A method for evaluating cold start capability of proton exchange membrane fuel cell stack

Abstract

The present invention relates to a method for evaluating the cold start capability of a fuel cell. The method comprises the following steps: 1) setting a maximum cell voltage deviation δ allowed by a fuel cell stack; max and cathode stoichiometric ratio SR c , when the cell voltage deviation δ≤δ max Under the condition of SRc and water production rate R WSRc ; 2) Using Q SRc =P SRc / R WSRc , and obtain the water heating value Q of the stack SRc ; 3) Use #imgabs0# to obtain the cold start capability index Per of the stack cs value, the Per cs The larger the value, the stronger the cold start capability of the stack. The method comprehensively evaluates the cold start capability of the stack through the relationship between the heating power, the water production rate and the water heating value, is not limited to the stack sequence and the manufacturer, and provides theoretical support, which can be used as a general method.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and specifically to a method for evaluating the cold start capability of a proton exchange membrane fuel cell stack. Background Technology

[0002] Fuel cells offer advantages such as high efficiency, low emissions, zero pollution, and diverse fuel sources, making them promising for applications in automobiles, aircraft, submarines, and communications. Particularly in the automotive sector, fuel cell vehicles, with their zero emissions, rapid refueling, and long driving range, have become a crucial future direction for new energy vehicles. However, fuel cells are prone to freezing at low ambient temperatures, leading to malfunctions or forced shutdowns after only a short period. Repeated restarts can damage the internal structure of the fuel cell, severely impacting its lifespan. Therefore, research on the cold-start capability of fuel cell stacks has become a hot topic.

[0003] Currently, research on cold start of fuel cell stacks mainly focuses on two aspects. One aspect is the research on cold start capability testing systems. For example, CN104111425A discloses a fuel cell cold start zone performance testing system and method. The testing system includes a fuel cell, an oxidant supply unit, a fuel supply unit, a clamping unit, a humidification unit, a cooling pipe, a high and low temperature chamber, a zone test plate, a load unit, a data acquisition unit, and a data processing unit. The testing method involves: replacing the anode plate of the fuel cell with the zone test plate; raising the temperature inside the high and low temperature chamber to the set low temperature environment temperature; supplying oxidant and fuel to the fuel cell to enable it to operate normally; the data acquisition unit collects the voltage drop across each embedded resistor, the voltage of each temperature resistor, and the current flowing through the temperature resistor in real time; and the data processing unit calculates the current density distribution of each zone inside the fuel cell and the zone temperature at each moment based on the received signals, obtaining a current density distribution map and a temperature distribution map.

[0004] CN108562783A discloses a zoned testing system for cold start current density and temperature of a fuel cell. The fuel cell system includes a fuel cell, thermocouples, an ice bath, an intake system module, a high-low temperature alternating chamber, cooling pipes, a data acquisition module, a data processing module, and a load. The testing method involves placing a current density test plate at the anode; both the cathode flow field plate and the cathode end plate have insertion holes into which the thermocouples are placed; the ice bath provides cold junction compensation for the thermocouples; the temperature inside the high-low temperature alternating chamber is set to the ambient temperature for cold start; the intake system module provides oxidant and fuel to the fuel cell and connects to the load to enable normal operation; the data acquisition module acquires the voltage of the sampling resistor and the thermoelectric potential of the thermocouples; and the data processing module converts the acquired signals into current density distribution maps and temperature distribution maps of the fuel cell at various times.

[0005] CN208060677U discloses a low-temperature cold start test research platform for fuel cell stacks, including a reducing agent supply device for supplying reducing agent, an oxidant supply device for supplying oxidant, and a coolant system for supplying coolant. The research platform also includes a high and low temperature environment test chamber for adjusting the ambient temperature of the fuel cell stack. The fuel cell stack is placed in the high and low temperature environment test chamber. The oxidant supply device is connected to the oxidant input end of the fuel cell stack, the reducing agent supply device is connected to the output end of the fuel cell stack, and the coolant system is connected to the coolant input end and coolant output end of the fuel cell stack. Temperature and humidity control devices are provided between the reducing agent supply device and the oxidant supply device and the fuel cell stack.

[0006] On the other hand, there is research on cold start capability testing methods, such as the national standard GB / T 31035-2014 Test Method for Low Temperature Characteristics of Proton Exchange Membrane Fuel Cell Stacks, which provides relevant test methods. The evaluation of low temperature start characteristics mainly considers three aspects: the time from power output to idle state, the time from idle state to rated power output, and the time from rated power output to peak power output.

[0007] The European Federal Institute for Fuel Cells and Hydrogen Joint Undertaking (FCH) has published a test method for low-temperature fuel cell stacks (see FCH: Test Module P-06: Low Temperature Test). Its goal is to obtain information on fuel cell stack startup and operation at low temperatures based on coolant loop parameters and environmental conditions. The main test measure is the time t required for the fuel cell stack to reach 50% of its rated power during startup at low temperatures. 50％ and the time t required to reach 100% rated power 100％ And record the temperature T of the fuel cell stack when the corresponding operating point is reached. 50％ and T 100％ .

