Method for determining a degree of fuel utilisation of a fuel cell unit in a fuel cell device, in particular an SOFC fuel cell device

Abstract

The invention relates to a method for determining a degree of fuel utilisation of a fuel cell unit in a fuel cell device (10a; 10b; 10c), in particular an SOFC fuel cell device, which has at least one fuel cell unit (12a; 12b; 12c), in particular a fuel cell stack, at least one fan unit (14a; 14b; 14c), and at least one open-loop and closed-loop control unit (16a; 16b; 16c), having an operating step (18a; 18b; 18c) in which the fuel cell unit (12a; 12b; 12c) obtains electrical energy from a gaseous medium, wherein the fan unit (14a; 14b; 14c) regulates and drives a recirculation circuit (20a; 20b; 20c) in the operating step (18a; 18b; 18c), and wherein operation of the fuel cell device (10a; 10b; 10c) is regulated by means of the open-loop and closed-loop control unit (16a; 16b; 16c) in the operating step (18a; 18b; 18c). According to the invention, in at least one comparison step (24a; 24b; 24c) a degree of fuel utilisation of the fuel cell unit (12a; 12b; 12c) is estimated by means of an empirical estimation.

Description

[0001] Description

[0002] Method for determining a fuel utilization factor of a fuel cell unit in a fuel cell device, in particular SOFC-

[0003] State of the art

[0004] A method for determining a fuel utilization factor of a fuel cell unit in a fuel cell device, in particular an SOFC fuel cell device, which has at least one fuel cell unit, in particular a fuel cell stack, at least one blower unit, and at least one control and regulating unit, with an operating step in which the fuel cell unit generates electrical energy from a gaseous medium, wherein the blower unit regulates and drives a recirculation circuit in the operating step and wherein an operation of the fuel cell device is regulated by means of the control and regulating unit in the operating step, has already been proposed.

[0005] Disclosure of the invention

[0006] The invention is based on a method for determining a fuel utilization factor of a fuel cell unit in a fuel cell device, in particular an SOFC fuel cell device, which has at least one fuel cell unit, in particular a fuel cell stack, at least one blower unit, and at least one control and regulating unit, with an operating step in which the fuel cell unit generates electrical energy from a gaseous medium, wherein the blower unit regulates and drives a recirculation circuit in the operating step and wherein an operation of the fuel cell device is regulated by means of the control and regulating unit in the operating step.

[0007] It is proposed that in at least one comparison step, a fuel utilization factor of the fuel cell unit is estimated by means of an empirical estimation.

[0008] In this context, a “fuel cell device” is to be understood in particular as a device which is configured to generate electrical energy in one operating step. The fuel cell device is preferably configured to provide an energy system. The fuel cell device is preferably designed as an SOFC fuel cell device, in particular a solid oxide fuel cell. The fuel cell device preferably has a supply element which supplies an energy carrier, for example natural gas, and / or electrical energy to the fuel cell device. The fuel cell system preferably has a discharge element which discharges exhaust gases and / or electrical energy from a fuel cell system. In particular, it is conceivable for the supply element to supply the fuel cell device with oxygen from the ambient air.Furthermore, it is conceivable for the fuel cell device to be supplied with pure oxygen via the supply element in order to ensure the efficiency of the fuel cell device. The supply element and the discharge element are preferably designed as a pipeline. Particularly preferably, the supply element and the discharge element are designed to guide a gaseous medium. In particular, it is conceivable for the fuel cell device to have a heat exchanger which is designed to utilize thermal energy generated in the fuel cell unit. In particular, it is conceivable for the fuel cell device to have a cooling unit in a recirculation circuit which is designed to cool a gaseous medium heated by a blower unit. “Designed” should be understood to mean, in particular, specially programmed, designed and / or equipped.The fact that an object is configured for a specific function should be understood in particular to mean that the object fulfills and / or performs this specific function in at least one application and / or operating state. Preferably, the fuel cell device has a fuel utilization factor. In this context, a "fuel utilization factor" should be understood in particular as a percentage or a ratio of the actually used fuel relative to the total amount of fuel used. Preferably, a fuel utilization factor of the fuel cell device is adjusted in an operating step.

[0009] In this context, a “fuel cell unit” is to be understood in particular as a unit which is designed to generate electrical energy from a gaseous medium in one operating step. The fuel cell unit is preferably designed as a fuel cell stack. The fuel cell unit is preferably designed to electrochemically generate electrical energy and heat from the chemical energy of an energy carrier. The fuel cell unit is preferably designed to generate electrical energy from a gaseous medium. The fuel cell unit is preferably designed to convert chemical reaction energy of a continuously supplied fuel and an oxidizing agent into electrical energy. Particularly preferably, natural gas, for example, is used as the fuel and oxygen as the oxidizing agent.Alternatively, other fuels that would appear appropriate to a person skilled in the art, for example methanol, butane, ammonia and / or hydrogen, are also conceivable. Preferably, in one operating step, electrical energy is generated in the fuel cell unit between an anode and a cathode. Preferably, the anode splits off the electrons from the fuel. Preferably, the electrons are conducted to the cathode via a connecting element. Preferably, the fuel cell unit has at least one fuel cell. Particularly preferably, the fuel cell unit has a plurality of fuel cells. Preferably, all fuel cells in a fuel cell unit are identical. Alternatively, it is conceivable for the fuel cell units to be differently designed. Preferably, each fuel cell has an anode and a cathode. Preferably, all fuel cells in a fuel cell unit are electrically connected to one another.Preferably, the fuel cells are electrically connected in series or parallel to achieve the desired output voltage and power. Preferably, the fuel cell unit has a fuel utilization factor. Preferably, a fuel utilization factor of the fuel cell unit is kept constant during an operating step.

