DE102021203562A1 - Electrochemical device and a method for operating such an electrochemical device - Google Patents

Abstract

An electrochemical device (10), in particular a fuel cell device, is proposed, which has a monitoring unit (12) which, for analyzing at least one state of an electrochemical unit (14), in particular a fuel cell unit, at least one input signal of the electrochemical unit (14) and at least measures an output signal of the electrochemical unit (14).

Description

State of the art

A diagnostic device for analyzing a state of a fuel cell has already been proposed, wherein a Nernst voltage of the fuel cell can be modulated based on a cell voltage of the fuel cell and a plurality of loss terms, such as ohmic losses and/or activation losses, with respect to the fuel cell.

Disclosure of Invention

An electrochemical device, in particular a fuel cell device, with a monitoring unit is proposed, which measures at least one input signal of the electrochemical unit and at least one output signal of the electrochemical unit to analyze at least one state, in particular a degradation state, of an electrochemical unit, in particular a fuel cell unit.

The configuration of the electrochemical device according to the invention advantageously makes it possible to determine and/or predict a state, in particular a degradation state, of an electrochemical unit with simplified technical means. In contrast to conventional devices, for example electrochemical impedance spectroscopy, which require complex, additional measuring devices to determine the condition, and/or complex and/or inaccurate calculation methods, possibly a Nernst voltage calculation of the electrochemical unit using loss terms of the electrochemical unit, due to the proposed electrochemical Device advantageously the state easily and efficiently, namely analyzed during operation of the electrochemical unit, preferably the Nernst voltage can be easily calculated during operation. This offers the advantageous possibility of monitoring the state of the electrochemical unit during operation at least periodically, in particular permanently, as a result of which critical states, preferably the state of degradation, can be recognized promptly and any countermeasures can be initiated at an early stage. A potential service life of the electrochemical unit can thus advantageously be lengthened. In addition, a particularly efficient, in particular cost-effective, electrochemical device for analyzing the state, in particular during operation, can be provided.

The electrochemical device could be part of an electrochemical system or encompass the entire electrochemical system, where the electrochemical system could be designed as a fuel cell system. Such a system is characterized in particular by boundary conditions which enable operation in at least one operating state, in particular with an optimal operating time, for the electrochemical device and/or electrochemical unit. In the present case, the electrochemical device is provided for the analysis and/or diagnosis of at least the, in particular current and/or future, state of the electrochemical unit, which is preferably designed as a fuel cell unit. The electrochemical system and/or the electrochemical device could have the electrochemical unit, which is provided in particular for converting at least one starting material into at least one product, preferably for converting a fuel. In particular, the electrochemical system handles at least the fuel, preferably an oxygen-containing fluid and/or an exhaust gas as the process fluid. The fuel preferably has hydrogen and/or carbon monoxide and/or at least one hydrocarbon, in particular methane, ethane, butane, propane, natural gas or the like, as an energy source. The fuel could optionally include inert components, in particular nitrogen and/or carbon dioxide and/or water. Pure oxygen or an oxygen mixture, in particular air, could be used as the oxygen-containing fluid. The exhaust gas is in particular a reaction product from the fuel and the oxygen-containing fluid. The electrochemical unit is preferably provided for converting the fuel and the oxygen-containing fluid into the exhaust gas.

The electrochemical unit, in particular the fuel cell unit, preferably has at least one electrochemical cell, specifically preferably a fuel cell, a stack of fuel cells and/or a composite of a plurality of stacks of fuel cells and/or a system of fuel cells. Without being limited to this, the fuel cell and/or the fuel cells of the fuel cell unit could/can preferably be used as a high-temperature fuel cell, in particular as a solid oxide fuel cell (SOFC), and/or as a molten carbonate fuel cell (MCFC) and/or proton exchange membrane fuel cell (PEMFC), and /or as a phosphoric acid fuel cell (PAFC) and/or as a direct methanol fuel cell (DMFC) and/or as an alkaline fuel cell (AFC) and/or as a fuel cell of another type. At least the fuel cell could at least at least have an oxygen electrode and/or a fuel electrode and/or an electrolyte.

Alternatively and/or additionally, the electrochemical device could be provided for analyzing and/or diagnosing at least the current and/or future state of the electrochemical unit, which is designed as an electrochemical unit that is different from a fuel cell unit and has at least one electrochemical cell. The electrochemical unit could, for example, have an electrolyzer or at least a component part of an electrolyzer, which comprises at least the electrochemical cell designed as an electrolytic cell. The electrolyzer could be used to convert at least the starting material into at least the product using electric current, for example for chlor-alkali electrolysis or for electrolytic refining of copper or other precious metals or for fused-salt electrolysis or for solid oxide electrolysis or for another electrolysis process, be provided.

