CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application Serial No. 63/363,237, filed on April 19, 2022, entitled “SENSOR ARRAY FOR MULT-CELL ELECTROLYZER STACK,” the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

[0002] Hydrogen gas is used in many chemical processes. As of 2019, roughly 70 million tons of hydrogen is produced annually worldwide for various uses, such as oil refining, in the production of ammonia (through the Haber process), in the production of methanol (though reduction of carbon monoxide), or as a fuel in transportation.

[0003] Historically, a large majority of hydrogen (-95%) has been produced from fossil fuels, such as by steam reforming of natural gas, partial oxidation of methane, or coal gasification. Other methods of hydrogen production include biomass gasification, low- or no-CO2 emission methane pyrolysis, and electrolysis of water. Water electrolysis uses electricity to split water molecules into hydrogen gas and oxygen gas. To date, electrolysis systems and methods have been generally more expensive than fossil-fuel based production methods. However, fossil-fuel based methods can be more environmentally damaging, generally resulting in increased CO2 emissions. Therefore, there is a need for cost-competitive and environmentally-friendly electrolysis systems and methods for the production of hydrogen gas.

SUMMARY

[0004] The present disclosure describes systems and methods for more environmentally-friendly and lower-cost production of hydrogen gas via electrolysis of water. The present disclosure relates to electrolysis systems comprising an electrolyzer stack of one or more electrolyzer cells with a sensor array for measuring one or more phenomena associated with the electrolyzer cells of the stack. The sensor arrays of the present disclosure can more efficiently and effectively measure the one or more phenomena and transmit the measurements to a central controller for the electrolyzer stack.

[0005] In an example, the present disclosure describes a sensor system comprising a sensor array comprising one or more sensors configured to produce sensory signals corresponding to one or more specified phenomena of an electrolyzer cell, a sensor board configured to amplify, filter, shape, or condition the sensory signals and to digitize the sensory signals to provide digitized information, a first communication link between the sensor board and a sensor array, and a second communication link configured to transmit the digitized information to a central controller outside the sensor system.

[0006] In another example, the present disclosure describes an electrolyzer system comprising an electrolyzer stack comprising one or more electrolyzer cells, wherein each electrolyzer cell comprises a first half-cell with a first electrode and a second half-cell with a second electrode, a central controller configured to control operation of one or more aspects of each of the one or more electrolyzer cells of the electrolyzer stack, a sensor array for each of one or more corresponding electrolyzer cells of the electrolyzer stack, wherein each sensor array comprises one or more sensors configured to produce sensory signals corresponding to one or more specified phenomena of the corresponding electrolyzer cell, a sensor board for each corresponding electrolyzer cell, wherein each sensor board is configured to amplify, filter, shape, or condition the sensory signals from a corresponding sensor array and to digitize the sensory signals to provide digitized information for the corresponding electrolyzer cell, and a communication link for each sensor board, wherein each communication link is configured to transmit the digitized information for the corresponding electrolyzer cell to the central controller.

[0007] In another example, the present disclosure describes a method of producing hydrogen gas, the method comprising providing or receiving an electrolyzer stack comprising one or more electrolyzer cells, wherein each electrolyzer cell comprises a first half-cell with an anode and a second half-cell with a cathode, producing hydrogen gas at the cathode, measuring one or more specified phenomena of a corresponding one of the one or more electrolyzer cells with a sensor array comprising one or more sensors associated with the corresponding one of the one or more electrolyzer cells, wherein the one or more sensors produces sensory signals corresponding to the one or more specified phenomena, modifying the sensory signals to provide digitized information corresponding to the sensory signals, and transmitting the digitized information to a central controller configured to control operation of one or more aspects of the one or more electrolyzer cells of the electrolyzer stack.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

[0009] FIG. l is a schematic diagram of an example electrolyzer cell for the electrolysis of water to produce hydrogen gas.

[0010] FIG. 2 is a front view of an example pan assembly that can form an anode half cell, a cathode half cell, or both in an electrolyzer cell.

[0011] FIG. 3 is a side view of the example pan assembly of FIG. 2.

[0012] FIG. 4 is a close-up perspective view of a top portion of the example pan assembly of FIGS. 2 and 3, showing a manifold of the pan assembly.

[0013] FIG. 5 is a close-up side view of the manifold of the example pan assembly of FIGS. 2 and 3.

[0014] FIG. 6 is a first perspective view that conceptually shows the flow of electrolyte into the manifold of the example pan assembly of FIGS. 2 and 3.

[0015] FIG. 7 is a second perspective view that conceptually shows the flow of electrolyte into the manifold of the example pan assembly of FIGS. 2 and 3.

[0016] FIG. 8 is a side view of a second example pan assembly that can form an anode half cell, a cathode half cell, or both, in an electrolyzer cell.

[0017] FIG. 9 is a front view of the second example pan assembly of FIG. 8.

[0018] FIG. 10 is a perspective view of the second example pan assembly of FIGS. 8 and 9, which shows details of a baffle assembly located within the second example pan assembly. [0019] FIG. 11 is a perspective view of the second example pan assembly of FIGS. 8 and 9 with an electrode coupled to the baffle assembly. [0020] FIG. 12 is a cross-sectional side view of the second example pan assembly of FIGS. 8 and 9 and a corresponding cross-sectional side view of a comparative pan assembly that does not include a baffle assembly.

[0021] FIG. 13 is schematic side view showing a simulated flow distribution of electrolyte within the second example pan assembly compared to a comparative flow distribution within the comparative pan assembly.

[0022] FIG. 14 is perspective view of a baffle plate that can form part of the baffle assembly in the second pan assembly of FIGS. 8 and 9.

[0023] FIG. 15 is a front view of a third example pan assembly that can form an anode half cell, a cathode half cell, or both, in an electrolyzer cell.

[0024] FIG. 16 is a cross-sectional side view of the third example pan assembly of FIG. 15.

[0025] FIG. 17 is a close-up cross-sectional side view of the third example pan assembly of FIGS. 15 and 16.

[0026] FIG. 18 is a perspective view of the third example pan assembly of FIGS. 15 and 16, which shows details of one or more ribs within the third example pan assembly.

[0027] FIGS. 19A-19C show perspective views of various alternative rib structures for the third example pan assembly.

[0028] FIG. 20 is a schematic view of an electrolyzer stack comprising a plurality of electrolyzer cells each including a sensor array, wherein a sensor board of each sensor array is directly electrically connected to a global power and communication bus for communication with a central controller.

[0029] FIG. 21 is a schematic view of an electrolyzer stack comprising a plurality of electrolyzer cells each including a sensor array, wherein a sensor board of each sensor array communicates wirelessly with a central controller of the electrolyzer stack.

[0030] FIG. 22 is schematic diagram of an example sensor board that can be used in one or more of the sensor arrays in the example electrolyzer stack of FIG. 21. [0031] FIG. 23 is a schematic circuit diagram for the example sensor board that can be used in one or more of the sensor arrays in the example electrolyzer stack of FIG. 21.

DETAILED DESCRIPTION

[0032] The following detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments, which are also referred to herein as “examples,” are described in enough detail to enable those skilled in the art to practice the invention. The example embodiments may be combined, other embodiments may be utilized, or structural, and logical changes may be made without departing from the scope of the present invention. While the disclosed subject matter will be described in conjunction with the enumerated claims, it will be understood that the exemplified subject matter is not intended to limit the claims to the disclosed subject matter. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.

[0033] References in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described can include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0034] Values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or subranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a concentration range of “about 0.1% to about 5%” should be interpreted to include not only the explicitly recited concentration of about 0.1 wt. % to about 5 wt. %, but also the individual concentrations (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.1% to 0.5%, 1.1% to 2.2%, and 3.3% to 4.4%) within the indicated range. The statement “about X to Y” has the same meaning as “about X to about Y,”” unless indicated otherwise. Likewise, the statement “about X, Y, or about Z” has the same meaning as “about X, about Y, or about Z,” unless indicated otherwise.

[0035] In this document, the terms “a,” “an,” or “the” are used to include one or more than one unless the context clearly dictates otherwise. The term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. Unless indicated otherwise, the statement “at least one of’ when referring to a listed group is used to mean one or any combination of two or more of the members of the group. For example, the statement “at least one of A, B, and C” can have the same meaning as “A; B; C; A and B; A and C; B and C; or A, B, and C,” or the statement “at least one of D, E, F, and G” can have the same meaning as “D; E; F; G; D and E; D and F; D and G; E and F; E and G: F and G; D, E, and F; D, E, and G; D, F, and G; E, F, and G; or D, E, F, and G.”

[0036] In the methods described herein, the steps can be carried out in any order without departing from the principles of the invention, except when a temporal or operational sequence is explicitly recited. Furthermore, specified steps can be carried out concurrently unless explicit language recites that they be carried out separately. For example, a recited act of doing X and a recited act of doing Y can be conducted simultaneously within a single operation, and the resulting process will fall within the literal scope of the process. Recitation in a claim to the effect that first a step is performed, and then several other steps are subsequently performed, shall be taken to mean that the first step is performed before any of the other steps, but the other steps can be performed in any suitable sequence, unless a sequence is further recited within the other steps. For example, claim elements that recite “Step A, Step B, Step C, Step D, and Step E” shall be construed to mean step A is carried out first, step E is carried out last, and steps B, C, and D can be carried out in any sequence between steps A and E (including with one or more steps being performed concurrent with step A or Step E), and that the sequence still falls within the literal scope of the claimed process. A given step or sub-set of steps can also be repeated.

[0037] Furthermore, specified steps can be carried out concurrently unless explicit claim language recites that they be carried out separately. For example, a claimed step of doing X and a claimed step of doing Y can be conducted simultaneously within a single operation, and the resulting process will fall within the literal scope of the claimed process.

[0038] The term “about” as used herein can allow for a degree of variability in a value or range, for example, within 10%, within 5%, within 1%, within 0.5%, within 0.1%„ within 0.05%, within 0.01%, within 0.005%, or within 0.001% of a stated value or of a stated limit of a range, and includes the exact stated value or limit of the range.

[0039] The term “substantially” as used herein refers to a majority of, or mostly, such as at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more, or 100%.

[0040] In addition, it is to be understood that the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation. Furthermore, all publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls.

Electrolyzer Cell

[0041] Hydrogen gas (H2) can be formed electrochemically by a watersplitting reaction where water is split into oxygen gas (O2) and H2 gas at an anode and a cathode of an electrochemical cell, respectively. Examples of such electrochemical processes include, without limitation, proton electrolyte membrane (PEM) electrolysis and alkaline water electrolysis (AWE). A generic water electrolyzer cell 101 that converts water into hydrogen and oxygen with electrical power is illustrated in FIG. 1. The electrolyzer cell 101 comprises two half cells: a first half cell 111 and a second half cell 121. In an example, the first and second half cells 111, 121 are separated by a separator 131 that can reduce unwanted migration of species between the half cells 111, 121, which can improve overall efficiency of the electrolyzer cell 101. In an example, the separator 131 comprises a porous membrane (e.g., a microporous membrane or a nanoporous membrane), an ion-exchange membrane, or an ion-solvating membrane. In examples wherein the separator 131 comprises an ion-exchange membrane, the ion-exchange membrane can be of different types, such as an anion exchange membrane (AEM), a cation exchange membrane (CEM), a proton exchange membrane (PEM), or a bipolar ion exchange membrane (BEM).

[0042] In examples where the separator 131 is a cation exchange membrane, the cation exchange membrane can be a conventional membrane such as those available from, for example, Asahi Kasei Corp, of Tokyo, Japan, or from Membrane International Inc. of Glen Rock, NJ, USA, or from The Chemours Company of Wilmington, DE, USA. Examples of cation exchange membranes include, but are not limited to, the membrane sold under the N2030WX trade name by The Chemours Company and the membrane sold under the F8020/F8080 or F6801 trade names by the Asahi Kasei Corp. Examples of materials that can be used to form a cationic exchange membrane include, but are not limited to, cationic membranes comprising a perfluorinated polymer containing anionic groups, for example sulphonic and/or carboxylic groups. It may be appreciated, however, that in some examples, depending on the need to restrict or allow migration of a specific cation or an anion species between the electrolytes, a cation exchange membrane that is more restrictive and thus allows migration of one species of cations while restricting the migration of another species of cations may be used. Similarly, in some embodiments, depending on the need to restrict or allow migration of a specific anion species between the electrolytes, an anion exchange membrane that is more restrictive and thus allows migration of one species of anions while restricting the migration of another species of anions may be used. Such restrictive cation exchange membranes and anion exchange membranes are commercially available and can be selected by one ordinarily skilled in the art. [0043] In some examples, the separator 131 may be selected so that it can function in an acidic and/or an alkaline electrolytic solution, as appropriate. Other properties for the separator 131 that may be desirable include, but are not limited to, high ion selectivity, low ionic resistance, high burst strength, and high stability in electrolytic solution in a temperature range of room temperature to 150 °C or higher.

[0044] In an example, the separator 131 is stable in a temperature range of from about 0 °C to about 150 °C, for example from about 0 °C to about 100 °C, such as from about 0 °C to about 90 °C, for example from about 0 °C to about 80 °C, such as from about 0 °C to about 70 °C, for example from about 0 °C to about 60 °C, such as from about 0 °C, to about 50 °C, for example from about 0 °C to about 40 °C, or such as from about 0 °C to about 30 °C.

[0045] It may be useful to use an ion-specific ion exchange membrane that allows migration of one type of ion (e.g., cation for a CEM and anion for an AEM) but not another, or migration of one type of ion and not another, to achieve a desired product or products in the electrolyte solution.

[0046] In an example, the first half cell 111 comprises a first electrode 112, which can be placed proximate to the separator 131, and the second half cell 121 comprises a second electrode 122, which can be placed proximate to the separator 131, for example on an opposite side of the separator 131 from the first electrode 112. In an example, the first electrode 112 is the anode for the electrolyzer cell 101 and the second electrode 122 is the cathode for the electrolyzer cell 101, such that for the remainder of the present disclosure the first half cell 111 may also be referred to as the anode half cell 111, the first electrode 112 may also be referred to as the anode 112, the second half cell 121 may also be referred to as the cathode half cell 121, and the second electrode 122 may also be referred to as the cathode 122. Each of the electrodes 112, 122 can be coated with one or more electrocatalysts to speed the reaction toward the hydrogen gas and/or the oxygen gas. Examples of electrocatalysts include, but are not limited to, highly dispersed metals or alloys of platinum group metals, such as platinum, palladium, ruthenium, rhodium, iridium, or their combinations such as platinum-rhodium, platinum-ruthenium, or nickel mesh coated with ruthenium oxide (RuCh). [0047] The ohmic resistance of the separator 131 can affect the voltage drop across the anode 112 and the cathode 122. For example, as the ohmic resistance of the separator 131 increases, the voltage across the anode 112 and the cathode 122 may increase, and vice versa. In an example, the separator 131 has a relatively low ohmic resistance and a relatively high ionic mobility. In an example, the separator 131 has a relatively high hydration characteristics that increase with temperature, and thus decreases the ohmic resistance. By selecting a separator 131 with lower ohmic resistance known in the art, the voltage drop across the anode 112 and the c at a specified temperature can be lowered.

