An energy storage device is constructed from a plurality of supercap cells. In each case, some of these supercap cells are interconnected electrically to a storage module. Each of the storage modules is disposed in a housing. The individual supercap cells are in at least indirect heat-conducting contact with the housing. A plurality of the housings are stacked above one another or adjacent to one another such that a fluid can flow through at least partial regions between the housings.