[zaarn]

They are big and expensive now. If they prove themselves then the economics of scale apply and the price goes down. And of course a lot more funding in the sciences to figure out how to make them cheaper because there is more economic interest.

[pfdietz]

The problem is, the exact same argument can be applied to all the things fusion would be competing against. In engineering, unlike children in Lake Woebegone, it's not possible for all competitors to come out on top.

To put it another way, the same argument you're making could be applied to (say) making computers from vacuum tubes, or balloons out of lead, or any of a myriad of approaches to solving problems that are losers regardless of effort expended. Why are we assuming fusion isn't also similarly a loser?

[zaarn]

There is a stark difference; the fuel for fusion reactors is the most common element in the universe. And literally every other energy source derives it's energy from fusion byproducts.

[pfdietz]

But this is no argument either. It's like arguing "vacuum tube computers have the advantage that they have no moving parts. And all other computer technologies use the electrons that are manipulated in vacuum tubes."

All that could be true, and fusion could still be hopelessly uncompetitive. The problem is the complexity, difficulty, and size of fusion reactors. Free fuel doesn't make up for that. All the long term beyond-fossil fuel competitors fusion has to beat are also only loosely constrained by fuel availability.

[zaarn]

Well, I would disagree, the computer comparison doesn't really hold since normal computers don't have a limited and localized supply of electrons (unless they are a laptop). It's more like arguing that a modern 4U Server has more performance than a laptop, really. Which is true.

Fusion reactors might be complex and difficult to figure out, but once it has been figured out the free market will inevitably make it cheaper.

Fuel availability is indeed a problem, IIRC the uranium reserves will hold us out for another 200 years before running out. At current energy demands. So realistically more like 100 years. Coal and oil will inevitably run out too. Sun and Wind don't produce a lot of power compared to Fusion when considering the rare earths required for the components. Fusion is just a lot more efficient and energy rich.

[pfdietz]

The analogy of course wasn't exact, but it fits the structure of your argument, so it shows your argument was wrong.

Fuel availability is NOT a problem. There is no shortage of sunlight, or wind, or uranium (if used in breeder reactors, and why are fusion reactors, which are breeders, allowed but fission breeders are not?) The 200 year figure for uranium assumes a once-through cycle. In breeders, ores with 50-100x less uranium per unit mass of ore would be usable, because breeder get so much more energy out of each unit of uranium mined.

Oh, and please don't repeat the Rare Earth canard. Solar doesn't use rare earths, and wind doesn't have to. I think you're just repeating talking points you haven't bothered to understand.