WO2006068527A2

WO2006068527A2 - Hydrogen- fuel cell stack with integrated cooling and air supply for use with a fixed pressure dead-ended supply configuration

Info

Publication number: WO2006068527A2
Application number: PCT/PT2005/000022
Authority: WO
Inventors: José João Santana CAMPOS RODRIGUES; Rui Pedro Da Costa Neto; Diogo Gonçalvo MOREIRA PINTO; Bruno Miguel Souto Lopes; Gonçalo José DE MOURA TRINDADE ELIAS; Joaquim José Inácio CAETANO TENREIRO
Original assignee: Sre-Soluções Racionais De Energia, S.A.
Priority date: 2004-12-21
Filing date: 2005-12-21
Publication date: 2006-06-29
Also published as: PT103221B; EP2097942A2; PT103221A; WO2006068527B1; WO2006068527A3

Abstract

The following invention includes a fuel cell stack where the fuel is hydrogen, the electrolyte is in the solid state and is a polymeric membrane which allows for the cationic exchange but not the electronic exchange, designed for the feeding only of hydrogen and air, designed for electricity production, where: at the anodes, the hydrogen' s dissociation in protons and electrons takes place; at the membranes, the protons are driven from the anodes to the cathodes; at an outer circuit, the electrons are driven from the anodes to the cathodes; and, at the cathodes, the recombination of protons, electrons and oxygen atoms takes place into water molecules. It is characterized by comprehending a bipolar diffusion plate 1, where on one side channels 3 and 4 are drawn for the hydrogen feeding, channels 3 and 4 enclosing, together with the polymeric membrane, a tight chamber who allows the dead-ended operation of the device under a fixed pressure, without any fuel recirculation; and on the other side are drawn the axial channels 5 for an easy air circulation, channels 5 eventually forming a perpendicularly intertwined grid helping a natural air feeding.

Description

DESCRIPTION

"HYDROGEN-FUEL CELL STACK WITH INTEGRATED COOLING AND AIR SUPPLY FOR USE WITH A FIXED PRESSURE DEAD-ENDED SUPPLY

CONFIGURATION"

Scope of the invention

The following invention relates to a fuel cell where the fuel is hydrogen and the oxidant is oxygen . It is essentially characterised by comprehending : one hydrogen diffusion plate who forms , together with the MEA - Membrane Electrode Assembly - a tight chamber allowing the operation under a dead-ended, fixed pressure configuration; an air diffusion plate with diffusion channels drawn perpendicularly as to form an intertwined grid allowing a natural air feeding ; the axial application and use of a small fan over the cell or stack allowing the reinforcement of the air flow according to operational requisites .

State of the Art

Hydrogen- fuel cells' basic principles Hydrogen-fuel cells ' basic principles are widely spread today . A fuel cell is an electrochemical device where a reductive reagent reacts with an oxidant one forming electricity, heat and water . The typical fuel supplied to a PEM (Proton Exchange Membrane , or Polymer Electrolyte Membrane) fuel cell is hydrogen, and usually the oxidant is oxygen from the air . There are other kinds of reductive reagents , or fuels , for use on fuel cells , such as methanol , methane or propane , depending on operational conditions and on the fuel cells ' technology and components .

On a hydrogen-fuel cell , this gas is introduced into the anode , where it reacts electrochemically by means of a catalyst forming ions H⁺ (protons) and electrons . These electrons move from the anode onto the cathode through an outer electrical circuit . Simultaneously, the protons , when surrounded by water molecules , move through the electrolyte onto the cathode side where they recombine with electrons , from the outer circuit , and oxygen molecules , from the air, also by means of a catalyst , forming water molecules . Electrical Work is produced by the movement of the electrons through the outer circuit if a load is applied . Thus , the reactions of reduction/oxidation associated with hydrogen-fuel cells are :

H₂ -> 2H⁺ + 2e^~ % O₂ + 2H⁺ + 2e^~ -> H₂O

Advantages The advantages of Hydrogen- fuel cells when compared to conventional power sources relate to their highly efficient energy conversion indicators and by being non-pollutant . Additionally, fuel cells can be assembled into modules of different sizes and shapes , allowing the design of an enormous variety of systems on a wide power range, allowing for their integration into many commercial applications . This commercial possibility shall keep on rising mainly due to the stricter environmental standards industry leaders shall comply to , and to the predictable decrease of the costs associated to the several components and raw materials .

