A method for constructing a model of an electrolytic hydrogen production system

Abstract

The present invention discloses a method for constructing an electrolytic hydrogen production system model, which includes the following sub-models: a. electrochemical model of an electrolyzer; b. power model of an electrolyzer; c. hydrogen production rate model of an electrolyzer; d. efficiency model of an electrolyzer; e. thermodynamic model of an electrolyzer; f. specific energy consumption model of an electrolyzer; g. compressor model; and h. hydrogen storage model. There is an influence relationship between the eight sub-models of the electrolyzer system. The electrolytic hydrogen production system model of the present application is scalable when applied to electrolyzers of different powers. The present invention achieves the establishment of a relatively simple and scalable electrolyzer system model while ensuring the accuracy of the model.

Description

Technical Field

[0001] The invention relates to the technical field of electrolyzer system models and relates to a method for constructing an electrolytic hydrogen production system model. Background Art

[0002] Energy is a crucial factor influencing global social, technological, and economic development. However, estimates indicate that the world's fossil fuel reserves will be completely depleted within a few decades. Furthermore, the continued use of fossil fuels is exacerbating environmental pollution, global warming, and climate change. To ensure energy security, some countries are shifting their energy sources primarily to renewable energy to meet their electricity needs. In Germany, the United Kingdom, Italy, Denmark, and other countries, wind and solar power account for over 20% of total electricity generation. Because renewable energy sources like solar and wind power are volatile and difficult to store, pollution-free and efficient energy storage methods are needed to address these challenges. Hydrogen is a recognized zero-emission clean energy carrier, achieving zero pollution from development to utilization. Therefore, water electrolysis as a green and environmentally friendly hydrogen production method has attracted widespread attention and application.

[0003] As hydrogen electrolysis systems are connected to the grid, establishing an accurate electrolyzer system model is crucial for studying the impact of the electrolyzer system on the entire system and the grid, observing its operational characteristics, and improving system stability. Furthermore, electrolyzer system models provide a foundation for research on energy management of renewable energy hydrogen production systems, as well as hydrogen production and supply chain modeling and optimization. Furthermore, electrolyzer system models can be used to select appropriate specifications for industrial applications.

[0004] Existing electrolysis hydrogen production system models have the following problems: relatively simple and easy-to-use models fail to consider certain important factors that affect model accuracy; models that consider factors that affect model accuracy more comprehensively have a more complex modeling process and cumbersome parameter calculations; and lack scalability when applied to electrolyzers of different types and powers. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for constructing an electrolysis hydrogen production system model, which can establish a relatively simple and expandable electrolyzer system model on the basis of ensuring the accuracy of the model, and provide the model requirements for the research of the electrolyzer system.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a method for constructing an electrolytic hydrogen production system model, which includes eight sub-models: a. electrochemical model of the electrolyzer; b. electrolyzer power model; c. electrolyzer hydrogen production rate model; d. electrolyzer efficiency model; e. electrolyzer thermodynamic model; f. electrolyzer specific energy consumption model; g. compressor model; h. hydrogen storage model. The specific expressions of the above sub-models are:

[0007] a Electrochemical model of electrolyzer: The voltage of alkaline and PEM electrolyzers is determined by the reversible voltage V rev , activation overpotential V act , mass transfer overpotential (concentration overpotential) V Diff , Ohmic overpotential V ohm 4-part composition, electrolytic cell voltage V=N cell V cell , N cell is the number of electrolytic units constituting the electrolytic cell, V cell is the voltage of the electrolytic cell, and the expression of the electrolytic cell voltage is as follows:

[0008] V cell =V rev +V act +V Diff +V ohm

[0009] Reversible voltage V rev Expressed as:

[0010]

[0011] Where N is the amount of transferred electrons;

[0012] Activation overpotential V act Expressed as:

[0013]

[0014] Where i is the current density of the electrolytic cell; i 0,an is the anode exchange current density; i 0,cn is the cathode exchange current density; an is the anode charge transfer function; ɑ cn is the cathode charge transfer function; T is the electrolytic cell temperature.

[0015] The electrolytic cell current density can be expressed as:

[0016]

[0017] Where z is the number of transferred electrons and R is the gas constant.

[0018] Mass transfer overpotential V Diff Expressed as:

[0019]

[0020] Where C is the gas concentration at the reaction interface; C0 is the reference gas concentration at the reaction interface.

