Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
  • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
  • H01M8/04492—Humidity; Ambient humidity; Water content
  • H01M8/04507—Humidity; Ambient humidity; Water content of cathode reactants at the inlet or inside the fuel cell
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
  • H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
  • H01M8/04119—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying
  • H01M8/04126—Humidifying
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
  • H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
  • H01M8/04119—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying
  • H01M8/04156—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying with product water removal
  • H01M8/04164—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying with product water removal by condensers, gas-liquid separators or filters
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
  • H01M8/04253—Means for solving freezing problems
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
  • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
  • H01M8/04537—Electric variables
  • H01M8/04604—Power, energy, capacity or load
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
  • H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
  • H01M8/04701—Temperature
  • H01M8/04708—Temperature of fuel cell reactants
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
  • H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
  • H01M8/04746—Pressure; Flow
  • H01M8/04753—Pressure; Flow of fuel cell reactants
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
  • H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
  • H01M8/04746—Pressure; Flow
  • H01M8/04768—Pressure; Flow of the coolant
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
  • H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
  • H01M8/04746—Pressure; Flow
  • H01M8/04776—Pressure; Flow at auxiliary devices, e.g. reformer, compressor, burner
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
  • H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
  • H01M8/04828—Humidity; Water content
  • H01M8/04835—Humidity; Water content of fuel cell reactants
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells

Definitions

• the invention relates to a method of operating a fuel cell device in a special operating state, preferably in the case of starting, in particular in the case of a sub-freezing start, and/or in the case of switch-off of the fuel cell device, the fuel cell device comprising a fuel cell assembly having at least one fuel cell and a fuel cell supply system having at least one continuous flow machine and one humidifier for feeding an oxidizing agent to the fuel cell assembly.
• the invention further relates to a fuel cell supply system adapted thereto and to a fuel cell device.
• Fuel cell systems may be used as energy generators for generating the drive energy for vehicles.
• Fuel cell systems implement an electrochemical process, wherein a fuel, generally hydrogen, is reacted with an oxidizing agent, generally ambient air or oxygen, chemical energy being converted into electrical energy.
• a proton-conducting membrane plays a decisive part in energy conversion, said membrane being arranged in fuel cell systems between anode and cathode areas.
• This membrane is a component of fuel cell systems which is susceptible to wear. When fuel cell systems are in operation, care must be taken to ensure that this membrane does not dry out, since premature wear is accelerated thereby. For this reason it is conventional for the oxidizing agent supply systems of fuel cell systems to comprise a device for humidifying the oxidizing agent supplied.
• Document US 7,141 ,326 B2 relates to a fuel cell system with a warm-up apparatus for a fuel cell, the problem of starting the fuel cell system being specifically addressed.
• the document proposes firstly to compress ambient air by means of a compressor, then to cool it by means of an intercooler, to humidify it and finally feed it to the fuel cell.
• the document on the one hand discloses providing a bypass for the intercooler, which is activated when operation is started in order to introduce the oxidizing agent into the fuel cell at a high temperature.
• the object of the invention is to propose a method of operating a fuel cell device, a fuel celt supply system and a fuel cell device which allow low-wear operation of the fuel cell device.
• a method for operating a fuel cell device in a special operating state differs from a normal operating state of the fuel cell device preferably in that it is a transient operating state as opposed to a steady, virtually steady or persistent operating state.
• Preferred examples of a special operating state are starting, in particular sub-freezing starting, i.e. starting of a fuel cell device or fuel cell at temperatures of below 0 0 C, and/or switch-off of the fuel cell device.
• the fuel cell device comprises a fuel cell assembly having at least one fuel cell, preferably at least 100, in particular at least 150 fuel cells.
• the fuel cell device preferably takes the form of a mobile unit for supplying energy to a vehicle.
• the at least one fuel cell or the fuel cell assembly has to be supplied with an oxidizing agent, for example ambient air or oxygen, for the electrochemical process for converting chemical energy into electrical energy.
• the fuel cell device comprises a fuel cell supply system, which, for preparation of the oxidizing agent, comprises at least one continuous flow machine, in particular a compressor or a radial compressor, and one humidifier for humidifying the oxidizing agent with water.
