NC State computer model plots best locations for EV chargers


With the number of electric vehicles expected to soar in coming years, transportation officials across the country are laying plans for a broad network of charging stations.

One thing they’ll have to keep in mind: A fast-charging power station needs a constant flow of electricity. A fast-charging power station that can recharge several vehicles at a time requires a constant flow of a whole lot of electricity — in some places more than today’s electric infrastructure can deliver.

To begin to address that problem, researchers at North Carolina State University have created a computer model that identifies places where drivers will need to recharge and aligns them with places that can actually supply enough electricity to handle the demand.

Transportation officials worry about how to design, build and maintain roads and traffic. The ideal charging locations would be where cars can get to easily — like grocery stores and places right off-highway.

Unlike gas stations, which fill underground tanks with a liquid product, charging stations require power networks to transmit electricity. Power grids, such as high voltage towers and transmission lines, may not be easily accessible.

“The best locations for a charging facility and for a power system are not the same,” said Asya Atik, a transportation engineer and one of the authors of the N.C. State report.

Other studies have tended to consider the problem from just one point of view — either the most convenient locations for people driving cars, or where can the grid supply enough power to recharge a steady stream of vehicles.

The N.C. researchers used a computer model to identify the best locations in cities by considering both.

“This study is exciting,” said Scott Moura, a professor in the Department of Civil and Environmental Engineering at the University of California, Berkeley, who also researches charging facilities, ”because it’s one of the few to understand how the power and transportation network interact when they are linked by fast-charging stations.”

The N.C. State model generates locations with the lowest building cost for both transportation and electricity networks.

People who want to charge their cars think and act in ways that network infrastructures do not. They look for the quickest solution to save time and money.

Detours for cheaper charging fees could change electricity and traffic flow. As a result, new energy and transportation infrastructure will have to accommodate the changes, such as how much power the chargers need to deliver.

The model mimics drivers’ behavior by ensuring that electric car users travel as quickly as possible. By considering the best interests of both networks and drivers, even before actually building out the stations, the computer model balances the needs of all of the players.

Interstate map of electric vehicle charging station across East Coast studied by Hajibabai at North Carolina State University Map courtesy of Leila Hajibabai

Juicing up on the road

Researchers used this approach to first study streets in Raleigh, Durham, and Chapel Hill that are within the commuting range of the university.

They highlighted the charging station candidates that link to the current power grid on N.C. State campus. Instructors, students, and visitors to campus who drive from one of the cities may find themselves charging their cars in one of the parking spaces in the future.

According to Leila Hajibabai, the professor who leads the research, the conversation about expanding the charging network on campus and in Raleigh is ongoing.

Raleigh has more than 200 public charging stations but only 13% of them are fast chargers. Durham has five fast chargers and Chapel Hill has none, according to Charge Hub, which maps charging stations.

Deployment of faster chargers, which requires high energy output, will be a future challenge for the federal and state governments as well as private local utilities, according to Moura.

The electricity consumption of charging stations is similar to people’s daily lives, but instead of a couple of kilowatts, “it’s hundreds of kilowatts for each person,” he said.

This new study could estimate how powerful each charging station should be without putting too much strain on the local power grid, Hajibabai said.

Hajibabai’s work is “a step forward in the planning for electric vehicle charging infrastructure,” said Ramteen Sioshansi, a professor in the Department of Electrical and Computer Engineering at Ohio State University.

Predicting drivers’ behavior, whether they would use the stations or not, is a challenge that future studies might need to address, he added.

Connecting the dots of in-city power and traffic networks is only one piece of the puzzle of finding the best charging locations.

If the riders need to drive farther than the range of their electric car, they must stop at least once. The question becomes where they can stop when on a road trip.

“One of my concerns … is the range restriction — whether I’ll be able to find charging stations available for long-range trips,” said Atik.

Researchers used the new algorithm to determine the best places to stop along the East Coast, from Atlanta to Philadelphia.

The interstate model selects large cities with a high density of charging needs for various car brands based on their maximum traveling distance. Raleigh and Charlotte are two of the major cities chosen for such East Coast networks.

Surprisingly, small towns that don’t often contemplate building charging stations require some of these capabilities, according to the study.

“People wouldn’t think about putting charging stations in a small city but they’re necessary,” Atik added.

Deploying in advance

The U.S. Office of Energy and Transportation will invest $5 billion in charging networks by 2030, and this study could help determine the best locations for charging stations throughout highways and roadways.

“We are modernizing America’s national highway system for drivers in cities large and small, towns and rural communities, to take advantage of the benefits of driving electric,” the press release said.

The experts in charging networks, Moura and Sioshansi, both said that government, especially regional planning organizations, should pay attention to this new computer model for public interests and policy decisions.

Hajibabai believes their findings will broaden charging options for diverse demographics, including the elderly and people with disabilities. Hospitals and airports, which face different issues than city neighborhoods, might also benefit from the study.

“We want to make a positive impact on society,” she added, “our existing efforts are ongoing.”

This story was originally published June 29, 2022 5:45 AM.

Profile Image of Chiungwei Huang

Chiungwei Huang covers science for The News & Observer as a 2022 AAAS Mass Media Science and Engineering Fellow. She is a UNC-CH graduate with a Ph.D. in physical chemistry and is from Taiwan.


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