Magnetic resonance imaging and nuclear magnetic resonance
The biggest application for superconductivity is in producing the large-volume, stable, and high-intensity magnetic fields required for magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR). This represents a multi-billion-US$ market for companies such as Oxford Instruments and Siemens. The magnets typically use low-temperature superconductors (LTS) because high-temperature superconductors are not yet cheap enough to cost-effectively deliver the high, stable, and large-volume fields required, notwithstanding the need to cool LTS instruments to liquid helium temperatures. Superconductors are also used in high field scientific magnets.
Particle accelerators and magnetic fusion devices
Particle accelerators such as the Large Hadron Collider can include many high field electromagnets requiring large quantities of LTS. To construct the LHC magnets required more than 28 percent of the world's niobium-titanium wire production for five years, with large quantities of NbTi also used in the magnets for the LHC's huge experiment detectors.[2]
Conventional fusion machines (JET, ST-40, NTSX-U and MAST) use blocks of copper. This limits their fields to 1-3 Tesla. Several superconducting fusion machines are planned for the 2024-2026 timeframe. These include ITER, ARC and the next version of ST-40. The addition of High Temperature Superconductors should yield an order of magnitude improvement in fields (10-13 tesla) for a new generation of Tokamaks.[3]
The commercial applications so far for high-temperature superconductors (HTS) have been limited by other properties of the materials discovered thus far. HTS require only liquid nitrogen, not liquid helium, to cool to superconducting temperatures. However, currently known high-temperature superconductors are brittle ceramics that are expensive to manufacture and not easily formed into wires or other useful shapes.[4] Therefore, the applications for HTS have been where it has some other intrinsic advantage, e.g. in:
low thermal loss current leads for LTS devices (low thermal conductivity),
RF and microwave filters (low resistance to RF), and
increasingly in specialist scientific magnets, particularly where size and electricity consumption are critical (while HTS wire is much more expensive than LTS in these applications, this can be offset by the relative cost and convenience of cooling); the ability to ramp field is desired (the higher and wider range of HTS's operating temperature means faster changes in field can be managed); or cryogen free operation is desired (LTS generally requires liquid helium, which is becoming more scarce and expensive).
HTS-based systems
HTS has application in scientific and industrial magnets, including use in NMR and MRI systems. Commercial systems are now available in each category.[5]
Also one intrinsic attribute of HTS is that it can withstand much higher magnetic fields than LTS, so HTS at liquid helium temperatures are being explored for very high-field inserts inside LTS magnets.
Early applications will be where the benefit of smaller size, lower weight or the ability to rapidly switch current (fault current limiters) outweighs the added cost. Longer-term as conductor price falls HTS systems should be competitive in a much wider range of applications on energy efficiency grounds alone. (For a relatively technical and US-centric view of state of play of HTS technology in power systems and the development status of Generation 2 conductor see Superconductivity for Electric Systems 2008 US DOE Annual Peer Review.)
Electric power transmission
This section needs to be updated. The reason given is: The LIPA mentioned here was only a 2 year run; Phase 2 of LIPA was delayed by weather and supposed to go into operation in 2013... Is it currently in use, or was the whole project killed?. Please help update this article to reflect recent events or newly available information.(April 2024)
The Holbrook Superconductor Project, also known as the LIPA project, was a project to design and build the world's first production superconducting transmission power cable. The cable was commissioned in late June 2008 by the Long Island Power Authority (LIPA) and was in operation for two years. The suburban Long Island electrical substation is fed by a 2,000 foot (600m) underground cable system which consists of about 99 miles (159km) of high-temperature superconductor wire manufactured by American Superconductor chilled to −371°F (−223.9°C; 49.3K) with liquid nitrogen,[dubious–discuss] greatly reducing the cost required to deliver additional power.[6] In addition, the installation of the cable bypassed strict regulations for overhead power lines, and offered a solution for the public's concerns[which?] on overhead power lines.[7][failed verification]
The Tres Amigas Project was proposed in 2009 as an electrical HVDCinterconnector between the Eastern Interconnection, the Western Interconnection and Texas Interconnection.[8] It was proposed to be a multi-mile, triangular pathway of superconducting electric cables, capable of transferring five gigawatts of power between the three U.S. power grids. The project lapsed in 2015 when the Eastern Interconnect withdrew from the project. Construction was never begun.[9]
Section of superconducting cable, as installed in Essen, Germany
Essen, Germany has the world's longest superconducting power cable in production at 1 kilometer. It is a 10 kV liquid nitrogen cooled cable. The cable is smaller than an equivalent 110 kV regular cable and the lower voltage has the additional benefit of smaller transformers.[10][11]
In 2020, an aluminium plant in Voerde, Germany, announced plans to use superconductors for cables carrying 200 kA, citing lower volume and material demand as advantages.[12][13]
Magnesium diboride
Magnesium diboride is a much cheaper superconductor than either BSCCO or YBCO in terms of cost per current-carrying capacity per length (cost/(kA*m)), in the same ballpark as LTS, and on this basis many manufactured wires are already cheaper than copper. Furthermore, MgB2 superconducts at temperatures higher than LTS (its critical temperature is 39K, compared with less than 10K for NbTi and 18.3K for Nb3Sn), introducing the possibility of using it at 10-20K in cryogen-free magnets or perhaps eventually in liquid hydrogen.[citation needed] However MgB2 is limited in the magnetic field it can tolerate at these higher temperatures, so further research is required to demonstrate its competitiveness in higher field applications.
