Excerpt:

Amber Kinetics connected its Alameda Point Test Site with AMP’s grid in February, and has now begun testing of its flywheel units.

Flywheels offer a number of advantages over chemical batteries: no chemicals or hazardous materials, unlimited cycling with no degradation and increased responsiveness. Flywheels convert electrical energy to kinetic energy when storing power and convert the energy back to electricity when needed by the grid. Amber Kinetics has demonstrated the only flywheel in the world capable of discharging for four straight hours here in Alameda.