Operational aspects of superconductive magnetic energy storage (SMES)

The use of superconducting magnetic energy storage (SMES) is assessed from an operational point of view. The useable storage size for an SMES unit is determined for real utility load demand curves of previous years. The SMES size to be added in the future then becomes an extrapolated size from the size that would have been suitable in past years. Some general conclusions are: SMES should be used for large scale load-leveling rather than small scale peaking; the most likely duty cycle is 8 hours charging at night and 15 hours discharging during day time; the high efficiency (98%) of storage leads to lifetime 15% fuel cost benefits vs. intermediate cycling generation and 30% fuel cost benefits vs. all other storage; and SMES is a new source of ± spinning reserve with rapid 50 msec complete power reversal.