What are fuel cell vehicles? Fuel cell vehicle classification. Advantages and disadvantages of fuel cell vehicles.

1. Introduction to Fuel Cell Vehicles

A fuel cell vehicle (FCV) is a vehicle that uses electricity generated by an onboard fuel cell device as its power source. The fuel used by the onboard fuel cell device is high-purity hydrogen or a high-hydrogen reformed gas obtained by reforming hydrogen-containing fuel. Compared with ordinary electric vehicles, the difference in power is that the electricity used by FCV comes from the onboard fuel cell device, while the electricity used by electric vehicles comes from batteries charged by the power grid. Therefore, the key to FCV is the fuel cell.

A fuel cell is a highly efficient power generation device that converts the chemical energy of fuel into electrical energy directly through electrochemical reactions without burning fuel. The basic principle of power generation is: hydrogen (fuel) is input into the anode (fuel pole) of the battery, and hydrogen molecules (H2) are dissociated into hydrogen ions (H+) and electrons (e-) under the action of the anode catalyst. H+ passes through the electrolyte layer of the fuel cell and moves toward the cathode (oxidation pole). Since e- cannot pass through the electrolyte layer, it flows to the cathode through an external circuit; oxygen (O2) is input into the cathode of the battery, and oxygen is dissociated into oxygen atoms (O) under the action of the cathode catalyst, and combines with e- flowing to the cathode through the external circuit and H+ of the fuel passing through the electrolyte to form water (H2O) with a stable structure, completing the electrochemical reaction and releasing heat. This electrochemical reaction is completely different from the violent combustion reaction of hydrogen in oxygen. As long as hydrogen is continuously input into the anode and oxygen is continuously input into the cathode, the electrochemical reaction will continue, and e- will continue to flow through the external circuit to form current, thereby continuously providing electricity to the car. This electrochemical reaction is completely different from the traditional principle of rotary mechanical power generation in which a conductor cuts magnetic lines of force. This electrochemical reaction is a static power generation method that generates electricity without the movement of an object. Therefore, fuel cells have the advantages of high efficiency, low noise, and no pollutant emissions, which ensures that FCV becomes a truly efficient and clean vehicle.

2. Working Principle of Fuel Cell Vehicles

In order to meet the requirements of automobile use, automotive fuel cells must also have the characteristics of high specific energy, low operating temperature, fast starting, and no leakage. Among the many types of fuel cells, proton exchange membrane fuel cells (PEMFC) fully possess these characteristics, so the fuel cells used in FCV are all PEMFC.

The working principle of a fuel cell vehicle is that hydrogen, as a fuel, undergoes an oxidation-reduction chemical reaction with oxygen in the atmosphere in the fuel cell installed in the vehicle, generating electrical energy to drive the electric motor, which in turn drives the mechanical transmission structure in the vehicle, and then drives the vehicle's front axle (or rear axle) and other walking mechanical structures to work, thereby driving the electric vehicle forward.

7. The core component is the fuel cell. The reaction of the fuel cell will produce very little carbon dioxide and nitrogen oxides, and the byproduct is mainly water, so it is called a green new environmentally friendly car. Fuel cell vehicles are a type of electric vehicle, and their core component is the fuel cell. Through the chemical reaction of hydrogen and oxygen, instead of combustion, it is directly converted into electrical power.

Hydrogen fuel for fuel cell vehicles can be obtained in several ways. Some vehicles carry pure hydrogen fuel directly, while others may be equipped with a fuel reformer that can convert hydrocarbon fuels into hydrogen-rich gas. Individual fuel cells must be combined into a fuel cell stack in order to obtain the necessary power to meet the requirements of vehicle use. The figure below is a schematic diagram of the fuel cell body of a fuel cell vehicle.

