Sunday, December 05, 2004

The Only Home Run Left: Fusion

We can't rely on non-renewable sources of energy; you should know that already or you wouldn't be here. At present, there are only a few truly renewable energy sources operating:
  • Hydroelectric. Nice, but not very extensible, and in any case, not dense enough to get us through the coming crisis.
  • Solar. Not dense enough, and too sporadic (when the sun's down, no juice).
  • Wind power. This is just another kind of solar energy, and suffers from even worse siting problems than solar.
  • Fusion. Now that's more like it. Fusion takes light atoms -- generally, deuterium and/or tritium, naturally-occuring isotopes of hydrogen -- and smushes them together. It's the reverse of nuclear fission, and is generally believed to be much cleaner because the radioactive waste products are much shorter-lived. Deuterium is cheap and available in effectively infinite supply in the seas; tritium can be manufactured by bombarding lithium with neutrons. Lithium is, however, a relatively scarce mineral; its leading producers (PDF) are Chile and Argentina, with significant production in the United States in Nevada. The frequent claims that fusion would be "limitless" are generally due to the idea that deuterium-deuterium reactions would power a second-generation fusion reactor, and this would truly require no exotic minerals.
Fusion power is the holy grail. It's dense, it's cheap -- it should be, anyway, but more on this presently -- and it's available to any country with capital and access to water. We can't power industrial civilization on wind or solar -- though it would be nice if we could. One estimate published in Mother Jones recently indicated the amount of landmass required to power the 48 conterminous states on a national solar power grid would be an area roughly the size of California. Needless to say, this isn't happening.

Since the end of World War II, a number of programs have attempted to create sustainable nuclear fusion. All of them have failed to produce electric power in any quantities, though some have claimed to be energy-positive, that is, in the parlance of thermodynamics, Qt>1. The highest rate of energy production thus far from a fusion reactor is 1.25, held by the JT-25 project in Japan.

Most fusion projects use a tokamak reactor to simulate conditions on the sun, but this is not necessarily the only way to achieve fusion. Philo Farnsworth, the actual inventor of television, came up with a blindingly simple device he called the fusor. Using inertial containment rather than powerful magnets, it was cheap and it actually worked, even though it wasn't energy positive. In fact, his device is so simple that freshman college students and even high schoolers have been known to construct examples. His efforts fell on hard times when the plasma physicists of the day blackballed him and stalled his research efforts; ITT, which owned his lab, found the opprobrium impossible to ignore, and kicked him out.

Similarly, the Migma fusion approach starts on the cheap; it gets ion streams to collide with one another, thus creating fusion. Its inventor, Bogdan Maglich, has a website that often sounds like a screed against the legions of plasma physicists.

Unfortunately for these two schemes, an MIT graduate student wrote a paper entitled "Fundamental limitations on plasma fusion systems not in thermodynamic equilibrium", which unfortunately all but eliminated both the migma and fusor systems as candidates for actual production of fusion energy. The problem, as it turns out, is that the devices must exert so much energy containing the plasma that unless they are very, very efficient at this, the systems will tend to go energy negative.

Littering the history of fusion was also Pons and Fleischman's notorious "cold fusion", which seemed more like a publicity stunt than actual physics. The Department of Energy, after a long hiatus, decided to revisit this topic, and issued a paper evaluating the experimental results thus far. The paper hemmed and hawed, but the skepticism was overwhelming, recommending against federal funding for any further research in this area.

So, for now, it looks like the only ticket to the nuclear fusion-powered future is in the guys with the big research grants and the big magnets. The latest iteration of this is the proposed ITER reactor, an international project without a site to go to. Unfortunately, these guys can't stop squabbling: they've already wasted more than a year debating where the project should go, France or Japan. The US and Japan back Japan, while everyone else wants this in the south of France. Not exactly encouraging news, but maybe with some political willpower delivered in the form of high gas prices this will work out.