Method for operating an anode subsystem, and computer program product

Abstract

The invention relates to a method for operating an anode subsystem for supplying at least one fuel cell of a fuel cell system with an anode gas that is enriched with product water created due to operation and is recirculated by means of a fan, an excessively high water content in the anode gas adversely affecting the degree of efficiency and the service life of the fuel cell system. For the purpose of monitoring the concentration of water in the recirculate, according to the invention electrical power consumption by the fan during stationary operation is observed and the power consumption is evaluated in respect of high-frequency peaks, which are caused by interference in the local flow conditions because of water droplets and indicate that a saturation concentration has been reached. The invention also relates to a computer program product having a program code for executing method steps.

Description

[0001] Description

[0002] Title:

[0003] Method for operating an anode subsystem, computer program product

[0004] The present invention relates to a method for operating an anode subsystem having the features of the preamble of claim 1. Furthermore, the invention relates to a computer program product for executing steps of the method.

[0005] State of the art

[0006] A PEM fuel cell has a polymer electrolyte membrane arranged between an anode and a cathode. With the help of the PEM fuel cell, hydrogen and oxygen, which are supplied to the cathode in the form of air, are converted into electrical energy, heat, and water. To increase the generated electrical voltage, several fuel cells are combined in practice to form a fuel cell stack.

[0007] Since the anode gas exiting a PEM fuel cell stack usually still contains unused hydrogen, it is recirculated via the so-called recirculation circuit and fed back to the anode of the fuel cell stack. Recirculation is usually achieved passively using a jet pump and / or actively using a blower. Due to the permeability of the polymer electrolyte membrane, product water diffuses from the cathode into the anode. Consequently, the anode gas becomes enriched with water, which can be in liquid or gaseous form. Excessive water enrichment of the anode gas can lead to hydrogen insufficiency within the anode, which reduces both the efficiency and the service life of the fuel cell stack.For proper operation of the fuel cell stack, the accumulation of product water in the anode gas must be monitored, and excessive water enrichment must be avoided by controlling or regulating the water content in the anode gas. Monitoring the product water enrichment of the anode gas is typically done indirectly, either through process modeling or by determining the fill level of a water separator installed in the recirculation circuit, in which condensed water is collected and at least partially removed via a so-called drain process. The fill level of the water separator is usually determined using suitable sensors. However, installing fill level sensors within the anode is costly and complex. The sensors must meet the high operational and material requirements of hydrogen applications.Furthermore, additional space is required on or in the water separator.

[0008] Another approach to monitoring product water enrichment in the anode gas involves indirect, predictive modeling during ongoing operation. Such models are particularly complex because they depend on many parameters. In particular, temperature-dynamic processes and their changes over time are difficult to describe. Individual component temperatures often do not correspond to steady-state conditions, which in turn can lead to increased liquid water accumulation. Such models must therefore incorporate significant safety factors to reliably prevent excessive water enrichment in the anode gas, which in turn hinders optimization of the monitoring process.

[0009] The present invention is therefore concerned with the task of providing an approach for monitoring water enrichment in the anode gas that requires neither a fill level sensor nor complex modeling of the product water enrichment. To achieve this task, the method with the features of claim 1 is proposed. Advantageous further developments of the inventions can be found in the subclaims. Furthermore, a computer program product for implementing the method or individual method steps is provided.

[0010] Disclosure of the Invention: A method for operating an anode subsystem for supplying at least one fuel cell of a fuel cell system with an anode gas is proposed. The anode gas is enriched with product water generated during operation and is recirculated by means of a blower. An excessively high water content in the anode gas impairs the efficiency and service life of the fuel cell system. According to the invention, the electrical consumption of the blower is monitored during steady-state operation to monitor the water concentration in the recirculated product. The consumption is evaluated for high-frequency peaks, which indicate the reaching of a saturation concentration.

[0011] In general, the fan's power consumption is relatively stable during steady-state operation. When a saturation concentration of water is reached in the anode gas, small water droplets condense from the anode gas. The invention is based on the finding that these water droplets, upon impacting the fan's impeller, which typically rotates at speeds greater than 20,000 rpm, 1which disrupts local flow conditions and causes high-frequency peaks in power consumption. The method uses the occurrence of these high-frequency power peaks as an indicator of the presence of excess water in the recirculated anode gas. This eliminates the need for complex sensors and / or modeling within the anode subsystem specifically installed for this purpose. Since the recirculation blower is typically an electric turbomachine with its own sensors for operational monitoring, the proposed method eliminates the need for additional measurement components for measuring power consumption.

[0012] In a further development of the invention, it is proposed to consider the operation of the fan as stationary when the rotational speed of the fan and its temporal change reach a predefined threshold. This ensures that high-frequency peaks in consumption power that occur during startup or a change in the operating point are not erroneously attributed to the anode gas reaching saturation with water. As a preferred embodiment, it is proposed to use a value greater than 3000 min' for the rotational speed. 1 and for the temporal change a value less than 100 min' 1 s' 1 to choose.