[0008] CN111199110A discloses a method and system for predicting the low-temperature start-up performance of a fuel cell. The method involves establishing a low-temperature start-up model of the fuel cell, inputting the stack parameters, environmental parameters, and operating conditions of the fuel cell to be predicted into the model. The low-temperature start-up model outputs the low-temperature start-up performance and internal state distribution of the fuel cell to be predicted. However, this patent actually provides a simulation calculation method for the cold start performance of a fuel cell. This simulation method requires multiple parameters, including internal geometry and various physicochemical properties, during the calculation process. For non-independently developed fuel cell stacks, many of these parameters are unavailable. Furthermore, the simulation model has certain limitations in its applicability; outside of its applicable range, its accuracy cannot be guaranteed, thus significantly affecting its scope of use.

[0009] The aforementioned literature all demonstrates the testing or evaluation of the cold-start capability of fuel cell stacks. However, current evaluation methods are still in a relatively rudimentary state, lacking both a unified evaluation methodology and sufficient theoretical support. Different manufacturers often employ different start-up procedures under specific low-temperature conditions for their stack products, ultimately evaluating their low-temperature start-up capability based on the stack's minimum start-up temperature and start-up time. This makes the cold-start performance incomparable between products from different manufacturers, and even between different product lines from the same manufacturer.

[0010] Based on existing research, how to develop a general method that can comprehensively evaluate the cold-start capability of fuel cell stacks, without being limited by stack series or manufacturers, and at the same time provide theoretical support, has become an urgent technical problem to be solved. Summary of the Invention

[0011] In view of the problems existing in the prior art, the present invention provides a method for evaluating the cold start capability of a proton exchange membrane fuel cell stack. This method comprehensively extracts the intrinsic correlation between differences in cold start capability from the perspectives of stack heat generation capacity, water production, and stack thermal mass, and obtains the stack's cold start capability index Per. cs Value, through Per cs This method assesses the cold start capability of fuel cell stacks without being limited by stack series or manufacturers, and provides theoretical support. It can serve as a general method for evaluating the cold start capability of fuel cell stacks and has high practical value.

[0012] To achieve this objective, the present invention provides the following technical solution:

[0013] This invention provides a method for evaluating the cold start capability of a fuel cell stack, particularly a method for evaluating the cold start capability of a proton exchange membrane fuel cell stack, the method comprising the following steps:

[0014] (1) Set the maximum allowable single-cell voltage deviation δ of the fuel cell stack. max and cathode metering ratio SR c When the voltage deviation δ of a single unit does not exceed the maximum voltage deviation δ max Under the given conditions, the fuel cell stack is operated to obtain the minimum permissible total output voltage value V of the fuel cell stack. SRc and the corresponding current value I SRc ;

[0015] (2) Using V SRc and I SRc The cathode metering ratio SR is obtained. c The heat output power P of the lower fuel cell stack SRc and water production rate R WSRc ;

[0016] (3) Utilizing the heating power P SRc and water production rate R WSRc The cathode metering ratio SR is calculated using the formula shown in equation (1). c Water heat tracing value Q of the lower fuel cell stack SRc ;

[0017] Q SRc =P SRc / R WSRc (1)

[0018] (4) Utilizing the water heat tracing value Q SRc The cold start capability index Per of the fuel cell stack is calculated using the formula shown in equation (2). cs value;

[0019]

[0020] Where, N cell N is the number of individual cells in the fuel cell stack. cell ≥1; A is the active surface area of ​​the monomer; C stack It is the average heat capacity of the fuel cell stack;

[0021] The Per cs The higher the value, the stronger the cold start capability of the fuel cell stack.

[0022] In this invention, the maximum allowable single-unit voltage deviation δ of the fuel cell stack max The δ value is set according to the requirements of the fuel cell stack manufacturer and the actual application needs. max It requires that the measured δ value under any operating condition should not exceed δ. max .

[0023] In this invention, the water heat tracing value is a custom term that refers to the heat generated by the fuel cell stack while generating a unit mass of water, and the unit is J / g.

[0024] In this invention, the voltage deviation δ of a single cell is controlled to not exceed the maximum voltage deviation δ. max This ensures the normal operation of the fuel cell stack; the heating power determines the heat generation capacity of the stack. The higher the heating power, the faster the stack can raise the temperature. Therefore, the higher the value, the more beneficial it is for the cold start process; the water production rate refers to the mass of water produced by the stack per second. When the amount of water produced is small, it can be discharged in time through flow or absorbed by the membrane even at low temperatures (below zero). However, when the amount of water produced is large, liquid water will remain in parts such as the proton exchange membrane, catalyst layer, microporous layer, gas diffusion layer, and flow channel, which may freeze at low temperatures, hindering or preventing the smooth progress of the cold start process.

