EP4695849A1 - Solid oxide cell system with thermally tolerant cells with passive thermal management structures - Google Patents

Abstract

An exemplary system and method are disclosed that employs a cell component level passive thermal management structure in the interconnect (IC) of solid oxide fuel cells or electrolyzer cells that geometrically alters the interconnect material at regions for the largest temperature gradients. The result is an increased passive flattening of temperature profiles that intrinsically increases thermomechanical reliability, given changing current supply and corresponding heat generation conditions, to make the cells more "thermally tolerant" to variable operation and facilitate reduced balance-of-plant operations.

Description

SOLID OXIDE CELL SYSTEM WITH THERMALLY TOLERANT CELLS WITH PASSIVE THERMAL MANAGEMENT STRUCTURES

Related Application

[0001] This PCT application claims priority to, and the benefit of, U.S. Provisional Patent Application No. 63/496,209, filed April 14, 2023, entitled “Thermally Tolerant Solid Oxide Cells via Interconnect Hollows,” which is incorporated by reference herein in its entirety.

Background

[0002] Hydrogen is a clean fuel that produces water vapor when burned. Solid Oxide Electrolyzer Cells (SOECs) can be used to electrolyze water and thereby produce hydrogen and oxygen. Solid Oxide Fuel Cells (SOFCs) can use hydrogen and oxygen to generate electricity and water. SOECs can benefit from running at high temperatures (e.g., 100 to 850 degrees Celsius), where electrolysis can be more efficient. Similarly, SOFCs can benefit from running at high temperatures.

[0003] One application of SOECs is to capture variable sources of renewable electricity as hydrogen, which can be stored. Variable capture of renewable electricity by SOECs can be performed by increasing the rate of electrolysis by increasing the amount of electricity and/or heat input to the SOEC when the renewable electricity source is producing more power than is required by the gird and decreasing the amount of electricity and/or heat input to the SOEC when the renewable electricity source is not producing sufficient electricity for the grid.

[0004] There is a benefit to improving solid oxide cells and their associated plant.

Summary

[0005] An exemplary system and method are disclosed that employs a cell component level passive thermal management structure in the interconnect (IC) of solid oxide fuel cells or electrolyzer cells that geometrically altered the interconnect material such that, per unit mass of interconnect material, more interconnect thermal conductance is precisely positioned in regions typically known for the largest, hence most problematic, temperature gradients. The result is an increased passive flattening of temperature profiles that intrinsically increases SOEC or SOFC thermomechanical reliability given changing current supply and corresponding heat generation conditions, to make the cells more “thermally tolerant” to variable operation (e.g., aggressive capture of dynamic renewable energy (RE) that is not constrained to thermal neutral voltage operation) and facilitate reduced balance-of-plant operations (e.g., air preheating).

[0006] In an aspect, a device is disclosed comprising a solid oxide cell comprising a substrate member comprising a top interconnect and a bottom interconnect extending therefrom to form channels for the respective flow of a hydrogen stream and an oxygen stream, the top interconnect and the bottom interconnect being configured to couple to a cathode structure and an anode structure, respectively, to form a unit cell, wherein multiple unit cells are stacked to form a solid oxide cell stack, and wherein each of the top interconnect and bottom interconnect of each solid oxide cell has a passive thermal management structure comprising a hollow structure configured to concentrate a thermal conductance of the interconnect at an end portion of the interconnect.

[0007] In some embodiments, the solid oxide cell includes (i) for a top portion formed by the top interconnect, the top portion comprising an inlet and an outlet, wherein the top interconnect defines a manifold comprising a plurality of channels between the inlet and the outlet, and (ii) for a bottom portion formed by the bottom interconnect, the bottom portion comprising a second inlet and a second outlet, wherein the bottom interconnect defines a second manifold comprising a plurality of channels between the second inlet and the second outlet.

[0008] In some embodiments, the passive thermal management structure comprising the hollow structure has a length spanning about 50% of the length of the interconnect of the solid oxide cell.

[0009] In some embodiments, the passive thermal management structure comprising the hollow structure has a length spanning between 30% and 70% of the length of the interconnect of the solid oxide cell.

[0010] In some embodiments, the passive thermal management structure comprising the hollow structure has a uniform cross-sectional area.

[0011] In some embodiments, the passive thermal management structure comprising the hollow structure has a non-uniform cross-sectional region.

