A company called Energy Vault[0] is (was?) working on this. I think it is relatively capital intensive compared to what the company in the article is doing. Of

A company called Energy Vault[0] is (was?) working on this. I think it is relatively capital intensive compared to what the company in the article is doing. Of course storing underground requires particular geology. I also remember reading about a system that moved dirt/rock up a mountain on a train. Can’t find a link, but that also seems capital intensive and requires different geology. There is also pumped hydro storage that works via gravity. That’s been around a while. My dad worked as an engineer on one in the 80s [1]. [0] https://www.energyvault.com/ https://www.energyvault.com/ [1] https://en.m.wikipedia.org/wiki/Helms_Pumped_Storage_Plant https://en.m.wikipedia.org/wiki/Helms_Pumped_Storage_Plant