A cryogenic liquefaction device comprising: a heat exchanger; a first phase separator; a first expansion device; a first expansion turbine; a second expansion turbine; a first arrangement of conduits, wherein: the operating inlet pressures of the first and second expansion turbines are different from one another; and the first arrangement of conduits is arranged such that: a first portion of a pressurised stream of gas is directed through the heat exchanger, the first expansion device and the first phase separator; a second portion of the pressurised stream of gas is directed through the first expansion turbine, then through the heat exchanger in a counter-flow direction to the first portion of the pressurised stream of gas, and then through the second expansion turbine;; a cold recovery circuit including a cold recovery stream of a first heat transfer fluid that is directed through the heat exchanger and enters the heat exchanger at an entry point, wherein the cold recovery circuit comprises: a thermal energy storage device; a means for circulating the first heat transfer fluid; and a second arrangement of conduits arranged to direct the first heat transfer fluid through the thermal energy storage device and the heat exchanger; a feed stream compressor adapted to output the pressurised stream of gas, wherein the first arrangement of conduits is arranged such that: a) a feed stream is directed to the input of the feed stream compressor; and b) the gaseous output stream from the first phase separator joins the feed stream after passing through the heat exchanger, characterised in that the cryogenic liquefaction device further comprises: a fourth expansion turbine and a fifth expansion turbine, and in that the first arrangement of conduits is further arranged such that a third portion of the pressurised stream of gas is directed through the fourth expansion turbine, and then through the heat exchanger in a counter-flow direction to the first portion of the pressurised stream of gas, and then through the fifth expansion turbine. a heat exchanger; a first phase separator; a first expansion device; a first expansion turbine; a second expansion turbine; a first arrangement of conduits, wherein: the operating inlet pressures of the first and second expansion turbines are different from one another; and the first arrangement of conduits is arranged such that: a first portion of a pressurised stream of gas is directed through the heat exchanger, the first expansion device and the first phase separator; a second portion of the pressurised stream of gas is directed through the first expansion turbine, then through the heat exchanger in a counter-flow direction to the first portion of the pressurised stream of gas, and then through the second expansion turbine;; the operating inlet pressures of the first and second expansion turbines are different from one another; and the first arrangement of conduits is arranged such that: a first portion of a pressurised stream of gas is directed through the heat exchanger, the first expansion device and the first phase separator; a second portion of the pressurised stream of gas is directed through the first expansion turbine, then through the heat exchanger in a counter-flow direction to the first portion of the pressurised stream of gas, and then through the second expansion turbine;; a first portion of a pressurised stream of gas is directed through the heat exchanger, the first expansion device and the first phase separator; a second portion of the pressurised stream of gas is directed through the first expansion turbine, then through the heat exchanger in a counter-flow direction to the first portion of the pressurised stream of gas, and then through the second expansion turbine;; a cold recovery circuit including a cold recovery stream of a first heat transfer fluid that is directed through the heat exchanger and enters the heat exchanger at an entry point, wherein the cold recovery circuit comprises: a thermal energy storage device; a means for circulating the first heat transfer fluid; and a second arrangement of conduits arranged to direct the first heat transfer fluid through the thermal energy storage device and the heat exchanger; a thermal energy storage device; a means for circulating the first heat transfer fluid; and a second arrangement of conduits arranged to direct the first heat transfer fluid through the thermal energy storage device and the heat exchanger; a feed stream compressor adapted to output the pressurised stream of gas, wherein the first arrangement of conduits is arranged such that: a) a feed stream is directed to the input of the feed stream compressor; and b) the gaseous output stream from the first phase separator joins the feed stream after passing through the heat exchanger, characterised in that the cryogenic liquefaction device further comprises: a fourth expansion turbine and a fifth expansion turbine, and in that the a) a feed stream is directed to the input of the feed stream compressor; and b) the gaseous output stream from the first phase separator joins the feed stream after passing through the heat exchanger, characterised in that the cryogenic liquefaction device further comprises: a fourth expansion turbine and a fifth expansion turbine, and in that the first arrangement of conduits is further arranged such that a third portion of the pressurised stream of gas is directed through the fourth expansion turbine, and then through the heat exchanger in a counter-flow direction to the first portion of the pressurised stream of gas, and then through the fifth expansion turbine.