Biodiesel to help fuel hydraulic hybrid bus

Students from the Georgia Institute of Technology in Atlanta, in collaboration with The Ford Motor Fund, are in the midst of converting a 16-passenger school bus—called the “Green Eco School Bus”—into a hydraulic hybrid vehicle that’s capable of running on biodiesel. Hydraulic hybrids are similar to electric hybrids but instead of using batteries, they use lightweight components and clean fluid to power the vehicle while at slow speeds. Atlanta Public Schools donated the bus for the project.

While focus is placed on the development of the hybrid hydraulic system, Michael Leamy, assistant professor of mechanical engineering at Georgia Tech and lead on the project, told Biodiesel Magazine that he and his students intend to look how they could get donations of used cooking oil from large restaurant chains to produce biodiesel. To get an idea of the feasibility of aggregating the used cooking oil, Leamy and his students conducted a two-week pilot study to see how much waste oil they could get at the school.

“We only got a couple gallons and that was a little disappointing, but we did get feedback from area restaurant owners within the community saying that they’d be willing to supply their waste grease in the future,” Leamy said. “So, I think there’s potential there to get oil from the community and then convert it into biodiesel. We’re also looking at the school kitchens themselves, state prisons, state offices and any office associated with the state where we might be able to get their oil to convert into biodiesel.”

Leamy said he’d like to eventually see the bus run on a B20 blend, but added that much more used cooking oil would have to be collected than during its pilot study. “If we can get to B20 that would be excellent,” he said, “but even B20 is probably going to require more oil than we could collect, I imagine.”

The project, funded by a $50,000 Ford College Community Challenge Grant, began about eight months ago, according to Leamy, and hopes to have the bus fully operational by summer. “We have the transfer case in, got the accumulators mounted and, with any luck, the pump motor will go in this week,” Leamy said.

Leamy said the project also includes a cost-benefit analysis of a large-scale conversion of a school bus fleet to hydraulic hybrid powertrains designed to recover lost braking energy. “In simulation, we predict around a 20 percent fuel economy improvement with this hydraulic hybrid onboard,” he said. “That’s a very high fidelity simulation that takes into account losses, inefficiencies and uses of drive-cycle, so it’s not a ‘back-of-the-envelope’ kind of ideal calculation.”

He added, “What we hope to do is wrap up the actual build and then start testing and see if our numbers compare to our simulation numbers, and then determine what the cost-benefit is doing both of these conversions—the biodiesel and they hydraulic hybrid components.”

Students at Mary Lin Elementary School are painting the bus green and organizing a drive to collect used cooking oil to be converted into biodiesel. Atlanta Public School officials are using the project to educate youth about the benefits of ecofriendly bioenergy and biofuels, such as biodiesel.

“Our students are eager to learn about new ways to care for the environment,” said Brian Mitchell, principal at Mary Lin Elementary. “The Green Eco School Bus turns a theoretical concept into a fun and exciting reality that stimulates their learning.”