Hydrogen energy is known as the ultimate energy source for mankind. Hydrogen energy storage is considered by the industry to be an important supplement to new energy storage technologies such as lithium batteries and sodium batteries because of its large capacity, long lifespan, large scale, high energy density, and flexible deployment.
However, hydrogen has an energy density three times that of gasoline, and the consequences of an accident would be unimaginable. But due to its inherent properties, hydrogen is prone to chemical reactions with many substances and has a low density, making it easy to dissipate. Therefore, hydrogen storage is a major problem that plagues industry professionals.
At present, the most mature hydrogen storage technology is physical hydrogen storage.
Physical hydrogen storage technology refers to changing the hydrogen storage conditions to increase the hydrogen density, thereby storing hydrogen. Its advantages are low cost and easy hydrogen release. There are two main types: high-pressure gaseous hydrogen storage and low-pressure liquefaction hydrogen storage.
Currently, the most mature and commonly used hydrogen storage technology is high-pressure gaseous hydrogen storage.
High-pressure gaseous hydrogen storage refers to compressing hydrogen gas under high pressure and storing it in a high-density gaseous form. Its advantages include low cost, low energy consumption, and easy dehydrogenation; its disadvantages include small storage capacity, the need for pressure-resistant containers, and risks such as hydrogen leakage and container explosion.
The technical challenge is that hydrogen storage density is easily affected by pressure. The higher the pressure, the greater the hydrogen mass density. When the pressure range is 30-40 MPa, the hydrogen mass density increases rapidly, but when the pressure is greater than 70 MPa, the change is very small.
It is understood that the material of the hydrogen storage tank is an important factor in determining the pressure. The normal operating pressure range of the hydrogen storage tank is 35-70MPa. Therefore, the industry is committed to improving the material of the hydrogen storage tank and manufacturing lightweight, high-pressure resistant hydrogen storage tanks.
Currently, high-pressure gaseous hydrogen storage containers are mainly divided into four types: pure steel metal cylinders (Type I), steel liner fiber circumferential wound cylinders (Type II), aluminum liner fiber fully wound cylinders (Type III), and plastic liner fiber wound cylinders (Type IV).
Type III and Type IV cylinders have a small density-to-volume ratio and a high hydrogen storage density per unit mass, making them suitable for use in hydrogen fuel cell vehicles.
In the future, cryogenic liquid hydrogen storage technology can effectively complement high-pressure gaseous hydrogen storage technology, ultimately achieving synergistic development of the two.
Cryogenic liquid hydrogen storage refers to the storage of hydrogen gas under low temperature and high pressure conditions, with a volume density that can reach 845 times that of the gaseous state, enabling high-efficiency transportation of hydrogen.
To ensure low temperature and high pressure conditions, cryogenic liquid hydrogen storage technology requires not only specific materials for the hydrogen storage tank, but also rigorous insulation solutions and cooling equipment.
In addition, cryogenic liquid hydrogen storage technology currently faces three challenges.
First, to control the ambient temperature, the hydrogen storage tank needs to be equipped with insulation. However, temperature affects the density of hydrogen. How can the temperature be controlled within a suitable range?
Second, during hydrogen storage, hydrogen vaporization typically results in a loss of about 1%. How can this loss be reduced?
Third, to ensure a low-temperature environment and store a certain amount of hydrogen, approximately 30% of the energy used for hydrogen storage must be lost. How can this loss be reduced?
Although cryogenic liquid hydrogen storage still faces many challenges, it has significant advantages in large-scale, long-distance storage and transportation. With the formal implementation of my country's three national standards for liquid hydrogen, continuous technological advancements, and decreasing costs, the future of cryogenic liquid hydrogen storage looks promising.