[0010] In this context, a “blower unit” should be understood in particular to mean an element which accelerates a gaseous medium. Preferably, the blower unit accelerates a gaseous medium to a medium flow. Preferably, the blower unit generates an air stream of the gaseous medium. Preferably, the blower unit has at least one rotor blade element, via which a rotary movement is converted into a linear movement of the gaseous medium. Preferably, the heat transfer device has a drive unit which drives the at least one rotor blade element in rotation. A “rotor blade element” should be understood in particular to mean an element which converts a converted enthalpy at least substantially entirely or partially into flow energy of a gaseous medium. Preferably, the blower unit is arranged in a recirculation circuit.The blower unit is preferably arranged at least substantially partially, preferably at least substantially, and particularly preferably entirely in a recirculation circuit. The expression “at least substantially” is to be understood as meaning in particular at least 55%, advantageously at least 65%, preferably at least 75%, particularly preferably at least 85%, and particularly advantageously at least 95%. In this context, “at least substantially” is to be understood as meaning in particular that a deviation from a predetermined value deviates by in particular less than 25%, preferably less than 10%, and particularly preferably less than 5% of the predetermined value. The guide vane element is particularly preferably arranged entirely in a recirculation circuit.

[0011] In this context, an “operating step” should be understood to mean, in particular, a method step in which the fuel cell device is operated, in particular regularly and / or continuously. Preferably, in the operating step, electrical energy is generated in a fuel cell unit. Preferably, in the operating step, operation of a fuel cell device is regulated and / or monitored by means of a control and regulating unit. Preferably, in an operating step, a fuel, in particular natural gas, is supplied to the fuel cell device. Preferably, in the operating step, a fuel utilization factor of the fuel cell device is varied by means of a control and regulating unit. Preferably, in the operating step, a fuel utilization factor of the fuel cell device is varied stepwise by means of a control and regulating unit. Preferably, in an operating step, a comparison step is carried out.In this context, a "comparison step" is understood to mean, in particular, a method step in which the fuel utilization rate of the fuel cell unit is determined empirically. Preferably, in the comparison step, the fuel utilization rate of the fuel cell unit is determined empirically based on at least one further parameter of the fuel cell device. Preferably, in the comparison step, the fuel utilization rate of the fuel cell unit is determined empirically based on the influence of the further parameters of the fuel cell device on a cell voltage.

[0012] In this context, a "recirculation circuit" is to be understood in particular as a circuit which is designed to provide a return flow of waste products and / or unused fuel, in particular natural gas. Preferably, in one operating step, a fuel, in particular natural gas, is supplied to the recirculation circuit by means of the supply element. Preferably, the recirculation circuit connects a blower unit and a fuel cell unit by means of a circuit. Preferably, a fuel, in particular natural gas, is supplied between the blower unit and the fuel cell unit by means of the supply element. Preferably, the recirculation circuit directs a volume flow of the discharge element at least partially, preferably to a large extent, from the discharge element to the blower unit.In particular, it is conceivable for the control and regulation unit to continuously regulate the proportion of the diverted volume flow from the diversion element via the speed of the fan unit. Preferably, the recirculation circuit is configured to regulate and ensure a supply to the fuel cell unit in one operating step. Preferably, the recirculation circuit is configured to regulate and maintain pressure and flow regulation of the volume flow in a fuel cell unit in one operating step. In particular, it is conceivable for the recirculation circuit to have a cooling element by means of which the operating temperature of the fuel is regulated in one operating step.

[0013] A “control and regulating unit” should be understood in particular to mean a unit with at least one control electronics unit. A “control electronics unit” should be understood in particular to mean a unit with a processor unit and with a memory unit as well as with an operating program stored in the memory unit. Preferably, the control and regulating unit is configured to adapt an operation of the fuel cell device in an operating step. Preferably, the control and regulating unit is configured to regulate the blower unit in an operating step. Preferably, the control and regulating unit is configured to adapt an operation of the fuel cell device in an operating step and to regulate the blower unit in parallel. Preferably, the control and regulating unit has a user interface via which a user can monitor and control an operating step and / or a comparison step.In particular, it is conceivable that the control and regulation unit automatically carries out an operating step in a cyclical sequence.

[0014] The inventive design of the method for determining a fuel utilization factor of a fuel cell unit in a fuel cell device, in particular an SOFC fuel cell device, makes it possible to provide advantageous properties with regard to simplified determination of the fuel utilization factor of a fuel cell unit. In particular, advantageous properties with regard to monitoring and regulating a fuel cell device can be provided. In particular, advantageous properties with regard to reduced complexity of the fuel cell device can be provided. In particular, a method can be provided without the use of a sensor for measuring a fuel utilization factor of a fuel cell unit. This makes it possible to provide particularly advantageous properties with regard to cost savings.

[0015] Furthermore, it is proposed that in at least one comparison step, the fuel utilization rate of the fuel cell unit is empirically estimated via a gradient of the cell voltage when a fuel utilization rate of the fuel cell device changes. Preferably, in the comparison step, the influence of a variation in the fuel utilization rate of the fuel cell device (FU_Sys) on the fuel utilization rate of the fuel cell unit (FU_Stk) is empirically determined. Preferably, in the comparison step, an influence of different fuel utilization rates of the fuel cell device on a cell voltage (u_cell) is represented. Preferably, in the comparison step, a fuel utilization rate of the fuel cell device is estimated via a function of the gradient of the cell voltage from the fuel utilization rate of the fuel cell device.Preferably, in the comparison step, a diagram is created using the function of the cell voltage gradient as a function of the fuel utilization factor of the fuel cell device. Preferably, in the comparison step, the function represented in the diagram is empirically evaluated. Preferably, in the comparison step, a fuel utilization factor of the fuel cell unit is empirically determined using the slope of the function of the cell voltage gradient as a function of the fuel utilization factor of the fuel cell device. Particularly preferably, in the comparison step, the fuel utilization factor of the fuel cell unit is determined using the formula. This makes it possible to provide particularly advantageous properties with regard to a simplified determination of the fuel utilization rate of a fuel cell unit.

[0016] It is further proposed that the fuel utilization factor of the fuel cell device and the current cell voltage be determined in at least one determination step. In this context, a “determination step” should be understood to mean, in particular, a method step in which the required parameters of the fuel cell device are determined for an empirical determination of the fuel utilization factor of the fuel cell unit. Preferably, the fuel utilization factor of the fuel cell device and the current cell voltage are determined in the determination step. Preferably, the fuel utilization factor of the fuel cell device (FU_Sys_1) is determined in the determination step via an energy balance at the fuel cell unit. Alternatively and / or additionally, the fuel utilization factor of the fuel cell device is determined in the determination step via the energy balance at the hotbox.Alternatively and / or additionally, the fuel utilization factor of the fuel cell device is determined in the determination step by measuring the gas volume flow and the associated calorific value in a current operating state. Furthermore, any other method of determining the fuel utilization factor of the fuel cell device that appears appropriate to a person skilled in the art is conceivable. Preferably, the current cell voltage (u_1) is measured in the determination step. Furthermore, any other method of determining the current cell voltage that appears appropriate to a person skilled in the art is conceivable. This makes it possible to provide particularly advantageous properties with regard to determining the fuel utilization factor of a fuel cell device and the current cell voltage.

