COMBINED SOLID OXIDE ELECTROLYZER CELL AND POLYMER ELECTROLYTE ELECTROLYZER CELL HYDROGEN GENERATION SYSTEM AND METHOD OF OPERATING THEREOF

Description

FIELD

The embodiments of the present invention are generally directed to hydrogen generation systems, and in particular, hydrogen generation systems that include solid oxide electrolyzer cells (SOECs) and a polymer electrolyte cells, such as proton exchange membrane (PEM) cells or anion exchange membrane (AEM) cells, and methods of operating the same.

BACKGROUND

Solid oxide fuel cells (SOFCs) can be utilized in an electrolyzer to produce hydrogen and oxygen, and can be referred to as solid oxide electrolyzer cells (SOECs) when configured for use in an electrolyzer. When SOFCs are configured to produce electricity (SOFC mode), oxygen ions are transported from the cathode side (air) to the anode side (fuel) and the driving force is the chemical gradient of partial pressure of oxygen across the electrolyte. When fuel cells are configured in SOEC mode, a positive potential is applied to the air side of the cell and oxygen ions are transported from the fuel side to the air side. Since the cathode and anode are reversed between SOFC mode and SOEC mode (i.e., SOFC cathode is SOEC anode, and SOFC anode is SOEC cathode), going forward, the SOFC cathode (SOEC anode) will be referred to as the air electrode, and the SOFC anode (SOEC cathode) will be referred to as the fuel or steam electrode. During SOEC mode, water in the steam stream is reduced (H₂O+2e→O²⁻+H₂) to form H₂ gas and O²⁻ ions, O²⁻ ions are transported through the solid electrolyte, and then oxidized on the air side (O²⁻ to O₂) to produce molecular oxygen.

SUMMARY

In various embodiments, provided is an electrolyzer system comprising: solid oxide electrolyzer cell (SOEC) modules configured to convert steam into a main product stream comprising hydrogen (H₂), each SOEC module comprising SOECs disposed in at least one stack and a mixer configured to mix inlet hydrogen with steam provided to the SOECs; a polymer electrolyte cell module comprising PECs and configured to generate the inlet hydrogen (H₂); an inlet conduit configured to fluidly connect the PEC module to the SOEC modules; and a product conduit configured to collect the main product stream from the SOEC modules.

In various embodiments, an electrolyzer system includes solid oxide electrolyzer cell (SOEC) modules configured to convert steam into a main product stream comprising hydrogen, each SOEC module comprising at least one SOEC stack; a polymer electrolyte cell (PEC) module comprising PECs and configured to generate the inlet hydrogen by electrolysis of water; an inlet conduit configured to fluidly connect an outlet of the PEC module to inlets of the SOEC modules; and a product conduit fluidly connected to outlets of the SEOC modules and configured to collect the main product stream from the SOEC modules.

In various embodiments, a method of operating an electrolyzer system includes electrolyzing water into oxygen and inlet hydrogen using a polymer electrolyte cell (PEC) module including PECs, providing the inlet hydrogen to solid oxide electrolyzer cell (SOEC) modules that each include at least one SOEC stack, providing steam to the SOEC modules, and electrolyzing the steam to generate oxygen and a main product stream containing hydrogen.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is a perspective view of a solid oxide electrolyzer cell (SOEC) stack, and FIG. 1B is a side cross-sectional view of a portion of the stack of FIG. 1A.

FIG. 2 is a schematic view showing process flows through an electrolyzer system according to various embodiments of the present disclosure.

FIG. 3A is a schematic view showing process flows in an integrated SOEC/polymer electrolyte cell (PEC) electrolyzer system, according to various embodiments of the present disclosure, FIG. 3B is a schematic view of a PEM cell that may be included in the PEC module of FIG. 3A, and FIG. 3C is a schematic view of an AEM cell that may be alternatively included in the PEC module of FIG. 3A.

FIG. 4 is a schematic view of an SOEC module of the system of FIG. 3A that includes optional components, according to various embodiments of the present disclosure.

FIGS. 5-7 are schematic views showing process flows in alternative integrated electrolyzer systems, according to various embodiments of the present disclosure.

DETAILED DESCRIPTION

FIG. 1A is a perspective view of a solid oxide electrolyzer cell (SOEC) stack 100, and FIG. 1B is a side cross-sectional view of a portion of the stack 100 of FIG. 1A. Referring to FIGS. 1A and 1B, the stack 100 includes multiple electrolyzer cells 1 that are separated by interconnects 10, which may also be referred to as gas flow separator plates or bipolar plates. Each electrolyzer cell 1 includes an air electrode 3, a solid oxide electrolyte 5, and a steam (fuel) electrode 7. The stack 100 also includes internal steam/fuel riser channels 22.

Each interconnect 10 electrically connects adjacent electrolyzer cells 1 in the stack 100. In particular, an interconnect 10 may electrically connect the steam/fuel electrode 7 of one electrolyzer cell 1 to the air electrode 3 of an adjacent electrolyzer cell 1. FIG. 1B shows that the lower electrolyzer cell 1 is located between two interconnects 10.

Each interconnect 10 includes respective steam/fuel side ribs 12A and air side ribs 12B that at least partially define steam channels 8A and air channels 8B. The interconnect 10 may operate as a separator that separates the steam side of one cell 1 from the air side of an adjacent cell 1. The air flow to the air electrode 3 serves as a sweep gas to entrain the O₂ transported by electrolysis. At either end of the stack 100, there may be an air end plate or steam end plate (not shown) for providing air or steam, respectively, to the end electrode.

