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
  • H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
  • H01M8/04052—Storage of heat in the fuel cell system
• • 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
  • H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
  • H01M8/04037—Electrical heating
• • 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
  • H01M8/04067—Heat exchange or temperature measuring elements, thermal insulation, e.g. heat pipes, heat pumps, fins
• • 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
• • 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 for suppressing icing up of a component in a fuel cell system, in particular in a motor vehicle, wherein it is restricted in the present case to those components which heat up to above the temperature in the environment surrounding the fuel cell system when the fuel cell system is in operation.
• the invention further relates to a fuel cell system having such a component and furthermore to a motor vehicle having such a fuel cell system.
• the invention may also be applied to mobile fuel cell systems not used in the automotive sector and to stationary fuel cell systems.
• Icing up of components in a fuel cell system regularly impairs operation of these components.
• the water remaining in the fuel cell system after operation of the same i.e. after the motor vehicle operated by the fuel cell system has been turned off, freezes and forms ice. If it is desired at a subsequent point in time to drive the motor vehicle again and thus to bring the fuel cell system back into operation, the ice then hinders operation of the fuel cell system.
• moving parts such as blowers, pumps and valves, but also to non-moving parts, such as for example pipes.
• DE 103 517 56 A1 discloses the use of an adsorption accumulator for releasing heat, this being used in particular in the case of a cold start. Such an adsorption accumulator is costly and is also troublesome with regard to weight.
• US 6,586,124 B2 discloses the use of hydrides, in particular metal hydrides, for heating up the fuel cell before start-up. In this way, the components of the fuel cell can be brought up to operating temperature even if ambient temperatures are low.
• the metal hydrides may be disposed in a heat pump.
• DE 109 421 95 A1 discloses use of the latent heat accumulator to stabilize temperatures when the fuel cell is in ongoing operation by buffer storage of the required heat.
• DE 103 37 898 A1 focuses on bringing about the minimum operating temperature of the fuel cell with the assistance of the latent heat accumulator.
• a latent heat accumulator is used which comprises a material which is converted from one phase into another phase by the input of heat and then remains in the latter phase even when it cools down.
• the object is achieved with a method having the features according to Patent Claim 1 , with a fuel cell system having the features according to Patent Claim 2 and with a motor vehicle having the features according to Patent Claim 9.
• the fuel cell system according to the invention comprises separate means which serve to supply thermal energy to the components and indeed are designed to supply this thermal energy in particular after termination of operation of the fuel cell system, while the component is still cooling down to the temperature of the environment surrounding the fuel cell system.
• the method according to the invention slows down cooling of the component, and the means in the fuel cell system according to the invention or in the motor vehicle according to the invention have the same effect. Slowing down cooling in comparison with the situation without separate measures has the advantage that water and atmospheric humidity can escape better during cooling.
• the invention is based on the recognition that preceding events play a significant part during start-up of the fuel cell system. It should not simply be assumed that certain components will ice up, a solution then being sought, as in the prior art, for clearing the ice. Instead, the present invention actively influences the events preceding restart, in that the means for supplying thermal energy become or are active on termination of operation of the fuel cell system or the motor vehicle.
• a passive system may be used.
• coupling the component of a fuel cell system with a latent heat accumulator is a possible option, specifically with a latent heat accumulator which absorbs heat above a first predetermined temperature and releases heat automatically, without needing activation, below a predetermined temperature.
• this latent heat accumulator differs from the latent heat accumulator in DE 103 37 898 A1 , in which a latent heat accumulator is deliberately selected in which a slight electrical, mechanical or chemical modification has purposefully to be introduced to release the stored thermal energy.
• Latent heat accumulators which automatically release the heat again are known for example from the field of building technology.
• phase change materials PCM
• these may for example be fine wax droplets with a diameter of approx. 2 to 20 ⁇ m, which have been cast in high strength plastics and may thus be introduced into other materials.
• these cast-in wax droplets are introduced for example into plaster, render etc.
• a suitable carrier material may be used, which merely has to have the property of not impeding operation of a fuel cell system.
• the material having the latent heat property may be introduced into plastics or a rigid foam, which is connected with the component to be protected, possibly to the extent that the component is completely clad or enclosed in the material.
• the material having the latent heat property may, where possible, also be introduced directly into component material, plastics components being particularly suitable, for example.
• the fuel cell system has more in the way of active heating means than passive heating means. These are then controlled by a control unit, which is designed to actuate the active means for heating the component after operation of the fuel cell system, specifically while the component is cooling down, so as to slow down the cooling process.
• a control unit which is designed to actuate the active means for heating the component after operation of the fuel cell system, specifically while the component is cooling down, so as to slow down the cooling process.
• Containers with chemical H2 storage materials e.g. metal hydrides
• two containers coupled together may form a heat pump, which at the same time as supplying heat to the one component draws heat from another component. In this way, the other component becomes colder sooner, and ice deposits form in case of doubt on this other component, such that the component to be protected remains ice-free.
• the latent heat accumulator or the active means may be incorporated into the components at risk of frost (blowers, pumps, valves, flood lines etc.) or at least brought into the immediate vicinity thereof in order then to be brought into heat-conducting contact, either via solids or a gas phase.
• frost blowwers, pumps, valves, flood lines etc.
• the gravity-induced convection effect could be utilized:
• the latent heat accumulator or the active heating means would then have to be mounted below the stated components, the term "below” relating to the typical position of the fuel cell system, in particular where a motor vehicle is concerned and said motor vehicle is standing on flat ground.
