NOVELTY - Hydrogen fed power system comprises: a high-pressure hydrogen container (150); at least one hydrogen operated energy converter connecting to the hydrogen container; a pressure converter (158) for hydrogen gas, located between the high-pressure hydrogen container and the lower pressure energy converter, having an ion-conductive membrane; and a heat guide connecting the energy converter to the pressure converter.    USE - The hydrogen fed power system is useful in transportation means; and in stand-alone electric power unit (all claimed). Also, the hydrogen fed power system is useful for generating power.    ADVANTAGE - The hydrogen fed power system has improved energy efficiency, cost effective, light in weight, and does not require regular maintenance.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are:    (1) transportation means provided with the hydrogen fed power system;    (2) stand-alone electric power unit provided with the hydrogen fed power system;    (3) a method of using the hydrogen fed power system, comprising: (a) at least partially de-compressing supplied high-pressure hydrogen via the ion-conductive membrane de-compressor; (b) driving the hydrogen fed energy converter with the de-compressed hydrogen; (c) supplying heat from the hydrogen fed energy converter to the ion-conductive membrane de-compressor, and (d) utilizing electric power provided by the ion-conductive membrane as a result of the hydrogen decompression, and utilizing the power from the energy converter; and    (4) a method for filling up the high-pressure hydrogen container of the hydrogen fed power system, comprising: (a) providing a hydrogen comprising gas at the low pressure side of the ion-conductive membrane de-compressor; (b) reverse driving the ion-conductive membrane de-compressor by electrically feeding the ion-conductive membrane; and (c) storing the compressed hydrogen high-pressure hydrogen container.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view for the use of liquefied hydrogen gas using a ionic decompression cell.    High-pressure hydrogen container (150)    Liquid hydrogen supply (151)    Valves (152, 154, 157)    Liquid hydrogen discharge line (153)    Evaporators (155)    Hydrogen gas line (156)    Pressure converter (158)    Fuel cell (159)    Channels (160)    Pump (161)