Engineering of the Diffusion / Collection Plates

A hydrogen-fuel cell stack comprises a stack of several fuel cells , which usually means the component which makes the separation between each cell is a bipolar plate which, besides doing the electricity collection, also has hydrogen diffusion channels on one side and oxygen, or air, diffusion channels on the other . These channels can have a number of configurations possible : with parallel channels on one side relative to the other, with perpendicular channels on one side relative to the other, or with a combination of these two designs . Usually, these channels have a width between lmm and 2mm, and their depth can vary between 0 , 2mm and 3mm, and they may have different dimensions throughout the gases ' pathways . The thickness of the plates depends on the channels ' depths on both faces , of the sealing applied and of the plate ' s material . Regarding the shapes commonly used, bipolar plates are usually rectangular envisaging the square , as this last shape allows for the optimization of the electrode ' s usable area, maximizing electricity collection . They can also present other useful shapes as , among others , hexagonal , octagonal , circular, etc .

Bipolar plates' material

Bipolar plates must be made from a material which allows for the stressful operation conditions ; this material must be good electrical conductor, chemically inert , hydrogen impermeable and mechanically sound . The materials normally used as bipolar plates are : graphite , or graphite compounds, titanium, titanium oxide , niobium, stainless steel and other metals with the electrodepositing of noble metals (usually gold) .

Sealings

The sealings usually used in hydrogen-fuel cells are from an elastic nature (rubber, silicon, PTFE , resins and glues) , they must have fair thermal and chemical stability and they must be impermeable to hydrogen .

Bipolar plates cooling

There is a large variety of strategies for the bipolar plates ' temperature stabilization over time , normally associated with their cooling . Usually the bipolar plate has in its core (between the hydrogen channels and the air channels , at its surface) special channels for the circulation of a cooling fluid, normally water or air, which makes easier to manufacture these plates as the junction of two separate plates , one with the hydrogen channels and the cooling channels and other with the oxidant channels and the cooling channels ; When water is used as the cooling fluid, an outer system is needed for the water to cool (radiator) , and the water travels between the radiator and the plate ; When air is used as a cooling fluid, it travels through the plate removing its heat and it is usually vented outside the device .

Membrane-Electrode Assemblies - MEAs

The heart of the fuel cell is the Membrane- Electrode Assemblies - MEAs ; the way these assemblies are made have a decisive influence on any fuel cell ' s performance . The assembly of the electrodes with the membrane depends on the initial deposition of the catalyst : if the catalyst is applied directly upon the membrane, the electrodes are usually applied upon the membrane on the manufacturing stage , so we deal with a pre-arranged set of electrodes - catalyst - membrane ; if the catalyst is applied on the electrodes , the MEA is usually done at the final stage of the cell assembly, and they can be done by merely compressing the components together between the bipolar plates . Almost all kinds of MEAs include the proton exchange membrane with a platinum film deposited on both sides and two hydrophobic electrodes , usually carbon paper or carbon cloth, on each side of the membrane . Technology issues

The maj or technology issues yet to be solved relate to : 1) how to manage the water formation and disposal ; 2 ) how to stack the cells as to ensure all receive the proper amounts of reagents , to ensure the temperature is balanced and to ensure each membrane has a stable and adequate water content . One should also make sure that all cells have the same ohmic resistance , which depends on the torque used, and that the hydrogen channels are hermetically sealed . One other requisite for a high performance fuel cell is the use of a membrane which must have a high ionic conductibility, an elevated lifespan and fair mechanic stability.

Many patents have been registered related to fuel cells ; among them, we have selected the ones we consider to be the most relevant regarding the state of the art : US6.770.394 , US6.677.071 , US6786937 , US6699613 , US6689500 and US6817097.

