I was talking about solar and it's benefits at shaving peak demand. I'm not talking about moving all of our power generation to solar and storing it in batteries. That would be silly. However, that you mention the huge slack in power demand at night helps illustrate my point. Solar matches up quite well with our needs for when electricity is consumed. No, the sun doesn't always shine, but yes, it can be a great tool in managing our power needs.
See the post you replied to--I'm not one that thinks all of our power should be coming from renewables at this point--but we could use a lot more solar (and also other renewables in different scales) than we already do. Is Germany's grid in shambles because they use so much solar? Are they doing widescale battery storage of extra energy? Of course not.
If there does end up being some sort of HUGE central energy storage happening, I doubt it would be in batteries. Talk about being difficult/expensive to scale...
Why would it be difficult/expensive to scale? As long as battery costs go down, there's absolutely no issue scaling. You just put as many of them as you want together.
Your car can receive a signal from the grid and either stop charging or actively feed power back in to the grid. This can be beneficial on even a very short timescale, e.g. lots of UK soccer fans put their kettles on during half-time of the FA cup, and all the electric cars currently plugged in stop charging for 30 seconds or so to counteract the demand spike.
I'm sure I saw an analysis that claimed you needed surprisingly few electric cars before that has a dramatic impact on the optimal way to design an electric grid.
Because feeding back to the grid is only a sustainable solution when a minimal number of entities are doing it. What happens when the majority of entities are feeding back to the grid? Where is all that energy supposed to go? The answer, of course, is storage.
And this isn't just some made up problem either; it happens right now with a different solution. There's a huge slack in power demand at night. Sometimes enough that the power providers will offer deep discounts to bulk buyers to get rid of excess supply. So you see some industries that use massive amounts of power, like aluminum refineries, shift to mostly night operations. But shifting demand around will only help so much.
Now, while distributed generation is fine, I don't think distributed storage is going to work. Storage cost (both economic and ecologic) and efficiencies are simply much better scaled up.