Rising hopes electric cars can play key role on grid

Will electric cars one day become part of a network of rechargeable batteries that can help smooth out the intermittent nature of wind and solar power? Many experts believe so, pointing to programs in Europe and the U.S. that demonstrate the promise of vehicle-to-grid technology.

Journalist Dave Levitan has the story in this Yale e360 repost.

The United States now has more than 35,000 megawatts of installed wind energy, enough to power close to 10 million homes. Close on the heels of this ongoing renewable energy revolution is another green technology: By next year tens of thousands of Nissan LEAFs, Chevy Volts, and other electric vehicles will start rolling off assembly lines.

The electricity generation and transportation sectors may seem like two disparate pieces of a puzzle, but in fact they may end up being intimately related. The connection comes in the form of the vehicle-to-grid concept, in which a large electric vehicle (EV) fleet “” essentially a group of rechargeable batteries that spend most of their time sitting in driveways and garages “” might be used to store excess power when demand is low and feed it back to the grid when demand is high. Utilities and electricity wholesalers would pay the EV owners for providing that power.

Vehicle-to-grid, or V2G, is not a new idea. In fact, it’s been floating around environmental and green tech circles for a decade at least. But it has always had the tough-to-shed image of a utopian technology. Now, though, V2G “” as well as simpler schemes based on smart-timed charging of the vehicles “” is slowly becoming reality, evolving in quiet synergy with the worldwide push for renewable energy.

The main drawback of wind and solar power has always been their intermittency: By now it is more than a clich© to say that the wind doesn’t always blow and the sun doesn’t always shine. To some extent, that claim is specious: Existing power supplies also vary by huge amounts, and flexible generators, such as natural gas power plants, are called on to balance out the blips. This is called frequency regulation.

Those generators can handle only so much variation, though, says Willett Kempton, director of the Center for Carbon Free Power Integration at the University of Delaware and one of the pioneers of the V2G concept. “And also, we’d rather not be using those generators at all. When you get to 40 percent, 50 percent generation coming from renewables, you need some kind of storage, and this [V2G] is a way of getting storage on the system.”

That storage takes the form of the lithium-ion battery pack on board most EVs being produced today. For V2G to work, though, the cars need to be able to communicate with system operators running the electrical grid “” this can be accomplished with a simple Internet connection that could be built into the car’s plug. That communication link and a power converter that lets electricity flow both in and out of the battery will allow an overtaxed electrical grid to draw power from a group of cars, and then charge them when there is plenty of electricity to go around. If renewable energy ever supplies a sizeable portion of a nation’s power needs, using EVs as a diffuse network for storing electricity “” and then feeding it back to the grid on demand “” could be an important tool in decarbonizing the economy.

V2G technology is beginning to emerge in a number of countries. Japanese carmakers, including Nissan and Mitsubishi, plan to start producing V2G-ready cars by mid-decade. Small pilot projects to test the idea are also underway in Europe, from Sweden to Italy.

Increasingly-green Denmark, though, has taken the lead in V2G adoption. Wind power already accounts for about 20 percent of its electricity supply, and additional planned wind farms will raise that level to 27 percent by the end of 2012 and beyond 50 percent by 2025. At times, when the wind blows strongest, the entire country’s power demand is already met and exceeded by wind turbines. But without a way to store that excess energy, it is essentially lost.

So could a large number of EVs actually help with the huge variations in wind that can occur? According to Claus Ekman, a researcher at the Ris¸ National Laboratory for Sustainable Energy in Frederiksborgvej, Denmark, it can, to an extent. Ekman recently published a paper in the journal Renewable Energy that modeled how well EVs could handle increasing wind power generation. He found that in a scenario involving 500,000 vehicles and 8 gigawatts of wind power, various strategies would reduce the excess, or lost, wind power by as much as 800 megawatts “” enough to power more than 200,000 homes. Ekman calls this a “significant but not dramatic” effect on the grid. Scenarios involving 2.5 million vehicles and even more wind power show an even greater impact.

“The limitation is the total amount of power that the EVs can absorb,” Ekman told Yale Environment 360. “The peaks in the wind power will be too high for the EVs to absorb them completely.”

