Well if you’re going to be that way, pretty much everything is other than nuclear and tidal.
Not clear to me without chasing down the study, though, if it relates only to conventional hydro, i.e. water comes in the top, goes out the bottom, it’s an energy source, vs. pumped-storage where water comes in the bottom, goes out the bottom, it’s basically a very damp battery, you could do it with piles of rocks instead of water as your potential energy sink except fluids are so much easier to work with.
(That said, I already speculated in my earlier post that it’s probably hard to find geography friendly to pumped-storage, at an affordable price.)
The Wikipedia “pumped-storage hydroelectricity” article sez “The round-trip energy efficiency of PSH varies between 70%–80%,with some sources claiming up to 87%”, which doesn’t seem like a “huge efficiency loss”? Actually it seems pretty reasonable, not far off from the 80-90% cited for LiIon batteries.
Related, ISTR the humongous Tesla battery farm going in to South Australia was (is?) competing with a pumped-storage facility. Actually it looks as though the fat lady may not have sung on that one yet.