[0048] In an example, the anode 112 is electrically connected to an external positive conductor 116 and the cathode 122 is electrically connected to an external negative conductor 126. When the separator 131 is wet and is in electrolytic contact with the electrodes 112 and 122, and an appropriate voltage is applied across the conductors 116 and 126, oxygen gas (O2) is liberated at the anode 112 and hydrogen gas (H2) is liberated at the cathode 122. In certain configurations, an electrolyte, e.g., one comprising of a solution of KOH in water, is fed into the half cells 111, 121. For example, the electrolyte can flow into the anode half cell 111 through a first inlet 114 and into the cathode half cell 121 through a second inlet 124. In an example, the flow of the electrolyte through the anode half cell 111 picks up produced O2 as bubbles 113, which exit the anode half cell 111 through a first outlet 115. Similarly, the flow of the electrolyte through the cathode half-cell 121 can pick up produced H2 as bubbles 123, which can exit the cathode half cell 121 through a second outlet 125. The gases can be separated from the electrolyte downstream of the electrolyzer cell 101 with one or more appropriate separators. In an example, the produced H2 is dried and harvested into high pressure canisters or fed into further process elements. The O2 can be allowed to simply vent into the atmosphere. The electrolyte is recycled back into the half cells 111, 121 as needed.

[0049] In an example, a typical voltage across the electrolyzer cell 101 is from about 1.5 volts (V) to about 3.0 V. In an example, an operating current for the electrolyzer cell 101 is from about 0.1 kiloamps (kA) to about 100 kA. As will be appreciated by those having skill in the art, operating an electrical power bus at such a low voltage and high current can be highly inefficient. Therefore, typically a plurality of the electrolyzer cells are assembled and electrically connected in series into an electrolyzer stack. The plurality of cells can operate at a much higher voltage and at the same current as a single electrolyzer cell 101, which makes the system far more efficient. In an example, an electrolyzer stack can comprise from about five (5) electrolyzer cells 101 to about 500 electrolyzer cells 101, for example eighty (80) electrolyzer cells 101 or more connected in series to provide an electrolyzer stack. In an example, an electrolyze stack comprising a plurality of electrolyzer cells 101 operates at a voltage of from about 120 V to about 450 V.

Electrolyzer Cell Pan Assembly

[0050] The physical configuration of the electrolyzer cell 101 can be any physical structure configured to allow for the liberation of oxygen gas at the anode 112 and for the liberation of hydrogen gas at the cathode 122. In an example, the electrolyzer cell can comprise components that can dynamically operate at high current densities (e.g., at 300 mA/cm ² or higher). By providing for operation at high current densities, the electrolyzer cells can allow operators to meet their targeted production rate with fewer cells, thereby reducing capital expenses. In addition, by allowing the electrolyzer cells to dynamically operate over a wide range of operational current densities, the electrolyzer cells can provide operators with a large turndown ratio, which can enable the operators to maximize production when power prices are low, and to reduce power consumption when power prices are high.

[0051] As will be appreciated by those having skill in the art, the operation of electrolyzer cells at high current densities can result in significant challenges, such as, but not limited to, large gas volumes produced at high current densities, significant temperature and pressure fluctuations, separator erosion or fatigue, large amount of heat generated in the cell, and/or high flow rates of electrolyte. Therefore, in an example, each electrolyzer cell 101 can include a configuration of an anode pan assembly and/or a cathode pan assembly that can overcome one or more of these challenges, such as, but not limited to, reducing or minimizing large temperature variations of the electrolyte along the height of the cell; reducing or minimizing masking of the nominal active area with gas; reducing or minimizing formation of a stagnant gas pocket that can result in localized drying out of the separator; and/or reducing or minimizing significant pressure fluctuations due to slug or plug flow at the cell outlets. [0052] Due to large gas volumes, static gas pockets can form on the electrode or at the top of the cell. Providing high electrolyte flow rates and utilizing features that cause gas lift to create high local shear rates may help to minimize static gas pocket formation on the electrode. However, the high electrolyte flow rates coupled with large production of gases and large amounts of electrolyte solution entering and exiting the cell, present significant challenges associated with slug and plug flow. This type of flow can be reduced or minimized by using a specified manifold and the outlet tube configuration, described in more detail below.

[0053] Applicants provide herein a pan assembly that can be used on the anode or the cathode side of the electrolyzer cell 101. The pan assembly includes an effective collection system at the top of the cell to minimize and in some cases prevent the formation of large stagnant gas pockets at the top of the cell. In an example, the collection system comprises a manifold and an outlet tube with large cross-sectional area that effectively provides space for gas to collect as well as electrolyte to flow while also reducing or minimizing the likelihood of masking of the separator and/or slug and plug flow. The pan assembly can provide for two phase (gas/liquid) flow that is effectively directed out of the cell. [0054] The pan assembly, manifold, and outlet tube are designed to ensure that the flow is uniform or substantially across the width of the cell, and that pressure fluctuations within the cell are minimal. The flow uniformity drives the need to ensure that the back pressure associated with the flow’s entry into the manifold is significantly greater than the pressure drop along the length of the manifold. Maintaining an essentially constant internal pressure distribution drives the requirement to avoid slug or plug flow through the manifold and the outlet tubing. Therefore, the pan assembly comprising the manifold and the outlet tube can provide for reliable cell operation across a high range of electrolyte flows and high current densities.

[0055] As the current density is increased in the cell, power dissipation can also rise dramatically. Large spatial and/or temporal temperature fluctuations can damage the separator. The contribution of internal power dissipation to the cell’s internal temperature distribution can be reduced or minimized through operating conditions such as the maintaining temperature, flow rate of the inflowing electrolyte, and/or re-circulation of the inflowing electrolyte. High electrolyte flow rates can provide for a high amount of convective heat transfer within the cell, thereby helping to reduce or minimize the heat buildup and concomitant temperature rise within the cell that may otherwise result from an increase in current density. In an example, the pan assembly of the electrolyzer cell includes a baffle plate configuration inside the pan assembly that can reduce or minimize the impact of fluctuating power dissipation on the internal temperature of the cell.

[0056] In the generic electrolyzer cell 101 described above with respect to FIG. 1, the anode half cell 111 can comprise an anode pan assembly that includes the anode 112 and the anode electrolyte (also referred to as “anolyte”). Similarly, the cathode half cell 121 can comprise a cathode pan assembly that includes the cathode 122 and the cathode electrolyte (also referred to as “catholyte”). The anode pan assembly and the cathode pan assembly can be separated by the separator 131 (e.g., a diaphragm, a membrane electrode assembly (MEA), or one or more ion exchange membranes (IEM)). The anode pan assembly and/or the cathode pan assembly can include components, such as a collection system that collects the gas and the electrolyte for flow out of the cell 101. An ion-exchange membrane assembly (“IEM assembly”) can include an anion exchange membrane (AEM), a cation exchange membrane (CEM), or both depending on the desired reactions at the anode 112 and the cathode 122. In between these components, various additional separator components can be provided, e.g., to separate the separator 131 from the anode 112, to separate the separator 131 from the cathode 122, or to separate a AEM from a CEM within the same IEM assembly, as well as provide mechanical integrity to the separator. In addition to these components, individual gaskets or gasket tape may be provided in between and along the outer perimeter of the components to seal the compartments from fluid leakage.

[0057] In an example, all of the components described above are aligned parallel or substantially parallel to each other and optional peripheral bolting may be provided to stack them together in the electrochemical cell 101. In a filter press configuration, no peripheral bolting may be required. In a stack of electrochemical cells, the anode 112 of one electrochemical cell 101 can be electrically connected with the cathode 122 of an adjacent electrochemical cell. The current passes through the stack of electrochemical cells during operation. [0058] FIGS. 2-7 show several views of an example pan assembly 140 that can be used as the anode pan assembly for the anode half cell 111 or as the cathode pan assembly for the cathode half cell 121 in the electrolyzer cell 101 shown in FIG. 1. FIG. 2 is a front view of the pan assembly 140. FIG. 3 is a cross sectional view of the pan assembly 140. It is to be understood that in the electrochemical cell 101, the pan assembly 140 can be used as the anode pan assembly or as the cathode pan assembly, or both, depending on the need and the reaction at the anode 112 and the cathode 122. The next component of the cell such as the anode 112 or the cathode 122 can be placed on top of the pan assembly 140 shown the front view of FIG. 2.

[0059] As illustrated in FIGS. 2 and 3, the pan assembly 140 includes a pan 142. Inside the depth of the pan 142 and at the top of the pan 142 is housed a manifold 144 (shown in FIG. 3). The manifold 144 can be connected to one outlet tube 146 or more depending on the requirements for the electrolyzer cell 101. For example, the design can incorporate 2, 3, 4, or more outlet tubes 146 on each pan assembly 140, on the same or either side of the pan 142 in order to minimize the cell thickness, and maximize the number of cells 101 that can fit in an electrolyzer frame of a particular size. FIGS. 4 and 5 show close-up details of the manifold 144 and the outlet tube 146.

[0060] In an example, a depth DManifoid of the manifold 144 and/or the cross sectional area of the manifold 144 and/or the outlet tube 146 is selected so that the pan assembly 140 provides a relatively large cross sectional area of the manifold 144 in order to reduce or minimize the occurrence of slug and plug flow of the two phase system, but also to provide enough space between the wall of the manifold 144 and the electrode placed on top of the pan 142 for the gas and electrolyte to have an unimpeded flow and for the separator 131 to stay wetted. The depth DManifoid of the manifold 144 and/or the cross sectional area of the manifold 144 and/or the outlet tube 146 can also dictate the overall thickness of the cell 101.

[0061] In an example of the pan assembly 140, the manifold 144 has a depth DManifoid (shown in FIGS. 4 and 5) that is from about 0.25 (25%) to about 0.75 (75%) of a depth Dp _an of the pan 142, for example from about 0.25 (25%) to about 0.6 (60%) of the depth Dp _an , such as from about 0.25 (25%) to about 0.5 (50%) of the depth Dp _an of the pan 142, for example from about 0.25 (25%) to about 0.4 (40%) of the depth Dp _an of the pan 142, such as from about 0.25 (25%) to about 0.3 (30%) of the depth Dp _an of the pan 142, for example from about 0.3 (30%) to about 0.75 (75%) of the depth Dp _an of the pan 142, such as from about 0.3 (30%) to about 0.6 (60%) of the depth Dp _an of the pan 142, for example from about 0.3 (30%) to about 0.5 (50%) of the depth Dp _an of the pan 142, such as from about 0.3 (30%) to about 0.4 (40%) of the depth Dp _an of the pan 142, for example from about 0.4 (40%) to about 0.75 (75%) of the depth Dp _an of the pan 142, such as from about 0.4 (40%) to about 0.6 (60%) of the depth Dp _an of the pan 142, for example from about 0.4 (40%) to about 0.5 (50%) of the depth Dp _an of the pan 142, such as from about 0.5 (50%) to about 0.75 (75%) of the depth Dp _an of the pan 142, for example from about 0.5 (50%) to about 0.6 (60%) of the depth Dp _an of the pan 142, such as from about 0.6 (60%) to about 0.75 (75%) of the depth Dp _an of the pan 142.

[0062] In an example, the manifold 144 has an upward taper at the top (best seen in FIG. 5). The upward taper creates an internal volume or zone above the upper edge of the separator 131 positioned next to the electrode, providing a small region for a gas-rich mixture to form without resulting in the drying out of the separator 131.

[0063] An example flow path for the gas and electrolyte mixture through the pan assembly 140 is shown by the dotted line 148 in FIGS. 6 and 7. As can be seen in FIGS. 6 and 7, in an example, the flow path 148 of the two phases of the gas and the electrolyte passes upwards from the main part of the pan 142 to the top of the manifold 144 and then down into the manifold 144 through a set of notches 150 at the top of the manifold 144. The gas and the electrolyte can then flow out through the outlet tube 146. [0064] In order to accommodate a large amount of the gas and the electrolyte solution flowing though the manifold 144 and the outlet tube 146, e.g., due to high current densities and high flow rates, and to reduce or minimize the occurrence of slug and plug flow, in an example, the cross sectional area of the manifold 144 and the outlet tube 146 is large enough to maintain the superficial liquid velocity of the electrolyte to be 0.1 m/s or less, for example 0.0 8m/s or less, such as 0.05 m/s or less, for example 0.01 m/s or less.

[0065] In order to accommodate the high current densities and the high flow rates as noted herein, in some examples, the cross sectional area of the manifold 144 (e.g. comprising the depth DManifoid of the manifold 144 of from about 0.25 (25%) to about 0.75 (75%) of the depth D ^Pan of the pan 142) is from about 520 square millimeters (mm ² ) to about 6200 mm ² , for example from about 520 mm ² to about 6000 mm ² , such as from about 520 mm ² to about 5000 mm ² , for example from about 520 mm ² to about 4000 mm ² , such as from about 520 mm ² to about 3000 mm ² , for example from about 520 mm ² to about 2000 mm ² , such as from about 520 mm ² to about 1000 mm ² , for example from about 600 mm ² to about 6200 mm ² , such as from about 600 mm ² to about 6000 mm ² , for example from about 600 mm ² to about 5000 mm ² , such as from about 600 mm ² to about 4000 mm ² , for example from about 600 mm ² to about 3000 mm ² , such as from about 600 mm ² to about 2000 mm ² , for example from about 600 mm ² to about 1000 mm ² , such as from about 800 mm ² to about 6200 mm ² , for example from about 800 mm ² to about 6000 mm ² , such as from about 800 mm ² to about 5000 mm ² , for example from about 800 mm ² to about 4000 mm ² , such as from about 800 mm ² to about 3000 mm ² , for example from about 800 mm ² to about 2000 mm ² , such as from about 800 mm ² to about 1000 mm ² , for example from about 1000 mm ² to about 6200 mm ² , such as from about 1000 mm ² to about 6000 mm ² , for example from about 1000 mm ² to about 5000 mm ² , such as from about 1000 mm ² to about 4000 mm ² , for example from about 1000 mm ² to about 3000 mm ² , such as from about 1000 mm ² to about 2000 mm ² , for example from about 2000 mm ² to about 6200 mm ² , such as from about 2000 mm ² to about 6000 mm ² , for example from about 2000 mm ² to about 5000 mm ² , such as from about 2000 mm ² to about 4000 mm ² , for example from about 2000 mm ² to about 3000 mm ² , such as from about 3000 mm ² to about 6200 mm ² , for example from about 3000 mm ² to about 6000 mm ² , such as from about 3000 mm ² to about 5000 mm ² , for example from about 3000 mm ² to about 4000 mm ² , such as from about 4000 mm ² to about 62000 mm ² , for example from about 4000 mm ² to about 6000 mm ² , such as from about 4000 mm ² to about 5000 mm ² , for example from about 5000 mm ² to about 6200 mm ² , such as from about 5000 mm ² to about 6000 mm ² .

