Distribution Side: Grid Needs to Plan for Plug-in Vehicles

By John Gartner

Utilities have been testing the impact of electric vehicles and consumer charging patterns for several years with small test fleets so that they can prepare to handle the additional load. Many of the utilities I’ve spoken with say that if “smart charging” intelligence is available, vehicle charging is likely to only have a marginal impact on peak loads. Smart charging would enable vehicle charging to be delayed or temporarily interrupted or slowed depending on the condition of the grid.

Still at risk, even with smart charging, are the transformers located in residential areas that provide power to 3-5 homes. At faster charging speeds (level 2 and 3), even plugging in a few EVs simultaneously could cause a transformer to blow. The size and age of transformers varies widely between regions, meaning some EV-friendly neighborhoods might be faced with frustrated customers who temporarily lose power. Utilities are looking to track where electric vehicles are purchased to anticipate where older transformers might need to be upgraded to higher capacities.

'Bottom Up and Localized'

However, regional energy planners don’t yet have a handle on how the added load of EVs should factor into their plans for upgrading their distribution infrastructure. Neither utilities nor automakers are making a concerted effort to share their projections of electric vehicle populations with regional grid operators and planners. “[EV planning] is completely bottom up and localized now,” according to Carl Imhoff, an engineer at the Pacific Northwest National Laboratory’s (PNNL) Energy Science and Technology Directorate.

Imhoff, who is participating in the Department of Energy’s Smart Grid research that will enable sharing of information about grid performance between regions, said that some regional energy commissioners “have no clue” on how to plan for EVs and are moving ahead with their existing roadmap until they hear differently.

EVs could also be an asset to the grid by absorbing surplus generation of renewable power and by slowing or speeding up charging in response to fluctuations in the grid frequency. PNNL’s Michael Kintner-Meyer has developed a prototype smart charger controller that automatically modulates the charge rate based on the needs of the grid. If deployed widely, the smart chargers could reduce utilities’ costly practice of spinning up and down reserves to match demand. The smart charger would communicate with onboard and stationary charging equipment, home energy monitoring devices, and smart meters, according to Kintner-Meyer, who is looking for utility and automotive partners to continue development.

Cost Impacts Unclear

Regional grid regulators also don’t know how EV charging will impact the cost of electricity. The percentage of charging done off-peak versus peak will likely impact whether wholesale prices go up or down, according to Kintner-Meyer. PNNL is addressing this void by preparing a report due out in February that will estimate the impact of EV charging on a state-by-state basis.

Grid operators need to take the long view in how EVs will impact the grid. Imhoff suggests formulating a 20-year plan that considers the regional and national implications of charging. Without a clear strategy, the response to EV charging will be ad hoc and less efficient.

John Gartner is a senior analyst with Pike Research, a market research and consulting firm that provides in-depth assessment of global clean technology markets.

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