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 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 of TriMet capital projects. "With Siemens as a partner, we know this pilot project is positioned to bring a new and efficient technology to the U.S."
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.
Siemens is providing additional solutions for the overall 7.3-mile line extension project that will connect the southeast corridor to downtown Portland and other regions that TriMet MAX serves. Siemens Rail Systems is manufacturing 18 rail vehicles at its Sacramento, Calif., facility for the Portland-Milwaukie extension and Siemens Mobility and Logistics will be implementing its Rail Automation signaling and communication technologies to center control on the line extension.
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.