One of the big problems with intermittent power sources like wind and solar is the difficulty of storing energy. But if we ever get a lot of electric vehicles, we’ll have a lot of batteries—and at any time, most of these vehicles are parked. So, they can be connected to the power grid.

This leads to the concept of vehicle-to-grid or V2G. In a V2G system, electric vehicles can connect to the grid, with electricity flowing from the grid to the vehicle or back. Cars can help solve the energy storage problem.

Here’s something I read about vehicle-to-grid systems in Sierra magazine:

At the University of Delaware, dozens of electric vehicles sit in a uniform row. They’re part of an experiment involving BMW, power-generating company NRG, and PJM—a regional organization that moves electricity around 13 states and the District of Columbia—that’s examining how electric vehicles can give energy back to the electricity grid.

It works like this: When the cars are idle (our vehicles typically sit 95 percent of the time), they’re plugged in and able to deliver the electricity in their batteries back to the grid. When energy demand is high, they return electricity to the grid; when demand is low, they absorb electricity. One car doesn’t offer much, but 30 of them is another story—worth about 300 kilowatts of power. Utilities will pay for this service, called “load leveling,” because it means that they don’t have to turn on backup power plants, which are usually coal or natural gas burners. And the EV owners get regular checks—approximately $2.50 a day, or about $900 a year.

It’s working well, according to Willett Kempton, a longtime V2G guru and University of Delaware professor who heads the school’s Center for Carbon-Free Power Integration: “In three years hooked up to the grid, the revenue was better than we thought. The project, which is ongoing, shows that V2G is viable. We can earn money from cars that are driven regularly.”

V2G still has some technical hurdles to overcome, but carmakers—and utilities, too—want it to happen. In a 2014 report, Edison Electric Institute, the power industry’s main trade group, called on utilities to promote EVs [electric vehicles], describing EV adoption as a “quadruple win” that would sustain electricity demand, improve customer relations, support environmental goals, and reduce utilities’ operating costs.

Utilities appear to be listening. In Virginia and North Carolina, Dominion Resources is running a pilot project to identify ways to encourage EV drivers to only charge during off-peak demand. In California, San Diego Gas & Electric will be spending $45 million on a vehicle-to-grid integration system. At least 25 utilities in 14 states are offering customers some kind of EV incentive. And it’s not just utilities—the Department of Defense is conducting V2G pilot programs at four military bases.

Paula DuPont-Kidd, a spokesperson for PJM, says V2G is especially useful for what’s called “frequency regulation service”—keeping electricity transmissions at a steady 60 cycles per second. “V2G has proven its ability to be a resource to the grid when power is aggregated,” she says. “We know it’s possible. It just hasn’t happened yet.”

I wonder how much, exactly, this system would help.

My quote comes from here:

• Jim Motavalli, Siri, will connected vehicles be greener?, Sierra, May–June 2016.

Motavalli also discusses vehicle-to-vehicle connectivity and vehicle-to-building systems. The latter could let your vehicle power your house during a blackout—which seems of limited use to me, but maybe I don’t get the point.

In general, it seems good to have everything I own have the ability to talk to all the rest. There will be security concerns. But as we move toward ‘ecotechnology’, our gadgets should become less obtrusive, less hungry for raw power, more communicative, and more intelligent.

17 Responses to Vehicle-to-Grid

  1. smallicoat says:

    Brilliant idea!

  2. Patrice Ayme says:

    Seems rather silly in the present state of tech, as Lithium Ion batteries have only 5,000 cycles in them, when discharging only 10%. (A 100% discharges enables only 500 cycles.) So if used massively, that system would shorten considerably the life of the battery of an electric vehicle.

    • You are right about that. Lithium is arguably as much of a non-renewable resource as crude oil. Lithium is elemental and therefore not reducible, yet every time it gets used and potentially recycled, it gets more and more dispersed. Helium is even worse in that regard.

  3. domenico says:

    I think that if the inverter is on the electric car, then the car can provide electricity directly to the grid.
    This can serve two purpose: sell the electricity to the grid, and it can providing alternating current in the car while travelling (normally the electrical devices work in alternating current).
    I think that can work with batteries of hybrid vehicles, providing electrical capacity with batteries.

  4. That’s all well and good, but I can’t help thinking about the physics of the battery itself. The constant cycling of Lithium-ion batteries results in degradation over the long-term.

    The discharge characteristics of these batteries is very interesting. The matrix itself is optimized to result in gradual discharge current. The key to this is to select the most randomized flow to prevent the ions from conducting all at once. My research into characterizing the stochastic transport of the ions is here:

    Moving the ions back and forth in alternating charge and discharge cycles results in the eventual rearrangement of the ions into less than optimal locations within the matrix composite. That’s part of the reason that they eventually lose their efficiency.

    Really what we want from a source of energy is the electrical equivalent of a gravity feed, such as a hydro dam. It’s trivial to generate a steady power source from a gravity feed since the outlet valve is so easily controllable. You just don’t get that kind of control with batteries as the stochastic flow is partly diffusive, and that has steep transient characteristics with tails.

