A new study from researchers at MIT uncovers the kinds of infrastructure improvements that would make the biggest difference in increasing the number of electric cars on the road, a key step toward reducing greenhouse gas emissions from transportation.

The researchers found that installing charging stations on residential streets, rather than just in central locations such as shopping malls, could have an outsized benefit. They also found that adding on high-speed charging stations along highways and making supplementary vehicles more easily available to people who need to travel beyond the single-charge range of their electric vehicles could greatly increase the vehicle electrification potential.

A paper on the findings is published in Nature Energy.

The researchers developed a new methodology to identify charging solutions that would conveniently fit into people’s daily activities. They used data collected from GPS tracking devices in cars, as well as survey results about people’s daily driving habits and needs, including detailed data from the Seattle area and more general data from the US as a whole.

Greatly increasing the penetration of electric cars into the personal vehicle fleet is a central feature of climate mitigation policies at local, state, and federal levels, says corresponding author MIT associate professor of energy studies Jessika Trancik. A goal of this study was “to better understand how to make these plans for rapid vehicle electrification a reality,” she adds.

In deciding how to prioritize different kinds of improvements in vehicle charging infrastructure, the team built a better understanding of people’s detailed energy consuming behavior, throughout the day and year.

While the vast majority of people’s daily driving needs can be met by the range provided by existing lower-cost electric cars, as Trancik and her colleagues have reported, there are typically a few times when people need to drive much farther. Or, they may need to make more short trips than usual in a day, with little time to stop and recharge.

These “high-energy days,” as the researchers call them, when drivers are consuming more than the usual amount of energy for their transportation needs, may only happen a handful of times per year, but they can be the deciding factor in people’s decision making about whether to go electric.

Even though battery technology is steadily improving and extending the maximum range of electric cars, that alone will not be enough to meet all drivers’ needs and achieve rapid emissions reductions. Addressing the range issue through infrastructure is essential, Trancik says. The highest-capacity batteries tend to be the most expensive, and are not affordable to many, she points out, so getting infrastructure right is also important from an equity perspective.

Being strategic in placing infrastructure where it can be most convenient and effective—and making drivers aware of it so they can easily envision where and when they will charge—could make a huge difference, Trancik says.

Providing easy access to alternative transportation for those high-energy days could also play a role, the study found. Vehicle companies may even find it advantageous to provide or partner with convenient rental services to help drive their electric car sales.

In their analysis of driving habits in Seattle, the team found that the impact of either adding highway fast-charging stations or increasing availability of supplementary long-range vehicles for up to four days a year meant that the number of homes that could meet their driving needs with a lower cost electric vehicle increased from 10% to 40%. This number rose to above 90% of households when fast-charging stations, workplace charging, overnight public charging, and up to 10 days of access to supplementary vehicles were all available.

Importantly, charging options at residential locations (on or off-street) is key across all of these scenarios.

The study’s findings highlight the importance of making overnight charging capabilities available to more people. While those who have their own garages or off-street parking can often already easily charge their cars at home, many people do not have that option and use public parking.

The study was supported by the European Regional Development Fund, the Lisbon Portugal Regional Development Program, the Portuguese Foundation for Science and Technology, and the US Department of Energy.

Resources

• Wei, W., Ramakrishnan, S., Needell, Z.A. et al. (2021) “Personal vehicle electrification and charging solutions for high-energy days.” Nat Energy 6, 105–114 doi: 10.1038/s41560-020-00752-y