Los Angeles Metro Goes Green with Regenerative Braking and Flywheels

When most people think about transportation in Los Angeles, they picture overcrowded freeways with vehicles of every size, shape, model and vintage barely moving in extended rush-hour traffic. While that image may be accurate enough, Los Angeles County is working diligently to create a world-class public transportation system, integrating new technologies to achieve better service and a lower carbon footprint.

In the next 25 years, Los Angeles’ changing demographics and expected growth and climate changes will require the county to significantly increase its public transportation capacity while also reducing pollution from current levels, a difficult task. In fact, Los Angeles County has long been at the forefront of adopting stricter regulations, emission controls and new technologies to combat toxic environmental pollutants and greenhouse gases. For the county’s Metro commuter rail line, this vision includes the incorporation of innovative systems and technologies that will affect a greener and sustainable transportation system.

To help fund this initiative, in 2009 Los Angeles County Metropolitan Transportation Authority received $4.5 million in federal stimulus funds through the FTA to install a wayside energy storage substation (WESS) at its Westlake/MacArthur Park Metro Red Line station. In the winning proposal, Ram Krishna, P.E., newly retired director of Project Engineering Systems for the Los Angeles County Metropolitan Transit Authority (LACMTA), detailed the various benefits of installing a WESS in a traction power application. To obtain the myriad of technical data needed to present his case, Krishna was assisted by his LACMTA staff in cooperation with Vycon Inc., a California-based flywheel energy storage manufacturer, and Turner Engineering, a leading U.S. consulting firm, specializing in rail traction power.

Krishna, now a consultant for his firm, Ram K Design and Construction Company, advocates building a technology solution that can store energy and put it to good use. In fact, during his tenure at LACMTA, Krishna helped the membership of the American Public Transportation Association (APTA) understand the advantages of energy storage and helped create the APTA Energy Storage Consortium. This consortium is now taking the lead for the rail industry in monitoring the progress of energy storage companies and any installations that may be accomplished in the United States.

Energy storage technologies applied to rail systems, says Krishna, “will improve the environment, save power costs, support utility companies’ peak power demands, and lower capital costs in new construction. Most transit traction power systems in the United States are missing an opportunity to save valuable energy.”

LACMTA is one of 43 transit agencies that will benefit from the $100 million U.S. Department of Transportation (USDOT) grant for cutting-edge environmental technologies to reduce global warming, lessen America’s dependence on foreign oil and create green jobs.

Capturing and Storing Energy

The WESS system will be a flywheel-based energy storage system, which captures the energy regenerated by trains as they brake into passenger stations. (Figure 1). In effect, the train propulsion motors are run in reverse to slow down and stop the train; therefore, these motors become generators, producing free energy using the train’s own inertia. Once this energy is captured, the WESS can store it until a peak load or strong energy demand is required. The maximum benefit is achieved by reducing the next peak-power demand, which is typically the same train leaving the passenger station a few minutes later. By capturing and reusing this wasted energy, LACMTA can reduce its total energy consumption and peak-power demand from the utility. The reduction of peak-power demand from these rail power systems is also a significant benefit for utility companies in Los Angeles, as demand can exceed supply during peak-usage periods, such as rush-hour afternoons and hot summer days. In addition, this process of energy demand reduction helps to reduce CO2 emissions — an ongoing goal in Los Angeles County.