New Hampshire, USA — Much of the buzz around electric vehicles has focused on automobiles, including the launch of production plug-in vehicles by Nissan and General Motors in December 2010. These vehicles are slated to be followed over the next 18 months by models from Ford, Mitsubishi, Toyota and Tesla, among others.
Autos get most of the headlines, but electrification extends to other parts of the transport economy. Think delivery vans, small and large transit buses, utility service vehicles and urban delivery trucks. Non-road electric transportation includes lift trucks and material handling equipment, airport ground equipment, truck stops, port electrification, mining and overland conveyers.
At the neighborhood level, Walgreen’s said that around 800 of its almost 8,000 locations will install electric vehicle charging stations. Ditto for some IKEA and WalMart stores. KwikTrip is installing charging stations and will let customers fill up for free, following the industry model of making money on snacks and soda pop. Dominion Virginia Power said in July it will move ahead with an electric vehicle recharging pilot program. The regulator-approved pilot will test whether electric vehicle owners will choose to recharge during off-peak hours – typically overnight – in exchange for lower electricity costs.
This last point figures in a new report the Electric Power Research Institute (EPRI) released July 19. It details the status of, and considers issues related to, efforts to electrify the transportation infrastructure. Titled “Transportation Electrification: A Technology Overview,” the 120-page report examines issues related to grid infrastructure and pricing.
Plug-in cars — let’s use that shorthand — are of interest to the renewable energy community because recharging can make good use of renewable resources such as wind that in some instances peak during nighttime hours. EV advocates also see a role for vehicle batteries in providing storage capacity to help meet peak load demand. What’s more, electrifying portions of the transportation system could offer power generators a new source of load growth, help ease U.S. dependency on imported oil and give consumers a break on the cost of gasoline. After all, electric vehicles are less expensive to fuel than gasoline-powered vehicles. (Of course, they also are more expensive to buy than the average conventional-fueled vehicles, but that seems likely to change with time.)
On the issue of vehicle recharging itself, the EPRI report concludes that problems could arise by ill-conceived charge control strategies. For example, if owners were restricted to recharging their vehicles until after 9 p.m., the charging load could hit rapidly. Assuming that around 500,000 plug-in vehicles are in the market by 2015 (a scenario EPRI sees as a “medium” adoption rate) a 9 p.m.-and-after rule could see demand reach nearly 1 GW. That’s because almost three-quarters of all electric vehicles would be charging at the same time. End result: a demand spike.
But how much of a demand spike? Not much, Mark Duvall, the report’s author, tells me. One million plug-in electric vehicles in California would add around 700 MW to the peak load. On an afternoon this past July, peak demand was forecast to be 37,500 MW. (Keep in mind that as of the end of May, Nissan and GM combined had delivered around 5,000 vehicles nationwide. We’re still in the very early days.)
Duvall says a charge management strategy that starts charging vehicles after peak hours and distributes charging throughout the off-peak will benefit the grid the most and use available capacity most efficiently.
For example, a recharge control strategy that shifts the load to nighttime hours would allow vehicle charging to be staged to start during one of seven hours from 9 p.m. until 3 a.m. In this scenario, the EPRI report said the average per-vehicle load would end up being about 0.7 kW and would hit at a more favorable time for power generators.
Of more concern near-term is the effect EVs may have on the local distribution network. Duvall points out that an individual transformer will see a 7.7-kW load increase regardless of when the vehicle begins charging. It’s at this level that the grid impacts of EVs will be felt first, affecting transformers with little or no remaining capacity.
Continued research by EPRI, Dominion and others in the coming months will shed still more light onto this emerging source of electric demand.