Energy from electric cars could power our lives—but only if we improve the system

November 22, 2017
Credit: CC0 Public Domain

Power stored in electric cars could be sent back to the grid - thereby supporting the grid and acting as a potential storage for clean energy - but it will only be economically viable if we upgrade the system first. In a new paper in Energy Policy, two scientists show how their seemingly contradictory findings actually point to the same outcome and recommendations: that pumping energy back into the grid using today's technology can damage car batteries, but with improvements in the system it has the potential to provide valuable clean energy - and improve battery life in the process.

Electric cars store excess when they are idle. Vehicle-to-grid (V2G) technology makes it possible to transfer that energy back to the grid when the car is not being used. This energy could help regulate the frequency of the electricity supply, reduce the amount of electricity purchased at peak times and increase the power output of the system.

Two recent studies, one by Dr. Kotub Uddin at the University of Warwick in the UK and the other by Dr. Matthieu Dubarry at the Hawaii Natural Energy Institute, seem contradictory, with one suggesting that V2G degrades car batteries and the other that it improves battery life. But the two scientists worked together to look at how their studies overlap, showing that they actually come to the same conclusion.

"Although both our papers seem contradictory, they are actually complimentary," said Dr. Dubarry. "V2G is not going to be easy, but, if done properly, it has a chance to make a difference for both utilities and electric vehicle owners. We need more research to understand the process better and benefit from the technology."

The two authors agreed that in order to be economically viable, V2G has to be optimized between the requirements of the car owner, the utilities and the capability of the grid. In other words, the needs of the different people and systems involved have to be balanced. The question then became 'can this technology be profitable?'

The previous studies had different approaches to answering this question: Dr. Dubarry showed that using today's V2G technology can be detrimental to the car battery, while Dr. Uddin found a smarter grid would make the process economically viable, and even improve the battery. In the new paper, they critiqued each other's work and found shared conclusions. With improvements to the system, V2G could actually improve electric car battery life and be profitable for everyone involved.

Measuring the impact of the technology on the battery is challenging. After two years of analyzing lithium-ion batteries, Dr. Uddin and his team developed an accurate battery degradation model that can predict the capacity and power fade in a battery over time under different conditions, such as temperature, state of charge and depth of discharge. That means the model can predict the impact of V2G on battery health. Using this model, they created a smart algorithm that shows how much charge a battery needs for daily use and how much can be taken away to optimize .

Dr. Uddin says funding is needed to develop new testing standards and control strategies to guide policies that support V2G. One key element to improving the system, he says, will be the measurement of battery degradation.

"The metrics used to define battery degradation may also impact the optimization process," he explained. "A critical component is who is responsible for estimating degradation? Utilities are currently taking the lead in the EU, but it might be more economical for the or car manufacturers to do it. In this case, standards need to be written which define what we mean by 'state of health' when it comes to batteries, and the metrics that are used to determine it."

Explore further: Clean energy stored in electric vehicles to power buildings

More information: Kotub Uddin et al, The viability of vehicle-to-grid operations from a battery technology and policy perspective, Energy Policy (2017). DOI: 10.1016/j.enpol.2017.11.015

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19 comments

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Eikka
2.6 / 5 (5) Nov 22, 2017
This study has the same flaw as the previous one.

If the owner of the car cares about the battery lifespan, they would not discharge the excess charge out to lower the average SoC of the battery - which is what creates the benefical effect - but instead not charge the battery so full in the first place.

Using any V2G scheme puts more cycles on the battery, shortening its lifespan as opposed to a case where no extra energy gets cycled through.
Eikka
2.6 / 5 (5) Nov 22, 2017

The compromise is to set limits on the amount of energy traded, based on prognostics. Indeed, by intelligently setting these limits, Uddin et al. show that V2G can both be viable and profitable.


So the point is, if you trade little enough energy though V2G then the damage you do to the battery is less than the worth of the electricity.

greenonions1
5 / 5 (4) Nov 22, 2017
if you trade little enough energy though V2G then the damage you do to the battery is less than the worth of the electricity
Eikka's statement is totally contradictory to the text of the article.
V2G could actually improve electric car battery life and be profitable for everyone involved
The word 'improve' - and the word 'damage' - are contradictory. This team of researchers analyzed the performance of lithium ion batteries for two years. Wonder how long Eikka and team have been analyzing batteries....
FM79
1 / 5 (1) Nov 22, 2017
Really what's the point of putting the energy back to the grid if then you need to recharge your car anyway. Since no process is ever 100% efficient, this would just result into a waste of energy.
betterexists
1 / 5 (4) Nov 23, 2017
Let Solar panels REVOLVE AROUND the Running Electric Car?
Will it OR Will it not help?
Too much Energy spent for such Revolutions?
greenonions1
5 / 5 (4) Nov 23, 2017
FM79
Really what's the point of putting the energy back to the grid if then you need to recharge your car anyway.
Point one - it may improve the battery life. That is pretty much the fundamental point of the article. Point two - grid balancing is a very big issue with renewables. This may be one part of the process of developing a smart grid - that can use intermittent sources - conserving power when there is excess - releasing when needed.
gkam
3.7 / 5 (3) Nov 23, 2017
Already put my money down for a Powerwall II system.
mackita
3 / 5 (1) Nov 23, 2017
U.S. average retail price per kilowatthour is 10.41 cents. Tesla's Powerwall can store 14 kilowatt-hours of energy and costs $6,200, which is the cost of 60.000,- kWh. For reference, the average electricity consumption for a residential customer in 2015 was 901 kWh a month, i.e. energy saved during 5.5 years. For full daily backup (29 kWh/day) you would need at least two units, for full week backup fifteen units.
greenonions1
5 / 5 (1) Nov 23, 2017
mackita - you are correct - that CURRENTLY from an economic stand point - battery back up does not make sense - used on a current u.s. home. I have a 2300 square foot home - full central heat and a/c - in Oklahoma. I averaged 462 kwh month last year - by being moderate with heat and a/c - summer keep at 80 F, winter at 70 F. We have good insulation. So insulation is surely the low hanging fruit. Batteries can be viable in a tiered rate system - charging overnight at 5 cents, and avoiding peak charges of 45 cents. Tesla Powerwall buyers are going to be early adopters - and like all early adopters (can you say $1,000 iphones) will be willing to pay. In time - batteries will come down in price. We have to start somewhere.
Lord_jag
not rated yet Nov 23, 2017
Point two - grid balancing is a very big issue with renewables.


