System and method for managing the degradation of fuel cells

Abstract

To provide a fuel cell system and method for operating a fuel cell system to control the amount of degradation to the fuel cell system.SOLUTION: In a fuel cell system 100, a fuel cell discharge controller 108 operates so as to switch switches S1 and S2 between two or more power sources (fuel cell assembly 102, fuel cell assembly 104) and provide power to a load 106, which is indicated by a current chart 110. The switching is set to minimize the fuel cell degradation in the fuel cell system.SELECTED DRAWING: Figure 1

Description

Background Art

[0001] The efficiency of batteries and fuel cells typically decreases due to degradation that is added to the battery or fuel cell during use. Degradation of the fuel cell or battery can be caused by various reasons. For example, degradation of the battery or fuel cell can be caused by property changes within the battery or fuel cell. In another embodiment, degradation of the battery or fuel cell can be caused by loss of active material. In some examples, the degradation process accelerates at higher temperatures.

[0002] Degradation causes an increase in the internal resistance or impedance of the battery or fuel cell, and thus reduces the efficiency of the battery or fuel cell. In some applications, degradation can reduce power performance. In a significant portion of the discharge situation, relatively large current draws often result in relatively high levels of degradation over increasing periods of time and become increasingly irreversible as the current draw increases or the discharge period is extended.

[0003] The disclosure herein is presented with respect to these and other matters.

Summary of the Invention

[0004] It should be understood that this summary is provided to introduce a selection of concepts in a simplified form that will be further described in the following detailed description. This summary is not intended to be used to limit the scope of the claimed subject matter.

[0005] A fuel cell system is provided according to one embodiment disclosed herein. The fuel cell system includes a first power source comprising a fuel cell assembly operable to provide power to a load, a second power source operable to provide power to a load, and a fuel cell controller responsively coupled to the first and second power sources and operable to reduce certain degradation of the fuel cell assembly by alternating the supply of power to the load between the fuel cell assembly and the second power source.

[0006] A method for operating a fuel cell system is provided according to another embodiment disclosed herein. The method includes receiving a fuel cell impedance degradation map for a first fuel cell assembly having internal impedance, the fuel cell impedance degradation map including acceptable impedances that are tuned to voltage and current; setting a first impedance value for the first fuel cell assembly; determining degradation variables; setting an impedance degradation criterion corresponding to an operating parameter causing a decrease in output voltage, a condition causing a decrease in output voltage, or a measured value of the decrease in output voltage; starting the first fuel cell assembly to supply power to a load; measuring degradation variables related to the first fuel cell assembly; calculating a second impedance value based on the measured degradation variables; and determining whether the second impedance value is within the range of the degradation criterion. If the second impedance value is within the range of the degradation criterion, the method further includes maintaining the fuel cell assembly to supply power to a load. If the second impedance value is outside the degradation criterion, the method further includes starting the second fuel cell assembly to supply power to a load and stopping the first fuel cell assembly.

[0007] A computer-readable storage medium is provided having computer-executable instruction commands that, when executed by a computer according to yet another embodiment disclosed herein, cause the computer to receive a fuel cell impedance degradation map for a first fuel cell assembly having internal impedance, the fuel cell impedance degradation map includes acceptable impedances that are tuned with respect to voltage and current; set a first impedance value for the first fuel cell assembly; determine degradation variables; set an impedance degradation criterion corresponding to an operating parameter that causes a decrease in output voltage, a condition that causes a decrease in output voltage, or a measured value of the decrease in output voltage; start the first fuel cell assembly to supply power to a load; measure degradation variables related to the first fuel cell assembly; calculate a second impedance value based on the measured degradation variables; and determine whether the second impedance value is within the range of the degradation criterion. If the second impedance value is within the range of the degradation criterion, the computer maintains the fuel cell assembly to supply power to a load. If the second impedance value is outside the degradation criterion, the computer starts the second fuel cell assembly to supply power to a load and stops the first fuel cell assembly.

[0008] The features, functions, and advantages described above can be realized independently in various embodiments of the present invention, or they can be combined in yet another embodiment, which can be understood in further detail by referring to the following description and drawings.

[0009] The embodiments presented herein can be fully understood from the detailed description and accompanying drawings. [Brief explanation of the drawing]

[0010] [Figure 1]Figure 1 is a schematic circuit diagram showing a fuel cell system configured to manage degradation according to at least one embodiment disclosed herein. [Figure 2] Figure 2 is a load distribution timing diagram showing an exemplary fuel cell degradation characteristic curve according to at least one embodiment disclosed herein. [Figure 3] Figure 3 is a schematic circuit diagram illustrating the use of a converter for moving back and forth between fuel cell assemblies according to at least one embodiment disclosed herein. [Figure 4] Figure 4 is a schematic circuit diagram showing an exemplary fuel cell system using a fuel cell discharge controller, operable to measure at least one degradation variable, according to at least one embodiment disclosed herein. [Figure 5] Figure 5 shows a routine configuration for minimizing degradation of a fuel cell assembly according to at least one embodiment disclosed herein. [Figure 6] Figure 6 shows an exemplary computer in which a fuel cell discharge controller can operate, according to at least one embodiment disclosed herein. [Modes for carrying out the invention]

[0011] The various drawings presented in this application illustrate variations and different aspects of embodiments of the present disclosure. Accordingly, a detailed description of each drawing will explain the differences identified in the corresponding drawing.

