short-term grid stability (on the order of seconds to hours) is essentially a non-issue with a renewable grid that has even the fraction of the storage needed t

short-term grid stability (on the order of seconds to hours) is essentially a non-issue with a renewable grid that has even the fraction of the storage needed to make up for longer term variability in supply (days/weeks). Inverter systems connected to batteries are already the best and most cost effective means of providing frequency control to a grid (they can simulate an incredible amount of rotor inertia): this is one of the ways in which Tesla's grid-scale battery in Australia is making lots of money (and eating the lunch of gas turbine operators who previously provided this). You can also add this capability to wind and solar generation, it's just not generally worth the extra effort (it's easier to coordinate a few larger providers somewhat specialised to the task than distribute it to everything on the grid).