It would also be conceivable for the electrochemical unit to be designed alternatively as an internal combustion engine, as a heating boiler, as a burner or as another unit which a person skilled in the art considers appropriate and which converts a fuel into exhaust gas while supplying oxygen. The electrochemical system and/or the electrochemical device advantageously has a peripheral device device. The peripheral device device could comprise all elements and units which are required for operation of the electrochemical unit and/or support operation of the electrochemical unit in at least the operating state. For example, the peripheral device device could have a supply of oxygen-containing fluid, in particular a fresh air supply, a fuel supply, a reformer unit and/or a recirculation line. In addition, the peripheral device device could, for example, have conveying elements for conveying the fuel, an oxidant and/or an exhaust gas, further reformer units and/or heat exchangers and the like.

The monitoring unit is provided for measuring the input and/or output signal of the electrochemical unit with sufficient accuracy for analyzing the condition. The monitoring unit preferably measures the input and/or output signal with a resolution of at least 8 bits, advantageously at least 12 bits, preferably at least 16 bits and particularly preferably with a resolution greater than 16 bits. The input and/or output signal of the electrochemical unit is preferably a physical and/or chemical signal that can be measured by the monitoring unit. The input and/or output signal is/are in particular at least one signal of a process fluid to be examined. Preferably, the input signal is an eductor signal, in particular a fuel signal, and the output signal is a product signal, in particular an exhaust signal, wherein the input and/or output signal could characterize the process fluid. The signal could be, but is not limited to, an electrical input and/or output current and/or preferably an electrical input and/or output voltage and/or an entropy and/or an enthalpy and/or a Act temperature and / or a pressure and / or a concentration and / or a particle and / or volume flow of one or more reactants and / or products of the electrochemical unit.

As used in this document, “designed” means specifically programmed, configured, designed and/or equipped. The fact that an object is provided for a specific function should be understood to mean that the object fulfills and/or executes this specific function in at least one application and/or operating state.

It is also proposed that the monitoring unit measures the input signal on an inlet side of the electrochemical unit on the combustion gas side. As a result, efficiency with regard to an analysis of a state of an electrochemical unit can be increased. The inlet side on the fuel gas side preferably defines a side of the electrochemical unit on which, starting from the fuel supply, the reactant, in particular the fuel, can be fed to the electrochemical unit via an inlet line of the electrochemical device and/or the electrochemical system, in particular the peripheral device device. The input line could be a cathode input line and/or preferably an anode input line.

If the monitoring unit measures the output signal on an outlet side of the electrochemical unit on the fuel gas side, a more efficient, in particular improved, measurement and/or analysis of a state of an electrochemical unit can be provided. The outlet side on the combustion gas side preferably defines a side of the electrochemical unit on which reacted fuel, in particular the exhaust gas, can be discharged from the electrochemical unit via an outlet line of the electrochemical device and/or the electrochemical system, in particular the peripheral device device is. The monitoring unit advantageously measures the output signal before the output line branches off to the recirculation line. The exit line could be a cathode exhaust line and/or preferably an anode exhaust line.

Advantageously, the input and/or output signal, measured on the fuel gas-side entry side and/or the fuel gas-side exit side, is/are of a gas composition on the fuel-gas-side entry side and/or the fuel-gas-side exit side, in particular of the educt, preferably the fuel, and/or or the product, preferably the exhaust gas. It would be conceivable that the input signal and/or the output signal is, for example, at least one fluid parameter of the process fluid and/or at least one electrical input and/or output power of the electrochemical unit. In order to provide an advantageously simple signal measurement and a reliable analysis of a state, in particular a degradation state, of an electrochemical unit, preferably during at least one operating state of the electrochemical unit, it is proposed that the input signal at an input, in particular the inlet side on the fuel gas side, of the electrical input voltage measured electrochemical unit. The input voltage measured at the input is in particular an input Nernst voltage, preferably an anode input Nernst voltage U _Nernst,An,in .

In addition, it is proposed that the output signal is an electrical output voltage measured at an output of the electrochemical unit, in particular the outlet side on the combustion gas side. Thus, a signal measurement can be simplified to the maximum and made more efficient. Furthermore, an analysis of a state of an electrochemical unit can be further improved. In addition, a Nernst voltage of the electrochemical unit can advantageously be calculated by measuring an electrical output voltage measured at an output of the electrochemical unit and possibly an electrical input voltage measured at an input of the electrochemical unit. The output voltage measured at the output is in particular an output Nernst voltage, preferably an anode output Nernst voltage U _{Nernst,on,off} ,. The input and/or output voltage, preferably the anode input Nernst voltage and/or the anode output Nernst voltage, could/could be dependent on the gas composition, in particular on the fuel-gas-side entry side and the fuel-gas-side exit side . It would be conceivable for the measured input and/or output voltage to describe and/or characterize a chemical composition of the process fluid being examined, in particular the fuel and/or the exhaust gas.