[0012] The following detailed description is directed to a system and method for fuel cell degradation management using a fuel cell discharge controller. In some configurations, the fuel cell discharge controller switches the power supply to the load between two or more power sources. In some embodiments, the switched power supply can reduce or minimize degradation to the two or more power sources. This disclosure is open to many different forms of embodiment. The principles of this disclosure are not intended to be limited to any particular disclosed embodiment. In the following detailed description, references are made to the accompanying drawings, which form part of this specification and are shown through specific exemplary embodiments or examples.

[0013] Aspects of this disclosure may be used in conjunction with various types of batteries or fuel cells. One type of fuel cell is a solid oxide fuel cell. Conventional solid oxide fuel cells can generally be constructed using four layers: a porous ceramic anode; a high-density ceramic electrolyte; a thin porous cathode; and a metal or ceramic interconnect. Degradation can occur due to the high temperatures often required to operate these types of fuel cells. Some embodiments of the types of degradation associated with solid oxide fuel cells include, but are not limited to, oxidation of the interconnect, delamination between the electrodes and electrolyte, delamination of the interface between the interconnect and electrolyte, and similar. Other types of power sources may be affected by the same types of degradation, or by other types of degradation depending on the construction and use of the power source.

[0014] It should be understood that this disclosure is not limited to any particular type of power source and may include, but is not limited to, various types of batteries and fuel cells. It should also be understood that this disclosure is not limited to any particular type of degradation. Now referring to the drawings, similar figures represent similar elements throughout several drawings, and aspects of this disclosure are presented.

[0015] Figure 1 is a schematic circuit diagram showing a fuel cell system 100 configured to manage degradation according to at least one embodiment disclosed herein. The fuel cell system 100 includes fuel cell assemblies 102 and 104, which, when configured in this way, are operable to supply power to a load 106. The fuel cell system 100 also includes a fuel cell discharge controller 108 that can communicate with a switch S1 associated with fuel cell assembly 102 and a switch S2 associated with fuel cell assembly 104. While two fuel cell assemblies are shown in Figure 1, it should be understood that more than two fuel cell assemblies may be used and may be considered within the scope of the subject matter of this disclosure. The two fuel assemblies are shown for the purpose of illustrating the configuration of the subject matter of this disclosure.

[0016] In some configurations, the fuel cell assembly 102 or fuel cell assembly 104 may be constructed from various types or categories of fuel cells, including, but not limited to, metal hydrides, electrogalvanic, direct formic acid, zinc air, microorganisms, upflow microorganisms, regenerative, direct hydrogen boride, proton exchange membranes, phosphoric acid, high temperature, solid oxides, molten carbonates, and similar materials.

[0017] In some configurations, fuel cell assembly 102 or fuel cell assembly 104 may be constructed from one or more fuel cells connected in series, parallel, or series / parallel configurations. Multiple fuel cells in a single assembly may be used when the power requirement is greater than that a single fuel cell can supply. Arranging fuel cells in various configurations can increase output voltage, current, power, and similar parameters.

[0018] In further configurations, either fuel cell assembly 102 or fuel cell assembly 104 may be replaced by a different type of power source, such as a battery or a flow cell. It should be understood that this disclosure is not limited in any way to any specific difference between fuel cells and batteries, and that they may be used interchangeably within the scope of this disclosure. Furthermore, it should be understood that some fuel cells can be considered batteries in some configurations, and vice versa.

[0019] During operation, fuel cell assemblies 102 and 104 are activated and operated via their respective switches. For example, fuel cell assembly 102 is activated when switch S1 is closed, forming an electrical connection between fuel cell assembly 102 and load 106. Similarly, fuel cell assembly 104 is activated when switch S2 is closed, forming an electrical connection between fuel cell assembly 104 and load 106. In some configurations, switches S1 and S2 can be closed simultaneously to facilitate cooperative power supply from both fuel cell assembly 102 and fuel cell assembly 104.

[0020] In some embodiments, power supply occurs within equal time periods, but it should be understood that different fuel cells can supply power over varying time periods. The switching time between the two power sources can be determined by the impedance value in comparison to a degradation criterion. In some examples, as the fuel cell degrades, the time between the two power sources becomes shorter due to the role of irreversible degradation.

