The advantages of using high-temperature superconductors in high-duty-cycle applications of SMES

Superconducting magnetic energy storage (SMES) has been proposed for use in applications with high-duty-cycle or discharge/charge cycling rate. Such applications include transit system electric support and frequency stabilization of transmission lines. When cycled frequently, the thermal load to the cooling system is dominated by eddy current or ac losses. In systems with small energy storage capacity, the refrigeration system cost associated with ac losses can dominate the total system cost if the coil uses conventional superconductor and liquid helium cooling. If high temperature superconductors operating at liquid nitrogen temperature could be used then significant savings in refrigeration cost and hence, system cost, are possible. The HTS conductor does require a twisted configuration to realize these savings. Analysis and results for SMES systems ranging in size from 1 MJ/1 MW to 10 MJ/10 MW and operating at up to 1 Hz are presented.<>