Force-balanced coils for SMES using REBCO tapes

REBCO tapes are strong candidates for high-field magnets because they keep a higher critical current density in a high magnetic field range. In addition, the Hastelloy substrate of the REBCO tapes can be used as support structures for electromagnetic forces. However, the winding configuration of superconducting coils should be optimized to enhance the stress limit caused by electromagnetic forces. Force-balanced coils can balance the electromagnetic forces through a helically wound configuration and minimize the required mass of support structures for energy storage based on virial theorem. This work discusses the design considerations of the force-balanced coil windings for SMES using REBCO tapes. The force-balanced coils with a geodesic winding pitch will be a feasible solution for HTS-SMES using REBCO tapes. The geodesic pitch enables minimizing the in-plane curvature of helical windings, which applies the edgewise bending strain to REBCO tapes and reduces the perpendicular magnetic field to 5% of the maximum toroidal magnetic field. These features will prevent a decrease in the critical current of REBCO tapes in a high magnetic field range.