[0021] During the operation of fuel cell assembly 102 or fuel cell assembly 104, degradation can occur. The type and degree of degradation can depend on various factors such as the type of fuel cell, the discharge rate, and the operating temperature of the fuel cell. Degradation can increase the internal resistance of the fuel cell, and thus increase the impedance and reduce the efficiency. Various types of degradation can be classified into two general categories: namely, non-recoverable and recoverable.

[0022] In non-recoverable degradation situations, it is very difficult and impossible to appropriately reverse the degradation. An example of non-recoverable degradation in a battery can be the expansion of lithium particles caused by current discharge. During the discharge of a lithium-ion battery, under certain conditions, the lithium pellets "swell" for ion exchange. The swelling of the pellets often breaks the interface between the pellet and the substrate, thus reducing the efficiency of the battery.

[0023] In recoverable degradation situations, the damage to the fuel cell is partially or fully recoverable, i.e., reversible. It should be understood that "damage" is not limited to structural deformations (such as substrate breakage) in the fuel cell, and can include other effects caused by the current output that reduces the voltage output of the fuel cell. For example, in a polymer-based fuel cell, degradation can occur in the polymer matrix due to chemical reactions that generate electrons for the current. Degradation can be a change in the chemical properties of the polymer matrix that reduces its chemical reactivity, probably reducing the current output.

[0024] A significant portion of the damage that can be considered recoverable can lead to irreparable degradation if the operating parameters causing the degradation remain unconfirmed, for example, if the output current is maintained. In some situations, removing the fuel cell from the circuit (i.e., stopping the fuel cell) can enable the fuel cell assembly to recover from the degradation caused by the operation of the fuel cell. Depending on the length and time the fuel cell is stopped, the fuel cell can partially or fully recover from the recoverable degradation caused by the operation of the fuel cell.

[0025] The fuel cell discharge controller 108 is operable to start and stop the fuel cell assembly 102 and the fuel cell assembly 104. When the fuel cell assemblies 102 and 104 are operating in an alternating mode, while the fuel cell assembly 102 is started, the fuel cell assembly 104 is stopped, as shown by the current chart 110. The fuel cell discharge controller 108 can cause the switch S1 to close, electrically connect the fuel cell assembly 102 to the load 106, and provide power to the load. In a different way, the fuel cell controller 108 can cause the switch S2 to open and stop the fuel cell assembly 104.

[0026] Depending on the configuration of the fuel cell controller 108, the fuel cell controller 108 can start and stop the fuel cell assembly 102 and the fuel cell assembly 104 and attempt to reduce the degradation of a specific fuel cell assembly 102 or 104. The fuel cell discharge controller 108 is operable to control the switches S1 and S2 to remove a specific fuel cell from service.

[0027] While Figure 1 shows that the fuel cell discharge controller 108 can electrically communicate with switches 1 and S2, it should be understood that this disclosure is not limited to, nor requires, such a configuration. For example, the fuel cell discharge controller 108 can be operated to transmit control signals to another (not shown) device, which can receive the control signals and operate to open or close the appropriate switches. Furthermore, it should be understood that this disclosure is not limited to, nor requires, physical switches, and various configurations of this disclosure can implement logical switches and are still considered to be within the scope of this disclosure.

[0028] The fuel cell discharge controller 108 may be configured to open or close switches S1 and S2 based on various factors. For example, the fuel cell discharge controller 108 may be configured to open or close switch S1 or switch S2 based on operating conditions such as the level of the fuel cell current output, a decrease or increase in the fuel cell voltage, the temperature of the fuel cell, the time the fuel cell has been started, and so on.

[0029] The fuel cell discharge controller 108 may also be configured to open or close switches S1 and S2 based on other factors such as the type of fuel cell, the measured or calculated capacity of the fuel cell to withstand various types of degradation, the structure of the fuel cell, the lifespan of the fuel cell, and similar factors. The fuel cell discharge controller 108 may be configured to use one or more factors, including, but not limited to, those listed above.

[0030] Figure 2 is a load distribution timing diagram showing an exemplary fuel cell degradation characteristic curve 200 for a fuel cell assembly 102 with respect to a constant current draw "I". The fuel cell degradation characteristic curve 200 includes an uncontrolled degradation curve 202 and a controlled degradation curve 204. The uncontrolled degradation curve 202 is used to show the effects of degradation without degradation control. The fuel cell degradation characteristic curve 200 has the Y axis as "magnitude of degradation" and the X axis as "time".

[0031] As shown in Figure 2, as time progresses from t0 to t1, the uncontrolled degradation curve 202 and the controlled degradation curve 204 overlap. However, as time progresses from t1 to t3, the curves diverge. The uncontrolled degradation curve 202 shows a continuous increase in the amount of degradation, while the controlled degradation curve 204 shows a pattern of increase and decrease. The uncontrolled degradation curve 202 increases because it represents a fuel cell that is running at a constant or continuous rate. As the fuel cell continues to discharge, the amount of degradation continues to increase.