Even if a large EV fleet couldn’t handle the full extent of a 50-percent wind power penetration in a country like Denmark, which could be fossil fuel-free by mid-century, it could clearly make a dent. And Denmark has already gone beyond the theoretical, with a V2G project called EDISON running on the small island of Bornholm. The goal is to use the storage capacity of EVs to bring the island’s wind power capacity up to 50 percent of the total demand. Because V2G will reduce the need to generate power from traditional sources, researchers estimate that the price of electricity on the island could drop by 50 percent or more. Though the island is home to only 40,000 people, the project could eventually be used as a proof-of-concept for larger systems, both in Denmark and elsewhere.

In the U.S., commercial-scale V2G projects are farther off, but then again so is 20 percent renewable energy penetration. (The U.S. is currently hovering around 2 percent.) Nonetheless, some progress is being made. For almost a year, several modified vehicles based at the University of Delaware have been providing power back to the grid, and getting paid for it.

Kempton, who runs the Delaware V2G pilot program, notes that using V2G storage, rather than huge centralized aggregations of batteries, eliminates the need for additional high-voltage infrastructure, and the economic benefits of using car batteries that consumers are buying anyway are undeniable.

Delaware Vehicle to Grid

“Maybe once a year you won’t have enough power in your battery to drive where you want to drive, and you’ll have to wait half an hour before you go somewhere,” says Kempton. “In exchange, you’ll get these payments and you’ll be helping bring more renewables onto the system. That’s the deal.”

The Delaware project involves fewer than 10 cars at this point, each earning about $6 per day for the power fed back into the grid. The price will depend on external factors like the cost of natural gas, so as fossil fuel prices rise in the future a plugged-in EV might generate even more money for its owner. And a common concern, that V2G might tax the car batteries too much and shorten their lifespan substantially, hasn’t proven to be an issue to this point.

Policy makers are also getting on board. Delaware now features a first-of-its-kind law requiring utilities to buy back electricity that EVs can offer up to the grid, and an energy storage bill recently passed in California could open the door to V2G in the future. Jon Wellinghoff, the chairman of the Federal Energy Regulatory Commission (FERC) “” which governs the interstate sale and movement of electricity “” has also expressed support.

Still, the need for further hardware on board the cars may present an economic challenge to large-scale V2G integration. A standard EV can receive a charge but lacks the equipment necessary to send it back out. Paul Denholm, a senior analyst at the National Renewable Energy Laboratory’s Strategic Energy Analysis Center, says that issue is far from resolved.

“I get the impression that the vehicle [manufacturers] aren’t particularly interested in V2G because that’s not a core vehicle technology,” Denholm says. “That would be a lot of extra costs, and they’re in the business of selling cars, not grid services.”

“It’s fine to talk about plug-ins, but it is really going to be a while until we see a sufficient number of vehicles on the road to have an impact on the grid,” Denholm says. “How many Volts are they going to sell, how many LEAFs are they going to sell this year and next year? We’ve got time to figure this all out.”

Chevrolet’s and Nissan’s EV entries won’t ramp up to full-scale production “” on the order of hundreds of thousands of vehicles “” for a few years, and 20,000 cars here or there won’t provide the type of grid impact that Kempton and others envision. President Obama, however, has set a goal of 1 million EVs and plug-in hybrids on the road by 2015, and last year the administration threw $2.4 billion of stimulus funding behind that goal.

And if slowly building a scattered fleet of residential vehicles won’t help the mass adoption of V2G and managed charging, there are other possibilities. Ken Huber, the senior technology and education principal at regional transmission organization PJM Interconnection “” they’re the ones paying that $6 per day to the University of Delaware cars “” says fleet vehicles like those of the U.S. Postal Service might make a very attractive place to start with V2G.

The EVs coming onto the market now “” including the Volt, LEAF, and Tesla’s Roadster “” aren’t equipped for V2G, but Kempton says he is working with manufacturers and hopes to see that change soon. He guesses that within five years, tens of thousands of V2G-ready cars will be produced, and within 10 years “it will be a major component of the vehicle fleet.”

The logical intermediate step before full V2G adoption, most seem to agree, is the use of managed- or smart-charging practices for EVs. With smart charging, a car won’t have to feed any power back to the grid. Instead, it will charge at certain times when demand is low or when the wind is blowing the strongest. Both of those often occur early in the morning, say, between the hours of 1 a.m. and 4 a.m.

