Reversible storage system for electrical energy, comprising charge-feeding or charge-diverting surface as a positive-pole collector and a charge-feeding or charge-diverting surface as a negative-pole collector and a flow electrode (3,4) having a pumpable dispersion which contains particles storing electrical energy in a capacitive and/or chemical manner, wherein these particles have an average grain size distribution of 1 nM to 500 μm, and at least one feed and at least one drain for the pumpable dispersion, in combination with a counter electrode which is likewise designed as a flow electrode, wherein the storage system further comprises at least one non-conductive spacer to separate the positive-pole and negative-pole collectors, wherein a positive electrode material is in contact with the positive-pole collector and a negative electrode material is in contact with the negative-pole collector, and wherein each flow electrode (3, 4) of one of said positive or negative electrode materials is contained in the form of the corresponding pumpable dispersion, which electrode material, together with the remaining wall regions of the flow electrode and with the corresponding positive-pole collector or with the corresponding negative-pole collector, and the at least one feed and the at least one drain, forms a cathode flow electrode and an anode flow electrode (3, 4) respectively, wherein, towards the side of the spacer(s), the contacting collectors (10, 11) are each not permeable to the particles of the pumpable dispersion but are permeable to electrolytes, and wherein the positive and negative electrode materials are disposed in parallel with the arrangement of the spacer(s) and in parallel with each other and, on mutually opposite flat sides of the arrangement of the spacer(s), are disposed in such a way that on the same side of the spacers only at least one positive electrode material and at least one positive-pole collector are provided and on the opposite side only at least one negative electrode material and one negative-pole collector are provided, wherein the pumpable dispersion is present on a side facing away from the flat side of the respective collector which lies against the spacers, wherein it can at least partially penetrate into the respective collector, and wherein, in said storage system, at least one container, which contains at least one of the pumpable dispersions, a liquid transport device and connecting means for transporting the pumpable dispersion from the container to the at least one feed and from the at least one drain of the respective flow electrode and back to the electrolyte container are additionally optionally provided, characterised in that the negative-pole collector and the positive-pole collector are of a flat construction with a single outer closed edge and lie with one of their flat sides against the respective spacer(s), and the particles are dispersed in a waterless electrolyte solution, wherein the charge-diverting collectors (10, 11) are perforated or porous such that the particles cannot penetrate the sides of the collectors which face one another and the at least one spacer but rather the liquid of the pumpable dispersion and ions dissolved therein, and wherein in order to separate the positive and negative collectors (10, 11) one or a plurality of non-conductive spacers are provided which comprise holes filled with electrolyte.