[0032] The controlled degradation curve 204 illustrates exemplary degradation behavior when the fuel cell is controlled by starting and stopping the fuel cell. In Figure 2, the on / off behavior of fuel cell assembly 102 is shown as current chart 206, and the on / off behavior of fuel cell assembly 104 is shown as current chart 208. From time t0–t1, fuel cell assembly 102 is started, resulting in increased degradation, as shown in both the uncontrolled degradation curve 202 and the controlled degradation curve 204.

[0033] At time t1, the fuel cell assembly 102 is stopped. At time t1, the uncontrolled degradation curve 202 and the controlled degradation curve 204 begin to diverge. When the fuel cell assembly 102 is stopped, recoverable degradation begins to recover, causing a decrease in the degradation level. The uncontrolled degradation curve 202 shows the degradation if the fuel cell assembly 102 were not stopped. The fuel cell assembly 102 is controlled by stopping and starting from time t1 to time t7. As can be observed in Figure 2, the controlled degradation curve 204 shows the variable level of degradation between level A and level B. Depending on the configuration, the degradation may be named as being controlled between level A and level B.

[0034] Figure 3 is a schematic circuit diagram showing a fuel cell system 300 configured to manage degradation using one or more converters, according to at least one embodiment disclosed herein. The fuel cell system 300 includes fuel cell assemblies 302 and 304, which are operable to supply power to a load 306. The fuel cell system 300 also includes a fuel cell discharge controller 308, which can communicate with a converter 310A associated with fuel cell assembly 302 and a converter 310B associated with fuel cell assembly 304.

[0035] During the operation of the fuel cell system 300, fuel cell assemblies 302 and 304 are either started or stopped by the fuel cell discharge controller 308 using converters 310A and 310B, respectively. Converter 310A or 310B may be DC-DC or DC-AC type power electronics converters using any existing converter topology. Converters 310A and 310B may be configured to receive input from the fuel cell discharge controller 308 and start or stop. As used herein, converters such as converter 310A or 310B may be in any configuration that is operable to convert the DC coming from fuel cell assembly 302 or 304 to AC to supply power to load 306. In another configuration, converter 310A or 310B may be in any configuration that is operable to convert the DC coming from fuel cell assembly 302 or 304 to DC to supply power to load 306.

[0036] Converter 310A or 310B is operable to be stopped or started by the fuel cell discharge controller 308. When stopped, converter 310A or 310B is not subjected to voltage to convert DC from the fuel cell assembly to the load and can effectively operate as an open switch. When started, converter 310A or 310B may be subjected to voltage to convert DC from the fuel cell assembly to the load and can effectively operate as a closed switch. Startup and shutdown may be seen in the context of the current chart 312. It should be noted that the use of the converter is merely illustrative, and any components or logical operations may be used to start and stop the fuel cell assembly 302 or fuel cell assembly 304 by acting as a switch.

[0037] Figure 4 is a schematic circuit diagram showing an exemplary fuel cell system 400 using a fuel cell discharge controller, operable to measure at least one degradation variable, according to at least one embodiment disclosed herein. As used herein, “degradation variable” may include any operating parameter that causes a decrease in the output voltage of one or more fuel cell assemblies, indicates the conditions that cause the decrease, or is a measured value of the decrease itself (e.g., voltage). For example, non-limitingly, degradation variables are current output, voltage, temperature, and time. Measuring degradation variables would be effective in reducing fuel cell degradation.

[0038] The fuel cell system 400 includes fuel cell assembly 402 and fuel cell assembly 404. Fuel cell assembly 402 and fuel cell assembly 404 are operable to supply power to a load 406. The fuel cell system 400 also includes a fuel cell discharge controller 408. The fuel cell discharge controller 408 is operable to start and stop fuel cell assembly 402 and fuel cell assembly 404 by causing switches S1 and S2 to open or close, respectively.

[0039] As described above, the fuel cell discharge controller 408 receives various inputs to determine when to start or stop a particular fuel cell assembly. Some embodiments described above involve time and temperature. Other embodiments described above involve the voltage of the fuel cell and the current output from the fuel cell. Embodiments of voltage and current are shown in Figure 4.

[0040] In Figure 4, the fuel cell discharge controller 408 is operable to receive as input a measured voltage V1 representing the voltage of fuel cell assembly 402, a measured voltage V2 representing the voltage of fuel cell assembly 404, a measured current I1 representing the output current from fuel cell assembly 402, and a measured current I2 representing the output current from fuel cell assembly 404. The voltages, V1 and V2, and the currents, I1 and I2, may represent various operational parameters used by the fuel cell discharge controller 408 to determine when to start or stop fuel cell assemblies 402 and 404.

