The fuel cell system has a fuel cell (8) receiving oxygen and hydrogen and providing water. An electrolyser (2) generates oxygen and hydrogen from water. The fuel cell and the electrolyser are each coupled to a hydrogen reservoir (7) for temporary storage of hydrogen. The electrolyser is coupled to the fuel cell via the hydrogen reservoir. Pref. the fuel cell and the electrolyser are contained in a common housing (1), the electrolyser pref. acting as an inverse fuel cell and having a sponge for storing the water.
