Siemens installing regenerative battery on TriMet train

Siemens is currently installing the first regenerative battery in the U.S. on the new TriMet Portland-Milwaukie light rail transit line — the 7.3-mile line extension project that will connect the southeast corridor to downtown Portland and other regions that TriMet MAX serves.

The southeast Portland Tacoma substation location will house the first U.S. storage unit that allows for energy created during braking to be stored and then re-used in one of two forms, energy savings or voltage stabilization, during peak demand times. TriMet will utilize the system in voltage stabilization mode.

In voltage stabilization mode, the Sitras SES Energy Storage Unit with supercapacitor technology allows the system to avoid problems that have led to disruptions in mass transit operations. If a number of vehicles accelerate simultaneously, system voltage can drop below a critical level and result in instances of undervoltage tripping in vehicles and, consequently, lead to disruptions in passenger service. The Sitras SES ensures the system voltage always remains within the required range and voltage-related disruptions no longer occur.

“The regenerative energy storage unit is an important piece of the many sustainable elements being incorporated in this light rail project,” said Dan Blocher, executive director, TriMet Capital Projects.

The Sitras Energy Storage unit is part of Siemens Smart Grid Rail Electrification portfolio, providing solutions to reliably connect railway systems to the power grid. In energy savings mode, the energy storage unit absorbs the energy generated by braking rail vehicles and stores it until the system can safely feed it back to the power supply during vehicle acceleration.

As a voltage stabilizer, the energy content is constantly kept at a high level and energy is discharged when the system voltage falls below a specified limit. Installation of the Sitras Energy Storage Unit also allows TriMet to avoid placing a utility-connected substation in the same location.

The Sitras SES has been successfully installed in Spain and Germany, reducing the energy demand at Cologne Transit Authority substation by 15,000 kWh in one month. The use of just a single energy storage unit could save a maximum of 500,000 kWh per year. In addition to the cost saving, the storage unit can reduce CO2 emissions by 300 tons per year with this reduction in energy generation.

The first substations will be installed beginning in October 2013. The Portland-Milwaukie Light Rail Transit Project is set to open in 2015 and will expand the MAX system to 60 miles and 97 stations.

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