## 2 Experimental Methods
### System Design and Control  
As shown in Figure 1, this system is designed to control the charging time and helium gas flow. Pressure and temperature sensors are installed in the helium gas storage to measure its internal flow characteristics. An electric valve, which is controllable by LabVIEW, is installed with Teflon tape to prevent helium gas leaks. The main components for system operation include T-sensors, P-sensors, a mass flow controller, a LabVIEW cDAQ, an oscilloscope, and a pressure regulator. \begin{table}
\begin{tabular}{c c} \hline
**Items** & **Specification** \\ \hline Atomic number & 2 \\ Atomic mass & 4.0026 g\(\cdot\)mol\({}^{-1}\) \\ Density & 0.178 \(\times\) 10\({}^{-3}\) g\(\cdot\)cm\({}^{-3}\) at 20 \({}^{\circ}\)C \\ Melting point & (-)272.2 (26 atm) \({}^{\circ}\)C \\ Boiling point & (-)268.9 \({}^{\circ}\)C \\ Energy of first ionization & 2372 kJ\(\cdot\)mol\({}^{-1}\) \\ \hline \end{tabular}
\end{table} 
Table 1: Chemical properties of helium. The helium storage system using hydrogen gas as an alternative is specified as 5000 cc of AL-based material to facilitate easy repetition of charging and discharging. When using Al as the material for helium gas storage, changes in temperature and pressure within the storage unit can be easily observed. The pressure in this system is regulated by a gas regulator from 150 bar to 30 bar in order to match the low-pressure requirements of the mass flow controller. Electronic valves are used to provide automatic ventilation, and they are designed with a LabVIEW algorithm. A PT-100 temperature sensor is installed inside the helium gas storage to detect changes in the thermal environment. Moreover, a pressure sensor is used to compare the thermal data with changes in temperature. A cDAQ-9172 chassis offered to NI-INSTRUMENT is connected with various boards such as analog input, analog output, and counter pulse, and it is designed to control the helium gas storage management system. The physical characteristics of helium gas differ from those of hydrogen gas. However, helium is very similar to hydrogen. A mass flow controller is used to minutely control helium gas, and it is controlled up to 10 L/m. In the operation of this experiment, the high-pressure gas stored in the main tank is first reduced to low pressure using an electronic solenoid valve within a regulator to control the flow rate. Subsequently, the flow rate is precisely measured using an MFC (Mass Flow Controller) and supplied to the experimental tank. Throughout this process, temperature and pressure sensors detect changes in physical behavior, collect data using LabVIEW cDAQ, and repeat the process of analyzing and verifying reliable data according to the experiment's conditions. In this experiment, a constant temperature and humidity system was employed to ensure consistent fluctuations in ambient temperature, allowing the experiment to commence when the temperature reached 20 degrees Celsius. Maintaining this ambient temperature can be seen as serving the purpose of ensuring the safety of the helium gas within the reservoir because it may undergo alterations depending on the movements of individual sensors and valves. In this experiment, the 0-5 V voltage control method was set to control the valves within the mass flow controller. The experiment was conducted with careful consideration of valve opening deviation, voltage control deviation, and current flow deviation  
Figure 1: Schematic diagram of helium gas storage management system. to minimize the impact of orifice errors in situations where gas movement, especially when charging helium gas, can be highly variable. Furthermore, to address any potential issues arising from micro-leakage during the helium gas charging process, we verified the integrity of all valves and gas lines by employing bubble testing. Additionally, a check valve is used with a maximum pressure of 12 bar, and the power supply applies 12.5 V entirely in this hydrogen storage management system.