It’s not often that a press event at the American Association for the Advancement of Science Meeting features a car. But the car that was driven into the press room today was an electric one, with some added communications skills: it could talk with the electric grid…
The University of Delaware is already working with the utility PJM to test the use of electric vehicles for stabilizing the frequency of the grid, and preliminary work suggests that the payback time for the extra communication equipment may be as short as two months.
In the US, utilities are required to have about one percent of their peak capacity available in forms that can respond rapidly to changing demand, so that the frequency of the current on the grid remains stable even as demand shifts. Many of the generating sources that can respond to the need for changes in power supply take a significant amount of time to ramp up or down. “Batteries can move faster than our signal,” PJM’s Kenneth Huber said. “This provides a very high value to the grid.”
The idea is that, in aggregate, plug-in hybrids and other electric vehicles will ultimately attach a very significant storage capacity to the grid. Without any control, they’d simply draw from the grid until charged. But, with some communication capacity and logic, they can also provide a reserve power capacity that can contribute to stabilize the grid’s frequency. Depending on how supply and demand work out, that could either mean sending power back to the grid, or drawing it back off at an accelerated pace. Right now, that function is largely performed by ramping up or down actual power plants, which generally can’t respond as rapidly or cheaply as a battery.
The panel took pains to emphasize that frequency regulation wouldn’t necessarily interfere with charging. On average, the grid’s frequency will vary above and below the ideal target; although the car’s battery will often be asked to supply power, it should be used just as often to take electricity off the grid, balancing things out. “Over the course of the evening, it all balances out,” said Huber.
Right now, the logic portion of things is pretty simple. Users enter their typical driving schedule and can add specific trips to the schedule; the software will ensure that, at a minimum, the battery will be ready to handle that use. Longer term, the hope is that software will be able to analyze typical driving patterns and adjust charge limits accordingly.
Any utility faces a bit of a chicken-and-egg problem. It needs electric vehicles on the grid in order to figure out how they work. But, with just a few demonstration vehicles available at the moment, their impact is negligible. So, what the University of Delaware has done is build a half-Megawatt battery, and simply supplements that with as many vehicles as it has (right now, three). The software is smart enough to break their impact out; in fact, a Web display of the tracking software updated live in the background, tracking the vehicles as between drawing power and sending it back out to the grid.
Because of the economics of grid stabilization, utilities have to pay for frequency stabilization capacity even if it’s not used. That means, on some level, a car’s battery provides value simply by being plugged into the grid. By the panel’s estimate, plugging in a vehicle would typically be worth anywhere from $5-10 a day. The additional communication and software equipment, at the manufacturing level, adds an incremental cost of less than $500, meaning that the system should pay for itself in only a few months. Lifecycle analysis suggests that the entire system should significantly reduce carbon emissions as well.
The battery itself, however, costs about $15,000 on its own, so the system doesn’t make much sense on a personal level unless that battery’s put to use in a car.
How close are we to getting beyond a handful of test vehicles? With several models of plugin hybrids that will be introduced over the next several years, the panel seemed to think that President Obama’s goal of a million vehicles nationwide might be possible—that would mean 180,000 vehicles in PJM’s footprint alone. There is also a lot of potential in vehicle fleets; the US Postal Service is viewed as an enticing target, since it has a huge fleet of vehicles that could spend the entire overnight hours plugged into the grid.
Eventually, enough vehicles might be on the road that they could entirely take over the frequency stabilization capacity. But, if anything, an increasing reliance on renewable power generation, especially wind power, will mean that supply will fluctuate more widely—that, in turn, will require even greater levels of stabilization. So, the group felt confident that the capacity to plug cars into the grid for stabilization would outpace the number of plug in vehicles for the foreseeable future.