Probably the cheapest and best option is to build more wind and not care too much if it increases curtailment.
Yes, all the things mentioned should be looked into and done when it makes financial sense but "wasting wind" is much less a thing to worry about than "burning gas", and I'd rather waste wind than waste money.
https://www.oecd-nea.org/upload/docs/application/pdf/2021-12...
... most of the modern light water nuclear reactors are capable (by design)
to operate in a load following mode, i.e. to change their power level once
or twice per day in the range of 100% to 50% (or even lower) of the rated
power, with a ramp rate of up to 5% (or even more) of rated power per minute.
One trouble is that changing the power output does put stress on components because of thermal expansion and contraction, potentially shortening their lifespan, but it something that can be designed for.You could just keep it spinning nonstop without a load I suppose, but for anything but nuclear it's not gonna be economical.
The thing is, they don't really want to do it if they can save fuel by shutting down.
You'll soon end up with a burning/melted generator.
> "pump some water in a loop"
OK, but you're going to need huge pumps (1000+ MW!). Expensive.
> "or discharge through some resistors"
Again, you'll need extremely large resistors, and a way to dissipate an awful lot of heat. We're talking about a huge amount of energy here!