Purdue Project Targets CVs, Buses for Hybrid Technology

Purdue University launches a research project aimed at cutting commercial-vehicle fuel consumption in half by perfecting hybrid technologies for bus and truck fleets worldwide.

The Hoosier Heavy Hybrid Center of Excellence is funded with a $1 million grant from the U.S. Department of Energy's Graduate Automotive Technology Education initiative.

Purdue is providing the center with more than $500,000 to cover tuition for up to eight fellowships.

Purdue doctoral students Dan Van Alstine and Karla Stricker work on diesel-engine test platform.

Gregory Shaver, an associate professor of mechanical engineering and the center's principal investigator, says buses and trucks, particularly vehicles used to transport goods, represent a huge percentage of global fuel consumption and tailpipe emissions.

“There is a lot of potential to increase the efficiency of these vehicles,” Shaver says in a statement.

The 5-year project, under the umbrella of the Purdue Energy Center Advanced Ground Vehicle Power and Energy Storage initiatives, aims for a 50% reduction in CV fuel consumption and greenhouse-gas emissions.

Center director Maureen McCann, a professor of biological sciences, says the savings in energy efficiency is critical. “If you can double energy efficiency, you are halving your fuel consumption. That's huge.”

Purdue says reducing CV fuel consumption by 50% would cut petroleum use by about 15 billion gallons (56.7 billion L) a year, corresponding to a reduction of 155 million tons (141 million t) of carbon dioxide.

Maryam Saeedifard, an assistant professor of electrical and computer engineering and co-director of the center, says growth in e-commerce is leading to significant increases in the number of trucks needed to transport goods.

Annual e-commerce spending in the U.S. grew by almost 100% last year, the university says.

“The explosive growth in e-commerce is a positive outcome for the U.S. and global economies, but requires an increase in the number of trucks to transport goods,” Saeedifard says.

“This need creates a significant economic opportunity for U.S. companies that are heavily engaged in the commercial-vehicle market. The center will work toward solving technical challenges and training engineers and scientists.”

The center already has signed up industrial partners including Cummins, Delphi, Ener1, Allison Transmission and the Energy Systems Network, an initiative of the Central Indiana Corporate Partnership focusing on clean-energy technologies in Indiana.

Commercial vehicles consume far more fuel on a per-vehicle basis than passenger cars, averaging 6.2 mpg (38 L / 100km) and 74,000 miles (119,000 km) a year, compared with 21.1 mpg (11.1 L / 100km) and 10,000-12,000 miles (16,100-19,300 km) a year for automobiles.

“As the global truck markets continue to grow, fuel consumption and greenhouse-gas emissions will increase,” Shaver says. “Any attempt to significantly reduce fuel consumption and emissions must focus not only on the U.S. truck market but also on global markets.”

Each CV consumes an average of 11,900 gallons (45,000 L) of fuel a year, while autos use an average of 570 gallons (2,150 L).

“The greater fuel consumption of commercial vehicles means that fuel reduction, associated with technology improvement, is much greater for commercial vehicles on a per-vehicle basis,” Shaver says.

“For each commercial hybrid vehicle on the road, 20 light-duty automotive hybrids would need to be in operation to achieve a comparable fuel savings.”

Hybrids also can provide considerable economic benefits.

“One of the biggest cost drivers for fleet owners and operators that run all these vehicles is fuel,” Shaver says. “If your fuel costs go down, your bottom line improves and you can hire more people.

"If we can help them in the short and medium term with their technology challenges, that's great for business, and at the same time we're training students to work in industry.”

Purdue is creating a certificate program for graduate students in medium- and heavy-duty hybrids.

“We keep hearing from industry that there is a shortage of engineers, and we're helping to address that issue,” says Vahid Motevalli, head of the department of mechanical engineering technology.

Challenges include learning how to better integrate vehicles' powertrain components, comprising the engine, transmission and other elements.

“Often the major parts of the powertrain are built by companies that don't make the vehicle itself, so they may not be tailored for the vehicle they are used in,” Shaver says. “For hybrids to be optimized, these components need to be integrated properly.”

Another challenge is to design heavy-duty regenerative braking systems, in which electric motors serve as generators while the vehicle is braking. Regenerative braking already is used in hybrid cars, but such systems are difficult to design for heavy vehicles.

“There are very large braking-energy rates in heavy-vehicle stopping and much more energy to capture,” Shaver says. “So, how do you capture the energy and also handle the energy flow?”

Researchers will develop regenerative braking systems that store energy by compressing hydraulic fluid in a tank-like accumulator. High-pressure fluid in the accumulator would drive a hydraulic motor, providing torque to the wheels and saving fuel.

They also will look to improve efficiency by recovering waste heat from the exhaust.

“More than half of diesel-engine exhaust is lost to waste heat out the tailpipe or radiator,” Shaver says. “If you could better harvest that waste heat, you could make the whole powertrain more efficient.”