• the continuous flow machine is suitable and/or designed for feeding energy to the oxidizing agent, i.e. in particular to achieve an increase in the pressure or velocity of the oxidizing agent.
• the moisture content is or has been reduced in the oxidizing agent relative to a normal operating state.
• the moisture content is preferably understood to mean a characteristic parameter of the quotient obtained by dividing the liquid or water quantity in a specific quantity or mass of oxidizing agent by this oxidizing agent quantity or mass.
• a reduction of the moisture content in the oxidizing agent appears advantageous for example in the event of switch-off of the fuel cell device, since the quantity of moisture remaining in the fuel cell assembly is thereby reduced.
• the reduction in the moisture content reduces the risk of moisture condensing in the fuel cell assembly.
• condensation of moisture may lead to ice formation and thus to partial or complete freezing up of the gas supply channels in the fuel cell assembly.
• the moisture content is reduced to the extent that the dew point of the oxidizing agent lies below the current temperature of the fuel cell assembly, in particular of one, a plurality or all of the individual fuel cells of the fuel cell assembly.
• the additionally cooled oxidizing agent is able to take up less moisture in the humidifier, such that its moisture content is reduced relative to the normal operating state.
• Another concept of the invention consists in cooling the oxidizing agent before a dehumidifier, in order to improve the efficiency and effectiveness of the dehumidifier. For example, in the event of switch-off of the fuel cell device it is preferable for the cooled oxidizing agent to be reheated in the fuel cell assembly, such that its capacity to take up moisture is increased again and the fuel cell assembly is dehumidified in this way.
• the additional cooling capacity is connected flow-wise after the continuous flow machine and before or in the humidifier.
• the oxidizing agent is initially increased in temperature. In this state the oxidizing agent is in a particularly good position to take up moisture in the humidifier.
• the oxidizing agent is cooled actively by the connectable cooling capacity, wherein the absolute or relative humidity of the oxidizing agent is increased before or in the humidifier.
• the humidity preferably corresponds to a characteristic number for the quotient obtained by dividing the liquid or water quantity in a specific volume of oxidizing agent by this oxidizing agent volume.
• the fuel cell supply system comprises a dehumidifier, which is preferably of connectable construction, such that the reduction in moisture content is achieved or improved by cooperation of the additional cooling capacity and the dehumidifier.
• the additional cooling capacity is connected after the continuous flow machine and before or in the dehumidifier.
• This embodiment is based on the strategy that the oxidizing agent is cooled by the additional cooling capacity and the relative or absolute humidity is increased thereby. Because the oxidizing agent flows with a very elevated relative or absolute humidity through the dehumidifier, the efficiency of the dehumidifier is improved, such that a greater dehumidifying action occurs with the cooled oxidizing agent than with an uncooled oxidizing agent.
• the additional cooling capacity is such that the oxidizing agent is cooled to below the current temperature in the fuel cell assembly.
• the oxidizing agent is cooled to a temperature differential of at least 10 0 C 1 preferably of at least 20 0 C and in particular of at least 30 0 C.
• the concept on which this strategy is based is that the cooled oxidizing agent enters the fuel cell assembly, is heated therein and undergoes a reduction in absolute or relative humidity. In the state where the relative or absolute humidity is reduced, the oxidizing agent may however particularly readily take up humidity from the fuel cell assembly, such that the latter is dehumidified.
• This alternative method is particularly preferred if the fuel cell device is to be switched off from a normal operating temperature of approx. 7O 0 C to 120 0 C.
• the present invention also provides a fuel cell supply system which is preferably designed to carry out the method just described or the method as claimed in one of the preceding claims.
• the fuel cell supply system serves to supply a fuel cell assembly having at least one fuel cell with an oxidizing agent, such as for example ambient air or oxygen.
• the fuel cell supply system and the fuel cell assembly together form a fuel cell device or a part thereof.
• the fuel cell supply system comprises a continuous flow machine for compressing and/or accelerating the oxidizing agent, which is preferably designed as a compressor, in particular as a radial compressor and is of one-, two- or multi-stage construction.
• a humidifier Connected flow-wise downstream of the continuous flow machine is a humidifier, which humidifies the accelerated or compressed oxidizing agent.
• the humidifier may optionally be controllable, such that the degree of humidification is adjustable.
