Patent Publication Number: US-2021179451-A1

Title: Systems and methods of water treatment for hydrogen production

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/948,966, filed on Dec. 17, 2019, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure is directed to water treatment in general and, more specifically, to systems and methods of water treatment for hydrogen production. 
     BACKGROUND 
     Hydrogen is a common gas that has many uses, such as petroleum refining, metal treatment, food processing, and ammonia production. For industrial applications, hydrogen is generally formed using processes requiring non-renewable energy sources and, in particular, access to large amounts of natural gas and reliable sources water and grid power. However, because of its combustibility in air, hydrogen is difficult to store and ship. For these reasons, hydrogen is generally used at or near the site of its production which, in turn, is limited by the local availability of non-renewable energy sources. 
     SUMMARY 
     In one embodiment, a method includes providing raw water into a first filter assembly to remove solids from the raw water to form a filtrate, providing the filtrate from the first filter assembly into a second filter assembly to electrochemically remove ionics from the filtrate to form purified water, and providing the purified water to an electrolyzer to generate hydrogen by electrolyzing the purified water. 
     In another embodiment, a system comprises a water source, a first filter assembly in fluid communication with the water source, wherein the first filter assembly is configured to remove solids from raw water from the water source to form a filtrate, an electrolyzer including an anode, a cathode, and a proton exchange membrane between the anode and the cathode, and a second filter assembly in fluid communication between the first filter assembly and the electrolyzer, the filtrate from the first filter assembly flowable into the second filter assembly, the second filter assembly electrically energizable to remove ionics from the filtrate to form purified water flowable to the anode of the electrolyzer. 
     In another embodiment, a method comprises providing purified water from an electrically energizable filter assembly to a hydrogen production system including an electrolyzer, providing power from a power source to the electrolyzer to electrolyze the purified water in the electrolyzer to generate hydrogen, storing at least a portion of the generated hydrogen in a hydrogen inventory, monitoring power availability from the power source, determining a power requirement for the hydrogen production system, comparing the power requirement of the hydrogen production system to the power availability from the power source, and if the power requirement is less than the power availability, then generating power by a generator fueled by hydrogen from the hydrogen inventory, and providing the generated power to the electrolyzer to continue to generate the hydrogen. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1A  is a block diagram of a system of a first embodiment for water treatment for hydrogen production, with the system including a first filtration system and a second filtration fed to an electrolyzer operable to form hydrogen. 
         FIG. 1B  is a schematic representation of the second filtration system of  FIG. 1A . 
         FIG. 1C  is a schematic representation of the electrolyzer of the system of  FIG. 1A , with the electrolyzer including a proton exchange membrane (PEM) between an anode and a cathode. 
         FIG. 1D  is a schematic representation of an ammonia synthesis reactor of the system of  FIG. 1A , with the ammonia synthesis reactor including a synthesis cell activatable to form ammonia from hydrogen and nitrogen. 
         FIG. 1E  is a schematic representation of an electrochemical cell of a hydrogen pump of the system of  FIG. 1A . 
         FIG. 2A  is a block diagram of a system of a second embodiment for water treatment for hydrogen production, with the system including a hydrogen inventory and a generator operable with hydrogen inventory to provide an uninterruptible power supply for the system of water. 
         FIG. 2B  is a block diagram of a power distribution of the system of  FIG. 2A . 
         FIG. 3  is a flowchart of an exemplary method for providing uninterruptible power to a system of water treatment for hydrogen production. 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     The embodiments will now be described more fully hereinafter with reference to the accompanying figures, in which exemplary embodiments are shown. The foregoing may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. All fluid flows may flow through conduits (e.g., pipes and/or manifolds) unless specified otherwise. 
     All documents mentioned herein are hereby incorporated by reference in their entirety. References to items in the singular should be understood to include items in the plural, and vice versa, unless explicitly stated otherwise or clear from the text. Grammatical conjunctions are intended to express any and all disjunctive and conjunctive combinations of conjoined clauses, sentences, words, and the like, unless otherwise stated or clear from the context. Thus, the term “or” should generally be understood to mean “and/or,” and the term “and” should generally be understood to mean “and/or.” 
     Recitation of ranges of values herein are not intended to be limiting, referring instead individually to any and all values falling within the range, unless otherwise indicated herein, and each separate value within such a range is incorporated into the specification as if it were individually recited herein. The words “about,” “approximately,” or the like, when accompanying a numerical value, are to be construed as including any deviation as would be appreciated by one of ordinary skill in the art to operate satisfactorily for an intended purpose. Ranges of values and/or numeric values are provided herein as examples only, and do not constitute a limitation on the scope of the described embodiments. The use of any and all examples or exemplary language (“e.g.,” “such as,” or the like) is intended merely to better illuminate the embodiments and does not pose a limitation on the scope of those embodiments. No language in the specification should be construed as indicating any unclaimed element as essential to the practice of the disclosed embodiments. 
