The most significant program on energy storage in the world is being carried out by Babcock and Wilcox (B&W) in the United States. This ~$50 million program is cost-shared by industry (70%) and the federal government (30%) through DARPA. B&W will construct and install a 500 kWh SMES primarily to provide spinning reserve to the Anchorage Municipal Light and Power (AML&P) utility. The Anchorage utility is part of the "Alaskan Railbelt System," one of the most isolated utility networks in the United States. The Anchorage area served by AML&P uses almost half of the railbelt system's peak load, which reaches approximately 600 MW during winter. AML&P is required as part of the railbelt interconnection agreement to designate ~30% of its generating capacity for spinning reserve; part of this reserve is provided by a hydroelectric facility at Bradley Lake. Physical restrictions at Bradley Lake result in dispatch time for this hydro capacity of approximately one minute or more, too long a time to prevent additional load shedding during an event such as a generator outage, which would lead to frequency instability on the system, resulting in programmed load shedding. The planned SMES system will instantly dispatch ~30 MW over a period of ~1 minute, which will provide sufficient time to ramp up the hydro capacity and put it on line to prevent further load shedding. As designed, the SMES will store 1,800 MJ in a low-aspect solenoid almost 7 m in diameter using an aluminum-stabilized Nb-Ti conductor operating in a "cryostable cooled" mode (Huang et al. 1995).

Several U.S. companies are producing small SMES systems, called micro-SMES, primarily to provide power quality improvements to selected customers rather than as grid or network solutions. These ~1 MW units with a few MJ stored energy are commercially produced by Superconducting, Inc. (SI), of Madison, Wisconsin, and by IGC of Latham, New York. SI and IGC have supplied micro-SMES systems to the United States Air Force (USAF) as part of a program to provide uninterruptable power capability and power conditioning, primarily for voltage stabilization, to selected USAF control centers. At present this "power quality" market is also served by battery storage or flywheel systems, especially in Japan and Germany. Outside of the United States there is no comparable activity for micro-SMES commercialization.

Published: September 1997; WTEC Hyper-Librarian