[0012] In some embodiments, the solid oxide cell is a solid oxide fuel cell.

[0013] In some embodiments, the solid oxide cell is a solid oxide electrolysis cell.

[0014] In another aspect, a system is disclosed comprising a plurality of solid-oxide cell stack, wherein each solid oxide cell comprises a substrate member comprising a top interconnect and a bottom interconnect extending there from to form channels for the respective flow of a hydrogen stream and an oxygen stream, the top interconnect and the bottom interconnect being configured to couple to a cathode structure and an anode structure, respectively, to form a unit cell, wherein multiple unit cells are stacked to form a solid oxide cell stack, and wherein each of the top interconnect and bottom interconnect of each solid oxide cell has a passive thermal management structure comprising a hollow structure configured to concentrate a thermal conductance of the interconnect at an end portion of the interconnect.

[0015] In some embodiments, each solid oxide cell includes (i) for a top portion formed by the top interconnect, the top portion comprising an inlet and an outlet, wherein the top interconnect defines a manifold comprising a plurality of channels between the inlet and the outlet, and (ii) for a bottom portion formed by the bottom interconnect, the bottom portion comprising a second inlet and a second outlet, wherein the bottom interconnect defines a second manifold comprising a plurality of channels between the second inlet and the second outlet.

[0016] In some embodiments, the passive thermal management structure comprising the hollow structure has a length spanning about 50% of the length of the interconnect of the solid oxide cell.

[0017] In some embodiments, the passive thermal management structure comprising the hollow structure has a length spanning between 30% and 70% of the length of the interconnect of the solid oxide cell.

[0018] In some embodiments, the passive thermal management structure comprising the hollow structure has a uniform cross-sectional area.

[0019] In some embodiments, the passive thermal management structure comprising the hollow structure has a non-uniform cross-sectional region.

[0020] In some embodiments, the solid oxide cell is a solid oxide fuel cell.

[0021] In some embodiments, the solid oxide cell is a solid oxide electrolysis cell.

[0022] It should be understood that the examples described herein are only nonlimiting examples and that embodiments of the present disclosure can be used for a variety of measurement techniques.

[0023] Additional advantages of the disclosed systems and methods will be set forth in part in the description that follows and in part will be obvious from the description. The advantages of the disclosed compositions and methods will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosed compositions and methods, as claimed.

Brief Description of the Drawings

[0024] Example features and implementations are disclosed in the accompanying drawings. However, the present disclosure is not limited to the precise arrangements and instrumentalities shown.

[0025] Fig. 1 shows a system comprising an exemplary solid oxide cell stack configured with a cell component-level passive thermal management structure comprising a hollow structure in the interconnects of individual cells in accordance with an illustrative embodiment.

[0026] Fig. 2A shows an example change in geometry of a solid oxide fuel cell of a base cell to a modified cell configured with the passive thermal management structure in accordance with an illustrative embodiment.

[0027] Figs. 2B - 2E each show example geometric configurations of the passive thermal management structure in accordance with an illustrative embodiment.

[0028] Fig. 2F shows an example solid oxide electrolysis cell with the passive thermal management structure in accordance with an illustrative embodiment.

[0029] Fig. 3A shows a simulated temperature profile contrast between a conventional solid oxide cell and a solid oxide electrolysis cell with the passive thermal management structure in accordance with an illustrative embodiment.

[0030] Fig. 3B shows a simulated gradient temperature profile contrast between a conventional solid oxide cell and a solid oxide electrolysis cell with the passive thermal management structure in accordance with an illustrative embodiment.

[0031] Fig. 3C shows an example performance profile for air supply turbomachinery.

[0032] Fig. 4A and 4B shows trends of local temperature gradients for each interconnect design (solid, Fig. 4A; hollow, Fig. 4B).

[0033] Fig. 4C shows example of tapered heat exchanger fin which has enhanced performance.

Detailed Specification

[0034] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings and from the claims.