“When people get home at 5 or 6 p.m., that’s typically when the grid peaks in terms of demand for air conditioning and things like that, so it’s a really bad idea to charge right when people get home and plug in,” says Denholm. “If you’re talking about thousands or millions of vehicles, some kind of controlled charging scheme is going to be absolutely necessary.”

In this case, the technology isn’t hard to come by, with smart meters already being deployed nationwide and software that could control the car’s charge readily available. Denholm says that on the simplest level, just a basic timer could do the trick. In Ekman’s Danish study, the best schemes he modeled combined V2G with smart-charging practices to maximize the benefit to wind power integration.

Even with managed charging, though, we may be years off from EVs playing a significant role in renewable energy’s growth.

“They park at the same place, they are very regular in their routes, they know the amount of distance and charge that they need, and they are typically available during those periods when we need it, those 12 off-peak hours,” he says. School bus fleets, which often sit for the entire summer in a parking lot, offer another opportunity.

Such vehicle fleets could fill a need immediately. According to Huber, PJM Interconnection “” which provides electricity to about 18 percent of the country’s population in 13 states and the District of Columbia “” currently has only about three gigawatts of wind power out of its peak capacity of 144 gigawatts. Even now, there are periods in the early morning when the price of electricity actually becomes negative: There is too much generation and not enough demand, demonstrating the need for power storage.

Huber said that if, as planned, wind generation in the PJM system eventually rises from the current three gigawatts to almost 50 gigawatts “” and if EVs in the area reach 1 million in the next five years “” the goal of large-scale V2G technology will become a reality in a market that supplies electricity to 51 million people in the mid-Atlantic, Midwestern, and southern states.

Dave Levitan via Yale e360. Levitan is a freelance journalist based in Brooklyn who writes about energy, the environment, and health.

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11 Responses to Rising hopes electric cars can play key role on grid

  1. spiritkas says:


    In some ways I object to the tempered tone of this article. It is important to have a controlled and reasonable level of enthusiasm for emerging technologies and I think this article would go a long way towards introducing the seed of this idea to people who are not very familiar with it.

    “Kempton, who runs the Delaware V2G pilot program, notes that using V2G storage, rather than huge centralized aggregations of batteries, eliminates the need for additional high-voltage infrastructure, and the economic benefits of using car batteries that consumers are buying anyway are undeniable.”

    The topic is addressed here and perhaps the framing appropriate for 5 years from now isn’t part of the focus of the article, but it seems to me there are no other competing technologies that will fufill the need for energy storage that are likely to have a high market penetration or have plans for built infrastructure. There are lots of really interesting R&D type technologies, but as for current and rapid deployment and roleout of energy storage technologies coninciding with the current ramping up of wind, solar, etc. I think the V2G technologies will be a great bridging technology and then continue to play an important role as we reach 50-80% and eventually near 100% renewable energy supplies.



  2. Sasparilla says:

    This sounds like a very good (from a big picture) idea, but there are some serious issues to surmount. While the article brushed aside lithium technology battery cycle limitations, lithium based batteries have cycle (the charge and discharge of the battery) life issues.

    The greater the numbers of charges and discharges the sooner the capacity of the battery pack starts to decline. This is why your cell phone or laptop battery doesn’t hold the charge like it used to after a year or two and eventually just has to be replaced. At this point lithium battery technology has not beat this problem.

    As an example the Chevy Volt initially only uses about 50% of its battery capacity (that’s right you pay for twice the battery capacity you need initially) so that Chevy can be sure it’ll still give you that 40 miles of range after 8 years or 100,000 miles that they have to guarantee (the pack costs more than $10k) and this is because of the negative effect of alot of charge / discharges will have on its capacity (amount of energy it will hold) over time.

    Another example of the finicky-ness of the lithium battery tech regarding charge / discharges and long term capacity effects, there was an article on the lithium batteries (in the Nissan Leaf I believe), different charge rates affected its long term capacity – 110 volt (normal US household wall plug) charging let keep its capacity the longest, going to 220 volt charging negatively affected the long term capacity of the batteries and 440 affected it even more. I wouldn’t expect these affects to be specific to the Leaf and probably applicable to lithium batts in general.