[0041] Degradation map 410 is an embodiment of a degradation map that may be used to determine the values ​​of degradation variables as inputs to a fuel cell system 400. It should be understood that degradation map 410 is provided for illustrative purposes only. The degradation map may vary depending on the configuration of the particular system from which the data is acquired. In some embodiments, voltage and current (sometimes measured as discharge rate) and temperature may be measured to determine the location of the corresponding impedance. In some embodiments, impedance may not be mapped. Degradation map 410 has "temperature" on the X axis and "degradation" on the Y axis. It should be understood that temperature is simply an embodiment of a degradation variable. Other degradation variables may be included alone or in combination with other degradation variables and are considered to be within the scope of this disclosure.

[0042] If the fuel cell assembly 402 or fuel cell assembly 404 is disconnected from the load 406, the fuel cell refueling device 412 may be used to refuel the fuel cell assembly 402 or fuel cell assembly 404. As used herein, “refueling” means providing one or more components to the fuel cell assembly 402 or fuel cell assembly 404 in order to enable the fuel cell assembly 402 or fuel cell assembly 404 to provide power.

[0043] In this embodiment, temperature is the internal temperature of the fuel cell in the fuel cell assembly 402 or 404, and degradation is the internal impedance of the fuel cell in the fuel cell assembly 402 or 404. As the temperature rises, the internal impedance (degradation) increases. In this context, temperature is an indicator of the conditions inside the fuel cell that can lead to degradation of the fuel cell. The degradation map 410 can be constructed using various methods.

[0044] In an exemplary use of the degradation map 410, the fuel cell system 400 may be configured to prepare to switch from an active fuel cell assembly to an inactive fuel cell assembly at temperature T1, and to perform the switch at temperature T2. The fuel cell system 400 may also be configured to shut down the active fuel cell assembly at temperature T3, regardless of whether the inactive fuel cell assembly has been started or not.

[0045] Temperature, T1, T2, and T3, one or more of these represent various states that are preferably affected by the fuel cell system 400 in various configurations. For example, temperature T2 may represent a degradation criterion D0, above which there may be a certain high risk of permanent damage to the fuel cell. By maintaining a temperature below T2, the degradation criterion D0 cannot be reached, thus increasing the likelihood that any damage to the fuel cell will be reversible. Thus, the degradation criterion D0 represents one or more acceptable impedances of the fuel cell, where impedance represents the amount of damage imposed on the fuel cell by the discharge of the fuel cell. The use of the degradation map 410 is explained in more detail in Figure 5 below.

[0046] Figure 5 shows one configuration of routine 500 for minimizing degradation of a fuel cell assembly according to at least one embodiment disclosed herein. Unless otherwise indicated, more or fewer operations may be performed than those shown in the drawings and described herein. Additionally, unless otherwise indicated, these operations may also be performed in a different order than described herein.

[0047] Routine 500 in Figure 5 is an interleaved method. In the interleaved method, the fuel cell discharge controller is configured to start a fuel cell assembly while keeping other fuel cell assemblies in their stopped state. In the stopped state, the fuel cell assembly is configured to allow a recovery period during which the fuel cell assembly can recover at least a portion of the degradation caused by the current discharge. Once the fuel cell discharge controller determines that the fuel cell assembly in use is ready to stop, the fuel cell discharge controller starts the next fuel cell assembly and stops the fuel cell assembly in use.

[0048] Routine 500 is initiated by Operation 502, where the fuel cell impedance degradation map is loaded into the fuel cell discharge controller. In some configurations, the fuel cell impedance degradation map may be a function with one or more variables. The fuel cell impedance degradation map may be used by the fuel cell discharge controller to calculate whether to start or stop the fuel cell assembly.

[0049] Routine 500 continues to Operation 504, where a first impedance value is set. The first impedance value may be a baseline value that the fuel cell discharge controller compares to a calculated or measured impedance value. The comparison may be used by the fuel cell controller to determine whether the currently active fuel cell controller should be shut down.

[0050] Routine 500 continues to Operation 506, where an impedance degradation criterion is set. The impedance degradation criterion may be a threshold or difference from the initial impedance value. The fuel cell discharge controller may use the impedance degradation criterion as a setpoint for measuring the change in impedance value or as a setpoint for measuring the absolute value of impedance.

[0051] Routine 500 continues to Operation 508, where the first fuel cell assembly is activated. As described above, the fuel cell discharge controller can "switch off", positioning the fuel cell assembly to be electrically communicative with the load and supplying power to the load.

[0052] Routine 500 continues to Operation 510, where degradation variables of the active fuel cell are measured. In some situations where it is undesirable or impossible to measure the impedance of the fuel cell assembly while the fuel cell assembly is active, the fuel cell discharge controller may receive various inputs as variables. These variables may be used by the fuel cell controller to calculate the impedance of the active fuel cell using a fuel cell impedance degradation map. Some variables may include, but are not limited to, time, current, and voltage. These variables are used in Routine 512 to calculate a second impedance value.

