WO2022191807A1

WO2022191807A1 - Fuel cell having intermediate reservoirs, multi-point feed, and secondary liquid discharge passages

Info

Publication number: WO2022191807A1
Application number: PCT/TR2022/050230
Authority: WO
Inventors: İrfan Karagöz; Erman ÇELİK
Original assignee: Karagoez Irfan; Celik Erman
Priority date: 2021-03-12
Filing date: 2022-03-11
Publication date: 2022-09-15
Also published as: TR202104685A2

Abstract

The invention is related to a bipolar plate (1) with an inlet manifold (2) by which the reactants are distributed to the flow channels (3), flow channels (3) and an outlet manifold (8) that allows the unused reactant and reaction output products to be carried out of the bipolar plate (1) comprising at least one intermediate reservoir (5), which provides pressure equalization by bringing together the flow channels (3) and collects liquid water in it, and includes intermediate feed/discharge ports; plate back feed/discharge holes (4) behind the plate (1), which ensures the transport of fresh reactant from the outside into the intermediate reservoir (5) and ensures that the water in the intermediate reservoir (5) is discharged, and also provides the connection between the inside and outside of the bipolar plate (1); a secondary channel (6) that allows material to pass between the intermediate reservoir (5) and an edge feed/discharge manifold (9).

Description

Fuel Cell Having Intermediate Reservoirs, Multi-Point Feed, and Secondary Liquid Discharge

Passages

FIELD OF THE INVENTION

The invention relates to a bipolar plate with a new channel system that distributes the reactant fluids more efficiently and ensures efficient discharge of excess reaction products in different types of fuel cells that generate electricity from reactants such as hydrogen and methanol by electrochemical methods.

BACKGROUND OF THE INVENTION

The fact that the only energy needed by humanity is met from fossil fuels, that fossil fuels cause environmental pollution and that fossil energy sources are rapidly depleting have led human beings to seek new energy sources. Hydrogen has the simplest atomic structure in nature and the highest energy content per weight of all conventional fuels. The need for alternative energy, which is rapidly spreading in the industrial sector, has led scientists to renewable energy sources and in addition, has led to the development of fuel cells. Fuel cells are devices in which energy is produced as a result of the electrochemical reaction of hydrogen which, obtained with the help of a fuel converter from alternative sources such as chemical products such as ammonia, methanol, biogas and waste materials, as well as fossil fuels such as coal, oil, natural gas refinery products or directly obtained by electrolysis, with oxygen. Fuel cells have advantages such as not causing environmental and noise pollution, not containing moving parts, and obtaining higher conversion rates from fossil fuels. Fuel cell systems have an efficiency of approximately 40-60%, depending on the type of fuel cell, and the total efficiency increases up to 80% in cases where the heat released is evaluated.

One of the most frequently used fuel cells is Proton Exchange Membrane (PEM) fuel cells. As electrochemical steps in a typical PEM fuel cell; on the anode side hydrogen molecules entering the system turns into electrons and protons by releasing the electrons. The resulting protons pass through the proton exchange membrane to the cathode side, and the electrons reach the cathode through the circuit. Finally, the oxygen atoms fed on the cathode side combine with the positive charged hydrogen atoms coming through the membrane and the electrons coming from the circuit to produce electric current, water and heat. Although the general state of the occurring electrochemical reaction is expressed as in equation 1.1, the total reaction consists of sub-reactions of oxidation or oxidation of hydrogen given in equation 1.2 on the anode side and reduction of oxygen given in equation 1.3 on the cathode side.

H2+½ 02 H2O + ISI (1.1)

H2®2H++2e- (1.2)

½ 02 + 2H++2e- ® H20 (1.3)

In a conventional fuel cell, there are bipolar plates (BPP) on the anode and cathode sides that house the gas flow channels. After the gas flow channels on the BPP, there are gas diffusion layers (GDT) placed on both sides, a polymer-based proton exchange membrane in the middle, and platinum-based Catalyst Layers (KT) positioned between the membrane and GDT on both sides.