[0021] Ohmic overpotential Vohm Expressed as:

[0022]

[0023] When the model is applied to a PEM electrolyzer, in the expression, δ = δ mem is the thickness of the proton membrane, σ=σ mem is the proton membrane conductance,

[0024]

[0025] Where, λ is the proton membrane humidity;

[0026] When the model is applied to alkaline electrolyzers, in the expression, δ = δ ele is the electrolyte thickness, σ=σ ele is the electrolyte conductivity:

[0027]

[0028] Where M is the electrolyte concentration.

[0029] b. Electrolyzer power model: electrolyzer power P = IV, where I is the electrolyzer current. This model can be expanded when modeling electrolyzers of different powers.

[0030] c Electrolyzer hydrogen production rate model: Hydrogen production rate of electrolyzer The expression is as follows:

[0031]

[0032] Among them, η F is the Faraday efficiency, z is the number of transferred electrons, and F is the Faraday constant;

[0033] dElectrolyzer efficiency model: electrolysis hydrogen production efficiency η el It is defined as the ratio of the theoretical power of hydrogen production to the actual power consumed by the electrolyzer, and the expression is as follows:

[0034]

[0035] Where ΔG is the Gibbs free energy;

[0036] e Electrolytic cell thermodynamic model: The thermodynamic model predicts the electrolytic cell temperature. By converting the thermal model, the electrolytic cell temperature can be obtained, and its expression is:

[0037]

[0038]

[0039] Where T0 is the initial temperature; Rt is the overall thermal resistance of the electrolytic cell; C t is the total heat capacity of the electrolytic cell; C cw is the heat capacity of the electrolyte; m cw is the inlet electrolyte mass flow rate; A HX is the overall heat transfer area; T a is the ambient temperature; η energy is energy efficiency; T cw,i is the inlet electrolyte temperature;

[0040] fElectrolytic cell specific energy consumption model: specific energy consumption E of electrolytic cell s According to the instantaneous voltage v(t), instantaneous electrolysis current i(t) and hydrogen production rate n H2 To calculate:

[0041]

[0042] Where m H2 is the mass flow rate of hydrogen; M is the molar mass of hydrogen molecules (M = 2g / mol). The higher calorific value of hydrogen is 39.4kWh / kg, which represents the energy consumption when the water electrolysis efficiency is 100%;

[0043] g Compressor model: The compressor power is expressed as:

[0044]

[0045] Among them, C p is the calorific value of hydrogen; T in is the temperature of hydrogen at the inlet; η comp is the compression efficiency, η comp =0.7; p in 、p sto is the compressor inlet and outlet pressure; r is the isentropic index of hydrogen, r = 1.4; m H2 is the hydrogen flow rate,

[0046] h Hydrogen storage tank model: the accumulated amount of hydrogen in the hydrogen storage tank n sto (t1) is expressed as:

[0047]

[0048] in, Hydrogen consumption rate, n sto (t0) is the accumulated amount of hydrogen in the hydrogen storage tank at the initial moment.

[0049] The hydrogen pressure in the hydrogen storage tank is expressed as:

[0050]

[0051] Among them, T sto is the operating temperature of the hydrogen storage tank, V sto is the volume of the hydrogen storage tank.

[0052] A further improvement of the technical solution of the present invention is that except for the different parameter calculation methods of PEM electrolyzer and alkaline electrolyzer when calculating the ohmic overpotential, the rest of the model is generally applicable to PEM and alkaline electrolyzers.

[0053] A further improvement of the technical solution of the present invention is that: when modeling electrolytic cells of different powers in the sub-model b, the specific method for expanding the model is:

[0054] The power of the electrolyzer can be expressed as:

[0055] P=IV

[0056] Where V = N cell V cell , N cell is the number of electrolytic units; I = kI cell , I cell is the current of the electrolytic unit, and k is the number of parallel branches. The polarization characteristics of the electrolytic cell are affected by the current density i, and the current density mainly depends on the material properties of the electrolytic cell itself. Therefore, when modeling the electrolytic cell model with different power requirements, in addition to V cell In addition to the parameters involved in cell And the number of parallel branches k is modified accordingly.

[0057] A further improvement of the technical solution of the present invention is that: there is an influence relationship between the eight sub-models of the electrolytic cell system, and the specific influence relationship is: the parameter temperature T in sub-model a is obtained by sub-model e; the parameter V in sub-model b is obtained by sub-model e; cell Obtained by sub-model a; the parameter P in sub-models d and f is obtained by sub-model b; the parameters in sub-models d and f are obtained by sub-model b. Obtained by sub-model c; parameter p in sub-model g sto Obtained by sub-model h.

