How many hurdles does V2G have to overcome before it can be commercialized?

Recently, Volkswagen Group announced that it will launch "Vehicle-to-grid" (V2G) bidirectional charging technology for all pure electric models based on the group's MEB platform from 2022, hoping to become the first automaker in Europe to put V2G into commercial use. This has once again attracted the industry's attention to V2G bidirectional charging of electric vehicles.

The reason why V2G bidirectional charging technology has attracted much attention is that it has practical significance for solving the shortage of electric energy and emergency power supply. "V2G includes bidirectional charging between electric vehicles and between electric vehicles and power grids, as well as the supply of civilian electricity in emergency situations. Once it is commercialized on a large scale, it will be beneficial to consumers, automobile companies, power companies and charging facility companies." Chen Xintai, a researcher at the New Energy Materials Research Center of Guangdong University of Technology, said in an interview with a reporter from China Automobile News, but there are still many "hurdles" to overcome on the road to large-scale commercialization of V2G.

♦ V2G will become the fulcrum of energy transformation

As of the end of 2020, the number of electric vehicles in the world has reached nearly 10 million, which is posing a new test to the power supply capacity of power grids in various countries. Data shows that global electric vehicle sales reached 3.24 million in 2020, a 43% increase from 2.26 million in 2019. Among them, there are very few vehicles with V2G bidirectional charging function. Once an emergency like the blackout in Texas, the United States in February this year occurs, charging ordinary electric vehicles will become difficult. Once V2G technology becomes popular, bidirectional charging between vehicles or between vehicles and power grids will greatly alleviate this dilemma.

“目前全球有50余项V2G试点示范项目，主要集中在美国、欧洲、日本和韩国等地，包括技术验证、示范推广、商业化运行等不同类型。”西安工业大学微电子技术实验室工程师魏冬在接受《中国汽车报》记者采访时谈到，V2G技术一旦商业化，不仅可以实现电动汽车与电网的双向能量互动，实现日常稳定供电和应急供电保障，而且还能够显著降低电动汽车的全周期成本，纯电动汽车可以通过电力市场交易获得额外辅助服务或峰谷差价收益，从而在经济性上达到甚至超过燃油车，加速电动汽车取代燃油车的进程。中国工程院院士黄其励也看好V2G技术成为能源转型的支点，因为该技术能促进车网一体。

In addition to Volkswagen, electric vehicles from Volkswagen Group's sub-brands such as Audi, Skoda, and Seat will also achieve V2G charging. Globally, Nissan Leaf has achieved V2G bidirectional charging function; Renault has also launched a V2G pilot project in Europe, with a fleet of ZOE pure electric vehicles to "feed back" to the power grid. During the epidemic prevention and control period in 2020, Fiat Chrysler (FCA) announced the launch of a V2G pilot project at its Italian factory, aiming to achieve bidirectional charging between FCA's pure electric vehicles and the power grid. Tesla is also actively preparing to equip its main models Model 3 and Model Y with V2G bidirectional charging function.

Domestic V2G development needs to be accelerated

Compared with the booming craze in Europe and the United States, V2G seems a bit "deserted" in China.

On April 13, Zhejiang Geely Holding Group Co., Ltd. was granted an invention patent for "a vehicle-to-vehicle charging device and method". The patent proposes a vehicle-to-vehicle charging device and method, which includes an on-board bidirectional charger, a charging and discharging connection device, and a control box. However, models equipped with V2G technology are rare in China. In 2013, BYD's pure electric vehicle e6 was equipped with a bidirectional inverter charging and discharging drive motor controller (referred to as "inverter"), and 42 related technical patents were applied for in China.

In general, the development of V2G in China still seems a bit slow. According to the relevant documents issued in the past two years, the plan for the development of V2G in China is to carry out small batches of V2G test verification before 2020. The number of electric vehicles participating in two-way charging can be controlled at 10 to 300. The main task is to verify the two-way charging technology between multiple electric vehicles and the power grid and realize the mutual charging and discharging of multiple electric vehicles. From 2020 to 2025, the demonstration operation of large-scale electric vehicles (generally not less than 500 vehicles) and the power grid will be carried out. After 2026, it will be gradually commercialized and promoted.

