The Promise of High-Temperature Superconductor Technology
Superconductivity is a phenomenon observed in specific materials at very low temperatures. A primary feature of superconductivity is the complete absence of dc electrical resistance. The need for low-temperature operation has historically hampered the viability of this technology, but in 1986 a Nobel prize-winning discovery of a new class of superconductors allowed operation at much higher temperatures. These so-called high temperature superconductors (HTS) are operable at the much more manageable temperature of liquid nitrogen (~77K). This represents a 25 to 100 times lower energy requirement for material cooling when compared to the 4K temperature required by previously existing superconductors.
Superconductors have applications ranging from MRI machines to levitating trains to ultra-fast computers to ultra-sensitive detectors for heart and brain waves. Promising future applications include ultra-efficient power lines and electric motors, high-performance transformers, power storage devices, and fault current limiters. The U.S. Department of Energy (DOE) is currently focused on HTS research and development of efficient cryogenic systems, 2G HTS wire, winding techniques, and magnetic field research.
Superconductor Technologies Inc. (STI) has been developing high quality superconducting materials and systems since 1987, focused on the radio frequency (RF) wireless communications market with the thin-film microelectronics in its SuperLink® product. STI’s recent HTS work involves the utilization of its innovative, proprietary deposition capabilities in the area of 2G HTS wire. 2G HTS wire offers the potential of replacing copper power transmission lines with superconducting cables that have higher capacity while minimizing resistive cable losses. HTS power distribution systems have the potential to become a key twenty-first century technology for improving the capacity, efficiency, and reliability of the electricity distribution network.
How Does It Work?
HTS technology enables extremely efficient power transmission by replacing copper wires with a ceramic superconductor alternative that has 5x higher capacity while reducing resistive losses. 2G HTS wire is expected to lose only about one-half of a percent of the power that it transmits, compared to the five to eight percent lost by traditional power cables.
The cable requires a cooling system to refrigerate the 2G HTS wire to a temperature at which resistance is minimized, about –321°F. In the cooling system, liquid nitrogen is circulated within a thermal envelope (cryostat) to cool the superconducting wire through which electricity flows. The superconducting tapes, which are wrapped around the core of the cable, make up the phase conductor, replacing the copper or aluminum in conventional cables.
HTS Power Transmission Market
As energy demands increase and concerted efforts are made to reduce the global footprint caused by fossil fuels usage, various technologies will need to be deployed to provide clean and efficient power. The use of HTS could be one of these breakthroughs. As just one example, HTS technology could provide a more efficient and environmentally friendly pathway to deliver electric power.
The DOE expects worldwide electricity consumption to double from 2004 to 2030. The Edison Electric Institute estimates that the U.S. transmission grid requires an investment of $56 billion over 10 years to meet new demands and maintain reliability. Much of that amount will go toward expanding the efficiency of power transmission systems. A recent Navigant Consulting Inc. report states that it is likely to take 5-10 years of niche applications and experimentation in most segments before broader, mass markets develop for HTS solutions (High Temperature Superconducting Market Readiness Review – 2006). But with recent achievements in 2G HTS wire and coated conductor development resulting in improved performance and cost, 2G HTS technology is expected to hasten entry into the cable market. In spite of the performance improvements addressed by second generation 2G HTS wire, however, cost remains a challenge for broad deployment.
STI’s Role
STI has pioneered development of advanced HTS materials and manufacturing processes, cryogenics and cooling technologies, and has demonstrated the performance advantages of its HTS filter systems over conventional technologies in both government and commercial applications. Over 6,000 HTS filter systems have been deployed and are operating today in public wireless networks, thereby proving the commercial and economic viability of HTS technology.
Recognized as world class experts in cryogenics and HTS materials development, STI’s research and development team is uniquely suited to explore new application spaces for HTS technology. In a collaborative effort with Los Alamos National Laboratory, STI is currently addressing 2G HTS wire technology for power applications. STI’s proprietary deposition techniques may offer an accelerated route to cost-effective improvements in 2G HTS wire production, providing answers to both the technical challenges and reduced costs needed to advance the commercial deployment of 2G HTS wire for power applications.
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