Monday, April 20, 2009

It's the helium, stupid

Cold fusion is suddenly in the news again because of a recent 60 minutes story. For anyone who thinks that there is anything to this, I have only one word:

Helium.

Excess energy is a red herring. There might be excess energy coming from somewhere, but if you're fusing hydrogen, then you produce helium. No helium, no fusion. It's as simple as that. And I'm not talking about the trace amounts that have been reported, there should be gobs and gobs of it, certainly enough to float a toy balloon and remove all doubt. There's also the problem that all known hydrogen-based fusion reactions produce energetic neutrons. Really, cold fusion researchers should be dropping dead left and right from radiation poisoning, but failing that the radiation should at least be detectable on a geiger counter. So where are the videos of the cold fusion apparatus with a geiger counter buzzing away next to it?

If there's no fusion, there could still be excess energy, but it's almost certainly coming from some prosaic source, and it's almost certainly consuming palladium somehow. Palladium might be an economically viable catalyst, but it makes a mighty expensive fuel.

UPDATE: Here's the math.

The specific heat of deuterium fusion is about 1 MeV, which is about 10^-13 joules. To produce enough helium to fill a balloon (let's say a liter at standard temperature and pressure, or about 0.05 mole) we'd need to produce ~5x10^7 joules of excess heat. That's actually quite a lot, enough to raise the temperature of a cubic meter of water by 50 degrees C. Not enough to vaporize the lab, but definitely enough to get someone's attention.

But here's the thing: some of these experiments run for months at a time. Measuring small amounts of excess heat over long periods of time is very hard. But collecting and storing even small amounts of putative excess helium is very easy. Let's say that the excess heat is only one watt, it would only take a year to accumulate a liter of helium, and the fact helium was being produced would be inarguable after only a few days. So I still say if it were there someone would have exhibited it by now.

UPDATE 2:

I made a mistake in my calculations. There are actually two different deuterium fusion reactions. One produces 3He (helium 3, with two protons and one neutron) and an extra neutron, i.e. radiation. The other produces 4He, with two protons and two neutrons, and no extra neutrons. The second "clean" reaction also produces 23 times as much energy as the first one (or, equivalently, only about 4% as much helium per unit energy produced). It is also very rare. As far as I have been able to determine (which at this point means looking at a few Wikipedia articles) it does not occur in nature, and has not been achieved in more traditional "hot fusion" experiments. So I wrote off the possibility of achieving this reaction at room temperature as too good to be true. However, there are some plausible-looking reports of 4He production correlated with excess heat production in about the right amounts. So at this point I have to say that the possibility cannot be definitively ruled out. I still wouldn't bet my life savings on it, but if a policy maker were to ask me at this point I think I would recommend funding some of this research. These experiments are dirt-cheap by contemporary standards, and if it can be made to work it would be the single greatest technological breakthrough in the history of mankind. So it's worth putting some resources into it to determine definitively what, if anything, is going on.

10 comments:

arthole said...

just a thought: I had read that there was helium produced in these reactions. but then, I'm not sure what a "trace" is in this context.

I think the question to ask is, if there is fusion taking place, how much is taking place? It should be possible to calculate the amount of fusion taking place from the amount of excess energy.

and without running any numbers, it's obvious the answer is VERY LITTLE. I have long felt that most criticisms of cold fusion are not criticisms of the process, so much as criticisms of the hyphothesis at scale.

what if this process is fusing deutrium, but at the nanoliter level? how much helium would result?

At these scales, there would be only TRACE amounts of helium. but there should be measurable excess heat.

Your criticism seems perfectly valid at larger scales. but not at very small scales. the Pons-Fleischman hypothesis is that the palladium process is producing the excess heat by means of fusion.

others have reproduced similar results from similar experiments. A criticism of the hypothesis of fusion is valid. But your hypothesis that the excess heat is "...coming from some prosaic source..." has not been borne out by experiment.

freshtonic said...

The level of fusion that must occur to fill a helium balloon would have melted the lab and much of the surrounding building. So no, at the levels of 'fusion' they are seeing, it would not fill a balloon.

Only trace amounts of helium are being observed, and some experimenters, while observing excess heat, are claiming that the amount of helium observed is consistent with background levels.

And although fusion seems to be the leading hypothesis for explaining the excess heat, it's not the only one. See the Wikipedia page on cold fusion.

Ron said...

> The level of fusion that must occur to fill a helium balloon would have melted the lab and much of the surrounding building.

That depends on how long the experiment was running. The only was to settle this is to actually do the math.

Jed Rothwell said...

I suggest you go to LENR-CANR.org and type in the word "helium" in the Google search box at the top. You will find dozens of cold fusion papers describing measurements of helium. It is found in the same ratio to heat as plasma fusion fusion.

I recommend you read the scientific literature before speculating about this research.

Ron said...

AFAIK, there has not been a reproducible production of helium that is definitively above background levels. If you want to point me to a specific paper that shows I'm wrong I'd be happy to read it. But I don't have time to wade through myriad bogus results. The burden of proof is on the person making the extraordinary claim.

Jed Rothwell said...

For Helium see Miles, SRI, ENEA. All claims are well above background.

The stuff about "extraordinary claims" is unscientific. All claims, extraordinary or not, should be held to the same standard of rigor. Cold fusion claims are best proved with ordinary means: conventional instruments.

Chris Thiessen said...

I think you may have got your numbers a little off.

According to: http://hyperphysics.phy-astr.gsu.edu/Hbase/NucEne/fusion.html#c4 , and other sources, the specific heat of deuterium-deuterium fusion is ~4MeV

And 1 MeV = 1.6e-13 Joules

A liter of gas is ~0.05 moles.

So (6e23 * .05) * (4*1.6e-13) = 19.2e9 Joules for each liter of helium gas produced.

That's 608 watts for a year. Enough energy to boil off 8.5 cubic meters of room-temperature water.

Ron said...

> The stuff about "extraordinary claims" is unscientific.

Not so. If I claim that unicorns are real I have a much higher burden of proof than if I claim that, say, Kazakhstan is real despite the fact that most people on earth have never seen either one.

> I think you may have got your numbers a little off.

You're right. I was assuming the D+D->3He reaction at 1 MeV, but looking at the papers I've found (yes, I really do look into these things with an open mind) they claim -- and actually provide some evidence for -- the D+D->4He reaction at 23 MeV. Not only does that reaction produce no radiation, it also produces 23 times less helium. The possibility of achieving the D+D->4He reaction at room temperature just seemed to me to be "too good to be true" so I just rejected that possibility out of hand, which I shouldn't have done.

I'm still looking into this, but at the moment I have to say it's looking slightly (but only slightly) plausible.

Bill Drissel said...

Ron,
Aren't there neutrons, too?
Bill Drissel

Ron said...

There have been reports of neutrons, but they have not been reliably reproduced. Also, even the reported sightings of excess neutrons are far below what theory would predict. There are only two possible reactions: D+D->4He @ 23MeV, and D+D->3He+n at 1MeV. (The more common deuterium/tritium fusion that occurs in hot fusion experiments (and in stars) can't be happening here because cold fusion doesn't use tritium.) So there are only three possibilities: either D+D->4He is occurring somehow for the first time since the Big Bang (and at room temperature no less), or D+D->3He+n is occurring, in which case geiger counters should be going nuts and researchers should be dropping like flies from radiation poisoning. Or, still by far the most likely, neither of these is occurring, the excess energy is coming from some prosaic source (my guess would be oxidizing palladium) and the excess helium is atmospheric contamination.