In recent two years, with the continuous development of energy industry and the maturity of electric vehicle technology, energy transformation+traffic electrification has long been the key direction of technology upgrading and transformation in many countries around the world. Under such a big framework, many people (mainly from the background of energy and electric power) put forward the concept of vehicle networking (V2G), that is, they hope that electric vehicles, as energy storage devices that can be flexibly connected to the power grid, can interact with the power grid in two directions and provide various auxiliary services for the power grid and get paid, which is regarded by many people as an important development trend of the energy industry. Here, Liu Bo does not intend to go into details. Interested friends (especially those with automobile and battery backgrounds) can search "What is the electric vehicle networking technology (V2G)? What research or application is there at present? " "This article should learn more.
Liu Bo put forward a point in the article: Electric vehicles can certainly interact with the power grid, but one-way energy transmission, that is, orderly charging (the interaction with the power grid is limited to the flexible and orderly charging of electric vehicles) is reliable, and the vehicle-electric interconnection (V2G) with two-way energy interaction with the power grid is not a good track: for automobiles, it is not worth the loss and cannot form an effective operation mode.
This paper has technical analysis and inference based on the observation of industry development, and also has spit. In short, my humble opinion is for your reference. Of course, it is estimated that many people in the power industry may have different views. Welcome to clap bricks.
The schematic diagram of V2G principle is taken from the article V2G: Enlightenment from the Development Experience of Europe, America and Japan.
Orderly charging is inherently reliable.
For the charging of power battery, how much current/power the battery can charge to how much state of charge (SOC) is obtained through a series of design verification work by battery factory and car factory, which also represents the maximum power/capacity of electric vehicle charging. In practical use, due to the influence of environmental temperature, the power of the charging pile itself, the safety boundary buffer value and other factors, the power that can be achieved by car charging generally cannot reach the maximum allowable power allowed by the battery/storage battery, or can only be achieved occasionally.
Step-by-step charging curve is an optimized charging curve obtained through the verification and development process of batteries. If the charging rate is lower than this value, there is no problem. It is extracted from the best fast charging document of lithium-ion bag battery based on local volume expansion standard.
In fact, as long as the charging power is lower than the allowable power of the battery, there is no problem in itself: compared with fast charging, the reaction kinetics of slow charging of the battery is milder, and the challenges encountered in heating are much smaller and easier. In essence, orderly charging means that the charging current is controlled by the power grid. If the power grid is heavily burdened, charge less/stop charging, and if the power grid supply exceeds demand at that time, charge more cars. Anyway, the power grid is always available, so we should try to keep the balance between supply and demand at all times. As long as the car is not in a hurry to use, charging for a period of time (first protect other loads in the power grid that require stability) will basically have no loss to the electric car, but it will give the battery more standing time, which is of great benefit to the reaction kinetics and is more conducive to the moderate charging of the battery.
In this regard, Liu Bo reported in the previous article how BMW cooperated with PG&; Company E cooperated to launch the iChargeForward project of smart charging service and power grid linkage. For details, please refer to "Innovative Attempt of Coordinated Operation of Electric Vehicles ~ Retired Batteries ~ Power Grid: BMW Joins Hands with PG &;; E makes charging smarter.
Why V2G is not a good track?
Then why does Liu Bo think V2G is not a good track?
1. Hard-working development, paid so much effort to get the battery life, and put it back into the power grid with V2G? ? Is this the good steel spirit used on the handle?
Anyone who is familiar with the development process of power batteries knows that many models of battery packs have development requirements: that is, how many kWh can be met by meeting XX cycles of charge and discharge/XX kilometers of full life cycle/full life cycle energy throughput, which is the most basic requirement in the industry.
There is no problem with simple and orderly charging: because electricity has to be charged anyway, orderly charging just makes charging more reasonable. But if I have to take the power battery to the power grid V2G, I will ask:
How much can the power grid pay for the loss of battery life? In fact, at present, the compensation for various auxiliary services in the power market is not very impressive, which is also a key factor restricting the development of the energy storage industry. For more information, see the discussion in Section 4 of this chapter.
The research and development of power battery is not easy, and it needs several years' cycle and repeated verification process. The higher the current high-energy system, the more it needs to balance all aspects of performance, and the technical threshold is not low. So: you should be like the power grid, after N years of painstaking adjustment, improve the battery life/life cycle energy throughput of power battery engineers, and the compensation given by the power grid is not high. Do you think this fully embodies Wang Duoyu's spirit of using steel well?
2. As long as the battery is fully charged and discharged, there will be life/aging loss.
Come on, read this title silently with me three times: "As long as the battery is fully charged and discharged, there will be life/aging loss".
Right: As long as there is a complete charge and discharge, there will be aging, but some batteries may be faster and some batteries may be slower, which is natural.
Orderly charging is only the charging, discharging or normal use when the vehicle is running, and it does not affect the operation/use mode of the electric vehicle at all.