[0066] In some examples wherein the cross-sectional area of the manifold 144 is as recited above, the outlet tube 146 fluidly connected to the manifold 144 can have an equivalent diameter EDoutiet (shown in FIG. 4) is from about 26 millimeters (mm) to about 89 mm, for example from about 26 mm to about 80 mm, such as from about 26 mm to about 75 mm, for example from about 26 mm to about 70 mm, such as from about 26 mm to about 60 mm, for example from about 26 mm to about 50 mm, such as from about 26 mm to about 40 mm, for example from about 26 mm to about 30 mm, such as from about 30 mm to about 89 mm, for example from about 30 mm to about 80 mm, such as from about 30 mm to about 75 mm, for example from about 30 mm to about 70 mm, such as from about 30 mm to about 60 mm, for example from about 30 mm to about 50 mm, such as from about 30 mm to about 40 mm, for example from about 40 mm to about 89 mm, such as from about 40 mm to about 80 mm, for example from about 40 mm to about 75 mm, such as from about 40 mm to about 70 mm, for example from about 40 mm to about 60 mm, such as from about 40 mm to about 50 mm, for example from about 50 mm to about 89 mm, such as from about 50 mm to about 80 mm, for example from about 50 mm to about 75 mm, such as from about 50 mm to about 70 mm, for example from about 50 mm to about 60 mm, such as from about 60 mm to about 89 mm, for example from about 60 mm to about 80 mm, such as from about 60 mm to about 75 mm, for example from about 70 mm to about 89 mm, such as from about 70 mm to about 80 mm, for example from about 70 mm to about 75 mm.

[0067] Those having skill in the art will appreciate that what may be considered a “high electrolyte flow rate” may be in comparison to the size of the electrochemical cell 101. For example, a “high flow rate” for a relatively narrow cell, e.g., from about 300 mm to about 600 mm wide, may correspond to a flow rate of about 200 kg/h, while a “high flow rate” for a large commercial size cell, e.g., from about 2 meters (m) to about 3 m wide, may correspond to a flow rate of about 800 kg/h or more. The cross sectional area of the manifold 144, the cross sectional area of the outlet tube 146, and/or the baffle assembly can accommodate high electrolyte flow rates and high gas flow rates associated with operation at high current densities as described herein and provide for a superficial liquid velocity that is less than about 0.1 m/s so that slug and plug flow are unlikely to develop.

[0068] In some examples, the pan assembly can include a baffle assembly inside the pan assembly, wherein the baffle assembly can reduce or minimize the impact of fluctuating power dissipation on the internal temperature of the electrolyzer cell. The baffle assembly can be suspended in the pan assembly, for example between a back pan wall and the electrode. In an example, the baffle assembly includes one or more ribs inside the pan. The one or more ribs can include one or more notches. A baffle plate comprising one or more slots can be included and configured to fit onto the one or more ribs such that a corresponding structure of the baffle plate can fit into the one or more notches of the one or more ribs.

[0069] FIGS. 8-14 show several views of a pan assembly 160 that includes an example baffle assembly 162. Similar to the pan assembly 140 described above with respect to FIGS. 2-7, the pan assembly 160 can be used as the structure for one or both of the anode half cell 111 and the cathode half cell 121 in the electrolyzer cell 101 of FIG. 1. For example, if the pan assembly 160 is used to form part of the anode half cell 111, then the pan assembly 160 can be an anode pan assembly. Similarly, if the pan assembly 160 is used to form part of the cathode half cell 121, then the pan assembly 160 can be a cathode pan assembly. Like the pan assembly 140, the pan assembly 160 includes a pan 164 (e.g., an anode pan and/or a cathode pan) and an outlet tube 166. The pan assembly 160 can also include a manifold 168 through which electrolyte and produced gas can flow before exiting the pan assembly 160 through the outlet tube 166, which can be similar or identical to the manifold 144 described above with respect to the pan assembly 140.

[0070] In an example, the baffle assembly 162 of the pan assembly 160 includes a baffle plate 170 that is fitted within the pan 162. In an example, the baffle plate 170 comprises one or more slots 172 (best seen in FIG. 9). Each slot 172 can interact with a corresponding rib 174 (shown in FIGS. 8, 10, and 11), wherein the one or more ribs 174 and the baffle plate 170 form the baffle assembly 162. The baffle plate 170 can have any number of slots 172 depending on the number of ribs 174 in the baffle assembly 162. The number of slots can be e.g., from 1 to about 200 in the baffle plate 170. The baffle plate 170 can be fitted over the ribs 174 in the pan 164. In an example, the one or more ribs 174 are perpendicular or substantially perpendicular to the baffle plate 170 and to the overall orientation of the pan 164. In other words, in an example, the baffle plate 170 is parallel or substantially parallel to a major surface of the pan 164, such as a back wall 178 of the pan 164. The electrode 176 associated with the pan assembly 160 (e.g., the anode 112 if the pan assembly 160 is an anode pan assembly or the cathode 122 if the pan assembly 160 is a cathode pan assembly) can be attached to the top of the pan assembly 160, e.g., on a side of the baffle assembly 162 that is opposite the back wall 178 of the pan 164.

[0071] In an example, each of the one or more ribs 174 can include one or more structures to position the baffle plate 170 relative to the pan 164 and/or relative to the electrode 176. In an example, these structures include one or more notches on each rib 174, wherein each notch engages with a corresponding slot 172 on the baffle plate 170 in order to position the baffle plate 170 relative to the pan 164, e.g., so that the baffle plate 170 is suspended at a specified location relative to the electrode 176 and/or relative to the back wall 178 of the pan 164, as can be seen in FIGS. 8, 10, and 11. The notches in the ribs 174 are not visible in the Figures because the notches have been filled with the baffle plate 170. The distance of the baffle plate 170 from the electrode 176 and from the back wall 178 of the pan 164 can be changed by modifying the depth of the notches along the ribs 174.

[0072] The positioning of the slots 172 in the baffle plate 170, the length of the slots 172, and/or the distance between the slots 172 can affect the fitting of the baffle plate 170 onto the one or more ribs 174. In an example, the baffle plate 170 is a solid plate with the slots 172 formed therein, as best seen in FIG. 9. In other examples, the baffle plate can be an expanded metal plate or a mesh. In an example, the baffle plate 170 is made from a conductive metal, such as, but not limited to, nickel, stainless steel, and the like.

[0073] As described earlier, the contribution of internal power dissipation to the internal temperature distribution within the electrolyzer cell 101 can be reduced or minimized through operating conditions such as the temperature and flow rate of the electrolyte flowing through the half cells 111, 121 (e.g., through the pan assemblies 160 that form the half cells 111, 121). High electrolyte flow rates can increase and in some examples maximize the convective heat transfer within the electrolyzer cell 101, thereby helping to reduce or minimize heat buildup and the corresponding concomitant temperature rise within the cell 101 that could otherwise result from the high current densities described herein. As discussed above, operating at high electrolyte flow rates and high current densities can lead to slugging or plug flow at the cell outlet, which can result in pressure fluctuations that can shorten the lifetime of the separator 131. The pan assemblies 140, 160 described herein with the manifold 144 and outlet configurations and/or the baffle assembly 162 are designed to reduce or minimize slug and plug flow. In particular, the baffle assembly 162 can provide for mixing of the electrolyte as it flows through the pan assembly 160.

[0074] In some examples, the baffle assembly 162 is designed and positioned in such a way that the gas produced at the electrode 176 can mix with the electrolyte on the side of the baffle plate 170 closest to the electrode 176, resulting in a relatively low density column and defining a riser section. The low density mixture can rise relatively quickly through the riser section. Once above the top of the baffle plate 170, the gas can disengage and flow into the manifold 168 and then into the outlet tube 166. A fraction of the electrolyte may then drop back down the side of the baffle plate 170 closer to the back wall 178 of the pan 164 into a down-comer region, thereby creating a circulation loop. This circulation loop (with a riser section 180 on the side of the baffle plate 170 closer to the electrode 176 and a down-comer section 182 on the side of the baffle plate 170 opposite the electrode 176) that is formed in the pan assembly 160 is illustrated conceptually in FIG. 12, where it is compared to a comparative pan assembly 184 that does not include a baffle assembly , such as one with a baffle plate like the baffle plate 170, such that there is no resulting formation of a circulation pattern. FIG. 13 shows vector plots of a simulated flow distribution of electrolyte in the pan assembly 160 with the baffle plate 170 included (left side of FIG. 13) and a comparative pan assembly 184 without a baffle assembly (right side of FIG. 13). As can be seen in FIG. 13, without a baffle assembly, the electrolyte solution rises slowly up though the pan assembly 184. The gas evolved at the electrode 176 impacts the flow of the electrolyte, dragging some of the electrolyte up, and buffeting some of the electrolyte laterally. Gas lift is evident along the upper left wall (adjacent to the electrode 176) in the comparative pan assembly 184. The pan assembly 160 that includes the baffle plate 170 creates a strong circulation within the pan assembly 160. As is evident from FIG. 13, the flow in the riser section 180, e.g., the side of the baffle plate 170 closest to the electrode 176, is strongly oriented upward due to gas lift, and the flow on the down-comer section 182, e.g., the side of the baffle plate 170 closest to the back wall 178 of the pan assembly 160, is strongly oriented downward. The relatively high velocities and shear rates in the riser section 180 help sweep gas from the electrode 176, provide efficient top to bottom mixing within the pan assembly 160, and drive increased convective cooling.

[0075] The baffle assembly 162 can be used to create rapidly flowing circulation loops so that the electrolyte remains substantially isothermal as it flows through the pan assembly 160. Due to the high degree of top-bottom mixing and circulation, rapid thermal equilibration of the electrolyte can be achieved as it flows into and through the pan assembly 160. Another advantage is that relatively cold electrolyte can be introduced into the pan assembly 160 which can equilibrate with warm circulating electrolyte fluid. The circulation rate (or laps of the recirculation loop during electrolyte transit through the pan assembly 160) can be anywhere from 1 to 200. The high circulation rate can also drive larger shear rates adjacent to the separator 131, helping to sweep gas away from the separator 131.

[0076] The positioning of the baffle plate 170 with respect to the electrode 176 as well as to the back wall 178 of the pan 164 and/or the width WBaffie and length LBafiie of the baffle plate 170 (shown in FIG. 14), can affect the velocity of the electrolyte through the riser section 180 as well as the down- comer section 182, thereby affecting the circulation rate of the electrolyte within the pan assembly 160. It has been found that if the baffle plate 170 is located farther than a specified critical distance from the electrode 176 then the circulation pattern of the riser section 180 and the down-comer section 182 may not be formed. Specifically, it has been found that when the gap between the baffle plate 170 and the electrode 176 is too large, free convection of the relatively light, gas-rich zone adjacent to the electrode 176 rises relatively rapidly compared to the slowly rising electrolyte farther away from the electrode 176. The resultant shear forces may drag up some of the electrolyte, which can then fall back down on the side of the baffle plate 170 closer to the electrode 176 as the gas disengages into the manifold 168 at the top of the pan assembly 160, resulting in a weak circulation forming on the side of the baffle plate 170 closest to the electrode 176. In such as configuration, the baffle plate 170 may not divide between a riser section and a down-comer section, and a strong circulation current may not form. If, on the other hand, the baffle plate 170 is too close to the electrode 176, then the space between the electrode 176 and the baffle plate 170 may fill with gas as the gas is formed at the electrode 176, choking off electrolyte flow in the space between the baffle plate 170 and the electrode 176. Moreover, the high volume fraction of gas in the space between the baffle plate 170 and the electrode 176 can result in the separator and/or the electrode 176 masking, and poor electrical and thermal transport.

[0077] The depth Dp _an of the pan 164, the relative depth DBafiie of the baffle plate 170 relative to the electrode 176, the height HBafiie of the baffle plate 170 relative to the total height Hp _an of the pan 164, and/or the vertical location of the baffle plate 170 within the pan 164 (e.g., as dictated by the vertical distance Hpop from a top edge of the baffle plate 170 to a top wall of the pan 164 and the corresponding vertical distance HBOI from a bottom edge of the baffle plate 170 to a bottom wall of the pan 164), as illustrated in FIG. 12, can impact the circulation pattern of the electrolyte within the pan 164.

[0078] In an example, the distance of the baffle plate 170 from the electrode 176 (i.e., the relative depth Daarne of the baffle as illustrated in FIG. 12) is from about 5 mm to about 15 mm, for example from about 5 mm to about 12 mm, such as from about 5 mm to about 10 mm, for example from about 5 mm to about 8 mm, such as from about 5 mm to about 6mm, for example from about 6 mm to about 15 mm, such as from about 6 mm to about 12 mm, for example from about 6 mm to about 10 mm, such as from about 6 mm to about 8 mm, for example from about 8 mm to about 15 mm, such as from about 8 mm to about 12 mm, for example from about 8 mm to about 10 mm, such as from about 10 mm to about 15 mm, for example from about 10 mm to about 12 mm, such as from about 12 mm to about 15 mm. In some embodiments, the distance Dnaffle of the baffle plate 170 from the electrode 176 is equivalent to the depth of the notches on the ribs 174.

[0079] In an example, the distance DBafiie from the baffle plate 170 to the electrode 176 is at from about 0.25 (25%) to about 0.5 (50%) of the total depth Dpan of the pan 164, for example from about 0.25 (25%) to about 0.4 (40%) of the total depth Dp _an of the pan 164, such as from about 0.25 (25%) to about 0.3 (30%) of the total depth Dp _an of the pan 164, for example from about 0.3 (30%) to about 0.5 (50%) of the total depth Dp _an of the pan 164, such as from about 0.4 (40%) to about 0.5 (50%) of the total depth Dp _an of pan 164.

[0080] In an example, the height Hurtle and the positioning of the baffle plate 170 is such that it leaves space at the top (HT _OP in FIG. 12) and/or a space at the bottom HBOI in FIG. 12) of the pan 164 for gas and liquid flow. In some examples where the manifold 168 and the baffle plate 170 both are present in the pan assembly 160, depending on the depth of the manifold 168 and the placement of the baffle plate 170 with respect to the depth Dp _an of the pan 164, the baffle plate 170 may run behind the manifold 168 (e.g., between the manifold 168 and the electrode 176) towards the top of the pan 164 or the baffle plate 170 may end below the manifold 168. In either case, there can be a space between the baffle plate 170 and the top and/or bottom of the pan 164 for gas and liquid flow.

