Description:FIELD OF THE INVENTION
The present invention relates to end plates with a transparent window for use with electrolyser cell stacks and a method of manufacture of said endplates.

BACKGROUND OF THE INVENTION
Energy from renewable and sustainable sources as an alternative to fossil fuels is a primary focus for most countries in the world. Hydrogen, generated from renewable sources and termed as Green Hydrogen has since emerged as a fuel of choice to replace fossil fuels, in the years to come.
An electrolyser is an equipment that splits water into Hydrogen and Oxygen using electricity. Electrolysers are generally an assembly of Electrolyser Cells, wherein each Electrolyser Cell comprises primarily of three components - a couple of Electrodes separated by a Bipolar Plate, with an optional membrane to prevent diffusion of the gases produced from electrolysis of water. An Electrolyser Cell stack is made by serially connecting multiple such single Electrolyser Cells into an Electrolyser. The Bipolar Plates are the serial-connecting conductive components in the Electrolyser cell stack that act as an anode for one cell and a cathode for the next cell. In the Electrolyser, multiple Electrolyser Cells are stacked and held together sandwiched between two End plates.
Conventional technologies for making Electrolysers Cell Stacks include Solid Oxide Electrolyser Cells (SOECs), Polymer Electrolyte Membrane cells(PEM) and Alkaline Electrolysis Cells (AECs). All these conventional technologies use End plates to hold together the Cell stacks.
End plates, being an important component in constructing a Electrolyser Cell Stack perform the primary function of holding all the Electrolyser Cells in the stack together, with sufficient pressure, ensuring that the gases produced or the electrolyte or the catalyst do not escape/leak. End plates require the following characteristics: good mechanical properties, impermeable to gases, resistance to corrosion, resistance to high temperature, and so on. End Plates currently are made of out of metals (generally SS or MS) or composites and are opaque. Non-transparent End Plates have the disadvantage of not permitting visual observation of the generation of gases in the Electrolyser Cell.
In view of the disadvantages of the prior art, there is a need for providing transparency in the End Plates, to enable visual observation of generation of gases in the Cell, without compromising on the primary function of the End Plates of holding the stack together, and retaining the requirements of good mechanical properties, impermeability to gases, resistance to corrosion, resistance to high temperature.
To achieve the above object, the present invention provides incorporation of a transparent window in both End Plates. This invention resides in an End plate and method of manufacture for permitting the visual observation of the gas generation in the electrolyser cell stacks while ensuring the operation of the electrolyser cell stack without leakages of gases, electrolyte, catalyst.

OBJECTS OF THE INVENTION
It is an object of the invention to provide end plates having a transparent window for visual observation of generation of gases in the Electrolyser Cell.
It is another object of the invention to ensure the operation of the electrolyser cell stack without leakages of gases, electrolyte, catalyst at desired level of operation temperature and pressure.
It is yet another object of the invention is to enable the analytical observation for the extent of gas generation and the flow pattern of gases in varying conditions of current density, operating temperature and operating pressure.

SUMMARY OF THE INVENTION
The present invention relates to end plates for use with electrolyser cell stacks, each of said end plates having a transparent window. The invention provides transparency in the End Plates to enable visual observation of generation of gases in the Cell, without compromising on the primary function of the End Plates of holding the stack together, and retaining the requirements of good mechanical properties, impermeability to gases, resistance to corrosion, resistance to high temperature.

BRIEF DESCRIPTION OF THE DRAWINGS
The preferred embodiment of the invention is described in detail below, with reference to the figures:
FIG. 1 is a schematic diagram showing the Electrolyser Cell Stack with a two Cell, in a Rectangular Shape, with the transparent sheet, being the present invention, incorporated within the End Plates, on both sides of the Stack.
FIG. 2 is a schematic sectional view of the End Plate.

