In a broader regional grid, where the "need to spill wind" is a net over Northern and Western Europe, and so a fraction of the "need to spill wind" in the UK alone, time-shifting Scandinavian conventional hydro-power and a modest amount of added reverse pumped hydro capacity seems like it could cope with quite a lot of storage capacity.

And then there are consumer side technologies to take advantage of a smart grid, which would all kick into top gear when "surplus" power is offered for little more than a transmission infrastructure surcharge.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.

What's wrong with spilling a bit of excess wind?

Suppose the wind segment cost was zero; in that case, whether you spill or not doesn't matter at all, right? So the importance of utilizing every Watt of wind blowing by is going to depend on the relative cost of the total wind infrastructure compared to the conventional infrastructure...