New software simulates the impact of alternative fuels for freight trains

What would it look like if freight trains across the U.S. got on track with moving away from diesel?

Researchers at the Virginia Tech Transportation Institute (VTTI) recently created a nationwide multi-train simulation software, called NeTrainSim, to provide a clearer picture of this very situation.

The open-sourced model ran multiple simulations of the country’s network of freight trains powered by alternative fuel sources, such as electricity, biodiesel, hydrogen, and hybrids. The results are perhaps the first comparative analysis of an industrywide shift away from diesel.

“We now have some solid results that quantify the savings of transitioning freight trains to electric and other alternative fuel sources across the U.S.,” said Hesham Rakha, director of the Center for Sustainable Mobility at VTTI. “And this tool is now out there to be used by others. Anyone can run it on any rail network they want.”

The alpha version of NeTrainSim is available for download and the team’s findings were recently featured in the academic journal Applied Energy.

When compared with the current diesel-reliant network, the NeTrainSim’s results show the following:

• Electric powertrains are most efficient with a 56 percent reduction in energy consumption.
• Biodiesel and biodiesel-hybrid created carbon dioxide emissions reductions of 6 percent and 21 percent, respectively, while diesel-hybrid technology resulted in a 16 percent reduction in carbon dioxide emissions.
• Hydrogen fuel cell technology showed a 15 percent decrease in energy consumption with no carbon dioxide emissions.

Both the tool and information were presented at the Transportation Research Board’s annual meeting in January. A part of the National Academies of Sciences, Engineering, and Medicine, the weeklong event in Washington, D.C., brings together policymakers and government representatives with industry experts and academic institutions.

“NeTrainSim isn't just another train simulator, it's a comprehensive, innovative tool that pushes the boundaries of train simulation and offers valuable insights for the future of train technology,” said Ahmed Aredah, a graduate student researcher on the project slated to attend the meeting. “It's this pioneering spirit and practical application that I most want attendees to take away.”

Along with Aredah, Rakha’s research team also includes Jainhe Du, VTTI senior research associate; George List, professor in North Carolina State University’s Department of Civil, Construction, and Environmental Engineering; Andreas Hoffrichter, principal consultant with Deutsche Bahn E.C.O.; and Yue Cao, assistant professor in electrical engineering and computer science at Oregon State University.

The multi-train network simulation is one of five tools created as part of the larger, multi-university and multiteam project, Achieving Sustainable Train Energy Pathways. Funded by the U.S. Department of Energy, the project focuses on the decarbonization of the freight train industry with a goal of creating some of the first state-of-the-art open-sourced tools to assess variables related to the effort.

List, who was principal investigator for the larger project, said Rakha’s simulator added the real-world context of trains needing to interact with one another on the tracks.

“Railroads are not like highways in terms of trains passing each other. They are more like work zones on a highway,” List said. “It’s that meet and pass problem that Hesham’s software has figured out, and that’s a big deal, because even if railroads have crew change points, it’s a challenge to stop trains and has to be factored into energy consumption.”

Some of the simulation’s other features that make it distinct include the following:

• The ability to simulate extensive multi-intersecting corridor networks at the scale of countries and cities
• The use of train-following algorithms to track every train at user-specified intervals, such as every second, to maximize energy estimation accuracy
• An ability to account for the forces acting on the train to compute maximum acceleration rates and to modelsdriver behavior during different conditions
• An ability to model current and future powertrain technologies
  

To ensure the network simulation was a realistic portrayal, Rakha’s team benchmarked the simulation of all the trains running on diesel with nationwide freight train diesel consumption statistics running those same networks in real life.

“We were only off by 0.9 percent,” Rakha said. “So we’re fairly comfortable our results are well benchmarked against real empirical data in the U.S.”

The VTTI model’s focus was measuring efficiency at the tank or engine of the train, which means additional studies will be needed to evaluate the impact of factors such as the life of the battery and the technologies used to generate the electricity needed to power the electric trains. But Rakha believes the simulation provides enough information to motivate others in working toward decarbonization.

“The results give us some incentives for going and moving in that direction,” Rakha said. “I think policy makers can use these results as a means for requesting funding to do so.”

Rakha is also the Samuel Reynolds Pritchard Professor of Engineering in the Charles E. Via, Jr. Department of Civil and Environmental Engineering and a courtesy professor in the Bradley Department of Electrical and Computer Engineering.

Aredah is also a graduate student studying civil and environmental engineering as well as computer science.