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Yeah, my surface level evaluation of these projects is that they're just not going to be viable - you have the height but you don't have the volume - mineshafts are by definition narrow - and some sort of automated load/unload system is going to run into issues of complexity and reliability and ease of access for maintenance to whatever's at the bottom end.

It's always going to be easier to move water around in an automated fashion, though, so I'm immediately skeptical of any system that isn't some variant of two tanks and a pump/turbine.

If you really do want to use gravity as a power source and don't want to go the hydro route you're better off building narrow-gauge train lines up the sides of hills. The lower-impact and lower-output version of that would be aerial ropeways.