DC Charging Could Accelerate Grid Impact

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Electric vehicle charging stations are now popping up at locations scattered across the country. Because of the low penetration rates of EVs and charging equipment during the next year, utilities are generally comfortable that their ability to reliably serve customers won’t be impacted.

This is partly because both categories of products can be programmed to delay charging until off-peak hours, so the only immediate risk is likely limited to neighborhoods with older transformers that might have several neighbors jumping on the EV bandwagon at once.

But that comfort zone has the potential to be penetrated if the momentum behind DC (fast) charging continues to accelerate. Many vendors, including most recently Eaton Corporation and Epyon Power, have announced DC charging equipment that can charge vehicles up to 80 percent in less than a half an hour. DC charging stations are showing up in Vacaville, CA, Vancouver B.C., and here in Oregon, where they will be installed along Interstate 5 all the way from the Washington to California borders.

The Department of Energy’s EV Project includes funding for 310 DC chargers. While the ability to charge quickly is seen as a positive to encourage EV adoption, it’s not so good for controlling peak demand. DC charging hasn’t been formalized as a standard in the U.S. yet, but dozens of global vendors have thrown their weight behind the CHAdeMO standard developed by the Tokyo Electric Power Company. CHAdeMO equipment can charge at up to 500V and 125 amps, or 62.5 kilowatts (kW).

Charging just one vehicle at this rate is equally to approximately 43 vehicles being charged via Level 1 (aka standard household current) or 9-18 vehicles at Level 2 using charging equipment. Complicating matters is that DC charging is by necessity immediate – delaying a 15-30 charge defeats the entire purpose. Plus, these charge locations are likely to be at truck stops, gas stations, or mini-marts, which aren’t places that most folks plan on spending a lot of time.

While DC charging is a much bigger drain on the grid, charging stations won’t ordinarily be placed to impact residential transformers or transmission lines But if fast charge spots are connected to substations that experience peak demand, the potential for making a bad situation worse exists. For example, in California, the average peak demand per household in most service territories is between 1.3 and 1.9 kW, so one DC charging station is tantamount to about 30-45 houses.

So if a consumer wants to charge her EV at 4pm on a hot afternoon, is a fast charge permitted at a full rate, partial rate (and how does that impact how much she pays?), or is it delayed? Whatever the choice, someone’s not going to be happy.

When I first started discussing dc charging with EV manufacturers 18 months ago, several stated concerns about the impact of battery life, but now Mitsubishi, Toyota, Nissan, Honda, Mazda, Isuzu and Think are all on board.

Article by John Gartner, appearing courtesy Matter Network.

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