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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.

A typical SMES system includes three parts: superconducting coil, power conditioning system and cryogenically cooled refrigerator. Once the superconducting coil is charged, the current will not decay and the magnetic energy can be stored indefinitely.

The stored energy can be released back to the network by discharging the coil. The power conditioning system uses an inverter/rectifier to transform alternating current (AC) power to direct current or convert DC back to AC power. The inverter/rectifier accounts for about 2–3% energy loss in each direction. SMES loses the least amount of electricity in the energy storage process compared to other methods of storing energy. SMES systems are highly efficient; the round-trip efficiency is greater than 95%.^[2]

Due to the energy requirements of refrigeration and the high cost of superconducting wire, SMES is currently used for short duration energy storage. Therefore, SMES is most commonly devoted to improving power quality.

Advantages over other energy storage methods[edit]

There are several reasons for using superconducting magnetic energy storage instead of other energy storage methods. The most important advantage of SMES is that the time delay during charge and discharge is quite short. Power is available almost instantaneously and very high power output can be provided for a brief period of time. Other energy storage methods, such as pumped hydro or compressed air, have a substantial time delay associated with the energy conversion of stored mechanical energy back into electricity. Thus if demand is immediate, SMES is a viable option. Another advantage is that the loss of power is less than other storage methods because electric currents encounter almost no resistance. Additionally the main parts in a SMES are motionless, which results in high reliability.

Current use[edit]

There are several small SMES units available for commercial use and several larger test bed projects. Several 1 MW·h units are used for power quality control in installations around the world, especially to provide power quality at manufacturing plants requiring ultra-clean power, such as microchip fabrication facilities.^{[citation needed]}

These facilities have also been used to provide grid stability in distribution systems.^{[citation needed]} SMES is also used in utility applications. In northern Wisconsin, a string of distributed SMES units were deployed to enhance stability of a transmission loop.^{[citation needed]} The transmission line is subject to large, sudden load changes due to the operation of a paper mill, with the potential for uncontrolled fluctuations and voltage collapse.

The Engineering Test Model is a large SMES with a capacity of approximately 20 MW·h, capable of providing 40 MW of power for 30 minutes or 10 MW of power for 2 hours.^{[citation needed]}

Calculation of stored energy[edit]

The magnetic energy stored by a coil carrying a current is given by one half of the inductance of the coil times the square of the current.

{\displaystyle E={\frac {1}{2}}LI^{2}}

Where

E = energy measured in joules

L = inductance measured in henries

I = current measured in amperes

Now let’s consider a cylindrical coil with conductors of a rectangular cross section. The mean radius of coil is R. a and b are width and depth of the conductor. f is called form function which is different for different shapes of coil. ξ (xi) and δ (delta) are two parameters to characterize the dimensions of the coil. We can therefore write the magnetic energy stored in such a cylindrical coil as shown below. This energy is a function of coil dimensions, number of turns and carrying current.

{\displaystyle E={\frac {1}{2}}RN^{2}I^{2}f\left(\xi ,\delta \right)}

Where

E = energy measured in joules

I = current measured in amperes

f(ξ,δ) = form function, joules per ampere-meter

N = number of turns of coil

Solenoid versus toroid[edit]

Besides the properties of the wire, the configuration of the coil itself is an important issue from a mechanical engineering aspect. There are three factors which affect the design and the shape of the coil – they are: Inferior strain tolerance, thermal contraction upon cooling and Lorentz forces in a charged coil. Among them, the strain tolerance is crucial not because of any electrical effect, but because it determines how much structural material is needed to keep the SMES from breaking. For small SMES systems, the optimistic value of 0.3% strain tolerance is selected. Toroidal geometry can help to lessen the external magnetic forces and therefore reduces the size of mechanical support needed. Also, due to the low external magnetic field, toroidal SMES can be located near a utility or customer load.

For small SMES, solenoids are usually used because they are easy to coil and no pre-compression is needed. In toroidal SMES, the coil is always under compression by the outer hoops and two disks, one of which is on the top and the other is on the bottom to avoid breakage. Currently, there is little need for toroidal geometry for small SMES, but as the size increases, mechanical forces become more important and the toroidal coil is needed.

