DE102014207594A1 - Bipolar plate for an electrolysis or fuel cell - Google Patents

Abstract

The invention relates to a bipolar plate (10) for an electrolysis or fuel cell with at least one heat pipe (12) formed on and / or in the bipolar plate (10). Likewise, the invention relates to a cooling device for an electrolysis or fuel cell with at least one such bipolar plate (10) and a heat exchanger (24) which is connected to the at least one heat pipe (12) of the at least one bipolar plate (10). Moreover, the invention relates to an electrolysis and / or fuel cell with at least one corresponding bipolar plate (10) or a cooling device equipped therewith. Furthermore, the invention relates to an electrolysis and / or fuel cell with at least one bipolar plate (10), wherein the electrolysis and / or fuel cell additionally comprises at least one heat pipe (12) which is close to the single bipolar plate (10) or at least one of Bipolar plates (10) of the electrolysis or fuel cell is arranged.

Description

The invention relates to a bipolar plate for an electrolysis or a fuel cell. Likewise, the invention relates to a cooling device for an electrolysis or fuel cell. Furthermore, the invention relates to electrolysis and / or fuel cells.

State of the art

Bipolar plates, often referred to as flow field plates or flow-field plates, for use in an electrolysis or fuel cell are known in the art. As a rule, such a bipolar plate has at least one meandering channel formed thereon / a meandering groove through which a gaseous or liquid medium is passed during operation of the electrolysis or fuel cell equipped with the bipolar plate. The gaseous or liquid medium is often an educt of a reaction carried out by means of the electrolysis or fuel cell, which is simultaneously used as the coolant medium. In this way, overheating of the electrolysis or fuel cell should be preventable due to the heat generated during their operation waste heat.

In the DE 10 2012 019 678 A1 a flow field plate for a bipolar plate unit is described, to which both channels for conducting a reactant / reactant and channels for conducting an additionally used coolant are formed. In addition, relief channels are formed in the support walls of the flow field plate, by means of which a tearing of the flow field plate should be prevented at an ice formation.

Disclosure of the invention

The invention provides a bipolar plate for an electrolysis or fuel cell, a cooling device for an electrolysis or fuel cell and an electrolysis and / or fuel cell.

Advantages of the invention

The equipment of the bipolar plate according to the invention with the at least one heat pipe formed on it and / or it allows a more uniform cooling of an electrolysis or fuel cell comprising the bipolar plate than in the prior art. Accordingly, even in the case of the electrolysis or fuel cell according to the invention with at least one heat pipe arranged close to the single bipolar plate or at least one of the bipolar plates, the more uniform cooling of the electrolysis or fuel cell is ensured.

In both cases, the uniform cooling is realized over a total volume of the electrolysis or fuel cell, in particular an entire surface of the bipolar plate. Thus, there are no temperature differences between an input and an output of a flow field of the respective bipolar plate. In this way it can be ensured that the (approximately) the same temperature is present over the entire volume of the respective electrolysis or fuel cell. This also allows a uniform current density over the respective electrolysis or fuel cell. This results in lower degradation rates and longer lifetimes of the respective electrolysis or fuel cell.

The advantages described in the preceding paragraph can be realized without a further cooling element / coolant being used in addition to the heat pipe formed at least on and / or in the bipolar plate or in addition to the heat pipe arranged close to the single bipolar plate / at least one of the bipolar plates. Moreover, when using the bipolar plate according to the invention, it is not necessary to use the at least one educt of a chemical reaction carried out / carried out by means of the electrolysis or fuel cell for cooling the bipolar plate / electrolysis or fuel cell. Since a reactant stream is thus no longer required for cooling, comparatively low volume flows of the at least one educt through the bipolar plate are sufficient. This allows a more compact construction of the bipolar plate according to the invention, since at least one channel / at least one groove, through which the at least one educt current is passed, can be smaller / narrower, or is flow-optimizable. Particularly in the case of electrolysis systems / fuel cell systems which have conventionally required cooling by means of deionized water, the construction of the overall system is also simplified, since substantially less water has to be processed and thus not as many components come into contact with the deionized water. In this case, since the deionized water is often aggressive and constituents sometimes dissolve therein, the danger of a pitting can thus be reliably remedied by means of the present invention.