[0025] In this invention, the water tracing value of the fuel cell stack is obtained by studying the relationship between the heating power of the stack and the water production rate. This water tracing value essentially characterizes the heat generated by the stack while producing a unit mass of water. A higher value indicates a faster temperature rise at or near the water production location, which is more conducive to timely water discharge and less prone to freezing. Then, the cold start capability index Per of the fuel cell stack is obtained through the average heat capacity of the stack. cs Value, through Per cs The value is used to evaluate the cold start capability of the fuel cell stack.

[0026] In this invention, the method comprehensively extracts the intrinsic correlation between differences in cold start capability from the perspectives of fuel cell stack heat generation capacity, water generation, and fuel cell stack thermal quality. It is not limited by fuel cell stack series or manufacturers, and provides theoretical support. It can be used as a general method for evaluating fuel cell stack cold start capability and has high practical value.

[0027] Preferably, the single-unit voltage deviation δ in step (1) is calculated using the formula described in equation (3).

[0028] δ=V mean -V min (3)

[0029] Among them, V mean It is the average value of the voltages of all individual cells in the fuel cell stack; V min It is the lowest value of all individual cell voltages in the fuel cell stack.

[0030] That is, the individual cell voltage deviation δ represents the average value V of the voltage of all individual cells in the stack. mean With the lowest value of single-unit voltage V min The difference.

[0031] In this invention, at least two different cathode metering ratios S are set. Rc Conducting tests helps improve the accuracy of the evaluation. During the fuel cell stack test, the air flow and other test conditions are kept constant, and only the cathode metering ratio is changed.

[0032] Preferably, the cathode metering ratio SR in step (1) c The value is 1-2.5, for example, it can be 1, 1.05, 1.08, 1.1, 1.2, 1.5, 1.7, 1.9, 2, 2.2 or 2.5, etc., preferably 1.05-1.8.

[0033] Preferably, step (1) involves setting the cathode metering ratio SR. c The number of groups n≥2, for example, can be 2, 3, 5, 8, 10, 15, 18 or 20, preferably 3-10, and more preferably 4-8.

[0034] Preferably, the heating power P in step (2) SRc The result is obtained using the formula shown in equation (4), and the unit is W.

[0035] P SRc =(V HHV -V SRc )×I SRc (4)

[0036] Among them, V SRc and I SRc These are the cathode metering ratios SR and SR. c Below, the minimum permissible total output voltage and corresponding current value of the fuel cell stack; V HHV It is the high calorific value potential of the fuel cell stack.

[0037] The high calorific value potential refers to the equivalent voltage generated from the high calorific value of hydrogen, which is approximately 1.481V.

[0038] Preferably, the water production rate R in step (2) WSRc The result is obtained using the formula described in equation (5), with the unit being g / s.

[0039]

[0040] in, is the molar mass of water; F is the Faraday constant.

[0041] As a preferred technical solution of the present invention, step (3) involves obtaining at least two sets of different cathode metering ratios SR. c The heat tracing value Q of the water below SRc The maximum value is defined as the characteristic water tracing value of the fuel cell stack. The characteristic water heat tracing value It is an inherent property of the fuel cell stack, representing the upper limit of heat that the stack under test can generate when producing a unit mass of water. Because the water heat tracing value of the stack will vary under different cathode metering ratios, the accuracy of evaluating the cold start capability of the fuel cell stack can be improved by setting and testing characteristic water heat tracing values.

[0042] Preferably, step (3) involves obtaining 3-10 groups of different cathode metering ratios (SR). c The heat tracing value Q of the water below SRc Preferably, 4-8 groups of different cathode metering ratios SR are obtained. c The heat tracing value Q of the water below SRc .

[0043] Preferably, the cold start capability index Per in step (4) cs The value is obtained using the formula shown in equation (6).

[0044]

[0045] in, This is the characteristic water heat tracing value of the fuel cell stack, expressed in J / g; N cell N is the number of individual cells in the fuel cell stack. cell ≥1; A is the active surface area of ​​the monomer, in cm². 2 C stack It is the average heat capacity of the fuel cell stack, expressed in J / ℃.

[0046] In this invention, C stack The data source is not specifically limited; it can be measured or estimated. Any data source commonly used by those skilled in the art is applicable to this invention.

[0047] In this invention, the method is applicable to single cells or fuel cell stacks, N cell The number of cells can be 1, 3, 10, 20, 100, 500, 1000, or 10000, etc. The method is not limited by the number of cells, the stack sequence, or the manufacturer. As long as it is a proton exchange membrane fuel cell stack in the art, it is applicable to this invention.

