Cooling of HTS applications in the temperature range of 66 K to 80 K

High temperature superconducting power cables require forced flow cooling. Today subcooled liquid nitrogen is circulated by a pump and cooled back by either an open or closed cycle refrigeration system. The temperature range of the nitrogen loop preferably is in the level of 80 K and below. The paper describes and compares refrigeration cycles for cooling of power cables. Possibilities of different coolants for the cable are also discussed. Efficiency calculations have shown that a helium Brayton cycle is the best choice in the investigated temperature range. However, cold compressors are also a good alternative.