Low temperature-steam generator, water electrolysis system, high-surface-area heat exchanger, and related methods

Abstract

A low-temperature steam generator includes a vessel. The vessel includes a gas inlet at a first end of the vessel, a gas outlet at a second end of the vessel, and a high-surface-area packing material within the vessel. The vessel includes at least one water inlet at one or more of the first end of the vessel or along a length of the vessel and at least one temperature region exhibiting a temperature gradient between the gas inlet and the gas outlet. A temperature is relatively lower at the gas inlet and relatively higher at the gas outlet. The low-temperature steam generator also includes a heat source configured to provide heat to the at least one temperature region of the vessel.

Description

[0001] LOW TEMPERATURE-STEAM GENERATOR, WATER ELECTROLYSIS SYSTEM, HIGH-SURFACE-AREA HEAT EXCHANGER, AND RELATED METHODS

[0002] PRIORITY CLAIM

[0003] This application claims the benefit of the filing date of United States Provisional Patent Application Serial No. 63 / 695,241, filed September 16, 2024, for “WATER EVAPORATION SYSTEMS, WATER ELECTROLYSIS SYSTEMS, AND RELATED METHODS,” and claims the benefit of the filing date of United States Provisional Patent Application Serial No. 63 / 831,123, filed June 26, 2025, for “STEAM-ASSISTED HYDROGEN EVAPORATION SYSTEM,” the disclosures of each of which are hereby incorporated herein in their entirety by this reference.

[0004] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0005] This invention was made with government support under Contract Number DE- AC07-05-1D14517 awarded by the United States Department of Energy. The government has certain rights in the invention.

[0006] TECHNICAL FIELD

[0007] This disclosure relates generally to water evaporation devices, water electrolysis systems, and methods of evaporating water.

[0008] Electrolysis systems are used to separate desirable chemical elements from base materials, which are more common chemical compounds that include the elements. For example, hydrogen (H2) may be collected by separating hydrogen from water (H2O). Electrolysis systems separate the base material into different compounds or elements by passing a current through the base material. The current through the base material is induced by a direct current (DC) voltage or potential applied across the electrolysis system.

[0009] Electrolysis may be conducted at ambient temperatures or at elevated temperatures. High-temperature electrolysis (HTE) of water is performed at temperatures ranging from about 700°C to about 1000°C using a solid oxide electrolyzer (SOE). Conventional approaches include using bubbler / humidifiers, boilers, and hot plate vaporizers, which result in inconsistent flow, pressure variations and an inability to exactly control the input feed stream (e.g., fuel stream) to a system. DISCLOSURE

[0010] In one aspect, a low-temperature steam generator includes a vessel. The vessel includes a gas inlet at a first end of the vessel, a gas outlet at a second end of the vessel, and a high-surface-area packing material within the vessel. The vessel includes at least one water inlet at one or more of the first end of the vessel or along a length of the vessel and at least one temperature region exhibiting a temperature gradient between the gas inlet and the gas outlet. A temperature is relatively lower at the gas inlet and relatively higher at the gas outlet. The low-temperature steam generator also includes a heat source configured to provide heat to the at least one temperature region of the vessel.

[0011] In one aspect, a water electrolysis system includes a water evaporator having a vessel. The vessel includes a gas inlet at a first end of the vessel, a gas outlet at a second end of the vessel, a high-surface-area packing material in the vessel, and a water inlet at the first end of the vessel. The water evaporator further includes one or more heaters arranged in heat zones along a length of the vessel. Each of the heat zones is heated to a different temperature. The water electrolysis system also includes an electrochemical cell configured to separate hydrogen and oxygen from a product stream exiting the gas outlet of the vessel.

[0012] In one aspect, a method for evaporating water includes introducing hydrogen gas to a first end of a vessel. The vessel contains a high-surface-area packing material. Water is introduced water to one or more locations along the vessel. The vessel is heated to produce a temperature gradient between the first end of the vessel and a second end of the vessel such that a temperature is relatively lower at the first end and relatively higher at the second end. The hydrogen gas and water are passed through the vessel and water is evaporated. A product stream of the hydrogen gas and the evaporated water is output.

[0013] In one aspect, a high-surface-area heat exchanger includes a vessel. The vessel includes a waste heat steam input configured to receive waste heat steam, a feed input configured to receive hydrogen and liquid water, a waste heat steam outlet configured to release condensation from the waste heat steam, and a feed outlet configured to output a H2 / H2O(g) feed stream created by evaporating the water via heat from the waste heat steam. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] For a detailed understanding of the disclosure, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements have generally been designated with like numerals, and wherein:

[0015] FIG. 1A is a simplified schematic of an evaporator according to embodiments of the disclosure;

[0016] FIG. IB is a perspective view of an exemplary evaporator in accordance with embodiments of the disclosure;

[0017] FIG. 1C is a side view of the exemplary evaporator shown in FIG. IB in accordance with embodiments of the disclosure;

[0018] FIG. 2 is a simplified schematic of a high-temperature electrolysis system according to embodiments of the disclosure;

[0019] FIG. 3 is a side view of a high surface area heat exchanger according to embodiments of the disclosure; and

[0020] FIG. 4 is a simplified schematic of a high-temperature electrolysis system according to embodiments of the disclosure.

