An electro-thermal energy storage system comprising a) a hot thermal storage arrangement comprising a hot storage heat exchanger, b) a cold thermal storage arrangement comprising a cold storage heat exchanger, c) a thermodynamic cycle unit configured to transfer thermal energy from the cold storage arrangement to the hot storage arrangement in a charging mode, convert thermal energy from the hot storage arrangement into work and, preferably, subsequently into electric energy in a discharging mode, wherein the thermodynamic cycle unit comprises a fluid circuit for circulating a working fluid through the hot storage heat exchanger as well as through the cold storage heat exchanger, 1 a pump for maintaining a circulation of working fluid in the discharging mode, a first turbine for expanding working fluid in the discharging mode, a second turbine for expanding working fluid in the discharging mode, said second turbine being connected in series with the first turbine so that working fluid may flow from the first to the second turbine in the discharging mode, and an intercooling heat exchanger located in the fluid circuit between the first turbine and the second turbine, characterized in that said intercooling heat exchanger is configured to cool working fluid by exchanging heat with an environment of the electro-thermal energy storage system, and in that the intercooling heat exchanger is configured to cool working fluid flowing from the first turbine to the second turbine in the discharging mode. a) a hot thermal storage arrangement comprising a hot storage heat exchanger, b) a cold thermal storage arrangement comprising a cold storage heat exchanger, c) a thermodynamic cycle unit configured to transfer thermal energy from the cold storage arrangement to the hot storage arrangement in a charging mode, convert thermal energy from the hot storage arrangement into work and, preferably, subsequently into electric energy in a discharging mode, wherein the thermodynamic cycle unit comprises a fluid circuit for circulating a working fluid through the hot storage heat exchanger as well as through the cold storage heat exchanger, 1 a pump for maintaining a circulation of working fluid in the discharging mode, a first turbine for expanding working fluid in the discharging mode, a second turbine for expanding working fluid in the discharging mode, said second turbine being connected in series with the first turbine so that working fluid may flow from the first to the second turbine in the discharging mode, and an intercooling heat exchanger located in the fluid circuit between the first turbine and the second turbine, characterized in that said intercooling heat exchanger is configured to cool working fluid by exchanging heat with an environment of the electro-thermal energy storage system, and in that the intercooling heat exchanger is configured to cool working fluid flowing from the first turbine to the second turbine in the discharging mode. arrangement to the hot storage arrangement in a charging mode, convert thermal energy from the hot storage arrangement into work and, preferably, subsequently into electric energy in a discharging mode, wherein the thermodynamic cycle unit comprises a fluid circuit for circulating a working fluid through the hot storage heat exchanger as well as through the cold storage heat exchanger, 1 a pump for maintaining a circulation of working fluid in the discharging mode, a first turbine for expanding working fluid in the discharging mode, a second turbine for expanding working fluid in the discharging mode, said second turbine being connected in series with the first turbine so that working fluid may flow from the first to the second turbine in the discharging mode, and an intercooling heat exchanger located in the fluid circuit between the first turbine and the second turbine, characterized in that said intercooling heat exchanger is configured to cool working fluid by exchanging heat with an environment of the electro-thermal energy storage system, and in that the intercooling heat exchanger is configured to cool working fluid flowing from the first turbine to the second turbine in the discharging mode.