WO2022177824A1

WO2022177824A1 - Two-stage fuel cell system

Info

Publication number: WO2022177824A1
Application number: PCT/US2022/016149
Authority: WO
Inventors: Irfan Saif Hussaini
Original assignee: Cummins Inc.
Priority date: 2021-02-22
Filing date: 2022-02-11
Publication date: 2022-08-25

Abstract

The present disclosure is directed to a two-stage fuel cell comprising air that flows in a first direction, a first stage comprising a first region and a second region. The first region has a first fuel that that comprises a fuel content that is greater than the a second fuel comprised in a second region.

Description

TWO-STAGE FUEL CELL SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This non-provisional application claims the benefit and priority, under 35 U.S.C. § 119(e) and any other applicable laws or statutes, to U.S. Provisional Application Serial No. 63/152,098 filed on February 22, 2021, the entire disclosure of which is hereby expressly incorporated herein by reference.

TECHNICAL FIELD

[0002] The present disclosure generally relates to a two-stage fuel cell that increases the efficiency of a fuel cell system.

BACKGROUND

[0003] High temperature fuel cell systems are known for their efficient use of fuel to develop direct current (DC) and or alternating current (AC) electric power. Under normal operation, a typical high temperature fuel cell system, such as a solid oxide fuel cell (SOFC) system maintains a system operating temperature of approximately 500°C or greater, ranging from about 600°C to about 1000°C, with optimal temperature at about 700°C. Typically, the fuel cell converts hydrogen (fuel) and oxygen (oxidant) into water (byproduct) to produce electricity.

[0004] Current cycle fuel cell systems routinely achieve at least 50% conversion efficiency. The efficiency of combined cycle fuel cell systems in converting hydrocarbon fuel into electrical energy is limited by mechanisms within the system that produce or lose heat. Additional heat or fuel losses of the fuel cell may also be due to partial utilization of fuel.

[0005] Typical or common attempts to improve performance or efficiency of combined cycle fuel cell systems at low fuel utilization have involved fuel and/or air recycling. Fuel recycling in combined cycle fuel cell systems, however, often require large reformers and/or high temperature blowers that are costly and technically challenging. Similarly, air recycling in combined cycle fuel cell systems requires high temperature blowers that are not cost-effective.

[0006] Thus, there exists a need to design and implement more efficient fuel cells that prevent such heat and fuel losses and inefficiencies that affect the overall fuel cell system performance. For these and other reasons, the present specification provides improved two-stage fuel cell systems and methods for increasing the efficiency of a fuel cell.

SUMMARY

[0007] Embodiments of the present disclosure are included to meet these and other needs. The present disclosure is directed to a two-stage fuel cell comprising air that flows in a first direction, a first stage comprising a first region and a second region. The first region has a first fuel that that comprises a fuel content that is greater than the a second fuel comprised in a second region.

[0008] The first fuel enters the second stage and does not mix with the second fuel after the first fuel enters the second stage. The first fuel and the second fuel flow in a second direction that crosses the first direction of the air. The first fuel may comprise about 10% to about 15% greater fuel content than the second fuel.

[0009] The first fuel and the second fuel flow in a second direction that crosses the first direction of the air. In one embodiment, the first fuel of the upper region of the first stage is exhausted out of the fuel cell after it enters the second stage. In one embodiment, the second fuel of the lower region of the first stage is recycled back into the fuel cell.

[0010] The present disclosure is also directed to a fuel cell stack comprising a plurality of the two-stage fuel cells. The present disclosure is further directed to a fuel cell system comprising a plurality of the two-stage fuel cells or the fuel cell stacks. The present disclosure also related to a two-stage fuel cell.

[0011] The two-stage fuel cell comprises air that flows in a first direction and a fuel flow that flows in a second direction that crosses the direction of the air. The fuel flow comprises an inlet fuel flow and an outlet fuel flow. The outlet fuel flow comprises a first region and a second region. The first region of the two- stage fuel cell has a first fuel that comprises a fuel content that is greater than a second fuel comprised by a second region. The first fuel is recirculated to mix with the inlet fuel flow and the second fuel and the outlet fuel flow are exhausted out of the two-stage fuel cell.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters represent like parts throughout the drawings, wherein: [0013] FIG. 1 is a thermal map of a typical fuel cell configuration.

[0014] FIG. 2 is a thermal map of a first embodiment of the present two-stage fuel cell comprising a more efficient configuration.

[0015] FIG. 3 is a block diagram of a second embodiment of the present two-stage fuel and the present two- stage fuel cell system.

[0016] FIG. 4 is a thermal map of the second embodiment of the present two-stage fuel cell configuration.

[0017] FIG. 5 is an efficiency simulation of the two-stage fuel cell.

[0018] FIG. 6 is a thermal map of an efficiency simulation of the second embodiment of the two-stage fuel cell.

[0019] These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings described herein. Reference is also made to the accompanying drawings that form a part hereof and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice what is claimed and it is to be understood that other embodiments may be utilized and that logical, mechanical, and electrical changes may be made without departing from the spirit and scope of the claims. The following detailed description is, therefore, not to be taken in a limiting sense.

DETAILED DESCRIPTION

[0020] The present disclosure is directed to a combined cycle fuel cell system, such as a two-stage fuel cell system. The combined cycle fuel cell system of the present disclosure comprises two stages of fuel usage. The first stage of the present two-stage fuel cell system, such as one that may be used in a vehicle and/or a powertrain system, comprises one or more of the following components: a fuel cell system, a coolant, water output from the fuel cell system, a radiator, a pump, and a radiator fan.

