GB2533015A - Method for starting a fuel cell system - Google Patents

Method for starting a fuel cell system Download PDF

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Publication number
GB2533015A
GB2533015A GB1512282.3A GB201512282A GB2533015A GB 2533015 A GB2533015 A GB 2533015A GB 201512282 A GB201512282 A GB 201512282A GB 2533015 A GB2533015 A GB 2533015A
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United Kingdom
Prior art keywords
fuel cell
cell system
preheating
vehicle
water
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GB1512282.3A
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GB201512282D0 (en
Inventor
Raju Gautham
Jalan Mayank
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Mercedes Benz Group AG
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Daimler AG
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Priority to GB1512282.3A priority Critical patent/GB2533015A/en
Publication of GB201512282D0 publication Critical patent/GB201512282D0/en
Publication of GB2533015A publication Critical patent/GB2533015A/en
Withdrawn legal-status Critical Current

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    • 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
    • H01M8/04223—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
    • H01M8/04225—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 during start-up
    • 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
    • H01M8/04223—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
    • H01M8/04268—Heating of fuel cells during the start-up of the fuel cells
    • 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
    • H01M8/043—Processes for controlling fuel cells or fuel cell systems applied during specific periods
    • H01M8/04302—Processes for controlling fuel cells or fuel cell systems applied during specific periods applied during start-up
    • 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
    • H01M8/0432—Temperature; Ambient temperature
    • H01M8/04358—Temperature; Ambient temperature 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
    • H01M8/04313—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
    • H01M8/0432—Temperature; Ambient temperature
    • H01M8/04365—Temperature; Ambient temperature of other components of a fuel cell or fuel cell stacks
    • 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
    • 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
    • H01M8/04731—Temperature of other components of a fuel cell or fuel cell stacks
    • 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
    • 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
    • H01M8/04858—Electric variables
    • H01M8/04895—Current
    • H01M8/04917—Current of auxiliary devices, e.g. batteries, capacitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2250/00—Fuel cells for particular applications; Specific features of fuel cell system
    • H01M2250/20—Fuel cells in motive systems, e.g. vehicle, ship, plane
    • 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
    • Y02E60/10—Energy storage using batteries
    • 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
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02T90/40—Application of hydrogen technology to transportation, e.g. using fuel cells

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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)

Abstract

Method for starting a fuel cell system 2 for providing electric power to a vehicle 1 when temperatures are below the freezing point of water, wherein the fuel cell system 2 is preheated before start-up by use of electrical heating means 28, where the heating means is from an external power source such as an electric power grid, characterised in that a departure time to for the vehicle 1 is set; a routine for the estimation of a preheating time period tp is started by estimating the amount of remaining water in the fuel cell system 2; and controlled preheating is started at the estimated time period tp before the departure time to. The remaining water is estimated by the amount of hydrogen consumed by the fuel cell 6 to calculate the generated mass of product water and using the mass of waste water output, wherein the remaining water in the fuel cell 6 is calculated from their difference.