FIG. 2 is a schematic view showing process flows in an SOEC module 200, according to various embodiments of the present disclosure. Referring to FIGS. 1A, 1B, and 2, the SOEC module 200 may include an electrolyzer cell (SOEC) stack 100 including multiple solid oxide electrolyzer cells (SOECs), as described with respect to FIGS. 1A and 1B. The SOEC module 200 may also include an optional steam generator 104, a steam recuperator heat exchanger 108, a steam heater 110, an air recuperator 112, and an air heater 114. The SOEC module 200 may also include an optional water preheater 102 and an optional mixer 106.

The SOEC module 200 may include a hotbox 210 to house various components, such as the stack 100, steam recuperator 108, steam heater 110, air recuperator 112, and/or air heater 114. In some embodiments, the hotbox 210 may include multiple stacks 100. The water preheater 102 and the steam generator 104 may be located external to the hotbox 210 as shown in FIG. 2. Alternatively, the water preheater 102 and/or the steam generator 104 may be located inside the hotbox 210. In another alternative embodiment, the water preheater 102 may be located inside the hotbox 210 and the steam generator 104 may be located outside the hotbox 210 (not shown). In another embodiment, the water preheater 102 may be omitted and the steam generator 104 may comprise an external source of steam (e.g., a boiler of a building, an industrial steam source that generates steam as a byproduct of an industrial process, etc.) As will be readily understood, other configurations are feasible without departing from the invention.

During operation, the stack 100 may be provided with steam and electric current or voltage from an external power source. In particular, the steam may be provided to the steam electrodes 7 of the electrolyzer cells 1 of the stack 100, and the power source may apply a voltage between the steam electrodes 7 and the air electrodes 3, in order to electrochemically split water molecules and generate hydrogen (e.g., H₂) and oxygen (e.g., O₂). Air may also be provided to the air electrodes 3, in order to sweep the oxygen from the air electrodes 3. As such, the stack 100 may output a main hydrogen stream and an oxygen-rich exhaust stream, such as an oxygen-rich air stream (“oxygen exhaust stream”).

In order to generate the steam, water may be provided to the SOEC module 200 from a water source 50 via a water inlet conduit 101. The water may be deionized (DI) water that is deionized as much as is practical (e.g., <0.1 μS/cm, or at least <1 μS/cm), in order to prevent and/or minimize scaling during vaporization. In some embodiments, the water source 50 may include deionization beds. In various embodiments, the SOEC module 200 may include a water flow control device (not shown) such as a mass flow controller, a positive displacement pump, a control valve/water flow meter, or the like, in order to provide a desired water flow rate to the SOEC module 200.

If the SOEC module 200 includes the water preheater 102, the water may be provided from the water source 50 to the water preheater 102. The water preheater 102 may be a heat exchanger configured to heat the water using heat recovered from the oxygen exhaust stream. Preheating the water may reduce the total power consumption of the SOEC module 200 per unit of hydrogen generated. In particular, the water preheater 102 may recover heat from the oxygen exhaust stream that may not be recoverable by the air recuperator 112, as discussed below. The oxygen exhaust stream may be output from the water preheater 102 via an exhaust conduit 103 at a temperature above 80° C., such as above 100° C., such as a temperature of about 110° C. to 120° C.

The water output from the water preheater 102 or the water source 50 may be provided to the optional steam generator 104. A portion of the water may vaporize in the water preheater. The steam generator 104 may be configured to heat the water not vaporized in the water preheater to convert the water into steam. For example, the steam generator 104 may include a heating element to vaporize the water and generate steam. For example, the steam generator 104 may include an AC or DC resistance heating element, or an induction heating element.

The steam generator 104 may include multiple zones/elements that may or may not be mechanically separate. For example, the steam generator 104 may include a pre-boiler to heat the water up to, or near to the boiling point. The steam generator 104 may also include a vaporizer configured to convert the pre-boiled water into steam. The steam generator 104 may also include a deaerator to provide a relatively small purge of steam to remove dissolved air from the water prior to bulk vaporization. The steam generator 104 may also include an optional superheater configured to further increase the temperature of the steam generated in the vaporizer. The steam generator 104 may include a device such as a demister pad located downstream of the heating element and/or upstream from the super heater. The demister pad may be configured to minimize entrainment of liquid water in the steam output from the steam generator 104 and/or provided to the superheater. Alternatively, the steam generator 104 may comprise an external steam source (e.g., building or industrial steam source).

The steam output from the steam generator 104 may be provided to the steam recuperator 108 via a steam inlet conduit 107. However, if the SOEC module 200 includes the optional mixer 106, the steam may be provided to the mixer 106 via a steam conduit 105 prior to being provided to the steam recuperator 108 from the mixer 106 via the steam inlet conduit 107. In particular, the steam may include small amounts of dissolved air and/or oxygen. As such, the mixer 106 may be configured to mix the steam with hydrogen gas, in order to maintain a reducing environment in the stack 100, and in particular, at the steam electrodes 7.

