Method for monitoring the operational performance of a membrane in an electrochemical cell and electrochemical system - Patents.com

Abstract

An electrical method and system is provided that can extend the efficiency and service life of an electrochemical cell or stack. Electrochemical or electrolytic cells and components thereof are disclosed. More specifically, methods and systems are disclosed for removing metal ions from a membrane of an electrochemical cell by introducing a cleaning composition (e.g., an acidic composition) into the water feed to the electrochemical cell. These systems and methods for removing metal ions from a membrane(s) of an electrochemical cell(s) can advantageously extend the efficiency and useful life of the electrochemical cell or stack.

Description

Priority

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 306,592, filed February 4, 2022, which is incorporated by reference herein in its entirety. [Technical field]

[0002] The following disclosures relate to washing metal ions from proton exchange membranes. [Background technology]

[0003] Electrolyzer systems use electrical energy to drive chemical reactions; for example, water is split into hydrogen and oxygen. The products can be used as an energy source for later use. In recent years, improvements in operational efficiency have made electrolyzer systems a competitive market solution for energy storage, generation, and / or transportation. For example, production costs can be less than $10 per kilogram of hydrogen in some cases. Increased efficiency and / or operational improvements continue to drive the installation of electrolyzer systems.

[0004] The performance of proton exchange membranes for proton exchange membrane electrolysers (PEMWEs) depends on many factors, including water quality. Metal ions in the water can become trapped within the pores of the membrane, reducing the efficiency of water splitting in the cell. Summary of the Invention

[0005] In one embodiment, a method for cleaning metal ions from a membrane of an electrochemical cell is provided, the method comprising adding a cleaning composition to a water source supplied to an electrochemical cell, reacting the cleaning composition with the metal ions at the membrane of the electrochemical cell, and transferring products of the reaction of the cleaning composition with the metal ions from the membrane and the electrochemical cell to remove at least a portion of the metal ions from the membrane of the electrochemical cell.

[0006] In another embodiment, a method of monitoring operational performance of a membrane of an electrochemical cell is provided, the method including: measuring, by a voltage sensor, a first operating voltage of the electrochemical cell at a first time; measuring, by the voltage sensor, a second operating voltage of the electrochemical cell at a second time; calculating, by a processor, a change in the operating voltage of the electrochemical cell over a period defined by dividing a difference between the first and second operating voltages by a difference between the first and second times; comparing, by the processor, the change in the operating voltage to a threshold; and providing, by the processor, a notification or alarm when the change in the operating voltage is equal to or greater than the threshold.

[0007] In yet another embodiment, an electrochemical system is provided. The system includes at least one electrochemical cell, at least one voltage sensor configured to measure a first operating voltage of each of the at least one electrochemical cell at a first time and a second operating voltage of the electrochemical cell at a second time, and a processor configured to receive the first operating voltage measured at the first time and the second operating voltage measured at the second time from the at least one voltage sensor, calculate a change in the operating voltage of each electrochemical cell over a period defined as the difference between the first operating voltage and the second operating voltage divided by the difference between the first time and the second time, compare the change in the operating voltage to a threshold value, and provide a notification or alarm when the change in the operating voltage is equal to or greater than the threshold value. In some examples, the system is further configured to provide instructions to add or inject a cleaning composition into a water source that is supplied to the at least one electrochemical cell to remove metal ions in the membrane of the at least one electrochemical cell.

[0008] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0009] In the following, exemplary embodiments are described with reference to the drawings. [Brief description of the drawings]

[0010] [Figure 1] An example of an electrolytic cell is shown. [Diagram 2] Further examples of electrochemical or electrolytic cells are shown. [Diagram 3] 1 shows an example of a section of a system having an electrolytic stack. [Figure 4] 1 shows an example flow chart of a method for in situ membrane metal ion cleaning. [Diagram 5] FIG. 1 illustrates an exemplary communication system between an electrolysis stack and a computing device having a controller over a connected network. [Figure 6] 1 illustrates an example of a computing device having a controller. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] FIG. 1 shows an example of an electrolysis cell for producing hydrogen and oxygen gases by the splitting of water. The electrolysis cell includes a cathode, an anode, and a membrane disposed between the cathode and the anode. Within the water splitting electrolysis reaction, one interface performs the oxygen evolution reaction (OER) and the other interface performs the hydrogen evolution reaction (HER). For example, the anode reaction is HO → 2H + +1 / 2O2+2e, and the cathodic reaction is 2H + +2e → H2. Water electrolysis has been attracting attention in recent years as it is considered to be of great importance as a potential basis for a decarbonized "hydrogen economy."

[0012] The electrolysis cell may include additional components / layers disposed between the electrodes of the cell. For example, the cell may include a porous transport layer (PTL) or a gas diffusion layer (GDL) disposed between the electrode (e.g., the cathode or anode) and the membrane. In certain examples, the membrane in the electrolysis cell may be referred to as a proton exchange membrane for water electrolyzer (PEMWE).

[0013] Figure 2 illustrates a further example of an electrochemical or electrolysis cell. Specifically, Figure 2 illustrates a portion of an electrochemical cell 200 having a cathode flow field 202, an anode flow field 204, and a membrane 206 disposed between the cathode flow field 202 and the anode flow field 204. In certain examples, the membrane 206 can have an overall thickness of less than 1000 microns, 500 microns, 100 microns, 50 microns, 10 microns, etc.