Description

Method for Starting a Fuel Cell System The invention relates to a method for starting a fuel cell system for providing power to a vehicle at temperatures below the freezing point of water, wherein the fuel cell system is preheated before start-up by use of electric heating means.
The need to heat a fuel cell or a fuel cell system comprising the fuel cell is well known for a person skilled in the art. In the US 6,675,573 B2 a vehicle with a fuel cell is claimed. The vehicle comprises a pre-heater electrically coupled to the fuel cell. This pre-heater is configured to receive a portion of the electric power from the fuel cell to heat up the fuel cell by the generated heat on the one hand and as an electrical load extracting electric power from the fuel cell which results in a faster heating of the fuel cell on the other hand. The main problem with this is that the start-up including the preheating occurs only after the user of the vehicle has started the vehicle. This leads to an undesired long start-up time of the vehicle until the full torque requested by the driver can be supplied.
In the US 2005/0181246 Al a fuel cell system and a method for starting-up the fuel cell system is described. The US application mentions the use of an electric heater to heat a coolant of the fuel cell system to warm up the fuel cell. Furthermore different starting routines can be selected based on the temperature. The idea is to start the fuel cell system with an electric pre-heating at a first range of temperatures. In a second range of temperatures which is below the first range of temperatures the fuel cell system can be started by burning hydrogen to generate more heat. This can also be done if there is not enough power in a battery for supplying the electrical power to start-up the fuel cell system and preheating it electrically. Furthermore, the electrical energy can be supplied by an external power supply if available. To overcome the above mentioned problem that the fuel cell system must be preheated and started after a starting signal provided by the user entering the vehicle the application suggests a remote control unit to allow the user to begin with the start-up before reaching it's vehicle. The problem here is that the fuel cell system still needs a certain and relatively long time to be started. lithe user is using the remote unit near the vehicle he will have almost the same undesired long starting time as in the above mentioned US patent. lithe user sends the starting signal by the remote control unit well before starting with the vehicle the preheating will start very early with the risk that the fuel cell system had to be kept warm over a longer period of time which needs a big amount of energy. If the battery cannot deliver this energy hydrogen must be burned to keep the fuel cell system warm.
It is the object of the invention to start-up a fuel cell system especially at temperatures below the freezing point of water at an appropriate timing for the user and which is as well energy as cost effective.
The above object is attained by a method for starting a fuel cell system for providing power to a vehicle at temperatures below the freezing point wherein the fuel cell system is preheated before start-up by use of electric heating means with the features of the characterizing part of claim 1.
According to the method of the invention a departure time for the vehicle is set. This departure time can according to a further embodiment of the invention be set by the user of the vehicle directly in the vehicle, for example before leaving the vehicle. Furthermore it can be set by a remote control system and/or via telecommunication means, such as a phone call, via a smartphone app or else. Especially when using the vehicle as part of a commercial vehicle fleet the start-up time can also be set by a data server. This is especially useful when using the vehicle in the vehicle fleet according to a known stored time schedule e.g. for a fleet of fuel cell buses for passenger transportation.
After a departure time for the vehicle is set a routine for estimating a preheating time period is started. A controlled preheating is then started at the estimated time period before the departure time. This estimation of the preheating time period allows the start of the preheating at the estimated time period before the departure time. This will lead to a fuel cell system which is preheated at the departure time on the one hand and on the other hand prevents that the fuel cell system has to be kept warm over a longer time period as needed. Therefore, a method according to the invention allows to start the fuel cell system at the set departure time without an undesired waiting time for preheating the fuel cell system. Furthermore, the method according to the invention is very energy effective which indeed leads to a very cost effective operation.
According to a further embodiment of the invention the estimation of the preheating time period is based on an estimation of remaining water in the fuel cell system especially in it's fuel cell. The idea behind this very advantageous embodiment is that only the water remaining in the fuel cell system and especially in the fuel cell itself can freeze when the temperatures are falling below the freezing point of water. Therefore, the estimated preheating time period can be calculated based on the estimated amount of remaining water which in fact can be the maximum of frozen water in the fuel cell.
According to a further development of this idea the estimation of remaining/frozen water is using the amount of hydrogen consumed by the fuel cell to calculate the mass of generated product water. It is furthermore using the mass of waste water output and calculates the remaining water in the fuel cell from the difference. The amount of water generated in the fuel cell system can be found by using stoichiometric analysis based on the formula 2H2+ Op = 21-120, which leads to the respective masses of 2*2g + 32g = 2"18g. Typically the input of hydrogen can be estimated very well in a fuel cell system. To achieve the total amount of water generated the amount of consumed hydrogen had to be multiplied by 18 g for each mole of H2. To find the total hydrogen consumed in the fuel cell system you need to have the hydrogen input which is typically known and the hydrogen output for example when purging the anode loop of a fuel cell system which always leads to the loss of hydrogen. Alternatively, we can use the hydrogen input and a so called hydrogen efficiency of the fuel cell which is in other words an estimated percentage of hydrogen used at the instant of time.
