NOVELTY - The generic, self-sufficient energy supply system comprises a photocatalytic electrolyzer for producing hydrogen using solar radiation, a hydrogen store, and an electrocatalytic fuel cell for generating electricity from the hydrogen. The photovoltaic electrolyzer is structurally combined with the electrocatalytic fuel cell in a reversible functional element. The functional element comprises an ion-leading membrane present between front-side and back-side of electrolyte chambers filled with water. The ion-leading membrane comprises an absorber layer.    USE - Used as an energy supply system.    DETAILED DESCRIPTION - The generic, self-sufficient energy supply system comprises a photocatalytic electrolyzer for producing hydrogen using solar radiation, a hydrogen store, and an electrocatalytic fuel cell for generating electricity from the hydrogen. The photovoltaic electrolyzer is structurally combined with the electrocatalytic fuel cell in a reversible functional element. The functional element comprises an ion-leading membrane present between front-side and back-side of electrolyte chambers filled with water. The ion-leading membrane comprises an absorber layer on its front-side provided for the solar radiation, and a photocatalytic coating that catalyzes, during the solar radiation, a dissociation of water. In the presence of solar radiation, the hydrogen is photovoltaically produced directly from the solar radiation without having a solar power, and in the absence of solar radiation, an electric power is electrocatalytically generated using supplied hydrogen. The photocatalytic coating and/or an electrocatalytic coating is provided in the form of a thin layer. A structure of the electrocatalytic coating is obtained from adjacent subregions in the form of nanoparticles, from two different catalyst materials in horizontal or vertical architectures or in arbitrary mixtures and form a bifunctional catalyst material. One of the catalyst materials is catalytically active with hydrogen reduction for hydrogen creation and other catalyst materials are catalytically active with hydrogen oxidation to the electrical electricity generation. The bifunctional catalyst material is catalytically active with both hydrogen reduction for hydrogen creation and with hydrogen oxidation to the electrical electricity generation. An integration of a hydrogen reservoir into the reversible functional element is carried out under formation of a reversible hybrid element. A connection of the hydrogen reservoir with a rear-side electrolyte chamber is carried out over a unidirectional valve serving hydrogen supply in the electrolyte chamber and a hydrogen removal from the electrolyte chamber or a bidirectional valve serving both the hydrogen supply and the hydrogen removal. A control of the uni-directional valve or the bidirectional valve is carried out by an energy management system, which actuates the hydrogen removal from the rear-side of the electrolyte chamber with the solar radiation and actuates the hydrogen supply into the rear-side of the electrolyte chamber without the solar radiation. A formation of the reversible hybrid elements as building attachment elements (24) is provided with the integrated hydrogen reservoir that is arranged in connection with the rear-side of the electrolyte chamber. A size formation of the integrated hydrogen reservoir is provided in such a way that the hydrogen stored during the solar radiation ensures an operation of an electrocatalytic fuel cell for half of the period of time without the solar radiation. A planar formation of the building attachment element is provided, with which the hydrogen reservoir is extended over the whole area of the reversible hybrid element. The formation of the hydrogen reservoir acts as a porous solid material storage, and a formation of the porous solid material storage acts as a ceramic metal hydride storage and a heat accumulator. The formation of the hydrogen reservoir further acts as pressure reservoirs, with which the unidirectional valve or the bidirectional valve stands in connection. The energy supply system provides a supplementary heat source independent of the solar radiation. A formation of the supplementary heat source acts as an electrical heating wire, which is integrated into the solid material storage. An arrangement of the building attachment elements is connected in rows (61) and columns (62) adjacent to each other on a building facade (25). A combination of the building attachment elements is provided with other functional elements (63) for direct photovoltaic current or heat generation and for warming or sound absorption and/or weather protection.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a generic energy supply system.    Building attachment element (24)    Building facade (25)    Rows (61)    Columns (62)    Other functional elements. (63)