[0021] FIG. 1 is a thermal profile of a typical one-stage fuel cell system known in the art. This one-stage fuel cell system comprises a crossflow configuration of the fuel and air, which aids in the increased efficiency of this fuel cell system embodiment. A crossflow configuration of fuel and air includes any flow configuration in a fuel cell system that allows the air to flow in one direction while the fuel flows in a separate direction. [0022] An exemplary embodiment shown in FIG. 1 demonstrates a crossflow configuration. Here, the air flows vertically in a North-to- South direction across the fuel cell, while the fuel flows horizontally in an West-to-East direction across the fuel cell. As such, the air flow and the fuel flow are perpendicular, and therefore cross one another providing the crossflow configuration.

[0023] Closer to the exit or exhaust of the fuel cell, the fuel content may be higher with a hydrogen content in the upper region of the fuel cell being about 10% to about 15% more than the hydrogen content of the fuel in the bottom-right lower region of the fuel cell. The fuel higher content of the upper regions of the fuel cell decreases in a gradient towards the bottom of the fuel cell system where the fuel content is relatively lower. After exiting the fuel cell system, the fuel across the electrolyte gradient is generally mixed in a single manifold that is external or internal to the fuel cell.

[0024] After mixture, a large portion of the fuel is recirculated back into the fuel cell for reuse. A smaller portion of the fuel is exhausted. The exhausted fuel content is then burned prior to release from the fuel cell system into the atmosphere to prevent or reduce any harmful toxins or chemical from entering the atmosphere.

[0025] FIG. 2 is a thermal profile of one embodiment of a two-stage fuel cell of the present disclosure that demonstrates better fuel efficiency. In this embodiment, the two- stage fuel cell may not comprise a second stage that is separate from the first stage. In another embodiment, the first stage and the second stage are one in the same stage. In a further embodiment of the present two-stage fuel cell, the fuel cell may comprise two or more stages, such as three, four, five, or more, such as a plurality of stages that are connected and/or separated as described herein for the first and second stages.

[0026] In this embodiment, the fuel from the upper region of the fuel cell, which has a higher fuel content, is mixed in a first manifold (i.e., Mixture-1) and recirculated into the fuel cell system. The fuel from the bottom portion of the fuel cell, which has a lower fuel content, is mixed in a second, separate manifold (i.e., Mixture-2), and is exhausted. The exhausted fuel content is then burned prior to release from the fuel cell system into the atmosphere to prevent or reduce any harmful toxins or chemicals from entering the atmosphere. Better fuel efficiency is achieved by mixing the fuel in two separate and different manifolds based on the fuel content gradient that is established in a fuel cell with a crossflow configuration. [0027] FIG. 3 is a block diagram of one embodiment of the two-stage fuel cell 300 of the present disclosure. The first and second stages of the two-stage fuel cell system are two separate units or structural components of the system where fuel is consumed. The first stage 310 and second stage 320 of the two-stage fuel cell system are built as part of the fuel cell and do not require a separate fuel cell stack. In exemplary embodiments, the fuel cell is a solid oxide fuel cell (SOFC). In other embodiments, any other type of fuel cell may be used.

[0028] The two-stage fuel cell system of the present disclosure is designed with two zones. The first zone comprises a longer fuel path-length that has an extended area ranging from about 20% to about 60% greater than the area of the second zone. The first zone with the longer fuel path serves as the first stage 310. Fuel enters the fuel cell at the first stage 310. The second active zone or area of the fuel cell serves as the second stage 320. The fuel that enters the second stage 320 has passed through the first stage 310 and comprises the higher fuel content at the exit of the first stage 310. Exhaust fuel and air from the second stage 320 are kept separate from the exhaust fuel and air of the first stage 310, such that the higher fuel content from the first stage 310 does not mix with the lower fuel content of the second stage.

[0029] Fuel exhaust from the first stage 310 is recycled back into the fuel cell whereas fuel exhaust from the second stage 320 is directed out of the fuel cell where any remaining chemical energy in the second stage 320 exhaust stream is converted into heat. This exhaust heat is recuperated by incoming air and fuel streams and recycled into and by the fuel cell system comprising the fuel cell 300.

[0030] Referring back to FIG. 3, the first zone with the longer fuel path serves as the first stage 310 of the fuel cell 300. The second active area or zone of the fuel cell 300 serves as the second stage 320. Fuel enters the first stage 310 at a location, such as a first, entry boundary or manifold of the first zone 324. Fuel exiting the first stage 310 forms a gradient across the first stage 310, from the first, upper region 314 to the second, lower region 316 of the first stage 310 of the fuel cell 300 in a direction that crosses (e.g., is perpendicular) to fuel flow, as shown in FIG. 4.

[0031] Higher fuel content (e.g., Mixture-1) is found in the first, upper region 314 of the first stage 310 compared to the fuel found at the second, lower region 316 of the first stage 310. The fuel content in the first, upper region may be about 5-25%, about 5-20%, about 5-15%, about 5-10%, about 10-25%, about 10-20%, or about 10-15% higher than the fuel content of the lower region of the fuel cell and any specific fuel content comprised therein. For example, a higher hydrogen content fuel may be found in the first, upper region 314 of the first stage 310 compared to the fuel found at the second, lower region 316 of the first stage 310. In some embodiment, the fuel hydrogen content in the first, upper region may be about 5-25%, about 5-20%, about 5-15%, about 5-10%, about 10-25%, about 10-20%, or about 10-15% higher than the fuel hydrogen content of the lower region of the fuel cell and any specific fuel hydrogen content comprised therein.

[0032] The exhaust fuel from the upper region 314 of the first stage 310 is sent to the second stage 320 through a second, exit boundary or manifold of the first stage 318. The fuel exhaust from the lower region 316 of the first stage 310 is recirculated into fuel cell 300 through the first stage 310.

[0033] In one embodiment, the upper region 314 of the first stage 310 of the fuel cell 300 is the about the top 50% of the fuel cell. In other embodiments, the upper region 314 ranges from about the top 50% to about the top 75% of the fuel cell 300. In some embodiments, the upper region 314 ranges from about the top 50% to about the top 25% of the fuel cell 300.