The mixer 106 may be configured to mix the steam with hydrogen received from a hydrogen source 52 via a hydrogen inlet conduit and/or with a portion of the hydrogen stream output from the stack 100 via the recycling conduit 117. The hydrogen source 52 may include a low/intermediate pressure storage tank for providing pressurized hydrogen to the stack 100 via the hydrogen inlet conduit 109 and the mixer 106.

In some embodiments, the hydrogen may be provided by the external hydrogen source 52 during system startup, shutdown and emergency (e.g., fault) operating modes when the SOEC module 200 is not generating hydrogen. For example, during startup, the hydrogen may be provided from the hydrogen source 52, and during steady-state, the hydrogen may be provided by diverting a portion of the hydrogen stream (i.e., hydrogen exhaust stream) from the main product conduit 115 that is generated by the stack 100 to the mixer 106. In particular, the SOEC module 200 may include a hydrogen separator 116, such as a splitter, pump, blower and/or valve, configured to selectively divert a portion of the generated hydrogen stream flowing from the stack 100 through main product conduit 115 to the mixer 106, during steady-state operation. In particular, the separator 116 may be fluidly connected to the mixer 106 by a recycling conduit 117. An optional recycle blower 121 may be located on the recycle conduit 117.

The steam recuperator 108 may be a heat exchanger configured to recover heat from the hydrogen stream output from the stack 100. As such, the steam recuperator 108 may be configured to increase the efficiency of the SOEC module 200. The steam may be heated to a range between 600° C. to 830° C. in the steam recuperator 108. In some instances, the steam is heated to within 10° C. to 150° C. of the stack operating temperature. For example, the stack operating temperature may be 700° C. or 750° C., or there between, and the steam may be heated to at least 600° C., such as 650° C. to 740° C. in the steam recuperator 108. Steam exiting from the steam recuperator 108 is below (e.g., 10-100° C. less than) the average stack 100 operating temperature.

The steam output from the steam recuperator 108 may be provided to the steam heater 110 which is located downstream from the steam recuperator 108, as shown in FIG. 2. The steam heater 110 may include a heating element, such as a resistive or inductive heating element. The steam heater 110 may be configured to heat the steam to a temperature above the operating temperature of the stack 100. For example, depending on the health of the stack 100, the water utilization rate of the stack 100, and the air flow rate to the stack 100, the steam heater 110 may heat the steam to a temperature ranging from about 900° C. to about 1200° C., such as 920° C. to 980° C. With the lower stack temperature between 700° C. and 750° C., the steam heater outlet temperature may be as low as 700° C. Accordingly, the stack 100 may be provided with steam or a steam-hydrogen mixture at a temperature that allows for efficient hydrogen generation. Heat may also be transported directly from the steam heater to the stack by radiation (i.e., by radiant heat transfer). In some embodiments, steam heater 110 is optional, and additional heat is obtained through air heater 114. In some embodiments, the steam heater 110 may include multiple steam heater zones with independent power levels (divided vertically or circumferentially or both), in order to enhance thermal uniformity.

The oxygen exhaust output from the stack 100 may be provided to the air recuperator 112. The air recuperator 112 may be provided with ambient air by an air blower 118 via an air conduit 119. The air recuperator 112 may be configured to heat the air using heat extracted from the oxygen exhaust stream flowing through the exhaust conduit 103. In some embodiments, the ambient air may be filtered to remove contaminants, prior to being provided to the air recuperator 112 or the air blower 118.

Air output from the air recuperator 112 may be provided to the air heater 114. The air heater may include a resistive or inductive heating element configured to heat the air to a temperature exceeding the operating temperature of the stack 100. For example, depending on the health of the stack 100, the water utilization rate of the stack 100, and the air flow rate to the stack 100, the air heater 114 may heat the air to a temperature ranging from about 900° C. to about 1200° C., such as 920° C. to 980° C. With lower stack temperatures, the air heater temperature could be as low as 800° C. Accordingly, the stack 100 may be provided with air at a temperature that allows for efficient hydrogen generation. Heat may also be transported directly from the air heater to the stack by radiation.

The air heater 114 may include multiple air heater zones with independent power levels (divided vertically or circumferentially or both), in order to enhance thermal uniformity, in some embodiments. In some embodiments, the air heater 114 may be disposed below the air recuperator 112, or between the stack 100 and the steam recuperator 108, or both. Air from the air heater 114 is provided to the air electrodes 3 of the stack 100.

In some embodiments, one or more additional stack heaters (not shown) may be located in the hot box 210 adjacent to the stack(s) 100. The one or more stack heaters may comprise a resistive or inductive heating elements configured to heat the stack(s) 100.

In one embodiment, the SOEC module 200 may include an optional air preheater heat exchanger (not shown) disposed inside or outside of the hotbox 210. In particular, the air preheater may be configured to preheat air flowing through the air conduit 119 to the hotbox 210 from the air blower 118 using main product H₂/residual steam exiting the steam recuperator 108 via the main product conduit 115. The air preheater functions as a cathode product cooler. It cools the main product H₂/residual steam in the main product conduit 115 to a lower temperature below the maximum temperature (e.g., 180° C., or 200° C.) of the hydrogen processor 120.

