Fuel cell stack for generating electrical energy

Abstract

The invention relates to a fuel cell stack (10) for generating electrical energy, comprising a main fuel cell system (100) having at least one main fuel cell stack (120) and at least one secondary fuel cell system (200) having at least one secondary fuel cell stack (220), the main fuel cell system (100) and the at least one secondary fuel cell system (200) being connected in an electrically parallel manner, the main fuel cell system (100) has a main control module (110) for variable control of a variable main operating point (HBP), and the secondary fuel cell system (200) has a secondary switching module (210) for switching between a switched-off state (AZ) and at least one predetermined switched-on state (EZ).

Description

Technical Field

[0001] The present invention relates to a fuel cell stack for generating electrical energy, a method for operating such a fuel cell stack, and a computer program product for performing such a method. Background Technology

[0002] It is known that fuel cells are used to generate electricity for stationary or mobile applications. These fuel cells are typically arranged in fuel cell stacks to form several fuel cell systems. A fuel cell system may contain one or more fuel cell stacks and requires appropriate connection interfaces and components for operation, such as supply lines, exhaust lines, control valves, cooling devices, etc. It is also known, particularly in stationary applications for generating electricity, that multiple fuel cell systems are combined into a fuel cell stack, thereby enabling a modular multiplication of available electrical power.

[0003] A known drawback of fuel cell stack solutions is that complexity can increase with the number of individual fuel cell systems used. Each of these fuel cell systems is an independent and fully functional fuel cell system, with its own connection interfaces, control components, etc. Summary of the Invention

[0004] The objective of this invention is to provide a highly efficient fuel cell stack. In particular, this objective is to provide fuel cell stacks with equal or even better variability in operation in a low-cost and simple manner, especially with reduced cost and / or complexity.

[0005] The aforementioned task is accomplished by a fuel cell stack having the features of claim 1, a method having the features of claim 8, and a computer program product having the features of claim 13. Other features and details of the invention are derived from the dependent claims, the specification, and the drawings. Herein, the features and details described with respect to the fuel cell stack of the invention also clearly apply to the method of the invention and the computer program product of the invention, and vice versa; therefore, the disclosures regarding various aspects of the invention are always cross-referenced or can be cross-referenced.

[0006] The fuel cell stack of the present invention is used to generate electrical energy. It can be designed for mobile or stationary applications. This fuel cell stack includes a main fuel cell system having at least one main fuel cell stack. Furthermore, this fuel cell stack is equipped with at least one auxiliary fuel cell system having at least one auxiliary fuel cell stack. The main fuel cell system and the at least one auxiliary fuel cell system are connected in parallel. The fuel cell stack of the present invention is characterized in that the main fuel cell system has a main control module for variable control of variable main operating states. The auxiliary fuel cell system is equipped with a secondary switching module for switching between a shutdown state and at least one predetermined on state.

[0007] The fuel cell stack of this invention is based on the fundamental concept that connecting two or more fuel cell systems in parallel can multiply the maximum available power. The modular configuration is known to provide a simple and therefore multiplicative power capability for this fuel cell stack in various applications. However, unlike known solutions, the main fuel cell system and at least one auxiliary fuel cell system are designed to differ from each other in at least one key structural feature. The main fuel cell system is a typical fuel cell system with a main control module for performing variable operating control. The primary operating point here can, for example, be the operating point related to the electrical power generated under this operating mode. The variable primary operating point can therefore be changed particularly continuously, thus providing fully variable control possibilities, allowing the main fuel cell system to operate substantially flexibly with a variety of different operating points as the primary operating point. In other words, the main fuel cell system can variably control the output electrical power according to the primary operating point, thereby flexibly meeting different power demands.

[0008] The auxiliary fuel cell system lacks this variable control utilizing a control module. Instead, it is replaced by a simple auxiliary switching module. Thus, the switching module cannot achieve variable control, but only allows switching between predetermined states. These predetermined states include an off state and at least one predetermined on state. A particularly simple implementation of this auxiliary fuel cell system has a single auxiliary switching module with exactly one predetermined on state, for example, corresponding to 100% of the maximum output power. Therefore, it is now feasible for the auxiliary switching module to simply turn the auxiliary fuel cell system on or off, instead of variably adjusting the operating point of the auxiliary fuel cell system through complex control. In other words, the auxiliary fuel cell system can provide and output its maximum available power in the on state, and cannot provide it in the off state.