     Co-locating hydrogen production with its ultimate industrial use is challenging in resource constrained areas. In particular, the infrastructure for purified water in such areas is typically insufficient or unreliable for producing cost-effective quantities of hydrogen, and the electrical infrastructure for powering water treatment is often similarly limited. Accordingly, there remains a need for reliable water treatment that can produce purified water in quantities compatible with large-scale hydrogen production while being robust with respect to interruptions in access to raw water and/or power used in the purification process. In the description that follows, various aspects of water treatment systems and methods for hydrogen production are described in the context of ammonia production, as ammonia production is a common use for hydrogen and offers certain synergies with respect to the various different systems and methods described herein. It shall be appreciated, however, that this is for the sake of explanation of certain features of the systems and methods described herein and should not be considered limiting. That is, unless otherwise specified or made clear from the context, it shall be understood that any one or more of the various different systems and methods described herein may be compatible with any one or more hydrogen end-use applications. By way of example and not limitation, such hydrogen end-use applications may include use in a forming gas for a reducing environment, as described in U.S. patent application Ser. No. 17/122,813, filed on Dec. 15, 2020, entitled “SYSTEMS AND METHODS OF ELECTROCHEMICAL HYDROGEN GENERATION TO PROVIDE A REDUCING AMBIENT FOR INDUSTRIAL FABRICATION” by Ballantine et al., the entire contents of which are incorporated herein by reference. 
     As used herein, the term “raw water” shall be understood to include water of quality unsuitable for prolonged operation in an electrochemical electrolyzer operated to form hydrogen. Thus, for example, raw water may include water that has been contaminated by human use (commonly referred to as wastewater), some examples of which include water used in domestic, commercial, and/or industrial settings. Further or instead, wastewater may include stormwater and/or sewer inflow. In some cases, raw water may include city water, water from atmospheric condensation, or a combination thereof. In some cases, raw water may include water from a natural body of water, such as a nearby lake, river, or ocean. Thus, raw water may be fresh water or seawater. Unless otherwise specified or made clear from the context, it shall be understood that any one or more of the various systems and methods described herein may facilitate treating any or more of the foregoing examples of raw water to form purified water. In one sense, as used herein the term “purified water” may be understood in relative terms, as may be useful in discussing of any one or more aspects of the overall filtration process. For example, purified water may include water of any quality, provided that such water has a lower concentration of total solids (e.g., suspended and/or dissolved solids), a lower concentration of organics (e.g., microbiologics, such as bacteria, etc.) and/or lower concentration of at least one ionic contaminant as compared to the raw water used as the starting material in a given overall filtration process (which may have multiple stages). In another sense, as used herein, the term “purified water” may be understood in absolute terms, as may be useful in discussing any one or more aspects of electrolyzers, hydrogen pumps, fuel cells, etc. that may be sensitive to water quality. Thus, for example, purified water may include water of any quality compatible with operation of an electrochemical cell as an electrolyzer over a prolonged period of time (e.g., greater than about 12 hours) without interruption. 
     Referring now to  FIGS. 1A-1E , a system  100  may include a water source  102 , a first filter assembly  104 , a second filter assembly  106 , and an electrolyzer  108 . The water source  102  (e.g., a raw water reservoir and/or pipe) may be in fluid communication with the first filter assembly  104  via a raw water conduit  110 . The second filter assembly  106  may be in fluid communication between the first filter assembly  104  and the electrolyzer  108 . For example, the second filter assembly  106  may receive a filtrate from the first filter assembly  104  via a filtrate conduit  112 , and the electrolyzer  108  may receive purified water from the second filter assembly  106  via a purified water conduit  114 . For example, the first filter assembly  104  may generally remove solids from the raw water to form the filtrate flowable to the second filter assembly  106  via filtrate conduit  112 . Additionally, or alternatively, the second filter assembly  106  may include one or more components that are electrically energizable to remove ionics (i.e., ionic impurities and/or contaminants, such as cations (e.g., metal ions) and/or anions (e.g., chlorite ions, bromate ions, arsenate ions, etc.)) from the filtrate to form the purified water flowable to the electrolyzer  108  via the purified water conduit  114 . The electrolyzer  108  may receive power from a power source  115  to electrolyze water to hydrogen. As described in greater detail below, water filtration carried out by the first filter assembly  104  and the second filter assembly  106  may be tightly integrated with hydrogen production carried out using the electrolyzer  108  such that the system  100  is robust with respect to interruptions in a supply of raw water from the water source  102 . Further, or instead, as also described in greater detail below, integration between the first filter assembly  104  and the second filter assembly  106  may be robust with respect to interruptions in a supply of power to the electrolyzer  108  from the power source  115 . Among other things, such robustness may facilitate sourcing power for the power source  115  from one or more sources of renewable energy to produce industrial quantities of hydrogen cost-effectively while being environmentally responsible. 
     In general, the first filter assembly  104  may include any one or more of various different types of equipment for removing solids from raw water received from the water source  102 . For example, the first filter assembly  104  may include filter media  116 . As raw water passes through the filter media  116  solids in the raw water may be physically separated from the water by restrictions in the filter media  116 . As an example, the filter media  116  may include a sand bed, as may be useful in instances in which the composition of the raw water at a given installation may be prone to varying over time. Further or instead, the filter media  116  may include a specifically designed filter useful for removing solids with specific characteristics associated with a known source of raw water. In some instances, the filter media  116  may be reusable through washing and/or regeneration. However, in some cases, the filter media  116  may be disposable to reduce the amount of skilled labor required to operate the system  100 . In addition to, or instead of, the use of filtration to remove solid particles, the first filter assembly  104  may carry out any one or more of various different other techniques for separating solids from the raw water. Examples of such techniques include, but are not limited to, sedimentation, dissolved air flotation, coagulation for flocculation, coagulant aids, or combinations thereof. 
