Technological applications of superconductivity
Encyclopedia
Some of the technological applications of superconductivity
Superconductivity
Superconductivity is a phenomenon of exactly zero electrical resistance occurring in certain materials below a characteristic temperature. It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum...

include:
  • the production of sensitive magnetometer
    Magnetometer
    A magnetometer is a measuring instrument used to measure the strength or direction of a magnetic field either produced in the laboratory or existing in nature...

    s based on SQUID
    SQUID
    A SQUID is a very sensitive magnetometer used to measure extremely weak magnetic fields, based on superconducting loops containing Josephson junctions....

    s
  • fast digital circuit
    Digital circuit
    Digital electronics represent signals by discrete bands of analog levels, rather than by a continuous range. All levels within a band represent the same signal state...

    s (including those based on Josephson junctions and rapid single flux quantum
    Rapid single flux quantum
    In electronics, rapid single flux quantum is a digital electronics technology that relies on quantum effects in superconducting devices, namely Josephson junctions, to process digital signals. Josephson junctions are the active elements for RSFQ electronics, like transistors are the active...

     technology),
  • powerful superconducting electromagnet
    Superconducting magnet
    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 can conduct much larger electric currents than ordinary wire, creating intense magnetic fields...

    s used in maglev trains, Magnetic Resonance Imaging
    Magnetic resonance imaging
    Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...

     (MRI) and Nuclear magnetic resonance
    Nuclear magnetic resonance
    Nuclear magnetic resonance is a physical phenomenon in which magnetic nuclei in a magnetic field absorb and re-emit electromagnetic radiation...

     (NMR) machines, magnetic confinement fusion
    Nuclear fusion
    Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...

     reactors (e.g. tokamak
    Tokamak
    A tokamak is a device using a magnetic field to confine a plasma in the shape of a torus . Achieving a stable plasma equilibrium requires magnetic field lines that move around the torus in a helical shape...

    s), and the beam-steering and focusing magnets used in particle accelerators
  • low-loss power cables
  • RF and microwave filter
    RF and microwave filter
    Radio frequency and microwave filters represent a class of electronic filter, designed to operate on signals in the megahertz to gigahertz frequency ranges...

    s (e.g., for mobile phone
    Mobile phone
    A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...

     base stations, as well as military ultra-sensitive/selective receivers)
  • fast fault current limiter
    Fault current limiter
    A Fault Current Limiter is a device which limits the prospective fault current when a fault occurs . The term is generally applied to superconducting devices, whereas non-superconducting devices are typically termed Fault Current Controllers...

    s
  • high sensitivity particle detectors
    Cryogenic particle detectors
    Cryogenic particle detectors operate at very low temperature, typically only a few degrees above absolute zero. These sensors interact with an energetic elementary particle and deliver a signal which can be related to the type of particle and the nature of the interaction...

    , including the transition edge sensor
    Transition edge sensor
    A transition edge sensor or TES is a type of cryogenic particle detector that exploits the strongly temperature-dependent resistance of the superconducting phase transition.-Principle of operation:...

    , the superconducting bolometer
    Bolometer
    A bolometer is a device for measuring the power of incident electromagnetic radiation via the heating of a material with a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley...

    , the superconducting tunnel junction detector, the kinetic inductance detector
    Kinetic inductance detector
    The kinetic inductance detector — also known as a microwave kinetic inductance detector — is a type of superconducting photon detector first developed by scientists at the California Institute of Technology and the Jet Propulsion Laboratory in 2003. These devices operate at cryogenic...

    , and the superconducting nanowire single-photon detector
    Superconducting nanowire single-photon detector
    The superconducting nanowire single-photon detector is a type of near-infrared and optical single-photon detector based on a current-biased superconducting nanowire. It was first developed by scientists at Moscow State Pedagogical University in 2001....

  • railgun
    Railgun
    A railgun is an entirely electrical gun that accelerates a conductive projectile along a pair of metal rails using the same principles as the homopolar motor. Railguns use two sliding or rolling contacts that permit a large electric current to pass through the projectile. This current interacts...

     and coilgun
    Coilgun
    A coilgun is a type of projectile accelerator that consists of one or more coils used as electromagnets in the configuration of a synchronous linear motor which accelerate a magnetic projectile to high velocity...

     magnets
  • electric motor
    Electric motor
    An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...

    s and generator
    Electrical generator
    In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...

    s

Magnetic Resonance Imaging (MRI) and Nuclear Magnetic Resonance (NMR)

The biggest application for superconductivity is in producing the large volume, stable, and high magnetic fields required for MRI and NMR. This represents a multi-billion US$ market for companies such as Oxford Instruments
Oxford Instruments
Oxford Instruments plc is a United Kingdom manufacturing and research company that designs and manufactures tools and systems for industry and research. The company is headquartered in Abingdon, Oxfordshire, England, with sites in the United Kingdom, United States, Europe, and Asia...

 and Siemens
Siemens
Siemens may refer toSiemens, a German family name carried by generations of telecommunications industrialists, including:* Werner von Siemens , inventor, founder of Siemens AG...

