Principal Research Results

Evaluation of Realizability of High-Tc SMES

Background
Recently, development of high-Tc superconducting wires and tapes is progressing. In particular, it is expected that YBCOcoated conductors are applied to SMES due to an advantage of wide operation temperatures. Therefore, feasibility study of High-Tc
SMES including some experiments using model coils and some numerical simulations have been carried out in a national project of“Technology Development of SMES System” from 1999 to 2003. This work is supported by METI and conducted by NEDO as a feasibility study of High-Tc SMES as a part of development of SMES system.

Objectives
Clarification of technical realization of high-Tc SMES and more cost reduction than that of low-Tc SMES

Principal Resultsa) Technical realization of high-Tc SMES
・ Investigation of high current conductors for high-Tc SMES
The world record of critical current (Ic) for the one turn model coil using the Bi2212 Rutherford conductor conductively
cooled using a cryocooler is achieved 4 kA at 26 K, which is satisfied to develop high-Tc SMES. Fig. 1 shows the equipment of critical current measurement for Bi2212 Rutherford conductor and the results of critical current measurement. It is also indicated that possibility of high-current superconducting conductors using a displacement of 6 Bi2223 superconducting tapes as a result from the examinations of trial conductors and trial model coils.
・Magnet technology
In the magnet technology, the conductive cryocooling technology and the current leads are indicated to be important issues
to realize high-Tc SMES using model coils. In the current leads, the new current leads with the pulse tube cryocooler are developed,
whose insulation characteristics are independent on vacuum pressures. Fig, 2 shows the photo of the developed current leads.
b) Cost estimation of high-Tc SMES
One of the advantages of high-Tc SMES is the wide operation temperature due to use of the cryocooling system. Initial costsof high-Tc SMES on the basis of the results from the conceptual design for the troidal coil system are estimated at each operation temperature. According to the comparison with the cases using high-Tc superconductors and low-Tc superconductors, it is found that thecost reduction using the YBCO-coated conductors at all of the temperature range is more expected than that of the low-Tc superconductors due to use at relatively high magnetic fields. Fig. 3 shows the results of the cost estimation and the coil shape of high-Tc
SMES designed at 20 K.
Main Researcher: Ataru Ichinose, Ph.D,
Research Scientist, Applied High Energy Physics Sector, Electric Power Engineering Research Laboratory
Reference
A. Ichinose, et al., “Research and Development of High-Tc SMES”, submitted to IEEE Transaction of Applied Superconductivity.

764. Power Delivery - Development of new technology of transmission facilities

Cooling HeadThe coil is con-ductively
cooled from here.

Fig.1 Critical measurement equipment of Bi2212 Rutherford conductor carried 4 kA under conductive
cooling conditions and critical current measurement results

Rotationvalve unit

Two paralleled current leads
at the backside

Fig.2 A photo of developed current leads with the GM pulse refrigerator and a construction of thehigh-Tc coil and the current leads

Fig.3 Summation of wire cost and refrigerator cost of power system stabilization of 500 kW/h (1.8GJ)
at each operation temperature and the conceptual design of high-Tc SMES using YBCO coatedconductors at 20 K.
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