Direct oxidation fuel cell system with uniform vapor delivery of fuel

Abstract

In one embodiment, a membrane electrode assembly of a fuel cell has an anode aspect and a cathode aspect. A fuel distribution structure is disposed adjacent to the anode aspect. The fuel distribution structure has a fuel feed port configured to receive and inject liquid fuel to a flow field plate. The flow field plate has flow channels formed therein that split and spread from the fuel feed port to exit ports. The flow channels are configured to convey heat to fuel passing there through to substantially convert the liquid fuel to vaporous fuel within the flow channels. The exit ports are configured to deliver the resulting vaporous fuel to the anode aspect to substantially uniformly distribute fuel across the anode aspect. Further, an enthalpy exchanger and heat spreader assembly is in thermal contact with the fuel distribution structure and configured to provide to it heat from fuel cell operation.

What is claimed is: 
     
         1 . A system comprising:
 a membrane electrode assembly of a fuel cell having an anode aspect and a cathode aspect;   a fuel distribution structure disposed adjacent to the anode aspect of the membrane electrode assembly, the fuel distribution structure having a fuel feed port configured to receive and inject liquid fuel to a flow field plate, the flow field plate having flow channels formed therein that split and spread from the fuel feed port to exit ports, the flow channels configured to convey heat to fuel passing there through to substantially convert the liquid fuel to vaporous fuel within the flow channels, the exit ports configured to deliver the resulting vaporous fuel to the anode aspect to substantially uniformly distribute fuel across the anode aspect; and   an enthalpy exchanger and heat spreader assembly in thermal contact with the fuel distribution structure and configured to provide heat from fuel cell operation to the fuel distribution structure.   
     
     
         2 . The system of  claim 1 , wherein the membrane electrode assembly includes a polymer electrolyte membrane having a catalyst disposed thereon and one or more diffusion layers, an anode current collector disposed adjacent to the anode aspect, and a cathode current collector disposed adjacent to the cathode aspect. 
     
     
         3 . The system of  claim 1 , further comprising:
 a fuel permeable diffusion film (FPDF) layer disposed adjacent to the fuel distribution structure and made of a material that is permeable to vaporous fuel.   
     
     
         4 . The system of  claim 3 , further comprising:
 a polyvinyliden fluoride (PVDF) layer disposed adjacent to the FPDF layer.   
     
     
         5 . The system of  claim 1 , wherein the fuel distribution structure has a generally planer shape, with the flow channels splitting and spreading in directions parallel to the plane, and the exit ports configured to deliver vaporous fuel in one or more directions perpendicular to the plane. 
     
     
         6 . The system of  claim 1 , comprising a pair of membrane electrode assemblies disposed on opposite sides of the fuel distribution structure, the fuel distribution structure configured with exit ports that deliver the vaporous fuel to the anode aspect of each of the pair of membrane electrode assemblies. 
     
     
         7 . The system of  claim 6 , further comprising:
 a fuel permeable diffusion film (FPDF) disposed adjacent to each of the opposite sides of the fuel distribution structure and made of a material that is permeable to vaporous fuel.   
     
     
         8 . The system of  claim 1 , wherein the flow channels have a serpentine shape. 
     
     
         9 . The system of  claim 1 , wherein the flow channels are arranged to provide a spiral shaped flow path. 
     
     
         10 . The system of  claim 1 , wherein the enthalpy exchanger and heat spreader assembly further comprises:
 a cold side element disposed adjacent to the cathode aspect of the membrane electrode assembly;   a hot side element that includes a flow field configured to receive air exiting the cathode aspect; and   an enthalpy exchange membrane located between the cold side element and the hot side element configured to transfer exhaust heat from the hot side element to the cold side element.   
     
     
         11 . The system of  claim 10 , further comprising:
 a heat switch coupled to a heat spreader of the enthalpy exchanger and heat spreader assembly and configured to, at a predetermined temperature, direct heat from the heat spreader to the fuel distribution structure.   
     
     
         12 . The system of  claim 10 , further comprising:
 an exhaust management system that is configured to receive exhaust from fuel cell operation and includes an exhaust travel path that flows through the cold side of the enthalpy exchanger.   
     
     
         13 . The system of  claim 12 , wherein the exhaust travel path is coupled to the heat spreader such that heat from the heat spreader increases temperature of the exhaust. 
     
     
         14 . The system of  claim 12 , wherein the exhaust travel path includes a catalyst disposed on a portion thereof that is reactive with excess fuel contained in the exhaust to convert the excess fuel to water and carbon dioxide. 
     
     
         15 . The system of  claim 12 , wherein the exhaust management system includes a carbon dioxide exhaust exit port allowing carbon dioxide to flow to an ambient environment. 
     
     
         16 . The system of  claim 1 , further comprising:
 a spring assembly configured to provide compression and stabilization to the system.   
     
     
         17 . A system comprising:
 a membrane electrode assembly of a fuel cell having an anode aspect and a cathode aspect;   a fuel distribution structure disposed adjacent to the anode aspect of a membrane electrode assembly, the fuel distribution structure having a fuel feed port configured to receive liquid fuel and exit ports or pores configured to deliver vaporous fuel to the anode aspect, the fuel distribution structure configured to receive heat from fuel cell operation and convey the heat to the liquid fuel within the fuel distribution structure to convert the liquid fuel to vaporous fuel therein; and   an enthalpy exchanger and heat spreader assembly that includes a heat spreader configured to collect heat generated from fuel cell operation, and a heat switch coupled to the heat spreader and configured to, at a predetermined temperature, direct heat from the heat spreader to the fuel distribution structure.   
     
     
         18 . The system of  claim 17 , wherein the fuel distribution structure comprises:
 a fuel feed vapor plenum having a nano-porous restrictor layer disposed as one wall of the plenum.   
     
     
         19 . A method comprising:
 introducing liquid fuel into a fuel feed port of a fuel distribution structure that is disposed adjacent to an anode aspect of a membrane electrode assembly of a fuel cell, the fuel distribution structure including a flow field plate having flow channels formed therein;   providing heat to the fuel distribution structure from an enthalpy exchanger and heat spreader assembly in thermal contact with the fuel distribution structure;   conveying the heat to fuel passing through the flow channels to substantially convert the liquid fuel to vaporous fuel within the flow channels; and   delivering the vaporous fuel via exit ports of the fuel distribution structure to the anode aspect to substantially uniformly distribute fuel across the anode aspect.   
     
     
         20 . The method of  claim 19 , wherein the providing further comprises:
 collecting heat generated from fuel cell operation at a heat spreader; and   directing the collected heat via a heat switch that, at a predetermined temperature, passes heat from the heat spreader to the fuel distribution structure.