[0021] DETAILED DESCRIPTION

[0022] Drawings presented herein are for illustrative purposes only and are not meant to be actual views of any particular material, component, structure, device, or system. Variations from the shapes depicted in the drawings as a result, for example, of manufacturing techniques and / or tolerances, are to be expected. Thus, embodiments described herein are not to be construed as being limited to the particular shapes or regions as illustrated, but include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as box-shaped may have rough and / or nonlinear features, and a region illustrated or described as round may include some rough and / or linear features. Moreover, sharp angles that are illustrated may be rounded, and vice versa. Thus, the regions illustrated in the figures are schematic in nature, and their shapes are not intended to illustrate the precise shape of a region and do not limit the scope of the present claims. The drawings are not necessarily to scale. Additionally, elements common between figures may retain the same numerical designation.

[0023] As used herein, the singular forms following “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term “may” with respect to a material, structure, feature, or method act indicates that such is contemplated for use in implementation of an embodiment of the disclosure, and such term is used in preference to the more restrictive term “is” so as to avoid any implication that other compatible materials, structures, features, and methods usable in combination therewith should or must be excluded.

[0024] As used herein, any relational term, such as “first,” “second,” “top,” “bottom,” “upper,” “lower,” “above,” “beneath,” “side,” “upward,” “downward,” etc., is used for clarity and convenience in understanding the disclosure and accompanying drawings, and does not connote or depend on any specific preference or order, except where the context clearly indicates otherwise. For example, these terms may refer to an orientation of elements of any apparatus or system when utilized in a conventional manner. Furthermore, these terms may refer to an orientation of elements of any apparatus or system as illustrated in the drawings.

[0025] As used herein, the terms “longitudinal,” “vertical,” “lateral,” and “horizontal” are in reference to a major plane of a substrate (e.g., base material, base structure, base construction, etc.) in or on which one or more structures and / or features are formed and are not necessarily defined by Earth’s gravitational field. A “lateral” or “horizontal” direction is a direction that is substantially parallel to the major plane of the substrate, while a “longitudinal” or “vertical” direction is a direction that is substantially perpendicular to the major plane of the substrate. The major plane of the substrate is defined by a surface of the substrate having a relatively large area compared to other surfaces of the substrate. With reference to the figures, a “horizontal” or “lateral” direction may be perpendicular to an indicated “Z” axis, and may be parallel to an indicated “X” axis and / or parallel to an indicated “Y” axis; and a “vertical” or “longitudinal” direction may be parallel to an indicated “Z” axis, may be perpendicular to an indicated “X” axis, and may be perpendicular to an indicated “Y” axis.

[0026] As used herein, the term “substantially” in reference to a given parameter, property, or condition means and includes to a degree that one skilled in the art would understand that the given parameter, property, or condition is met with a small degree of variance, such as within acceptable manufacturing tolerances. By way of example, depending on the particular parameter, property, or condition that is substantially met, the parameter, property, or condition may be at least 90.0% met, at least 95.0% met, at least 99.0% met, or even at least 99.9% met. As used herein, the term “about” or “approximately” in reference to a numerical value for a particular parameter is inclusive of the numerical value and a degree of variance from the numerical value that one of ordinary skill in the art would understand is within acceptable tolerances for the particular parameter. For example, “about” or “approximately” in reference to a numerical value may include additional numerical values within a range of from 90.0 percent to 110.0 percent of the numerical value, such as within a range of from 95.0 percent to 105.0 percent of the numerical value, within a range of from 97.5 percent to 102.5 percent of the numerical value, within a range of from 99.0 percent to 101.0 percent of the numerical value, within a range of from 99.5 percent to 100.5 percent of the numerical value, or within a range of from 99.9 percent to 100.1 percent of the numerical value.

[0027] As used herein, spatially relative terms, such as “beneath,” “below,” “lower,” “bottom,” “above,” “upper,” “top,” “front,” “rear,” “left,” “right,” and the like, may be used for ease of description to describe one element’s or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. Unless otherwise specified, the spatially relative terms are intended to encompass different orientations of the materials in addition to the orientation depicted in the figures. For example, if materials in the figures are inverted, elements described as “below” or “beneath” or “under” or “on bottom of’ other elements or features would then be oriented “above” or “on top of’ the other elements or features. Thus, the term “below” can encompass both an orientation of above and below, depending on the context in which the term is used, which will be evident to one of ordinary skill in the art. The materials may be otherwise oriented (e.g., rotated 90 degrees, inverted, flipped) and the spatially relative descriptors used herein interpreted accordingly.

[0028] Generating a consistent, exact, and stable steam feed stream for use in high- temperature electrolysis systems allows for high efficiencies in HTE. Methods and devices to provide a stable source of steam are desired to replace conventional approaches that use bubblers or humidifiers, boilers, and hot plate vaporizers which result in inconsistent flow, pressure variations, and an inability to precisely control the feed “fuel” stream to a HTE system. Furthermore, approaches for integrating low-temperature waste heat offer opportunities for increased efficiency and lower energy costs of the HTE systems according to embodiments of the disclosure. High-temperature electrolysis systems need a source to provide stable steam. The disclosed device enables lower temperature waste heat to be used to generate the stable, consistent steam feed stream for these HTE systems.

