Abstract: In order to improve a heat storage device comprising a storage container which has an inner chamber for accommodating alkali and alkaline earth compounds, in particular alkali and alkaline earth halides, and their eutectics as storage medium such that mechanical stresses no longer occur and the behavior of the heat storage device is such that its capability for receiving and discharging energy may be calculated as far as possible, it is suggested that a substantially open-pored structure consisting of a material wettable by the storage medium be arranged in the inner chamber and that the structure be soaked with the storage medium.