Key design selections for the 20.4 MWh SMES/ETM

The 20.4-MWh superconducting magnetic energy storage engineering test model (SMES/ETM) will be the world´s largest superconducting magnet by nearly two orders of magnitude in stored energy. Its size, Lorentz loads, and power delivery requirements dictate a number of fundamental design requirements. In addition, the SMES/ETM must fully accomplish its primary mission of demonstrating large-scale SMES technology, while at the same time minimizing technical, schedule, and cost risks. A discussion is presented of nine key design decisions that are fundamental to meeting these challenging goals. These are a conductor current of 200 kA, helium containment within the conductor, an operating temperature of 1.8 K, a CICC conductor with a hollow core, a conductor premanufactured in half-turn lengths, a circular and continuous coil pac structure, fiberglass-reinforced plastic pultrusion for the coil pack structure material, a coil pack operating position that is precompressed radially inward, and a liner for vacuum enclosure