Design of a 30-K/4-kJ HTS Magnet Cryocooled With Solid Nitrogen

High-performance high-temperature superconductor superconducting magnetic energy storage (HTS-SMES) is a promising technology to play an important role in stabilizing the future power system. However, due to the high prices of HTS materials, a hybrid energy storage system consisting of micro HTS-SMES and Li-ion battery is proposed as a transitional solution. In this paper, a 30-K/4-kJ HTS-SMES magnet is designed and manufactured. The solenoidal magnet spends 500-m 4.55-mm-wide rare-earth-barium-copper-oxide (REBCO) tape and its geometry is optimized to achieve a balance between energy capacity and charging/discharging rate. A flexible and extensible cryogenic system with dual Gifford-McMahon (G-M) cryocoolers is designed for maintaining the operating temperature of the magnet. Solid nitrogen is utilized to enhance the thermal stability during dynamic operation. According to our design, the magnet can deliver/absorb an instant high power with a minimum risk of thermal runaway. A preliminary test of the cryogenic system successfully demonstrated the capability of nitrogen solidification.