. The magnets typically use low temperature superconductors
Conventional superconductor
Conventional superconductors are materials that display superconductivity as described by BCS theory or its extensions.Critical temperatures of some simple metals:ElementTc Al1.20Hg4.15Mo0.92Nb9.26Pb7.19...

 (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
Liquid helium
Helium exists in liquid form only at extremely low temperatures. The boiling point and critical point depend on the isotope of the helium; see the table below for values. The density of liquid helium-4 at its boiling point and 1 atmosphere is approximately 0.125 g/mL Helium-4 was first liquefied...

 temperatures. Superconductors are also used in high field scientific magnets.

High-temperature superconductivity (HTS)

The commercial applications so far for high temperature superconductors
High-temperature superconductivity
High-temperature superconductors are materials that have a superconducting transition temperature above . From 1960 to 1980, 30 K was thought to be the highest theoretically possible Tc...

 (HTS) have been limited.

HTS can superconduct at temperatures above the boiling point of liquid nitrogen
Liquid nitrogen
Liquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colourless clear liquid with density of 0.807 g/mL at its boiling point and a dielectric constant of 1.4...

, which makes them cheaper to cool than low temperature superconductors (LTS). However, the problem with HTS technology is that the currently known high temperature superconductors are brittle ceramics which are expensive to manufacture and not easily formed into wires or other useful shapes.
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
    Operating temperature
    An operating temperature is the temperature at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the...

     means faster changes in field can be managed); or cryogen free operation is desired (LTS generally requires liquid helium
    Liquid helium
    Helium exists in liquid form only at extremely low temperatures. The boiling point and critical point depend on the isotope of the helium; see the table below for values. The density of liquid helium-4 at its boiling point and 1 atmosphere is approximately 0.125 g/mL Helium-4 was first liquefied...

     that 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.

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.

Promising future industrial and commercial HTS applications include Induction heater
Induction heater
An induction heater is a key piece of equipment used in all forms of induction heating. Typically an induction heater operates at either medium frequency or radio frequency ranges. Three main components form the basis of a modern induction heater including the power unit , the work head and the...

s, transformer
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...

s, fault current limiter
Fault current limiter
A Fault Current Limiter is a device which limits the prospective fault current when a fault occurs . The term is generally applied to superconducting devices, whereas non-superconducting devices are typically termed Fault Current Controllers...

s, power storage, motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...

s and generators, fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...

 reactors (see ITER
ITER
ITER is an international nuclear fusion research and engineering project, which is currently building the world's largest and most advanced experimental tokamak nuclear fusion reactor at Cadarache in the south of France...

) and magnetic levitation
Magnetic levitation
Magnetic levitation, maglev, or magnetic suspension is a method by which an object is suspended with no support other than magnetic fields...

 devices.

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.)

Holbrook Superconductor Project

The Holbrook Superconductor Project
Holbrook Superconductor Project
The Holbrook Superconductor Project is the world's first production superconducting transmission power cable. The lines were commissioned in 2008...

 is a project to design and build the world's first production superconducting transmission
Electric power transmission
Electric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...

 power cable. The cable was commissioned in late June 2008. The suburban Long Island
Long Island
Long Island is an island located in the southeast part of the U.S. state of New York, just east of Manhattan. Stretching northeast into the Atlantic Ocean, Long Island contains four counties, two of which are boroughs of New York City , and two of which are mainly suburban...

 electrical substation is fed by about 600-meter-long underground cable system consists of about 99 miles of high-temperature superconductor wire manufactured by American Superconductor
American Superconductor
American Superconductor is an American energy technologies company based in Devens, Massachusetts specializing in the design and manufacture of power systems and superconducting wire...

, installed underground and chilled with liquid nitrogen
Liquid nitrogen
Liquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colourless clear liquid with density of 0.807 g/mL at its boiling point and a dielectric constant of 1.4...

 greatly reducing the costly right-of-way required to deliver additional power.

Tres Amigas Project

American Superconductor
American Superconductor
American Superconductor is an American energy technologies company based in Devens, Massachusetts specializing in the design and manufacture of power systems and superconducting wire...

 was chosen for The Tres Amigas Project
Tres Amigas Project
The Tres Amigas SuperStation focuses on uniting North America’s two major power grids and one minor grid to enable faster adoption of renewable energy and increase the reliability of the U.S...

, the United States’ first renewable energy market hub. The Tres Amigas renewable energy market hub will be a multi-mile, triangular electricity pathway of superconductor electricity pipelines capable of transferring and balancing many gigawatts of power between three U.S. power grids (the Eastern Interconnection, the Western Interconnection and the Texas Interconnection). Unlike traditional powerlines, it will transfer power as DC instead of AC current. It will be located in Clovis, New Mexico.

Magnesium diboride

Magnesium diboride
Magnesium diboride
Magnesium diboride is a simple ionic binary compound that has proven to be an inexpensive and useful superconducting material.Its superconductivity was announced in the journal Nature in March 2001. Its critical temperature of is the highest amongst conventional superconductors...

 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 39 K, compared with less than 10 K for NbTi and 18.3 K for Nb3Sn), introducing the possibility of using it at 10-20 K in cryogen-free magnets or perhaps eventually in liquid hydrogen. 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.
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