• a connectable bypass may be provided around the humidifier, such that the humidifier may be completely or partially isolated from the fuel cell supply system.
• the fuel cell supply system comprises a cooling device, which may take the form for example of a cryostat, a heat exchanger or an intercooler or charge air cooler.
• a control means is provided which may take the form of a separate arithmetic and logic unit or of an integral module of a higher-level open-loop controller.
• control device be designed to connect in and/or increase the cooling capacity of the cooling device in a special operating state using software and/or circuitry, preferably in the event of starting, in particular in the event of a sub-freezing start, and/or in the event of switch-off of the fuel cell assembly, such that the moisture content of the oxidizing agent is reduced relative to a normal operating state.
• the cooling device takes the form of a or the intercooler or charge air cooler, which is arranged flow-wise after the continuous flow machine, the cooling capacity of the intercooler being increased in the special operating state.
• Such an intercooler is often used in fuel cell supply systems, in order to cool the temperature of the oxidizing agent after the continuous flow machine to the normal operating temperature of the fuel cell assembly.
• the intercooler is actuated by the control device in such a way that the additional cooling capacity is brought about in the special operating state.
• the fuel cell supply system likewise comprises an intercooler
• the cooling device for generating the additional cooling capacity is embodied as a separate component or a separate assembly in the fuel cell supply system.
• This alternative takes account of the fact that the intercooler often takes the form of a water cooler, which cools the oxidizing agent stream against the cooling water of a cooling circuit, it being difficult to control or open-loop control the intercooler with regard to cooling capacity.
• the cooling device takes the form of an integral component of the humidifier, such that, if required, the oxidizing agent may be cooled in the humidifier and in this way the humidifying action of the humidifier is reduced.
• the fuel cell supply system may comprise a dehumidifier, which is arranged downstream of the humidifier.
• the dehumidifier may for example take the form of a membrane dryer, an absorption device, an adsorption device, an enthalpy wheel or a chemical reactor.
• the dehumidifier may take the form of a temporary or permanent sink for moisture, i.e. it may store the moisture extracted from the oxidizing agent merely temporarily and release it again at a later time, for example when the fuel cell assembly is in a normal operating state, or alternatively the moisture may be permanently dissipated.
• the cooling device in accordance with the method according to the invention it is possible for the cooling device to be arranged flow-wise before or in the dehumidifier.
• the present invention also provides a fuel cell device having the features of claim 13, which comprises the fuel cell supply system as claimed in one of the preceding claims, the fuel cell device being designed for mobile use, in particular in a vehicle as a generator for the drive energy.
• Figure 1 shows a block diagram of a fuel cell supply system as a first exemplary embodiment of the invention
• Figure 2 shows a block diagram of a fuel cell supply system as a second exemplary embodiment of the invention
• Figure 3 shows a block diagram of a fuel cell supply system as a third exemplary embodiment of the invention
• Figure 4 shows a block diagram of a fuel cell supply system as a fourth exemplary embodiment of the invention.
• Figure 5 shows a block diagram of a fuel cell supply system as a fifth exemplary embodiment of the invention.
• Parts which are identical or correspond to one another are in each case provided with identical or mutually corresponding reference numerals.
• Fig. 1 is a highly schematic representation in the form of a block diagram of a portion of a fuel cell device 1 as a first exemplary embodiment of the invention.
• the fuel cell device 1 comprises a plurality of fuel cells 2, just one individual fuel cell 2 being shown by way of illustration.
• the fuel cells 2 each comprise a cathode area 3 and an anode area 4, which are separated from one another by a membrane 5, in particular a proton-conducting membrane 5 (PEM).
• PEM proton-conducting membrane 5
• the fuel cell device 1 is used as a mobile unit for example for driving a vehicle.
• the fuel cell device 1 To supply the fuel cells 2 with an oxidizing agent, in particular ambient air or oxygen, the fuel cell device 1 exhibits a fuel cell supply system 6, wherein in the representation in figure 1 the components necessary for the first exemplary embodiment are shown with a solid line and the optional components with a broken line.