[0035] Example System [0036] Fig. 1 shows a system 100 comprising an exemplary solid oxide cell stack 102, e.g., for a solid oxide fuel cell or solid oxide electrolyzer, configured with a cell component-level passive thermal management structure 104 comprising a hollow structure in the interconnects 106 of individual cells 108 (shown as 108a, 108b) in accordance with an illustrative embodiment. As shown in Fig. 1, the cross-section of the interconnect 106 of each cell 108 (also referred to herein as thermally tolerant cell 108) is made to be non- uniform with respect to a solid interconnect material via placement of the hollow structures 104. To this end, the fixed total amount of thermal conductance can be locally allocated or “weighted” where temperature gradients are conventionally more problematic. Plot 110 shows an example temperature profile 112 across the length of a conventional cell and a modified temperature profile 114 across a thermally tolerant cell 108. Indeed, the average temperature gradient (difference in the maximum temperature and the minimum temperature) is decreased as compared to the convention cell. The change in interconnect structure and the resultant decrease in average temperature gradient can facilitate occasional operation off the thermal neutral voltage. The geometrically altered interconnect hollow structure can be precisely positioned in regions typically known for the lowest temperature gradients.

[0037] Improved stack configurations. Typically, an attempt at increasing the thermal conductance of the interconnect (e.g., 106) is directly proportional to an increase in total interconnect mass and size, which may result in increased cost for the stack and, in some embodiments, decreased stack- and system- portability. The exemplary solid oxide cell stack 102 with the cell component- level passive thermal management structure 104, however, can keep the total interconnect mass fixed while providing for a slightly larger volume. Alternatively, the exemplary solid oxide cell stack 102 with the cell component- level passive thermal management structure 104 can keep the volume fixed while decreasing the mass while still providing a similar cell output performance.

[0038] Improved overall plant performance. Notably, the thermally tolerant cell 108 can decrease the costs and performance parasitics associated with stack thermal management, for example, (i) the air preheat requirements such as gas-to-gas heat exchangers 116 (shown as “Process Thermal Management” 116), (ii) the large excess airflows of air supply turbomachinery, e.g., blowers 118 (that can deplete net power into electrolysis), etc.). Fig. 3C shows an example performance profile for air supply turbomachinery. Indeed, with a decrease in air volume requirement, there is a corresponding decrease in power.

[0039] The thermally tolerant cell 108 is driven by two considerations. First, the interconnect component simultaneously routes charge, fluid, and thermal transport. Per the latter feature, the interconnect is an integral internal heat exchanger for the SOEC or SOFC. Second, the Optimal allocation of the interconnect’s thermal conductance (that is, the product of interconnect material thermal conductivity and axial cross-sectional area) entails non- uniform distribution, which can counter tendencies for locally steep temperature gradients (temperature gradients can be considered as thermally induced stresses). Indeed, the overall interconnect mass would remain constant via a hollowed structure along the interconnect in locations where temperature gradients tend to be smaller, e.g., near the reactant streams’ exit in a co-flow SOEC where local Nemst potential is closer to the cell potential.

[0040] While operational and development “bottlenecks” (i.e., hindrances) to SOFC commercialization have been in existence for decades, a leading operational hindrance of conventional approaches has been with respect to the thermal management of SOFC stacks. Thus, the thermally tolerant cells 108 in intrinsically becoming more thermally tolerant to operations that are off the thermal-neutral voltage settings because of constraints to the temperature variation along the SOEC, can facilitate the safer storage of dynamic renewable energy as well as the opportunity for productivity gains via hydrogen-dense electrolysis. [0041] Referring still to Fig. 1, the solid oxide cell stack 102 is a component in a system plant 110 comprising air supply turbomachinery 118 and heat exchangers 116. In a typical solid oxide balance-of-plant, the air is preheated before serving as the stack oxidant stream. Air is also employed to be a primary means of dissipating the cells’ byproduct thermal energy. This is done in order to influence a more uniform set of temperatures along the electroactive region, thus (i) better approaching intended temperatures for electrochemical and chemical (i.e., fuel stream) reactions to proceed and (ii) reducing or precluding the possibility of damaging thermally induced stresses arising within the ceramic, ceramic/metal stack structure.

