WO2023163989A1

WO2023163989A1 - Energy recovery from electrolysis compression for use in water circulation

Info

Publication number: WO2023163989A1
Application number: PCT/US2023/013615
Authority: WO
Inventors: Curt C. EBNER; James Daniel Smith
Original assignee: Electric Hydrogen Co
Current assignee: Electric Hydrogen Co
Priority date: 2022-02-22
Filing date: 2023-02-22
Publication date: 2023-08-31
Anticipated expiration: 2024-08-22
Also published as: US20250116006A1

Abstract

The following disclosure relates to electrolysis systems having an electrolysis cell stack and a fluids processing system (e.g., an oxygen and water gas separator). In certain examples, a portion of the fluids processing system is configured to operate at a reduced (lower) pressure than the electrolysis cell stack within the electrochemical processing system through the use of a recovery turbine positioned between the electrolysis cell stack and the oxygen and water gas separator along a fluids transfer line, wherein the recovery turbine is configured to reduce a pressure within the fluids transfer line from an elevated pressure at the electrolysis cell stack to the lower pressure at the separator.

Description

ENERGY RECOVERY FROM ELECTROLYSIS COMPRESSION FOR USE IN WATER CIRCULATION

[0001] The present patent document claims the benefit of United States Provisional Patent Application No. 63/312,660, filed February 22, 2022, which is hereby incorporated by reference in its entirety.

FIELD

[0002] The following disclosure relates to an electrolysis processing system having an electrolysis cell stack and a fluids processing system. Specifically, the disclosure relates to a fluids processing system (e.g., an oxygen and water gas separator) configured to operate at a reduced (lower) pressure than the electrolysis cell stack within the electrochemical processing system.

BACKGROUND

[0003] An electrochemical or electrolysis cell or system uses electrical energy to drive a chemical reaction. For example, the electrolysis cell conducts a water splitting electrolysis reaction, wherein water is split to form hydrogen and oxygen. The products may be used as energy sources for later use. In recent years, improvements in operational efficiency have made electrolyzer systems competitive market solutions for energy storage, generation, and/or transport. For example, the cost of generation may be below $10 per kilogram of hydrogen in some cases. Increases in efficiency and/or improvements in operation will continue to drive installation of electrolyzer systems.

SUMMARY

[0004] In one embodiment, electrochemical system includes an electrochemical stack having a plurality of electrochemical cells, wherein the electrochemical stack is configured to receive water and generate gas through a water splitting reaction within the electrochemical stack. The system further includes a gas-liquid separator configured to receive unreacted water and the generated gas from the electrochemical stack and separate at least a portion of the generated gas from the unreacted water. The system further includes a recovery turbine positioned between the electrochemical stack and the gas-liquid separator. The system further includes a first fluids transfer line connecting the electrochemical stack and the recovery turbine. The system further includes a second fluids transfer line connecting the recovery turbine and the gas-liquid separator. The electrochemical stack and first fluids transfer line are configured to operate at an elevated pressure greater than atmospheric pressure. The gas-liquid separator and second fluids transfer line are configured to operate at a lower pressure than the electrochemical stack. The recovery turbine is configured to reduce the elevated pressure within the first fluids transfer line to the lower pressure within the second fluids transfer line.

[0005] In a second embodiment, a fluids processing system in communication with an electrochemical stack of an electrochemical system is provided. The fluids processing system includes a recovery turbine configured to receive unreacted water and a generated gas from the electrochemical stack. The fluids processing system further includes a gasliquid separator configured to separate at least a portion of the generated gas from the unreacted water. The fluids processing system further includes a fluids transfer line connecting the recovery turbine and the gas-liquid separator. The gas-liquid separator and fluids transfer line are configured to operate at a lower pressure than an elevated pressure of the electrochemical stack. Additionally, the recovery turbine is configured to reduce the elevated pressure of the electrochemical stack to the lower pressure within the fluids transfer line and gas-liquid separator.

[0006] 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.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Exemplary embodiments are described herein with reference to the following drawings.

[0008] Figure 1 depicts an example of an electrolytic cell.

[0009] Figure 2 depicts an additional example of an electrolytic cell.

[0010] Figure 3 depicts an example of an electrolysis system having an electrolysis cell stack and a fluids processing system (e.g., oxygen gas and water separator) operating at a same high pressure. [0011] Figure 4 depicts an alternative example of an electrolysis system having an electrolysis cell stack operating at a high pressure and a portion of a fluids processing system (e.g., an oxygen gas and water separator) operating at low pressure.

