For Gustav-Level Outages, Cities Tap Hybrid Buses for Power

By Joe Pappalardo
Secretary Michael Chertoff called this weekend’s evacuation measures involving charter and school buses in the New Orleans area a success, but BAE Systems may soon leverage military research to tap emergency power from hybrid-electric bus fleets for cities like San Francisco. (Photograph by Mike Lutz/DHS via Getty Images)

The reinforced levees held, battle-worn residents evacuated, and Hurricane Gustav faded over the Gulf Coast this Labor Day weekend with just one glaring lesson of Katrina left unfulfilled: Storm survivors need more emergency power.

In a stroke of good timing by city planners and bus manufacturers as approximately 1 millions homes and business fought to recover power throughout Louisiana and Mississippi, hybrid-electric bus fleets were beginning plans to retrofit to provide electricity during emergencies. Cities are already buying these vehicles because they reduce fuel costs and air pollution, but as the buses generate more power and manage it better with onboard computers, San Francisco and other trailblazing cities could become models for the hidden power of mass transit to disaster-prone urban centers like New Orleans, which has only restocked on biodiesel buses since Katrina.

Researchers at BAE Systems, a major vendor of municipal hybrid buses, are leveraging research done for the military to pitch cities on tapping power from mass transit buses. “If you’re going to have these power plants rolling around, it would be good to have them do something when they are not rolling around,” says Sean Bond, president of BAE’s Platform Solutions group. “The primary demand [for hybrid buses] was emissions reduction, and that has morphed into preventing greenhouse gasses and fuel savings. Another unintended consequence is the ability to provide power off the vehicle.”

Diesel-powered engines in hybrid electric buses store energy in batteries and use software to determine where and when extra power is needed, such as when a bus climbs a hill. These technologies could serve as the basis of mobile generators. However, it will take more than extension cords to make the scheme work. City buses run off DC power, but the electric grid uses AC at a different amplitude and frequency, so a converter is needed to use vehicles to connect to a power distribution panel.

The U.S. Army will power its next generation vehicles with hybrid power technology, but they are also planning to export power from the vehicles when they are not operating in the field. (The Army is also considering instilling the ability to export power from its current fleet of Mine Resistant Ambush Protected vehicles.) The Army uses a suitcase-size device called an Exportable Power Inverter to tap an armored vehicle’s supply of DC power for use on applications that run on AC power. In civilian disaster response, these converters could be installed on the buses, kept at the sites of vital facilities or included in the deployment kits of first responders. New buses could be built with outlets in place, while current fleets would need a retrofit in order to export power.

Diesel-powered engines in hybrid-electric buses provide energy that is stored in batteries, with software that determines where and when the extra power is needed, such as when a bus climbs a hill. BAE’s newest buses, expected to reach full rate production next year, produce 200 kilowatts when the engine speed is at 2300 rpms. BAE, using data of power consumption from national surveys, estimate a single city bus could provide power to 36 households for a full day or a 12,400 sq.-ft. hospital for 22 hours, on a single tank of diesel gas.

Ironically, cities with fleets of hybrid buses tend to be the places that already have the best contingency-power plans and generators. Still, having additional sources of power can only improve a city’s disaster planning. In 2006 San Francisco city officials chose to buy diesel electric buses in part because they could power command centers and move stalled electric vehicles like streetcars from intersections, according to Marty Mellera, the chief of green programs for the city’s transit authority. The buses are not yet ready to provide emergency power, but Mellera says planning with first responders is well underway.

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