In a bid to boost its energy resiliency, cut costs and support the stability of Philadelphia's electrical grid, SEPTA this week announced plans for a battery storage network that will capture and reuse stored energy from braking subway cars, marking the first deployment of its kind in a U.S. transit operation.
The sustainability project will be implemented through a partnership with Constellation and Viridity Energy. It will operate using an 8.75-megawatt battery storage network at seven SEPTA substations, bringing the agency's total battery storage capacity to more than 10 megawatts.
“SEPTA’s Sustainability Program is all about finding and deploying cutting-edge innovations to reduce costs in addition to improving environmental performance," said SEPTA General Manager Jeffrey D. Knueppel. "This project is right in that sustainability sweet spot, and we are pleased to partner with Constellation and Viridity in bringing it to market right here in the Philadelphia region, an emerging hub for innovative energy projects."
The project will be financed through a 20-year battery services agreement with Constellation, co-funded with a grant from the U.S. Department of Energy, and will require no upfront capital investment from SEPTA. It is expected to generate $26 million in guaranteed savings in efficiency improvements.
SEPTA's initial battery storage projects, launched in 2012, have already generated an estimated $40,000 in electricity costs at substations where they were installed, with an additional $250,000 in annual revenue, according to the New York Times.
The software-powered batteries work by recovering kinetic energy from braking subways as they approach designated substations. That energy is then directed to battery banks where it can be resold to the grid.
Gary Fromer, senior vice president for distributed energy at Constellation, said the key to realizing savings from the regenerative braking system is the capacity to resell the energy.
“This battery storage network, along with $26 million in guaranteed savings from efficiency improvements Constellation is implementing for SEPTA, will help SEPTA deliver on its budget and energy resiliency goals.”
As a whole, stored energy from the new system will be used to help balance the electric load on the regional PJM Interconnection, which manages the transmission of wholesale electricity to 13 states and Washington, D.C. The flow of electricity will match generation with demand and enable Viridity Energy to efficiently market energy services for the project.
"Our ground-breaking regenerative braking pilot at SEPTA proved that energy storage can be used by transit systems to create substantial cost savings, generate revenue, and contribute to sustainability goals," said Viridity Energy CEO Mack Treece. "By expanding the pilot to a full deployment, SEPTA will demonstrate to rail transit systems throughout the world that energy storage can be a core part of their overall energy and sustainability strategy when paired with the right technologies and market expertise."
Construction at the additional SEPTA substations is expected to begin in the second quarter of 2016 and will likely be ready for commercial operation toward the end of the year.