U.S. Department of Energy - Energy Efficiency and Renewable Energy

Distributed Energy Program

Superconducting Magnetic Energy Storage

Superconducting Magnetic Energy Storage (SMES) systems store energy in the magnetic field created by the flow of direct current in a coil of superconducting material that has been cryogenically cooled.

How It Works

A superconducting material enhances storage capacity. In low-temperature superconducting materials, electric currents encounter almost no resistance. The challenge is to maintain that characteristic without having to keep the systems quite so cold.

Advantages

Power is available almost instantaneously, and very high power output is provided for a brief period of time. There is no loss of power, and there are no moving parts.

Disadvantages

The energy content of SMES systems is small and short-lived, and the cryogenics (cold temperature technology) can be a challenge.

Applications

Already dramatically used in such applications as high-speed, magnetic-levitated trains, superconductors are also being developed for use in microelectronics and communications.

SMES is also used in utility applications. Several 1-MW units are used for power quality control in installations around the world.

In northern Wisconsin, a string of distributed SMES units was deployed to enhance stability of a transmission loop. 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. Besides stabilizing the grid, the six SMES units also provide increased power quality to customers served by connected feeders.