Abstract: Processes and units are provided, which carry out cyclic steps of zinc oxidation and reduction of zinc oxide to combine an exothermic heat delivering step with an endothermic syngas production step, respectively. Both steps use zinc as the pivotal element that enables the process to be carried out cyclically. Heat is delivered from the exothermic step to the endothermic syngas via heat storage elements of various types which are arranged according to the reaction's conditions and characteristic temperatures. Thus, energy efficient syngas production methods and units are provided.