Superconducting direct current (DC) cables, capable of moving thousands of megawatts of electricity between regions, are ready for commercial development using today’s technology, according to a new report by the Electric Power Research Institute (EPRI).
The EPRI analysis points to significant efficiency gains using superconducting DC transmission lines, with the capability to reduce transmission losses at full load by more that 150% compared to alternating current (AC) or high-voltage DC systems. Assuming the trend continues for cost-performance improvements in superconducting wire, such a line could become an option within a decade along with Extra High Voltage (EHV) AC lines that are currently used to move large amounts of power over long distances.
The EPRI report indicates that the builders of superconducting DC transmission lines could rely on commercially available technology and construction methods similar to those used in natural gas pipeline construction. These include factory manufactured, transportable sections of an outer carbon steel pipe containing inner stainless steel piping for the flowing coolant and superconducting cable, and trucking to the site for assembly, welding and burial.
The lighter, thinner, higher-capacity superconducting cable might be fabricated, shipped and installed with methods and equipment now used for conventional underground transmission cable. Production capacity of superconducting wire today is limited but given substantial demand capacity could possibly be expanded sufficiently for longer lines. Refrigeration and vacuum requirements of the line might be met by equipment and methods utilized in the industrial gas industry.
“In the future we may see the development of generation facilities, such as large wind farms or nuclear “farms” capable of producing five to 10 gigawatts (GW), but located far from urban centers of demand. It will then be necessary to move large amounts of power over long distances,” said Arshad Mansoor, vice president of Power Delivery and Utilization for EPRI.
As designed, the superconducting cable system outlined in the report would provide 10 GW power capacity with a nominal current and voltage of 100 kiloamps and 100 kilovolts. The report also points to the cable system’s potential to enhance the safety, reliability and efficiency of the existing AC power grid.
EPRI also has published two companion superconducting reports. These highlight the practical issues of integrating a long-distance, high-power superconducting DC link into the existing, lower-power AC transmission and distribution systems, and states that the operation and control of this link will be a key to the viability and acceptance of the concept.
The reports can be downloaded at the link below.
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