The monitoring unit could have at least one sensor for measuring the input and/or output signal and/or the fluid parameter of at least the process fluid to be examined. It would be conceivable for the sensor to be a magnetic and/or electrical and/or optical sensor, for example. With regard to determining the gas composition by means of the input and/or output signal, the monitoring unit could, for example, have a gas sensor and/or a sensor for measuring partial pressures within the process fluid, in particular the fuel and/or the exhaust gas, and/or a sensor for gas chromatography and/or or IR spectroscopy and/or a mass spectrometer.

So that an advantageously efficient and/or convenient analysis of a state of an electrochemical unit can be made possible, it is proposed that the monitoring unit have at least one electrode-based sensor. In particular, the electrode-based sensor has at least one electrode. The electrode could be in direct contact with the process fluid to be examined, in particular the fuel and/or the exhaust gas. At least the electrode-based sensor could be arranged in the input and/or the output line, for example. In addition, the electrode-based sensor and/or another electrode-based sensor could be arranged in the recirculation line. The electrode-based sensor could include the entire electrode-based sensor and/or components of the electrochemical sensor, for example an amperometric electrochemical gas sensor, which has at least one electrochemical sensor cell. The electrode-based sensor is intended to measure at least the input and/or the output signal. The electrode-based sensor preferably detects the input and/or output voltage. The input and/or output voltage is preferably an electrical voltage which can be measured by means of the electrochemical sensor cell and in particular drops at the electrochemical sensor cell during at least quasi-stationary, preferably stationary, operation of the electrochemical unit in at least the operating state.

In particular, the electrode-based sensor is provided as a degradation sensor for measuring degradation of the electrochemical unit hen. The electrode-based sensor is preferably adapted to the present electrochemical unit, in particular a type and/or configuration of the fuel cell, in particular with regard to a material composition. If the electrode-based sensor is designed as a jump lambda probe, an analysis of a state, in particular a degradation state, of an electrochemical unit can be simplified and monitoring of the electrochemical unit, preferably in at least one operating state of the electrochemical unit, can be improved. In addition, a Nernst voltage of the electrochemical unit can be measured using the jump lambda probe and a gas composition of a process fluid to be examined, in particular the fuel and/or the exhaust gas, can be inferred preferably using the Nernst voltage.

The jump lambda probe could measure an oxygen excess and/or oxygen deficiency in relation to the stoichiometric composition in the process fluid to be examined, in particular the fuel gas and/or the exhaust gas. Alternatively, the jump lambda probe could also be a two-point lambda probe. In particular, the jump lambda probe has the electrochemical sensor cell. Alternatively and/or additionally, the electrochemical sensor, in particular instead of the jump lambda probe, could have a currentless single fuel cell, in particular SOFC cell, in which case an open terminal voltage of that cell would correspond to the Nernst voltage.

In a further embodiment of the invention it is proposed that the electrochemical device has a computing unit which analyzes the state, in particular the degradation state, using at least the input and output signals and determines at least one degradation parameter of the electrochemical unit. As a result, in an operating state of an electrochemical unit, a Nernst voltage of the electrochemical unit can be determined and a degradation parameter, which describes a degradation of the electrochemical unit, can be calculated. Furthermore, an analysis of a state, in particular a degradation state, of the electrochemical unit can be made more efficient, advantageously simplified. In addition, a prediction can be made about a potential service life of the electrochemical unit.

The arithmetic unit could apply at least one algorithm to the input and/or output signal. In this context, an “algorithm” should be understood to mean at least one computing rule that the computing unit uses to analyze the state of the measured input and/or output signal. The algorithm could be self-learning and in particular include at least one result of a previous analysis of a previous state of the electrochemical unit in an analysis of a current and/or future state. The phrase that the processing unit “analyzes” the state is to be understood as meaning that the processing unit determines and/or predicts the state, preferably the degradation state. The state which the computing unit determines and/or predicts is preferably based on at least one current and/or future operating parameter of the electrochemical unit, for example the current and/or future electrical input and/or output voltage and/or a cell voltage of the electrochemical unit and /or a cell current of the electrochemical unit and/or a conversion rate of at least the starting material and/or the like. The state which the computing unit determines and/or predicts is possibly characterized by all current and/or future operating parameters of the electrochemical unit, individual operating parameters of the electrochemical unit being able to be weighted differently in the analysis by the computing unit. A result of the state analyzed by the computing unit could be output purely quantitatively, for example in the form of a current and/or future operating parameter of the electrochemical unit. The result of the state analyzed by the computing unit preferably includes, in addition to a quantitative indication of at least the operating parameter, also a qualitative assessment of the current and/or future state and an indication of potential causes for a current or expected change in state, in particular a degradation profile of the electrochemical unit.

