October 2010
Table of Contents
Status of the DOE Program on Advanced Conductors
Brookhaven National Laboratory
Los Alamos National Laboratory
National Institute of Standards and Technology
STATUS OF THE DOE PROGRAM ON ADVANCED CONDUCTORS
The American Recovery and Reinvestment Act is making long-term impacts on American families and communities by reducing energy costs, creating green jobs and improving the quality of life for people across the country. A key component of the effort is the improvement of the antiquated United States transmission system. One of President Obama’s priorities is the Smart Grid for which funding through the stimulus package provides a tremendous opportunity to “jump start” implementation of the initiatives. Also, on December 18, 2009, Energy Secretary Steven Chu announced award selections for $60 million in ARRA funding to support transmission planning for the country’s three interconnection transmission networks. The six awards will promote collaborative long-term analysis and planning for the Eastern, Western and Texas electricity interconnections, which will help states, utilities, grid operators, and others prepare for future growth in energy demand, renewable energy sources, and Smart Grid technologies.
High-Temperature Superconductivity (HTS) will enhance the United States Electrical Power Grid by increasing grid reliability, security, and efficient power interconnections with high capacity, such as, Superconducting fault current limiters (FCL) that create a more stable electrical grid because they do not add impedance to the circuit during normal operations. HTS also reduces right-of-way requirements while minimizing environmental impacts.
The DOE Office of Electricity Delivery and Energy Reliability’s (OE) Applied Superconductivity Program and the National Labs work in partnership with industry to develop HTS wire and applications. Their collaborations in research and development are leading efforts to commercialize HTS electric power applications in the United States.
Applied Superconductivity relates to superconducting power technologies, high field magnet technology, and related applications such as medical sciences. The National Labs focus on research and development characteristics of high critical temperature (Tc) superconductors, large-scale applications of superconductors, such as HTS cables; transformers, fault current limiters, motors and generators, coated conductors, and understanding AC losses. Through research and development, the National Labs, in collaboration with universities and industry, work toward continually developing new materials and advancing the development of materials targeted for specific applications. They also work to reduce losses in superconductivity applications and increase and enhance manufacturing production, thereby enabling superconductivity applications to be developed at a lower cost and accepted commercially.
This newsletter highlights selected efforts of DOE’s National Labs and industry that support applied superconductivity.
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ARGONNE NATIONAL LABORATORY (ANL)
Argonne National Laboratory and American Superconductor (AMSC) are working together to optimize the performance of their long-length, 2G REBCO wire by elucidating the effects of processing parameters and fabrication procedures on microstructure and properties. Specifically, ANL provides materials science insight through comprehensive characterization of key samples provided by AMSC. The particular strength of this project is the use of coupled capabilities that are unique to the ANL program, including optical imaging, electron- and ion-beam microscopy, and Raman spectroscopy. The coordinated application of these approaches provides insight into the underlying materials processes relevant to the production of long-length metal-organic deposited conductors. This project is carried out as part of the AMSC-led Wire Development Group (WDG). Through discussions with AMSC and within WDG, key issues for the scale-up of AMSC’s MOD process are identified, research strategies are developed, and those strategies are implemented, often through collaborations involving two or more of the research partners in WDG.
The ANL/AMSC CRADA research is carried out largely under the sponsorship of WDG, ensuring that research topics address AMSC’s highest priority concerns. Active collaborations with WDG partners provide critical interactions, enhancing the value of new discoveries that can impact other areas of research.
Argonne National Laboratory and Superpower, Inc. (SP) are also working together to improve the performance of their long-length 2G HTS wire through detailed characterizations and analyses that identify key factors influencing wire performance. |
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The focal points for the studies are understanding the factors that lead to critical current (Ic) dropouts in SP’s long-length production wire, identifying pathways for increasing the overall critical current performance of the MOCVD coated conductor, and elucidating the microstructural and chemical characteristics that contribute to enhanced flux-pinning in MOCVD-type REBCO films. Based on the insights gained from these studies, ANL recommends process modifications to improve properties and provide additional guidance through follow-up characterization. |
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BROOKHAVEN NATIONAL LABORATORY (BNL)
Brookhaven National Laboratory’s (BNL) applied superconductivity group is funded by DOE’s Office of Electricity Delivery and Energy Reliability (OE). OE’s mission is the modernization of the U.S. power grid. One direction of the modernization is replacement of normal metal (copper, aluminum) transmission lines with High Temperature Superconductivity (HTS) cables. |
A group inspects pipes containing the HTS cables, |
The applied Superconductivity Group focuses on these projects: Isotropic HTS materials, Nucleation efficiency of Industrial oxide buffers, and Third generation (3G) wire development. The isotropic HTS materials project focuses on the exact nature of the isotropic behavior of HTS materials. HTS materials are intrinsically isotropic. Unlike traditional YBCO material, isotropic YBCO has virtually flat angular dependence of the critical current in magnetic fields up to 4 Tesla, which is reflected by a low anisotropy factor of gamma = 1.5, as compared to gamma = 7 for standard YBCO. (See figure below.) Having low anisotropy is very desirable for the design of high-field devices.