[0017] Furthermore, it is proposed that in at least one adaptation step, an active variation, in particular in at least two stages, of the fuel utilization factor of the fuel cell device is carried out by changing the supplied natural gas volume flow. In this context, an "adaptation step" is to be understood in particular as a method step in which a parameter of the fuel cell device is adjusted. Preferably, in the adaptation step, a fuel utilization factor of the fuel cell device is adjusted. Preferably, the fuel utilization factor of the fuel cell device is adjusted by changing the supplied natural gas volume flow. Preferably, in the adaptation step, an active variation of the fuel utilization factor of the fuel cell device is carried out.Particularly preferably, in the adaptation step, an active variation of the fuel utilization factor of the fuel cell device is carried out in at least two stages. Furthermore, any other number of stages of the active variation of the fuel utilization factor of the fuel cell device that appears reasonable to a person skilled in the art is conceivable. Preferably, in the adaptation step, a supplied natural gas volume flow to the fuel cell device is regulated by means of the control and regulating unit. In particular, it is conceivable for the fuel cell device to have a further blower unit via which the supplied natural gas volume flow to the fuel cell device is regulated. In particular, it is conceivable for the control and regulating unit to regulate a supplied natural gas volume flow to the fuel cell device via the further blower unit in the adaptation step.Preferably, in the adjustment step, a supplied natural gas volume flow is increased by means of the control and regulation unit. Alternatively, it is conceivable that in the adjustment step, a supplied natural gas volume flow is reduced by means of the control and regulation unit. Preferably, in the adjustment step, the fuel utilization factor of the fuel cell device is reduced by increasing the supplied natural gas volume flow. This makes it possible to provide particularly advantageous properties with regard to regulating the fuel cell device. Particularly advantageous properties with regard to simplified determination of the fuel utilization factor of a fuel cell unit can be provided.

[0018] It is further proposed that in at least one adjustment step, a fuel utilization factor of the fuel cell unit is kept constant by means of the blower unit, in particular by adjusting the recirculation volume flow of the recirculation circuit. Preferably, in the adjustment step, a blower unit is automatically regulated via the control and regulating unit. Preferably, in the adjustment step, a recirculation volume flow of the recirculation circuit is regulated via the blower unit. Preferably, in the adjustment step, a recirculation volume flow of the recirculation circuit is regulated via the speed of the blower unit. Preferably, in the adjustment step, the speed of the blower unit is regulated via the control and regulating unit depending on a measured value determined in the fuel cell unit in order to keep the fuel utilization factor of the fuel cell unit constant.Preferably, in an adjustment step, the fuel utilization rate of the fuel cell unit is kept constant by means of the recirculation volume flow, simultaneously with the adjustment of the fuel utilization rate of the fuel cell device. Preferably, in the adjustment step, a recirculation flow is increased if the fuel utilization rate of the fuel cell device is reduced. Alternatively, in the adjustment step, a recirculation flow is reduced if the fuel utilization rate of the fuel cell device is increased. This makes it possible to provide particularly advantageous properties with regard to regulating the fuel cell device. In particular, advantageous properties with regard to simplified determination of the fuel utilization rate of a fuel cell unit can be provided.

[0019] Furthermore, it is proposed that, in at least one further determination step, the fuel utilization factor of the fuel cell device and the current cell voltage be determined after an adaptation step. Preferably, the further determination step is carried out after an adaptation step. Preferably, the further determination step is carried out identically to the determination step. Preferably, in the further determination step, the fuel utilization factor of the fuel cell device (FU_Sys_2) is determined via an energy balance at the fuel cell unit. Alternatively and / or additionally, in the further determination step, the fuel utilization factor of the fuel cell device is determined via the energy balance at the hotbox.Alternatively and / or additionally, in the further determination step, the fuel utilization factor of the fuel cell device is determined by measuring the gas volume flow and the associated calorific value in a current operating state. Furthermore, any other determination of the fuel utilization factor of the fuel cell device that appears appropriate to a person skilled in the art is conceivable. Preferably, in the further determination step, the current cell voltage (u_2) is measured after an adjustment step. Furthermore, any other determination of the current cell voltage that appears appropriate to a person skilled in the art is conceivable. This makes it possible to provide particularly advantageous properties with regard to determining the fuel utilization factor of a fuel cell device and the current cell voltage after an adjustment step.

[0020] It is further proposed that, in at least one calculation step, the cell voltage gradient be calculated based on the values ​​determined in the determination step and the further determination step. Preferably, in the calculation step, the cell voltage gradient is calculated based on the fuel utilization factors of the user device (FU_Sys_1, FU_Sys_2) and the associated cell voltages (u_1, u_2) determined in the determination step and the further determination step. In this context, a "calculation step" is to be understood in particular as a method step in which the cell voltage gradient (du_cell / dFU_Sys) is determined. Preferably, the cell voltage gradient is calculated in the calculation step. Preferably, in the calculation step, the cell voltage gradient is determined using the formula dUceii (Ui ~ U2) Calculated. Preferably, a calculation step is performed in the operating step. Preferably, the calculation step is performed after the determination step, the adjustment step, and the further determination step in the operating step. This makes it possible to provide particularly advantageous properties with regard to determining the fuel utilization rate of a fuel cell device and the current cell voltage after an adjustment step.