[0012] Figure 5 depicts an example communication system between an electrolytic stack and a computing device having a controller over a connected network.

[0013] Figure 6 depicts an example of a computing device having a controller.

[0014] While the disclosed compositions and methods are representative of embodiments in various forms, specific embodiments are illustrated in the drawings (and are hereafter described), with the understanding that the disclosure is intended to be illustrative and is not intended to limit the claim scope to the specific embodiments described and illustrated herein.

DETAILED DESCRIPTION

[0015] Figure 1 depicts an example of an electrolytic cell for the production of hydrogen gas and oxygen gas through the splitting of water. The electrolytic cell includes a cathode, an anode, and a membrane positioned between the cathode and anode. The membrane may be a proton exchange membrane (PEM). Proton Exchange Membrane (PEM) electrolysis involves the use of a solid electrolyte or ion exchange membrane. Within the water splitting electrolysis reaction, one interface runs an oxygen evolution reaction (OER) while the other interface runs a hydrogen evolution reaction (HER). For example, the anode reaction is H2O->2H⁺+¹/₂O2+2e and the cathode reaction is 2H⁺+2e->H2. The water electrolysis reaction has recently assumed great importance and renewed attention as a potential foundation for a decarbonized "hydrogen economy." Other types of electrolyzers may be used as well.

[0016] Since the performance of a single electrolytic cell may not be adequate for many use cases, multiple cells may be placed together to form a "stack" of cells, which may be referred to as an electrolyzer stack, electrolytic stack, electrochemical stack, or simply just a stack. In one example, a stack may contain 50-1000 cells, 50-100 cells, 500-700 cells, or more than 1000 cells. Any number of cells may make up a stack.

[0017] Figure 2 depicts an additional example of an electrochemical or electrolytic cell. Specifically, Figure 2 depicts a portion of an electrochemical cell 200 having a cathode flow field 202, an anode flow field 204, and a membrane 206 positioned between the cathode flow field 202 and the anode flow field 204.

[0018] In certain examples, the membrane 206 may be a catalyst coated membrane (CCM) having a cathode catalyst layer 205 and/or an anode catalyst layer 207 positioned on respective surfaces of the membrane 206. As used throughout this disclosure, the term "membrane" may refer to a catalyst coated membrane (CCM) having such catalyst layers. [0019] In certain examples, additional layers may be present within the electrochemical cell 200. For example, one or more additional layers 208 may be positioned between the cathode flow field 202 and membrane 206. In certain examples, this may include a gas diffusion layer (GDL) 208 may be positioned between the cathode flow field 202 and membrane 206. This may be advantageous in providing a hydrogen diffusion barrier adjacent to the cathode on one side of the multi-layered membrane to mitigate hydrogen crossover to the anode side. In other words, the GDL is responsible for the transport of gaseous hydrogen to the cathode side flow field. For a wet cathode PEM operation, liquid water transport across the GDL is needed for heat removal in addition to heat removal from the anode side.

[0020] 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) positioned between the membrane 206 (e.g., the anode catalyst layer 207 of the catalyst coated membrane 206) and the anode flow field 204.

[0021] Similar to the GDL, the PTL is configured to allow the transportation of the reactant water to the anode catalyst layers, remove produced oxygen gas, and provide good electrical conductivity for effective electron conduction. In other words, liquid water flowing in the anode flow field is configured to permeate through the PTL to reach the CCM. Further, gaseous byproduct oxygen is configured to be removed from the PTL to the flow fields. In such an arrangement, liquid water functions as both reactant and coolant on the anode side of the cell.

[0022] In some examples, an anode catalyst coating layer may be positioned between the anode flow field 204 and the PTL. [0023] The cathode flow field 202 and anode flow field 204 of the cell may individually include a flow field plate composed of metal, carbon, or a composite material having a set of channels machined, stamped, or etched into the plate to allow fluids to flow inward toward the membrane or out of the cell.

[0024] Figure 3 depicts an example of an electrochemical system having an electrochemical stack and a fluids processing system (e.g., oxygen gas and water separator). In this example, the electrochemical stack includes a plurality of electrochemical cells (such as depicted in Figures 1 and 2) stacked on top of each other to form the stack. Additionally, in this example, the electrochemical stack and the fluids processing system are configured to operate at a same (e.g., elevated pressure greater than atmospheric pressure).

[0025] In this electrochemical system, the electrochemical stack is configured to receive energy (electricity) via an energy source to operate the stack. A rectifier may be positioned between the energy source to convert an alternating current (AC) to a direct current (DC) for the energy needed to operate the stack.

