Pumped hydro storage currently makes up the largest share of energy storage systems in the world. But finding a good spot to build a regular hydro dam is getting difficult enough. And for pumped hydro, you need 2 big dams in close proximity yet with as much altitude separation as possible - that's damn hard to find. And of course you enough consistent water inflow to at least keep up with evaporation and seepage, which is a very tall order for many places in the world.

These alternate systems with concrete blocks / heavy trains / gravel / etc are interesting because they can be constructed just about anywhere with a steep hill and some empty space. And adding capacity is as simple as adding more blocks.
I think in the future, these mechanical solutions will provide cheap bulk storage, and battery systems will provide expensive but instant response grid stabilization systems.

For using hydro, I've been thinking of using one of these:



I collect pallets for various projects, and figure to build a platform from them, place the tote on top, then plumb it in. The totes have at least 1.5" outlet. Some even have 2 or 2.25" outlet. Not sure if that'd be high enough to produce enough pressure to run anything worth while, though. 

Altho, pallets are free for me, and the totes cost about $50 a piece around here. So I can always build more water towers 

From The Engineering Toolbox:
"A body of 1000 kg is elevated 10 m. The change in potential energy can be calculated as
Ep = (1000 kg) (9.81 m/s2) (10 m)
= 98100 J
= 98 kJ
= 0.027 kWh"

And that's before taking into account any pumping and turbine losses.
I doubt containers on towers will ever make sense vs a simple battery system. One really needs 2 dams and a mountain for this to be competitive.