4 ms·

First I'll note that the remaining problems seems to be engineering more than plasma physics -- and most of the show stoppers seems to be solved. If that don't

First I'll note that the remaining problems seems to be engineering more than plasma physics -- and most of the show stoppers seems to be solved. If that don't make you go "wow", well... >>what distinguishes a power plant from other sorts of nuclear reactors? Again: I argued the main difference here is connecting a heat exchanger, you had nothing to say? >>What I'm missing are numbers: how much power do they expect to generate from fusion Again: The target is 6X the used energy for the pistons, according to the presentation. (It is a private company, details for investors.) (You know the number of pistons, their size/speed. That should be enough to make a good guess on the target energy from fusion. You can also guess quite well the volume of the lead and hence wuite a bit of the pumping needs.) There are other GF sources on the internet over the last few years, but since you ignore what I write please check them yourself.

dalke 12y ago
My apologies. I did overlook your mention of a heat exchanger as being the requirement for a power reactor. To me a heat exchanger is something which moves heat from one medium to the other, and is not necessarily part of power production. The radiator in a car is a heat exchanger, and not a power generator. Thus, I did not understand your viewpoint. Quoting from the first link you gave: "Pumped through a heat exchanger, that hot lead will help generate steam just like a conventional thermal power plant". Thus, I consider it as not a power plant, because it only produces steam. While I see that you consider the production of steam to be sufficient, likely because it reduces the issue to a previously solved problem. I am satisfied that the General Fusion design, which hasn't even started, is not a nuclear fusion power plant of the sort that Asimov predicted would be available by 2014. That is my primary interest in this discussion. FWIW, after more looking around, I found this quote from http://www.technologyreview.com/news/414559/a-new-approach-to-fusion/page/2/ http://www.technologyreview.com/news/414559/a-new-approach-t... : > However, if the company can pull off its test reactor, it hopes to attract enough attention to easily raise the $500 million for a demonstration power plant. Note how that magazine author also distinguishes between "test reactor" and "demonstration power plant"? The information I found are not sufficient to make the estimates that you mentioned. For example, while I found pictures of the small sphere experimental setup, and a mention that the final velocity is 50 m/s, I did not find learn the mass of the piston, or equivalently the amount of power used to drive it. Nor did I find out how much power goes into the plasma injectors. There are images of some pretty hefty capacitor banks, but I couldn't tell if they are discharged at once, or if they are rotated through in order to lengthen the charge time for any one bank of capacitors. Estimating the pumping needs is very complicated. I found no reference of what the internal surface of the sphere looks like. If liquid extends into each piston then there well be turbulence at each interface, causing power loss. Even if it's laminar, I still need to know the rotational speed. The depictions I've seen show that the lead surface is a near cylinder, which means a very high speed, as the natural shape of a rotating fluid is a parabola. Assuming 0.25 meter radius for the upper part of the cylinder and a height of 3 meters gives 400-500 Hz. That seems rather a lot, given that they're talking about some 50 cubic meters of lead, or 500 tons, moving at some 2,000 m/s. (I used the equation for a liquid mirror telescope: h = 1/(2g) * (omega * r) ^ 2. Hopefully I didn't calculate it incorrectly.) Since the information I've found doesn't make sense, either my math is wrong, or the information I've found is incomplete. Since you are the one who believes that this is a near-term power plant, then surely you must have worked out these details already, or read them some place. That is, how fast is the molten lead mixture supposed to rotate, and how much energy is needed to keep it at that speed?
- BugBrother 12y ago
  Again: I used the term "full sized prototype" in the first comment. Which is not exactly what Asimov wrote. The remaining possible show stoppers are less plasma physics and more mechanical, which is certainly better than what Asimov predicted. (I wrote repeatedly that the main thing missing from the planned prototype to be a prototype power plant is a heat exchanger, like most every other power plant that heats a medium. It boggles incredibility to assume you failed reading that.) Your link is from 2009, when they were new to building experimental hardware. Hardly an authoritative reference. Edit: A simulation of the vortex. It was hard to find, took me 3 minutes with Google: http://www.cs.ubc.ca/~jgregson/images/JamesGregsonMAScThesis.pdf http://www.cs.ubc.ca/~jgregson/images/JamesGregsonMAScThesis... Edit 2: The old papers, before much experiments: http://www.generalfusion.com/wp-content/uploads/2013/08/GF_Scientific_References_list.pdf http://www.generalfusion.com/wp-content/uploads/2013/08/GF_S... Edit 3: The recent TED talk is (claimed) to be up today, but the ted.com site is down as I write.
  - BugBrother 12y ago
    Addendum: The TED talk was on Youtube (and ted.com is up now). It was for a non-technical audience, the message is that the GF target is to make economical power plants. A commercial venture, as I wrote. The only real news is that the plasma injectors are probably done now, over the last month.
  - dalke 12y ago
    Thank you for the find for #1. I am pleased and surprised to see that my back-of-the-envelope calculation on the speed is correct. I am still gob-smacked to think of that much lead spinning a 2km/sec. I don't have the knowledge of supersonic fluid flows to be able to evaluate that. The paper itself points out various difficulties, including delamination, decavitation, jet formation with speeds up to 6km/sec, and: > practically generating shocks mechanically at Mach numbers greater than 1.5 without destroying the machine that creates them (as is the focus of this work) seems challenging. For example, a steel piston impacting liquid lead to produce an approximately Mach 1.1 shock would see a compressive stress of approximately 2 GPa, well above the yield stress of most steels. The paper talks about pressures up to 400 GPa. Another back-of-the-envelope calculation suggests 20 GPa of centrifugal force at the equator, which of course means the pumps need all the more force. This is well beyond a regime where I can make any mechanical estimates. At this point I suggest that the biggest problem is the engineering to bring the lead up to speed, keeping the sphere in shape with that much force on it, generating a plasma collapse through all of that, and connecting everything to the heat exchanger. That will be a huge challenge in its own right, and must be solved before I would call it an experimental power plant. BTW, this vortex simulation is from 2008, ... "hardly an authoritative reference" by your own criterion. ;) Indeed, I note that the simulation says 100 kg pistons impacting at 100 m/s, while this 2012 PDF http://fire.pppl.gov/FPA12_Richardson_GF.pdf http://fire.pppl.gov/FPA12_Richardson_GF.pdf says the target impact velocity is 50 m/s, which is 1/4th the total amount of energy. Link #2 directs me to http://generalfusion.com/downloads/ICC2008_MGL.pdf http://generalfusion.com/downloads/ICC2008_MGL.pdf, which shows that in 2008 they indeed planned on a 100 m/s impact, so parameters from 2008 are obviously no longer valid for 2014.