Each component that constituting the PEM fuel cell is responsible for performing functions such as providing the best water and heat management while determining the performance and durability of the fuel cell, as well as providing a good reactant distribution throughout the electrochemically active area. Flow field design in BPP has effects on reactant distribution as well as water and heat management and it is an important parameter that also determines the total weight of the fuel cell stack. In addition, flow fields are effective in cell voltage stability depending on the cell operating characteristics.

Bipolar plates host flow fields, or flow channels, or flow patterns with its alternative names. The parallel flow field consists of straight channels, whose inlet ends are connected to the main distributor manifold, and outlet ends are connected to a collector manifold and arranged parallel to each other between these two manifolds. Despite some disadvantages of this flow field type; It is the flow field that offers reactant flow with the lowest pressure loss. Since the fluids tend to flow from the path with lower resistance to flow, in the parallel flow field the reactants tend to flow in parallel channels connected to the end of the main distributor manifold close to the inlet port thus low flow rate is observed in the channels opposite the inlet end of the distributor manifold. As a result of this flow field architecture, the concentration differences between the channels create a distribution with exaggerated high and low reactant partial pressure in the reactive area as well. Unstable temperature zones are formed on the membrane due to different reaction rates as a result of the uneven distribution of the reactants along the active surface. If water droplets form in the channel, parallel channels are insufficient to discharge the formed water out of the cell. The tendency of the reactants flow in the open channel instead of the clogged channels also leads to concentration imbalances. The low pressure losses in batteries with parallel flow fields cause the reactants to tend to flow parallel to the cell layers instead of being forced towards the chemically active catalyst layer, resulting in concentration losses and low current densities in the battery.

The serpentine flow field can basically be defined as the flow field formed by a single channel starting from the inlet manifold and sweeping the bipolar plate (BPP) to form parallel channels by making turns. The serpentine flow field emerges as an efficient design for water discharge from the battery to the outside. However, there is a significant difference in reactant concentration from inlet to outlet. Due to the concentration difference, different reaction rates occur along the active surface and the formation of different temperature zones in the membrane is frequently observed. In order to prevent hot spot formation that causes permanent damage to the membrane in the future; In many serpentine flow applications, the method of cross-linking the inlets and outlets on the anode and cathode side and sending the hydrogen on the anode side and oxygen on the cathode side into the system is applied. In this way, more stable reaction rates are obtained on the surface and it is protected from the formation of an extremely hot zone. In case the plate size is too large, serpentine flow fields with more than one channel can be used to balance the concentration and pressure difference in the channel between the inlet and the outlet.

The pin type flow field is generally defined as the flow field formed by the spaces between the square or circular pins arranged in a sequential or deflected order on the BPP. Although the pin type flow field is another low loss flow field in case of droplet formation, as in the parallel flow field, reactants choosing the low resistance direction have the potential to form regions of disordered reaction and temperature. Another disadvantageous aspect of the pin type flow field is that when high gas flow rates are reached in the battery, regions where the flow turns in to eddy motion behind the pins and concentration losses is observed in these flow regions due to concentration losses.

Many flow field architectures are designed in such a way that the fluid enters into the inlet of the channel or channels, travels the length of the channel from one end to the other and leaves the cell at the outlet end. In the interdigitated flow field, there is no channel structure directly connecting the inlet and outlet manifolds on the BPP. In the interdigitated flow field, the reactants basically diffuse through the gas diffusion layer (GDT) after entering closed channels connected to the inlet manifold. The reactants diffusing in the GDT reach the outlet by passing through the channels with one end closed and the other ends connected to the outlet manifold, similar to the channels connected to the inlet manifold. Due to the flow field architecture, the reactants that cannot reach the outlet by traveling parallel to the membrane and GDT layers in closed channels; they are forced in the normal direction of the layers, and thus, the diffusion effects that will support the efficiency of the reactants reaching the catalyst layer (KT) layer are strengthened. The convection effects that strengthen the reactant diffusion also function as supporting the active transport of the water from the porous layer to the channel. On the other hand, since the passage of gases from the channels connected to the inlet manifold to the channels connected to the outlet manifold is only possible through the porous GDT; The reactants suffer significant pressure loss in the porous layer and the need for pumping load arises, creating parasitic power consumption.