While conventionally a reduction of the flow rate of the at least one educt used as coolant through the bipolar plate increases a temperature spread (between an input and an output of a channel used to conduct the at least one reactant), this problem is eliminated in the present invention. In the case of the bipolar plate according to the invention, the throughput of the at least one educt current can thus be reduced by a factor of up to one hundred.

For example, the at least one heat pipe comprises at least one heat pipe and / or at least one two-phase thermosyphon. Thus, cost-effective embodiments of the at least one heat pipe can be used, which can be formed in a comparatively simple manner and / or in the bipolar plate. (Also close to the single bipolar plate or at least one of the bipolar plates of the electrolysis and / or fuel cell according to the invention at least one heat pipe and / or at least a two-phase thermosyphon can be arranged as the at least one heat pipe.)

In a preferred embodiment, at least one meander-shaped channel is additionally formed on the bipolar plate, through which at least one gaseous or liquid medium can be conducted. The at least one gaseous or liquid medium may be at least one starting material of a chemical reaction which can be carried out / carried out by means of the electrolysis or fuel cell and / or at least one product of the chemical reaction. The at least one educt and / or the at least one product can thus be easily and reliably introduced and / or led out into the electrolysis or fuel cell. (At least one such meandering channel can also be formed on the single bipolar plate or at least one of the bipolar plates of the electrolysis and / or fuel cell according to the invention.)

Advantageously, the at least one heat pipe (the bipolar plate according to the invention or the electrolysis or fuel cell according to the invention) is filled with at least one refrigerant. The at least one heat pipe (the bipolar plate according to the invention or the electrolysis or fuel cell according to the invention) can be filled, for example, with carbon dioxide, R410a (ASHRAE classification), water and / or alcohol as the at least one refrigerant. Thus, a variety of advantageous refrigerant for cooling the bipolar plate according to the invention and the electrolysis or fuel cell according to the invention can be used.

In an advantageous embodiment, the bipolar plate has an active side, which is aligned after arranging the bipolar plate in the electrolysis or fuel cell to another bipolar plate, and the at least one heat pipe extends perpendicular to the active side through the bipolar plate. This allows a uniform cooling of the bipolar plate, or a so-equipped electrolysis or fuel cell.

In a further advantageous embodiment, the at least one heat pipe extends continuously through the bipolar plate parallel to the active side. Also in this case, the advantageous uniform cooling of the bipolar plate / the electrolysis or fuel cell is ensured by means of at least one heat pipe.

The above listed advantages are also realized in a cooling device for an electrolysis or fuel cell, which comprises at least one corresponding bipolar plate and a heat exchanger, which is connected to the at least one heat pipe of the at least one bipolar plate.

Accordingly, the advantages are also ensured in an electrolysis and / or fuel cell with at least one such bipolar plate or a corresponding cooling device.

Furthermore, the electrolysis and / or fuel cell with at least one bipolar plate and at least one heat pipe, which is arranged close to the single bipolar plate or at least one of the bipolar plates of the electrolysis or fuel cell, also realizes the advantages described above. The electrolysis and / or fuel cell may also have some of the above-described features of the bipolar plate according to the invention.

Brief description of the drawings

Further features and advantages of the present invention will be explained below with reference to the figures. Show it:

1 a schematic representation of an embodiment of the bipolar plate;

2 a schematic representation of the electrolysis or fuel cell.

Embodiments of the invention

1 shows a schematic representation of an embodiment of the bipolar plate.

In the 1 schematically illustrated bipolar plate 10 may also be referred to as a flow field plate or as a flow-field plate. The bipolar plate 10 can be used both in an electrolysis cell and in a fuel cell. In particular, the bipolar plate can 10 in a PEM cell (Proton Exchange Membrane), which is often referred to as a PEM stack (Proton Exchange Membrane Stack), are used. Also for use in other electrochemical devices used as cells for performing a chemical reaction and / or for Power generation are denominated, is the bipolar plate 10 suitable.

