TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Component: The fuel cell unit and the electrolyzer unit are juxtaposed, preferably integral with one another.They respectively include end plates facing one another.An end plate of the fuel cell unit adjacent an end plate of the electrolyzer unit includes the second ports.The apparatus includes an insulator between the pair of adjacent end plates.The end plates (70, 80) of the fuel cell and electrolyzer units are integral and are provided as a common separator plate (40), including the second ports.The electrolyzer unit comprises individual cells each having a membrane exchange assembly (33), an anode bipolar plate (31) and a cathode bipolar plate (32).The electrolyzer anode comprises the anode bipolar plates.The electrolyzer cathode comprises the cathode bipolar plates.The gas bypass conduit of the electrolyzer comprises bypass conduits each extending between an adjacent pair of electrolyzer cells.The fuel cell unit comprises individual fuel cells each having a membrane exchange assembly (23), an anode bipolar plate (21) and a cathode bipolar plate (22).The fuel cell anode comprises the anode bipolar plates of the fuel cells.The fuel cell cathode comprises the cathode bipolar plates of the fuel cells.The coolant channel comprises coolant channels provided between adjacent pair of fuel cells.The electrolyzer unit is provided above the fuel cell unit.The fuel cell unit includes a third fuel cell anode port, and a conduit providing a direct passage between the second and third fuel cell anode ports, where, in use, in a fuel cell mode of operation, hydrogen gas passes between the first and second fuel cell anode ports and across the individual fuel cell anode bipolar plates, and in an electrolyzer mode of operation, the generated hydrogen can pass between the first and third fuel cell anode ports.The first electrolyzer cathode port is closable, where in the electrolyzer mode of operation, hydrogen is withdrawn through the fuel cell unit. It is adapted to withdraw hydrogen from the electrolyzer in the electrolyzer mode.A purge valve is provided for purging water from the cathode of the electrolyzer in the electrolyzer mode.It is connected to the second electrolyzer cathode port.A valve is provided between the second electrolyzer cathode port and the second fuel cell anode port.A discharge line for hydrogen is provided and connected to the valve.The electrolyzer and fuel cell units have similar cross-sections and include common clamping elements securing the regenerative fuel cell apparatus together.