[0081] In an example, the space HBOI between a bottom edge of the baffle plate 170 and the bottom wall of the pan 164 is from about 6 mm to about 75 mm, for example from about 6 mm to about 65 mm, such as from about 6 mm to about 50 mm, for example from about 6 mm to about 40 mm, such as from about 6 mm to about 30 mm, for example from about 6 mm to about 20 mm, such as from about 6 mm to about 10 mm, for example from about 10 mm to about 75 mm, such as from about 10 mm to about 65 mm, for example from about 10 mm to about 50 mm, such as from about 10 mm to about 40 mm, for example from about 10 mm to about 30 mm, such as from about 10 mm to about 20 mm, for example from about 10 mm to about 15 mm, such as from about 20 mm to about 75 mm, for example from about 20 mm to about 65 mm, such as from about 20 mm to about 50 mm, for example from about 20 mm to about 40 mm, such as from about 20 mm to about 30 mm, for example from about 30 mm to about 75 mm, such as from about 30 mm to about 65 mm, for example from about 30 mm to about 50 mm, such as from about 30 mm to about 40 mm, for example from about 40 mm to about 75 mm, such as from about 40 mm to about 65 mm, for example from about 50 mm to about 75 mm, such as from about 50 mm to about 65 mm, for example from about 60 mm to about 75 mm.

[0082] In some embodiments, the space HT _OP between a top edge of the baffle plate 170 and the top wall of the pan 164 or the bottom of the manifold 168 is between about 6 mm to about 150 mm, for example from about 6 mm to about 140 mm, such as from about 6 mm to about 130 mm, for example from about 6 mm to about 120 mm, such as from about 6 mm to about 110 mm, for example from about 6 mm to about 100 mm, such as from about 6 mm to about 80 mm, for example from about 6 mm to about 70 mm, such as from about 6 mm to about 50 mm, for example from about 6 mm to about 25 mm, such as from about 10 mm to about 150 mm, for example from about 10 mm to about 140 mm, such as from about 10 mm to about 130 mm, for example from about 10 mm to about 120 mm, such as from about 10 mm to about 110 mm, for example from about 10 mm to about 100 mm, such as from about 10 mm to about 80 mm, for example from about 10 mm to about 70 mm, such as from about 10 mm to about 50 mm, for example from about 10 mm to about 25 mm, such as from about 25 mm to about 150 mm, for example from about 25 mm to about 140 mm, such as from about 25 mm to about 130 mm, for example from about 25 mm to about 120 mm, such as from about 25 mm to about 110 mm, for example from about 25 mm to about 100 mm, such as from about 25 mm to about 80 mm, for example from about 25 mm to about 70 mm, such as from about 25 mm to about 50 mm, for example from about 50 mm to about 150 mm, such as from about 50 mm to about 140 mm, for example from about 50 mm to about 130 mm, such as from about 50 mm to about 120 mm, for example from about 50 mm to about 110 mm, such as from about 50 mm to about 100 mm, for example from about 50 mm to about 80 mm, such as from about 50 mm to about 70 mm, for example from about 100 mm to about 150 mm, such as from about 100 mm to about 140 mm, for example from about 100 mm to about 130 mm, such as from about 100 mm to about 120 mm, for example from about 125 mm to about 150 mm, such as from about 125 mm to about 140 mm, for example from about 130 mm to about 150 mm, such as from about 75 mm to about 120 mm. It is to be understood that any of aforementioned dimensions for the space between the baffle plate and bottom of the anode and/or the cathode pan and the dimensions for the space between the baffle plate and top of the anode and/or the cathode pan or the bottom of the manifold, may be combined in order to achieve the optimum circulation pattern of the electrolyte.

[0083] In some embodiments, the anode and/or the cathode pan assembly provided herein, with the aforementioned manifold and the outlet tube and/or the baffle assembly provide several advantages such as, but not limited to, accommodating the aforementioned high flow rate of anolyte or catholyte and/or reducing or minimizing the incidence of slug or plug flow; reducing or minimizing large spatial and/or temporal temperature fluctuations; reducing or minimizing pressure fluctuations due to multiphase flow in the cell, e.g., to less than 0.5 psi; and/or reducing or minimizing separator erosion and/or fatigue.

[0084] As noted above, operation of the electrolyzer cell 101 at high current densities can result in significant challenges, such as, but not limited to, large amount of heat generated in the cell 101. In an electrolyzer cell 101 producing a large amount of gas at high current densities, the gas/electrolyte mixture can have a lower specific heat, a lower density, and/or a lower thermal conductivity than the electrolyte alone. Therefore, the heat removal efficiency of the electrolyte can be reduced as the gas hold up increases. Local temperatures can then rise quickly if a gas pocket masks a region of the electrode. If a significant region of the electrode is masked, the unmasked region will have to work harder, increasing the local Joule heating. Local hot spots thus developed can damage the separator. As the current density is increased in the cell, power dissipation can also rise dramatically. Large spatial and/or temporal temperature fluctuations can damage the separator.

[0085] FIGS. 15-19 show an illustrative example of a pan assembly 190 that can be used as the anode pan assembly for the anode half cell 111 or as the cathode pan assembly for the cathode half cell 121, or both, in the electrolyzer cell 101 shown in FIG. 1. The pan assembly 190 can reduce or minimize the contribution of internal power dissipation to the cell’s internal temperature distribution within a pan 192 through the use of a plurality of ribs 194 with specified geometry and/or spacing, and/or via the use of one or more welds 196 having a specified weld density and cross-sectional configurations in the pan assembly 190.

[0086] The rib geometry, rib spacing, and/or weld density and cross- sectional configurations in the pan assembly 190 can reduce or minimize the effect of one or more of these challenges, such as, but not limited to, by more effectively distributing current across the pan assembly 190 to reduce the chance of hot spot formation, reduce or avoid large spatial and/or temporal temperature fluctuations of the electrolyte along the height of the pan assembly 190, and/or reduce or minimize separator damage due to hot spots.

[0087] The design of the pan assembly 190 comprising the one or more ribs 194 and the welds 196, as described below, can provide for efficient current distribution across the active area of the cell when operating at high current densities. The cross-sectional area of the ribs 194 and the welds 196 can also allow the cells to be more effective for operational and economical purposes.

[0088] Similar to the pan assemblies 140 and 160 described above with respect to FIGS. 2-14, the pan assembly 190 can be used as the structure for one or both of the anode half cell 111 and the cathode half cell 121 in the electrolyzer cell 101 of FIG. 1, i.e., the pan assembly 190 can form the anode half cell 111 such that the pan assembly 190 is an anode pan assembly and/or the pan assembly 190 can form the cathode half cell 121 such that the pan assembly 190 is a cathode pan assembly. The pan 192 can include an interior for receiving an electrolyte (i.e., an anolyte if the pan assembly 190 is an anode pan assembly and a catholyte if the pan assembly 190 is a cathode pan assembly) and an electrode 198 (i.e., the anode 112 in an anode pan assembly 190 or the cathode 122 is a cathode pan assembly 190). The anode pan assembly and the cathode pan assembly can be separated by a separator (i.e., the separator 131), which can be, for example, one or more of a diaphragm, a membrane electrode assembly (MEA), or an ion exchange membrane (IEM). The pan assembly 190 can further comprise components, such as a collection system (e.g., a manifold such as the manifold 144 or 168 described above) that collects the gas and the electrolyte for flow out of the pan assembly 190. Various additional separator components can be provided, e.g., to separate the one or more separators from the anode, to separate the one or more separators from the cathode, to separate one separator from another separator (e.g., to separate an anion exchange membrane (AEM) from a cation exchange membrane (CEM)), and/or to provide mechanical integrity to the one or more separators. In addition to these components, individual gaskets or gasket tape may be provided in between and along the outer perimeter of the components to seal the compartments from fluid leakage.

[0089] In an example, the pan assembly 190 includes a pan 192, one or more ribs 194 positioned vertically inside the pan 192, an electrode 198 coupled to the one or more ribs 194, and one or more welds 196 that weld the electrode 198 to the one or more ribs 194. FIG. 15 is a front view of an illustrative example of the pan assembly 190, FIG. 16 is a side cross-sectional view of the pan assembly 190, and FIG. 17 is an enlarged view of the cross-section taken along line 17 in FIG. 16. The Figures show the one or more structures that can form the one or more ribs 194. As can be seen particularly in the view of FIG. 17, in an example, the one or more ribs 194 can be perpendicular or substantially perpendicular to a major dimension of the pan 192. For example, each of the one or more ribs 194 can be perpendicular or substantially perpendicular to one or more major faces of the pan 192, such as the electrode 198 or a back pan wall 200.

[0090] On top of the pan 192 and on top of the one or more ribs 194 is placed the electrode 198. As can be seen, in an example, the electrode 198 is welded to the one or more ribs 194 with one or more welds 196. In an example, each of the one or more ribs 194 is coupled to the back wall 200 of the pan 192 by one or more tabs 202 that are coupled to the back wall 200 with one or more tab welds 204.

[0091] In an example, the electrode 198 can be electrically coupled to the supplied electrical current via the one or more welds 196. During operation of a cell that uses the pan assembly 190 to form the cathode half cell, current flows into the cathode (e.g., the electrode 198 of the cathode pan assembly 190) through the welds 196 of the cathode pan assembly 190. Then, the current flows from the cathode 198 to the one or more ribs 194 of the cathode pan assembly 190. The current then flows through the one or more ribs 194 of the cathode pan assembly 190 through the tabs 202 and finally into a conductor contacting the pan 192 of the cathode pan assembly 190 (e.g., to the anode half cell of an adjacent cell or to a contact plate). During operation of a cell that uses the pan assembly 190 to form the anode half cell, current flows from a conductor contacting the pan 192 of the anode pan assembly 190 (e.g., from the cathode half cell of an adjacent cell or from a contact plate) to the ribs 194 of the anode pan assembly 190 through the tabs 202, then to the anode (e.g., the electrode 198 of the anode pan assembly 190), and then into a conductor that is electrically connected to one or more of the welds 196 of the anode pan assembly 190. As noted above, the one or more ribs 194 can be welded to the back wall 200 of the pan 192 via the tabs 202 and the tab welds 204. In an example, the tabs 202 set the spacing of the tab welds 204 between the bottom of the ribs 194 and the back wall 200 of the pan 192. Since the current flows between the back wall 200 of the pan 192 and the electrode 198 through the ribs 194, the tabs 202 can provide adequate weld cross-section between the ribs 194 and the pan 192. The tabs 202 can facilitate better current distribution across the active area and provide electrical contact between the ribs 194 and the pan 192. However, in other examples, the ribs 194 can be directly welded to the back wall 200 of the pan 192 and may not be connected through tabs.

[0092] The geometry and spacing of the one or more ribs 194 can dictate current flow through the pan assembly 190. The geometry of the ribs 194 include, but not limited to, the number of the ribs 194, the height HR* of the ribs 194, the physical design of the ribs 194, the pitch PRibs between adjacent ribs 194, and/or the thickness TR* of the ribs 194. As the current flows in through the welds 196, the geometry, spacing or density, and/or cross-sectional area of the welds 196 can also impact current flow through the pan assembly 190. As increasingly high currents flow through the cell, the density and the cross sectional area of the welds 196 can significantly impact the local Joule heating and avoid separator damage from local hot spots. Provided herein are a unique geometry, spacing, and cross-sectional area of the ribs 194 as well as the welds 196 that can facilitate efficient operation of the electrochemical cell made up of one or two of the pan assemblies 190 at high current densities.

[0093] The physical configuration, i.e., the overall shape, of the one or more ribs 194 can be selected for one or more purposes. For example, one or more of the ribs 194 can be solid plates, such as solid plates of conductive metal, such as the example ribs 194A shown in FIG. 19 A. In another example, the one or more ribs 194 can include one or more holes or openings that allow the electrolyte to move laterally within the pan 192, such as the one or more ribs 194B having holes 206 as shown in FIG. 19B. In an example, the one or more ribs 194 include one or more notches for receiving one or more other structures, such as the ribs 194C shown in FIG. 19C that include one or more notches 208 for receiving portions of a baffle plate 210 (which is described in more detail below). In an example, the one or more ribs 194 can include both holes 206 and notches 208, as with the ribs 194C shown in FIG. 19C, or can include only the holes 206 or only the notches 208.

[0094] The number of ribs 194 inside the pan 192 can impact the current distribution and the power dissipation within the pan assembly 190. In an example, the number of ribs 194 inside the pan 192 is from 1 to 75 of the ribs

194, such as from 1 to 60 of the ribs 194, for example from 1 to 50 of the ribs

194, such as from 1 to 40 of the ribs 194, for example from 1 to 30 of the ribs

194, such as from 1 to 20 of the ribs 194, such as from 1 to 10 of the ribs 194, for example from 1 to 5 of the ribs 194, such as from 5 to 75 of the ribs 194, for example from 5 to 60 of the ribs 194, such as from 5 to 50 of the ribs 194, for example from 5 to 40 of the ribs 194, such as from 5 to 30 of the ribs 194, for example from 5 to 20 of the ribs 194, such as from 5 to 10 of the ribs 194, for example from 10 to 75 of the ribs 194, such as from 10 to 60 of the ribs 194, for example from 10 to 50 of the ribs 194, such as from 10 to 40 of the ribs 194, for example from 10 to 30 of the ribs 194, such as from 10 to 20 of the ribs 194, for example from 20 to 75 of the ribs 194, such as from 20 to 60 of the ribs 194, for example from 20 to 50 of the ribs 194, such as from 20 to 40 of the ribs 194, for example from 20 to 30 of the ribs 194, such as from 30 to 75 of the ribs 194, for example from 30 to 60 of the ribs 194, such as from 30 to 50 of the ribs 194, for example from 30 to 40 of the ribs 194, such as from 40 to 75 of the ribs 194, for example from 40 to 60 of the ribs 194, such as from 40 to 50 of the ribs 194, for example from 50 to 75 of the ribs 194, such as from 50 to 60 of the ribs 194, for example from 60 to 75 of the ribs 194. For example, the pan assemblies 190 shown in FIGS. 15-18 and 19A-19C show the pan 192 containing five (5) ribs 194.

[0095] An enlarged cross-sectional view of the exemplary pan assembly 190 is shown in FIG. 18. The electrode 198 and the welds 196 are not shown in FIG. 18. As described above, the pan assembly 190 includes one or more ribs 194 positioned vertically in the pan 192, wherein the ribs 194 are welded to the back wall 200 of the pan 192 with the tabs 202. In FIG. 18, the pitch, or distance between, two adjacent ribs 194 is labeled as PRibs, the height of the one or more ribs 194 is labeled as HRib, and the thickness of the one or more ribs 194 is labeled as TRA,. The ribs 194 are shown in FIG. 18 as comprising holes 206 for the movement of the electrolyte as well as notches 208. The notches 208 facilitate fitting of specified sections of a baffle plate 210 into the space formed by the notches 208 in order to secure the baffle plate 210 to the one or more ribs 194. The baffle plate 210 can be similar or identical to the baffle plate 170 described above with respect to the pan assembly 160 of FIGS. 8-14. In an example, the one or more ribs 194 are made of a conductive metal, such as, but not limited to, nickel, stainless steel, etc.

