How should one select the appropriate pressure and volume for hydrogen spherical tanks?

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I. Introduction: Thanks to the rapid development of green energy industries such as solar and wind power, and considering factors like insufficient voltage stability and difficulties in grid integration that are common with green electricity, the green hydrogen production industry has seen rapid growth in recent years. Against the backdrop of the rapid development of the green hydrogen production industry, how to store and utilize green hydrogen in an economical and efficient manner has become a major challenge. Currently, the relatively mature hydrogen storage technologies are mainly high-pressure gaseous hydrogen storage and medium- to low-pressure gaseous hydrogen storage. Liquid hydrogen storage and other forms of hydrogen storage have not yet been put into commercial use. II. High-pressure gaseous hydrogen storage. The relevant explanation from Baidu Baike regarding high-pressure hydrogen storage technology is as follows: “High-pressure hydrogen storage is a method of storing hydrogen.” Hydrogen can be transported in gas cylinders under high pressure (15.2–70.9 MPa); it can be released directly by adjusting the pressure-reducing valve. Convenient and reliable, it is the most common and straightforward method for storing hydrogen. With the advancement of materials science, high-pressure gas cylinders made of carbon fiber and aluminum composites have been developed, **reducing the weight of the cylinders themselves and improving the efficiency of storage capacity, thereby making high-pressure hydrogen storage a more competitive option for storing hydrogen in vehicles. A demonstration fuel cell bus uses high-pressure hydrogen storage tanks to supply hydrogen directly to the vehicle, enabling a driving range of up to 250 kilometers. ” III. Medium and low-pressure gaseous hydrogen storage: For medium and low-pressure gaseous hydrogen storage, steel pressure vessels are still the most commonly used. Cylindrical tanks are generally employed when the PV value is low, while spherical tanks are typically used when the PV value is high (above 10,000). However, in practice, there have been cases where vertical cylindrical tanks were still used even when the PV value reached 25,000 (bar.m3). Based on my understanding of spherical tanks, when the PV value reaches 10,000 (bar·m³), a spherical tank should be given priority in terms of the equipment’s own cost. IV. How to select the appropriate pressure P and volume V? So, when considering medium and low-pressure hydrogen storage, how exactly should one choose the appropriate PV value? In fact, the current hydrogen station standards clearly specify the PV value for hydrogen storage tanks. The main current regulations related to hydrogen are GB4962-2008 \"Technical Regulations for Safe Use of Hydrogen\" and GB50177-2005 \"Design Code for Hydrogen Stations\". GB50177-2005 specifies a clear upper limit for the PV value of hydrogen storage tanks. That is, the PV value for a single cylinder should not exceed 30,000 (bar(A)·m³). The screenshot of the standard text is as follows: The total volume mentioned in the standard terms is explained in the \"Explanations to the Provisions\" of this standard as follows: the total volume referred to in the standard conditions is actually the PV value of the hydrogen tank, which is calculated by multiplying the water volume of the hydrogen tank by its operating pressure (absolute pressure, expressed in kg/cm2). Screenshots of the original text from the standard “Explanatory Notes” are as follows: V. Conclusion In summary, when the operating pressure of the hydrogen storage tank is 1.4 MPaG (gauge pressure), which corresponds to an absolute pressure of 1.5 MPaA, the water volume capacity of the hydrogen storage tank should be less than or equal to 2,000 m³. In other words, until the GB50177 standard is updated, when determining the operating pressure and water volume of hydrogen spherical tanks, we should still consider that the PV value for each tank must not exceed 30,000 (bar(A)·m³). In other words, the water volume (in m3) of the hydrogen balloon tank should be less than or equal to the value obtained by dividing 30,000 by (10 times the operating pressure + 1).