Trapped field magnets
Exposing superconducting materials to a brief magnetic field can trap the field for use in machines such as generators. In some applications they could replace traditional permanent magnets.[14][15][16]
Notes
↑ Fischer, Martin. New Path to 10 MWRenewable Energy World, 12 October 2010. Retrieved: 14 October 2010.
In physics, cryogenics is the production and behaviour of materials at very low temperatures.
Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike an ordinary metallic conductor, whose resistance decreases gradually as its temperature is lowered, even down to near absolute zero, a superconductor has a characteristic critical temperature below which the resistance drops abruptly to zero. An electric current through a loop of superconducting wire can persist indefinitely with no power source.
Superconducting magnetic energy storage (SMES) systems store energy in the magnetic field created by the flow of direct current in a superconducting coil which has been cryogenically cooled to a temperature below its superconducting critical temperature. This use of superconducting coils to store magnetic energy was invented by M. Ferrier in 1970.
A SQUID is a very sensitive magnetometer used to measure extremely weak magnetic fields, based on superconducting loops containing Josephson junctions.
Unconventional superconductors are materials that display superconductivity which does not conform to conventional BCS theory or its extensions.
High-temperature superconductors are defined as materials with critical temperature above 77 K, the boiling point of liquid nitrogen. They are only "high-temperature" relative to previously known superconductors, which function at even colder temperatures, close to absolute zero. The "high temperatures" are still far below ambient, and therefore require cooling. The first break through of high-temperature superconductor was discovered in 1986 by IBM researchers Georg Bednorz and K. Alex Müller. Although the critical temperature is around 35.1 K, this new type of superconductor was readily modified by Ching-Wu Chu to make the first high-temperature superconductor with critical temperature 93 K. Bednorz and Müller were awarded the Nobel Prize in Physics in 1987 "for their important break-through in the discovery of superconductivity in ceramic materials". Most high-Tc materials are type-II superconductors.
Magnesium diboride is the inorganic compound with the formula MgB2. It is a dark gray, water-insoluble solid. The compound has attracted attention because it becomes superconducting at 39 K (−234 °C). In terms of its composition, MgB2 differs strikingly from most low-temperature superconductors, which feature mainly transition metals. Its superconducting mechanism is primarily described by BCS theory.
A superconducting magnet is an electromagnet made from coils of superconducting wire. They must be cooled to cryogenic temperatures during operation. In its superconducting state the wire has no electrical resistance and therefore can conduct much larger electric currents than ordinary wire, creating intense magnetic fields. Superconducting magnets can produce stronger magnetic fields than all but the strongest non-superconducting electromagnets, and large superconducting magnets can be cheaper to operate because no energy is dissipated as heat in the windings. They are used in MRI instruments in hospitals, and in scientific equipment such as NMR spectrometers, mass spectrometers, fusion reactors and particle accelerators. They are also used for levitation, guidance and propulsion in a magnetic levitation (maglev) railway system being constructed in Japan.
Yttrium barium copper oxide (YBCO) is a family of crystalline chemical compounds that display high-temperature superconductivity; it includes the first material ever discovered to become superconducting above the boiling point of liquid nitrogen [77 K ] at about 93 K.
The National High Magnetic Field Laboratory (MagLab) is a facility at Florida State University, the University of Florida, and Los Alamos National Laboratory in New Mexico, that performs magnetic field research in physics, biology, bioengineering, chemistry, geochemistry, biochemistry. It is the only such facility in the US, and is among twelve high magnetic facilities worldwide. The lab is supported by the National Science Foundation and the state of Florida, and works in collaboration with private industry.
Niobium–tin is an intermetallic compound of niobium (Nb) and tin (Sn), used industrially as a type-II superconductor. This intermetallic compound has a simple structure: A3B. It is more expensive than niobium–titanium (NbTi), but remains superconducting up to a magnetic flux density of 30 teslas [T] (300,000 G), compared to a limit of roughly 15 T for NbTi.
