Evaporatively cooled fuel cell system and method for operating an evaporatively cooled fuel cell system

Abstract

A fuel cell system ( 10 ) comprises a fuel cell ( 14 ) and an evaporative cooling system ( 16 ), which is in thermal contact with the fuel cell ( 14 ), in order that heat generated by the fuel cell ( 14 ) during operation of the fuel cell ( 14 ) is absorbed through evaporation of a cooling medium and is removed from the fuel cell ( 14 ). The fuel cell system ( 10 ) further comprises a device ( 22 ) for sensing the pressure in the evaporative cooling system ( 16 ). A control unit ( 24 ) is adapted to control the operating temperature of the fuel cell ( 14 ) in dependence on signals that are supplied to the control unit ( 24 ) from the device ( 22 ) for sensing the pressure in the evaporative cooling system ( 16 ), in such a way that the cooling medium of the evaporative cooling system ( 16 ) is transferred from the liquid to the gaseous state of matter by the heat generated by the fuel cell ( 14 ) during operation of the fuel cell ( 14 ).

1 . A fuel cell system comprising:
 a fuel cell;   an evaporative cooling system, which is in thermal contact with the fuel cell wherein heat generated by the fuel cell during operation of the fuel cell is absorbed through evaporation of a cooling medium and is removed from the fuel cell;   a device for sensing the pressure in the evaporative cooling system; and   a control unit, which is adapted to control an operating temperature of the fuel cell in dependence on signals that are supplied to the control unit from the device for sensing the pressure in the evaporative cooling system, in such a way that the cooling medium of the evaporative cooling system is transferred from a liquid to a gaseous state of matter by the heat generated by the fuel cell during operation of the fuel cell.   
     
     
         2 . A fuel cell system according to  claim 1  wherein the control unit is set up to control the operating temperature of the fuel cell in dependence on the signals that are supplied to the control unit from the device for sensing the pressure in the evaporative cooling system, in such a way that the evaporation of the cooling medium of the evaporative cooling system by the heat generated by the fuel cell during operation of the fuel cell is effected in a wet-steam region of the cooling medium. 
     
     
         3 . A fuel cell system according to  claim 1 , wherein a fuel-cell operating-pressure generating system is adapted to generate a desired pressure in the fuel cell, and a control unit is adapted for controlling the fuel-cell operating-pressure generating system. 
     
     
         4 . A fuel cell system according to  claim 3 , wherein the control unit for controlling the fuel-cell operating-pressure generating system is adapted to control the fuel-cell operating-pressure generating system such that there is generated in the fuel cell a pressure at which unwanted evaporation of substances and/or substance mixtures usually present in liquid form in the fuel cell is prevented. 
     
     
         5 . A fuel cell system according to  claim 3 , wherein the control unit for controlling the fuel-cell operating-pressure generating system is adapted to control the pressure in the fuel cell in dependence on the operating temperature of the fuel cell and/or in dependence on the signals of the device for sensing the pressure in the evaporative cooling system. 
     
     
         6 . A fuel cell system according to  claim 1 , wherein the evaporative cooling system comprises a condenser, for condensing the cooling medium evaporated during operation of the fuel cell for the purpose of cooling the fuel cell. 
     
     
         7 . A fuel cell system according to  claim 6 , wherein the condenser is realized in the form of an outerskin cooler. 
     
     
         8 . A fuel cell system according to  claim 1 , further comprising at least one device for utilizing heat stored in the cooling medium. 
     
     
         9 . A fuel cell system according to  claim 8 , wherein the device for utilizing the heat stored in the cooling medium is a steam heating means, a water desalination installation or a deicing installation of an aircraft. 
     
     
         10 . A fuel cell system according to  claim 1 , further comprising an apparatus for removing the cooling medium to the environment. 
     
     
         11 . A method for operating a fuel cell system comprising a fuel cell and an evaporative cooling system, which is in thermal contact with the fuel cell, in order that heat generated by the fuel cell during operation of the fuel cell is absorbed through evaporation of a cooling medium and is
 removed from the fuel cell,   comprising the steps of:
 sensing the pressure in the evaporative cooling system by means of a pressure sensing device and 
 controlling the operating temperature of the fuel cell by means of a control unit in dependence on signals that are supplied to a control unit from the pressure sensing device, in such a manner that the cooling medium of the evaporative cooling system is transferred from a liquid to a gaseous state of matter by the heat generated by the fuel cell during operation of the fuel cell. 
   
     
     
         12 . A method according to  claim 11 , wherein the operating temperature of the fuel cell is controlled, in dependence on the signals that are supplied to the control unit from the pressure sensing device, in such a manner that the evaporation of the cooling medium of the evaporative cooling system by the heat generated by the fuel cell during operation of the fuel cell is effected in a wet-steam region of the cooling medium. 
     
     
         13 . A method according to  claim 11 , wherein a desired pressure is generated in the fuel cell by means of a fuel-cell operating-pressure generating system. 
     
     
         14 . A method according to  claim 13 , wherein the fuel-cell operating-pressure generating system, by means of a control unit for controlling the fuel-cell operating-pressure generating system, is controlled such that there is generated in the fuel cell a pressure at which unwanted evaporation of substances and/or substance mixtures usually present in liquid form in the fuel cell is prevented. 
     
     
         15 . A method according to  claim 11 ,
 wherein the control unit for controlling the fuel-cell operating-pressure generating system controls the pressure in the fuel cell in dependence on the operating temperature of the fuel cell and/or in dependence on the signals of the pressure sensing device.   
     
     
         16 . A method according to  claim 11 ,
 wherein the cooling medium evaporated during operation of the fuel cell for the purpose of cooling the fuel cell is condensed in a condenser.   
     
     
         17 . A method according to  claim 16 ,
 wherein the cooling medium is condensed by a condenser in the form of an outer-skin cooler.   
     
     
         18 . A method according to  claim 11 ,
 wherein heat stored in the cooling medium is supplied to at least one device for the utilization of the heat.   
     
     
         19 . A method according to  claim 18 ,
 wherein the heat stored in the cooling medium is supplied to a device for the utilization of the heat, which device is realized in the form of a steam heating means, a water desalination installation or a de-icing installation of an aircraft.   
     
     
         20 . A method according to  claim 11 ,
 wherein the cooling medium is removed to the environment.   
     
     
         21 . An aircraft comprising a fuel cell system according to  claim 1 . 
     
     
         22 . An aircraft according to  claim 21 ,
 wherein the fuel cell system is arranged in a non-pressurized region of the aircraft.