• the fuel cell supply system 6 comprises a continuous flow machine 7, which takes the form for example of a compressor or radial compressor. Downstream of the continuous flow machine 7 is an intercooler 8 (also known as a charge air cooler), which cools the oxidizing agent compressed and consequently heated by the continuous flow machine 7. A humidifier 9 is provided after the intercooler 8, which humidifier feeds water to the compressed and cooled oxidizing agent, such that the membrane 5 is sufficiently humidified when the fuel cell device 1 is in operation. In the simplest embodiment of the first exemplary embodiment the humidified oxidizing agent is guided from the humidifier 9 to a cathode area inlet 10.
• the fuel cell supply system 6 exhibits a control means 11 , which controls the cooling capacity of the intercooler 8 and, optionally additionally, the humidification capacity of the humidifier 9.
• the control means 11 is of software and/or circuit design, in order to actuate the intercooler 8 or the humidifier 9 in such a way that the oxidizing agent is humidified as little as possible.
• the humidifier 9 initially to be throttled to a minimum with regard to its humidifying action.
• the cooling capacity of the intercooler 8 is increased, such that the oxidizing agent is cooled more severely than in a normal operating state.
• the relative or absolute humidity thereof moisture per unit volume
• the moisture content (moisture per unit mass) in the oxidizing agent may thus be reduced.
• the risk of moisture condensing out in the fuel cell 2 and, in particular in the event of a sub-freezing start, freezing, is reduced as a result of the reduced moisture content.
• the temperature of the oxidizing agent is cooled to a temperature below the operating temperature of the fuel cell 2. If the oxidizing agent then enters the fuel cell 2, it is heated, the relative or absolute humidity falls and the fuel cell 2 is dried out, undesired moisture being removed from the fuel cell 2.
• the fuel cell supply system 6 exhibits a dehumidifier 12, which may be connected via a three-way valve 13.
• a dehumidifier 12 which may be connected via a three-way valve 13.
• a shut-off valve in a main branch 14 or in a sub-branch 15, in order to convey the oxidizing agent stream to the cathode area inlet 10 directly or alternatively via the dehumidifier 12.
• the dehumidifier 12 serves to lower further the moisture content of the oxidizing agent.
• Figure 2 shows a second exemplary embodiment in the same representation as in figure 1 , the difference between the first exemplary embodiment and the second exemplary embodiment being that an intercooler 8 and an additional cooling device 16 connected downstream are provided in the second, which latter applies the additional cooling capacity in the event of starting, in particular of a sub-freezing start, or of switch-off of the fuel cell device 1.
• FIG. 3 shows a third exemplary embodiment of the invention, wherein, as opposed to the first and second exemplary embodiments, the cooling device 16 is positioned in the sub-branch 15 flow-wise before the dehumidifier 12. In this position the cooling device 16 has the task of cooling the oxidizing agent and in this way increasing the relative or absolute humidity, such that the efficiency of the dehumidifier 12 is improved.
• the temperature of the oxidizing agent may be lowered before the humidifier 9 by the intercooler 8 or a further cooling device.
• a bypass line 17 may be provided, which bypasses the humidifier 9.
• the bypass line may for example be connectable by means of one or more shut-off valves or via a three-way valve.
• FIG 4 shows a fourth exemplary embodiment of the invention in the same representation as in the preceding figures, wherein the humidifier 9 is coupled directly to the cooling device 16, such that they are arranged for mass and/or heat transfer.
• the oxidizing agent is cooled, so as to increase the absolute or relative humidity thereof and to reduce its capacity for taking up moisture from the humidifier 9.
• Further possible additions, such as for example the dehumidifier 12 and a further cooling device 18, are shown with broken lines.
• FIG. 5 finally shows a further modified embodiment as a fifth exemplary embodiment, wherein the humidifier 9 is coupled directly to the dehumidifier 12 and optionally in addition to the cooling device 16, so as to prevent the humidifier 9 from having a humidifying action in a special operating state.
• the further cooling device 18 Connected upstream of the coupled humidifier/dehumidifier 9, 12 is on the one hand the further cooling device 18 and optionally in addition the intercooler 8, so as to be able to achieve additional cooling capacity and thus a reduction in absolute or relative humidity.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Fuel Cell (AREA)

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Citations (4)

• 2008
  • 2008-02-13 DE DE102008008871A patent/DE102008008871A1/de not_active Withdrawn
• 2009
  • 2009-02-04 WO PCT/EP2009/000736 patent/WO2009100843A1/en active Application Filing

Patent Citations (4)

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