[0021] According to a further exemplary embodiment, it is proposed that in at least one adaptation step, the settings of the adaptation step are revoked, and subsequently the fuel utilization rate of the fuel cell device and the current cell voltage are determined. Preferably, in the adaptation step, the natural gas volume flow and the recirculation flow are reset to an initial state. In this context, an "adaptation step" is to be understood in particular as a method step in which all adaptations of the adaptation step are revoked. Preferably, in the adaptation step, the fuel utilization rate of the fuel cell device and the current cell voltage are determined. Preferably, in the adaptation step, the fuel utilization rate of the fuel cell device is determined via an energy balance on the fuel cell unit.Alternatively and / or additionally, in the adaptation step, the fuel utilization rate of the fuel cell device is determined via the energy balance at the hotbox. Alternatively and / or additionally, in the adaptation step, the fuel utilization rate of the fuel cell device is determined via a measurement of the gas volume flow and the associated calorific value in a current operating state. Furthermore, any other determination of the fuel utilization rate of the fuel cell device that appears reasonable to a person skilled in the art is conceivable. Preferably, the current cell voltage is measured in the adaptation step. Furthermore, any other determination of the current cell voltage that appears reasonable to a person skilled in the art is conceivable. This makes it possible to achieve particularly advantageous properties with regard to monitoring the fuel cell device.

[0022] According to a further embodiment, it is proposed that, in at least one control step, the values ​​determined in an adaptation step are correlated with the values ​​determined in a determination step in order to check the influence of the adaptation step on the fuel utilization rate of the fuel cell device and the current cell voltage. Preferably, in the control step, the values ​​determined in an adaptation step are compared with the values ​​determined in a determination step and evaluated. Preferably, in the control step, a result of the evaluation of the comparison of the fuel utilization rate of the fuel cell device and the cell voltage in a determination step and an adaptation step is determined for the control and regulation unit.Preferably, in a control step, an adaptation step and a further determination step are restarted if the fuel utilization rate of the fuel cell device and the cell voltage in an adaptation step differ from the fuel utilization rate of the fuel cell device and the cell voltage in a determination step. Preferably, in a control step, the fuel cell device is regulated based on the empirically determined fuel utilization rate of the fuel cell unit if the fuel utilization rate of the fuel cell device and the cell voltage in an adaptation step are identical to the fuel utilization rate of the fuel cell device and the cell voltage in a determination step. In this context, a "control step" is to be understood in particular as a method step in which the results are validated.This allows particularly advantageous properties with regard to monitoring the fuel cell device to be achieved. According to a further exemplary embodiment, it is proposed that, in at least one comparison step, the fuel utilization factor of the fuel cell unit is empirically estimated based on a change in a natural gas volume flow of the fuel cell device and / or a recirculation volume flow of the recirculation circuit. Preferably, in the comparison step, the influence of a variation in a natural gas volume flow of the fuel cell device and / or a recirculation volume flow of the recirculation circuit of the fuel cell device on the fuel utilization factor of the fuel cell unit is empirically determined.Preferably, in the comparison step, the influence of different natural gas volume flows of the fuel cell device and / or a recirculation volume flow of the recirculation circuit on a cell voltage is determined. Preferably, in the comparison step, the fuel utilization rate of the fuel cell device is estimated using a function of the cell voltage gradient. In particular, it is conceivable that measured and / or calculated variables, such as a temperature value or the calorific value of the natural gas used, are included in the correlation. Preferably, in the comparison step, an empirical correlation is derived from measurement and / or simulation campaigns and stored on the control and regulation unit using characteristic curves, characteristic maps, polynomial approaches, or other data-based models.This makes it possible to provide particularly advantageous properties with regard to a simplified determination of the fuel utilization rate of a fuel cell unit.

[0023] Furthermore, it is proposed that in at least one operating step, the fuel cell device comprise a battery element that compensates for energy fluctuations by buffering. Preferably, in the operating step, energy fluctuations resulting from the adjustment step are compensated for by means of the battery element. Preferably, in the operating step, energy fluctuations resulting from the increase in the supplied natural gas volume flow are stored by means of the battery element. Furthermore, it is conceivable for the fuel cell device to be used in a cluster operating strategy, with another fuel cell device assuming at least substantially partial, preferably at least a large part, and particularly preferably completely, buffering.Preferably, a constant total electrical energy is provided in one operating step using the cluster operating strategy. The term "at least a large part" is understood to mean, in particular, at least 55%, advantageously at least 65%, preferably at least 75%, particularly preferably at least 85%, and particularly advantageously at least 95%. This allows particularly advantageous properties with regard to the operation of a fuel cell device to be achieved.

[0024] According to a further exemplary embodiment, it is proposed that the fuel utilization factor of the fuel cell unit is determined in at least one evaluation step by detecting the time of a gradient change. In this context, an "evaluation step" should be understood in particular as a method step in which a gradient is evaluated and assessed. Preferably, in the evaluation step, the time of a gradient change in the fuel utilization factor of the fuel cell unit is determined using the function. Preferably, in the evaluation step, a fuel utilization factor of the fuel cell unit is detected when the function bends horizontally. Preferably, in the evaluation step, an operating step is cyclically evaluated by means of an evaluation step in order to determine the fuel utilization factor of the fuel cell unit.Preferably, the time of a gradient change at a high fuel utilization rate of the fuel cell device is detected in the evaluation step. Preferably, a gradient change occurs in an evaluation step only at a high fuel utilization rate of the fuel cell device. This makes it possible to provide particularly advantageous properties with regard to an evaluation and assessment of the fuel utilization rate of the fuel cell unit.

[0025] According to a further embodiment, it is proposed that in at least one monitoring step, an exceedance of the permissible fuel utilization rate of the fuel cell unit is detected by detecting the time of a gradient change. In this context, a "monitoring step" is to be understood in particular as a method step in which the operation of a fuel cell device is monitored. Preferably, a cyclical execution of the operating step is monitored in the monitoring step. Preferably, in the monitoring step, a message is transmitted to the control and regulation unit as soon as the fuel utilization rate of the fuel cell unit exceeds and / or reaches a maximum fuel utilization rate of the fuel cell unit.Preferably, in the operating step, a fuel utilization rate of the fuel cell unit is regulated based on the message transmitted in a monitoring step. This can provide particularly advantageous properties with regard to monitoring the operation of a fuel cell device.

