A method for calculating the DC energy consumption of a water electrolysis hydrogen production stack

Abstract

The present application discloses a method for calculating the DC energy consumption of a water electrolysis hydrogen production stack, comprising the following steps: step one: calculating the resistance value of the electrolyte in each section of the water electrolysis hydrogen production stack according to the calculated electrolyte pipeline structure of the water electrolysis hydrogen production stack; step two: calculating the bypass current of the water electrolysis hydrogen production stack according to the resistance value of the electrolyte in each section of the pipeline, the voltage of each electrolysis chamber, and the resistance value of the electrolyte in each section of the pipeline calculated in step one; step three: calculating the hydrogen production of the water electrolysis hydrogen production stack according to the bypass current of the water electrolysis hydrogen production stack; step four: calculating the DC power consumption according to the hydrogen production of the water electrolysis hydrogen production stack.

Description

Technical Field

[0001] The invention relates to the field of hydrogen production by water electrolysis, and in particular to a method for calculating the direct current energy consumption of a hydrogen production stack by water electrolysis. Background Art

[0002] In the context of the "dual carbon" goal, with the release of the medium- and long-term plan for the development of the hydrogen energy industry, hydrogen energy will become one of the important directions for future energy development and is seen as the only way to achieve carbon peak and carbon neutrality. Hydrogen produced by electrolyzing water using renewable energy electricity is considered green hydrogen and is considered the ultimate direction of hydrogen production.

[0003] The working principle of the water electrolysis hydrogen production system is that a pair of electrodes immersed in the electrolyte are separated by a diaphragm to prevent gas penetration. When a certain direct current is applied, the water decomposes, hydrogen is precipitated at the cathode, and oxygen is precipitated at the anode. In the actual application of the water electrolysis hydrogen production system, in order to ensure the efficient transmission and conversion of electric energy, single stacks are usually connected in series to form a stack to obtain a high voltage. In order to ensure that the electrolyte can be evenly delivered to each stack, the electrolyte is generally transported by a unified parallel pipeline, so the electrolyte pipelines between the single cells of the stack are connected. These connected pipelines and electrolysis chambers form a new charge transfer circuit. Due to the potential difference between the electrolysis chambers, the ions move in a directional manner in the pipeline under the action of the potential difference to form a current, which is called bypass current, leakage current or branch current. Bypass current will not only cause power loss and reduce the efficiency of the entire fuel cell stack, but also greatly increase the impact of bypass current, exceeding 10%, especially in alkaline water electrolysis hydrogen production devices with a capacity of more than 2MW, where the number of fuel cell stack chambers is 200 or even 400. The accuracy of measuring hydrogen production energy consumption will also be greatly affected.

[0004] The national standard uses the current test value calculation and the volumetric method to test the gas production and DC energy consumption for calculating the gas production from water electrolysis. Both methods have a certain degree of error in the actual production process of high-power electrolytic hydrogen production equipment: the current test value method for calculating the gas production method has a large error in the current efficiency data due to the bypass current in the production process of the electrolytic hydrogen production equipment, which will have a great impact on the actual energy consumption data. The volumetric method for testing gas production requires finding the temperature, pressure and volume difference in a closed container for a period of time for calculation. This method is suitable for laboratory measurements. It cannot be accurately measured in the actual production process of high-power electrolyzers due to temperature differences and pressure changes.

[0005] Therefore, it is necessary to propose a calculation method for the DC energy consumption of the water electrolysis hydrogen production stack. Summary of the invention

[0006] The present invention provides a method for calculating the DC energy consumption of a water electrolysis hydrogen production stack, so as to solve the problem of inaccurate DC energy consumption calculation of a water electrolysis hydrogen production stack in the prior art.

[0007] A method for calculating the DC energy consumption of a water electrolysis hydrogen production stack comprises the following steps:

[0008] Step 1: Calculate the resistance value of the electrolyte in each section of the pipeline in the water electrolysis hydrogen production stack according to the electrolyte pipeline structure of the water electrolysis hydrogen production stack;

[0009] Step 2: Calculate the bypass current of the water electrolysis hydrogen production stack according to the resistance value of the electrolyte in each section of the pipeline and the voltage of each electrolysis chamber;

[0010] Step 3: Calculate the hydrogen production of the water electrolysis hydrogen production stack according to the bypass current of the water electrolysis hydrogen production stack;

[0011] Step 4: Calculate the DC power consumption based on the hydrogen production of the water electrolysis hydrogen production stack.

[0012] Optionally, the resistance value of the electrolyte in each pipe section of the water electrolysis hydrogen production stack in step one includes: cathode branch pipe resistance, anode branch pipe resistance, cathode main pipe resistance, and anode main pipe resistance.

