How much EV storage capacity could be used for the grid?

IME, BEV batteries offer an outstanding opportunity to add real amounts of storage to the electrical grid with a minimal amount of environmental impact. For this to become a reality, several things need to happen:

- EV batteries need to become more durable. In other words, adding a second function to the batteries should not shorten the life of the primary function to the point where more EV batteries need to be produced.
- EV batteries need to have more capacity. Some already have enough today so that some capacity could be shared each day without impacting the primary function of the EV.
- EV chargers (both off-board and on-board) need to be upgraded to allow bi-directional power flow. Some ChaDeMo chargers already have this capability.
- A control and communications system needs to be implemented to allow the grid to optimize generation and consumption with access to the instant, on-demand, distributed storage capabilities which EVs offer. This implementation needs to included rate-plan updates to compensate EV owners for battery access, ways to define how much capacity must remain at certain times, and also many other details.

My expectation is that EV batteries WILL become much more durable and have much more capacity as time and technology march on, to the point where those two current limitations really become enablers of EV-based grid storage rather than barriers. The other two items will require some action from both the utilities and the governing bodies to enable this idea to move foreward.

For now, let's just assume all of this is in place today and have a look at how much EV storage might be brought online as the EV market grows. I'll do this for the U.S. for now.

I'll use InsideEVs scorecard and evnow's comparison chart to estimate total EV battery capacity.


So, all-told, including the other entries, about 4 GWh of BEV battery capacity and about 1.5 GWh of PHEV battery capacity has been delivered. That's about five times the total storage capacity used by an island of about 10,000 people.

Since we are talking about 225,000 EVs which probably represent about 500,000 people, we are talking about 5 times as much storage for about 50 times as many people. Plus, the EV storage is not nearly all available. In fact, MOST of it is not available. So, clearly, today's overall EV fleet is not suitable for this purpose.

So, let's just take the Model S as the prototype of the "everyday" car of the future. And let's put two such vehicles in each garage for each three people. In that case, you would have about 4 MWh for each 75,000 people, or about 4 times the storage of the small island for 8 times the number of people. But perhaps only about 50% of that capacity would be available for grid use, so perhaps twice the storage for 8 times the number of people.

So I will conclude that BEV storage will likely never cover ALL of our future grid storage needs, but perhaps it can cover as much as 25% of it if we are smart about how we use it.

Of course, the major barrier to this type of technology is that CA electricity rate plans are already entirely incomprehensible, so it is quite inconceivable to add further considerations into any of those plans. :lol: :lol: But perhaps some of the rest of us have a chance to get this working!

Some thoughts:
1. EVs will tend to flatten out the electricity demand curve by mostly charging at night. As EVs with bigger capacities come on board, then some will only need to charge on the weekends. Those with low commute miles.
2. As solar keeps dropping in price, predictions suggest that it will become cheaper than the grid for many. Of course this requires offline storage. The giga battery factory is counting on this for demand of the batteries.
3. The smart grid will have to be very smart about when local houses supply demand from batteries or solar. For example if I'm concerned about battery degradation then I may only want to supply the grid when I'm getting paid more than 20 cents a kwh.
4. Will people be able to run local generators of any sort to the power the smart grid?
5. California and other bureaucracies can be bypassed by homes working cooperatively or just disconnecting since it will be cheaper to do so in the future.
6. I think you are way to ahead of the ball game for EV batteries being durable so that people won't care enough about degradation. I'm thinking 10 years.

DanCar said:

Some thoughts:
1. EVs will tend to flatten out the electricity demand curve by mostly charging at night. As EVs with bigger capacities come on board, then some will only need to charge on the weekends. Those with low commute miles.

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Agreed, but I think some daytime charging when PV is peaking will eventually be needed to provide energy for the peak evening load. Charge at work off PV, come home, plug in and provide some energy to the grid at the same time.

DanCar said:

5. California and other bureaucracies can be bypassed by homes working cooperatively or just disconnecting since it will be cheaper to do so in the future.

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In the past I may have argued this point, but given the prices I see being charged for electricity in CA, I have to agree it could happen.

DanCar said:

6. I think you are way to ahead of the ball game for EV batteries being durable so that people won't care enough about degradation. I'm thinking 10 years.