[0034] Air enters the one or more inlet ports 302 of a fuel cell 300 after passing through an air pre-heater 330. In some embodiments, air directly enters the fuel cell 300 through one or more inlet ports 302 after being preheated. In some embodiments of a SOFC two- stage system, air enters the air pre-heater 330 at about 20°C and exits the air pre-heater 330 at about 700°C to about 820°C, the normal operating temperature of a SOFC system.

[0035] In some embodiments, air may enter and exit air pre-heater 330 and the one or more inlet ports 302 at a different temperature, particularly depending on the type of fuel cell being utilized for the two-stage fuel cell system. Air passes through both the first stage 310 and the second stage 320 of the fuel cell 300 in a direction perpendicular to the direction of fuel flow. Fuel enters the first stage 310 of the fuel cell 300 through a fuel pre heater 360, a reformer 350, and an air fuel heat exchanger 340.

[0036] In some embodiments, the fuel is pressurized. For example, the fuel may be pressurized to about 4.5 psi. In other embodiments, the fuel is pressurized after passing through a pressurizer 326, such as an air compressor or an air blower. In some embodiments, fuel enters the pressurizer 326 at about 20°C. In other embodiments, fuel enters the pressurizer 326 at a different temperature. For example, in some embodiments, after passing through the fuel pre-heater 360, a reformer 350, and the air fuel heat exchanger 340, fuel enters the first stage 310 of the solid oxide fuel cell 300 at about 700°C and at about 2.5 psi pressure.

[0037] In some embodiments, the fuel may enter the first stage 310 of the solid oxide fuel cell 300 at different temperatures and pressures, which also changes dependent on the type of fuel cell utilized. Fuel from the upper region 314 of the first stage 310 exits the first stage 310 and passes to the second stage 320 through the second, exit boundary 318.

[0038] The air exits the first stage 310 of the fuel cell 300 at the outlet ports 304 passes through the air fuel heat exchanger 340 prior to passing through the air pre-heater 330, and the fuel cooler 370 prior to exiting. In some embodiments, the air exits the first stage 310 of the fuel cell 300 at a temperature of about 820°C and at about 1.5 psi.

[0039] In some embodiments, the temperature of air or fuel exiting the fuel cell (e.g., at the fuel cell exhaust) does not exceed 820°C, since air or fuel temperatures exiting the fuel cell at temperatures greater than about 820°C may damage the solid oxide fuel cell. In other embodiments, the air exits the first stage 310 of the solid oxide fuel cell 300 at the outlet ports 304 at different temperatures and pressures, which also change dependent on the type of fuel cell utilized.

[0040] The exhaust fuel from the second stage 320 of the fuel cell 300, pass through a manifold 308 and then a catalytic oxidizer (catox) 380 before passing through the air fuel heat exchanger 340, the air pre-heater 330, and the fuel cooler 370 prior to exiting the fuel cell. The exhaust fuel from the second stage 320 of the fuel cell 300 is not recycled back into the fuel cell 300. In some embodiments, the fuel exhaust exits the second stage 320 of the fuel cell 300 at about 820°C and at about 2 psi. In some embodiments, the fuel exhaust exits the second stage 320 of the solid oxide fuel cell 300 at different temperatures and pressures, which also change dependent on the type of fuel cell utilized.

[0041] The exhaust air from the second stage 320 of the fuel cell 300, pass through a manifold 312, through a catalytic oxidizer (catox) 380 before passing through the air fuel heat exchanger 340, the air pre-heater 330, and the fuel cooler 370 and exiting the fuel cell. In some embodiments, the air exhaust exits the second stage 320 of the fuel cell 300 at about 2 psi.

[0042] In some embodiments, the air exhaust exits the second stage 320 of the fuel cell 300 at a different pressure. In other embodiments, the air and fuel exhaust exits the catox 380 at about 900°C and at about 1.5 psi before passing through the air fuel heat exchanger 340.

[0043] In some embodiments, the air exhaust from both the first stage 310 and the second stage 320 of the fuel cell 300, and the fuel exhaust from the second stage 320 of the fuel cell 300 exit the air pre-heater 330 at about 200°C and at about 0.5 psi. In other embodiments, the air exhaust from both the first stage 310 and the second stage 320 of the fuel cell 300, and the fuel exhaust from the second stage 320 of the fuel cell 300 exit the air pre -heater 330 at different temperatures and pressures.

[0044] For example, in some embodiments, the fuel exits the lower region 316 of the first stage 310 of the fuel cell 300 at about 820°C and at about 2 psi through a manifold 306, and passes through the fuel pre-heater 360 and the fuel cooler 370 before being pressurized and recycled back into fuel cell 300 at the first stage 310 through the manifold 322. In other embodiments, the fuel exits the lower region 316 of the first stage 310 of the fuel cell 300 at different temperatures and pressures.

[0045] In some embodiments, the fuel exits the fuel pre-heater 360 at about 250°C. In other embodiments, the fuel exits the fuel pre-heater 360 at different temperatures. In additional embodiments, the fuel exits the fuel cooler 370 at about 200°C and at about 1 psi. In further embodiments, the fuel exits the fuel cooler 370 at different temperatures and pressures.

[0046] Notably, a crossflow configuration of the present two-stage fuel cell system may comprise any embodiment where the air (e.g., the air flow) and the fuel (e.g., the fuel flow) cross. For example, a crossflow configuration may comprise a perpendicular (e.g., about a 90 degree angle) flow of air and fuel that cross, as well as any degree or angle at which the air flow and the fuel flow may cross. Importantly, in one embodiment, a crossflow configuration of the present two-stage fuel cell system does not comprise air flows and fuel flows or streams that do not cross at all, such as air and fuel flows that are parallel.

