The San Francisco Municipal Transportation Agency (SFMTA) has selected BAE Systems to supply electric power and propulsion systems for its transit buses. BAE Series-ER (Electric Range) systems will operate on 68 transit buses and support designated green zone routes throughout San Francisco that are free of emissions.

BAE’s series hybrid system features no mechanical link between the diesel engine and the axle. All power comes from the electric motor. Power flows in series from engine to generator to traction motor.

Series-ER, based on the same components of BAE’s Series-E series hybrid electric system, extends electric driving range and provides electric operating modes such as:

• Extended EV range: Driving on all-electric power in no- or low-emission areas can be programmed according to each transit agency’s specifications, to shut the engine off in a tunnel or other preferred areas.

• Electric accessories: Accessory Power System options can power all conventional electric loads, such as cooling fans and pumps, plus all hybrid cooling systems.

• Stop/start technology: With bus accessories powered by the Accessory Power Systems (APS), the engine can be shut off at stops to prevent idling and emissions. The stop/start function can be programmed with a global positioning system to automatically shut down the engine at specified locations.

• Depot drive: The engine can be shut down in specified locations to allow for electric drive mode in low- and no-emission areas, when traveling < 500 yards.

Series-ER components

The system opens a new door for San Francisco to get to zero emissions by 2035, as each bus will now be able to drive on clean electric power through each of the areas – known as “green zones.” Buses can now switch to battery power from a combustion engine, temporarily eliminating diesel emissions when they cross the threshold of a green zone. The technology allows the city to convert the fleet into part-time electric buses as an intermediate step to full electrification.

This technology helps San Francisco get one step closer to full zero emissions operations, improving the health of the city’s environment and its residents. With Series-ER, buses are programmed using global positioning software to turn off the bus engine once it enters the green zone and operate solely on electric battery energy.

—Steve Trichka, vice president and general manager of BAE Systems’ Power and Propulsion Solutions business

BAE Systems is helping cities around the world get to zero emissions with electric power and propulsion systems for transit buses. But the path to zero for each city is unique, so the company is getting creative. For cities like San Francisco, that means using BAE Systems technology to create green zones.

The nine green zones are located in population-dense neighborhoods most affected by air pollution. Each of the zones have a large presence of traffic that is contributing to a high rate of air pollution.

Initial SF Muni Green Zone routes.

While green zones are picking up speed in San Francisco, the city is not alone. Boston, Louisville, Montreal, Nashville, and Seattle are using Series-ER technology to cut down emissions. Series-ER has also made the trip overseas to the United Kingdom, where it is powering new double deck buses in Brighton.