QotW: How good is fusion power?

17 March 2020

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Question

With the advent of fusion power apparently only being 20 years away, how much do we expect to get out of this energy-wise for what we put in? Is it twice as much out or 1000 times as much out? And is it also true that nobody has managed to get out more than they’ve put in to date?

Answer

Phil Sansom has powered through for us, to get an answer about fusion power, to this question from Steve...

Steve - With the advent of fusion power apparently only being 20 years away, how much do we expect to get out of this energy-wise for what we put in? Is it twice as much out or 1000 times as much out? And is it also true that nobody has managed to get out more than they’ve put in to date?"

Phil - Fusion power is nuclear power, but not the kind you’re thinking of - the type from Chernobyl and Fukushima. That type is fission, where the nucleus of an atom gets split into two smaller nuclei, whereas Steve is talking about fusion - that’s two nuclei combining to form one. And according to Steven Cowley, this version - combining two to make one - doesn’t have any of the messy nuclear issues you’d expect.

Steven - It is truly sustainable for millions of years, has minimal waste, is environmentally benign, can be turned on and off at will, and is safe. However, it is hard to do. The fuel needs to be heated to temperatures of about 200 million degrees for the atoms to fuse to make Helium.

Phil - This is the big challenge - fusion just takes so much energy. But it’s such a tempting target to aim for, because it in theory provides a ton of power, and you can get the fuel cheaply and easily from seawater.

Steven - The record for fusion output is held by the Joint European Torus, JET, where 16 million watts of fusion power was generated. However, to sustain the reaction, 24 million watts of heating power was injected into the fuel.

Phil - So yes, it’s true that to date we’ve never got more power out of fusion than we’ve put in. But Steven Cowley is working on an scientific megaproject called the International Thermonuclear Experimental Reactor, or ITER.

Steven - The goal of the fusion experiment ITER being built in southern France is to produce at least ten times as much fusion energy as the energy that goes into the fuel.

Phil - It’ll do this partly thanks to a myriad of technical achievements, and partly thanks to being twice as big as any fusion reactor before. However, there’s a technical point here - while ITER should generate more heat power than it uses, this doesn’t translate to electrical power - which ITER will still use more of than it makes, as evan_au pointed out on our forum. That doesn’t stop Steven from being optimistic for this tech.

Steven - ITER will be followed by commercial fusion electricity-generating plants that will be totally self-sufficient. Fusion power has been anticipated for many years but now we can see the light at the end of the tunnel.

Phil - In the meantime, we may as well take advantage of the handy dandy fusion reactor just a few billion metres away and invest in a little solar power. Thanks Steve and Steven for asking and answering respectively. Next week’s question comes from Jon:

Jon - I just purchased some dart frogs which need to live in high humidity conditions. In order to attain this we basically sealed off the terrariums. The question is whether a really sealed terrarium could provide enough oxygen for the frogs through plant photosynthesis.

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