Future technology has arrived! Hydrogen fuel cell vehicle technology analysis

Hydrogen fuel cell vehicles have been very hot recently. On November 18, Toyota Motor Corporation officially released its production version of the hydrogen fuel cell car mirai in Japan and plans to list in Japan; and in mid-November, Honda also released its latest hydrogen fuel cell car fcv sedan, and Said that it will be listed in March next year; at the same time, Volkswagen Group did not show weakness, at the Los Angeles Auto Show demonstrated its three hydrogen fuel cell vehicles, including the Audi a7 sportback h-tron quattro.

The intensive movement of car companies is delivering a clear signal: Hydrogen fuel cell vehicles are no longer a “future legend” but the latest generation of green car technologies that will soon be marketized. As a word that is a bit strange to us, what exactly is a "hydrogen fuel cell car"? How does it work? Compared with other models such as pure electric vehicles, what are their advantages? This article will give you a one-by-one explanation.

What exactly is a hydrogen fuel cell vehicle?

At present, hybrid vehicles and pure electric vehicles are gradually being accepted in the market, which has become a major change in the form of power after ordinary diesel locomotives.

Hybrid vehicles rely on the cooperation of a fuel engine and an electric motor to provide vehicle driving force. In general, a hybrid vehicle is driven by a pure electric motor at a low speed such as a start, and a dual-powered drive of a fuel oil machine and a motor is used under conditions such as sudden acceleration to achieve an effect of increasing fuel economy. (such as the Toyota Prius, the Volkswagen Golf gte, the Ford Mondeo Hybrid, etc. are all typical hybrids)

There is also a type of extended-range hybrid vehicle that also has a fuel engine and an electric motor. However, the vehicle itself is driven by the electric motor. Usually the task of the fuel machine is to charge the on-board battery, so the fuel machine itself does not participate in the vehicle driving process. (eg BMW i3 Extended Range, Chevrolet Vollanda)

Pure electric vehicles are relatively simple. Vehicle drivers rely entirely on electric motors. The car is not equipped with any conventional internal combustion engine. The electric energy required by the electric motor comes from the batteries carried on the car. (such as Tesla Model s, Nissan Leaf, Renault Zoe, etc. are all such models)

Now back to the topic: hydrogen fuel cell vehicles. Although the name is very long, in short, it is more like an extended-range electric car.

Some people may think that hydrogen fuel cell vehicles are powered by burning hydrogen raw materials. In actuality, hydrogen fuel cells refer to the device through which hydrogen reacts with oxygen to produce electrical energy. (Hydrogen diesel locomotives that are driven solely by burning hydrogen have also appeared, such as BMW's hydrogen energy 7 series)

The driving force of a hydrogen fuel cell vehicle comes from the motor on the vehicle, just like a pure electric vehicle. So it can be understood as a "electric vehicle with a hydrogen fuel generator." The concept is similar to that of an extended-range model, except that the source of electrical energy has been changed from a fuel oil to a hydrogen fuel power unit.

What is the working principle of a hydrogen fuel cell vehicle?

At present, the hydrogen fuel cell vehicles of various automobile enterprises are relatively consistent on the basic principle, but differ in the details of design. The following Xiaobian uses the hydrogen fuel cell car mirai just released by Toyota as an example to analyze the “secret” of hydrogen fuel cell vehicles for you.

The power system of mirai is called tfsc (toyota fc stack), Toyota's fuel cell stack. It is a complex hybrid system with a fuel cell stack as its core component. It also includes fuel cell boosters, high pressure gas tanks, and drive motors. The fuel cell stack is located in the lower part of the vehicle body and is a place where hydrogen and oxygen react. It is also the key to hydrogen fuel cell vehicles.

In the fuel cell stack, a combination of hydrogen and oxygen will be carried out. During this process, there will be charge transfer, which will generate current. At the same time, hydrogen reacts with oxygen to produce dihydrogen monoxide, water.

