WO2024110992A1

WO2024110992A1 - Alkaline electrolyser system and process of manufacturing thereof

Info

Publication number: WO2024110992A1
Application number: PCT/IN2023/051087
Authority: WO
Inventors: Suhas Ramdas Sope; Neha Shankarrao Marghade
Original assignee: Brise Chemicals Private Ltd
Current assignee: Brise Chemicals Private Ltd
Priority date: 2022-11-24
Filing date: 2023-11-24
Publication date: 2024-05-30
Anticipated expiration: 2025-05-24

Abstract

An alkaline water electrolyser with low capex, low power consumption and its process of manufacturing without need of skilled work force is described. The said alkaline electrolyser is made of a compact stack (A) of plurality of bipolar plate assemblies (20) consisting of bipolar plate, anode electrode plate (23), current collector (24), corrugated cushion mat (25) supporting adjacent cathode electrode plate (26), stacked together in series. Each bipolar plate is moulded in single process by embedding partition plate (22) in non-metallic outer frame (21) bearing degassing slots (21A) to avoid foaming; electrolyte inlets (21C, 21D); interlocking means (21B) and sealing serrations (21E) which prevent mixing of gases, ensures optimum interlocking of adjacent bipolar plates and no leakage of electrolyte and current at higher operating pressure. The partition plate (22) is provided with unique orientation of ribs to reduce buckling at high temperature.

Description

TITLE

ALKALINE ELECTROLYSER SYSTEM AND PROCESS OF MANUFACTURING

THEREOF

FIELD OF INVENTION

The proposed invention relates to process engineering for industrial gases. More particularly, it relates to a simplified, compact alkaline electrolyser for generation of hydrogen using Green Technology.

BACKGROUND OF INVENTION

For several years, hard-to-abate sectors like aviation, steel and shipping have relied on coal, oil and natural gas. These hard-to-abate sectors are some of the largest CO2 emitters globally and face a challenge of complete decarbonization. Also, changes in environment and depleting levels of fossil fuels have led to the need to carry out research and development of sustainable and cleaner alternative energy sources.

Hydrogen promises to be an ideal contender in this regard. There are several means for hydrogen production. However, hydrogen production by water electrolysis has a significant position in the market. Electrolysers are the devices that generate hydrogen and oxygen by splitting water through the application of electricity. The process is simple and produces high level of pure gas without emitting pollutant gases into the atmosphere. It is the most used method for hydrogen generation.

Electrolyser consists of several electrolytic cells stacked in series. Each electrolytic cell is made up of hydrogen and oxygen gas generating elements through which water flows on passage of low voltage direct current. Electrolytic cells are primarily made of two types namely, monopolar and bipolar. In the monopolar design, the electrodes are either negative or positive with the parallel electrical connection of the individual cells, while in the bipolar design the individual cells are linked in series electrically and geometrically making it the most preferred option for electrolyser manufacturers. Bipolar cell design is more compact than monopolar systems leading to shorter current paths in the electrical wires and electrodes. This reduces the losses due to the internal Ohmic resistance of the electrolyte and therefore, increases the electrolyser operational efficiency.

Widespread use of the alkaline electrolyser has been hindered due to its poor efficiency. Also, bulk manufacturing of bipolar electrolytic cells is technically challenging, time consuming and expensive. At present, research and development needs to be focused mainly on the realization of long-lasting materials to extend the lifetime and the performance of electrolysis stacks. Reduction in system complexity also remains a major challenge.

Existing electrode coating seems to be improper leading to higher power consumption. Current cell designs are not guided, thus longer stacking becomes a challenging task. Also, non-guided stack design requires higher attention and skill. Existing designs do not address foaming issues appropriately leading to cell drying and temperature related issues. Metallic outer frame manufacturing of the electrolyser is a tedious, costly, time-consuming and non-efficient process. Hence, efforts towards simplified and low carbon manufacturing technique of bipolar electrolytic cell could bring attractive benefits to this global green mission.

The present invention addresses some of these issues offering a reliable and affordable Bipolar electrolytic cell with an outer frame having better resistivity to electrical current, thermal conduction at the outer surface and operates at lower risk. Non-metallic moulded outer frame reduces manufacturing cost and time, thereby improving production efficiency and resolving foaming issues with unique shape of degassing slots. Overall, less time and effort are required for manufacturing and assembly of the bipolar plate with the outer frame.

OBJECTS OF THE INVENTION

The primary object of the present invention is to provide a solution for generating Green Hydrogen in the form of alkaline electrolyser.

Another object of the present invention is to offer a novel method of operating the alkaline electrolyser to generate Green Hydrogen. Yet another object of the present invention is to offer a novel alkaline electrolyser wherein the electrolytic cells in the form of bipolar plates are embedded in non-metallic outer frame moulded in unique manner such as to reduce manufacturing and material cost significantly.

Yet another object of the present invention is to offer a novel alkaline electrolyser having the non- metallic frame made from unique material to reduce the carbon footprint, thus directing the product towards GREEN TECHNOLOGY.