[0029] Methods of producing a hydrogen-steam (Hz / FbOig)) product stream are disclosed. The H2 / H2O(g) product stream may be used as a feed stream in a high-temperature steam electrolysis system. To produce the Eb / FhOfe) product stream, hydrogen is introduced (e.g., fed) at a known rate into a vessel, such as a column (e.g., horizontal or vertical), of an device, which contains a high-surface-area packing material. The vessel may, alternatively, be one or more heat exchangers. The device may, for example, be an evaporator. The vessel may be temperature controlled and exhibits a temperature gradient from a relatively cool inlet to a relatively hot outlet. The temperature gradient may be a continuous gradient or an incremental (e.g., step wise) gradient. Therefore, regions of the vessel may be maintained at different temperatures. Thermal energy may be supplied to the vessel via electric heaters or an embedded heat exchanger with a thermal fluid to achieve the different temperature regions. Water is introduced (e.g., injected) into the vessel at a controlled flow rate at the inlet and / or throughout a bed of the vessel. The water may, thus, be introduced at one or more locations along the bed of the vessel. By controlling the hydrogen and water flow rates through the evaporator, a controlled and defined mass flow rate and ratio of H2 / H2O(g) product stream may be produced via evaporation, rather than via vaporization, at temperatures below about 100°C. This allows thermal energy at a much lower temperature to be used to generate the H2 / H2O(g) product stream, which is used to fuel (e.g., used as a feed stream) the high-temperature steam electrolysis system.

[0030] There are two ways to generate steam. The first is vaporization where water is heated to the boiling temperature using some external energy. Examples of devices used to vaporize water include, but are not limited to, hot plate vaporizers and boilers. An advantage of vaporization is that vaporization is generally mass flow controlled, either in the gas phase or liquid phase. However, vaporization struggles with pressure variations and condensation because the temperature must remain above boiling everywhere in the device. In addition, condensation results in loss of “fuel” (e.g., the feed stream) to the system. Vaporization also uses any external thermal integration to be at temperatures above the boiling temperature of water (i.e., above about 100°C). The second approach is evaporation where a carrier gas is used and is passed over or through water. Examples of devices used to evaporate water include, but are not limited to, humidifiers or bubblers. The advantages of evaporation are that the carrier gas may be humidified at a temperature below the boiling point of water, such as from about 65°C to about 90°C and evaporation tends to exhibit much more stable pressure. Externally supplied thermal energy may also be at a lower temperature. However, evaporation does not directly control mass flow and small deviations in temperature may result in large deviations in mass flow.

[0031] Referring to FIG. 1A, a simplified schematic view of an evaporator 100 (e.g., a low-temperature steam generator) is provided. A vessel 102, such as a column configured to allow passage of fluids therethrough, contains (e.g., is packed with) a high-surface area packing material (not shown). The column may be oriented horizontally or vertically. Liquids may travel through the vessel 102 via surface interactions (e.g., capillary flow, wicking, gravity) in the high-surface-area packing material. Gases are able to travel through interstitial spaces and gaps in the packing material. The high-surface-area packing material may be selected to allow the flow of liquids and gases through the vessel 102. The high-surface-area packing material may, for example, be formulated to allow the flow of water and H2 through the vessel 102.

[0032] At least one gas inlet 104 is provided at a first end 106 of the vessel 102. At least one gas outlet 108 is provided at a second end 110 of the vessel 102. A carrier gas 112 (e.g., H2) may be introduced to the vessel 102 via the gas inlet 104 and exits the vessel 102 via the gas outlet 108. Water 114 may be introduced at controlled, known rates to the vessel 102 via one or more water inlets 115 positioned along the vessel 102. The carrier gas 112 and water 114 introduced to the gas inlet 104 and the water inlets 115 may be mass controlled. While FIG. 1A shows six water inlets 115, fewer or more water inlets 115 may be present.

[0033] A heat source 116 (shown separately from the vessel 102) is coupled to the vessel 102 to heat the contents of the vessel 102 and is configured to form a temperature gradient along the vessel 102 with a relatively lower temperature being at the first end 106 and a relatively higher temperature at the second end 110. The heat source 116 may be laterally adjacent to the vessel 102 as shown in FIG. 1A. Alternatively, the heat source 116 may be located (e.g., embedded) in the vessel 102. As the carrier gas 112 (e.g., hydrogen) passes through vessel 102, water 114 on the high-surface-area material evaporates and is transported (e.g., carried) to the gas outlet 108. A constant flow of carrier gas 112 through the vessel 102 provides transport of water vapor out of vessel 102 and prevents a buildup of humidity in the evaporator 100. The H2 / H2O( ) product stream 113 exiting the evaporator 100 may be recovered. The ability to tightly control both water and carrier gas mass and flow rates produces a precisely mixed and controlled composition of the H2 / H2O(g) product stream 113 exiting the evaporator 100.

[0034] In various embodiments, the vessel 102 is temperature controlled with a gradient from a cool inlet to a hot outlet. While FIG. 1A shows different temperature regions at various locations within the vessel 102, the regions may exhibit other temperatures that are below the boiling point of water. The temperature gradient may be a continuous gradient or an incremental (e.g., step wise) gradient. The vessel 102 may be segmented into distinct zones or regions (e.g., each zone or region may be heated to a different temperature) or may be made up of multiple vessels (e.g., heat exchangers) in series. The regions of the vessel 102 may be heated to a sufficiently high temperature that the introduced water 114 substantially completely (e.g., fully) evaporates into the fluid stream (e.g., earner gas 112) passing through the vessel 102. By adjusting the temperature, a ratio of H2:H2O(g) in the Fb / FbO g) product stream may be tailored. By way of example only, if the temperature of the vessel 102 is maintained at about 78°C, the Fb / FbOfg) product stream 113 may include about 50% H2 and about 50% steam. If the temperature of the vessel is maintained at about 95°C, the H2 / H2O(g) product stream 113 may include about 5% H2 and about 95% steam.

