> Night" reaches across more time-zones than you can build your grid across. > Never mind "winter".

Demand isn't at an even level across the night ( high early evening, low 3 am ) - if your grid spans time-zones you can smooth that out, and renewables span more than solar. Wind doesn't stop at night, hydro doesn't stop at night etc.

> nuclear powerstations are not as reliable as you might think - they often go offline.

Maybe it's a UK thing with nuclear reactors operating beyond their initial design life - but there was a situtation last year where the majority of them were down at the same time and the UK had to make high use of our interconnect with france ( using their nuclear capacity ). In the UK the 2025 nuclear output was 12% down on the previous year due to outages.

The point here is that a grid that expands beyond national boundaries - helps in general, not just specifically for renewables. And before you go on about energy sovereignty - where do you think the Uranium comes from?