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MIT-designed project achieves major advance toward fusion energy

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Re: MIT-designed project achieves major advance toward fusion energy

#31

Post by nielsbot »

sdeyerle wrote: post #21
nielsbot wrote: post #18

Earlier quoted context omitted.

The article says this is from an "MIT-CFS collaboration" which is "on track to build the world’s first fusion device that can create and confine a plasma that produces more energy than it consumes. That demonstration device, called SPARC, is targeted for completion in 2025." So, sounds like it's for SPARC.

Yeah, they are definitely building SPARC. I had just been under the impression they were trying to do the separable magnets in SPARC, and was curious if I misunderstood their plan or if their plan had changed.

Yeah--I misread your question. :)

Re: MIT-designed project achieves major advance toward fusion energy

#32

Post by phscguy »

jcfrei wrote: post #20

Lots of negative comments in this thread. I've been following CFS for a few years now and I honestly believe this is an historic event - probably the beginning of the "fusion age".

Yeah, any positive news on fusion progress and there always seems to be the same set of comments appear that are overwhelmingly critical of fusion development. Fusion is not well funded and imo has been let down by mismanagement of ITER, and despite this keeps making progress.

I feel that fusion is one of humanity's best shots at actively reversing climate change, and it is disheartening to see such widespread pessimism about it. Yeah it's hard. There are huge hurdles in making it economicly viable, but if we can go from first powered flight to the moon in 70 years, and put billions of transistors on a chip in 50, then maybe we can get fusion going. It's clearly possible.

Re: MIT-designed project achieves major advance toward fusion energy

#34

Post by dfdx »

Plenty of skepticism in these comments. I've been following CFS for a while and can present a point of view for why this time might be different.

Fusion energy was actually making rapid progress in the latter half of the twentieth century, going from almost no power output in the fifties and sixties to a power output equal to 67% of input power with the JET reactor in 1997. By the eighties there was plenty of experimental evidence to describe the relationships between tokamak parameters and power output. Particularly that the gain is proportional to the radius to the power of 1.3 and the magnetic field cubed. The main caveat to this relationship was that we only had magnets that would go up to 5.5 Tesla, which implied we needed a tokamak radius of 6 meters or so in order to produce net energy.

Well that 6 meter tokamak was designed in the eighties and is currently under construction. ITER, being so large, costs tens of billions of dollars and requires international collaboration; the size of the project has led to huge budget overruns and long delays. Recently however, there have been significant advances in high-temperature super conductors that can produce magnetic fields large enough that we (theoretically) only need a tokamak with a major radius of about 1.5 meters to produce net gain. This is where SPARC (the tokamak being built by the company in the article) comes in. The general idea is that since we have stronger magnets now, we can make a smaller, and therefore cheaper tokamak quickly.

Small tokamaks do have downsides, namely that the heat flux through the walls of the device is so large that it will damage the tokamak. There have been breakthroughs with various divertor designs that can mitigate this, but to the best of my knowledge I'm not sure that CFS has specified their divertor configuration.

This was just a short summary of the presentation by Dennis Whyte given here [0]. I do not work in the fusion community.

[0] https://www.youtube.com/watch?v=KkpqA8yG9T4

Re: MIT-designed project achieves major advance toward fusion energy

#35

Post by TrainedMonkey »

This is exciting. Magnetic field strength is a key component for enabling magnetic confinement fusion. This is because energy gain and power density scales to the 3rd and 4th power with magnetic field strength but only ~linearly with reactor size. See following equations for more details: https://youtu.be/xJ2h3vbOag4?t=306

So, why is this particular announcement exciting? There are 3 factors:

1. This is a high temperature superconductor. I can't find any references, but as far as I remember the substrate they are using needs to be cooled to (WRONG, it was cooled to 20degK, see reply by MauranKilom) 60-70 degK to achieve super conductivity. Compare to magnets used in ITER which need to be cooled to 4degK. This is the difference between using relatively cheap liquid nitrogen vs liquid helium.