dalke 12y ago

My apologies. I did overlook your mention of a heat exchanger as being the requirement for a power reactor. To me a heat exchanger is something which moves heat from one medium to the other, and is not necessarily part of power production. The radiator in a car is a heat exchanger, and not a power generator. Thus, I did not understand your viewpoint. Quoting from the first link you gave: "Pumped through a heat exchanger, that hot lead will help generate steam just like a conventional thermal power plant". Thus, I consider it as not a power plant, because it only produces steam. While I see that you consider the production of steam to be sufficient, likely because it reduces the issue to a previously solved problem. I am satisfied that the General Fusion design, which hasn't even started, is not a nuclear fusion power plant of the sort that Asimov predicted would be available by 2014. That is my primary interest in this discussion. FWIW, after more looking around, I found this quote from http://www.technologyreview.com/news/414559/a-new-approach-to-fusion/page/2/ http://www.technologyreview.com/news/414559/a-new-approach-t... : > However, if the company can pull off its test reactor, it hopes to attract enough attention to easily raise the $500 million for a demonstration power plant. Note how that magazine author also distinguishes between "test reactor" and "demonstration power plant"? The information I found are not sufficient to make the estimates that you mentioned. For example, while I found pictures of the small sphere experimental setup, and a mention that the final velocity is 50 m/s, I did not find learn the mass of the piston, or equivalently the amount of power used to drive it. Nor did I find out how much power goes into the plasma injectors. There are images of some pretty hefty capacitor banks, but I couldn't tell if they are discharged at once, or if they are rotated through in order to lengthen the charge time for any one bank of capacitors. Estimating the pumping needs is very complicated. I found no reference of what the internal surface of the sphere looks like. If liquid extends into each piston then there well be turbulence at each interface, causing power loss. Even if it's laminar, I still need to know the rotational speed. The depictions I've seen show that the lead surface is a near cylinder, which means a very high speed, as the natural shape of a rotating fluid is a parabola. Assuming 0.25 meter radius for the upper part of the cylinder and a height of 3 meters gives 400-500 Hz. That seems rather a lot, given that they're talking about some 50 cubic meters of lead, or 500 tons, moving at some 2,000 m/s. (I used the equation for a liquid mirror telescope: h = 1/(2g) * (omega * r) ^ 2. Hopefully I didn't calculate it incorrectly.) Since the information I've found doesn't make sense, either my math is wrong, or the information I've found is incomplete. Since you are the one who believes that this is a near-term power plant, then surely you must have worked out these details already, or read them some place. That is, how fast is the molten lead mixture supposed to rotate, and how much energy is needed to keep it at that speed?