[0013] Optionally, the method for calculating the bypass current in step 2 is: the internal current passing through each electrolytic chamber is calculated based on the cathode branch tube resistance, the anode branch tube resistance, the cathode main tube resistance, the anode main tube resistance and the voltage of each electrolytic chamber, and the bypass current is the sum of the internal currents of each electrolytic chamber.

[0014] Optionally, the internal current of each electrolysis chamber is calculated using the following formula:

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023] Among them, R N is the cathode branch resistance, R Pis the anode branch resistance, R MN is the cathode total tube resistance, R MP is the anode total tube resistance; V n is the voltage of the nth electrolysis chamber; is the positive total tube current; is the positive branch current; is the negative total tube current; is the negative branch current; I t is the input and output current of the battery stack; i n is the internal current passing through the nth electrolytic cell.

[0024] Optionally, the method for calculating the hydrogen production of the water electrolysis hydrogen production stack in step 3 is:

[0025] Calculate the current efficiency η through the bypass current;

[0026] The hydrogen production is then calculated based on the current efficiency, the DC working current passing through the electrolysis chamber and the number of electrolysis chambers.

[0027] Optionally, the current efficiency is calculated as follows:

[0028] η=Ii 旁路 / I

[0029] η is the current efficiency; i 旁路 is the bypass current; I is the total DC current of the water electrolysis hydrogen production stack.

[0030] Optionally, the hydrogen production is calculated using the following formula:

[0031]

[0032] Where: Q is the hydrogen production; I is the DC working current passing through the electrolytic chamber; n is the number of electrolytic chambers; η is the current efficiency.

[0033] Optionally, in step 4, the DC power consumption is calculated by the total DC current of the water electrolysis hydrogen production stack, the total DC voltage of the water electrolysis hydrogen production stack, the hydrogen output and the time.

[0034] Optionally, the method for calculating the DC power consumption in step 4 is:

[0035]

[0036] in is the DC power consumption; I 总 is the total DC current of the water electrolysis hydrogen production stack; U is the total DC voltage of the water electrolysis hydrogen production stack; Q is the hydrogen output; T is the time.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention introduces the calculation of bypass current influence into the energy consumption measurement method of water electrolysis hydrogen production, and quantitatively analyzes the actual working current by establishing a mathematical model, and effectively calculates the influence of current efficiency on the actual hydrogen production. The calculation accuracy of the metered energy consumption is improved, which is conducive to the manufacturer's accurate evaluation of the technical level of water electrolysis hydrogen production equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 It is an equivalent circuit model obtained based on the structure of the hydrogen production stack by electrolysis of water. DETAILED DESCRIPTION

[0041] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0042] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0043] Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. Various raw materials used in the examples are commercially available products.

[0044] Embodiment 1:

[0045] The purpose of the present invention is to provide a method for calculating the DC energy consumption of a water electrolysis hydrogen production device. The method can quantitatively analyze the actual working current in the water electrolysis hydrogen production system and effectively reduce the influence of current efficiency on the actual hydrogen production.

[0046] According to the structure and basic principle of the hydrogen production stack by electrolysis of water, the calculation method of the present invention is proposed on the following basis: ① The electrolyte inlet and outlet main pipes are insulators. ② The common flow channel and distribution pipeline inside the stack are filled with electrolyte, and the electrochemically active substances migrate in the electrolyte in the form of ions, and the migration resistance can be represented by a resistor element. ③ The resistance in the distribution pipeline connecting each electrolytic chamber and the common flow channel is the same. ④ The ohmic resistance of the electrodes and bipolar plates of each electrolytic chamber is considered as a whole. ⑤ The electrolyte in each electrolytic chamber has a uniform potential. ⑥ Ignore the delay caused by the flow of electrolyte in the common flow channel and the migration of water.

[0047] like Figure 1 As shown in the figure, based on the above conditions, the structure of the water electrolysis hydrogen production stack can be constructed according to Kirchhoff's law and Ohm's law to construct an equivalent circuit model of the liquid flow electrolysis chamber. Based on this model, quantitative analysis of the actual working current can effectively reduce the impact of current efficiency on the actual hydrogen production. N is the cathode branch resistance, R P is the anode branch resistance, R MN is the cathode total tube resistance, R MP is the total anode pipe resistance, Re is the ohmic resistance of each electrolytic chamber electrode and bipolar plate (this resistance is not involved in the energy consumption calculation method of this application).

[0048] A method for calculating the DC energy consumption of a water electrolysis hydrogen production stack based on the above model includes the following steps:

[0049] Step 1: Calculate the resistance value of the electrolyte in each pipeline of the water electrolysis hydrogen production stack according to the electrolyte pipeline structure of the water electrolysis hydrogen production stack; including: cathode branch pipe resistance, anode branch pipe resistance, cathode main pipe resistance, and anode main pipe resistance.

