> Question is - how can pumped hydro be probably ever "maxed out"? Playing devil's advocate: once you've run out of places with enough height difference to bui

> Question is - how can pumped hydro be probably ever "maxed out"? Playing devil's advocate: once you've run out of places with enough height difference to build one upper and one lower reservoir. It's going to take a long time (there are many more places suitable for pumped hydro than places suitable for traditional hydro), but it's possible. > Let's say if we take all the (normal, not "pumped") hydro we have and increase number of turbines on them 10x, or 100x, and make them reversible, that will easily cover all the storage needs in terms of power. That's usually not feasible. Pumped hydro needs both a lower and an upper reservoir, while non-pumped hydro normally has only an upper reservoir, and discharges water directly into a river. That is: even if you made the turbines reversible (or added pumps in parallel with them), there would be no water for them to pump upwards.