The older large SMES concepts usually featured a low aspect ratio solenoid approximately 100 m in diameter buried in earth. At the low extreme of size is the concept of micro-SMES solenoids, for energy storage range near 1 MJ.

Low-temperature versus high-temperature superconductors[edit]

Under steady state conditions and in the superconducting state, the coil resistance is negligible. However, the refrigerator necessary to keep the superconductor cool requires electric power and this refrigeration energy must be considered when evaluating the efficiency of SMES as an energy storage device.

Although the high-temperature superconductor (HTSC) has higher critical temperature, flux lattice melting takes place in moderate magnetic fields around a temperature lower than this critical temperature. The heat loads that must be removed by the cooling system include conduction through the support system, radiation from warmer to colder surfaces, AC losses in the conductor (during charge and discharge), and losses from the cold–to-warm power leads that connect the cold coil to the power conditioning system. Conduction and radiation losses are minimized by proper design of thermal surfaces. Lead losses can be minimized by good design of the leads. AC losses depend on the design of the conductor, the duty cycle of the device and the power rating.

The refrigeration requirements for HTSC and low-temperature superconductor (LTSC) toroidal coils for the baseline temperatures of 77 K, 20 K, and 4.2 K, increases in that order. The refrigeration requirements here is defined as electrical power to operate the refrigeration system. As the stored energy increases by a factor of 100, refrigeration cost only goes up by a factor of 20. Also, the savings in refrigeration for an HTSC system is larger (by 60% to 70%) than for an LTSC systems.

Cost[edit]

Whether HTSC or LTSC systems are more economical depends because there are other major components determining the cost of SMES: Conductor consisting of superconductor and copper stabilizer and cold support are major costs in themselves. They must be judged with the overall efficiency and cost of the device. Other components, such as vacuum vessel insulation, has been shown to be a small part compared to the large coil cost. The combined costs of conductors, structure and refrigerator for toroidal coils are dominated by the cost of the superconductor. The same trend is true for solenoid coils. HTSC coils cost more than LTSC coils by a factor of 2 to 4. We expect to see a cheaper cost for HTSC due to lower refrigeration requirements but this is not the case. So, why is the HTSC system more expensive?

To gain some insight consider a breakdown by major components of both HTSC and LTSC coils corresponding to three typical stored energy levels, 2, 20 and 200 MW·h. The conductor cost dominates the three costs for all HTSC cases and is particularly important at small sizes. The principal reason lies in the comparative current density of LTSC and HTSC materials. The critical current of HTSC wire is lower than LTSC wire generally in the operating magnetic field, about 5 to 10 teslas (T). Assume the wire costs are the same by weight. Because HTSC wire has lower (J_c) value than LTSC wire, it will take much more wire to create the same inductance. Therefore, the cost of wire is much higher than LTSC wire. Also, as the SMES size goes up from 2 to 20 to 200 MW·h, the LTSC conductor cost also goes up about a factor of 10 at each step. The HTSC conductor cost rises a little slower but is still by far the costliest item.

The structure costs of either HTSC or LTSC go up uniformly (a factor of 10) with each step from 2 to 20 to 200 MW·h. But HTSC structure cost is higher because the strain tolerance of the HTSC (ceramics cannot carry much tensile load) is less than LTSC, such as Nb₃Tior Nb₃Sn, which demands more structure materials. Thus, in the very large cases, the HTSC cost can not be offset by simply reducing the coil size at a higher magnetic field.

It is worth noting here that the refrigerator cost in all cases is so small that there is very little percentage savings associated with reduced refrigeration demands at high temperature. This means that if a HTSC, BSCCO for instance, works better at a low temperature, say 20K, it will certainly be operated there. For very small SMES, the reduced refrigerator cost will have a more significant positive impact.

Clearly, the volume of superconducting coils increases with the stored energy. Also, we can see that the LTSC torus maximum diameter is always smaller for a HTSC magnet than LTSC due to higher magnetic field operation. In the case of solenoid coils, the height or length is also smaller for HTSC coils, but still much higher than in a toroidal geometry (due to low external magnetic field).

