so... youse guyses know how fusion works, right? If one fuses two hydrogen nuclei to make one helium nucleus, the latter weighs a little less than the sum of the former. That little bit less is the "atomic mass deficit". Where did it go? It "became" energy, according to Einstein's equation, E = m*c^2. Now... "m" is very small, but "c" (the speed of light in a vacuum, 3 x 10^9 meters/second) is pretty big, and "c^2" is farking big (I get 9 x 10^18 m^2/sec^2). Thus, a little mass becomes a lot of energy.
Now, here's the trick. Nuclei don't just spontaneously fuse... if for no other reason than they don't like to get close to each other (they're positively charged, and they repel each other). How do you get them together? Well, you need to add a lot of energy... the classic way to do it (i.e., the way Edward Teller and his buddies did it) is to use a nuclear fission explosion to collapse a sphere of plutonium containing a mixture of hydrogen isotopes. Works a charm. Not terribly practical for energy production; great for annihilation. Sustainable fusion does hold promise for cheap,clean energy... but ya gotta initiate it, and ya gotta maintain it.
The idea of the Pons/Fleischman "cold fusion" was that the "activation energy" (so to speak) for fusion could be lowered tremendously by carefully orienting and concentrating hydrogen atoms (nuclei, for our purposes) on a surface (e.g., palladium, or something like that, as I recall). Like most pseudo-science, there's a spark of truth and a little common sense that makes one say... "yeah, maybe...". But the problem is, no one ever replicated any evidence of significant fusion in carefully controlled experiments. The original claims were based on neutron emission, not energy production per se.
The first law of thermodynamics says, in essence, "you can't win", and the second law says "you can't even break even". Cold fusion, if it ever occurs, will not violate the laws of thermodynamics - the energy to start it will have to come from somehere. Ah, there's the rub.