The computing unit preferably evaluates at least one signal measured by the monitoring unit, in particular at least the input signal and at least the output signal. In particular, the computing unit evaluates the input and/or the output voltage. The computing unit could, for example, record a mean value, an asymptotic limit value, a position and/or a value of maxima and/or turning points, a position of a zero crossing, a transient response when a setting of the electrochemical unit changes, in particular a transient frequency, a transient amplitude and/or calculate and/or evaluate a transient period, a time delay compared to a change in the setting or the like. It would be conceivable that the rake unit calculates loss terms of the electrochemical unit, such as ohmic losses and/or activation losses and/or diffusion losses. In particular, the computing unit is provided to calculate at least one electrical variable. The computing unit preferably calculates a Nernst voltage of the electrochemical unit, in particular of the fuel cell. The arithmetic unit could calculate at least one arithmetic mean value from the input voltage, in particular from U _Nernst,on,in , and the output voltage, in particular from U _{Nernst,on,off} , particularly preferably thereby determining the Nernst voltage U _Nernst,cell . In particular, the computing unit calculates the Nernst voltage during the operating state of the electrochemical unit.

The degradation parameter is advantageously a parameter that describes the degradation state of the electrochemical unit, in particular the fuel cell. Degradation and/or degradation mechanisms within the electrochemical unit describe/describe in particular an at least essentially occurring aging of the electrochemical unit, in particular of electrodes and/or cell components of the electrochemical unit, for example due to diffusion processes and/or microstructural changes. Microscopically relevant mechanisms within the electrochemical unit, for example transport and/or accumulation of charge carriers and/or formation of oxide layers and/or deposition of solids, for example carbon, can preferably be characterized by physical and/or chemical parameters of the electrochemical unit. which can be determined in particular by means of the monitoring unit. Without being limited to this, the degradation mechanisms could, for example, poisoning of the electrodes of the electrochemical unit, which can be caused, for example, by components from educts with which the electrochemical unit is operated, and/or an operating temperature that is too high or too low, and /or an operating pressure that is too high or too low, and/or an unsuitable ratio of the starting materials or components of the starting materials to one another, for example an unsuitable ratio of water vapor to carbon or of oxygen to carbon, and/or various adsorption and/or absorption processes, such as such as agglomeration of catalyst materials and/or blockage of membranes and/or pores, wear of components such as seals of the electrochemical unit and/or the like.

wobei j_Zelle vorteilhaft eine Stromdichte der elektrochemischen Einheit, insbesondere der Brennstoffzelle und/oder des Stacks, beschreibt. Die Stromdichte j_Zelle könnte an der elektrochemischen Einheit messbar sein, möglicherweise mittels der elektrochemischen Vorrichtung und/oder der Überwachungseinheit. Vorzugsweise ist/sind zumindest die Zellspannung U_Zelle und/oder der Zellstrom I_Zelle und/oder eine Zelltemperatur T_Zelle der elektrochemischen Einheit in zumindest dem Betriebszustand bekannt, insbesondere derart, dass die Recheneinheit zur Analyse des Zustands und bei Ermittlung des Degradationsparameters auf die Werte der Zellspannung und/oder des Zellstroms und/oder der Zelltemperatur zugreifen könnte. Insbesondere ist der ASR-Wert ein flächenspezifischer Widerstand, welcher temperatur- und druckabhängig ist. In Abhängigkeit von der Zeit könnte mittels einer Veränderung des ASR-Werts die Degradation der elektrochemischen Einheit vorteilhaft zeitlich beschrieben werden. Beispielsweise könnte die Recheneinheit den Zustand anhand eines aktuellen Betriebsparameters, beispielsweise der gemessenen Eingangs- und/oder Ausgangsspannung und/oder der Nernst-Spannung, und/oder des ermittelten Degradationsparameters, insbesondere des ASR-Werts, angeben und zusätzlich mit einer qualitativen Angabe, beispielsweise „vorzeitige Alterung durch potentielle Vergiftung“ oder „kritische Kohlenstoffablagerung“ oder dergleichen, versehen.Based on the input and/or output signal, the computing unit could examine known degradation mechanisms of the electrochemical unit and derive the state of the electrochemical unit therefrom. The computing unit preferably uses the Nernst voltage U _Nernst,cell to determine the degradation parameter, in particular the ASR value, preferably according to the formula $${\text{u}}_{\text{cell}}={\text{u}}_{\text{Nernst}\text{,Cell}}-{\text{j}}_{\text{cell}}\times \text{ASR}\text{,}$$