But if you start interacting with V2G in two ways, well, there is a part of the whole life cycle energy throughput &; The accompanying battery cell aging will be sent to the power grid. At this point, I would like to ask those who advocate V2G:
Will you tell the consumer that V2G will accelerate the aging of his battery? Mileage anxiety is still a pain point that everyone cares about, and the mileage will shrink with the service life, which makes everyone dissatisfied with the current situation of electric vehicles. There are higher expectations and requirements. At this moment, you want me to hand over my precious charging and discharging ability to the power grid? Still think my battery is not decaying fast enough? So here still echoes what the first section just said: what is a good steel flower on the handle?
In addition, some people will say, "At present, the life of the power battery is 1K times ... so the cruising range of 400 kilometers multiplied by 1000 times can get 400,000 kilometers, which is obviously enough, and the surplus is V2G."
There seems to be nothing wrong with this logic at first glance, but Liu Bo wants to tell you here and ask a few questions: Is the life of battery material 1000 times/cell 1000 times/battery pack 1000 times the same as the actual service life of battery pack? Do you know how much effort it takes from the 1 thousand life of battery materials to the 1 thousand practical life of the final battery pack?
So the theoretical value is very good, but how many cars on the market can actually run 400 thousand kilometers without changing the battery? I think people who advocate V2G should take out the data in this respect and demonstrate it in detail, so as to better support the continued development of this piece.
Here, Liu Bo wants to further emphasize one point: Actually, I'm not saying that V2G will definitely not work. Since there is a loss to the interests of my car, why not directly compensate me? The great Marx also said: "If there is 20% profit, capital will move;" If there is 50% profit, capital will take risks; If there is a profit of 100%, capital will dare to take the risk of strangulation. "
-How much is the grid willing to pay for V2G? With this question, let's look at the third section: legal affairs and responsibilities. Then in the last section 4, Liu Bo answered this question again.
3. Automobile users, automobile companies and power grid companies: legal affairs and limitation of liability.
In BMW's orderly charging project, the energy interaction scene is simpler, and BMW, PG & amp; E carefully drafted the contract, which clearly stipulated the rights and obligations to participate in the demand response, so that participants could have a clear account to calculate, and the activities would naturally be carried out more smoothly.
Some brief information about legal affairs/contracts in the project.
And if you want to supply energy in two directions, the problems will only multiply, such as:
In this way, the battery life/energy throughput of the car is lost-who will be responsible for battery aging in case the energy service/mileage demand of the whole life cycle cannot be met? For this reason, most car companies don't want to toss V2G (at least, they don't want to toss it very quickly and actively): There are still many things and challenges to develop power batteries, so what about V2G? Is it good for me? Do you know how difficult it is to handle high specific energy batteries? Do you know how difficult it is to have both high specific energy and high power? You give me a reason to participate and persuade me to participate. ...
And when it comes to persuasion, don't forget that the best way to persuade a person is to appeal to interests, not reason/feelings/feelings. If there is no interest, rational people in economics will inevitably choose more than less. After all, electrification is recognized as the development direction in the automotive field (everyone is happy in into the pit), but V2G is not. Since it is not a recognized development direction, you should use more sufficient reasons to convince auto companies to be happy with into the pit.
This two-way complex interaction, the determination of business model, and the responsibilities and obligations that all parties should bear in law will definitely be more troublesome to design than orderly charging.
Of course, compared with other challenges, these difficulties are relatively easy to overcome. Liu Bo just wants to raise this issue here for your consideration.
So to put it bluntly, in fact, everyone can see clearly: if you give enough benefits (rear &; Client), V2G may not be impossible to develop, so let's look at the next part and see how much the power grid may actually pay for V2G.
4. If V2G really works, the reward given by the power grid must be high enough. At this time, there is no reason why fixed energy storage cannot erupt on a large scale first.
If these conditions are ripe, the power grid is willing to pay a lot of rewards to promote the development of V2G. Considering that the power battery is definitely more expensive than the fixed energy storage, there is no reason why the fixed energy storage with lower cost and longer service life should not seize this market first to meet the demand of two-way energy exchange and service with the power grid.
As you can see, the recent bidding result of energy storage is cheaper than that of power battery.
Some people say that trams are flexible, plug and play, and can be deployed back and forth-boy, you have to go before you can run. The interaction between fixed energy storage and power grid is always clearer and more adaptive than the automobile model-people developed it for power grid, so what about the application of fixed energy storage in power grid now?
To tell the truth, Liu Bo is also trying to keep up with the electricity market, electricity reform and the update of auxiliary services. For the convenience of laymen, Liu Bo boldly summarized the development status of the fixed energy storage-power grid interaction industry in China for everyone's understanding (welcome to clap bricks). Generally speaking:
The reform in the field of electric power is not easy, because the existing system is huge, the operation inertia is large, and there is a set of existing logic. Electricity reform is a topic that has been debated by various energy groups since it was mentioned, and it is often difficult to reach a conclusion and consensus, and it is really not easy to implement it (Document No.9 has been published for several years).