The hydrogen stream output from the steam recuperator 108 and the optional hydrogen separator 116 via the main product conduit 115 at a temperature of 120° C. to 150° C. may be compressed and/or purified in an optional hydrogen processor 120, which may include a high temperature hydrogen pump that operates at a temperature of from about 120° C. to about 150° C., in order to remove from about 70% to about 90% of the hydrogen from the hydrogen stream. A remaining unpumped effluent from the hydrogen pump is a water rich stream that is already fully vaporized. This water rich stream may be fed to a recycle blower 121 for recycling into the mixer 106 or stream recuperator 108, reducing the need for water vaporization in the steam generator 104.

In various embodiments, the hydrogen processor 120 may include at least one electrochemical hydrogen pump, liquid ring compressor, diaphragm compressor, other compression device, or combination thereof. For example, the hydrogen processor may include a series of electrochemical hydrogen pumps, which may be disposed in series and/or in parallel with respect to a flow direction of the hydrogen stream, in order to compress the hydrogen stream. Electrochemical compression may be more electrically efficient than traditional compression. The final product from compression may still contain traces of water. As such, the hydrogen processor 120 may include a dewatering device, such as a condenser, a temperature swing adsorption reactor or a pressure swing adsorption reactor, to remove this residual water, if necessary. The system may be configured to repurify (e.g., in DI beds) the residual water and provide the residual water removed from the compressed hydrogen stream to the water preheater 102.

According to various embodiments, the SOEC module 200 may include a controller 122, such as a central processing unit, that is configured to control the operation of the SOEC module 200. For example, the controller 122 may be wired or wirelessly connected to various elements (e.g., valves, blower(s), power source etc.) of the SOEC module 200 to control the same.

Integrated SOEC/PEC Systems

The use of a hydrogen storage container (e.g., storage tank) 52 as a hydrogen source and/or recycling generated hydrogen from the main product conduit 115 into incoming steam in the steam inlet conduit 107 via a recycling conduit 117 using a recycle blower 121 and/or a mass flow controller may increase the cost and complexity of SOEC module 200. Accordingly, various embodiments provide hydrogen generation systems that utilize both SOEC hydrogen generation modules and at least one polymer electrolyte cell (“PEC”) hydrogen generation module, such as the proton exchange membrane (PEM) cell or the anion exchange membrane (AEM) cell hydrogen generation module.

FIG. 3A is a schematic view showing process flows in an integrated SOEC/PEC electrolyzer system 300, according to various embodiments of the present disclosure, FIG. 3B is a schematic view of an ion exchange cell 360 that may be included in the PEC module 350 of FIG. 3A, and FIG. 3C is a schematic view of an anion exchange cell 370 that may be alternatively included in the PEC module 350 of FIG. 3A. Same element numbers in FIGS. 2 and 3A denote the same elements.

Referring to FIG. 3A, the system 300 may include SOEC modules 200A and a polymer electrolyte cell (PEC) module 350 fluidly connected thereto. In various embodiments, the system 300 may include any suitable number of SOEC modules 200A, such as from 2 to 10, such as 4 to 8, SOEC modules 200A. The SOEC modules 200A may be similar to the SOEC modules 200 of FIG. 2. As such, only the differences therebetween will be discussed in detail.

The PEC module 350 is fluidly connected to the water source 50 via the water inlet conduit 101. The water source 50 may provide liquid water at a temperature between room temperature (e.g., 20° C.) and 99° C. to an inlet of the PEC module 350 via the water inlet conduit 101. In some embodiments, the water source 50 may also be fluidly connected to the SOEC modules 200A thorough the steam generator 104 for steam generation, as shown in FIG. 2.

The system 300 may also include an inlet conduit (e.g., an inlet manifold) 302 that fluidly connects an outlet of the PEC module 350 to the hydrogen inlets (e.g., hydrogen inlet conduits 109) of the SOEC modules 200A, a product conduit (e.g., a product manifold) 304 that is fluidly connected to main product outlets (e.g., the main product conduits 115) of the SOEC modules 200A, shutoff valves 310, 312, and optional flow orifices 314, such as orifice plates, fixed orifices, flow control orifices, etc. The flow orifices 314 may be used instead of mass flow controllers, which simplifies the system 300 and reduces the system cost. The system 300 may be fluidly connected to the steam generator 104 configured to provide steam to mixers 106 of the SOEC modules 200A via the steam conduit 105. The system 300 may also include a system controller 322 configured to control the operation of the PEC module 350, the SOEC modules 200A, and/or the valves 310, 312.

During operation of the system 300, the PEC module 350 may generate hydrogen (H₂) (i.e., an inlet hydrogen stream), portions of which are provided to each of the SOEC modules 200A via the inlet manifold 302 and respective hydrogen inlet conduit 109. The PEC module 350 may generate a sufficient amount of hydrogen to satisfy the hydrogen needs of each SOEC module 200A. For example, the PEC module 350 may provide hydrogen to the SOEC modules 200A if and when required, such as during the start-up, shut-down and/or emergency operating modes of the SOEC modules 200A when the SOEC modules 200A are not generating hydrogen. Alternatively or in addition, the PEC module 350 may provide hydrogen to the mixer 106 of SOEC modules 200A operating in a steady-state mode in case it is desirable to provide a mixture of hydrogen and steam to the SOEC stacks 100 in the SOEC modules 200A. The amount of hydrogen generated by the PEC module 350 may be controlled by controlling an amount of power that is supplied to the PEC module 350 to generate hydrogen (e.g., by controlling a DC current setpoint of the PEC module 350) and/or by an amount of water provided to the PEC module 350 (e.g., by controlling a water flow valve at the water source 50).

