The article & video about Energy Vault using concrete blocks to store energy can be found here: https://qz.com/1355672/stacking-concrete-blocks-is-a-surprisingly-efficient-way-to-store-energy/
Energy Vault's Introductory Presentation: https://www.dropbox.com/s/pd8uauwr4379gr4/Energy%20Vault%20Introductory%20Presentation%20-%20Dec%202018.pdf?dl=0
