Abstract: The invention relates to a device for thermoelectric storage or energy conversion, reducing the complexity, the thermodynamic irreversibilities and the costs of previous solutions. The device consists of main pressurized tanks (1THERMO) (1TRANSIT), containing the hydraulic fluid (3), the propellant fluid (2), liquid communications (7), equipped with hydroelectric conversion assemblies for pumping (6) or turbining (5) and including heat exchange systems (8COND) (8EVAP). The device may include mobile physical separations (11) between fluids, hot (15), or cold (16) thermal reserves, secondary tanks (13) equipped with pipes (14). The device is intended for energy storage, in particular intermittent renewable energies, economical production of Cold and Hot, and net electricity generation exploiting weak thermal sources.