     In some instances, the first filter assembly  104  may be passive such that the flow of raw water through the first filter assembly  104  is generally throttled only by pressure drop the first filter assembly  104 . Such a configuration may be useful, for example, for operating the first filter assembly  104  without the use of external power. In installations in which power interruptions are frequent and/or of long duration, operating the first filter assembly  104  without the use of power may be useful with respect to the overall power budget of the system  100 . 
     While operating the first filter assembly  104  without the use of power may have certain advantages in some installations, it shall be appreciated that the first filter assembly  104  may be advantageously include one or more aspects of active control by electronically activated equipment in some cases. For example, the first filter assembly  104  may include one or more valves  118  electrically actuatable to control (e.g., interrupt, reduce and/or increase) the flow of raw water through the first filter assembly  104  and, thus, to downstream components. Such control of the flow may be useful for, among other things, interrupting the flow of water to replace and/or regenerate the filter media  116  without interrupting operation of the electrolyzer  108 , as described in greater detail below. The remaining residue (i.e., water with contaminants) may be recycled via the recycling conduit  119  from the first filter assembly  104  and/or the second filter assembly  106  back into the water source  102  or the raw water conduit  110 , or it may be discarded. 
     In general, the second filter assembly  106  may include any one or more of various different types of filtration equipment electrically energizable to remove ionics from the filtrate received into the second filter assembly  106  via the filtrate conduit  112 . As used in this context, electrically energizable may include electrochemical removal of ionics, electrical actuation of pressure-driven processes, or combinations thereof. Thus, for example, as shown in  FIG. 1B , the second filter assembly  106  may include an electrodialysis cell  120  electrically actuatable to remove salts from the filtrate. As another example, the second filter assembly  106  may include an electrooxidation cell  122 , which may be electrically actuated to remove contaminants, such as industrial effluents, that may be present in the filtrate. Further, or instead, the second filter assembly  106  may include a reverse osmosis reactor  124 , in which electrical actuation may include moving a piston to apply pressure to the filtrate until the pressure applied to the filtrate is sufficient to overcome osmotic pressure and move the filtrate through a permeable membrane. The contaminants removed by reverse osmosis reactor  124  may depend, for example, on the permeability of the membrane, with salts and biological material being removable in some cases. 
     The treatment of the filtrate flowing through the filtrate conduit  112  is shown as occurring in a particular order in  FIG. 1B , with the electrodialysis cell  120  followed by the electrooxidation cell  122  followed by the reverse osmosis reactor  124 . However, it shall be appreciated that this is for the sake of clear and efficient description and the order of processing in the second filter assembly  106  may occur in any order, and need not be sequential, as may be useful for achieving reduction in concentration of ionics in the filtrate while making efficient use of the energy used to electrically energize the second filter assembly  106 . More generally, it shall be appreciated that the second filter assembly  106  may accommodate reduction in ionics in the filtrate formed from any sources of raw water available to be used by the system  100  while achieving such reduction within a power budget afforded by other equipment of the system  100  also directly, or indirectly, being powered by the power source  115 . 
     Filtration effectiveness of one or more portions of the second filter assembly  106  may degrade over time as ionics are removed from the filtrate to produce purified water. In some cases, such as in the case of the reverse osmosis reactor  124 , performance may be restored by replacing the permeable membrane, for example. In the case of electrochemical removal components of the second filter assembly  106 , electricity may be advantageously used to recover filtration effectiveness without the need to access or otherwise disturb the installation of the given component. As an example, the electrodialysis cell  120  may be flushed with purified water. With potential to electrodes of the electrodialysis cell  120  reversed, such flushing with purified water may drive accumulated impurities off of the electrode during a maintenance procedure. Performance of the electrooxidation cell  122  may be similarly recovered through reversal of polarity of electrodes while the electrooxidation cell  122  is flushed with purified water. 
     While all of the purified water formed by the second filter assembly  106  may flow from the second filter assembly  106  to the electrolyzer  108 , it may be useful to divert at least a portion of the purified water into a supplemental water conduit  128  and into a water inventory  126  for any one or more of various different reasons. For example, in some cases, a control valve  129 A may be selectively actuatable based on a state of flow of purified water from the second filter assembly  106 . For example, under normal operating conditions, the control valve  129 A may be actuated to divert purified water to the water inventory  126 . Additionally, or alternatively, returning to the example of flushing discussed above, the control valve  129 A may be selectively actuatable to direct purified water from the water inventory  126  to the second filter assembly  106 . 