[0009] From a structural perspective, the main advantage of the fuel cell stack of this invention lies in the significant simplification of the auxiliary fuel cell system by abandoning variable control possibilities. In particular, various sensors, bypasses, flow control valves, etc., can be eliminated. The workload of subsequent monitoring and switching of the auxiliary fuel cell system is also significantly reduced because complex variable control loops are no longer required. Specifically, the auxiliary fuel cell system can be switched using a simple control method, whereas the main control module of the main fuel cell system must provide a regulation loop containing feedback information related to the actual operating status of the main fuel cell system. Another example of reduced complexity is that humidity regulation is preferably eliminated, as a regulation loop including a humidity sensor and a humidifier bypass valve can be eliminated. Furthermore, for this simplified auxiliary fuel cell system, a smaller humidifier or no humidifier at all can be provided. It should also be noted that only special operating conditions need to be considered for the main fuel cell system, such as the start-up of the fuel cell stack, especially cold starts in cold ambient temperatures. Therefore, components such as preheating devices only need to be included in the main fuel cell system, thus eliminating the need for such costly additional components in single or multiple auxiliary fuel cell systems. These special operating conditions, such as cold starts, are always provided and satisfied by the main fuel cell system. The auxiliary fuel cell system is only used to enhance and multiply the output power of the fuel cell stack during normal operation.

[0010] In the fuel cell stack of the present invention, the auxiliary fuel cell system and / or auxiliary switching module are designed to switch between a shutdown state and exactly one predetermined on state, which offers advantages. The basic concept of reducing the complexity of the auxiliary fuel cell system is already realized when two or more on states can be distinguished from each other and switched in a predetermined manner; this advantage is further enhanced when only one on state is set. In particular, this single on state of the auxiliary fuel cell system is the maximum power that the auxiliary fuel cell system can output as a continuous power source; therefore, this implementation can also be called a binary switching method. In other words, the auxiliary switching module in this implementation is designed to completely shut down or fully turn on the auxiliary fuel cell system to the desired maximum power. With a simplified design of the auxiliary fuel cell system, the change between the single shutdown state and the single on state is no longer necessary and therefore no longer possible. Reducing to a single predetermined on state thus enhances the advantages achievable by the fuel cell stack of the present invention.

[0011] Further advantages can be obtained when the auxiliary fuel cell system in the fuel cell stack of the present invention is designed not to include at least one of the following components:

[0012] -Bypass valve for intake humidifiers

[0013] -A bypass valve for the intake turbine.

[0014] - A dehydrator for exhausting wastewater.

[0015] -Thermostatic valves used in cooling cycles,

[0016] - Heat exchangers used for fuel supply and / or fuel discharge.

[0017] - A purging valve for combustion exhaust gases.

[0018] - Temperature sensor at the inlet of the cooling cycle reactor.

[0019] - Temperature sensor at the outlet of the cooling cycle stack

[0020] - Pressure sensor in the exhaust section.

[0021] The above is a non-exhaustive list. It is clearly preferable to structurally remove two or more, and especially all, of the components that can be omitted from the auxiliary fuel cell system, thereby optimizing, and in particular maximizing, the reduction of the auxiliary fuel cell system's complexity. It is evident that not only can complexity be reduced at a lower cost, but the reduction in components also leads to smaller space requirements and less wear. In particular, the ability to pre-set precise switching between a single off state and one or more predetermined on states allows undesirable operating conditions in partially loaded areas that could exacerbate wear or aging of the auxiliary fuel cell system to be virtually completely eliminated. This concentrates wear caused by such partially loaded areas on the main fuel cell system, allowing the auxiliary fuel cell system to operate with significantly less wear.

