Since the early 1900s, the Letterly Substation in Philadelphia’s Kensington neighborhood has been providing the power needed to run one of the city’s busiest train lines.

Now this facility is on the cutting-edge of 21st-century technology that is making public transit more sustainable and efficient, thanks to an innovative program to reduce power consumption and costs by harnessing the energy generated by trains.

The Southeastern Pennsylvania Transportation Authority (SEPTA) and Viridity Energy, a Philadelphia-based smart-grid firm, have launched a pilot project to bring regenerative braking energy—similar to that used by hybrid vehicles—to subway/elevated trains on the Market-Frankford Line. This line is SEPTA’s busiest route, serving nearly 190,000 riders daily.

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—the energy released when trains apply the brakes, usually dissipated as heat—building on the idea of an on-board battery. Instead of a single battery as in a car or bus, however, SEPTA’s system comprises several large batteries (produced by Saft Batteries Inc.) and a controller (produced by ABB Envitech Inc.) located offsite—or wayside—at SEPTA’s Letterly Substation.

Together with Viridity, SEPTA, a gold-level signatory to APTA’s Sustainability Commitment, will connect to the frequency regulation market—used to keep the electricity grid in a state of equilibrium—and other demand-response programs to sell the excess electricity captured by the wayside energy storage device on the electric market. Later, SEPTA can use the stored energy to meet a variety of energy needs on the portion of the Market-Frankford Line served by that substation, including powering additional trains.

This process will help the agency conserve energy and cut down on electric costs. It also creates an opportunity to generate new revenue, as the captured energy can be sold on the power market.

SEPTA has more than 30 substations, many of which could eventually take advantage of this technology.

Other public transit agencies will be able to share results from this pilot to assist their efforts to similarly reduce energy use and greenhouse gas emissions. SEPTA and others hope that soon economies of scale will allow the expansion of this promising partnership to generate economic gains without external support.

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

SEPTA anticipates that the energy optimization program could provide approximately 10 percent of the energy needed at Letterly Substation, which could reduce power bills by up to $190,000 a year. In addition, the agency could generate up to $250,000 in new revenues by selling captured power.

The pilot project, funded by a $900,000 grant awarded to Viridity by the Pennsylvania Energy Development Authority, is just the beginning of SEPTA’s wayside energy storage initiative.

SEPTA is exploring additional grant and funding opportunities that could allow for similar energy optimization projects at other power substations. The transit authority recently 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.

These projects build on efforts undertaken as part of SEPTA’s Sustainability Program, a major goal of which is making the public transit agency greener and more efficient, and providing for improvements to an aging system that are vital to keeping it moving for current and future customers.

Kyle Bell, APTA program manager, environment and infrastructure, contributed to this story.

Focus on Sustainability
SEPTA’s role as an industry leader on these types of energy-saving initiatives will be in the national spotlight Aug. 5-8, when the agency hosts the 2012 APTA Sustainability and Public Transportation Workshop in Philadelphia.

The workshop will explore how emerging partnerships are paving the way to implement cutting-edge sustainable practices. Hear from speakers with a wealth of knowledge in these areas, including APTA Sustainability Commitment signatories. Learn how APTA members are improving efficiency, saving money, mitigating environmental impacts, and promoting strategies that encourage public transit use.
Register for the workshop by clicking here.

Captions
This chart describes the regenerative braking/wayside storage process.

The battery at SEPTA’s Letterly Substation.