U. S . Patent N° . 6.770.394 concerns an electrochemical fuel cell containing a first and a second monolithic electrically conducting flow field-bipolar plate assemblies arranged essentially parallel to each other such that an inside surface of the first bipolar separator plate is facing an inside surface of the second bipolar separator plate, wherein the bipolar separator plates are electrically and mechanically connected by intervening layers that are directly bonded to each other . The fuel cells can be stacked between endplates and supplied with hydrogen and oxygen to generate electric power . An air cooled condenser for use with a fuel cell stack is composed of a porous foam condensing element and a porous foam cooling element . The condenser can be placed by a fuel cell stack for cooling purposes .

US Patent N° . 6 , 677 , 071 concerns an invention related to a bipolar plate for a fuel cell , the bipolar plate comprising a central area and a surrounding area, wherein the central area has a first side surface and a second side surface opposed to the first side surface , the central area is in a form of continuous corrugation which defines a plurality of grooves that are substantially parallel with and complementary to each other on each of the first side surface and the second side surface . The thickness of the bipolar plate of this invention can be very thin so as to decrease the dimension and weight of the fuel cell . The grooves are connected to elongated holes in the surrounding area by channels which are formed in a longitudinal direction on a first side and in a direction transverse to a longitudinal direction on a second side .

US Patent N° . 6 , 786 , 937 concerns a fuel cell stack including a stack of flow plates , a first gasket that is compatible with a coolant and a second gasket that is incompatible with the coolant . The stack of flow plates includes openings to form a coolant passageway that communicates the coolant and a reactant manifold passageway. The second gasket forms a seal around the reactant manifold passageway between an adj acent pair of the plates . The first gasket forms a seal around the coolant manifold passageway between the adj acent pair of plates . At least one region of a particular plate may be associated with a reactant flow, and this plate may include internal passageways that extend between manifold passageways to communicate a coolant . A seal that is substantially permanent isolates the internal passageways from the region (s) of the fuel cell plate that may be associated with reactant flow (s) .

US Patent N° . 6 , 699 , 613 concerns a fuel cell comprising : a membrane electrode assembly having a solid polymer electrolyte membrane , an anode side diffusion electrode (an anode electrode , and a second diffusion layer) disposed at one side of the solid polymer electrolyte membrane , and a cathode side diffusion electrode (a cathode electrode , and a first diffusion layer) disposed at the other side of the solid polymer electrolyte membrane ; a pair of separators which hold the membrane electrode assembly; a proj ecting portion which extends from the solid polymer electrolyte membrane and which proj ects from the peripheries of the anode side diffusion electrode and the cathode side diffusion electrode ; and a seal , provided on the separators , which was liquid sealant at the time of application . The seal makes contact with the proj ecting portion while the membrane electrode assembly is disposed between the separators .

US Patent N° . 6 , 689 , 500 concerns a fuel cell system including a first reactant intake manifold, a first reactant output manifold, a second reactant intake manifold, a second reactant output manifold, a cooling gas intake manifold, a cooling gas output manifold, a liquid intake manifold, fuel cells and a cooling elements distributed among the fuel cells . Each cooling element defines a coolant passage . During operation, a cooling gas flows from the cooling gas intake manifold into the cooling gas output manifold through the coolant passage . Each cooling element also includes a water inj ection path . During operation water from the liquid intake manifold is inj ected into the coolant passage to mix with the cooling gas passing there through .

US Patent N° . 6 , 817 , 097 concerns a heat pipe assembly including a base plate and a corrugated lid j oined to the base plate to form a plurality of tubes between the base plate and the corrugated lid . Each of the plurality of tubes forms an envelope of a respective heat pipe within the heat pipe assembly. The heat pipe assembly may be included in a fuel cell stack. As one may infer from what is going to be presented, the following invention has many and substantial differences to the actual state of the art .

Brief description of the drawings

The drawings we attach are merely indicators to allow a better understanding of the invention' s description to follow, and they should not be seen as limitable indicators of the invention' s application . The drawings :

1 represents a view from the top of a bipolar diffusion plate , with the hydrogen flowfields clearly visible ;

- 2 represents a view from the bottom of a bipolar diffusion plate , with the air flowfields clearly visible ;

- 3 represents a schematic of the components of an individual hydrogen cell ; and

- 4 represents a view of a fuel cell stack by the integration, or stacking, of five individual fuel cells .