Based on the total amount of generated water the remaining water in the fuel cell can now be calculated from the difference of the total amount of generated water on the one hand and the amount of waste water output from the fuel cell system, typically via water traps in the anode and cathode waste line.
According to a further favorable development of this idea the estimating of the remaining water in the fuel cell system is carried out until any waste water flow stops. Typically the fuel cell system has a so called shutdown routine which means that the fuel cell system is electrically switched off. Afterwards the fuel cell system can be dried by blowing out residual water in the fuel cell and especially in the pipes of the fuel cell system. This water will also increasing the amount of waste water output. Therefore, the estimation of remaining water should be carried out until any waste water flow stops.
According to a further embodiment of the idea the preheating time period can now be calculated based on the amount of remaining water and the temperatures in the fuel cell system and it's coolant. This will lead to the required amount of heat for preheating the fuel cell system and therefore the time period needed for the preheating can be calculated. The preheating time period tp can be calculated based on the parameters and mathematical formulas mentioned below: Current temperature of fuel cell = Ts Current temperature of coolant = Tc = f(t)wherein: t = time (to = 0 when preheating starts) Final temperature of fuel cell -Tsp Initial temperature of fuel cell = Ts, Amount of heat required = Y in [Joules] Preheating time period = tp Amount of heat transfer in flowing liquid per second = Kc * (Tc-Ts) Temperature of fuel cell = Ts,+(Heat transfer)/(calorific value of fuel cell) Ts = Tsi+Kc1*(Tc-Ts) Ts = Tsi+Kc1"Tc/(1+Kc1) Heat transfer per second = Kc*(Tc+Ts1)+Kc*Kc1*Tc/(1+Kc1) Total heat transfer in t seconds: Kc* c Kci * Tc/( Kci dt Time period required: tp= Y *10tP Kc (Tc Ts!) Kc Kc *Tc/(1 + Kci.) dt After the time period tp for preheating is known the preheating can start at this estimated time period before the set departure time. If there is a very big time gap between the end of the calculation of the preheating time period on the one hand and the start of the preheating at the other hand this calculation could be re-done from time to time, because typically the temperatures of the fuel cell stack and/or of the temperatures of the coolant might have changed.
The heat generated for preheating is according to a further embodiment of the invention transferred to the fuel cell system by heating and circulating a coolant of the fuel cell system. This is a very simple method to heat up the fuel cell using the cooling circuit which always exists in a fuel cell system.
In a very advantageous further embodiment of the method according to the invention the electric power for preheating is transferred to the vehicle from an external power source such as an electric power grid. The use of an external electric power source allows to preheat the fuel cell system electrically without checking the battery in the vehicle. This leads to a very effective preheating which can also be done when the fuel cell vehicle, which is then built up as a so called plug in fuel cell vehicle is connected to an external power source, for example an electric power grid. Furthermore, the energy for the electrical power grid is typically available on battery efficiency and at lower costs than electrical energy which is generated by the fuel cell system and which is stored in the onboard battery.
According to a further embodiment of this idea the electrical power from the external power source can also be used for charging the battery of the vehicle, so the battery is always well charged when the vehicle is departing.
Further favorable and advantageous embodiments and developments of the method according to the invention can also be found in an exemplary embodiment of a fuel cell vehicle and the method for starting the fuel cell system of the vehicle which is described below with respect to the drawings.
In the drawings Fig. 1 shows a schematically sketch of a fuel cell vehicle which can be started by a method according to the invention; Fig. 2 a control scheme showing the estimation of remaining water in the fuel cell system; Fig. 3 a diagram of the variation of the temperature in the coolant and in the fuel cell over time; and Fig. 4 a control scheme of a preferred embodiment of the method according to the invention.
In figure 1 a vehicle 1 including a fuel cell system 2 is shown in a schematically way. The vehicle 1 has an electric drive motor 3 to drive exemplary shown wheels 4. The electric drive motor is connected to an electric power unit 5 which furthermore is connected to the fuel cell 6 of the fuel cell system 2 as well as to a battery 7. The fuel cell 6 of the fuel cell system 2 should be a PEM-fuel cell. Other kinds of fuel cells could be used in principal as well. An anode side 8 of the fuel cell 6 is supplied with hydrogen (H2) from a pressure reservoir 9. The pressure reservoir 9 is connected to the anode side 8 of the fuel cell 6 via a hydrogen piping including a shut-off valve 10 and a pressure regulation system 11. The hydrogen is supplied to the anode side 8 of the fuel cell 6 via a so called ejector 12. Unused hydrogen and water generated on the anode side 8 of the fuel cell 6 leaves the anode side 8 via a so called recirculation line 13 of an anode loop. The recirculation line 13 leads back to the ejector 12 which creates a suction force on the recirculated gases and propels them together with fresh hydrogen into the anode side 8 of the fuel cell 6. In the recirculation line 13 a water trap 14 which is also known as anode water knockout is connected via a purge and drain line 15, for example to an off gas line 16, of the cathode side 17 of the fuel cell 6. Via a purge and drain valve 18 water and gas can be blown out for example from time to time or in accordance with the concentration of hydrogen or nitrogen in the anode loop. Instead of the ejector 12 or in addition to the ejector 12 a recirculation blower can be used.