where j _cell advantageously describes a current density of the electrochemical unit, in particular the fuel cell and/or the stack. The current density j _cell could be measurable at the electrochemical unit, possibly by means of the electrochemical device and/or the monitoring unit. Preferably, at least the cell voltage U _cell and/or the cell current I _cell and/or a cell temperature T _cell of the electrochemical unit is/are known at least in the operating state, in particular in such a way that the computing unit analyzes the state and when determining the degradation parameter on the values the cell voltage and/or the cell current and/or the cell temperature. In particular, the ASR value is an area-specific resistance that depends on temperature and pressure. The degradation of the electrochemical unit could advantageously be described in terms of time as a function of time by means of a change in the ASR value. For example, the computing unit could indicate the status based on a current operating parameter, for example the measured input and/or output voltage and/or the Nernst voltage, and/or the determined degradation parameter, in particular the ASR value, and additionally with a qualitative indication, for example "premature aging due to potential poisoning" or "critical carbon deposition" or the like.

Furthermore, it is proposed that the electrochemical device has a control unit which, in the event of a deviation of the analyzed state from a target state, initiates at least one measure in order to at least mitigate premature degradation of the electrochemical unit. As a result, the service life of an electrochemical unit can be lengthened. Furthermore, there can advantageously be a possibility for timely initiation of countermeasures in order to at least mitigate, preferably prevent, premature degradation of the electrochemical unit.

The target state preferably corresponds to a state of the electrochemical unit in which no mechanisms are active that lead to the premature degradation of the electrochemical unit. The control unit is preferably active mechanically connected to at least one unit and/or at least one element of the electrochemical unit. Measures which the control unit initiates in order to at least mitigate the premature degradation of the electrochemical unit could, for example, change an operating point of the electrochemical unit and/or change a volume flow and/or a composition of educts which are supplied to the electrochemical unit in the operating state , or other measures that appear sensible to those skilled in the art. The control unit preferably controls at least the fuel supply and/or a flow of the recirculation line. Alternatively, instead of recirculating the exhaust gas, in particular an anode exhaust gas, an external supply of steam to the electrochemical system for steam reforming could be provided. The control unit could control and/or regulate the external supply. It would be conceivable for the computing unit to be part of the control unit.

In addition, it is proposed that the control unit is provided for activating the electrochemical unit, with the control unit taking the degradation parameter into account during the activation. A particularly reliable and efficient control of an electrochemical unit can thereby be provided, wherein a service life of the electrochemical unit can advantageously be extended on the basis of an analyzed state of the electrochemical unit, in particular taking into account a degradation parameter. Furthermore, a value and/or a profile of the degradation parameter can advantageously be assigned to a specific physical and/or chemical parameter, in particular operating parameters, of the electrochemical unit, which advantageously allows targeted initiation of countermeasures to mitigate, preferably completely prevent, premature degradation the electrochemical unit can be made possible. The control unit particularly preferably controls at least the fuel supply and/or the flow of the recirculation line, taking the degradation parameter into account. Alternatively and/or additionally, the control unit could control and/or regulate the cell current and/or the cell voltage of the electrochemical unit.

The monitoring unit could, for example, measure the input and/or output signal once in the operating state of the electrochemical unit. However, it is preferably proposed that the monitoring unit monitors the input signal and/or the output signal in an operating state of the electrochemical unit, in particular in the operating state, at least periodically. This can advantageously enable a particularly precise and/or reliable analysis of a state of an electrochemical unit by means of a monitoring unit. In addition, a permanent analysis of the state can advantageously be made possible, as a result of which changes in the state of the electrochemical unit can be detected at an early stage and any countermeasures can be initiated in good time. In addition, the analysis of the state could possibly be further improved by means of a memory unit for storing an input and/or output signal; in particular, changes in the signal over time can advantageously be used to analyze the state. Furthermore, the measured input and/or output signal can/could be compared with stored values in the memory unit and the analysis of the state can thus be further optimized.

The monitoring unit could partially monitor the input signal and/or the output signal in the operating state of the electrochemical unit, for example at regular or irregular time intervals. The monitoring unit preferably continuously monitors the input signal and/or the output signal in the operating state. It would be conceivable for the electrochemical device and/or the monitoring unit to have a storage unit for storing at least the input signal and/or the output signal, in particular in the form of at least one time-dependent function. In this context, a “memory unit” should be understood to mean a unit of the electrochemical device and/or the monitoring unit, which is intended to store at least one piece of information, advantageously independently of a power supply, in particular permanently. In addition to storing at least the input signal and/or the output signal, the memory unit is preferably provided for storing further data, such as operating conditions of the electrochemical unit and/or operating parameters and/or analysis parameters and/or states of the electrochemical unit.