[0058] Due to the adoption of the above technical solution, the technical advancements achieved by the present invention are:

[0059] The present invention establishes a method for constructing an electrolysis hydrogen production system model, which includes eight sub-models and fully considers the influence relationship between the eight sub-models of the electrolyzer system. In addition, the model is scalable when applied to electrolyzers of different powers, thereby achieving a relatively simple and scalable electrolyzer system model while ensuring the accuracy of the model. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a schematic diagram of the influence relationship between the sub-models of the electrolytic cell system model of the present invention. DETAILED DESCRIPTION

[0061] The present invention is described in further detail below in conjunction with the embodiments:

[0062] like Figure 1 As shown, the method for constructing a hydrogen production system model established by the present invention includes the following sub-models:

[0063] a Electrochemical model of electrolyzer: The voltage of alkaline and PEM electrolyzers is determined by the reversible voltage V rev , activation overpotential V act , mass transfer overpotential (concentration overpotential) V Diff , Ohmic overpotential V ohm 4-part composition, electrolytic cell voltage V=N cell V cell , N cell is the number of electrolytic units constituting the electrolytic cell, V cell is the voltage of the electrolysis unit, and the expression of the electrolysis unit voltage is as follows:

[0064] V cell =V rev +V act +V Diff +V ohm

[0065] Reversible voltage V rev Expressed as:

[0066]

[0067] Where N is the amount of transferred electrons;

[0068] Activation overpotential V act Expressed as:

[0069]

[0070] Where i is the current density of the electrolytic cell; i 0,an is the anode exchange current density; i 0,cn is the cathode exchange current density; α an is the anode charge transfer function; α cn is the cathode charge transfer function; T is the electrolytic cell temperature.

[0071] The electrolytic cell current density can be expressed as:

[0072]

[0073] Where z is the number of transferred electrons and R is the gas constant.

[0074] Mass transfer overpotential V Diff Expressed as:

[0075]

[0076] Where C is the gas concentration at the reaction interface; C0 is the reference gas concentration at the reaction interface.

[0077] Ohmic overpotential V ohm Expressed as:

[0078]

[0079] When the model is applied to a PEM electrolyzer, in the expression, δ = δ mem is the thickness of the proton membrane, σ=σ mem is the proton membrane conductance,

[0080]

[0081] Where, λ is the proton membrane humidity;

[0082] When the model is applied to alkaline electrolyzers, in the expression, δ = δ ele is the electrolyte thickness, σ=σ ele is the electrolyte conductivity:

[0083]

[0084] Where M is the electrolyte concentration.

[0085] b. Electrolyzer power model: electrolyzer power P = IV, where I is the electrolyzer current. This model can be expanded when modeling electrolyzers of different powers.

[0086] c Electrolyzer hydrogen production rate model: Hydrogen production rate of electrolyzer The expression is as follows:

[0087]

[0088] Among them, η F is the Faraday efficiency, z is the number of transferred electrons, and F is the Faraday constant;

[0089] dElectrolyzer efficiency model: electrolysis hydrogen production efficiency η el It is defined as the ratio of the theoretical power of hydrogen production to the actual power consumed by the electrolyzer, and the expression is as follows:

[0090]

[0091] Where ΔG is the Gibbs free energy;

[0092] e Electrolytic cell thermodynamic model: The thermodynamic model predicts the electrolytic cell temperature. By converting the thermal model, the electrolytic cell temperature can be obtained, and its expression is:

[0093]

[0094] Where T0 is the initial temperature; R t is the overall thermal resistance of the electrolytic cell; C t is the total heat capacity of the electrolytic cell; C cw is the heat capacity of the electrolyte; m cw is the inlet electrolyte mass flow rate; A HX is the overall heat transfer area; T a is the ambient temperature; η energy is energy efficiency; T cw,i is the inlet electrolyte temperature;

[0095] fElectrolytic cell specific energy consumption model: specific energy consumption E of electrolytic cell s According to the instantaneous voltage v(t), instantaneous electrolysis current i(t) and hydrogen production rate n H2 To calculate:

[0096]

[0097] Where m H2 is the mass flow rate of hydrogen; M is the molar mass of hydrogen molecules (M = 2g / mol). The higher calorific value of hydrogen is 39.4kWh / kg, which represents the energy consumption when the water electrolysis efficiency is 100%;

[0098] g Compressor model: The compressor power is expressed as:

[0099]

[0100] Among them, C p is the calorific value of hydrogen; T in is the temperature of hydrogen at the inlet; η comp is the compression efficiency, η comp =0.7; p in 、p sto is the compressor inlet and outlet pressure; r is the isentropic index of hydrogen, r = 1.4; m H2 is the hydrogen flow rate,

[0101] h Hydrogen storage tank model: the accumulated amount of hydrogen in the hydrogen storage tank n sto (t1) is expressed as:

[0102]

[0103] in, Hydrogen consumption rate, n sto(t0) is the accumulated amount of hydrogen in the hydrogen storage tank at the initial moment.