[0042] The counter-intuitive irony, however, is that the system has to extensively preheat the very medium that is meant to serve as a critical heat sink. The issue is further compounded in that a larger heat capacitance rate of air (e.g., easily six to eight times the Faradaic need) has to be supplied to the stack 102 in order to compensate for the smaller temperature differences (i.e., between cells and air) when such preheating occurs. Thus, larger balance-of-plant components are necessary (e.g., larger blowers and gas-to-gas heat exchangers) that have severe performance ramifications (e.g., significantly greater blower parasitics). There is a substantial benefit to reducing the average temperature gradient for the stack 102 as provided by the thermally tolerant cell 108. [0043] While improvements have been made to balance-of-plant (e.g., enhancements to air supply turbomachinery, heat exchangers, etc.), the thermally tolerant cell 108 can complement such balance-of-plant improvement measures with a new cell- and stack-level paradigm to passively increase the thermal tolerance of SOFCs. Increased thermal tolerance can translate to “tougher” SOFCs/SOECs that can permit less rigorous, hence less costly, preconditioning of reactant streams.

[0044] Example Passive Thermal Management Structure

[0045] Fig. 2A shows an example change in geometry of a cell 108 of a base cell 200 to a modified cell 202 configured with the passive thermal management structure 104. In the example shown in Fig. 2A, the cell 108 is employed as a solid oxide fuel cell. In Fig. 2F, the cell 108 is employed as a solid oxide electrolyzer cell.

[0046] In Fig. 2A, the base cell 200 (shown as 200’) has a length (204) and width (206). With the inclusion of the passive thermal management structure 104, a modified cell 202a can be made wider (208) as compared to the base cell 200 while preserving the overall cell mass. Alternatively, the modified cell 202b can be made longer (210).

[0047] Figs. 2B - 2E show example geometric configurations of the passive thermal management structure 104 for a thermally tolerant cell 108. In Fig. 2B, the passive thermal management structure 104 (shown as 104a) has a uniform sectional profile. In Fig. 2B, the structure 104 has a length about 50% of that of the cell 108. The length of the structure 104 can be between 75% and 25% of the length of the cell 108, e.g., 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, and 25%.

[0048] In Fig. 2C, the passive thermal management structure 104 (shown as 104b) has a non-uniform sectional profile with the channel being tapered 212.

[0049] In Fig. 2D and Fig. 2E, the passive thermal management structure 104 (shown as 104c and 104d, respectively) has a region 214 that is uniform, followed by a region 216 that is non-uniform.

[0050] Experimental Results and Additional Examples

[0051] A study was conducted to develop and validate a passive thermal management approach on the cell- and (short) stack- levels that would have system- wide benefits for solid oxide fuel cell (SOFC) technology using “interconnect (partial) hollow structures” that are interconnect structures geometrically altered such that, per unit mass of interconnect material, more interconnect thermal conductance is precisely positioned in regions typically known for the largest (hence most problematic) temperature gradients. The passive thermal management for the cell and/or stack can provide an increased passive flattening of temperature profiles that intrinsically increases SOFC electrochemical and thermomechanical reliability. The fuel cells become more “thermally tolerant” to less air preheating and prereformation of fuel; because the redesigned cells more intrinsically diminish would-be temperature gradients caused by such reductions in reactants stream processing. The “thermal tolerance” can correspondingly decrease the costs and performance parasitics associated with traditional stack thermal management (i.e., extensive air preheat requirements such as gas-to-gas heat exchangers, large excess airflows causing blowers depletion of net power output, extensive reformation catalyst chambers, etc.).

[0052] Aiding cell- and stack- level thermal design and management could be a significant industrial engagement opportunity.

[0053] The study can validate the thermal management approach via the lower temperature SOFCs to partially address the challenge of using furnaces (i.e., artificial thermal environments) during cell and short- stack level tests of conventionally higher temperature (e.g., 750°C +) technologies.

[0054] Interconnect (Partial) Hollows. There are variations in interconnect designs, yet the traditional approach for planar cells includes solid structure with typically rectangular flow passageways that are either parallel (co-flow, counterflow) or perpendicular (cross-flow) on respective sides of the interconnect) still has benefits. The benefits, in comparison or complement to “foam” interconnect approaches, include amenability to manufacture and placement, mechanical integrity under load, and enhanced ability to conduct by-product heat. As an emphasis of this last benefit, given a SOFC stack, the interconnect critically routes electronic charge from cell to cell, reactants streams along the cell, and finally heat away from the cells for thermal management.

[0055] The premise of the interconnect (partial) hollows concept is to constrain the total mass of interconnect material, yet re-distribute that mass such that more thermal conductance is positioned in regions typically known for the largest (hence most problematic) temperature gradients. The result is a passive flattening of temperature profiles that intrinsically increases fuel cells reliability as well as decreases the exorbitant costs, performance challenges and parasitics associated with traditional stack thermal management (e.g., extensive air preheat requirements such as gas-to-gas heat exchangers, large excess airflows causing blowers depletion of net power output, etc.).

