DC superconducting power cables are typically used and temperatures lower than the freezing point of liquid nitrogen. Hence these cables are cooled using a flow of cooled helium gas in the range of 20 to 50K.
Stirling Cryogenics can provide such cooling power with the two-stage Stirling Cryogenerators which can provide a cold helium gas flow down to 20K.
For this the Cryogenerator has an integrated heat-exchanger being a coil around the cold head, combined with a CryoFan to pump the helium gas around.
The helium gas is cooled in the heat-exchanger and fed to the cable conduit surrounding the superconductive tape. Over the length of the cable the helium flow is warmed up, removing some heat from the tape but mainly removing heat flowing in through the cable insulation.
This heat inleak will be the main source of heat, which is why often the return flow of He is in a circular conduit around the centre one to intercept heat before it gets to the superconductive tape.
The return conduit is connected to the Cryogenerators inlet in which the heat will be removed and the He gas cooled to the required inlet temperature to the cable.
Set up of DC cable cooled by an SPC-1T, courtesy of Advanced Conductor, Boulder, Colorado, USA
Stirling can design and offer a customized system for your specific project, please contact us to discuss your requirements
HTS leaflet Stirling Cryogenics