Yet another object of the present invention is to provide a novel alkaline electrolyser wherein non- metallic frame encasing the bipolar plates offers better resistivity to electrical current and thermal conduction at outer surface, thus leading to operation of entire assembly at lower risk with better performance.

Yet another object of the present invention is to provide a novel alkaline electrolyser with improved production efficiency due to the unique method of moulding the bipolar plate with outer frame in short duration.

Further object of the present invention is to provide a novel alkaline electrolyser which offers a guided electrolytic cell assembly that reduces stacking time and can be performed without the need of high skilled work force, thus reducing overall cost of stacking.

Further object of the present invention is to provide a novel alkaline electrolyser having elliptical de-gassing slots instead of circular conduits with improved flow features, thus solving problems of defoaming and cell drying up which affect the overall cell performance and life.

Further object of the present invention is to provide a novel alkaline electrolyser with unique Nobel metal coating for longer electrode life, thus significantly improving operating performance.

SUMMARY OF THE PRESENT INVENTION

This section is provided to introduce certain objects and aspects of the present disclosure in a simplified form that are further described below in the detailed description. This summary is not intended to identify the key features or the scope of the claimed subject matter.

Embodiments of the present disclosure may relate to a compact and power efficient alkaline electrolyser system comprised of a stack which further consists of a plurality of bipolar plate assemblies, a pair of electrode end covers, a plurality of means of sealing and a cell stacking assembly.

The bipolar plate assemblies are arranged sequentially in the stack and each includes a bipolar plate, an anode electrode plate, a current collector, a cushion mat and a cathode electrode plate. The bipolar plate consists of an outer frame and a partition plate wherein outer frame is made up of non-conducting material having inner rubber lining to prevent leakage of electrolyte, gases and current. It is provided with a plurality of degassing slots at its vertically upper side; interlocking means on its peripheral area; electrolyte inlets 1 and 2 at vertically lower side of the outer frame; sealing serrations placed vertically parallel to both sides of wall of the partition plate and interlocking means of the outer frame. Additionally, the edges of plurality of degassing slots and electrolyte inlets 1 and 2 are sealed with rubber lining to prevent leakage issues. The partition plate is having plurality of vertical ribs facing the anode electrode plate, plurality of horizontal ribs facing the cathode electrode plate and plurality of feed terminals, wherein the feed terminals project towards the anode electrode plate situated at an anode end cover and towards cathode electrode plate positioned at cathode end cover in the bipolar plate assembly. The partition plate is welded with anode electrode plate at its one side while other side of partition plate is fused with current collector which is sequentially followed by cushion mat and cathode electrode plate. The anode electrode plate and cathode electrode plate of two adjacent bipolar plate assemblies constitute an electrolytic cell.

The electrode end covers include an anode end cover and a cathode end cover which are present at the front and rear end of the stack, respectively. Both end covers are having four terminal slits present in their central part, a plurality of holes present on their periphery and a support present at the bottom for the entire stack. Alternatively, the terminal slits are present on the circumference of both end covers. The anode end cover also has electrolyte inlets 1 and 2 which are present at its vertically lower side adjacent to each other and communicatively connected to electrolyte inlets 1 and 2 of outer frame of the bipolar plate assemblies, and gas collectors 1 and 2 which are present at vertically upper side of the cover opposite to the electrolyte inlets 1 and 2, respectively and communicates with degassing slots of the outer frame. The plurality of means of isolation comprises of plurality of gaskets engaging a diaphragm which sits between two adjacent bipolar plate assemblies and a pair of insulation gaskets which are positioned between a gasket and each electrode end cover.

The cell stacking assembly includes plurality of tie rods passing through plurality of holes present on the end covers, plurality of insulations for encasing the tie rods, plurality of insulation washers affixed at terminal ends of tie rods which are in turn fastened by plurality of spring washers followed by plurality of tightening means.

Embodiments of the present disclosure relate to a process of manufacturing of electrolyser stack including single step process of fabricating bipolar plate assembly resulting into cost effective approach to hydrogen generation with improved efficiency and energy conservation.

For manufacturing of the alkaline electrolyser system of the proposed invention, firstly bipolar plate assemblies are fabricated. To construct a bipolar plate assembly, plurality of vertical ribs is welded at anode side of the partition plate with a plurality of horizontal ribs at its cathode side and is then held in pre-fabricated mould at pre-determined position. The pre-fabricated mould is coated with rubber lining. A non- conductive material is poured in the pre-fabricated mould and the outer frame along with rubber lining is moulded with a plurality of degassing slots, interlocking means, electrolyte inlets 1 and 2, and sealing serrations to embed partition plate in it. The degassing slots and electrolyte inlets of outer frame are then sealed with rubber lining to yield a bipolar plate. One side of obtained bipolar plate having plurality of vertical ribs is linked with anode electrode plate and its other side having plurality of horizontal ribs is spot welded with current collector followed by sequential sewing of cushion mat and then fusing cathode electrode plate to yield the bipolar plate assembly.

