Technical analysis: How can a pure electric bus be more reasonable?

In recent years, the development speed of pure electric city buses has grown by leaps and bounds, and all major cities in China have accelerated the pace of replacing traditional power buses with pure electric city buses. However, in the daily ride, reporters often hear complaints from passengers, and the focus of complaints is mainly on fewer seats in the car, and the accessibility is not ideal.

At present, most domestic pure electric city buses generally adopt a layout in which the battery pack is placed in the middle of the vehicle. Taking a 12-meter large passenger bus as an example, due to the arrangement of the battery packs, most of the cars are arranged in the lateral arrangement of the seats.

A technician from Futian Ouhui told the reporter: "For pure electric bus, the low floor design and the arrangement of the battery pack will occupy some interior space, so it is necessary to change the seat arrangement. At present, the domestic pure electric bus The design of the bus does have an impact on the accessibility of the car."

Urban buses pursue high-efficiency transport of passengers, so they need to open the door and lower the floor, so that passengers can quickly ride and drop, and ensure good in-car passage and ride comfort. So, how can we optimize the existing design to make the layout of the pure electric bus more reasonable?

Improving battery energy density is key

How can we significantly improve the interior layout of pure electric buses? Many bus companies interviewed by the reporter said in unison that increasing battery energy density is the most critical solution.

The technicians of Xi'an Jinlong Automobile Co., Ltd. said: “Currently, the biggest factor affecting the internal space of pure electric buses is the battery pack arrangement. Due to the current low energy density of the battery, the volume and weight are large, in order to ensure the pure electric bus. For the driving range, there are more batteries to be placed. For example, a car has a quality of 18 tons, and the battery has 2.5 tons, which reduces the passenger load."

According to him, after the lithium iron phosphate battery is put into a box, the energy density can generally reach 100Wh/kg, and the ternary lithium battery can reach 110Wh/kg. The national goal is to reach 300Wh/kg by 2020. For urban buses, this indicator can basically meet the needs of use. "We hope that battery technology has a revolutionary breakthrough. If the battery energy density is increased, electric buses do not need to load so many batteries, and the interior space will naturally be designed more rationally," he said.

In the view of most bus company technicians, the most critical issue in optimizing the layout of pure electric buses is the need for breakthroughs in battery technology. After the energy density of the battery is increased, the light weight level and driving range of the pure electric bus will increase. Suzhou Jinlong technicians even said: "If the battery energy density is greatly improved, all problems of the electric bus will be solved."

Battery dispersion or current solution

Although improving the energy density of the battery is a prerequisite for perfecting the space structure of pure electric bus, the breakthrough of battery technology is not a one-off event. Is there any way to make it easier at this stage?

Wang Jian, a public transportation scholar at Chongqing Jiaotong University, told the reporter: “When the weight of the front, middle and rear of the bus is balanced, the operating efficiency is the highest. For a pure electric bus, the battery should be evenly distributed throughout the vehicle.” It means that if the battery is scattered under the chassis or at the top of the vehicle, it will no longer occupy the space inside the car, the space inside the car is larger, and the balance of the bus will be greatly improved.

When designing a bus, the main consideration is to make the interior space better accessible. In order to ensure the internal space of the bus, the battery will be dispersed as much as possible. The battery can be placed in the lower part of the floor between the two axles of the vehicle, the rear of the vehicle, the top of the wheel and the roof. "With the current technology, it is possible to disperse the battery and not affect the interior space. However, the distributed arrangement is more difficult for the thermal management and protection of the battery. If the battery is centrally arranged, the battery temperature control and protection measures will be better. Implementation.” Xi’an Jinlong’s technical staff told reporters that “the two arrangements of batteries have their own problems. There is currently no solution for the best of both worlds.”

Yutong technicians said that a pure electric bus will need a total of 80,000 ampere to 100,000 ampere-hour batteries, which are composed of multiple small batteries of 80-100 ampere hours. With Yutong's current technology, the battery can be reasonably arranged according to actual needs, which can completely prevent the interior space. He said: "The space for Yutong pure electric buses is comparable to that of traditional buses, even better than traditional buses." The technician also said that Yutong has its own new energy bus quality and design standards, including the safety of new energy buses. , reliability and comfort standards, for internal space design, the requirements are better than, at least not worse than the traditional power bus.

However, the experts and corporate personnel interviewed by the reporter stressed that the battery pack's safety performance still needs to be improved. Wang Jian said: "If the battery is placed on the top of the vehicle, it will be exposed to sunlight, the efficiency will be reduced, and there is a safety hazard of fire. When it is placed on the chassis of the vehicle, the waterproof and anti-intrusion performance of the battery pack needs to be strengthened. These technical problems are still Need to study. In addition, the technical staff of many bus companies said that due to frequent changes in the environment outside the car, the thermal management of the battery pack and its own adaptability also need to be improved.

Decentralized drive is becoming a trend

According to the reporter's understanding, at present, the driving mode commonly used in domestic pure electric bus buses is centralized driving. The motor is placed in the middle of the rear of the chassis and occupies a lot of area. "With the development of technology, the pure electric bus will gradually adopt the form of decentralized drive, that is, wheel drive or hub drive. With distributed drive, the differential, transmission and drive shaft are no longer needed, which can be lightweight. It can save space. Increasing the width of the rear passage of the vehicle is estimated to increase the interior space by 20%." Wang Jian said, "And there is no drive shaft, the passenger car floor can be made lower, and passengers get on and off more conveniently."

The technicians of Suzhou Jinlong and Yutong said that the research on wheel-drive is to solve the problem of driving efficiency and improve energy utilization. The expansion of the space is only an additional advantage.

According to Yutong technical personnel, Yutong is studying a distributed drive platform, which is suitable for urban buses, using wheel motors and independent suspensions. “One of the potential advantages of wheel-drive is that the width of the interior lane between the two drive wheels is wider than that of the centralized drive,” he said. “However, the electric drive decentralized drive technology is not yet mature. At this stage, Centralized drives are superior to distributed drives in terms of safety, reliability and comfort."

Suzhou Jinlong technicians said that in 2012, the passenger car with wheel-side drive was developed. Because of its high cost, it is mainly aimed at overseas markets. In addition, Foton Ou Hui also completed the sample car driven by the wheel, and there is no mass production yet.

In addition, the installation of a super single tire can also make the interior space more reasonable to a certain extent. Wang Jian said that the main advantage of using super single tires in passenger cars is that the resistance of the vehicle is reduced, fuel economy is better, and the cost of use is reduced. On the other hand, the passage at the rear of the vehicle can be made wider.

The technicians of Yutong and Suzhou Jinlong told the reporter that the passenger car will use super single tires, the frictional resistance will be reduced, the efficiency will be improved, and the interior space can be further optimized. At the same time, it has the function of light weight, but it is subject to cost, versatility, etc. The reason is that there is no universal application yet.

For Oil Immersed Power Transformer, we can produce voltage from 35kV to 500kV, capacity upto 460MVA. We use the best quality of raw material and advance design software to provide low noise, low losses, low partial discharge and high short-circuit impedance for power transformer.

Our power transformer are widely used in national grid, city grid, rural grid, power plant, industrial and mining enterprise, and petrochemical industry.

Power Transformer

Cast Resin Transformer,Power Transformer,Renewable Transformer,Power Transformer With Oltc

Hangzhou Qiantang River Electric Group Co., Ltd.(QRE) , https://www.qretransformer.com