At least one degradation mechanism could be stored in the memory unit. The physical parameters, in particular operating parameters, which characterize the known degradation mechanisms are preferably stored in the memory unit in the form of a database. The control unit may access the operating parameters stored in the memory unit when the electrochemical unit is activated. It would also be conceivable for the storage unit to store at least the determined degradation parameter in the operating state. The algorithm used by the computing unit to analyze the condition and in particular to determine the degradation parameter could possibly be self-learning and advantageously include at least one result of a previous analysis of the previous condition in an analysis of the current and/or future condition, with in particular the previous state and/or information regarding the previous state could be stored in the memory unit. In addition, the computing unit and/or the control unit could be networked with at least further computing units and/or at least further control units of the electrochemical device and/or of further electrochemical devices.

It would be conceivable for the electrochemical device and/or the monitoring unit to have an output unit for outputting the analyzed state of the electrochemical unit. In the event that the monitoring unit has determined and/or predicted a state of the electrochemical unit that deviates from a target state, which indicates and/or predicts premature degradation of the electrochemical unit and/or the electrochemical system, a possible cause for the harmful state are displayed. The output unit can be provided for optical and/or acoustic output of the state of the electrochemical unit and can have a display, for example. The output unit could have a loudspeaker, for example, for the acoustic output of the state. In addition to outputting the state, the output unit is preferably also provided for outputting further data, for example analysis parameters and/or fluctuation functions and/or operating parameters and/or the like. It is also conceivable for the electrochemical device and/or the monitoring unit to have a data transmission unit, which can be used to transmit, in particular by cable and/or wirelessly, the determined status and/or other data, for example by means of a Bluetooth or WLAN signal, to at least an external unit, for example to a smartphone and/or to a tablet and/or to a laptop of the user and/or possibly to a central location for data collection or the like.

In addition, a method for operating an electrochemical device, in particular as described above, is proposed, wherein at least one input signal of the electrochemical unit and one output signal of the electrochemical unit are measured, in particular automatically, to analyze at least one state of an electrochemical unit. Such a method according to the invention can advantageously be used to make a determination and/or a prediction of a state, in particular a degradation state, of an electrochemical unit more efficient, in particular simpler. In contrast to conventional imprecise methods, in particular calculation methods, possibly a Nernst voltage calculation using loss terms of the electrochemical unit, the proposed method can advantageously analyze the state efficiently, specifically during operation of the electrochemical unit. This offers the advantageous possibility of monitoring the state of the electrochemical unit during operation at least periodically, in particular permanently, as a result of which critical states, preferably the state of degradation, can be recognized promptly and any countermeasures can be initiated at an early stage. A potential service life of the electrochemical unit can thus advantageously be lengthened.

The method could have several partial method steps. In particular, in a first method step of the method for analyzing the state of the electrochemical unit, referred to as a detection step, at least the input signal and at least the output signal are measured, in particular at least the input voltage and at least the output voltage, preferably by means of the monitoring unit. In the detection step, the electrode-based sensor could be in direct contact with the process fluid to be examined, in particular the fuel and/or exhaust gas. Along the course of the method over time, the detection step could be followed by a second partial method step, specifically an evaluation step of the method. In the evaluation step, in particular by means of the computing unit, the state is advantageously analyzed by means of at least the input signal and the output signal and at least the degradation parameter of the electrochemical unit is determined. A third sub-step of the method, which is referred to as a control and/or regulation step, could take place after the evaluation step with regard to the course over time. Preferably, in the control and/or regulation step, if the analyzed state deviates from the target state, at least one measure is initiated, advantageously by means of the control unit, in order to at least mitigate the premature degradation of the electrochemical unit. For example, in the open-loop and/or closed-loop control step, at least the fuel supply and/or the current of the recirculation line and/or the cell voltage and/or the cell current and/or the supply of the oxygen-containing fluid, preferably taking into account the degra dation parameters, regulated and / or controlled.

The electrochemical device and the method according to the invention should not be limited to the application and embodiment described above. In particular, the electrochemical device can have a number of individual elements, components and units as well as method steps that differs from the number of individual elements, components and units as well as method steps specified here in order to fulfill a functionality described herein.

character list

Further advantages result from the following description of the drawings. In the drawing an embodiment of the invention is shown. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into further meaningful combinations.

• 1 eine als Brennstoffzellenvorrichtung ausgebildete elektrochemische Vorrichtung mit einer Überwachungseinheit und
• 2 ein schematisches Flussdiagramm eines Verfahrens zum Betrieb der elektrochemischen Vorrichtung.

Show it:

• 1 an electrochemical device designed as a fuel cell device with a monitoring unit and
• 2 a schematic flow diagram of a method for operating the electrochemical device.