The obtained plurality of bipolar plate assemblies is clasped sequentially using plurality of means of sealing with anode terminal cell positioned at the anode end cover and cathode terminal cell placed at the cathode end cover and are then stacked together by means of cell stacking assembly to form stack of the proposed alkaline electrolyser system.

BRIEF DESCRIPTION OF DRAWINGS

The objects, features and advantages of the present invention will best be understood from the following exemplary accompanying drawings. These drawings incorporated herein, constitute part of this disclosure, illustrate exemplary embodiments of the disclosed system and method with respect to alkaline electrolyser.

FIG. 1 is a perspective view of stack (A) of alkaline water electrolyser of the present invention depicting disposition of various components.

FIG. 2 is a detailed view of bipolar plate assembly (20) of said stack (A) depicting sequential disposition of various components of said bipolar plate assembly (20).

FIG. 3 is a perspective view of electrode end covers (20) of said stack (A).

DETAILED DESCRIPTION OF THE INVENTION

Before the present invention is described, it is to be understood that this invention is not limited to particular methodologies described, as these may vary as per the person skilled in the art. It is also to be understood that the terminology used in the description is for the purpose of describing the particular embodiments only and is not intended to limit the scope of the present invention.

Throughout this specification, the word “comprises”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results.

This will be readily apparent to those skilled in the art, the present invention may easily be produced in other specific forms without departing from its essential characteristics. The present embodiments are, therefore, to be considered as merely illustrative and not restrictive, the scope of the invention being indicated by the claims rather than the foregoing description, and it will be appreciated that many variations in detail are possible without departing from the scope and spirit of the invention and all such variations therefore intended to be embraced therein.

In the following description, for the purposes of explanation, various specific details are set forth in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent, however, that embodiments of the present disclosure may be practiced without these specific details. Several features described hereafter can each be used independently of one another or with any combination of other features. An individual feature may not address any of the problems discussed above or might address only one of the problems discussed above. Some of the problems discussed above might not be fully addressed by any of the features described herein.

Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by the way of explanation of the invention and not meant as limitation of the invention. Features illustrated or described as part of one embodiment to yield still third embodiment. It is intended that the present invention includes these and other modifications and variations. The variation and inclusion of components and their positional arrangement w.r.t. the variations in the orientation shall not limit the scope of the invention.

The “hydrogen economy” refers to the vision of using hydrogen as a CLEAN, low-carbon energy resource to meet the world’s energy needs, replacing traditional fossil fuels in various applications and forming a substantial part of a CLEAN ENERGY portfolio. Hydrogen is emerging as one of the most promising energy carriers for a decarbonised global energy system. In order to be self- reliant and proceed towards becoming developing nation before India celebrates “Suvarna Mahotsav”, it is important to become energy independent. With growing global energy needs and limited resources of fossil fuels, newer renewable energy resources need to be invented taking into consideration environmental impact with zero emission approach. Plurality of alternatives to fossil fuels such as renewables, nuclear, natural gas, coal and oil are known. Among all, Hydrogen seems to be proficient selection for storing energy from renewables and looks promising to be a lowest- cost option for storing electricity over days, weeks or even months. Utilization of hydrogen will have impact on reduction in greenhouse gas emission by confronting the various critical energy challenges. Investments in hydrogen will help foster new technological and industrial development in economies around the world, creating skilled jobs. Today, hydrogen is used mostly in oil refining and for the production of fertilizers. For it to make a significant contribution to clean energy transitions, it also needs to be adopted in sectors where it is almost completely absent at the moment, such as transport, buildings and power generation.

Considering these factors, the cautious efforts of the inventors have resulted into an invention which proposes a power efficient process of hydrogen generation with water electrolyser employing GREEN TECHNOLOGY and operating at a reduced OPEX and CAPEX. The present invention offers the solution for energy generation by Green Hydrogen with manufacturing of one of its kind of “Green Hydrogen generating Alkaline Water Hydrogen Electrolyser”.

The present invention describes the electrolyser having components in table 1.

Table 1

DETAILED DESCRITION OF DRAWINGS FIG. 1 is a perspective view of stack (A) of alkaline water electrolyser of the present invention depicting disposition of various components such as plurality of bipolar plate assemblies (20); plurality of means of sealing (40) such as gasket (41), diaphragm (42) and insulation gasket (43); anode end cover (31), cathode end cover (32) and cell stacking assembly (10) including plurality of tie rods (11), plurality of insulations for tie rods (12), plurality of insulation washers (13), plurality of spring washers (14) and plurality of tightening means (15).

FIG. 2 is a detailed view of bipolar plate assembly (20) of said stack (A) depicting sequential disposition of various components such as an outer frame (21) with plurality of degassing slots (21A), interlocking means (21B), electrolyte inlets 1 and 2 (21C, 21D), sealing serrations (21E) and rubber lining (21F), an anode electrode plate (23), a partition plate (22), a current collector (24), a corrugated cushion mat (25) and a cathode electrode plate (26). The present diagram also displays vertical ribs (22A) and feed terminals (22C) on said partition plate (22) of an anode terminal cell.

