Heritage has some material on this, and I’ve done some simple calculations, too. Many assume proper storage would be a modest adder to green power, or maybe even double the cost. But that is simply not true–the cost of battery storage to cover a few days of dark, calm conditions is a couple orders of magnitude on top of the green power $$. Yes, 50x or more. Which makes a complete conventional fuel burning power plant a cheaper backup than any significant capacity battery storage.
The calculations get even worse when trying to size the storage to level the output across an entire year.
(And if you have to build a complete fuel-burning plant as backup, at max capacity, why bother building any green power in the first place?)