An increase in peak magnetic field yields a reduction in both volume (higher energy density) and cost (reduced conductor length). Smaller volume means higher energy density and cost is reduced due to the decrease of the conductor length. There is an optimum value of the peak magnetic field, about 7 T in this case. If the field is increased past the optimum, further volume reductions are possible with minimal increase in cost. The limit to which the field can be increased is usually not economic but physical and it relates to the impossibility of bringing the inner legs of the toroid any closer together and still leave room for the bucking cylinder.

The superconductor material is a key issue for SMES. Superconductor development efforts focus on increasing Jc and strain range and on reducing the wire manufacturing cost.

Technical challenges[edit]

The energy content of current SMES systems is usually quite small. Methods to increase the energy stored in SMES often resort to large-scale storage units. As with other superconducting applications, cryogenics are a necessity. A robust mechanical structure is usually required to contain the very large Lorentz forces generated by and on the magnet coils. The dominant cost for SMES is the superconductor, followed by the cooling system and the rest of the mechanical structure.

Mechanical support

Needed because of Lorentz forces.

Size

To achieve commercially useful levels of storage, around 1 GW·h (3.6 TJ), a SMES installation would need a loop of around 100 miles (160 km). This is traditionally pictured as a circle, though in practice it could be more like a rounded rectangle. In either case it would require access to a significant amount of land to house the installation.

Manufacturing

There are two manufacturing issues around SMES. The first is the fabrication of bulk cable suitable to carry the current. The HTSC superconducting materials found to date are relatively delicate ceramics, making it difficult to use established techniques to draw extended lengths of superconducting wire. Much research has focussed on layer deposit techniques, applying a thin film of material onto a stable substrate, but this is currently only suitable for small-scale electrical circuits.

Infrastructure

The second problem is the infrastructure required for an installation. Until room-temperature superconductors are found, the 100 mile (160 km) loop of wire would have to be contained within a vacuum flask of liquid nitrogen. This in turn would require stable support, most commonly envisioned by burying the installation.

Critical magnetic field

Above a certain field strength, known as the critical field, the superconducting state is destroyed.

Critical current

In general power systems look to maximize the current they are able to handle. This makes any losses due to inefficiencies in the system relatively insignificant. Unfortunately, large currents may generate magnetic fields greater than the critical field due to Ampere’s Law. Current materials struggle, therefore, to carry sufficient current to make a commercial storage facility economically viable.

Several issues at the onset of the technology have hindered its proliferation:

1. Expensive refrigeration units and high power cost to maintain operating temperatures
2. Existence and continued development of adequate technologies using normal conductors

These still pose problems for superconducting applications but are improving over time. Advances have been made in the performance of superconducting materials. Furthermore, the reliability and efficiency of refrigeration systems has improved significantly.

See also[edit]

• Grid energy storage
• United States Department of Energy International Energy Storage Database

References[edit]

Bibliography[edit]

• Sheahen, T., P. (1994). Introduction to High-Temperature Superconductivity. Plenum Press, New York. pp. 66, 76–78, 425–430, 433–446.
• El-Wakil, M., M. (1984). Powerplant Technology. McGraw-Hill, pp. 685–689, 691–695.
• Wolsky, A., M. (2002). The status and prospects for flywheels and SMES that incorporate HTS. Physica C 372–376, pp. 1,495–1,499.
• Hassenzahl, W.V.,”Applied Superconductivity,Superconductivity, an enabling technology for 21st century power systems?”, IEEE Transactions on Magnetics, pp. 1447-1453, Volume: 11, Issue: 1, Mar 2001

Further reading[edit]

• Browne, Malcome W. New Hunt for Ideal Energy Storage System

  , The New York Times, January 6, 1988.

External links[edit]

• Cost Analysis of Energy Storage Systems for Electric Utility Applications
• Loyola SMES summary

Superconducting Magnetic Energy Storage

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El almacenamiento de energía magnética por superconducción (en inglés Superconducting Magnetic Energy Storage o SMES) designa un sistema de almacenamiento de energía que permite almacenar ésta bajo la forma de un campo magnético creado por la circulación de una corriente continua en un anillo superconductor que está refrigerado a una temperatura por debajo de la temperatura crítica de superconductividad.

Estructura y funcionamiento[editar]

Un sistema SMES típico tiene tres componentes:

• Una bobina superconductora.
• Un sistema de electrónica de potencia.
• Un sistema de refrigeración criogénico.