[0022] In the fuel cell stack of this invention, the fuel cell stack has exactly one unique main fuel cell system and / or at least two auxiliary fuel cell systems, which brings further advantages. This means providing scalability by utilizing two or more fuel cell systems, which can have the same or different designs from each other, as detailed below. This embodiment clearly demonstrates the modular construction possibility of such fuel cell stacks, particularly in that regardless of the size of the fuel cell stack or the number of auxiliary fuel cell systems, there is always exactly one unique main fuel cell system. In other words, when expanding the fuel cell stack according to the required output power, only the number of low-cost and simple auxiliary fuel cell systems is increased until the desired output power can be provided. Only one expensive and complex main fuel cell system is needed to provide the necessary flexibility to meet power requirements through the control methods detailed below.

[0023] A further advantage is that the fuel cell stack of the present invention includes at least two auxiliary fuel cell systems with the same or substantially the same power output. This further optimizes the modular structure of the fuel cell stack, as all auxiliary fuel cell systems are preferably designed to have the same or substantially the same power output. This significantly simplifies control, and in particular simplifies scalability. The cost of constructing, installing, and manufacturing identical auxiliary fuel cell systems is also significantly reduced. In other words, arbitrary expansion is possible, so that whenever the maximum required power output of the fuel cell stack is increased, the required number of auxiliary fuel cell systems can be added during the design of the fuel cell stack through simple factorization.

[0024] In the fuel cell stack of the present invention, at least two fuel cell systems with different power outputs are provided, which also brings advantages. Here, the different power outputs of the auxiliary fuel cell systems can also be doubled. Obviously, this implementation of auxiliary fuel cells with different power outputs can also be used in conjunction with fuel cell stacks having two or more identical auxiliary fuel cell systems. Here, "identical" or "different" auxiliary fuel cell systems specifically refer to the same power output as the maximum power output in the context of the present invention. However, such identical auxiliary fuel cell systems are preferably designed to be identical or substantially identical in terms of the components used, construction methods, etc.

[0025] Furthermore, a potential advantage is that, in the fuel cell stack of the present invention, the at least one main fuel cell system has the same or greater power as the smallest auxiliary fuel cell system. Here, "same power" refers to the auxiliary fuel cell system with the minimum power among all auxiliary fuel cell systems included in the design. Since the main fuel cell system does not have a minimum power but rather a greater power than the smallest auxiliary fuel cell system, switching from the main fuel cell system to the auxiliary fuel cell system can always be achieved when the maximum power of the smallest auxiliary fuel cell system is exceeded. This can also be considered an advantage in structural design, and will be further clarified, particularly through the subsequent explanation of different control methods.

[0026] The subject matter of this invention also includes providing a method for controlling the fuel cell stack of this invention, the method comprising the following steps:

[0027] - Obtain the power requirements for the fuel cell stack.

[0028] - Determine the required number of auxiliary fuel cell systems that need to operate in the predetermined on-state to meet the power demand.

[0029] - Determine the primary operating point of the variable-operation primary fuel cell system to satisfy the difference between the power required by the auxiliary fuel cell system to be operated and the power demand obtained.

[0030] - Set the determined number of auxiliary fuel cell systems and the determined main operating point of the main fuel cell system to operate the main fuel cell system.

[0031] The method of the present invention, by using the fuel cell stack of the present invention, brings the same advantages detailed regarding the fuel cell stack of the present invention. According to the present invention, by acquiring the power demand, the amount of electrical power that the fuel cell stack needs to provide is set in a known manner. In the determination step, the acquired power demand is allocated in the most optimal way possible by the control method of the present invention. Thus, in the first step, it is determined how many auxiliary fuel cell systems are needed to satisfy an integer multiple of the main part of the power demand, particularly by operating in their respective predetermined on states. Only the remaining difference, which is therefore variable and depends on the actual power demand, relative to the main part satisfied by the auxiliary fuel cell systems, is subsequently borne by the main fuel cell system, since only the main fuel cell system can operate variably. Therefore, for subsequent operation, the selected and determined auxiliary fuel cell systems are switched from the off state to the on state, and the remaining difference required to fully satisfy the power demand is generated by the corresponding control and adjustment of the variable main operating state by the main fuel cell system.