[0035] In some embodiments, the heat source 1 16 is a thermal fluid in a heat exchanger (not shown), which is embedded in vessel 102. The heat source 116 may, for example, be integrated into the interior of vessel 102. The thermal fluid flows through the heat exchanger in an opposite direction to the flow of the fluids through the vessel. The flow of thermal fluid in the heat exchanger produces a temperature gradient that decreases as the thermal fluid travels through the heat exchanger from the second end 1 10 of the vessel to the first end 106 of the vessel. In various such embodiments, the thermal fluid may be an H2 / H2O(g) product stream exiting an HTE system or other waste heat source. In other embodiments, the vessel 102 is equipped with a heat source 116 as heating elements (e.g., electrical resistance heating elements) distributed along the vessel 102 wherein each heating element is configured to operate at a different temperature, which produces the temperature gradient.

[0036] Because the water is fully evaporated prior to exceeding about 100°C, there are substantially no pressure fluctuations within the vessel 102. Because the method according to embodiments of the disclosure is mass flow controlled, precise (e.g., exact) material compositions of the Fb / EbOfg) product stream are achievable. In other words, the relative amounts of H2 and H2O(g) in the th / thO® product stream 113 may be tailored by adjusting the flow rates of H2 and H O introduced to the vessel 102. Each temperature “region” of the vessel 102 may be maintained at a temperature which is lower than the temperature used to substantially completely evaporate the water present in that region. Finally, because reaching the boiling point of water is not utilized to evaporate the water, the thermal energy temperature of the evaporator 100 is lower, thus enabling lower quality (i.e., lower temperature) sources of heat to be used.

[0037] FIG. IB is a perspective view of an exemplary evaporator in accordance with some embodiments and FIG. 1C is a side view of the evaporator of FIG. IB. In FIGS. IB and 1C, an evaporator 100 (low-temperature steam generator) includes a vessel 102 having a gas inlet 104 at a first end 106. The gas inlet 104 is configured to facilitate the introduction of an H2 gas stream (e.g., carrier gas 112) to the vessel 102. The vessel 102 further includes a gas outlet 108 at a second end 110 from which the Fh / bOtg) product stream (e.g., product stream 113) exits the vessel 102. One or more water inlets 115 introduce water (e.g., water 114) into the vessel 102 at controlled flow rates.

[0038] As mentioned above, a heat source 116 heats the vessel 102. In FIGS. IB and 1C, a plurality of electric heaters 118 (e.g., electric band heaters) are mounted along the vessel 102. Each of the electric heaters 118 may be independently controlled. The vessel 102 may further include a first endcap 126 and a second endcap 130. The first endcap 126 may be attached to the vessel 102 via, for example, a first mounting flange 128 and the second endcap 130 may be attached to the vessel 102 via, for example, a second mounting flange 132. The first mounting flange 128 and the second mounting flange 132 may facilitate assembly and maintenance of the vessel 102. An optional outlet-side tank 134 may be fluidly coupled to the gas outlet 108 and may be configured to collect condensate, if any.

[0039] The vessel 102 may be formed of and include a conductive material, such as a thermally conductive material. The vessel 102 may be packed with a high-surface-area packing material configured to enable capillary transport of liquid and concurrent gas-phase flow through interstitial passages. In some embodiments, the vessel 102 is formed of and includes stainless steel and the packing material is formed of and includes a thermally conductive, heat-spreading material, such as an anodized aluminum extrusion and high-surface-area bodies such as alumina (ceramic) beads. However, other materials may be used. The high-surface-area packing material promotes lateral heat distribution within the vessel while also providing surfaces for wetted areas for evaporation.

[0040] In some embodiments, the electric heaters 118 may be configured in different zones (e.g., regions) of the vessel 102. For example, as shown in FIGS. IB and 1C, the electric heaters may be configured in a first heating zone 120, a second heating zone 122, and a third heating zone 124. The first heating zone 120 may comprise electric heaters 118 near the first end 106, the third heating zone 124 may comprise electric heaters 118 near the second end 110, and the second heating zone 122 may be located between the first heating zone 120 and the third heating zone 124. The electric heaters 118 of the various heating zones 120, 122, 124 may be configured to heat the water introduced through the water inlets 115 and the hydrogen introduced through the gas inlet 104 to produce the Fb / EbOtg) product stream. The heating zones 120, 122, 124 are exemplary and fewer or greater number of heating zones may be used on a vessel 102. The number of heating zones may depend on a volume of the carrier gas 112 and water to be transported through the vessel 102. Further, any number of electric heaters 118 may be used in each of the heating zones. Each of the heating zones may have the same number of electric heaters 118, or a different number of electric heaters 118. In some embodiments, a temperature sensor (not shown) may be provided on the vessel 102 at each of the zones. In some embodiments, temperatures sensors are incorporated into the electric heaters 118.