[0026] The invention further proposes a fuel cell device, in particular an SOFC fuel cell device, for carrying out a method according to the invention. Preferably, the fuel cell device is configured to carry out an operating step. Preferably, the fuel cell device is configured to generate electrical energy. Preferably, the fuel cell device has a supply element which supplies an energy carrier, for example natural gas, and / or electrical energy to the fuel cell device. Preferably, the fuel cell system has a discharge element which discharges exhaust gases and / or electrical energy from a fuel cell system. Preferably, the fuel cell device is configured as an SOFC fuel cell device. Particularly preferably, the fuel cell device is operated with natural gas. Preferably, the fuel cell device is configured in several parts.The fuel cell device preferably has at least one fuel cell unit. The fuel cell device preferably has at least one blower unit. The fuel cell device preferably has at least one recirculation circuit. In particular, it is conceivable for the fuel cell device to have a cooling unit in a recirculation circuit, which cooling unit is designed to cool a gaseous medium heated by a blower unit. This makes it possible to provide particularly advantageous properties with regard to a method according to the invention for operating a fuel cell device. The method according to the invention for operating a fuel cell device should not be limited to the application and embodiment described above.In particular, the method according to the invention for operating a fuel cell device to fulfill a functional function described herein may comprise a number of individual elements, components, and units, as well as method steps, that differs from the number stated herein. Furthermore, in the value ranges specified in this disclosure, values ​​within the stated limits are also to be considered disclosed and can be used arbitrarily.

[0027] drawing

[0028] Further advantages will become apparent from the following description of the drawings. The drawings illustrate three exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will also expediently consider the features individually and combine them into useful further combinations.

[0029] They show:

[0030] Fig. 1 shows a fuel cell device according to the invention in a schematic representation,

[0031] Fig. 2 is a schematic flow diagram of a method for operating a fuel cell device according to the invention,

[0032] Fig. 3 is a schematic flow diagram of an embodiment of a method for operating a fuel cell device according to the invention and

[0033] Fig. 4 is a schematic flow diagram of an embodiment of a method for operating a fuel cell device according to the invention.

[0034] Description of the Embodiments Fig. 1 shows a fuel cell device 10a, in particular an SOFC fuel cell device, for carrying out a method according to the invention. The fuel cell device 10a is configured to carry out an operating step 18. The fuel cell device 10a is configured to generate electrical energy. The fuel cell device 10a has a supply element 28a, which supplies an energy carrier, for example hydrogen, and / or electrical energy to the fuel cell device 10a. The fuel cell device 10a has a discharge element 26a, which discharges exhaust gases and / or electrical energy from a fuel cell device. The fuel cell device 10a is designed as an SOFC fuel cell device. The fuel cell device 10a is operated with natural gas. The fuel cell device 10a is designed in several parts.The fuel cell device 10a has at least one fuel cell unit 12a. The fuel cell device 10a has at least one blower unit 14a. The fuel cell device 10a has at least one recirculation circuit 20a. In particular, it is conceivable that the fuel cell device 10a is supplied with oxygen from the ambient air via the supply element 28a. Furthermore, it is conceivable that the fuel cell device 10a is supplied with pure oxygen via the supply element 28a in order to increase the efficiency of the fuel cell device 10a. The supply element 28a and the discharge element 26a are designed as a pipeline. The supply element 28a and the discharge element 26a are designed to conduct a gaseous medium.In particular, it is conceivable for the fuel cell device 10a to have a heat exchanger configured to utilize thermal energy generated in the fuel cell unit 12a. In particular, it is conceivable for the fuel cell device 10a to have a cooling unit in a recirculation circuit 20a configured to cool a gaseous medium heated by a fan unit 14a.

[0035] The fuel cell unit 12a is designed as a fuel cell stack. The fuel cell unit 12a is configured to electrochemically generate electrical energy and heat from the chemical energy of an energy carrier. The fuel cell unit 12a is configured to generate electrical energy from a gaseous medium. The fuel cell unit 12a is configured to convert chemical reaction energy of a continuously supplied fuel and an oxidizing agent into electrical energy. For example, natural gas is used as the fuel and oxygen as the oxidizing agent. Alternatively, other fuels deemed appropriate by a person skilled in the art, such as methanol, butane, ammonia, and / or hydrogen, are also conceivable. In an operating step 18a, electrical energy is generated in the fuel cell unit 12a between an anode and a cathode. The anode splits off the electrons from the fuel.The electrons are guided to the cathode via a connecting element. The fuel cell unit 12a has at least one fuel cell. The fuel cell unit 12a has a plurality of fuel cells. All fuel cells in a fuel cell unit 12a are identically designed. Alternatively, it is conceivable for the fuel cells to be differently designed. Each fuel cell has an anode and a cathode. All fuel cells of a fuel cell unit 12a are electrically connected to one another. The fuel cells are electrically connected in series or parallel to achieve the desired output voltage and power. The fuel cell unit 12a has a fuel utilization factor.

[0036] The blower unit 14a generates an air flow of the gaseous medium. The blower unit 14a has at least one rotor blade element, via which a rotary movement is converted into a linear movement of the gaseous medium. The blower unit 14a has a drive unit that drives the at least one rotor blade element in rotation. The blower unit 14a is arranged in a recirculation circuit 20a. The blower unit 14a is arranged at least substantially partially, preferably at least largely, and particularly preferably completely in a recirculation circuit 20a.

[0037] In an operating step 14a, a fuel, in particular natural gas, is supplied to the recirculation circuit 20a by means of the supply element 28a. The recirculation circuit 20a connects a blower unit 14a and a fuel cell unit 12a by means of a circuit. A fuel, in particular natural gas, is supplied between the blower unit 14a and the fuel cell unit 12a by means of the supply element 28a. The recirculation circuit 20a directs a volume flow of the discharge element 26a at least partially, preferably to a large extent, from the discharge element 26a to the blower unit 14a. In particular, it is conceivable that a control and regulating unit 16a continuously regulates the proportion of the diverted volume flow from the discharge element 26a via the speed of the blower unit 14a. The recirculation circuit 20a is designed to regulate and ensure a supply to the fuel cell unit 12a in an operating step 18.The recirculation circuit 20a is configured to regulate and maintain pressure and flow regulation of the volume flow in a fuel cell unit 12a in an operating step 18a. In particular, it is conceivable for the recirculation circuit 20a to have a cooling element by means of which the operating temperature of the fuel is regulated in an operating step 18a.