In order to overcome the problems faced with standard flow fields, inclined bipolar plate designs have been made to limit the channel volume by decreasing the channel depth from the inlet to the outlet in order to increase the battery performance by keeping the reactant partial pressure constant in some flow fields and to provide active water discharge. However, this design method causes the entire channel section to be filled with liquid water in the regions close to the outlet, due to the narrowing channel section. It has the potential to cause severe concentration losses in areas filled with liquid water. In order to actively push the reactant gases through the channels into the porous layer and from there to the catalyst layer, thus increasing the fuel cell performance; placing blocking or guiding elements in channels is one of the methods encountered in applications. However, these methods have the potential to cause high pressure losses between the beginning and the end of the flow length and prevent the water formed in the channel from being discharged out of the channel without spreading to the porous layer. In order to ensure that the reactants are distributed homogeneously throughout the plate, in practice, the channel structure formed by the spaces between the obstacles arranged radially in a circular-section cavity and the flow areas that allow the fluid flowing between these spaces to be collected and redistributed in the middle of the circle are seen. In these designs, since the fluids will tend to flow from the section where they encounter the least flow resistance, there is a potential for the reactant partial pressures to decrease as the reactants prefer the flow paths in the region close to the center of the circle and cause concentration losses as they move away from the center towards the edges.

An example of these is patent application US7524575 B2. This document describes the flow field plate for use in fuel cells. In this plate, there are small pools that periodically bring together the multiple serpentine flow channels, consisting of many channels running parallel to each other, and then allow the reactants to be redistributed. However, in this invention, which is the subject of this patent, while the pools balance the concentration difference between the channels; Since it has a single inlet and an outlet port far from each other, it is insufficient to prevent the formation of a high-speed reaction zone and a low-speed reaction zone between the inlet and outlet. Since the concentration is still high in the regions close to the entrance, the reaction takes place at a higher rate than desired in these regions and the reactants are consumed rapidly. For this reason, areas with higher temperatures are formed in the regions close to the entrance compared to other regions. It is aimed to keep the partial pressures higher by compressing the reactants into a smaller volume by reducing the number of channels after the pools connecting the channels in order to keep the decreasing reactants at higher pressure as they approach the exit. Although this method is partially successful in keeping the pressure in the channel high and directing the reactants into the gas diffusion layer more effectively; since the reactants dispersed from the channel to the gas diffusion layer will spread over a large volume, their pressure in the region where they will react will decrease again. For this reason, it is not possible to distribute the reactants at a homogeneous flow rate over the entire surface area by using such a design. Another document belonging to the state of the art is the patent numbered US6099984 A. This document describes mirrored serpentine flow channels for a fuel cell designed to reduce the pressure and concentration difference between inlet and outlet in a single channel serpentine flow field. In this flow field, each serpentine channels start from the same distributor at the inlet and are connected to a single collector at the outlet after making two or three u turns without crossing along whole bipolar plate surface from one end to the other. Thus, it is aimed to reduce the local losses that the reactants are exposed to by keeping the flow length short. However, in the present invention, if one of the channels is clogged with liquid water, since the reactants will flow through other channels with low flow resistance, concentration losses will occur as the reactant reaches some regions, as the reactant does not reach these regions under the clogged channels. In the patent numbered US 8029942 B2, adjacent duct systems with different pressures and reactant flow rates used to discharge the liquid water formed in the cell were designed. Liquid water accumulating in the channels passes into the high-speed channel and is discharged from there. There are multiple inputs and outputs in this system. However, although there is more than one entrance, all of the entries are at the same level. There is no additional entry from an intermediate point between the inlet and outlet along the flow length. This invention also prone to fail on providing homogeneous reactant distribution across the surface. In the patent numbered US 8715871 B2, a bipolar plate is described by combining a certain number of thin layers with a random mesh structure and high water absorbency for passively evacuating the liquid water droplets formed on the catalyst layer. It is aimed to absorb the water formed in the catalyst layer into the porous volume obtained by superimposing the patterns made of hydrophilic material, and thus to keep the water away from the active catalyst surface. In the invention US 8715871 B2 35, a porous medium is described. This, in case of prolonged liquid water flow, causes a large part of the pores to be filled with water and a structure that is suitable to prevent the access of the reactants to the active surface. As a result, the invention has the potential to fail to provide homogeneous reactant distribution in the case of a severe liquid water flooding.