The core of the fuel cell stack as a chemical reaction cell is the "proton exchange membrane."

On both sides of the film, a catalyst layer is pressed to decompose the hydrogen into a charged ion state. The electrons carrying hydrogen then pass through this thin film, leaving behind the body's electrons, becoming positive-priced hydrogen protons, and reaching the other end through the membrane. Immediately afterwards, hydrogen protons combine with oxygen at the other end of the membrane while the lost electrons are “returned” to produce water. Water became the only "scrap" in the reaction process.

As the oxidation reaction progresses, electrons continue to transfer, creating the current needed to drive the car. If we say that the technical breakthrough of hydrogen fuel cell vehicles is to invent a kind of car, it would be better to invent a brand new "generator" and then integrate it into a car.

In the fuel cell stack, a large number of thin films are arranged, which can generate a large amount of electron transfer to form the current required for the vehicle to travel. Under normal circumstances, the overall voltage generated by these currents is about 300v, which is not enough to drive a high-power motor for a vehicle. Therefore, hydrogen fuel cell vehicles such as mirai are also equipped with step-up transformers, which raise the voltage to more than 600 volts, thereby smoothly driving the motor.

In addition to the fuel cell stack produced by electrical energy, the hydrogen fuel cell vehicle power system also includes a hydrogen storage tank for storing the hydrogen raw material needed to generate electrical energy. Since hydrogen has a low density under a general atmospheric pressure and is in a gas state, it is necessary to perform compression while trying to obtain sufficient hydrogen to supply the fuel cell stack. Therefore, the design and strength of the hydrogen storage tank are also very important. The Toyota mirai has three hydrogen storage tanks, and the Audi a7 sportback h-tron quattro has four.

Of course, hydrogen fuel cell vehicles are also equipped with a battery, which normally stores excess power generated by the hydrogen fuel stack. During braking, the recovered power can also be stored.

What are the advantages of hydrogen fuel cell vehicles?

1 Zero emissions

As mentioned earlier, the hydrogen fuel cell stack generates only water in the process of generating electricity, so its most dazzling advantage is that it truly achieves the “zero emission” goal. This may seem strange, but it is indeed the case.

2 Eliminate "mileage worry"

Under normal circumstances, hydrogen fuel cell vehicles require approximately one kilogram of hydrogen per 100 kilometers. For models like the Toyota mirai and the Audi a7 sportback h-tron quattro, about 5 kilograms of compressed hydrogen can be stored. In theory, it is no problem that the cruising range can reach 500 kilometers under the full hydrogen state.

3 The fuel replenishment time is equivalent to the fuel vehicle

Hydrogen fuel cell vehicles are very quick and easy to add hydrogen, and dedicated hydrogenation equipment can be filled with hydrogen feedstock within minutes. Compared to pure electric vehicles, the advantages of charging for a long time are extremely obvious.

4 performance fuel truck

The Audi a7 sportback h-tron quattro is a hydrogen fuel cell vehicle. Each front and rear axle is equipped with a motor with a maximum output power of 85kw and a maximum torque of 270nm. The total power is 170kw, and it also provides up to 540nm of torque. The car 0-100km acceleration 7.9 seconds, the maximum speed of 180km / h, comparable to gasoline vehicles.

Conclusion:

As a hydrogen fuel cell technology that has just entered the practical stage, there are still some drawbacks. For example, in the price, Toyota mirai's proposed price of 7.236 million yen, about 380,000 yuan, is still higher than ordinary cars. At present, supporting facilities such as hydrogen refueling stations are also relatively rare, and the convenience of refuelling is far from being comparable to that of fuel vehicles.

However, with the advancement of technology, follow-up of infrastructure construction, and gradual listing of new products, hydrogen fuel cell vehicles that take into account environmental protection, performance, and practicality will become the ultimate solution for new energy vehicles, thereby completely replacing traditional internal combustion. locomotive. We can try to imagine what a world that no longer mentions "cylinder", "displacement", and "exhaust" will look like.