Shulou(Shulou.com)11/24 Report--

In 1894, Musk's idol Nicholas Tesla lit an incandescent lamp by wirelessly transmitting electricity in his laboratory at 35 Fifth Avenue in New York. Then an even crazier idea grew in his mind, and he planned to build a "Walden Clifford Tower" on long Island, New York-treating the earth's ionosphere and surface as two plates of capacitors, creating a low-frequency resonance field at a frequency of about 8Hz through radial electromagnetic wave oscillations.

In short, it is necessary to build a global radio transmission network. In this way, human beings will get rid of the wires completely and only need to install a small device to get electricity. Unfortunately, due to the lack of financial support, Nicholas Tesla's crazy move could not be realized.

More than a hundred years later, his disciple Musk followed his fantasies and set up a company called Tesla to bring the world to the age of electric cars.

In 2021, global sales of new energy vehicles reached 6.75 million, the penetration rate of domestic new energy vehicles has been close to 15%, the outbreak of electric vehicles is unstoppable. However, the contradiction in the energy supplement link has become increasingly prominent. Under this background, the dream of wireless transmission begins to revive in the hearts of many people, and wireless charging technology is also trying to get out of the laboratory and join the market application army.

On December 28, the city of Balingen in Germany partnered with Electreon to build wireless charging lines for electric buses. Denso, the world's second-largest auto parts supplier, is also working with Japanese construction companies to develop wireless charging road technology for electric vehicles. The two companies have started testing in Tokyo and plan to go commercial by 2025. Around this phenomenon, this paper tries to answer the following questions:

1. What is the research progress of wireless charging technology in the field of electric vehicles?

2. Why has wireless charging not become popular yet?

3. How far is it from wireless charging to the explosion?

1. New ideas Wireless charging is only an icing on the cake for mobile phones, computers, cameras and other electronic products, but for the electric car industry, it may be the key to start the entire market.

Statistics show that by the end of 2021, there are 1.147 million public charging piles in China (470000 DC fast charging piles and 677000 AC charging piles). If private charging piles are added, the total number of public charging piles will reach 2.61 million. However, the inconvenience of charging still bothers a considerable number of electric vehicle users. Wireless charging is an emerging solution in the context of this industry.

Wireless power transmission (WP T) mainly realizes contactless power transmission by means of electromagnetic induction, electromagnetic resonance, radio frequency, microwave and laser. According to the different technical principles, there are three main technologies used in wireless charging of electric vehicles: electromagnetic induction type, electric field coupling type and electromagnetic resonance type.

Among them, the electromagnetic induction type, in short, is the principle of the transformer, which transmits electric energy to the primary coil, causing the secondary coil to couple and induce current, thus realizing the "wireless" transmission of energy from one end to the other. The principle and hardware requirements of this method are relatively simple, and it is the most mature and widely used wireless charging technology in WPT technology.

The electromagnetic resonance type is the "upgraded version" of the electromagnetic induction type, which is essentially through the electromagnetic resonance technology to improve the electromagnetic induction transmission efficiency in the case of loose coupling, so as to ensure the efficiency and achieve a longer transmission distance at the same time. The charging distance and charging area are more than 10 times higher than those of electromagnetic induction. Compared with electromagnetic induction, the characteristics of electromagnetic resonance are more in line with the needs of wireless charging of electric vehicles.

Many electric vehicle manufacturers are actively exploring the possibility of commercial use of WPT technology. BYD applied for a patent for contactless induction charger as early as December 2005. In 2012, they were equipped with the latest WAVE wireless charging pads on a 40-foot all-electric bus sold to the University of Utah. Just park the bus on the charging mat and wait for a few minutes to be fully charged.

WiTricity, as the leader of automobile wireless charging technology, took the lead in developing electromagnetic resonance wireless charging technology. Shortly after the technology show was announced, WiTricity received olive branches from Audi, BMW, Chrysler, Jaguar, Nissan and Toyota.

In June, Siemens, a global car and vehicle supplier, invested $25 million in WiTricity solutions for homes, parking lots, workplaces or fleets.

