Flow cell flow channel optimization design method

Abstract

The invention relates to the technical field of flow batteries, and discloses a flow battery flow channel optimization design method, which adopts simulation software to independently change the resistance of each battery flow channel so as to find a balance point between balancing leakage current and reducing flow resistance. According to the method, the resistance at the runner can be more accurately controlled, and the problem that the flow resistance is too high due to overall increase of the resistance of the runner is avoided. Meanwhile, the accurate control can also reduce energy loss and safety problems caused by overlarge resistance. Simulation software can simulate the running condition of the electric pile in a virtual environment, so that possible problems can be found and solved in advance. Therefore, the time and cost in actual operation can be saved, and the reliability and safety of the electric pile can be improved. Generally speaking, compared with the prior art, the leakage current and the flow resistance can be more accurately controlled, the efficiency and the service life of the electric pile are improved, and the intelligent electric pile has intellectualization and a wide application prospect.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of liquid flow batteries, and in particular to a liquid flow battery flow channel optimization design method. Background Art

[0002] Liquid flow battery is a new type of energy storage technology that stores energy by converting electrochemical energy into chemical energy in liquid electrolyte. Liquid flow battery has many advantages, such as intrinsic safety, long cycle life and good scalability. However, there is a common problem when assembling liquid flow battery stack, namely leakage current. Leakage current refers to the unexpected flow of current in the battery pack, which can lead to energy loss and safety problems. The existing solution is mainly to reduce leakage current by increasing the resistance at the flow channel. The flow channel is the channel for the flow of electrolyte in the liquid flow battery. Increasing the resistance at the flow channel can reduce leakage current. However, this approach also has some disadvantages. Although increasing the resistance at the flow channel can reduce leakage current, it will also lead to an increase in flow resistance when the battery stack is running. Flow resistance refers to the resistance encountered by liquid when it flows in the flow channel. Increasing flow resistance will lead to an increase in pump consumption, that is, an increase in the energy required for the pump to work. In addition, too high flow resistance will also affect the charge and discharge efficiency and life of the liquid flow battery. Therefore, how to find a balance between reducing leakage current and reducing flow resistance is an urgent problem to be solved in the field of liquid flow battery technology. Summary of the invention

[0003] In view of the shortcomings and defects of the prior art, the present invention provides a method for optimizing the flow channel design of a liquid flow battery, calculates the leakage current of the battery stack through simulation software, finds the balance between leakage current and flow resistance, achieves the best system efficiency, and improves the charging and discharging efficiency and life of the liquid flow battery.

[0004] The purpose of the present invention can be achieved through the following technical solutions.

[0005] A method for optimizing the design of a flow channel of a liquid flow battery comprises the following steps.

[0006] S1, input the flow battery flow channel data and calculate the equivalent flow channel resistance R.

[0007] S2, number all batteries sequentially from 1 to N.

[0008] Update the equivalent flow path resistance value of each battery: the equivalent flow path resistance value of the batteries with serial numbers 1 and N remains unchanged; the equivalent flow path resistance value of the battery with serial number X is 0; the equivalent flow path resistance values ​​of the batteries with serial numbers X to N are both decreasing and the equivalent flow path resistance values ​​of the batteries with serial numbers 1 to X are decreasing symmetrically; if N is an even number, then X=N / 2, (N / 2)+1, otherwise X=(N+1) / 2;

[0009] S3, substituting the updated equivalent flow path resistance value R into the leakage model to calculate the leakage loss.

[0010] S4, compare the leakage loss with the loss threshold in the design index: if the leakage loss is less than the loss threshold, directly execute step S5; otherwise, increase the equivalent flow path resistance value of the battery numbered 1 and N by Δr1 and then execute step S3.

[0011] S5, calculating the pressure loss corresponding to the current equivalent flow channel resistance value according to R.

[0012] Compare whether the pressure loss meets the set pressure loss range: if not, reduce the equivalent flow path resistance of the batteries numbered 1 and N by Δr2 and jump to step S3; otherwise, execute step S6.

[0013] S6, calculating the current corresponding flow channel structure parameters and outputting the flow channel optimization design scheme.

[0014] Preferably, the flow battery includes but is not limited to an all-vanadium flow battery, a zinc-based flow battery, an iron-based flow battery, and a sodium polysulfide-bromine flow battery.

[0015] Preferably, the leakage model is constructed by Kirchhoff's law or an equivalent circuit.

[0016] Preferably, in step S2, the equivalent flow channel resistance value is decreased in an arithmetic or geometric manner or according to a preset function.

[0017] Preferably, the loss threshold in step S4 and the pressure loss range in step S5 are determined according to the design and production requirements of the fuel cell stack.

[0018] Preferably, Δr1>Δr2.

