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Vehicle-to-Grid Technology: Electric Cars Become Power-Grid Batteries

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Imagine a car that runs quietly, burns no gas, produces no emissions, stores renewable energy, and sometimes even pays you back. Seem like a pipe dream? Soon it won’t be. Vehicle-to-grid technology allows networks of electric vehicles (EVs) to function like a giant battery with an intelligent software interface feeding power from car to grid or grid to car on an as-needed basis. It’s now one step closer to U.S. commercialization.

Professor Willett Kempton

American cars sit parked and unused for an average of 23 hours per day, and the storage capacity of our current electrical grid infrastructure is limited at best. This inspired vehicle-to-grid (V2G) pioneer Willett Kempton at the University of Delaware (UD) to develop the ‘vehicle as power storage’ concept in 1997 with Vermont’s Green Mountain College economist Steve Letendre. Kempton has since taken V2G from idea through proof of concept to commercial pilots in both Delaware and Denmark.

Kempton sold the international license for the technology to the Danish company Nuuve in June of 2011. Now in Delaware, the U.S. license has been purchased by New Jersey-based NRG Energy. The new business partnership between NRG and the University of Delaware (UD), known as “eV2g,” was announced with fanfare on September 26th, and featured a visit to the UD’s Newark campus by U.S. Senator Chris Coons.

At the UD announcement, Kempton humorously referred to Thomas Edison’s famous statement that genius is 1% inspiration and 99% perspiration, saying, “I think he underestimated the amount of perspiration required”. His remark is justified. It’s been more than a decade of perspiration following inspiration for Kempton in his journey to make V2G technology a reality. Noting that Newark, Delaware, was the site of a busy Chrysler tank factory during the Korean War, Kempton says his vision is a “post-petroleum repurposing of this facility.”

Officials sign the partnership agreement. Pictured are, from left, seated, Denise Wilson, president of NRG's Alternative Energy Services; University of Delaware (UD) President Patrick Harker; and Drew Murphy, NRG executive vice president and regional president, Northeast; and, standing, David Weir, director of UD's Office of Economic Innovation and Parternships; Nancy Targett, dean of the College of Earth, Ocean, and Environment; Prof. Willett Kempton; U.S. Sen. Chris Coons (D-Del.); and Alan Levin, Delaware Economic Development secretary.

Despite the announcement, the ability of EV owners to register for the eV2g service is still two to three years away, according to NRG Communications Director Lori Neuman. Initially conceived as a technological service that will be available to EV fleet operators, eV2g eventually plans to roll the service out to individual EV owners. Kempton estimates eV2g electricity regulation services could earn $10,000 per car in revenue over the lifetime of an EV, offsetting these vehicles’ currently high purchase costs.

Vehicle-to-grid is a technology that promises to provide the short bursts of back-and-forth power used to correct imbalances in the electric power grid, explains Kempton, adding that in future, the technology may also prove useful in smoothing out the fluctuations inherent in renewable energy production such as wind and solar power.

Wind generated power production, for example, is often greatest at night, when demand for power is typically low. In our current power grid there is limited capacity for power storage, so any nocturnally generated wind energy above and beyond what’s used immediately goes to waste. V2G is an obvious solution, at least in part, for storing that power, and then drawing on the stored electricity during periods of high power demand.

Nobel laureate and physician Albert Szent-Györgyi once said, “Discovery consists of seeing what everybody has seen and thinking what nobody has thought”. Kempton epitomizes this key to technological and scientific innovation. During the birth of the automotive industry, vehicles were never conceived of as potentially being part of a national electrical grid. “They evolved on disparate paths and really didn’t connect,” said U.S. Senator Coons at the UD NRG announcement.

You’ve got automobiles powered by petroleum, individually owned, highly mobile, free-standing, independent, and dramatically under-utilized, and then you’ve got the base-load mostly coal-fired national grid, that increasingly has strains and demands on it,” remarked Senator Coons, applauding the new potential for connectedness between energy and transportation.

Professor Willett Kempton next to an electric car outfitted for ev2g capability

While V2G links problem with solution, one technical challenge that remains is V2G’s impact on battery life. Putting power back into the grid rather than only one-way charging results in more battery charge-discharge cycles, which can shorten the battery’s useful life.

It’s an issue that battery manufacturers will need to address. Nevertheless, with the initial target market for both Danish and U.S. companies being frequency regulation, batteries are used for only minutes at a time to upload or download power (see illustration) a practice that has less impact than subjecting the battery to deep charge-discharge cycling.

Denmark is encouraging the transition from internal combustion to electric powered vehicles with substantial tax exemptions for EV purchasers. U.S. energy expert Benjamin Sovacool suspects that widespread acceptance of eV2g will require the same type of political support in the US, including the types of subsidies, tax breaks, and regulations the petroleum industry currently receives. A visiting Professor at the Vermont Law School and the founding Director of the Energy Justice Program at their Institute for Energy and Environment, Sovacool thinks the eV2g initiative is a step in the right direction, but likely won’t produce real change until these issues are addressed.

“If the history of energy transitions has told us anything, barriers related to politics and social attitudes and values can be just as salient as these technical and economic ones. People need to have faith in V2G technology and see it as complementing, rather than disrupting, their lifestyles,” Sovacool says.

That’s a sentiment echoed by Richard Hirsh, a Professor of History, Science and Technology Studies, at Virginia Polytechnic Institute and State University. “Too often, people just look at the potential benefits of technologies and don't evaluate what needs to be done -- in terms of infrastructure, behavior, markets, regulation, government incentives -- to make the technologies a reality.” In the 1950s and 1960s, for example, electric utilities thought that nuclear reactors were just another way to boil water in power plants, explains Hirsh, but history has shown us that these reactors weren't really such simple devices -- they had difficulty gaining acceptance in the U.S. and elsewhere.

The concept of V2G (PDF). (NRG Energy and the University of Delaware).

Nevertheless, Hirsh views Willett Kempton as a visionary in many ways, noting that Kempton’s technology has already caught the attention of the Federal Energy Regulatory Commission. “Thinking about a car as something beyond a transportation device is a huge intellectual accomplishment,” says Hirsh, adding that the technical potential of Kempton's re-imagined electric vehicle is large. Getting the car integrated into the social, political, infrastructural, and market systems will constitute the big challenge, says Hirsh, but is one he hopes Kempton and others can master.

It’s been a long road to this potentially transformative technology, and there are likely more roadblocks ahead before it becomes mainstream. Nevertheless, it’s a technology that promises many advantages. What does the future hold for vehicle-to-grid technology in the U.S. and beyond? Only time (and energy) will tell.

The views expressed are those of the author and are not necessarily those of Scientific American.

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