A typical system consists of a flywheel supported by connected to a . The flywheel and sometimes motor–generator may be enclosed in a to reduce friction and energy loss. First-generation flywheel energy-storage systems use a large flywheel rotating on mechanical bearings. Newer systems use composite
[pdf] The typical flywheel energy storage system costs $1,500-$3,000 per kW installed. While this appears higher than lithium-ion's $800-$1,200 upfront cost, the long-term savings are dramatic: Example: A 1MW system operating 10 cycles daily: By year 15, the flywheel solution becomes 34% cheaper overall.
[pdf] Power to gas, power to heat, battery storage and flexible load management provide a solution to deal with the challenges of long-term (5 to 12 hours) grid stability, while fast response storage technologies such as Flywheel Storage provides an efficient and affordable solution to manage the short-term (0 seconds to 5 minutes) challenges of grid stability.
[pdf] 