FIG. 3 is a perspective view of electrode end covers (30) of said stack (A) with electrolyte inlets 1 and 2 (30A, 30B), gas collectors 1 and 2 (30C, 30D), terminal slits (30E), plurality of holes (30F) and a support (30G).

PREFERRED EMBODIMENTS OF THE INVENTION

Embodiments of the present disclosure relate to the process engineering of the industrial gases. More specifically, it pertains to a compact and power efficient electrolyser system and process of manufacturing the same for hydrogen generation by electrolysis of alkaline water.

One or more embodiments are now described more fully hereinafter with reference to the accompanying drawings in which example embodiments are shown. In the following description for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the various embodiments. However, the various embodiments can be practiced without these specific details.

According to one embodiment of the present invention refers to the power efficient alkaline electrolyser system for hydrogen generation using GREEN Technology is comprised of a stack(A) which includes a cell stacking assembly (10), plurality of bipolar plate assemblies (20), electrode end covers (30) and plurality of means of sealing (40) where plurality of bipolar plate assemblies (20), plurality of means of sealing, terminal cells at both ends and electrode end covers (30) are sequentially arranged. The stacking is done by cell stacking assembly (10).

CELL STACKING ASSEMBLY (10)

The cell stacking assembly (10) is used to form the stack (A) where plurality of tie rods (11) encased in plurality of insulations for tie rods (12) pass through plurality of holes (3 OF) present on electrode end covers (30). The terminal ends of these tie rods (11) are affixed by plurality of insulation washers (13) followed by plurality of spring washers (14) and are then screwed by plurality of tightening means (15).

BIPOLAR PLATE ASSEMBLY (20)

The bipolar plate assembly (20) is the heart of electrolyser stack (A) where water gets split into oxygen and hydrogen at respective electrode i.e., Oxygen at anode and Hydrogen at cathode.

The bipolar plate assemblies (20) are the conductive plates on which both anode and cathode electrode plates (23, 26) are placed back-to-back. These assemblies constitute the backbone of the stack (A) as they isolate the electrolytic cells, conduct current between them, facilitate water and thermal management through the cell and provide degassing slots for reactant gases as well as removing reaction product. Eventually, these assemblies are helpful in decreasing the stack (A) length and optimize dimension.

Each of the bipolar plate assembly (20) includes a bipolar plate, an anode electrode plate (23), a current collector (24), a corrugated cushion mat (25) and a cathode electrode plate (26). Each bipolar plate consists of a non- conductive outer frame (21), the inner surface of which is coated with rubber lining (2 IF) to avoid electrolyte leakage and encasing a conductive partition plate (22), wherein outer frame is made up of non-conductive materials PU resin, epoxy resin, PU resin with rubber lining, thermosetting plastic with rubber lining, cement, ceramic with rubber lining, combination of resin and ceramic. The outer frame (21) is having plurality of degassing slots (21 A) present at its vertically upper side, the elliptical shape of which prevents drying up of the electrolytic cells due to foaming; interlocking means (21B) provided on its peripheral area; electrolyte inlets 1 and 2 (21 C, 21D) present at its vertically lower side; sealing serrations (21E) placed vertically parallel to both sides of wall of the partition plate (22); and rubber lining (21F) provided on the edges of plurality of degassing slots (21 A) and electrolyte inlets 1 and 2 (21 C, 21D). The interlocking means (21B) include but not limited to dowel holes, dowels and protrusions and are helpful in positioning of electrolytic cell and longer stack assembly. Additionally, it does not require skilled labour. Interlocking means cells fitted with each other using dowels in radial direction such that only axial movement is allowed. The sealing serrations (2 IE) present on the outer frame (21) are provided with guides which facilitate the stacking of the adjacent bipolar plate assemblies (20) via interlocking mechanism ensure easy and safe handling, eliminate the possibility of leakage of electrolyte, mixing of gases and thus exclude current losses at high operation pressure.

The partition plate (22) is having unique orientation of ribs such as plurality of vertical ribs (22A) facing anode electrode plate (23) and plurality of horizontal ribs (22B) facing cathode electrode plate (26). In case of electrode terminal cells, the partition plate (22) or outer frame (21) is also provided with plurality of feed terminals (22C) in its central part or at its circumference, respectively, which correspondingly project through terminal slits present in the central part or at circumference of the electrode end covers (30) and enable current conduction. These feed terminals (22C) projecting towards anode electrode plate (23) in the bipolar plate assembly (20) constitute anode terminal cell and if projecting towards cathode electrode plate (26) then form cathode terminal cell. These are second important part of the stack (A) as current enters through the feed terminals (22C) at anode terminal cell and leaves the stack through feed terminals (22C) at cathode terminal cell, thus resulting into splitting of water into hydrogen and oxygen. These cells are present at two ends of the electrolyser, one for anodic input and the other for cathodic output.

The partition plate having vertical ribs (21 A) is placed with anode electrode plate (23) while its other side having horizontal ribs (2 IB) is positioned with current collector (24) made of perforated and expanded nickel mesh and is sequentially followed by corrugated cushion mat (25) and cathode electrode plate (26). The anode electrode plate (23) is coated with nickel by cold thermal spray method to prevent its degradation, thus improves electrode life and operating performance significantly. The cathode electrode plate (26) supported with uniquely fabricated cushion mat (25) ensures maximum surface contact and is easily manufactured with the help of cold metal forming.