[0041] During operation, a carrier gas 112 (e.g., hydrogen) is introduced through the gas inlet 104 and passes through the high-surface-area packing material within the vessel 102 while water is injected via the one or more water inlets 115. The electric heaters 118 are controlled to maintain a longitudinal temperature profde within the vessel 102 that increases from the first end 106 toward the second end 110 so that water fully evaporates into the carrier gas within the vessel 102 at temperatures below the boiling point of water. By controlling the mass flow rates of hydrogen and water, a precisely defined H2:H2O(g) ratio is produced at the gas outlet 108.

[0042] For example, a first heating zone 120 may include the electric heaters 118 configured to heat the vessel 102 to a temperature below about 90°C. The second heating zone 122 may include the electric heaters 118 configured to maintain the vessel 102 at a temperature from about 89°C-93°C. The third heating zone 124 may include the electric heaters 118 configured to maintain the vessel 102 at or above about 95°C. In some embodiments, the heating zones 120, 122, 124 are configured such that a region near the gas outlet 108 is above the dew point of the H2 / H2O(g) product stream. An outlet line (not shown) connected to the gas outlet 108 may be superheated to suppress condensation in the product stream.

[0043] In some embodiments, a downstream composition sensor (not shown) may be provided in an outlet line connected to the gas outlet 108 to provide closed-loop feedback that allows adjustment to the carrier gas 112 input to the gas inlet 104 and the water input to the water inlets 115. The evaporator 100 may be operated in a feed-forward mode in which hydrogen and water are metered (e.g., by mass-flow controllers) to determine the H2 / H2O(g) material composition. In some embodiments, the downstream composition sensor is used in a closed-loop arrangement to adjust one or more of zone temperatures and feed delivery to maintain a target material composition of the fb / fhO g) product stream.

[0044] Electrolysis systems according to embodiments of the disclosure may be used to separate elements (e.g., chemical elements) from a material (e.g., a base material) by applying a voltage across the material. A feed stream for such an electrolysis system may be obtained using the evaporator 100 and methods according to embodiments of the disclosure described herein. An applied voltage causes charged species (protons or ions) to separate from a respective bulk composition (H2O, CO2, etc.). The charged species may pass through a membrane separating the elements from the material. For example, base materials including oxygen, such as water (FEO) and carbon dioxide (CO2), may be separated through electrolysis to produce hydrogen (H2) or a combination of carbon monoxide (CO) and oxygen (O2) when a voltage is passed through the associated base material.

[0045] Referring to FIG. 2, a simplified schematic of an HTE system 200 is shown. H2 source 206 introduces H2 stream 208 to an evaporator 204. Water stream 202 is also introduced to the evaporator 204 to produce an b / FEOtg) feed stream 210. Evaporator 204 may be substantially similar to evaporators 100 described with reference to FIGS. 1 A-1C. Similar to evaporators 100 described above, the evaporator 204 may utilize a heat source 201 (e.g., 116) to produce a feed stream 210 (e.g., product stream 113). The H2 / H2O(g) feed stream 210 may be preheated using so-called ‘‘waste heat'’ from electrolyzer 228 producing a preheated Fb / FEOfg) feed stream 214 in a heat exchanger 212. The feed stream 214 may be heated again via a fuel trim heater 215 utilizing thermal energy 217 (e.g., an electric heater or other thermal heat source) to form a fully heated H2 / H2O(g) feed stream 216 that is at the temperature desired for the HTE system 200. In some embodiments, a so-called “safe-gas” bypass path is provided that bypasses the evaporator 204 when the evaporator 204 is offline.

[0046] The electrolyzer 228 receives the fully heated H2 / H2O(g) feed stream 216 and an air stream 230. The steam (H2O<g)) is electrolyzed following the application of electrical current 239 between electrodes of the electrolyzer 228 (e.g., a fuel electrode 229 and an air electrode 231), producing H2 on the steam side and O2 on the air side of the electrolyzer 228. The H2 and any unreacted H2O® (e.g., an H2 / H2O(g) product stream 222) may be removed from the electrolyzer 228 and used as a heat source to preheat the H2 / H2O(g) feed stream 210, as mentioned above, cooling the H2 / H2O(g) product stream 222 to form a H2 / H2O(g) product stream 224. The H2 / H2O(g) product stream 224 is introduced to a condenser 225 to separate the H2O and H2, producing an H2 product stream 220. The condensate 226 (e.g., HzOp)) is removed and may be recycled to the evaporator 204. A portion of the H2 product stream 220 may be recycled to the H2 source 206 via a recycle blower 237. To the extent the H2 product stream 220 is not recycled, it may be discharged via a fuel exhaust 218. An air / Ch stream 232 produced by the electrolyzer 228 is removed from the electrolyzer 228 and may be used to heat incoming air stream 236.

[0047] The incoming air stream 236 may be introduced (e.g.. fed) into a heat exchanger 240 for preheating the air stream 238. The air stream 238 may be heated via an air trim heater 233 utilizing thermal energy 235 (e.g., an electric heater or other thermal source) to an operating temperature of the electrolyzer 228, producing air stream 230. Air / Oz stream 232 from the electrolyzer 228 may be recycled (e.g.. back to air stream 238) or released (e.g. via air outlet stream 234).