[0053] Routine 500 continues to Operation 514, where it is determined whether the second impedance value is outside the degradation criterion. In one embodiment, the second impedance value may be outside the acceptable range for impedance values. In another embodiment, the second impedance value may be within the acceptable range for absolute impedance values, but outside the acceptable range for the rate of change of impedance values. These and other embodiments are considered to be within the scope of the present disclosure.

[0054] If the second impedance value is within the degradation criterion, routine 500 proceeds to operation 516, where the currently active fuel cell assembly is maintained. Routine 500 may then proceed to operation 510, where the degradation variable is measured and similar decisions are subsequently made.

[0055] If the second impedance value is outside the degradation criterion, routine 500 proceeds to operation 518, where the next fuel cell assembly is started and the current fuel cell assembly is shut down. If the next fuel cell assembly is started and supplies power, the same impedance monitoring process is applied to the started fuel cell assembly. If the fuel cell assembly's impedance value is outside the degradation criterion, it is shut down, and the first or another fuel cell assembly is started to supply power to the load. It should be understood that this disclosure is not limited to any particular way in which the next fuel cell assembly is brought into an active state. For example, in some configurations, the current fuel cell assembly may be shut down prior to starting the next fuel cell assembly. In another embodiment, a third fuel cell assembly may be started, the current fuel cell assembly may be shut down, the next fuel cell assembly may be started, and the third fuel cell assembly may be shut down. These and other embodiments are considered to be within the scope of this disclosure.

[0056] Routine 500 may proceed to Operation 510, where degradation variables are measured and similar decisions are subsequently made. In some configurations, the next fuel cell assembly may have different degradation maps, first impedance values, and similar ones. In these configurations, routine 500 may proceed from Operation 518 to Operation 502 and continue as described above for the previous fuel cell assembly.

[0057] Figure 6 shows an exemplary computer 600 in which a fuel cell discharge controller may operate, according to at least one embodiment disclosed herein. The computer 600 shown in Figure 6 includes one or more central processing units ("CPU") 602, system memory 604 including random access memory ("RAM") 606 and read-only memory ("ROM") 608, and a system bus 610 connecting the memory 604 to the CPU 602. A basic input / output system, including routines that help transfer information between elements within the computer 600, such as during startup, may be stored in the ROM 608.

[0058] CPU 602 may be a standard programmable processor that performs arithmetic and logical operations for the operation of computer 600, such as routine 500 described above. CPU 602 can perform operations by transitioning from one discrete physical state to the next through the operation of switching elements that differentiate between and change these states. Switching elements may generally include electrical circuits that maintain one of two binary states, such as flip-flops, and electrical circuits that provide an output state based on the logical combination of the states of one or more other switching elements, such as logic gates. These basic switching elements can be combined to form more complex logic circuits, including registers, adders-subtractors, numerical arithmetic units, floating-point arithmetic units, and similar.

[0059] Computer 600 may also include a mass storage device 612. The mass storage device may be an optical disk, a magnetic storage device, or a semiconductor storage device. The mass storage device 612 is operable to store one or more instruction commands for controlling the fuel cell discharge controller. In another configuration, the random access memory 606, the read-only memory 608, and the mass storage device 612 may be operable to store instruction commands for controlling the fuel cell discharge controller, either individually or in any combination thereof.

[0060] Computer 600 can store programs and data in the mass storage device 612 by altering the physical state of the mass storage device 612 to reflect the stored information. The specific alteration of the physical state may depend on various factors in the various implementations of this disclosure. Embodiments of such factors may include, but are not limited to, the techniques used to implement the mass storage device 612, whether the mass storage device 612 is characterized as primary or secondary storage and similarly.

[0061] For example, computer 600 can cause information to be stored in the mass storage device 612 by issuing instruction commands via a storage controller to change the magnetic properties of a specific location within a magnetic disk drive, the reflective or refractive properties of a specific location within an optical storage device, or the electrical properties of a specific capacitor, transistor, or other individual component within a semiconductor storage device. Other modifications of the physical medium can be made using the embodiments described above, provided solely to facilitate this description, without departing from the scope and spirit of the disclosure. Computer 600 can further read information from the mass storage device 612 by detecting the physical state or properties of one or more specific locations within the mass storage device 612.

[0062] Random access memory 606, read-only memory 608, or mass storage device 612 can operate as a computer-readable storage medium. Various aspects of the present disclosure may be stored in, but are not limited to, other types of computer-readable storage media, such as RAM, ROM, EPROM, EEPROM, flash memory or other semiconductor memory technologies, CD-ROM, digital versatile disc ("DVD"), HD-DVD, Blu-ray or other optical storage devices, magnetic cassettes, magnetic tapes, magnetic disc storage devices or other magnetic storage devices, or any other medium that can be used to store desired information and can be accessed by computer 600. If the claims are interpreted under the present disclosure, it should be understood that a computer-readable storage medium does not contain energy in the form of waves or signals.

