storage in hydrogen and allow a 80% devaluation of the energy that was used. That doesn't matter because the energy would be thown away otherwise like it is today.
I'd expect some - actually probably quite a lot - of excess CAPEX on wind+solar, and some deficit (less CAPEX, but buying some electricity at retail) so you don't have electrolysers and thermal plants just lying around.
You're still stuck with the investment issue: either you pay (Hinckley-scale!) fees to providers to just lie around, or the public sector runs it itself, and the "private more efficient" bollocks is exactly that, because the private sector isn't providing the value. The people providing SLAs are.
You need huge amounts of "base load" hydrogen generation capacities for these industries alone. Flexible generation, i.e. produce more to soak up excess renewable energy which you can then export or turn back into electricity (at a huge loss) later, is just the cherry on top.
The initial funding will absolutely come from the steel and chemical industry (and also government subsidies to get the transformation started).
For ammonia this will eventually be required.
But you still must get a way to put carbon in it. This is usually done by mixing the steel with CO, and the easiest way to get from renewables to CO is by reacting CO2 and H2.
I don't think anybody has enough information to know what is the way to go. But well, I'm an outsider with very little information.
Nuclear neat is totally green, you actually get 100% utility out of the plant rather then having constant highly inefficient 'start-stop' operations.
And its actually a better less complex process then electrolysis.
But I guess its much better to absurdly gigantically over-provision renewables so one in a while we can run electrolysers and then by inefficent fossil fuels to drive inefficent electrolysers the rest of the time.
And its not at all clear that hydrogen as storage is actually a good idea, and its also not at all clear its the only thing that scales. It very much unproven at the kind of production scale AND storage scale you suggest. And even in the best case its incredibly inefficient and incredibly expensive make/store/produce.
Something like Iron based batteries will likely turn out to be a better solution.
There's more hydrogen in a liter of gasoline than in a liter of liquid hydrogen.
Electricity to gasoline produces a safe product that is easily storable for years and easily transportable requiring only minor safety precautions. Not something that can be said for hydrogen.