Basic design considerations for a medium-size superconducting magnetic energy storage system (SMES)

In a feasibility study, a 2 MWh magnet system suitable for electric utility application (primary control reserve) is analyzed. Basic choices for a realistic SMES design are considered taking into account practical industrial feasibility. Compared to a large solenoid, advantages are seen for a modular, toroidal configuration with circular coils. To achieve a robust coil pack, internal cooling with supercritical helium for an impregnated winding is selected. System parameters are derived from a cost optimization approach. Possible conductor concepts, a thin-walled coil casing, and a corresponding refrigeration system based on a cryogenic loss estimate are presented.