@cstross Nobody is self-sufficient on »renewables« (if by that you mean solar+wind). When the peak of solar+wind generation hits the demand line, the downs and ups mean that they meet only about 40% of live demand. Everything else must come from storage or other »backup«.

And nuclear energy is one of the best backup solutions there is. (So much so that it begs the question why only backup, but that's the fear of the renewables-only lobby.)

@Ardubal @cstross only an idiot would design a renewables-powered network where demand was only just met by nameplate capacity.

Surplus energy is the name of the game. Dump it into batteries, thermal storage, hydrogen electrolysis, or other industrial processes that are flexible in output, and could really benefit from some free (or almost free) electricity.

Nobody serious expects a renewables system to not have periods of surplus generation.

@Bern @cstross

That point of just-met-demand is not an ideal or proposal, but a plausibilization case. It is the point up to which solar+wind scale roughly linear.

Yes, after that point comes overbuild plus storage. Every MW of that overbuild must be matched by storage with the same power output and hours or days of energy capacity. And every MW of that overbuild is diminished by storage and transmission losses. So, this point is like a sound barrier for ROI.

@Ardubal @Bern The ROI on renewables/gridscale storage looks a whole lot better, though, if you first cancel all the subsidies (visible and hidden) for fossil fuels. And better still if you bear in mind that PV prices per kWh are still dropping and battery prices are *also* falling.

Whereas nuclear reactor prices only ever seem to increase (unless like France in the 1970s you build them on a conveyor belt—politically non-feasible today).

@cstross @Bern Not really. The build cost of each model fall build-by-build, even if the FOAKs seem always more expensive (which has reasons).

The biggest hurdle now is restarting the building industry, but that is actually happening. And it's already politically feasible in many european countries.

And these hurdles are all not fate-given, intrinsic, unchangeable. They are challenges to overcome, not /if/ but /how/.

@cstross @Bern If even a fraction of the techno-optimism propping up hopes for solar/wind+batteries was applied to existing nuclear technology, fossil burning could already be history.

Nuclear advocates usually say »yes, do solar + wind, but it will not be enough, also do nuclear«, while Renewables-Only advocates say »no, don't do nuclear at all, and kill the existing ones«. I think it is rather clear which side is the favourite of the fossil lobby.

@Ardubal @cstross I'm quite familiar with the arguments from nuclear advocates - I used to be one myself, a decade or more ago. Back in the 90s, something like the Integral Fast Reactor would have been an absolute godsend, and produced vast amounts of clean and safe electricity.

But we've had several decades of maturation of renewables since then, and the cost differential now is so great that it just makes no sense to build nuclear, except in relatively niche applications.
Wind and solar combined get effective capacity factors over 60% in many locations, and even a 10x overbuild is *still* going to be cheaper than nuclear. Grid-scale batteries mean you don't have to go anywhere near that far, though.