[0026] Within the electrochemical stack, water is transferred to the stack via an anodic inlet stream to facilitate the water splitting reaction and generation of oxygen and hydrogen gases. As noted below, the water stream or at least a portion thereof may be provided from a fluid processing system associated with the electrochemical stack.

[0027] The water received via the anodic inlet line/fluid processing system is subsequently provided to each individual electrolytic cell within the cell stack to conduct the water splitting electrolysis reaction as described above and depicted in Figure 1. In some embodiments, a second inlet water source may be provided to the cathode sides of the cells within the stack via a cathodic inlet stream. Again, this water stream or at least a portion thereof may be supplied from a fluid processing system associated with the electrochemical stack. Such a cathode water stream may function as a cooling source for the exothermic water splitting reaction, therein assisting in maintaining a desired operating temperature on the cathode sides of the cells within the stack.

[0028] In the water splitting reaction within the electrochemical cell, oxygen gas and hydrogen gas are generated. Some of the water supplied to the cell stack may not react or split into oxygen and hydrogen gases. [0029] Specifically, on the anodic side of the system, generated oxygen gas and unreacted water are transferred out of the stack via a fluids transfer line that is operating at a similar high/elevated pressure as the electrochemical stack.

[0030] Figure 3 depicts an example in which the fluids transfer line is on the anode side of the stack, such that oxygen gas and water are within the first fluids transfer line. While not depicted in the figure, a similar system may exist for the cathode side of the stack as well, wherein the fluids transfer line includes the generated hydrogen gas and water being circulated through the system on the cathode side of the stack. As such, while discussing the fluids processing system for oxygen gas and water, a similar system may be applicable for the generated hydrogen gas and water on the cathode side of the stack.

[0031] In this example in Figure 3, the fluids transfer line is configured to transfer the generated oxygen gas and unreacted water to a gas-liquid separator that is configured to separate the oxygen gas from the unreacted water.

[0032] Further, a back pressure device may be connected to the gas-liquid separator to control the pressure within the separator. In other words, the back pressure device may be configured to open to release or transfer oxygen gas within the separator when the separator reaches or begins to exceed a predefined or threshold pressure.

[0033] As depicted in Figure 3, unreacted water that has been separated from the oxygen within the gas-liquid separator may be returned or recycled to the cell stack via the water transfer line and water pump. In other words, a water pump may be positioned between the gas-liquid separator and the electrochemical stack to transfer water to the cell stack at a desired or predefined pressure (e.g., at an elevated pressure greater than atmospheric pressure). A first water transfer line may connect the gas-liquid separator and the water pump. A second water transfer line may connect the water pump and the electrochemical stack.

[0034] As noted above, the water supply to the anodic or cathodic inlets of the electrochemical stack may be provided from the fluids processing system connected to the stack. This water supply may come from the second water transfer line extending from the water pump of the fluids processing system. [0035] In this example of Figure 3, the fluids processing system and the electrochemical stack are configured to operate at a same pressure (e.g., an elevated pressure greater than atmospheric) pressure. For example, the operating pressure of the cell stack, gas-liquid separator, transfer lines to and from the cell stack, and the water pump may be configured to operate at a pressure greater than 0 atm, greater than 1 atm, greater than 2 atm, greater than 5 atm, greater than 8 atm, greater than 10 atm, greater than 20 atm, or greater than 30 atm, and less than 40 atm. The operating pressure may be in a range of 1-40 atm, 2-40 atm, 5-40 atm, or 8-40 atm.

[0036] Operating the electrochemical stack and fluids processing system at an elevated pressure may have certain disadvantages. For one, it is more expensive for the fluids processing system to operate at elevated pressures, as the equipment (e.g., water pump and gas-liquid separator) and transfer lines have to be designed for higher pressures. This may equate to higher cost equipment and additional safety measures for higher pressure equipment. Conversely, on the other hand, operation of an electrochemical stack at a lower pressure (e.g., atmospheric pressure) may have certain disadvantages as well, such as added costs, as the water splitting reaction mechanism and separation of water and oxygen gas may become less efficient. Further, the mass transport of reactants/products to and from the cell stack may be less efficient as well.

[0037] In other words, the system depicted in Figure 3 with a high pressure operation within the cell stack and fluids processing system may advantageously provide improved mass transport and reaction mechanisms within the cell stack at the disadvantage of higher operating costs. As such, there remains a need for an improved operating system within the cell stack and fluids processing system that maximizes mass transport/reaction mechanisms while reducing the overall operating cost of the system.

