Abstract: Operation of an energy storage system comprising a thermodynamic cycle including first and second thermal reservoirs and a turbomachinery as energy converter for two-way conversion between electrical energy and thermal energy. For controlling the temperature in the system, the compression ratio of the turbomachinery is adjusted in real-time during charging on the basis of temperature measurements downstream of the compression and/or during discharging on the basis of temperature measurements downstream of the expansion.

Abstract: A method of operating an energy storage system (100), the system (100) comprising a thermodynamic cycle including a first thermal energy storage container (5) and an energy converter (1, 2, 3) for converting between electrical energy and thermal energy of the working fluid in the thermodynamic fluid cycle. For controlling the thermocline in the system without large thermal energy loss, it is pushed only partially out of the first thermal energy storage container (5).

Abstract: Thermal energy storage system with phase change material and method of its operation An energy storage system (100) comprises a hot thermal energy storage medium (5?) and a cold thermal energy storage medium (4?), which are interconnected in a thermo-dynamic gas flow circuit. An energy converter with a motor/generator system (1A, 1B) is functionally connected to a compressor/expander system (2) for converting between electrical energy and thermal energy of the gaseous working fluid in the thermodynamic fluid circuit. A latent thermal energy storage working fluid is thermally connected to the gas flow circuit through heat exchanger (8) for providing a limit for the temperature in the cold TES medium (4?).