[0038] The control and regulation unit 16a is configured to adapt the operation of the fuel cell device 10a in an operating step 18a. The control and regulation unit 16a is configured to regulate the blower unit 14a in an operating step 18a. The control and regulation unit 16a is configured to adapt the operation of the fuel cell device 10a in an operating step 18a and, in parallel, to regulate the blower unit 14a. The control and regulation unit 16a has a user interface via which a user can monitor and control an operating step 18a and / or a comparison step 24a. In particular, it is conceivable for the control and regulation unit 16a to automatically perform an operating step 18a in a cyclic sequence.

[0039] Fig. 2 shows a method for determining a fuel utilization factor of a fuel cell unit 12a in a fuel cell device 10a, in particular an SOFC fuel cell device, which has at least one fuel cell unit 12a, in particular a fuel cell stack, at least one blower unit 14a, and at least one control and regulation unit 16a. The method for operating a fuel cell device 10a has an operating step 18a in which the fuel cell unit 12a generates electrical energy from a gaseous medium, wherein the blower unit 14a regulates and drives a recirculation circuit 20a in the operating step 18a, and wherein operation of the fuel cell device 10a is regulated by means of the control and regulation unit 16a in the operating step 18a.In at least one comparison step 24a, a fuel utilization factor of the fuel cell unit 12a is estimated by means of an empirical estimation. In the operating step 18a, electrical energy is generated in a fuel cell unit 12a. In the operating step 18a, operation of a fuel cell device 10a is regulated and / or monitored by means of a control and regulating unit 16a. In the operating step 18a, a fuel, in particular natural gas, is supplied to the fuel cell device 10a. In the operating step 18a, a fuel utilization factor of the fuel cell device 10a is varied by means of a control and regulating unit 16a. In the operating step 18a, a fuel utilization factor of the fuel cell device 10a is varied stepwise by means of a control and regulating unit 16a. In the operating step 18a, a comparison step 24a is carried out.In comparison step 24a, the fuel efficiency of the fuel cell unit 12a is empirically determined depending on at least one further parameter of the fuel cell device 10a. In comparison step 24a, the fuel efficiency of the fuel cell unit 12a is empirically determined based on the influence of the further parameters of the fuel cell device 10a on a cell voltage.

[0040] In at least one comparison step 24a, the fuel utilization rate of the fuel cell unit 12a is empirically estimated using a cell voltage gradient when a fuel utilization rate of the fuel cell device 10a changes. In the comparison step 24a, the influence of a variation in the fuel utilization rate of the fuel cell device 10a (FU_Sys) on the fuel utilization rate of the fuel cell unit 12a (FU_Stk) is empirically determined. In the comparison step 24a, an influence of different fuel utilization rates of the fuel cell device 10a on a cell voltage (u_cell) is determined. In the comparison step 24a, a fuel utilization rate of the fuel cell unit 12a is empirically estimated using a function of the cell voltage gradient of the fuel utilization rate of the fuel cell device 10a.In comparison step 24a, a diagram is created using the function of the gradient of the cell voltage as a function of the fuel utilization factor of the fuel cell device 10a. In comparison step 24a, the function shown in the diagram is empirically evaluated. In comparison step 24a, a fuel utilization factor of the fuel cell unit 12a is empirically determined using the slope of the function of the gradient of the cell voltage as a function of the fuel utilization factor of the fuel cell device 10a. In comparison step 24a, the fuel utilization factor of the fuel cell unit 12a is determined using the formula. calculated.

[0041] In at least one determination step 22a, the fuel utilization factor of the fuel cell device 10a and the current cell voltage are determined. In the determination step 22a, the fuel utilization factor of the fuel cell device 10a (FU_Sys_1) is determined via an energy balance at the fuel cell unit 12a. Alternatively and / or additionally, in the determination step 22a, the fuel utilization factor of the fuel cell device 10a is determined via the energy balance at the hotbox. Alternatively and / or additionally, in the determination step 22a, the fuel utilization factor of the fuel cell device 10a is determined via a measurement of the gas volume flow and the associated calorific value in a current operating state. Furthermore, any other determination of the fuel utilization factor of the fuel cell device 10a that appears appropriate to a person skilled in the art is conceivable.In determination step 22a, the current cell voltage (u_1) is measured. Furthermore, any other method of determining the current cell voltage that a person skilled in the art considers appropriate is conceivable.

[0042] In at least one adaptation step 30a, an active variation, in particular in at least two stages, of the fuel utilization factor of the fuel cell device 10a is carried out by changing the supplied natural gas volume flow. In the adaptation step 30a, a fuel utilization factor of the fuel cell device 10a is adjusted. In the adaptation step 30a, the fuel utilization factor of the fuel cell device 10a is adjusted by changing the supplied natural gas volume flow. In the adaptation step 30a, an active variation of the fuel utilization factor of the fuel cell device 10a is carried out. In the adaptation step 30a, an active variation of the fuel utilization factor of the fuel cell device 10a is carried out in at least two stages. Furthermore, any other number of stages of the active variation of the fuel utilization factor of the fuel cell device 10a that appears reasonable to a person skilled in the art is conceivable.In the adaptation step 30a, a supplied natural gas volume flow to the fuel cell device 10a is regulated by means of the control and regulation unit 16a. In particular, it is conceivable that the fuel cell device 10a has a further blower unit via which the supplied natural gas volume flow to the fuel cell device 10a is regulated. In particular, it is conceivable that in the adaptation step 30a, the control and regulation unit 16a regulates a supplied natural gas volume flow to the fuel cell device 10a via the further blower unit. In the adaptation step 30a, a supplied natural gas volume flow is increased by means of the control and regulation unit 16a. Alternatively, it is conceivable that in the adaptation step 30a, a supplied natural gas volume flow is reduced by means of the control and regulation unit 16a.In the adaptation step 30a, a fuel utilization factor of the fuel cell device 10a is reduced by increasing the supplied natural gas volume flow.

