By - Jim Vess

Seattle’s grid could be overwhelmed by ambitious plans for electric trucks and buses

Energize Weekly, September 18, 2019

Seattle’s ambitious plans for electrifying the city’s transportation sector could destabilize the metropolitan area’s electric grid by the addition of large numbers of electric trucks and buses, a study finds.

The study by the Rocky Mountain Institute (RMI) in collaboration with Seattle City Light offers a series of steps to deal with the potentially high and uneven load demand created by a significant increase in electric trucks and buses.

In 2015, Seattle City Light, the municipal utility, conducted a study of the impact of electric vehicles (EVs) on the grid and concluded the EVs would not significantly affect grid operations.

Since then, however, the push to electrify transport in the Seattle area has increased on several fronts.

Seattle’s major public transit agency, King County Metro, has established a goal to fully electrify its fleet of more than 1,400 buses by 2040.

The Port of Seattle has implemented a Clean Truck program, as a partner in the Northwest Seaport Alliance. It is part of the port’s strategic objective to be the greenest, most efficient port in North America.

The city of Seattle has set a target of 30 percent EV adoption, along with a commitment to a fossil fuel-free municipal fleet, both by 2030.

New state legislation has created significant financial mechanisms for clean transportation investment from the utility sector.

It was against this backdrop that the RMI study was conducted to evaluate the impact of these policies and initiatives on the grid.

The analysis concluded that City Light’s distribution network can accommodate the load from the increase in passenger EVs, although it advises that this be monitored.

Seattle is already is among the top metro areas outside of California for EVs with more than 8,000 personally owned electric vehicles (POVs) registered, representing 5 percent of new vehicle sales.

The grid challenges come with the broad adoption of electric trucks and buses, which come with larger and longer charging demands.

“Electric trucks offer a double-edged sword in terms of their impact to the grid: they are likely to concentrate in industrial areas of cities making load planning simpler, but they draw significantly more power per charging event than POVs, potentially straining distribution grid capacity at those locations,” the study said.

Based on Washington State Department of Licensing data for new commercial vehicle registrations, RMI forecast 1,300 electric medium-duty trucks operating by 2025 with more than 4,000 in operation by 2030.

RMI advised that City Light has to be proactive in supporting both location and operation of truck charging stations to minimize the impact.

The impact of bus electrification could be similar to those of trucks, but may offer more flexible management options.

Buses are expected to be charged in centralized yards overnight, both allowing for infrastructure planning and avoiding peak demand periods. “Opportunity charges” at transit hubs, transfer point or the end of routes could provide short, on-route charging.

“If planned well, electric buses can improve grid asset utilization and present a new source of predictable revenue,” the study said.

Among the study’s recommendations were to:

  • Invest in charging infrastructure to make direct current (DC) fast charging available to all residents
  • Support deployment of nonutility-owned DC fast charges for ridesharing drivers and for residents of multi-unit dwellings and underserved communities
  • Develop pilot electricity rates that make electric transportation cost competitive with transportation by conventional vehicles and that make it possible to operate profitable private-sector DC fast-charging networks
  • Establish standards to encourage “smart charging” during low-cost hours and support the use of EVs as flexible grid assets
  • Offer responsive rates, incentives and grid infrastructure for heavy-duty electrification, as well as support the electrification needs of partner agencies such as Metro and the Port, by offering responsive rates, incentives and grid infrastructure
  • Support urban fleet and freight operators by developing packaged charging solutions and incentives for charging depots

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