Industrial oxide buffers used as the template for 2G wires tend to have low nucleation efficiency. This results in granularity of the YBCO layer and low performance. The goal of this project is to understand mechanisms of the nucleation and find ways to improve the nucleation efficiency.
Third generation wire development is working toward new concepts for the design and fabrication of third generation, 3G, coated superconductors. The design is based on 3D epitaxy of thick, strained, YBCO layers. The design retains the positive features of 2G tapes, such as use of inexpensive, non-toxic elements and operation at liquid nitrogen temperatures, but offers potentially greater superconducting critical current and improved conductor aspect ratio. The design also promises much lower fabrication costs due to elimination of the need for heteroepitaxial oxide buffers and a biaxially textured substrate
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LOS ALAMOS NATIONAL LABORATORY
The production of reproducible, engineered, pinning microstructures in YBCO films is critical to coated conductor wire manufacturers who need to be able to control the critical current, Ic, of long wires to close tolerances. A modular approach to system development using commercially available components has allowed Los Alamos National Laboratory (LANL) to adjust to the continually evolving understanding of superconductivity in HTS conductors. LANL modified an existing IC (75K, H, angle) system and developed software which uses the Jc model to quantify pinning. This new measurement is referenced as the Full Angle Ic because the field dependence is measured at all angles relevant to the microscopic properties of the tape. Using the Full Angle Ic LANL investigated the range of field dependent behavior exhibited by a wire supplied by American Superconductor. The results assist AMSC in identifying process variations, which is a CRADA goal.
The program also focuses on AC losses. LANL developed and employed advanced measurements and numerical simulations for predicting and minimizing the AC losses in conductors and superconducting power devices. The core AC loss research program at LANL was extended by developing experimental techniques and numerical models applicable to the increasingly complex “real” world geometries and designs being utilized by our partners. These tools are then used to generate confidential AC loss results for CRADA or other projects.
Tri-axial Cable (Southwire, Inc.) |
Perhaps the most complex HTS device from an electromagnetic viewpoint is the three phase tri-axial cable utilizing 2G RABiTS conductor. This design has been used by Southwire in the Bixby installation using simpler 1G material, and is planned to be used in the Department of Homeland Security (DHS) “Hydra” cable. In three-phase tri-axial cables, the sensitivity of electrical measurements is necessary to understand the loss mechanisms. |
This is very challenging because of the strong magnetic interaction between the phases. LANL developed the theoretical background showing that three-phase AC loss measurements by the electromagnetic method are, in principle, possible. This theory was then implemented in practical measurements using cable samples from, and in support of, the DHS “Hydra” project. The data represent the first electromagnetic multiphase AC loss measurements. Therefore, the technique is applicable to HTS devices in general, not just cables, with arbitrary phase differences between currents and/or magnetic fields, not just balanced three phase systems.
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NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY (NIST)
The National Institute of Standards and Technology (NIST) focuses on the electromechanical research needed to develop YBCO coated conductors for electric power grid applications. The project performs the measurements needed to ensure that the conductor can withstand the stresses and strains that develop during operation. The project also uses its expertise in electromechanical research to help industry, universities and National Laboratories to enhance the performance of YBCO coated conductors and to help resolve key issues related to their application. |
Preparing to measure electromechanical properties of superconductor tape. (NIST) |
NIST also performed stress-strain measurements at room temperature and at 76 K on fibers that were prepared at Oak Ridge National Laboratory (ORNL). Electromechanical tests of YBCO coated conductor splices to determine their mechanical integrity have been performed on lap joints in conjunction with ORNL. The YBCO coated conductor cabling concept for low AC-loss and high-field magnet applications is an on-going program. The strain dependence of the critical current of a number of YBCO coated conductors made by SuperPower, American Superconductor and Bruker has been measured as a function of magnetic field and field angle at 65 K and 76 K. Understanding the fundamental origin of the reversible strain effect in YBCO will help improve the performance of coated conductors and may lead to more effective pinning defects.