[0043] In at least one adjustment step 30a, a fuel utilization factor of the fuel cell unit 12a is kept constant by means of the blower unit 14a, in particular by adjusting the recirculation volume flow of the recirculation circuit 20a. In the adjustment step 30a, a blower unit 14a is automatically regulated via the control and regulating unit 16a. In the adjustment step 30a, a recirculation volume flow of the recirculation circuit 20a is regulated via the blower unit 14a. In the adjustment step 30a, a recirculation volume flow of the recirculation circuit 20a is regulated via the speed of the blower unit 14a. In the adaptation step 30a, the speed of the blower unit 14a is regulated via the control and regulation unit 16a depending on a measured value determined in the fuel cell unit 12a in order to keep the fuel utilization rate of the fuel cell unit 12a constant.In adjustment step 30a, the fuel efficiency of the fuel cell unit 12a is kept constant by means of the recirculation volume flow, simultaneously with the adjustment of the fuel efficiency of the fuel cell device 10a. In adjustment step 30a, a recirculation flow is increased when the fuel efficiency of the fuel cell device 10a is reduced. Alternatively, in adjustment step 30a, a recirculation flow is reduced when the fuel efficiency of the fuel cell device 10a is increased.

[0044] In at least one further determination step 32a, the fuel utilization factor of the fuel cell device 10a and the current cell voltage are determined after an adaptation step 30a. The further determination step 32a is carried out after an adaptation step 30a. The further determination step 32a is carried out identically to the determination step 30a. In the further determination step 30a, the fuel utilization factor of the fuel cell device 10a (FU_Sys_2) is determined via an energy balance at the fuel cell unit 12a. Alternatively and / or additionally, in the further determination step 32a, the fuel utilization factor of the fuel cell device 10a is determined via the energy balance at the hotbox.Alternatively and / or additionally, in the further determination step 32a, the fuel utilization factor of the fuel cell device 10a is determined by measuring the gas volume flow and the associated calorific value in a current operating state. Furthermore, any other determination of the fuel utilization factor of the fuel cell device 10a that appears reasonable to a person skilled in the art is conceivable. In the further determination step 30a, the current cell voltage (u_2) is measured after an adjustment step 30a. Furthermore, any other determination of the current cell voltage that appears reasonable to a person skilled in the art is conceivable.

[0045] In at least one calculation step 34a, the cell voltage gradient is calculated based on the values ​​determined in the determination step 22a and the further determination step 32a. In the calculation step 34a, the cell voltage gradient is calculated based on the fuel utilization factors of the user device 10a (FU_Sys_1, FU_Sys_2) and the associated cell voltages (u_1, u_2) determined in the determination step 22a and the further determination step 32a. In the calculation step 34a, the cell voltage gradient is calculated using the formula dUceii (Ui ~ U2) calculated. A calculation step 34a is performed in operating step 18a. The calculation step 34a is performed after the determination step 22a, the adaptation step 30a, and the further determination step 32a in operating step 18a.

[0046] In at least one operating step 18a, the fuel cell device 10a has a battery element 42a, which compensates for energy fluctuations by buffering. In the calculation step 34a, the battery element 42a compensates for energy fluctuations that occur during the adjustment step 30a. In the calculation step 34a, the battery element 42a stores energy fluctuations that arise from the increase in the supplied natural gas volume flow. In addition, it is conceivable for the fuel cell device 10a to be used in a cluster operating strategy and for another fuel cell device 10a to take over the buffering at least substantially partially, preferably at least a large part, and particularly preferably completely. In the calculation step 34a, a constant total electrical energy is provided by means of the cluster operating strategy.

[0047] Figures 3 and 4 show two further embodiments of the invention. The following descriptions and the drawings are essentially limited to the differences between the embodiments, whereby with regard to components with the same designation, in particular with regard to components with the same reference numerals, reference can in principle also be made to the drawings and / or the description of the other embodiments, in particular Figures 1 to 2. To distinguish the embodiments, the letter a is placed after the reference numerals of the embodiment in Figures 1 to 2. In the embodiments in Figures 3 and 4, the letter a is replaced by the letters b and c.

[0048] Fig. 3 shows a schematic flow diagram of an embodiment of a method for operating a fuel cell device 10b according to the invention. In an operating step 18b, an adaptation step 30b is carried out. In at least one adaptation step 36b, the settings of adaptation step 30b are revoked, and subsequently the fuel utilization factor of the fuel cell device 10b and the current cell voltage are determined. In adaptation step 36b, the natural gas volume flow and the recirculation flow are reset to an initial state. In adaptation step 36b, the fuel utilization factor of the fuel cell device 10b and the current cell voltage are determined. In adaptation step 36b, the fuel utilization factor of the fuel cell device 10b is determined via an energy balance on a fuel unit 12b.Alternatively and / or additionally, in adaptation step 36b, the fuel utilization factor of the fuel cell device 10b is determined via the energy balance at the hotbox. Alternatively and / or additionally, in adaptation step 36b, the fuel utilization factor of the fuel cell device 10b is determined via a measurement of the gas volume flow and the associated calorific value in a current operating state. Furthermore, any other determination of the fuel utilization factor of the fuel cell device 10b that appears reasonable to a person skilled in the art is conceivable. In adaptation step 36b, the current cell voltage is measured. Furthermore, any other determination of the current cell voltage that appears reasonable to a person skilled in the art is conceivable.

[0049] In at least one control step 38b, the values ​​determined in an adaptation step 36b are correlated with the values ​​determined in a determination step 22b in order to check the influence of the adaptation step 30b on the fuel utilization factor of the fuel cell device 10b and the current cell voltage. In the control step 38b, the values ​​determined in an adaptation step 36b are compared with the values ​​determined in a determination step 22b and evaluated. In the control step 38b, a result of the evaluation of the comparison of the fuel utilization factor of the fuel cell device 10b and the cell voltage in a determination step 22b and an adaptation step 36b is determined for the control and regulation unit 16b.In control step 38b, an adaptation step 22b and a further determination step 32b are restarted if the fuel utilization rate of the fuel cell device 10b and the cell voltage in an adaptation step 26b differ from the fuel utilization rate of the fuel cell device 10b and the cell voltage in a determination step 22b. In control step 38b, the fuel cell device 10b is regulated based on the empirically determined fuel utilization rate of the fuel cell unit 12b if the fuel utilization rate of the fuel cell device 10b and the cell voltage in an adaptation step 36b are identical to the fuel utilization rate of the fuel cell device 10b and the cell voltage in a determination step 22b.

