Abstract
Projections of electric power production suggest a
major shift to renewables, such as wind and solar, which will be
in remote locations where massive quantities of power are
available. One solution for transmitting this power over long
distances to load centers is direct current (dc), high temperature
superconducting (HTS) cables. Electric transmission via dc
cables promises to be effective because of the low-loss, highcurrent-
carrying capability of HTS wire at cryogenic
temperatures. However, the thermal management system for the
cable must be carefully designed to achieve reliable and energyefficient
operation. Here we extend the analysis of a superconducting
dc cable concept proposed by the Electric Power
Research Institute (EPRI), which has one stream of liquid
nitrogen flowing in a cryogenic enclosure that includes the power
cable, and a separate return tube for the nitrogen. Refrigeration
stations positioned every 10 to 20 km cool both nitrogen streams.
Both go and return lines are contained in a single
vacuum/cryogenic envelope. Other coolants, including gaseous
helium and gaseous hydrogen, could provide potential
advantages, though they bring some technical challenges to the
operation of long-length HTS dc cable systems. A discussion of
the heat produced in superconducting cables and a system to
remove the heat are discussed. Also, an analysis of the use of
various cryogenic fluids in long-distance HTS power cables is
presented.