    So, why wouldn’t the auto manufacturers want to get in on this hook your battery car to the grid so it can be cycled at will by the power company while they are mandated to have warranties on their cars battery capacity? Pretty simple, they’d be on the hook for some seriously expensive liability – they’d be crazy to let it happen to their vehicles without voiding the battery warrantees.

    Long term I’d expect large strides to be made with Lithium battery tech for cars with regards to cycle effects on battery capacity, but at this point the problem exists and is so important Chevy has to put in a battery that’s twice as big / expensive as it needs to be just to make sure the Volt will still have that 40 mile range at 8 years or 100k miles.

    For those that are questioning the cycle capacity issue with regards to the Toyota Prius, whose battery rarely ever needs to be replaced, that’s because the battery in the Prius is a Nickel Metal Hydride battery, whose chemistry has a unique cycle capacity behavior – if you keep a NiMH battery charged between 30% and 70% of capacity (or something along those lines) cycles have little to no effect on long term battery capacity – so Toyota keeps the Prius batteries charged in this range at all times during their use and they rarely have to replace them – they should last the life of the car. Honda didn’t learn this trick (or didn’t use large enough capacity batts to allow them to keep it in this charge range) for its hybrids and you only have to google Honda Insight battery failure or Civic Hybrid battery failure to see what happens (they aren’t cheap).

    So this sounds like a great idea, but at this point its a bit of an ivory tower solution that the real world (auto manufacturers) would not let happen till Lithium battery technology surmounts the lithium battery cycle life capacity issue – which they are desperately trying to surmount (so they don’t have to put in such oversized batts and reduce cost). It’ll probably get there, but not for a while (2020’s might be a guess).

  3. paulm says:

    This is a disturbing figure. We’re in trouble.

    now add to it ice sheet collapse and oh oh.

    [JR: Link won’t work for me.]

  4. Prokaryotes says:

    The electric vehicle is the biggest step in human transportation evolution. Similar to the industrial revolution a second energy revolution will take place, just this time it will affect the world without most of the harmful implications of fossil fuel usage.

    Like what the apple computer has become, electric transportation devices are chosen as the leading technology for transportation and electricity – energy security.

    And apple will loose the position of the most valuable business to a company which makes electric vehicle.

    People who invest now into clean energy solutions have the chance to make the same success story like the standard oil company did during the first energy revolution.

    This might be a slow start so far, but this is the next big thing, the biggest thing in our lifetime. So no matter what, renewable energy is the future.

  5. spiritkas says:

    at #2:

    There are two comments I have:

    1. The battery technology is irrelevent as we move forward. People will get paid for having their batteries on the grid and can choose to do so or not. By doing so they’ll also access cheaper electricity for their total home use as well. Both of these options will create incentives for battery owners to be V2G.

    2. It is likely that adoption of electric vehicals with battery energy storage will be accelerating by non-ownership of batteries through leasing/rental schemes that will dramatically reduce the price point for the vehicals. A supporting reason to dissasociate battery ownership is to increase driving distance by having swappable batteries. If the battery is changable and upgradable on the same model car by newer technologies as they emerge on the market and recharge stations begin to carry them, then battery owernship doesn’t make any sense at all. Also this solves the problem of auto manufacturer concerns as the battery swapping companies (as the oil companies of today do) will use market pressure and possible partnerships with automanufacturers in order to make sure their electric vehicals are V2G ready. Not to mention the swapping stations themselves will be on the grid and you betcha they’ll buy up all that 1am-4am cheap electricity.

    There is no reason to wait 10 years as you suggest for hyper capacity, fast charge, long life cycle battery technology to emerge at a price point reasonable enough to promote battery ownership. A more rapid deployment of swappable batteries is cheaper, allows for a leasing model, and invovles the profitable building of battery swapping station infrastructure all across the country. Which will be another large source of energy storage as these stations are lilkey to have 50-100 batteries on hand.

    Also if you’re buying an electric car you’d be better off leasing. It lowers your up front costs and rather than being stuck with the battery of 3 or 4 or 5 years ago and dealing with reduced charge capacity due to charge cycling, you’ll be able to clip in the newest battery models as they come out.

    I think by 2015 these stations will be popping up around cities and by 2017 they’ll be common along major interstate routes, i.e. I-95/NJ turnpike bos-wash area etc., and then by 2020 you’ll be seeing multiple battery swap stations opening up in your area with competitive pricing.



