The big yellow school bus drops the kids off at school and returns to the bus yard for a few hours of rest before the afternoon run.
Then it does something unique among Wake County school buses: it plugs in.
The bus—which runs on diesel and an electric battery—is part of a growing movement among school districts to cut down on gas costs while helping the environment. Spurring it on is Ewan Pritchard, a doctoral student in mechanical engineering who helped develop the hybrid plug-in technology.
“The plug-in hybrid kind of gives you all the benefits of the electric vehicle as well as the reliability of both systems added on to one another,” he said.
Pritchard dates his fascination with hybrids to the 11 th grade at Raleigh's Enloe High School. He wasn't a very good student at the time, but when he was assigned a project on alternative-fueled vehicles, the hybrid bug hit him. He got his grades up, and decided he wanted to spend the rest of his life working on new ways to power cars and trucks.
“It was like a light switch,” he said. “I mean, it just flipped.”
So Pritchard headed to NC State, eventually getting bachelors and masters degrees in mechanical engineering. His master's thesis examined the possibilities of the plug-in hybrid school bus, finding that school districts could save money and cut emissions by using them. He estimates that such buses can achieve a 95 percent increase in fuel economy for the first 45 miles of a trip, with a 40 percent improvement the rest of the way. School buses usually average between 50 and 150 miles per day.
It takes money and energy, of course, to recharge the buses' batteries. But in the end, Pritchard notes, the cost of electricity is equal to a gallon of fuel that costs 60 cents.
These days, Pritchard is pursuing is doctoral degree and working for Advanced Energy, a non-profit on Centennial Campus that's working with governments in several states to bring hybrid buses to more schools. Thirteen buses have been delivered to date and several more are on the way.
Sponsors of the project include Duke Energy, Progress Energy and the New York Power Authority. At NC State, Pritchard is working with Dr. Mo-Yuen Chow in the Department of Electrical and Computer Engineering; Dr. Chris Frey in the Department of Civil, Construction and Environmental Engineering; and Dr. Rich Gould in the Department of Mechanical and Aerospace Engineering.
Eventually, Pritchard and the company want to demonstrate the successful operation of an entire fleet of plug-in hybrid school buses. Adding heft to the plan is International Truck and Engine, the largest bus manufacturer in North America, which is producing the hybrid buses. And while auto manufacturers are promising plug-in models in the next few years, Pritchard said, the plug-in school bus is available today.
“We fully believe,” Advanced Energy's Web site reads, “that (the) final phase of the project will complete the transformation of the school bus market so that all new school buses will be plug-in hybrids.”
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