As a result, due to the above-mentioned disadvantages and the inadequacy of the existing solutions on the subject, it was necessary to develop a bipolar plate.

SUMMARY OF THE INVENTION

The present invention relates to a bipolar plate that meets the above-mentioned requirements, eliminates all the disadvantages and brings some additional advantages.

The primary aim of the invention is to distribute the reactants entering the cell homogeneously over the entire cell active surface area thanks to the developed bipolar plate thus providing efficient use of reactants and high power output.

An aim of the invention is to ensure that the liquid water or excess reaction is discharged through the openings in its structure that serve to feed the reactant from the outside of the cell, and to keep the reactant partial pressures, which decrease due to the consumption of the reactants, constant throughout the flow by ejecting them.

Another aim of the invention is to provide homogeneous reactant distribution thanks to the different number of intermediate feeding points in the section or sections of different lengths of the channel length from the inlet to the outlet in its structure.

In order to fulfill the above-described purposes, the subject of the invention is; a bipolar plate with an inlet manifold on which the reactants are distributed into the channels, flow channels, and an outlet manifold that allows the unused reactant and reaction output products to be carried out of the plate; establishing a connection between the inside and outside of the bipolar plate, which provides pressure balancing by bringing together the flow channels and collects the liquid water in it, contains at least one intermediate reservoir, which includes intermediate feed/discharge ports, ensures the transport of fresh reactant from the outside into the intermediate reservoir, and discharges the water in the intermediate reservoir. The back of the plate contains the feed/discharge holes and a secondary channel that provides the passage of material between the intermediate reservoir and a side feed/discharge manifold.

The structural and characteristic features of the invention and all its advantages will be understood more clearly thanks to the detailed explanation written below, and therefore the evaluation should be made by taking this detailed explanation into consideration.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1. Front view of the plate back feed/discharge type flow field with intermediate reservoir

Figure 2. Perspective and detailed view of the plate back feed/discharge type flow field with intermediate reservoir.

Figure 3. Back view of the plate back feed/discharge type flow field with intermediate reservoir

Figure 4. Plate edge feed/discharge type flow field solid model with intermediate reservoir

Figure 5. Plate edge concealed feed/discharge type flow field solid model with intermediate reservoir

Figure 6. Plate edge concealed feed/discharge type flow field solid model front view with intermediate reservoir

Figure 7. Plate edge concealed feed/discharge type flow field solid model perspective view with intermediate reservoir

Figure 8. Plate edge concealed feed/discharge type intermediate reservoir flow field secondary channel cover layout detail view

Figure 9. Detail view of the plate edge concealed feed/discharge type flow field with intermediate reservoir before placing the secondary channel cover

Description of References

1 Bipolar plate

2 Inlet manifold

3 Flow channels

4 Plate back feed/discharge holes

5 Intermediate reservoir

6 Secondary channel

7 Alignment pin slots

8 Outlet manifold

9 Edge feed/discharge manifold

10 Secondary channel cover DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In this detailed description, the bipolar plate (1), which is the subject of the invention, is explained only for a better understanding of the subject and without any limiting effect.