As Alex Gruzen, chief executive of WiTricity, said: "in the end, you will feel like you have an unlimited mileage car. There is no extra work to do except driving and parking." Wireless charging seems to save the process of picking up the charging gun and inserting it into the charging port, but in fact, wireless charging can completely unify the charging specification and interface, save space compared with wired charging layout, solve many charging pile safety problems, and provide completely unmanned operation for self-driving travel business.

Once the technology is mature, it has a great application prospect. Market research firm Allied Market Research (AMR) gives a positive forecast for the future market development: the global market for wireless charging of electric vehicles is expected to grow from $2.2 million in 2017 to $1.4 billion in 2025.

2. The reality hinders that the last wireless charging technology is so lively, which can be traced back to the early stage of promoting new energy vehicles in our country. In October 2014, ZTE unveiled the world's first wireless rechargeable microcirculation electric bus jointly developed with Shudu bus at the "West Expo" in Chengdu.

However, the development of wireless charging technology applied to electric vehicles has not been as good as expected. On the contrary, the charging pile and power exchange mode have gradually become the main force of energy replenishment. What obstacles have been encountered in the process of industrialization of wireless charging?

For mobile phones, low-power wireless charging has been realized by electromagnetic induction. To put it simply, there is a built-in coil on the wireless charger and the mobile phone respectively. When the mobile phone and the charger approach, the alternating current of a certain frequency in the wireless charger generates current in the receiving coil of the mobile phone through electromagnetic induction, thus charging the mobile phone. But it is suddenly more difficult to apply this technology to electric cars.

1. The charging power is insufficient to replace the slow charger: the initial technical limitation lies in the charging speed and power conversion efficiency. The efficiency of transmitting electric energy through a magnetic field is never as efficient as that of wired charging directly through the wire. In addition, the greater the charging power, the greater the energy loss and equipment heating.

2. High parking accuracy is required: "Wireless chargers can be in close contact with mobile phones, but it is difficult to accurately locate the vehicle on the charger, and the distance between the charger (energy emitter) and the receiver installed on the vehicle is much greater than the distance required for wireless charging of mobile phones," said Dr. Milan Rosina, chief power electronics and battery analyst at Yole Development.

In other words, the transmitter and receiver of wireless charging need to be precisely aligned. In order to overcome the above problems, the solution is to provide guidance to the driver through the car camera screen and align the induction board at the bottom of the car with the charging board on the garage floor. But this operation is obviously more convenient than inserting the plug manually.

3. Charging security is unstable: the bottleneck hindering the large-scale application of wireless induction charging technology is mainly the concern about radiation, because wireless charging will produce a strong magnetic field. It is possible to cause electromagnetic injury when people or animals are located between the electric vehicle and the charging device. Therefore, in the electromagnetic induction wireless charging, there can be no metal foreign body or animal between the charging transmitter and the receiving end.

4. High cost: for most new technologies, the biggest difficulty in the process of popularization is not the breakthrough of technology, but the reduction of cost. The key components needed for wireless charging have not been mass-produced, such as coils, capacitors and so on. Zhou Deyong, product manager of Zhonghui Chuangji, estimates that the private wireless charging price of 7.7kw is about 12000 yuan, and even if the future wireless charging reaches an order of magnitude of 1 million sets, its cost is still about 30% higher than that of traditional charging piles. Therefore, wireless charging will be mainly configured in high-end models, early sales will have a "climbing" process.

These practical problems have hindered the dream of wireless charging of electric vehicles in the past.

3. The current situation of wireless charging in the second spring is a little bit at the initial stage of domestic new energy vehicles: we all know that it is a major trend, but everyone is worried about whether they can wait until the day the big trend appears. However, several important changes have taken place in the current development of wireless charging, which has indeed ushered in the second spring for wireless charging.

New technological breakthrough: the industry has not stopped the pursuit of wireless charging. At this stage, the system performance, charging speed and power conversion efficiency of wireless charging technology are similar to those of plug-in slow charging. In terms of conversion rate, the power conversion efficiency of plug-in slow charge is about 95%, and wireless charging can also achieve 90% level. In terms of charging power, it is also gradually improved from 3kW level to 7kW, 11kW and 22kW level.

