Earlier quoted context omitted.
My impression as a layperson is that the economic feasibility of pumped hydro is very location-dependent, and our electrical grid isn't so fungible that storage in one region can meaningfully store energy generated in another region. Is my understanding correct? And if so, how do we tackle that?
Pumped hydro is very dependent on location. But the supply of energy would not need to be. Electricity grids and DC interconnectors work really well. Having a few massive sites spread across a continent could work well.
Even places without hills often have deep underground cavities, which also serve.