[0104] The hydrogen pressure in the hydrogen storage tank is expressed as:

[0105]

[0106] Among them, T sto is the operating temperature of the hydrogen storage tank, V sto is the volume of the hydrogen storage tank.

[0107] Except for the difference in the parameter calculation methods of PEM electrolyzer and alkaline electrolyzer when calculating the ohmic overpotential, the rest of the model is applicable to both PEM and alkaline electrolyzers.

[0108] like Figure 1 As shown, in the sub-model b, when modeling electrolyzers of different powers, the specific method for expanding the model is as follows:

[0109] The power of the electrolyzer can be expressed as:

[0110] P=IV

[0111] Where V = N cell V cell , N cell is the number of electrolytic units; I = kI cell , I cell is the current of the electrolytic unit, and k is the number of parallel branches. The polarization characteristics of the electrolytic cell are affected by the current density i, and the current density mainly depends on the material properties of the electrolytic cell itself. Therefore, when modeling the electrolytic cell model with different power requirements, in addition to V cell In addition to the parameters involved in cell And the number of parallel branches k is modified accordingly.

[0112] Therefore, when modeling the electrolyzer model with different power requirements, the expansion method is: 1) V cell The parameters involved are described in the electrochemical model of the electrolytic cell a above; 2) k depends on the connection method of the electrolytic cells in the electrolytic cell. For example, if an electrolytic cell contains n electrolytic cells, all n electrolytic cells are connected in series to the circuit, then k = 1; if two groups of n / 2 electrolytic cells are connected in series and then in parallel to the circuit, then k = 2; 3) N cell Calculated by the following formula:

[0113]

[0114] like Figure 1As shown, there is an influence relationship between the eight sub-models of the electrolytic cell system, and the specific influence relationship is: the parameter temperature T in sub-model a is obtained by sub-model e; the parameter V in sub-model b is obtained by cell Obtained by sub-model a; the parameter P in sub-models d and f is obtained by sub-model b; the parameters in sub-models d and f are obtained by sub-model b. Obtained by sub-model c; parameter p in sub-model g sto Obtained by sub-model h.

Claims

1. A method for constructing a hydrogen production system model by electrolysis, characterized in that: Includes the following sub-models: a Electrochemical model of electrolytic cell: The voltage of alkaline electrolytic cell and PEM electrolytic cell is determined by the reversible voltage V rev , activation overpotential V act , mass transfer overpotential V Diff , Ohmic overpotential V ohm 4-part composition, electrolytic cell voltage V=N cell V cell , N cell is the number of electrolytic units constituting the electrolytic cell, V cell is the voltage of the electrolytic cell, and the expression of the electrolytic cell voltage is as follows: V cell =V rev +V act +V Diff +V ohm b. Electrolytic cell power model: electrolytic cell power P = IV, where I is the electrolytic cell current. When modeling electrolytic cells with different powers, the parameters in the model are modified according to the actual conditions of the different electrolytic cells to expand the model and obtain the corresponding model; c Electrolyzer hydrogen production rate model: Hydrogen production rate of electrolyzer The expression is as follows: Among them, η F is the Faraday efficiency, z is the number of transferred electrons, and F is the Faraday constant; dElectrolyzer efficiency model: electrolysis hydrogen production efficiency η el It is defined as the ratio of the theoretical power of hydrogen production to the actual power consumed by the electrolyzer, and the expression is as follows: Where ΔG is the Gibbs free energy; e Electrolytic cell thermodynamic model: The thermodynamic model predicts the electrolytic cell temperature. By converting the thermal model, the electrolytic cell temperature can be obtained, and its expression is: Where T0 is the initial temperature; R t is the overall thermal resistance of the electrolytic cell; C t is the total heat capacity of the electrolytic cell; C cw is the heat capacity of the electrolyte; m cw is the inlet electrolyte mass flow rate; A HX is the overall heat transfer area; T a is the ambient temperature; η energy is energy efficiency; T cw,i is the inlet electrolyte temperature; fElectrolytic cell specific energy consumption model: specific energy consumption E of electrolytic cell s According to the instantaneous voltage v(t), instantaneous electrolysis current i(t) and hydrogen production rate n H2 To calculate: Where m H2 is the mass flow rate of hydrogen; M is the molar mass of hydrogen molecules, M = 2g / mol; the higher calorific value of hydrogen is 39.4kWh / kg, which represents the energy consumption when the water electrolysis efficiency is 100%; g Compressor model: The compressor power is expressed as: Among them, C p is the calorific value of hydrogen; T in is the temperature of hydrogen at the inlet; η comp is the compression efficiency, η comp =0.7; p in 、p sto is the compressor inlet and outlet pressure; r is the isentropic index of hydrogen, r = 1.4; m H2 is the hydrogen flow rate, h Hydrogen storage tank model: the accumulated amount of hydrogen in the hydrogen storage tank n sto (t1) is expressed as: in, Hydrogen consumption rate, n sto (t0) is the accumulated amount of hydrogen in the hydrogen storage tank at the initial moment; The hydrogen pressure in the hydrogen storage tank is expressed as: Among them, T sto is the operating temperature of the hydrogen storage tank, V sto is the volume of the hydrogen storage tank.