[0032] One advantage of this method is that, in determining the required number of auxiliary fuel cell systems to be operated, the combination with the smallest number of possible components is selected and set in the final step. Typically, especially in complex fuel cell stacks with two or significantly more auxiliary fuel cell systems, there are various situations where the power demand can be met by different combinations of various auxiliary fuel cell systems. In this embodiment of the method, the combination with the smallest number of auxiliary fuel cell systems is selected. This reduces wear and tear because the minimum number of auxiliary fuel cell systems is always running.

[0033] Alternatively or additionally, in the method of the present invention, when setting the number of auxiliary fuel cell systems, it is advantageous to preferentially select auxiliary fuel cell systems that are already in the on state at the set time. This can be done as a single optimization or selection step, or it can be combined with other optimization conditions. If the fuel cell stack is already operating at a condition that meets the current power demand, the power demand may change, for example, increase. In this case, when setting the number of auxiliary fuel cell systems for the increased power demand, all auxiliary fuel cell systems can be freely recombined and / or the already operating auxiliary fuel cell systems and their current operating states can be considered. In other words, this may result in a reduction in the number of switching operations when the power demand increases or changes, although it is not possible to select all possible combinations of the minimum number of auxiliary fuel cell systems that meet the power demand, unlike the implementation according to the previous paragraph.

[0034] It may also be advantageous in the method of the present invention to consider the proximity of the auxiliary fuel cell systems to the main fuel cell system when setting the number of auxiliary fuel cell systems. This is particularly suitable for special operating conditions, such as cold starts. As mentioned earlier, auxiliary fuel cell systems can be designed to be significantly simpler in terms of structure and components. In cold start situations, they can, for example, omit their own preheating devices, as they are only activated after the preheating of the main fuel cell stack has been completed by the operation of the main fuel cell system. Especially in such cold start conditions, the heat generated by the main fuel cell system propagates at different times depending on its proximity to different auxiliary fuel cell systems. The closer the auxiliary fuel cell systems are spatially to the main fuel cell system in cold start conditions, the faster the heat is transferred to the nearest auxiliary fuel cell system. It is thus clear that the spatial association settings between auxiliary fuel cell systems and the main fuel cell system can also be temporarily specified in time, for example, only at specific ambient temperatures and / or only for special operating conditions.

[0035] A further advantage may be that, in the method of the invention, after setting, the available power of the at least one main fuel cell system and / or at least one auxiliary fuel cell system is monitored and compared with the power demand. In other words, a control loop or regulation loop can be introduced here by means of a control method, so that not only can the desired power demand be met in a controlled manner, but also the degree to which the proposed power demand is met can be monitored and confirmed. This further enhances the advantages of the invention because the satisfaction can be practically monitored in a quantitative manner.

[0036] The subject matter of this invention also includes a computer program product comprising instructions that, when executed by a computer, cause the computer to perform the steps of the method of the invention. Therefore, this computer program product provides the same advantages detailed with respect to the method of the invention. Attached Figure Description

[0037] Other advantages, features, and details of the invention will become apparent from the following description, wherein embodiments of the invention are described in detail with reference to the accompanying drawings. The drawings schematically illustrate:

[0038] Figure 1 This invention illustrates one embodiment of the fuel cell stack of the present invention.

[0039] Figure 2 Another embodiment of the fuel cell stack of the present invention is shown.

[0040] Figure 3 This illustrates one possible operating condition.

[0041] Figure 4 This illustrates another possible operating condition.

[0042] Figure 5This illustrates another possible operating condition.

[0043] Figure 6 This illustrates possible power configurations within the fuel cell stack.

[0044] Figure 7 Other possible power configurations within the fuel cell stack are shown. Detailed Implementation

[0045] Figure 1 A fuel cell stack 10 is schematically shown. It is equipped with a main fuel cell system 100 and a single auxiliary fuel cell system 200. The main fuel cell system 100 includes a main fuel cell stack 120 having a main anode section 122 and a main cathode section 124. Corresponding gas supply and exhaust sections are provided to supply the required gas to the main fuel cell system and to exhaust the generated waste gas therefrom. Similarly, an auxiliary fuel cell system 200 including an auxiliary fuel cell stack 220 is provided within the fuel cell stack 10, the auxiliary fuel cell stack having a sub-anode section 222 and a sub-cathode section 224.