2. Field strength of 20 Tesla is significantly higher than 13 Tesla used in ITER. Given that magnetic confinement fusion scales significantly better with field strength vs reactor size, this will enable much smaller reactor to be power positive. See following links for more details on ITERs magnets: https://www.newscientist.com/article/2280763-worlds-most-pow... https://www.iter.org/newsline/-/2700

3. Finally, the magnet was assembled from 16 identical subassemblies, each of which used mass manufactured magnetic tape. This is significantly cheaper and more scalable than custom magnet design/manufacturing used by ITER.

The kicker is how 3 of the factors above interact with the cost of the project. Stronger magnets allow smaller viable reactors. High temperature superconductors + smaller reactors allow for a much simpler and smaller cooling system. Smaller reactors + scalable magnet design further drives down the cost. Finally, cost of state of art mega projects scales somewhere between 3rd and 4th power with the size of the device. Combining all of the above factors, SPARC should be here significantly sooner than ITER and cost a tiny fraction (I would guesstimate that fraction to be between 1/100 and 1/10,000).

edit: typos + looked at the cost of ITER and refined my cost fraction guesstimate + corrected some stuff based on the reply by MauranKilom.

Re: MIT-designed project achieves major advance toward fusion energy

#37

Post by apendleton »

pfdietz wrote: post #28
tppiotrowski wrote: post #5

Earlier quoted context omitted.

My understanding is that the volume of the magnet is smaller and thus the entire reactor size goes down significantly leading to lower cost. ITER was designed to use weaker electromagnets and therefore needs a massive building and tons of cranes and a massive budget.

The ARC reactor design has 10x the volumetric power density of ITER. Unfortunately, the ARC design also had 40x worse power density than a PWR primary reactor vessel.

Is that the right metric? You wouldn't need to build a huge containment structure around it like you would for a PWR, so I'd imagine the power density of the plant as a whole wouldn't be anywhere near 40x worse. Why focus just on the primary reactor vessel?

Re: MIT-designed project achieves major advance toward fusion energy

#38

Post by zardo »

apendleton wrote: post #29
shmageggy wrote: post #7

These university press releases are always very positively framed. This one makes the new magnet seem incredibly promising and fusion seem like almost an inevitability now, but decades of failure have us conditioned for skepticism. What's the catch this time?

I think the framing of what's happened so far as "failure" is probably the main thing responsible for this perception. It's true that progress has been slower than many had hoped and the most optimistic had projected, but "failure" sort suggests that the things the research community have been trying haven't represented meaningful progress towards the goal of power production, which isn't the case. Q (the ratio of en…

Would stellarators see the same benefits as tokomaks from higher field strength magnets?

Re: MIT-designed project achieves major advance toward fusion energy

#39

Post by apendleton »

phicoh wrote: post #25
ChrisMarshallNY wrote: post #6

Earlier quoted context omitted.

The running joke has always been that “Fusion is 20 years away,” and has been, for the last 50 years. I really want this to work. I am a bit concerned, with how “the old guard” will react, once we have successful, productive, fusion. I foresee an astroturf NIMBY campaign against construction of fusion plants.

At the moment it is very far for clear that fusion will be cost effective. The article says this about the fuel of fusion: "The fuel used to create fusion energy comes from water, and “the Earth is full of water — it’s a nearly unlimited resource. [...]" They forgot to say that it is not the H2O that comes out of your tap. The earth is especially not full of tritium.

The plan is for them to breed their own tritium, though, so the consumables coming in the front door would just be deuterium and lithium, both of which (while less common than tap water) are not rare.

Re: MIT-designed project achieves major advance toward fusion energy

#40

Post by bb88 »

azalemeth wrote: post #13
shmageggy wrote: post #7

These university press releases are always very positively framed. This one makes the new magnet seem incredibly promising and fusion seem like almost an inevitability now, but decades of failure have us conditioned for skepticism. What's the catch this time?

Agreed. Whilst it may well be the largest, highest-field "only" high Tc superconductor design in the world, it's definitely not the highest-field high Tc superconducting magnet -- I believe that honour belongs to another bit of MIT with a 1.3 GHz NMR machine [1] (but I do remember something about Bruker collaborating with the US's National Magnet Lab and building a 30T machine -- I can't easily find a link). I really…

This was a 32T field created, not sure if it's the same, but similar.

https://english.cas.cn/newsroom/research_news/tech/201912/t2...

Googling "30T magnetic field" shows some papers that have apparently "pulsed" 30T.

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