Swiss startup Energy Vault is stacking concrete blocks to store energy — Quartz
▻https://qz.com/1355672/stacking-concrete-blocks-is-a-surprisingly-efficient-way-to-store-energy
mix substances that cities often pay to get rid off, such as gravel or building waste, along with cement to create low-cost concrete blocks. The cost saving comes from having to use only a sixth of the amount of cement that would otherwise have been needed if the concrete were used for building construction