Apparatus and method for transfering and cooling a compressed fuel gas

A method of cooling a compressed fuel gas 220 during transfer from a source vessel 230 to a receiving vessel 240, comprises receiving a fuel gas portion from the source vessel in an intermediate vessel 250, fluidly isolating the intermediate vessel from the source vessel, causing or allowing expansion of the fuel gas, thereby cooling the fuel gas, and releasing the cooled gas portion to the receiving vessel (e.g. automobile vehicle fuel tank, enabling a fast rate of refuelling). The fuel gas may include hydrogen, methane, or biogas. An second or auxiliary intermediate vessel 280 may be in selective fluid communication with the source and receiving vessels. Work may be extracted from the fuel gas by positive displacement. A positive displacement expander means may comprise a reciprocating compressor, ionic liquid column 270, diaphragm (373, figure 10), or piston (556a, 556b, figure 14) for displacing and expelling cooled gas portion to the receiving vessel.