[0096] It is to be understood that the holes 206 and the notches 208 may not be present, e.g., the ribs 194 may be a solid plate, such as the ribs 194A of FIG. 19A, or the ribs 194 can have notches 208 but not have holes 206, or the ribs 194 can have the holes 206 and not the notches 208. The holes 206, if present, need not be of any specific shape or size. For example, the holes 206 can be circular openings, slits, perforations, or a mesh. [0097] In an example, the length LRA, of the one or more ribs 194 (FIG. 15) is from about 0.25 meters (m) to about 1 m, for example from about 0.25 m to about 0.8 m, such as from about 0.25 m to about 0.6 m, for example from about 0.25 m to about 0.5 m, such as from about 0.25 m to about 0.4 m, for example from about 0.25 m to about 0.3 m, such as from about 0.5 m to about 1 m, for example from about 0.5 m to about 0.8 m, such as from about 0.5 m to about 0.6 m, for example from about 0.6 m to about 1 m, such as from about 0.6 m to about 0.8 m, for example from about 0.7 m to about 1 m, such as from about 0.7 m to about 0.8 m, for example from about 0.8 m to about 1 m. In an example, the length of the notch 208 in each of the one or more ribs 194 is from about 5 millimeters (mm) to about 100 mm, for example from about 5 mm to about 80 mm, such as from about 5 mm to about 60 mm, for example from about 5 mm to about 50 mm, such as from about 5 mm to about 40 mm, for example from about 5 mm to about 30 mm, such as from about 5 mm to about 20 mm, for example from about 5 mm to about 10 mm, such as from about 10 mm to about 100 mm, for example from about 10 mm to about 50 mm, such as from about 10 mm to about 40 mm, for example from about 10 mm to about 30 mm, such as from about 10 mm to about 20 mm, for example from about 20 mm to about 100 mm, such as from about 20 mm to about 50 mm, for example from about 20 mm to about 40 mm, such as from about 20 mm to about 30 mm, for example from about 30 mm to about 100 mm, such as from about 30 mm to about 50 mm, for example from about 30 mm to about 40 mm, such as from about 40 mm to about 100 mm, for example from about 40 mm to about 50 mm, such as from about 50 mm to about 100 mm, for example from about 75 mm to about 100 mm.

[0098] In an example, the thickness TRA, of the one or more ribs 194 is from about 1 mm to about 3 mm, for example from about 1 mm to about 2.5 mm, such as from about 1 mm to about 2mm, for example from about 1 mm to about 1.5 mm, such as from about 2 mm to about 3 mm, for example from about 2 mm to about 2.5 mm, such as from about 2.5 mm to about 3 mm.

[0099] In an example, the height HRib of the one or more ribs 194 is from about 10 mm to about 110 mm, for example from about 10 mm to about 100 mm, such as from about 10 mm to about 75 mm, for example from about 10 mm to about 70 mm, such as from about 10 mm to about 60 mm, for example from about 10 mm to about 50 mm, such as from about 10 mm to about 40 mm, for example from about 10 mm to about 30 mm, such as from about 20 mm to about 110 mm, for example from about 20 mm to about 75 mm, such as from about 20 mm to about 70 mm, for example from about 20 mm to about 60 mm, such as from about 20 mm to about 50 mm, for example from about 20 mm to about 40 mm, such as from about 20 mm to about 30 mm, for example from about 30 mm to about 110 mm, such as from about 30 mm to about 75 mm, for example from about 30 mm to about 70 mm, such as from about 30 mm to about 60 mm, for example from about 30 mm to about 50 mm, such as from about 30 mm to about 40 mm, for example from about 40 mm to about 110 mm, such as from about 40 mm to about 75 mm, for example from about 40 mm to about 70 mm, such as from about 40 mm to about 60 mm, for example from about 40 mm to about 50 mm, such as from about 50 mm to about 110 mm, for example from about 50 mm to about 75 mm, such as from about 50 mm to about 70 mm, for example from about 50 mm to about 60 mm, such as from about 60 mm to about 110 mm, for example from about 60 mm to about 75 mm, such as from about 70 mm to about 110 mm, for example from about 70 mm to about 80 mm.

[0100] In an example, the pitch PRAS between two adjacent ribs 194 is from about 40 mm to about 200 mm, for example from about 40 mm to about 150 mm, such as from about 40 mm to about 140 mm, for example from about 40 mm to about 130 mm, such as from about 40 mm to about 120 mm, for example from about 40 mm to about 110 mm, such as from about 40 mm to about 100 mm, for example from about 40 mm to about 80 mm, such as from about 40 mm to about 70 mm, for example from about 60 mm to about 200 mm, such as from about 60 mm to about 150 mm, for example from about 60 mm to about 140 mm, such as from about 60 mm to about 130 mm, for example from about 60 mm to about 120 mm, such as from about 60 mm to about 110 mm, for example from about 60 mm to about 100 mm, such as from about 60 mm to about 80 mm, for example from about 80 mm to about 200 mm, such as from about 80 mm to about 150 mm, for example from about 80 mm to about 100 mm, such as from about 100 mm to about 200 mm, for example from about 100 mm to about 150 mm, such as from about 100 mm to about 140 mm, for example from about 100 mm to about 130 mm, such as from about 100 mm to about 120 mm, for example from about 125 mm to about 200 mm, such as from about 125 mm to about 150 mm, for example from about 125 mm to about 140 mm, such as from about 130 mm to about 150 mm, for example from about 75 mm to about 120 mm.

[0101] As shown in FIGS. 17 and 19A-19C, the electrode 198 can be welded to the top of the one or more ribs 194 with a plurality of welds 196. In an example, the electrode 198 is a planar electrode or an expanded metal or a mesh. In examples where the electrode 198 is an expanded metal or a mesh, the thickness of each strand that forms the mesh can be from about 0.5 mm to about 3 mm, for example from about 0.5 mm to about 2.5 mm, such as from about 0.5 mm to about 2 mm, for example from about 0.5 mm to about 1.5 mm, such as from about 0.5 mm to about 1 mm, for example from about 1 mm to about 3 mm, such as from about 1 mm to about 2.5 mm, for example from about 1 mm to about 2 mm, such as from about 1 mm to about 1.5 mm, for example from about 1.5 mm to about 3 mm, such as from about 1.5 mm to about 2.5 mm, for example from about 1.5 mm to about 2 mm, such as from about 2 mm to about 3 mm, for example from about 2.5 mm to about 3 mm.

[0102] The geometry, spacing, density, and/or cross-sectional area of the welds 196 can impact current flow through the pan assembly 190. As the operational current density is increased and more current flows through the cell, the density of the welds 196 (e.g., the cross-sectional area of the welds 196 and the spacing between welds 196) can impact the local Joule heating. The density of the welds 196 can be selected to reduce the or minimize the chances of separator damage due to the formation local hot spots. The example welds 196 in FIGS. 19A-19C are illustrated as spots. However, the welds 196 can be in form of lines, spots, patterns, or any other shape, or combinations thereof. For example, a spot welder can form the welds 196 as spots, while a laser welder can produce the welds 196 as lines and/or spots and/or patterns. Patterns that the welds 196 can be formed as include, but are not limited to, a combination of dots, an array of dots, dashes, spots, lines, and line segments, which can be arranged in the pattern of any geometrically regular shape, such as a generally rectangular geometry, a generally circular geometry, or a generally hexagonal geometry, or can be arranged in an irregular shape. [0103] Examples of welding techniques that can be used to form the welds 196 include, but are not limited to: laser welding, TiG welding, and spot welding. Laser welding may enable a single linear weld 196 along a substantial portion of the length LRU, of one of the ribs 194 up to and including the entire length LRib of the rib 194 in order to weld the rib 194 to the electrode 198. For example, when the one or more ribs 194 are a solid plate (e.g., ribs 194A of FIG. 19A) or a plate with holes that does not include notches 208 (e.g., the ribs 194B of FIG. 19B), there may be a single linear weld 196 along the entire length LRib of the rib 194 in order to join the rib 194 to the electrode 198. Laser welding or TiG welding may also be used to create welds 196 in the form of line segments. For example, when the one or more of the ribs 194 include notches 208 (e.g., the ribs 194C of FIG. 19C), there may be segments of weld lines over the portions of the ribs 194 that come into contact with the electrode 198, but not over the notches 208. Laser welding can also produce weld patterns comprising dots, an array of dots, dashes, spots, line segments, long lines, and any specified geometry, such as an oval geometry, rectangular geometry, circular geometry, hexagonal geometry, or combinations thereof. The weld geometries may be dictated by the shape of the welding tip and anvil. TiG welds may be created manually, and they can be in arbitrary form.

[0104] In an example, the geometry of the welds 196 includes the number of welds in the pan 192. The number of the welds 196 coupling the electrode 198 to the ribs 194 can impact the current distribution and the power dissipation within the pan assembly 190. In an example, the number of welds 196 per rib 194 that are in the form of the spots (such as the example spot welds 196 shown in FIGS. 15 and 19A-19C) is from 10 to 50 of the welds 196 per rib 194, for example from 10 to 40 of the welds 196 per rib 194, such as from 10 to 30 of the welds 196 per rib 194, for example from 10 to 20 of the welds 196 per rib 194, such as from 20 to 50 of the welds 196 per rib 194, for example from 20 to 40 of the welds 196 per rib 194, such as from 20 to 30 of the welds 196 per rib 194, for example from 30 to 40 of the welds 196 per rib 194, such as from 35 to 40 of the welds 196 per rib 194, for example from 40 to 50 of the welds 196 per rib 194. [0105] In an example, the distance between the welds 196 when in the form of spot welds is from about 25 mm to about 200 mm, for example from about 25 mm to about 150 mm, such as from about 25 mm to about 100 mm, for example from about 25 mm to about 75 mm, such as from about 25 mm to about 50 mm, for example from about 50 mm to about 200 mm, such as from about 50 mm to about 150 mm, for example from about 50 mm to about 100 mm, such as from about 50 mm to about 75 mm, for example from about 75 mm to about 200 mm, such as from about 75 mm to about 150 mm, for example from about 75 mm to about 100 mm, such as from about 100 mm to about 200 mm, for example from about 100 mm to about 150 mm, independently in x- and y- directions.

[0106] In an example, the number of the welds 196 per rib 194 that are in the form of line welds or line segment welds is between 1 to 75 of the welds 196 per rib 194, for example from 1 to 70 of the welds 196 per rib 194, such as from 1 to 60 of the welds 196 per rib 194, for example from 1 to 50 of the welds 196 per rib 194, such as from 1 to 40 of the welds 196 per rib 194, for example from 1 to 30 of the welds 196 per rib 194, such as from 1 to 20 of the welds 196 per rib 194, for example from 1 to 10 of the welds 196 per rib 194, such as from 2 to 75 of the welds 196 per rib 194, for example from 2 to 70 of the welds 196 per rib 194, such as from 2 to 60 of the welds 196 per rib 194, for example from 2 to 50 of the welds 196 per rib 194, such as from 2 to 40 of the welds 196 per rib 194, for example from 2 to 30 of the welds 196 per rib 194, such as from 2 to 20 of the welds 196 per rib 194, for example from 2 to 10 of the welds 196 per rib 194, such as from 10 to 75 of the welds 196 per rib 194, for example from 10 to 70 of the welds 196 per rib 194, such as from 10 to 60 of the welds 196 per rib 194, for example from 10 to 50 of the welds 196 per rib 194, such as from 10 to 40 of the welds 196 per rib 194, for example from 10 to 30 of the welds 196 per rib 194, such as from 10 to 20 of the welds 196 per rib 194, for example from 25 to 75 of the welds 196 per rib 194, such as from 25 to 50 of the welds 196 per rib 194, for example from 50 to 75 of the welds 196 per rib 194, such as from 60 to 75 of the welds 196 per rib 194.

[0107] In an example, the distance between the welds 196 when in the form of the line welds or line segment welds is from about 40 mm to about 200 mm, for example from about 40 mm to about 150 mm, such as from about 40 mm to about 100 mm, for example from about 40 mm to about 75 mm, such as from about 75 mm to about 200 mm, for example from about 75 mm to about 150 mm, such as from about 75 mm to about 100 mm, for example from about 100 mm to about 200 mm, such as from about 100 mm to about 150 mm, for example from about 150 mm to about 200 mm, independently in x- and y- directions.

[0108] In an example, when the one or more ribs 194 comprise the one or more notches 208 and the welds 196 comprise one or more line segments that weld the electrode 198 to the ridges of the ribs 194 formed between notches 208, the line segment of a particular weld 196 can run along the entire length of a ridge between notches 208 or along only a partial length of a ridge between notches 208. In an example, the length of a line segment weld 196 is the length of the ridge between notches 208 or the length of the line segment weld 196 is from about 0.25 m to about 1 m, for example from about 0.25 m to about 0.8 m, such as from about 0.25 m to about 0.6 m, for example from about 0.25 m to about 0.5 m, such as from about 0.25 m to about 0.4 m, for example from about 0.25 m to about 0.3 m, such as from about 0.5 m to about 1 m, for example from about 0.5 m to about 0.8 m, such as from about 0.5 m to about 0.6 m, for example from about 0.6 m to about 1 m, such as from about 0.6 m to about 0.8 m, for example from about 0.7 m to about 1 m, such as from about 0.7 m to about 0.8 m, for example from about 0.8 m to about 1 m.

[0109] In an example, the distance between two adjacent line segment welds 196 is from about 5 mm to about 100 mm, for example from about 5 mm to about 80 mm, such as from about 5 mm to about 60 mm, for example from about 5 mm to about 50 mm, such as from about 5 mm to about 40 mm, for example from about 5 mm to about 30 mm, such as from about 5 mm to about 20 mm, for example from about 5 mm to about 10 mm, such as from about 10 mm to about 100 mm, for example from about 10 mm to about 50 mm, such as from about 10 mm to about 40 mm, for example from about 10 mm to about 30 mm, such as from about 10 mm to about 20 mm, for example from about 20 mm to about 100 mm, such as from about 20 mm to about 50 mm, for example from about 20 mm to about 40 mm, such as from about 20 mm to about 30 mm, for example from about 30 mm to about 100 mm, such as from about 30 mm to about 50 mm, for example from about 30 mm to about 40 mm, such as from about 40 mm to about 100 mm, for example from about 40 mm to about 50 mm, such as from about 50 mm to about 100 mm, for example from about 75 mm to about 100 mm.