[0038] Figure 4 depicts such an example of an improved electrochemical system having an electrochemical stack and fluids processing system. In this improved system, the electrochemical stack is configured to operate at an elevated pressure (e.g., greater than atmospheric pressure) while a portion of a fluids processing system (e.g., including the gasliquid separator) is configured to operate at a lower pressure less than the operating pressure of the electrochemical stack. [0039] This advantageously provides an improved operating system that maximizes mass transport and reaction mechanisms in the electrochemical stack while taking advantage of lower operating costs due to the lower operating pressure within the gasliquid separator (as well as portions of the transfer lines to and from the gas-liquid separator).

[0040] In this example of Figure 4, similar to the example in Figure 3, the electrochemical stack includes a plurality of electrochemical cells (such as depicted in Figures 1 and 2) stacked on top of each other to form the stack. The electrochemical stack is configured to operate at an elevated or higher pressure (e.g., a pressure greater than atmospheric pressure) than a portion of the fluid processing system (e.g., gas-liquid separator) in communication with the electrochemical stack.

[0041] In this electrochemical system, the electrochemical stack is configured to receive energy (electricity) via an energy source to operate the stack. A rectifier may be positioned between the energy source to convert an alternating current (AC) to a direct current (DC) for the energy needed to operate the stack.

[0042] Within the electrochemical stack, water is transferred to the stack via an anodic inlet stream to facilitate the water splitting reaction and generation of oxygen and hydrogen gases. As noted below, the water stream or at least a portion thereof may be provided from a fluid processing system associated with the electrochemical stack.

[0043] The water received via the anodic inlet line/fluid processing system is subsequently provided to each individual electrolytic cell within the cell stack to conduct the water splitting electrolysis reaction as described above and depicted in Figure 1. In some embodiments, a second inlet water source may be provided to the cathode sides of the cells within the stack via a cathodic inlet stream. Again, this water stream or at least a portion thereof may be supplied from a fluid processing system associated with the electrochemical stack. Such a cathode water stream may function as a cooling source for the exothermic water splitting reaction, therein assisting in maintaining a desired operating temperature on the cathode sides of the cells within the stack. [0044] In the water splitting reaction within the electrochemical cells, oxygen gas and hydrogen gas are generated. Some of the water supplied to the cell stack may not react or split into oxygen and hydrogen gases.

[0045] Specifically, on the anodic side of the system, generated oxygen gas and unreacted water are transferred out of the stack via a first fluids transfer line that is operating at a similar high/elevated pressure as the electrochemical stack.

[0046] As noted in the example in Figure 3, this first fluids transfer line may be on the anode side of the stack, such that oxygen gas and water are within the first fluids transfer line. While not depicted in Figure 4, a similar system may exist for the cathode side of the stack as well, wherein the first fluids transfer line includes the generated hydrogen gas and water being circulated through the system on the cathode side of the stack. As such, while discussing the fluids processing system for oxygen gas and water, a similar system may be applicable for the generated hydrogen gas and water on the cathode side of the stack. [0047] In this example in Figure 4, the first fluids transfer line is configured to transfer the generated oxygen gas and unreacted water to a restrictor or recovery turbine. The recovery turbine is configured to provide back pressure downstream of the cell stack and drop the pressure from the cell stack from a higher operating pressure to a lower operating pressure. While the recovery turbine adds a cost to the system due to the additional piece of equipment in comparison to the system in Figure 3 and potentially wastes energy, the recovery turbine may nonetheless advantageously provide an overall cost savings in the operation of the electrochemical system. For example, due to the drop down in pressure, the gas-liquid separator may operate at a lower pressure than the cell stack. This may provide a cost savings in the design/configuration of the gas-liquid separator itself, which is now only needed to be configured for operation at lower pressures (e.g., atmospheric pressure). This may also provide cost savings in the amount or type of safety equipment required at or near the gas-liquid separator due to its lower operating conditions. In other words, due to lower operating pressures, safety blow off valves or other high pressure safety equipment may not be required in this section of the fluids processing system. [0048] Further, the recovery turbine may also advantageously provide an energy source for operation of the water pump within the system, therein reducing the water pump's power input and energy costs. For example, once the electrochemical system is in operation, energy generated from the step down in pressure at the recovery turbine can be transferred to operate the water pump, wherein little to no additional energy source to the water pump may be needed during operation (e.g., 100% of the energy needed to operate the water pump may be provided from the recovery turbine). In additional examples, the generated energy at the recovery turbine may be large enough to provide an energy source for other components within the electrochemical system in addition to the water pump. For instance, energy generated by the recovery turbine may be directed back to the electrochemical stack to reduce the additional operating energy provided from the rectifier. [0049] In other words, in this example of Figure 4, a portion of the fluids processing system and the electrochemical device are designed to operate at a different pressures, wherein the cell stack operates at a higher/elevated (e.g., greater than atmospheric) pressure and the gas-liquid separator operates at a lower (e.g., atmospheric) pressure. [0050] As depicted in Figure 4, downstream of the recovery turbine, a second fluids transfer line is positioned between the recovery turbine and the gas-liquid separator. This second fluids transfer line is configured to operate at the step-down or lower pressure as a result of the recovery turbine.

