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Harnessing the Kinetic Energy of Braking: A New Pilot Project in Philadelphia

The transit authority in metropolitan Philadelphia is launching a pilot project under which the energy created by braking subway trains will be transferred to a large battery that can then either use the electricity to help power the transit system or sell the power to the region’s electricity grid. The Southeastern Pennsylvania Transportation Authority (SEPTA), which is installing the battery in one of its 38 transit substations, said the power generated by harnessing the kinetic energy of braking trains can either be used to power accelerating trains or stored for sale to the grid. SEPTA estimated that if the system is installed in all of its substations, the agency could eventually cut its electricity bills by up to 40 percent and generate millions of dollars a year by selling energy back to the grid. Each train car in the system would be equipped with a generator to harness the power from braking. SEPTA is working with a Philadelphia-based company, Viridity, to choose a sufficiently large battery and apply smart-grid technology to allocate the power created by the braking trains.

This post originally appeared on e360 digest. | Image: A Philadelphia Market-Frankford Line subway train; Credit: SEPTA

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WOW! that is amazing, these things need more funding so that we can stop using such high energy ways to make electricity and gas etc these days. Whatever will they think of next?

Posted by: Steve Brooks on 6 Oct 10

I don't see why you would sell it to the grid... If a train stops it has to accelerate again when leaving the station. The amount of energy needed is theoretically the same as the amount lost while braking, but in reality there's always a certain loss of efficiency.
It sounds a bit strange to me... Even the 40% cut of electricity costs seems a little far-fetched.

Posted by: Joris Van Dael on 6 Oct 10 mean they had electrified rail, but weren't doing this already?
That seems bizarre to me--regenerative breaking was demonstrated on the first electric railways over a hundred years ago.

Posted by: Tyler August on 11 Oct 10

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