[0048] Because evaporator 204 operates at a lower temperature relative to conventional devices (e.g.. boilers), it may use a variety of different heat sources as the heat source 201. These heat sources may include a heat source referred to as a waste heat source or a low- quality heat source. A waste heat source or a low-quality heat source may be a heat source that is at a lower temperature as compared to heat sources used in conventional systems (e.g., boilers). The evaporator 204 may be operated at precisely controlled rates (e.g., mass flow rates of the H2O(g> and H2), making downstream regulation of the H2 / H2O(g) feed stream 210 unnecessary. The use of “waste heat” from the H2 / H2O(g) product stream 222 is able to sufficiently heat the H2 / H2O(g) feed stream 210 that the overall energy consumption of the evaporator 100 and the H2 / H2O(g) feed stream heater is significantly less than with a conventional system. In various embodiments, the electrolyzer 228 comprises a cathode (e.g., fuel electrode 229) and an anode (e.g., air electrode 231). One or both of the anode and cathode may comprise catalytic materials configured to accelerate the electrolysis reaction(s). Materials of the electrodes may be selected based on the reactions to be conducted in the electrolyzer 228.

[0049] The reduced heat requirements of the evaporator 204 (e.g., evaporator 100) according to embodiments of the disclosure makes it possible to produce steam using a heat source at relatively low temperatures. This allows the HTE system 200 to be highly compatible with renewable energy sources (e.g., wind, solar, geothermal) that may efficiently produce power and / or heat at the lower temperatures utilized in the HTE system 200.

[0050] In some embodiments, waste heat may be utilized as the heat source with an evaporator to provide a H2 / H2O(g) output stream. For example, waste heat from other processes (e.g., waste heat from a nuclear power plant or other industrial facility) may be used to produce steam for an HTE system (e.g., HTE system 200). FIG. 3 shows an exemplary high-surface-area heat exchanger 300 (a low-temperature steam generator), which may be utilized in place of the evaporator 204 shown in FIG. 2. The high-surface- area heat exchanger 300 may be configured to utilize waste heat to provide a H2 / H2O<g) feed stream (e.g., H2 / H2O(g) feed stream 210) for an HTE system (e.g., HTE system 200). The waste heat may be steam at a relatively low temperature, such as between about 100°C and about 150°C. In some embodiments, the waste heat may be steam that is at about 110°C, which is referred to herein as waste heat steam. The waste heat steam may be a byproduct of an industrial process such as food processing, chemical processing or the like. The waste heat steam may also or alternatively be a byproduct of a power generation process such as from a nuclear power plant.

[0051] The high-surface-area heat exchanger 300 may comprise a waste heat steam inlet 302 in which the waste heat steam is input to the high-surface-area heat exchanger 300. The waste heat steam inlet 302 may be configured to operate similar to a one-pipe steam system. The waste heat steam may be input to the waste heat steam inlet 302 at a temperature from about 100°C to about 150°C. In some embodiments, the waste heat steam may be input to the waste heat steam inlet 302 at a temperature of about 110°C. The input of the w aste heat steam to the w aste heat steam inlet 302 may be controlled via a pressure regulator. Hy drogen gas and liquid water may be fed in at a feed input 304. The hydrogen gas and liquid water are heated by the waste heat steam in the high-surface-area heat exchanger 300, creating a temperature gradient from the bottom to the top of the high-surface-area heat exchanger 300 with the relatively hotter zone on the bottom. The heat transfer from the condensation of the thermal steam vaporizes the introduced (e.g., injected) water and results in atb / FbOfe) feed stream that exits the high- surface-area heat exchanger 300 at a feed outlet 306. The H2 / H2O(g) feed stream may be passed on to a HTE system (e.g., a Eh / TEOig) feed stream 210 to HTE system 200) coupled to the high-surface-area heat exchanger 300. As the waste heat steam condenses, it exits the high-surface-area heat exchanger 300 via a waste heat outlet 308, allowing more of the waste heat steam to enter the waste heat steam inlet 302 via the pressure regulator.

[0052] As shown in FIG. 3, the feed input 304 may be disposed towards a top end 310 (e.g.. a first end) of the high-surface-area heat exchanger 300. The feed outlet 306 may be disposed towards a bottom end 312 (e.g., second end) of the high-surface-area heat exchanger 300. The waste heat steam inlet 302 and the waste heat outlet 308 may each be disposed towards the bottom end 312 of the high-surface-area heat exchanger 300. However, other configurations of the high-surface-area heat exchanger 300 are possible.

[0053] In some embodiments, high-surface-area packing material (not shown) may be used to increase the heat transfer surface area of a shell side of the high-surface-area heat exchanger 300. The hydrogen and liquid water may be introduced (e.g., metered) into the feed input 304 at the top of the shell side of the high-surface-area heat exchanger 300 at a controlled rate. For example, the hydrogen and liquid water are metered to control the mass of the water input to the feed input 304. As the hydrogen and the liquid water pass through the shell side of the high-surface-area heat exchanger 300, the liquid w ater evaporates and creates a clean and controlled process gas feed exiting the high-surface-area heat exchanger 300 at the feed outlet 306. This output may then be utilized as a feed stream (e.g.. a H2 / H2O(g) feed) for the HTE system (e.g., HTE system 200).

