story by Samantha WittchenInnovation” might not be the first word Philadelphians associate with SEPTA—two tokens sold in a plastic bag that says “Go Green” seems, um, not innovative—but that reputation deserves to change. SEPTA is piloting a cutting-edge regenerative braking project that saves energy and money, and positions Philadelphia as a global leader in public transportation sustainability.
This change couldn’t come at a better time. In August, Philadelphia will host the 2012 American Public Transportation Association’s “Sustainability and Public Transportation Workshop.” As hundreds of the industry’s leading sustainability and environmental policy professionals descend on the city, SEPTA will showcase its progress on the Wayside Energy Storage System, a regenerative braking and energy storage system implemented at one of SEPTA’s electrical substations on the Market-Frankford Line.
The project began in 2010 when SEPTA announced a partnership with local power technology firm Viridity Energy. Backed by funding from the Pennsylvania Energy Development Authority and the federal government, the pilot is set to reduce electrical usage at the substation by 10 percent. The project will conclude by the end of 2012.
Regenerative braking itself isn’t new. New York, Seattle, Portland and Los Angeles all currently employ this technology, and SEPTA uses it to power the lights and air conditioning on trains. What makes SEPTA’s pilot system innovative is its use of a large battery to store the electricity generated by braking trains. Viridity will monitor the battery using their software to determine whether it’s more cost-effective for SEPTA to use the energy for powering trains or to sell the energy back to the grid.
Here’s how regenerative braking works on SEPTA trains: Instead of using brake pads to create friction to slow the train, the braking mechanism puts the electric motor in reverse, turning it into an electric generator. The generator can then provide electricity to a variety of applications, like lights, air conditioning, other trains and storage devices (batteries). Any excess electricity that can’t be stored is sent to a resistor bank on top of the train car and converted to heat. In the SEPTA pilot project, electricity stored in the battery can then flow to the grid.
The technology’s scalability is what makes it so important and potentially transformative. There are more than two dozen substations where this technology could be replicated, explains Andy Gillespie, SEPTA’s chief engineer for power, which would fundamentally change the way SEPTA manages power for its subways and trolleys.
The project may also save SEPTA a good chunk of change. Between reducing electricity costs and revenue generated by selling electricity, they’re expecting a net annual benefit of $300,000. The savings will provide the capital to fund future projects at other substations, creating a positive loop of savings. The demonstration phase began on March 1, and the transit industry is closely watching this project to see if it can be a model for other transit systems throughout the country. The workshop in August will be a great opportunity to further the project (by attracting more federal transit dollars) and demonstrate Philadelphia’s growth as an innovative sustainability leader.
Now, if we could just talk to them about those tokens. - Samantha Wittchen