The cathode side 17 of the fuel cell 6 is fed with air to deliver oxygen via an air compressor 19 which is connected to an off gas turbine 20 in the off gas line 16. Furthermore, a part of the compressor 19 and the turbine 16 and their connection is an electric machine 21. This assembly is also known as electric turbo charger (ETC) or motor assisted turbo charger. Upstream of the turbine 20 in the off gas line 16 a further water trap 22, a so called cathode knockout is positioned. It prevents the turbine 20 from damage by water drops in the off gas.
The further part of the fuel cell vehicle 1 is a cooling system 23 which is shown here only in a very schematically way. It consists of a heat exchanger 24 collecting the waste heat from the fuel cell 6 and the radiator 25 to deliver the waste heat to the environment. Furthermore, the cooling system 23 has a coolant pump 26 as well as a bypass line 27 to allow the coolant to bypass the cooler 25 e.g. when preheating the fuel cell 6 for start-up. Furthermore, an electrical heater 28 is placed in the cooling system 23 and is connected to the electric power unit 5. As the fuel cell vehicle 1 should be a so called plug-in fuel cell vehicle 1 in electrical connection to the electric power unit 5 there is a connection plug 29 which can be connected via an electric power cable 30 to an external power source 31, e.g. an electric power grid.
According to the method of the invention the fuel cell system 2 and especially its fuel cell 6 should be preheated for an instant start of the vehicle 1 at a set departure time to. To achieve a very effective preheating first of all a preheating time period tp for the preheating is estimated. Therefore, the amount of remaining water in the fuel cell 6 when the vehicle 1 is stopped should be estimated to know the maximum possible amount of frozen water in the fuel cell system 2. A flow chart for the estimation of the remaining water is shown in figure 2. The routine for estimating the amount of remaining water in the fuel cell system starts in step Si with the start of the operation of the fuel cell 6. Afterwards according to step S2 the amount of total water generated is calculated: Amount of water generated by fixed amount of air blown can be found using Stoichiometric analysis 2H2+ 02 = 2H20 2*2g 32g 2"18g Calculation of waste water at any instant when fuel cell is running: I. Find total H2 input, H2 output and total water output during fuel cell operation that was used II. Using H2 input and output we can find out what is the total amount of water generated.
Alternatively using input H2 and efficiency of fuel cell (estimated percentage of H2 used) at that instant of time Total water generated = (H2(input)-H2(output))(9)*18g Afterwards according to step S3 a total waste water output from the fuel cell system 2 is calculated or measured for example from the volume of waste water and its density. In step 01 the system asks if the fuel cell 6 is still operated or if the fuel cell operation has stopped. lithe fuel cell is still operated steps S2 and S3 are repeated. If the fuel cell 6 operation stops only step S3 is carried out until according to step 02 the waste water flow stops. Afterwards in step S4 the remaining water is calculated from the difference of the generated water and the waste water output.
Afterwards a time required for the preheating of the fuel cell system can be calculated. This preheating time period tp can be calculated using the parameters and variables as well as the equations noted below: Current temperature of fuel cell = Is Current temperature of coolant = Tc = f(t)wherein: t = time (to = 0 when preheating starts) Final temperature of fuel cell cell = TsF Initial temperature of fuel cell cell = Ts, Amount of heat required = Y in [Joules] Preheating time period = tp Amount of heat transfer in flowing liquid per second = Kc * (Tc-Ts) Temperature of fuel cell = 1s1+(Heat transfer)/(calorific value of fuel cell) Ts = Tsi+Kc1*(Tc-Ts) Is = Tsi+Kc1*Tc/(1+Kc1) Heat transfer per second = Kc*(Tc+Ts1)+Kc*Kc1*Tc/(1+Kc1) Total heat transfer in t seconds: -tP I^C (Tc Ts1) + FCc Kci Te/(1 -F Kci) dt The only unknown variable in the above equation is the preheating time period tp. Enhanced we can determine the time required for preheating: tp= Y 1 -tp Kc (Tc + TsI) + Kc Kc Tc/(1. Kci) dt -:e To use an architecture of the fuel cell vehicle 1 which is as close as possible to the standard architecture the preheating takes place via the electrical heater 28 in the cooling system 23. To achieve a given temperature of the fuel cell at the departure time to e.g. about 35°C at a start of the preheating the coolant is heated. Figure 3 is showing a temperature curve of the heating of coolant as a dashed line. This leads to the preheating of the fuel cell 6 starting at a temperature of about -15°C shown in a diagram with the dotted line. In fact the time period tp lasts from the start of the preheating at the time to to the set departure time to.
The overalls flow chart for the method according to the invention is finally shown in the control scheme of figure 4. In step 55 the start of charging the vehicle 1 by plug-in the cable 30 for the power connector 29 also starts the control scheme for the method according to the invention. In step 03 it is proven if a departure time tn is set. If the departure time is not set the routine will be aborted. If the departure time is set in step S6 the preheating time tp is estimated according to the above mentioned estimations and calculations. In step S7 the vehicle 1 is waiting to reach the time at which the preheating should be started. Afterwards in step 58 the preheating is started and during the preheating a control, for example of the temperatures of the fuel cell and/or the coolant, takes place. This is shown in step 59 as labeled controlled preheating. Afterwards in step S10 the preheating is stopped at the set departure time tn.
Additional to this control scheme in the flow chart according to figure 4 the steps 56 and 37 can be repeated if the waiting time is very long, for example more than ten times longer, as the preheating time period. This allows to react to changes in the temperatures which might fall significantly for example in the night. This will lead to a higher accuracy of the estimation of the preheating time and a more effective starting of the fuel cell system at temperatures below the freezing point of water.

