Boston Takes Charge of a Zero-Emissions Opportunity

At a Glance

  • Client(s)
  • Massachusetts Bay Transportation Authority (MBTA)
  • Project Location(s)
  • Boston
LTK-designed railcarCharging forward in Boston. 

The MBTA used an award from the Federal Transit Administration (FTA) to acquire five electric, battery-powered, articulated buses, which have been deployed on the Silver Line. The batteries are recharged at on-route locations, and at the Southampton Depot facility using high-power, fast-charging stations.

LTK, at the request of MBTA, inspected the Southampton Depot and the unit substation and conducted equipment and power demand audits to determine the electrical parameters of the equipment and the loading of the auxiliary transformers. LTK also performed a depot site survey to determine the most suitable battery charger locations and supply cable routing. LTK performed comprehensive load flow studies to determine loading on the distribution system, charger feeder cable, and busbar voltages.

The following options for the charger feeding were developed:

  • Supplying the chargers from existing auxiliary transformers in the unit substation
  • Replacing insufficiently-rated auxiliary transformers with larger capacity units
  • Procuring and installing a new transformer dedicated to the bus chargers
  • Obtaining a new power supply from Eversource, the area’s power utility company

The option to obtain a new power source from the utility was eliminated due to its high cost. Preliminary engineering was performed for each of the remaining options. The work included determining transformer parameters, switchgear configuration and rating, cable sizing, locations for equipment, and cable routing. The options were evaluated for their advantages, disadvantages, technical feasibility and costs. Based on these factors, LTK recommended that one additional transformer dedicated to the bus chargers would be the best choice for MBTA.