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No argument there. But I'm confident it will happen at some point.

this "could" create a very beneficial relationship for both the power companies and the EVer. the first need would be making the power available to the grid which means the car must be plugged in somewhere all the time except when its moving from place to place. this would require several stations designed for this purpose.

As mentioned the cars could be used for load leveling and that could be done if the Electric company subsidized a portion of the battery allowing the EVer to get a larger battery for occasional use without having to pay for it, say 12 kwh per vehicle. Their only requirement is to charge it up every night as a portion of it is likely to used during peak demand that day. Should they actually need that extra capacity, a button on the dash should be available to push that would take the car out of the grid for the day. One would be allowed to select this option X amount of times in a set time period. One could also set a larger allocation for the day if they simply don't need it, etc.

it would be a project requiring a lot of cooperation but its doable. Not sure Americans have the right kind of mindset for it but I do see countries like Japan being able to work it out

DaveinOlyWA said:

As mentioned the cars could be used for load leveling and that could be done if the Electric company subsidized a portion of the battery allowing the EVer to get a larger battery for occasional use without having to pay for it, say 12 kwh per vehicle. Their only requirement is to charge it up every night as a portion of it is likely to used during peak demand that day. Should they actually need that extra capacity, a button on the dash should be available to push that would take the car out of the grid for the day. One would be allowed to select this option X amount of times in a set time period. One could also set a larger allocation for the day if they simply don't need it, etc.

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+1

This is exactly the type of arrangement that I envision, as well. Instead of a direct battery subsidy, I picture homeowners getting a special tariff arrangement that would allow them to justify the purchase of a larger battery knowing they have a way to recoup the costs by buying electricty when it is cheap and selling it when it is expensive.

All three of the plans being implemented today use BEV and FCEV for load-shifting and grid stabilization duties. The numbers are covered in gory detail.

An 80-100% renewable grid is a very different problem than a single off-grid house. That's one of the primary lessons from places with higher levels of renewables on the grid today - and the likely reason that they're finding that they don't need nearly as much storage as they first modeled.

More vehicles on-line means each can do a much smaller portion of the work. This means that the overall load on batteries is significantly less than in a power backup situation (IE UPS for a house). This means that today's batteries are already 'good enough' to do the required work. Since it'll be a number of years before the US will have a higher percentage of renewables on the grid or a significant number of vehicle to grid-capable vehicles on the road, there's plenty of time for battery tech to improve and for us to field more FCEV.

This Sandia lab report of tests performed on LiFePO4 cells shows the difference between what most think of as a 'backup power load' and the real-world work required for grid stabilization.
http://www.rechargeablelithiumpower.com/media/SANDIA2008-5583_PSI.pdf (I've shut this domain down.)

New location for the Sandia report: https://www.dropbox.com/s/3b8zfm0m2ajylx5/SANDIA2008-5583_PSI.pdf?dl=0

edit...update URL

Load management aka grid stabilization doesn't require the car owner do buy or do anything different. Shouldn't have much impact on battery life as well. Of course, more effective at night.

If the utility had the ability to start/stop a charge honoring the ending timer, and if there were just 10 million EV's on the road, and overnight most of which would plugged in and in need of a charge, that would be 60 GW of load, about 6% of US current total capacity, that could be switched on or off as mostly needed.

As for charge/discharge:

Suppose a Leaf battery costing $5,000 could do 2000 cycles before end of life, which is optimistic. At 20kWh per cycle, round turn efficiency of 60%, the net cost of storage is around $0.21 per kWh for just battery replacement. A full cost is more like twice that for a short storage (hours). Maybe, for Hawaii or other high cost island power systems. Maybe even for peak leveling.

Long term storage, to cover the few days per year when renewable power isn't available, is going to be driven by calendar life. If this is two cycles per year and the battery lasts 10 years, that is 20*20kWh delivered over the life of the battery, at $12.5 per kWh. Twelve fifty per kilo Watt hour. I doubt that such storage will ever make sense. So I doubt if 100% renewable grid is possible.

WetEV said:

Long term storage, to cover the few days per year when renewable power isn't available, is going to be driven by calendar life. If this is two cycles per year and the battery lasts 10 years, that is 20*20kWh delivered over the life of the battery, at $12.5 per kWh. Twelve fifty per kilo Watt hour. I doubt that such storage will ever make sense. So I doubt if 100% renewable grid is possible.