     In some cases, the water inventory  126  may serve as a backup source of purified water in the event that filtration of raw water from the water source  102  is interrupted or wanes as a result of corresponding interruptions and/or fluctuations of the raw water of the water source  102 , energy produced by the power source  115 , cleaning or repair of the first or second filter assemblies, or a combination thereof. That is, in the event of an interruption to the flow of purified water from the second filter assembly  106  for any reason, the control valve  129 A may be selectively actuatable to direct the purified water stored in water inventory  126  (e.g., in the excess pure water module (e.g., water storage vessel)  130 ) to the electrolyzer  108  to sustain uninterrupted operation of the electrolyzer  108  for a period of time until the supply of raw water from the water source  102  and/or electricity from the power source  115 , as the case may, returns to a level sufficient to support filtration of purified water. Given this robustness with respect to intermittency, the water inventory  126  may facilitate including renewable photovoltaic and/or wind power sources in the power source  115 . That is, continuing with this example, these intermittent power sources may be used to power at least the second filter assembly  106  directly (e.g., with little or no battery) such that purified water is directed to the water inventory  126  when renewable power is available. When such renewable power is unavailable or in the event of a power outage in cases of energy source from the grid, the purified water in the water inventory  126  may be used as a source of purified water for the electrolyzer  108 , ammonia synthesis, or other consumer use (e.g., drinking or cooking). In certain instances, the water inventory  126  may additionally, or alternatively, include a heated water module (e.g., a heated and/or thermally insulated water storage vessel)  132 . The heated water module  132  is supplied with purified water heated by the electrolyzer  108  through a heated water conduit  131 . The flow of heated water through the heated water conduit  131  may be controlled by another selectively actuatable control valve  129 B. Such water may be useful, for example, for certain consumer uses. 
     In general, the electrolyzer  108  may include at least one instance of an electrochemical cell shown in  FIG. 1C . For example, the electrolyzer  108  may include an anode  134 , a cathode  136 , and a medium  138  therebetween. The medium  138  may include any one or more of various different proton exchange media (e.g., electrolyte) and, in particular, may include a polymer proton exchange membrane (PEM). Purified water introduced into the electrolyzer  108  via the purified water conduit  114  may flow along the anode  134 . Electricity input from the power source  115  (e.g., directly and/or via a battery) may be coupled to the anode  134  and the cathode  136  to form an electric field across the medium  138 . The purified water may be separated into oxygen and pressurized hydrogen in the presence of the electric field across the medium  138 . More specifically, oxygen may be formed along the anode  134 , and pressurized hydrogen may be formed along the cathode  136  as protons move through the medium  138  and recombine into molecular hydrogen along the cathode  136 . Thus, the cathode  136  may be in fluid communication with any one or more of various different downstream applications, via a hydrogen conduit  140  shown in  FIG. 1A , such that the pressurized hydrogen formed from only water and electricity may be delivered to the downstream application on a continuous basis. As described in greater detail below, in instances in which the system  100  is used to provide hydrogen for ammonia synthesis, at least a portion flowing along the hydrogen conduit  140  may flow to an ammonia synthesis reactor  150  shown in  FIG. 1A . 
     To facilitate forming purified water through efficient use of energy, the system  100  may include a first oxygen conduit  142  in fluid communication between the electrolyzer  108  and the water source  102 . Continuing with this example, the oxygen-enriched water flowing along the anode  134  of the electrolyzer  108  may flow to the water source  102  (and/or to the raw water conduit  110 ) via the first oxygen conduit  142 . This oxygen-enriched water may be useful in the water source  102  to enhance bacterial water clean-up. Under otherwise identical conditions, this may reduce one or more filtration demands on the first filter assembly  104  and/or the second filter assembly  106  and, in some cases, may reduce the power consumption associated with filtration to form purified water. 
     Having described certain aspects of the system  100  for treating water for hydrogen production, attention is now directed to certain additional or alternative features of the system  100  that may be useful for, among other things, achieving suitable control over various different aspects of coordination of processes carried out by the system  100 , making beneficial use of the hydrogen produced, and/or reducing the likelihood of premature degradation of elements of the system  100 . 
     In some instances, the system  100  may include a controller  144  including a processing unit  146  and a non-transitory, computer-readable storage medium  148  having stored thereon computer-readable instructions for causing the processing unit  146  to carry out any one or more of the various different techniques described herein. For example, returning to the discussion of the water inventory  126  above, the controller  144  may control the selective actuation of the control valves  129 A and/or  129 B to direct purified water into and out of the water inventory  126  as useful for increasing the likelihood of sustaining hydrogen production during interruption of one or both of raw water and/or power. As described in greater detail below, operation of the controller  144  and other electrically powered aspects of the system  100  may be sustained through the use of a back-up power source such as a battery and/or a generator fueled with hydrogen from a hydrogen inventory. 
     In certain instances, the system  100  may include an ammonia synthesis reactor  150  and a nitrogen source  152 . The ammonia synthesis reactor  150  may receive hydrogen via the hydrogen conduit  140 . The ammonia synthesis reactor  150  may be in fluid communication with the electrolyzer  108  and the nitrogen source  152 . In particular, the nitrogen source  152  may produce nitrogen that is flowable to the ammonia synthesis reactor  150  via a nitrogen conduit  154 . With these hydrogen and nitrogen inputs and power from the power source  115 , the ammonia synthesis reactor  150  may form ammonia. For example, the ammonia synthesis reactor  150  may form ammonia through electrochemical synthesis, such as described in U.S. patent application Ser. No. 17/101,224, filed on Nov. 23, 2020, entitled “SYSTEMS AND METHODS OF AMMONIA SYNTHESIS,” by Ballantine et al., the entire contents of which are incorporated herein by reference. 