[0054] Referring to FIG. 4, a simplified schematic of an HTE system 400 is shown. The HTE system 400 is similar to the HTE system 200 except that the HTE system 400 may utilize waste heat by incorporating the high-surface-area heat exchanger 300 shown in FIG. 3. H2 source 406 introduces H2 stream 408 to high-surface-area heat exchanger 404. Water stream 402 is also introduced to the high-surface-area heat exchanger 404 to produce an H2 / H2O(g) feed stream 410. High-surface-area heat exchanger 404 may be substantially similar to high-surface-area heat exchanger 300 described with reference to FIG. 3. Similar to the high-surface-area heat exchanger 300 described above, the high-surface-area heat exchanger 404 may utilize a waste heat steam 442 to produce a feed stream 410. The H2 / H2O(g) feed stream 410 may be preheated using so-called "‘waste heat” from electrolyzer 428 producing a preheated H2 / H2O<g) feed stream 414 in a heat exchanger 412. The feed stream 414 may be heated again via a fuel trim heater 415 utilizing thermal energy 417 (e.g., an electric heater or other thermal heat source) to form a fully heated H2 / H2O(g) feed stream 416 is at the temperature desired for the HTE system 400. In some embodiments, a so-called “safe-gas” bypass path is provided that bypasses the high- surface-area heat exchanger 404 when the high-surface-area heat exchanger 404 is offline.

[0055] The electrolyzer 428 receives the fully heated Eb / EbO(g) feed stream 416 and an air stream 430. The steam (EkO(g)) is electrolyzed following the application of electrical current 439 between electrodes of the electrolyzer 428 (e.g., a Fuel electrode 429 and an air electrode 431), producing Eb on the steam side and O2 on the air side of the electrolyzer 428. The Fb and any unreacted EbO(g) (e.g., an Eb / EbO(g) product stream 422) may be removed from the electrolyzer 428 and used as a heat source to preheat the H2 / EbO(g) feed stream 410, as mentioned above, cooling the Eb / H2O(g) product stream 422 to form a Eb / EbO(g) product stream 424. The Eb / EbO(g) product stream 424 is introduced to a condenser 425 to separate the FbO and Eb, producing an Eb product stream 420. The condensate 426 (e.g., E O(i)) is removed and may be recycled to the high-surface-area heat exchanger 404. A portion of the Eb product stream 420 may be recycled to the Eb source 406 via a recycle blower 437. To the extent the Eb product stream 420 is not recycled, it may be discharged via a fuel exhaust 418. An air / Ch stream 432 produced by the electrolyzer 428 is removed from the electrolyzer 428 and may be used to heat incoming air stream 436.

[0056] The incoming air stream 436 may be introduced (e.g.. fed) into a heat exchanger 440 for preheating the air stream 438. The air stream 438 may be heated via an air trim heater 433 utilizing thermal energy 435 (e.g., an electric heater or other thermal source) to an operating temperature of the electrolyzer 428, producing air stream 430. Air / Ch stream 432 from the electrolyzer 428 may be recycled (e.g., back to air stream 438) or released (e.g. via air outlet stream 434).

[0057] Because the high-surface-area heat exchanger 404 operates at a lower temperature relative to conventional devices (e.g., boilers), it may use a variety of different sources for the waste heat steam 442. A waste heat source or a low-quality heat source may be a heat source that is at a lower temperature as compared to heat sources used in conventional systems (e.g., boilers). The high-surface-area heat exchanger 404 may be operated at precisely controlled rates (e.g., mass flow rates of the H2O(g> and H2), making downstream regulation of the H2 / H2O(g) feed stream 410 unnecessary. The use of “waste heat” from the H2 / H2O(g) product stream 422 is able to sufficiently heat the H2 / H2O(g) feed stream 410 that the overall energy consumption of the high-surface-area heat exchanger 300 is significantly less than with a conventional system.

[0058] In various embodiments, the electrolyzer 428 comprises a cathode (e.g., Fuel electrode 429) and an anode (e.g., air electrode 431). One or both of the anode and cathode may comprise catalytic materials configured to accelerate the electrolysis reaction(s). Materials of the electrodes may be selected based on the reactions to be conducted in the electrolyzer 428.

[0059] One of the advantages of the disclosed low-temperature steam generators (e.g., evaporator 100 and high-surface-area heat exchanger 300) that the generation of mass-controlled steam occurs below the boiling point of water. This results in advantages in system design and stability. Since the low-temperature steam generators operates at a lower temperature than a conventional boiler (e.g., at temperatures less than about 150°C), relatively lower temperature heat sources may be used with the evaporator 100 or the high- surface-area heat exchanger 300 according to embodiments of the disclosure. This provides the ability to use waste heat streams whereas in conventional systems, many waste heat streams do not provide sufficient heat at a high enough temperature (e.g.. not enough energy to operate one or more boilers). The quantity of waste heat available increases drastically as the temperature requirement decreases. Renewable sources, such as photothermal and geothennal heat, may become viable heat sources at these lower temperatures. Heat pumps, in contrast, are generally limited by their sink (high) and source (low) temperature streams, also known as temperature lift. For example, using a gas stream at 38°C would not readily be usable by a heat pump to drive a boiler to 177°C. However, reaching 93°C with the same stream is possible. The disclosed evaporator 100 and high- surface-area heat exchanger 300 make it possible to produce steam using lower temperature waste heat as efficiently, given a coefficient of perfonnance (COP) greater than 3, as conventional methods using relatively high-temperature heat (e.g., steam from a nuclear plant). Thermal generation plants are about 33% efficient, which means it takes three units of thermal energy to make one unit of elec tn city. In other words, three units of thermal energy are turned into one unit of electricity. Conversely, a COP of three means that three units of thermal energy are created using one unit of electricity. This means that a heat pump driven evaporation system may exhibit the same efficiency overall as a high- temperature electrolysis system coupled with a heat source, such as a nuclear facility. Thus, the disclosed system may be implemented in many areas that lack such high-temperature heat sources.

