Superconducting magnetic energy storage
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).[1] 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 storage capacity of SMES is the product of the self inductance of the coil and the square of the current flowing through it:
- E is the energy stored in the coil (in Joules)
- L is the inductance of the coil (in Henrys)
- I is the current flowing through the coil (in Amperes)
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.[1]
Applications of SMES
SMES is a specific technology with applications that can be applied to power quality and very high power distribution or transmission networks on the electrical grid. They have been commercially installed for several large industrial users.[2] Although SMES systems are very expensive, they are extremely efficient, have almost instantaneous charge and discharge, are easily scalable, and have little environmental impact.[1]
References
- ↑ 1.0 1.1 1.2 Bradbury, K. (2010). Energy Storage Technology Review. Duke University. Retrieved October 4, 2013, from http://people.duke.edu/~kjb17/tutorials/Energy_Storage_Technologies.pdf
- ↑ “Energy Storage: Making Intermittent Power Dispatchable,” Alberta Innovates - Technology Future, Alberta, 2011.