A new study of the impact of high EV adoption on the Western US power grid by a team from Pacific Northwest National Laboratory (PNNL) has found that 2028 grid resource adequacy—from generation through transmission—is likely to be sufficient for high EV penetration.

Under a high-penetration scenario with national electric fleets of ~24 million light-duty vehicles (LDVs), 200,000 medium-duty vehicles (MDVs), and 150,000 heavy-duty vehicles (HDVs) for a 2028 time-frame, PNNL does not expect resource adequacy issues in the Western power grid (Western Electricity Coordinating Council [WECC]) under normal operating conditions (normal system, weather, and water conditions).

The corresponding electric fleet sizes for the WECC footprint are 9 million LDVs, 70,000 MDVs and 94 HDV charging stations.

The team estimated the EV resource adequacy for the entire WECC interconnection for a likely unmanaged charging scenario under which most LDVs were charging at home starting in the evening (Home High power No Delay: HHND). Unmanaged charging is predicated on arrival time at home in the evening—the time at which the PNNL team assumed charging would begin.

The maximum number of LDVs when projected to the national fleet was about 30 million (national value) or 9 million for the WECC footprint. Alternatively, if managed charging was applied (a price-minimization scheme), the EV resource adequacy could be expanded to 65 million (national fleet number) or 19.6 million for the WECC.

The researchers said that this suggests a significant opportunity to substitute additional generation and transmission requirements with smart charging strategies and much better utilization of the existing grid.

They also found that at the maximum number of LDVs, transmission congestion was the limiting factor—i.e., although there are some available power plants in the WECC the electric power could not be delivered to the load centers because of transmission limitations. The largest transmission congestions were in California.

On the operational side, the PNNL team found that a number of changes could accommodate EVs:

• The additional generation for charging EVs is likely to be provided by natural gas combined cycle plants and combustion turbines predominantly throughout the WECC (85%–89% of all new generation).

• Storage is used in California to meet the peaks set by EVs. Hydropower generation in Washington State is redispatched to resemble a commonly observed charging/discharge cycle of an energy storage technology. No new hydropower generation is expected because hydropower generation is energy limited—no more water is expected in the Columbia River system.

• All EV charging load is likely to reduce renewable curtailments between 25% and 75% based on when EVs are charged. Managed charging could reduce the curtailment the most by an additional 16%.

• The production cost implications due to the additional load varied from 3% in Arizona, where there is some available coal generation, to 23% in California, where combustion turbines are required to meet the peak load set by EVs. All cost estimates were done keeping the generation capacity constant. It is likely, the researchers said, that capacity expansion in anticipation of additional load may mitigate the cost increase, particularly if the additional generation is renewable generation resources.

• Managed charging has significant operational benefits in solar-rich areas such as California. It reduced the duck curve in two ways: (1) it reduced the coincident peak (duck height) and (2) it reduced the ramp requirements in the evening when the sun sets (steepness of the duck’s neck).

Source: PNNL

In a follow-on study, researchers will take a closer look at ways to integrate EVs into local and regional power distribution systems across the nation.