Theoretical and experimental investigation of R&W and W&R SMES coils wound with large-scale MgB2 Rutherford cables operated around liquid hydrogen temperature

Abstract

We have developed the system called Advanced Superconducting Power Conditioning System (ASPCS) composed of a Superconducting Magnetic Energy Storage (SMES), a fuel cell and a water electrolyzer for effective use of renewable energy such as wind and solar power generation. We have been investigating about the SMES coil using the large-scale Rutherford-type conductors made of commercially-available MgB2 wires. Due to strain sensitivity even before heat treatment for MgB2 production, the design for large-scale Rutherford cables both in the wind and react (W&R) method, and the react and wind (R&W) method applied to coil fabrication has to be done cautiously to prevent the degradation of the IC by the optimizing design parameters such as the twist pitch and the cable compaction. Especially for the R&W method using heat-treated wires, other factors like handling during the coil production process which affect the conductor and coil IC should be also considered. To evaluate the applied strains during the manufacturing process, we conducted theoretical investigation on the strains applied to individual filaments caused by wire-bending. We developed a test coil designed for the R&W method based on analyzing those factors. Furthermore, we measured the coil IC-B-T characteristics and compared to those of other test coils made by the W&R method.