By Robbie Webber
As of the end of June, the Southeast Pennsylvania Transit Authority (SEPTA) east-west subway line has started feeding electricity back into the power grid as well as using it to run its trains. With the installation of a battery bank next to the tracks, the energy generated by braking trains can be stored. The system works the same way hybrid cars use regenerative braking to charge their batteries. When the train starts up again, it can pull energy from the batteries, saving SEPTA some money. Or if the electricity is not needed the energy can be fed back into the power grid, helping even out demand throughout the system.
Previously, the energy from braking trains would be fed back into the third rail and available to the system instantaneously. However, energy could not be stored, so excess energy was dissipated as heat, essentially lost to SEPTA and the larger power grid.
Because the program is new, and it is still unknown how much SEPTA will save in electrical consumption, or how much it will be able to sell back to the power company, estimates of total economic benefit range from $165,000 to $400,000 per year. The system will also cut carbon emissions by 1,258 tons annually, the equivalent of 100 households.
The innovative pilot progam was installed at no cost to SEPTA. Funded by a grant from the Pennsylvania Energy Development Authority and support from Ben Franklin Technology Partners, the first of its kind system is generating excitement in both transit and alternative energy circles.
Robbie Webber is a Transportation Policy Analyst at SSTI.