Making public transit greener

Posted on July 13, 2012 by Heather Redfern - Also by this author

Public transit has always been the green transportation alternative. How do you make it even more environmentally-friendly and efficient for the 21st Century? The Southeastern Pennsylvania Transportation Authority (SEPTA), in partnership with Viridity Energy Inc. — a Philadelphia smart grid company — is bringing the regenerative braking energy technology long used by hybrid-electric vehicles to its Market-Frankford Line elevated trains.

But where hybrid-electric buses and cars have onboard batteries to capture and store energy created when the vehicle brakes, trains don’t have a storage capability and the energy created during the regenerative braking process can only be used by a nearby accelerating train. And if there’s no train?  That energy is lost, vanishing into the air.  

Until now.

SEPTA and Viridity have devised a way to capture, store and reuse braking “El” trains’ energy, building upon the idea of an on-board battery.
SEPTA and Viridity have devised a way to capture, store and reuse braking “El” trains’ energy, building upon the idea of an on-board battery.


In a first-of-its kind “wayside energy storage” project, SEPTA and Viridity have devised a way to capture, store and reuse braking “El” trains’ energy, building upon the idea of an on-board battery. Instead of just one battery like that on a car or bus, SEPTA’s system is several large batteries (produced by Saft Batteries Inc.) and a controller (produced by ABB Envitech, Inc.) located offsite (“wayside”) at SEPTA’s Letterly Substation. The stored energy can later be used by SEPTA to meet a variety of energy needs on the portion of the Market-Frankford Line served by that substation, including powering additional trains.  

Wayside energy storage is green for reasons other than being socially responsible by reducing the amount of energy SEPTA needs from the power grid. The project will be a money saver and revenue generator for SEPTA — an important outcome at a time when transportation organizations are being looked upon to develop innovative means of creating income.  

Much like SEPTA’s hybrid buses reduce fuel consumption, the battery is projected to decrease the electric bills at Letterly Substation by up to $190,000 per year. Additionally, the excess energy captured and stored by the battery can provide support to the electric grid via the frequency regulation market. Through its partnership with Viridity, SEPTA will deploy its energy surplus as virtual power into PJM Interconnection’s wholesale power frequency regulation and energy markets. SEPTA anticipates that frequency regulation and other demand response programs could generate up to $250,000 annually in new revenue.

“Through this pilot project, SEPTA will become even more energy efficient, which will help control operating costs — benefiting both customers and taxpayers. We’ve made our system cleaner, greener and more efficient in recent years: things like replacing traditional diesel buses with diesel-electric hybrids and installing energy-efficient lighting at stations, facilities and offices,” said SEPTA GM Joseph Casey. “These measures are helping us control costs in tough economic conditions and making us a better neighbor in the communities we serve."

The Letterly Substation project, funded by a $900,000 grant from the Pennsylvania Energy Development Authority, is just the first in SEPTA’s wayside energy storage initiative. The agency received a $1.44 million FTA grant to install another device at a substation in Northeast Philadelphia. That grant will also be used to test alternative battery technology and determine the best fit for SEPTA’s propulsion system. The results will be shared within the transportation industry, allowing other rail transit agencies to determine how they might be able to use the wayside storage technology in their systems.

In case you missed it...

Read our METRO blog, "Finalizing bus stop placement" here.

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