A train on SEPTA's Market�Frankford Line (credit Adam Moreira)

Train braking energy used to support the grid

A railway operator has become the first to combine regenerative braking and energy storage with support for the electricity grid.

The Southeastern Pennsylvania Transportation Authority (SEPTA) pilot project captures the braking energy of trains on the Market-Frankford line and will integrate that power into the regional electric grid.

What is novel about this project is that it brings together two applications of energy storage that have been proven separately but never before been brought together to create a recurring economic value.

SEPTA’s smart grid solution captures the regenerative braking energy of trains through a large scale battery storage system and uses it within the rail network, thereby reducing electricity supply costs, but in addition it offers virtual power into the wholesale power frequency regulation and energy market in the region, operated by PJM.

SEPTA launched the pilot project in partnership with Viridity Energy, a smart grid technology firm that specialises in electric market integration.

Saft was selected to provide the design, manufacturing and commissioning of a megawatt-level lithium-ion battery energy storage system.

Envitech Energy provided power controls, power conversion and system integration using its Envistore system.

The Envitech equipment and the battery container are both installed in the Letterly substation that serves the line.

Viridity Energy’s VPower optimiser software enables the simultaneous process of regenerative capture, regulation performance, and energy market participation by selecting which market to participate in based upon market pricing, battery state of charge, and availability of regenerative energy from the trains.

“In a smart-grid world, two-way digital information exchange opens up new horizons,” explained Viridity Energy CEO Audrey Zibelman.

“This project truly showcases the potential of that world, particularly as it applies to the transportation industry.

“By harnessing the regenerative braking power of the trains and empowering SEPTA to become a virtual power generator that can provide valuable and environmentally responsible service to the electric grid, we can fulfil the promise of interconnected systems on the grid and behind the meter responding dynamically to reliability and economic signals to strengthen the grid.”

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