[0046] like Figure 1 As clearly shown, control and switching occur at the system level. For this purpose, the main fuel cell system 100 is equipped with a main control module 110, which can influence various control components (especially valves or other devices) to variably adjust the main operating point (HBP) of the main fuel cell system 100. The auxiliary fuel cell system 200 does not have control functions, but only switching functions in the form of a secondary switching module 210, which specifically ensures the simple on / off switching of the auxiliary fuel cell system 200. The specific switching functions and logic will be described in detail later.

[0047] Figure 2 Show Figure 1 Extension of the implementation method. Only the main fuel cell system 100 is shown here, which, for example, can... Figure 1 The configuration is similar or identical. Furthermore, three identical auxiliary fuel cell systems 200 are provided, each equipped with its own independent auxiliary switching module 210. The switching logic for different operating conditions will be explained below.

[0048] Figure 3The chart on the left shows the main fuel cell system 100 with a power LH, which here essentially corresponds to the maximum power LN of the auxiliary fuel cell system 200. It is clearly visible here that the maximum power LN of the auxiliary fuel cell system 200 is defined here as the only on state EZ, while complete shutdown is defined as the off state AZ. To execute the control method, the power demand LA is obtained in the first step, which here exceeds the single maximum power LN and LH, and is represented by the third bar on the right. To meet the power demand LA, it is evident that the auxiliary fuel cell system 200 is turned on in the first step, placing it in the on state EZ according to the sum of the rightmost power. Only a portion of the maximum possible power LH of the main fuel cell system 200 is needed to compensate for the remaining difference; therefore, the variable main operating point HBP is adjusted accordingly so that the on state EZ of the auxiliary fuel cell system 200 is added to the main operating point HBP of the main fuel cell system 100, together precisely or substantially precisely achieving and meeting the power demand LH.

[0049] Figure 4 Showing with Figure 3 The only difference in the operating conditions is the setting of a lower power demand LH. However, the combination of these two modules (i.e., the main fuel cell system 100 and the auxiliary fuel cell system 200) still needs to meet this slightly reduced power demand LA. The switching state of the auxiliary fuel cell system 200 remains unchanged because it remains in the on state EZ. But unlike... Figure 3 As the remaining difference between the on-state EZ of the auxiliary fuel cell system 200 and the power demand LA decreases, the variable main operating point HBP can be lowered through the variable control action of the main control module 110, allowing the main fuel cell system 100 to operate at a lower power. Nevertheless, the power demand LA is still met through the combined operation of the main fuel cell system 100 and the auxiliary fuel cell system 200.

[0050] Figure 5 Based on Figure 3 and 4 The explanation is as follows, but the power demand LA is further reduced, especially below the maximum efficiencies LH and LN of the main fuel cell system 100 and the auxiliary fuel cell system 200. It is clearly visible here that the auxiliary fuel cell system 200 is placed in a shutdown state AZ, and the reduced power demand LA is only achieved through [the process] relative to [other factors]. Figure 4 The further improved variable main operating point HBP is satisfied solely by the main fuel cell system 100.

[0051] Figure 6 and 7 Two possible configurations of different designs for the fuel cell stack 10 are shown. According to... Figure 6The main fuel cell system 100 and three (I, II, III) auxiliary fuel cell systems 200 are designed to have the same power outputs LH and LN. This allows the combination of these auxiliary fuel cell systems 200 with a variable main operating point HBP to meet different power demands LA, similar to a jigsaw puzzle, as... Figure 3 , 4 As stated in section 5, the maximum available power is derived from the sum of three power units LN and one power unit LH.

[0052] Figure 7 A variation is shown in which the maximum power LN of the different auxiliary fuel cell systems 200 differs from one another. Here, we can see the maximum power LN increasing progressively from I to II to III. However, by switching on and off and adjusting the single main fuel cell system 100, various forms of power demand LA can still be met variably and flexibly through the combined control of the main fuel cell system 100 and the switching of the auxiliary fuel cell systems 200.

[0053] The above explanation of the embodiments describes the present invention only within the scope of examples.

