Superconducting Magnetic Energy Storage (SMES)

A device for storing electromagnetic energy is an attractive potential application for high-temperature superconductors (HTS).

In 1998 we built  an HT-SMES, a superconducting magnetic energy storage (SMES) based on HTS coil made of Bi–Sr–Ca–Cu–O (Bi-2223) wires, operating at liquid nitrogen (LN2) temperatures. In order to improve the efficiency of this SMES we have introduced a ferromagnetic core and designed a special converter circuit. The core, made of laminated iron surrounding the HTS coil, contributes a gain of  x14 and x6 in the stored energy at temperatures 77 and 64K, respectively. Moreover, the core is designed to prevent the coil from being exposed to the magnetic self-fields, allowing for relatively high operation currents in the presence of high self-fields. A specially designed converter enables simultaneous charge and discharge of the HTS coil, adding another factor of 2 in the transmitted power. To reduce energy losses in the converter, most of its elements were immersed in liquid nitrogen. The resistance of the switches drops from 7 mOhm at room temperature to 2 mOhm at LN2 temperatures.

The SMES operating at nitrogen triple point 64 K was capable of storing electromagnetic energy of 131 J. The device was successfully tested by the Israel Electricity Company. For details see

Superconducting Magnetic Energy Storage device operating at liquid nitrogen temperatures
A. Friedman, N. Shaked, E. Perel, M. Sinvani, Y. Wolfus, and Y. Yeshurun
Cryogenics 39, 53 (1999).

In 2000 we built  an upgraded HT-SMES for the Israel Electricity Company. The progress in production of HTS conductors allowed us to increase the stored energy up to 1500 J. We successfully demonstrated capacity of this SMES to compensate voltage dips in 400 V electric grid with power of 20 kVA. The converter design was patented.

For details see

 HT-SMES Operating at Liquid Nitrogen Temperatures for Electric Power Quality Improvement A. Friedman, N. Shaked, E. Perel, F. Gartzman, M. Sinvani, Y. Wolfus, D. Kottick, J. Furman, and Y. Yeshurun
IEEE Trans. Appl. Supercond., 13, No. 2 (2003).

For an analitical solution of the optimization of  the ferromagnetic core see
Design of a laminated-steel magnetic core for use in a HT-SMES  
A. Friedman, M. Zarudi, N. Shaked, M. Sinvani, Y. Wolfus, Y. Yeshurun
Journal of Materials Processing Technology, 161, 28 (2005).