13 Jun '11, 12pm

In Philly, batteries will convert wasted energy into subway-moving power (via @nytimesgreen)

Septa On the Market-Frankford subway line of the Southeast Pennsylvania Transit Authority, batteries will capture some energy that is generated when a train brakes, and hold it until it is needed. Subway trains need a lot of electricity to get going, turning electricity into kinetic energy, the energy of movement. When they pull into a station, many of them can do the opposite: generate electricity from their momentum. They turn their motors into generators to slow the train, producing current. But in many systems, some of that energy goes to waste because of a bottleneck: the third rail, which carries current to the train, cannot handle as much energy as the train is generating during deceleration. Too much current pushes up the voltage, and when the voltage gets too high, the electricity is dissipated by running it through a piece of metal that converts it into heat. But...

Full article: http://green.blogs.nytimes.com/2011/06/13/batteries-will-...

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