• the fuel cell system according to the invention is installed in a motor vehicle.
• the invention may also be applied to mobile fuel cell systems not used in the automotive sector and to stationary fuel cell systems.
• Fig. 1 is a schematic representation of a fuel cell system according to a first aspect of the invention and Fig. 2 is a schematic representation of a fuel cell system according to a second aspect of the invention.
• a fuel cell stack 10 of a fuel cell system is illustrated symbolically, together with the anode circuit 12, which consists of a plurality of components 14, 16 and 18, which are decoupled thermally from one another at least to the extent that they may display different temperatures.
• An anode circuit is distinguished in that unused hydrogen from the fuel cells is recirculated. The invention is also applicable to anode arrangements lacking this recirculation.
• a first container 20 containing metal hydride is thermally coupled to the component 14, and a second container 22 containing another type of metal hydride is coupled to the component 16.
• the containers 20 and 22 may be connected together via a valve 24.
• the metal hydrides in the containers 20 and 22 differ from one another in their equilibrium pressure. In the initial situation, which should be brought about at the latest during operation of the fuel cell system shown in Fig. 1 , the container 20 with the higher equilibrium pressure is charged with hydrogen and the other not. Metal hydrides are known to absorb hydrogen. Provision is then made for the valve 24 to be opened on termination of operation of the fuel cell system, at least when the external temperature falls below a critical temperature such that it could be expected that water in the fuel cell system might freeze into ice.
• a control unit 26 which on the one hand receives information about whether and when operation of the fuel cell system has been terminated. This information may for example be provided by a signal from an ignition lock. Information about temperature is additionally supplied to the control unit 26 via a temperature sensor 28, which measures the external temperature or indeed the temperature of a component of the fuel cell system (cf. broken line from the temperature sensor 28 to the component 18), such that the control unit 26 can use a threshold criterion to compare whether it should open the valve after termination of operation of the fuel cell system. If the valve is then opened, the hydrogen in the container 20 is desorbed and flows into the container 22, where it is then absorbed. In this way, the container 20 cools down considerably, whilst the container 22 warms up.
• the container 22 heats up the component 16.
• the component 16 therefore does not cool down as quickly as the components 14 and 18 of the anode circuit 12.
• the ambient temperature which has actually fallen below a suitably defined threshold value, results in freezing of water. Because the component 16 is being heated, this occurs preferentially on components 14 and 18.
• the component 16 is selected to be that component which is most disturbed by ice when in operation (in the event of subsequent restarting of the fuel cell system).
• the ice is not critical.
• component 14 becomes even cooler than the component 18 (and optionally also cooler than the surrounding environment) and serves as a condensation trap, on which the water is purposefully condensed and either drained away or frozen solid.
• the component 14 is selected such that the ice arising thereon does not impede cold starting of the fuel cell system.
• the components 14, 16, 18 heat up automatically, such that the hydrogen in the container 22 is automatically released again.
• This may either be returned to the container 20, so embodying the principle of a heat pump, or it may be used for system operation.
• an optional line 30 is used, which leads into a line 32 with a valve 34, via which hydrogen is supplied to the fuel cell stack 10.
• the line 30 may also be used to supply fresh hydrogen to the container 20 in the event of a cold start, such that this container warms up and any ice which may be located there is thawed off.
• Freezing water may also be a problem for components other than those in the anode module (anode circuit). Provision may also be made, in a fuel cell system, for components of the cathode module or of the humidifier or indeed the throttle valve etc. to be exposed to heat upon termination of operation, in particular using containers containing metal hydrides.
• FIG. 2 An alternative embodiment of the invention is described with reference to Fig. 2.
• the only part of the fuel cell system illustrated symbolically here is the fuel cell stack 10, together with the anode circuit 12'.
• Components 14', 16,' and 18' form the anode circuit 12'.
• the components 14', 16' and 18' differ from conventional components of an anode circuit in that they are coupled to a latent heat energy accumulator. This is shown symbolically in the illustration according to Fig. 2 by a layer 36 on the components 14', 16' and 18'.
• the layer consists for example of plastics or a rigid foam, with which the components 14', 16' and 18' are clad.
• a "phase change material", or PCM as known from building technology is embedded in this material.
• a phase change material is used which absorbs heat at temperatures above a predetermined temperature and automatically releases the absorbed heat again after cooling to below a predetermined temperature.
• a typical instance of such a phase change material is for example wax droplets with a diameter of for example 2 to 20 ⁇ m cast in high strength plastics. However, other materials which exhibit such phase changes may also be used. These may be finely dispersed in the layer 36 of plastics or rigid foam. If these wax droplets cast in high strength plastics are heated, as occurs automatically during operation of the fuel cell system, the wax melts with an enthalpy of fusion of for example 100 J/g. The melting temperature and the enthalpy of fusion may be set on selection of the material. When the system cools down, the enthalpy of fusion is released again upon solidification of the wax, and thermal energy is fed to the components 14', 16' and 18' by their respective cladding 36.
• Fig. 2 shows a layer applied to the components 14', 16' and 18'
• the phase change material may also be fitted inside the components 14', 16', 18'. It is also possible to form a separate component which is coupled to the components 14', 16' and 18' solely by way of heat transfer without affecting the appearance of components 14', 16' and 18'.
• latent heat accumulators for the purpose of preventing icing up of certain materials is completely novel within the context of automotive technology. Applications outside fuel cells are likewise possible. For instance, latent heat accumulators of the stated type may also be used in catalysts, batteries, electronic components, gas tanks and tanks for other service fluids.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Fuel Cell (AREA)

Applications Claiming Priority (4)

Publications (1)

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Citations (6)

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• 2008
  • 2008-04-16 DE DE102008019099A patent/DE102008019099A1/de not_active Withdrawn
  • 2008-11-19 WO PCT/EP2008/009760 patent/WO2009080162A1/en active Application Filing

Patent Citations (6)

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