Grid balancing is a very big issues period. Demand surges and dips throughout the day. You want to keep supply as close to demand as possible. It doesn't matter whether supply changes or demand, its the difference between them that matters.
MR166
not rated yet Nov 23, 2017
The most useful grid function that electric autos could provide is short term backup for renewables. If there is a sudden dip in renewable output their batteries could provide power while fossil plants come fully online. The would have minimal effect on the range of the auto and make managing the grid a whole lot easier. Of course, each charging station would need to have an inverter and full communications capabilities.
24volts
1 / 5 (1) Nov 25, 2017
There is no way in hell that using the car batteries to support the grid is not going to cause wear on the batteries. Every time you charge and discharge that is one less cycle your going to get on those batteries when using the car. Partial or full discharge/charge it doesn't matter. It's a cycle and that's what counts for the longevity time of them. I've used and gone through far too many batteries in electric vehicles over the years to even begin to fall for this bullcrap.
greenonions1
1 / 5 (1) Nov 25, 2017
24volts - you get upset when you are challenged. But look at the tenor of your last post. Now compare it to this information - https://www.clean...atteries
Don't you think that extensive real world research - probably trumps your personal experience with a couple of EV's? It just sounds to me like the same attitude I hear from the Deniers. Basically - my personal experience - trumps controlled/published scientific research.
24volts
1 / 5 (1) Nov 25, 2017
Geenonions1 - what I said applies to every rechargable battery ever made. I'm not denying anything. Scientists can't beat basic physics. The fact is that every time you discharge and recharge a battery the life shortens by 1 cycle and they only have so many times they can be recharged before the capability loss makes them useless for the purpose they were made for. The same thing applies to lead acid, lithium types, nicads, and the nickle metal hydride types. If you know any that don't fall under that I would really like to know what they are. I've gotten really tired of buying batteries over the last 15 years and none of them have been cheap. Someone pays $50k for a nice electric car they are NOT going to be happy when they find out that by working with the power company they will have to replace VERY expensive batteries a lot sooner
TheGhostofOtto1923
5 / 5 (2) Nov 26, 2017
Scientists can't beat basic physics
- But in order to make that statement you would have to know basic physics and I'm guessing the educated and experienced scientists in the article know far more than you.

Yes? No?

So why don't you do a little research and find out what they know that you don't?

There are systems that improve with use you know. Like the brain. Using the brain rather than the mouth can generate more substantive results.

Give it a try why don't you?

Sorry it just really bugs me when some asshole comes here and says something like 'well I've used batteries and so I know more about batteries than battery scientists'.

Makes me want to laugh and puke simultaneously.
mackita
1 / 5 (1) Nov 26, 2017
It's contradictory to the original intention of having water heating utilizing the night hours to use 'off-peak'  electricity. In cases of solar energetics, this is actually the peak – and off-peak has shifted to the middle of the day. A large water boiler can accumulate way more energy than battery of car. Whereas the utilizing the car batter for balancing of grid is necessarily connected with degradation of batteries and availability of cars, the utilizing of boilers for energy storage has way less adverse effects.
tekram
not rated yet Nov 26, 2017
Scientists can't beat basic physics...
This is one explanation from another forum and the same reason that many owners keep their lithium ion batteries at 20°C and avoid a constant full charge.
Nino Dvorsak
Drawing energy from a battery produces heat that helps a battery maintain it's internal temperature as close to it's optimal temperature (around 20°C). At it's optimal temperature, the battery's degradation is the lowest, while low and especially high temperatures speed up battery degradation.
Also, the best State of Charge (how much juice it has in it) regarding battery degradation is around 50%. If V2G helps a car has a State of Charge 90% rather than 100%, it lessens battery degradation.
greenonions1
not rated yet Nov 26, 2017
Someone pays $50k for a nice electric car they are NOT going to be happy when they find out that by working with the power company they will have to replace VERY expensive batteries a lot sooner
And if that is the case - they will of course not work with the utility - and just charge - recharge on a traditional schedule. But the information presented in the article I linked - suggests there may be patterns of charging/discharging that optimize the life of the battery. Of course the controllers would have to be complex - but that is what the research is about. So if you could supply some power to your utility, get paid for that power, and optimize the life of your battery - that would be a win/win.
24volts
not rated yet Nov 26, 2017
There is only one asshole on here otto and that is you. You never post any damn thing worthwhile but just put down everything everyone else posts. I had you on ignore and that's where your going back to.

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