[0048] Preferably, the N in step (4) cell The range is 3-5000, for example, it can be 3, 5, 10, 50, 100, 300, 500, 1000, 2000, 3000, 4000, 4500 or 5000, etc., preferably 50-1000.

[0049] In this invention, the N cellWhen the temperature is ≤50°C, the exposed surface of the fuel cell stack is too large relative to its volume, which will cause the endplate of the fuel cell stack to dissipate heat too quickly, reducing the ability to start coldly at low temperatures. In order to improve the accuracy of the cold start capability assessment, equation (6) needs to be modified.

[0050] Preferably, the N in step (4) cell ≤50, the formula (6) also includes a correction term B, which is obtained using the formula shown in (7).

[0051] B = N cell / 50 (7)

[0052] As a preferred technical solution of the present invention, the formula (2) in step (4) further includes the film electrode thickness correction index X. m Dimensionless, the X m It is obtained using the formula shown in (8).

[0053] X m =d m / d0 (8)

[0054] Where, d m d0 is the thickness of the CCM in the single-cell membrane electrode of the fuel cell stack; d0 is a constant, preferably a common thickness of CCM used in the single-cell membrane electrode of the fuel cell stack currently on the market.

[0055] In this invention, the membrane electrode thickness correction index is used to take into account the water absorption effect of ionomers in the membrane electrode. For example, when the CCM area is large and thick, it can absorb more water, and the membrane water can exist at a lower temperature without freezing, which is beneficial to the cold start process.

[0056] In this invention, the CCM refers to a three-layer structure comprising an anode catalyst layer, a proton exchange membrane, and a cathode catalyst layer.

[0057] Preferably, d0 is 30 μm.

[0058] Preferably, the d m When X cannot be obtained, m Take 1.

[0059] As a more preferred technical solution of the present invention, the cold start capability index Per in step (3) cs The value is obtained using the formula shown in equation (9).

[0060]

[0061] Among them, X m It is the film electrode thickness correction index.

[0062] Preferably, the N in step (4) cell≤50, the cold start capability index Per cs The value is obtained using the formula shown in equation (10).

[0063]

[0064] As a further preferred technical solution of the present invention, the method includes the following steps:

[0065] (1) Set the maximum allowable individual voltage deviation δ of the fuel cell stack. max And 3-10 different cathode metering ratios SR c When the voltage deviation δ of a single unit does not exceed the maximum voltage deviation δ max Under the conditions, the SR c By taking any value between 1.05 and 1.8, and operating the fuel cell stack, different cathode metering ratios SR were obtained. c Minimum permissible total output voltage V of the lower fuel cell stack SRc and the corresponding current value I SRc ;

[0066] (2) Using V SRc and I SRc Different cathode stoichiometric ratios SR were obtained. c The heat output power P of the lower fuel cell stack SRc and water production rate R WSRc ;

[0067] The individual voltage deviation δ is calculated using the formula shown in equation (3);

[0068] δ=V mean -V min (3)

[0069] The heating power P SRc It is calculated using the formula shown in equation (4);

[0070] P SRc =(V HHV -V SRc )×I SRc (4)

[0071] The water production rate R WSRc It is calculated using the formula described in equation (5);

[0072]

[0073] (3) The heating power P obtained in step (2) SRc and water production rate R WSRc Substituting into the formula shown in equation (1), we obtain the different cathode stoichiometric ratios SR. c Water heat tracing value Q of the lower fuel cell stackSRc The maximum value is taken as the characteristic water tracing value of the electric stack.

[0074] Q SRc =P SRc / R WSRc (1)

[0075] (4) The characteristic water heating value obtained in step (2) Substituting into the formulas shown in equation (9) or (10), the cold start capability index Per of the fuel cell stack is obtained. cs value;

[0076]

[0077]

[0078] The Per cs The higher the value, the stronger the cold start capability of the fuel cell stack.

[0079] Compared with the prior art, the present invention has at least the following beneficial effects:

[0080] (1) The evaluation method provided by the present invention, through the relationship between heating power, water production rate and the water tracing value of the electric stack, comprehensively extracts the intrinsic correlation of the difference in cold start capability from the perspectives of electric stack heat production capacity, water production amount and electric stack thermal quality. It is not limited by electric stack series and manufacturers, and provides theoretical support. It can be used as a general method for evaluating the cold start capability of electric stacks.

[0081] (2) The evaluation method provided by the present invention further improves the accuracy and feasibility of the evaluation method by adjusting the number of groups of cathode metering ratio, the selection of characteristic water heat tracing value of fuel cell stack, and the correction of film thickness correction index. Attached Figure Description

[0082] Figure 1 This is a flowchart of the cold start capability evaluation method provided by the present invention. Detailed Implementation

[0083] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. The technical means adopted by the present invention to achieve the intended technical effect are described in detail below.