[0047] FIG. 4 is a thermal profile of an exemplary embodiment of a two-stage fuel cell of the present disclosure. In this embodiment, the higher fuel content from the upper region 314 of the first stage 310 of the fuel cell 300 is (e.g., Mixture- l)provided for use in the additional second stage 320 of the fuel cell 300. In the second stage, Mixture-1 provides more current and power production for the fuel cell 300. After use in the second stage 320, the fuel of Mixture-1 is exhausted. In some embodiments, Mixture-1 is not mixed. [0048] The fuel exhaust from the second stage 320 is not recirculated back into the fuel cell 300. Fuel from the lower region 316 of the first stage 310 of the fuel cell 300 is mixed in the manifold 306 (e.g., Mixture-2) of the fuel cell and recirculated back into the fuel cell. The exhaust from the lower region 316 of the first stage 310 of the fuel cell 300 comprises lower content fuel content compared to the exhaust from the upper region 314 of the fuel cell 300.

[0049] Importantly, the fuel utilization in the first stage of the two- stage fuel cell system usually ranges from about 80% to about 90%. Additional fuel consumption of about 50% to about 70% is implemented in the second stage of the fuel cell. This additional fuel consumption and fuel recycling that come from the second stage fuel increases the efficiency of the present two-stage fuel cell system by about 2% to about 5%, which provides a significant improvement on the life, durability, performance, and maintenance of the fuel cell system.

[0050] FIG. 5 is an end-of-life simulation of an embodiment of a two-stage fuel cell of the present disclosure. FIG. 5 illustrates that a two-stage fuel cell allows higher total fuel utilization, and shows a gross electrical efficiency of about 60%. The use of the present two-stage fuel cell system demonstrates a gain of about 2% in efficiency when compared to using a fuel cell with only one-stage as demonstrated in FIG. 1. While the efficiency gain may be even more, a 2% efficiency gain for a two-stage fuel cell system provides significant improvement for the life, durability, and overall performance of the present two-stage fuel cell and its system over current fuel cell systems.

[0051] FIG. 6 illustrates a thermal profile of the simulation illustrated in FIG. 5 when both air and reformate fuel enter the two-stage fuel cell system at about 700°C. After the second stage, the fuel exhaust exits to a catalytic oxidizer (catox) at about 750°C. The fuel exhaust is recirculated through the fuel cell system and exits the fuel cell at about 800°C.

[0052] Referring back to FIG. 3, in some embodiments, one or more or a plurality of fuel cells 300 may be connected. Each of those fuel cells 300 may be a two-stage fuel cell system. In other embodiments, a plurality of two-stage fuel cells 300 may be connected to either one or a plurality of one-stage fuel cell systems. In other embodiments, a fuel cell 300 may be used to power a moving object, such as a vehicle (e.g., a truck, a car, or a train). In other embodiments, a fuel cell 300 may be used to power stationary object, such as an immovable powertrain or an industrial facility. [0053] A typical fuel cell is designed in a fuel cell stack comprising multiple fuel cells, where the fuel cells are designed to a configuration where one or more separate stages (e.g., a first stage and a second stage) are arranged as cascaded units. The cascaded units of the first and second stages may be configured to be in direct contact with one another such that no device is necessary to connect the first and second stages. In a separate embodiment, the cascaded units of the first and second stages may be separated, such as by a second, structural boundary or a manifold 318.

[0054] Typically, the first and second stages are configured to be in contact with one another, even if not direct contact, in order to enable ease of fuel flow from one stage (e.g., the first stage) to another stage (e.g., the second stage), even if through any existing structural boundary 318. In some embodiments, the boundary of the first stage and/or the boundary of the second stage may comprise a structural component or apparatus, such as any type of a pipe, a passage, a conduit, a membrane, a material, or a portal that allows or enables fuel to flow from the first stage to the second stage (not shown). In some embodiments, no such additional apparatus is required for the fuel to flow from the first stage directly into the second stage.

[0055] In an embodiment of the present two-stage fuel cell system, the two stages are built into the fuel cell itself. Thus, the staging is done in or on the fuel cell, forming a single stack that is designed with a fixed recirculation ratio. The recirculation ratio (RR) refers to the amount of recirculated fuel flow compared to the amount of the full fuel flow, including the recirculated fuel flow and the exhaust fuel flow.

[0056] The two- stage design or configuration of the fuel cell that requires only a single fuel cell stack and helps achieve high efficiency at a lower overall system cost. The present two-stage fuel cell eliminates the need for intermediate heat exchangers, since gas or fuel is hot and is led directly from the first stage into the into the second stage of the fuel cell 320, allowing the voltage to remain the same. However, having a single fuel cell stack also requires having to operate both stages at a fixed voltage and/or a fixed recirculation ratio. Having a fixed recirculation ratio that does not change in each stage is desirable as it provides stable and predictable operation of the two-stage fuel cell system.

[0057] In contrast, with a two-stage fuel cell system comprising two or more separate fuel cell stacks, voltages of each fuel cell stack can be different. Consequently, the first and second stages of each of the two or more fuel cell stacks may also be different. This multi-stack embodiment of the present two-stage fuel cell system provides a slightly higher power output and also allows for the recirculation ratio to be changed during operation as compared to a single fuel cell stack embodiment described above. In most instances, having the two stages at the same voltage is preferable as it simplifies power electronics and control requirements and their associated costs.

[0058] To achieve high efficiency, fuel cell systems need to run at as high an overall fuel utilization as possible. In a one-stage design, high overall fuel utilization drives the system towards higher single-pass fuel utilization (about 0.75 and up). High single -pass fuel utilization can be countered by a higher recirculation ratio, but at the expense of lower Nernst potential, higher blower parasitic s, and bigger pipes to accommodate the flow.

