SMM News: this year can be said to be the first year of electric vehicle safety. In the past, both manufacturers and users who bought electric vehicles were only concerned about performance and mileage, and no one was concerned about battery safety. It was not until Tesla exposed the spontaneous combustion incident that people began to pay more and more attention to the safety of electric vehicles. This also makes a lot of unknown in the past, manufacturers avoid talking about the performance defects of ternary lithium batteries gradually surfaced, making people gradually aware of the benefits of lithium iron phosphate.
If you compare ternary lithium with lithium iron phosphate, I believe many people will soon know that lithium iron phosphate is better than ternary lithium battery in terms of safety, but if you compare ternary lithium with hydrogen fuel cell, who is safer? In the past, people used to talk about hydrogen color change, thinking that hydrogen is a much more dangerous way to store energy than gasoline. Is that really the case? How does hydrogen fuel cell work? How is its security designed? Who is safer than ternary lithium? This issue will be interpreted for you.
Core Technology of hydrogen fuel Cell Power system: hydrogen Storage Tank + fuel Cell reactor
Like the battery packs in electric cars, hydrogen storage tanks are used to store hydrogen gas, and fuel cell reactors are used to convert hydrogen and oxygen into electricity and water. Taken together, these two constitute the equivalent of an electric vehicle battery pack, which can continue to provide electricity for the motor and the whole vehicle electrical equipment.
The benefits of hydrogen fuel cells are obvious, the power conversion efficiency is extremely high, and the process is very quiet and does not require a lot of heat dissipation. This is why the Toyota Mirai can carry 700km + just with 5kg hydrogen. Great energy density and high energy conversion efficiency are the most important characteristics of hydrogen fuel cell. The core technology of fuel cell reactor is proton exchange membrane and catalyst. At present, these technologies are mainly monopolized by large European and American companies, and there is no large-scale industrialization in China. So it's easy to understand that reactors are listed as core technologies, so why are gas tanks also core technologies?
The sealing and durability determine the performance of the gas storage tank.
Just like the equipment manufacturing level of a large country, in the industrial and civil fields, the performance of sealing materials is also an important basis to measure the manufacturing level of a large country. Many countries in Europe and the United States are absolutely confidential about the formulation and manufacturing process of high-performance sealing materials. That is why in traditional cars, top-performance brakes and fuel common rail systems for gasoline-diesel direct injection engines come from European and American suppliers because their core technology is sealing technology.
Structure of hydrogen fuel cell gas storage tank
The same is true for hydrogen fuel cell vehicles, in order to improve the mileage, you need to thank the hydrogen gas, and the pressure vessel that can store hydrogen gas to bear the pressure is the key to how much hydrogen gas can carry. Because the density of hydrogen gas is very small, it must be compressed or even liquefied at low temperature before it can be stored in a pressure vessel to obtain sufficient energy density. the greater the pressure the container can bear, the more hydrogen gas will be carried per unit volume. The greater the pressure the container can withstand, the higher the requirements for sealing performance and pressure resistance. Toyota Mirai is the world leader in hydrogen storage performance, and the model has been mass produced, even so, the hydrogen gas carrying 5kg still needs two large gas storage tanks, so it takes up a lot of space in the back of the car, making the whole vehicle different from the traditional electric car in shape, and the rear height of the vehicle is relatively high.
What are the safety designs for hydrogen storage tanks? Who is safer than ternary lithium batteries?
In the whole process of fuel cell vehicle operation, fuel cell reactor is a place of chemical reaction. It only needs a continuous supply of a small amount of hydrogen gas to continue to work, in the event of hydrogen gas leakage or safety accident, it can quickly cut off the supply path of hydrogen gas to prevent the combustion of hydrogen gas. As everyone can think of, the most likely to affect the safety of fuel cell vehicles is the gas storage tank.
Therefore, the problem of safe collision must be fully considered in the design of gas storage tank: on the one hand, the shell material of gas storage tank needs to be light enough, on the other hand, it needs enough strength to withstand impact. As a result, hydrogen storage tanks are generally made of costly carbon fiber and other composite materials. However, we know that not using very strong materials to make gas tank shells can only ensure the safety of collision at a certain speed. However, the actual speed of road driving is bound to be much higher than the speed of safe collision in the laboratory, so once the hydrogen storage tank ruptures, will there be an explosion when the hydrogen leak is mixed with the air?
In fact, this is taken into account in the design of hydrogen storage. Because of the high hydrogen pressure in the hydrogen storage tank, an emergency pressure relief valve is designed on the gas storage tank. In the event of hydrogen leakage or fire, the emergency pressure relief valve will automatically open and quickly release the hydrogen gas in the gas storage tank. We know that the density of hydrogen gas is much smaller than that of air, and it must be combined with oxygen to produce combustion or explosion. The hydrogen gas released by high pressure near the gas storage tank has little chance to come into contact with oxygen due to the high pressure and extremely fast flow velocity. And the hydrogen gas far away from the gas storage tank will rise rapidly in the air because of its low density. Even if there is an open fire in the air at this time to meet the ignition conditions, then only in the air to form a fireball, will not cause casualties. This high-speed hydrogen release technology is also used in large gas storage tanks at hydrogenation stations.
Core Technology of hydrogen fuel Cell vehicle
Hydrogen storage should be safer than ternary lithium batteries because dangerous hydrogen can be quickly released from people by isolating oxygen or releasing it rapidly. in a sense, it is even safer than liquid gasoline. The ternary lithium battery will age with the passage of time, may occur in the internal short-circuit phenomenon, or due to the impact of external forces lead to internal short-circuit spontaneous combustion. The worst thing is that whether it's spontaneous combustion from the inside out or combustion from the outside, a lot of oxygen is released during the process, which means that even if isolated from the air, the battery will burn more and more.
Development Prospect of hydrogen Energy and Ternary Lithium Battery
In China, the biggest advantage of ternary lithium battery is that in recent years, the tilt of national policy to encourage production has been greatly developed, it can be said that Chinese companies have mastered its core technology, and has become the world's largest producer of lithium battery, the cost has been greatly reduced, has fully formed a large-scale industry. However, hydrogen fuel cell technology, whether it is the reactor catalyst process formula, or the core technology of gas storage tanks, China has not formed a large-scale industry, so the cost is extremely high. However, China has very good industrial conditions for the development of hydrogen energy. Every year, the by-products of hydrogen produced by the domestic petrochemical industry are enough for vehicles, and the cost of obtaining hydrogen is relatively low. Moreover, it does not need to rely on the high energy consumption way of electrolytic water to obtain hydrogen gas, which lays a good foundation for the large-scale development of fuel cell vehicles.