Electric car batteries can do more than power electric cars. They can send current to homes and buildings, or send it back to the grid when demand is high. Some experts even believe EV batteries might one day boost the prominence of renewables by storing the energy from wind and solar farms.
The idea of so-called “vehicle-to-grid” schemes inevitably stirs debate among engineers. But make no mistake: The concept has a huge following. Googling the term “vehicle-to-grid” yields an astounding 526 million hits. That’s one reason electric utilities, auto manufacturers, and university researchers are all studying the concept.
We collected photos and diagrams from ongoing vehicle-to-grid programs. From pure EVs to plug-in hybrids to wild-looking concept cars, we offer a peek at some of the vehicles that could one day power your home.
Click on the image of Willett Kempton to start the slideshow.
Willett Kempton of the University of Delaware has been a driving force behind the idea of vehicle-to-grid (V2G) technology. In 2013, Delaware teamed with NRG Energy to launch the world’s first revenue-generating V2G project. Here, Kempton is shown with a Honda Accord Plug-In Hybrid that’s being used as part of a demonstration project by the university. (Source: Honda)
Cap'n, this is nice in theory, but not really practical. The issue with plug in electrics today is range. One good aspect is that they can be charged off-peak. I guess that, in an emergency, the car battery could be used to supplement the grid. On the other hand, that electricity will not be available for transportation, the vehicle's primary purpose. If you have a car like the Volt, that might not be a problem, because there is a ICE to charge it. On the other hand, the Volt's battery is not that large. The vehicles with the large batteries, pure EVs, which would be most useful in this scenario, are the ones for which this is the biggest problem.
It is much cheaper to site batteries or fuel cells in houses, or at substations. My understanding is that many new homes in Japan are powered by fuel cells. This is much more reliable. Take slide 7. What happens if the building is drawing from the cars and someone needs to go somewhere. The car battery will be depleted, and the driver will have to wait until it can be charged again.
It is true that EVs can be useful in terms of renewables. The whole idea of being able to store energy from renewables is advanced if that energy can be used to charge vehicles. There should be a cost advantage for doing so.
"What happens if the building is drawing from the cars and someone needs to go somewhere. The car battery will be depleted, and the driver will have to wait until it can be charged again."
Another question springs into my mind, what happens to the battery life? It depends on the value being extracted from the battery by the grid. The controllers designed to use in the EVs are intelligent, so that battery life can be utilized to its maximum potential. Will the grid also work intelligently or will it extract all the power it can and leave the driver stranded with a damaged battery.
I guess a better alternative is utilizing this money and making a static energy setup instead of a moving car.
This is a really interesting slideshow, and I am not sure I agree with you, naperlou, although you have a really good point. But when I was researching a recent story on the Army and its use of renewable energy, I learned about how they are plugging Army vehicles into microgrids they have designed (that use renewable energy as part of their source of electricity) to recharge electric cars. This sounds like the reverse of the concept here, but also if I understood them correctly the connection went both ways--to charge and also to send energy back to the grid. So it is quite feasible that this could work.
Charles, thanks for this story. naperlou, i have one disagreement with what you said: this is a lousy idea even in theory!
To me, the idea of using your PEV to power your house is kind of like running your house off of a bunch of D-batteries. Eventually, the D-cells will be drained, & then you're left with a grid-connected house and a bunch of dead batteries. So, if your Leaf can power your (Japanese) house for a couple of days, where are you after that couple of days? You may have saved some money by avoiding peak electricity charges, but now you can't go anywhere!
The flaw in this scheme, to me, is that the EV car can only get its resupply from the grid; it has no independent electricity generation. Using an analogy, it's a pressure tank on an air compressor; it only gets filled at the spot from which it's drained, and the compressor has to be running or the tank runs out and you get no more air. The Volt does have its own generator, yes, but generating that electricity from the Volt to replace that which was sucked out onto the grid is a considerably less efficient process than what can be generated by the grid. Either way it's a loss: either you lose range to the grid or the whole system loses efficiency.
If somebody can enlighten me with a use case that makes sense, please do so!
FM, Your use case happens in many major thunderstorms - Power outages. Typically, power would be out for a day or two, and a fully charged car battery can run the important things in your house for that duration (e.g the refrigerator, the oil furnace, and the well, as well as a few lights).
Here in the northeast, we can typically expect one or two days without power every year. Right now, we have a gas generator ($1000) in the garage that we have to wheel out and plug into the external outlet ($1000 to install). We have to maintain that gas engine as well.
If we can just plug our car into the house, that would have saved the costs of the generator and the associated effort to keep it available for use.