The PEC module 350 may have a lower operating temperature, and thus, a faster startup time than the SOEC modules 200A. As such, the PEC module 350 may operate as a hydrogen source during start-up of the SOEC modules 200A, obviating the need for a hydrogen storage vessel 52 for providing startup hydrogen to the SOEC modules 200A. Thus, a hydrogen storage vessel for providing start-up hydrogen may be omitted from the system 300.

The amount of hydrogen provided to each SOEC module 200A may be regulated by the orifices 314. In particular, the orifices 314 may provide a flow restriction to a hydrogen stream provided from the PEC module 350. The SOEC modules 200A may each include a steam generator 104 or may be fluidly connected to a common steam generator 104. For example, the steam generator 104 may comprise an industrial process stream source.

Hydrogen generated by the SOEC modules 200A may be collected by the product manifold 304 as a product stream. In some embodiments, the product manifold 304 may fluidly connect the SOEC modules 200A to a hydrogen processing device (e.g., hydrogen processor 120), a hydrogen storage device, a hydrogen consumer (i.e., customer), such as an industrial plant that uses hydrogen, or a combination thereof.

The valves 310, 312 may operate to individually isolate the SOEC modules 200A. For example, the valves 310, 312 may include upstream shutoff valves 310 that are configured to selectively prevent hydrogen from the inlet manifold 302 from flowing into the SOEC modules 200A, and downstream shutoff valves 312 that are configured to selectively prevent hydrogen in the product manifold 304 from backflowing into the SOEC modules 200A. Accordingly, the SOEC modules 200A may be individually isolated from the system 300. For example, one or more of the SOEC modules 200A may be isolated and serviced after closing its respective valves 310, 312, while a remainder of the SOEC modules 200A in the system 300 remain in operation.

Since the PEC module 350 generates pressurized hydrogen, the hydrogen separator 116, the recycle conduit 117 and the recycle blower 121 of SOEC module 200 may be omitted from the SOEC modules 200A. As such, the SOEC modules 200A of the system 300 may be more efficient and less expensive than the SOEC module 200 of FIG. 2.

Thus, the electrolyzer system 300 includes SOEC modules 200A configured to convert steam into a main product stream comprising hydrogen, each SOEC module 200A comprising at least one SOEC stack 100; a polymer electrolyte cell (PEC) module 350 comprising PECs (360 or 370) and configured to generate the inlet hydrogen by electrolysis of water; an inlet conduit (e.g., inlet manifold) 302 configured to fluidly connect an outlet of the PEC module 350 to inlets of the SOEC modules 200A; and a product conduit (e.g., product manifold) 304 fluidly connected to outlets of the SEOC modules 200A and configured to collect the main product stream from the SOEC modules 200A.

In one embodiment, each of the SOEC modules 200A includes a steam conduit 105 configured to provide the steam to the SOEC modules 200A; a mixer 106 fluidly connected to the steam conduit 105 and configured to mix the inlet hydrogen with the steam; a hydrogen inlet conduit 109 fluidly connecting the inlet conduit (e.g., inlet manifold) 302 to the mixer 106; and a first flow control orifice 314 located on the hydrogen inlet conduit 109, and configured to control a mass flow rate of the inlet hydrogen from the inlet conduit 302 to the mixer 106.

A method of operating the electrolyzer system 300 comprises electrolyzing water into oxygen and inlet hydrogen using a polymer electrolyte cell (PEC) module 350 utilizing PECs; providing the inlet hydrogen to solid oxide electrolyzer cell (SOEC) modules 200A that each comprise at least one SOEC stack 100; providing steam to the SOEC modules 200A; and electrolyzing the steam to generate oxygen and a main product stream comprising hydrogen.

In one embodiment, the inlet hydrogen and the steam are mixed. In this embodiment, the step of providing the inlet hydrogen to the SOEC modules 200A and the step of providing the steam to the SOEC modules 200A comprises providing the mixed inlet hydrogen and steam to the SOEC stacks 100 located in the respective modules 200A. In one embodiment, the step of mixing the inlet hydrogen and the steam occurs at least during a start-up mode of the SOEC modules. In one embodiment, the step of providing the inlet hydrogen to the SOEC modules occurs during the start-up mode, during a shut-down mode and during an emergency mode of the SOEC modules (where the SOEC modules do not generate the main product stream comprising hydrogen during the emergency mode). In one embodiment, the inlet hydrogen is not provided to the SEOC modules 200A during a steady-state operating mode of the SOEC modules 200A; and the steam is provided to the SOEC modules 200A during the steady-state operating mode of the SOEC modules. In an alternative embodiment, the inlet hydrogen is provided to the SEOC modules 200A even during the steady-state operating mode of the SOEC modules 200A.

Referring to FIGS. 3A and 3B, the PEC module 350 may include at least one proton exchange membrane (PEM) cell 360. For example, the PEC module 350 may include one or more stacks of PEM cells 360. The ion exchange cell 360 may include an anode 364, a cathode 366, and a proton exchange membrane 362 disposed therebetween. The PEM cell 360 may be electrically connected to a voltage source 368. The membrane 362 may be formed of a solid polymer material, such as a sulfonated tetrafluoroethylene based fluoropolymer-copolymer, for example, a perfluorosulfonic acid (PFSA) membrane that is a copolymer of PFSA and polytetrafluoroethylene (PTFE) (e.g., Nafion®). The anode 364 may include a supported platinum group catalyst, such as iridium supported on a titanium support. The cathode 366 may include a supported platinum group catalyst, such as platinum supported on a carbon support.

