Minimizing EV impact on the grid


National and global plans to combat climate change include increasing the use of electric vehicles and the percentage of electricity generated from renewable sources. But some projections show that these trends could require new power plants to meet peak loads in the evening when cars are plugged in to charge after the workday. What’s more, overproduction of solar energy during the daytime can waste valuable electricity-generation capacity, according to a new study by the Massachusetts Institute of Technology (MIT).

MIT researchers have found that it’s possible to mitigate or eliminate daily EV charging demand and solar over-capacity without the need for technological upgrades of connected devices and real-time communications, which could add to costs and energy consumption. The study was published in the March 15 issue of Cell Reports Physical Science journal by Zachary Needell (PhD, 2022), post-doc Wei Wei and Professor Jessika Trancik of MIT’s Institute for Data, Systems and Society.

Instead, the placement of EV charging stations in strategic locations and setting up charging systems to initiate charging at delayed times could potentially make all the difference.

In the MIT analysis, researchers culled data collected in New York and Dallas. Data was gathered from anonymous records collected from onboard EV devices, as well as surveys that sampled populations to examine travel behavior. The data tracked residential, workplace, shopping and entertainment location EV driving habits.

Better availability of charging stations at workplaces, for example, could help EVs “soak up peak power being produced at midday from solar power installations,” which might otherwise go to waste because it is not economical to build enough battery or other storage capacity to save all of this solar energy for later in the day. Thus, workplace chargers can provide a double benefit, helping to reduce the evening peak load from EV charging and also making use of the solar electricity output, according to Trancik.

The effects on the electric grid are considerable, especially if the system must meet charging demands for a fully electrified personal EV fleet alongside demand energy peaks in other instances such as late summer energy usage of air conditioning units. If unmitigated, the evening peaks in EV charging demand could require installing close to 20% more power generation capacity, the researchers said.

“Slow workplace charging can be more preferable than faster charging technologies for enabling a higher utilization of midday solar resources,” said postdoc student Wei Wei.

Meanwhile, using delayed home charging, each EV charger can be accompanied by a simple app to estimate the time of charging cycles so that the EV charges just before it is needed the next day. Unlike other system proposals that require a centralized control of the charging cycle, such a system needs no inter-device communication of information and can be preprogrammed to accomplish a major shift in the demand on the grid caused by increasing EV penetration.

For home charging, the researchers aren’t just referring to charging equipment in garages or parking areas. They say it is expanded to include on-street parking locations and apartment building areas as well.

Trancik says the findings highlight the value of combining the two measures — workplace charging and delayed home charging — to reduce peak demand, store solar energy, and meet drivers’ charging needs on all days. As the team showed in earlier 2021 research, home charging can be an effective component of a strategic package of charging locations. Workplace charging, they have found, is not a good substitute for home charging to meet drivers’ needs on all days.

“Given that there’s a lot of public money going into expanding charging infrastructure, how do you incentivize the location such that this is going to be efficiently and effectively integrated into the power grid without requiring a lot of additional capacity expansion?,” said Trancik. This research offers some guidance to policymakers on where to focus rules and incentives.

“I think one of the fascinating things about these findings is that by being strategic you can avoid a lot of physical infrastructure that you would otherwise need,” she says. “Your EVs can displace some of the need for stationary energy storage, and you can also avoid the need to expand the capacity of power plants, by thinking about the location of chargers as a tool for managing demands — where they occur and when they occur.”

Delayed home charging could make a surprising amount of difference, the MIT team found. “It’s basically incentivizing people to begin charging later. This can be something that is pre-programmed into EV chargers. You incentivize people to delay the onset of charging by a bit, so that not everyone is charging at the same time, and that smooths out the peak,” Trancik said.

It’s not a given that all this would line up just right, and putting in place the right mix of incentives would be crucial. “If you want EVs to act as an effective storage technology for solar energy, then the [EV] market needs to grow fast enough in order to be able to do that,” Trancik says.

To best use public funds to help make that happen, she says, “you can incentivize charging installations, which would go through ideally a competitive process — in the private sector, you would have companies bidding for different projects, but you can incentivize installing charging at workplaces, for example, to tap into both of these benefits.” Chargers people can access when they are parked near their residences are also important. Home charging is one of the ways to meet charging needs while avoiding inconvenient disruptions to people’s travel activities.

The study was supported by funding from the European Regional Development Fund Operational Program for Competitiveness and Internationalization, the Lisbon Portugal Regional Operation Program, and the Portuguese Foundation for Science and Technology.

Jessika Trancik has been an MIT professor at the Institute for Data, Systems and Society since 2010, and focuses on energy service projects including electricity, transportation, heating, and industrial processes. Her work spans solar, wind power, energy storage, low-carbon fuels, EVs, and nuclear fission.

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