Metro officials met with representatives from the Federal Transit Administration and the National Renewable Energy Laboratory last week to review promising results of the agency’s first-of-a-kind use of flywheel technology to recycle power generated from rail cars.
Officials met at the Westlake/MacArthur Park Metro Red/Purple Line Station to see firsthand how the Wayside Energy Storage Substation works. The pilot project started in August and is now saving Metro up to 18 percent of the energy normally used to power subway trains entering and leaving the station. That, in turn, helps lower Metro’s electricity bills.
The project is managed by Metro’s Project Engineering Department and uses a state-of-the-art flywheel system built by Vycon of Cerritos. The brain of the system, which assures the precise control of the flow of power, was developed by Turner Engineering of Venice. Metro performed its installation in-house, without external contractors.
The system was therefore entirely developed and implemented with resources local to the Los Angeles County. It is estimated that Metro will eventually save approximately $100,000 per year in electricity costs because of the project.
A grant of $4.5 million was awarded to Metro by the FTA TIGGER (Transit Investments for Greenhouse Gas and Energy Reduction) grant program that helps transit agencies implement new strategies to cut greenhouse gas emissions and energy use for transit operations.
Here’s how it works. The trains have regenerative braking systems that create electricity as the train slows to a stop at the station. The flywheel is like a mechanical battery that stores energy in a kinetic form by rotating a heavy steel cylinder up to 20,000 rpm. In order to keep friction to a very minimum, the flywheel cylinders are kept in a vacuum chamber and in magnetic levitation. They are more reliable, cleaner and more efficient than chemical batteries.
That stored energy in the flywheel is then reapplied to the train’s propulsion system to help the acceleration of the same or other trains departing the station. During this pivotal high power, short discharge sequence, the flywheel’s stored electricity actually replaces power that would otherwise have come from the electric utility company and turned into heat in the train cars’ resistors.
The system consists of a flywheel-based substation with a two-megawatt power rating (pictured above) and approximately eight kilowatt-hours of energy per cycle. The system is ready to have its capacity extended to six megawatts to further increase its energy savings capabilities. Even though the costs of this initial prototype are somewhat high due to the development and research effort involved, the system is expected to save, in one year, enough energy to power an average household in California for about 100 years.