On and / or in the bipolar plate 10 is at least one heat pipe 12 educated. (The bipolar plate 10 with the at least one heat pipe 12 thus forms a compact unit.) Under the at least one heat pipe 12 can be understood a heat exchanger, which allows the use of heat of vaporization of a medium / refrigerant, a high heat flux density. Thus, on a comparatively small cross-sectional area of the at least one heat pipe 12 large amounts of heat are transported. For example, the at least one heat pipe 12 comprise at least one heat pipe and / or at least one two-phase thermosyphon. Particularly in the case of the exemplary embodiments enumerated here for the at least one heat pipe 12 the transport of the medium / refrigerant is generally possible without additional mechanical aids, such as a pump (circulating pump). Reliable cooling of the bipolar plate 10 by means of the at least one heat pipe 12 is thus comparatively energy efficient. In addition, when equipped with the bipolar plate 10 with the at least one heat pipe 12 the cost of an associated pump, such as a circulating pump, can be saved.

As a rule, for each bipolar plate 10 an active page 14 definable, which after placing the bipolar plate 10 is aligned in the electrolysis or fuel cell to another bipolar plate and / or a semipermeable membrane. The active side 14 can also be described as a reactant side. (One after placing the bipolar plate 10 In the electrolysis or fuel cell from the further bipolar plate and / or the semipermeable membrane away side is often as a passive side 16 designated.) In the embodiment of the 1 has the bipolar plate 10 several heat pipes 12 on which is parallel to the active side 14 (and parallel to the passive side 16 ) through the bipolar plate 10 extend continuously. Also, provided that at least one heat pipe 12 perpendicular to the active side 14 (and perpendicular to the passive side 16 ) through the bipolar plate 10 extends, is the desired uniform cooling of the bipolar plate 10 possible.

In the 1 shown number of five heat pipes 12 is to be interpreted only as an example. The number of heat pipes 12 the bipolar plate 10 can be easily chosen so that a uniform cooling of the bipolar plate 10 by means of the at least one heat pipe 12 is realized.

Preferably, on the bipolar plate 10 (in addition to the at least one heat pipe 12 ) at least one meandering channel 18 formed, through which at least one gaseous or liquid medium is conductive. The at least one meandering channel 18 may also be referred to as at least one meandering groove. Through the at least one meandering channel 18 (or the at least one meander-shaped groove), at least one starting material of a chemical reaction which can be carried out / carried out by the electrolysis or fuel cell and / or at least one product of the chemical reaction can be transported or discharged as the at least one gaseous or liquid medium. For example, oxygen and / or water as the at least one gaseous or liquid medium through the at least one meandering channel 18 be conductive. The at least one meandering channel 18 can have at least one channel input (input / product input) 20 and / or at least one channel output (educt output / product output) 22 exhibit.

Due to the advantageous features of the bipolar plate 10 with the at least one heat pipe 12 eliminates the need that at least one gaseous or liquid medium (which through the at least one meandering channel 18 is conductive) for cooling the bipolar plate 10 use. Thus, a flow rate of the at least one medium is already sufficient, which is below a necessary minimum flow rate of a coolant. Accordingly, the at least one meandering channel 18 be formed narrower.

Another advantage of the omitted need for cooling the bipolar plate 10 by means of the at least one meandering channel 18 conductive medium is that (almost) the same temperature at the channel entrance 20 and at the channel exit 22 is present. The commonly occurring temperature spread (up to 10 Kelvin) between the channel entrance 20 and the channel output 22 , which can lead to a spatially different degradation of the electrolysis or fuel cell (eg the PEM stack), must therefore not be accepted. In addition, due to the temperature equality at the channel entrance 20 and at the channel output 22 same diffusion rates for ions, resulting in an equality of the present at each location electric current. This eliminates the risk that a locally higher current in turn eliminates more local heating of the bipolar plate 10 causes. Accordingly, no locally higher current can trigger a locally higher degradation of the electrolysis or fuel cell (eg of the PEM stack).

