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

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


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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.

Lesley Evans Ogden About the Author: Lesley Evans Ogden is a freelance science writer based in Vancouver, Canada, who specializes in topics including sustainability, natural history, ecology, and animal behaviour. Lesley has worked as a research scientist and university lecturer in environmental sciences and biology. Originally from Kingston, Ontario, she has a BSc in Zoology from the University of Toronto, a MSc in Biological Sciences from York University (Canada), and a PhD in Wildlife Ecology from Simon Fraser University. She has written three children’s books, and recently participated in the Science Communications program at the Banff Centre. When not writing, researching, or interviewing scientists, Lesley can be found running, cycling, hiking, canoeing, taking photographs, watching her kids play soccer, or volunteering. Follow on Twitter @ljevanso.

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






Comments 12 Comments

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  1. 1. alan6302 3:21 pm 10/27/2011

    It would be more practical to switch to robot electric cars. This is an insurance company killer and highway patrol killer.

    Link to this
  2. 2. quincykim 3:45 pm 10/27/2011

    alan6302: I don’t follow either of your comments…could you explain?

    Link to this
  3. 3. Postulator 4:13 pm 10/27/2011

    Nice idea technically, but zero chance of social acceptance.

    Link to this
  4. 4. RDH 4:41 pm 10/27/2011

    So will I find the wife going into labor at 2 am, rush to the car and pull out – and die on the road halfway to the hospital because my charge was drained by the smart grid?

    Link to this
  5. 5. William Fairholm 5:12 pm 10/27/2011

    @RDH. I would think that 2am would be when the car would be near maximum charge. 2pm would be when it would be partly discharged. Don’t know what limit they would put on this, but it might be set by the owner. There would be some renumeration for this service, and it would be up to the owner of the car to decide on what level of capacity to lend. That makes the most sense to generate acceptance.

    Link to this
  6. 6. Damarch 5:22 pm 10/27/2011

    This is a stupid idea. In a world with large amounts of EVs on the road the very time the energy is needed (when you plug your car in after work, crank up your ac/heater, turn on the tv, charge your phone, turn on your computer and start cooking dinner) is the same time when there are fewer charged cars to draw from. Not to mention that at any given time when you go to drive your car there’s a chance you wont be able to make it because the grid stole its power. The people hurt most by this will be people who start work when others stop working, night shift people.

    No, EVs just don’t work. When the public realizes this and calls for politicians to stop subsidizing them is when we’ll start working on more viable technologies to replace fossil fuels.

    Link to this
  7. 7. bshell 6:03 pm 10/27/2011

    What people are totally forgetting is the advent of smart electric meters. http://en.wikipedia.org/wiki/Smart_meter
    In Canada millions of these are being installed across the country. They communicate over radio networks like cellphones. There are smartphone apps that shows you what electricity your house is using. And there are also smartphone apps that communicate with your car to check it’s charge status, and even to warm up the seats before you leave the house or office. We are about to enter an era whereby your car can communicate to your house, or to you via your phone or to the grid itself. These capabilities already exist in new electric cars such as the Chevy Volt and the Nissan Leaf. And these are early models. The future will have MUCH smarter cars, meters, phones, homes, power utilities, etc. The kinds of scenarios in some of the naysayer comments above will seem hilarious to our children in about 20 years. The idea that a car would not have enough charge to get nearly anywhere will be similar to people worrying that the icebox is running out of ice. Who worries about that anymore? No one. Same will happen as we transition to the much more intelligent technology of electric cars for transportation. Your grandchildren will be amazed that you had a car that burned smelly gasoline, just as I am amazed my grandfather only had a horse, and never even owned a car.

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  8. 8. r0b3m4n 7:55 pm 10/27/2011

    bshell +1

    Two thoughts
    1. The car owner should be able to determine the price they sell their energy back to the power company for. This is partially to offset power losses in charging and dis-charging. But mainly so if I never want my energy stolen – well you can do it, but it’s gonna cost you a $1000 per KWh. Then the energy company can choose which cars to drain first and those who want the money most get paid out first.

    2. It seems to me your app to control the car charging would be wisely designed in tiers tailored by the car owner. ie when I get home from work top me off to a 20% charge then @ 4am when power costs less money top me off to the full 100%.
    It seems to me the naysayers are being incredibly short sighted with the logic they will be able to program into their cars charge maintenance system. All this same Electricity top off logic could even be applied to solar panel battery systems. I could even imagine in the future as energy costs more and is in shorter supply (yet batteries cost less and are more efficient) Entire companies could be feasibly built around battery storage stations that charge for cheap at night then sell back during the day for a profit (location would be key). The primary thing as noted in the article is regulations need to be favored more for the individual and small companies rather than the huge mega corps and utilities…

    Link to this
  9. 9. chimesickle 9:11 pm 10/27/2011

    Ha ha, I think the few that said it would never work, had their minds set before they read anything. It seems they did not even read the article,(only the headline) some of the concerns were addressed already. Intelligent software will control the charge/discharge, and batteries will only be used a minute at a time to control fluctuations. You do not need to worry about a dead battery!! At some point in the night, your battery is charged anyways. It will always be held at the highest state.

    Link to this
  10. 10. cor_van_de_water 4:33 pm 10/28/2011

    Interesting that Prof Willett developed the concept two years *after* my V2G capable EV was delivered by WaveDriver to PG&E for testing of the V2G technology, in 1995. Many years later I bought that converted US Electricar S10 EV, installed new batteries and used it 3 years mainly for my commute and for show-n-tell. I sold it to someone who wanted to use it as demo vehicle for Google. I find it very shrewd of the prof that he licenses a concept that already existed but apparently is long forgotten… To the naysayers like Damarch: EVs do work, I know from experience and no, I did not get a penny of subsidy when I had my EV.

    Link to this
  11. 11. Jerzy New 6:21 am 11/1/2011

    Hi, The Economist had a rather more thoughtful article on this few weeks ago.

    I agree with them for a certral premise: electric cars are uncomfortable to use anyway, why users should on top of it suffer to have their battery used by electric company?

    Link to this
  12. 12. Kingwood electrician 1:15 am 07/10/2012

    It would be more practical to switch to robot electric cars. This is an insurance company killer and highway patrol killer.

    Link to this

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