[0051] The second fluids transfer line is configured to transfer the generated oxygen (or hydrogen on the cathode side of the system) and unreacted water to the gas-liquid separator. Similar to the example in Figure 3, a back pressure device may be connected to the gas-liquid separator in Figure 4 to control the pressure within the separator. In other words, the back pressure device may be configured to open to release or transfer oxygen gas within the separator when the separator reaches or begins to exceed a predefined or threshold pressure (e.g., when the separator exceeds atmospheric pressure).

[0052] As depicted in Figure 4, unreacted water that has been separated from the oxygen within the gas-liquid separator may be returned or recycled to the cell stack via the water transfer line and water pump. In other words, a water pump may be positioned between the gas-liquid separator and the electrochemical stack to transfer water to the cell stack at a desired or predefined pressure (e.g., at an elevated pressure greater than atmospheric pressure). A first water transfer line may connect the gas-liquid separator and the water pump. A second water transfer line may connect the water pump and the electrochemical stack.

[0053] In this example, the water pump is configured to receive the separated water from the gas-liquid separator at a low pressure (e.g., atmospheric pressure) and step the pressure up to a higher operating pressure within the electrochemical stack. A first water transfer line is configured to supply separated water from the gas-liquid separator to the water pump. Following the step up in pressure via the water pump (in some cases, supplied with energy from the recovery turbine), the water pump is configured to transfer the higher pressurized water to the electrochemical stack via a second water transfer line.

[0054] As noted above, the water supply to the anodic or cathodic inlets of the electrochemical stack may be provided from the fluids processing system connected to the stack. This water supply may come from the second water transfer line extending from the water pump of the fluids processing system.

[0055] In this example of Figure 4, the fluids processing system and the electrochemical stack are configured to operate at a different pressures. For example, the operating pressure of the cell stack and transfer lines to and from the cell stack may be configured to operate at a pressure greater than 1 atm, greater than 2 atm, greater than 5 atm, greater than 8 atm, greater than 10 atm, greater than 20 atm, or greater than 30 atm, and less than 40 atm. The operating pressure of the cell stack may be in a range of 1-40 atm, 2-40 atm, 5- 40 atm, or 8-40 atm, while being greater than the operating pressure of a remaining portion of the fluid processing system. Specifically, the operating pressure of the gas-liquid separator and transfer lines connected to the gas-liquid separator from the recovery turbine and to the water pump may be greater than 0 atm and less than or equal to 10 atm, 8 atm, 5 atm, 2 atm, or 1 atm, or in a range of 0-10 atm, 0-8 atm, 0-5 atm, 0-2 atm, or 0-1 atm while being less than the operating pressure of the electrochemical stack.

[0056] To operate such a fluids processing system, where there is a step up in pressure in the water supply line from a lower pressure at the oxygen gas and water separator to a higher pressure at the cell stack, a high differential pump may be required to pump fluid up to the pressure of the electrochemical device as the water enters the cell stack. The pumping at high differential pressure into the electrochemical device may require a larger amount of energy than a pump operating with no or minimal pressure differential across the pump.

[0057] Similar to the example in Figure 2, unreacted water may exit the cell stack on the anode side of the stack along with the oxygen gas produced. This mixture of water and oxygen gas may be transferred in a fluids transfer/supply line to the oxygen gas and water separator of the fluids processing system. The oxygen gas and water separator is configured to separate the oxygen gas from the unreacted water. A back pressure device may be connected to the oxygen gas and water separator to control the pressure within the separator. In other words, the back pressure device may be configured to open to release or transfer oxygen gas within the separator when the separator reaches or begins to exceed a predefined or threshold pressure.

[0058] Figure 5 illustrates an exemplary system 120 for controlling operation of an electrochemical cell or stack (e.g., including monitoring or controlling the operational conditions of the stack, gas-liquid separator, recovery turbine, and water pump). The system 120 includes the electrochemical cell/stack 10 (such as depicted in Figure 4), a monitoring system 121, a workstation 128, and a network 127. Additional, different, or fewer components may be provided.