[0056] Fig. 1 provides renditions of the SOFC analysis transformations to convey the concept and shows the decomposition of a typical co- or counter-flow SOFC (represented by solid interior P-E-N structure bounded by solid structure interconnect halves) into a “unit cell”, which is the conceptual repeating unit structure that fundamentally captures the full cell in a normalized manner. The unit cell is further divided into the computationally symmetric half-unit cell.

[0057] Given the half-unit cell rendition, the premise of the interconnect redesign is to reallocate the interconnect mass from being uniformly distributed along the reactants passageway to being “frontloaded” with more interconnect material placed near the reactant streams’ leading edge. This is shown in Fig. 2A, not to scale. As can be seen, given a fixed interconnect mass, more interconnect material cross-sectional area (hence thermal conductance; i.e., the “kA” product of thermal conductivity and cross-sectional area) is placed near the inlet edge of the reactants streams where the largest temperature gradients would previously tend to occur due to larger heat sink effects of: (1) convection to reactant streams at their lowest (supply) temperatures and (2) possibly rapid direct internal reformation. The gross volume of the interconnect envelope increases; however, the net volume (hence mass) of interconnect material remains the same because “hollows” or voids are strategically left in downstream axial regions wherein temperature profiles are naturally flatter. The hollows are defined by curved, contoured corners to minimize stress concentrations due to discontinuities associated with “sharp” corners.

[0058] The impact of such a physical change has been computationally simulated using a retrofitted code developed and verified for a NETL Hyper platform and a case study is now highlighted. A co-flow SOFC design was revised to permit a (partial) hollow interconnect design of the same net volume, hence mass, as the original co-flow interconnect design. The “baseline,” conventional interconnect design had square channel passageways with 2 mm sides and 2 mm “rib” contact width between each pair of channels. Given the alternative design, the hollows were slightly more than half the length of the cell with predominant placement in the latter half of the reactant flow path. A load current (average) of 625 mA/cm² was prescribed for a hydrogen-steam fuel stream scenario with 80% fuel utilization, and the oxidant stream was prescribed with 12.5% utilization.

[0059] Fig. 3A shows a temperature profile contrast between traditional (dashed) and redesigned (solid) IC cases. As shown in Fig. 3 A, the 1-D cell temperature profile of the “(partial) hollow” scenario is shifted to a higher range and shows approximately a 30% reduction in temperature rise (metric scale) when compared to the traditional (non-hollow) design’s temperature profile. Particularly noteworthy, the maximum local temperature gradient was also reduced by approximately 30%, i.e., from 7°C/cm to nearly 5°C/cm, as shown in Fig. 3B. This higher and flatter temperature range implies that lower temperature air, and hence lower flowrate for a given heat sink effect, can be supplied for a targeted cell operating temperature. [0060] Fig. 4A and 4B show trends of local temperature gradients for each interconnect design (solid, Fig. 4A; hollow, Fig. 4B). The figures again show the benefit is the re-allocation of a fixed amount of interconnect material. There is less thermal conduction resistance in the first part of the cell (relative to the reactants flow path) because of the increased investment of cross-sectional area in that region. The counter-result is that there is smaller conductance in the latter part of the cell, manifesting as a higher range of local temperature gradients in that region; hence, there is the intersection of curves shown in Fig. 3B. The maximum temperature gradient of the (partial) hollow design remains significantly smaller than that of the traditional design. The combined effect is that (partial) hollow interconnect designs result in a smaller range of temperature gradients than seen in the traditional design. SOFCs can thus become thermally tolerant to less reactant stream pretreatment (e.g., air preheating, fully processed reformate), and this results in system designs with less balance-of-plant expense, bulk, and parasitics.

[0061] In the given simulation, the ohmic impact of interconnect mass re-allocation was not a significant detriment, as the corresponding adjustments in temperature and local current distribution allowed for voltage production to be nearly the same (i.e., 5% decrease in voltage when the alternative interconnect was simulated for the given conditions).

