Abstract:
A process and apparatus to modify the conventional proton exchange fuel cell by applying a non-conductive proton exchange material ( 5 ), a separate semiconductor ( 8 ), cylindrical-conical fuel cell elements ( 1,3 ), and internally stacking the fuel cell elements by a simple method. These modifications in the operating principle and construction configuration of the proton exchange fuel cell are designed to result in a major increase in the power density output necessary for transport vehicle and stationary power generation applications.

Description:
REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a Continuation-In-Part of U.S. patent application Ser. No. 10/474,340 dated 9 Apr. 2002, which in turn claims priority from Australian Patent Application No. 2003906746 filed 8 th  December 2003, Australian Patent Application No. 2004900745 filed 17 Feb. 2004 and Australian Patent Application No. 2004901465 filed 22 Mar. 2004. Applicants claim the benefits of 35 U.S.C. §120 as to the said U.S. Application and priority under 35 U.S.C. §119 as to said Australian applications, and the entire disclosures of all applications are incorporated herein by reference in their entireties. 
     
    
     FIELD OF INVENTION  
       [0002]     This invention relates to a modified operating principle, construction and configuration of fuel cells and a method of internal stacking of the fuel cell elements to produce higher power density to make fuel cells suitable for use in transport vehicles and for small to large stationary electric power generation units.  
         [0003]     The invention will be particularly discussed with reference to the proton exchange fuel cell using hydrogen fuel but is also applicable to other fuels and to other types of fuel cells such as solid oxide fuel cells.  
       PRIOR ART  
       [0004]     Fuel cells under development during the last four decades include the phosphoric acid fuel cell, the proton electrolytic membrane fuel cell, the molten carbonate fuel cell and the solid oxide fuel cell. While phosphoric acid fuel cells up to 250 kilowatts capacity are commercially available, the most advanced fuel cell is the proton electrolytic membrane fuel cell, however, its further commercial application is limited by the low power density of current designs and reported highest power capacity for transport vehicles and stationary power generation units is about 300 kilowatts.  
         [0005]     This invention consists of modifying the operating principle and the construction of the proton electrolytic membrane fuel cell and a method of internal stacking of the fuel cell elements to increase the power density of the fuel cell group so that it is suitable for application to transport vehicles and small and large stationary power generation. The objective is about 85 to 120 kilowatts for small transport vehicles and 300 to 400 kilowatts for large transport vehicles. In stationary power generation, the objective is to provide 3 to 5 kilowatts for home use, 250 kilowatts and 1,000 kilowatts for dispersed community power requirements and 10,000 to 500,000 kilowatts for centralized power generation.  
         [0006]     Most proton electrolytic membrane fuel cells are planar in construction such as the Ballard Power fuel cell where the fuel cell elements have been “stacked” in a neat cubical configuration. Passageways are provided for the supply of hydrogen and oxygen and the removal of the reaction products. The disadvantage of this construction is that pressure on the hydrogen side is limited as high pressure may cause rupture and seal failure allowing the hydrogen to mix directly with the oxygen with catastrophic results.  
         [0007]     A cylindrical cell construction would offer the possibility of higher pressure differential between the hydrogen side and the oxygen side. Several U.S. patents have been granted for proton electrolytic membrane fuel cells that are cylindrical in shape such as: 
        U.S. Pat. No. 5,458,989 (Oct. 17, 1995)—Tubular fuel cells with structural current collectors—Dodge, C. et al,     U.S. Pat. No. 5,509,942 (Apr. 23, 1996)—Manufacture of tubular fuel cells with structural current collectors—Dodge C. et al,     U.S. Pat. No. 6,001,500 (Dec. 14, 1999)—Cylindrical proton exchange membrane fuel cells and methods of making same—Bass E. et al,     U.S. Pat. No. 6,007,932 (Dec. 28, 1999)—Tubular fuel cell assembly and method of manufacture—Steyn W. et al,     U.S. Pat. No. 6,060,188 (May 9, 2000)—High pressure coaxial fuel cell—Muthuswamy S. et al, and     U.S. Pat. No. 6,063,517 (May 16, 2000)—Spiral wrapped cylindrical proton exchange membrane fuel cells and method of making same—Montemayor A. et al.        