ANODE COATING

In the present embodiment, the anode comprises of conductive base material with at least one type of element selected from metal nickel, SS 304, SS 316 L, SS Duplex, nickel in the form of net or expanded mesh. The conductive base material is equipped for further coating by surface treatment like shot blasting. This enhances affinity between catalytic layer and base material.

The thickness of the conductive base material is preferably 1 mm with short way of opening 7.9 and long way of opening 25.4. The anode base material is 500 pm coated with the catalytic layer with optimum pore size, surface area and pore volume. The anode with its coating ensures smooth lysis of electrolyte and stable generation of Oxygen although subjected to power fluctuation from renewable energy to GRID or vice versa.

Plasma spraying followed by reduction for coating to set under high temperature around 5000°C has been reported in the prior arts. In the present invention, coating of anode is made very simple and cost effective. In this case, spot blast is followed by cold spraying in the temperature range of 150-350°C which is very simple and cost-effective as compared to Plasma spraying followed by reduction of coating and yet achieves equivalent and better performances in terms of energy requirement for same quantity of hydrogen generation.

CATHODE COATING

The cathode base material is made of nickel metal mesh of size 40 which is deposited with Ruthenium Oxide film of thickness- 3 pm having pore number- 15.75 ea/cm² and ratio of pore width to strand width- 4.8. The characteristic structural surface area is 2938 cm² with 28% coverage area.

ELECTROLYTIC CELL

The anode electrode plate (23) of bipolar plate assembly (20) with cathode electrode plate (26) of adjacent bipolar plate assembly (20) constitutes electrolytic cell.

ELECTRODE END COVER (30) The electrode end covers (30) comprise an anode end cover (31) present at one end and a cathode end cover (32) present at other end of the stack (A) and include electrolyte inlets 1 and 2 (30A, 30B), gas collectors 1 and 2 (30C, 30D), with or without terminal slits (30E), plurality of holes (30F) and a support (30G). Terminal slits (30E), plurality of holes (30F) and support (30G) are present on both the electrode end covers (30) in their central or peripheral part, on their periphery and at the bottom for entire stack (A), respectively of the present electrolyser while electrolyte inlets (30A, 30B) and gas collectors 1 and 2 (30C, 30D) are present only on anode end cover (31). The electrolyte inlets 1 and 2 (30A, 30B) are present adjacent to each other at vertically lower side of the anode end cover (31) and are communicatively connected to electrolyte inlets 1 and 2 (21C, 21D) present on outer frame (21A), while the gas collectors 1 and 2 (30C, 30D) are present at vertically upper side of anode end cover (31) opposite to electrolyte inlets 1 and 2 (30 A, 3 OB) and communicatively connected to degassing slots (21 A) present on outer frame (21) of the bipolar plate assembly (20).

PLURALITY OF MEANS OF SEALING (40)

For separation and avoid mixing of product gases, plurality of means of sealing (40) such as plurality of gaskets (41) accompanying plurality of diaphragms (42) are placed between two adjacent bipolar plate assemblies (20) and a pair of insulation gaskets (43) is fitted between gasket (41) and each electrode end cover (31, 32).

Another embodiment of the present invention refers to the process of manufacturing of alkaline electrolyser system using Green Technology.

For manufacturing of stack (A) of alkaline electrolyser system, first bipolar plate assemblies (20) are fabricated. For this, the partition plate (22) is welded with plurality of vertical ribs (22A) at its anode side and with plurality of horizontal ribs (22B) at its cathode side and is then held in prefabricated mould at predefined position. The inner surface of the prefabricated mould is provided with rubber lining (2 IF). Following this, pre-fabricated mould is poured with non-conductive material to mould outer frame (21) having plurality of degassing slots (21 A), interlocking means (2 IB), electrolyte inlets 1 and 2 (21 C, 2 ID) and sealing serrations (2 IE) and to embed the partition plate (22) having ribs in the outer frame (21). The rubber lining (2 IF) at the inner surface of mould results into partition plate (22) along with said outer frame (21) having inner rubber lining (21F). The rubber lining (2 IF) at degassing slots (21 A) and electrolyte contact faces such as electrolyte inlets 1 and 2 (21 C and 21D) and electrolyte path in bi-polar plates prevents leakage of electrolyte, current, gases and degradation of material. The partition plate (22) embedded in the outer frame (21) results in formation of a bipolar plate. One side of partition plate (22) having plurality of vertical ribs (22A) is linked with anode electrode plate (23) while its other side having plurality of horizontal ribs (22B) opposite to said anode electrode plate (23) is spot welded with current collector (24) followed by sequential sewing of corrugated cushion mat (25) and then fusing cathode electrode plate (26) to form bipolar plate assembly (20).

In second step, plurality of fabricated bipolar plate assemblies (20) is clasped sequentially using plurality of means of sealing (40) with anode terminal cell positioned at anode end cover (31) and cathode terminal cell placed at cathode end cover (32).

