We focused on a flywheel energy storage system (FESS) because
it has a long operating life, is free from harmful waste and its state
of charge is clear. A conventional FESS whose flywheel is supported
by mechanical bearings is introduced in some railway companies,
but it is not so popular due to its demerits such as careful maintenance
of mechanical bearings and its rather small storage capacity.
Using superconducting magnetic bearing (SMB) to FESS is promising
candidate for high efficiency energy storage. Many laboratories
have studied superconducting magnetic bearing [1–6] to eliminate
bearing friction and to store larger energy