[TaylorAlexander]

I’m not sure I follow, but you’re saying the power plants are very large relative to their power output, and this size correlates to cost, thus making them so expensive that they are not economical?

You’re probably right, but I guess what I’m saying is that we’ve never had a fusion power plant that produces net energy gain at any cost. I believe SPARC is on the path to doing so. It will still take a long time to make fusion actually affordable. For what it’s worth I am a huge advocate of wind and solar power. But fusion is neat and I’m excited for us to get to a point where we actually have sustained Q total greater than 1.

[pfdietz]

Yes, that's right. View it this way: a fission power plant and a DT fusion power plant are pretty much the same, except for the reactor. The fusion reactor is many times the size (and mass) of the fission reactor, made of much more sophisticated materials, with a much more complex design, operating at higher stresses (loads on supports of the magnets, thermal power/area at the wall, neutron flux). So how is it that it's expected the fusion reactor will produce power more cheaply than the fission reactor? Note that fuel is today a small fraction of the cost of power from a fission reactor.

[TaylorAlexander]

Ah, yeah that is totally valid. My thinking is not exactly that fusion power will be cheaper than fission any time soon, but that the technology has the potential to deliver safer power, and as important as wind and solar are to our transition over the next few decades, I believe that fusion has the potential to deliver much higher levels of power than wind and solar, allowing for new uses for electricity previously considered impractical. I wonder what kind of new manufacturing processes we can come up with if we have enough power to deliver huge amounts of process heat, for example.

I agree with you that in a practical sense fusion power will not be economical in the next 50 years, but then solar power was not economical for most of my life either. I am excited for the technology to get to the point where at the very least it is producing power, as this will stimulate more investment in lowering the costs, and has been such a dream for longer than I have been alive.

[pfdietz]

Solar and wind potential is enormous. The current world average primary energy demand is 18 TW, but the Earth is constantly being struck by 100,000 TW of sunlight. In no sense is a shortage of sun and wind an argument for fusion.

As for safety, the problem with fission isn't safety, it's cost. Trading off economics to obtain better safety is solving the wrong problem.

If fusion is not to be economical for 50 years, it will be competing against renewables (and storage) that have gone fully down their experience curves. In a world fully powered by PV, on the demonstrated historical experience curve, the LCOE from PV could be below $0.01/kWh (in today's dollars). Fusion will have a very difficult time competing against that.