Lastly, plurality of bipolar plate assemblies (20) obtained in second step are stacked by means of cell stacking assembly (10) to form stack (A) of alkaline electrolyser system. The spring washers (14) of the cell staking assembly (10) pressed on electrode end covers (20) ensures stacking with adequate pressure on the cells and sealing gaskets all the time.

The process of manufacturing of bipolar plate with outer frame (21) in a single step saves lots of manufacturing steps for outer frame (21) and bipolar plates, thus the process is less time consuming, involves low capital and hence with improved production efficiency. The unique arrangement of welded ribs on partition plate (22) prevents buckling during high temperature operation and helps to reduce thickness for larger cross-sectional areas. The outer frame (21) made up of non-metallic and non-conductive material shows improved resistivity to electrical current and eliminates the possibility of thermal conduction at outer surface. Hence, the entire system operates at lower risk with better performance.

ADVANTAGES OF THE PRESENT INVENTION

The present invention provides many advantages, few are listed out below:

1) The present invention offers an alkaline electrolyser having a stack of bipolar plate assemblies making it more compact and power efficient than monopolar system.

2) The electrolyser of the present invention has an outer frame which is serrated and provided with guides to facilitate the stacking of the adjacent electrolytic cells via interlocking mechanism to ensure easy and safe handling, eliminates the possibility of leakage of electrolyte and thus eliminates current losses at high operation pressure.

3) The uniquely molded outer frame of the bipolar plate in present invention bears electrolyte holes, degassing slots, interlocking means, dowels, dowel holes and sealing serrations. The unique shape of degassing slots aids in foaming issues and thus prevents drying up of the electrolytic cells due to foaming.

4) The process of manufacturing of bipolar plate with outer frame is less time consuming and hence with improved production efficiency. Moreover, the manufacturing itself saves lots of manufacturing steps for outer frame and bipolar plates, thus ensures involvement of low capital.

5) The unique process used for coating surface of anode in the bipolar plate is such that it improves electrode life and operating performance.

6) The electrolytic and degassing path is made up of non-conductive material as an integral part of the outer frame. It is manufactured directly through mould as a cavity.

7) The alkaline electrolyser of the present invention having a cell staking assembly with spring washers pressed on electrode end covers ensures stacking with adequate pressure on the cells and sealing gaskets all the time.

8) The sealing means such as gaskets present between two adjacent bipolar plate assemblies are provided with serrations to ensure better sealing.

9) Thus, the present invention provides a commercially viable solution for hydrogen generation in the form of alkaline electrolyser with i) reduced overall weight, ii) low manufacturing and operating cost, iii) low power consumption, iv) single step molding of the bipolar plate with low cost-capital setup, v) reduced manufacturing and material cost due to the use of non-metal outer frame, vi) reduced overall cost of stacking due to use of guided cell assembly eliminating the need of skilled work force and vii) reduced stacking time.

INVENTIVE CONCEPT Some of the features that make the proposed invention novel and inventive are disclosed below:

1 ) The present invention provides an alkaline electrolyser with series of individual electrolytic cells in the form of bipolar plate assemblies stacked together.

2) The bipolar plate assemblies are formed by an innovative single step process of moulding a non-conductive material in specially fabricated mould so as to have electrolyte holes, degassing slots, interlocking means, sealing serrations, dowels, dowel holes and protrusions as a part of outer frame integrated with partition plate.

3) The present invention provides an alkaline electrolyser where the presence of interlocking means, dowels, dowel holes andsealing serrations on the non-metallic and non-conductive outer frame ensure no leakage at higher operating pressure, optimum interlocking of adjacent bipolar plates without mixing of gases and avoid bending. Thus, improvement in flow features improves overall performance and life of the system.

4) The non-metallic and non-conductive material of outer frame of the present invention improves resistivity to electrical current and eliminates the possibility of thermal conduction at outer surface. Hence, the entire system operates at lower risk with better performance.

5) The present invention provides an alkaline electrolyser with bipolar plates having outer frame with uniquely shaped degassing slots. These slots provide larger surface area, thus help in easy evacuation of bubbles and improve flow features which help to avoid foaming of the electrolytic solution and prevent drying up of the electrolytic cells. Existing designs does not address foaming issues appropriately which could lead to cell drying up issues and higher electrode temperatures related issues.

6) The present invention provides an alkaline electrolyser where bipolar plates are provided with partition plates having uniquely welded ribs. The partition plate has vertically welded ribs towards anode side and horizontally welded ribs towards cathode side. This type of arrangement prevents buckling during high temperature operation and helps to reduce thickness for larger cross-sectional areas. 7) The present invention is provided with an improvised corrugated cushion mat which can be easily manufactured with the help of cold metal forming and it offers support to the cathode electrode plate and prevents damage to the diaphragm.

