Light-Rail Line Accelerates Brake-Energy Storage

Energy storage technology that’s already a part of Spanish and German light rail systems is coming to Oregon. Siemens says its Sitras SES Energy Storage Unit, which will collect energy absorbed from the braking of trains, will be installed on a new line by TriMet on the Portland-area transit system.

The storage system, to be installed on TriMet’s new 7.3-mile line that will run from Portland southeast to Milwaukie, can operate in two modes: voltage stabilizer or energy saving. Siemens said in a release that TriMet is going for voltage stabilization.

max regenerative braking storage

image via TriMet

“As a voltage stabilizer,” Siemens said, the unit’s “energy content is constantly kept at a high level and it discharges when the system voltage falls below a specified limit.” These big draws on energy come when several trains simultaneously accelerate, which can risk tripping the system and disrupting service.

With the Sitras Energy storage unit TriMet will avoid putting in a utility-connected substation at the Tacoma Street station in southeast Portland where the unit will go.

“The regenerative energy storage unit is an important piece of the many sustainable elements being incorporated in this light rail project,” Dan Blocher, executive director of TriMet capital projects, said in a statement. “With Siemens as a partner, we know this pilot project is positioned to bring a new and efficient technology to the U.S.”

TriMet is already in the process of taking advantage of new technology to boost the ability of its trains to take advantage of regenerative braking. It won a $4.2 million federal grant to install double-layer capacitor units from American Maglev Technology on 20 vehicles that will release previously stored electrical energy upon acceleration. This will help boost captured regenerative power from 70 percent to nearly 100 percent, according to information prepared by the National Renewable Energy Laboratory for the Federal Transportation Administration.


  • Reply June 10, 2013

    Peter Javsicas

    SEPTA, Philadelphia’s transit authority, has had regenerative breaking and energy storage for about a year.

    • Reply June 10, 2013

      Pete Danko

      Thanks for that reminder, Peter. We wrote about that project as it was being developed: Readers might also be interested in a really good blog post from SEPTA about the system:

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