[0059] A two-stage design of a fuel cell, as described herein, allows for a comfortable single-pass fuel utilization of about 0.6 and a reasonably low recirculation ratio to maintain a healthy steam-to-carbon ratio. These are advantages of the present two-stage fuel cell system as compared to one-stage or two-stage systems currently in the market.

[0060] Notably, embodiments presented herein involve systems and methods for increasing the efficiency of a fuel cell system. Advantageously, these two-stage fuel cell system embodiments provide a paradigm shift in fuel cell design for achieving high efficiency fuel cell systems. These embodiments allow for the two-stage fuel cell system to be more compact and economical.

[0061] These two-stage fuel cell system embodiments are also preferably designed for solid oxide fuel cells. However, the two-stage fuel cell configuration of the present disclosure may be adapted for any type of fuel cell configured to have air and fuel crossflow. In an exemplary embodiment, a fuel cell comprises a crossflow configuration when the fuel and air flow in perpendicular directions.

[0062] The following numbered embodiments are contemplated and non-limiting:

1. A two-stage fuel cell, comprising: (i) air that flows in a first direction, (ii) a first stage comprising a first region and a second region, wherein the first region has a first fuel that comprises a fuel content that is greater than the a second fuel comprised in a second region, (iii) a second stage, wherein the first fuel enters the second stage, wherein the first fuel does not mix with the second fuel after the first fuel enters the second stage, and wherein the first fuel and the second fuel flow in a second direction that crosses the first direction of the air.

2. A two-stage fuel cell, comprising: (i) air that flows in a first direction, (ii) a fuel flow that flows in a second direction that crosses the direction of the air, wherein the fuel flow comprises an inlet fuel flow and an outlet fuel flow, (iii) wherein the outlet fuel flow comprises a first region and a second region, (iv) wherein the first region has a first fuel that comprises a fuel content that is greater than a second fuel comprised by a second region, and (v) wherein the first fuel is recirculated to mix with the inlet fuel flow and the second fuel and the outlet fuel flow are exhausted out of the two-stage fuel cell.

3. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the two-stage fuel cell includes a plurality of two- stage fuel cells.

4. The two-stage fuel cell of clause 3, any other suitable clauses, or any combination of suitable clauses, wherein the plurality of two-stage fuel cells is comprised in a two-stage fuel cell stack, a two-stage fuel cell system, a high temperature fuel cell system, a combined cycle fuel cell system, and/or a fuel cell stack.

5. The two-stage fuel cell of clause 4, any other suitable clauses, or any combination of suitable clauses, wherein the high temperature fuel cell system is a solid oxide fuel cell system.

6. The two-stage fuel cell of clause 4, any other suitable clauses, or any combination of suitable clauses, wherein the high temperature fuel cell system maintains a system operating temperature of approximately 500°C or greater, ranging from about 600°C to about 1000°C, and / or at or about 700°C.

7. The two-stage fuel cell of clause 4, any other suitable clauses, or any combination of suitable clauses, wherein the combined cycle fuel cell system comprises two stages of fuel usage.

8. The two-stage fuel cell of clause 4, any other suitable clauses, or any combination of suitable clauses, wherein the two-stage fuel cell stack and/or fuel cell stack comprises multiple fuel cells.

9. The two-stage fuel cell of clause 8, any other suitable clauses, or any combination of suitable clauses, wherein the fuel cells are designed to a configuration where one or more separate stages and/or a first stage and a second stage are arranged as cascaded units.

10. The two-stage fuel cell of clause 9, any other suitable clauses, or any combination of suitable clauses, wherein the cascaded units of the first and second stages are configured to be in direct contact with one another such that no device is necessary to connect the first and second stages.

11. The two-stage fuel cell of clause 9, any other suitable clauses, or any combination of suitable clauses, wherein the cascaded units of the first and second stages are separated by a structural boundary and/or a manifold. 12. The two-stage fuel cell of clause 11, any other suitable clauses, or any combination of suitable clauses, wherein the structural boundary of the first stage and/or the second stage is a structural component or apparatus, a pipe, a passage, a conduit, a membrane, a material, and/or a portal that allows or enables fuel to flow from the first stage to the second stage.

13. The two-stage fuel cell of clause 3, any other suitable clauses, or any combination of suitable clauses, wherein one or more of the plurality of two-stage fuel cells are connected to each other, and/or one or a plurality of one-stage fuel cell systems.

14. The two-stage fuel cell of clause 13, any other suitable clauses, or any combination of suitable clauses, wherein each of the fuel cells in the plurality of two-stage fuel cells are two- stage fuel cell systems.

15. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the two-stage fuel cell has two stages built into the fuel cell.

16. The two-stage fuel cell of clause 15, any other suitable clauses, or any combination of suitable clauses, wherein the staging of the two stages is done in or on the fuel cell to form a single stack that is designed with a fixed recirculation ratio.

17. The two-stage fuel cell of clause 16, any other suitable clauses, or any combination of suitable clauses, wherein the recirculation ratio is the amount of recirculated flow compared to the amount of the full fuel flow, the recirculated fuel flow and/or the exhaust fuel flow.

18. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the two-stage fuel cell is used in a vehicle, a powertrain system, a moving object, a truck, a car, a train, a power stationary object, an immovable powertrain, and/or an industrial facility.

19. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the two-stage fuel cell is a solid oxide fuel cell and/or any other type of fuel cell.

20. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the two-stage fuel cell does not comprise a second stage that is separate from the first stage.

21. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the two-stage fuel cell comprises two or more stages, three stages, four stages, five stages, and/or a plurality of stage that are connected and/or separated. 22. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the air enters one or more inlet ports of a fuel cell after passing through an air pre -heater.

23. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the two-stage fuel cell has a crossflow configuration which allows the air or the air flow and the fuel or the fuel flow to cross.

24. The two-stage fuel cell of clause 23, any other suitable clauses, or any combination of suitable clauses, wherein the crossflow configuration comprises a perpendicular or 90 degree angle flow of air and fuel that cross, and/or any degree or angle at which the air flow and fuel flow may cross.

25. The two-stage fuel cell of clause 23, any other suitable clauses, or any combination of suitable clauses, wherein the crossflow configuration comprises air flows and fuel flows that are parallel.

26. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the two-stage fuel cell allows air and reformate fuel to enter at about 700°C, allows exhaust fuel to exit a catalytic oxidizer at about 750°C after the second stage, and allows exhaust fuel to recirculate through the fuel cell and exit the fuel cell at about 800°C.

27. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the air directly enters the fuel cell through the one or more inlet ports after being preheated.

28. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the air enters the air pre-heater at about 20°C and exits the air pre -heater at about 700°C to about 820°C.

29. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the air enters and exits the air pre-heater and the one or more inlet ports at a different temperature.

30. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the air passes through both the first stage and the second stage in a direction perpendicular to the direction of fuel flow.

31. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the air exits the first stage by passing through the air pre-heater, a fuel cooler, and one or more outlet ports. 32. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the air exits the first stage at a temperature of about 820°C and/or at about 1.5 psi.

33. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the air, the first fuel, and/or the second fuel exiting the fuel cell does not exceed 820°C.

34. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first stage comprises one or more fuel cell systems, one or more coolants, one or more water outputs from the fuel cell system, one or more radiators, one or more pumps, and/or one or more radiator fans.

35. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first stage and the second stage are one in the same stage.

36. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first stage includes mixing the fuel with the higher fuel content from the first region in a first manifold and/or recirculating the higher fuel content into the two-stage fuel cell and/or the fuel cell system.

37. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first stage includes mixing the fuel with the lower fuel content from the second region in a second manifold and/or exhausting the fuel.

38. The two-stage fuel cell of clause 37, any other suitable clauses, or any combination of suitable clauses, wherein the exhausted fuel content is burned prior to release from the two- stage fuel cell and/or the fuel cell system.

39. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first stage and the second stage are two separate units and/or structural components of the system.

40. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first stage and the second stage are built as part of the two-stage fuel cell and/or do not require a separate fuel cell stack.

41. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first stage is a first zone.

42. The two-stage fuel cell of clause 41, any other suitable clauses, or any combination of suitable clauses, wherein the first zone has an extended area ranging from about 20% to about 60% greater than the area of a second zone. 43. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first stage allows fuel to enter the two-stage fuel cell.

44. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first stage includes an entry boundary or manifold.

45. The two-stage fuel cell of clause 44, any other suitable clauses, or any combination of suitable clauses, wherein the entry boundary or manifold allows fuel to enter the first stage.

46. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first stage outputs exhaust fuel and air.

47. The two-stage fuel cell of clause 46, any other suitable clauses, or any combination of suitable clauses, wherein the exhaust fuel and/or air from the first stage is recycled back into the two-stage fuel cell.

48. The two-stage fuel cell of clause 46, any other suitable clauses, or any combination of suitable clauses, wherein the exhaust fuel and/or air exits from the first region and/or the second region.

49. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first stage outputs fuel.

50. The two-stage fuel cell of clause 49, any other suitable clauses, or any combination of suitable clauses, wherein the output fuel exiting the first stage forms a gradient across the first stage from the first region to the second region of the first stage in a direction that crosses and/or is perpendicular to fuel flow.

51. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first stage includes an exit boundary or manifold.

52. The two-stage fuel cell of clause 51, any other suitable clauses, or any combination of suitable clauses, wherein the exit boundary or manifold allows exhaust fuel from the first region to pass through and enter the second stage.

53. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first stage provides fuel with higher fuel content from the first region to the second stage.

54. The two-stage fuel cell of clause 53, any other suitable clauses, or any combination of suitable clauses, wherein the fuel with higher fuel content provides more current and power production in the fuel cell when in the second stage.

55. The two-stage fuel cell of clause 53, any other suitable clauses, or any combination of suitable clauses, wherein the fuel with higher fuel content is not mixed. 56. The two-stage fuel cell of clause 53, any other suitable clauses, or any combination of suitable clauses, wherein the fuel with higher fuel content is exhausted after the second stage.

57. The two-stage fuel cell of clause 56, any other suitable clauses, or any combination of suitable clauses, wherein the exhausted fuel is not recirculated back into the fuel cell.

58. The two-stage fuel cell of clause 53, any other suitable clauses, or any combination of suitable clauses, wherein the first stage mixes fuel from the second region in a manifold and/or recirculates the mixed fuel into the fuel cell.

59. The two-stage fuel cell of clause 58, any other suitable clauses, or any combination of suitable clauses, wherein exhaust of the fuel from the second region comprises lower fuel content compared to the exhaust from the first region.

60. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first stage has fuel utilization which ranges from about 80% to about 90%.

61. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first stage and the second stage are configured to be in contact with one another and/or in direct contact with one another.

62. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first region is an upper region of the first stage.

63. The two-stage fuel cell of clause 62, any other suitable clauses, or any combination of suitable clauses, wherein the upper region is about the top 50% of the fuel cell, ranges from about the top 50% to about the top 75% of the fuel cell, and/or ranges from about the top 50% to about the top 25% of the fuel cell.

64. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first region holds fuel with a fuel content of about 5-25%, about 5-20%, about 5-15%, about 5-10%, about 10-25%, about 10-20%, and/or about 10-15% higher than the fuel content of the second region of the fuel cell and/or any specific fuel content comprised therein.

65. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein first region holds fuel with a fuel hydrogen content of about 5-25%, about 5-20%, about 5-15%, about 5-10%, about 10-25%, about 10-20%, or about 10-15% higher than the fuel hydrogen content of the second region of the fuel cell and/or any specific fuel hydrogen content comprised therein.

66. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the second region is a lower region of the first stage. 67. The two-stage fuel cell of clause 66, any other suitable clauses, or any combination of suitable clauses, wherein the lower region holds lower fuel content.

68. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the second region has fuel exhaust that is recirculated into the two-stage fuel cell through the first stage.

69. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first fuel has about 10% to about 15% greater fuel content than the second fuel.

70. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first fuel is exhausted out of the fuel cell after it enters the second stage.

71. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first fuel and/or the second fuel enters the first stage through a fuel pre-heater, a reformer, and/or an air fuel heat exchanger.

72. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first fuel and/or the second fuel is pressurized and/or pressurized to about 4.5 psi or about 2.5 psi.

73. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first fuel and/or the second fuel is pressurized after passing through a pressurizer, an air compressor, and/or an air blower.

74. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first fuel and/or the second fuel enters the pressurizer at about 20°C, about 700°C or at a different temperature.

75. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first fuel and/or the second fuel passes through the fuel pre-heater, the reformer, the air fuel heat exchanger and enters the first stage at about 700°C and/or about 2.5 psi, and/or a different temperature and/or pressure.

76. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first fuel and/or the second fuel exit the fuel pre-heater at about 250°C or a different temperature.

77. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the first fuel and/or the second fuel exit the fuel cooler at about 200°C and/or at about 1 psi, or a different temperature and/or pressure. 78. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the second fuel of the second region of the first stage is recycled back into the fuel cell.

79. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the second fuel exits the second region of the first stage at about 820°C and/or at about 2 psi, or a different temperature and/or pressure.

80. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the second fuel exits the second region of the first stage through a manifold, the fuel pre-heater, and the fuel cooler before being pressurized and recycled back into the fuel cell at the first stage through the manifold.

81. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the second stage is the second zone.

82. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the second stage allows fuel that has passed through the first stage to enter the second stage.

83. The two-stage fuel cell of clause 82, any other suitable clauses, or any combination of suitable clauses, wherein the fuel that enters the second stage comprises the higher fuel content at the exit of the first stage.

84. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the second stage outputs exhaust fuel and air.

85. The two-stage fuel cell of clause 84, any other suitable clauses, or any combination of suitable clauses, wherein the exhaust fuel and/or air from the second stage is kept separate from exhaust fuel and air from the first stage.

86. The two-stage fuel cell of clause 84, any other suitable clauses, or any combination of suitable clauses, wherein the exhaust fuel and/or air from the second stage is directed out of the two-stage fuel cell.

87. The two-stage fuel cell of clause 84, any other suitable clauses, or any combination of suitable clauses, wherein the exhaust fuel from the second stage passes through a manifold, a catalytic oxidizer, the air fuel heat exchanger, the air pre -heater, and/or the fuel cooler before exiting the fuel cell.

88. The two-stage fuel cell of clause 84, any other suitable clauses, or any combination of suitable clauses, wherein the exhaust fuel from the second stage is not recycled back into the fuel cell. 89. The two-stage fuel cell of clause 84, any other suitable clauses, or any combination of suitable clauses, wherein the exhaust fuel from the second stage exits the two-stage fuel cell at about 820°C and/or at about 2 psi, and/or at a different temperature and/or pressure.

90. The two-stage fuel cell of clause 84, any other suitable clauses, or any combination of suitable clauses, wherein the exhaust air from the second stage passes through a manifold, a catalytic oxidizer, the air fuel heat exchanger, the air pre-heater, and/or the fuel cooler before exiting the fuel cell.

91. The two-stage fuel cell of clause 84, any other suitable clauses, or any combination of suitable clauses, wherein the exhaust air from the second stage exits the second stage at about 2 psi or a different pressure.

92. The two-stage fuel cell of clause 84, any other suitable clauses, or any combination of suitable clauses, wherein the exhaust air and/or exhaust fuel from the second stage exits the catalytic oxidizer at about 900°C and/or at about 1.5 psi before passing through the air fuel heat exchanger.

93. The two-stage fuel cell of clause 84, any other suitable clauses, or any combination of suitable clauses, wherein the exhaust air and the exhaust fuel from the second stage and the exhaust air from the first stage exit the air pre-heater at about 200°C and/or at about 0.5 psi, or at a different temperature and/or pressure.

94. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the second stage has an exhaust stream with chemical energy.

95. The two-stage fuel cell of clause 94, any other suitable clauses, or any combination of suitable clauses, wherein the exhaust stream with chemical energy is converted into heat.

96. The two-stage fuel cell of clause 95, any other suitable clauses, or any combination of suitable clauses, wherein the heat is recuperated by incoming air and fuel streams and recycled into and by the fuel cell system comprising the two-stage fuel cell.

97. The two-stage fuel cell of clauses 1 and/or 2, any other suitable clauses, or any combination of suitable clauses, wherein the second stage implements fuel consumption of about 50% to about 70%.

98. The two-stage fuel cell of clause 97, any other suitable clauses, or any combination of suitable clauses, wherein the fuel consumption and/or fuel recycling increases the efficiency of the two-stage fuel cell by about 2% to about 5%.

[0063] The features illustrated or described in connection with one exemplary embodiment may be combined with any other feature or element of any other embodiment described herein. Such modifications and variations are intended to be included within the scope of the present disclosure. Further, a person skilled in the art will recognize that terms commonly known to those skilled in the art may be used interchangeably herein.

[0064] As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the presently described subject matter are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Specified numerical ranges of units, measurements, and/or values comprise, consist essentially or, consist of all the numerical values, units, measurements, and/or ranges including or within those ranges and/or endpoints, whether those numerical values, units, measurements, and/or ranges are explicitly specified in the present disclosure or not.