Detailed Description of the Invention

As one can see from the drawings attached, Figure 1 represents the hydrogen flowfield side of a bipolar diffusion plate 1 , with 17mm x 42mm, where highlighted channels 3 are for hydrogen diffusion. On said Figure 1 , references 2 and 4 represent the hydrogen' s circuit connections to the following Individual Cell . This portion' s depth/ and of the surrounding area, is 1 mm, as to facilitate the flow between the plates . Also visible are the channel 3 from the hydrogen circuit , whose depth is less than lmm ( 0 , 6mm at the Figure) , and its width is lmm, for an optimized proportion between contact area and the active area .

On Figure 2 we see the gas diffusion plate 1 , from the air side , with 17mm x 42 mm, the air diffusion channels 5 , with a lmm width . The intercrossing of these channels will allow an improved diffusion of the vented air, while still maintaining a good proportion between contact area and the active area .

Figure 3 presents all the components of an Individual Cell :

- Structural plates 6 ;

- Current collection plates 7 ;

- Gas diffusion plates 1 with air diffusion channels 5 ;

- Polymeric cationic exchange membrane 8 ; - Sealing adhesives 9 ;

- Carbon paper 10 ;

- Sealing adhesives 11 ;

- Hydrogen circuit ' s terminal connections 12.

Figure 4 presents a hydrogen- fuel cell with five integrated Individual Cells , where the following specifications are to be noticed :

- Gas diffusion plates 1 , with air diffusion channels 5 ;

- Holes 13 for the blower' s application; - Current collection plates 7 ;

- Structural plates 6 ;

- Hydrogen circuit ' s terminal connections 14.

System' s description

The present fuel cell is characterized by : Gas diffusion plate 1 , with the hydrogen side making, together with the Membrane electrode assembly 8 , a tight chamber who allows the operation under a dead-ended configuration;

- Gas diffusion plate 1 , with the air side having the supply channels 5 forming an intertwined network allowing for a natural air feeding; - Use of a blower (not in the Figure) applied axially to the cell or stack enhancing the air supply according to the operations ' requirements .

The air supply system performs simultaneously three functions all crucial to the stacks fine performance :

- Oxygen supply, oxygen being a primary reagent of the electrochemical reaction;

- Membrane cooling;

- Extraction of water formed on the air side .

The system being presented allows for a permanent humidification of the membranes 8 , dispensing with the usual previous humidification of the hydrogen, all because of the pronounced osmosis effect on said membranes . An excess water formation can sometimes happen, easily manageable by a periodic purge to the outside of the stack .

The drawing of the hydrogen diffusion channels 3 follows a principle of maximization of the reactional area relative to the plates ' total area ( 65%) , maximization accomplished by the perpendicular communication between channels (because the supply is dead-ended, the hydrogen flow within the plate is made into all directions) and by determining the distance between channels at 1 millimetre . This maximization was accomplished without interfering with the current collection . The depth of the hydrogen channels which seems to provide the best results is between 0 , 5 and 1 , 5 millimetres , perfectly in tune with the cells ' operation pressures . However, it is possible to draw hydrogen distribution channels with other depths .

The width of plate 1 , which corresponds to the length 'of the air diffusion channel 5 , is determined depending on the power and of the static pressure of the blower used . The goal is to limit the pressure fall through the channel 5 to values under the blower' s static pressure .

In this system, where one wants to minimize the blower' s power (namely in small power applications where there is small power available for auxiliary systems) , such goal translates into rectangular plates where their width is several times smaller than their length . This system allows for the fuel cell stack to operate :

Without the complexity brought by the auxiliary systems and typical of the fuel cells marketed today (temperature management , water extraction management , hydrogen humidification management and oxygen supply management) ;

- With the energy cost reduced to the blower' s feed, allowing for a balance-of-plant energy costs under 5% .

Independent tests presented results of around 300 mW . cm^"2 (with peak power around 420 mW . cm^"2) with the hydrogen being supplied at pressures onto ΞOOmBar, and at temperatures around 30 °C, because of the efficiency of the referred ventilation system.