3. Characteristics of Fuel Cell Vehicles

Compared with traditional cars, fuel cell cars are different from traditional internal combustion engine-driven cars in terms of structure and power transmission, which puts forward new requirements for the overall design of cars. The engine-transmission powertrain of traditional internal combustion engine cars no longer exists in fuel cell cars, and is replaced by fuel cell reactors, batteries, hydrogen tanks, electric motors, DC/DC converters and other equipment. The braking system and suspension also change accordingly. Therefore, according to the characteristics of fuel cell cars themselves, corresponding changes and improvements should be made during the design. Fuel cell cars have the following advantages:

1. Zero emission or near zero emission.

2. Reduce water pollution caused by oil leakage.

3. Reduced greenhouse gas emissions.

4. Improved fuel economy.

5. Improved engine combustion efficiency.

6. Smooth operation and no noise.

The characteristics of fuel cell vehicles are as follows:

Fuel cell vehicle chassis layout

The fuel cell powertrain includes: hydrogen tank assembly, battery assembly, fuel cell stack assembly, power output system assembly, etc. Among them, the hydrogen storage tank is generally placed in the middle of the chassis, or in the space below the rear seats (the fuel tank position of traditional internal combustion engine cars), and the hydrogen tanks are stored in a dispersed manner. In addition to the fuel cell powertrain, the automobile brake assembly, front and rear suspension assembly and tires should also be adjusted and tested accordingly. In particular, with the development of wheel hub motor technology, fuel cell vehicles have new options for the placement of electric motors, which increases the interior space of the vehicle. The driving force of each electric wheel can also be directly controlled to improve the driving performance of the vehicle under harsh road conditions. The chassis layout should evenly distribute the vast majority of the load to the front and rear ends of the chassis, lower the overall center of gravity of the vehicle, give the car good handling performance, and improve the overall safety of the vehicle.

Fuel Cell Vehicle Management System

The power system of a fuel cell vehicle is generally composed of a proton exchange membrane fuel cell, a battery, a motor, and a system control device. The electrical energy generated by the fuel cell is converted by a DC/DC converter, a DC/AC inverter, etc., to drive the motor, converting the electrical energy into mechanical energy to provide power for the vehicle. In some key components, such as proton exchange membrane fuel cells and batteries, their thermal characteristics and heat transfer properties are very different from those of traditional vehicles, which puts forward new goals and requirements for the water and heat management of fuel cell vehicles.

Fuel Cell Vehicle Electronic Control

Similar to traditional cars, electronic control will play an increasingly important role in the development of fuel cell vehicles. Various control systems of cars will develop in the direction of electronicization and electrification, realizing "wire control", that is, replacing mechanical transmission mechanisms with wires, such as "wire braking" and "wire steering". The existing 12V power supply can no longer meet the needs of all electrical systems in cars. The implementation of the new 42V automotive electrical system standard will bring about major changes in the design and structure of automotive electrical components, and mechanical relays and fuse protection circuits will also be eliminated. At the same time, the characteristics of fuel cells have their own characteristics:

a. Low voltage and high current;

b. The output current will increase with the increase of temperature, and the output voltage will decrease with the increase of output current;

c. From the beginning of output voltage and current to gradually entering a stable state, the dynamic response time staying within the transition zone is relatively long. It is precisely because of the above characteristics that most electrical appliances and motors are difficult to adapt to their voltage characteristics, so they must be used in conjunction with DC/DC converters and DC/AC inverters, and a large amount of power regulation is required for the fuel cell system to ensure voltage stability.

(1) When the output power of the fuel cell is greater than the vehicle's needs, the excess power can be used to charge the battery, and the battery can provide power to the auxiliary system when the power system is started;

(2) When the power of the fuel cell cannot meet the needs of the car to accelerate or climb a hill, the battery can provide additional power and be used together with the fuel cell.

Therefore, the vehicle can use a 42V auxiliary power supply to independently provide power for various electronic and electrical equipment. Since fuel cell vehicles are essentially different from traditional internal combustion engine vehicles in terms of driving mode, the design of chassis layout, water and heat management, electronic control and many other aspects is also very different.

Fuel cell vehicles are a type of electric vehicle. The energy of its battery is directly converted into electrical energy through the chemical reaction of hydrogen and oxygen, rather than through combustion. The chemical reaction process of the fuel cell does not produce harmful products, so fuel cell vehicles are pollution-free vehicles. The energy conversion efficiency of fuel cells is 2 to 3 times higher than that of internal combustion engines. Therefore, from the perspective of energy utilization and environmental protection, fuel cell vehicles are an ideal vehicle.