BugBrother 12y ago
Again: I used the term "full sized prototype" in the first comment. Which is not exactly what Asimov wrote. The remaining possible show stoppers are less plasma physics and more mechanical, which is certainly better than what Asimov predicted. (I wrote repeatedly that the main thing missing from the planned prototype to be a prototype power plant is a heat exchanger, like most every other power plant that heats a medium. It boggles incredibility to assume you failed reading that.) Your link is from 2009, when they were new to building experimental hardware. Hardly an authoritative reference. Edit: A simulation of the vortex. It was hard to find, took me 3 minutes with Google: http://www.cs.ubc.ca/~jgregson/images/JamesGregsonMAScThesis.pdf http://www.cs.ubc.ca/~jgregson/images/JamesGregsonMAScThesis... Edit 2: The old papers, before much experiments: http://www.generalfusion.com/wp-content/uploads/2013/08/GF_Scientific_References_list.pdf http://www.generalfusion.com/wp-content/uploads/2013/08/GF_S... Edit 3: The recent TED talk is (claimed) to be up today, but the ted.com site is down as I write.
- BugBrother 12y ago
  Addendum: The TED talk was on Youtube (and ted.com is up now). It was for a non-technical audience, the message is that the GF target is to make economical power plants. A commercial venture, as I wrote. The only real news is that the plasma injectors are probably done now, over the last month.
- dalke 12y ago
  Thank you for the find for #1. I am pleased and surprised to see that my back-of-the-envelope calculation on the speed is correct. I am still gob-smacked to think of that much lead spinning a 2km/sec. I don't have the knowledge of supersonic fluid flows to be able to evaluate that. The paper itself points out various difficulties, including delamination, decavitation, jet formation with speeds up to 6km/sec, and: > practically generating shocks mechanically at Mach numbers greater than 1.5 without destroying the machine that creates them (as is the focus of this work) seems challenging. For example, a steel piston impacting liquid lead to produce an approximately Mach 1.1 shock would see a compressive stress of approximately 2 GPa, well above the yield stress of most steels. The paper talks about pressures up to 400 GPa. Another back-of-the-envelope calculation suggests 20 GPa of centrifugal force at the equator, which of course means the pumps need all the more force. This is well beyond a regime where I can make any mechanical estimates. At this point I suggest that the biggest problem is the engineering to bring the lead up to speed, keeping the sphere in shape with that much force on it, generating a plasma collapse through all of that, and connecting everything to the heat exchanger. That will be a huge challenge in its own right, and must be solved before I would call it an experimental power plant. BTW, this vortex simulation is from 2008, ... "hardly an authoritative reference" by your own criterion. ;) Indeed, I note that the simulation says 100 kg pistons impacting at 100 m/s, while this 2012 PDF http://fire.pppl.gov/FPA12_Richardson_GF.pdf http://fire.pppl.gov/FPA12_Richardson_GF.pdf says the target impact velocity is 50 m/s, which is 1/4th the total amount of energy. Link #2 directs me to http://generalfusion.com/downloads/ICC2008_MGL.pdf http://generalfusion.com/downloads/ICC2008_MGL.pdf, which shows that in 2008 they indeed planned on a 100 m/s impact, so parameters from 2008 are obviously no longer valid for 2014.