@MattMastodon@Sodis Careful about labels. »Renewables« often includes biomass (which is just fast-track fossil tbh) and hydro (which is not so volatile). I'm talking about wind and solar specifically (volatiles).
40% is roughly the mean capacity factor of a good mix of volatiles. This is what you can directly feed to the user from the windmill/panel, without storage. You can expand a bit by massive overbuilding, but you can't overbuild your way out of no wind at night.
@Sodis@MattMastodon Nuclear power plants can quite easily do load following. It happens regularly e. g. in France. However, since it has the lowest running costs, other sources are usually cut first as far as possible.
@MattMastodon@Sodis Only about 40% of demand can be directly met from volatiles (wind and solar), i. e. no intermediate storage. The rest has to come from »backup« or »storage« or however you call it.
Current storage tech is still almost 100% pumped hydro. Batteries have not made a real dent there yet. But pumped hydro is not enough by far, even potentially, and batteries have a long way to go to be even as scalable as pumped hydro.
So, backup. The only clean, scalable backup is nuclear.