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Effect of Electric Vehicle Concentration

August 26, 2011

A study by the Pacific Northwest National Laboratory (PNNL) established that the existing grid and power supply could support approximately 87 million plug-in electric vehicles (PHEVs) and battery electric vehicles (BEVs) if the batteries were charged during off-peak hours. (See earlier series of articles on the Hidden Cost of PHEVs, Part I of 3) This was a macro study and didn’t focus on whether electric vehicles would be concentrated in specific areas.

A new study by an ISO/RTO Council has attempted to establish whether PHEVs and BEVs would be concentrated in specific areas or cities, and how any such concentration might affect the grid.

The study assumed that purchases of PHEVs and BEVs would follow the same pattern as did purchases of Prius’, coupled with purchases by fleets, such as cities and delivery services.

The study also assumed that one million PHEVs and BEVs would be purchased in five years.

Based on these assumptions, the study predicted that PHEVs and BEVs would be concentrated along the East and West coasts and in certain cities.

According to the study, cities with more than 25,000 PHEVs and BEVs by 2017 were:

Los Angeles 119,069

San Francisco 91,005

New York 54,069

Washington DC 37,520

Boston 31,976

Chicago 27,892

Seattle –Tacoma 26,088

The study reaffirmed that charging must be done during off-peak hours, otherwise unduly large loads would result, especially in cities with high concentrations of PHEVs and BEVs.

Using Los Angeles as an example from the study, if all vehicles were charged simultaneously, it would create a new load of 658 MW, which is roughly equivalent to a new mid-sized coal-fired or NGCC power plant.

If charging occurred over an 8 hour period, the predicted load would be 147 MW.

Other cities with 25,000 or more vehicles would be similarly affected. Comparable loads predicted for Chicago were 154 MW if all units were charged simultaneously and 34 MW if they were charged over an 8 hour period.

This would suggest that smaller cities would likely not be affected by the new loads created from charging PHEVs and BEVs, if they were charged during off-peak hours.

It should be noted that all cities could be affected locally through overloading of their distribution systems, even when there is sufficient generation capacity. (See Hidden Cost of PHEVs, Part 3) Charging done during peak periods is almost certain to create new, unwanted peaks that will likely cause problems.

A main purpose of the study was to determine whether PHEVs and BEVs would afford an opportunity for Demand Response or other services, using the batteries concentrated in specific cities or areas.

The study suggested that controlling the charging cycle of batteries, located throughout an area or city, might allow for Demand Response (DR). Demand Response is used to shed load or curtail peak load during periods of high demand.

The study also pointed out that modifying the rates at which batteries are charged could affect warranties, and that additional studies and arrangements with manufacturers would be necessary before DR or any other services using the batteries from these vehicles could be implemented.

The study also introduced the idea that middle-men, between the utility and vehicle owner, could aggregate vehicles for the purpose of DR or for providing other services.

Like so many concepts swirling around PHEVs and BEVs, this is highly problematic.

The study also contains maps showing cities where PHEVs and BEVs are likely to occur.

The auto industry and government are still at the stage of hyping PHEVs and BEVs without any real time data on which to base forecasts or decisions.


Note: The study can be obtained at:

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Additional TSAugust web sites:

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[To find earlier articles, click on the name of the preceding month below the calendar to display a list of articles published in that month. Continue clicking on the name of the preceding month to display articles published in prior months.]

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2 Comments leave one →
  1. Mark permalink
    August 26, 2011 11:20 pm


    Thanks for yet another informative post.

    I saw an interesting post over at seeking alpha that you might find of interest- It’s Time To Kill The Electric Car, Drive A Stake Through Its Heart And Burn The Corpse

  2. August 27, 2011 10:27 am

    I missed the Alpha article for which you have provided the link, but have just read it.
    The article is outstanding and I hope others will use your link to also read the article.
    My article, and the earlier ones to which I link, approach electric vehicles from a different perspective, but reach the same general conclusion as the author of the Alpha article:
    PHEVs and BEVs are a costly distraction.
    He suggests they should be killed because of resource limitations – I suggest they will fail for economic reasons, some of which relate to resource costs.

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