Wayside Energy Storage Pilot

April 24th, 2014


Wayside Storage Battery Power System

For more than 20 years, Metro’s rail cars have captured and reused some of the electric energy that would otherwise be wasted when they brake through a process called regenerative braking. This process converts the excess kinetic energy, as the vehicle slows, to electric energy which can be stored and reused for propulsion power. Building on this technology, Metro recently completed tests to capture and utilize even more of the energy during braking through wayside battery storage.

The pilot project tests the energy storage efficiency and return on investment of a wayside Battery Power System (BPS). The BPS uses an innovative nickel-metal hydride battery that is characterized by low internal resistance. As a consequence, the battery can charge and discharge in a matter of seconds, making it perfect for wayside applications where rapid storage and discharge of propulsion power is required. Through this BPS storage system, the kinetic energy that would previously have been dissipated as waste heat can now be productively reused to power railcars and reduce overall energy consumption.

For the WMATA pilot project, Kawasaki Rail Car Inc supplied and installed a 2 megawatt BPS system at WMATA’s West Falls Church substation. The yearlong BPS test process assessed the system under a variety of operating conditions and railcar configurations. Results from the project showed a 24% saving in annual energy consumption (approximately 2,294 MWh) due to the BPS substation with the system completing over 2,000 charge and discharge cycles during a day of normal rail operations. This resulted in estimated annual savings of $250,000 at the test location.

Through technology such as wayside storage, Metro’s facilities and operational fleet are actively striving to be more energy efficient, to reduce operating costs and to improve overall efficiency as Metro rebuilds and expands to serve the growing region.

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  1. jnb
    April 25th, 2014 at 09:01 | #1

    What would installation of these batteries on a system-wide basis mean for power consumption and cost? How much would it cost to install batteries system-wide, and what would the annual dollar savings be and how long would they last?

    Thanks! Good stuff…

    • Dan
      May 1st, 2014 at 09:44 | #2

      Metro is still completing tests on the BPS system to answer these questions.
      A report will be submitted to the FTA later in the year to provide a complete picture of the impacts wayside BPS could provide.

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