Kimiyuki Shinoda

Test results of the 100 kWh SMES model coil – AC loss performance

Abstract In order to establish a technology needed for a small-scale 100 kWh SMES device, an SMES model coil was fabricated. Performance tests were carried out at the Japan Atomic Energy Research Institute (JAERI) in 1996. After that, the coil was installed in the Lawrence Livermore National Laboratory (LLNL) facility and tested in 1998, in collaboration between Japan and the United States. The AC losses measured at LLNL were in good agreement with those measured at JAERI. It was reconfirmed that the coupling loss of the coil could be expressed in two components: one with a short and another with a long coupling time constant. We found out from the Hall probe signals that the loop currents with long decay times were induced in the CIC conductor by varying magnetic field. These currents resulted in additional AC loss in the coil. To develop a concept of CIC with low AC loss, we made a sub-scale CIC conductor of strands coated with CuNi. We fabricated a small coil out of this conductor and measured the AC loss. The measured AC loss in this coil was about 1/6 of that in the SMES model coil conductor per strand volume. Thus, the CuNi coating of the strands was demonstrated to be effective to reduce the AC loss in the coil.

Test results of the SMES model coil—pulse performance

A model coil for superconducting magnetic energy storage (SMES model coil) has been developed. To establish the technology needed for a small-scale 100 kW h SMES device, a SMES model coil was fabricated and tested in 1996. The coil was successfully charged up to about 30 A and down to zero at the designed magnetic-field ramp rate for the SMES. Alternating current (AC) losses in the coil were measured by an enthalpy method. The results were analyzed and compared with the test results from a short sample. The measured hysteresis loss is in good agreement with that estimated from the short sample results. It was found that the coupling loss of the coil could be described as consisting of two components with different coupling time constants. One has a short time constant of about 220 ms, which is in agreement with the test result of a short conductor. The other has a long time constant of about 30 s, which was not expected from the test results for the short sample.

An evaluation of the inlet flow reduction for a cable-in-conduit conductor in pulsed operation

Abstract The cable-in-conduit conductor (CICC) is applied for large devices, such as the fusion magnets, because it has a high mechanical and electrical performance potential. Also, CICC has advantages when applied for pulsed operation coils, such as the fusion magnets and superconducting magnetic energy storage coils, because of its thermal and hydraulic performance. Superconducting coils made from CICC have a cooling path and the coolant of the supercritical helium circulates through the inside of the CICC. When the coil has heat generation due to the AC losses, the CICC has the advantage of being able to remove heat due to the large wet perimeter. The inlet flow reduction is caused by the heat generation of the conductor. The inlet flow reduction provides a limit to the stable pulsed operation of the coil. The inlet flow reduction is measured and discussed for the CICC in this paper. The design criteria of the inlet flow reduction is introduced for the CICC. The zero flow temperature is defined to achieve this purpose. The initial flow rate can be estimated by this criteria, which is applicable for the forced flow conductor, as well as for CICC.

Development of the Current Lead Using YBCO Rods for SMES

The current lead using the High-Tc superconductor is suitable for improving the efficiency of the superconducting devices such as SMES because of a low heat load. Especially, the YBCO rod is the best material for the current lead because it has high current density and low thermal conductivity. We established the mass production technology of the rod having a good mechanical property by the MTG(Melt Textured Growth) method. Then, the application research of the current lead using YBCO rods for a lOOkWh class SMES was conducted. A 5kA-3kV superconducting current lead was fabricated and successfully tested by feeding current up to 5 kA and loading voltage up to 10kV. Moreover, it was confirmed that the current lead had the sufficient performance for the practical use through various tests.

Development of the 20kA Class HTS Current Lead for A SMES

HTS current leads using YBCO leads for a l00kWh SMES pilot plants were developed. Moreover, a HTS lead experimental device that had a rated capacity of 20kA class and 3kV was produced and current loading tests and voltage loading tests were carried out. As a result, it was confirmed that the HTS current lead using YBCO leads had sufficient performances for practical uses through the various tests.