NOVELTY - The process for producing hydrogen by means of electrolysis, comprises supplying water to an electrolyzer and then producing hydrogen by means of electrolysis in the electrolyzer. The water processed from a drinking water supply and/or saltwater, brackish water or freshwater taken from a saltwater or brackish water or freshwater source from a sea and/or a stream and/or a river and/or a lake is supplied as freshwater preheated below the evaporation or boiling temperature, to a carrier gas stream. The freshwater/carrier gas mixture is brought by means of a compressor (39) to such a temperature.    USE - Process useful for producing hydrogen by means of electrolysis.    ADVANTAGE - The process ensures simple, reliable and efficient production of hydrogen by means of electrolysis.    DETAILED DESCRIPTION - The process for producing hydrogen by means of electrolysis, comprises supplying water to an electrolyzer and then producing hydrogen by means of electrolysis in the electrolyzer. The water processed from a drinking water supply and/or saltwater, brackish water or freshwater taken from a saltwater or brackish water or freshwater source from a sea and/or a stream and/or a river and/or a lake is supplied as freshwater preheated below the evaporation or boiling temperature, to a carrier gas stream. The freshwater/carrier gas mixture is brought by means of a compressor (39) to such a temperature that a steamladen carrier gas stream is present as a hot steam-carrier gas stream, which is supplied to the electrolyzer (41) in which hydrogen and optionally oxygen are eliminated from the carrier gas conducted in a carrier gas circuit and, after the elimination of the hydrogen and optionally oxygen, the hydrogen and optionally oxygen are recycled indirectly or directly into the carrier gas circuit. The fresh water supplied to the carrier gas stream in evaporated form is supplied as carrier gas-water steam mixture to a condenser by which it is subjected to a temperature that distributes a hot steam-carrier gas stream. The fresh water is supplied for pre-heating a pre-heating device in which the fresh water is pre-heated in dependent upon respective predominant pressure at a defined temperature below the evaporation- and boiling temperature of the fresh water so that a part of the fresh water supplied to the carrier gas stream form a wet carrier gas-/steam mixture. The wet carrier gas-steam mixture is supplied to a carrier gas/steam mixture-heat exchanger by which the wet carrier gas-steam mixture is over-heated so that a defined residual water portion is produced. The residual water portion is supplied to a concentrate separator in which the residual water portion is deposited together with salt as concentrate. The carrier gas-/dry steam mixture is condensed by a condenser under simultaneous temperature increase on a defined pressure and subsequently supplied to part directly to the electrolyser and/or to carrier gas-steam mixture heat exchanger in which a portion of the steam is condensed. The carrier gas-dry steam mixture is supplied subsequently to a condensate separator in which the condensate is deposited and a damp carrier gas is produced that is supplied to an electrolyser. The fresh water is supplied before its supply to carrier gas circuit and/or before its pre-heating to a pumping plant (7) that is arranged downstream to a pump conveying the freshwater to the carrier gas circuit and that is associated to a cleaning device by which the supply of the fresh water is supplied into the pumping plant and/or the reception of the fresh water is carried out by the pumping plant. The condensate occurring in the condensate depositor is supplied by the supply to the pumping plant for heat exchanging the pre-heating device in which the fresh water is pre-heated in a defined temperature below the boiling temperature of the fresh water. The condensate occurring in the condensate container is supplied before the supply to pumping plant and to a relaxation device such as a further condensate separator in which pressure suppression is carried out. The concentrate occurring in the concentrate depositor is supplied to concentrate-/freshwater heat exchanger in which the freshwater is pre-heated in a condensate-/freshwater-heat exchanger. The concentrate separator is arranged downstream to a droplet separator with a discharge means, whose deposited droplet separator-concentrate is supplied to the concentrate-/freshwater-heat exchanger. The droplet separator concentrate is supplied together with the concentrate of the concentrate separator. The freshwater sucked by a suction line from a salt- or fresh water source is supplied from the supply to carrier gas circuit and/or from the supply to a pump plant and to a sieving device and/or a sedimentation basin. A defined quantity of the wastewater having deposited impurities is supplied to a pump plant near to a defined quantity of the freshwater so that the carrier gas circuit is supplied to a defined freshwater-wastewater-mixture. The energy for the operation of current consumer of the plant is supplied to a rectifier of the electrolyser and/or to a pump downstream to the carrier gas circuit and/or to a compressor to part by a wind turbine and/or to a photovoltaic plant and/or to a biogas plant and/or to a biomass chip station and/or a fuel cell loaded with hydrogen and oxygen. An INDEPENDENT CLAIM is included for a device for producing hydrogen by means of electrolysis.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of a plant for the production of hydrogen.    Pre-cleaning stage (2)    Pumping plant (7)    Compressor (39)    Electrolyzer (41)    Condensation discharge line. (44)