Energy Vault is going public on the NYSE. They are a new company building grid level energy storage using mechanical instead of chemical means. When there is surplus energy a crane stacks concrete blocks. When energy is needed the crane unstacks the blocks and recovers the potential energy stored in the block. Pretty cheap ($150 / kWh) and simple and they claim 85% efficiency. Same concept as pumped hydro but much smaller and not dependent on geography.
https://www.wsj.com/articles/renewab...ic-11631136600
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