[0110] In example, the cross-sectional area of each weld 196 is from about 6 square millimeters (mm ² ) to about 3300 mm ² , for example from about 6 mm ² to about 3000 mm ² , such as from about 6 mm ² to about 2000 mm ² , for example from about 6 mm ² to about 1000 mm ² , such as from about 6 mm ² to about 500 mm ² , for example from about 6 mm ² to about 300 mm ² , such as from about 6 mm ² to about 100 mm ² , for example from about 50 mm ² to about 3300 mm ² , such as from about 50 mm ² to about 3000 mm ² , for example from about 50 mm ² to about 2000 mm ² , such as from about 50 mm ² to about 1000 mm ² , for example from about 50 mm ² to about 500 mm ² , such as from about 50 mm ² to about 300 mm ² , for example from about 50 mm ² to about 100 mm ² , such as from about 100 mm ² to about 3300 mm ² , for example from about 100 mm ² to about 3000 mm ² , such as from about 100 mm ² to about 2000 mm ² , for example from about 100 mm ² to about 1000 mm ² , such as from about 100 mm ² to about 500 mm ² , for example from about 100 mm ² to about 300 mm ² , such as from about 500 mm ² to about 3300 mm ² , for example from about 500 mm ² to about 3000 mm ² , such as from about 500 mm ² to about 2000 mm ² , for example from about 500 mm ² to about 1000 mm ² , such as from about 1000 mm ² to about 3300 mm ² , for example from about 1000 mm ² to about 3000 mm ² , such as from about 1000 mm ² to about 2000 mm ² , for example from about 2000 mm ² to about 3000 mm ² , such as from about 2500 mm ² to about 3000 mm ² .

[OHl] In an example, the geometry, spacing or density, and/or cross- sectional area of the welds 196 is such that a ratio of the cross-sectional area of the electrode 198 relative to the total cross-sectional area of the welds 196 is from about 15: 1 to about 2000: 1, for example from about 15: 1 to about 1000: 1, such as from about 15: 1 to about 500: 1.

[0112] In an example, the geometry, spacing or density, and/or cross- sectional area of the welds 196 is such that the current density through each weld 196 is about 6 amps per square millimeter (A/mm ² ) or less, for example about 5 A/mm ² or less, such as 4 A/mm ² or less, for example about 3 A/mm ² or less, such as 2 A/mm ² or less, for example about 1 A/mm ² or less, or from about 1 A/mm ² to about 6A/mm2, such as from about 1 A/mm ² to about 4 A/mm ² . [0113] In one specific and non-limiting example, the welds 196 are in the form of spot welds and there are from 10 to 50 of the welds 196 per rib 194, the distance between adjacent spot welds 196 is from about 25 mm to about 200 mm (independently in the x- and y-directions), the cross-sectional area of each spot weld 196 is from about 6 mm ² to about 3300 mm ² , and the current density through each spot weld 196 is 6 A/mm ² or less, for example 4 A/mm ² or less. In another specific and non-limiting example, the welds 196 are in the form of line welds and there from 1 to 75 of the welds 196 per rib 194, the distance between adjacent line welds 196 is from about 40 mm to about 200 mm (independently in the x- and y-directions), the cross-sectional area of each line weld 196 is from about 6 mm ² to about 3300 mm ² , and the current density through each line weld 196 is 6 A/mm ² or less, for example 4 A/mm ² or less.

[0114] In an example, an electrochemical cell 101 comprising a pan assembly with one or any combination of the structures described above for the pan assemblies 140, 160, 190 for one or both of the anode half cell 111 and the cathode half cell 121 can operate at a current density of from about 300 mA/cm ² to about 6000 mA/cm ² , for example from about 300 mA/cm ² to about 5000 mA/cm ² , such as from about 300 mA/cm ² to about 4000 mA/cm ² , for example from about 300 mA/cm ² to about 3000 mA/cm ² , such as from about 300 mA/cm ² to about 2000 mA/cm ² , for example from about 300 mA/cm ² to about 1000 mA/cm ² , such as from about 300 mA/cm ² to about 800 mA/cm ² , for example from about 300 mA/cm ² to about 600 mA/cm ² , such as from about 300 mA/cm ² to about 500 mA/cm ² , for example from about 500 mA/cm ² to about 6000 mA/cm ² , such as from about 500 mA/cm ² to about 5000 mA/cm ² , for example from about 500 mA/cm ² to about 4000 mA/cm ² , such as from about 500 mA/cm ² to about 3000 mA/cm ² , for example from about 500 mA/cm ² to about 2000 mA/cm ² , such as from about 500 mA/cm ² to about 1000 mA/cm ² , for example from about 500 mA/cm ² to about 800 mA/cm ² , such as from about 500 mA/cm ² to about 600 mA/cm ² , for example from about 600 mA/cm ² to about 6000 mA/cm ² , such as from about 600 mA/cm ² to about 5000 mA/cm ² , for example from about 600 mA/cm ² to about 4000 mA/cm ² , such as from about 600 mA/cm ² to about 3000 mA/cm ² , for example from about 600 mA/cm ² to about 2000 mA/cm ² , such as from about 600 mA/cm ² to about 1000 mA/cm ² , for example from about 600 mA/cm ² to about 800 mA/cm ² , such as from about 800 mA/cm ² to about 6000 mA/cm ² , for example from about 800 mA/cm ² to about 5000 mA/cm ² , such as from about 800 mA/cm ² to about 4000 mA/cm ² , for example from about 800 mA/cm ² to about 3000 mA/cm ² , such as from about 800 mA/cm ² to about 2000 mA/cm ² , for example from about 800 mA/cm ² to about 1000 mA/cm ² , such as from about 1000 mA/cm ² to about 6000 mA/cm ² , for example from about 1000 mA/cm ² to about 5000 mA/cm ² , such as from about 1000 mA/cm ² to about 4000 mA/cm ² , for example from about 1000 mA/cm ² to about 3000 mA/cm ² , such as from about 1000 mA/cm ² to about 2000 mA/cm ² , for example from about 2000 mA/cm ² to about 6000 mA/cm ² , such as from about 2000 mA/cm ² to about 5000 mA/cm ² , for example from about 2000 mA/cm ² to about 4000 mA/cm ² , such as from about 2000 mA/cm ² to about 3000 mA/cm ² , for example from about 3000 mA/cm ² to about 6000 mA/cm ² , such as from about 3000 mA/cm ² to about 5000 mA/cm ² , for example from about 3000 mA/cm ² to about 4000 mA/cm ² , such as from about 4000 mA/cm ² to about 6000 mA/cm ² , for example from about 4000 mA/cm ² to about 5000 mA/cm ² , such as from about 5000 mA/cm ² to about 6000 mA/cm ² . In some examples, an electrochemical cell 101 comprising any one of the pan assemblies 140, 160, 190 for one or both of the anode half cell 111 and the cathode half cell 121 operates at high current densities of from about 300 mA/cm ² to about 3000 mA/cm ² , such as from about 300 mA/cm ² to about 2000 mA/cm ² , for example from about 300 mA/cm ² to about 1000 mA/cm ² , such as from about 300 mA/cm ² to about 800 mA/cm ² , for example from about 300 mA/cm ² to about 600 mA/cm ² , such as from about 300 mA/cm ² to about 500 mA/cm ² for example from about 300 mA/cm ² to about 400 mA/cm ² .

[0115] In an example, a pan assembly comprising one or any combination of the structures described above for the pan assemblies 140, 160, 190 can accommodate a high flow rate of electrolyte (either anolyte through an anode pan assembly or catholyte through a cathode pan assembly), for example from about 200 kilograms per hour (kg/h) to about 10,000 kg/h, such as from about 200 kg/h to about 9000 kg/h, for example from about 200 kg/h to about 8000 kg/h, such as from about 200 kg/h to about 7000 kg/h, for example from about 200 kg/h to about 6000 kg/h, such as from about 200 kg/h to about 5000 kg/h, for example from about 200 kg/h to about 4000 kg/h, such as from about 200 kg/h to about 3000 kg/h, for example from about 200 kg/h to about 2000 kg/h, such as from about 200 kg/h to about 1000 kg/h, for example from about 500 kg/h to about 10,000 kg/h, such as from about 500 kg/h to about 9000 kg/h, for example from about 500 kg/h to about 8000 kg/h, such as from about 500 kg/h to about 7000 kg/h, for example from about 500 kg/h to about 6000 kg/h, such as from about 500 kg/h to about 5000 kg/h, for example from about 500 kg/h to about 4000 kg/h, such as from about 500 kg/h to about 3000 kg/h, for example from about 500 kg/h to about 2000 kg/h, such as from about 500 kg/h to about 1000 kg/h, for example from about 800 kg/h to about 10,000 kg/h, such as from about 800 kg/h to about 9000 kg/h, for example from about 800 kg/h to about 8000 kg/h, such as from about 800 kg/h to about 7000 kg/h, for example from about 800 kg/h to about 6000 kg/h, such as from about 800 kg/h to about 5000 kg/h, for example from about 800 kg/h to about 4000 kg/h, such as from about 800 kg/h to about 3000 kg/h, for example from about 800 kg/h to about 2000 kg/h, such as from about 800 kg/h to about 1000 kg/h, for example from about 1000 kg/h to about 10,000 kg/h, such as from about 1000 kg/h to about 9000 kg/h, for example from about 1000 kg/h to about 8000 kg/h, such as from about 1000 kg/h to about 7000 kg/h, for example from about 1000 kg/h to about 6000 kg/h, such as from about 1000 kg/h to about 5000 kg/h, for example from about 1000 kg/h to about 4000 kg/h, such as from about 1000 kg/h to about 3000 kg/h, for example from about 1000 kg/h to about 2000 kg/h, such as from about 3000 kg/h to about 10,000 kg/h, for example from about 3000 kg/h to about 9000 kg/h, such as from about 3000 kg/h to about 8000 kg/h, for example from about 3000 kg/h to about 7000 kg/h, such as from about 3000 kg/h to about 6000 kg/h, for example from about 3000 kg/h to about 5000 kg/h, such as from about 5000 kg/h to about 10,000 kg/h, for example from about 5000 kg/h to about 8000 kg/h, such as from about 5000 kg/h to about 6000 kg/h, for example from about 6000 kg/h to about 10,000 kg/h, such as from about 6000 kg/h to about 8000 kg/h, for example from about 8000 kg/h to about 10,000 kg/h. [0116] In an example, a pan assembly comprising one or any combination of the structures described above for the pan assemblies 140, 160, 190 can provide for a superficial liquid velocity of the electrolyte through the pan assembly 140, 160, 190 of 0.1 m/s or less, for example 0.08 m/s or less, such as 0.05 m/s or less, for example 0.01 m/s or less.

Sensor Array

[0117] It is common to incorporate one or more sensors into or onto each electrolyzer cell in an electrolyzer stack, for example to monitor performance of one or more of the electrolyzer cells in the stack, for safety interlocks, or for open-loop or closed-loop control of one or more aspects of the operation of the individual electrolyzer cells or of the electrolyzer stack as a whole. Examples of such sensors include, but are not limited to: one or more cell voltage sensors (e.g., to measure a voltage across one or more individual electrolyzer cells in the stack); one or more cell temperature sensors (e.g., to measure a temperature at one or more specified locations within one or more of the electrolyzer cells); one or more pH sensors (e.g., to measure a pH at one or more specified locations within one or more of the electrolyzer cells); one or more specific heat sensors (e.g., to measure a specific heat of the material or materials at one or more specified locations within one or more of the electrolyzer cells); one or more optical bubble measurement sensors (e.g., to measure the amount of oxygen gas or hydrogen gas being generated within one or more of the electrolyzer cells); and the like. Often, such sensors utilize specified physical phenomena to create a stimulus that is converted to an electrical signal (e.g., to an electrical voltage or current), which, after being locally conditioned can be relayed to a central controller for further calculation, analysis, and action.

[0118] FIG. 20 shows a schematic diagram of a conventional implementation of a sensor system on a stack 300 of electrolyzer cells 302A- 302N (collectively referred to as “electrolyzer cells 302” or “electrolyzer cell 302”). Each cell 302 in the stack 300 can include one or more of the structures described above, e.g., with one or both of the anode half cell 111 and the cathode half cell 121 of the electrolyzer cell 101 of FIG. 1, which can each include one or more of the structures of the pan assemblies 140, 160, 190 described above with respect to FIGS. 2-19C.

[0119] In an example, the electrolyzer cells 302 are connected electrically in series with conductors 304. In an example, the stack 300 comprises eighty (80) electrolyzer cells 302 connected in series. The individual electrolyzer cells 302 in the example electrolyzer stack 300 are labeled with reference numbers 302 A through 302N, with only the first electrolyzer cell 302A, the second electrolyzer cell 302B, and the last (i.e., the eightieth) electrolyzer cell 302N being shown in FIG. 2. In an example, the electrical positive conductor (e.g., the positive conductor 116 in FIG. 1) of one cell 302A is electrically connected to the electrical negative conductor of the subsequent cell 302B (e.g., the negative conductor 126 in FIG. 1), with the following exceptions: (a) the positive conductor of the final cell 302N at the highest voltage is connected to a power supply 306; and (b) the negative conductor of the first cell 302A at the lowest voltage is connected to a ground 308 of the electrical circuit. In an example wherein each cell 302 operates at a nominal voltage of 3 V, the cell positive conductors 304 of the cells 302 A, 302B, and 302N are at the voltages of 3, 6, and 240 volts, respectively. In an example, the power supply 306 is a constant-current voltage-limited rectifier that converts grid AC power to a suitable DC power level.

[0120] As can be seen in FIG. 20, a plurality of sensors is associated with each electrolyzer cell 302. In the example shown, the plurality of sensors includes a temperature sensor 310 to measure a temperature at a specified location within the electrolyzer cell 302, a pH sensor 312 to measure a pH at a specified location within the electrolyzer cell 302, and a voltage sensor 314 to measure a voltage across the electrolyzer cell 302. However, as will be appreciated by those having skill in the art, the sensor array for any particular electrolyzer cell 302 need not include the exact same combination of sensors shown in FIG 20, but rather can include any sub-combination of the types of sensors shown in FIG. 20, including one or more additional types of sensors in place of or in addition to one or more of the sensor types described above. [0121] As shown in FIG. 20, the sensors 310, 312, 314 are attached to specified locations within each electrolyzer cell 302, e.g., so that each sensor 310, 312, 314 can measure the phenomena for which it is configured. In an example, the sensing wires of each sensor 310, 312, 314 are connected to a corresponding sensor board 316 dedicated to each electrolyzer cell 302. For example, a first sensor board 316A corresponds to the first electrolyzer cell 302A and is electronically connected to the sensors 310A, 312A, and 314A that are measuring temperature, pH, and voltage for the first electrolyzer cell 302 A, respectively. A second sensor board 316B corresponds to the second electrolyzer cell 302B and is electronically connected to the sensors 310B, 312B, 314B that are measuring temperature, pH, and voltage for the second electrolyzer cell 302B, respectively. And a final sensor board 316N corresponds to the final electrolyzer cell 302N in the stack 300, which is electronically connected to the sensors 310N, 312N, 314N that are measuring temperature, pH, and voltage for the final electrolyzer cell 302N, respectively. In an example, each sensor board 316 is connected to a global power and communication bus 318 through a corresponding local bus 320 (e.g., with the first sensor board 316A connected to the global bus 318 via a first local bus 320A, the second sensor board 316B connected to the global bus 318 with a second local bus 320B, and the final sensor board 316N connected to the global bus 318 via a final local bus 320N). Each sensor board 316 is powered by electricity generated by the power supply 306 that is transmitted through the global bus 318 and its corresponding local bus 320. In an example, the same electricity that is supplied to each sensor board 316 through the global bus 318 and local bus 320 also provides power to the corresponding sensors 310, 312, 314 that are connected to the sensor board 316. The sensing signals are processed on the sensor boards 316 and communicated to a central controller 322 via the local buses 320 and the global bus 318 for further analysis and decisions for actuations.

