NOVELTY - The redox fuel cell comprises stack of membrane electrode assemblies, an anode chamber, a cathode chamber, a unit for supplying a fuel to the anode chambers of the cell, a unit for supplying an oxidant to the cell, a unit for providing an electrical circuit between respective anodes and cathodes of the cell, a catholyte solution comprising a non-volatile catholyte component and a redox mediator couple, optionally upstream and/or downstream unit of the cathode chambers for cooling the catholyte solution, and a regeneration zone separated from the membrane electrode assemblies.    USE - The redox fuel cell is: useful for the combined generation of heat and power; useful to provide motive power to a vehicle; useful to generate power in an electronic component (all claimed); and useful as a source of power for stationary applications such as back-up power for computer systems and mobile telephone masts.    ADVANTAGE - The redox fuel cell is less expensive, has improved cell performance and durability, and is capable of easily and efficiently generating the power.    DETAILED DESCRIPTION - The redox fuel cell comprises stack of membrane electrode assemblies, an anode chamber, a cathode chamber, a unit for supplying a fuel to the anode chambers of the cell, a unit for supplying an oxidant to the cell, a unit for providing an electrical circuit between respective anodes and cathodes of the cell, a catholyte solution comprising a non-volatile catholyte component and a redox mediator couple, optionally upstream and/or downstream unit of the cathode chambers for cooling the catholyte solution, a regeneration zone separated from the membrane electrode assemblies, a unit for recovering heat from the regeneration zone, a unit for supplying the recovered heat to a location outside of the cell, and a condenser. Each membrane electrode assembly comprises an anode and a cathode separated by an ion selective polymer electrolyte membrane. The anode chamber is placed adjacent to the anode of each membrane electrode assembly. The cathode chamber is placed adjacent to the cathode of each membrane electrode assembly. The oxidant supplying unit further supplies the oxidant to the regeneration zone. A volume of catholyte solution in the regeneration zone is 25-85% of the total combined volume of catholyte solution in the regeneration zone and the cathode chambers. The regeneration zone is maintained in operation of the cell at a higher operating temperature than the cathode chambers of the cell and/or at a higher operating temperature than that of the cooling unit. The cathode chamber comprises an inlet port for receiving partially regenerated redox mediator couple from the regeneration zone, and an outlet port for supplying partially reduced redox mediator couple to the regeneration zone. The regeneration zone comprises: a chamber in which the regeneration reaction takes place; a first inlet port for receiving reduced redox mediator couple from the cathode region of the cell into the chamber; a first outlet port for supplying oxidized redox mediator couple to the cathode region of the cell; a second inlet port for receiving a supply of oxidant; and/or a second outlet port for venting water vapor and heat from the chamber. The condenser is provided in an upstream of the second outlet port of the regeneration zone for condensing water vapor and optionally returning the condensed vapor to the regeneration zone. The catholyte solution further comprises a redox catalyst for assisting electron transfer between the oxidant and the partially reduced redox mediator couple. INDEPENDENT CLAIMS are included for:    (1) a process for operating a redox fuel cell; and    (2) a combined heat and power system.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a fuel cell.