Methods for optimizing operating parameters and arrangement

Abstract

Method for optimizing the operating parameters of an arrangement with a first fuel cell system and with a second fuel cell system, each having a fuel cell stack, comprising the steps: a. Operation of the arrangement in a partial load range (S1), b. Provision of power for the partial load range by the second fuel cell system (S2), c. Determination of an initial performance value maxη (1) where the efficiency of the first fuel cell system is maximized by increasing the power of the first fuel cell system from an open-circuit voltage (2) until the efficiency of the first fuel cell system is maximized (S3), d. Use of the first performance value thus obtained maxη (1) for the future allocation of power to the fuel cell systems (S4).

Description

[0001] The invention relates to a method for optimizing the operating parameters of an arrangement comprising a first fuel cell system and a second fuel cell system, each comprising a fuel cell stack. The method further relates to an arrangement comprising a first fuel cell system and at least one second fuel cell system, each comprising a fuel cell stack with a plurality of fuel cells.

[0002] Fuel cells utilize the chemical reaction of a fuel with oxygen to produce water, thereby generating electrical energy. They consist of an anode and a cathode, which are separated and electrically insulated by a polymer electrolyte membrane or an electrolyte, creating a gas-tight seal. During operation, a fuel, such as hydrogen, is supplied to the anode, and an oxygen-containing gas, such as air, is supplied to the cathode. At the anode, the fuel undergoes electrochemical oxidation, for example, to protons (H₂). + This process takes place with the release of electrons. The electrons are conducted away through an external circuit and flow through an electrical load, such as an electric motor, to the cathode. At the cathode, the oxygen is reduced to O₂. 2- A mobile ion produced during fuel cell reactions, for example H + , H3O + or O 2-The hydrogen diffuses through the electrolyte into the adjacent electrode compartment. In the case of hydrogen-powered fuel cells, protons are the mobile ions that diffuse to the cathode and react there with oxygen anions to form water. Various types of fuel cells are known, utilizing different fuels and differing in their construction. For example, polymer electrolyte membrane fuel cells (PEMFCs) and phosphoric acid fuel cells (PAFCs) use hydrogen, direct methanol fuel cells (DMFCs) use methanol, and solid oxide fuel cells (SOFCs) can use hydrogen, methanol, carbon monoxide, or synthesis gas. In the latter, the fuel used in the fuel cell is typically produced from hydrocarbons, such as compressed natural gas (CNG), by an upstream reformer.

[0003] Fuel cell systems, particularly in commercial vehicles, are often designed as so-called multi-systems, meaning that several fuel cell systems are connected in parallel. At the start of operation, the optimal performance point—the power value at which efficiency is maximized—is determined for each fuel cell system, and the fuel cell system is operated at or near this point / value. This power value can change during operation due to component variations or aging, making the fuel cell system, and therefore the entire configuration, less efficient. The optimal performance point / maximum power value can change asynchronously for each fuel cell system in the configuration.

[0004] WO 2004 059 767 A2 discloses an energy generation control system for a fuel cell, which includes a function for learning fuel cell performance characteristics. The control system disclosed in DE 10 336 743 A1 also discloses a learning scheme to compensate for systematic errors or tendencies due to aging or manufacturing variations. DE 103 32 336 A1 discloses a method for operating a fuel cell device with multiple fuel modules, in which a control device switches on or off at least one additional fuel cell module depending on the efficiency of the fuel cell modules supplying a load. DE 10 2018 218 086 A1 discloses a method for operating a fuel cell device with multiple fuel cell stacks, which can be selectively activated or deactivated.Performance data for each individual fuel cell stack is recorded, and the degree of degradation is determined based on this data. When the load demand increases, the fuel cell stack with the lowest degree of degradation is activated. A fuel cell device with multiple fuel cell stacks is also described in US 2008 / 0166604 A1, where operating data is recorded and provided to a modeling computer that models the operating characteristics in real time and adjusts the operation of the fuel cell device accordingly. CN 111755719 A discloses a method for power distribution in a fuel cell cluster, in which one fuel cell stack is started first, and when a load demand threshold is reached, another fuel cell stack is started to distribute the load across all started fuel cell stacks. This step is repeated as needed.From CN 108987770 A it is known to theoretically determine the efficiency of a fuel cell stack in a fuel cell device with a plurality of fuel cell stacks and to analyze the relationship between the efficiency and the power output.