8) TERMINAL CELLS DESIGN: The anode terminal cell is provided with anode feed terminals projecting toward the anode end cover and the cathode terminal cell is provided with cathode feed terminals projecting towards cathode end cover through the terminal slits formed at electrode end covers. All the slits are lined with rubber and resin or nonconductive material to ensure leakproof operation. The slits are located at central part of the plate, perpendicular to width of the plate or at the peripheral edge, parallel to width of the plate.

9) ANODE COATING: The anode base material is coated with the catalytic layer of optimum pore size, surface area and pore volume. The anode with its coating ensures smooth lysis of electrolyte and stable generation of Hydrogen and Oxygen although subjected to power fluctuation from renewable energy to GRID or vice a versa. Plasma spraying followed by reduction for coating to set under high temperature around 5000°C has been reported in the prior arts. In the present invention, coating of anode is made very simple and cost effective. In this case, spot blast is followed by cold spraying in the temperature range 150-350°C which is very simple and cost-effective as compared to Plasma spraying followed by reduction of coating and yet achieves equivalent and better performances in terms of energy requirement for same quantity of hydrogen generation.

10) ELECTRODE END COVER DESIGN: The end cover portion is provided with a latticeshaped reinforcing rib. Furthermore, the anode end cover is provided with electrolyte inlet 1 as anode liquid inlet nozzle, electrolyte inlet 2 as a cathode liquid inlet nozzle, gas collector 1 as anode gas outlet nozzle and gas collectors 2 as cathode gas outlet nozzle, all of which penetrate the end cover portion. Additionally, the anode end cover has terminal slit in its central part or at its circumference through which anode feed terminals are inserted.

At Cathode end cover, terminal slits are given but the electrolyte inlets and degassing slots are not provided on it. The terminal slits are present at the central part or at circumference of the cathode end cover. Alternatively, the outer frame of the electrode terminal cell is provided with feed terminals in its central part or over the circumference to prevent leakages at high pressure. ) ELECTROLYTIC FLOW PATH AND PRODUCT GAS FLOW PATH: The gasket has four channel holes. Out of these holes, first and second channel hole communicates with the electrolyte inlet 1 and 2 of anode end cover respectively, while third channel hole communicates with anode liquid and gas collector 1 and fourth channel hole communicates with the cathode liquid and gas collector 2 of anode end cover.

The electrolytic inlet holes 1 and 2 present at vertically lower side of resin outer frame are circular in shape and having a diameter of 6- 8 mm while the degassing slots (anode and cathode gas passing holes) present at its vertically upper side are of elliptical shape and their number varies from 3 to 5. The degassing slots on cathode side and on anode side are 35mm x 8mm and 35mm x 4mm in size, respectively.

Claims

We claim:

1. An alkaline electrolyser system comprising of a stack (A) wherein said stack (A) further comprising:

I. a cell stacking assembly (10) wherein, said cell stacking assembly (10) comprises: i) plurality of tie rods (11) passing through plurality of holes (30F) present on electrode end covers (30), ii) plurality of insulations for tie rods ( 12) encasing said tie rods (11), iii) plurality of insulation washers (13) affixed at terminal ends of said tie rods (11), iv) plurality of spring washers (14) affixed on said insulation washers (13) and v) plurality of tightening means (15) screwed on said spring washers (14);

II. a plurality of bipolar plate assemblies (20) arranged sequentially in said stack (A) including: i) said outer frame (21) made of non-conducting material having: a) plurality of degassing slots (21 A) present at vertically upper side of said outer frame (21), b) interlocking means (2 IB) provided on the peripheral area of said outer frame (21), c) electrolyte inlets 1 and 2 (21C, 21D) present at vertically lower side of said outer frame (21), d) sealing serrations (21E) placed vertically parallel to both sides of wall of a partition plate (22) and said interlocking means (2 IB) and e) rubber lining (21F) on the edges of said plurality of degassing slots (21A), said electrolyte inlets 1 and 2 (21C, 21D) and inner wall of said outer frame (21) facing said partition plate (22), ii). said partition plate (22) embedded in said outer frame (21) and having: a) plurality of vertical ribs (22A) facing an anode electrode plate (23), b) plurality of horizontal ribs (22B) facing a cathode electrode plate (26) and c) plurality of feed terminals (22C), iii). said anode electrode plate (23) welded at one side of said partition plate (22), iv). a current collector (24) welded on the other side of said partition plate (22) opposite to said anode electrode plate (23), v). a corrugated cushion mat (25) welded sequentially adjacent to said current collector (24) and vi). said cathode electrode plate (26) welded sequentially adjacent to said cushion mat (25);

III. said electrode end covers (30) comprising said anode end cover (31) present at one end and a cathode end cover (32) at other end of said stack (A) wherein, said electrode end covers (30) include: i) an electrolyte inlet 1 (30A) present at vertically lower side of said anode end cover (31) and communicatively connected to said electrolyte inlet 1 (21C), ii) an electrolyte inlet 2 (30B) present adjacent to said electrolyte inlet 1 (30A) on said anode end cover (31) and communicatively connected to said electrolyte inlet 2 (2 ID), iii) a gas collector 1 (30C) present opposite to said electrolyte inlet 1 (30A) at vertically upper side of said anode end cover (31) and communicatively connected to said degassing slots (21 A), iv) a gas collector 2 (30D) present opposite to said electrolyte inlet 2 (3 OB) at vertically upper side of said anode end cover (31) and communicatively connected to said degassing slots (21 A), v) terminal slits (30E) present on the said electrode end covers (30) vi) said plurality of holes (3 OF) present on periphery of said electrode end covers (30) and vii)a support (30G) for entire stack (A) present at the bottom of said electrode end covers (30) and

