[apendleton]

> It would require a technological breakthrough that we have not yet imagined.

Maybe, but not necessarily. The necessary breakthrough might have been high-temperature superconducting magnets, in which case not only has it been imagined, but it has already occurred, and we're just waiting for the engineering atop that breakthrough to progress enough to demonstrate a working prototype (the magnets have been demonstrated but a complete reactor using them hasn't yet).

Or it might be that the attempts at building such a prototype don't pan out, and some other breakthrough is indeed needed. It'll probably be a couple of years until we know for sure, but at this point I don't think there's enough data to say one way or the other.

> And already, solar plus storage is cheaper than new nuclear.

It depends how much storage you mean. If you're only worried about sub-24h load-shifting (like, enough to handle a day/night cycle on a sunny day), this is certainly true. If you care about having enough to cover for extended bad weather, or worse yet, for seasonal load-shifting (banking power in the summer to cover the winter), the economics of solar plus storage remain abysmal: the additional batteries you need cost just as much as the ones you needed for daily coverage, but get cycled way less and so are much harder to pay for. If the plan is to use solar and storage for _all generation_, though, that's the number that matters. Comparing LCoE of solar plus daily storage with the LCoE of fixed-firm or on-demand generation is apples-and-oranges.

I think solar plus storage absolutely has the potential to get there, but that too will likely require fundamental breakthroughs (probably in the form of much cheaper storage: perhaps something like Form Energy's iron-air batteries).

[bruce511]

One can discuss base load and season shifting all day long. But ultimately fusion will fail for two simple reasons; time and money.

If we started building a fusion commercial scale plant today (ie started by planning, permits, environmental assessments, public consultation, inevitable lawsuits, never mind actual construction and provisioning) it'd come online in what? 10 years? 15 years? 20 years?

Want to deploy more batteries? It can be online in months. And needs no more construction than a warehouse.

Financially fusion requires hundreds of billions, committed now, with revenue (not returns) projected at 10 years away (which will slide.) Whereas solar + storage (lots and lots of storage) requires anything from thousands to billions depending on how much you want to spend. We can start tomorrow, it'll be online in less than 2 years (probably a lot less) and since running costs are basically 0, immediate revenue means immediate returns.

Of course I'm not even allowing for fusion being "10 years" from "ready". It's been 10 years from ready for 50 years. By the time it is ready, much less the time before it comes online, it'll be redundant. And no one will be putting up the cash to build one.

[pfdietz]

High temperature superconducting magnets are not a panacea for the problems with DT fusion. Those issues follow from limits on power/area at the first wall, and the needed thickness of the first wall; these ensure DT reactors will have low volumetric power density, regardless of the confinement scheme used.

With HTSC magnets, a tokamak much smaller than ITER could be built, but ITER is so horrifically bad that one can be much better than it and still be impractical.

[epistasis]

And these are not new issues, they've been known for more than 40 years, but never addressed. From the 1983 Led

> But even though radiation damage rates and heat transfer requirements are much more severe in a fusion reactor, the power density is only one-tenth as large. This is a strong indication that fusion would be substantially more expensive than fission because, to put it simply, greater effort would be required to produce less power.

https://orcutt.net/weblog/wp-content/uploads/2015/08/The-Tro...

[apendleton]

Oh for sure, I'm not claiming that CFS (or Tokamak Energy or Type One or whoever else) will for sure succeed, or if they do, that they've already solved all the problems that will need solving to do so. My only assertion/prediction is that I think if they end up succeeding, when future historians look back and write the history of this energy revolution or whatnot, HTSC magnets will turn out to have been the key breakthrough that made it possible.

[pfdietz]

> needed thickness of the first wall

I meant, needed thickness of the tritium breeding blanket.

[cesarb]

> If the plan is to use solar and storage for _all generation_, though, that's the number that matters.

And that's the problem with these Internet discussions: that's almost never the plan, but commenters trying to make solar look bad assume it is (to your credit, you made it explicit; many commenters treat it as an unspoken assumption).

In real life, solar and batteries is almost always combined with other forms of generation (and other forms of storage like pumped hydro), in large part due to being added to an already existing large-scale grid. The numbers that matter are for a combination of existing generation (thermal power plants, large-scale hydro, etc) with solar plus storage. Adding batteries for just a few hours of solar power is enough to mitigate the most negative consequences of adding solar to the mix (non-peaking thermal power plants do not like being cycled too fast, but solar has a fast reduction of generation when the sun goes down; batteries can smooth that curve by releasing power they stored during the mid-day peak).

[adrianN]

In the end we're still making steam and running a turbine. Just the steam turbine part of the power plant has a hard time competing with solar in sunny locations.