In operation, a voltage is applied between the anode 364 and the cathode 366 by the voltage source 368, and water (H₂O) is provided to the anode 364. At the anode 364, the water is spilt into oxygen (O₂), protons (H⁺) and electrons (e⁻) according to the following reaction: 2H₂O→4H⁺+O₂+4e⁻. The electrons are transported from the anode 364 to the cathode 366 via an external power circuit connected to the voltage source 368, which provides the driving force (cell voltage) for the reaction. The protons are conducted through the membrane 362 to the cathode 366, where the protons combine with the electrons to form hydrogen (H₂) according to the following reaction: 2H⁺+2e⁻→2H₂.

Referring to FIGS. 3A and 3C, in an alternative embodiment the PEC module 350 may include at least one anion exchange membrane (AEM) cell 370. For example, the PEC module 350 may include one or more stacks of AEM cells 370. The AEM cell 370 may include an anode 364, a cathode 366, and an anion exchange membrane 372 disposed therebetween. The AEM cell 370 may be electrically connected to a voltage source 368. The membrane 372 may be a solid polymer membrane including an ionomer, such as a poly (fluorenyl-co-aryl piperidinium) material. The anode 364 and cathode 366 may include supported metal catalysts, such as Ni, Fe, Co, Mn, and/or Cu disposed on a support.

In operation, a voltage is applied between the anode 364 and the cathode 366 by the voltage source 368, and water (H₂O) is provided to the anode 364. Water is transported from the anode 364 to the cathode 366 through the anion exchange membrane 372. The water is electrolyzed at the cathode 366 to produce hydrogen and hydroxyl ions (OH⁻). The hydrogen is discharged from the cathode 366 chamber, while the hydroxyl ions are transported back from the cathode 366 to the anode 364 through the anion exchange membrane 372. Oxygen is produced at the anode 364 from the hydroxyl ions and mixed with the remaining water. The oxygen and remaining water mixture is discharged from the anode chamber.

FIG. 4 is a schematic view of an SOEC module 200A that includes optional components, according to various embodiments of the present disclosure. Referring to FIG. 4, the SOEC module 200A may include multiple orifices 314A, 314B, 314C and multiple shutoff valves 310A, 310B, 310C. The orifices 314A, 314B, 314C may vary in size (e.g., diameter), and thereby may generate different amounts of flow restriction (e.g., provide different mass flow rates for the inlet hydrogen stream).

In operation, the shutoff valves 310A, 310B, 310C may be independently controlled to select which of the orifices 314A, 314B, 314C hydrogen flows through and how much flow restriction is applied to the hydrogen stream. In other words, a mass flow rate of the inlet hydrogen stream may be controlled by selecting which of the orifices 314A, 314B, 314C the inlet hydrogen stream flows through. As such, different hydrogen flow rates may be generated based on which of the orifices 314A, 314B, 314C is selected for controlling the mass flow rate of the inlet hydrogen stream.

In an alternative embodiment of FIG. 4, each of the SOEC modules 200A comprises: a first flow control orifice 314A and second flow control orifice 314B both of which are configured to control a mass flow rate of the inlet hydrogen to the mixer 106, wherein the first flow control orifice 314A has a different diameter than the second flow control orifice 314B; a first valve 310A is configured to control the inlet hydrogen flow from the hydrogen inlet conduit 109 to the first flow control orifice 314A; and a second valve 310B is configured to control the inlet hydrogen flow from the hydrogen inlet conduit 109 to the second flow control orifice 314B. In this embodiment, the third flow control orifice 314C and third valve 310C are omitted.

FIG. 5 is a schematic view showing process flows in an alternative integrated SOEC/PEC system 500, according to various embodiments of the present disclosure. The system 500 may be similar to the system 300. As such, only the differences therebetween will be discussed in detail. The steam generator 104, the steam conduit 105 and the mixer 106 are not shown in FIG. 5 for clarity. However, it should be noted that the steam generator 104, the steam conduit 105 and the mixer 106 may be present in the system 500.

Referring to FIG. 5, the system 500 may include the hydrogen source 52 rather than a PEC module 350. In addition, the system 500 may include a heat exchanger 340 and a hydrogen pump 380 fluidly connected to the product manifold 304. The heat exchanger 340 and the hydrogen pump 380 may comprise at least a portion of the hydrogen processor 120.

In some embodiments, the system 500 may optionally include one or more vents 305 on the product manifold 304 configured to vent the output of the SOEC modules 200A, in order to provide system flexibility and/or to reroute the hydrogen stream in case of hydrogen pump 380 failure.

During steady-state mode operation, wet hydrogen (H₂+H₂O) output from the SOEC modules 200A may be provided to the heat exchanger 340 by the product manifold 304. The heat exchanger 340 may be configured to cool the wet hydrogen stream before the hydrogen stream reaches the hydrogen pump 380, in order to protect the hydrogen pump 380 from thermal damage. For example, the heat exchanger 340 may be configured to cool the hydrogen stream to a temperature of less than about 150° C., such as a temperature of less than about 120° C., or less than about 110° C. The heat exchanger 340 provides the cooled wet hydrogen stream to the hydrogen pump 380 via the pump inlet conduit 308.