[0062] Balance-of-plant consideration. Additionally, results indicate that attempts at reducing balance-of-plant reactant streams pretreatment (e.g., air supply closer to Faradaic requirements and with less sensible preheating, affording some direct “on-anode” fuel stream reformation) further promote the (partial) hollows design concept as a significant means of passively alleviating deleterious thermally induced stresses.

[0063] Fuel cells and heat exchangers. Fuel cells and heat exchangers have numerous similarities. Both technologies are used to produce an “energy-in-transit.” Heat exchangers foster thermal transport (i.e., heat) as a result of thermal potential differences between streams; fuel cells foster charge transport (i.e., current generation across an electrochemically induced voltage, hence power generation) as a result of electrochemical potential differences between the reactants streams’ Nernst potential and the actual fuel cell voltage. Both sets of energy components have dedicated regions for the respective transport phenomenon (e.g., the area in “UA” for heat exchangers and the “electroactive area” for fuel cells). Table 1 summarizes the parallel relationships.

Table 1: Parallel relationships between Heat Exchangers and Fuel Cells

[0064] A more explicit connection can be realized when one considers the heat transfer and thermal routing duties of select parts of the fuel cell (stack), such as the interconnects’ service as thermal conductors. These similarities have generally motivated the PI to look for extensions of heat exchanger design philosophies to fuel cell development [1], and the concept of optimized heat exchanger designs promoted the (partial) hollows concept. [0065] Heat exchanger conductance is often distributed “evenly” along the length of a heat exchanger, such that the “UA” (i.e., reciprocal of heat transfer resistance) per unit length is constant. Bejan [2], however, discussed the possible thermodynamic benefit of non-even distribution. His premise was to vary the heat exchange area, per unit length, along the heat exchanger such that total entropy generation was minimized. Analysis of one heat exchanger scenario revealed the benefit of concentrating UA in regions of intense heat transfer, poor thermal contact, and lower absolute temperature. Similarly, SOFC solid structure interconnects are usually arranged in geometries that have uniformly distributed thermal conductance along the flow paths of the reactant streams, but again judiciously varying axial thermal conductance in the same manner of placing more conductance where heat transfer is more intense and across lower absolute temperatures has been simulated to be beneficial as shown and discussed in the preceding section.

[0066] As another indicator of merit, Incoprera and DeWitt’s well-regarded Heat Transfer text series highlighted the maximized thermal transport possibilities of extended surfaces (i.e., “fins”) when non-uniform, tapered cross-sections were incorporated. A tapered fin design is illustrated in Fig. 5. Likewise, the text authors promote the greatest allocation of thermal conductance at the “base” of the fins, wherein the temperature difference between the object and cooling medium is greatest. The authors’ emphasis on better heat exchange per unit mass of fin material maps to better heat exchange per unit mass of interconnect in the present case. Fig. 4C shows an example of a tapered heat exchanger fin that has enhanced performance.

[0067] Discussion. Much of the publicly available research focuses on materials science upon important considerations such as stability under the duality of high-temperature oxidizing and reducing environments that the interconnects endure [5-6] as well as the interconnects’ compatibility with other components (e.g., cathode) [7-9]. The exemplary hollow interconnect, in contrast, focused upon geometrical innovation and integrally includes thermal “routing” considerations along with charge (i.e., electrons) and fluidic routing duties; i.e., the interconnect as a pivotal and enhanced in situ heat exchanger is now promoted.

[0068] Modeling and simulation. The study is conducting modeling and simulation efforts of the cell- and short stack levels to verify and characterize the innovation’s impact, e.g., re-verify for the increases in gross volume and associated increases in characteristic lengths along the re-designed interconnects, e.g., using a multi-physics software package (e.g., COMSOL), as well as the local, reactions-based by-product heat generation fields, along with reactant streams and cell structure thermophysical and geometric properties. [0069] The study is evaluating different material sets (e.g., lanthanum strontium cobalt ferrite (LSCF ) as a lower-temperature cathode material alternative to strontium-doped lanthanum manganite (LSM)). The precise geometry (e.g., size, location) of the interconnect hollows may be determined based on the optimal mitigation of temperature variation along the cells.

[0070] The study may employ direct internal reformation (DIR), such as on-anode reactions, to synergistically match endothermic fuel processing needs with exothermic electrochemical reactions. Highly localized and intense “heat sink” effects can result in excessive temperature gradients. The exemplary “front-loading” of thermal conductance can alleviate this issue.

