A laboratory-scale superconducting energy storage (SMES) device based on a high-temperature superconducting coil was developed. This SMES has three major distinctive features: (a) it operates between 64 and 77K, using liquid nitrogen (LN2) for cooling; (b) it uses a ferromagnetic core with a variable gap to increase the stored energy while retaining the critical current value; (c) it has the option for simultaneous energy charge and discharge which increases the power available at the SMES output by a factor of ≤ 2 when operating as a converter. The present prototype of liquid nitrogen operating SMES stores 130 J at 64K and 60 J at 77K.
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We thank Gadi Pinkovich for help in the converter construction. We also thank J. Kellers and A.P. Malozemoff of ASC Inc. for useful discussions and for sharing with us available information. The Ministry of Energy and Infrastructure supported this work under contract no. 93-11-039. A.F. acknowledges a support from the Ministry of Sciences and Humanities under contract no. 6781-1-95.