In its most basic form, the bipolar plate with an inlet manifold (2), flow channels (3) (preferably 4 units) that provides the distribution of the reactants to the channels, and an outlet manifold (8) that allows the unused reactant and reaction output products to be transported out of the plate, which is the subject of the invention, comprises at least one intermediate reservoir (5) comprising intermediate feed/discharge ports that bring together the flow channels (3) to provide pressure equalization and accumulate liquid water in it; the plate back feed/discharge holes (4) behind the bipolar plate (1), which ensures the transport of fresh reactant from the outside into the intermediate reservoir (5) and allows the water in the intermediate reservoir (5) to be discharged and to establish a connection between the inside and outside of the bipolar plate (1); a secondary channel (6) that provides the passage of material between the intermediate reservoir (5) and an edge feed/discharge manifold (9).

In a preferred embodiment of the invention, the bipolar plate (1) includes alignment pin slots (7) that enable the bipolar plates (1) to align with each other and with the support plate when they are lined up one after the other. When the bipolar plates (1) are arranged one after the other, channels are formed through which gas passage is provided through the inlet manifold (2), the outlet manifold (8) and the edge feed/discharge manifolds (9). The bipolar plate (1) preferably includes a secondary channel cover (10) that covers the secondary channel (6). Secondary channel cover (10) is an additional plate section that closes the secondary channels (6) and creates a hidden channel between the secondary channel base and itself, while ensuring that the upper surface of the secondary channels is flat.

Bipolar plate (1) is an electrically conductive plate piece made of sheet metal or carbon composite material, which includes flow channels (3), intermediate reservoirs (5), secondary channels (6) and inlet manifold (2) and outlet manifold (8). Said inlet manifold (2) is a hollow-shaped plate section that forms a distribution line on the plate edge by arranging more than one plate in a row. Flow channels (3) are recesses engraved on the bipolar plate (1) or obtained by plastic forming methods. The edge feed/discharge manifold (9) is the groove on the plate edge, which provides the connection between the intermediate reservoirs (5) and the external environment through secondary channels, and forms a secondary channel line on the plate edge when cascaded.

In the invention, an intermediate-feeding flow field is formed and this flow field has a reservoir that effectively collects the excess of the water formed as the reaction product and sent for humidification of the reactants and the water produced as the reaction product, and a secondary discharge and feeding channel that connects this reservoir with the external environment. In this way, while allowing the water accumulated inside to be thrown out; It is also possible to send additional reactant inside the channel to compensate for the pressure and concentration losses experienced due to flow losses and consumption of the reactant in the channel. Due to the fact that the flow area has intermediate feeding points, the reactant concentration losses from the inlet to the exit are compensated and the concentration is kept homogeneous everywhere. Thus, by providing a balanced reaction rate distribution; the overall cell performance is increased by ensuring that the reaction heat is also distributed evenly. For this purpose, intermediate reservoirs (5) are located in certain regions on the flow channels (3). There are plate back feed/discharge holes (4) behind thebipolar plate (1) on which additional reactant will be fed to the system on the intermediate reservoirs. Feeding the total amount of reactant planned to be sent to the cell from a single inlet causes a high pressure center in the area close to the inlet manifold (2). As the reactants are consumed along the flow length, the in-channel reactant pressure decreases towards the outlet. Decreasing reactant pressure causes the loss of the driving force required to drive the water molecules that may occur in the channel out of the channel in addition to creating concentration losses. Thanks to the plate back feed/discharge holes (4) behind the bipolar plate (1), which is opened into the intermediate reservoirs (5), the reactant is fed to the channels at different rates at different flow lengths.

It is aimed to collect water in the intermediate reservoirs (5) and to discharge the accumulated water. Intermediate reservoirs (5) can preferably be connected to the edge feed/discharge manifold (9) via secondary channels (6), as well as preferably intermediate reservoirs (5) can be directly connected to the back of the bipolar plate (1). In the case where the intermediate reservoirs (5) are connected with the edge feed/discharge manifold (9), feeding/discharging is provided from the edge of the bipolar plate (1). In cases where the intermediate reservoirs (5) are directly connected to the back of the bipolar plate (1), feeding/discharging takes place behind the bipolar plate (1). In Figure 1, the front view of the plate back feed/discharge type intermediate reservoir flow field, in Figure 2 the perspective and detail view of the plate back feed/discharge type intermediate reservoir flow field, and in Figure 3 rear view of the plate back feed/discharge type intermediate reservoir flow field is given. Plate edge feed/discharge type flow field solid model is given in Figure 4. Plate edge concealed feed/discharge type flow field solid model is given in Figure 5. Plate edge concealed feed/discharge type flow field front view is given in Figure 6. In Figure 7 perspective view of plate edge concealed feed/discharge type flow field is given. Detail view of secondary channel cover positioning on plate edge concealed feed/discharge type flow field is represented in Figure 8. Figure 9 represents the detail view of the plate edge concealed feed/discharge type flow field with intermediate reservoir secondary channel before placing the cover.

