Fuel cell thermal management system

Abstract

The invention provides fuel cell systems and methods of operation where a fuel cell system is used as a backup power supply in a cold environment where the system must be maintained at a suitable temperature to allow the fuel cell to operate when needed. In one embodiment, the invention provides a thermal protection system for a fuel cell backup power generator. An enclosure houses a fuel cell and a coolant circuit. The coolant circuit is coupled to the fuel cell. A temperature sensor is provided that is adapted to indicate a system temperature. A heater is provided to increase the system temperature when actuated. For example, the heater can be an electric resistive heater or a burner coupled to a combustible fuel supply such as a propane tank. The heater can be located in the interior of the enclosure, in the coolant circuit, etc. A control circuit is provided that is adapted to actuate the heater when the system temperature is below a predetermined threshold.

1 . A method of regulating the temperature of a dormant fuel cell backup power supply, comprising: 
 coupling a fuel cell system to a load and a primary power supply, wherein the fuel cell system is adapted to supply power to the load upon a failure of the primary power supply;    measuring a temperature of the fuel cell system to generate a temperature signal;    communicating the temperature signal to a control circuit;    determining whether the temperature is below a predetermined threshold; and    actuating a heater when the temperature is below the predetermined threshold.    
   
   
       2 . The method of  claim 1 , further comprising: 
 actuating a pump to circulate a heat transfer fluid through the fuel cell system when the temperature is below the predetermined threshold.    
   
   
       3 . The method of  claim 1 , wherein a temperature sensor located in an atmosphere of the fuel cell system is used to generate the temperature signal.  
   
   
       4 . The method of  claim 1 , wherein a temperature sensor located in a coolant circuit of the fuel cell system is used to generate the temperature signal.  
   
   
       5 . The method of  claim 1 , wherein the predetermined threshold is in the range of 0 to 15° C.  
   
   
       6 . The method of  claim 1 , wherein the heater is located in an atmosphere of the fuel cell system.  
   
   
       7 . The method of  claim 1 , wherein the heater is an electric resistive heater powered by the primary power supply.  
   
   
       8 . The method of  claim 1 , wherein the heater is a burner coupled to a combustible fuel supply.  
   
   
       9 . The method of  claim 1 , wherein the heater is a flow of heat transfer fluid circulated from a source external to the backup power supply.  
   
   
       10 . The method of  claim 1 , wherein the source is a hot water tank in a building.  
   
   
       11 . A method of regulating the temperature of a dormant fuel cell backup power supply, comprising: 
 coupling a fuel cell system to a load and a primary power supply, wherein the fuel cell system is adapted to supply power to the load upon a failure of the primary power supply;    measuring a temperature of the fuel cell system to generate a temperature signal;    communicating the temperature signal to a control circuit;    determining whether the temperature is below a predetermined threshold; and    flowing a heat transfer fluid through a portion of the system to raise the temperature when the temperature is below the predetermined threshold, wherein the backup power supply is located outside a building, wherein the heat transfer fluid is circulated between the building and the backup power supply.