From this concept , we forecast a strengthening of the viability of portable and small traction systems , without the need for complex auxiliary systems nor large hard-to-manage energy costs , with greater efficiencies than comparable systems , as for example the Direct Methanol ones .

At this stack concept , bipolar diffusion plates 1 are used where on one side hydrogen supply channels 3 are drawn and on the other side axial air channels 5 are drawn .

The polymeric membrane MEA 8 forms a j oined set with the bipolar plate on the hydrogen side by the use of adhesive materials 9 , while the materials used on the air side are non-adhesive .

This concept allows for the stack' s easy disassembly for the eventual substitution of any cell without damaging the rest of the stack .

The hydrogen supply is made through a single circuit traversing all cells , which means the fuel reaches one cell after travelling through all previous cells (accumulating some moisture from cell to cell , improving the fuel ' s ability to reach the reactional points) . As the hydrogen supply is dead-ended (instead of being in a regular flow) the main goal changes from the hydrogen' s carriage at the surface of the membrane to its reposition as it is being spent , goal easily obtained by a homogeneous hydrogen distribution throughout all plates and through the entire surface of each plate .

When the hydrogen supply circuit has two extremities , as to make a purge of the water excess , the hydrogen supply can be made alternately between the two ends ; this rotation will allow a greater fuel homogenization and humidification, overcoming the traditional poorer performance of the cells closer to the fuel entry.

One other point to mention is that this system has a combined strategy of periodic purges of the hydrogen supply circuit and of microscopic cuts of the connection to the load as a way to ensure the stabilization of the voltage over time . These purges can be made simply by drastically reducing the pressure on one pf the supply circuit ' s ends , leading to the expansion, on the microscopic level , of the water condensed on the membranes ' surface .

Comparison between traditional systems and the system being described

Traditional systems usually need pressurized gas operation, with both hydrogen and oxygen being supplied usually between 1 , 5 and 2 , 5 Bar above atmospheric pressure for better results ; with the system being described, the best results are obtained with low pressures , the hydrogen being supplied at values typically under 0 , 5 Bar and with the air being supplied at the atmospheric pressure , making the system more reliable , more functional and simpler .

On another hand, traditional stacks have their flowfield channels without any contact with the atmosphere ; the system being described has its hydrogen channels tightly sealed, but its air channels are directly in touch with the atmospheric air, allowing for an improved temperature homogenization within the cell , an improved water removal on the air side and an oxygen supply which is quicker and simpler . Traditional stacks usually need both hydrogen and oxygen humidification and heating before being supplied to the stack, involving greater volumes , costs and energy loads . The system being described does not need any pre- treatment of the gases : the hydrogen enters the stack dry and the stack itself humidifies the hydrogen while heating it , while the air enters the cathodes of the stack coming directly from the atmosphere .

The hydrogen supply on traditional stacks is fixed, meaning it always enters through the same orifice and always exits through another . In the system being described, the entry and exit points change periodically as to homogenise the moisture within the hydrogen chamber .

All other traditional systems use compressor for the air supply, while the system being described uses low- power, high performance blowers who allow for the air supply to be made without involving considerable pressures nor great energy consumptions .

Considering the system' s power density, the only stacks which may eventually compete with the system being described are Direct Methanol ones ; however, considering the membrane poisoning issues Direct Methanol stacks present , these have to have their fuel supply channels with a greater surface area, implying a greater volume for the same amount of energy produced . Note also that the typical power density of a Direct Methanol stack is quite smaller (around 0 , lW/cm²) than the system now being described energy density ( 0 , 3 - 0 , 4 W/cra²) .

Traditional auxiliary, or peripheral , systems show an energy consumption between 15% and 50% of the stack' s total produced energy; the system being described will involve a value under 5% of the total energy being produced by the stack .

Furthermore , the temperature reached by the units being tested with the ventilation system being described does not exceed 40 ° Celsius , meaning its operation does not involve any potential risks or setbacks (many hydrogen stacks reach much higher temperatures , around 80- 90 ° C, involving a more delicate handling) .