@naperlou, absolutely, and consider that a battery is only good for a limited No. of cycles, does that mean that because they wore your car battery out in 12 months instead of the the usual 6 years that they would pay 5/6 of the price of your new battery and fitting? I think that along with your reservations make this really a pipedream. A grid battery needs to have a really long life that includes 1000,s of cycles and/or be very cheap per kW and doesn't need to be light. None of these criteria are a match for on-board batteries. Telecoms companies used to have banks of lead acid batteries so that phones would work during a blackout, I don't know whether that is universally the case now but they were permanently on low float to extend their life. Grid batteries will be going through deep cycle almost daily.
I am not sure how the bidirectional power is going to work. Don't most power companies charge their customers a different (higher) rate for power they send to customers than the rate they pay for power supplied to them? So the customer will in effect end up paying the power company for the previlege of helping them supply power by using power from their EV battery! Sounds like a winning situation for the power company and a loosing situation for consumers.
Also I agree with Naperlou on the possibility of leaving EV owners without a useable vehicle.
Yes, Davek3gau, I think it wouldn't work if someone had to deal with an electricity or power provider. I think the Army's scenario works because it is based on a microgrid the Army set up itself. Now if someone has their own home electricity grid based on, say, solar or wind power (this is possible in the countryside), then they could charge their car on their grids and also power the grid with the car battery in case of an emergency or something (provided they don't need to drive the car at that moment).
But if the goverment is willing to offer our money then agency's and univerisities will take and waste it studing ideas that a 4yr old could tell you do not pass the smell test.
I do not really need to explain why this is a bad Idea other have and quite frankly common sense of a 4yr could tell you as well.
But it is another way they can try to say see look how good an EV fleet would be we.
EV's need to stand or fall on their own, If they are cost effective then they will stand. If they are not then until they are we should let them be a novelty, and not force all car buyers and taxpayers to pay to support them.
Using PEVs as a source of peaking current and/or storage of intermittent renewable electricity sources is an excellent idea.
I've been involved with the design, build and application of high power bi-directional power converters for the past decade and the efficiency and features of these devices has improved dramatically. Thinking that a PEV would be utilized to the point of fully discharging the battery pack is naive. The on-board battery management systems in these vehicles are very sophisticated and would not allow full discharge of the battery pack in ANY condition (mobile or stationary). On-demand vehicle operation would still be possible, since the battery pack would maintain a minimum state of charge (probably no less than 65%). Note that a vehicle battery pack will rarely, if ever, be charged to 100% - there needs to remain some charge capacity to accommodate regenerative braking.
One of the objectives of the smart grid effort is to enable a means by which alternative energy sources can be connected/disconnected to the national grid easily. With the additional data communication link, PEV's can source to or sink from the grid intelligently.
The battery packs also perform better when they are used and over time, become more efficient (due to cell balancing). As was stated in one of the previous comments, these are not Pb-Acid batteries that have a limited life and small kW-H ratings; most are now Li+ chemistries that actually improve and have a service life of about 10 years.
Again, the flaw in this whole logic is thinking of a PEV as an energy source. It is not. A PEV is an energy sink, and always will be! Sure, you can hook it to a smart grid, and sure you can siphon energy from the PEV to the smart grid, and sure we can figure out how to do this smartly and efficiently without causing damage to either thing ... but on the whole, it is a good idea? Nope.
The charge/discharge controller may be highly intelligent and communicative, the power conversion may be 99.8% efficient, and the batteries may last forever, but at a system/user standpoint this thing falls apart. I would rather not go out to my garage, needing to drive across town, and find that my PEV is only at a 75% state of charge, and if i can't find a charging station out there & wait an hour i might not get back. Leaving your customers walking is a bad scenario.
A PHEV (Volt-ish car) isn't much better. Yes, it won't leave me walking, but if i walk out to my garage and can only go 5 miles on batteries before it starts up the on-board generator, then suddenly i am using more gasoline and i am charging my batteries with a gas engine that's maybe 20% efficient at doing so. Again, at the system/user level it's a bad idea.
If our automobiles had on-board nuclear-powered generators then yes, feeding the grid would be a good idea. Until then, not so much.
Hi fm, I think 94-95% is going to be the best converter efficiency and an ICE is around 40-50% if its a diesel, but otherwise I agree a PHEV is a user not a storage supplier and until we have PHEV's that have such large batteries that 75% charge gets you anywhere you want to go AND BACK I don't think they are viable. It's the power companies that want a way to make renewables work without investing in significant grid infrastructure themselves that are pushing this.
We need a viable working renewable energy grid and a similarly working renewable vehicle propulsion system but this will just sick millions out of the public purse without returning any real benefit.
If renewables and storage in batteries isn't going to work then we need to use renewables to converts power plant waste (ie. CO2) back into carbon so that the carbon fuel itself becomes a renewable.
The only other alternative (in the short term only) is to use Thorium reactors for base load and renewables up to 15-25% while improving user efficiency.
