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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

#401

Post by codethief »

danuker wrote: post #334
codethief wrote: post #293

Earlier quoted context omitted.

I don't think it'll be easy . We would have the same (if not higher) energy consumption per capita on any other planet. And unless that planet is humongously large (which would also increase its surface-level gravity, thus rendering it uninhabitable), the relation between surface temperature and energy consumption will be similar[0]. Now there's only a finite number of planets in our solar system and leaving our sola…

> So the surface temperature issue there is just the same. On an interstellar ship far from a star, I think you're more likely to freeze to death, because temperature in space is near zero Kelvin. Inside the solar system however, you could reflect away the received radiation (and heat) using mirrors.

> I think you're more likely to freeze to death, because temperature in space is near zero Kelvin.

We're talking about a civilization on board an interstellar ship that had to leave their home planet because they were consuming so much energy that the resulting waste heat ended up making the oceans boil. So the assumption that they'll keep on consuming lots of energy (and producing lots of waste heat) on board such a ship sounds rather reasonable to me.

> Inside the solar system however, you could reflect away the received radiation (and heat) using mirrors.

The discussion is about getting rid of heat produced on board the space ship, not heat that's received from elsewhere.

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

#402

Post by snek_case »

anonuser123456 wrote: post #214
snek_case wrote: post #172

Earlier quoted context omitted.

I'm wondering, fusion reactors themselves produce neutron radiation as a byproduct. Once you have a fusion reactor running, could you use the fusion reactor itself to breed tritium? Also thinking, we target deuterium + tritium fusion because it's the least energy intensive. However, once we have working proof of concept reactors, could we just make them slightly bigger and fuse more abundant molecules/isotopes instea…

While not listed in the article, this is the design goal of the SPARC reactor. Their plan is to use FLiBe (Google it) blanket to breed tritium. The Be acts as a neutron multiplier. As for non D-T fusion, the next best candidate is D-He3. Unfortunately, the only large scale source of He3 is on the surface of the moon and it would have to be mined, on the moon, and sent back to Earth.

According to wikipedia:

"Fusing two deuterium nuclei is the second easiest fusion reaction."

"The optimum energy to initiate this reaction is 15 keV, only slightly higher than that for the D-T reaction."

https://en.wikipedia.org/wiki/Fusion_power#Fuels

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

#403

Post by DanielVZ »

codethief wrote: post #400
DanielVZ wrote: post #344

Earlier quoted context omitted.

I'd take that statement with a grain of salt. If there's something that COVID has taught me is that in reality exponential curves almost always turn into sigmoids wherever there are limiting factors. The key here is where the curve starts flattening. The same goes for infinite growth. In the close future it sure looks infinite, but I'd say it's infinitely hard too to predict what will happen in say a 100 years (a fou…

Sigh. I really shouldn't have included a quote in my comment and instead only linked to the full text. That text is exactly an argument against infinite economic growth – and it carries out said argument by looking at energy consumption (which necessarily grows with economic activity).

Yeah I read it. Thats why I said that bit about infinite economic growth. I felt that by saying that exponential heat growth is probably sigmoid I was somehow validating the notion of infinite growth, which I think sometime in an unforeseeable future will just plateau.

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

#404

Post by pfdietz »

lyaa wrote: post #325
codethief wrote: post #281

Earlier quoted context omitted.

> Fusion is in theory something that could give us true energy abundance. Well, at least for a few hundred years but then: > if you plot the U.S. energy consumption in all forms from 1650 until now, you see a phenomenally faithful exponential at about 3% per year over that whole span. The situation for the whole world is similar. […] the Earth has only one mechanism for releasing heat to space, and that’s via (infrar…

The quoted argument is too simplistic and ignores feedback processes that would prevent reaching the catastrophic prediction. We can't predict 400 years so flippantly. The population will most definitely not continue to grow (in fact it will start to decrease slightly the more countries reach "developed" status), and the energy consumption per-capita will also stagnate. After all, there is a huge difference between g…

US per capita energy consumption peaked in 1980.

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

#405

Post by codethief »

DanielVZ wrote: post #403
codethief wrote: post #400

Earlier quoted context omitted.

Sigh. I really shouldn't have included a quote in my comment and instead only linked to the full text. That text is exactly an argument against infinite economic growth – and it carries out said argument by looking at energy consumption (which necessarily grows with economic activity).

