusion plant, you need burn 1.42GW/(3.15MJ-2.6MJ) = 2581 pellets per second.

I don't know how long it takes to reset the experiment. But that's an interesting engineering challenge to rotate in new pellets that fast (about 3 times faster than a typical machine gun) and build lasers that can fire that rapidly.

The 2581 is the absolute minimum presuming all other aspects of the system are 100% efficient. If the laser energy is 20% efficient, we're talking 12500/pellets per second, and so on.

Please verify my math.

The Q factor link above distinguishes between "scientific" breakeven, "engineering" breakeven, and "commercial" breakeven. This is good distinction and should have been highlighted in the reporting. What we're talking about here is scientific breakeven. Only commercial breakeven is going to revolutionize society. Note that traditional fission power, which is technologically much simpler, is barely beyond commercial breakeven.

In terms of where we are with fusion, this is the equivalent of the first fission experiments in the late 1930s where people learned that moving two clumps of fissile material near each other would generate heat. This was initially done by hand. The guy who did it later died.

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Re: Net Energy Gain from Fusion! What?!

Post by M »

As much as I love the idea of fusion, I have slowly accepted the idea of solar panels and sodium ion batteries as my eventual fate.

https://www.nextbigfuture.com/2022/10/c ... -2023.html

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Re: Net Energy Gain from Fusion! What?!

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Re: Net Energy Gain from Fusion! What?!

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Hey that was interesting. They mention on their website that D2O is abundant in the sea. Does anyone have any idea how scalable the production of isotopic water is on a large enough scale to support fusion energy plants?

I built the signal processing chain on a deuterium detector mid career. The chemist on the team concentrated D2O by settling water in a big drum in the lab. I recall it was critical it wasn’t agitated. It was a slow process to get slightly elevated concentrations of D2O from tap water.

I kind of recall a PBS show about the Nazi atomic bomb effort where Heisenberg and his team couldn’t get enough deuterium.

Ahh…Wikipedia. I guess it is possible to refine significant amounts of deuterium. The supply of Deuterium is likely not the problem when compared to fusion engineering.

https://en.wikipedia.org/wiki/Norwegian ... r_sabotage

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Re: Net Energy Gain from Fusion! What?!

Post by jacob »

Sclass wrote:
Mon Dec 19, 2022 11:43 am
Hey that was interesting. They mention on their website that D2O is abundant in the sea. Does anyone have any idea how scalable the production of isotopic water is on a large enough scale to support fusion energy plants?
The current market for deuterium is small, but deuterium is already extracted at an industrial scale from salt water or any water.

The concentration of D20 in water is 1 in 5000-10000 water molecules. There are a lot of different trace elements in water. For example, the world's oceans also contain an enormous amount of gold or uranium. It, therefore, comes down to the key question of whether the combined process reaches "economical break even".

Insofar fusion turns out to have a high EROI, the sky(*) is pretty much the limit. Someone made a scale that related the "level of civilization" to the EROI of the prevailing energy resource. Something like,

150 ~ The ability to build a 20th century civilization
10 ~ The ability to maintain a 17th century civilization

If fusion has an EROI of say 800, it would make it possible to do things that are currently unimaginable. Humanity has never had access to anything over 200. The current energy mix, having depleted the easy oil, is somewhere around 20-40ish.

(*) Actually that idiom would need some revision. The limit would definitely go beyond the sky and into interplanetary space with this capability. The moon, for example, contains deposits of deuterium and tritium and it's a lot easier to launch from than the earth. After that interstellar space would be a whole other ballgame, but something an order of magnitude more potent than fossil fuels would definitely "unlock" the solar system.
Sclass wrote:
Mon Dec 19, 2022 11:43 am
I built the signal processing chain on a deuterium detector mid career. The chemist on the team concentrated D2O by settling water in a big drum in the lab. I recall it was critical it wasn’t agitated. It was a slow process to get slightly elevated concentrations of D2O from tap water.
I got a better story. I knew an experimental physicist who once got to drink some D20 (because why not?). Apparently, it has a slight intoxicating effect. Being slightly heavier than H20, it might shift some chemical balances in the brain. Also, the going rate at the time was about $1000/liter, so it was like an extremely expensive bottle of wine. BTW, you can order deuterium right off the internet these days. I just checked. Apparently, it has gotten a bit more expensive since then.

I'm almost sure there's an Alistair McLean novel about the sabotage of the Norwegian heavy water plants during WWII? Or maybe it was someone else. There's definitely a 1960s movie about it.

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Re: Net Energy Gain from Fusion! What?!

Post by Sclass »

Man that is wild!

Is that safe? Well it must be according to Google. Wow.

Reminds me of my classmate who took a swig of liquid nitrogen accidentally while showing us he could roll it around in his mouth without freezing his tongue. He buckled over on the floor belching uncontrollably for a few minutes while a professor looked on silently shaking his head.

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Re: Net Energy Gain from Fusion! What?!

Post by chenda »

Sclass wrote:
Tue Dec 20, 2022 3:55 pm
He buckled over on the floor belching uncontrollably for a few minutes while a professor looked on silently shaking his head.
:lol:

Lessons learned by the body educate the mind.

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Re: Net Energy Gain from Fusion! What?!

Post by Jean »

All researcher i met that worked on fusion i talked to gave me the impression that they didn't believe in the possibility for fusion to be doable.
They just thought it was a nice goal to fund research for.
Also, I don't see how fusion is radicaly better than fission if we were to build modern reactor (like fast neutron reactors).
At least on earth. Of course if we want to launch from other bodies, deuterium and tritium are probably easier to get than uranium or thorium.

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