     In certain instances, the ammonia synthesis reactor  150  may include an electrochemical cell, such as a synthesis cell  155  (e.g., a proton-exchange membrane (“PEM”) cell) operable for electrochemical synthesis of ammonia from hydrogen and nitrogen. The synthesis cell  155  may include an anode  156 , a cathode  157 , and a medium (e.g., electrolyte)  158 , as shown in  FIG. 1D . The medium  158  may be disposed between the anode  156  and the cathode  157  and, for example, may be ionically conductive to protons. As a more specific example, the medium  158  may be a proton-exchange membrane electrolyte. Additionally, or alternatively, the synthesis cell  155  may receive power from the power source  115  connected to the anode  156  and to the cathode  157  to create an electric field in the medium  158  disposed between the anode  156  and the cathode  157  (to apply a voltage between the anode  156  and the cathode  157 ). 
     The hydrogen introduced into the ammonia synthesis reactor may flow over the anode  156 , where the hydrogen may break down into protons according to the following reaction: 
       3H 2 →6H + +6 e   − 
 
     In turn, under the electric field provided by the power source  115 , the protons may flow from the anode  156  to the cathode  157  through the medium  158 . The nitrogen introduced into the ammonia synthesis reactor  150  may flow over the cathode  157 , where the nitrogen may react with the protons to form ammonia according to the following reaction: 
       N 2 +6H + +6 e   − →2NH 3  
 
     While the ammonia synthesis reactor  150  has been described as including a single instance of the synthesis cell  155 , it shall be appreciated that this is for the sake of clarity and efficient description. More specifically, the ammonia synthesis reactor  150  may include additional instances of the synthesis cell  155  (e.g., as part of an electrochemical stack) without departing from the scope of the present disclosure. The number of additional instances of the synthesis cell  155  may depend, for example, on desired ammonia output from the system  100 . While the ammonia synthesis reactor  150  has been described as including an electrochemical cell, it shall be appreciated that the ammonia synthesis reactor  150  may include a catalyst (e.g., a catalyst operated in a Haber-Bosch processes) or a plasma-driven reactor. 
     The nitrogen source  152  may include a pressure swing adsorber that separates nitrogen from air using pressure swing adsorption, producing nitrogen-depleted air as a byproduct. In some instances, the nitrogen source  152  may be in fluid communication with the water source  102  to direct nitrogen-depleted air to the water source  102  (e.g., via a second oxygen conduit  159 ). This nitrogen-depleted—and thus oxygen enriched—air may enhance bacterial cleanup of the raw water in the water source  102 . 
     In some implementations, the system  100  may include a hydrogen pump  160 . Operation of the hydrogen pump  160  may, for example, re-establish humidification conditions of the medium  138  of the electrolyzer  108  in instances in which the medium  138  includes a proton exchange membrane. For example, the hydrogen pump  160  may be operable (e.g., via control by the controller  144 ) to pump hydrogen from the anode  134  to the cathode  136 , cathode  136  to anode  134 , or both in a sequence of fully humidified volumes. 
     In certain implementations, the hydrogen pump  160  may be an electrochemical membrane hydrogen pump which includes at least one instance of an electrochemical cell  161 , as shown in  FIG. 1E . For the sake of clarity of illustration and description, a single instance of the electrochemical cell  161  is shown. However, it shall be appreciated that the hydrogen pump  160  may include additional electrochemical cells in other instances, without departing from the scope of the present disclosure. The total number of electrochemical cells in the hydrogen pump  160  may be influenced by, among other considerations, the pressure required to move hydrogen from the hydrogen conduit  140 , via the recirculation circuit  162 . 
     The electrochemical cell  161  may include a proton exchange membrane  163 , an anode  164 , and a cathode  165 . For example, the proton exchange membrane  163  may be disposed between the anode  164  and the cathode  165 . Electrical power may be delivered to the anode  164  and the cathode  165  by the power source  115  to provide a positive charge along the anode  164  and a negative charge along the cathode  165 . The resulting electrical field may result in a higher pressure concentrated along the cathode  165  than along the anode  164 . As an example, at the anode  164 , lower pressure hydrogen may separate into protons and electrons, and the electrical field may drive protons across the proton exchange membrane  163  to the cathode  165 . Continuing with this example, the protons may recombine at the cathode  165  to form hydrogen at a higher pressure. As may be appreciated from the foregoing, sequential pumping of hydrogen may be repeated using as many instances of the electrochemical cell  161  as necessary or desirable to remove hydrogen from the hydrogen conduit  140  and electrochemically pump the removed hydrogen to a target pressure for reintroduction back into the electrolyzer  108 . 
     Having described various aspects of the system  100  that are electrically powered by the power source  115 , attention is now directed to certain aspects of the power source  115  operable to provide electricity supporting any one or more of the various different aspects of the system  100  described herein. 
