Powering Strong Communities

Western grid planning does not fully account for EV penetration: PNNL report

Current grid planning in the Western power grid does not adequately account for an expected influx of electric vehicles, according to a new report from the Pacific Northwest National Laboratory (PNNL).

In the report, Electric Vehicles at Scale – Phase I Analysis: High EV Adoption Impacts on the Western U.S. Power Grid, the authors argue that a massive influx of electric vehicles will exacerbate stresses already present on the grid.

Specifically, they say, if owners choose to charge their electric vehicles in the evening it could create a steeper demand curve just as electric power supplies are falling because as solar power fades for the day, a phenomena that has come to be known as the duck curve. This could lead to the curve of the evening ramp-up of demand to become even steeper and could drive up electricity costs, they warned.

Smart charging strategies, such as avoiding charging electric vehicles during peak hours in the morning and early evening, can smooth out demand peaks and fill in the duck curve, the authors say.

Otherwise, there is little risk that even a high level of electric vehicle penetration would lead to resource adequacy problems in the Western Electricity Coordinating Council (WECC) region, according to the report.

The report defines high penetration as 24 million light duty electric vehicles, 200,000 medium duty electric vehicles and 150,000 heavy duty electric vehicles by 2028. For WECC, that translates to 9 million light duty electric vehicles, 70,000 medium duty electric vehicles, and 94 heavy duty electric vehicle charging stations.

There are currently about 1.5 million electric vehicles, mostly cars and sport utility vehicles, in the U.S., the report notes.

Problems could arise, however, as electric vehicle penetration numbers rise to about 30 million nationally and 9 million in WECC. At that level, insufficient generation and transmission bottlenecks would begin to emerge, requiring both transmission and generation expansion, the report said.

And, the authors added, transmission congestion is likely to be the most limiting factor. In PNNL’s modeling, transmission bottlenecks were most likely to appear in parts of California, such as Los Angeles, and could be made more acute by the spread of fast charging stations that can draw 400 amps through a circuit for as long as 45 minutes, instead of 15 to 20 amps over six to eight hours as is now the case for most electric vehicle chargers.

To date, many cities have not had to factor electric vehicles charging into their growth plans, but some cities are already looking into intelligent controls and other ways to modify their distribution systems and operations, according to Dennis Stiles, who oversees PNNL’s energy efficiency and renewable energy research portfolio. “The key is to figure out now how to avoid large capital outlays in the future,” Stiles said in a statement. “Adding a new transformer here and there is a lot different than a substation overhaul.”

Managing new loads from electric vehicle chargers is also a potent tool, the report’s authors said. If managed charging practices are put in place, resource adequacy limits could be expanded to 65 million electric vehicles nationally or to 19.6 million in the WECC region. “This suggests a significant opportunity to substitute additional generation and transmission requirements with smart charging strategies and much better utilization of the existing grid,” the report says.

The PNNL report integrates multiple factors not evaluated before, such as electric trucks for delivery and long haul, as well as smart electric vehicle charging strategies, the authors said.

In a follow-on, phase-two study, PNNL plans to analyze the effect of electric vehicle penetration on the distribution system and take a closer look at ways to integrate electric vehicles into local and regional power distribution systems across the nation.