Oh yeah, water works well, because you can raise it very efficiently. It's a very well worked through technology. Moving billions of tons of concrete verticall

Oh yeah, water works well, because you can raise it very efficiently. It's a very well worked through technology. Moving billions of tons of concrete vertically is a lot harder. (Most dams also supply their own water. Hydro storage is trickier, and needs you to build pumping systems, and sometimes to hollow out mountains)