[0005] If the optimal performance points for maximum system efficiency are unknown, this leads to higher fuel consumption and worsens the effectiveness of the arrangement's operating strategy.

[0006] Therefore, the object of the present invention is to provide a method for optimizing the operating parameters of an arrangement and an arrangement that can be operated more effectively.

[0007] The problem relating to the method is solved by a method having the features of claim 1, and the problem relating to the arrangement is solved by an arrangement having the features of claim 10. Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims.

[0008] The method according to the invention comprises in particular the following steps: a. Operation of the arrangement in a partial load range, b. Provision of power for the partial load range, in particular solely, by the second fuel cell system, c. Determination of an initial performance value maxη where the efficiency of the first fuel cell system is maximized by increasing the power of the first fuel cell system from an open-circuit voltage until the efficiency of the first fuel cell system is maximized. d. Use of the first performance value thus obtained maxη for the future distribution of power across the fuel cell systems.

[0009] This enables the best point, i.e., the performance value maxη The system determines the optimal operating point of the first fuel cell system during operation, thereby detecting any changes in the fuel cell system's optimal point. A control unit can then use this new optimal point when distributing future power among the fuel cell systems, allowing them to operate at or near their maximum power output / optimal point. This increases the efficiency with which the first fuel cell system, and consequently the entire system, can operate. This also leads to a reduction in fuel consumption. The fuel cell system can also include more than two fuel cell systems.

[0010] To further increase efficiency, it is particularly advantageous if the process also includes the following additional steps: e. Provision of power for the partial load range, in particular by the first fuel cell system alone, f. Determination of a second performance value maxη , where the efficiency of the second fuel cell system is maximized by increasing the power of the second fuel cell system from an open-circuit voltage until the efficiency of the second fuel cell system is maximized, g. Use of the second performance value thus obtained maxη for the future distribution of power across the fuel cell systems.

[0011] This also makes it possible to determine the best point, i.e., the second maximum power value of the second fuel cell system, during operation of the arrangement and to take both fuel cell systems into account when distributing the power.

[0012] This enables an increase in the efficiency of the arrangement, as even asynchronous changes in the optimal operating point of the various fuel cell systems can be detected and taken into account when distributing power. This also leads to a reduction in fuel consumption.

[0013] In particular, it is advantageous if the determination of the performance value maxη This is repeatedly performed under partial load. This means it is particularly preferred when determining the first power value. maxη and / or the second maximum power value is measured at regular intervals, especially alternately.

[0014] The partial load range is understood in particular to mean that the arrangement is subject to a load requirement in the range of 20% to 70%, preferably 30% to 70% and most preferably 40% to 50% of the maximum load requirement.

[0015] Within the framework of this process, it is advantageous if the control unit compensates for the excess power generated when determining the maximum power value of one of the fuel cell systems by reducing the power demand on the other fuel cell system. Alternatively, it is also preferred if the control unit, when determining the power value maxη The excess power generated by one of the fuel cell systems is transferred to an energy storage device. In this case, the power supply for the partial load range is provided exclusively by the fuel cell system with the highest power output. maxηThe energy stored in the energy storage system can be used for other components within the system.

[0016] To operate the system with maximum efficiency, it is preferable for the control unit to also consider the operating time of each fuel cell system when allocating power to them. For example, a higher proportion of the power can be allocated to the fuel cell system with the shorter total operating time.

