Community
BART Commissions 2-Megawatt Magnetic-Levitation Flywheel Energy Storage Substation at Warm Springs/South Fremont Station
Vacuum-sealed steel rotors spinning at 16,000 RPM on Warm Springs Boulevard capture 1,000-volt third-rail braking bursts and return traction power in milliseconds.
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Traction power engineers with the Bay Area Rapid Transit District (BART) and clean-grid specialists from the California Energy Commission commissioned a 2-megawatt high-speed magnetic-levitation wayside flywheel energy storage array on Saturday evening inside the traction power substation at Warm Springs/South Fremont Station at 45193 Warm Springs Boulevard in Fremont. Connected directly across the 1,000-volt direct-current (DC) third-rail bus serving the Berryessa/North San José and Orange/Green Line junction, the kinetic storage plant captures intense 25-second regenerative braking surges from arriving ten-car Fleet of the Future trainsets.
When a 650,000-pound BART train brakes from 70 miles per hour into Warm Springs Station, its three-phase AC traction motors regenerate up to 4 megawatts of electrical power onto the third rail. If no opposing train is accelerating nearby on the same electrical section, trackside voltage rises above 1,150 volts DC, forcing onboard dynamic braking resistors to dissipate excess energy as waste heat. Inside the new Warm Springs vault, eight vacuum-sealed solid-steel flywheel rotors levitated on frictionless active magnetic bearings spin up from 8,000 to 16,000 revolutions per minute to absorb those braking spikes with zero chemical battery degradation.
Rated for more than one million full charge-discharge cycles over a 25-year service life, the flywheel bank discharges stored kinetic energy back into the third rail within four milliseconds whenever a train departs toward Fremont or Milpitas. This rapid voltage support reduces substation peak power draw by 27 percent and saves 1.9 gigawatt-hours of electricity annually.
The $3.8 million wayside kinetic storage demonstration was funded through a Federal Transit Administration Low or No Emission grant and BART Measure RR traction power funds. Riders can review transit sustainability metrics on the BART Sustainability Portal.
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