This invention relates to an assembly for securing and compressing a stack electrolysis cell.
Electrolysis cells have long been used to generate hydrogen from water, generally in the form of an electrolyte solution.
In a particular electrolysis cell, porous anode and cathode plates are arranged in a stack with an electrolyte permeable-gas impermeable membrane placed between each anode and cathode pair (WO2004/020701; CA2,400,775 ELECTROLYZER, Helmke et al., incorporated herein by reference). By providing separate channels to each of the anodes and cathodes, the product gases generated at each of the anodes and cathodes may be separately output from the cell. Electrolyte is circulated through the porous anodes and cathodes. In order to circulate the electrolyte and provide an outlet for the product gases, the channels are created by cutting holes or slots in each plate that align when the plates are stacked. The aligned holes and slots form the channels to circulate electrolyte and provide for output of the product gases.
An advantageous method of manufacturing such a cell has been to stack the anode plates, cathode plates and membranes and encase the resulting stack in an electrolyte impermeable-gas impermeable membrane such as epoxy resin. The epoxy is used to assist in sealing the edges of the plates and to secure the plates in an aligned stack. The resultant electrolyser may thus be comprised of multiple electrolysis cells encased in an epoxy resin casing. Ports may be provided through the epoxy casing to permit circulation of electrolyte and output of the product gases. Electricity may be provided to the cells via an electrical connection that extends out of the epoxy.
While this method of creating an electrolyser from a stack of anode and cathode plates has been successful, it does suffer from some limitations. The resulting electrolysers are limited in their gas output rate as elevated internal pressures cause the epoxy to swell and allow the plates to separate. Once the plates separate, even by a relatively small amount, the channels may no longer be completely separate. Even a small breakdown in channel integrity may result in co-mingling of product gases and electrolyte, reducing output from the electrolyser.
A further limitation of the cells is that the electrolyte circulation ports and product gas output ports are connected to external plumbing via connectors screwed directly into the epoxy. While for light duty applications this may be sufficient, it would be preferable to provide for connectors with higher pull out strength and improved sealing.
Thus, it would be advantageous to provide for a stack cell and a method of manufacturing such a stack cell that alleviates these limitations.
In drawings which illustrate embodiments of the invention by way of example only:
a is an isometric exploded view of a stack of electrolysis plates.
b is an isometric view of an assembled electrolysis cell.
a is a further isometric view of the compression plate of
b and 6c are a side view cut-away illustration of the guide locators and compression plate of
a is an isometric illustration of the compression plate of
b is an enlarged side view of a guide locator
a is an isometric view of a cell positioned over the elastomer layer of
b and 8c are side view cut-away views of the cell and guide locators of
a and 13b are isometric views of a further embodiment of the invention.
a and 14b are isometric view illustrations of a further embodiment of a compression plate.
Referring to
The electrolysis plates 12 may be assembled into the stack 10 and maintained in alignment by encasing the stack 10 in a sealant such as epoxy, a silicone compound or any other suitable sealant, to seal the edges of the plates and maintain the stack 10 in alignment to provide an electrolysis cell 100 as illustrated in
During operation of the cell 100, a current supplied to electrodes 14 results in hydrogen and oxygen gas being generated in the electrolysis plates 12 of the cell 100. The generation of these product gases increases the internal pressure of the cell 100, causing the product gases to egress through the product gas ports 210, 215. In order to increase the gas output of the cell 100, a higher electrical input may be supplied to the electrodes 14. The higher electrical input results in the product gases being generated more quickly, the internal pressure of the cell 100 increasing and a higher flow rate of product gases from product gas ports 210, 215. It has been found that a cell 100 manufactured as described above has a maximum effective gas output rate before the cell 100 swells and allows product gases and electrolyte to mix within the cell 100.
It has surprisingly been found that a cell 100 may be operated at higher levels of gas output, and subsequent higher internal operating pressures, if a substantially even compressive force is applied to opposite ends of the cell 100 and maintained during operation. It has also been found that accommodation is preferably made for thermal expansion of the cell 100 while under the compressive force. In one embodiment accommodation for thermal expansion of the cell 100 is made by inserting an elastomer layer between the compressive force and at least one end of the cell 100.