[0122] The conventional implementation of a sensor system, such as the example electrolyzer stack 300 shown in FIG. 20, has two fundamental issues: First, each sensor board 316A, 316B, 316N in the stack 300 is operating at a different common-mode voltage, corresponding to the voltage of the cell 302 A, 302B, 302B to which it is attached, respectively. In the example described above for the stack 300 shown in FIG. 20, i.e., with each electrolyzer cell 302 operating at a nominal voltage of 3 V, the sensor board 316A for the first electrolyzer cell 302 A must operate at 3 V, the sensor board 316B for the second cell 302B must operate at 6 V, and the sensor board 316N for the last (i.e., eightieth) cell 302N must operate at 240 V. The local bus 320A, 320B, 320N for each electrolyzer cell 302A, 302B, 302N and the global bus 318 therefore must be compliant to the whole voltage range, e.g., from 0 V all the way up to 240 V. Methods of measuring small signals offered by the sensors 310, 312, 314 in such large ranges of voltages are inaccurate and expensive.

[0123] Second, the many wires or other conductors of the global bus 318 must be routed to the sensor boards 316A, 316B, 316N of each cell 302A, 302B, 302N through the local buses 320A, 320B, 320N, respectively. Therefore, when only one or a subset of all of the cells 302 is to be removed for maintenance from the stack 300, the global bus 318 must be disconnected or otherwise reconfigured. Operator and installation errors for these maintenance operations can be significant.

[0124] In an example, the system of the present disclosure:

(a) provides a method for the sensors and/or the sensor boards to derive the power it needs from the cell from which it is taking measurements; and

(b) provides a method for the sensors and/or the sensor board to communicate with a central controller without any wires between the two, e.g., without having to use a global power and communication bus.

[0125] FIG. 21 shows an example stack 400 of electrolyzer cells 302 comprising a sensor system according to the present disclosure. As can be seen in FIG. 21, relative to the conventional stack 300, the stack 400 of the cells 302 and the sensors 310, 312, 314 attached thereto are the same (and hence use the same reference numbers). However, the sensor boards 416A, 416B, 416N (collectively or generically referred to as “sensor board 416” or “sensor boards 416”) in the stack 400 of FIG. 21 are designed differently.

[0126] For example, instead of transmitting data between the sensor boards 416 and a central controller 422 via a hard-wired communication bus, as with the global bus 318 in the example stack 300 of FIG. 20, each sensor board 416 is configured to transmit information to and receive information from the central controller 422 wirelessly via a corresponding wireless transponder 420A, 420B, 420A (referred to collectively or generically as “wireless transponder 420” or “wireless transponders 420”) that is electrically connected to the sensor board 416A, 416B, 416N. Each wireless transponder 420A, 420B, 420N wirelessly communicates information regarding its corresponding sensor board 416A, 416B, 416N to and from a corresponding wireless transponder 418 that is electrically connected to the central controller 422. For example, the first wireless transponder 420A wirelessly transmits data corresponding to the sensors 310A, 312 A, 314 A associated with the first sensor board 416A, the second wireless transponder 420B wirelessly transmits data corresponding to the sensors 310B, 312B, 314B associated with the second sensor board 416B, and the final wireless transponder 420N wirelessly transmits data corresponding to the sensors 310N, 312N, 314N associated with the final sensor board 416N. For example, the first wireless transponder 420A can wirelessly transmit data corresponding to one or more of: a temperature within the first electrolyzer cell 302 A from the temperature sensor 310A, a pH within the first electrolyzer cell 302 A from the pH sensor 312 A, and a voltage across the first electrolyzer cell 302 A from the voltage sensor 314 A. The second wireless transponder 420B can wirelessly transmit data corresponding to one or more of: a temperature within the second electrolyzer cell 302B from the temperature sensor 310B, a pH within the second electrolyzer cell 302B from the pH sensor 312B, and a voltage across the second electrolyzer cell 302B from the voltage sensor 314B. Similarly, the final wireless transponder 420N can wireless transmit data corresponding to one or more of: a temperature within the final electrolyzer cell 302N from the temperature sensor 310N, a pH within the final electrolyzer cell 302N from the pH sensor 312N, and a voltage across the final electrolyzer cell 302N from the voltage sensor 314N. The physical and logical protocols of the transponders 418 and 420 can be predetermined. Such protocols may be customized or standard, including, but not limited to, Wi-Fi, Bluetooth or ZigBee. However, as will be appreciated by those having skill in the art, the sensor board 416 of the present disclosure can also be configured to be used in a system where sensor signals are transmitted to the controller 422 without the use of wireless communication, e.g., through a hard-wired communication bus. In other words, the sensor boards 416 of the present disclosure can be configured to still obtain their power from the corresponding cell 302 to which each sensor board 416 is attached, but can communicate the sensing signals from the sensors 310, 312, 314 via one or more wired communication buses. Alternatively, the sensor boards 416 can obtain power from a source external to the cells 302 and can communicate via one or more wired communication buses.

[0127] In some examples, instead of deriving power via a global power and communication bus, the power to operate the sensor board 416A, 416B, 416N for each electrolyzer cell 302A, 302B, 302N is derived partially or completely from the cell 302 to which it is attached. For example, power for the first sensor board 416A and the sensors 310A, 312 A, 314A connected to it can be supplied by the first electrolyzer cell 302A, power for the second sensor board 416B and its sensors 310B, 312B, 314B can be supplied by the second electrolyzer cell 302B, and power for the final sensor board 416N and its sensors 310N, 312N, 314N can be supplied by the final electrolyzer cell 302N.

However, as will be appreciated by those having skill in the art, each sensor board 416 of the present disclosure can also be configured to be used in a system where the sensor board 416 is powered by a source other than the electrolyzer cell 302 to which it is attached. Examples of power sources that can provide electrical energy to one or more of the sensor boards 416 in addition to or in place of the electrolyzer cell 302 to which the sensor board 416 is attached include, but are not limited to: a hard-wired power bus (e.g., a common power bus similar to the global bus 318 in FIG. 3, but that only provides electrical power instead of electrical power and communication), standard electrical power (e.g., wall power via standard electrical plugs), or one or more batteries electrically connected to one or more of the sensor boards 416. In an example where the power supplied to the one or more sensor boards 416 comprises one or more batteries, the one or more batteries can comprise one or more rechargeable batteries, wherein the one or more rechargeable batteries can be recharged with power from one or more of the electrolyzer cells 302A, 302B, 302N. [0128] An example architecture for a sensor board 500 is shown schematically in FIG. 22. In an example, the sensor board 500 having the architecture shown in FIG. 22 can be used as one or more of the sensor boards 416 in the stack 400 of FIG. 21. However, the sensors boards 416 are not limited to the architecture shown in FIG. 22. In an example, a two-stage power supply is used in the example sensor board 500.

[0129] A supply voltage 502 is provided to the sensor board 500, which drives the action of the sensor board 500, including the power supply portion of the sensor board 500 (described in more detail below). The supply voltage 502 can be provided from any source, as discussed above. For example, if the power source for the sensor board 500 is a hard-wired power bus, then the supply voltage 502 can be the voltage of the power bus at the location of the sensor board 500. If the power source is one or more batteries, than the supply voltage 502 can be the voltage provided by the one or more batteries. If the power source is the electrolyzer cell 302 with which the sensor board 500 is associated (e.g., the first electrolyzer cell 302A if the sensor board 500 is the first sensor board 416A in FIG. 21). The example sensor board 500 shown in FIG. 22 is described with respect to the first electrolyzer cell 302 A of FIG. 21, however those having skill in the art will appreciate that a similar or identical architecture could be used for the sensor boards of all of the cells 302B through 302N in the stack 400.

[0130] In an example, the supply voltage 502 can be rather low. For example, if the power source is the electrolyzer cell 302A, then the supply voltage 502 from the electrolyzer cell 302A can be as low as 1.23 V. In an example, such a low voltage is unable to drive the electronics on the sensor board 500. Boosting to a useful voltage, such as to 5 V, while providing a sufficient amount of power (such as from about 1 watt (W) to about 3 W) is typically not efficient or practical to be done in one step. In addition, the supply voltage 502 can vary greatly during operation of the stack 400, such as from variation in operating voltage across the cells 302.

[0131] In an example, the sensor board 500 of the present disclosure comprises a first stage power supply 504 that provides a stable intermediate voltage 506 (for example, about 3.3 V), but with a relatively low power capability, even from a variable supply voltage 502, such as one being received from the electrolyzer cell 302 A (which can range from about 1.23 V to about 4 V). As used herein, the term “stable” when referring to the voltage being provided by the power supply stages 504, 508 of the sensor board 500, refers to the voltage (e.g., the intermediate voltage 506 or the voltage output 510 from a second stage power supply 508) remaining within a specified voltage from the particular power supply stage 504, 508. In an example, the first stage power supply 504 is a switch-mode pulse width modulated power supply of buck-boost topology, with a variable input of from about 1.2 V to about 4 V and with a constant voltage output 411 of about 3.3 V.

[0132] In an example, the intermediate voltage 506 of about 3.3 V from the first stage power supply 504 is used as the bootstrap bias for a second stage power supply 508, which can boost the supply voltage 502 to an appropriate rail voltage (e.g., about 5V). Once the second stage power supply 508 produces a regulated voltage output 510, the first stage power supply 504 can be driven to hibernation, and the regulated voltage output 510 can be used to bias the gate drive of the second stage power supply 508 itself.

[0133] In an example, the regulated voltage output 510, generally known as VCC, is capable of driving all the circuits on the sensor board 500. The VCC 510 can power a set of shaper circuits 512 for the sensors (e.g., one shaper circuit 512 for the temperature sensor 310, another shaper circuit 512 for the pH sensor 312, and yet another shaper circuit 512 for the voltage sensor 314). Each shaper circuit 512 can include amplifiers and filters to make the incoming electronic signals larger and consistent. Each of these shaped signals 514 can be fed into a multiplexer 516 before being quantified with an Analog to Digital Converter (ADC) 518. A microcontroller 520 can read the digital representations of the sensor signals from the ADC 518 and can process them as programmed and transmit them as necessary to a central controller for the system, such as the controller 422 shown in FIG. 21. As noted above, in an example, the sensor board 500 is configured for wireless communication. In an example, the microcontroller 520 can direct a wireless driver 522 to wirelessly communicate with the central controller 422 (or another device) through a wireless transponder 524. However, as noted above, in an example, the sensor board 500 can be configured to communicate with an outside device, such as the central controller 422, via a wired communication bus, in which case the wireless driver 522 and/or the wireless transponder 524 is omitted from the architecture of the sensor board 500.

[0134] An example design implementation for the two-stage power supply is shown in FIG. 23. As can be seen in FIG. 23, an overall power supply circuit 550 can include the first stage power supply 504 and the second stage power supply 508. In an example, the first stage power supply 504 can be made out of the chipset sold under the tradename LTC3526 and the second stage power supply 508 can be made out of the chipset sold under the tradename LTC3124, both sold by Linear Technology Corp. (Milpitas, CA, USA). In an example, a diode DI protects the circuit from negative voltage. The voltage LV OUT from the LTC3526 chipset corresponds to the output of the first stage power supply 504, which as noted above is also referred to as the intermediate voltage 506. The intermediate voltage 506 in turn can be fed to the driving pin of the LTC3124 chipset, which forms the second stage power supply 508. In an example, the output 510 of the second stage power supply 508 is a 5 V supply that can be made powerful enough to drive many watts of power, thus catering to all the circuits, including the wireless transponder 524 on the sensor board 500. [0135] To further illustrate the electrolyzer systems and methods disclosed herein, a non-limiting list of EXAMPLES is provided here:

[0136] EXAMPLE 1 can include subject matter (such as an apparatus, a device, a method, or one or more means for performing acts), such as can include a two-stage switch mode power supply comprising a first stage with a switch mode pulse width modulated buck-boost power supply topology configured to convert an electrolyzer voltage from an electrolyzer cell to an intermediate voltage, a second stage with a switch mode boost topology configured to convert the intermediate voltage to a specified output voltage by using the intermediate voltage as a bias voltage, wherein the bias voltage is used as a bootstrap for activating the second stage so that when the second stage is fully activated the first stage hibernates and the specified output voltage biases the second stage. [0137] EXAMPLE 2 can include, or can optionally be combined with the subject matter of EXAMPLE 1, to optionally include the intermediate voltage being higher than the electrolyzer voltage.

[0138] EXAMPLE 3 can include, or can optionally be combined with the subject matter of one or a combination of EXAMPLE 1 and EXAMPLE 2, to optionally include the specified output voltage being higher than the electrolyzer voltage.

[0139] EXAMPLE 4 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 1-3, to optionally include the specified output voltage being higher than the intermediate voltage. [0140] EXAMPLE 5 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 1-4, to optionally include the electrolyzer voltage being from about 1.2 volts to about 4 volts.

[0141] EXAMPLE 6 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 1-5, to optionally include the intermediate voltage being from about 3 volts to about 5 volts.

[0142] EXAMPLE 7 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 1-6, to optionally include the specified output voltage from the second stage being from about 3.3 volts to about 24 volts.

[0143] EXAMPLE 8 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 1-7 to include subject matter (such as an apparatus, a device, a method, or one or more means for performing acts), such as can include a sensor system, the sensor system comprising a sensor array comprising one or more sensors associated with an electrolyzer cell, wherein the one or more sensors produce sensory signals corresponding to one or more specified phenomena of the electrolyzer cell, a sensor board configured to amplify, filter, shape, or condition the sensory signals and to digitize the sensory signals to provide digitized information, a first communication link between the sensor board and the sensor array, and a second communication link configured to transmit the digitized information to a central controller outside the sensor system. [0144] EXAMPLE 9 can include, or can optionally be combined with the subject matter of EXAMPLE 8, to optionally include the second communication link comprising a wireless transponder configured for wireless communication between the sensor board and the central controller.

[0145] EXAMPLE 10 can include, or can optionally be combined with the subject matter of EXAMPLE 9, to optionally include the wireless transponder operating on a wireless communication protocol.