[0014] In certain examples, additional layers may be present in the electrochemical cell 200. For example, one or more additional layers 208 may be disposed between the cathode flow field 202 and the membrane 206. In certain examples, this may include a gas diffusion layer (GDL) 208 that may be disposed between the cathode flow field 202 and the membrane 206. This may be advantageous to provide a hydrogen diffusion barrier adjacent to the cathode on one side of the multilayer membrane to mitigate hydrogen crossover to the anode side. In other words, the GDL is responsible for transporting gaseous hydrogen to the cathode side flow field. For wet cathode PEM operation, in addition to heat removal from the anode side, liquid water transport across the GDL is required for heat removal.

[0015] In a particular example, the GDL is made from carbon paper or woven carbon fabric. The GDL is configured to allow the flow of hydrogen gas through it. The thickness of the GDL may be, for example, in the range of 100 to 1000 microns. As used herein, the "thickness" characterizing the film refers to the distance, or the median of the measured distance, between the top and bottom surfaces of the film in a direction perpendicular to the plane of the film layer. As used herein, the top and bottom surfaces of the film refer to the two sides of the film that extend in a parallel direction in the plane of the film that has the greatest surface area.

[0016] Similarly, one or more additional layers 210 may be present in the electrochemical cell between the membrane 206 and the anode 204. In certain examples, this may include a porous transport layer (PTL) disposed between the membrane 206 (e.g., the anode catalyst layer 208 of the catalyst coated membrane 206) and the anode flow field 204.

[0017] In one embodiment, the PTL is made of titanium (Ti) mesh / felt. As used herein, Ti mesh / felt may refer to a structure made of microporous Ti fibers. The Ti felt structure can be sintered together by fusing some of the fibers together. The Ti felt can be made by a special laying process and a special ultra-high temperature vacuum sintering process. The Ti felt can have excellent three-dimensional mesh structure, porous structure, high porosity, large surface area, uniform pore size distribution, special pressure and corrosion resistance, and can be rolled and processed.

[0018] Similar to the GDL, the PTL is configured to allow transport of reacted water to the anode catalyst layer, remove generated oxygen gas, and provide good electrical conductivity for effective electron conduction. That is, liquid water flowing through the anode flow field is configured to permeate through the PTL to reach the catalyst coated membrane (CCM). Additionally, gaseous by-product oxygen is configured to be removed from the PTL into the flow field. In such a configuration, liquid water serves as both a reactant and a coolant on the anode side of the cell.

[0019] The thickness of the PTL may be, for example, in the range of 100-1000 microns. The thickness may affect not only the durability / deformability and electrical / thermal conductivity of the PTL, but also the mass transport within the cell. In other words, a thinner PTL may provide better mass transport compared to a thicker PTL (e.g., 1 mm). However, if the PTL is too thin (e.g., less than 100 microns), the PTL may suffer from poor two-phase flow effects as well. The PTL is less likely to deform compared to the GDL. The thickness of the PTL may also affect the lateral electronic conduction resistance along the lands between the channels.

[0020] In some embodiments, an anode catalyst coating layer may be positioned between the anode 204 and the PTL.

[0021] The cathode 202 and anode 204 of the cell may each include a flow field plate constructed from metal, carbon, or a composite material with a set of channels machined, stamped, or etched into the plate to allow fluid to flow inward toward the membrane or out of the cell.

[0022] Because the performance of a single electrolysis cell may not be suitable for many use cases, multiple cells can be placed together to form a "stack" of cells, which can be referred to as an electrolyzer stack, electrolysis stack, electrochemical stack, or simply stack. In one example, a stack can include 50-1000 cells, 50-100 cells, 500-700 cells, or more than 1000 cells. Any number of cells may make up a stack.

[0023] FIG. 3 illustrates an example of a portion of an electrolysis system for producing hydrogen gas and oxygen gas from water. The system includes a stack including a plurality of electrochemical or electrolytic cells, such as the cells of FIG. 1 or FIG. 2. The stack is configured to receive water through an anode inlet. The system further includes a cathode outlet at the outlet of the stack. The cathode outlet transports the hydrogen gas produced from the electrolytic cells to further downstream components for further processing. In certain configurations, a water by-product is also provided at the cathode outlet (water may be used as a coolant for the produced hydrogen gas). Additional downstream components following the cathode outlet are not illustrated, but may include a water-gas separator, purifier, heat exchanger, circulation pump, pressure regulator, etc. In FIG. 3, a cathode pressure regulator is shown at the cathode outlet. This pressure regulator may be located further downstream from the cathode outlet after one or more additional components, such as a water-gas separator or purifier, but is shown in a specific location in FIG. 3 for simplicity.

[0024] Additionally, the electrolysis system includes an anode outlet that transports the oxygen gas produced from the electrochemical cells in the stack, as well as the unreacted water by-product, to further downstream components for further processing. Again, additional downstream components following the anode outlet are not shown, but may include water-gas separators, purifiers, heat exchangers, circulation pumps, pressure regulators, and the like. In FIG. 3, an anode pressure regulator is shown at the anode outlet. This pressure regulator may be located further downstream from the anode outlet after one or more additional components, such as a water-gas separator or purifier, but is shown in a specific location in FIG. 3 for simplicity.

