The development of low energy consumption and new energy vehicles is imperative. Therefore, while efficiently using coal resources, seeking new clean and efficient energy, especially energy for motor vehicles, reducing pollution, and protecting the ecological environment is a major issue facing the scientific, technological and industrial communities.

Low energy consumption and new energy vehicles mainly include: pure electric vehicles (EV), hybrid electric vehicles (HEV) and fuel cell electric vehicles (FCV).

Hybrid electric propulsion systems usually have two separate power sources. One of the primary power sources is a heat engine or a fuel cell. It should work as long as possible in the highest efficiency zone and have a constant power output, so that its harmful gas or particle emissions are the smallest and the fuel utilization rate is the highest. It means that the one-time running distance is extended; the other is the secondary power source, which can be a battery, a super capacitor or an energy storage flywheel. When the vehicle is going uphill or accelerating, the required power will be increased. At this time, the secondary power source will provide additional power output according to the instruction, so that the heat engine is still working at (or close to) the optimal output power state; When slopes or decelerating, the kinetic energy of the car will be immediately converted into electric energy and stored in the battery, which recovers the energy, thereby improving the energy utilization rate of the power system and extending the driving distance.

In the case that pure electric vehicles cannot be fully introduced to the market, as a transitional product, hybrid electric vehicles are forming a new round of technology development hotspots. Hybrid electric vehicles can greatly improve fuel economy and reduce emissions. Compared with fuel vehicles, CO2 emissions can be reduced by 50%, CH, NOx and other emissions can be reduced by 90%. The disadvantage is that it cannot achieve zero emissions, but the cost is much lower than that of pure electric vehicles. Even if pure electric vehicles become dominant in the future, hybrid electric vehicles will occupy their due position. It is expected that in 2010, the development of hybrid electric vehicles will be even more rapid.

Since the 1990s, as a new technology, the development of hybrid electric vehicles has received great attention from many developed countries and regions such as the United States, Japan, Western Europe, and has achieved some significant results and progress. The U.S. Department of Energy put forward short-term and long-term requirements for energy storage devices used in HEVs in 1994.

hybrid electric vehicles

Toyota Motor Corporation of Japan took the lead in launching the hybrid Prius sedan on the domestic market in December 1997, and then in the North American market at the beginning of 2000. The monthly production was increased from 1,000 to 2,000, and 45,000 were sold within three years. In 2005, Toyota had an annual output of 30 hybrid vehicles. Some experts believe that in the next ten years, there may be 40% of cars will use hybrid technology.

The U.S. Department of Energy signed a hybrid electric vehicle development contract with the three major automobile companies. Among them, General Motors invested 148 million U.S. dollars and Krasler invested 80.84 million U.S. dollars for a five-year research and development work. Prototype hybrid vehicles were exhibited at the North American International Auto Show. American newspapers commented: "Hybrid electric vehicles herald the direction of future automobile development."

In Europe, major automobile manufacturers scrambled to launch hybrid vehicles developed by the company. Recently, the six major European automobile companies jointly conducted discussions and comprehensive reviews on hybrid electric vehicle technology, and concluded that their technical achievements
It is expected that the cost of hybrid vehicles will be close to that of traditional vehicles, making it affordable for users and profitable for manufacturers. Experts generally appraise that hybrid vehicles are a revolution in the automotive industry at the beginning of the 21st century. Only hybrid vehicles can meet the environmental and energy-saving requirements for automobiles at the beginning of the century.

Hybrid commercial vehicles have also developed rapidly, especially hybrid buses. The most representative ones are OrionBus Ⅵ, NovaBus buses, Hino HIMB buses and HAЕ floor series hybrid buses that have been put into demonstration operation in New York. International hybrid vehicles have completed the commercialization process and are entering a stage of rapid growth.

Hybrid bus

In recent years, a new type of HEV has been developed. The vehicle is equipped with a battery and a gasoline generator. When driving, it usually uses the energy of the battery. When the battery energy is nearly exhausted, the gasoline generator charges it so that it can be driven to the limit. Where to charge. This type of vehicle is called a "plugin" HEV. SVE, a subsidiary of French Dassault Company, has developed prototype vehicles. This kind of vehicle is very suitable for families and "office workers". It requires the use of a battery with both capacity and power.

At present, there are two kinds of batteries that are widely used internationally and suitable for hybrid electric vehicles, namely: nickel-metal hydride batteries (Ni-MH) and lithium-ion batteries (LIB). All factors are considered. First of all, lithium-ion batteries are better than nickel. Hydrogen batteries are a well-known fact in the industry. For example, according to the analysis of Nomura Research Institute in Japan, from 1999 to 2005, nickel-hydrogen batteries were the mainstay (95%), and lithium-ion batteries were auxiliary (5%). Over time, the latter will dominate. From 2006 to 2010, nickel-metal hydride batteries accounted for 50%, and lithium-ion batteries accounted for 50%. Because lithium-ion batteries can withstand high-current charging and discharging, the power density can reach 1500w/kg within 10s; secondly, lithium-ion batteries are used in hybrid electric vehicles, and the effective utilization rate can reach 90%, which is much higher than the 50% of nickel-hydrogen batteries. %, after 2005, it will have a better performance-price ratio. Internationally, there has been an upsurge in the development of lithium-ion batteries for hybrid electric vehicles and their special materials. Table 1 compares the performance of different types of batteries.

Table 1 Comparison of performance parameters of different types of batteries

According to reports, the Japan Railway Company has developed a new type of energy train-NE train, which uses a lithium-ion battery energy storage hybrid system, which is not only good for environmental protection, but also improves energy efficiency. Through running experiments, it is confirmed that the function of this hybrid system has almost the same impact on vehicle performance and energy efficiency as the design. It can be seen that lithium-ion batteries have become unstoppable in the field of hybrid electric vehicles.

The appearance of the NE train