Una vez que la bobina superconductora se carga, la corriente ya no disminuye y la energía magnética puede almacenarse indefinidamente. La energía almacenada puede ser entregada a la red descargando al anillo. Para extraer la energía se interrumpe la corriente que circula por la bobina abriendo y cerrando repetidamente un conmutador de estado sólido del sistema de electrónica de potencia. Debido a su alta inductancia, la bobina se comporta como una fuente de corriente que puede utilizarse para cargar un condensador que proporciona una entrada de tensión continua a un inversor que produce la tensión alterna requerida. El sistema de potencia origina del 2% al 3% de pérdidas de energía. Sin embargo los SMES son muy eficientes, pues sus pérdidas son muy bajas comparadas con las de otros sistemas de almacenamiento de energía.

Aplicaciones[editar]

Debido a la energía absorbida por el sistema de refrigeración y a los costes de los materiales superconductores, los SMES se utilizan para el almacenamiento de energía de corta duración, siendo su aplicación más común la mejora de la calidad de onda en las redes públicas de distribución de electricidad, típicamente la neutralización de los huecos de tensión y los microcortes.

Wiki

Superconductividad de alta temperatura

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Problemas no resueltos de la física: Superconductores de alta temperatura: ¿Por qué ciertos materiales muestran superconductividad a temperaturas mucho mayores de 50 K?

Muestra de 1 mm del superconductor de alta temperatura Bi-2223.

Con superconductividad de alta temperatura se puede hacer referencia a dos clasificaciones de los superconductores: o bien se refiere a aquellos que no responden a la teoría BCS, o bien se refiere a superconductores con temperatura crítica mayor que la temperatura de ebullición del nitrógeno (77K). Que haga referencia a estas dos clasificaciones se debe a que, por lo general, la temperatura crítica de los superconductores que no cumplen la BCS es mayor que las de aquellos que sí la siguen, aunque existen múltiples excepciones.

Este tipo de superconductividad fue descubierta en 1986 por Karl Alexander Müller y Johannes Georg Bednorz y fue inmediatamente reconocida por el Premio Nobel de Física de 1987. Desde el punto de vista de la clasificación hecha anteriormente, estos estudios se corresponden con los superconductores que no cumplen la teoría BCS, aunque su temperatura crítica es mayor que la de todos los superconductores convencionales conocidos por aquel entonces.

La búsqueda de una comprensión teórica de la superconductividad de alta temperatura se considera como uno de los problemas más importantes sin resolver en la física. Actualmente sigue siendo un tema de intensa investigación experimental y teórica, con más de 100.000 documentos publicados sobre el tema.

Pese a las intensas investigaciones, una explicación satisfactoria sigue eludiendo a los científicos. Una de las razones para ello es que los materiales en cuestión son por lo general muy complejos, con varias capas de cristales (por ejemplo, BSCCO), lo que hace difícil el modelado teórico. Sin embargo, con el rápido ritmo de nuevos descubrimientos en este campo, muchos investigadores son optimistas en una completa comprensión del proceso dentro de la próxima década más o menos.

Ejemplos[editar]

Ejemplos de superconductores de alta temperatura incluyen al La_1.85Ba_0.15CuO₄, y el YBCO (Itrio–Bario–Cobre–Óxido), el cual es famoso por ser el primer material descubierto mostrando la superconductividad por encima del punto de ebullición del nitrógeno líquido. Todos los superconductores de alta temperatura son de tipo II y no convencionales.

A veces se dice que el diboruro de magnesio (MgB₂) es un superconductor de alta temperatura lo cual no es muy riguroso, dado que su temperatura crítica es 39 K; esto quiere decir que el nitrógeno líquido no es suficiente para obtenerlo en estado superconductor. La razón de tal confusión es que entre los superconductores convencionales es el que tiene la termperatura crítica más elevada con mucha diferencia con respecto a los demás superconductores de su categoría (como el niobio, con T_c = 9 K, o el germaniuro de niobio, que tiene T_c = 23 K y es el segundo en su categoría, tras del diboruro de magnesio), por lo que su T_c es relativamente muy alta.