[0025] In certain examples, the electrolysis system downstream of the anode outlet includes one or more separator units configured to separate one or more of metal ions, acidic metal compounds, salts, or unreacted cleaning composition in the anode outlet stream that is washed from the membrane in a cleaning process described in more detail below.

[0026] In another embodiment, a configuration with multiple cell stacks in series / parallel is provided.

[0027] As shown in Figure 3, the electrolysis system further includes at least one voltage sensor or monitor configured to measure the operating voltage of a particular cell, group of cells, or stack in the system. The voltage sensor may be configured to transmit the measured voltage (and recorded time) to a monitoring system associated with the electrolysis system. This signaling may occur via a connected network between the electrochemical cell / stack and the associated monitoring system.

[0028] As discussed above in Figures 1 and 2, each cell includes a membrane disposed between and separating the anode and cathode sides of the cell. The membrane in each electrolysis cell is sometimes referred to as a Proton Exchange Membrane for Water Electrolyzers (PEMWE).

[0029] The performance of a PEMWE depends on a variety of factors, one of which is water quality. In certain instances, metal ions from the water can become trapped within the pores of the membrane. These trapped metal ions can reduce the efficiency of water splitting. For example, the voltage required to perform electrolysis in the cell can increase over time as metal ions accumulate in the membrane. This accumulation can occur in membranes made from perfluorosulfonic acid and / or polytetrafluoroethylene (such as Nafion™ membranes) or other materials. The increase in voltage caused by metal ion accumulation can be greater over time than expected, typical, or within specifications for a cell without metal accumulation.

[0030] Thus, there is a need to clean (e.g., in-situ) PEMWE membranes to improve cell performance and to enable extended life of cells and / or stacks having multiple cells. The following disclosure provides examples of in-situ membrane cleaning to advantageously maintain or improve membrane water splitting performance characteristics and / or extend cell / stack life.

[0031] PEMWE membranes can capture metal ions due to their high proton affinity. Metal ion accumulation at the membrane can cause cascading or compounding problems that significantly accelerate performance loss. For example, the concentration of metal ions present at the membrane can increase due to additional leaching events over the course of the battery's useful life. In certain instances, metal ions can enter the water stream during a leaching event. Leaching can occur at the plant or system level from metal dissolution in pipes and other components (e.g., hot water tanks). Leaching can also occur from degradation of cell components such as bipolar plates, and more rapidly from degradation of porous transport layers (e.g., due to the layer's proximity to the acidic membrane). During leaching, ions containing Fe, Al, Cu, or other elements can enter the water if electrodes or other parts of the electrolysis cell are compromised. If Fe ions enter the water, reactions with Fenton's reagent can occur. Fe ions in solution can cause oxidation of organic compounds such as those present in the membrane, thereby causing membrane dissociation and resulting in membrane thinning.

[0032] As a result of such metal ion deposition or reaction in the membrane, the membrane may deteriorate and thin over time. Ultimately, damage to the membrane caused by the reaction of Fenton's reagent or other metal ions may result in a soft short (e.g., a partial or minor short) or a hard short (a complete short) between the anode and cathode in the cell, reducing the cell's performance or rendering the cell unable to perform electrolysis / water splitting reactions. Additionally or alternatively, metal ions in the water may bind to electrons generated during electrolysis, thereby reducing the electrons available for electrolysis and reducing the cell's performance. Because the electrolysis process does not remove or dilute the metal ions, the adverse effects on electrolysis performance may also increase over time.

[0033] Therefore, there is a need for a method for cleaning or removing metal ions from membranes of electrochemical or electrolytic cells.

[0034] 4 shows an example of a flow chart of a method for in-situ membrane metal ion cleaning of an electrochemical cell (such as a water electrolyzer cell) or stack of cells. The method advantageously increases the performance and useful life of the cell or stack. In some examples, one or more of the operations in FIG. 4 may be skipped or omitted. For example, operations 102 and / or 104 may be omitted. In other examples, additional operations may be included in the process of cleaning the cell / stack in-situ.

[0035] In operation 102, operating voltage data may be measured or received over a period of time for individual cells, one or more groups of less than all of the cells in the electrochemical stack, or all of the cells in the electrochemical stack. For example, a first voltage measurement for a particular cell, group of cells, or stack may be recorded at a first time and a second voltage measurement for the same cell, group of cells, or stack may be recorded at a second time.

[0036] In a particular example, an electrolysis system (such as that shown in FIG. 3) includes one or more sensors or voltage monitors configured to acquire or monitor the operating voltage(s) of one or more cells or groups of cells in the stack over a particular time period. The monitored voltage(s) may be transferred to a memory or database within the electrolysis system or external to the electrolysis system for further processing. In particular, the voltage measurements over a period of time may be processed by a processor or controller within the electrolysis system or external to the electrolysis system.

