https://beaconpower.com/carbon-fiber-flywheels/ https://beaconpower.com/carbon-fiber-flywheels/ These guys have two projects (check their operating plants) usi

https://beaconpower.com/carbon-fiber-flywheels/ https://beaconpower.com/carbon-fiber-flywheels/ These guys have two projects (check their operating plants) using flywheels. They're used for frequency regulation. About 20MW each.