IV. plurality of means of sealing (40) comprising: i) plurality of gaskets (41) wherein, said plurality of gaskets (41) sits between two said adjacent bipolar plate assemblies (20), ii) plurality of diaphragm (42) accompanying said plurality of gaskets (41) rests between two said adjacent bipolar plate assemblies (20) and iii) a pair of insulation gaskets (43) wherein, said insulation gasket (43) fits between said gasket (41) and each said electrode end cover (31, 32). The alkaline electrolyser system as claimed in claim 1, wherein said bipolar plate assembly (20) having bipolar plate consisting of said partition plate (22) embedded in said outer frame (21). The alkaline electrolyser system as claimed in claim 1 , wherein said interlocking means (2 IB) present on said outer frame (21) include but not limited to dowel holes, dowels and protrusions. The alkaline electrolyser system as claimed in claim 1, wherein said feed terminals (22C) are present in the central part of said partition plate (22) of said bipolar plate assembly (20). The alkaline electrolyser system as claimed in claim 1, wherein said feed terminals (22C) are present on the rim of said outer frame (21) of said bipolar plate assembly (20). The alkaline electrolyser system as claimed in claim 1, wherein said anode electrode plate (23) of said bipolar plate assembly (20) constitutes electrolytic cell with said cathode electrode plate (26) of adjacent said bipolar plate assembly (20). The alkaline electrolyser system as claimed in claim 4, wherein said bipolar plate assembly (20) having said feed terminals (22C) project through said terminal slits (30E) present on the central part of said anode end cover (31) constituting anode terminal cell. The alkaline electrolyser system as claimed in claim 4, wherein said bipolar plate assembly (20) having said feed terminals (22C) project through said terminal slits (30E) present on the central part of said cathode end cover (32) constituting cathode terminal cell. The alkaline electrolyser system as claimed in claim 5, wherein said bipolar plate assembly (20) having said feed terminals (22C) project through said terminal slits (30E) present on the circumference of said anode end cover (31) constituting anode terminal cell. The alkaline electrolyser system as claimed in claim 5, wherein said bipolar plate assembly (20) having said feed terminals (22C) project through said terminal slits (30E) present on the circumference of said cathode end cover (32) constituting cathode terminal cell. A process of manufacturing of said alkaline electrolyser system comprising steps of:

I. fabrication of said bipolar plate assembly (20): i) welding said plurality of vertical ribs (22A) at anode side of said partition plate (22), ii) welding said plurality of horizontal ribs (22B) at cathode side of said partition plate (22), iii) placing said rubber lining (2 IF) at the inner surface of a pre-fabricated mould, iv) holding said partition plate (22) at predefined position along with pre-fabricated mould having the inner rubber lining (21F), v) moulding said outer frame (21) having said plurality of degassing slots (21A), said interlocking means (21B), said electrolyte inlets 1 and 2 (21C, 21D) and said sealing serrations (2 IE) by pouring non-conductive material in pre-fabricated mould to get said partition plate (22) embedded in said outer frame (21) with inner rubber lining (2 IF), vi) welding said feed terminals (22C) at said partition plate (22) embedded in said outer frame (21), vii) sealing said plurality of degassing slots (21 A) and said electrolyte inlets 1 and 2 (21C, 21D) of said outer frame (21) with the help of rubber lining (2 IF) to yield a bipolar plate, viii) welding said anode electrode plate (23) at one side of said partition plate (22) having said plurality of vertical ribs (22A), ix) spot welding said current collector (24) on the other side of said partition plate (22) having said plurality of horizontal ribs (22B) opposite to said anode electrode plate (23), x) sewing said cushion mat (25) sequentially adjacent to said current collector (24) and xijfusing said cathode electrode plate (26) sequentially adjacent to said cushion mat (25) to form said bipolar plate assembly (20);

II. clasping said plurality of bipolar plate assemblies (20) sequentially using said plurality of means of sealing (40) with anode terminal cell positioned at said anode end cover (31) and cathode terminal cell placed at said cathode end cover (32) and III. stacking said plurality of bipolar plate assemblies (20) obtained in step II by means of said cell stacking assembly (10) to form stack (A) of alkaline electrolyser system. The process of manufacturing of said alkaline electrolyser system as claimed in claim 11 step (vi), wherein said feed terminals (22C) are welded towards said anode electrode plate (23) in said bipolar plate assembly (20) to form anode terminal cell. The process of manufacturing of said alkaline electrolyser system as claimed in claim 11 step (vi), wherein said feed terminals (22C) are welded towards said cathode electrode plate (26) in said bipolar plate assembly (20) to form cathode terminal cell.