DETAILED DESCRIPTION OF THE INVENTION
The present invention provides incorporation of a see through window in the End Plates located on both sides of an Electrolyser cell stack.
The End plates and the method of manufacture ensure visual and analytical observation of the following under varying conditions of density of current, operating temperature and pressure:
• Extent of gas generation;
• Flow patterns of gases.
The end plates and the method of manufacture also ensure consistent performance, without leakages of gases, electrolyte or catalyst.
FIG. 1is a schematic diagram showing the Electrolyser Cell Stacks in Rectangular shape. The Electrolyser Cell Stacks may also be of other shapes, for example, Round or Square shaped.
The End Plates (1, 2) of the Electrolyser cell stacks (18) have the required design and outer profile to enable them to perform the function of mechanically holding together the stack cells sandwiched between the two End Plates.
As seen in Fig. 2. the End Plates are formed with a window (3), cut out in the material of the end plate, leaving an end plate frame (4) with a window opening (5). The window (3) is located substantially in the centre of the end plate.
A transparent sheet (6) is disposed in the window (3), enabling visual observation of the generation of gases in the Electrolyser. The dimensions of the transparent sheet are sufficient to provide visual observation of the Electrode in the Electrolyser. The dimensions of the transparent sheet are smaller than the dimensions of the window.
The shape of the End plate (1, 2), the window (3) and the transparent sheet (6) correspond to the shape of the Electrolyser Cell (for example, Round, Square or Rectangular). The End Plate may be formed of Metal (SS, MS Nickel or any other metal) or Composite or polymer.
The transparent sheet may be formed from toughened glass or polymer of choice. The thickness of the transparent sheet is less than the thickness of the End plate as seen in Fig. 2.
A holding plate (7) secures the transparent sheet (6) to the end plate (1, 2). The holding plate is provided with an opening (8). The shape of the holding plate (7) and the opening (8) correspond to the shape of the transparent sheet (6) and the window (3). The inner dimensions of the holding plate (7) [dimensions of opening (8)] are smaller than the dimensions of the transparent sheet (6). Further, the inner dimensions of the holding plate (7) are smaller than the inner dimensions of the End Plate Frame [dimensions of window (3)]. The outer dimensions of the Holding Plate (7) are smaller than the outer dimensions of the end plate frame (4). The said dimensions are length and breadth; or diameter.
The holding plate is generally made from the same material as the End plate.
The holding plate (7) is provided with two oppositely placed, first L-shaped notch (9) and second L-shaped notch (10) in its inward facing profile.
The outside edge of the transparent sheet (6) is aligned with and secured to the first L-shaped notch (9) in the holding plate as shown in Fig. 2. A first gasket (11) is disposed between the transparent sheet (6) and the vertical arm (12) of the first L-shaped notch (9) in the holding plate.
The holding plate with the attached transparent sheet is secured to the end plate on its outward facing side such that inner edge (13) of the end plate frame (4) is aligned with and secured to the second L-shaped notch (10) of the holding plate. A second gasket (14) is disposed between the end plate and the vertical arm (15) of the second L-shaped notch (10) in the holding plate, preventing leakages of gases, electrolyte, catalyst.
The gaskets (11, 13) may be formed from natural rubber, Synthetic rubber, polymer, composite.
The holding plate may further be bolted to the end plate frame using bolts (16). The entire assembly is locked with the help of lock nut (17).
The Electrolyser Cell Stack (18) is assembled by sandwiching the Cells Series (19) between the two End Plates (1,2) with Lock Nuts (17) and Tie Rods (20).

