I wouldn't assume all or even most renewables. I would assume you'd continue to use existing hydro and nuclear. The nuclear would help a little, but the hydro helps a lot. It's capacity can be saved for times when wind and solar are low.

In that scenario 90% is very easy to hit. A couple of hours worth of storage, maybe.

> But "some" wind or sun is not enough to support the whole grid.

The less there is, the more you have to over build to compensate. Doesn't make it impossible.