V2G Generates Electricity--And Cash

The price of oil this year has been in record-high territory, but a new UD prototype vehicle demonstrates how the cost of the black stuff could become a concern of the past.

A team of faculty members has created a system that enables vehicles not only to run on electricity alone but also to generate revenue for their owners by storing electricity and selling it back to utility companies. The technology—known as V2G, for vehicle-to-grid—lets electricity flow from the car’s battery to power lines and back.

The concept has been a longtime labor of love for Willett Kempton, associate professor of marine policy, who began developing the technology more than a decade ago and now is testing the new prototype vehicle.

“When I get home, I’ll charge up [the car’s batteries] and then switch into V2G mode,” says Kempton, who routinely drives the vehicle around campus and beyond. It’s likely that few people notice the innovative prototype since its body is the standard, boxy Scion.

The researchers bought the converted Scion from California-based AC Propulsion. Under the hood, components include a three-phase alternating current motor in a composite-materials housing, a 400-volt battery and high-current power electronics. Additional batteries are located in the space once filled by a now-unnecessary gas tank. The motor’s temperature, which can reach 70 degrees Celsius, is monitored from the dashboard, and the batteries are cooled by fans or the car’s standard air-conditioning system.

“In a sense, the batteries work like a sponge,” says Ajay Prasad, professor of mechanical engineering and a member of the research team. “They store up power to run the car, and when they have excess power, it’s fed back to the [electric power] grid.”

Other members of the V2G team are Suresh Advani, George W. Laird Professor of Mechanical Engineering, and Meryl Gardner, associate professor of business administration, along with several students. Prasad and Advani, who also are part of another team that is operating a demonstration bus powered by hydrogen fuel cells, say the V2G car is a good fit for their interests.

Kempton “was looking for somebody to believe in this concept of storing energy and giving it back to the grid,” Advani says. “We all needed funding, so the three of us went to DNREC [the Delaware Department of Natural Resources and Environmental Control] to assist us with the car and the bus. That’s what really got the ball rolling.” Additional funding has since been provided by such firms as Google.org, the philanthropic arm of Google, and Delmarva Power’s parent company.

When the car is in the V2G setting, the battery’s charge goes up or down depending on the needs of the grid operator, which sometimes must store surplus power and other times requires extra power to respond to surges in customer use. The ability of the V2G car’s battery to act like a sponge provides a solution for utilities, which pay millions to generating stations that help balance the grid, Kempton says. He estimates that the value for utilities could be up to $4,000 a year for the service, part of which could be paid to drivers.

The technology will work on a large scale, Kempton says, because on average 95 percent of all cars are parked at any given time. One hour a day of car usage is the average in America.

“A car sitting there with a tank of gasoline in it, that’s useless,” he says. “If it’s a battery storing a lot of electricity and a big plug that allows moving power back and forth quickly, then it’s valuable.”
Kempton already has one of those large plugs at his home. It’s a 240-volt plug—“a household plug, but a large-capacity one, like an electric range uses”—that gives the battery a full charge, for a range up to 150 highway miles, in just two hours. A smaller, standard 110-volt plug works but takes about 12 hours to provide a full charge. The smaller plug also moves less power for the grid operator when the car is in V2G mode.

“The bigger the plug, the more power you can move, the more revenue,” Kempton says. But the smaller plug is seen as an important option for the convenience of consumers, who sometimes may want to plug in the car at their workplaces, motels or other locations away from home.

Such considerations are part of the research being conducted by Gardner, who brings her expertise in marketing and consumer behavior to the project. Some of her students have surveyed drivers at the Delaware Division of Motor Vehicles to try to gauge support for the V2G concept.

“We need to know how much consumers would be willing to pay for this type of vehicle, for example,” she says. “And we want to know the features that are important to them. How much space for passengers do they need? How do they feel about the maximum range of 150 miles a day?”

In addition to individual drivers, Gardner is examining the needs of fleet owners. Corporations might be especially interested in the new technology, she says, because employees typically drive a company car a relatively short distance each day and park it back at the business overnight. Also, with a large number of cars selling excess electricity back to the power grid, a fleet owner could reap larger financial rewards.
As for Kempton, although the prototype car is supplying power to the grid, he’s not yet getting paid for it.

PJM, the grid operator for Delaware and 13 other states, is keen on the technology and even hosted the second-ever public demonstration of the V2G car in action in November. (The first was at the Federal Energy Regulatory Commission, two weeks earlier.) But PJM requires at least 1 megawatt for a contract to purchase power. That means the UD team and its collaborators must get 100 cars up and running.

The prototype car is a steppingstone to that goal. Prasad and Advani plan to add V2G capability to the University’s fuel cell bus. Next, the team, including AC Propulsion, will test the prototypes and fix any potential problems that arise. The researchers will then begin creating a user interface that will let drivers, for example, tell the car to never drop below 50 percent charge while in V2G mode or to always be fully charged by 7 a.m.

By the time that interface is ready, Gardner says, she hopes to have some specific information about how best to market the car, including a sense of how drivers feel about a car that’s better for the environment than a gasoline-powered vehicle.

Kempton, who also is involved in College of Marine and Earth Studies research on offshore wind farms, says the environmental issue is the most exciting aspect of the new car. He explains that even if the electricity used to charge the battery is produced by a coal-fired power plant, the vehicle itself produces no carbon dioxide emissions—in fact, it doesn’t even have a tailpipe. If wind or solar sources fueled the electricity from the power plant, he says, the car and its power source would be emissions free.

And even though the green aspect of the car is key for Kempton, he knows consumers might have some other questions, such as, “What’s it like to drive?”

The car is zippy yet quiet, and being behind its wheel is a thrill, he says: “I hate getting back in my old gas burner. It feels sluggish.”

For more information about V2G technology at UD, visit [www.udel.edu/V2G].