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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

#421

Post by Firadeoclus »

nobody9999 wrote: post #353
qPM9l3XJrF wrote: post #309

Earlier quoted context omitted.

"Fusion is in theory something that could give us true energy abundance." What does fusion give us that existing nuclear power plant tech doesn't?

>What does fusion give us that existing nuclear power plant tech doesn't? The energy generated per unit mass in a fusion reaction is ~9 times that generated in a fission reaction[0]: Considering the mass of the four protons/hydrogen nuclei (4.029106u) and the mass of the Helium produced (4.002603u) we get a mass difference of 0.026503u or 24.69MeV. So it is easy to see that fusion reactions give out more energy per r…

Would you be willing to elaborate why "energy per unit mass" matters when the mass in question is a completely different substance with different cost and availability profile?

If we found a way to extract 10x as much energy from coal as we currently do, electricity from coal wouldn't become 10x cheaper, nor would we build power plants 10x as big.

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

#422

Post by danans »

jonnycomputer wrote: post #419
danans wrote: post #399

Earlier quoted context omitted.

> which it should be. Solar power will never need to remove more than a tiny fraction of tree cover from Appalachia. What's a far bigger threat to the ecosystem, including animal migration, is mountaintop removal for coal mining: https://law.lclark.edu/live/blogs/134-de-regulation-of-mount...

Whatever. You can stop mountain removal mining for coal, and prevent environmentally sensitive land from being devastated for solar farms. Its not an either/or, since there is, in fact, plenty of other land that can be used for solar farms.

> there is, in fact, plenty of other land that can be used for solar farms.

If such land were available at an equivalent price to the hillside in question, why would anyone clear a hillside to install solar? All else equal, it's strictly more work/expense to build a solar farm on an incline. The price for the "other land" must not be right, or must have some other serious disadvantage.

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

#423

Post by nobody9999 »

Firadeoclus wrote: post #421
nobody9999 wrote: post #353

Earlier quoted context omitted.

>What does fusion give us that existing nuclear power plant tech doesn't? The energy generated per unit mass in a fusion reaction is ~9 times that generated in a fission reaction[0]: Considering the mass of the four protons/hydrogen nuclei (4.029106u) and the mass of the Helium produced (4.002603u) we get a mass difference of 0.026503u or 24.69MeV. So it is easy to see that fusion reactions give out more energy per r…

Would you be willing to elaborate why "energy per unit mass" matters when the mass in question is a completely different substance with different cost and availability profile? If we found a way to extract 10x as much energy from coal as we currently do, electricity from coal wouldn't become 10x cheaper, nor would we build power plants 10x as big.

>Would you be willing to elaborate why "energy per unit mass" matters when the mass in question is a completely different substance with different cost and availability profile?

Sure. Specific energy (or energy per unit mass) between different types of materials makes a huge difference. For example (Source here[0]):

   Material   Type of generation   Specific energy (MJ/Kg)
   Hydrogen   Fusion               639,780,320
   
   Coal       Oxidation            24.0-35.0
Note the specific energy of a Kg of burned coal compared with a Kg of fused hydrogen. Fused hydrogen generates roughly 200,000 times the energy per unit mass than burning coal.

You're right. Cost and availability play into this as well. There are estimated to be ~1.06 trillion tons of coal on earth[1], hydrogen is the most abundant element in the universe and even makes up a significant amount of the mass of coal.

Burning hydrogen/hydrocarbons is, compared to fusing hydrogen, an incredibly inefficient process.

I'd say that being able to generate 200,000 times the energy per unit mass is an important consideration.

As for availability, hydrogen is more abundant and cheaper to produce (unless you have petatons of plant matter, the right conditions and a few tens of millions of years at no cost to you) than any fossil fuels. Or just about anything else.

[0] https://en.wikipedia.org/wiki/Energy_density#List_of_materia...

[1] https://www.worldcoal.org/coal-facts/what-is-coal-where-is-i...

Edit: Clarified availability.

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

#424

Post by emteycz »

pfdietz wrote: post #418
tsimionescu wrote: post #280

Earlier quoted context omitted.

> This is the opposite of how economies of scale work. If you make something bigger, the variable costs scale linearly and the fixed costs stay the same but are amortized over more units. That's not how construction works. Past some small scale, construction cost scales quadratically or worse with size. Building a 100m tall sky scraper is not 10 times as expensive as building a 10m tall 3-story house - it is at least…

I will note that fusion reactors have serious diseconomies of scale. First, the power output of a fusion reactor is limited by what the first wall can withstand. Therefore, the power goes as radius^2, where as the cost goes (at least) as radius^3. Second, the larger a fusion reactor becomes, the more parts it has, and the more reliable each individual part has to be (since there will be no redundancy in many; an leak…

Wouldn't running many small fusion reactors instead of one per facility help with these issues?

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

#425

Post by pfdietz »

nobody9999 wrote: post #423
Firadeoclus wrote: post #421

Earlier quoted context omitted.

Would you be willing to elaborate why "energy per unit mass" matters when the mass in question is a completely different substance with different cost and availability profile? If we found a way to extract 10x as much energy from coal as we currently do, electricity from coal wouldn't become 10x cheaper, nor would we build power plants 10x as big.