 
         [0014]     The proton electrolytic membrane fuel cells above describe several cylindrical configurations of the proton electrolytic membrane fuel cell. A major shortcoming of the above construction is how to maintain good contact between the proton exchange membrane and the anode and cathode electrodes under all operating conditions of the proton electrolytic membrane fuel cell, particularly under varying temperatures. Loosening of the contact between the membrane and the electrodes would increase the impedance of the proton electrolytic membrane fuel cell and even cause the proton electrolytic membrane fuel cell to cease functioning.  
         [0015]     U.S. Pat. No. 5,244,752 (Sep. 14, 1993)—Apparatus tube configuration and mounting for solid oxide fuel cell—Zymboly, G. concerns a tubular configuration for a solid oxide fuel cell.  
         [0016]     The proton membrane fuel cell described in U.S. patent application Ser. No. 10/474,340 operates with a proton membrane that is also a semi-conductor that allows electric current to flow from the cathode electrode to the anode electrode only. The proton exchange membrane is described as a homogenous membrane that allows the hydrogen proton to move from the anode electrode to the cathode electrode and electrons to travel from the cathode electrode to the anode electrode.  
         [0017]     The proton membrane fuel cell described in U.S. patent application Ser. No. 10/474,340 shows the oxygen-nitrogen mixture or air passing from the first fuel cell to the last fuel cell of a stack of fuel cells.  
         [0018]     It is an objective of this invention to present a further improvement to the structure and features of fuel cells of this type.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0019]     In one form therefore the invention is said to reside in a proton exchange fuel cell comprising an anode, a cathode, a proton exchange material between the anode and the cathode that allows movement of hydrogen ions from the anode to the cathode and a separate semiconductor arrangement electrically connected to the anode and the cathode and which allows movement of electrons from the cathode to the anode.  
         [0020]     Preferably the proton exchange material is fused to the anode and the cathode. The proton exchange material may be fused to the anode and the cathode by a process selected from the group comprising gluing, welding, brazing and soldering.  
         [0021]     Preferably the anode has a catalytic surface adapted to catalyze hydrogen to hydrogen ions. The anode catalytic surface may be fine platinum.  
         [0022]     Preferably the cathode has a catalytic surface. The cathode catalytic surface may be selected from the group comprising platinum and nickel.  
         [0023]     The anode may comprise a frusto-conical surface on an inner surface thereof and the cathode may comprise a frusto-conical surface on an outer surface thereof and matching the frusto-conical inner surface of the anode, the proton exchange material being held between the frusto-conical inner surface and the frusto-conical outer surface.  
         [0024]     In a further form the invention comprises a fuel cell comprising an anode cell and an anode at one wall thereof, a cathode cell and a cathode at one wall thereof and a proton exchange material between the anode cell and the cathode cell and engaged against the anode and the cathode and a separate semiconductor electrically connected to the anode and the cathode and which allows movement of electrons from the cathode to the anode.  
         [0025]     Preferably the cathode and anode are formed from a material which allows easy passage of hydrogen ions. The cathode and anode may be formed from a material selected from the group comprising carbon, metal hydrides, metal carbides or alloys thereof.  
         [0026]     Preferably the anode is formed from a material which allows easy passage of hydrogen and the anode has a catalytic surface engaged against the proton exchange material.  
         [0027]     The proton exchange material may be selected from a group comprising a polymer, a rubber or a ceramic.  
         [0028]     A surface of each of the anode and cathode not being the faces engaged against the proton exchange material may have an increased surface area by means including grooving, pyramiding or roughening of the surface.  
