A compressed air energy storage unit includes an electrical input and output circuit, a compressor and expansion device and an artificially created compressed air reservoir. The compressor and expansion device includes a piston pump having pistons formed of an electrically and thermally conductive liquid, e.g. galinstan, and is switchable between pumping operation and generator operation. A method for the production of a compressed air energy storage unit of this type includes manufacturing at least some components by 3D printing.