A suitable design method of SMES coil for reducing superconducting wire usage considering maximum magnetic flux density

Generally, high magnetic flux density is adopted in superconducting magnetic energy storage (SMES) coil design to reduce superconducting coil size and increase energy density. However, critical current density of the SMES coil is degraded by applying the high magnetic flux density to superconducting wire. This means that adopting the high magnetic flux density is not necessarily suitable for the superconducting wire reduction of the SMES coil. In this paper, the relationship between the maximum magnetic flux density within coil and superconducting wire usage of the SMES coil composed of solenoid or toroidal coil wound by MgB₂, Bi2223, or REBCO wire was investigated. As a result, most suitable magnetic flux density within SMES coil for realizing the minimum superconducting wire usage in MgB₂, Bi2223, and REBCO wires were clarified. How to estimate the most suitable maximum magnetic flux density within coil for realizing the minimum wire usage in each superconducting wire was also investigated. Comparison between the rate of change of coil radius times maximum magnetic flux density and critical current density with respect to themaximum magnetic flux density is useful for obtaining the suitable maximum magnetic flux density for the minimum superconducting wire usage.