The method of manufacturing the end plate (1, 2) of the present invention is as follows:
The first Gasket (11) is secured to the vertical arm (12) of the first L-shaped notch (9) in the holding plate (7), using an adhesive or sealant. The edge of the transparent sheet (6) is aligned with and secured to the first L-shaped notch (9) in the holding plate using adhesive or sealant, such that the first gasket (11) is wedged between the transparent sheet and the holding plate, thus preventing leakages.
The second gasket (14) is fixed to vertical arm (15) of the second L-shaped notch (10) in the holding plate, using an adhesive or sealant.
The holding plate with the attached transparent sheet is placed over the window opening (5) of the end plate and is secured to the end plate on its outward facing side. The inner edge (13) of the end plate frame (4) is aligned with and secured to the second L-shaped notch (10) of the holding plate using adhesive or sealant, such that the second gasket (14) is wedged between the end plate and the holding plate, thus preventing leakages.
All the open edges of the joints between the End plate (1, 2) and the transparent sheet (6) and between the holding plate (7) and the transparent sheet (6) are sealed using a Sealant of choice to prevent leakage of of gases, electrolyte, catalyst.
The holding plate (7) may further be bolted to the end plate frame (4) with bolts (16). The entire assembly is held together by the Tie Rods (20) and locked in place with lock nuts (17).
The Electrolyser Cell Stack (18) is assembled by sandwiching the Cells Series (19) between the two End Plates (1,2) with Tie Rods (20).
The method of manufacture of the present invention ensures that there are no leakages of the gases generated in the Electrolyser stack.
The End Plate of the present invention enable visual observation of the generation of gases – for both extent and patterns of flow – at varying levels of:
o Current Density,
o Operating temperature and
o Operating pressure
o Electrode Life
The End Plate design and method of manufacture, while permitting visual observation of gas generation, will ensure operation of the Electrolyser Cell Stack:
o Without leakages of gases, electrolyte, catalyst
o At desired levels of:
 Operating temperature
 Operating Pressure , Claims:We claim:
1. An end plate (1, 2) with transparent window for use in electrolyser cell stacks, said end plate comprising of:
an end plate frame (4) provided with a window (3);
a transparent sheet (6); and
a holding plate (7) securing the transparent sheet (6) to the end plate frame (4).
2. The end plate as claimed in claim 1 wherein the window (3) is centrally located.
3. The end plate as claimed in claim 1 wherein the dimensions of the transparent sheet (6) are smaller than the dimensions of the window (3).
4. The end plate as claimed in claim 1 wherein the holding plate (7) is provided with an opening (8), wherein the shape of the opening corresponds to the shape of the transparent sheet (6).
5. The end plate as claimed in claim 1 wherein the holding plate (7) is provided with oppositely placed, first L-shaped notch (9) and second L-shaped notch (10) in its inward facing profile.
6. The end plate as claimed in claim 5 wherein the edge of the transparent sheet (6) is aligned with and secured to the first L-shaped notch (9) in the holding plate.
7. The end plate as claimed in claim 6 wherein a first gasket (11) is disposed between the transparent sheet (6) and the first L-shaped notch (9) in the holding plate.
8. The end plate as claimed in claim 5 wherein the inner edge (13) of end plate frame (4) is aligned with and secured to the second L-shaped notch (10) in the holding plate.
9. The end plate as claimed in claim 8 wherein a second gasket (14) is disposed between the end plate and the second L-shaped notch (10) in the holding plate.
10. The end plate as claimed in claim 1 wherein the shape of the end plate (1,2), holding plate (7), window (3) and transparent sheet (6) correspond to the shape of the Electrolyser Cell in the electrolyser cell stack.
11. The end plate as claimed in claim 1 wherein the material forming the end plate (1, 2) and the holding plate (7) comprises metal including stainless steel and mild steel nickel or composite or polymer.
12. The end plate as claimed in claim 1 wherein the material forming the transparent sheet (6) comprises toughened glass or polymer.
13. The end plate as claimed in claim 1 wherein the material forming the gasket (11, 14) comprises natural rubber, synthetic rubber, polymer, composite.
14. The end plate as claimed in claim 1 wherein bolts (16) are used to secure the holding plate (7) to the end plate frame (4).
15. The end plate as claimed in claim 1 wherein said end plate has dimensions sufficient to mechanically holding together cell stacks sandwiched between said end plates (1,2).
16. A method of manufacturing the end plate (1, 2) as claimed in claims 1 to 15, comprising the steps:
a. securing a first gasket (11) to the holding plate (7);
b. securing the transparent sheet (6) to the holding plate (7);
c. securing a second gasket (14) to the holding plate (7);
d. securing the holding plate (7) with the attached transparent sheet (6) to the end plate frame (4).

17. The method as claimed in claim 16 wherein,
in step (a), the first gasket (11) is secured to the first L-shaped notch (9) in the holding plate, with an adhesive or sealant;
in step (b), the outside edge of the transparent sheet (6) is aligned with and secured to the first L-shaped notch (9) in the holding plate with an adhesive or sealant, such that the first gasket (11) is wedged between the transparent sheet and the holding plate;
in step (c), the second gasket (14) is secured to the second L-shaped notch (10) in the holding plate, using an adhesive or sealant; and
in step (d),
the holding plate (7) with the attached transparent sheet (6) is placed over the window opening (5) of the end plate and is secured to the end plate on its outward facing side; and
the inner edge (13) of the end plate frame (4) is aligned with and secured to the second L-shaped notch (10) of the holding plate using adhesive or sealant, such that the second gasket (14) is wedged between the end plate and the holding plate.

18. The method as claimed in claim 16 comprising step (e) wherein, sealant is used to seal joints between the End plate (1, 2) and the transparent sheet (6) and between the holding plates (7) and the transparent sheet (6).
19. The method as claimed in claim 16-18 wherein, the holding plate is bolted to the end plate frame with bolts (16).