They can increase or decrease generation with 30 mins notice.
Are you sure they didn't say 30 seconds?
If a nuclear station losses a unit, the control supervisor lifts the phone and calls the grid. The grid controller might call on Cruachan to make up the difference. It can do 0 -440Mw in about 30 seconds. That buys time to get to reconfigure and get other stuff online.
The generators that produce at a continuous rate are of course nuclear. Nobody dares/knows how to turn them off!
Nuclear reactors are not very flexible, they are designed to run pretty much flat out round the clock week in week out, it takes time to adjust output. Part of base load. So, during the night the excess generation is used to pump water back up into pumped storage hydro dams.
If you’ve ever wondered why wind turbines sometimes spin on windless days. Why that’s just excess generation being absorbed.
Of course, key to become greener is the European DC super grid. Means we can transmit generation efficiently over thousands of miles. There’s, just in wind alone potentially enough power to run the whole of the EU – if it isn’t blowing here, it’ll be blowing there.
Another reason why BREXIT is so fuckin dumb.