[0050] Step 2: Calculate the bypass current of the water electrolysis hydrogen production stack according to the resistance value of the electrolyte in each section of the pipeline, the voltage of each electrolysis chamber, and the resistance value of the electrolyte in each section of the pipeline calculated in step 1;

[0051] The calculation process uses the following formula:

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060] Among them, V n is the voltage of the nth electrolysis chamber; is the positive total tube current; is the positive branch current; is the negative total tube current; is the negative branch current; I t is the input and output current of the battery stack; i n is the internal current passing through the nth electrolysis cell;

[0061] The bypass current of the water electrolysis hydrogen production stack is the internal current i of each electrolysis chamber. n sum.

[0062] i 旁路 =i1+i2……i n

[0063] Step 3: Calculate the hydrogen production of the water electrolysis hydrogen production stack according to the bypass current of the water electrolysis hydrogen production stack;

[0064] Calculate the current efficiency η=Ii by bypass current 旁路 / I;

[0065] I is the total DC current of the water electrolysis hydrogen production stack;

[0066] The hydrogen production is calculated using the following formula:

[0067]

[0068] Where: Q—hydrogen production, in cubic meters per hour (m 3 / h); I is the DC working current passing through the electrolytic chamber, in ampere (A); n is the number of electrolytic chambers, in pieces; η is the current efficiency, in %.

[0069] Step 4: Calculate the DC power consumption based on the hydrogen production of the water electrolysis hydrogen production stack. The calculation method is:

[0070]

[0071] Where W H2 is the DC power consumption; I is the total DC current of the water electrolysis hydrogen production stack; U is the total DC voltage of the water electrolysis hydrogen production stack; Q H2 is the hydrogen production; T is the time.

[0072] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for calculating the DC energy consumption of a water electrolysis hydrogen production stack, characterized in that: The steps include: Step 1: Calculate the resistance value of the electrolyte in each section of the pipeline in the water electrolysis hydrogen production stack according to the electrolyte pipeline structure of the water electrolysis hydrogen production stack; Step 2: Calculate the bypass current of the water electrolysis hydrogen production stack according to the resistance value of the electrolyte in each section of the pipeline and the voltage of each electrolysis chamber; Step 3: Calculate the hydrogen production of the water electrolysis hydrogen production stack according to the bypass current of the water electrolysis hydrogen production stack; Step 4: Calculate the DC power consumption based on the hydrogen production of the water electrolysis hydrogen production stack; The resistance value of the electrolyte in each section of the pipeline in the water electrolysis hydrogen production stack in step 1 includes: cathode branch pipe resistance, anode branch pipe resistance, cathode main pipe resistance, and anode main pipe resistance; The method for calculating the bypass current in the step 2 is: according to the cathode branch pipe resistance, the anode branch pipe resistance, the cathode main pipe resistance, the anode main pipe resistance and the voltage of each electrolytic chamber, the internal current passing through each electrolytic chamber is calculated, and the bypass current is the sum of the internal currents of each electrolytic chamber; The internal current of each electrolytic cell is calculated using the following formula: Among them, R N is the cathode branch resistance, R P is the anode branch resistance, R MN is the cathode total tube resistance, R MP is the anode total tube resistance; V n is the voltage of the nth electrolysis chamber; is the positive total tube current; is the positive branch current; is the negative total tube current; is the negative branch current; I t is the input and output current of the battery stack; i n is the internal current passing through the nth electrolytic cell.

2. The method for calculating the DC energy consumption of the water electrolysis hydrogen production stack according to claim 1, characterized in that: The method for calculating the hydrogen production of the water electrolysis hydrogen production stack in step 3 is: The current efficiency is calculated by the bypass current; the hydrogen production is then calculated based on the current efficiency, the DC working current passing through the electrolysis chamber and the number of electrolysis chambers.

3. The method for calculating the DC energy consumption of the water electrolysis hydrogen production stack according to claim 2, characterized in that: The current efficiency is calculated as follows: η=I-i 旁路 / I η is the current efficiency; i 旁路 is the bypass current; I is the total DC current of the water electrolysis hydrogen production stack.

4. The method for calculating the DC energy consumption of the water electrolysis hydrogen production stack according to claim 2, characterized in that: The hydrogen production is calculated using the following formula: Where: Q is the hydrogen production; I is the DC working current passing through the electrolytic chamber; n is the number of electrolytic chambers; η is the current efficiency.

5. The method for calculating the DC energy consumption of the water electrolysis hydrogen production stack according to claim 1, characterized in that: In the step 4, the DC power consumption is calculated by the total DC current of the water electrolysis hydrogen production stack, the total DC voltage of the water electrolysis hydrogen production stack, the hydrogen production and the time.

6. The method for calculating the DC energy consumption of the water electrolysis hydrogen production stack according to claim 5, characterized in that: The method for calculating the DC power consumption in step 4 is: in is the DC power consumption; I 总 is the total DC current of the water electrolysis hydrogen production stack; U is the total DC voltage of the water electrolysis hydrogen production stack; Q is the hydrogen output; T is the time.

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