Superconducting Magnetic Energy
Superconducting magnetic energy storage (SMES) systems store energy in the magnetic field created by the flow of direct current through a large coil of superconducting material that has been super-cooled. In low-temperature superconducting materials, electric currents encounter almost no resistance, so they can cycle through the coil of superconducting wire for a long time without losing energy. This allows such superconducting coils to serve as effective energy storage devices.
Power is available almost instantaneously from SMES systems, and very high power output can be provided for a brief period of time. There are no moving parts. However, the energy content of SMES systems is small and short-lived, and the cryogenics (super-cooling technology) can be a challenge. Researchers are trying to find ways to maintain the special qualities of SMES without having to keep the systems quite so cold. Low-temperature SMES cooled by liquid helium is commercially available today, and "high temperature" (less cold) SMES cooled by liquid nitrogen is in development.
SMES systems are used to address power quality problems and short-term power losses, such as those that may occur while switching from grid electricity to a backup power supply. They have also been used for electricity-grid support, helping to prevent voltage collapse, voltage instability, and system outages.