Sorta curious how this compares to pumped hydro with a giant water tower - or a deep pit and store the water at ground level.
I would expect it would be pretty similar, in each case you’re lifting a mass to create some potential energy and then draining it later. I can’t imagine the work involved in pumping up water is all that different in terms of efficiency from lifting concrete. The advantage with concrete is that you can do it in places where you don’t have huge amounts of water to spare though.
High friction is my guess.
I mean, it’s not like concrete is scraping on the walls going up and down, it’s on a pulley system which would be efficient in terms of doing energy transfer. The article mentions round-trip efficiency above 80 percent, so I’m not sure pumping water could be much more efficient than that.
