Not to mention, this requires huge over-production, which is a problem in areas with already high land usage, such as Europe. It is probably much less of a problem in the USA, so maybe there the calculations are different.
I just love reactionary conservative nuclear logic.
"Let's just use fusion for all our energy needs. We don't need fission, nor do we need wind and solar. Just because it hasn't been done now, doesn't mean it'll never happen. If you don't support this you're just an anti-fusion conservative reactionary!"
The worst case for renewables would be that costs stop declining. Stack the deck just right and nuclear might end up a bit cheaper. But this is just a financial risk, not a risk of the planet. And if one is looking at financial risks, one must also look at the risk of cost overruns in nuclear. Unlike with renewables, which typically come in within 10% of the contracted cost, nuclear plants are famously subject to enormous cost overruns. Factors of 2, 3, or even more.
Pretending that the promises of nuclear will absolutely come true, but that renewables haven't absolutely demonstrated their cost declines will continue, is a blatant double standard and not how one does proper analysis. That's why utilities and financiers have walked away from new nuclear, especially in markets where they're not allowed to foist overruns off on the ratepayers.
We have lots of experience with hydroelectricity. So we can just build more dams, it's all just a question of cost right? With more money we can just build more dams until we reach 100% hydroelectric generation right? This is the kind of logic you're using.
Possibility and feasibility are two different things. Lithium ion batteries exist, but we'll never deploy a day's worth of battery storage. The scale just isn't there. No amount of money thrown at the problem is going to make it possible.
Sure things like hydroelectricity and electrolysis exist, but they have significant barriers to feasibility. The likely path for an attempt at solar and wind grid is to build a bunch of solar and wind, try to build storage, fail, and keep using fossil fuels. Nobody, and I mean nobody has ever built grid scale storage for more than an hour's worth of electricity use (let alone total energy use). Energy storage remains an unsolved problem, and it's not just a question of cost. There's no telling if it can be done even with unlimited financial resources.
By comparison we just need to build 4 nuclear plants for every existing one in the US. No massive 10,000x increase in storage capacity required. No reliance on technology that's never been deployed at scale.
So if 70% is insufficient to demonstrate feasibility, then solar and wind are even worse off.
We're also not going to run out of industrial processes that produce large amounts of carbon dioxide, at least as long as we still build things out of concrete, so if for some reason hydrogen is too hard to transport or store, we can pay the extra price of turning it into methane and use all the infrastructure that we already have for natural gas. We can even recapture most of the carbon when we burn the methane again.