Yeah I read it. Thats why I said that bit about infinite economic growth. I felt that by saying that exponential heat growth is probably sigmoid I was somehow validating the notion of infinite growth, which I think sometime in an unforeseeable future will just plateau.

Ah, sorry, looks like I misunderstood. :)

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

#406

Post by sokoloff »

thow-58d4e8b wrote: post #294
veltas wrote: post #284

Earlier quoted context omitted.

How do we know that global temp rise isn't just due to energy usage? I mean "does that calculation fit at all?", not "carbon dioxide is fake".

Not even close. Global energy use is around 170,000 TWh/year (1). This includes electricity generation, as well as fuel for transport, burning wood for heat, etc. Heat flow from mantle is 403,000 TWh/year (2) Solar irradiance is ~1200W/m2, which adds up to massive 5B TWh/year. Extra radiative forcing from greenhouse gases in IPCC scenarios is ~3W/m2, or around 12.5M TWh/year. The radiative forcing is two orders of ma…

I believe total annual solar irradiance is closer to 1.5BTWh/yr.

The 1200-ish W/m/m figure is hitting a flat plate circle, not hitting the whole spherical surface.

Taking 173,000TW of continuous solar energy* times 24h/d times 365.25 d/yr yields a little over 1.5B TWhr/yr

* https://news.mit.edu/2011/energy-scale-part3-1026

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

#407

Post by lambdatronics »

kwertyoowiyop wrote: post #71
sbierwagen wrote: post #57

Earlier quoted context omitted.

Here's a render of the completed reactor: https://www.iter.org/doc/all/content/com/gallery/media/7%20-... Note human for size. It's all completely bespoke scientific equipment hand made for this project only. The cryostat will be the largest stainless steel vacuum vessel ever made-- all welded by hand. After welding, a substantial number of in-vessel components have to be installed by threading them through access po…

That will become a level in an FPS game for sure.

Lol, I have the same though. They'll probably need to make the equipment a little sparser though, because it gets super crowded once everything is installed. Those cut-aways don't show all the detail.

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

#408

Post by lambdatronics »

onlyrealcuzzo wrote: post #84
orbital-decay wrote: post #81

Earlier quoted context omitted.

Expensive because it's a custom built physics lab, not a commercial power plant. Slow because it's an international project. Not just that, but it also requires lots of infrastructure to be built and entire industries to develop in multiple countries, before it can be useful. ITER is massive, but it's also just a tip of the iceberg. >It just doesn't strike me as obvious that reducing the major radius by a few meters…

Is it massive because it's 6 meters? Like - a 6 meter diamond would be "massive" - but a 6 meter boat isn't that impressive. Or is it massive like the tokamak is a 6 meter engine to a 100 km collider? Like there's a ton of other stuff being built in a massive structure?

The magnets are so large they had to build a factory on-site to put them together. If you can make the magnets small enough to transport from a centralized factory, that's a huge win.

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

#409

Post by lambdatronics »

neltnerb wrote: post #69
sbierwagen wrote: post #60

Earlier quoted context omitted.

LIGO did take decades to construct, like the LHC. According to LIGO's wikipedia article, it was the most expensive project ever funded by the NSF in 1994.

LIGO's size is also deceptive, the legs are kilometers long but the design is an L with the important bit being to vibrationally isolate things, maintain dimensional stability, and maintain vacuum. ITER is likely bigger in terms of volume of concrete or actual footprint.

Hmm, looks like ITER and LHC both use about the same amount of superconductor: around 500 tons.

[0]https://ieeexplore.ieee.org/document/1018583 [1]https://www.iter.org/mach/Magnets

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

#410

Post by lambdatronics »

sigmoid10 wrote: post #329
dfdx wrote: post #34

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 experim…

>The general idea is that since we have stronger magnets now, we can make a smaller, and therefore cheaper tokamak quickly. It's not that simple. The big problem with magnetic confinement fusion is that you need to control turbulence in the plasma so that you can contain the reactions for a reasonable amount of time to extract useful energy. However, turbulence increases with stronger magnetic field gradients, which…

>However, turbulence increases with stronger magnetic field gradients

Mmm, this isn't right. The stronger magnetic field reduces turbulence, it's the gradient of the pressure that generates turbulence. As best as anyone can tell, SPARC should be able to get Q~10 without any miracles involved -- the engineering rules of thumb and the advanced simulations all say the same.

https://www.cambridge.org/core/journals/journal-of-plasma-ph...

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