[0017] Alternatively or additionally, it is preferable for the control unit to also consider the number of air-to-air starts when allocating power to the fuel cell systems in the future. This means that, in particular, the fuel cell system with a higher number of air-to-air starts and thus greater aging, will be allocated a smaller share of the power by the control unit.

[0018] Alternatively or additionally, it is advantageous if the control unit also takes into account the respective shutdown times and / or the proportion in full load operation (VLL) and / or the proportion in low load operation (LL) of the total operating time of the respective fuel cell systems and / or the refueling cycles when distributing the power to the fuel cell systems in the future.

[0019] The arrangement according to the invention is characterized in particular by the presence of a control unit configured to carry out the method. The advantages, advantageous embodiments, and effects mentioned in connection with the method according to the invention apply equally to the arrangement according to the invention. This arrangement can, in particular, be a motor vehicle or a truck.

[0020] The features and combinations of features mentioned above in the description, as well as those subsequently mentioned in the figure description and / or shown in the figures alone, can be used not only in the combinations specified, but also in other combinations or on their own, without departing from the scope of the invention. Thus, embodiments that are not explicitly shown or explained in the figure, but which can be derived and generated from the explained embodiments by separate combinations of features, are also to be considered as encompassed and disclosed by the invention.

[0021] Further advantages, features, and details of the invention will become apparent from the claims, the following description of preferred embodiments, and the drawings. These show: Fig. 1 a schematic representation of the process of the method according to the invention, and Fig. 2 a schematic diagram of the system efficiency η as a function of the power P of one of the fuel cell systems in the multi-system network.

[0022] Fig. Figure 1 shows the process according to the invention for optimizing the operating parameters of an arrangement with a first fuel cell system and with at least one second fuel cell system, each comprising a fuel cell stack. The fuel cell systems preferably operate within the range of their optimal operating point, i.e., their maximum power output. maxη1, at which the efficiency is maximum. This is usually determined at the beginning of the operating period for each of the fuel cell systems. In order to operate the arrangement efficiently throughout its entire operating period, a control unit repeatedly checks this optimal value during operation of the arrangement using the method according to the invention. For this purpose, when the arrangement is operated in a partial load range (step S1), the control unit orders that the power supply for the partial load range is provided solely by the second fuel cell system (step S2). The determination of a first power value maxη Step 1, at which the efficiency of the first fuel cell system is at its maximum, is achieved by increasing the power of the first fuel cell system from an open-circuit voltage 2 until the efficiency of the first fuel cell system is at its maximum (step S3) and then decreases again, as in Fig. 2 shown. This first performance value maxη Value 1 is stored in the control unit and used by the control unit for the future distribution of power to the fuel cell systems (step S4). This means that the control unit ensures that the first fuel cell system operates at or near its newly achieved best value / first maximum power value.

[0023] Since fuel cell systems can age asynchronously, the best point / second performance value will now also be determined. max 1 is determined for the second fuel cell system. For this purpose, the power for the partial load range is provided solely by the first fuel cell system (step S5). The power of the second fuel cell system is increased from an open-circuit voltage 2 until the efficiency of the second fuel cell system is at its maximum (step S6) and then decreases again, as in Fig. 2 shown. The second performance value is also shown. max1 is stored in the control unit and used for the future distribution of power to the fuel cell systems (step S7).

[0024] Determining the performance value maxη 1, i.e., the first performance value maxη 1 and the second performance value maxη 1. This process is repeated, particularly at regular intervals and alternately. The control unit always uses the most recent of the respective power values ​​to distribute the power to the fuel cell systems. maxη The method is used. The procedure is carried out in the partial load range, and in particular is carried out when the partial load range is 20% to 70% of the maximum load requirement, preferably 30% to 70% and especially preferably 40% to 50% of the maximum load requirement.