In an embodiment, the invention provides an apparatus for securing an electrolyser comprised of a stack of electrolysis plates, the apparatus comprising, a pair of compression plates for locating at opposite ends of the stack of electrolysis plates and, a compression means adapted to engage the plates and urge them towards one another, compressing the cell.
In another embodiment, there is provided an electrolyser comprising a stack of electrolysis plates, the plates being maintained in alignment to comprise an electrolysis cell, and a press for applying a compressive force transversely to opposed ends of the cell whereby the press maintains the electrolysis plates in substantial alignment when the electrolyser is in operation.
Further, the press may comprise a first compression plate for locating at one end of the cell and a second compression plate for locating at the opposed end of the cell and a compression member for acting on the first and second compression plates to apply a compressive force to the cell.
Further, at least one elastomer layer may be positioned between the compression plates and the electrolysis cell. Preferably the elastomer layer is composed of, at least in part, Ethylene Propylene Dieene Monomer.
In an embodiment an elastomer layer is introduced between the compressive force and the cell to allow for thermal expansion or contraction of the cell. Depending upon the material properties of the cell, and the desired range of operating temperatures, it is possible that the cell could swell. In such circumstances, the elastomer layer accommodates the expansion of the cell minimising the risk that the cell might rupture or crack.
Referring to
Preferably a compression plate 610a is first positioned on guide locators 605. Inserts 627, not shown in this view, may also be positioned with the guide locators 605 to align the elastomer layer 625 and an O-ring 627. The cell 100 may then be positioned on the inserts 627 and guide locators 605. An O-ring 627, which may be formed integrally with the elastomer layer 625 about the port openings or installed as a separate component, provides sealed engagement between the product gas ports 210, 215, electrolyte ports 220, 230 and the compression plate 610a. Preferably, as shown, an elastomer layer 625 may also be positioned between the cell 100 and the compression plate 610a. An opposed compression plate 610b may then be positioned on top of the cell 100. Optionally a second elastomer layer 625 may be positioned between the cell 100 and the opposed compression plate 610b. In the embodiment illustrated in
A compression member such as the threaded element 630 illustrated in
In the embodiment of
Alternatively, the compression member may comprise a compression bracket where the compression bracket both engages with the compression plates 610 and applies a compressive force without the need for a separate compression element (not shown). This could be achieved, for instance, where the compression bracket comprises an elastically deformable material that may be elastically deformed under an external force to engage the compression plates 610, and when the external force is removed the compression bracket imparts a compressive force on the compression plates 610.
In an optional arrangement (not shown), one compression plate may comprise an internal wall of a container for housing the cell 100 and a second compression plate 610 may be employed to impart a compressive force to the cell 100 by using a compression member to engage with the second compression plate 610 and another wall of the container. As will be appreciated, in this arrangement a wall of the container comprises a compression plate 610 and at least one other wall of the container comprises the compression bracket 650 for engaging with a compression member 630 to apply a compressive force to the second compression plate 610 and subsequently the cell 100.
Preferably, after assembly of the bracket 650 and application of a compressive force, end walls 653 may affixed in place to provide a protective container for the cell 100.
a shows inserts 627 located in the port apertures 615 of the compression plate 610a. Preferably as shown the port apertures 615 are conveniently threaded, to assist in securing input and output connectors in communication with a cell 100.
As shown in
a shows the cell 100 positioned over the elastomer layer 625.
As shown in
As illustrated in
In an alternate embodiment depicted in
The compression plates 400 illustrated in the embodiment of
In a preferred embodiment illustrated in
Various embodiments of the present invention having been thus described in detail by way of example, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention. The invention includes all such variations and modifications as fall within the scope of the appended claims.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CA07/00837 | 5/10/2007 | WO | 00 | 12/20/2010 |