2. The method for constructing a hydrogen production system model by electrolysis according to claim 1, characterized in that: In the sub-model a, the reversible voltage V rev , activation overpotential V act , mass transfer overpotential V Diff and the ohmic overpotential V ohm The specific meaning and expression are: The potential difference between the cathode and anode of the electrolyzer unit is called the reversible voltage, which corresponds to the minimum energy required to electrolyze water, where N is the amount of transferred electrons; Activation overpotential V act It is caused by the slow reaction on the electrode surface, where i is the electrolytic cell current density; i 0,an is the anode exchange current density; i 0,cn is the cathode exchange current density; ɑ an is the anode charge transfer function; ɑ cn is the cathode charge transfer function; T is the electrolytic cell temperature; The electrolytic cell current density can be expressed as: Where z is the number of transferred electrons; R is the gas constant; Mass transfer overpotential V Diff Also known as concentration difference overpotential, it is the potential difference caused by the change in reactant concentration at the reaction interface, thereby reducing the reactant concentration and hindering the reaction. Where C is the gas concentration at the reaction interface; C0 is the reference concentration of the gas at the reaction interface; Ohmic overpotential V ohm It is the voltage loss caused by the resistance of the electrolyzer itself during operation. When the model is applied to the PEM electrolyzer, in the expression, δ=δ mem is the thickness of the proton membrane, σ=σ mem is the proton membrane conductance, Where, λ is the proton membrane humidity; When the model is applied to alkaline electrolyzers, in the expression, δ = δ ele is the electrolyte thickness, σ=σ ele is the electrolyte conductivity: Where M is the electrolyte concentration.

3. The method for constructing a hydrogen production system model according to claim 2, characterized in that: The calculation method of the parameters of the PEM electrolyzer and the alkaline electrolyzer in the electrolysis hydrogen production system model is the same. When calculating the ohmic overpotential V ohm When the parameters are calculated, the methods for calculating the parameters of PEM electrolyzer and alkaline electrolyzer are different.

4. The method for constructing a hydrogen production system model according to claim 1, wherein: When modeling electrolyzers of different powers in the sub-model b, the specific method for expanding the model is as follows: The power of the electrolyzer can be expressed as: P=IV Where V = N cell V cell , N cell is the number of electrolytic units; I = kI cell , I cell is the current of the electrolysis unit, k is the number of parallel branches, when modeling the electrolytic cell model with different power requirements, except for V cekk In addition to the parameters involved in cell And the number of parallel branches k is modified accordingly.

5. The method for constructing a hydrogen production system model by electrolysis according to claim 1, characterized in that: There is an influence relationship between the eight sub-models of the electrolytic cell system. The specific influence relationship is: the parameter temperature T in sub-model a is obtained by sub-model e; the parameter V in sub-model b is obtained by cell Obtained by sub-model a; the parameter P in sub-models d and f is obtained by sub-model b; the parameters in sub-models d and f are obtained by sub-model b. Obtained by sub-model c; parameter p in sub-model g sto Obtained by sub-model h.

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