Exergy valorization of a water electrolyzer and CO(2) hydrogenation tandem system for hydrogen and methane production

In this work, we introduce a water electrolysis and CO(2) hydrogenation tandem system which focuses on methane generation. The concept consists of a water electrolyzer thermally coupled to a CO(2) hydrogenation reactor, where the power required to generate hydrogen comes from renewable energy. A thermodynamic analysis of the tandem system was carried out. Our analysis exposes that it is possible to increase the exergy efficiency of the water electrolyzer and CO(2) hydrogenation system by thermal coupling, where the thermal energy required to split water into H(2) and O(2) during the electrolysis process is compensated by the heat generated during the CO(2) hydrogenation reaction. Here, the conditions at which high exergy efficiency can be achieved were identified.