[0065] Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terms “first,” “second,” “third” and the like, as used herein do not denote any order or importance, but rather are used to distinguish one element from another. The term “or” is meant to be inclusive and mean either or all of the listed items.

In addition, the terms “connected” and “coupled” are not restricted to physical or mechanical connections or couplings, and can include electrical connections or couplings, whether direct or indirect.

[0066] Moreover, unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property. The term “comprising” or “comprises” refers to a composition, compound, formulation, or method that is inclusive and does not exclude additional elements, components, and/or method steps. The term “comprising” also refers to a composition, compound, formulation, or method embodiment of the present disclosure that is inclusive and does not exclude additional elements, components, or method steps.

[0067] The phrase “consisting of’ or “consists of’ refers to a compound, composition, formulation, or method that excludes the presence of any additional elements, components, or method steps. The term “consisting of’ also refers to a compound, composition, formulation, or method of the present disclosure that excludes the presence of any additional elements, components, or method steps. [0068] The phrase “consisting essentially of’ or “consists essentially of’ refers to a composition, compound, formulation, or method that is inclusive of additional elements, components, or method steps that do not materially affect the characteristic(s) of the composition, compound, formulation, or method. The phrase “consisting essentially of’ also refers to a composition, compound, formulation, or method of the present disclosure that is inclusive of additional elements, components, or method steps that do not materially affect the characteristic(s) of the composition, compound, formulation, or method steps.

[0069] Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, and “substantially” is not to be limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged.

Such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.

[0070] As used herein, the terms “may” and “may be” indicate a possibility of an occurrence within a set of circumstances; a possession of a specified property, characteristic or function; and/or qualify another verb by expressing one or more of an ability, capability, or possibility associated with the qualified verb. Accordingly, usage of “may” and “may be” indicates that a modified term is apparently appropriate, capable, or suitable for an indicated capacity, function, or usage, while taking into account that in some circumstances, the modified term may sometimes not be appropriate, capable, or suitable.

[0071] It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used individually, together, or in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the subject matter set forth herein without departing from its scope. While the dimensions and types of materials described herein are intended to define the parameters of the disclosed subject matter, they are by no means limiting and are exemplary embodiments. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the subject matter described herein should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

[0072] This written description uses examples to disclose several embodiments of the subject matter set forth herein, including the best mode, and also to enable a person of ordinary skill in the art to practice the embodiments of disclosed subject matter, including making and using the devices or systems and performing the methods. The patentable scope of the subject matter described herein is defined by the claims, and may include other examples that occur to those of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

[0073] While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Claims

WHAT IS CLAIMED IS:

1. A two-stage fuel cell, comprising: air that flows in a first direction, a first stage comprising a first region and a second region, wherein the first region has a first fuel that comprises a fuel content that is greater than the a second fuel comprised in a second region, a second stage, wherein the first fuel enters the second stage, wherein the first fuel does not mix with the second fuel after the first fuel enters the second stage, and wherein the first fuel and the second fuel flow in a second direction that crosses the first direction of the air.

2. The two-stage fuel cell of claim 1, wherein the first fuel has about 10% to about 15% greater fuel content than the second fuel.

3. The two-stage fuel cell of claim 1, wherein the first fuel is exhausted out of the fuel cell after it enters the second stage.

4. The two-stage fuel cell of claim 1, wherein the second fuel of the second region of the first stage is recycled back into the fuel cell.

5. The two- stage fuel cell of claim 4, wherein the second fuel of the second region exits the second region of the first stage through a manifold, a fuel pre-heater, and a fuel cooler.

6. The two-stage fuel cell of claim 5, wherein the second fuel is pressurized before being recycled back into the fuel cell.

7. The two- stage fuel cell of claim 4, wherein the second fuel of the second region exits the second region of the first stage at about 820°C and at about 2 psi.

8. A two-stage fuel cell stack comprising a plurality of two-stage fuel cells of claim 1.

9. A two-stage fuel cell system comprising a plurality of two-stage fuel cell stacks of claim 8.

10. The two-stage fuel cell of claim 1, wherein the two-stage fuel cell is used in a vehicle or a powertrain system.

11. A two-stage fuel cell, comprising: air that flows in a first direction, a fuel flow that flows in a second direction that crosses the direction of the air, wherein the fuel flow comprises an inlet fuel flow and an outlet fuel flow, wherein the outlet fuel flow comprises a first region and a second region, wherein the first region has a first fuel that comprises a fuel content that is greater than a second fuel comprised by a second region, and wherein the first fuel is recirculated to mix with the inlet fuel flow and the second fuel and the outlet fuel flow are exhausted out of the two- stage fuel cell.

12. The two-stage fuel cell of claim 11, wherein the first fuel has about 10% to about 15% greater fuel content than the second fuel.

13. The two-stage fuel cell of claim 11, wherein the first fuel is exhausted out of the fuel cell.

14. The two-stage fuel cell of claim 11, wherein the second fuel of the second region is recycled back into the fuel cell.

15. The two-stage fuel cell of claim 14, wherein the second fuel of the second region exits the second region through a manifold, a fuel pre-heater, and a fuel cooler.

16. The two-stage fuel cell of claim 15, wherein the second fuel is pressurized before being recycled back into the fuel cell.

17. The two-stage fuel cell of claim 14, wherein the second fuel of the second region exits the second region at about 820°C and at about 2 psi.

18. A two-stage fuel cell stack comprising a plurality of two-stage fuel cells of claim 11.

19. A two-stage fuel cell system comprising a plurality of two-stage fuel cell stacks of claim 18.

20. The two-stage fuel cell of claim 11, wherein the two-stage fuel cell is used in a vehicle or a powertrain system.