         [0029]     In a further form the invention comprises a proton exchange fuel cell arrangement comprising a plurality of fuel cell elements, each fuel cell element comprising an anode, a cathode, a proton exchange material between the anode and the cathode that allows movement of hydrogen ions from the anode to the cathode and a separate semiconductor arrangement electrically connected to the anode and the cathode and which allows movement of electrons from the cathode to the anode, and the fuel cell arrangement comprising a simple internal stacking of the fuel cell elements in a cylindrical cell container to allow high pressure hydrogen operation of the fuel cell arrangement.  
         [0030]     The proton exchange fuel cell arrangement may further comprise means to supply pressurized hydrogen to the anode.  
         [0031]     The proton exchange fuel cell arrangement may further comprise a manifold within the cylindrical cathode to supply air or oxygen to each of the fuel cell elements.  
         [0032]     The manifold may comprise means to provide good contact between the oxygen or air and the cathode surface.  
         [0033]     Preferably there is a first manifold within the cylindrical cathode to supply air or oxygen to each of the fuel cell elements and a second manifold within the cylindrical cathode to remove waste products from each of the fuel cell elements.  
         [0034]     Preferably the proton exchange fuel cell arrangement comprises the fuel cell elements electrically connected in series. Alternatively the fuel cell elements may be electrically connected in parallel.  
         [0035]     There may be included annular non-conducting seals between the fuel cell elements, the seals incorporating electrical connections between the adjacent fuel cells.  
         [0036]     There may be included force application means on the stack of fuel cell elements to promote sealing at each of the annular seals and to promoting engagement of the respective anodes and cathodes to the proton exchange material therebetween.  
         [0037]     In a further form the invention comprises a process to produce electricity from the reaction of hydrogen and oxygen to produce water in a proton exchange fuel cell arrangement as discussed above, the process including the steps of: 
        a) pressurizing hydrogen at the outer catalyst surface of the outer cylindrical anode;     b) catalyzing the hydrogen to hydrogen ions and electrons at the outer catalyst surface of the outer cylindrical anode wherein the electrons travel from the anode to an external electrical circuit through an electrical load to an inner cylindrical cathode through the semiconductor to the anode and the hydrogen ions travel through the anode, the proton exchange material between the anode and the cathode and the cathode to an inner catalytic surface of the cathode; and     c) reacting the hydrogen ions with oxygen at the inner catalytic surface of the cathode to produce water.        
 
         [0041]     The hydrogen may be at a pressure of up to 333 bars at the anode and the oxygen may be provided at a pressure up to 10 bars at the cathode.  
         [0042]     The proton exchange fuel cell arrangement can be operated at a temperature of up to 250° C. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0043]     This then generally describes the invention but to assist with understanding of the invention reference will now be made to the accompanying drawings which show preferred embodiments of the invention.  
         [0044]     In the drawings:  
         [0045]      FIGS. 1A and 1B  show schematic views of proton exchange fuel cells with a proton exchange materials and a separate semiconductor arrangement according to various embodiments of the invention;  
         [0046]      FIG. 2  shows a cross section of an embodiment of a fuel cell according to one embodiment of this invention;  
         [0047]      FIG. 3  shows a cross section of a stack of fuel cells of the type shown in  FIG. 2 ;  
         [0048]      FIG. 4  shows a cross section of an alternative embodiment of a stacked fuel cell according to the invention; and  
         [0049]      FIG. 5  shows a still further embodiment of a fuel cell stack according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0050]     The operating principle of various embodiments of the proton exchange fuel cell according to the present invention is shown in schematic views in  FIGS. 1A and 1B .  
         [0051]     Referring to  FIG. 1A , the fuel cell element has an anode  1  and a cathode  3  separated by a homogenous proton exchange material  5  wherein the proton exchange material is a material which allows protons to pass therethrough from the anode to the cathode but is electrically non-conductive. A separate semiconductor  8  is connected between the cathode  3  and anode  1 . Each of the anode  1  and the cathode  3  have a catalytic surface  2  and  4  respectively. The catalytic reaction at the anode converts hydrogen to hydrogen ions or protons and these are allowed to travel from the anode  1  through the proton exchange material  5  to the cathode  3  while electrons produced are allowed to travel to the external load  7  then to the cathode  3  and then through the separate semiconductor  8  to the anode  1 . This provides a complete electronic circuit. The semiconductor  8  is illustrated as a diode oriented to allow electron flow from the cathode to the anode.  