     In addition to uninterrupted operation facilitated by various different redundancies with respect to water and power described herein, cost-effective operation of the system  100  may be a function of the power source  115  that provides electricity to various different components of the system  100 . For example, the power source  115  may include multiple types of electricity generators that may be advantageously operated in parallel and/or individually at different times of the day. For example, in certain installations, the power source  115  may include the electrical grid and, even in locations in which the electrical grid is reliable, it may be useful to switch to local sources of electricity to make use of lower-cost electricity. Examples of such local sources include, but are not limited to, one or more of a diesel generator, a natural gas-fired generator, a generator powered by biofuel sources such as bio-methane, an ethanol fired generator, a gasoline fired generator, a propane fired generator, a photovoltaic array, a wind power generator (e.g., one or more wind turbines), a hydroelectric generator or turbine (e.g., tidal or dam type), a geothermal power generator, a thermoelectric power generator, a heat engine (e.g., a turbine, piston engine, or other engine which uses heat and/or fuel as an input), or a fuel cell power generator. 
     As may be appreciated from these foregoing examples, the power source  115  may include local sources that are nominally continuous and/or intermittent. Thus, in the case of intermittent electricity availability from a local source such as a photovoltaic array or a wind turbine, the power source  115  may preferentially be the local source when power from the local source is available without separate storage. Additionally, or alternatively, the system  100  may include a battery, as described in greater detail below, in electrical communication with the power source  115  and at least the second filter assembly  106  and the electrolyzer  108  of the system  100 , such as may be useful for managing variations in power from one or more intermittent power sources by storing excess power from the local source when the excess power is available (e.g., during daytime from a photovoltaic array or during windy periods from a wind turbine) and then releasing it to the plurality of cores when the excess power is not available (e.g., during nighttime or during windless periods). As another example, in certain locations, the electrical grid may be unreliable or nonexistent such that the power source  115  primarily or exclusively includes any one or more of various different local sources, such as those listed above. 
     As may be appreciated from the foregoing, the power source  115  may be intermittent as a result of the mix of local power generation sources that make up the power source  115 , resource constraints in the vicinity of the system  100 , or a combination thereof. Accordingly, attention is now directed to certain aspects of systems and methods that may facilitate uninterrupted operation of certain functions of the system and, in particular, may be useful for the cost-effective production of hydrogen using one or more renewable energy sources that may be prone to intermittency. For the sake of clear and efficient description, elements having numbers with the same last two digits shall be should be understood to be analogous to or interchangeable with one another, unless otherwise explicitly made clear from the context and, therefore, are not described separately from one another, except to note differences or emphasize certain features. Thus, for example, the electrolyzer  108  of  FIGS. 1A and 1C  shall be understood to be analogous to the electrolyzer  208  of  FIGS. 2A and 2B , unless otherwise indicated or made clear from the context. 
     Referring now to  FIGS. 2A and 2B , a system  200  may include a water source  202 , a first filter assembly  204 , a second filter assembly  206 , and an electrolyzer  208 . Raw water in the water source  202  may be formed into purified water delivered to the electrolyzer  208  according to any one or more of the various different techniques described herein. Further, or instead, the system  200  may include a water inventory  226  operable in a manner analogous to the water inventory  126  discussed above with respect to  FIG. 1A  to facilitate sustaining hydrogen production through interruptions in a supply of raw water. 
     In certain implementations, the system  200  may include a hydrogen inventory  266  and a generator  267 . The hydrogen inventory  266  may be a hydrogen storage vessel, such as at least one gas storage tank or cylinder. In general, the hydrogen inventory  266  may be in fluid communication with the electrolyzer  208  to receive hydrogen from the electrolyzer  208 . For example, a first hydrogen valve  268  may be selectively actuatable (e.g., by a controller  244  including a processing unit  246  and a non-transitory computer-readable storage medium  248 ) to direct at least a portion of the hydrogen flowing from the electrolyzer  208  to the hydrogen inventory  266  via a first hydrogen supply conduit  269 . For example, during normal operation, the first hydrogen valve  268  may be controlled to direct a portion of the hydrogen from the electrolyzer  208  to the hydrogen inventory  266 , with the remainder of the hydrogen moving along a hydrogen conduit  240  to be used according to any one or more of various different end-uses described herein. Additionally, or alternatively, the first hydrogen valve  268  may be selectively actuatable to stop the flow of hydrogen to the hydrogen inventory  266  in the event of an interruption of electricity from a power source  215  providing electricity to various different aspects of the system  100  during normal operation. That is, during an interruption of power from the power source  215 , the first hydrogen valve  268  may be actuated to direct all of the hydrogen produced by the electrolyzer  208  to an end-use application to reduce the likelihood of interrupting hydrogen production in a way that might cascade to the end-use of the hydrogen. Additionally, or alternatively, in the event of interruption of electricity from the power source  215 , fluid communication between the hydrogen inventory  266  and the generator  267  may be established along a second hydrogen supply conduit  270  via selective actuation of a second hydrogen supply valve  271 . 
     With fluid communication established between the hydrogen inventory  266  and the generator  267  when power from the power source  215  is interrupted, the generator  267  may operate on hydrogen from the hydrogen inventory  266  to provide power to sustain operation of at least one of the first filter assembly  204 , the second filter assembly  206 , or the electrolyzer  208 . For example, in certain implementations, the generator  267  may sustain operation of the first filter assembly  204  and the second filter assembly  206  to continue producing purified water that may be used by the system  200 . Additionally, or alternatively, the generator  267  may power the electrolyzer  208  to allow the electrolyzer  208  to continue making hydrogen while power from the power source  215  is interrupted. In some cases, the electrolyzer  208  may continue to produce hydrogen using purified water from the water inventory  226 . Further, or instead, the electrolyzer  208  may continue to produce hydrogen using purified water as it is being produced by the second filter assembly  206 . 