While conventionally in an operation of an electrolysis or fuel cell the The warmest point in it determines a lifetime of the electrolysis or fuel cell and affects their possible operating modes, by means of the cooling of the bipolar plate 10 through the at least one heat pipe 12 an advantageous long life and a comparatively low degradation rate for the respective electrolysis or fuel cell can be achieved. In addition, it does not have to be accepted that colder places of the electrolysis or fuel cell are used under their potential. Thus, by means of the uniform cooling of the bipolar plate 10 through the at least one heat pipe 12 an improved efficiency of the electrolysis or fuel cell can be achieved, which can contribute to a reduction of a necessary cell area / a required space of the electrolysis or fuel cell. By means of the advantageous cooling of the bipolar plate by the at least one heat pipe 12 More uniform utilization of the electrolysis or fuel cell thus smaller and lighter electrolysis or fuel cell systems can be realized, which are particularly advantageous for mobile applications.

Preferably, this is at least one heat pipe 12 filled with at least one refrigerant. For example, the at least one heat pipe 12 be filled with carbon dioxide, R410a, water and / or alcohol as the at least one refrigerant. All of the refrigerants listed here provide uniform and reliable cooling of the bipolar plate 10 for sure. It should be noted that other refrigerants for reliable cooling of the bipolar plate 10 in the at least one heat pipe 12 can be used. The use of water as a refrigerant is easy to carry out and completely harmless. In addition, in a simple manner, a negative pressure of a few millibars in the at least one heat pipe 12 (or in a connected two-phase cooling circuit) can be adjusted so that the boiling point of water can be reduced to a few degrees Celsius. For many applications, such as when using the bipolar plate 10 however, in a high-temperature PEM cell / high-temperature PEM stack (with a temperature of up to 200 ° C), it is not necessary to pressurize the refrigerant water with a negative pressure.

In the embodiment of the 1 is a heat exchanger 24 to the at least one heat pipe 12 the illustrated bipolar plate 10 tethered. The at least one heat pipe 12 can at one end of a first collector section 26 and at each other end via a second header section 28 on the heat exchanger 24 be connected. The bipolar plate 10 and the heat exchanger 24 thus form (possibly with the collector sections 26 and 28 ) a cooling device for an electrolysis or fuel cell.

In particular by means of the collector sections 26 and 28 is the cooling device as a pressure equal, closed system feasible, so that in all heat pipes 12 the same pressure prevails. The refrigerant may be present in the closed system as a two-phase mixture. For example, the refrigerant is in the first header section 26 and in the at least one heat pipe 12 liquid, while the refrigerant in the second header section 28 and in the heat exchanger 24 is present in gaseous form.

In the same pressure, closed system can heat in the heat exchanger 24 be discharged, resulting in the condensation of the refrigerant in the heat exchanger 24 leads. The condensation of the refrigerant creates a local pressure reduction in the heat exchanger 24 , whereby gaseous refrigerant from the at least one first header section 26 and / or the at least one heat pipe 12 nachströmt. In the at least one heat pipe 12 then evaporates the same amount of refrigerant as in the heat exchanger 22 is condensed. Particularly noteworthy is that in a pressure equal, closed system, the refrigerant always evaporates at the warmest point. By means of this mechanism is thus automatically over the entire surface of the bipolar plate 10 the same temperature.

In the same pressure, closed system and no electrical drive energy for heat transfer is necessary. Instead, the heat transfer is carried out automatically by means of the mechanism described in the preceding paragraph. The automatically adjusting heat transfer is also a factor of about 100 faster than a water transport in a conventional cooling circuit, since the significant pressure differences between a vaporization and a condensation point with the speed of sound of the selected refrigerant are compensated.

2 shows a schematic representation of the electrolysis or fuel cell.

In the 2 illustrated electrolysis or fuel cell may be referred to as a PEM cell / PEM stack (Proton Exchange Membrane Stack). The electrolysis or fuel cell comprises at least one membrane 50 which is permeable to hydrogen ions. The hydrogen-ion-permeable membrane 50 is between two electrodes 52 arranged. In addition, the electrolysis or fuel cell still has two bipolar plates 10 on. Each of the bipolar plates 10 is on one of the for hydrogen ions permeable membrane 50 away side of an electrode 52 arranged.