Claims (10)

  1. Claims 1. Method for starting a fuel cell system (2) for providing electric power to a vehicle (1) at temperatures below the freezing point of water, wherein the fuel cell system (2) is preheated before start-up by use of electrical heating means (28), characterized in that a departure time (tD) for the vehicle (1) is set; a routine for the estimation of a preheating time period (tp) is started; and a controlled preheating is started at the estimated time period (tp) before the departure time (to).
  2. 2. Method according to claim 1, characterized in that the estimation of the preheating time period (tp) is based on an estimation of remaining water in the fuel cell system (2), especially in it's fuel cell (6).
  3. 3. Method according to claim 2, characterized in that the estimation of remaining water is using the amount of hydrogen consumed by the fuel cell (6) to calculate the generated mass of product water and is using the mass of waste water output, wherein the remaining water in the fuel cell (6) is calculated from their difference.
  4. 4. Method according to claim 3, characterized in that the estimation of remaining water in the fuel cell system (2) is carried out until the waste water flow stops.
  5. 5. Method according to one of claims 2, 3 and/or 4, characterized in that based on the amount of remaining water and temperatures in the fuel cell system (2) the required amount of heat for preheating the fuel cell system (2) and thereof the time period (tp) needed for preheating is calculated.
  6. 6. Method according to claim 5, characterized in that the temperatures include at least the temperatures in the fuel cell (6) and the temperature of the coolant.
  7. 7. Method according to one of claims 1 to 6, characterized in that the heat for preheating is transferred to the fuel cell (6) by heating and circulating a coolant of the fuel cell system (2).
  8. 8. Method according to one of claims 1 to 7, characterized in that the electric power for preheating of the fuel cell system (2) is transferred to the vehicle (1) from an external power source (31), such as an electric power grid.
  9. 9. Method according to claim 8, characterized in that the electric power from the external power source (31) is also used for charging the battery (7) of the vehicle (1).
  10. 10. Method according to one of claims 1 to 9, characterized in that the departure time (tD) is set by a user of the vehicle (1) directly in the vehicle (1), via a remote control system and/or via telecommunication means.
GB1512282.3A 2015-07-14 2015-07-14 Method for starting a fuel cell system Withdrawn GB2533015A (en)