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I agree that a single-use battery for that purpose doesn't pencil out, but doesn't that make the case for using BEV batteries for this type of storage? This extra application would hardly impact the life of the battery in the BEV while offering a distributed storage solution for the grid.

RegGuheert said:

This extra application would hardly impact the life of the battery in the BEV while offering a distributed storage solution for the grid.

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Only if is capacity that the car owner doesn't need. If not needed, why would the car owner buy the extra capacity?

Do notice that there are two cases that do make sense, grid stabilization and short term storage on a higher cost power network, such as an island.

RegGuheert said:

WetEV said:

Long term storage, to cover the few days per year when renewable power isn't available, is going to be driven by calendar life. If this is two cycles per year and the battery lasts 10 years, that is 20*20kWh delivered over the life of the battery, at $12.5 per kWh. Twelve fifty per kilo Watt hour. I doubt that such storage will ever make sense. So I doubt if 100% renewable grid is possible.

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I agree that a single-use battery for that purpose doesn't pencil out, but doesn't that make the case for using BEV batteries for this type of storage? This extra application would hardly impact the life of the battery in the BEV while offering a distributed storage solution for the grid.

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I agree with you here, Reg. When one assumes the battery load/discharge curve (constant current discharge, etc.) looks like an uninterruptable power supply or off-grid house battery at night then they'll have numbers that look similar to what Wet proposes. But on a full-scale grid with geographically-dispersed generation, the demand looks a lot closer to the power cycle test that can be seen in the Sandia report linked above. This type of 'burst' energy transfer does not degrade a battery nearly as much as driving the car.

Europe's transition to 100% renewables has been fully modeled and documented - they've discovered they need only about 1/4 of their vehicle fleet to be grid-connected at any one time to provide all support the grid needs - and that's the full range from stabilization/frequency management to load matching.

RMI's book "Reinventing Fire" models a number of options for the US grid, as does the peer-reviewed papers behind The Solutions Project. Rifkin's book and the documents from Europe's Third Industrial Revolution roll-out do the same for the EU's project. We need much less storage than many assume for a 100% renewable grid.

WetEV said:

Only if is capacity that the car owner doesn't need. If not needed, why would the car owner buy the extra capacity?

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Well, you would buy more because you need it *sometimes*. But on days when you don't need it, you could let the utilities use it. The 85 kWh battery in the Tesla Model S is a prime example. Most days this capacity could be rented out to generate a bit of extra cash. As Dave said, it's like the power company subsidizing larger BEV batteries.

WetEV said:

Do notice that there are two cases that do make sense, grid stabilization...

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Yes, grid stabilization seems quite doable. But all these schemes need about the same infrastructure in place, so the question is how do we get there from here? Frankly, the utilities have shown much less interest in BEVs than I ever thought possible.

WetEV said:

...and short term storage on a higher cost power network, such as an island.

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Yeah, I think we are all agreed that it makes little sense to pay $0.32/kWh for electricity when there is wind and solar available and some means of storage.

As the owner of the battery, I don't want the utility to ever take 80% of my charge, unless I've explicitly OK'd it. Owner needs to establish parameters that ensure their battery is available to use when THEY want it... or that a quick charge is available to me on the 3 days a year that my trip is impaired by the peak shaving.

Gets messy quickly to have the utility buy a portion of every battery. What if they just allow me to establish a rate for which they can purchase my power? You can take 5kWh for $.xx, the next 5 will cost you $.yy, the next 5 are available for $.zz. This, I would think, more resembles the open market for peak providers. Although, get enough EVers around and you are not locked in to a contract for a period of years the way I believe the industry does.

Another approach, what if I agree to give up to half of my charge up to the grid ANY time they need it, and they agree to let me charge for free at all of the QC stations they install in my area? The idea being that my QC might not be required, and that it would be done after the peak has passed. And if they have not installed QC density or location to my liking then I choose not to participate. Wouldn't this be more of a market-driven, symbiotic relationship? It's only reasonable that they leave me with enough charge to reach the next QC. However, apply this situation to the entire area of EVs, and we'll all want for a QC at the same time too. Perhaps the provider modifies the QC such that it will only deliver 6kW during peak periods as well.

