Electric Vehicles

NREL Report Assesses Value In Managed EV Charging Strategies

Managed electric vehicle charging offers “significant potential benefits for the grid,” such as demand side flexibility, according to a new report from the National Renewable Energy Laboratory (NREL).

The NREL researchers conducted a literature review of research papers on the potential value of electric vehicle charging to better understand how electric vehicles and the electric grid can work together as the electric and transportation sectors become more intertwined.

The simplest form of electric vehicle managed charging – sometimes called smart charging – is time-of-use pricing that offers lower electricity rates to charge an electric vehicle during off-peak periods. More sophisticated managed charging plans control charging based on a user’s travel needs and grid conditions. In the most sophisticated managed charging systems, electric vehicles can act as temporary electricity suppliers by sharing power back to the grid.

The report, published in Energy & Environmental Science, summarizes findings from hundreds of studies considering multiple value streams for the power system, enablement costs, and perspectives of different stakeholders, including utilities, electric vehicle owners, charging station operators, and rate payers.

“Managed charging can be a tremendous resource for the grid but there are trade-offs to solutions at different levels of commercial readiness,” Matteo Muratori, NREL analyst and principal investigator of the study, said in a statement. “Some solutions offer a wider range of grid services and value streams but require increasingly complex communication and control technology and demands on users, which come with a cost.”

Among the benefits, the NREL researchers identified decreased emissions, improved reliability, support for large-scale deployment of variable generation, and lower power system costs. “Some studies show that EV managed charging could provide thousands of dollars of value per EV every year,” the researchers said.

Although the power system will likely require upgrades to handle higher levels of electric vehicle charging, managed charging has the potential to improve system efficiency and lower average retail electricity rates for all consumers, not just electric vehicle owners, the researchers found. Managed charging is particularly valuable in systems with high levels of variable renewables to provide flexibility to match supply and demand, they said. In contrast, power system cost savings from managed charging is lower in systems with other sources of flexibility, they added.

The strategy used to deploy electric vehicle charging stations can change the benefits available to the grid. If electric vehicle managed charging is based solely on minimizing owner costs with no consideration of the grid, “it could negatively impact system cost and operation,” the NREL researchers said.

In addition, the benefits of managed charging for distribution systems are more difficult to nail down, the researchers found. “Distribution system issues are location and system-specific, so it’s very hard to generalize insights,” Muratori said.

Overall, managed charging can noticeably reduce distribution system peak loads and congestion across the board, but more modeling and analysis is needed in collaboration with utilities, the researchers said. They also warned that the enablement and implementation costs in the report are “highly uncertain due to limited market implementations and a lack of scale.”

Many questions about the potential value of electric vehicle managed charging remain to be answered, the NREL researchers said. Among other things, they recommended a complete benefit-cost assessment that considers the entire extent of value streams for the power system, enablement costs, and the perspectives of all stakeholders.