     In general, the generator  267  may be any one or more of various different energy sources operable to produce electricity from hydrogen. Thus, in some instances, the generator  267  may include an internal combustion engine. Further, or instead, the generator  267  may include a fuel cell (e.g., a proton exchange membrane fuel cell). In such instances, a water supply line  272  may couple the water inventory  226  in fluid communication with the generator  267  such that water from the water inventory  226  may be delivered to the generator  267 . While the generator  267  may be sized to provide power for at least water purification and/or hydrogen production via electrolysis, it shall be appreciated that the generator  267  may be sized to support operation of one or more other types of equipment (e.g., ammonia synthesis) during power interruption to reduce the likelihood of cascading interruptions of downstream processes. 
     In some cases, the system  200  may further include a battery  273  in electrical communication with the generator  267 , which may be useful for providing energy storage providing a buffer for operation of equipment that may have surges in demand. Additionally, or alternatively, to the extent the power source  215  includes DC renewable power sources, the battery  273  may be in electrical communication with the power source  215 , as described in greater detail below with respect to  FIG. 2B . 
       FIG. 3  is a flow chart of an exemplary method  390  for providing uninterruptible power to a system of water treatment for hydrogen production. Unless otherwise specified or made clear from the context, the exemplary method  390  may be implemented using any one or more of the various different systems, and components thereof, described herein. Thus, for example, the exemplary method  390  may be implemented as computer-readable instructions stored on the non-transitory computer-readable storage medium  248  and executable by the processing unit  246  of the controller  244  to operate the system  200 , as shown in  FIG. 2A . 
     As shown in step  391 , the exemplary method  390  may include monitoring power availability from a power source. Such monitoring may include, for example, monitoring power availability from the power source in real-time, such as through measurement of voltage and/or current at one or more points in the power source. As a specific example, monitoring power availability from the power source may include detecting an outage as the outage occurs, such as may be achievable using one or more switches and/or sensors. In some cases, monitoring may further or instead include predictions of power availability, such as based on past fluctuations and/or environmental conditions known to impact power generation by the power source. 
     As shown in step  392 , the exemplary method  390  may include determining a power requirement for a hydrogen system, such as any one or more of the various different hydrogen production systems described herein. Thus, in particular, the hydrogen production system may include at least an electrolyzer receiving purified water from an electrically energizable filter assembly. 
     As shown in step  393 , the exemplary method  390  may include comparing the power requirement of the hydrogen production system to power availability from the power source. In general, this comparison may serve as a basis for whether or not to use a hydrogen fueled generator and/or the battery as a power supply to sustain operation of the hydrogen production. The hydrogen fueled generator may include, for example, the generator  267  in  FIG. 2A  and thus may be a generator fueled by hydrogen output from an electrolyzer (e.g., hydrogen stored in a hydrogen inventory). Further, or instead, the hydrogen fueled generator may be operable to convert hydrogen into power for operation of the electrolyzer. 
     As shown in step  395 , the exemplary method  390  may include generating power at the generator if the power available from the power source is less than the power required for operation of the hydrogen production system to produce hydrogen (with a margin of safety applicable in some instances). Additionally, or alternatively, generating power at the generator may include controlling a flow of hydrogen into a hydrogen inventory from the electrolyzer and out of the hydrogen inventory to the generator. As a specific example, such control may include interrupting flow of hydrogen into the hydrogen inventory from the electrolyzer while establishing a flow of hydrogen out of the hydrogen inventory to the generator. That is, all of the hydrogen produced by the system while the generator is operable may be directed out of the system, thus reducing the likelihood that hydrogen demands of the end-use application will not be met. 
     In instances in which the generator includes a fuel cell power generator, generating power at the generator may include controlling a flow of purified water from the electrically energizable filter assembly into a water inventory and controlling the flow of purified water from the water inventory to the generator. In particular, such control may include interrupting a flow of purified water from the electrically energizable filter assembly into the water inventory while establishing a flow of purified water from the water inventory to the generator. 
     As shown in step  396 , the exemplary method  390  may checking whether a shutdown condition is appropriate and shutting down if so. Otherwise, the exemplary method  390  may continue to repeat any one or more of the steps described above as part of a continuing monitoring process useful for reducing the likelihood of disruption to a hydrogen production process in the event of intermittent availability of electricity. 
     Having described various aspects of systems and methods useful for avoiding or mitigating disruptions in one or both of water or electricity inputs to hydrogen production, attention is now directed to certain aspects of power distribution that are useful in any one or more of the various different systems described herein. 