[0071] Per unit mass of interconnect material, the redesigned cells passively promote more temperature uniformity, and this can translate to less extensive reactant stream processing, such as air preheating and fuel processing. The reductions in financial, performance, and size costs associated with such balance-of-plant rigors are the leading benefits that should supersede stack-specific trade-offs such as reduced stack-level power density given the more voluminous interconnects, i.e., the net improvement in system-level metrics should warrant any negative effects in stack-level metrics. Beyond a static, purely computational attempt to corroborate this expectation, there are two synchronized leverage opportunities to test the system- wide, dynamic performance impact via a pioneering NETL facility.

[0072] Discussion

[0073] The relevance, hence motivation, for the effort, stems from operational and developmental “bottlenecks” (i.e., hindrances) to SOFC commercialization that have been in existence for decades. The operational hindrance regards the conventional approach taken to thermally manage SOFC stacks. Fig. 1 shows an industrial example, wherein even an aggressive attempt to develop “power dense” SOFC systems for small vehicular/portable applications is evidently limited by substantial “process thermal management” needs (i.e., reference the relative size and centrality of this process in the overall process flow diagram). [0074] Typically, air is preheated before serving as the stack oxidant stream, despite the fact that air is also intended to be a primary means of dissipating the cells’ byproduct thermal energy. This is done in order to influence a more uniform set of temperatures along the electroactive region, thus: 1) better approaching intended temperatures for electrochemical and chemical (i.e., fuel stream) reactions to proceed; 2) reducing or precluding the possibility of damaging thermally induced stresses arising within the ceramic, ceramic/metal stack structure. The counter-intuitive irony, however, is that one has to extensively preheat the very medium that is meant to serve as a critical heat sink. This issue is compounded in that a larger heat capacitance rate of air (e.g., easily six to eight times the Faradaic need) has to be supplied to the stack in order to compensate for the smaller temperature differences (i.e., between cells and air) when such preheating occurs. Commercialization is thus opposed because of greater balance-of-plant investment requirements (e.g., larger blowers, gas-to-gas heat exchangers) and performance ramifications (e.g., significantly greater blower parasitics).

[0075] The exemplary system and method can provide a new paradigm for flexible SOFC operation (anionic or cationic/protonic) without rigid constraint upon thermal neutral voltage settings, that can operate at higher voltage, “hydrogen-dense” electrolysis (i.e., heightened intensity of hydrogen production per unit electroactive area).

[0076] The exemplary system and method can reduce the thermal management balance-of-plant, e.g., reduced turbomachinery for excess reactants stream supply, reduced reactants stream pre-heat exchangers, with cells that naturally dampen temperature gradients that might otherwise occur.

[0077] Conclusion

[0078] Various sizes and dimensions provided herein are merely examples. Other dimensions may be employed.

[0079] Although example embodiments of the present disclosure are explained in some instances in detail herein, it is to be understood that other embodiments are contemplated. Accordingly, it is not intended that the present disclosure be limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The present disclosure is capable of other embodiments and of being practiced or carried out in various ways.

[0080] It must also be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” or “ 5 approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, other exemplary embodiments include from the one particular value and/or to the other particular value.

[0081] By ‘ ‘comprising” or “containing” or “including” is meant that at least the name compound, element, particle, or method step is present in the composition or article or method, but does not exclude the presence of other compounds, materials, particles, method steps, even if the other such compounds, material, particles, method steps have the same function as what is named.

[0082] In describing example embodiments, terminology will be resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art and includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. It is also to be understood that the mention of one or more steps of a method does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified. Steps of a method may be performed in a different order than those described herein without departing from the scope of the present disclosure. Similarly, it is also to be understood that the mention of one or more components in a device or system does not preclude the presence of additional components or intervening components between those components expressly identified.

[0083] The term “about,” as used herein, means approximately, in the region of, roughly, or around. When the term “about” is used in conjunction with a numerical range, it modifies that range by extending the boundaries above and below the numerical values set forth. In general, the term “about” is used herein to modify a numerical value above and below the stated value by a variance of 10%. In one aspect, the term “about” means plus or minus 10% of the numerical value of the number with which it is being used. Therefore, about 50% means in the range of 45%-55%. Numerical ranges recited herein by endpoints include all numbers and fractions subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.90, 4, 4.24, and 5).

