Two-layer superconductive magnetic energy storage structure and protection system design

Superconductive magnetic energy storage (SMES) for electric utility applications has been studied by the Wisconsin group since 1970. Currently there are two preferred designs: two-layer low aspect ratio rippled and non-rippled solenoids mounted in surface trenches. A 5500 MWh, 200 kA, 4 tesla, 504 turn, 18.9 m high and 472.4 m radius two-layer solenoid is the basis of this study. The current UW nonrippled design is an improvement over a recently published design. Stress analyses of each structural design is described. Open pool cooling in superfluid helium provides heat removal of 2.5 W/cm²for long term cryogenic stability. A helium dump system to protect the coil from overheating during an emergency energy discharge is outlined.