It would be a monumental achievement for collaboration between many many different entities but then again; considering the possible ramifications of climate change and the errosion of our natural resources including fresh air and water, I think monumental efforts in many different areas is our only real option left

kikngas said:

As the owner of the battery, I don't want the utility to ever take 80% of my charge, unless I've explicitly OK'd it. Owner needs to establish parameters that ensure their battery is available to use when THEY want it... or that a quick charge is available to me on the 3 days a year that my trip is impaired by the peak shaving.

Gets messy quickly to have the utility buy a portion of every battery. What if they just allow me to establish a rate for which they can purchase my power? You can take 5kWh for $.xx, the next 5 will cost you $.yy, the next 5 are available for $.zz. This, I would think, more resembles the open market for peak providers. Although, get enough EVers around and you are not locked in to a contract for a period of years the way I believe the industry does.

Another approach, what if I agree to give up to half of my charge up to the grid ANY time they need it, and they agree to let me charge for free at all of the QC stations they install in my area? The idea being that my QC might not be required, and that it would be done after the peak has passed. And if they have not installed QC density or location to my liking then I choose not to participate. Wouldn't this be more of a market-driven, symbiotic relationship? It's only reasonable that they leave me with enough charge to reach the next QC. However, apply this situation to the entire area of EVs, and we'll all want for a QC at the same time too. Perhaps the provider modifies the QC such that it will only deliver 6kW during peak periods as well.

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Taking a look at the Sandia Lab report for battery testing is useful. Starting on page 14, looking at the Utility PSOC. https://www.dropbox.com/s/3b8zfm0m2ajylx5/SANDIA2008-5583_PSI.pdf?dl=0

Some important points about grid stabilization is that we're not storing energy that would otherwise be curtailed, not providing back-up power, and not pulling large amounts out of the battery. This is not the same as Wet's earlier comment about 'load management' because this process both removes energy from the battery and puts it back. A PSOC "cycle" is not the same as a battery "cycle" - a battery cycle consists of a full swing from fully charged to fully discharged and back to fully charged (or from empty to full to empty). Using a BEV for grid stabilization only uses about 10% of the overall state of charge of the battery, requires a bi-directional vehicle-to-grid (V2G) EVSE/interface, and still results in the battery being charged on time for a morning departure if that's what the owner has programmed. Also, it appears from V2G tests conducted in both the US and in Europe, the V2G interface provides real-time cost accounting for the battery use - a debit when charging the battery (as happens now) and a credit when energy is drawn from the battery.

This is a situation where a BEV has one type of advantage and a FCEV has another. A BEV can provide a bi-directional interface for grid support, while a FCEV cannot - but a FCEV can provide energy to the grid in larger amounts while still maintaining a significant driving range. They work together to support the grid in ways neither can alone.

RegGuheert said:

WetEV said:

Only if is capacity that the car owner doesn't need. If not needed, why would the car owner buy the extra capacity?

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Well, you would buy more because you need it *sometimes*. But on days when you don't need it, you could let the utilities use it.

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That negelect the calculations of the cost of charge/discharge cycles on total battery life. Partial cycles don't count as full cycles, but they still affect battery life - think of kWh in/out as a life figure. As such that value of the battery gets eaten up by the utility - but they paid for it... But, the driver is still hauling that weight/mass around (lowering the efficiency of his transportation).

You would be better to have the utility pay for a battery they put in a box at the end of the block on the line feeding the local power drops. This way, only a single charger/inverter is needed, the capacity is not driving off during the daytime, and it is not being hauled around at significant energy expense.

alanlarson said:

RegGuheert said:

WetEV said:

Only if is capacity that the car owner doesn't need. If not needed, why would the car owner buy the extra capacity?

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Well, you would buy more because you need it *sometimes*. But on days when you don't need it, you could let the utilities use it.

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That negelect the calculations of the cost of charge/discharge cycles on total battery life. Partial cycles don't count as full cycles, but they still affect battery life - think of kWh in/out as a life figure. As such that value of the battery gets eaten up by the utility - but they paid for it... But, the driver is still hauling that weight/mass around (lowering the efficiency of his transportation).

You would be better to have the utility pay for a battery they put in a box at the end of the block on the line feeding the local power drops. This way, only a single charger/inverter is needed, the capacity is not driving off during the daytime, and it is not being hauled around at significant energy expense.