[0146] EXAMPLE 11 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 8-10, to optionally include a power supply configured to convert an electrolyzer voltage from the electrolyzer cell to a specified output voltage,

[0147] EXAMPLE 12 can include, or can optionally be combined with the subject matter of EXAMPLE 11, to optionally include the sensor board using the specified output voltage from the power supply to amplify, filter, shape, or condition the sensory signals from the sensor array and to digitize the sensory signals to provide the digitized information.

[0148] EXAMPLE 13 can include, or can optionally be combined with the subject matter of one or a combination of EXAMPLE 11 and EXAMPLE 12, to optionally include the specified output voltage being higher than the electrolyzer voltage.

[0149] EXAMPLE 14 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 11-13, to optionally include the electrolyzer voltage being from about 1.2 volts to about 4 volts.

[0150] EXAMPLE 15 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 8-14, to optionally include the power supply comprising a first stage with a switch -mode pulse width modulated buck-boost power supply topology configured to convert the electrolyzer voltage from the electrolyzer cell to an intermediate voltage, and a second stage with a switch mode boost topology configured to convert the intermediate voltage to the specified output voltage by using the intermediate voltage of the first stage as a bias voltage, wherein the bias voltage is used as a bootstrap for activating the second stage so that when the second stage is fully activated the first stage hibernates and the specified output voltage biases the second stage.

[0151] EXAMPLE 16 can include, or can optionally be combined with the subject matter of EXAMPLE 15, to optionally include the intermediate voltage being higher than the electrolyzer voltage.

[0152] EXAMPLE 17 can include, or can optionally be combined with the subject matter of one or a combination of EXAMPLE 15 and EXAMPLE 16, to optionally include the specified output voltage being higher than the electrolyzer voltage.

[0153] EXAMPLE 18 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 15-17, to optionally include the specified output voltage being higher than the intermediate voltage.

[0154] EXAMPLE 19 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 15-18, to optionally include the intermediate voltage from the first stage being from about 3 volts to about 5 volts.

[0155] EXAMPLE 20 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 15-19, to optionally include the specified output voltage from the second stage being from about 3.3 volts to about 24 volts.

[0156] EXAMPLE 21 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 8-20, to optionally include the one or more specified phenomena of the electrolyzer cell comprising at least one of a voltage across the electrolyzer cell, a pH in at least a portion of the electrolyzer cell, and a temperature at a specified location of the electrolyzer cell.

[0157] EXAMPLE 22 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 1-21, to include subject matter (such as an apparatus, a device, a method, or one or more means for performing acts), such as can include an electrolyzer system comprising an electrolyzer stack comprising one or more electrolyzer cells, wherein each electrolyzer cell comprises a first half-cell with a first electrode and a second half-cell with a second electrode, a central controller configured to control operation of one or more aspects of each of the one or more electrolyzer cells of the electrolyzer stack, a sensor array for each of one or more corresponding electrolyzer cells of the electrolyzer stack, wherein each sensor array comprises one or more sensors associated with the corresponding electrolyzer cell, wherein the one or more sensors produce sensory signals corresponding to one or more specified phenomena of the corresponding electrolyzer cell, a sensor board for each corresponding electrolyzer cell, wherein each sensor board is configured to amplify, filter, shape, or condition the sensory signals from a corresponding sensor array and to digitize the sensory signals of the corresponding sensor array to provide digitized information for the corresponding electrolyzer cell, and a communication link for each sensor board, wherein each communication link is configured to transmit the digitized information for the corresponding electrolyzer cell to the central controller.

[0158] EXAMPLE 23 can include, or can optionally be combined with the subject matter of EXAMPLE 22, to optionally include the electrolyzer stack comprising a plurality of electrolyzer cells connected in series.

[0159] EXAMPLE 24 can include, or can optionally be combined with, the subject matter of one or a combination of EXAMPLE 22 and EXAMPLE 23, to optionally include the electrolyzer stack comprising from about 5 to about 500 electrolyzer cells.

[0160] EXAMPLE 25 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 22-24, to optionally include the one or more specified phenomena of the corresponding electrolyzer cell comprising at least one of: a voltage across the corresponding electrolyzer cell, a pH in at least a portion of the corresponding electrolyzer cell, and a temperature at a specified location of the corresponding electrolyzer cell. [0161] EXAMPLE 26 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 22-25, to optionally include the communication link comprising a sensor board wireless transponder configured to wirelessly communicate between the sensor board and the central controller. [0162] EXAMPLE 27 can include, or can optionally be combined with the subject matter of EXAMPLE 26, to optionally include the sensor board wireless transponder operating on a wireless communication protocol.

[0163] EXAMPLE 28 can include, or can optionally be combined with the subject matter of one or a combination of EXAMPLE 26 and EXAMPLE 27, to optionally include the central controller comprising a central controller wireless transponder configured to communicate with the sensor board wireless transponder.

[0164] EXAMPLE 29 can include, or can optionally be combined with the subject matter of EXAMPLE 28, to optionally include the central controller wireless transponder receiving data from the sensor board wireless transponder. [0165] EXAMPLE 30 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 22-29, to optionally include the central controller processing data received from the sensor board with a specified logic.

[0166] EXAMPLE 31 can include, or can optionally be combined with, the subject matter of EXAMPLE 30, to optionally include the central controller taking one or more specified actions based on the processed data.

[0167] EXAMPLE 32 can include, or can optionally be combined with, the subject matter of EXAMPLE 31, to optionally include the one or more specified actions comprising activating a mechanism that controls operation of one or more of the electrolyzer cells of the electrolyzer stack.

[0168] EXAMPLE 33 can include, or can optionally be combined with, the subject matter of one or any combination of EXAMPLES 22-32, to optionally include the sensor board and the sensor array for each corresponding electrolyzer cell deriving power from an electrolyzer voltage from the corresponding electrolyzer cell.

[0169] EXAMPLE 34 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 22-32, to optionally include each sensor board deriving power solely from the corresponding electrolyzer cell, without any wired power connection to another structure in the electrolyzer stack. [0170] EXAMPLE 35 can include, or can optionally be combined with the subject matter of EXAMPLE 33 or EXAMPLE 34, to optionally include each sensor board including a power supply configured to convert the electrolyzer voltage from the corresponding electrolyzer cell to a specified output voltage.

[0171] EXAMPLE 36 can include, or can optionally be combined with, the subject matter of EXAMPLE 35, to optionally include the specified output voltage being higher than the electrolyzer voltage.

[0172] EXAMPLE 37 can include, or can optionally be combined with, the subject matter of one or a combination of EXAMPLE 35 and EXAMPLE 36, to optionally include the electrolyzer voltage being from about 1.2 volts to about 4 volts.

[0173] EXAMPLE 38 can include, or can optionally be combined with, the subject matter of one or any combination of EXAMPLES 35-37, to optionally include the sensor board using the specified output voltage to amplify, filter, shape or condition the sensory signals from the corresponding sensor array and to digitize the sensory signals to provide the digitized information for the corresponding electrolyzer cell.

[0174] EXAMPLE 39 can include, or can optionally be combined with, the subject matter of one or any combination of EXAMPLES 35-38, to optionally include the power supply comprising a first stage with a switch mode buck-boost topology configured to convert the electrolyzer to an intermediate voltage, and a second stage with a switch mode boost topology configured to convert the intermediate voltage to the specified output voltage by using the intermediate voltage of the first stage as a bias voltage, wherein the bias voltage is used as a bootstrap for activating the second stage so that when the second stage is fully activated the first stage hibernates and the specified output voltage biases the second stage.

[0001] EXAMPLE 40 can include, or can optionally be combined with, the subject matter of EXAMPLE 39, to optionally include the intermediate voltage being higher than the electrolyzer voltage.

[0002] EXAMPLE 41 can include, or can optionally be combined with, the subject matter of one or a combination of EXAMPLE 39 and EXAMPLE 40, to optionally include the specified output voltage being higher than the intermediate voltage.

[0003] EXAMPLE 42 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 39-41, to optionally include the intermediate voltage from the first stage being from about 3 volts to about 5 volts.

[0004] EXAMPLE 43 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 39-42, to optionally include the specified output voltage from the second stage being from about 3.3 volts to about 24 volts.

[0005] EXAMPLE 44 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 1-43, to include subject matter (such as an apparatus, a device, a method, or one or more means for performing acts), such as can include a method of producing hydrogen gas, the method comprising providing or receiving an electrolyzer stack comprising one or more electrolyzer cells, wherein each electrolyzer cell comprises a first half-cell with an anode and a second half-cell with a cathode, producing hydrogen gas at the cathode, measuring one or more specified phenomena of a corresponding one of the one or more electrolyzer cells with a sensor array comprising one or more sensors associated with the corresponding one of the one or more electrolyzer cells, wherein the one or more sensors produce sensory signals corresponding to the one or more specified phenomena, modifying the sensory signals to provide digitized information corresponding to the sensory signals, and transmitting the digitized information to a central controller configured to control operation of one or more aspects of the one or more electrolyzer cells of the electrolyzer stack.

[0006] EXAMPLE 45 can include, or can optionally be combined with, the subject matter of EXAMPLE 44, to optionally include producing oxygen gas at the anode.

[0007] EXAMPLE 46 can include, or can optionally be combined with, the subject matter of EXAMPLE 45, to optionally include a separator that separates the first and second half-cells of each electrolyzer cell. [0008] EXAMPLE 47 can include, or can optionally be combined with, the subject matter of EXAMPLE 46, to optionally include the separator comprising an ion-exchange membrane.

[0009] EXAMPLE 48 can include, or can optionally be combined with, the subject matter of one or any combination of EXAMPLES 44-47, to optionally include the modifying of the sensory signals from each of the one or more sensors comprising at least one of amplifying, filtering, shaping, or conditioning the sensor signal to produce the digitized information.

[0010] EXAMPLE 49 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 44-48, to optionally include the electrolyzer stack comprising a plurality of electrolyzer cells connected in series.

[0011] EXAMPLE 50 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 44-49, to optionally include the electrolyzer stack comprising from about 5 to about 500 electrolyzer cells.

[0012] EXAMPLE 51 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 44-50, to optionally include the one or more specified phenomena comprising at least one of: a voltage across the corresponding one of the one or more electrolyzer cells, a pH in at least a portion of the corresponding one of the one or more electrolyzer cells, and a temperature at a specified location of the corresponding one of the one or more electrolyzer cells.

[0013] EXAMPLE 52 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 44-51, to optionally include receiving the digitized information at the central controller. [0014] EXAMPLE 53 can include, or can optionally be combined with, the subject matter of EXAMPLE 52, to optionally include processing the received digitized information with specified logic at the central controller.

[0015] EXAMPLE 54 can include, or can optionally be combined with, the subject matter of one or any combination of EXAMPLES 44-53, to optionally include taking one or more specified actions with the central controller.

[0016] EXAMPLE 55 can include, or can optionally be combined with, the subject matter of EXAMPLE 54, to optionally include the one or more specified actions comprising activating a mechanism that controls the operation of the electrolyzer stack.

[0017] EXAMPLE 56 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 44-55, to optionally include supplying power for the one or more sensors from the corresponding one of the one or more electrolyzer cells.

[0018] EXAMPLE 57 can include, or can optionally be combined with the subject matter of EXAMPLE 56, to optionally include the supplying power for the one or more sensors comprising converting an electrolyzer voltage from the corresponding one of the one or more electrolyzer cells to a specified output voltage.

[0019] EXAMPLE 58 can include, or can optionally be combined with, the subject matter of EXAMPLE 57, to optionally include using the specified output voltage to amplify, filter, shape, or condition sensory signals from the sensor array to provide the digitized information.

[0020] EXAMPLE 59 can include, or can optionally be combined with, the subject matter of one or a combination of EXAMPLE 58 and EXAMPLE 59, to optionally include the specified output voltage being higher than the electrolyzer voltage.

[0021] EXAMPLE 60 can include, or can optionally be combined with, the subject matter of one or any combination of EXAMPLES 57-59, to optionally include the electrolyzer voltage being from about 1.2 volts to about 4 volts.

[0022] EXAMPLE 61 can include, or can optionally be combined with, the subject matter of one or any combination of EXAMPLES 57-60, to optionally include the converting of the electrolyzer voltage to the specified output voltage comprising converting the electrolyzer voltage from the corresponding electrolyzer cell to an intermediate voltage in a first stage of a power supply, and converting the intermediate voltage to the specified output voltage in a second stage of the power supply.

[0023] EXAMPLE 62 can include, or can optionally be combined with, the subject matter of EXAMPLE 61, to optionally include the first stage of the power supply comprising a switch mode pulse width modulated buck-boost power supply topology.

[0024] EXAMPLE 63 can include, or can optionally be combined with, the subject matter of one or a combination of EXAMPLE 61 and EXAMPLE 62, to optionally include the second stage of the power supply comprising a switch mode boost topology.

[0025] EXAMPLE 64 can include, or can optionally be combined with, the subject matter of EXAMPLE 63, to optionally include the second stage using the intermediate voltage of the first stage as a bias voltage.

[0026] EXAMPLE 65 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 61-64, to optionally include using the bias voltage as a bootstrap for activating the second stage so that when the second stage is fully activated the first stage hibernates and the specified output voltage biases the second stage.

[0027] EXAMPLE 66 can include, or can optionally be combined with the subject matter of one or any combination of EXAMPLES 61-65, to optionally include the intermediate voltage being higher than the electrolyzer voltage.

[0028] EXAMPLE 67 can include, or can optionally be combined with, the subject matter of one or any combination of EXAMPLES 61-66, to optionally include the specified output voltage being higher than the intermediate voltage.

[0029] EXAMPLE 68 can include, or can optionally be combined with, the subject matter of one or any combination of EXAMPLES 61-67, to optionally include the intermediate voltage from the first stage being from about 3 volts to about 5 volts.

[0030] EXAMPLE 69 can include, or can optionally be combined with, the subject matter of one or any combination of EXAMPLES 61-68, to optionally include the specified output voltage from the second stage being from about 3.3 volts to about 24 volts.

[0031] EXAMPLE 70 can include, or can optionally be combined with, the subject matter of one or any combination of EXAMPLES 44-69, to optionally include the transmitting of the digitized information to the central controller comprising wirelessly transmitting the digitized information to the central controller.

[0032] The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein. [0033] In the event of inconsistent usages between this document and any documents so incorporated by reference, the usage in this document controls.

[0034] In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In this document, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.

[0035] Method examples described herein can be machine or computer- implemented at least in part. Some examples can include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code can include computer readable instructions for performing various methods. The code may form portions of computer program products. Further, in an example, the code can be tangibly stored on one or more volatile, non- transitory, or non-volatile tangible computer-readable media, such as during execution or at other times. Examples of these tangible computer-readable media can include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like.

[0036] The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R. § 1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.