Historia[editar]

Karl Alexander Müller y Johannes Georg Bednorz trabajaban desde 1983 en un laboratorio de investigación de IBM en Zürich con estructuras de perovskitas según trabajos anteriores de A. Sleight de DuPont. En abril de 1986 descubrieron la superconductividad de alta temperatura, siendo presentado el resultado en una reunión de la Sociedad Americana de Física en Nueva York. En poco tiempo muchos otros centros de investigación comprobaron el descubrimiento. En paralelo comenzó una búsqueda de sustancias similares con temperaturas críticas más altas. Así en 1987 se descubrió el YBa₂Cu₃O₇ con 93 K y en 1988 el Bi₂Sr₂Ca₂Cu₃O₁₀ con 110 K. El récord lo tiene desde el 2000 el Hg_0,8Tl_0,2Ba₂Ca₂Cu₃O₈ con 138 K.

---

 

Como candidato MgB2 que permite hacer bobinas.

Dejo aquí cómo fabricarlo por si se cae la página

”

Los superconductores pueden conducir la electricidad sin resistencia. Actualmente se encuentran a temperaturas muy bajas, a menudo por debajo de la temperatura del nitrógeno líquido, que hierve a -321 grados Fahrenheit. Los superconductores que no son un elemento se hacen generalmente mediante la combinación de diferentes elementos. Hay cientos de estos superconductores, cada uno con un método diferente de preparación. En la mayoría de los casos, la mezcla íntima de los elementos, la presión y la cocción a altas temperaturas son pasos necesarios en el proceso de creación de los superconductores. La descripción aquí es específico de la llamada diboruro de magnesio superconductor, MgB2, descubierto en 2001 y cuya temperatura de transición es de unos 39 grados Kelvin. Desde 2001, los métodos más sofisticados que se describe aquí se desarrollaron para la preparación de diboruro de magnesio como películas, cintas e hilos.

Pesar, mezclar y cocinar diboruro de magnesio

Compra muestras de magnesio y boro con 99,99 por ciento de pureza. Pesar balanza analítica, un mol de polvo de magnesio a 2 moles de potencia de boro. Un mol de Mg pesa 24,31 gramos y dos moles de boro pesa 21,62 gramos.

Mezclar las partes pesadas de magnesio y boro en un mortero guantera y se muelen a una muestra íntimo en una atmósfera de argón.

 

Convertir el polvo mezclado en gránulos utilizando un manual de pellet máquina de la prensa. Obtener muchas muestras de sedimentos de unos 2 mm de espesor.

Envolver con papel de pellet tantalio. Colocar en un tubo de cuarzo lavó abundantemente con gas argón de aire a muy alta presión de hasta 196 megapascales (MPa). Selle el tubo con un machine.Place celebró una prensa (HIP) horno isostática en caliente. Calentar a 973 ° C durante al menos 10 horas.

Apagar el horno, y la muestra enfriar lentamente a temperatura ambiente. Cortar el tubo y el surgimiento de una muestra de pellets para la prueba de la superconductividad.

Sumergir la muestra en el helio líquido para enfriar durante 30 minutos. Prueba para la superconductividad colocando un pequeño imán en un dewar disco delgado que contiene la muestra. El imán se rechaza si la muestra se superconductor. De lo contrario, afilar las otras muestras, sedimentar y repetir el proceso de calentamiento durante otras 20 horas.

”

Aproximación a superconductor YBa ₂ Cu ₃ O _{7 en polvo que se compacta, y luego se hace trefilando con magnesio una camisa metálica.}

O por deposición química capa a capa sobre el cable de magnesio.

(20-Nov-2021)

NbTiCu

s41598-019-50549-7
Juntas superconductoras de niobio-titanio (Nb-Ti) para funcionamiento en modo persistente _ Informes científicos copia
04NbTisuperconductorwireswithCuasartificialpinningcenters.en.es_removed

Tabla del 2013, desde entonces han mejorado.

 

Tendría muchos usos: Aviones, barcos de gran tonelaje, máquinas muy pesadas, y un sin fin de usos, que el normal, de almacenar energía producida.

Visitar

Por esto es necesaria la nuclear.

También existe la posibilidad de embutir el superconductor en un plástico de alta resistencia

(El plástico se puede unir con calor?)Y utilizar un superconductor a megapascales,como es más resistente que el acero, se podría hacer. Resultando un dispositivo más barato.