Energy storage device and method for storing energy

Abstract

An energy storage device having: a high-temperature regenerator containing a solid, particularly porous storage material (S); a working gas (A) as the heat transfer medium to transfer heat between the storage material (S) and the working gas (A) flowing through; and a charging circuit and a discharging circuit for the working gas (A). The charging circuit is designed such that starting from a pre-heating unit at least one first heat transfer duct of a recuperator, a first compressor (HO), the high-temperature regenerator, a second heat transfer duct of the recuperator and then a first expander are interconnected, thus forming a circuit, so as to conduct fluid. The first compressor is coupled with the first expander, and the first compressor forms part of a first piston machine (K) and the first expander forms part of a second piston machine (K), the piston machines (K, K) being operable either as a compressor or as an expander such that the first compressor of the charging circuit forms a second expander in the discharging circuit and that the first expander of the charging circuit forms a second compressor in the discharging circuit. The high-temperature regenerator can be connected to either the charging circuit or the discharging circuit to conduct fluid and can be controlled such that the high-temperature regenerator, the compressor and the expander form either part of the charging circuit or part of the discharging circuit. The charging circuit, the discharging circuit and the high-temperature regenerator have the same working gas (A) so that the working gas (A) comes into direct contact with the storage material of the high-temperature regenerator both in the charging circuit and in the discharging circuit.