[0013] In a further development of the invention, it is proposed to amplify the intensity of the high-frequency peaks in the fan's power consumption by filtering them with a high-pass filter. On the one hand, this makes the power consumption peaks indicating excess water more clearly identifiable, and on the other hand, power peaks attributable to other causes can be largely filtered out, thus preventing the risk of incorrectly inferring the existing water concentration.

[0014] Furthermore, it is proposed to perform the evaluation by determining the accumulated additional energy demand of the fan, which is determined by integrating the high-frequency peaks in the consumption power over time. If the high-frequency peaks are caused by an increasing water load in the anode gas, which steadily increases during operation until a scheduled drain process is triggered, the accumulated additional energy demand of the fan increases continuously. An increasing water load in the anode gas as the cause of the accumulated additional energy demand can thus be better differentiated from other causes. Furthermore, the evaluation is available for further control engineering and signal analysis devices and methods.

[0015] In a further development of the invention, it is proposed to trigger the intended drain process when the accumulated additional energy demand of the fan exceeds a predefined activation value. In this way, the water concentration in the anode gas can be regulated using the proposed method without the need for additional components or processes.

[0016] Furthermore, it is proposed that the fuel cell system be shut down to prevent damage if the accumulated additional energy demand of the fan exceeds a predefined safety value. This is particularly advantageous because operational damage or complete failure of the fuel cell system due to hydrogen insufficiency caused by excessive water concentration in the anode gas can be detected and prevented at an early stage, eliminating the need for additional sensors.

[0017] Furthermore, a computer program product is proposed which contains program code designed to carry out individual steps of the method. The computer program product can be used, in particular, to identify the stationary operation of the blower and to initiate the proposed method, as well as for high-pass filtering the consumption power and / or its integration into the accumulated additional consumption of the blower. Furthermore, the computer program product can be used to detect when the activation value and / or the safety value have been exceeded. Furthermore, the computer program product can be used to initiate a drain process and / or shut down the fuel cell system to prevent damage based on the monitoring performed in the proposed method.

[0018] Further measures improving the invention are described in more detail below, together with the description of the attached figure. This shows a schematic representation of the sequence of a method according to the invention.

[0019] Detailed description of the figure

[0020] The method according to the invention, which serves to monitor the water enrichment in an anode gas of a fuel cell system, comprises several process steps that are carried out sequentially. The figure illustrates these steps by way of example for a preferred process sequence.

[0021] In a first step S1, the power consumption of a fan used to recirculate an anode gas is examined for the occurrence of high-frequency power peaks during stationary operation. These are caused by condensed water droplets hitting an impeller installed in the fan. Step S1 can be supported by a further step S2, which consists of isolating high-frequency components of the power consumption using a high-pass filter. For further analysis, in a step S3, an accumulated additional energy requirement is determined by integrating the high-pass filtered power consumption of the fan over time. In a preferred embodiment of the method, this step S3 is conditioned by the presence of stationary operation. Stationary operation is defined as a boundary condition RB based on a rotation speed and its change over time.A rotation speed greater than 3000 min' is preferred. 1 and as a time change a value less than 100 min' 1 s' 1 chosen.

[0022] In a further step S4, operating and / or action instructions can be derived from the analysis of the accumulated additional energy demand. For example, an activation value can be set, which, if exceeded, triggers a designated drain process. Furthermore, a safety value can be set, which, if exceeded, shuts down the fuel cell system to prevent damage.

Claims

Claims 1. A method for operating an anode subsystem for supplying at least one fuel cell of a fuel cell system with an anode gas which is enriched with product water generated during operation and is recirculated by means of a blower, wherein an excessively high water content in the anode gas impairs the efficiency and service life of the fuel cell system, characterized in that in order to monitor the water concentration in the recirculate, an electrical consumption power of the blower is observed during stationary operation and the consumption power is evaluated with regard to high-frequency peaks which are caused by a disturbance of the local flow conditions caused by water droplets and which indicate that a saturation concentration has been reached.

2. Method according to one of the preceding claims, characterized in that the operation of the fan is considered to be stationary when the rotational speed of the fan and its temporal variation reach a predefined threshold value, wherein preferably the rotational speed has a value greater than 3000 min' 1 and the change in time is less than 100 min' 1 s' 1 .

3. Method according to one of the preceding claims, characterized in that the expression of the high-frequency peaks in the consumption power of the fan is amplified by filtering with a high-pass filter.

4. Method according to claim 3, characterized in that the evaluation is carried out by determining an accumulated additional energy requirement of the fan, which is determined by integrating the high-frequency peaks in the consumption power over time.

5. Method according to one of the preceding claims 3 to 4, characterized in that when a predefined activation value of the accumulated additional energy requirement of the fan is exceeded, a drain process is initiated.

6. Method according to the preceding claims 3 to 5, characterized in that if a predefined safety value of the accumulated additional energy requirement of the blower is exceeded, the fuel cell system is shut down to prevent damage.

7. A computer program product comprising program code designed to carry out steps of a method according to any one of the preceding claims.

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