         [0052]     The chemical reactions in the cell are as follows. Hydrogen is provided at the anode and is catalysed in the following reaction: 
 
H 2 →2H + +2e − 
 
         [0053]     At the cathode oxygen is supplied and the reaction is catalysed as follows: 
 
½O 2 +2H + +2e − →H 2 O 
 
         [0054]     The proton exchange material that allows the hydrogen ions or protons to pass from the anode to the cathode may be constructed of a homogenous polymer, rubber or ceramic material. It must be sufficiently pliable so that it will conform to the surfaces of the anode electrode and the cathode electrode with which it is in contact. Further, the material must be stable at the operating temperature and pressure of the fuel cell.  
         [0055]     A further aspect of the invention relates to a cubical-trapezoidal configuration of the fuel cell but preferably a cylindrical-conical configuration of the fuel cell. Axial opposing forces may be applied to a fuel cell with such a configuration forcing the cathode electrode against the anode electrode with the proton exchange material sandwiched between. This will allow good contact to be maintained between the material and the anode and cathode electrodes for a proper operation of the fuel cell under all operating conditions.  
         [0056]     The catalytic surface  2  of the anode  1  may be formed from fine platinum. The catalytic surface  4  of the cathode  3  may be formed from a material selected from the group comprising platinum and nickel.  
         [0057]     The cathode  3  and the anode  1  may be formed from a material which allows easy passage of hydrogen and hydrogen ions and the catalytic surface  2  of the anode may be engaged against the proton exchange material  5 . The cathode  3  and anode  1  may be formed from a material selected from the group comprising carbon, metal hydrides, metal carbides or alloys thereof.  
         [0058]     In one embodiment a fuel cell constructed according to the principle shown in  FIG. 1A  may have frusto-conical engaging surfaces of the anode and cathode with the anode and cathode compressed together with the proton exchange material sandwiched between them as will be discussed in relation to the various embodiments shown in FIGS.  2  to  5 . An alternative embodiment can have the proton exchange material fused to the anode and cathode on its opposite sides respectively and providing good electrical connection between them. This embodiment would not require forcing together of the anode and cathode to give good electrical contact.  
         [0059]     Referring to  FIG. 1B , the fuel cell element has an anode  1  and a cathode  3  separated by both a homogenous proton exchange material  5   b  wherein the proton exchange material is electrically conductive and a separate semiconductor layer  8   b  which only allows electron flow from the cathode to the anode. Both the proton exchange material  5  and the semiconductor layer  8   b  allow transfer of protons from the anode to the cathode. Each of the anode  1  and the cathode  3  have a catalytic surface  2  and  4  respectively. The catalytic reaction at the anode converts the hydrogen to hydrogen ions or protons and these are allowed to travel from the anode  1  through the proton exchange material  5   c  and the semiconductor layer  8   b  to the cathode  3  while electrons produced are allowed to travel to the external load  7  then to the cathode  3  and then through the semiconductor layer  8   b  and the proton exchange material  5   b  to the anode  1 . This provides a complete electronic circuit.  
         [0060]     As discussed above the proton exchange material may be connected to the anode and the cathode by fusing. The term fusing in intended to mean the use of a conductive glue, sintering, fusing, soldering, brazing or resistance welding. If the anode and cathode and the proton exchange are well connected, it may not be necessary to provide a differential force between the anode and the cathode to maintain a firm contact with the proton exchange. Only a force compressing the fuel cell elements against seals may be required in stacking the fuel cell elements to prevent mixing of the hydrogen or fuel and the oxygen or oxidant. This construction will also allow a higher temperature to be used in the operation of the fuel cell leading to increased capacity. The anode catalyst may be located at the anode outer surface or between the anode and the proton exchange component.  
         [0061]      FIG. 2  shows the preferred construction of one embodiment of a cell element of a cylindrical-conical fuel cell.  