[0050] In at least one comparison step 24b, the fuel utilization factor of the fuel cell unit 12b is empirically estimated based on a change in a natural gas volume flow of the fuel cell device 10b and / or a recirculation volume flow of the recirculation circuit 20b. In the comparison step 24b, the influence of a variation in a natural gas volume flow of the fuel cell device 10b and / or a recirculation volume flow of the recirculation circuit 20b of the fuel cell device 10b on the fuel utilization factor of the fuel cell unit 12b is empirically determined. In the comparison step 24b, the influence of different natural gas volume flows of the fuel cell device 10b and / or a recirculation volume flow of the recirculation circuit 20b on a cell voltage is determined.In comparison step 24b, the fuel efficiency of fuel cell device 10b is estimated using a function of the cell voltage gradient. In particular, it is conceivable that measured and / or calculated variables, such as a temperature value or the calorific value of the natural gas used, are included in the correlation in comparison step 24b. In comparison step 24b, an empirical correlation is derived from measurement and / or simulation campaigns and stored on control unit 16b using characteristic curves, characteristic maps, polynomial approaches, or other data-based models.

[0051] Fig. 4 shows a schematic flow diagram of an embodiment of a method for operating a fuel cell device 10c according to the invention. In at least one evaluation step 40c, the fuel utilization factor of a fuel cell unit 12c is determined by detecting the time of a gradient change. In the evaluation step 40c, the fuel utilization factor of the fuel cell unit 12c is determined using the function of the time of a gradient change. In the evaluation step 40c, a fuel utilization factor of the fuel cell unit 12c is detected when the function bends horizontally. In the evaluation step 40c, an operating step 18c is cyclically evaluated by means of an evaluation step 40c in order to determine the fuel utilization factor of the fuel cell unit 12c.In evaluation step 40c, the time of a gradient change at a high fuel utilization rate of the fuel cell device 10c is detected. In evaluation step 40c, a gradient change occurs only at a high fuel utilization rate of the fuel cell device 10c.

[0052] In at least one monitoring step 44c, an exceedance of the permissible fuel utilization rate of the fuel cell unit 12c is detected by recognizing the time of a gradient change. In the monitoring step 44c, a cyclical execution of the operating step 18c is monitored. In the monitoring step 44c, a message is transmitted to a control and regulation unit 16c as soon as the fuel utilization rate of the fuel cell unit 12c exceeds and / or reaches a maximum fuel utilization rate of the fuel cell unit 12c. In the operating step 18c, a fuel utilization rate of the fuel cell unit 12c is regulated based on the message transmitted in a monitoring step 44c.

Claims

Claims 1 . Method for determining a fuel utilization factor of a fuel cell unit (12a; 12b; 12c) in a fuel cell device (10a; 10b; 10c), in particular an SOFC fuel cell device, which has at least one fuel cell unit (12a; 12b; 12c), in particular a fuel cell stack, at least one blower unit (14a; 14b; 14c), and at least one control and regulating unit (16a; 16b; 16c), with an operating step (18a; 18b; 18c) in which the fuel cell unit (12a; 12b; 12c) obtains electrical energy from a gaseous medium, wherein the blower unit (14a; 14b; 14c) in the operating step (18a; 18b; 18c) has a recirculation circuit (20a; 20b; 20c) and wherein an operation of the fuel cell device (10a; 10b; 10c) is regulated by means of the control and regulating unit (16a; 16b; 16c) in the operating step (18a; 18b; 18c), characterized in that in at least one comparison step (24a; 24b;24c) a fuel utilization factor of the fuel cell unit (12a; 12b; 12c) is estimated by means of an empirical estimate; 2. Method according to claim 1, characterized in that in at least one comparison step (24a) the fuel utilization factor of the fuel cell unit (12a) is empirically estimated via a gradient of the cell voltage in the event of a change in a fuel utilization factor of the fuel cell device (10a).

3. Method according to claim 1 or 2, characterized in that in at least one determination step (22a) the fuel utilization rate of the fuel cell device (10a) and the current cell voltage are determined.

4. Method according to one of the preceding claims, characterized in that in at least one adaptation step (30a) an active variation, in particular in at least two stages, of the fuel utilization factor of the fuel cell device (10a) is carried out by means of a change in the supplied natural gas volume flow.

5. Method according to one of the preceding claims, characterized in that in at least one adaptation step (30a) by means of the blower unit (14a), in particular by adjusting the recirculation volume flow of the recirculation circuit (20a), a fuel utilization factor of the fuel cell unit (12a) is kept constant.

6. Method according to one of the preceding claims, characterized in that in at least one further determination step (32a) the fuel utilization rate of the fuel cell device (10a) and the current cell voltage are determined after an adaptation step (30a).

7. Method according to one of the preceding claims, characterized in that in at least one calculation step (34a) the cell voltage gradient is calculated on the basis of the values determined in the determination step (22a) and the further determination step (32a).

8. Method according to one of the preceding claims, characterized in that in at least one adaptation step (36b) the settings of the adaptation step (30b) are revoked and then the fuel utilization factor of the fuel cell device (10b) and the current cell voltage are determined.

9. Method according to one of the preceding claims, characterized in that in at least one control step (38b) the values determined in an adaptation step (36b) are correlated with the values determined in a determination step (22b) in order to check the influence of the adaptation step (30b) on the fuel utilization factor of the fuel cell device (10b) and the current cell voltage.

10. The method according to claim 1, characterized in that in at least one comparison step (24b) the fuel utilization factor of the fuel cell unit (12b) is empirically estimated via a change in a natural gas volume flow of the fuel cell device (10b) and / or a recirculation volume flow of the recirculation circuit (20b).

11. Method according to one of the preceding claims, characterized in that in at least one operating step (18a) the fuel cell device (10a) has a battery element (42a) which compensates for energy fluctuations by buffering.

12. The method according to claim 1, characterized in that in at least one evaluation step (40c) the fuel utilization rate of the fuel cell unit (12c) is determined by detecting the time of a gradient change.

13. Method according to claim 12, characterized in that in at least one monitoring step (44c) the detection of the At the time of a gradient change, an exceedance of the permissible fuel utilization rate of the fuel cell unit (12c) is detected.

14. Fuel cell device (10a; 10b; 10c), in particular SOFC fuel cell device, for carrying out a method according to one of the preceding claims.

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