[0063] The computer 600 may also include an input / output controller 616 for receiving and processing inputs from any number of other devices, including a keyboard, mouse, or electronic stylus. Similarly, the input / output controller 616 may provide outputs to a display screen, printer, or other type of output device.

[0064] One or more embodiments may include a computer-readable storage medium such that, when read by a properly configured computer device, instructions can be provided to control a fuel cell discharge assembly and manage fuel cell degradation.

[0065] Furthermore, the present invention includes embodiments as defined below.

[0066] Article 1 A first power source comprising a fuel cell assembly capable of operating to provide power to a load; A second power source that can be operated to provide power to the aforementioned load; and A fuel cell system comprising a fuel cell discharge controller that is communicatively coupled to the first power supply and the second power supply, and is operable to reduce certain degradation of the fuel cell assembly by alternating the supply of power to the load between the fuel cell assembly and the second power supply.

[0067] Article 2 The fuel cell system according to Clause 1, wherein the second power source comprises a second fuel cell assembly.

[0068] Article 3 The fuel cell assembly comprises a fuel cell, as described in Clause 1.

[0069] Article 4 The fuel cell assembly comprises a plurality of fuel cells, as described in Clause 1.

[0070] Article 5 The fuel cell system according to Clause 4, wherein the fuel cell discharge controller is further capable of alternating the supply of power from the fuel cell assembly to the load by alternating the power discharge from one or more of the plurality of fuel cells.

[0071] Article 6 The fuel cell system according to Clause 1, wherein the fuel cell discharge controller is operable to reduce certain degradation of the fuel cell assembly by alternating the supply of power to the load between the fuel cell assembly and the second power source by measuring the temperature of the fuel cell assembly, the discharge rate of the fuel cell assembly, or the discharge time of the fuel cell assembly.

[0072] Article 7 The fuel cell discharge controller is further operable to minimize certain degradations based on the temperature, discharge rate, discharge time, or any combination thereof, as described in Clause 6 of the fuel cell system.

[0073] Article 8 The fuel cell system according to Clause 1, wherein the fuel cell discharge controller is operable to reduce certain degradation of the fuel cell assembly by alternating the supply of power to the load between the fuel cell assembly and the second power supply so that the fuel cell assembly and the second power supply supply power to the load for equal amounts of time.

[0074] Article 9 The fuel cell discharge controller is further operable to control a first converter at the output of the fuel cell assembly and a second converter at the output of the second power supply, and the fuel cell discharge controller either starts or stops the first converter and the second converter, as described in Clause 1.

[0075] Clause 10 The fuel cell system according to Clause 1, further comprising a refueling device for refueling the fuel cell assembly or the second power source when disconnected from the load.

[0076] Article 11 A method for operating a fuel cell system, the method being: Receiving a fuel cell impedance degradation map for a first fuel cell assembly having internal impedance, wherein the fuel cell impedance degradation map includes acceptable impedances that are tuned with respect to voltage and current; Setting a first impedance value for the first fuel cell assembly; Determining the degradation variables; Setting impedance degradation criteria that correspond to operating parameters that cause a decrease in output voltage, conditions that cause a decrease in output voltage, or measured values ​​of the decrease in output voltage; To start the first fuel cell assembly that provides power to the load; Measuring the degradation variables related to the first fuel cell assembly; Calculate a second impedance value based on the measured degradation variable; To determine whether the second impedance value is within the range of the degradation criterion; If the second impedance value is within the range of the degradation criterion, the fuel cell assembly will maintain a state of supplying power to the load; and A method comprising starting a second fuel cell assembly to supply power to the load and stopping the first fuel cell assembly when the second impedance value is outside the degradation criterion.

[0077] Article 12 If the second impedance value is outside the degradation criterion, the method further comprises charging the stopped first fuel cell assembly, according to the method of Clause 11.

[0078] Article 13 Receiving a second fuel cell impedance degradation map for the second fuel cell assembly having internal impedance, wherein the second fuel cell impedance degradation map includes acceptable impedances that are tuned with respect to voltage and current; Setting a first impedance value for the second fuel cell assembly; Determining the second degradation variable; Establish a second impedance degradation criterion; Measuring the second degradation variable related to the second fuel cell assembly; Calculating a second impedance value of the second fuel cell assembly based on the measured second degradation variable; To determine whether the second impedance value of the second fuel cell assembly is within the range of the second degradation criterion; If the second impedance value of the second fuel cell assembly is within the range of the second degradation criterion, the second fuel cell assembly will maintain a state of supplying power to the load; and The method according to clause 11, further comprising starting the first fuel cell assembly to supply power to the load and stopping the second fuel cell assembly if the second impedance value of the second fuel cell is outside the degradation criterion.

[0079] Article 14 The method according to Clause 13, wherein if the second impedance value of the second fuel cell assembly is outside the degradation criterion, the method further comprises charging the deactivated second fuel cell assembly.