         [0062]     In this embodiment the anode catalyst  10  is located outside of the anode electrode  12  in a cylindrical anode cell  11 . Where the hydrogen fuel has impurities such as carbon oxides, the anode catalyst may be located in the inside of the anode electrode. As shown in  FIG. 2 , the cylindrical anode electrode  12  with the anode catalyst  10  located on the outer surface is slightly conical on the inside. In an alternative arrangement a layer of material may be installed over the catalyst layer to screen out any carbon oxides in the fuel which would otherwise poison the catalyst. The proton exchange material  14  is also slightly conical and fits into the inside of the anode electrode  12 . The outer surface of the cylindrical cathode electrode  16  is slightly conical and fits into the cone of the proton exchange material  14  and the inside cone of the anode electrode  12 . The cathode electrode  16  is pushed axially upward  18  while the anode electrode is restrained so that there is a force causing the inside of the anode electrode  12  to maintain contact with the outside of the cathode electrode  16  with the proton exchange material  14  sandwiched in-between. The material of the anode and cathode electrode is electrically conducting and needs to allow easy passage of the hydrogen ion and must have structural strength to withstand the high pressure differential between the hydrogen in the anode cell  11  and the air or oxygen in the cathode cell  17  at the operating temperature of the fuel cell. The inner surface of the cathode electrode  16  has a catalyst  20  on it.  
         [0063]     A semiconductor  19  is connected between cathode  16  and the anode  12  so as to allow electron to flow from the cathode to the anode.  
         [0064]     The anode and cathode electrodes are made of electrically conducting material such as metals, alloys, hydrides and carbon that allows easy passage of the hydrogen ion through the crystal lattice or grain boundaries of the material. There are many such materials known due to the extensive research into the use of these materials for the storage of hydrogen.  
         [0065]     In operation, the hydrogen atom is catalyzed to hydrogen ion by the anode catalyst at the anode electrode. The electrons travel to the external circuit via the electrical load  22  and return to the cathode electrode. The hydrogen ion travels to the cathode catalyst  20  located at the inner surface of the cathode electrode  16  where the hydrogen ion reacts with the oxygen and the electrons from the external electrical circuit to form water. The electronic circuit is completed by the passage of electrons from the cathode electrode through the semiconductor  19  to the anode electrode.  
         [0066]     The external or separate semiconductor may be in the form of a bridge or a plate shaped an sized as required to mate with the shape of the anode and cathode electrodes and to efficiently and adequately conduct the electric current of the fuel cell.  
         [0067]     This embodiment is shown with the separate semiconductor of the type shown in schematic view of  FIG. 1A  but it may also be constructed with the type of semiconductor arrangement shown in  FIG. 1B .  
         [0068]     A simple model to explain the operating principle of the fuel cell is that there is a continuous flow of electrons in the electronic circuit. At the anode, electrons from the oxidation of the hydrogen join this electronic circuit. The hydrogen ion travels to the cathode. At the cathode, some electrons are used by the cathode reaction to carry out the reaction forming water from the hydrogen ions and the oxygen available at the catalyst surface of the cathode electrode.  
         [0069]     The cylindrical-conical construction allows a large pressure differential between the anode (hydrogen) and the cathode (oxygen). This creates a stronger driving force for the diffusion of the hydrogen ion due to the substantially higher concentration of hydrogen ions at the anode electrode. This will result in a higher current density for the fuel cell even without considering the higher power density of the fuel cell as a result of the complete electronic circuit provided by the semiconductor.  
         [0070]     It is projected that the fuel cell according to the invention can operate at hydrogen pressures of up to 333 bars and up to 10 bars of air or oxygen pressure. The higher the operating temperature, the higher the diffusion rate of the hydrogen ion through the anode and cathode electrodes. The normal operating temperature of the fuel cell may range from 25° C. up to 250° C. or more. The operating temperature will be limited mainly by the materials of construction of the fuel cell.  
