Blog Post

Korean Subway to Put Regenerative Braking to the Test

Ultracapacitors are getting a trial run on the South Korean subway system, with San Diego’s Maxwell Technologies (s MXWL) announcing today that its ultracapacitor energy storage systems will be used in a regenerative braking demonstration by the Korean Railroad Research Institute.

A regenerative braking system can save the kinetic energy from braking for later use in acceleration, or feed that energy back into the grid. It’s also being used in some hybrid and electric cars, as well as in the development of Formula One racing cars.

According to Maxwell, ultracapacitors, a next-generation battery technology, can offer faster recharge and discharge rates over traditional batteries, making them ideal for regenerative braking systems, as well as for a burst of power for acceleration. Some reports say the technology could have the potential to replace traditional battery systems.

Texas-based EEStor, a stealthy competitor in the ultracapacitor field, has made its own strong claims about the power of its technology, but unlike Maxwell, EEStor has yet to ship any of its products.

Maxwell said it shipped 72 ultracapacitor modules to the contractor on the project, Korea’s Woojin Industrial Systems, earlier this year for testing on a light rail system, and delivered another 220 modules to Woojin in October for the subway demonstration. The financial terms of the deals were not disclosed.

The smaller batch was used in a 750-volt DC system on Korea’s Gyengsan light rail transit track, with the bigger group of modules to be installed in a 1,500-volt DC system in the second quarter of next year.

In the light rail installation, Maxwell said preliminary testing projected that the system would reduce grid power consumption by more than 20 percent. If that’s matched in actual operation, the company said the regenerative braking system could save enough energy to recoup the initial investment in less than four years.

The New York subway system, one of the world’s largest, is already using regenerative braking in some of its rail cars and is looking at expanding its use of the technology, along with other energy-saving initiatives.

In addition to regenerative braking, Maxwell has also made deals for its ultracapacitors for use in consumer electronics, wind turbines, and industrial applications. In September, Maxwell announced a deal to supply its ultracapacitors to Germany’s LTi REEnergy for use in LTi’s blade pitch control system. Maxwell said its ultracapacitors will supply backup power for a safe system shutdown of the turbines in the event of a power failure.