At least one of the bipolar plates 10 can with at least one integrated heat pipe (not shown) 12 be formed, which on and / or in the bipolar plate 10 is trained. For example, the embodiment of the 1 as a bipolar plate 10 be used in the electrolysis or fuel cell. Alternatively, however, it can also be close to at least one of the bipolar plates 10 the electrolysis or fuel cell at least one (not sketched) heat pipe 12 be arranged. In particular, the at least one heat pipe 12 the respective bipolar plate 10 Contact without the bipolar plate 10 and the at least one heat pipe 12 form a compact subunit in the electrolysis or fuel cell. Thus, the benefits described above can also be achieved without integration of the at least one heat pipe 12 on / in the bipolar plate 10 will be realized.

The permeability of the membrane 50 for hydrogen ions may be used to perform electrolysis or perform a fuel cell function. To perform an electrolysis, the electrodes 52 usually subjected to a voltage. The applied voltage can be used, for example, for the splitting of molecules (eg water molecules) into their individual atoms. In this case, the cations (eg hydrogen ions / hydrogen atoms) accumulate at the cathode, while the anions (eg oxygen ions / oxygen atoms) accumulate on the anode. (As starting material, deionized water can be passed through at least one meandering channel 18 a bipolar plate 10 be supplied.)

To perform a fuel cell function different educts are the electrodes 52 fed. For example, hydrogen is introduced at the anode while oxygen is supplied to the cathode. In this case, hydrogen ions migrate through the membrane 50 and react at the cathode to water. The electrons released at the anode generate a current which can be used to operate an electrical device.

Both when performing an electrolysis and when performing a fuel cell function by means of in 2 schematically shown cell is formed between the electrodes 52 and the membrane 50 Waste heat. This waste heat is caused in both processes by the flowing current, which is an electrical resistance of the membrane 50 , the electrodes 52 and the connected contacts must overcome. (The decreasing heat output results from the square of the current strength times the electrical resistance.) In addition, the energy of the exothermic reaction is released as additional heat in fuel cell operation. By means of the at least one heat pipe 12 which is either close to at least one bipolar plate 10 is arranged or in at least one of the bipolar plates 10 is integrated, but in both cases, a uniform cooling of the electrolysis or fuel cell can be ensured. Damage to the electrolysis or fuel cell due to an increase in their temperature must therefore not be feared.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102012019678 A1 [0003]

Claims (10)

Bipolar plate ( 10 ) for an electrolysis or fuel cell, characterized by at least one on and / or in the bipolar plate ( 10 ) formed heat pipe ( 12 ). Bipolar plate ( 10 ) according to claim 1, wherein the at least one heat pipe ( 12 ) comprises at least one heat pipe and / or at least one two-phase thermosyphon. Bipolar plate ( 10 ) according to claim 1 or 2, wherein on the bipolar plate ( 10 ) additionally at least one meander-shaped channel ( 18 ) is formed, through which at least one gaseous or liquid medium is conductive. Bipolar plate ( 10 ) according to one of the preceding claims, wherein the at least one heat pipe ( 12 ) is filled with at least one refrigerant. Bipolar plate ( 10 ) according to claim 4, wherein the at least one heat pipe ( 12 ) is filled with carbon dioxide, R410a, water and / or alcohol as the at least one refrigerant. Bipolar plate ( 10 ) according to one of the preceding claims, wherein the bipolar plate ( 10 ) an active page ( 14 ), which after arranging the bipolar plate ( 10 ) in the electrolysis or fuel cell to another bipolar plate ( 10 ), and the at least one heat pipe ( 12 ) perpendicular to the active side ( 14 ) through the bipolar plate ( 10 ) extends continuously. Bipolar plate ( 10 ) according to one of claims 1 to 5, wherein the at least one heat pipe ( 12 ) parallel to the active side ( 14 ) through the bipolar plate ( 10 ) extends continuously. Cooling device for an electrolysis or fuel cell with at least one bipolar plate ( 10 ) according to one of the preceding claims, and a heat exchanger ( 24 ), which at the at least one heat pipe ( 12 ) of the at least one bipolar plate ( 10 ) is attached. Electrolysis and / or fuel cell with at least one bipolar plate ( 10 ) according to one of claims 1 to 7 or a cooling device according to claim 8. Electrolysis and / or fuel cell with at least one bipolar plate ( 10 ); characterized by at least one heat pipe ( 12 ), which is close to the single bipolar plate ( 10 ) or at least one of the bipolar plates ( 10 ) of the electrolysis or fuel cell is arranged.

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