Why are many hydrogen balloon tanks 1,875 cubic? Let’s see how the experts answer it

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To answer this question, it is necessary to refer to the current version of the national standard GB50177; the draft version was finalized last August, but for some reason it has not yet been released. Draft design standards for hydrogen stations – Regulations on hydrogen storage capacity: The current version stipulates that the storage capacity for hydrogen per unit should not exceed 30,000 cubic meters. Formula for calculating the total cubic volume: its water volume (in m3) * operating pressure (absolute pressure, which is one atmosphere above the maximum operating pressure). Typically, the pressure at the outlet of the electrolyzer upstream of hydrogen storage is around 1.4 MPa; the exact operating pressure is determined by the client and the main design agency based on the process requirements, and the water volume varies depending on this operating pressure. Example 1: It is known that the operating pressure of the hydrogen balloon tank is 1.5 MPa, and the total volume of a single tank is 30,000 cubic meters. What is the water volume inside the tank? Answer: 30000/(15+1)=1875 cubic ； 1875 cubic units is obtained in this way. Example 2: It is known that the operating pressure of the hydrogen balloon tank is 1.4 MPa, and the total volume of a single tank is 30,000 cubic meters. What is the water volume inside the tank in cubic meters? Answer: 30,000/(14+1) = 2,000 cubic ； Note that the 2000 cubic units mentioned here refers to the geometric volume, not the nominal volume; therefore, the diameter cannot be calculated using the standard value of 15700 mm (which corresponds to a geometric volume of 2026 cubic units), otherwise the specifications will be exceeded. For specific details, refer to the national standard GB/T 17261 on the types and basic parameters of spherical tanks. So in such cases, we will adjust the diameter slightly using the formula for the volume of a sphere; for example, by changing it to 15600, the geometric volume will be 1988 cubic units. Working backwards: 1988*15=29,820 cubic meters, which is within the limit – exactly right. By the way, abroad, there are no restrictions on the capacity of hydrogen balloon tanks; they can be made as large as possible. In the Middle East’s first project for producing green ammonia from green hydrogen, the hydrogen storage tanks do not have a fixed capacity limit; they are much larger than those with a capacity of 30,000 cubic meters used in China. We can discuss the topic of volume abroad in more detail later, if there’s interest.