Toward a greener tomorrow

Multidisciplinary research is leading to clean, efficient, fuel-flexible vehicles.

Tight budgets, environmental pressures and rising energy demand — all challenges facing the world today. 

The International Energy Agency (IEA) says the highest priority should be on becoming energy-efficient, as this offers the highest potential for reducing carbon emissions at the lowest cost. In practice, however, it can be challenging to capture these benefits. 

Right now, the energy we use doesn’t work nearly hard enough for us. The process of transforming energy resources and then using them is so inefficient that we lose most of the potential energy value of our energy resources. Faced with finite fossil fuel supplies and rising demand, this situation is simply unsustainable.

This is why Purdue Engineering researchers are examining ways to make the energy we already use work harder for us while developing new, cost-effective alternatives. By increasing our energy productivity, or efficiency, we can do more with less.

Hoosier Heavy Hybrid Center of Excellence

The Hoosier Heavy Hybrid Center of Excellence (H3CoE) at Purdue was funded with a $1 million grant from the U.S. Department of Energy’s Graduate Automotive Technology Education initiative.  The goal is aimed at cutting fuel consumption in half for commercial vehicles by perfecting hybrid technologies for the world’s burgeoning bus and truck fleets.

Purdue doctoral students Dan Van Alstine and Karla Stricker, who now works at the Cummins Technical Center, work on a diesel-engine test platform at the Ray W. Herrick Laboratories. The work is related to a new effort aimed at cutting fuel consumption in half for commercial vehicles by perfecting hybrid technologies for the world's burgeoning bus and truck fleets. The new 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 University photo/Mark Simons)

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

“There is a lot of potential to increase the efficiency of these vehicles,” says Shaver, who co-directs the center with Maryam Saeedifard, assistant professor of electrical and computer engineering.

Additional faculty making up the project management team include Vahid Motevalli, professor of mechanical engineering technology; James Caruthers, the Reilly Professor of Chemical Engineering; Eric Dietz, associate professor of computer and information technology; and Monika Ivantysnova, Maha Fluid Power System Professor of Mechanical Engineering and Agricultural and Biological Engineering.

The project, which falls under the umbrella of the Purdue Energy Center Advanced Ground Vehicle Power and Energy Storage initiatives, seeks to achieve a 50 percent reduction in commercial vehicle fuel consumption and greenhouse gas emissions. The five-year project began Oct. 1, 2011.

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

Reducing fuel consumption for commercial vehicles by 50 percent would cut petroleum use by about 15 billion gallons per year, corresponding to a reduction of 155 million tons of carbon dioxide. 

The United States is the world’s largest oil user, consuming nearly 20.7 million barrels per day. U.S. consumption is expected to grow moderately, but consumption in developing countries is expected to skyrocket in coming years. China consumes about 7.6 million barrels per day, and the rate is expected to grow at 9 percent annually.

“This trend in China is due in large part to the increased use of commercial vehicles,” Shaver says. 

Growth in e-commerce is one phenomenon leading to significant increases in the number of trucks needed to transport goods. Annual e-commerce spending in the United States grew by nearly 100 percent in 2010.

“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. Indiana companies can benefit through the global market. The center will work toward solving technical challenges and training engineers and scientists who will be ready to make contributions.”

The work includes industrial partners Cummins Inc., Allison Transmission Inc., Navistar and the Energy Systems Network, an initiative of the Central Indiana Corporate Partnership focusing on clean-energy technologies in Indiana. The project management team is reaching out to additional prospective industry partners, Shaver says.

Commercial vehicles consume far more fuel per vehicle than passenger cars, averaging 6.2 mpg and 74,000 miles per year, compared with 21.1 mpg and between 10,000 and 12,000 miles per year for light-duty automotive vehicles.

“This results in a drastic difference in fuel consumption on an annual basis,” Shaver says. “As the global truck markets continue to grow, fuel consumption and greenhouse gas emissions will increase. 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 commercial vehicle consumes an average of 11,900 gallons of fuel per year, whereas light-duty automotive vehicles consume an average of 570 gallons of fuel annually.

“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 could provide large economic benefits

Shaver says one of the biggest costs for fleet owners and operators is fuel. “If your fuel costs go down, your bottom line improves and you can hire more people.”

Companies operating in Indiana, such as Cummins and Allison, sell vehicle components globally, so solving technological challenges associated with medium- and heavy-duty hybrid vehicles could benefit
the local economy.

“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,” Shaver says.

The program includes fellowships for students, an annual workshop, seminar series and the creation of a new course on medium- and heavy-duty electric hybrid vehicles. A new certificate program for graduate students in medium- and heavy-duty hybrids has been developed.

“We keep hearing from industry that there is a shortage of engineers, and we’re helping to address that issue,” Motevalli says. “This graduate student research and education grant, along with the Advanced Electric Drive Vehicle Education Program and EcoCar 2 Student Vehicle competition, are putting Purdue in a unique position to play a leading role in the emerging field of hybrid vehicles and powertrain electrification.”

Challenges include learning how to better integrate the various components in the vehicles’ powertrains, encompassing the engine and 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.”

Putting the brakes on lost energy

Another challenge is to design heavy-duty regenerative braking systems, in which electric motors can serve as generators while the vehicle is braking, producing power to recharge the battery pack. Researchers involved in the center also are developing regenerative braking systems that store energy by compressing hydraulic fluid in a tanklike “accumulator.” High-pressure fluid in the accumulator would be used to drive a hydraulic motor, providing torque to the wheels and saving fuel.

While regenerative braking already is used in hybrid cars, such systems are especially 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?” Saeedifard’s research is focused on using power electronics-based solutions to address these issues. 

Another step needed to improve efficiency is 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 power train more efficient.”

The research will be performed at the Ray W. Herrick Laboratories, Maha Fluid Power Research Center, Energy Conversion Research and Energy Systems Simulation Laboratories and others.