[0084] This invention provides a method for evaluating the cold start capability of a fuel cell stack, the flowchart of which is shown below. Figure 1 As shown. The maximum allowable individual cell voltage deviation δ of the fuel cell stack is set. max Individual voltage deviation δ = V mean -V min , when δ≤δmax Under these conditions, keeping other conditions constant, the cathode metering ratio SR is set. c The corresponding cathode metering ratios SR were obtained from the values ​​of 1.8, 1.6, 1.4, 1.2, 1.1, and 1.05. c Minimum permissible total output voltage V of the fuel cell stack SRc and the corresponding current value I SRc The corresponding cathode metering ratio SR is calculated according to equation (4). c The heat output power P of the lower fuel cell stack SRc The corresponding cathode metering ratio S is calculated according to equation (5). Rc Water production rate R of the lower fuel cell stack WSRc Then, calculate the water tracing value Q according to formula (1). SRc To determine or estimate the average heat capacity C of the fuel cell stack. stack Finally, the cold start capability index Per of the fuel cell stack is calculated according to equation (8). cs Value, the Per cs The higher the value, the stronger the cold start capability of the fuel cell stack.

[0085] Example 1

[0086] This embodiment provides a method for evaluating the cold start capability of a fuel cell stack, the method comprising the following steps:

[0087] (1) Provide a fuel cell stack of model MR1, wherein the number of individual cells of the stack is N. cell The value is 370, and the active surface area of ​​the monomer is 267 cm². 2 The bipolar plates used in this fuel cell stack are made of titanium alloy.

[0088] (2) Set the maximum allowable single-unit voltage deviation δ of the fuel cell stack. max =0.1V, with cathode metering ratios set to 1.8, 1.6, 1.4, 1.2, 1.1, and 1.05, the fuel cell stack was operated to obtain the minimum permissible total output voltage V of the stack under the corresponding cathode metering ratio. SRc and the corresponding current value I SRc The heating power P is calculated using equations (4) and (5). SRc and water production rate R WSRc ;

[0089] P SRc =(V HHV -V SRc )×I SRc (4)

[0090]

[0091] (3) The maximum water heat tracing value was calculated using formula (1) and the result was 11042.2 J / g;

[0092] Q SRc =P SRc / R WSRc (1)

[0093] (4) The average heat capacity of the fuel cell stack was measured to be 28000 J / ℃, and the CCM thickness d of the fuel cell stack was measured to be... m The cold start capability index Per of the fuel cell stack is calculated using Equation (9) with a diameter of 30 μm. cs The value is 3.89.

[0094]

[0095] Example 2

[0096] This embodiment provides a method for evaluating the cold start capability of a fuel cell stack, the method comprising the following steps:

[0097] (1) Provide a fuel cell stack of model NM1, wherein the number of individual cells of the stack is N. cell The value is 300, and the active surface area of ​​the monomer is 190 cm². 2 The bipolar plates used in this fuel cell stack are made of stainless steel.

[0098] (2) Set the maximum allowable single-unit voltage deviation δ of the fuel cell stack. max =0.05V, with cathode metering ratios set to 2.4, 2.2, 1.8, 1.6 and 1.4 respectively, the fuel cell stack is operated to obtain the minimum allowable total output voltage V of the fuel cell stack under the corresponding cathode metering ratio. SRc and the corresponding current value I SRc The heating power P is calculated using equations (4) and (5). SRc and water production rate R WSRc ;

[0099] P SRc =(V HHV -V SRc )×I SRc (4)

[0100]

[0101] (3) The maximum water heat tracing value was calculated using formula (1) and the result was 8898.1 J / g;

[0102] Q SRc =P SRc / R WSRc (1)

[0103] (4) The average heat capacity of the fuel cell stack was measured to be 16155.48 J / ℃, and the CCM thickness d of the fuel cell stack was... mThe cold start capability index Per of the fuel cell stack is calculated using Equation (9) with a diameter of 30 μm. cs The value is 3.14.

[0104]

[0105] Example 3

[0106] This embodiment provides a method for evaluating the cold start capability of a fuel cell stack, the method comprising the following steps:

[0107] (1) Provide a fuel cell stack of model SM1, wherein the number of individual cells of the stack is N. cell The value is 350, and the active surface area of ​​the monomer is 250 cm². 2 The bipolar plates used in this fuel cell stack are made of graphite.

[0108] (2) Set the maximum allowable single-unit voltage deviation δ of the fuel cell stack. max =0.1V, with cathode metering ratios set to 1.8, 1.6, 1.4, 1.2, 1.1, and 1.05, the fuel cell stack was operated to obtain the minimum permissible total output voltage V of the stack under different cathode metering ratios. SRc and the corresponding current value I SRc The heating power P is calculated using equations (4) and (5). SRc and water production rate R WSRc ;

[0109] P SRc =(V HHV -V SRc )×I SRc (4)

[0110]

[0111] (3) The maximum water heat tracing value is calculated using formula (1) and the maximum water heat tracing value is 10020 J / g;

[0112] Q SRc =P SRc / R WSRc (1)

[0113] (4) The average heat capacity of the fuel cell stack was measured to be 37200.12 J / ℃, and the CCM thickness d of the fuel cell stack was measured to be... m The cold start capability index Per of the fuel cell stack is calculated using Equation (9) with a diameter of 30 μm. cs The value is 2.36.