The invention being described allows superior performances than the ones obtained with other hydrogen- cell stacks , or than the ones obtained with conventional systems such as battery packs , on the power range between 5 and 500 Watt , making the system particularly fit for its integration into portable or mobile electrical power sources .

Prefered embodiments

At the system being described, each cell includes (Fig . 3 ) : - One plate 1 made from copper, graphite or other electrically conductive material , with the gas diffusion channels drawn on its surface ;

- An adhesive sealing 9 ; - A Torey carbon paper, or carbon cloth, 10 ;

- A polymeric cationic exchange membrane 8

- One other adhesive sealing;

- One piece of non-adhesive sealing;

- One other Torey carbon paper, or carbon cloth, 10 ; - One plate 1 made from metal or any bonding polymer that is an easy gas diffuser electrically conductive material , made in such a way that one of its sides has a hydrogen diffusion flowfield and the other has an air diffusion flowfield; the plate from Fig . 1 shows quite visibly these hydrogen diffusion channels 3 , while Fig . 2 shows the same plates opposite side with the air diffusion channels 5.

On the plate ' s hydrogen side , an adhesive sealing piece 9 , easily commercially available , will be affixed; this sealing constitutes a frame , or window, for the remaining central components of the Individual Cell (Fig .

3 ) to be affixed, allowing for the hydrogen diffusion chamber to be completely tight ; this piece , 9 and 11 of Fig . 3 , can be cut with an adequate cutting tool to whatever shape desired .

The carbon paper, 10 at Fig . 3 , used can also be easily acquired at any specialist manufacturer, being cut with a simple cutting tool to the framing shape defined by the sealing piece .

Similarly, the polymeric cationic exchange membrane (8 at Fig . 3 ) is also cut in the shape defined by the sealing piece .

To the previous set we add one other previously cut sealing piece , added in such a way the sealing material faces the membrane , and the outskirts of this membrane are completely surrounded by the sealing pieces .

On this manufacturing stage , a non-adhesive piece is applied to the outer side of the sealing, to prevent the previous adhesive sealing to touch the air side of the following plate .

At last , one other carbon paper piece is applied inside the window, or frame, composing an assembly we shall call "Individual Cell" , "IC" , here from.

With the juxtaposition of Individual Cells we form stacks (Fig . 4 ) guided by screws . On the air side an elastic polymer is applied near the hydrogen' s passageway to ensure the set becomes entirely leak-proof .

Figure 4 shows a hydrogen-cell stack composed by 5 ICs , each with 3 , 8 square centimetres of active area, allowing an approximate 1OW output , of which between 0 , 4 and IW will be to feed the auxiliary systems . This stack is composed by two structural plates 6 , two golden copper electricity collectors 7 and by two electrically insulated screws . Structural plates 6 show two holes 13 at which the driving screws pass through, one other central hole with a M5 inward spiral and a 2 millimetre hole for the hydrogen entry . There is also a special channel on these plates , with a width of two millimetres and a depth of three millimetres linking the previous hole to the central M5 hole , so the hydrogen supply is made through the central hole .

At last , the system being described can obtain maximized results by the use of microscopic interruptions (well below one second) of the connection to the load as to stabilize the voltage ; this is particularly useful when the system is not directly connected to the final application but instead is part of an hybrid system, which can act as a single system where the battery supplies enough power to hold the final applications ' consumption peaks while the fuel cell supplies the energy which will allow for an enlarged autonomy of the system.

While the invention has been disclosed with respect to a limited number of embodiments , those skilled in the art , having the benefit of this disclosure , will appreciate numerous modifications and variations there from. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of the invention .

Claims

1. A hydrogen fuel cell stack in which the electrolyte is in a solid condition and it consists in a polymeric membrane that allows the cationic exchange but not the electronic exchange , for the production of electricity, only with the supply of hydrogen and air, in which at the anodes happens the dissociation of the hydrogen in protons and electrons , in the membranes the conduction of the protons onto the cathodes , on an external circuit the electronic conduction from the anodes to the cathodes , and in the cathodes the recombination of protons , electrons and oxygen atoms into water molecules , characterized by comprehending : A bipolar diffusion plate 1 at which : in one of the sides , channels 3 and 4 are drawn specifically for the hydrogen diffusion, and these channels constitute , together with the polymeric membrane , a hydrogen-tight chamber which allows the operation under a dead-ended concept , with a fixed pressure and without recirculation of the fuel ; and, in the other side , axial channels 5 are drawn to allow the natural circulation of the air, channels that form an intertwined grid which allows a natural air supply over the cells ' entire surface ; a blower, applied axially over the cell or stack, reinforcing the air flow according to the operations ' requirements .

