Saving Money Everyday: LA Metro Subway Wayside Energy Storage Substation

The Los Angeles County Metropolitan Transportation Authority (LA METRO) subway provides service with up to six-car trains at up to 65 mph at five minute headways on weekdays. To reduce energy usage, LA METRO implemented a flywheel-based Wayside Energy Storage Substation (WESS), which reduces energy usage by capturing and reusing braking energy generated by trains when they decelerate and brake approaching the passenger station. The LA METRO WESS has a 2 MW, 15 second capacity, or 8.33 kWh, and can charge and discharge with a 1.5 minute cycle rate. WESS has been in daily full operation since August 2014. WESS has saved 10 to 18% of the traction power energy at the Westlake TPSS, every day.