[0114]

[0115] Example 4

[0116] This embodiment provides a method for evaluating the cold start capability of a fuel cell stack, the method comprising the following steps:

[0117] (1) A fuel cell stack of model MR2 is provided, which differs from Example 1 in that the CCM thickness d of this stack is [not specified]. m It is 40μm;

[0118] (2) Set the maximum allowable single-unit voltage deviation δ of the fuel cell stack. max =0.1V, with cathode metering ratios set to 1.8, 1.6, 1.4, 1.2, 1.1, and 1.05, the fuel cell stack was operated to obtain the minimum permissible total output voltage V of the stack under different cathode metering ratios. SRc and the corresponding current value I SRc The heating power P is calculated using equations (4) and (5). SRc and water production rate R WSRc ;

[0119] P SRc =(V HHV -V SRc )×I SRc (4)

[0120]

[0121] (3) The maximum water heat tracing value was calculated using formula (1) and the result was 10538.2 J / g;

[0122] Q SRc =P SRc / R WSRc (1)

[0123] (4) The average heat capacity of the fuel cell stack was measured to be 29800 J / ℃. Then, the cold start capability index Per of the fuel cell stack was calculated using equation (9). cs The value is 4.65.

[0124]

[0125] A comparison of this embodiment and Embodiment 1 shows that different CCM thicknesses d can be set according to actual conditions. m This helps improve the accuracy of assessing the cold start capability of the fuel cell stack.

[0126] Example 5

[0127] This embodiment provides a method for evaluating the cold start capability of a fuel cell stack, the method comprising the following steps:

[0128] (1) A fuel cell stack of model MR3 is provided, which differs from Example 1 in that the maximum allowable single-cell voltage deviation δmax =0.05V;

[0129] (2) Set the cathode metering ratios to 1.8, 1.6, 1.4, 1.2, 1.1 and 1.05 respectively, operate the fuel cell stack, and obtain the minimum allowable total output voltage V of the fuel cell stack under different cathode metering ratios. SRc and the corresponding current value I SRc The heating power P is calculated using equations (4) and (5). SRc and water production rate R WSRc ;;

[0130] P SRc =(V HHV -V SRc )×I SRc (4)

[0131]

[0132] (3) The maximum water heat tracing value was calculated using formula (1) and the result was 8165 J / g.

[0133] Q SRc =P SRc / R WSRc (1)

[0134] (4) The average heat capacity of the fuel cell stack was measured to be 28000 J / ℃. Then, the cold start capability index Per of the fuel cell stack was calculated using equation (9). cs The value is 2.88.

[0135]

[0136] A comparison between this embodiment and Embodiment 1 shows that the maximum allowable individual cell voltage deviation δ of the fuel cell stack is set according to the actual situation. max This helps improve the accuracy of assessing the cold start capability of the fuel cell stack.

[0137] Example 6

[0138] This embodiment provides a method for evaluating the cold start capability of a fuel cell stack, the method comprising the following steps:

[0139] (1) A fuel cell stack of model MR4 is provided, which differs from Example 1 in that the number of individual cells N in this stack is [not specified]. cell It is 200;

[0140] (2) Set the maximum allowable single-unit voltage deviation δ of the fuel cell stack. max=0.1V, with cathode metering ratios set to 1.8, 1.6, 1.4, 1.2, 1.1, and 1.05, the fuel cell stack was operated to obtain the minimum permissible total output voltage V of the stack under different cathode metering ratios. SRc and the corresponding current value I SRc The heating power P is calculated using equations (4) and (5). SRc and water production rate R WSRc ;

[0141] P SRc =(V HHV -V SRc )×I SRc (4)

[0142]

[0143] (3) The maximum water heat tracing value was calculated using formula (1) and the result was 11245.3 J / g;

[0144] Q SRc =P SRc / R WSRc (1)

[0145] (4) The average heat capacity of the fuel cell stack was measured to be 15135.14 J / ℃. Then, the cold start capability index Per of the fuel cell stack was calculated using equation (9). cs The value is 3.97.

[0146]

[0147] A comparison of this embodiment and Embodiment 1 shows that the number of individual fuel cell units N in this embodiment can be set according to the actual situation. cell This helps improve the accuracy of assessing the cold start capability of the fuel cell stack.