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OAK RIDGE NATIONAL LABORATORY
Oak Ridge National Laboratory is the leading DOE national laboratory in High Temperature Superconducting (HTS) applications including Superconductivity Partnership with Industry (SPI) projects in the areas of HTS cables, transformers, fault current limiters, motors and generators. As a partner of these CRADA projects, ORNL provides technical expertise in the applied superconductivity (performance of 1st generation and 2nd generation HTS conductors and coils), cryogenics and high voltage dielectrics. The Applied Superconductivity Group also conducts strategic research in the areas of performance optimization of HTS conductors (higher current densities, lower AC losses, stability, quench detection and protection,) cryogenic cooling interfaces with HTS application cryogenic dielectrics (innovative materials, and effective high voltage insulation systems).
Transmission lines and Tower. (ORNL) |
In addition to Superconducting applications, ORNL continues to do pioneering work on advanced, ambient and high temperature conductors for transmission line upgrades. First products of this genre, called ACCR, are now operating effectively in many locations around the world. |
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SANDIA NATIONAL LABORATORY (SNL)
Sandia National Laboratory’s (SNL) superconductivity program aims to commercialize and technology-transfer manufacturable, high-speed methods of coated conductor fabrication based on solution deposition technologies. In 2002, Sandia demonstrated the first all-solution route to a 1 MA/cm2 coated conductor, using a single composition solution-deposited buffer layer (SrTiO3 on NiW). Since then, Sandia has worked to increase the manufacturability of both the YBCO and buffer layer processes, and collaborated with industrial and national laboratory partners to enhance the research program. Currently, the process is being scaled up to produce 10m-1km lengths of YBCO-based superconducting wire for use in Zenergy Power Systems Inc.-designed utility fault current controllers, energy-efficient induction heaters, and compact green power (wind power, hydroelectric) applications. In addition, solution deposition planarization has been developed jointly between SNL and LANL, and the prototype systems exist both at LANL and Superpower.
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FLORIDA STATE UNIVERSITY (FSU)
Florida State University’s (FSU) program goal is to understand and ameliorate the current-limiting mechanisms (CLM) of coated conductors (CC), recognizing that the drive for CC performance improvement in cost and Ic always drives conductors into territory where enhanced vortex pinning and YBCO thickness is compromised by degraded connectivity.
As a partner of the Wire Development Group, FSU has made detailed studies of the temperature dependent pinning and of the operative CLMs in the latest generation of MOD-RABiTS. They have been able to distinguish domains of T, H and Ѳ in which correlated pins such as stacking faults and intrinsic, CuO ab-planes control the vortex pinning. At 77K, ab-plane stacking faults and randomly distributed RE2O3 pins control Jc, while at 30 K intrinsic pinning and SFs are important. FSU is also working on the fabrication of a 32 T, 40 mm bore, all superconducting user magnet. This magnet will provide a field more than one third higher than any previous all-superconducting magnets and enable experiments that presently require use of 20 MW resistive magnets costing about $125,000 in power per week.
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CONCLUSION
The efforts of DOE’s National Labs in the field of Applied Superconductivity have enabled the advancements of various HTS Applications. The Labs, in collaboration with universities and industry, have worked to continually develop new materials, reduce energy losses, and advance HTS Applications. Their goal is to ultimately have the HTS Application accepted commercially. In moving toward this goal, they work with industry to increase and enhance manufacturing production which lowers costs, thereby increasing its acceptance in the marketplace.
ABOUT THIS UPDATE
The High-Temperature "Superconductivity News Update" is compiled by Bob Lawrence & Associates, Inc. on behalf of the U.S. Department of Energy's superconductivity program and is issued periodically as events warrant.
Please let me know if you would like more information or have story ideas on any of these news items involving high-temperature superconductivity---a clean and capable new electricity technology for the 21st century.
If you have any other comments or questions, please let me know.
Thank you very much.
Ashley Thompson
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