Superconducting magnetic energy storage (SMES) is the only energy storage technology that stores electric current. This flowing current generates a magnetic field, which is the means of energy storage. The current continues to loop continuously until it is needed and discharged. The superconducting coil must be super cooled to a temperature below the material's superconducting critical temperature that is in the range of 4.5 – 80K (-269 to -193°C). The direct current that flows through the superconducting material experiences very little resistance so the only significant losses are associated with keeping the coils cool.
The maximum current that can flow through the superconductor is dependent on the temperature, making the cooling system very important to the energy storage capacity. The cooling systems usually use liquid nitrogen or helium to keep the materials in a superconductor state.
SMES is a specific technology with applications that can be applied to transmission networks on the electrical grid. They have been commercially installed for several large industrial users. Although SMES systems are very expensive, they are extremely efficient, have almost instantaneous charge and discharge, are easily scale-able, and have little environmental impact.
For further information please see the related pages below: