(71f) Conduction-Cooling of a High-Temperature Superconducting Cable

Several materials conduct electricity with zero resistance below a certain temperature, called critical temperature (Tc). Some examples of such superconducting materials are: (Bi,Pb)2Sr2Ca2Cu3O10, also called BSCCO-2223 (Tc = 110 K), YBa2Cu3O7 (Tc = 90 K) and MgB2 (Tc = 39 K). Power transmission lines using high-temperature superconducting cables are among the most promising applications of high-Tc superconductors. Low cost cooling of superconducting cables below the transition temperature is an important goal for researchers who work in the field of energy applications in cryogenics.

Current generation high-temperature-superconducting (HTS) power transmission cables use liquid nitrogen as a coolant that circulates along the cable in order to attain temperatures that are below the superconductor's critical temperature. In this work, the use of axial conduction-cooling in attaining HTS temperatures in transmission lines is proposed and modeled. The use of liquid coolant is envisioned only at periodic length intervals along the transmission lines, in combination with insulation and copper, but no axial flow of liquid helium or nitrogen as coolant. The proposed concept is feasible due to the high thermal conductivity of pure copper at cryogenic temperatures. A basic design for the insulated cable is proposed and a detailed numerical simulation of two-dimensional heat transfer in such a cable is carried out for various studies case considering MgB2 and BSCCO-2223 as superconducting materials. Steady state simulations of heat transfer in such cables are used to demonstrate the feasibility of the proposed concept, and also the cable's initial cool down from ambient temperature is calculated through simulation of heat transfer in the cable under transient conditions.