TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Components: The apparatus further comprises: a heat-to-electricity converting means, operative to convert energy derived from solar radiation into electricity; and at least one radiation diffuser exposed to the solar radiation and operative to redirect and re-radiate energy towards the reaction assembly. In the apparatus, the cavity with at least one optical window is configured to define an irradiated region. At least one optical window comprises at least one of: an opening; a transparent element; or radiation diffuser adapted to re-direct and re-radiate the incident solar radiation in a wide range of angles. The energy reaching the reaction assembly comprises at least one of: the collected solar radiation that has been re-directed from inner walls of the cavity onto the reaction assembly; or infrared thermal radiation generated from the cavity walls after the latter have been heated by the radiation introduced to the cavity. The reaction units are arranged: such as to be substantially uniformly distributed within the irradiated region, where the reaction units are arranged substantially symmetrically with respect to general propagation directions of the radiation propagating towards the irradiated region, preferably arranged in at least one circular or linear array. The reaction assembly comprises: many reaction units arranged in a spaced-apart relationship in at least arrays within the irradiated region; at least two reaction units, where at least one of the reaction units is configured for carrying out first electrolysis process of a first raw fluid, and at least one other reaction unit is configured for carrying out second electrolysis process of a second raw fluid; or at least one reaction unit (preferred) adapted for carrying out an electrolysis process of carbon dioxide, and at least one reaction unit adapted for carrying out an electrolysis process of water. The reaction assembly comprises at least one reaction unit comprising: an inner shell comprising an arrangement of electrodes and a solid membrane, and electrical conductors attached to the reaction unit and adapted to convey electricity for carrying out the electrolysis process, where the arrangement of electrodes comprises at least an external electrode and an inner electrode, and the electrical conductors comprise an inner electrode conductor and an outer electrode conductor. In the apparatus: one of the electrodes is located an outwardly facing surface of the inner shell and the other electrode is located at inwardly facing surface of the inner shell, where the outer electrode conductor is connected to an outwardly facing surface of the outer electrode, and the inner electrode conductor is connected to an outwardly or inwardly facing surface of the inner electrode; and the multi-layer structure of the inner shell of the reaction unit comprises at least one intermediate layer located between the electrodes and the solid membrane. The reaction assembly further comprises: an outer shell enclosing at least one inner shell; at least one ingress utility to enable introduction of gas to be electrolyzed or an ingress utility operative to allow introduction of a carrier gas to the reaction assembly so that it can be mixed with the flow of the oxygen product within the apparatus; and at least two egress utilities to enable exit of the process products from the reaction assembly. The multi-layer structure of the inner shell comprises at least three layers comprising the cathode electrode layer, an electrolyte layer and the anode electrode layer, where the anode is located at the outwardly facing surface of the inner shell and the cathode is located at the inwardly facing surface of the inner shell and the electrical conductors are located at the outwardly facing surface of the inner shell. The apparatus has one of the configurations including: the electrolyte layer forms an inner shell supporting structure, and the cathode and anode electrodes layers are deposited or coated on it; and the cathode or anode electrode layer forms an inner shell supporting structure, and the other layers are deposited on it. The electric conductors of the cathode and anode electrodes are located at the same side of an inner shell supporting structure. Preferred Method: The method further comprises converting some of the energy derived from the solar radiation into electricity. In the method, a fluid is circulated and heated in the cavity and conveyed to the heat-to-electricity converter for generating electricity; at least part of the energy derived from solar radiation is stored in a form of chemical energy, and at least part of the electricity generated by the heat-to-electricity converter is used in the electrolysis process; and the reaction assembly is exposed to direct solar radiation entering the cavity via at least one optical window.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The electrolyte layer is made from at least one material comprising yttria-stabilized zirconia or gadolinium doped ceria.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: At least one raw fluid comprises at least one of carbon dioxide and/or water.