Previous Entry Share Next Entry
Electrodynamic fusion is not the solution to the helium crisis.
blaisepascal
One of the things to come to my attention recently has been work done over the past 15 years by EMC2 on electrodynamically contained fusors. This is a different approach towards fusion energy than has been pursued by the DoE (Tokamak reactors) for the past 30 years.

I've also been made aware of the fact that we are having a helium shortage globally.

My thought was: since fusion reactors generate helium, perhaps commercially viable fusion plants will help offset the helium shortage.

Then I ran the numbers: A PolyWell fusion plant using the p-B11 reaction that meets the electric generation usage of the world today would make about 1 tonne of helium per year, while consuming about 1 tonne of boron and 100kg of hydrogen. That's assuming 100% efficiency, which is ridiculous. However, assuming only 5% efficiency means that it'll generate only 20t of helium.

That's nowhere near enough to offset the helium shortage.

  • 1
(Deleted comment)
So I'm assuming that my calculation was in the right ballpark (neglecting the 1t B + 100kg H -> 1t He equation doesn't quite add up)?

My actual calculations yielded 20 TWh of energy for 1029kg of resulting He4, based on p + 11B -> 3 4He + 8.7MeV. I get 78 MWh (er, 280 GJ or so) per mol of He produced. That yields 280 kmol of helium produced for 20TWh, or about 1 tonne of helium.

(Or, working backwards, 1 mol H + 1 mol B -> 3 mol He + 840 GJ, or 86kmol H + 86kmol B -> 258Kmol He + 20TWh.)

As for going into physics.... I still don't understand Lie Groups, which is holding me back somewhat ;-).

(Semi-seriously... I tried to gulp maths too fast in high-school. I took college-level pre-calc algebra and trig during summer vacation between 7th and 8th grade, and Calc I during summer vacation between 8th and 9th grade, got an A in both, but failed to succeed in Calc II after school in 9th grade. As such, I never really mastered the skill of integration. I didn't have to do any further maths until university, where I took probability, statistics, and discrete math, none of which really called for understanding higher calculus. I ended up taking category theory before taking abstract or linear algebra (which was fun, since the two categories used for examples of everything were the category of sets and functions between sets (aka abstract algebra) and the category of vector spaces and linear transformations between vector spaces (aka linear algebra)). I didn't get into differential equations, topology, differential geometry, etc. Even with group theory, I find there are odd holes in my understanding (I just realized two weeks ago, for instance, that conjugation between subgroups is an equivalence relation. I haven't worked out the full details of what that means, but it seems like it should be very important, but I don't recall it ever being mentioned before). I find most discussions of "higher maths" to be too abstract -- I get lost in a sea of symbols without anything to tie it down to in my brain. This hurts me when it comes to higher physics because a lot of things become very abstract. I know SU(n) is the special Unitary group (group of nXn matrices with UU=I with determinant of 1), and I can even tell you what each of those symbols mean, but that doesn't mean I understand its properties or could give a rough guess (without looking it up) as to its dimensions, etc. I know of the Pauli and Dirac matrices, but get confused when I see γ5, as that doesn't appear to be like the other Dirac matrices. I get lost by Einstein's summation convention.

So I'm not sure I was cut out for physics.

Electrodynamic fusion might not solve the helium shortage... but it's a hell of a good way to generate neutrons, and it might eventually be a viable source of power.

The userpic is a Farnsworth fusor in operation; I didn't even have to adjust the picture to make it purple! ;-)



Neutrons... not necessarily so much. The EMC2 folks feel that the future isn't in D-D (or D-T) fusion, but in p-11B fusion, which (a) takes a lot more energy to do via heating the plasma, but not so much more if you drop the nuclei down an electric potential well a la Farnsworth, and (b) does not produce neutrons.

EMC2's technique is descended from a Farnsworth fusor. It uses magnetically-contained electrons to make a potential well. The idea behind that is that if there is no grid (which a Farnsworth fusor has), then the ions can't collide with it (which limits a Farnsworth fusors gain).

Their last fusor (before the funding ran out) ran D-D and exceeded the neutron count of the best Farnsworth-Hirsch fusor by several orders of magnitude. Their research goal (if they can get the necessary $200M in funding over 8 years) is to produce a 100MW commercial demonstration fusor running p-B. As their website puts it "Successful phase 2 marks the end of fossil fuels".

I didn't see any descriptions of the concept on that website. I'd really like to know how it works!

As far as I know, all fusion devices(*) use some form of magnetic (or at least electromagnetic) containment field to keep the plasma from burning through the physical container. The problem with magnetic containment was that the plasma could still escape out the ends; the reason for the tokamak's toroidal design was basically to eliminate the ends by connecting them together.

(*) I just remembered the SHIVA design, which fed a machine-gun belt full of lithium deuteride pellets into a chamber where they were bombarded from all sides by laser beams, causing the LiD to fuse. If I remember correctly, the biggest drawback was the fact that it took a fairly long time for the capacitors that fired the lasers to charge up again between pellets, which severely limited the output.



Farnsworth fusors (a) don't use a hot plasma, and (b) use an electrostatic, not magnetic or electromagnetic[*], field to accelerate the deuterium ions to fusion energies. So it's surprising that you'd not know of a fusor that didn't use magnetic or electromagnetic fields.

The EMC2 site isn't well designed for saying "here's what we're doing!". Even the link to papers on the bottom isn't very good. The best description I've read of it was in the most recent issue of Analog, in the Alternate View column.

On the EMC2 site, the link to the paper "The Advent of Clean Nuclear Fusion: Super-performance Space Power and Propulsion" probably gets to the meat of what the proposed technology is, as well as what they've done to date experimentally.

[*] electrostatic fields are static, and it takes a moving electric field to generate a magnetic effect. So I wouldn't consider an electrostatic field to be electromagnetic.


ah - thanks for the link. (the main page is atrocious for actually finding anything.) it looks, to my math-impaired-technician's mind, as if they took some of the basic structure of the Farnsworth design and modified it so that magnetic rather than electrostatic fields moved the particles around. this, of course, introduced other design constraints, such as forcing the device into a polyhedral rather than strictly spherical configuration. the output figures are amazing... WHY ISN'T ANYBODY PICKING UP ON THIS???

(oh, and i take it that's Bussard as in "ramjet"?)



You do realize that most people's hobbies don't involve p-B11 reactions, right?

Oh, and I wanna get my PS2 back at some point. :)

Yes I know that most people's hobbies don't involve p-B11 reactions.

Oh, and let's set up a time to do that, shall we?

  • 1
?

Log in

No account? Create an account