Ether
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Whither hot and cold fusion?
Jun 23, 2004, 13:42
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Anybody know how far we are away from these being viable? With hot fusion people say, "in 50 years", but they were saying the same thing 20 years ago.
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ratcni01
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grufty .. haloooo
Jun 23, 2004, 14:29
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Grufty Jim would know, if you search on here you'll find a link to his blog which is a great reference for energy issues
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grufty jim
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Re: Whither hot and cold fusion?
Jun 23, 2004, 15:12
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My thoughts...
There's no evidence that cold fusion is even *theoretically* possible, let alone practically. I tend to put it in the same category as zero-point energy... i.e. it ain't ever escaping the realm of science-fiction. Would love to be proved wrong. But i advise people against holding their breaths.
With regards to "hot" fusion; sometimes described as "magnetic fusion" (so-called because there is no physical chamber that could withstand contact with a fusion reaction, so it needs to be contained within a magnetic field), we know - of course - that it's theoretically possible... it's the energy-generating process that occurs within every star. What's perhaps less well known is that fusion reactions are successfully and regularly produced within the various supercolliders scattered over the globe. And have been since the 1960s.
Sadly the amount of energy put in to drive the reaction currently exceeds the amount of energy produced by the reaction. This makes it interesting from a scientific viewpoint, but of no practical use.
The critical issue when measuring the performance of fusion reactions is:
plasma density (in particles per cubic metre)
(times)
average particle confinement time (in seconds)
(times)
temperature (in degrees Kelvin)
The resulting number is known as the Lawson parameter (after someone called Lawson, i suspect), and the units are kilo-electron Volts (keV). What's important to know is that the fusion reaction breaks even (i.e. you get the same amount of energy out as you put in) at 15keV. This is known as "Ignition point".
The first fusion reactions (in the mid 60s) produced a plasma at less that 0.001 keV. In the late 1990s a plasma at 14.8 keV was achieved. This represents a raising of the Lawson parameter by a factor of over 10,000; in a little over 30 years.
So *huge* progress has been made, and the extremely underfunded men and women carrying out this research should be applauded. However, it's one of those exponential things. The closer you get to ignition, the more difficult it is to raise the Lawson parameter any further. Hence the current cries from the fusion research community to give them some more cash to build a much larger supercollider. There is certainly a feeling that one last big leap could get us to Ignition point.
On the other hand, i'm in touch with someone working in a facility at Chicago University who is right on the cutting edge of this research. He feels strongly that the work he is engaged in (scaling down the fusion reactor size to make the process capable of commercial energy production) will take generations, not years, to complete.
This is quite sad really, as commercial fusion could potentially solve our energy problems without the production of any radioactive waste. Well, the most common fusion reaction uses deuterium which produces small amounts of waste with a half-life of roughly 10 years... not 10,000 like the waste produced by fission. And i think we can trust humanity (just about!) to keep the stuff safely contained for a decade.
[the helium-3 reaction produces no radioactive waste whatsoever - though the main source of that is the moon... whereas deuterium can be easily produced from sea-water; so it probably makes sense to start with the deuterium reaction].
Of course, fusion's gift of virtually limitless clean energy doesn't solve all the problems of fossil fuel depletion (plastics, fertilisers, pesticides, etc.) but it could dramatically reduce our consumption of fossil fuels, providing additional time to work towards a more sustainable society.
My own personal opinion is - i'm afraid - that the investment in fusion research has been underfunded for way too long. And it's now a little late in the day for such a high-tech solution to our energy problems.
Fusion idealist opinion: if we put all the money we currently spend on the military into fusion research, it's very possible that we'd have commercial fusion in less than 20 years. Sadly... it ain't likely to happen.
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Ether
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Re: Whither hot and cold fusion?
Jun 23, 2004, 16:32
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Thanks Grufty! Thank you for such a detailed reply. I'm going to print it off.
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