University of Delaware professor Willett Kempton is a pioneer of vehicle-to-grid (V2G) technology. In fact, he and his team of EV researchers at the university have been turning electric vehicles into grid batteries since 2007, when they kicked off a first-of-a-kind experiment that’s since been replicated in V2G projects around the world.
But Kempton is well aware of the technology and policy gaps that are holding V2G back from mainstream adoption. That’s why he’s spent years working with colleagues and students on updates to a technology standard that he hopes will make mass-market V2G a realistic option for automakers, utilities and drivers alike.
The standard is called SAE J3068, and last month, automotive standards organization SAE International formally adopted key new V2G capabilities for it. Kempton calls them a “practical, low-cost and implementable” way to turn every EV into a roaming grid battery.
Now he’s hoping that automakers will quickly build these new capabilities into their EVs and that utilities will invest in the communications and control systems they’ll need to work with them. If the technology takes off, it could help millions of EV owners use their spare battery power to earn extra money — and provide what experts say would be a significant boost to an increasingly stressed power grid.
As a first step, his team at the University of Delaware’s Science, Technology and Advanced Research Campus plans to start a pilot project next month with Delaware-based utility Delmarva Power, one of six regulated utilities owned by Chicago-based Exelon. That pilot will test the newly standardized capabilities on a handful of utility-owned vehicles.
The big challenge, Kempton said, is providing utilities with all of the data points they need in order to feel comfortable receiving power from EVs. “When something’s pushing power onto the grid, they want to know what that is,” Kempton said. “They don’t want to be like, ‘We’re 95 percent sure which car it is.’”
What’s so complicated about V2G?
To understand why V2G hasn’t taken off yet, it’s important to consider all the things that utilities need to know will happen for an EV battery to safely and seamlessly send power back to the grid. At present, the charging technologies in use in EVs and charging stations just aren’t set up to provide and manage that information, Kempton said.
V2G is particularly complicated when it’s the EV itself, rather than the charging station it’s plugged into, that needs to communicate with the utility. And that’s likely to be the most common arrangement. That’s because Level 1 and Level 2 chargers — the kinds of chargers that people use at home, at workplaces or in longer “dwell-time” locations like shopping mall parking garages — are the lowest-cost and most abundant chargers, but their alternating-current (AC) charging systems are not equipped to send utilities the data they need for V2G.
In contrast, direct-current fast-charging systems — the kind meant to top off EV batteries as fast as possible — contain inverters, devices that convert AC grid power to direct current. These inverters manage the interplay of the grid with the charger and vehicle. But with Level 1 and Level 2 charging, “the inverter is in your car,” Kempton said.
In essence, that makes every V2G-capable EV “a roaming inverter” — and it’s more complicated for utilities to certify an inverter to push power onto their grids when it moves from place to place, compared to one that’s permanently connected to the same point of the grid.
At present, the SAE technology standard used for Level 1 and Level 2 charging, J1772, is simply not capable of telling utilities everything they need to know, he said. The current standard “can say three or four things,” including whether it’s “connected to a charging station” and whether it’s “ready to charge.” It can also limit how much power an EV draws from the charging station.
“That’s the whole repertoire of signals,” he said. “That’s great if you want to plug in and charge — but not for much else.”
By contrast, EVs that comply with the newly adopted standard would be equipped with “about 200 signals,” he said. What’s more, instead of using the simple analog communications system used in the previous iteration, the new standard adopts technology that uses digital communications that can be carried via an existing wire in the power charging cord itself or via wireless signals.
That makes the new standard far more useful for communicating all kinds of things that most of today’s chargers can’t, he said. For example, EVs using the old standard can’t send the various diagnostic codes and error signals that charging stations rely on to troubleshoot charging glitches that can cause charging errors — a gap that’s partly responsible for the problematic performance of many public EV chargers today.
Last year, SAE adopted another update to the standard, J3068/1, that includes the diagnostic and identifying capabilities that EV drivers, automakers and charging station operators are eager to tap into to better troubleshoot charging problems. It can also identify the car or account to the charging station, enabling payment without always swiping a credit card.
J3068/2, the V2G-capable version of the standard approved last month, allows all of these features to be put to use for managing bidirectional power flows between cars and the grid, Kempton explained. That includes using EV batteries to back up homes and buildings during power outages or helping them to provide power in ways that don’t feed electricity back to the grid — known as vehicle-to-home and vehicle-to-building capabilities — which don’t require the same kind of utility integration as V2G operations.
Enabling EVs to move from serving as a backup battery to being a grid-connected resource is more complicated, however. Kempton highlighted key features of the J3068/2 standard that can make that task easier. One is its ability to provide “electrical certification” of individual vehicles, he said — in essence, recognizing each EV via a unique digital identifier that utilities can reference to check whether they’re authorized to supply power to the grid.
The same certification system can enable the utility to communicate “grid codes” with EVs to stop discharging power if local grid circuits are overloaded, for example, or to request that it supply power to mitigate grid disruptions, he said. And importantly, it can allow utilities to pay EV owners for volunteering their battery capacity.
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