[0054] List of reference numerals

[0055] 10. Fuel Cell Stack

[0056] 100 Main fuel cell system

[0057] 110 Main Control Module

[0058] 120 main fuel cell stack

[0059] 122 Main anode section

[0060] 124 Main cathode section

[0061] 200 auxiliary fuel cell systems

[0062] 210 Sub-Switching Module

[0063] 220 auxiliary fuel cell stacks

[0064] 222 Sub-anode section

[0065] 224 Sub-cathode section

[0066] HBP Main Working Point

[0067] AZ shutdown status

[0068] EZ On Status

[0069] LA power requirements

[0070] LN auxiliary fuel cell system power

[0071] LH main fuel cell system power

Claims

1. A fuel cell stack (10) for generating electrical energy, comprising: A main fuel cell system (100) having at least one main fuel cell stack (120) and at least one auxiliary fuel cell system (200) having at least one auxiliary fuel cell stack (220), wherein the main fuel cell system (100) and the at least one auxiliary fuel cell system (200) are connected in parallel. Its characteristics are, The main fuel cell system (100) has a main control module (110) for variable control of the variable main operating point (HBP). The auxiliary fuel cell system (200) has an auxiliary switching module (210) for switching between a shutdown state (AZ) and at least one predetermined on state (EZ).

2. The fuel cell stack (10) according to claim 1, characterized in that, The auxiliary fuel cell system (200) and / or the auxiliary switching module (210) are designed to switch between a shutdown state (AZ) and exactly one predetermined on state (EZ).

3. The fuel cell stack (10) according to any of the preceding claims, characterized in that, The auxiliary fuel cell system (200) is designed not to include at least one of the following components: -Bypass valve for intake humidifiers -A bypass valve for the intake turbine. - A dehydrator for exhausting wastewater. -Thermostatic valve used in cooling circulation, - Heat exchangers used for fuel supply and / or fuel discharge. - A purging valve for combustion exhaust gases. - Temperature sensor at the inlet of the cooling cycle reactor. - Temperature sensor at the outlet of the cooling cycle stack - Pressure sensor in the exhaust section.

4. The fuel cell stack (10) according to any of the preceding claims, characterized in that, The fuel cell stack (10) has at least two auxiliary fuel cell systems (200).

5. The fuel cell stack (10) according to any of the preceding claims, characterized in that, There are at least two auxiliary fuel cell systems (200) with the same or substantially the same power (LN).

6. The fuel cell stack (10) according to any one of claims 1 to 4, characterized in that, There are at least two auxiliary fuel cell systems (200) with different power (LN).

7. The fuel cell stack (10) according to any of the preceding claims, characterized in that, The at least one main fuel cell system (100) has the same or greater power (LH) as the minimum auxiliary fuel cell system (200).

8. A method for controlling a fuel cell stack (10) having any of the features of claims 1 to 7, comprising the following steps: - Obtain the power requirement (LA) of the fuel cell stack (10), - Determine the required number of auxiliary fuel cell systems (200) that need to operate in the predetermined on-state (EZ) to meet the acquired power demand (LA). - Determine the primary operating point (HBP) of the primary fuel cell system (100) to be operated in variable mode to meet the difference between the power output and the power demand (LA) of the secondary fuel cell system (200) to be operated. - Set the determined number of the auxiliary fuel cell systems (200) and the determined main operating point (HBP) of the main fuel cell system (100) to operate the main fuel cell system (100).

9. The method according to claim 8, characterized in that, To determine the required number of auxiliary fuel cell systems (200) to be operated, the combination with the fewest possible combinations is selected and set together in the final step.

10. The method according to claim 8 or 9, characterized in that, in When setting the number of the auxiliary fuel cell systems (200), the auxiliary fuel cell systems that are already in the ON state (EZ) at the set time are selected first.

11. The method according to any one of claims 8 to 10, characterized in that, When determining the number of the auxiliary fuel cell systems (200), their proximity to the main fuel cell system (100) is taken into consideration.

12. The method according to any one of claims 8 to 11, characterized in that, in After the setting is completed, the available power of the at least one main fuel cell system (100) and / or the at least one auxiliary fuel cell system (200) is monitored and compared with the power demand (LA).

13. A computer program product comprising instructions that, when executed by a computer, cause the computer to perform steps of the method having any one of the features of claims 8 to 12.

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