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That's a good proposal, alan, and is being implemented in a number of areas. But real-world testing and experience shows that grid support causes very little battery degradation even before comparing it to battery stress from driving. It also shows that less then 25% of the vehicle fleet is needed to provide both grid stabilization and storage, and that vehicle owners make a financial profit when they share their battery with the grid.

If we describe the two ends of the 'yard stick' as today's info seems to support, we have a BEV owner that does not allow V2G and one that does. The 'do not connect' owner will spend money on the car, spend money on energy to charge, will keep the car until it no longer serves its purpose or the driver decides she needs a new toy after 2-4 years. On this end of the scale, all of the money flows away from the owner, the battery degrades relatively quickly, and the car has a fairly short 'first life.'

At the other end of the 'yard stick' is a person that buys a BEV, connects it to the grid 24/7, and never drives it. They pay for the car, the power company pays them for grid services. The payments from the power company more than reimburse the owner for the battery which can be replaced for a profit after 5-10 years of grid support.

No, it doesn't make ecological sense or life-cycle energy sense to buy a car, leave it in the garage, and use it as a grid battery. But if that vehicle is used as part of a grid support business, it could still generate a positive cash flow, and would still be an available car if/as needed.

Ya; I think we need to get away from this "it doesn't work if I have to sacrifice ANYTHING" attitude. There are trade offs to EVERY plan. But this can really work out pretty well for both sides and in a "corporate heavy" World we currently put up with, its hard to not get excited about this.

On the consumer side, we get larger pack, no range anxiety for local day to day even in the worst of weather, and the ability to make the occasional road trip with much less hassle. Now that is a lot of up in exchange for simply scheduling your driving in advance.

Now this does not even include preferential parking which would be needed during the day in order to be connected to the grid during highest demand. THAT alone is worth more than nearly anything in certain super congested downtown areas where the cost of parking is like another car payment, only bigger

On the business side; the ability to take a single power plant off line during peak demand can pay the cost of the battery program for thousands in a region. Not sure what the percentages would be but guessing on any given day, more than 80% of the participants would be available to contribute to the grid. There will be "crunch" days like last day before a major holiday when you have the double whammy of having most businesses open along with a lot of people leaving early to get a jump on the holiday traffic but that happens only a few times a year.

The public benefits from a much larger public charging presence that might be busy during business hours but would be empty and available during off hours. This also takes the high initial cost of installation and puts it on the power company where, I am guessing , can probably get a better deal on install costs.

This is a win win all the way around. When the power company realizes that they can save millions by a major conversion of their gas fleet to electric (since they will have a charging network in place) they will have even more incentive to make it work


but yes, this all does mean that we the consumer will have a battery pack that does double duty and will degrade quicker and it does require us to plan our driving and inform our PUD when those plans change so we are not caught short.

But batteries are getting better and comm.... oh wait!! I forgot, the HUGE advances of computers and technology has currently only enabled a small advance in unifying various communication platforms... but we only need to pay someone enough money and that can be fixed as well

I find it unlikely they'll incentivize this enough to counter the potential inconvienece and unknown battery damage. Count me out for the first 10 years.

Considering that they wouldn't be pulling power every day, the battery life wouldn't necessarily even make a blip. I mean, start with modest expectations, how big a dent can you put in the power peaks if you limit the utility to pulling no more than 20% of battery capacity from any given car, and to using a given car just 10 times per year? I think you combine that with the uptrends in solar PV installations and total BEV kWh capacity on the roads and you quickly are making a pretty noticeable dent in peak demand.

Sublime said:

I find it unlikely they'll incentivize this enough to counter the potential inconvienece and unknown battery damage. Count me out for the first 10 years.

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this is truly an individual decision each must make based on how often they plan to stress the current range and capacity OR your willingness to pay for additional range every day from your own pocket.

I really see this as a way for MOST people to afford an EV. Right now, that is not true. the LEAF may mean "Affordable" but that is true for much less than half the population.

I see this subsidy from the PUDs (which might conveniently start when Uncle Sam's stops ) allowing even lower middle income people to drive EV when subsidies puts the car into the mid teens.

Sure people with money will not participate in this program no matter what the level of discounts just like I wont shop tomorrow even if they were giving away 60 inch plasmas to the first 500 people to my local Walmart.

So ya, I understand your position but seems like someone in your income bracket could at least afford spellchecker?