- Washington Metropolitan Area Transit Authority
- Kawasaki, Federal Transit Administration
- Washington, D.C.
- Our Role
- Providing Technical Support to WMATA on Technology Assessment, Analysis of Test Data, and Report Preparation.
- 2 Megawatts
- 3 years
- Developed the pass/fail criteria and test scenarios for the evaluation of battery storage devices
- Demonstrated the feasibility and cost effectiveness of BPS to reduce peak current demand, voltage sags, and energy consumption.
- Test data indicates that a single 2-megawatt battery power system has potential energy savings of 1,347 Megawatt-hours (MWh) per year.
As the second busiest rapid transit system in the U.S., the Washington Metro Area Transit Authority (WMATA) Metrorail System consumes approximately 500,000 MWh per year, at a cost of $48 million. Committed to improving energy efficiency and achieving cost savings, WMATA decided to evaluate the use of energy generated from braking trains, coupled with energy storage, to reduce power costs.
The authority turned to Gannett Fleming for technical support on a demonstration project sponsored, in part, by the U.S. Department of Transportation Federal Transit Administration (FTA). The demonstration examined a wayside energy storage system that could capture and reuse regenerative brake energy. Gannett Fleming analyzed the system’s feasibility and cost effectiveness, which assisted WMATA in formulating engineering design and capital investment strategies.
Regenerative braking technology for transit systems is beneficial if another train is accelerating in the immediate area. If no other train is ready to tap into that power, the power is dissipated as heat. Gannett Fleming analyzed the feasibility and cost effectiveness of capturing and reusing regenerative brake energy. After an extensive assessment of different wayside energy storage technologies, WMATA and Gannett Fleming selected the Battery Power System (BPS). The BPS was installed in the West Falls Church Yard traction power substation on WMATA’s Orange Line. During a two-year demonstration, Gannett Fleming analyzed and verified the energy savings, peak power savings, and system voltage improvements. The results revealed that a fully charged BPS can support 19 train movements with a full load of passengers, in succession.
We assisted WMATA in gauging its ability to use the BPS for emergency power, an important safety feature. We provided technical support on the project findings in discussions with the Federal Transit Administration and collaborated on preliminary and final reports. Following the demonstration project’s successful completion, Gannett Fleming continued to conduct cost/benefit analyses of deploying wayside energy storage throughout the entire WMATA network. Although the application of this technology for the transit and rail industry is at an early stage of development, this project offers the potential for energy savings and power optimization for the entire industry.
- First deployment of the BPS technology in transit operations for WMATA and FTA
- Valuable data from in-service conditions will help WMATA formulate future engineering design and capital investment strategies
- Uses high-capacity GIGACELL® nickel-metal hydride technology developed specifically for rail and transit applications, which provide an economical and stable power supply
- Electronic data recorders collect performance data, downloaded regularly for analysis.
- BPS saves between 7.2 percent and 15.4 percent in energy costs per year for the substations affected by the BPS installation
- Reduces peak power between 121 kilowatt (kW) and 436 kW
- Helps maintain the DC system voltage level to support normal train services when a substation has no rectifier to convert alternating current to direct current
- Batteries use no toxic materials and are easy to disassemble for recycling
- Contributes to WMATA’s goal of reducing energy use 15 percent by 2025
- Continue follow-up studies to assess systemwide energy-saving potential at selected locations.