Wireless charging is expected to relieve the "mileage anxiety" of electric vehicles

Volvo Cars tests new wireless charging technology in Sweden. Image source: American Auto World Media

  Intern reporter Zhang Jiaxin.

  [World tide of scientific and technological innovation]

  One of the biggest obstacles to the promotion of electric vehicles is charging, or the lack of charging infrastructure. There is a general "mileage anxiety" among car owners, who are worried about running out of electricity and being trapped far away from the charging station of electric vehicles. However, what if the car doesn’t need a charging pile at all?

  According to a report recently released by Nikkei Asia, roads with built-in wireless charging technology have been tested in Japan and may become a practical facility by 2025.

  At the Dalin Group Research Center of Tokyo Construction Company, Japan, electric vehicles can travel at a speed of 15 kilometers per hour on this road. Uninterrupted electronic coils are buried under the surface of the road, and separate coils are also installed inside the electric vehicle. Using magnetic field induction, current can be generated in the coils of the automobile. The concrete used in the pavement is reinforced with fibers to increase durability. Driverless buses running around the clock will be one of the main beneficiaries of this breakthrough technology.

  However, the report adds that the technology is still far from perfect. It points out that wireless charging is not as effective as using traditional cables because of transmission loss.

  At present, not only in Japan, enterprises and institutions in many countries and regions have carried out research on wireless charging of electric vehicles, trying to fundamentally solve the "mileage anxiety" problem.

  The idea is not new.

  In fact, people have long been used to charging their smartphones wirelessly. Gizmodo, a well-known American technology blog, posted on September 20th that the global standardization organization for promoting wireless charging technology — — Wireless power consortium introduced the first "wireless charging" standard QI in 2008. The first widely used mobile phone adopting QI standard was Nokia Lumia 920 in 2012.

  This technology can be traced back to 1894, when nikola tesla, a famous scientist, realized the wireless lighting of incandescent bulbs in new york City by resonant inductive coupling. Therefore, the idea of wireless power transmission is not new. Demonstration facilities have been installed or are being built in many parts of the world.

  In 2017, a 100-meter-long section of France was equipped with wireless charging. When the car is driving on this "wireless highway" at a speed of 40 kilometers per hour, it can be recharged for about 2 kilometers per kilometer. The maximum speed of vehicles on this road can reach 100 kilometers per hour.

  In 2018, a 2-kilometer-long road in Sweden was installed with electric rails and charging facilities on the central shaft. A special device is installed on the electric car, which will fall into the groove of the electric rail and charge the car while driving. It’s just like the track racing we played when we were young, except that the toy car was replaced by a real car.

  In 2020, Israel installed wireless charging cables on a 600-meter-long road. The technology is being tested, and if all the tests are successful, it will be built into an 18-kilometer bus lane between the city and the airport.

  In June this year, Italy built a 1.05km dedicated wireless charging highway to demonstrate dynamic wireless power transmission. The road is wired in the asphalt pavement, and vehicles can collect electricity through special receivers. When the car is driving at a speed of 40 kilometers per hour, it can be charged at a speed of 1.5 kilometers per kilometer.

  In 2023, a 1.6-kilometer-long wireless charging road will be put into use in Detroit, USA, and this road will be reconstructed. At that time, cars with special receivers will be able to charge while driving on the road.

  How far is the future?

  Like many other emerging technologies that have gradually entered the mainstream market, wireless charging in vehicles is not yet mature and still faces many technical problems that need to be overcome.

  Eetasia.com website reported that the positioning of wireless charging is not to completely replace wired charging, but to provide a convenient experience. This means that electric vehicles can use wireless charging mode in public places or outdoor situations, and can be directly charged without wiring after parking, and there is no need to unplug the charging cable when leaving; When used outdoors, it is safe to charge even under the conditions of snow, water and dust pollution.

  According to the article, from the technical point of view of wireless charging of electric vehicles, the biggest R&D challenge is safety and mass production.

  Wireless charging is to transmit power wirelessly. Even the low-power 5W wireless charging on mobile phones faces many security problems, including electromagnetic interference, heating, metal foreign bodies and so on. The biggest security threat is metal foreign bodies, which will absorb electromagnetic energy and generate intense heat, leading to disastrous consequences. The charging power of electric vehicles is more than 1000 times that of mobile phones, and the threat of metal foreign bodies will be more serious. In the system design, it is necessary to monitor whether there is a threatening metal foreign body between the two ends of the battery.

  The problems of mass production include verification, reliability and cost. The first problem encountered in commercial mass production is related regulatory certification. The wireless charging product itself is a powerful electromagnetic energy emitter, and it is difficult to pass the relevant electromagnetic interference regulations; The coil in the system is a very unstable component, and its characteristics will change due to the interference of various factors such as production deviation and temperature. The system needs to overcome the coil factor through the adjustment mechanism to keep its functional operation. The biggest problem in mass production is cost. At present, the cost of wireless charging system for electric vehicles is very high.

  The American media Auto World website reported that many participants, including Nissan, BMW and Renault, have been exploring wireless technology for many years. In fact, the BMW 530e inductive charging pilot project was rated as the 2020 green car technology by Green Car Magazine. However, it has not "taken off" in any meaningful way. High cost and lack of standards are stumbling blocks to the development of car wireless charging.

  Generally speaking, in view of the hot trend of energy saving and green energy development, wireless charging solutions for electric vehicles are expected to grow at a considerable speed in the next few years. With the continuous innovation of future transportation through disruptive technology, worrying about where to charge electric vehicles may soon become a thing of the past.