         [0071]     Fuel cells can produce high currents but the voltage of each cell is theoretically 1.229 volts for the hydrogen-oxygen fuel cell and is usually lower under load in an operating system. It is desirable to connect the cells in series or “stack” these to produce a high working voltage. Alternatively they can be connected in parallel.  
         [0072]     The fuel cell elements may be stacked internally as shown in an alternative embodiment in  FIG. 3 . Each cell is the same as that shown schematically in  FIG. 2  and the same reference numerals are used for the same components.  
         [0073]     Each fuel cell element comprises an anode  12  with an anode catalyst  10  is located outside of the anode electrode  12  in a cylindrical anode cell  30 . Where the hydrogen fuel has impurities such as carbon oxides, the anode catalyst may be located in the inside of the anode electrode. The cylindrical anode electrode  12  with the anode catalyst  10  located on the outer surface is slightly conical on the inside. The proton exchange material  14  is also slightly conical and fits into the inside of the anode electrode  12 . The outer surface of the cylindrical cathode electrode  16  is slightly conical and fits into the cone of the proton exchange material  14  and the inside cone of the anode electrode  12 . The cathode electrode  16  is pushed axially upward  18  while the anode electrode is restrained so that there is a force causing the inside of the anode electrode  12  to maintain contact with the outside of the cathode electrode  16  with the proton exchange material  14  sandwiched in-between. The material of the anode and cathode electrode is electrically conducting and needs to allow easy passage of the hydrogen ion and must have structural strength to withstand the high pressure differential between the hydrogen in the anode cell  11  and the air or oxygen in the cathode cell  17  at the operating temperature of the fuel cell. The inner surface of the cathode electrode  16  has a catalyst  20  on it. A semiconductor  19  is connected between cathode  16  and the anode  12  so as to allow electron to flow from the cathode to the anode.  
         [0074]     The cell elements are held in a tube  30  pressurized with hydrogen. Each cell element is electrically isolated by a non-conducting annular ring  32  that is made of a plastic or ceramic material. An outer annular conducting ring  34  in contact with the anode electrode and an inner annular conducting ring  35  in contact with the cathode electrode are imbedded in the non-conducting ring. These two rings are connected by a conductor wire  36  imbedded in the non-conducting annular ring  32 . Sealing O-rings  38  or similar are installed between the anode electrode  12  and the non-conducting annular ring  32  to separate the hydrogen from the oxygen. The dimension and compressibility of the inner and outer conducting rings and the O-ring seals selected so that when a compressive force is applied to the fuel cell elements, the anode electrodes are forced against the annular ring  32  to seal against it and at the same time achieve sealing of the hydrogen from the air or oxygen and the conical surfaces of the anode and cathode electrodes forced against each other to hold the proton exchange material in good contact.  
         [0075]     Larger diameter non-conducting rings  40  with holes are installed at appropriate intervals to center the fuel cell elements within the cylindrical container  30 . An inner cylinder  42  with continuous helical vane or baffle  44  is installed in the cathode cell cavity to ensure good contact of the air or oxygen with the cathode catalyst and to effect the efficient removal of the fuel cell reaction product.  
         [0076]     The electronic circuit is described as follows. Starting from cell element  46 , electrons travel from the cathode electrode to the anode electrode, to the outer conducting ring through the embedded wire conductor  36 , to the inner conducting ring of cell element  48  to the cathode electrode of cell element  48 , through the semiconductor  19  to the anode electrode of cell element  48 , to the outer conducting ring through the embedded wire conductor to the inner conducting ring of cell element  50 , to the cathode electrode of cell element  50 , through the semiconductor  19  to the anode electrode, to the outer conducting ring through the embedded wire conductor to the inner conducting ring of cell element  52 , to the cathode electrode of cell element  52 , through the semiconductor  19  to the anode electrode of cell element  52 , to the external conductor to the electrical load  54  and to the cathode electrode of cell element  46 .  
         [0077]     This embodiment is shown with the separate semiconductor of the type shown in schematic view of  FIG. 1A  but it may also be constructed with the type of separate semiconductor arrangement shown in  FIG. 1B .  