[0060] The embodiments of the disclosure described above and illustrated in the accompanying drawings do not limit the scope of the disclosure, which is encompassed by the scope of the appended claims and their legal equivalents. Any equivalent embodiments are within the scope of this disclosure. Indeed, various modifications of the disclosure, in addition to those shown and described herein, such as alternate useful combinations of the elements described, will become apparent to those skilled in the art from the description. Such modifications and embodiments also fall within the scope of the appended claims and equivalents.

Claims

CLAIMSWhat is claimed is:1 . A low-temperature steam generator, comprising: a vessel, comprising: a gas inlet at a first end of the vessel; a gas outlet at a second end of the vessel; a high-surface-area packing material within the vessel; at least one water inlet at one or more of the first end of the vessel or along a length of the vessel; and at least one temperature region exhibiting a temperature gradient between the gas inlet and the gas outlet, a temperature relatively lower at the gas inlet and relatively higher at the gas outlet; and a heat source configured to provide heat to the at least one temperature region of the vessel.

2. The low-temperature steam generator of claim 1, further comprising a source of gas coupled to the gas inlet at a pressure sufficient to flow the gas through the vessel and out the gas outlet.

3. The low-temperature steam generator of claim 2, wherein the source of gas comprises a source of hydrogen gas.

4. The low-temperature steam generator of claim 1, wherein the heat source comprises heaters spaced along a length of the vessel.

5. The low-temperature steam generator of claim 4, wherein the heaters comprise electric band heaters configured to surround the vessel.

6. The low-temperature steam generator of claim 4, wherein the heaters are grouped into a first heating zone and a second heating zone, the heaters of the first heating zone configured to maintain the vessel at a different temperature than the heaters of the second heating zone.

7. The low-temperature steam generator of claim 1, wherein the heat source comprises a heat exchanger containing a thermal fluid within the vessel.

8. A water electrolysis system, comprising: a water evaporator, comprising: a vessel, comprising: a gas inlet at a first end of the vessel; a gas outlet at a second end of the vessel; a high-surface-area packing material in the vessel; and a water inlet at the first end of the vessel; and one or more heaters arranged in heat zones along a length of the vessel, each of the heat zones heated to a different temperature; and an electrochemical cell configured to separate hydrogen and oxygen from a product stream exiting the gas outlet of the vessel.

9. The water electrolysis system of claim 8, wherein the heaters comprise electric band heaters surrounding the vessel.

10. The water electrolysis system of claim 8, wherein the high-surface-area packing material comprises aluminum and alumina beads.

11. The water electrolysis system of claim 8, wherein the electrochemical cell comprises an anode comprising a catalytic material formulated to accelerate formation of O2 from H2O.

12. The water electrolysis system of claim 8, wherein the electrochemical cell comprises a cathode comprising a catalytic material formulated to accelerate formation of H2 from H2O.

13. A method for evaporating water, comprising: introducing hydrogen gas to a first end of a vessel, the vessel containing a high-surface- area packing material;introducing water to one or more locations along the vessel; heating the vessel to produce a temperature gradient between the first end of the vessel and a second end of the vessel, a temperature at the first end relatively lower than a temperature at the second end; passing the hydrogen gas and water through the vessel; evaporating the water; and outputting a product stream of the hydrogen gas and the water.

14. The method for evaporating water of claim 13, wherein heating the vessel to produce a temperature gradient comprises placing electric heaters along the vessel.

15. The method for evaporating water of claim 14, further comprises operating the electric heaters in a first heating zone at a first temperature near the first end of the vessel and a second heating zone at a second temperature near the second end of the vessel, the second temperature being higher than the first temperature.

16. The method for evaporating water of claim 15, further comprises operating the electric heaters in a third heating zone at a third temperature, the third heating zone disposed between the first and second heating zones, the first temperature being below about 90°C, the second temperature being above about 95°C, and the third temperature being from about 89°C-93°C.

17. The method for evaporating water of claim 15, wherein heating the vessel comprises introducing waste heat steam into the vessel at a temperature from about 100°C to about 150°C.

18. A high-surface-area heat exchanger, comprising: a vessel, comprising: a waste heat steam input configured to receive waste heat steam; a feed input configured to receive hydrogen and liquid water; a waste heat steam outlet configured to release condensation from the waste heat steam; anda feed outlet configured to output a H2 / H2O(g) feed stream created by evaporating the water via heat from the waste heat steam.

19. The high-surface-area heat exchanger of claim 18, wherein the waste heat steam is input into the waste heat steam input at a temperature of from about 100°C to about 150°C.

20. The high-surface-area heat exchanger of claim 18. wherein the feed input is disposed at a first end of the vessel and the waste heat steam input, the waste heat steam outlet, and the feed outlet are disposed at a second end of the vessel.

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