[0080] Article 15 The degradation variable is as described in Clause 11, including voltage, current, time, or temperature.

[0081] Article 16 The method according to clause 11, wherein the impedance degradation criterion includes the magnitude of the difference between the acceptable impedance value adjusted for voltage and current and the second impedance calculated based on the measured degradation variables.

[0082] Article 17 The method according to clause 11, further comprising setting a degradation variable switching setting point, and if the measured degradation variable is above the degradation variable switching setting point, starting the second fuel cell assembly to supply power to the load, and stopping the first fuel cell assembly.

[0083] Article 18 The degradation variable switching setting point is the method according to Clause 17, including the maximum allowable temperature, the maximum allowable discharge current, the maximum allowable time, or the maximum allowable voltage.

[0084] Article 19 A computer-readable storage medium having computer-executable instructions stored therein, wherein when executed by a computer, the computer-executable instructions are: Receiving a fuel cell impedance degradation map for a first fuel cell assembly having internal impedance, wherein the fuel cell impedance degradation map includes acceptable impedances that are tuned with respect to voltage and current; Setting a first impedance value for the first fuel cell assembly; Determining the degradation variables; Setting impedance degradation criteria that correspond to operating parameters that cause a decrease in output voltage, conditions that cause a decrease in output voltage, or measured values ​​of the decrease in output voltage; To start the first fuel cell assembly that provides power to the load; Measuring the degradation variables related to the first fuel cell assembly; Calculate a second impedance value based on the measured degradation variable; To determine whether the second impedance value is within the range of the degradation criterion; If the second impedance value is within the range of the degradation criterion, the fuel cell assembly will maintain a state of supplying power to the load; and A computer-readable storage medium that causes a computer to start the second fuel cell assembly to supply power to the load and to stop the first fuel cell assembly when the second impedance value is outside the degradation criterion.

[0085] Article 20 When executed by a computer: Receiving a second fuel cell impedance degradation map for the second fuel cell assembly having internal impedance, wherein the second fuel cell impedance degradation map includes acceptable impedances that are tuned with respect to voltage and current; Setting a first impedance value for the second fuel cell assembly; Determining the second degradation variable; Establish a second impedance degradation criterion; Measuring the second degradation variable related to the second fuel cell assembly; Calculating a second impedance value of the second fuel cell assembly based on the measured second degradation variable; To determine whether the second impedance value of the second fuel cell assembly is within the range of the second degradation criterion; If the second impedance value of the second fuel cell assembly is within the range of the second degradation criterion, the second fuel cell assembly will maintain a state of supplying power to the load; and The computer-readable storage medium according to Clause 19, further comprising computer-executable instruction commands that cause the computer to start the first fuel cell assembly to supply power to the load, and to stop the second fuel cell assembly, if the second impedance value of the second fuel cell is outside the degradation criterion.

[0086] The subject matter described above is provided for illustrative purposes only and should not be constrained. Various modifications and variations may be made to the subject matter without following the exemplary embodiments and uses described and without departing from the true spirit and scope of the disclosure as described in the following claims. [Explanation of symbols]

[0087] 100 Fuel Cell Systems 102 Fuel Cell Assembly 104 Fuel Cell Assembly 106 load 108 Fuel Cell Discharge Controller 200 Fuel cell deterioration characteristic curve 202 Uncontrolled Degradation Curve 204 Controlled Degradation Curves 206 Current Chart 208 Current Chart 300 Fuel Cell Systems 302 Fuel Cell Assembly 304 Fuel Cell Assembly 306 load 308 Fuel Cell Discharge Controller 310A converter 310B converter 400 Fuel Cell Systems 402 Fuel Cell Assembly 404 Fuel Cell Assembly 406 load 408 Fuel Cell Discharge Controller 410 Degradation Map 412 Fuel cell refueling device 500 routines 502 Operation 504 Operation 506 Operation 508 Operation 510 Operation 512 Operation 514 Operation 516 Operation 518 Operation 600 Computer 602 Central Processing Unit 604 System Memory 606 random access memory 608 Read-Only Memory 612 Mass storage device 616 Input / Output Controllers

Claims

1. A first power supply comprising a fuel cell assembly electrically connected to a load, A second power supply electrically connected to the aforementioned load, The first power supply and the second power supply are coupled together in a communicative manner to a fuel cell discharge controller, The fuel cell discharge controller is programmed to receive the internal temperature from the first power supply, determine the internal impedance of the fuel cell, and transmit a control signal based on the internal impedance of the fuel cell. A fuel cell system in which the control signal alternates operation between the first power supply and the second power supply, and switches the power supplied to the load between the first power supply and the second power supply based on the internal impedance of the fuel cell, thereby reducing the degradation of the first power supply.

2. The fuel cell system according to claim 1, wherein the second power source comprises a second fuel cell assembly.

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