Energy Solutions: SEPTA's Hybrid Subway

Energy cannot be created or destroyed, and SEPTA is using this principle to go hybrid in its subway system. Armed with a $900,000 grant from The Pennsylvania Energy Development Authority, SEPTA announced Wednesday that it will use the kinetic energy from braking trains to generate electricity. This project has been designed by Viridity Energy Inc, a Conshohocken smart-grid innovator. This Inquirer article, which details the process:

The electricity will be stored in a large, railside battery array and reused when the train accelerates. The system is expected to reduce electrical power purchases 10 percent to 20 percent at each location of the batteries, said Andrew Gillespie, SEPTA's chief engineering officer for power.

But the system is designed to do more than capture power from the subway's dynamic braking system, said Audrey Zibelman, the chief executive officer of Viridity Energy Inc., the Conshohocken smart-grid innovator that devised the project for SEPTA.

The power-storage system is potentially so large - each battery array would store one megawatt of power - that SEPTA could further reduce its electric bill by buying cheap power at night to use or resell during expensive peak hours.

This system could save SEPTA more than 20 percent on energy, and one battery may be able to generate $500,000 a year in value. The subway system will act just like a hybrid car, which can generate power when slowing down.

For more on Viridity, check out this story from Grid's Energy Issue.