The holes used to feed additional reactants to the intermediate reservoirs (5) or to discharge excess water from the intermediate reservoir (5) can be opened directly from the rear surface of the bipolar plate (1) to reach the front surface of the bipolar plate (1). There is also a secondary channel (6) that extends from the intermediate reservoir (5) to the side feed/discharge line on the side of the bipolar plate (1) or provides the transport of reactant to the intermediate reservoir (5) from the edge feed/discharge manifold (9) on the side of the bipolar plate (1). In this way, instead of giving all of the reactants to the cell from the main entrance; the total reactant flow is divided at certain rates and sent to the system from the intermediate reservoir (5) regions, which can be designed in different locations and numbers, and the reactants are evenly distributed to the system along the flow length. The ratio of the channel width to the depth can be different values depending on the need. In addition, the width of the ribs between the channels can be different from the channel width. The system preferably includes 4 flow channels (3). The reason why the number of flow channels (3) is chosen as four is to perform its function with a lower pressure loss during the application of the relevant flow field to batteries with large active surface area. In the design with two separate intermediate feeding ports in addition to the inlet manifold (2), the ratio of reactant to be fed from the main inlet and intermediate feed ports can be determined according to the need.

Plate edge feed/discharge type intermediate reservoir flow field, which is one of the preferred embodiments of the invention, is used when it is desired to form fuel cell stacks by arranging a large number of plates in order to produce high power cell stacks. Plate edge feed/discharge type intermediate reservoir flow field include edge feed/discharge manifolds (9) thus It can feed or drain water from a common line on the edge of the stack of each bipolar plate without compromising the surface integrity of the active surface area. On the other hand Plate edge feed/discharge type intermediate reservoir flow field includes secondary channels (6) which lays along between edge feed/discharge manifold (9) and intermediate reservoirs (5) ensuring reactant and water transport on both sides. Another preferred type, the plate edge concealed supply/discharge type intermediate reservoir type flow field model includes secondary channel covers (10) which covers the surface of the secondary channels (6) up to the plate back feed/discharge holes (4) behind the bipolar plate (1) and forms a concealed channel between the secondary channel (6) and itself. In this way, the bipolar plate (1) surface is kept flat so that the secondary channel flow is not affected by the porosity of the gas distribution layer. The secondary channel covers (10) form another hidden channel beneath itself covering the secondary channel's (6) open face hiding secondary channel's (6) and running from the intermediate reservoir (5) to the edge feed/discharge manifold (9). In this way, concealed feed/discharge can be made from the edge of the bipolar plate (1) and the surface of the bipolar plate (1) is guaranteed to be planar. There are holes on the said secondary channel cover (10), the shape and number of which can be determined according to need. These holes will narrow the suction section, especially during water discharge, and will allow the gases to flow faster by confining them to a narrower section. In this way, it is ensured that the accumulated water is absorbed more strongly and carried out of the plate.