  5. Gosh, you are finally wandering into my seciality of transport so I don’t have to feel like an ameteur trying to say something interesting about category theory or number theory to an expert :)

    I think your assumption that the electric vehicles will be parked has a limited lifespan. It is true that today most cars are mostly parked. However it is widelt expected that over 5-10 years, autonomous vehicles will become common place. The economic analysis suggests that individuals won’t bother to own an autonomous vehicle but that they will hire them wwith an Uber style app. Thus the electric vehicles will be moving most of the time.

    However the vehicle to grid idea may still be good. There are experiments on connecting moving vehicles to the grid using electrical induction.

    So we may end up with better utilisation of vehicles, better utilisation of road space and better utilisation of renewables. The real big risk to this utopian vision occurs if people stop using buses and trains in favour of autonomous vehicles. Obviously it is much more environmentally friendly to transport 40 people in 1 bus than to transport 40 people in 40 cars.

    • “Obviously it is much more environmentally friendly to transport 40 people in 1 bus than to transport 40 people in 40 cars.” Agree with you, Roger, on both the economic forces pushing to orphan public transport, and that, still, public transport is more environmentally friendly.

      The work of Karl Ragabo, formerly of Austin Energy, and now at the Pace Energy and Climate Center, suggests something similar of residential PV energy: If solar owners are compensated via net metering or worse, with net metering that does not return energy generated to them at retail, they are being incentivized to both consume more than they would, had their homes and habits been more energy efficient, and to leave the grid, depriving it of advantages of resiliency, peak load support, and support of their non-solar neighbors which would accrue had they remained. Ragabo’s solution is to separate charges: Compensate for generation but, separately, charge for consumption, potentially at different, time-varying rates. (Economically, it is an attempt to achieve a price of indifference from both sides.) It’s another example where without coordination the least energy intensive path/least emissions path won’t be tracked.

  6. Todd McKissick says:

    While Lithium-Ion batteries (the base form of V2G storage) may have economic benefits in specialized scenarios for certain individuals and at certain times, it’s definitely not the case for all. Other scenarios should rely on local market forces to ensure the correct balance there and then.

    The only solutions being publicly advocated today are utility run proposals. It should be noted that all of these proposals ensure the future is profitable for those utilities but not necessarily for their customers. The real solution is an open market grid based on instant conditions – a living smart grid. This would allow grid balance to be negotiated constantly in the same way internet traffic is done for every data packet sent around the world. Doing so would separate transmission and distribution costs from all load and generation costs, pitting every watt generated as equal to every one used. In this way, the floating price will cause incentive for only the cheapest solutions to exactly what is needed in all cases. And the result of that will be many new technologies will emerge in automated demand control first, automated generation second and automated storage to fill the rest.

    This is a key point because storage should be the last consideration, not the first. Not only that but electro-chemical batteries should be the last storage technology considered, not the first. There are far too many technologies available which, due to utility and energy company caused problems in subsidized economics, investor opinion and regulator thinking, cannot yet enter the market.

    The proposal can be found at and as expected, it gets no consideration from anyone who deems the utilities’ opinion as justified. Maybe it’s time that changes.

  7. Darin says:

    There are also companies that facilitate dispatchable negawatts if your local power company supports them.

    When they need to reduce demand, they send out email/text notifications so you can turn off/unplug stuff yourself, and they can also reduce turn off or slow down networked devices automatically if they have access to the manufacturer’s API.

    In terms of V2G, different battery chemistries tolerate addition cycling in different ways. In particular, NCA, which I think what Toyota and Tesla uses, seems to tolerate cycling well (Page 18 of the pdf linked below). Capacity loss is mostly a function of depth of discharge and battery temperature.

    Click to access 45048.pdf

  8. davetweed says:

    One factor that needs to be considered whenever a plan says “lots of nearby small things will be combined to…” (eg, wind-turbines, solar panels, cars, etc) is if there’s an unfortunate correlation going to happen. In this case that looks like it’s unlikely to happen precisely because the more people are in their cars at any time, the fewer there are at home/work making demands for grid electricity. So while it’s likely a sizeable fraction of electric cars will still participate in a rush hour (and hence be unavailable to the grid) demand should also be lower during rush hours, etc.

    • davetweed says:

      As an illustration of the unfortunate correlation problem mentioned above, in this interview the late David McKay made the point that “The key for the UK, he said, was a zero-carbon solution that works in the winter, when energy demand is highest but sunshine is lowest and winds can drop for days at a time.”

    • What I meant, Dave, is that the model you are proposing assumes that EVs when at scale will be used in the same way ICEs are. I understand making that assumption for purposes of simplifying analysis, but the future of widespread EV use, with distributed generation looks little like the present energy system.

      Consider Uber, for instance, which charges its customers more for rush hour use. In order for this all to work, it’s clear that large efficiencies are needed and, so, people need to be encouraged to reduce consumption. Karl Ragabo makes the point (which I just recently learned) that while net metering on residential PV is a nice, simple concept, it rewards customers who are sloppy about electricity use in their homes. Accordingly, he’s been a champion of separating the generating benefit to the home from the consumption charge, and making these time varying. So, this applies to the EV case by making recharge of EVs during rush hour comparatively expensive, something which could be automated simply based upon demand. Sure, people can still drive, but they’ll be disincentivized to make it a habit.

      The Uber economy is getting people used to the idea of there not being fixed rates on things.

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