[rcxdude]

I mean, Scotland has more wind power than it can use (or transfer to England) at the moment, so solar is probably not the main focus. The price of nuclear plants also means you can afford to overbuild renewables by quite a lot to make up for seasonal variation and still come in at the same price.

[Zanfa]

The problem is still long periods (up to weeks) of single-digit percentage of nominal capacity of power generation from wind farms. Overbuilding doesn’t help much, so a non-renewable option still needs to be available.

[roryirvine]

Wind droughts lasting a week or more are a 1-in-5 year event in the UK so, yes, must be accounted for.

Nuclear is prone to similar issues - statutory outages for inspections and refuelling, and emergency outages which often affect multiple plants at the same time (eg. a cracked steam valve in one plant requiring remediation on the same component in the others).

Keeping existing gas generators around, ready to be put into use when needed, is the simplest way of dealing with this until sufficient storage capacity is built out.