In one embodiment, the heat exchanger 340 may be an air heat exchanger in which air is used to cool the wet hydrogen stream. In this embodiment, the air heat exchanger 340 may be fluidly connected to an air blower 342 to facilitate cooling of the wet hydrogen product stream. For example, the air heat exchanger 340 may comprise one or more finned tubes carrying the wet hydrogen stream, and the air blower 342 provides an air flow stream on the outer surface of the one or more finned tubes. Alternatively, the air blower 118 shown in FIG. 2 may be used to provide both an air inlet stream into the SOEC stack(s) 100 and onto the air heat exchanger 340.

The hydrogen pump 380 may be a multi-stage electrochemical hydrogen compressor that includes multiple PEM cells 360 (shown in FIG. 3B) in series to generate higher output pressures. The cells 360 may be configured to catalytically split hydrogen at the anode 364 and pump the resulting protons across the membrane 362 to the cathode 366. Electrons may flow from the anode 364 to the cathode 366 and recombine with the protons to form hydrogen at a higher pressure than the received pressure. The processes may be repeated as the hydrogen is pumped through each of the cells 360 and out from the cathode 366 sides of the cells 360 to a hydrogen consumer conduit 309, to further increase the hydrogen pressure. In some embodiments, the hydrogen may be pressurized to a pressure of at least about 10 bar, such as a pressure ranging from about 10 bar to about 40 bar, such as from about 20 bar to about 30 bar, or about 25 bar. The hydrogen pump 380 may also output an effluent stream including residual water from the anode 364 sides of the cells 360 to a water outlet conduit 311. The water may be stored, disposed of, or used to generate steam provided to the SOEC modules 200A.

The pressurized hydrogen may be output from the hydrogen pump 380 via the hydrogen consumer conduit 309 and provided to a hydrogen consumer (e.g., customer) or stored on site. In some embodiments, the system 500 may include a return conduit 306 fluidly connecting an outlet of the hydrogen pump 380 to the hydrogen source 52 and/or the inlet manifold 302. For example, the system 500 may include a diversion valve 307 located on the hydrogen consumer conduit 309 and configured to control the diversion of the pressurized hydrogen to the inlet manifold via the return conduit 306 and/or to the hydrogen consumer via the hydrogen consumer conduit 309. The pressurized hydrogen may be provided directly to the SOEC modules 200A by the inlet manifold 302. In some embodiments, some or all of the pressurized hydrogen may be provided to the hydrogen source 52 for storage.

Thus, in the embodiment of FIG. 5, the system 500 also comprises a heat exchanger 340 configured to cool the product stream in the product conduit (e.g., product manifold) 304, and a hydrogen pump 380 comprising electrochemical hydrogen pumping cells (e.g., PEM cells 360). The hydrogen pump 380 has an inlet fluidly connected to an outlet of the heat exchanger 340 by a hydrogen pump conduit 308. The hydrogen pump 380 is configured to separate water from product hydrogen in the product stream and to pressurize the product hydrogen. A hydrogen consumer conduit 309 is fluidly connected to an outlet of the hydrogen pump 380 and configured to provide pressurized product hydrogen output from the hydrogen pump to a hydrogen consumer. A return conduit 306 fluidly connects the hydrogen consumer conduit 309 to the inlet conduit (e.g., inlet manifold) 302. A diversion valve 307 is located at the junction of the hydrogen consumer conduit 309 and the return conduit 306 and is configured to control diversion of the pressurized product hydrogen from the hydrogen consumer conduit 309 to the inlet conduit 302.

The method of operating the system 500 includes cooling the product stream in a heat exchanger 340; electrochemically separating water from product hydrogen in the product stream and electrochemically pressurizing the product hydrogen; and providing at least a first portion of the pressurized product hydrogen to a hydrogen consumer. In one embodiment, the method also includes recycling at least a second portion of the product hydrogen into the steam provided to the SOEC modules 200.

FIG. 6 is a schematic view showing process flows in an alternative integrated SOEC/PEC system 600, according to various embodiments of the present disclosure. The system 600 may be similar to the system 500. As such, only the differences therebetween will be discussed in detail. The steam generator 104, the steam conduit 105 and the mixer 106 are not shown in FIG. 6 for clarity. However, it should be noted that the steam generator 104, the steam conduit 105 and the mixer 106 may be present in the system 600.

Referring to FIG. 6, the system 600 may include a PEC module 350 in place of the hydrogen source 52 of the system 500. The system 600 may also include the heat exchanger 340 and the hydrogen pump 380. The PEC module 350 may operate to provide hydrogen to the SOEC modules 200A, as described above with respect to the system 300. The heat exchanger 340 and a hydrogen pump 380 may generate pressurized hydrogen using wet hydrogen received from the SOEC modules 200A, as described above with respect to the system 500.

Accordingly, the system 600 may include at least two stacks of PEC cells, with each stack performing a different function, namely hydrogen generation or hydrogen compression. The PEC module 350 may start generating hydrogen at system startup, and the hydrogen pump 380 may be operated after the SOEC modules 200A are provided with steam and generate the wet hydrogen product stream during the steady-state mode. The PEC module 350 may also generate hydrogen during shut-down mode, during the emergency mode and optionally during the steady-state mode.

