HERCULES introduces a novel breakthrough approach towards thermal energy storage of surplus renewable energy via a hybrid thermochemical/sensible heat storage with the aid of porous media made of refractory redox metal oxides and electrically powered heating elements. The heating elements use surplus/cheap renewable electricity (e.g. from PVs, wind, or other sources) to charge the metal oxide-based storage block by heating it to the metal oxide reduction temperature (i.e. charging/energy storage step) and subsequently (i.e. upon demand) the fully charged system transfers its energy to a controlled airflow that passes through the porous oxide block which initiated the oxidation of the reduced metal oxide. It is an exothermic process thus a hot air stream is produced during this step which can be used to provide exploitable heat for industrial processes. The proposed research will be conducted by an interdisciplinary consortium constituting leading research centers, universities, innovative SMEs, and large enterprises including ancillary service providers and technology end-users.