[0059] In this system 120, one or more pressure sensors associated with the electrochemical system 10 may monitor the operating conditions (e.g., operating pressures) of the cell/stack, the gas-liquid separator, and transfer lines to/from the recovery turbine and water pump, and transmit the operating conditions to the monitoring system 121 over the connected network.

[0060] The monitoring system 121 includes a server 125 and a database 123. The monitoring system 121 may include computer systems and networks of a system operator (e.g., the operator of the electrochemical cell/stack 10). The server database 123 may be configured to store information regarding the operating conditions or setpoints for optimizing the performance of the electrochemical cell/stack 10.

[0061] The monitoring system 121, the workstation 128, and the electrochemical cell/stack 10 are coupled with the network 127. The phrase "coupled with" is defined to mean directly connected to or indirectly connected through one or more intermediate components. Such intermediate components may include hardware and/or software-based components.

[0062] The optional workstation 128 may be a general-purpose computer including programming specialized for providing input to the server 125. For example, the workstation 128 may provide settings for the server 125. The workstation 128 may include at least a memory, a processor, and a communication interface.

[0063] 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 use inputs made via the workstation 128 or a separate electronic device.

[0064] The controller or processor 302 may include a general processor, digital signal processor, an application specific integrated circuit (ASIC), field programmable gate array (FPGA), analog circuit, digital circuit, combinations thereof, or other now known or later developed processor. The controller or processor 302 may be a single device or combination of devices, such as associated with a network, distributed processing, or cloud computing. [0065] 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 pressures from the one or more pressure sensors of the electrochemical system over a period of time. The processor or controller may then provide instructions to increase or decrease the operating pressure of a specific component within the system. For example, the controller may be configured to instruct a back pressure device attached to the gasliquid separator to release gas from the line due to a build-up in pressure in the separator. The controller could be configured to instruct the recovery turbine to adjust operation to create a larger or smaller step down in pressure due to the monitored pressure conditions within the attached transfer lines or stack and gas-liquid separator.

[0066] The memory 301 may be a volatile memory or a non-volatile memory. The memory 301 may include one or more of a read only memory (ROM), random access memory (RAM), a flash memory, an electronic erasable program read only memory (EEPROM), or other type of memory. The memory 301 may be removable from the device 122, such as a secure digital (SD) memory card.

[0067] The communication interface 305 may include any operable connection. An operable connection may be one in which signals, physical communications, and/or logical communications may be sent 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.

[0068] In the above-described examples, the network 127 may include wired networks, wireless networks, or combinations thereof. The wireless network may be a cellular telephone network, an 802.11, 802.16, 802.20, or WiMax network. Further, the network 127 may be a public network, such as the Internet, a private network, such as an intranet, or combinations thereof, and may utilize a variety of networking protocols now available or later developed including, but not limited to TCP/IP based networking protocols.

[0069] While the non-transitory computer-readable medium is described to be 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" shall also include any medium that is capable of storing, encoding, or carrying a set of instructions for execution by a processor or that cause a computer system to perform any one or more of the methods or operations disclosed herein.

[0070] In a particular non-limiting example, the computer-readable medium can include a solid-state memory such as a memory card or other package that houses one or more non-volatile read-only memories. Further, the computer-readable medium can be a random-access memory or other volatile re-writable memory. Additionally, the computer- readable medium can include a magneto-optical or optical medium, such as a disk or tapes or other storage device to capture carrier wave signals such as a signal communicated over a transmission medium. A digital file attachment to an e-mail or other self-contained information archive or set of archives may be considered a distribution medium that is a tangible storage medium. Accordingly, the disclosure is considered to include any one or more of a computer-readable medium or a distribution medium and other equivalents and successor media, in which data or instructions may be stored.

[0071] In an alternative example, dedicated hardware implementations, such as application specific integrated circuits, programmable logic arrays and other hardware devices, can be constructed to implement one or more of the methods described herein. Applications that may include the apparatus and systems of various examples can broadly include a variety of electronic and computer systems. One or more examples described herein may implement functions using two or more specific interconnected hardware modules or devices with related control and data signals that can be communicated between and through the modules, or as portions of an application-specific integrated circuit. Accordingly, the present system encompasses software, firmware, and hardware implementations.

[0072] In accordance with various embodiments of the present disclosure, the methods described herein may be implemented by software programs executable by a computer system. Further, in an exemplary, non-limited embodiment, implementations can include distributed processing, component/object distributed processing, and parallel processing. Alternatively, virtual computer system processing can be constructed to implement one or more of the methods or functionalities as described herein.

