process illustrated in fig4 which is operatively connected to the steam water circuit of the respective solar thermal power station so that by means of the heat exchanger apparatus illustrated in fig4 heat is emitted to a water steam medium to be supplied to a steam turbine in the steam water circuit of the respective solar thermal power station from the heat carrier medium 5 as is indicated by the symbolically illustrated steam turbine it is also possible to provide only one type of heat transmission apparatus through which flow is passed both during the charging process and the discharging process of the energy store and which is exclusively operatively connected for example to the primary circuit or to the steam water circuit of the solar power station it is therefore possible for a heat carrier medium for example a molten salt to flow between the tanks t 1 t 2 and t 3 which is connected via a heat transmission apparatus 4 a to a primary circuit of a solar thermal power station in which a molten salt is likewise passed through the solar collectors as a heat carrier medium in the primary circuit this heat carrier medium in the primary circuit is then connected by means of a second heat transmission apparatus to the steam water circuit of the solar thermal power station in sunshine phases the heat carrier medium 5 now absorbs energy from the primary circuit via a heat.