         [0078]     Another method of internal stacking is shown on  FIG. 4 . Each cell is the same as that shown in  FIG. 2  and the same reference numerals are used for the same components. In this method, instead of opposing forces achieving contact between the proton exchange material and the electrodes, each fuel cell element is bolted to the next fuel cell element to achieve the force to keep the proton exchange material in contact with the electrodes.  
         [0079]     The device consists of a plurality of fuel cells  60  each composed of an anode  12  and a cathode  16  separated by a proton exchange material  14 . Each cell is connected to adjacent cells by insulated bolts  62  and compressible seals  64  are filled between the cells and electrical connection  66  is provided between the cathode of one cell and the anode of the next. Separate semiconductors (not shown) are provided to allow electron flow from the cathodes to the anodes.  
         [0080]     The entire stack is received in a cylindrical tank  68  so that hydrogen can be pressurised around the anodes of the cells. The cylindrical inner surfaces of the cathodes are exposed to air or oxygen and a central cylinder  70  with helical baffles  70   a  ensures good contact of the air with the catalytic surface  20  of the cathode  16 .  
         [0081]     To ensure good supply of air or oxygen to the cathode a pair of pipes  71  and  72  extend through the central cylinder  70 . The pipe  71  supplies air or oxygen to each cathode through apertures  73  and pipe  72  withdraws reaction products from each cathode through apertures  74 . By this arrangement maximum concentration of oxygen can be supplied to each cell and waste products do not build up in the stack. A baffle  75  is provided between each cell to maintain oxygen concentration in each cell.  
         [0082]     In the device shown in  FIG. 4 , the dimension and compression characteristics of the seals  64  are important to achieve the seal between the hydrogen and the oxygen and the force required to maintain contact between the anode electrode  12  the material  14  and the cathode electrode  16 .  
         [0083]     Another method of internal stacking the fuel cells is shown in  FIG. 5 .  
         [0084]     The assembly in  FIG. 5  shows an anode electrode stack  77  installed inside a cylindrical container  81  with seals  85  to contain hydrogen at the anode side. A cathode electrode stack  78  with matching conical dimensions are installed inside the anode electrode stack  77  with a proton exchange material  80  sandwiched between the anode electrodes and the cathode electrodes. A force  82  is applied at bottom end of the cathode electrode stack so that the cathode electrodes  78  are firmly in contact with the material  80  and the anode electrodes  74 . An inner cylinder  84  with helix  86  is installed through the cathode electrode  78  stack to ensure good contact of the air or oxygen with the catalyst  83  of the cathode electrodes  78 . The semiconductors  87  are connected between each cathode and anode and as in the earlier embodiments and allow the transfer of electrons from the cathode stack to the anode stack. The fuel cell elements in the stack shown in  FIG. 5  are electrically connected in parallel to complete the electronic circuit. An electrical conductor  88  connects adjacent cathodes  78  and an electrical conductor  89  connects adjacent anodes  77 .  
         [0085]     This embodiment is shown with the separate semiconductor of the type shown in schematic view of  FIG. 1A  but it may also be constructed with the type of separate semiconductor arrangement shown in  FIG. 1B .  
         [0086]     Heat is produced during the fuel cell reaction. Part of this heat is used for pre-heating the hydrogen and the oxygen or oxygen-nitrogen feed to the fuel cell. Excess heat from the fuel cell may be used for external application such as domestic or industrial heating or water desalination.  
         [0087]     It is desirable to have the largest specific surface of the electrodes to achieve the highest possible power density for a given volume of the fuel cell. The active surfaces of the anode and cathode electrodes may be grooved or of pyramidal structure to give a high specific surface area of the catalysts.  
         [0088]     Throughout this specification various indications have been given as to the scope of this invention but the invention is not limited to any one of these but may reside in two or more of these combined together. The examples are given for illustration only and not for limitation.  
         [0089]     Throughout this specification and the claims that follow unless the context requires otherwise, the words ‘comprise’ and ‘include’ and variations such as ‘comprising’ and ‘including’ will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.