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You're still going to need a heckuva storage system to manage even the daytime fluctuations. There's no way around the fact that environmental conditions will significantly impact a solar operation, even in relatively sunny areas. This is especially true if the facility is spread out over hundreds of sq. miles, which it would have to be to have the output you envision.

Imagine you are sitting in the "hot seat" of the regional grid control center (as I have). Your primary source of capacity is a solar-based system in West Texas. You have some spinning reserve in a coal or nuclear plant here or there, and a few GT peakers, but those probably can't handle a significant drop in primary output. So now you see a fairly strong weather front moving across the Southwest. The edge of the front is ragged, the winds chaotic as they are wont to be, there is significant turbulence and unpredictable variation in cloud cover. As the front approaches the PV array the output begins to fluctuate, manageable at first but increasingly variable. You switch in your spinning reserve and maybe fire up some peakers, which calms things a bit but only temporarily. As the weather front covers more of your generating array, you start getting serious voltage sags. You try to balance the load with regional grid interties, but your neighbors have their own worries for capacity and don't have much to give. They see your regional grid instability growing and in fact are starting to think about isolation more than intertie. They don't want to be dragged down into a blackout if you go under. The front has cleared part of your PV array so a little more capacity is available, but the ragged leading edge is still causing worrisome fluctuations and line drops. You start thinking about reducing voltage, but for industrial users brownouts can be more problematic than a straight blackout, because of equipment damage. You look up your contingency plan for rotating blackouts and voluntary load shedding. Just as you're about to pull the switch, the front breaks up and you're in the clear as long as you've got that spinning reserve and those peakers, for awhile. Whew! Close one. But you made it through that one, no worse for the wear but for some extra grays hairs and maybe a little closer to a coronary. Then you look at the weather charts for next week. There's this front sweeping in from the west...