The restrictions on the location of the vehicle and the height of the chassis from the ground have also been relaxed. Wireless charging configuration suppliers claim to cover a wide range of models, including the SUV with a high chassis. Control technology is also constantly optimized, when there is a foreign body between the coils of the WPT charging system, there will be measures to prevent the occurrence of overheating events.

The new policy promotes: the development of any industry is standard first, and so is the wireless charging industry of electric vehicles. As early as 2020, China completed the compilation of four standards for wireless charging of electric vehicles. Zhang Bo, a member of the national standard working group on wireless charging of electric vehicles and a professor of the School of Electric Power of South China University of Technology, said, "these are four of the first series of national standards for wireless charging of electric vehicles in China." it fills the gap in China's national standards in this technical field, and will help China's electric vehicles move forward from technical research and development and engineering demonstration to industrialization, which is of great practical significance. "

Last year, the New Energy vehicle Industry Development Plan (2021-2035) issued by the General Office of the State Council clearly proposed to "strengthen the research and development of new charging technologies such as intelligent orderly charging, high-power charging and wireless charging." This is another great benefit for the R & D enterprises of high-power wireless charging of electric vehicle power battery.

In the past, the development of the charging pile industry, because there is no unified standard, different charging pile interfaces go their own way and are not compatible with each other. At present, wireless charging has great potential to unify standards at the early stage of the development of the industry, and finally achieve interconnection.

Open a new scene: intelligence and self-driving have become an important development direction of electric vehicles, and wireless charging will become a key part of self-driving in the future. Liu Yongdong, director of the Standardization Management Center of China Electric Power Enterprise Federation, believes that electric vehicle wireless charging technology is at the forefront of industrialization and has two major advantages: first, it is naturally combined with self-driving, "it is difficult for us to imagine that the vehicle can drive and park automatically, and people have to go to the parking space to complete the last charging action"; second, electric vehicles can be well connected with the power grid through App remote operation.

According to Hu Chao, deputy general manager of ZTE New Energy, there are two clear commercial application scenarios for wireless charging of electric vehicles: one is automatic charging of electric vehicles, such as self-driving scenario, which will be gradually popular in the future; the other is wireless charging in a three-dimensional garage scene. As the state has certain requirements on the proportion of charging parking spaces in parking spaces, if it is a high-rise three-dimensional parking lot, the conductive charging line is very difficult to pull up, so it is necessary to assemble wireless charging.

There is no doubt that wireless charging, as a new breakthrough in the way of replenishing energy for new energy vehicles, is about to usher in large-scale promotion. However, the development of wireless charging is not achieved overnight, and it will take some time for wireless charging technology to really hit the ground on a large scale. According to the optimistic prediction of the industry, the wireless charging industry will enter a mature period after 2025, when wireless charging facilities will be produced and landed on a large scale.

4. At the end of the development process of domestic new energy vehicle industry, there is a common phenomenon: route choice often presents an one-sided trend, either three-dimensional force to press iron lithium, or charging to replace electricity. In fact, in complex and diverse China, it is difficult to have a single solution to meet all the needs.

At present, with the rapid growth of the number of electric vehicles, a diversified energy replenishment system will better fill the gap of energy replenishment. Charging and changing electricity, wired charging and wireless charging will not be either or substitutes. Its ultimate goal is to eliminate energy anxiety and finally realize the mileage freedom of electric vehicles.

In the future, with the further liberalization and improvement of the self-driving car policy, wireless charging, like self-driving, will usher in its own spring.

[full text reference]

[1] "will wireless charging detonate the electric car market", Finance and Economics, Xie Lirong

[2] "the wireless charging prospect of the first national standard is unlimited", China Automobile News, Zhao Jianguo

[3] China New Energy vehicle Industry Development report (2020 New Energy vehicle Blue Book), China Automotive Technology Research Center

[4] "will the wireless charging of electric vehicles accelerate if the wireless charging of electric vehicles is combined?", electric vehicle observer, Qiu Xiejun

This article comes from the official account of Wechat: che Bai think Tank (ID:EV100_Plus). Author: Zhou Shuangjiang.

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