>Would you be willing to elaborate why "energy per unit mass" matters when the mass in question is a completely different substance with different cost and availability profile? Sure. Specific energy (or energy per unit mass) between different types of materials makes a huge difference. For example (Source here[0]): Material Type of generation Specific energy (MJ/Kg) Hydrogen Fusion 639,780,320 Coal Oxidation 24.0-35…

It's not that cost plays into it, it's that cost (broadly defined) matters, and the metric you have chosen doesn't matter. As a consumer I don't care how energy dense a fuel is; I care only about what it costs me to get that energy.

You might try to argue high fuel energy density implies low cost, but this is clearly not the case in general.

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

#426

Post by pfdietz »

nobody9999 wrote: post #354
kongin wrote: post #233

Earlier quoted context omitted.

>You are right, people who flippantly dismiss fusion just don't understand it. I have a couple of physics degrees, hot fusion is the energy of the future and it always will be. This is not a physics problem, this is an engineering problem and we are just not willing to invest enough money to solve the engineering.

>I have a couple of physics degrees, hot fusion is the energy of the future and it always will be. This is not a physics problem, this is an engineering problem and we are just not willing to invest enough money to solve the engineering. You're spot on. Which makes no sense at all. Given the potential of commercial fusion, we should be (globally) spending at least several tens of billions per year on R&D. Assuming th…

If things are not making sense, you need to reexamine your assumptions. I will argue that fusion actually doesn't have much potential, and the relatively low interest in it (as reflected by money being spent vs. alternatives) reflects that.

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

#427

Post by jonnycomputer »

danans wrote: post #422
jonnycomputer wrote: post #419

Earlier quoted context omitted.

Whatever. You can stop mountain removal mining for coal, and prevent environmentally sensitive land from being devastated for solar farms. Its not an either/or, since there is, in fact, plenty of other land that can be used for solar farms.

> there is, in fact, plenty of other land that can be used for solar farms. If such land were available at an equivalent price to the hillside in question, why would anyone clear a hillside to install solar? All else equal, it's strictly more work/expense to build a solar farm on an incline. The price for the "other land" must not be right, or must have some other serious disadvantage.

Well, clearing the trees is already a profitable opportunity, if that is what happened. But my guess is we are talking about the idiosyncratic decisions of one landowner. Who knows if they did any kind of serious cost-benefit analysis. Or were you assuming that a solar company bought the land specifically to install solar. Possibly, but that's hardly clear to me. Besides, in the mountains, wind is probably the better bet.

Now .. putting solar farms on top of already strip mined mountains makes sense to me. You've already flattened them, and farming is of the question. And it ... looks like that is happening. Tjough I don't know how the Surface Mining Control and Reclamation Act plays into that.

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

#428

Post by qPM9l3XJrF »

kamaal wrote: post #328
qPM9l3XJrF wrote: post #309

Earlier quoted context omitted.

"Fusion is in theory something that could give us true energy abundance." What does fusion give us that existing nuclear power plant tech doesn't?

>>What does fusion give us that existing nuclear power plant tech doesn't? Water is more abundant than Uranium?

Fair enough, I hope fusion plants aren't adjacent to bomb technology in that case? Because that could lead to a lot of nuclear proliferation.

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

#429

Post by mlindner »

anonuser123456 wrote: post #165
worldvoyageur wrote: post #94

Earlier quoted context omitted.

Tritium is a natural byproduct of CANDU fusion reactors, of which there are some 25 or so in operation globally, mostly in Canada. CANDUs use heavy water as a neutron moderator (D20 instead of H2O), making T2O a natural byproduct. Though most of the reactors do not harvest the tritium, a small number do. CANDU operators have long been ready to make the capital investments in tritium harvesting, once demand materializ…

I think the SPARC guys are going to eat all the CANDU tritium before ITER ever gets a chance light up. If we have to scale up fission reactors to produce enough tritium to scale fusion reactors, then don't need the fusion reactors.

Tritium only has a half life of 12 years. It's not like there's stockpiles of the stuff. It's constantly being produced. Also as mentioned up thread, they'll breed their own Tritium.

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

#430

Post by mlindner »

rnhmjoj wrote: post #90
speed_spread wrote: post #58

Earlier quoted context omitted.

It sounds like the T production chain might itself be quite messy. Molten isotopes salt and lead? How much of that stuff would you need? What do you do with when it goes bad? It may not go boom Chernobyl-style, but it's still far from the birds-in-the-sky deuterium-from-the-sea fusion dream.

> It sounds like the T production chain might itself be quite messy. It is: it's definitely the biggest challenge after plasma confinement. > Molten isotopes salt and lead? There are two main blanket technology in development: ceramic and liquid breeders. They're called breeders but are very different from the kind of breeders you have in a fission reactor. Both are based on converting lithium to tritium by capturing…

> Both are based on converting lithium to tritium by capturing fusion neutrons, but in one case the lithium is in the form of solid pebbles, while in the other, in a molten mixture of lithium-lead (there are no salts AFAIK).

https://en.wikipedia.org/wiki/FLiBe

> FLiBe is a molten salt made from a mixture of lithium fluoride (LiF) and beryllium fluoride (BeF2).

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