Description of the embodiment

1 1 shows an electrochemical system 40. The electrochemical system 40 is embodied as a fuel cell system, for example, and has an electrochemical device 10 embodied as a fuel cell device. In the present case, the electrochemical system 40 has an electrochemical unit 14 which is provided for converting at least one reactant into at least one product, in the present case for converting a fuel. Alternatively, the electrochemical unit 14 could also be part of the electrochemical device 10 . Here, the electrochemical unit 14 is represented functionally as a single fuel cell. The electrochemical unit 14 preferably comprises a multiplicity of fuel cells which, for example, could be arranged grouped in one or more fuel cell stacks. At least the fuel cell could have at least one oxygen electrode and/or one fuel electrode and/or one electrolyte (not shown).

Furthermore, the electrochemical system 40 has a peripheral device 38 . The peripheral device device 38 includes all elements and units which are required for operation of the electrochemical unit 14 , specifically the fuel cell in the present case, and/or support operation of the electrochemical unit 14 . In the present simplified representation, the peripheral device 38 has a supply of oxygen-containing fluid 28 , a fuel supply 30 , a reformer unit 32 and a recirculation line 42 . In addition, the peripheral device device 38 could, for example, have conveying elements for conveying a fuel, an oxidant and/or an exhaust gas, further reformer units and/or heat exchangers and the like. 1 12 shows that the reformer unit 32 is positioned between the fuel supply 30 and the electrochemical unit 14. FIG. In the present case, the electrochemical system 40 has an afterburner unit 44 downstream of the electrochemical unit 14 , the electrochemical system 40 having a cathode exhaust gas line 46 and an anode exhaust gas line 18 , 48 which connect the electrochemical unit 14 to the afterburner unit 44 . In turn, an exhaust gas line 50 of the electrochemical system 40 leads from the afterburner unit 44 . In this exemplary embodiment, the recirculation line 42 feeds back the anode exhaust gas line 18, 48 to an input line 16 of the electrochemical system 40 which is designed as a fuel input line and which supplies the electrochemical unit 14 with fuel.

The electrochemical device 10 has a monitoring unit 12 for analyzing at least one state of the electrochemical unit 14 . The monitoring unit 12 has at least one electrode-based sensor 24, 26. In this embodiment, the electrode-based sensor 24, 26 is designed as a jump lambda probe. As in 1 As can be seen, the electrode-based sensor 24 is arranged in the input line 16 . Furthermore, the electrode-based sensor 26 is arranged in an output line 18 of the electrochemical system 40 emanating from the electrochemical unit 14 .

In at least one operating state, the monitoring unit 12 measures at least one input signal of the electrochemical unit 14 and at least one output signal of the electrochemical unit 14, precisely by means of the electrode-based sensor 24, 26. Regarding 1 monitoring unit 12 measures the input signal by means of electrode-based sensor 24 on an inlet side 20 of electrochemical unit 14 on the combustion gas side. Monitoring unit 12 uses electrode-based sensor 26 to measure the output signal on an outlet side 22 of electrochemical unit 14 on the combustion gas side.

The electrode-based sensor 24, 26 is intended to generate an input and/or output signal dependent on a process fluid to be examined in the input line 16 and/or the output line 18. In the present case, the input signal is an electrical input voltage measured at an input of the electrochemical unit 14, specifically the inlet side 20 on the combustion gas side. Furthermore, the output signal is an electrical output voltage measured at an output of the electrochemical unit 14, specifically the outlet side 22 on the combustion gas side. The electrical input voltage and/or output voltage can be measured at the input and/or output by means of the electrode-based sensor 24, 26 designed as a jump lambda probe. In this exemplary embodiment, the input voltage is an anode input Nernst voltage U _Nernst,An,in . In the present case, the output voltage is an anode output Nernst voltage UNernst,on,off.

In order to make monitoring the state of electrochemical unit 14, preferably the state of degradation, more efficient and convenient, monitoring unit 12 monitors the input signal and/or the output signal in the operating state of electrochemical unit 14 at least periodically, preferably at regular time intervals and particularly preferably continuous. In the present case, the electrochemical device 10 includes a computing unit 34 which analyzes the state by means of at least the input signal and the output signal and determines at least one degradation parameter of the electrochemical unit 14 . The arithmetic unit 34 is provided to calculate at least one electrical variable. In the present case, the computing unit 34 calculates a Nernst voltage U _Nernst,cell of the electrochemical unit 14, present, at least from an arithmetic mean of the input voltage, namely U _Nernst,An,in , and the output voltage, namely U _{Nernst,An,aus} the fuel cell.