[0037] In some examples, in act 102, the processor or controller may calculate, measure, or identify the change in voltage over time (dV / dt) in a cell, group of cells, or all of the cells in the electrochemical stack based on the difference between the two recorded measurements divided by the difference between the first time and the second time. The period between voltage measurements for the dV / dt calculation may be predefined for a particular period of time, e.g., 1 minute, 5 minutes, 10 minutes, 15 minutes, 30 minutes, 1 hour, 2 hours, etc., or an operator of the electrochemical system may view the collected voltage data and select a particular period for analysis (e.g., input via an input device of the electrochemical system).

[0038] In certain examples, this may include calculating an average dV / dt obtained from multiple voltage monitors in a cell or stack of cells, and in some examples, this dV / dt calculation may be weighted in favor of a particular voltage monitor over other voltage monitors in the cell stack, for example, based on the measurement location of the particular sensor or monitor in the stack.

[0039] In operation 104, the determined change in voltage within a particular cell, group / cells, or entire cell stack may be compared to a threshold dV / dt value. For example, the threshold may be determined or predefined from the specifications, design, or expected performance of the electrolysis cell or stack over a period of time. For example, a change in voltage over a period of time equal to or greater than a predetermined threshold may indicate a problem with the operation of the electrolysis cell, cell, or stack. This operational problem may indicate that metal ion accumulation in the membrane is beginning or worsening, reducing the efficiency of electrolysis in the identified cell, cell, or stack. Thus, when the calculated dV / dt reaches or exceeds such a predetermined threshold, an intervention may be triggered. This intervention may include providing instructions to an operator to perform (e.g., in-situ) cleaning of the membrane of metal ions that have accumulated in the membrane within the operating window of the cell. Alternatively, the intervention may include providing a signal or instruction to the electrochemical system to automatically clean the membrane at a specific time to remove the metal ion buildup.

[0040] In other words, the timing of the cleaning process may be determined based on deviations from a specified or predetermined change in the voltage of the cell or stack over time. During the useful life of an electrolysis cell, the efficiency of the electrolysis process decreases over time, resulting in a higher minimum voltage required for the electrolysis reaction to occur. Below this minimum voltage, electrolysis does not occur. Beyond the regular or expected deterioration of the membrane's performance over time, and the associated increase in the minimum voltage over time to account for this expected membrane performance deterioration, the accumulation of metal ions may cause the efficiency of electrolysis to decrease more quickly and more significantly. For example, in a brand new cell, voltage V1 is the minimum voltage at which electrolysis occurs. As electrolysis is performed using the cell, a voltage V2 greater than V1 may be the minimum voltage at which electrolysis occurs. As a result, a cell with accumulated metal ions in the membrane may experience a greater change (i.e., increase) in the required operating voltage over time than specified or expected.

[0041] In act 106, a cleaning agent or composition is added to the water stream to remove buildup of metal ions in the membrane (e.g., within the pores of the membrane) to advantageously extend the membrane's life and improve performance. In certain examples, the cleaning composition is added to the inlet water stream or source that is fed to the cell or stack for the water splitting reaction. For example, the cleaning composition may be added to the water fed to the anode inlet of a stack of cells, as shown in FIG. 3.

[0042] In certain examples, the cleaning composition is a composition configured to react with metal ions to form acidic metal compounds or salts in the water stream that is washed from the membrane and subsequently removed from the electrolysis system. The cleaning composition may be an acidic composition or solution.

[0043] In certain examples, an acidic composition or solution is provided or prepared at a specific pH to clean the membrane of metal ions during electrolysis. Since the membrane can be cleaned during operation, cleaning can advantageously be performed in situ without disassembling the cell. In certain examples, the in situ cleaning process may be performed during standard operation of the electrochemical cell or stack, with the acidic composition being injected or added to the water inlet with the remaining operating variables remaining the same. Alternatively, the in situ cleaning process may be performed during shutdown or start-up of the cell or stack, with the product stream containing the generated acidic metal or salt compounds being diverted from the typical downstream separation process.

[0044] In one example, the acidic composition can include an acid such as selenic acid, sulfuric acid, hydroiodic acid, hydrobromic acid, hydrochloric acid, nitric acid, orthophosphoric acid, arsenic acid, selenic acid, chromic acid, citric acid, hydrofluoric acid, nitrous acid, isocyanic acid, formic acid, hydrogen selenide, molybdic acid, lactic acid, acetic acid, carbonic acid, hydrogen sulfide, arsenous acid, hydrocyanic acid, boric acid, silicic acid, or combinations thereof. In one particular example, the acidic composition includes citric acid.

[0045] In particular examples, the pH of the acidic composition is in the range of 1 to 7, in the range of 2 to 6, or in the range of 3 to 5. The pH and particular composition of the acidic composition can be selected based on its ability to react with and / or remove metal ions from the membrane without affecting other properties of the electrochemical system. Specifically, certain acidic compositions at certain pH levels can disadvantageously leach other metals into aqueous solution, potentially damaging sensitive elements of the cell, stack, or overall system.

[0046] In act 108, the added cleaning composition reacts with the metal ions at the membrane to form an acid-metal compound that is subsequently removed from the membrane. In the particular example where the cleaning composition added to the feedwater is citric acid, the metal organic compound or complex formed may include ferric citrate or another combination of citric acid and metal ions.

