Method for operating a storage system for storing electrical energy by conversion into thermal energy, in which - in a charging process via a charging side , by means of a charging arrangement, a high-temperature storage device is charged by storing energy, in particular fed-in electrical energy, in the form of thermal energy, wherein the charging process takes place via a heat pump process within the charging assembly, which is designed as a first Joule arrangement comprising a low-pressure side and a high-pressure side , with an interposed compressor assembly and turbine assembly , and - in a discharging process, by means of a Rankine process , the high-temperature storage device is discharged via a discharging side with the thermal energy being released from the high-temperature storage device and converted into electrical energy, wherein an energy conversion arrangement provided in the storage system , in addition to the charging arrangement, in the form of a second Joule arrangement , comprising a low-pressure side and a high-pressure side and compressor/turbine assemblies arranged therebetween, is operated during the charging process and/or during the discharging process of the storage system in a heat pump process and/or in a thermal power process , wherein in particular during the second discharging process and/or the second charging process of the second Joule arrangement and the charging process via the charging side , thermal energy is transferred between the second Joule arrangement and the charging side , characterized in that , during the second discharging process and/or the second charging process of the second Joule arrangement and the discharging process via the discharging side , thermal energy is transferred between the second Joule arrangement and the discharging side . - in a charging process via a charging side , by means of a charging arrangement, a high-temperature storage device is charged by storing energy, in particular fed-in electrical energy, in the form of thermal energy, wherein the charging process takes place via a heat pump process within the charging assembly, which is designed as a first Joule arrangement comprising a low-pressure side and a high-pressure side , with an interposed compressor assembly and turbine assembly , and - in a discharging process, by means of a Rankine process , the high-temperature storage device is discharged via a discharging side with the thermal energy being released from the high-temperature storage device and converted into electrical energy, wherein an energy conversion arrangement provided in the storage system , in addition to the charging arrangement, in the form of a second Joule arrangement , comprising a low-pressure side and a high-pressure side and compressor/turbine assemblies arranged therebetween, is operated during the charging process and/or during the discharging process of the storage system in a heat pump process and/or in a thermal power process , wherein in particular during the second discharging process and/or the second charging process of the second Joule arrangement and the charging process via the charging side , thermal energy is transferred between the second Joule arrangement and the charging side , characterized in that , during the second discharging process and/or the second charging process of the second Joule arrangement and the discharging process via the discharging side , thermal energy is transferred between the second Joule arrangement and the discharging side . <EOS>