um, yes, it's happening already in areas where intermittent supplies make up a sufficient percentage of the energy mix (e.g. South Australia). In an ideal world we'd keep the rollout of intermittent sources below the level at which they cause instability until grid scale batteries are invented, however that's not the world we live in.
My understanding is that neither of the major outages in SA in recent times have been related to intermittent supply issues (i.e. the first major incident was related to trips caused by weather, the second was related to a gas using supplier failing to increase supply due to some market regulation minutiae that was subsequently changed).
Regardless of the realities in SA (I’m not convinced by the offical explanation of the first outage at least, there are credible alternative theories), it’s well understood that beyond a certain level, introducing intermittent suppliers into a network designed for baseload generation will cause instability. I don’t have the figures to hand but IIRC more than very low double figures as a percentage starts causing trouble.
