Exists, just not with rocks. I think the modern versions use heavy metal blocks embedded in carbon fibre. https://en.m.wikipedia.org/wiki/Flywheel_storage_powe

Exists, just not with rocks. I think the modern versions use heavy metal blocks embedded in carbon fibre. https://en.m.wikipedia.org/wiki/Flywheel_storage_power_system https://en.m.wikipedia.org/wiki/Flywheel_storage_power_syste...