How old is that white paper? I am going to guess a good 10 years old now.
You are basing all your assumptions on a 1980's / 1990's concept of electricity grid, as well as the generating mix, and even usage ... not to mention with the exception of northern climates where they don't have much sun anyway, a cloudy/stormy day is not the peak usage. In places where sun can make for a large portion of the year round supply, a cloudy/stormy day will be a low usage day. House systems with backup would also be able to on that cloudy/stormy day extend their storage.
In a northern/cold climate, sun cannot provide a significant portion of the year round power so it is moot. More likely a mix or traditional wind and solar. Wind blowing normally when solar is low (cloud/storm).
Also expect grid scale storage to get much larger, something your white paper absolutely would not have taken into account, not to mention it probably have very low generation prices for fossil fuels, something quite out of data too. Gee, almost like I know the white paper ...