Mounting health concerns coupled with soaring prices at the gas pump this summer have several school bus and engine manufacturers exploring an emerging technology already gaining traction in the consumer automotive market: hybrid engines.

Experts say the half diesel, half battery-powered machines would work similar to the environmentally friendly engines now being offered in the Toyota Prius or Honda Civic. The goal is to reduce overall fuel consumption and therefore limit the outflow of harmful emissions pumped into the air.

Bill Paul, editor of the industry publication School Transportation News, said school districts around the country already have begun testing variations of the technology through grants and corporate research projects.

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    Headquartered in San Diego, ISE Corp., a manufacturer of fuel-efficient technologies and drive systems for public transit, is in talks with The Education Foundation of Harris, Texas, and the state’s Adopt-A-School Bus Program–an extension of the EPA’s Clean School Bus USA initiative–to demonstrate 10 hybrid diesel-electric, ultra-low sulfur diesel school buses in the Houston area. The deal is still waiting for final approval.

    In an eMail message to eSchool News, Paul wrote that the school bus engine “would work similar to most hybrid cars, in that applying the brake would activate an integrated motor alternator, an electrical device that doubles as a motor and generator. When the vehicle is stopping, braking force is applied to the alternator that allows the vehicle’s momentum [to] create an energy current and send it to a battery pack. The stored energy also works in reverse, sent to the axle when the vehicle needs to accelerate.”

    According to ISE, this “mild-hybrid” drive system, which is a less expensive variant of a full-hybrid system used in transit and large truck fleets for decades, not only reduces brake pad wear, but also reduces fuel consumption.

    Energy consulting firm Advanced Energy is pursuing a similar project in North Carolina. The company says it hopes the engines will improve the overall efficiency of energy use, making power sources cleaner and easier to control, while letting school bus operators switch between battery and diesel fuel power to reduce smog-causing emissions.

    Schools also have begun to experiment with the concept of full-electric school buses, charged on batteries and natural-gas engines, which reportedly emit 10 times less soot and 40 percent less smog-producing pollutants than their commercial diesel counterparts, according to a 2002 journal article published by the Union of Concerned Scientists. But a lack of available fueling and power sources means those technologies are expensive. The alternatives also have run into problems when it comes to generating enough horsepower to drive the larger buses. So far, there are no hybrid school bus engines available for schools to buy. Chuck Hanlon of engine manufacturer Cummins Inc. says that’s because the technology remains largely cost-prohibitive for most school bus fleets. According to Hanlon, hybrid engines sell for 50 percent more than the cost of a standard EPA-approved, low-emission diesel device.

    In one of the largest hybrid/public transit experiments in the country, Cummins is currently working with New York City to install the breakthrough engines in several of its metro transit buses, Hanlon said, though specifics were not available.