[0025] The factors used in determining the performance value maxηThe additional power generated by one of the fuel cell systems is compensated for by a reduction in the power demand on the other fuel cell system. Alternatively, it is also possible that the control unit, which determines the power value, maxη The excess power generated by one of the fuel cell systems is transferred to an energy storage device. In this case, the power for the partial load range is provided exclusively by the fuel cell system whose optimal operating point cannot be determined at that time.

[0026] To make the arrangement even more efficient, the control unit is designed to consider additional factors when distributing power between the fuel cell systems. Specifically, the control unit can take into account the operating time of each fuel cell system when distributing power, so that the system with the shorter operating time is allocated a higher power share. The number of air-to-air starts can also be considered when distributing power between the fuel cell systems. This allows the fuel cell system with fewer air-to-air starts to be allocated a higher power share.Furthermore, the total downtime and / or the proportion of full-load operation and / or the proportion of low-load operation of the total operating time of the respective fuel cell systems can also be taken into account when allocating power in the future. This also applies to the number of refueling cycles.

[0027] The arrangement, not shown in detail, comprises a first fuel cell system and at least one second fuel cell system. Each fuel cell system includes at least one fuel cell stack with a plurality of fuel cells. The fuel cell systems are connected in parallel. A control unit is also provided, which is configured to carry out the method according to the invention. REFERENCE MARK LIST: 1 Performance value maxη 2 Open circuit voltage

Claims

[1] Method for optimizing the operating parameters of an arrangement with a first fuel cell system and with a second fuel cell system, each having a fuel cell stack, comprising the steps: a. Operation of the arrangement in a partial load range (S1), b. Provision of power for the partial load range by the second fuel cell system (S2), c. Determination of an initial performance value maxη (1) where the efficiency of the first fuel cell system is maximized by increasing the power of the first fuel cell system from an open-circuit voltage (2) until the efficiency of the first fuel cell system is maximized (S3), d. Use of the first performance value thus obtained maxη (1) for the future allocation of power to the fuel cell systems (S4). [2] Method according to claim 1, characterized by the following further steps: e. Provision of power for the partial load range by the first fuel cell system (S5), f. Determination of a second performance value maxη (1) where the efficiency of the second fuel cell system is maximized by increasing the power of the second fuel cell system from an open-circuit voltage (2) until the efficiency of the second fuel cell system is maximized (S6), g. Use of the second performance value thus obtained maxη (1) for the future allocation of power to the fuel cell systems (S7). [3] Method according to claim 1 or 2, characterized by , that the determination of the maximum power value (1) is carried out repeatedly under partial load operation. [4] Method according to any one of claims 1 to 3, characterized by, that the procedure is carried out when the load requirement on the arrangement is in the range of 20% to 70%, preferably 30% to 70% and particularly preferably 40% to 50% of the maximum load requirement. [5] Method according to any one of claims 1 to 4, characterized by that the control unit, when determining the power value maxη (1) compensates for the increased power output generated by one of the fuel cell systems by reducing the power requirement on the other of the fuel cell systems. [6] Method according to any one of claims 1 to 4, characterized by that the control unit, when determining the power value maxη (1) transfers the excess power generated by one of the fuel cell systems to an energy storage device. [7] Method according to any one of claims 1 to 6, characterized bythat the control unit additionally takes into account the operating time of the respective fuel cell systems when distributing the power among the fuel cell systems in the future. [8] Method according to any one of claims 1 to 7, characterized by that the control unit also takes into account the number of air-to-air starts when future power distribution to the fuel cell systems. [9] Method according to any one of claims 1 to 8, characterized by , that the control unit additionally takes into account the respective shutdown times and / or the proportion of full load operation in the total operating time and / or the proportion of low load operation in the total operating time of the respective fuel cell systems and / or the refueling cycles when distributing the power to the fuel cell systems in the future. [10] Arrangement comprising a first fuel cell system and at least one second fuel cell system, each comprising at least one fuel cell stack comprising a plurality of fuel cells and a control unit configured to carry out the method according to any one of claims 1 to 9.

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