  6. Inverse says:

    With around a billion cars in the world how many more power plants are going to be required to feed them all if they all become electric cars. The governments will not want to miss out on the tax petrol generates so these taxes will by default be passed onto electricity, I don’t want to pay a petrol equivalent tax on my power bill.

    Also, battery swap stations sounds great fun, more danger, more staff, longer waits and more acid\chemicals to dump somewhere. This idea just gets better.

  7. Anne van der Bom says:


    That is a quite simple question to answer. You can look up the numbers yourself. Take the vehicle kilometres traveled per year and divide by ~6 for the number of kWh’s you’d need to cover those in an electric car. In an average western country that would increase electricity consumption by less than 20%. Add freight transport and buses and you’re looking at an increase of ~25-30%. If those electric vehicle charge mostly at off-peak hours, there would be very little new generating and grid capacity necessary.

    Knowing how much energy is wasted, by focusing on energy efficiency we could be driving our electric cars for free.

    Energy efficiency doesn’t get the focus it deserves. I guess it is not as sexy as sleek wind turbines or square kilometres of shining solar panels or high tech nuclear plants.

  8. Lewis C says:

    Anne at 7 –

    it may be that you are right about electric cars not posing a need for additional generating and grid capacity, but for the wrong reasons.

    Your maths seem optimistic when I run them:
    A modest 12,000kms/yr driven, divided by 6 gives 2,000kwHr power need or 2,670 HPhrs, spread over 150 hrs driving at 80 kms/hr, which implies the vehicle is using less than 19 HP on average.

    As I drove a very light 20HP citroen for many years, that would get up hills if you took a run at them, I think that to be saleable electric cars will be two or three times as powerful to meet modern expectations.

    However, with the oil market’s cushion between supply and demand forecast by DoE to be used up in 2012 as oil depletion bites, with supply falling exponentially by ~4%/yr from 2015 onwards, the prospect is of a ruinously high oil price spike, followed by a slump as the unresolved problems exposed in 2008 become obvious.

    After which, the prospect of a large enough number of electric vehicles being sold in a long-term slump to affect power generating capacities seems really remote.



  9. Anne van der Bom says:


    I don’t really get your point, where exactly is my math optimistic? I don’t understand why you’re calculating average power and then arrive at the conclusion that the average power somehow dictates the maximum power.

    The big advantage of an electric motor is that it’s efficiency is more or less the same across the power range, unlike an internal combustion engine. This means you can easily fit an EV with a very powerful motor while only sacrificing very little efficiency. The 180 kW Tesla roadster (0-100 in 4s) is a nice example of that.

  10. Lewis C says:

    Anne, I’m sorry I didn’t write more clearly.

    What I meant was that from my own experience I’d expect the average power consumed by a contemporay electric passenger vehicle to be in the 40 to 60 horsepower range, rather than below 20 HP.

    I didn’t mean to suggest that this average level would limit the maximum power available, which of course it wouldn’t.

    I’m afraid my real point is that we appear unlikely to have the economic conditions, as a result of PO, to allow novel electric vehicles to get near a mass market in the coming years.



  11. Anne van der Bom says:


    “I’d expect the average power consumed by a contemporay electric passenger vehicle to be in the 40 to 60 horsepower range”

    Do not trust your gut feeling on this.

    IIRC a Prius needs 12 kW at 100 km/h and ~18 at 120 km/h. Higher cruising speeds are rare. At 50 km/h it is probably somewhere around the 2-3 kW mark. Higher power is only necessary for brief moments of acceleration. While decelerating, it is 0, and an EV will do regenerative braking, effectively consuming negative power.

    The 6 km/kWh is a real-world figure for an EV comparable to today’s ICE powered cars, under common, every-day driving conditions.

    Approached from another angle: The Prius engine has a peak efficiency of 37%, but under every-day use 30% seems a likely average. The fuel consumption is ~5 l/100 km. A litre of gasoline contains 9 kWh of energy, so that is 45 kWh / 100 km.

    A good electric motor is about 90% efficient, or three times better than the Prius’ hybrid engine, and would need a third of that energy, or 15 kWh/100 km.

    My conclusion: you are being pessimistic ;-).