SEPTA-Viridity Energy

SEPTA / Viridity Energy
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EPTA's Market Frankford line, the busiest transit line in
Philadelphia and referred to locally as the “El,” has moved
commuters, shoppers and visitors for more than 100 years.
Moving these trains requires a large amount of electricity. In 2010,
SEPTA partnered with Viridity Energy to implement a new strategy to
cost-effectively reduce SEPTA's energy consumption. The El's electrically
powered trains also have regenerative braking capabilities. When trains
brake, their electric motors produce energy—a six-car train on the
Market-Frankford Line can produce up to three megawatts in 15 seconds
of braking. The problem is, unlike hybrid vehicles, 20th century trains
were not designed with an energy storage capacity. Regenerated energy
from a braking train can only be used if there is another train
accelerating in the immediate area. Otherwise, the regenerated energy
is wasted—dissipating as heat through resistor banks on the top of
the train.
Viridity applied for and was awarded a $900,000 Pennsylvania Energy
Development Authority (PEDA) grant to enable SEPTA to install an energy
storage device at the Letterly Substation in the Kensington section of
Philadelphia, thereby effectively "hybridizing" a key portion of the MarketFrankford Line. The device captures much of the regenerated energy,
stores it, and pumps it back into the system as needed. The project team
selected Saft Batteries to manufacture the storage device and Envitech to
supply the electronic controls for system integration. SEPTA anticipated
that the device would supply approximately 10 percent of the power
demand at Letterly, reducing electricity bills by more than $100,000.
Actual results have been close to estimates since commissioning in
June 2012.
In addition to energy savings, the storage device has served as a
distributed energy resource for the regional grid operator, PJM. During
extreme weather (very hot or very cold) events, the grid can become
destabilized by large fluctuations in demand. SEPTA's energy storage
device has helped PJM regulate grid frequency, which in turn has
generated additional revenue from the project. During the unusually cold
month of January 2014, for example, the storage device generated more
than $55,000 in revenue from frequency regulation services—more than
one-fifth of the total annual estimate of revenue potential.
Photo courtesy: SEPTA
Photo courtesy: Viridity
The capture, storage, and reuse of electricity generated from braking
trains improves energy efficiency and reduces demand for SEPTA and the
entire PJM grid. The success of this project has led to SEPTA scoping
work for another energy storage system along their Market Frankford
line—and ultimately to many other substations across the system
—resulting in continued savings for SEPTA commuters.
Pennsylvania Energy Development Authority
0120-FS-DEP4515
2/2016
G1595