Specifically, you can recommend an article "Why is electricity reform more difficult than eliminating pneumonia?" Published by Zhang in Energy magazine, friends who are interested in electricity reform can go and see what it is.
100 people reported the news that the compensation for auxiliary services in Meng Xi was afraid of being cut off.
Then let's take a look at the current development of energy storage. In China, the regulations of provinces where energy storage participates in auxiliary power grid services are different, and the compensation mechanism is often adjusted, which is actually related to a simple but core question, whether energy storage can be used for power grid to make money. Here, Liu Bo is not going to give you a bunch of formulas for frequency modulation, life calculation and compensation. He just wants to think about this problem in a different way: that is, to infer the difficulties and challenges encountered by the industry from its actual development and perfection:
In the past two years, the installed capacity of energy storage has been greatly affected by the policy;
The power grid seems unwilling to spend more money on the use of energy storage, and it doesn't want to spread too much (stop the incident) and it doesn't seem to be really enthusiastic;
Judging from everyone's efforts to find a business model, the economic estimation of energy storage projects is still challenging, which may only be fundamentally solved by technological progress.
GGII summarizes the development of energy storage industry in China on 20 19.
Excerpted from Commercial Development of Energy Storage Industry in China, published in Zhongguancun Energy Storage Industry Technology Alliance.
Therefore, it is not difficult to see that the current technical level of energy storage+operation rules of power grid system+operation mode of power market is not easy to make the current technical level of energy storage achieve good enough economy in China's power market, so China's energy storage industry has been developing tepidly.
To be honest, the energy storage industry is very important, which can promote the development of various technologies and is of great significance to energy transformation. However, this is not the place to discuss feelings: there are signs that there are still many difficulties in using energy storage in the power grid and various challenges need to be overcome. If the fixed energy storage designed to interact with the power grid can't meet the requirements of the power grid well, there are some challenges in the development, but you insist on putting electric vehicles with more troublesome interaction, higher cost and more complicated ownership responsibilities into the power grid and developing V2G with vehicle-electricity interconnection. Have you not learned to walk (energy storage-power grid interaction)? Is it necessary to do something with obvious high cost and low income based on the current technical level?
Therefore, for Liu Bo, it is not surprising that in the first stage of the BMW project, the interaction between the car and the power grid is only orderly charging, and there is no V2G.
PS: Speaking of income, Liu Bo thinks that it is obviously more reliable to use an electric car to drive Didi than V2G-the cost per 100 kilometers is obviously more cost-effective than burning engine oil, and he can meet people. In terms of income, it is much larger than V2G. You old irons might as well consider it.
Postscript &; luantan
A few years ago, Liu Bo saw this project of BMW and found it very interesting, so he wrote this manuscript. I will go back to bmwchargeforward.com these days to see if there is any update. Unfortunately, the website says that the second phase of this project began on 20 18, but there is no reliable information on the website to introduce the latest progress of this project, so if anyone knows the follow-up situation of this project, please inform and share the information so that Liu Bo can learn another one. ...
As for V2G, Liu Bo doesn't think it is useless, but thinks its input-output ratio is relatively poor. At present, it is better to store energy and engage in some demonstration projects. But if we have to draw a pie for its future development, it is more concept than substance. At present, there are many discussions about the innovation of energy Internet business model. For V2G, I think the question can be further simplified as: What kind of users will be willing to pay high marginal costs for V2G services provided by electric vehicles? Don't talk to me about feelings, ideals and trends. As a battery engineer, Liu Bo is studying the future development direction. Liu Bo also knows what feelings are, so let's talk about whether this account can be understood.
In addition, there are many platforms/business models at present, and the interaction advocated in them is very complicated, which seems confusing, but Liu Bo thinks there is a big problem: many powerful things need to be explained quickly with very refined language and logic, and this kernel should not be complicated. Behind these complicated interactive platforms/business models, Liu Bo sees that the biggest bottleneck is the immaturity/lack of economy of each technology: if the technology is strong and can achieve good economic benefits, who will bother to engage in those complicated business models? Why don't you just violence Man Cang?
Finally: So in contrast, for the real rise of China's manufacturing industry, it is the right way to build one or several C companies in each segment, and the priorities of other things can really be reversed.
Disclaimer: This article was written by the author in his spare time and does not represent the views of any organization or institution.
Confirm:
Thank you for your suggestions. xEV Water Blowing Group at Wudaokou, the development of cross-domain communication industry should be like this ~
Thanks to the old driver Qi Ge and the battery expert Xu Dage for their support in the discussion.
Figure | Network and related screenshots
About the author: Liu Guanwei, Ph.D., graduated from Tsinghua University Department of Materials, engaged in research and development of power batteries for many years, and currently works in the battery development department of a foreign-funded automobile enterprise.
This article comes from car home, the author of the car manufacturer, and does not represent car home's position.