The City of Philadelphia has begun exploring opportunities to recycle energy created when trains brake.

Philadelphia’s transit agency has embarked on a pilot program that stores this energy in a battery system. Opportunities to access the battery's stored energy would be available for use at a later time or the energy can be returned to the grid for more immediate use.

Storing power is an attractive opportunity for transit agencies as systems and ridership widen because millions of dollars in energy costs can potentially be saved.

New York has already begun storing this power while Los Angeles and Washington are considering it as well.

Philadelphia is partnering with a private energy company as it explores this program. It is being funded by a $900,000 grant from the Pennsylvania Energy Development Authority.

Philadelphia is looking to save as much as 10 percent of power costs on a system that requires $22 million to operate.