This method is used to manage a pressure accumulator (1) as a component of an energy storage system, consisting of a work machine (4), a collecting tank (7), a displacement apparatus (6) and a pressure accumulator (1) for storing a pressurised gaseous medium. The pressure accumulator (1) is partially filled with a liquid medium so as to be able to control the gas storage volume therewith. Feeding compressed gas (3) into the pressure accumulator (1) involves removing liquid (2). Removing compressed gas (3) from the pressure accumulator (1) involves feeding in liquid (2) so that the storage pressure is kept under control as necessary, in particular is kept constant. To this end, one pressurised unit of gas (3) is introduced into the pressure accumulator (1) with the removal of one unit of liquid (2) from the pressure accumulator (1) by means of the displacement apparatus (6) and vice versa. The present method and the present arrangement make it possible to fill the pressure accumulator (1) completely with and to empty the pressured storage unit (1) completely of pressurised gas (3) at a controllable pressure, which leads to improved utilisation of the pressure accumulator volume and thus increases the energy density of the energy storage system. The method further makes it possible to operate the energy storage system at a constant operating point, thus increasing the efficiency of the individual components and of the entire system, and minimising the compression and expansion processes in the pressure accumulator (1).