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US10590942B2 (en) 2017-12-08 2020-03-17 Toyota Motor Engineering & Manufacturing North America, Inc. Interpolation of homotopic operating states
US10665875B2 (en) 2017-12-08 2020-05-26 Toyota Motor Engineering & Manufacturing North America, Inc. Path control concept
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US10871519B2 (en) 2017-11-07 2020-12-22 Toyota Motor Engineering & Manufacturing North America, Inc. Fuel cell stack prediction utilizing IHOS
US10916788B2 (en) 2019-01-31 2021-02-09 Toyota Jidosha Kabushiki Kaisha Hydrogen supply system low pressure state estimator
US10971748B2 (en) 2017-12-08 2021-04-06 Toyota Motor Engineering & Manufacturing North America, Inc. Implementation of feedforward and feedback control in state mediator
US10985391B2 (en) 2018-03-06 2021-04-20 Toyota Motor Engineering & Manufacturing North America, Inc. Real time iterative solution using recursive calculation
CN113135104A (en) * 2020-01-16 2021-07-20 奥迪股份公司 Charging method for electric vehicle
US11482719B2 (en) 2017-12-08 2022-10-25 Toyota Jidosha Kabushiki Kaisha Equation based state estimate for air system controller

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10871519B2 (en) 2017-11-07 2020-12-22 Toyota Motor Engineering & Manufacturing North America, Inc. Fuel cell stack prediction utilizing IHOS
US10714767B2 (en) 2017-12-07 2020-07-14 Toyota Motor Engineering & Manufacturing North America, Inc. Fuel cell air system safe operating region
US10590942B2 (en) 2017-12-08 2020-03-17 Toyota Motor Engineering & Manufacturing North America, Inc. Interpolation of homotopic operating states
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US10971748B2 (en) 2017-12-08 2021-04-06 Toyota Motor Engineering & Manufacturing North America, Inc. Implementation of feedforward and feedback control in state mediator
US11482719B2 (en) 2017-12-08 2022-10-25 Toyota Jidosha Kabushiki Kaisha Equation based state estimate for air system controller
US10985391B2 (en) 2018-03-06 2021-04-20 Toyota Motor Engineering & Manufacturing North America, Inc. Real time iterative solution using recursive calculation
US10547070B2 (en) 2018-03-09 2020-01-28 Toyota Motor Engineering & Manufacturing North America, Inc. STL actuation-path planning
US10916788B2 (en) 2019-01-31 2021-02-09 Toyota Jidosha Kabushiki Kaisha Hydrogen supply system low pressure state estimator
DE102019208313A1 (en) * 2019-06-07 2020-12-10 Audi Ag Method for starting a fuel cell device and fuel cell device
CN113135104A (en) * 2020-01-16 2021-07-20 奥迪股份公司 Charging method for electric vehicle
CN113135104B (en) * 2020-01-16 2024-10-11 奥迪股份公司 Charging method for electric vehicle

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