Traditionally in fuel cells, the reactants enter the cell from the inlet manifold (2), pass through the channels (3), which are constituted on bipolar plates (1) and connected to outlet manifold (8), and they are distributed along the surface then remaining unused reactants are ejected out from the outlet manifold (8). However, during this process, the pressure of the reactants drops excessively from the inlet manifold (2) to the outlet manifold (8). For this reason, intermediate reservoirs (5) are positioned on the bipolar plate (1), which collect the fluids in the flow channels (3) at certain intervals and then distribute them back to the flow channels (3). In the present invention, unlike the bipolar plates with a conventional flow field, the plate back feed/discharge holes (4) are placed directly behind the bipolar plate (1) from the intermediate reservoir (5) section to the outside. In this way, instead of feeding all of the reactants from the inlet manifold (2), the plate back feed/discharge holes (4) behind the bipolar plate (1), which can be designed in different shapes, numbers and sizes, reactants can be sent into the cell from different points by dividing the total reactant flow rate. Thus, the excessive pressure loss met along the whole flow channel (3) length from the inlet manifold (2) to the outlet manifold (8) is eliminated and the reactants are distributed more homogeneously. The plate back feed/discharge holes (4) line behind the plate also ensures that the liquid water accumulated in the intermediate reservoirs (5) is discharged by creating a reverse pressure center.

In conventional fuel cells, multiple bipolar plates are usually used in tandem order to create a stack thus increasing the total cell power. In such a case, feeding the flow channels (3) directly behind the bipolar plate (1) causes technical difficulties. In order to solve this problem, secondary channels (6), which connect the intermediate reservoirs (5) to an edge feed/discharge manifold (9) on the plate edge, are positioned for discharge and feeding operations. The secondary channels (6) face the same surface as the flow channels (3) carrying the reactants and have an open top structure. The edge feed/discharge manifolds (9) can be opened in the desired shape, size and number, and when bipolar plates (1) lined one after another the edge feed/discharge manifolds form a channel from one end to the other carrying the water collected from each plate or the reactants to be fed to each bipolar plate (1).

The secondary channel covers (10) included in the invention support the creation of sufficient pressure difference for the suction of water from the intermediate reservoirs (5). The secondary channel cover (10) forms a hidden channel between itself and the bottom of the secondary channel (6) and completely covers the surface in the intermediate reservoir (5) section forming another hidden channel between itself and the intermediate reservoir (5) floor area. The secondary channel cover (10) contains holes in different numbers, shapes and sizes that provide the connection from surface to the hidden channel below the intermediate reservoir (5). In this way, the required suction force during water discharge is obtained.

Claims

1. A bipolar plate (1) with an inlet manifold (2) that ensures the distribution of the reactants to the channels, flow channels (3) and an outlet manifold (8) that enables the unused reactant and reaction output products to be transported out of the plate which comprises at least one intermediate reservoir (5) comprising intermediate supply/discharge ports, which brings together the flow channels (3), provides pressure equalization and collects liquid water in it; feeding/discharging holes (4) on the back of the bipolar plate (1), which provides connections between the inside and outside of the bipolar plate (1), which ensures the transport of fresh reactant from the outside into the intermediate reservoir (5) and discharges the water in the intermediate reservoir (5); secondary channels (6) that provides the passage of matters between the intermediate reservoir (5) and Edge feed/discharge manifolds (9).

2. A bipolar plate (1) as claimed claim 1 and its feature is that it includes alignment pin slots (7).

3. A bipolar plate (1) as claimed claim 1 and its feature is that it includes a secondary channel cover (10) that covers the secondary channel (6).

4. A bipolar plate (1) as claimed claim 1 and its feature is that it includes plurality of flow channels (3) preferably 4.

5. A bipolar plate (1) as claimed claim 1 and its feature is that the intermediate reservoirs (5) are connected to the edge feed/discharge manifold (9) via secondary channels (6).

6. A bipolar plate (1) as claimed claim 1 and its feature is that the intermediate reservoirs (5) are directly connected to the back of the bipolar plate (1).

7. A bipolar plate (1) as claimed claim 1 and its feature is that the formation of channels through which gas passage is provided through the inlet manifold (2), the outlet manifold (8) and the edge feed/discharge manifold (9) when the bipolar plates (1) are lined up one after the other.

8. A bipolar plate (1) as claimed claim 3 and its feature is that the secondary channel covers (10) form another channel between the secondary channel (6) and the intermediate reservoir (5).

9. A bipolar plate (1) as claimed claim 3 and its feature is the presence of holes on the other channel.