The point was made earlier, Utility companies pay you less for providing power than they charge for using it. This is a Utility companies wet dream.
And a nightmare for the customers.
The Utility company charges you X to fill the battery, than pays back 70% of X to take the power back, repeat forever. This is totally ignoring the fact that when you need your car it won't have full range.
Besides, where I live in the far north, Power is at highest demand for heating at night, same time I would need to charge the car (Since at last count there was exactly ONE public charging station in the entire state. And it is over 40 miles away from my daily use area.)
This is silly, the Power companies need to make their own storage on site at generation locations or at substations. Non Mobile setups can be far more efficient.
The batteries may improve over time, but only for a short time. If that improvement were constant, they would last forever.
A service life of 10 years is predicated on a given number of charge/discharge cycles. If half of the charge/discharge cycles come from supplying power to the grid, the service life of your battery will be 1/2 what it would be powering the vehicle. If the utility company is willing to make it worth your while by paying enough for the energy provided by the battery to cover the cost of battery replacement, then fine. Otherwise the utility gets the gravy.
Rosek said "On-demand vehicle operation would still be possible, since the battery pack would maintain a minimum state of charge (probably no less than 65%)."
On-demand would be possible but even more limited than before so now your meager 80mile range is pushed down to 52, but wait their more many pack warentees only garentee 80% power of new battery (LEAF) so now that 80 mile range is 38.4. But wait their is more what if it is a hot day and you want AC or a cold day and need heat now you have even less.
just a bad IDEA.
I am not an EV fan but hey if you like EV's great but let the EV be an EV. The only time you should be using your vechile for power is when the CA electric grid starts to fail again and you have no power.
The owner of the car has an option as to what % of their battery charge may be used. 3% is the number I have seen. I agree 65% is too much for most people. In fact the batteries are generally replaced when they have less than 75% of their capacity, at which point they should be used for stationary grid stabilization, then recycled.
It's biggest value is in frequency/spinning reserve replacement, where the electronics can respond in micro seconds, better than any existing mechanical generator, long enough for the gas turbine peaking units to come online. I have read that some 30% of our electrical energy fuels are spent on spinning reserve and frequency control. That's wasted standby power, not the power actually delivered. Vehicle to grid and vehicle batteries to grid would eliminate that with better performance.
Great points about spinning reserve, trenth. I do wonder, though, how many consumers will be willing to sell their battery charge back to the utility, especially if the EV is a BEV and is their primary form of transportation. If I own a BEV, and it's my primary means of getting to work, and it takes five hours to recharge, how often will I be willing to sell my power back to the grid?
I'm not a big fan of the battery only electric car anyway, you always risk getting stuck. I think that the plug in, multi fuel hybrids will dominate. The articles I have read say the owner could pay for their batteries just doing 3% spinning reserve and frequency stabilization for the utilities. We will have emergency generators on BEV's the size of a shoo box, always ready to go, at the very least. Till the market for batteries is saturated, we can't afford to waste batteries on all electric cars anyway.
Distributed grid stabilization and generation reduce grid losses. Locally generated electricity is mostly locally consumed. Centrally generated electricity must traverse the entire path on the grid. The grid is inherently bi directional at the local levels. The other huge advantage of personally owned backup power is the security and effect on attempts by gov and private companies to gouge the people as is happening with gas on the east coast right now.
The big problem is the whole business model for private utilities is obsolete. The utilities view the grid, spinning reserves, frequency stabilization and reserve capacity to be sunk costs. They are not profit centers without gov help. Let's skip the private utilities and have the gov directly provide all those services and part of the national electrical grid freeways. Private companies cut corners till things break. Private companies are notorious for the failure to spend the money on rare contingencies. Gov on the hand is good at this.
The problem that is ignored with the idea of borrowing power is that battery packs wear out. Every charge and discharge cycle uses up some of that lifetime. Improper use uses it up much faster, but even following the very best practice, each cycle uses up some of the lifetime.
Would the utility be willing to pay extra for that portion of the lifetime that their borrowing power used up? I rather doubt that. Would they really be willing to only have a 3% drawdown on a charge? I doubt that even more. And what happens if I need to make a 2AM emergency run to the hospital with a sick kid? Woulkd the utility suddenly and instantly return the energy that they borrowed? They could not do it even if they wanted to.
Letting the utility take power from your battery does not make as much sense as letting a stranger siphon gas from your tank, except that I I am feeling really generous I may choose to gift some stranger with a gallon or two. But that would be my call to save a stranger in need, instead of a utility unwilling to cut off service to areas that have been drawing excess power. Let folks set the AC at 76 degrees instead of 67 degrees and the power shortage might be a lot less critical.
