Estimation of Electricity Storage Density of Compact SMESs Composed of Si-wafer Stacks Loaded with Superconducting Thin Film Coils in Spiral Trenches under the Constraints of the Critical Magnetic Flux Density

Abstract

Abstract Numerical estimations of electricity storage volume density: W for a proposed compact superconducting magnetic energy storage system composed of 4 stacks of 20 to 1800 Si-wafers loaded with superconducting YBa2Cu3O7-δ thin film coils in spiral trenches formed by MEMS process were performed in conjunction with estimations of magnetic flux density and electromagnetic hoop stress applied to the coil. Changing the design parameters such as trench depth, trench width, trench wall thickness, number of stacked Si wafers, the inner-radius of the spiral coil under the fixed outer-radius of 47.45 mm, the maximum W was obtained to be 13.6 Wh/l under the constraint of the maximum magnetic flux density applied to the coil: Bmax < 20 T. The maximum hoop stress applied to the coil was estimated to be much lower than the mechanical strength limit of the Si wafer :4 GPa, indicating that other substrate materials such as typical engineering ceramics can be used in place of Si wafer if microfabrication of spiral trenches is feasible.