"It can be seen that compared with the pace of Europe, the United States and Japan, this needs to be accelerated." Yang Jianping, an expert from the Shandong Battery Industry Association Council, said in an interview with a reporter from China Automotive News that domestic research shows that when the growth of pure electric vehicles in cities accelerates (it is expected that the number of urban electric vehicles will exceed 3 million in 2035) and the proportion of fast charging mode is relatively high, the increase in the peak load of my country's urban power grid may cause a gap in the installed power capacity and transmission line capacity in some areas in extreme cases. "Therefore, my country should promote the application and commercialization of V2G technology as soon as possible," he said.

♦ Multiple bottlenecks of “car-pile-network” need to be broken

"The commercialization potential of V2G technology is undoubtedly huge, but there are still some bottlenecks and problems that need to be solved in terms of vehicles, charging piles, networks, and people." Qin Xiaopeng, an automotive industry analyst at Orient Securities, told a reporter from China Auto News that only by facing up to and seriously solving these problems can the commercialization of V2G be accelerated.

In terms of cars, it is mainly restricted by the life of the battery. "There are two major problems to be solved when configuring V2G technology on electric vehicles. One is the key core technology, which is the research and development of inverter technology. The other is the impact of the life of the on-board power battery, which is also the key to whether the owner can accept V2G." Chen Xintai introduced that on the one hand, in layman's terms, ordinary inverters can only output 200W of current, which is equivalent to only supplying one or several traditional incandescent bulbs, while the charging and discharging of the V2G inverter can directly drive 10 to 25kW of electrical appliances, which is equivalent to a small mobile energy storage power station. On the other hand, V2G technology will inevitably increase the number of charge and discharge times of the on-board power battery, which will affect the life of the battery. This is also the main reason why Tesla has been reluctant to deploy V2G bidirectional charging technology "on board" in the past few years. Therefore, for some electric vehicle brands with relatively small production and sales scales, it is not very meaningful.

In terms of charging piles, the existing charging piles need to be technically modified. Wei Dong told reporters that there are two solutions for charging piles or charging stations that adapt to V2G technology. One is to directly modify the circuit; the other is to equip the charging piles or charging stations with energy storage batteries. The two technical solutions have the same purpose, which can charge electric vehicles normally, and electric vehicles can also return electricity to the energy storage batteries of the charging piles, but the modification costs are very similar. Regardless of which solution is adopted, the charging piles or charging stations need to be modified. At present, most charging piles and charging pile equipment only have output current, without input current function, and cannot adapt to V2G applications.

In terms of the power grid, Yang Jianping explained that there are two major challenges. The first is V2G bidirectional charging, which requires technical solutions to vehicle-grid coordinated control and management. As we all know, social electricity consumption is very obviously in a state of peaks and troughs. At present, it is mainly the peak of electricity consumption in summer and winter. However, with the continuous increase of electric vehicles, and the charging and discharging time of electric vehicles is highly random, if it cannot be uniformly coordinated and controlled and managed, it will have a huge impact on the grid loss and power stability. The second is to solve the problem of unstable return current technically, especially when electricity is returned to the grid, a stable current is required. If a large-scale change in electricity supply and demand occurs at a certain moment, it will have a certain impact on the power grid itself. In severe cases, it may even cause unstable grid current, which may cause the substation to trip, and the tripping will lead to power outages and other accidents.

Lu Wengang, marketing director of Teladian, also believed in an interview with a reporter from China Automotive News that the biggest challenge for the commercial application of V2G lies in the system energy management in the smart grid. "When electric vehicles are to achieve large-scale charging and discharging, they need to build a multi-functional microgrid system with distributed photovoltaics and distributed energy storage in the region. On the one hand, regional autonomy is achieved, and energy in the region is uniformly dispatched and managed to achieve self-generation and self-use, self-discharge and self-use, and economical electricity use; on the other hand, the role of load aggregation service provider is played, and friendly interaction and coordination with large power grids is achieved to achieve load dispatching, peak shaving and valley filling, frequency regulation and voltage regulation, etc." He said, "The charging network technology route that Teladian has been practicing is a microgrid system, which is the best solution for large-scale charging and discharging of electric vehicles."