[0047] By adding a cleaning composition (e.g., an acid composition) to the cell or cell stack, the metal ions trapped in the membrane are advantageously released from the pores of the cell membrane. In certain instances, the acid-metal compounds migrate out of the membrane on the anode side of the cell along with the oxygen and water by-products produced. Separation of the acid-metal compounds from the oxygen and water can occur downstream in one or more separation units. Removal of these trapped ions can significantly increase cell / stack life by reducing the dV / dt required to operate the cell / stack and prevent the combined effect of metal ions leaching into and damaging the membrane.

[0048] In some examples, the process may be repeated immediately or for a predetermined period of time, and further operational voltage readings are collected from the cell / stack to determine whether the operational problem has been mitigated (e.g., whether the operational dV / dt has been reduced below a threshold to the expected operational value for the cell / stack). In some cases, to the extent the operational problem still exists, further cleaning sequences may be initiated. This process may continue until the measured voltages and calculated dV / dt are at acceptable levels.

[0049] 5 illustrates an exemplary system 120 for controlling the operation of an electrochemical cell or stack (including, for example, monitoring or controlling the operating voltage of a cell, multiple cells in a stack, or the entire stack). System 120 includes an electrochemical cell / stack 10 (as shown in FIG. 3), a monitoring system 121, a workstation 128, and a network 127. Additional, different, or fewer components may be provided.

[0050] In this system 120, one or more voltage sensors or monitors associated with the electrochemical cell / stack 10 can monitor the operating voltage of the cell / stack 10 and transmit the operating voltage information to a monitoring system 121 via a connected network.

[0051] The monitoring system 121 includes a server 125 and a database 123. The monitoring system 121 may include a computer system and network of a system operator (e.g., an operator of the electrochemical cell / stack 10). The server database 123 may be configured to store information regarding operating conditions or set points for optimizing the performance of the electrochemical cell / stack 10.

[0052] The monitoring system 121, the workstation 128, and the electrochemical cell / stack 10 are coupled to a network 127. The phrase "coupled to" is defined to mean directly connected to one or more intermediate components or indirectly connected through one or more intermediate components. Such intermediate components may include hardware and / or software based components.

[0053] Optional workstation 128 may be a general-purpose computer that includes specialized programming for providing input to server 125. For example, workstation 128 may provide settings to server 125. Workstation 128 may include at least a memory, a processor, and a communication interface.

[0054] Figure 6 illustrates an exemplary server 125 of the system of Figure 5. The server 125 includes a memory 301, a controller or processor 302, and a communication interface 305. The server 125 may be coupled to a database 123 and a workstation 128. The workstation 128 may be used as an input device for the server 125. The communication interface 305 receives data indicative of usage inputs made via the workstation 128 or a separate electronic device.

[0055] The controller or processor 302 may include a general purpose processor, a digital signal processor, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), analog circuitry, digital circuitry, a combination thereof, or other now known or later developed processor. The controller or processor 302 may be a single device or a combination of devices, such as those associated with a network, distributed processing, or cloud computing.

[0056] The controller or processor 302 may also be configured to cause the electrochemical cell or stack to perform one or more of the method acts described herein. For example, the controller or processor 302 may be configured to receive measured operating voltages from one or more voltage sensors / monitors of the electrochemical cell / stack over a period of time. The processor or controller may then calculate or determine from the received operating voltages the change in voltage over time (dV / dt) in the cell, group of cells, or all of the cells in the electrochemical stack. As mentioned above, the period between voltage measurements for dV / dt calculations may be predefined for a particular period of time, e.g., 1 minute, 5 minutes, 10 minutes, 15 minutes, 30 minutes, 1 hour, 2 hours, etc., or an operator of the electrochemical system may view the collected voltage data and select a particular period for analysis by the controller or processor (e.g., input via an input device of the electrochemical system). In this particular case, the controller or processor may further receive input information from the operator at a particular time window to calculate the dV / dt value(s) of a particular cell, group of cells, or the entire stack.

[0057] The controller or processor 302 may be further configured to compare the calculated dV / dt to a predetermined threshold dV / dt value. As described above, the threshold may be determined or predefined from the specifications, design, or expected performance of the electrolysis cell or stack over a period of time. Based on this comparison, the controller or processor 302 may be configured to identify a potential operational problem of the cell / stack when the calculated dV / dt is equal to or greater than the predetermined threshold.

[0058] In such cases, following identification of an operational problem, the controller / processor may provide an operator with a warning signal or message of the potential problem. In some cases, the controller / processor will then take action and await further input from the operator as to whether to address the dV / dt problem. Alternatively, the controller / processor may automatically trigger an intervention, and the system may be instructed to perform a cleaning of the cell / stack membrane(s) to remove any buildup of metal ions in the membrane(s) for a specified period of time.

[0059] The controller / processor can automatically (or via instructions from an operator) provide instructions to inject a cleaning agent / composition into the water vapor to assist in removing metal ion buildup in the membrane. As noted above, this injection instruction can occur in situ, for example, while the electrochemical cell / stack continues to operate, or during start-up or shutdown of the cell / stack system.

[0060] In some examples, the controller / processor can provide instructions to inject a particular volume of cleaning composition based on the identified dV / dt problem. The amount of cleaning composition can be based on the height at which dV / dt exceeds a threshold, or can be a predetermined volume regardless of the calculated dV / dt value.