[0148] Example 7

[0149] This embodiment provides a method for evaluating the cold start capability of a fuel cell stack, the method comprising the following steps:

[0150] (1) A fuel cell stack of model MR5 is provided, which differs from Example 1 in that the active area of ​​a single unit of the stack is 200 cm². 2 ;

[0151] (2) Set the maximum allowable single-unit voltage deviation δ of the fuel cell stack. max =0.1V, with cathode metering ratios set to 1.8, 1.6, 1.4, 1.2, 1.1, and 1.05, the fuel cell stack was operated to obtain the minimum permissible total output voltage V of the stack under different cathode metering ratios. SRc and the corresponding current value I SRcThe heating power P is calculated using equations (4) and (5). SRc and water production rate R WSRc ;

[0152] P SRc =(V HHV -V SRc )×I SRc (4)

[0153]

[0154] (3) The maximum water heat tracing value is calculated using formula (1) and the maximum water heat tracing value is 10500 J / g;

[0155] Q SRc =P SRc / R WSRc (1)

[0156] (4) The average heat capacity of the fuel cell stack was measured to be 20973.78 J / ℃. Then, the cold start capability index Per of the fuel cell stack was calculated using equation (9). cs The value is 3.70.

[0157]

[0158] A comparison of this embodiment and Embodiment 1 shows that setting the individual active area A of the fuel cell stack according to the actual situation is beneficial to improving the accuracy of evaluating the cold start capability of the fuel cell stack.

[0159] Example 8

[0160] This embodiment provides a method for evaluating the cold start capability of a fuel cell stack, the method comprising the following steps:

[0161] (1) A fuel cell stack of model NM2 was provided. Unlike Example 2, the cathode metering ratios were set to 1.8, 1.6, 1.4, 1.2, 1.1 and 1.05 during the test. The stack was operated to obtain the minimum allowable total output voltage V of the stack under different cathode metering ratios. SRc and the corresponding current value I SRc The heating power P is calculated using equations (4) and (5). SRc and water production rate R WSRc ;

[0162] P SRc =(V HHV -V SRc )×I SRc (4)

[0163]

[0164] (2) The maximum water heat tracing value was calculated using formula (1) and the result was 9002 J / g;

[0165] Q SRc =P SRc / R WSRc (1)

[0166] (4) The average heat capacity of the fuel cell stack was measured to be 16155.48 J / ℃. Then, the cold start capability index Per of the fuel cell stack was calculated using equation (9). cs The value is 3.18.

[0167]

[0168] A comparison of this embodiment and Embodiment 2 shows that the selection of the cathode metering ratio during testing can affect the final calculation result of the cold start capability index. Therefore, selecting a reasonable cathode metering ratio is beneficial to improving the accuracy of evaluating the cold start capability of the fuel cell stack.

[0169] Example 9

[0170] This embodiment provides a method for evaluating the cold start capability of a fuel cell stack, the method comprising the following steps:

[0171] (1) A fuel cell stack of model NM3 is provided, which differs from Example 2 in that the number of individual cells N in the stack is [not specified]. cell With a voltage rating of 24, the lowest permissible total output voltage V of the fuel cell stack was obtained under different cathode metering ratios. SRc and the corresponding current value I SRc The heating power P is calculated using equations (4) and (5). SRc and water production rate R WSRc ;

[0172] P SRc =(V HHV -V SRc )×I SRc (4)

[0173]

[0174] (2) The maximum water heat tracing value was calculated using formula (1) and the result was 9105 J / g;

[0175] Q SRc =P SRc / R WSRc (1)

[0176] (3) The average heat capacity of the fuel cell stack was measured to be 1292.4 J / ℃. Then, the cold start capability index Per of the fuel cell stack was calculated using equation (10). csThe value is 1.54.

[0177]

[0178] A comparison of this embodiment and Embodiment 2 shows that changing the number of individual fuel cell units affects the assessment of cold start capability. This is because when the number of individual fuel cell units is too low, the exposed surface of the fuel cell is too large relative to its volume, leading to excessively rapid heat dissipation from the endplates and reducing the cold start capability of the fuel cell. Therefore, considering the number of individual fuel cell units helps improve the accuracy of assessing the cold start capability of the fuel cell.

[0179] In summary, the evaluation method provided by this invention, through the relationship between heating power, water production rate, and fuel cell stack water tracing value, comprehensively extracts the intrinsic correlation of cold start capability differences from the perspectives of fuel cell stack heat production capacity, water generation, and fuel cell stack thermal mass, and obtains the fuel cell stack cold start capability index Per. cs Value, through Per cs This method assesses the cold start capability of fuel cell stacks without being limited by stack series or manufacturers, and provides theoretical support. It can serve as a general method for evaluating the cold start capability of fuel cell stacks and has high practical value.

