@Scott th Ratbag; the lifting block could be made of anything at all as long as its a great big heavy weight.
Spare energy can be used to lift it up, when energy is needed it can be allowed to reverse direction head down and drive a turbine ... simple and could be located anywhere at all!
The block could even be full of water and have a dual purpose use as water storage / pressure.
The principle is no different from pumped hydro except the motors move the block up and a turbine generates power when the blocks moves downwards.