Furthermore, the electrochemical device 10 has a control unit 36 which, in the event of a deviation of the analyzed state from a target state, initiates at least one measure in order to at least mitigate premature degradation of the electrochemical unit 14 . In this case, the desired state is a state of the electrochemical unit 14 in which no mechanisms leading to the premature degradation of the electrochemical unit 14 are at work. Measures that control unit 36 initiates in order to at least mitigate the premature degradation of electrochemical unit 14 could include, for example, a change in an operating point of electrochemical unit 14 and/or a change in a volume flow and/or a composition of educts that are present in electrochemical unit 14 in be supplied to the operating state via the input line 16, or include other measures that appear sensible to those skilled in the art. In the present case, the control unit 36 controls at least the fuel supply 30 and/or the flow of the recirculation line 42, specifically taking into account the degradation parameter. In addition, the control unit 36 is provided for activating the electrochemical unit 14, the control unit 36 taking the degradation parameter into account during the activation. When controlling the electrochemical unit 14, the control unit 36 could, for example, control and/or regulate a current, in particular a cell current I _cell , and/or a voltage, in particular a cell voltage U _cell , of the electrochemical unit 14 in order to thereby reduce the degradation of the electrochemical unit 14 at least mitigate it. In addition, the control unit 36 could be provided for controlling the supply of the oxygen-containing fluid 28, with the control unit 36 taking the degradation parameter into account during the control (not shown).

In 2 a flowchart of a method for operating the electrochemical device 10 described above is shown schematically. The method comprises several partial method steps. In a first sub-step of the method, referred to as detection step 100, at least the input signal and at least the output signal are automatically measured by the monitoring unit 12 for analyzing the state of the electrochemical unit 14. Along the course of the method over time, the detection step 100 is followed by a second partial method step, specifically an evaluation step 110 of the method. In the evaluation step 110, the state is analyzed using at least the input signal and the output signal, in particular using the computing unit 34, and at least the degradation parameter of the electrochemical unit 14 is determined. A third sub-step of the method, which is referred to as control and/or regulation step 120, takes place after evaluation step 110 with regard to the time profile. In control and/or regulation step 120, preferably by means of control unit 36, in the event of a deviation of analyzed state initiates at least one measure from the desired state in order to at least mitigate the premature degradation of the electrochemical unit 14 . At least the fuel supply 30 and/or the flow of the recirculation line 42 and/or the supply of oxygen-containing fluid 28 and/or the cell voltage U _cell and/or the cell current I _cell , preferably taking into account the Degradation parameters, regulated and / or controlled.

Claims (13)

Electrochemical device (10), in particular fuel cell device, with a monitoring unit (12) which, for analyzing at least one state of an electrochemical unit (14), in particular a fuel cell unit, at least one input signal of the electrochemical unit (14) and at least one output signal of the electrochemical unit ( 14) measures. Electrochemical device (10) after claim 1 , characterized in that the monitoring unit (12) measures the input signal on an inlet side (20) of the electrochemical unit (14) on the combustion gas side. Electrochemical device (10) according to one of the preceding claims, characterized in that the monitoring unit (12) measures the output signal on an outlet side (22) of the electrochemical unit (14) on the combustion gas side. Electrochemical device (10) according to one of the preceding claims, characterized in that the input signal is an electrical input voltage measured at an input of the electrochemical unit (14). Electrochemical device (10) according to one of the preceding claims, characterized in that the output signal is an electrical output voltage measured at an output of the electrochemical unit (14). Electrochemical device (10) according to one of the preceding claims, characterized in that the monitoring unit (12) has at least one electrode-based sensor (24, 26). Electrochemical device (10) after claim 6 , characterized in that the electrode-based sensor (24, 26) is designed as a jump lambda probe. Electrochemical device (10) according to one of the preceding claims, characterized by a computing unit (34) which analyzes the state using at least the input and output signals and determines at least one degradation parameter of the electrochemical unit (14). Electrochemical device (10) according to one of the preceding claims, characterized by a control unit (36) which, if the analyzed state deviates from a target state, initiates at least one measure in order to at least mitigate premature degradation of the electrochemical unit (14). Electrochemical device (10) according to claims 8 and 9 , characterized in that the control unit (36) for controlling the electrochemical unit (14) is provided, wherein the control unit (36) takes into account the degradation parameter in the control. Electrochemical device (10) according to one of the preceding claims, characterized in that the monitoring unit (12) monitors the input signal and/or the output signal in an operating state of the electrochemical unit (14) at least periodically. Electrochemical system (40), in particular fuel cell system, with an electrochemical device (10) according to one of the preceding claims. Method for operating an electrochemical device (10), in particular according to one of Claims 1 until 11 , wherein at least one input signal of the electrochemical unit (14) and one output signal of the electrochemical unit (14) are measured to analyze at least one state of an electrochemical unit (14).

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