[0180] The applicant declares that the detailed structural features of the present invention are illustrated through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components selected in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for evaluating the cold start capability of a fuel cell stack, characterized in that: The method comprises the following steps: (1) Setting the maximum cell voltage deviation allowed by the fuel cell stack and cathode stoichiometry , the cell voltage deviation Do not exceed the maximum voltage deviation Under the condition of ; (2) Utilization and , the cathode stoichiometric ratio is calculated Heat generation power of the lower battery stack and water production rate ; (3) Utilizing heat generation power and water production rate , and formula (1) to calculate the cathode stoichiometric ratio Water heating value Q of lower stack SRc ; （1） (4) Using water heating value Q SRc , and formula (2), the cold start capability index of the stack is calculated value; （2） in, is the number of cells in the stack, ≥1; is the active area of ​​the monomer; is the average heat capacity of the stack; Said The larger the value, the stronger the cold start capability of the stack; The cell voltage deviation in step (1) Calculated using formula (3); （3） in, It is the average value of all cell voltages in the battery stack; It is the lowest value of all single cell voltages in the battery stack.

2. The method according to claim 1, characterized in that Step (1) The cathode stoichiometric ratio It is 1-2.

5.

3. The method according to claim 1, characterized in that Step (1) The cathode stoichiometric ratio It is 1.05-1.

8.

4. The method according to claim 1, characterized in that: Step (1) Setting cathode stoichiometric ratio The number of groups n≥2.

5. The method according to claim 4, characterized in that Step (1) Setting cathode stoichiometric ratio The number of groups n is 3-10.

6. The method according to claim 5, characterized in that Step (1) Setting cathode stoichiometric ratio The number of groups n is 4-8.

7. The method according to claim 1, characterized in that The heating power in step (2) Calculated using formula (4); （4）； in, and The cathode stoichiometric ratio is The minimum allowable total output voltage value and corresponding current value of the battery stack; It is the high heating value potential of the battery stack.

8. The method according to claim 1, characterized in that The water production rate in step (2) Calculated using formula (5); （5） in, is the molar mass of water; F is the Faraday constant.

9. The method according to claim 1, characterized in that: Step (3) Obtain at least two groups of different cathode stoichiometric ratios Water heating value under , the maximum value is defined as the characteristic water heating value of the stack .

10. The method according to claim 1, characterized in that Step (3) Obtain 3-10 groups of different cathode stoichiometric ratios Water heating value under .

11. The method according to claim 10, characterized in that Step (3) Obtain 4-8 groups of different cathode stoichiometric ratios Water heating value under .

12. The method according to claim 1, characterized in that Step (4) Cold start capability index The value is obtained using formula (6); （6） in, is the characteristic water heating value of the stack; is the number of cells in the stack, ≥1; is the active area of ​​the monomer; is the average heat capacity of the battery stack.

13. The method according to claim 1, characterized in that Step (4) 3-5000.

14. The method according to claim 1, characterized in that Step (4) It is 50-1000.

15. The method according to claim 12, characterized in that Step (4) ≤50, the formula (6) also includes a correction term B, which is specifically expressed as: , the correction term B is obtained using formula (7); （7）。 16. The method according to claim 1, characterized in that Step (4) The formula (2) also includes the membrane electrode thickness correction index , specifically expressed as: , Using formula (8), we can get: （8） in, is the thickness of the CCM in the single membrane electrode in the stack; is a constant.

17. The method according to claim 16, characterized in that Said Take the common thickness of CCM used in single membrane electrodes in fuel cells currently on the market.

18. The method according to claim 16, characterized in that Said Take 30μm.

19. The method according to claim 16, characterized in that Said When it is not available, Take 1.

20. The method according to claim 15, characterized in that Step (4) Cold start capability index The value is obtained using formula (9); （9） in, is the membrane electrode thickness correction index.

21. The method according to claim 16, characterized in that Step (4) ≤50, the cold start capability index The value is obtained using formula (10); （10）。 22. The method according to claim 21, characterized in that The method comprises the following steps: (1) Set the maximum cell voltage deviation allowed by the stack and 3-10 groups with different cathode stoichiometric ratios , the cell voltage deviation Do not exceed the maximum voltage deviation Under the conditions, the Take any value between 1.05-1.8, operate the stack, and obtain different cathode stoichiometric ratios The minimum allowable total output voltage of the battery stack ; (2) Utilization and , different cathode stoichiometric ratios were obtained Heat generation power of the lower battery stack and water production rate ; The cell voltage deviation Calculated using formula (3); （3） The heating power Calculated using formula (4); （4） The water production rate Calculated using formula (5); （5） (3) Substitute the heating power obtained in step (2) and water production rate , substituting into formula (1), we can get different cathode stoichiometric ratios Water heating value Q of lower stack SRc , taking the maximum value as the characteristic water heating value of the stack ; （1） (4) The characteristic water heating value obtained in step (3) Substituting into formula (9) or formula (10), the cold start capability index of the stack is obtained: value; （9） （10） Said The larger the value, the stronger the cold start capability of the fuel cell stack.

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