Niobium–titanium (Nb-Ti) is an alloy of niobium and titanium, used industrially as a type II superconductor wire for superconducting magnets, normally as Nb-Ti fibres in an aluminium or copper matrix.
In superconductivity, a type-II superconductor is a superconductor that exhibits an intermediate phase of mixed ordinary and superconducting properties at intermediate temperature and fields above the superconducting phases. It also features the formation of magnetic field vortices with an applied external magnetic field. This occurs above a certain critical field strength Hc1. The vortex density increases with increasing field strength. At a higher critical field Hc2, superconductivity is destroyed. Type-II superconductors do not exhibit a complete Meissner effect.
Flux pumping is a method for magnetising superconductors to fields in excess of 15 teslas. The method can be applied to any type II superconductor and exploits a fundamental property of superconductors, namely their ability to support and maintain currents on the length scale of the superconductor. Conventional magnetic materials are magnetised on a molecular scale which means that superconductors can maintain a flux density orders of magnitude bigger than conventional materials. Flux pumping is especially significant when one bears in mind that all other methods of magnetising superconductors require application of a magnetic flux density at least as high as the final required field. This is not true of flux pumping.
Superconducting wires are electrical wires made of superconductive material. When cooled below their transition temperatures, they have zero electrical resistance. Most commonly, conventional superconductors such as niobium–titanium are used, but high-temperature superconductors such as YBCO are entering the market.
Magnetic resonance imaging (MRI) is a medical imaging technique mostly used in radiology and nuclear medicine in order to investigate the anatomy and physiology of the body, and to detect pathologies including tumors, inflammation, neurological conditions such as stroke, disorders of muscles and joints, and abnormalities in the heart and blood vessels among others. Contrast agents may be injected intravenously or into a joint to enhance the image and facilitate diagnosis. Unlike CT and X-ray, MRI uses no ionizing radiation and is, therefore, a safe procedure suitable for diagnosis in children and repeated runs. Patients with specific non-ferromagnetic metal implants, cochlear implants, and cardiac pacemakers nowadays may also have an MRI in spite of effects of the strong magnetic fields. This does not apply on older devices, and details for medical professionals are provided by the device's manufacturer.
Superconducting electric machines are electromechanical systems that rely on the use of one or more superconducting elements. Since superconductors have no DC resistance, they typically have greater efficiency. The most important parameter that is of utmost interest in superconducting machine is the generation of a very high magnetic field that is not possible in a conventional machine. This leads to a substantial decrease in the motor volume; which means a great increase in the power density. However, since superconductors only have zero resistance under a certain superconducting transition temperature, Tc that is hundreds of degrees lower than room temperature, cryogenics are required.
The ARC fusion reactor is a design for a compact fusion reactor developed by the Massachusetts Institute of Technology (MIT) Plasma Science and Fusion Center (PSFC). ARC aims to achieve an engineering breakeven of three. The key technical innovation is to use high-temperature superconducting magnets in place of ITER's low-temperature superconducting magnets. The proposed device would be about half the diameter of the ITER reactor and cheaper to build.
Rare-earth barium copper oxide (ReBCO) is a family of chemical compounds known for exhibiting high-temperature superconductivity (HTS). ReBCO superconductors have the potential to sustain stronger magnetic fields than other superconductor materials. Due to their high critical temperature and critical magnetic field, this class of materials are proposed for use in technical applications where conventional low-temperature superconductors do not suffice. This includes magnetic confinement fusion reactors such as the ARC reactor, allowing a more compact and potentially more economical construction, and superconducting magnets to use in future particle accelerators to come after the Large Hadron Collider, which utilizes low-temperature superconductors.
Hydrogen cryomagnetics is a term used to denote the use of cryogenic liquid hydrogen to cool the windings of an electromagnet. A key benefit of hydrogen cryomagnetics is that low temperature liquid hydrogen can be deployed simultaneously both as a cryogen to cool electromagnet windings and as an energy carrier. That is, powerful synergistic benefits are likely to arise when hydrogen is used as a fuel and as a coolant. Even without the fuel/coolant synergies, hydrogen cryomagnetics is an attractive option for the cooling of superconducting electromagnets as it eliminates dependence upon increasingly scarce and expensive liquid helium. For hydrogen cryomagnetic applications specialist hydrogen-cooled electromagnets are wound using either copper or superconductors. Liquid-hydrogen-cooled copper-wound magnets work well as pulsed field magnets. Superconductors have the property that they can operate continuously and very efficiently as electrical resistive losses are almost entirely avoided. Most commonly the term "hydrogen cryomagnetics" is used to denote the use of cryogenic liquid hydrogen directly, or indirectly, to enable high temperature superconductivity in electromagnet windings.
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