So the whole concept of the vehicle batery serving as a utility source is a bad idea.
It appears that some of the posts on here are a too little narrowly focused. Adoption of PEV's is still immature and infrastructure changes/modernization take time to implement. If one lives in a sparsely populated area, in the great frozen North, it would probably be wise to consider some alternate energy sources besides super long electrical transmission lines from a central power station.
The power grid has to under go some pretty dramatic changes to make it more robust and to increase capacity. PEV's, either sourcing to the grid or simply not sinking from the grid during peak demand, will play a role in this modernization.
These types of microgrids are the future of the power grid. Utilization of such systems will mitigate the need for rapid responses from large power generation plants enabling the overall effect of a much more stable grid.
In fact, power companies can (and do) encourage these investments on the consumption side by providing cost savings or other incentives directly to consumers. Natural gas peaking plants are a lot more expense to build, operate and maintain than providing cash incentives to consumers.
I love when people do effeciecy calculations they always make assumptions so they can leave out losses they do not want to accept or deal with.
The report inverter effeciencies of 97% each way. But they always leave facts out when calculating these effeciencys. They assume power is right their from you meter. Well in most case the charger it is 0-50 ft of 10AWG wire for a 30-40A circuit. Assume the mid point here as average and you loose 44W (30Sq *25ft *10AWG(R/ft) * 2) (1.2% just to wire resistance from breaker box to charger) of power when charging and 44W of power when selling back to the grid just in heat loss of cable If you ise 12AWG legal in some areas for a 30A circuit that goes to 66W. And that is just one of the losses ignored their are coupling resistances, contact resistances, control circuit power used, (yes most eff calculation leave out the power used by the controllers they just calc the high voltage power eff. Even a 20W system is another 1% of loss, *2 because you have the charger Controller and the onboard controller both operating at this time)
All of these 1% losses add up to an overall loss of 7-8% each way. That is 15% overall loss once you buy - sell. How does that make any sense, you buy 1KW and then of that 1KW you sell 0.85KW??
Good point; i wasn't considering wire losses in this mix. There's so many other downsides to this even without considering that.
Wire losses and power in/out finances notwithstanding, consider too that the utility would also get to use some expensive load-leveling equipment that their customers pay for. They don't have to pay a dime; such a deal for them!
On the other hand...
I can see the transient peak load leveling provided by a bunch of PEVs as being valuable to the utilities (and all of us) - ok, that's reasonable. Short-term use with a minimal energy drain, and energy replacement within minutes. That would be acceptable to me. BUT only if the utility kicked in some coin for it. They'd be getting a benefit from this at my expense. If they would want this, they need to be prepared to pay me for providing that service. A lease agreement, if you will, with limits on siphoned power and guaranteed time-limited replacement! How 'bout that?
Just thought of another loss left out of their calculation. To do this now you need to leave the controller on your car & wall charger in some form of wait/ready state. This state will drawn power even if the power company is not needing power from your PEV at the time yes it is only 2*15w(30W) of power but this is far more than the 5W or less drawn while off. And this power adds up even when no grid update is needed. to be able to source at a moments notice you need the controller in some semi awake state to respond.
Their goes another few percent out the window that nobody mentions. so now if you are in this program you loss money even if they draw no power. Good Idea????
OK, so i'm not that smart. If you search on "Vehicle to Grid", you'll find concepts similar to what i've posted. The utility doesn't get your EV for free; they're proposing to pay for the service where you hook up wherever (home or elsewhere) & they can use a certain user-defined percentage of your battery for either siphoning or storing extra. You would be essentially renting some of your EV range for a fee. You gain a little rental income and the utility gains by not having to build out and maintain as much infrastructure.
Correct! That's the point I tried to make in my last post. As far as reducing the overall usuable life of the vehicle's battery pack, there needs to be some structure in place whereby the packs are traded in for fresh packs - this could be financed by the same power companies. These same power companies could then take the used vehicle packs and utilize them for stationary peaking facilities.
Of course there is some energy usage by the in-home or publically installed Bi-Di unit in standby mode. I bet that all of the little vampires that are always plugged into duplex outlets throughout one's home gobble much more power than a single charging station. If one is that concerned about wasted energy, then you just have to disconnect your home's mains feed at night or every time you leave to go to work - cool!
One would hope that the PPA (Power Purchase Agreement) that enables this bi-di power sharing would factor in lost battery life and standby converter power in the $$ paid to the EV-owner for this service. Sort of the same kind of thing as a mileage allowance for cars driven for business purposes - the 51.5 cents per mile is far greater than just the cost of the gas, and factors in auto maintenance and depreciation. Same principle here.
Having someplace for the semi-exhausted batteries to go after their utility in cars has diminished sounds like a secondary market to me. Maybe one would develop around battery salvage!
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