2. A hydrogen fuel cell stack, according to claim 1 , characterized by the cathode sides of the several polymeric membranes being in direct contact with the atmospheric oxygen, forced to that contact by an air supply system (blower) , positioned axially to the stack, forcing the air through the channels 5.

3. A Hydrogen fuel cell stack, according to claims 1 and 2 , is characterized by the air supply system having the following functions :

Supply of oxygen, primary reagent of the electrochemical reaction for electricity production; - Membrane cooling;

Extraction of the excess water appearing on the air side .

4. A hydrogen fuel cell stack, according to claim 1 , characterized by the channels 3 , for hydrogen diffusion, having to obey to a maximization principle of the reactional area regarding the total area of the plate (at least 65%) , maximization reached through the transversal communication between channels , considering that the supply is dead-ended, that the gas flow inside the plate operates in all directions simultaneously and that the distance between channels should be of 1 millimetre .

5. A hydrogen fuel cell stack, according to claim 4 , characterized by the said channels having depths between

0 , 5 e 1 , 5 millimetres .

6. A hydrogen fuel cell stack, according to claim 1 , characterized for the permanent humidification of the membranes , dispensing with any previous humidification of the hydrogen, due to the pronounced osmosis effect that happens at the membranes during the electrochemical reaction .

7. A hydrogen fuel cell stack, according to claim 1 , characterized for periodic purges to the stack' s exterior to eliminate water that eventually forms on the anode side .

8. A hydrogen fuel cell stack, according to the previous claims , characterized by the said plates having a rectangular format with its length being bigger than its width, and with the width matching to the length of the air flow channels , being this distance determined so that the pressure loss on the airflow channels is smaller than the static pressure of the blower used, blower with a power that has to be smaller than a tenth of the power produce by the stack.

9. A hydrogen fuel cells stack, according to claim 1 , characterized by the said channels of the air side having a width of 1 millimetre .

10. A hydrogen fuel cell stack, according to claim 9 , characterized by the said channels constituting a sideward, or perpendicularly, interrupted net that allows the optimization of the contact area between the air and the membrane , facilitating a homogenous distribution of the gas at the whole length of the plate .

11. A hydrogen fuel cell stack, according with claim 1 , characterized by the hydrogen flow network having only one extremity, only in the first cell , where the fuel enters , supplying the other cells by a serpentine flow exiting the first cell .

12. A hydrogen fuel cell stack, according to claim 1 , characterized by the hydrogen flow network having two extremities , one where the hydrogen enters and another, in the most distant cell from the one where the hydrogen enters , through which a periodic purge , to extract the water excess eventually accumulated on the side of the anode , is made .

13. A hydrogen fuel cell stack, according with to claim 12 , characterized by the purge being made by a simple pressure drop on one of the extremities of the supply circuit , leading to the expansion, at the microscopic level , of the water condensed at the surface of the membranes .

14. A hydrogen fuel cell stack, according to claim 12 , characterized by the said extremities functioning alternately and periodically as hydrogen entry and as purge, leading to a bigger homogenization and humidification of the fuel inside the stack .

15. A hydrogen fuel cell stack, according to the previous claims , characterized by the existence of microscopic cuts of the connection to the load, as to ensure the voltage stabilization .

16. A hydrogen fuel cell stack, according to the previous claims , characterized by the manufacturing of j oined sets membrane/electrodes/diffusion plates being made through the use of adhesive materials between the hydrogen side of the diffusion plate and the membrane/electrodes set and through the use of non-adhesive materials between the membrane/electrodes set and the air side of the diffusion plate, allowing a simplified disassembly of the stack for maintenance effects and the quick replacement of any set that eventually shows evidence of damages or need for maintenance .