Posted on: 12th March 2012

The sun pours out an amazing amount of energy. Only a small fraction of the sun’s total output reaches us, yet it powers our entire ecosystem. All the plants and animals on planet earth rely on this warmth for light and food. Surprisingly, though, the sun is not a terribly good fusion reactor, for its size. In terms of power output per volume, JET at its best is over 700 times better, and ITER will be a staggering 2150 times more efficient fusion reactor than the sun.

JET’s peak power of 16.1 megawatts was generated by a plasma about 80 cubic metres, from only a gram or two of deuterium and tritium. The sun on the other hand fuses about 620 million tonnes of hydrogen each second, producing a total 3.8 x 1020 megawatts. But this only equates to about one quarter of a watt per cubic metre, because the sun’s total volume is so large, at 1.412 x 1027 cubic metres. Even if you consider only the core of the sun, where most of the fusion occurs, models estimate the power output at 276.5 watts per cubic metre, about the same amount that an active human generates (in chemical processes, not nuclear fusion).

ITER’s plasma volume will be 840 cubic metres, which with the target of 500 megawatt output power equates to nearly 600 kilowatts per cubic metre – the most efficient fusion reactor not only on earth, but in the whole solar system!