A vessel of a heat storage and release apparatus, the vessel comprises a shell comprising a metallic material, the shell having an elongated shape with a first end region and a second end region remote from the first end region, and an internal surface defining a cavity configured to contain a heat storage and release device and to guide gas-flow; a first opening through the shell for a flow of gas at high temperature and high pressure, the first opening being located in the first end region; a second opening through the shell for a flow of gas at low temperature and high pressure, the second opening being located in the second end region; and a lining of thermally insulating material adjacent to the internal surface and only partially covering the internal surface, the lining being located at least in the first end region.