Regarding pumped storage hydropower,
In the case of some high altitude upper reservoir that feeds several turbines located at the bottom of a valley, where there's a lower reservoir too.
Assuming in this case turbines are not reversible by design, and cannot act like pumps, and therefore separate dedicated pumps are required to pump up water to the upper reservoir.
Should those pumps be fed electrically? Or should those pumps be directly linked to turbines using some clutch? How does efficiency of "converting hydraulic to electrical and back to hydraulic" compare to only "convert hydraulic to hydraulic" ?