Superconducting magnetic energy storage (SMES) has long been pursued as a large-scale technology because it offers instantaneous energy discharge and a theoretically infinite number of recharge cycles. Until recently, however, the material costs for SMES devices have been prohibitively high for all but very small applications. Now a project funded by the U.S. Department of Energy (DOE) could pave the way for SMES technology that offers megawatt hours of energy storage. Such capacity is becoming increasingly necessary for electricity grids that need to balance the intermittency of renewable energy sources.

At a DOE Advanced Research Projects Agency for Energy (ARPA-E) conference in Washington, D.C. on March 2, Swiss-based engineering firm ABB outlined plans for a 3.3 kilowatt-hour proof-of-concept SMES prototype. The device will store electricity in the form of a magnetic field generated by direct current circulated through superconducting wires. The geometry of the superconducting coils creates a highly contained electromagnetic field, but relatively little energy is needed to sustain the field. The energy is released by discharging the coils.

ABB is collaborating with superconducting wire manufacturer SuperPower, Brookhaven National Laboratory, and the University of Houston as part of the $4.2 million ARPA-E grant. The group's ultimate goal is to develop a 1-to-2-megawatt-hour commercial-scale device that is cost-competitive with lead-acid batteries, says ABB project manager V.R. Ramanan.

Matching the price of lead-acid batteries would make SMES systems less expensive than flywheels but more expensive than pumped hydro or compressed air, according to a recent study by the Electric Power Research Institute. Pumped hydro, which stores energy by pumping water uphill, and compressed air, which stores energy in the form of air compressed in underground caverns, are the two leading methods for storing energy on a large scale today. These approaches are, however, limited to areas with lakes or other reservoirs at high elevations or with underground caverns. 

A key advantage that SMES has over other energy-storage technologies is its ability to rapidly release stored energy. "It can go from full charge to full discharge—no other technology can do that," says Cesar Luongo the senior magnet-division coordinator for the International Thermonuclear Experimental Reactor project in Cadarache, France, who is not involved with the project.