[0073] Although the present specification describes components and functions that may be implemented in particular embodiments with reference to particular standards and protocols, the claim scope is not limited to such standards and protocols. For example, standards for Internet and other packet switched network transmission (e.g., TCP/IP, UDP/IP, HTML, HTTP, HTTPS) represent examples of the state of the art. Such standards are periodically superseded by faster or more efficient equivalents having similar functions. Accordingly, replacement standards and protocols having the same or similar functions as those disclosed herein are considered equivalents thereof.

[0074] 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 it can be deployed in any form, including as a standalone 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 in a portion 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 coordinated files (e.g., files that store one or more modules, sub programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

[0075] The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0076] As used in this application, the term "circuitry" or "circuit" refers to all of the following: (a)hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) to combinations of circuits and software (and/or firmware), such as (as applicable): (i) to a combination of processor(s) or (ii) to portions of processor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) to circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.

[0077] This definition of "circuitry" applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term "circuitry" would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term "circuitry" would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in server, a cellular network device, or other network device. [0078] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and anyone 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 performing instructions and one or more memory devices for storing instructions and data. Generally, a computer also includes, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. However, a computer need not have such devices. Moreover, a computer can be embedded in another device, e.g., a mobile telephone, a personal digital assistant (PDA), a mobile 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., E PROM, 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 the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

[0079] To provide for interaction with a user, embodiments of the subject matter described in this specification can 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 a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input.

[0080] Embodiments of the subject matter described in this specification can be implemented in a computing system that includes a back end component, e.g., as a data server, or that includes a middleware component, e.g., an application server, or that includes a front end component, e.g., a client computer having a graphical user interface or a Web browser through which a user can interact with an implementation of the subject matter described in this specification, or 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 a local area network ("LAN") and a wide area network ("WAN"), e.g., the Internet.

[0081] The computing system can include clients and servers. A client and server may be remote from each other and may 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 with each other.

[0082] One or more embodiments of the disclosure may be referred to herein, individually and/or collectively, by the term "invention" merely for convenience and without intending to voluntarily limit the scope of this application to any particular invention or inventive concept. Moreover, although specific embodiments have been illustrated and described herein, it should be appreciated that any subsequent arrangement designed to achieve the same or similar purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all subsequent adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, are apparent to those of skill in the art upon reviewing the description.

[0083] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0084] As used herein, "for example," "for instance," "such as," or "including" are meant to introduce examples that further clarify more general subject matter. Unless otherwise expressly indicated, such examples are provided only as an aid for understanding embodiments illustrated in the present disclosure and are not meant to be limiting in any fashion. Nor do these phrases indicate any kind of preference for the disclosed embodiment.

[0085] The Abstract of the Disclosure is provided to comply with 37 C.F.R. §1.72(b) and is submitted with the understanding that it will not be used to interpret or limit the scope or 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 is not to 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, inventive subject matter may be directed to less than all of the features of any of the disclosed embodiments. Thus, the following claims are incorporated into the Detailed Description, with each claim standing on its own as defining separately claimed subject matter.

[0086] It is intended that the foregoing detailed description be regarded as illustrative rather than limiting and that it is understood that the following claims including all equivalents are intended to define the scope of the disclosure. The claims should not be read as limited to the described order or elements unless stated to that effect. Therefore, all embodiments that come within the scope and spirit of the following claims and equivalents thereto are claimed as the disclosure.

Claims

1. An electrochemical system comprising: an electrochemical stack comprising a plurality of electrochemical cells, the electrochemical stack configured to receive water and generate gas through a water splitting reaction within the electrochemical stack; a gas-liquid separator configured to receive unreacted water and the generated gas from the electrochemical stack and separate at least a portion of the generated gas from the unreacted water; a recovery turbine positioned between the electrochemical stack and the gas-liquid separator; a first fluids transfer line connecting the electrochemical stack and the recovery turbine; and a second fluids transfer line connecting the recovery turbine and the gas-liquid separator; wherein the electrochemical stack and first fluids transfer line are configured to operate at an elevated pressure greater than atmospheric pressure, wherein the gas-liquid separator and second fluids transfer line are configured to operate at a lower pressure than the electrochemical stack, and wherein the recovery turbine is configured to reduce the elevated pressure within the first fluids transfer line to the lower pressure within the second fluids transfer line.

