Gas supply system and method for estimating infernal pressure of gas tank

A method for estimating an internal pressure of a gas tank in a gas supply system including the gas tank that stores a compressed gas, the gas supply system further including

• a gas supply path connecting the gas tank and a gas consuming device that consumes the gas,
• an unbalanced pressure reducing valve in which an outlet-side pressure changes with an increase in inlet-side pressure and which is disposed in the gas supply path and reduces a pressure of the gas supplied from the gas tank,
• a pressure sensor that detects the outlet-side pressure of the pressure reducing valve, and
• a flow rate changing unit that changes an outlet-side flow rate of the pressure reducing valve, the method comprising:
• driving the flow rate changing unit to change the outlet-side flow rate of the pressure reducing valve between a first flow rate and a second flow rate different from the first flow rate;
• obtaining a first pressure and a second pressure from the pressure sensor, the first pressure being a detection value of the pressure sensor when the outlet-side flow rate is the first flow rate, and the second pressure being a detection value of the pressure sensor when the outlet-side flow rate is the second flow rate;
• and
• estimating the inlet-side pressure of the pressure reducing valve using a relationship among the first flow rate, the second flow rate, and a difference between the first pressure and the second pressure.