[0084] Similarly, numerical ranges recited herein by endpoints include subranges subsumed within that range (e.g., 1 to 5 includes 1-1.5, 1.5-2, 2-2.75, 2.75-3, 3-3.90, 3.90-4, 4-4.24, 4.24-5, 2-5, 3-5, 1-4, and 2-4). It is also to be understood that all numbers and fractions thereof are presumed to be modified by the term “about.”

[0085] The following patents, applications, and publications, as listed below and throughout this document, describes various application and systems that could be used in combination the exemplary system and are hereby incorporated by reference in their entirety herein.

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Claims

What is claimed is:

1. A device comprising: a solid oxide cell comprising a substrate member comprising a top interconnect and a bottom interconnect extending there from to form channels for the respective flow of a hydrogen stream and an oxygen stream, the top interconnect and the bottom interconnect being configured to couple to a cathode structure and an anode structure, respectively, to form a unit cell, wherein multiple unit cells are stacked to form a solid oxide cell stack, and wherein each of the top interconnect and bottom interconnect of each solid oxide cell has a passive thermal management structure comprising a hollow structure configured to concentrate a thermal conductance of the interconnect at an end portion of the interconnect.

2. The device of claim 1, wherein the solid oxide cell includes (i) a top portion formed by the top interconnect, the top portion comprising an inlet and an outlet, wherein the top interconnect defines a manifold comprising a plurality of channels between the inlet and the outlet, and (ii) a bottom portion formed by the bottom interconnect, the bottom portion comprising an second inlet and a second outlet, wherein the bottom interconnect defines a second manifold comprising a plurality of channels between the second inlet and the second outlet.

3. The device of claim 1 or 2, wherein the passive thermal management structure comprising the hollow structure has a length spanning about 50% of a length of the interconnect of the solid oxide cell.

4. The device of claim 1 or 2, wherein the passive thermal management structure comprising the hollow structure has a length spanning between 30% and 70% of a length of the interconnect of the solid oxide cell.

5. The device of any one of claims 1 - 4, wherein the passive thermal management structure comprising the hollow structure has a uniform cross-sectional area.

6. The device of any one of claims 1 - 4, wherein the passive thermal management structure comprising the hollow structure has a non-uniform cross sectional region.

7. The device of any one of claims 1 - 6, wherein the solid oxide cell is a solid oxide fuel cell.

8. The device of any one of claims 1 - 6, wherein the solid oxide cell is a solid oxide electrolysis cell.

9. A system comprising: a plurality of solid-oxide cell stack, wherein each solid oxide cell comprises: a substrate member comprising a top interconnect and a bottom interconnect extending there to form channels for the respective flow of a hydrogen stream and an oxygen stream, the top interconnect and the bottom interconnect being configured to couple to a cathode structure and an anode structure, respectively, to form a unit cell, wherein multiple unit cells are stacked to form a solid oxide cell stack, and wherein each of the top interconnect and bottom interconnect of each solid oxide cell has a passive thermal management structure comprising a hollow structure configured to concentrate a thermal conductance of the interconnect at an end portion of the interconnect.

10. The system of claim 9, wherein each solid oxide cell includes (i) a top portion formed by the top interconnect, the top portion comprising an inlet and an outlet, wherein the top interconnect defines a manifold comprising a plurality of channels between the inlet and the outlet, and (ii) a bottom portion formed by the bottom interconnect, the bottom portion comprising an second inlet and a second outlet, wherein the bottom interconnect defines a second manifold comprising a plurality of channels between the second inlet and the second outlet.

11. The system of claim 9 or 10, wherein the passive thermal management structure comprising the hollow structure has a length spanning about 50% of a length of the interconnect of the solid oxide cell.

12. The system of claim 9 or 10, wherein the passive thermal management structure comprising the hollow structure has a length spanning between 30% and 70% of a length of the interconnect of the solid oxide cell.

13. The system of any one of claims 9 - 12, wherein the passive thermal management structure comprising the hollow structure has a uniform cross-sectional area.

14. The system of any one of claims 9 - 12, wherein the passive thermal management structure comprising the hollow structure has a non-uniform cross-sectional region.

15. The system of any one of claims 9 - 14, wherein the solid oxide cell is a solid oxide fuel cell.

16. The system of any one of claims 9 - 14, wherein the solid oxide cell is a solid oxide electrolysis cell.