[0061] In certain examples, the controller / processor may continue to receive and analyze additional voltage readings from the cell / stack to determine whether the operational problem has been mitigated (e.g., whether the operational dV / dt has dropped below a threshold to the expected operational value for the cell / stack). As long as the operational problem remains, further cleaning sequences may be initiated. This process may continue until the measured voltages and calculated dV / dt are at acceptable levels.

[0062] The memory 301 may be a volatile or non-volatile memory. The memory 301 may include one or more of a read only memory (ROM), a random access memory (RAM), a flash memory, an electronically erasable programmable read only memory (EEPROM), or other types of memory. The memory 301 may be removable from the device 122, such as a secure digital (SD) memory card.

[0063] The communication interface 305 may include any operable connection. An operable connection may be one through which signals, physical communications, and / or logical communications may be transmitted and / or received. An operable connection may include a physical interface, an electrical interface, and / or a data interface. The communication interface 305 provides for wireless and / or wired communications in any now known or later developed format.

[0064] In the above examples, network 127 may include a wired network, a wireless network, or a combination thereof. The wireless network may be a cellular network, an 802.11, 802.16, 802.20, or a WiMax network. Additionally, network 127 may be a public network, such as the Internet, a private network, such as an intranet, or a combination thereof, and may utilize a variety of currently available or later developed networking protocols, including, but not limited to, TCP / IP-based networking protocols.

[0065] Although the non-transitory computer-readable medium is described as being a single medium, the term "computer-readable medium" includes a single medium or multiple media, such as a centralized or distributed database and / or associated caches and servers that store one or more sets of instructions. The term "computer-readable medium" is also intended to include any medium capable of storing, encoding, or carrying a set of instructions for execution by a processor or causing a computer system to perform any one or more of the methods or operations disclosed herein.

[0066] In a specific, non-limiting example, the computer-readable medium can include solid-state memory, such as a memory card or other package that houses one or more non-volatile read-only memories. Additionally, the computer-readable medium can be a random access memory or other volatile re-writable memory. Additionally, the computer-readable medium can include magneto-optical or optical media, such as a disk or tape or other storage device for capturing a carrier wave signal, such as a signal communicated over a transmission medium. A digital file attachment to an email or other self-contained information archive or set of archives can be considered a distribution medium that is a tangible storage medium. Thus, the present disclosure is considered to include any one or more of computer-readable or distribution media and other equivalents and successor media on which data or instructions may be stored.

[0067] In alternative examples, dedicated hardware implementations such as application specific integrated circuits, programmable logic arrays, and other hardware devices may be constructed to implement one or more of the methods described herein. Applications that may include the various example devices and systems may broadly include various electronic and computer systems. One or more examples described herein may implement functions using two or more specific interconnected hardware modules or devices, with associated control and data signals that may be communicated between and through the modules, or as part of an application specific integrated circuit. Thus, the present system encompasses software, firmware, and hardware implementations.

[0068] According to various embodiments of the present disclosure, the methods described herein may be implemented by a software program executable by a computer system. Furthermore, in exemplary and non-limiting embodiments, the implementation may include distributed processing, component / object distributed processing, and parallel processing. Alternatively, a virtual computer system processing may be constructed to perform one or more of the methods or functions described herein.

[0069] Although this specification describes components and functions that may be implemented in certain embodiments with reference to certain standards and protocols, the claims are not limited to such standards and protocols. For example, standards for Internet and other packet-switched network transmissions (e.g., TCP / IP, UDP / IP, HTML, HTTP, HTTPS) represent examples of the state of the art, and such standards are periodically superseded by faster or more efficient equivalents having similar functions. Thus, replacement standards and protocols having the same or similar functions as those disclosed herein are considered equivalents thereof.

[0070] A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored as part of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple cooperating files (e.g., files that store one or more modules, subprograms, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers located at one site or distributed across multiple sites and interconnected by a communication network.

[0071] The processes and logic flows described herein may be performed by one or more programmable processors executing one or more computer programs that perform functions by operating on input data and generating output. The processes and logic flows may also be performed by, and an apparatus may be implemented as, special purpose logic circuitry, such as an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit).

[0072] As used in this application, the term "circuitry" or "circuit" refers to any circuit, such as (a) a hardware-only circuit implementation (such as an implementation with only analog and / or digital circuitry); (b) a combination of circuitry and software (and / or firmware), such as (where applicable), a combination of (i) a processor(s), or (ii) a processor(s) / software (including digital signal processor(s)), software, and portions of memory(s) that work together to cause a device such as a mobile phone or a server to perform various functions; or (c) a microprocessor(s) or portions of a microprocessor(s) that require software or firmware for operation, even when the software or firmware is not physically present.

[0073] This definition of "circuitry" applies to all uses of the term in this application, including any claims. As a further example, the term "circuitry" as used in this application also covers merely a processor (or processors) or part of a processor and its (or their) accompanying software and / or firmware implementations. The term "circuitry" also encompasses, for example, a baseband integrated circuit or an application processor integrated circuit for a mobile phone, or similar integrated circuits in a server, cellular network device, or other network device, as applicable to certain claim elements.

[0074] Processors suitable for executing computer programs include, by way of example, both general-purpose and special-purpose microprocessors, as well as any one or more processors of any kind of digital computer. Generally, a processor receives instructions and data from a read-only memory or a random-access memory or both. The essential elements of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data. Generally, a computer also includes one or more mass storage devices, e.g., magnetic disks, magneto-optical disks, or optical disks, for storing data, or is operatively coupled to receive data from or transfer data to them, or both. However, a computer need not have such devices. Furthermore, a computer can be incorporated into another device, e.g., a mobile phone, a personal digital assistant (PDA), a portable audio player, a global positioning system (GPS) receiver, to name just a few. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, including, by way of example, semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices, magnetic disks, e.g., internal hard disks or removable disks, magneto-optical disks, and CD-ROM and DVD-ROM disks. The processor and memory may be supplemented by, or incorporated in, special purpose logic circuitry.

[0075] To provide for user interaction, embodiments of the subject matter described herein may be implemented on a device having a display, e.g., a CRT (cathode ray tube), LCD (liquid crystal display), or LED (light emitting diode) monitor, for displaying information to the user, and a keyboard and pointing device, e.g., a mouse or trackball, by which the user can provide input to the computer. Other types of devices may also be used to provide for user interaction, e.g., feedback provided to the user may be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback, and input from the user may be received in any form, including acoustic, speech, or tactile input.

[0076] An embodiment of the subject matter described herein can be implemented in a computing system that includes a back-end component, e.g., as a data server, or includes a middleware component, e.g., an application server, or includes a front-end component, e.g., a client computer having a graphical user interface or web browser through which a user can interact with an implementation of the subject matter described herein, or includes any combination of one or more such back-end, middleware, or front-end components. The components of the system can be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include local area networks (LANs) and wide area networks (WANs), e.g., the Internet.

[0077] A computing system may include clients and servers. Clients and servers may be remote from each other or interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other.

[0078] One or more embodiments of the present disclosure may be referred to herein, individually and / or collectively, by the term "invention" merely for convenience, without any intention to spontaneously limit the scope of the present application to any particular invention or inventive concept. Furthermore, although specific embodiments have been illustrated and described herein, it should be understood that any subsequent configurations designed to achieve the same or similar purpose may be substituted for the specific embodiments shown. The present disclosure is intended to encompass any and all subsequent adaptations or variations of the various embodiments. Combinations of the above embodiments, as well as other embodiments not specifically described herein, will be apparent to those of skill in the art upon review of this specification.

[0079] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0080] As used herein, "for example," "for instance," "such as," or "including" is meant to introduce examples that further clarify a more general subject matter. Unless otherwise expressly stated, such examples are provided only as an aid to understanding the embodiments set forth in the present disclosure and are not meant to be limiting in any way. These phrases do not imply any kind of preference for the disclosed embodiments.

[0081] The Abstract of the Disclosure is provided to comply with 37 CFR 1.72(b) and is submitted with the understanding that it will not be used to interpret or limit the meaning of the claims. In addition, in the foregoing Detailed Description, various features may be grouped together or described in a single embodiment for the purpose of streamlining the disclosure. This disclosure should not be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, the inventive subject matter may be directed to less than all of the features of any of the disclosed embodiments. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as defining separately claimed subject matter.

[0082] It is intended that the foregoing detailed description be regarded as illustrative rather than limiting, and it is understood that the following claims, including all equivalents, are intended to define the scope of the present disclosure. The claims should not be construed as limited to the described order or elements unless stated to that effect. Accordingly, all embodiments that come within the scope and spirit of the appended claims and equivalents thereto are claimed as the present disclosure.

Claims

1. 1. A method for washing metal ions from a membrane of an electrochemical cell, comprising the steps of: adding a cleaning composition to a water source that supplies the electrochemical cell; reacting the cleaning composition with the metal ions at the membrane of the electrochemical cell; transferring products of the reaction of the cleaning composition with the metal ions from the membrane and the electrochemical cell to remove at least a portion of the metal ions from the membrane of the electrochemical cell.

2. The method of claim 1, wherein the cleaning composition is an acidic composition that reacts with the metal ions to form an acid-metal compound.

3. The method of claim 2 , wherein the acidic composition comprises citric acid.

4. The method of claim 2, wherein the acidic composition has a pH in the range of 3 to 5.

5. further comprising measuring a first operating voltage of the electrochemical cell at a first time with a voltage sensor; measuring a second operating voltage of the electrochemical cell at a second time with the voltage sensor; calculating, by a processor, a change in operating voltage of the electrochemical cell over a defined period of time by dividing the difference between the first operating voltage and the second operating voltage by the difference between the first time and the second time; comparing, by the processor, the change in operating voltage to a threshold; 2. The method of claim 1, further comprising: if the change in the operating voltage is equal to or greater than the threshold, providing a notification or alert and / or automatically triggering the addition of the cleaning composition to the water source, by the processor.

6. 6. The method of claim 5, further comprising the step of receiving, by the processor, an input from an operator to add the cleaning composition to the water source at a defined time.

7. Following said adding, reacting, and transferring, repeating the measuring of the first operating voltage, the measuring of the second operating voltage, the calculating of the change in the operating voltage, and the comparing of the change in the operating voltage to determine whether the cleaning composition reduces the change in the operating voltage below the threshold; 6. The method of claim 5, further comprising the step of repeating the adding, reacting, and transferring steps again if the change in the operating voltage remains above the threshold.

8. The method of any one of claims 1 to 7, wherein the addition of the cleaning composition is performed in situ during operation of the electrochemical cell, during a start-up procedure of the electrochemical cell, or during a shut-down procedure of the electrochemical cell.

9. The method of any one of claims 1 to 7, wherein the electrochemical cell comprises a plurality of electrochemical cells in an electrochemical stack.

10. 1. A method for monitoring the operational performance of a membrane of an electrochemical cell, comprising: measuring a first operating voltage of the electrochemical cell at a first time with a voltage sensor; measuring a second operating voltage of the electrochemical cell at a second time with the voltage sensor; calculating, by a processor, a change in operating voltage of the electrochemical cell over a defined period of time by dividing the difference between the first operating voltage and the second operating voltage by the difference between the first time and the second time; comparing, by the processor, the change in operating voltage to a threshold; and providing, by the processor, a notification or alarm when the change in the operating voltage is equal to or greater than the threshold.

11. adding a cleaning composition to a water source that supplies the electrochemical cell; reacting the cleaning composition with metal ions at a membrane of the electrochemical cell; 11. The method of claim 10, further comprising: transferring products of the reaction of the cleaning composition with the metal ions from the membrane and the electrochemical cell to remove at least a portion of the metal ions from the membrane of the electrochemical cell.

12. The method of claim 11 , wherein the cleaning composition is added automatically following notification that the change in operating voltage is equal to or greater than the threshold value.

13. 12. The method of claim 11, wherein the cleaning composition is added after the processor receives an operator command input to clean the membrane of the electrochemical cell.

14. The method of claim 11, wherein the cleaning composition is an acidic composition that reacts with the metal ions to form an acid-metal compound.

15. The method of claim 14 , wherein the acidic composition comprises citric acid.

16. The method of claim 14, wherein the acidic composition has a pH in the range of 3 to 5.

17. Following said adding, reacting, and transferring, repeating the measuring of the first operating voltage, the measuring of the second operating voltage, the calculating of the change in the operating voltage, and the comparing of the change in the operating voltage to determine whether the cleaning composition reduces the change in the operating voltage below the threshold; 12. The method of claim 11, further comprising a repeating step of repeating the adding, reacting, and transferring steps again if the change in the operating voltage remains above the threshold.

18. The method of any one of claims 11 to 17, wherein the addition of the cleaning composition is performed in situ during operation of the electrochemical cell, during a start-up procedure of the electrochemical cell, or during a shut-down procedure of the electrochemical cell.

19. The method of any one of claims 10 to 17, wherein the electrochemical cell comprises a plurality of electrochemical cells in an electrochemical stack.

20. 1. An electrochemical system comprising: at least one electrochemical cell; at least one voltage sensor configured to measure a first operating voltage of each of the at least one electrochemical cell at a first time and to measure a second operating voltage of each of the electrochemical cells at a second time; a processor; The processor, receiving the measured first operating voltage at the first time and the second operating voltage at the second time from the at least one voltage sensor; calculating a change in operating voltage of each electrochemical cell over a defined period of time by dividing the difference between the first operating voltage and the second operating voltage by the difference between the first time and the second time; comparing the change in the operating voltage to a threshold; The electrochemical system is configured to provide a notification or alarm if the change in the operating voltage is equal to or greater than the threshold value.

21. The processor further comprises:

21. The electrochemical system of claim 20 configured to provide instructions to add a cleaning composition to a water source supplied to the at least one electrochemical cell to remove metal ions in a membrane of the at least one electrochemical cell.

22. 22. The electrochemical system of claim 21, wherein the cleaning composition is added automatically following the notification that the change in the operating voltage is equal to or greater than the threshold value.

23. The processor further comprises: receiving an input by an operator to add a cleaning composition to clean the at least one electrochemical cell; 21. The electrochemical system of claim 20 configured to provide instructions to add the cleaning composition to a water source supplied to the at least one electrochemical cell to remove metal ions in a membrane of the at least one electrochemical cell.

24. The electrochemical system of any one of claims 21 to 23, wherein the cleaning composition is an acidic composition that reacts with the metal ions to form an acid-metal compound.

25. 25. The electrochemical system of claim 24, wherein the acidic composition comprises citric acid.

26. The electrochemical system of claim 24, wherein the acidic composition has a pH in the range of 3-5.

27. Following addition of the cleaning composition, the processor further comprises: repeating the steps of measuring the first operating voltage, measuring the second operating voltage, calculating the change in the operating voltage, and comparing the change in the operating voltage to determine whether the cleaning composition reduces the change in the operating voltage below the threshold; 24. The electrochemical system of any one of claims 21 to 23, configured to provide additional instructions to add additional cleaning composition if the change in the operating voltage remains above or equal to the threshold value.

28. 24. The electrochemical system of any one of claims 21 to 23, wherein the addition of the cleaning composition is performed in situ during operation of the at least one electrochemical cell, during a start-up procedure of the at least one electrochemical cell, or during a shut-down procedure of the at least one electrochemical cell.

29. The electrochemical system of any one of claims 21 to 23, wherein the at least one electrochemical cell comprises a plurality of electrochemical cells in an electrochemical stack.

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