2. The electrochemical system of claim 1, wherein the generated gas is oxygen gas.

3. The electrochemical system of claim 1, wherein the generated gas is hydrogen gas.

4. The electrochemical system of claim 1, further comprising: a water pump positioned between the gas-liquid separator and the electrochemical stack; a first water transfer line configured to supply water from the gas-liquid separator to the water pump; and a second water transfer line configured to supply water from the water pump to the electrochemical stack, wherein the water pump is configured to step up a pressure in the first water transfer line from the lower pressure to the elevated pressure in the second water transfer line.

5. The electrochemical system of claim 4, wherein energy is generated at the recovery turbine through the reduction in pressure from the elevated pressure to the lower pressure, and wherein at least a portion of the generated energy is configured to be provided to the water pump to assist in operation of the water pump.

6. The electrochemical system of claim 5, wherein the generated energy provides 100% of an energy required to operate the water pump during operation of the electrochemical system.

7. The electrochemical system of claim 5, wherein at least a portion of the generated energy is configured to be provided to at least one additional component of the electrochemical system to assist in operation of the at least one additional component of the electrochemical system.

8. The electrochemical system of claim 7, wherein the at least one additional component of the electrochemical system is the electrochemical stack.

9. The electrochemical system of claim 1, further comprising: a back pressure device; and a gas line connecting the back pressure device and the gas-liquid separator, wherein the back pressure device is configured to release gas from the gas-liquid separator to atmosphere via the gas line, therein assisting in controlling an operating pressure at the gas-liquid separator.

10. The electrochemical system of claim 1, further comprising: a controller in communication with the electrochemical stack, the recovery turbine, and/or the gas-liquid separator via a connected network.

11. The electrochemical system of claim 10, wherein the controller is configured to provide instructions to adjust an operating pressure of the electrochemical stack or the gasliquid separator.

12. The electrochemical system of claim 10, wherein the controller is configured to provide instructions to adjust operation of the recovery turbine to increase or decrease a step down in pressure between the electrochemical stack and the gas-liquid separator.

13. The electrochemical system of any of claims 1-12, wherein the elevated pressure is in a range of 8-40 atm.

14. The electrochemical system of any of claims 1-12, wherein the lower pressure is greater than 0 atm and less than or equal to 10 atm.

15. A fluids processing system in communication with an electrochemical stack of an electrochemical system, the fluids processing system comprising: a recovery turbine configured to receive unreacted water and a generated gas from the electrochemical stack; and a gas-liquid separator configured to separate at least a portion of the generated gas from the unreacted water; and a fluids transfer line connecting the recovery turbine and the gas-liquid separator, wherein the gas-liquid separator and fluids transfer line are configured to operate at a lower pressure than an elevated pressure of the electrochemical stack, and wherein the recovery turbine is configured to reduce the elevated pressure of the electrochemical stack to the lower pressure within the fluids transfer line and gas-liquid separator.

16. The fluids processing system of claim 15, wherein the generated gas is oxygen gas.

17. The fluids processing system of claim 15, wherein the generated gas is hydrogen gas.

18. The fluids processing system of claim 15, further comprising: a water pump positioned between the gas-liquid separator and the electrochemical stack; and a water transfer line configured to supply water from the gas-liquid separator to the water pump, wherein the water pump is configured to step up a pressure from the lower pressure to the elevated pressure of the electrochemical stack.

19. The fluids processing system of claim 18, wherein energy is generated at the recovery turbine through the reduction in pressure from the elevated pressure to the lower pressure, and wherein at least a portion of the generated energy is configured to be provided to the water pump to assist in operation of the water pump.

20. The fluids processing system of claim 19, wherein the generated energy provides 100% of an energy required to operate the water pump during operation of the electrochemical system.

21. The fluids processing system of claim 19, wherein at least a portion of the generated energy is configured to be provided to at least one additional component of the electrochemical system to assist in operation of the at least one additional component of the electrochemical system.

22. The fluids processing system of claim 21, wherein the at least one additional component of the electrochemical system is the electrochemical stack.

23. The fluids processing system of claim 15, further comprising: a back pressure device; and a gas line connecting the back pressure device and the gas-liquid separator, wherein the back pressure device is configured to release gas from the gas-liquid separator to atmosphere via the gas line, therein assisting in controlling an operating pressure at the gas-liquid separator.

24. The fluids processing system of claim 15, further comprising: a controller in communication with the recovery turbine and/or the gas-liquid separator via a connected network.

25. The fluids processing system of claim 24, wherein the controller is configured to provide instructions to adjust an operating pressure of the gas-liquid separator.

26. The fluids processing system of claim 24, wherein the controller is configured to provide instructions to adjust operation of the recovery turbine to increase or decrease a step down in pressure between the electrochemical stack and the gas-liquid separator.