     Referring again to  FIG. 2B , the system  200  may include a common directed current (DC) bus  274  (e.g., a 400 V bus or another suitable voltage bus) in electrical communication with power electronics  275  (e.g., fully isolated such that ground faults do not result in ground faults in the rest of the plant), such as may be useful for integrating power electronics of the second filter assembly  206  and the electrolyzer  208 . In instances in which the second filter assembly  206  and the electrolyzer  208  operate on the same DC voltage, the power electronics  275  may be a single integrated unit (e.g., a single DC/DC converter). In instances in which the second filter assembly  206  and the electrolyzer  208  operate on a different DC voltages, the power electronics  275  may include plural DC/DC converters 
     In some instances, the power electronics  275  may be useful for diagnosing degradation of second filter assembly  206 , the electrolyzer  208 , or a combination thereof. For example, the power electronics  275  may include impedance monitoring of electrochemical cells of the second filter assembly  206  and/or the electrolyzer  208  to trigger reductions in current and/or promote achieving long component life (e.g., by triggering one or more recovery processes such as reversal of polarity along the common DC bus  274  through actuation by the controller  244 ). For example, the power electronics  275  may be operable to generate ripple current for impedance measurement and to monitor impedance of the electrolyzer  208 . The power electronics  275  and the controller  244  which controls the power electronics  275  may be able to then conduct fast Fourier transform analysis to derive the frequency and amplitude of component impedance values. 
     Other equipment used to operate the system  200  may be coupled to the common DC bus  274  to receive power. For example, in some cases, pump equipment  276  used for balance of plant pumping and compression may be coupled to the common DC bus  274 . For example, the pump equipment  276  may comprise fluid pumps, fans and/or blowers which operate on alternating current (AC). In this configuration, the pump equipment  276  may be connected to the common DC bus  274  via one or more DC/AC inverters  282 . 
     The power source  215 , the battery  273 , and the generator  267  may each be electrically coupled to the input side of the common DC bus  274  and to one another. For example, the power source  215  may include one or more of an AC grid power source  277 , an AC renewable power source  278  (e.g. a wind turbine), and/or a DC renewable power source  279  (e.g., a photovoltaic array). In instances, in which the power source  215  includes the DC renewable power source  279 , the generator  267  and the DC renewable power source  279  may each be in electrical communication with the battery  273  and with a DC/DC converter  280  such that each source of power may be directed to the battery  273  and/or to the common DC bus  274  as needed to meet power demands. The AC grid power source  277  and the AC renewable power source  278  (e.g. a wind turbine) may be electrically connected to the common DC bus  274  through one or more additional AC/DC inverters  281 . 
     In certain implementations, the controller  244  may be configured to auctioneer power at the common DC bus  274  to direct available power proportionally at least to the second filter assembly  206  and the electrolyzer  208 . This may facilitate optimal plant operation within the budget of available power. Further, or instead, the controller  244  may allocate power for water purification flushing and other periodic plant activities and accommodate such power allocation by cutting back power to the electrolyzer  208 . 
     The above systems, devices, methods, processes, and the like may be realized in hardware, software, or any combination of these suitable for the control, data acquisition, and data processing described herein. This includes realization in one or more microprocessors, microcontrollers, embedded microcontrollers, programmable digital signal processors or other programmable devices or processing circuitry, along with internal and/or external memory. This may also, or instead, include one or more application specific integrated circuits, programmable gate arrays, programmable array logic components, or any other device or devices that may be configured to process electronic signals. It will further be appreciated that a realization of the processes or devices described above may include computer-executable code created using a structured programming language such as C, an object oriented programming language such as C++, or any other high-level or low-level programming language (including assembly languages, hardware description languages, and database programming languages and technologies) that may be stored, compiled or interpreted to run on one of the above devices, as well as heterogeneous combinations of processors, processor architectures, or combinations of different hardware and software. At the same time, processing may be distributed across devices such as the various systems described above, or all of the functionality may be integrated into a dedicated, standalone device. All such permutations and combinations are intended to fall within the scope of the present disclosure. 
     Embodiments disclosed herein may include computer program products comprising computer-executable code or computer-usable code that, when executing on one or more computing devices, performs any and/or all of the steps of the control systems described above. The code may be stored in a non-transitory fashion in a computer memory, which may be a memory from which the program executes (such as random access memory associated with a processor), or a storage device such as a disk drive, flash memory or any other optical, electromagnetic, magnetic, infrared or other device or combination of devices. In another aspect, any of the control systems described above may be embodied in any suitable transmission or propagation medium carrying computer-executable code and/or any inputs or outputs from same. 
     The method steps of the implementations described herein are intended to include any suitable method of causing such method steps to be performed, consistent with the patentability of the following claims, unless a different meaning is expressly provided or otherwise clear from the context. So, for example performing the step of X includes any suitable method for causing another party such as a remote user, a remote processing resource (e.g., a server or cloud computer) or a machine to perform the step of X. Similarly, performing steps X, Y and Z may include any method of directing or controlling any combination of such other individuals or resources to perform steps X, Y and Z to obtain the benefit of such steps. Thus, method steps of the implementations described herein are intended to include any suitable method of causing one or more other parties or entities to perform the steps, consistent with the patentability of the following claims, unless a different meaning is expressly provided or otherwise clear from the context. Such parties or entities need not be under the direction or control of any other party or entity, and need not be located within a particular jurisdiction. 
     It will be appreciated that the methods and systems described above are set forth by way of example and not of limitation. Numerous variations, additions, omissions, and other modifications will be apparent to one of ordinary skill in the art. In addition, the order or presentation of method steps in the description and drawings above is not intended to require this order of performing the recited steps unless a particular order is expressly required or otherwise clear from the context. Thus, while particular embodiments have been shown and described, it will be apparent to those skilled in the art that various changes and modifications in form and details may be made therein without departing from the scope of the disclosure.