The considered sub-process of this study is embedded in an overall process scheme, which is depicted in Figure . The energy supply for heating, cooling and work intensive unit operations is assumed to be secured via solar modules and not further elaborated. The considered process consists of a methanation reactor, a water separation unit and a gas purification unit for the product stream and is indicated by a grey box. For providing the complete picture, storage units, the origin of the raw materials and the energy supply unit for heating, cooling and providing electrical power for e.g. compressors and the electrolysis are also shown. These of the reactor are defined as follows: