Electrode system

An electrode system comprising: a plurality of first electrode plates (3) and a plurality of second electrode plates (5′) arranged alternatingly to form an electrode stack, each first electrode plate having a first electrode plate first busbar opening and a first electrode plate second busbar opening extending through the first electrode plate, the first electrode plate second busbar opening being larger than the first electrode plate first busbar opening, each second electrode plate (5′) having a second electrode plate first busbar opening (27a′) extending through the second electrode plate (5′), the second electrode plate first busbar opening (27a′) being dimensioned larger than each of the first electrode plate first busbar openings and aligned with the first electrode plate first busbar openings, and a second electrode plate second busbar opening (27b′) extending through the second electrode plate (5′), the second electrode plate second busbar opening (27b′) being dimensioned smaller than each of the first electrode plate second busbar openings and aligned with the first electrode plate second busbar openings, a first busbar extending through the first electrode plate first busbar openings and the second electrode plate first busbar openings (27b′), the first busbar being configured to be in mechanical contact with an inner first busbar surface of the first electrode plate first busbar openings only, and a second busbar extending through the first electrode plate second busbar openings and the second electrode plate second busbar openings (27b′), the second busbar being configured to be in mechanical contact with an inner second busbar surface of the second electrode plate second busbar openings (27b′) only.

The present application is the U.S. national phase under § 371 of International Application No. PCT/EP2020/054514, having an international filing date of Feb. 20, 2020, which claims priority to EP Patent Application No. 19158309.5, filed Feb. 20, 2019. Each of the above-mentioned prior-filed applications is hereby expressly incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to the powering of electrodes of an electrode stack, for example of an electrolyser.

BACKGROUND

A stack of electrodes may be used in a great plurality of applications. One application which may utilise a stack of electrodes is that of electrolysis.

Electrolysis of water is a process in which water molecules are decomposed, forming hydrogen gas and oxygen gas. This process occurs as a result of an electric current flowing between two electrodes submerged in water.

In existing solutions, the mechanical connection between the power source and the electrodes may be relatively bulky. Furthermore, it may be relatively laborious to make the necessary connections to the power source during installation.

SUMMARY

In view of the above, a general object of the present disclosure is to provide an electrode system which solves or at least mitigates the problems of the prior art.

There is hence provided an electrode system comprising: a plurality of first electrode plates and a plurality of second electrode plates arranged alternatingly to form an electrode stack, each first electrode plate having a first electrode plate first busbar opening and a first electrode plate second busbar opening extending through the first electrode plate, the first electrode plate second busbar opening being larger than the first electrode plate first busbar opening, each second electrode plate having a second electrode plate first busbar opening extending through the second electrode plate, the second electrode plate first busbar opening being dimensioned larger than each of the first electrode plate first busbar openings and aligned with the first electrode plate first busbar openings, and a second electrode plate second busbar opening extending through the second electrode plate, the second electrode plate second busbar opening being dimensioned smaller than each of the first electrode plate second busbar openings and aligned with the first electrode plate second busbar openings, a first busbar extending through the first electrode plate first busbar openings and the second electrode plate first busbar openings, the first busbar being configured to be in mechanical contact with an inner first busbar surface of the first electrode plate first busbar openings only, and a second busbar extending through the first electrode plate second busbar openings and the second electrode plate second busbar openings, the second busbar being configured to be in mechanical contact with an inner second busbar surface of the second electrode plate second busbar openings only.

The busbar connections with the electrode stack are hence internal, extending through the interior of the electrode stack, which thus reduces the external footprint of the busbars and their connections to the first and second electrode plates. Additionally, the external surfaces of the electrode stack may thereby be directly accessible, for example for external cooling purposes of the first electrode plates and the second electrode plates.

The first busbar is hence dimensioned to be in mechanical contact with the inner first busbar surfaces of the first electrode plate first busbar openings only of the first electrode plate first busbar openings and the second electrode plate first busbar openings.

The second busbar is hence dimensioned to be in mechanical contact with the inner second busbar surfaces of the second electrode plate second busbar openings only of the first electrode plate second busbar openings and the second electrode plate second busbar openings.

The first busbar may for example be made of copper or aluminium. The second busbar may for example be made of copper or aluminium.

The first busbar and the second busbar may have the same external diameter. The first busbar and the second busbar may for example be identical or essentially identical.

One example may comprise a plurality of first busbars, and each first electrode plate may comprise a plurality of first electrode plate first busbar openings, wherein each first busbar extends through and is in mechanical contact with the inner first busbar surface of a respective first electrode plate first busbar opening.

One example may comprise a plurality of second busbars, and each second electrode plate may comprise a plurality of second electrode plate second busbar openings, wherein each second busbar extends through and is in mechanical contact with the inner second busbar surface of a respective second electrode plate second busbar opening.

According to one example each first electrode plate second busbar opening is configured to receive a plurality of second busbars. The first electrode plate second busbar opening of each first electrode plate may be dimensioned such that none of the second busbars extending through it is in electrical contact with the first electrode plate. According to one example the second electrode plate first busbar openings are configured to receive a plurality of the first busbars. The second electrode plate first busbar opening of each second electrode plate may be dimensioned such that none of the first busbars extending through it is in electrical contact with the second electrode plate.

Preferably, the number of first busbars and the second busbars is the same.

According to one embodiment the first busbar is an anode busbar and the second busbar is a cathode busbar.

According to one embodiment every first electrode plate is an anode and every second electrode plate is a cathode.

According to one embodiment each first electrode plate has a first frame which delimits a first inner volume, the first frame having a first oxygen gas channel, a first hydrogen gas channel, wherein of the first oxygen gas channel and the first hydrogen gas channel only the first oxygen gas channel is connected to the first inner volume, and a water channel connected to the first inner volume.

According to one embodiment each second electrode plate has a second frame which delimits a second inner volume, the second frame having a second oxygen gas channel aligned with the first oxygen gas channels, a second hydrogen gas channel aligned with the first hydrogen gas channels, wherein of the second oxygen gas channel and the second hydrogen gas channel only the second hydrogen gas channel is connected to the second inner volume, and a second water channel aligned with the water channel.

According to one embodiment the first busbar is configured to engage with the inner first busbar surfaces and the second busbar is configured to engage with the inner second busbar surfaces.

According to one embodiment the inner first busbar surfaces are threaded and the first busbar is provided with external threads configured to form a threaded connection with the threads of the inner first busbar surfaces, and the inner second busbar surfaces are threaded and the second busbar is provided with external threads configured to form a threaded connection with the threads of the inner second busbar surfaces.

According to one embodiment the first busbar and the second busbar have a circular cross section. The first busbar may thereby for example be screwed into the first electrode plate first busbar openings and the second busbar may for example be screwed into the second electrode plate second busbar openings.

According to one embodiment the first busbar is provided with a plurality of radially outwards extending first fins, the first fins being provided with a respective first fin locking structure, and the inner first busbar surface is provided with a plurality of radially inwards extending first protrusions each provided with an inner first locking structure, each inner first locking structure being configured to mate with a respective first fin locking structure.

The second electrode plate first busbar openings may have a smallest dimension which is greater than the largest cross-sectional dimension of the first busbar along the length of the first busbar extending through the electrode stack. The first busbar will hence not be in mechanical contact with the inner surfaces of the second electrode plate first busbar openings.

The surface contact volume between the first busbar and the first electrode plates may be increased and therefore more current can be passed to the first electrode plates from the first busbar.

According to one embodiment the first fin locking structures are tangential protrusions configured to snap-fit with a respective inner first locking structure.

The first busbar may thereby be mechanically locked with the first electrode plates by twisting the first busbar during installation.

The first fin locking structures may extend tangentially from their respective first fin towards the next first fin, one after the other in a first circumferential direction of the first busbar.

According to one embodiment the second busbar is provided with a plurality of radially outwards extending second fins, the second fins being provided with a respective second fin locking structure, and the inner second busbar surface is provided with a plurality of radially inwards extending second protrusions each provided with an inner second locking structure, each inner second locking structure being configured to mate with a respective second fin locking structure.

The first electrode plate second busbar openings may have a smallest dimension which is greater than the largest cross-sectional dimension of the second busbar along the length of the second busbar extending through the electrode stack. The second busbar will hence not be in mechanical contact with the inner surfaces of the first electrode plate second busbar openings.

The surface contact volume between the second busbar and the second electrode plates may be increased and therefore more current can be passed to the second electrode plates from the second busbar.

According to one embodiment the second fin locking structures are tangential protrusions configured to snap-fit with a respective inner second locking structure.

The second busbar may thereby be mechanically locked with the second electrode plates by twisting or rotating the second busbar during installation.

The second fin locking structures may extend tangentially from their respective second fin towards the next second fin, one after the other in a first circumferential direction of the second busbar.

According to one embodiment the first busbar comprises two separated first halves extending parallel with each other in the axial direction of the first busbar, and a first distance setting assembly configured to enable adjustment of a distance between the two first halves to thereby enable a tight fit with the first electrode plate first busbar openings, and wherein the second busbar comprises two separated second halves extending parallel with each other in the axial direction of the second busbar, and a second distance setting assembly configured to enable adjustment of the distance between the two second halves to thereby enable a tight fit with the second electrode plate second busbar openings.

The two first halves of the first busbar may thereby be pressed towards the inner first busbar surface to obtain better mechanical contact between the first busbar and the first electrode plates. The two first halves may be moved away from each other by rotating the

According to one embodiment the first distance setting assembly includes a first screw in each end region of the first busbar, extending radially through the two first halves and each first screw is provided with two first nuts enabling the adjustment of the distance between the two first halves, and the second distance setting assembly includes a second screw in each end region of the second busbar, extending radially through the two second halves and each second screw is provided with two second nuts enabling the adjustment of the distance between the two second halves.

The two second halves of the second busbar may thereby be pressed towards the inner second busbar surface to obtain better mechanical contact between the second busbar and the second electrode plates.

According to one embodiment the electrode system is an electrolyser system. The electrolyser system may be a high-pressure electrolyser system.

One embodiment comprises a plurality of electrically conducting planar spacers, each spacer having a through-opening configured to receive a first busbar or a second busbar, wherein the first electrode plates and the second electrode plates are coated with a heat conductive polymer, wherein the first electrode plates and second electrode plates have an exposed region where the underlying metal core has been exposed, the exposed region of the first electrode plates being provided with a respective one of the first electrode plate first busbar opening and the exposed region of the second electrode plates being provided with a respective one of the second electrode plate second busbar opening, wherein for each first electrode plate one spacer is arranged on one side of the first electrode plate first busbar opening and another spacer is arranged on an opposite side of the first electrode plate first busbar opening, and for each second electrode plate one spacer is arranged on one side of the second electrode plate second busbar opening and another spacer is arranged on an opposite side of the second electrode plate second busbar opening, the spacers thereby being arranged in mechanical and electrical contact with both the front and rear surfaces of the exposed regions.

The thickness of the conducting material with which the busbars are in contact is thereby increased. The spacers and hence act as an additional contact surfaces for the busbars. This increases the length with which the busbars are in electrical contact with the electrode plates, which is advantageous in case the electrode plates are very thin and large currents are to be passed to the electrode plates. The current passed from the busbars to the electrode plates may thereby be increased.

The spacers may alternatively be referred to as contact elements.

According to one example the electrode system may comprise: a cabinet and a plurality of first busbars, each first electrode plate comprising a plurality of first electrode plate first busbar openings, and a plurality of second busbars, each second electrode plate comprising a plurality of second electrode plate second busbar openings, the electrode system comprising first pantographs connected between pairs of first busbars, the first pantographs being configured to press the first busbars towards the first electrode plates, and second pantographs connected between pairs of second busbars, the second pantographs being configured to press the second busbars towards the second electrode plates.

The plurality of first electrode plates may for example be two first electrode plates. The plurality of second electrode plates may for example be two second electrode plates.

According to one example, the electrode system may comprise a cabinet provided with electrical connectors configured to be connected to the first busbar and the second busbar, and an electromagnet, wherein the electrode stack forms part of an electrolyser, the electrolyser comprising ferromagnetic material configured to magnetically interact with the electromagnet when the electrolyser is arranged inside the cabinet.

The electromagnet may be energised when the electrolyser is placed inside the cabinet to properly align the electrolyser inside cabinet and to secure an electrical connection between the electrical connectors and the first busbar and second busbar. When the electrolyser is to be removed, the electromagnet may be deenergised.

DETAILED DESCRIPTION

FIG.1depicts an example of an electrode system comprising a plurality of electrode plates forming an electrode stack. In the following, the electrode system will be exemplified by an electrolyser system for electrolysis. It should however be understood that an electrode stack for any application may benefit from the busbar structure as will be described herein in the context of electrolysis.

The exemplified electrode system1comprises a plurality of first electrode plates3and a plurality of second electrode plates5. The first electrode plates3and the second electrode plates5are arranged alternatingly and form an electrode stack. Each pair of first electrode plate3and adjacent second electrode plate5forms an electrolytic cell.

The electrode system1may comprise membranes such as separator membranes. A respective membrane may be arranged between a pair of a first electrode plate3and a second electrode plate5. Thus, a respective membrane may be sandwiched between a first electrode plate3and a second electrode plate5.

The first electrode plates3are electrically insulated from the second electrode plates5.

The exemplified electrode system1has two end plates, one at each end of the electrode stack. InFIG.1only one end plate7is visible. The end plates7may comprise a plurality of openings9distributed along the perimeter of the end plates7. The openings9may be configured to receive fasteners to hold the electrode stack together. The fasteners may for example comprise compression rods extending through the electrode stack and nuts and/or bolts for attaching the compression rods to the electrode stack.

The exemplified end plate7furthermore comprises two gas channels. In this example a first gas channel is an oxygen gas channel11aand a second gas channel is a hydrogen gas channel11b. The exemplified end plate7furthermore comprises water channels13. The end plate7has first and second busbar openings15aand15b.

The electrode system1furthermore comprises a first busbar17aand a second busbar17b. The first busbar17aextends through the first busbar opening15aand through the entire electrode stack, and the second busbar17bextends through the second busbar opening15bof the first end plate7and through the entire electrode stack. The exemplified first busbar17aand the second busbar17bhence extend through the entire electrode stack, including all first electrode plates3, all second electrode plates5and both end plates.

The first busbar17aand the second busbar17bare according to the example shown inFIG.1in no mechanical or electrical contact with the end plate7. Hereto, for example, the first busbar opening15aand the second busbar opening15bmay have at least somewhat larger dimensions than the cross-sectional dimensions of the first busbar17aand the second busbar17b. According to one variation the end plate7may be provided with solid electrical insulation between the first busbar17aand the first busbar opening15aand between the second busbar17band the second busbar opening15b.

FIG.2ashows a front view of one example of a first electrode plate3. The first electrode plate3has an electrically conductive first frame19awhich delimits a first inner volume21a. The first frame19amay for example comprise a metal core such as copper or aluminium. The first frame19a, in particular the metal core, may be coated with a heat conductive polymer. The coating of the heat conductive polymer may for example be obtained by means of injection moulding.

The first electrode plate3is provided with a plurality of coils23extending inside the first inner volume21abetween opposite sides delimiting the first inner volume21a. The coils23are electrically connected to the first frame19a. The coils23may be arranged in parallel with each other.

The first electrode plate3furthermore comprises a first and a second water channel22aand22bof which only the second water channel22bis connected to the first inner volume21a. Hence, only the second water channel22bof the first water channel22aand the second water channel22bis in fluid communication with the first inner volume21a. In the electrode stack, the first and second water channel22aand22bare connected to a respective one of the water channels13of the end plate7.

The first electrode plate3furthermore comprises a first gas channel24a, e.g. a first oxygen gas channel and a second gas channel24b, e.g. a first hydrogen gas channel. Only one of the first gas channel24aand the second gas channel24bis connected to the first inner volume21a. In the example shown inFIG.2athe first gas channel24ais connected to the first inner volume21a. The first gas channel24ais hence in fluid communication with the first inner volume21a.

The first electrode plate3comprises a first electrode plate first busbar opening25a. The first electrode plate first busbar opening25aextends through the first electrode plate3. The first electrode plate first busbar opening25ais in the example arranged in a lower region of the first electrode plate3.

The first electrode plate3comprises a first electrode plate second busbar opening25b. The first electrode plate second busbar opening25bextends through the first electrode plate3. The first electrode plate second busbar opening25bis in the example arranged in a lower region of the first electrode plate3.

The first electrode plate second busbar opening25bis larger than the first electrode plate first busbar opening25a.

FIG.2bshows a front view of one example of a second electrode plate5. The second electrode plate5has an electrically conductive second frame19bwhich delimits a second inner volume21b. The second frame19bmay for example comprise a metal core such as copper or aluminium. The second frame19b, in particular the metal core, may be coated with a heat conductive polymer. The coating of the heat conductive polymer may for example be obtained by means of injection moulding.

The second electrode plate5is provided with a plurality of coils23extending inside the second inner volume21bbetween opposite sides delimiting the second inner volume21. The coils23are electrically connected to the second frame19b. The coils23may be arranged in parallel with each other.

The second electrode plate5furthermore comprises a first and a second water channel28aand228bof which only the first water channel28ais connected to the second inner volume21b. Hence, only the first water channel28aof the first water channel28aand the second water channel28bof the second electrode plate5is in fluid communication with the second inner volume21b. In the electrode stack, the first and second water channel28aand28bare connected to a respective one of the water channels22aand22bof the first electrode plates3and the water channels13of the end plate7.

The second electrode plate5furthermore comprises a first gas channel26a, e.g. a second oxygen gas channel and a second gas channel26b, e.g. a second hydrogen gas channel, which are aligned with and connected to the corresponding gas channels of the first electrode plate3. Only one of the first gas channel26aand the second gas channel26bis connected to the second inner volume21b. In the example shown inFIG.2bthe second gas channel26bis connected to the second inner volume21b. The second gas channel26bis hence in fluid communication with the second inner volume21b.

The second electrode plate5comprises a second electrode plate first busbar opening27a. The second electrode plate first busbar opening27aextends through the second electrode plate5. The second electrode plate first busbar opening27ais in the example arranged in a lower region of the second electrode plate5.

The second electrode plate5comprises a second electrode plate second busbar opening27b. The second electrode plate second busbar opening27bextends through the second electrode plate5. The second electrode plate second busbar opening27bis in the example arranged in a lower region of the second electrode plate5.

The second electrode plate first busbar opening27ais larger than the second electrode plate second busbar opening27b.

In the electrode stack, the first electrode plate first busbar opening25aof each first electrode plate3is aligned with the second electrode plate first busbar openings27aof the second electrode plates5and with the first electrode plate first busbar openings25aof the other first electrode plates3.

In the electrode stack, the first electrode plate second busbar opening25bof each first electrode plate3is aligned with the second electrode plate second busbar openings27bof the second electrode plates5and with the first electrode plate second busbar openings25bof the other first electrode plates3.

The first busbar17aextends through all of the first electrode plate first busbar openings25aand second electrode plate first busbar openings27a. The first busbar17ais dimensioned to be in mechanical contact with an inner first busbar surface of the first electrode plate first busbar openings25a. The second electrode plate first busbar openings27ahave a larger dimension than the first electrode plate first busbar openings25aand the first busbar17ais not in mechanical contact with any surface of the second electrode plate first busbar openings27a. The first busbar17awill thereby be able to feed current to the first electrode plates3only.

The second busbar17bextends through all of the first electrode plate second busbar openings25band second electrode plate second busbar openings27b. The second busbar17bis dimensioned to be in mechanical contact with an inner second busbar surface of the second electrode plate second busbar openings27b. The second electrode plate second busbar openings27bhave a smaller dimension than the first electrode plate second busbar openings25band the second busbar17bis not in mechanical contact with any surface of the first electrode plate second busbar openings25b. The second busbar17bwill thereby be able to feed current to the second electrode plates5only.

The first busbar17amay be an anode busbar and the second busbar17bmay be a cathode busbar. The first electrode plates3may hence form anodes and the second electrode plates5may form cathodes.

According to the example depicted inFIGS.2a-2bthe first busbar17aand the second busbar17bhave the same diameter or dimensions. The first busbar17aand the second busbar17bmay have a circular cross-section. This may apply to any example disclosed herein.

The first busbar17ais configured to engage with the first electrode plate first busbar openings25a, in particular the inner first busbar surfaces. The second busbar17bis configured to engage with the second electrode plate second busbar openings27b, in particular the inner second busbar surfaces.

The inner first busbar surfaces may be provided with threads and the outer surface of the first busbar17amay be provided with corresponding external threads. The first busbar17amay thereby obtain a threaded connection with the inner first busbar surfaces and hence with the first electrode plates3.

The inner second busbar surfaces may be provided with threads and the outer surface of the second busbar17bmay be provided with corresponding external threads. The second busbar17bmay thereby obtain a threaded connection with the inner second busbar surfaces and hence with the second electrode plates5.

FIG.3ashows a cross-section of another example of busbars, i.e. first busbar and second busbar. The exemplified busbar will in the following be a first busbar18, but according to this variation, the second busbar may have the same or essentially the same configuration. The first busbar18comprises a plurality of radially outwards extending first fins18adistributed along the periphery of the first busbar18. Each first fin18ahas a first fin locking structure18b. In the depicted example the first fin locking structures18bextend essentially perpendicular to or perpendicular to the longitudinal axis of the corresponding first fin18a. Each first fin locking structure18bis hence an orthogonal protrusion with respect to the corresponding first fin18b. Each first fin locking structure18bmay hence extend in a respective tangential direction of the first busbar18. Each of the first fin locking structures18bextends towards the subsequent first fin18awhen moving in a clockwise or in an alternative example, counter-clockwise direction along the periphery of the first busbar18.

FIG.3bshows a close-up view of a busbar of the type depicted inFIG.3afitted in one of a first electrode plate3′ and a second electrode plate5′. The first electrode plate3′/second electrode plate5′ are similar to those described with reference toFIGS.2a-b, except that at least the first electrode plate first busbar openings and second electrode plate second openings differ. The first electrode plate first busbar opening25a′ and the second electrode plate second busbar opening may in this case be provided with a plurality of radially inwards extending first protrusions or fins29. Each first fin18ais configured to extend between pairs of radially inwards extending first protrusions29. Each radially inwards extending first protrusion29has an inner first locking structure29aconfigured to mate with and engage with a respective first fin locking structure18b. The first fin locking structures18band the corresponding inner first locking structure29may have a snap-fit engagement. The first fin locking structure18bmay for example comprise a head-structure and the inner first locking structures29may comprise a waist-structure, and the head-structure may be configured to be locked by the waist-structure. During assembly, a first busbar18, for example, may first be lead through all of the first electrode plate first busbar openings in a position shown inFIG.3b. Next, the first busbar18may be rotated or twisted clockwise such that the first fin locking structures18bengage with the corresponding inner first locking structures29.

The first electrode plate second busbar openings and the second electrode plate first busbar openings are in this case preferably made larger than the largest cross-sectional dimension of the corresponding busbar. Hence, these openings are large enough so that they do not come into mechanical contact with the first busbar and the second busbar.

FIG.4ashows another example of a first busbar or second busbar in perspective view. Both the first busbar and the second busbar may in this example be similar or the same. The first electrode plate first busbar opening and the second electrode plate second busbar opening may have a shape adapted to the cross-sectional envelope shape of the first/second busbar, i.e. the cross-sectional contour shape.

The exemplified first busbar31comprises two separated elongated halves31aand31bwhich are fixed to each other and arranged in parallel. The first/second busbar furthermore comprises means for adjusting the distance between the two halves31aand31b. The distance between the two halves31aand31bmay beneficially be adjusted after the first/second busbar has been fitted in the corresponding first/second electrode plate first/second openings, to obtain a tight fit and good electrical contact. According to the example depicted inFIGS.4aand4b, the busbar comprises a first distance setting assembly33a.

The first distance setting assembly33acomprises two first screws35aand37b, each extending radially through both halves31a-31b, and four first nuts35band37b, two first nuts35bbeing fitted on the first screw35abetween the two halves31a-31band two first nuts37bfitted on the first screw37bbetween the two halves31a-31b. The two first screws35aand35bmay be arranged in opposite end regions/portions of the busbar31.

By screwing the two first nuts35bfitted on the first screw35ain opposite directions towards the two halves31aand31b, the distance between the two halves31a-31bon that end of the busbar31can be adjusted. Similarly, by screwing the two first nuts37bin opposite directions, the distance between the two halves31a-31bon the other end of the busbar31can be adjusted. The busbars31may thereby be installed with a tight fit in the first electrode plate first busbar opening and the second electrode plate second busbar opening. The first screws35aand37amay beneficially be arranged outside of the electrode stack to allow adjustment after installation.

FIG.5ashows another example of a second electrode plate5′ andFIG.5bshows a corresponding first electrode plate3′. The second electrode plate5′ is similar to the one described with reference toFIG.2a. The second electrode plate5′ however has an exposed area or region39where the underlying metal core has been exposed. The heat conductive polymer has hence been removed in the exposed region39. The exposed region39is provided with a second electrode plate first busbar opening27a′ extending through the second electrode plate5′ and a second electrode plate second busbar opening27b′ which is smaller than the second electrode plate first busbar opening27a′.

The first electrode plates are in this example similar to the exemplified second electrode plate5′, as shown inFIG.5b, except that the first electrode plate first busbar opening25a′ has the structure of the second electrode plate second opening27b′ and located in the corresponding location where the second electrode plate first busbar opening27a′ is located, and that the first electrode plate second busbar opening25b′ has the structure of the second electrode plate first opening27a′ and is located in the corresponding location where the second electrode plate second busbar opening27b′ is located, in addition to the differences regarding the water channels and the two gas channels, which are alternatingly connected to the inner volume.

In the present example, there are a plurality of second electrode plate second busbar openings27b′ in the exposed region39in order to be able to feed more current to the second electrode plate5′. The electrode system may comprise more than one busbar per polarity, i.e. two or more cathode busbars and two or more anode busbars. This may apply to variations of any of the example disclosed herein.

The exemplified electrode system may furthermore comprise a plurality of electrically conducting spacers41aand41b. The spacers41aand41bmay for example comprise or consist of copper or aluminium. The spacers41aand41bare essentially planar or planar. Each spacer41a-41bhas a through-opening configured to receive a first or second busbar.

Each of the one or more second electrode plate second busbar openings27b′, and one or more first electrode plate first busbar openings, may be associated with respective two spacers41aand41b. In particular, two spacers41aand41bmay be arranged in electrical connection with the exposed region39and hence the wall in which the second busbar second openings27b′ are provided. One spacer41ais arranged on one side of the corresponding opening27′band another spacer41bis arranged on the opposite side of the opening27′b. Both the front and the rear surfaces of the exposed region39are hence in mechanical and electrical contact with a respective spacer41a,41b. The thickness of the conducting material with which the busbars are in contact may thereby be increased. The spacers41aand41bhence act as an additional contact surfaces for the busbars. This increases the length by which the busbars are in electrical contact with the electrode plates, which is advantageous in case the electrode plates are very thin and large currents are to be passed to the electrode plates. The current passed from the busbars to the electrode plates may thereby be increased. Each electrode plate is provided with such spacers41a-41barranged in contact with the exposed regions.

During assembly, all of the spacers for a busbar may be provided around the busbar one after the other with the appropriate distance between them so that they can be arranged in mechanical contact with the rear and front surfaces of the regions39of every e.g. second electrode plate of the electrode stack. There are hence typically twice as many spacers mounted around a busbar than there are electrode plates of a certain type, i.e. first electrode plates or second electrode plates. The same applies also for the first electrode plates and their spacers.

Each busbar may be provided with end threads on both ends. By providing a respective nut or similar fastening means on both ends and screwing them in opposite directions, they will move towards each other and eventually bear against the two outermost spacers on opposite sides of the electrode stack. The spacers will thereby be fixed tightly in the electrode stack.

The top surface43of the second electrode plate first busbar opening27a′ of each second electrode plate5′ may be provided with an insulating material, such as a heat conducting polymer. Electrical insulation may thereby be provided against spacers extending from the busbar in the second electrode plate first busbar opening27a′. Similarly, the top surface43of the first electrode plate second busbar openings may be provided with an insulating material such as a heat conducting polymer, to provide electrical insulation from the spacers.

FIG.6ashows a perspective view of another example of a first/second busbar45. The busbar45has a generally H-shaped configuration in cross-section and a ladder configuration in perspective or longitudinally. The busbar45has a first bar45aand a second bar45bextending parallel, and a plurality of rungs45cextending between the first bar45aand the second bar45b. The first bar45aand the second bar45bmay typically both be cathodes or both be anodes. The rungs45care attached in a flexible or movable manner to the first bar45aand the second bar45b. Alternatively or additionally, the rungs45cmay themselves be flexible. The first bar45aand the second bar45bare hence movable relative to each other. The first electrode plate and the second electrode plate may in this case have corresponding first electrode plate first busbar openings and second electrode plate second busbar openings. These openings may hence also have a generally H-shaped structure, as shown for a first electrode plate3″ inFIG.6b. The first electrode plate3″ has a first electrode plate first busbar opening25a″ which is generally H-shaped and configured to receive and be arranged in mechanical contact with the busbar45when the busbar45extends therethrough. The first electrode plate3″ has a first electrode plate second busbar opening25b″ which is larger than the corresponding cross-sectional dimensions of the busbar45. A second busbar of the type shown inFIG.6amay then extend through this opening without any mechanical contact with the first electrode plate3″. The shape of the openings is interchanged on the second electrode plates in a similar manner as has been described above with respect to other examples.

The shape of the openings may for example be cut by means of laser. Due to the flexible design of the busbar45, any tolerance or alignment problems may be mitigated when inserting the busbar45into the openings of the electrode stack during assembly.