In the embodiment of FIG. 6, the SOEC modules 200A exclude a recycling conduit (e.g., return conduit 306) configured to recycle the hydrogen from the product stream back to the at least one SOEC stack 100. Thus, in this embodiment, the product hydrogen is not recycled back to the at least one SOEC stack 100.

FIG. 7 is a schematic view showing process flows in an alternative integrated SOEC/PEM system 700, according to various embodiments of the present disclosure. The system 700 may be similar to the system 500. As such, only the differences therebetween will be discussed in detail. The steam generator 104, the steam conduit 105 and the mixer 106 are not shown in FIG. 7 for clarity. However, it should be noted that the steam generator 104, the steam conduit 105 and the mixer 106 may be present in the system 700.

Referring to FIG. 7, the system 700 may include a heat exchanger 340, and a combined PEC module and hydrogen pump 750 fluidly connected to an outlet of the heat exchanger 340 by the product manifold 304. The heat exchanger 340 may output cooled wet hydrogen to the combined PEC module and hydrogen pump 750 via the manifold 308. Pressurized hydrogen output from the combined PEC module and hydrogen pump 750 may be provided to the SOEC modules 200A via the inlet manifold 302.

According to various embodiments, the system 700 may be operated according to the following method. During system start-up mold (e.g., cold start-up), the SOEC modules 200A may be heated to an initial startup temperature. The SOEC modules 200A may be heated, for example, using internal stack heaters. The combined PEC module and hydrogen pump 750 receives water from the water source 50 and generates hydrogen by electrolyzing water into the hydrogen and oxygen. The hydrogen is provided from the combined PEC module and hydrogen pump 750 to the SOEC modules 200A operating in the start-up mode via the inlet manifold 302.

The initial start-up temperature may be less than the steady-state SOEC module operating temperature. For example, the initial startup temperature may range from about 100° C. to about 400° C. Once the SOEC modules 200A reach the initial startup temperature, steam may be supplied to the SOEC modules 200A from the steam generator 104 (not shown) and the temperature of the SOEC modules 200A may be increased to a steady-state operating temperature. For example, the SOEC modules 200A may be heated to the steady-state temperature ranging from about 700° C. to about 900° C., for example.

While the SOEC modules 200A are heated to the steady-state operating temperature, hydrogen and steam may be output from the SOEC modules 200A to the heat exchanger 340 via the product manifold 304. The cooled hydrogen and steam output from the heat exchanger may be provided to the combined PEC module and hydrogen pump 750 and a portion of the steam may be converted into hydrogen. Any hydrogen in excess of the requirements of the SOEC modules 200A may be output from a diversion valve 307 located on the hydrogen supply conduit 313 which fluidly connects the outlet of the combined PEC module and hydrogen pump 750 to the inlet manifold 302. For example, the hydrogen may be output to a hydrogen consumer via the hydrogen consumer conduit 309.

Once the SOEC modules 200A reach the steady-state operating temperature, the SOEC modules 200A output a cooled hydrogen stream to the combined PEC module and hydrogen pump 750 via the product manifold 304, the heat exchanger 340 and the pump inlet conduit 308. The combined PEC module and hydrogen pump 750 may operate to increase the pressure of the hydrogen product stream. In some embodiments, the combined PEC module and hydrogen pump 750 may also reduce the water content of the hydrogen product stream. Excess condensed water may be output from the combined PEC module and hydrogen pump 750 via the water outlet conduit 311.

During the steady-state mode, the cooled hydrogen and steam output from the heat exchanger 340 are provided to the combined PEC module and hydrogen pump 750 and a portion of the steam is converted into hydrogen. Any hydrogen in excess of the requirements of the SOEC modules 200A operating in the steady-state mode may be output from a diversion valve 307 located on the hydrogen supply conduit 313 via the hydrogen consumer conduit 309.

Thus, in the embodiment of FIG. 7, the PEC module of system 700 comprises a combined PEC module and hydrogen pump 750 which is fluidly connected to the product conduit (e.g., product manifold 304) and configured to separate water from product hydrogen in the product stream and to pressurize the product hydrogen. The system 700 also includes the heat exchanger 340 configured to cool the product stream in the product conduit 304, and a pump inlet conduit 308 fluidly connecting the heat exchanger 340 to the combined PEC module and hydrogen pump 750 and configured to recycle the cooled product stream from the heat exchanger 340 to the combined PEC module and hydrogen pump 750. The system 700 also includes the hydrogen consumer conduit 309, and a hydrogen supply conduit 313 fluidly connecting an outlet of the combined PEC module and hydrogen pump 750 to the hydrogen consumer conduit 309 and to the inlet conduit (e.g., inlet manifold 302). The hydrogen supply conduit 313 is configured to recycle the pressurized product hydrogen to the inlet conduit 302. A diversion valve 307 is configured to control diversion of the product hydrogen from the hydrogen supply conduit 313 to the hydrogen consumer conduit 309. Thus, in the method of operating the system 700, the steps of electrochemically separating water from product hydrogen in the product stream and the electrochemically pressurizing the product hydrogen occur in the PEC module which comprises a combined PEC module and hydrogen pump 750.

Electrolyzer cell systems of the embodiments of the present disclosure are designed to reduce greenhouse gas emissions and have a positive impact on the climate.

The preceding description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects without departing from the scope of the invention. Thus, the present invention is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.