[0019] Preferably, the equivalent flow channel resistance value is a physical quantity used to reflect the flow channel structure of the liquid flow battery and the change in the resistivity of the electrolyte, and is calculated based on the parameters of the liquid flow battery stack.

[0020] Preferably, the pressure loss corresponding to the current equivalent flow channel resistance value is .

[0021] Where k is the standard pressure loss coefficient; Q represents the flow rate through the flow channel; ρ represents the fluid density.

[0022] Preferably, k is the pressure loss corresponding to the standard flow channel actually designed and produced.

[0023] Preferably, the average leakage current of the battery stack is obtained through the leakage model, and then the leakage loss is calculated in combination with the number of battery stacks and the average voltage.

[0024] Beneficial technical effects of the present invention: The resistance of each battery flow channel is changed individually by using simulation software, so as to find a balance between balancing the leakage current and reducing the flow resistance. This method can more accurately control the resistance at the flow channel, avoiding the problem of excessive flow resistance due to an overall increase in the flow channel resistance. At the same time, this precise control can also reduce energy loss and safety problems caused by excessive resistance. The simulation software can simulate the operation of the battery stack in a virtual environment, so as to discover and solve possible problems in advance. This can not only save time and cost in actual operation, but also improve the reliability and safety of the battery stack. In general, compared with the prior art, the present invention can not only more accurately control the leakage current and flow resistance, improve the efficiency and life of the battery stack, but also has intelligent and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the overall flow chart of the present invention.

[0026] Figure 2 The figure is a comparison of leakage current distribution before and after optimization in the embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the present invention.

[0028] like Figure 1 As shown, a method for optimizing the flow channel design of a liquid flow battery provided by an embodiment of the present invention includes the following steps.

[0029] S1, input the stack parameters of the flow battery and calculate the equivalent flow channel resistance R.

[0030] S2: All batteries are numbered sequentially from 1 to N, and X is calculated based on the number of battery cells.

[0031] Update the equivalent flow path resistance value of each battery: the equivalent flow path resistance value of the batteries with serial numbers 1 and N remains unchanged; the equivalent flow path resistance value of the battery with serial number X is 0; the equivalent flow path resistance values ​​of the batteries with serial numbers X~N and the equivalent flow path resistance values ​​of the batteries with serial numbers 1~X are both decreasing and the degree of decrease is symmetrical; if N is an even number, then X=N / 2, (N / 2)+1, otherwise X=(N+1) / 2.

[0032] S3, substituting the updated equivalent flow path resistance value R into the leakage model to calculate the leakage loss.

[0033] S4, if the leakage loss is less than the loss threshold, directly execute step S5; otherwise, increase the equivalent flow path resistance of the batteries numbered 1 and N by Δr1 and then execute step S3.

[0034] S5, calculating the pressure loss corresponding to the current equivalent flow channel resistance value according to R.

[0035] Compare whether the pressure loss meets the set pressure loss range: if not, reduce the equivalent flow path resistance of the batteries numbered 1 and N by Δr2 and jump to step S3; otherwise, execute step S6.

[0036] S6, calculating the current corresponding flow channel structure parameters and outputting the flow channel optimization design scheme.

[0037] The leakage loss can be calculated through the leakage model. The leakage model has no clear definition and is defined by technical personnel in this field in combination with existing technologies and actual conditions. For example, the updated equivalent flow path resistance value R is substituted into the leakage model to obtain the average leakage current of the battery stack. The total leakage loss is obtained by multiplying the average leakage current of the battery stack, the number of battery stacks and the average voltage of the battery stack.

[0038] The above-mentioned flow battery flow channel optimization design method is further described below based on embodiments.

[0039] For the same zinc-based flow battery, before executing this method, the leakage current is tested to obtain a leakage current distribution diagram, and then this method is executed under the same conditions:

[0040] S1, input the stack parameters of the zinc-based liquid flow battery (number of battery cells N=40), calculate the equivalent flow channel resistance R=1500Ω, substitute this value into the equivalent circuit leakage model built based on Simulink for calculation, and obtain the initial leakage loss of 41W.

[0041] S2, number all batteries sequentially from 1 to N, and then calculate X=[20, 21] based on the number of battery cells.

[0042] Update the equivalent flow path resistance value of each battery: the equivalent flow path resistance values ​​of batteries with serial numbers 1 and 40 remain unchanged. ; The equivalent flow channel resistance values ​​of the batteries with serial numbers 20 and 21 are 0; the equivalent flow channel resistance values ​​corresponding to the batteries with serial numbers 21 to 40 decrease in geometric proportion to the equivalent flow channel resistance values ​​corresponding to the batteries with serial numbers 1 to 20, and the degree of decrease is symmetrical.

[0043] S3, update the equivalent flow path resistance value in the leakage model according to the result of the previous step, obtain the leakage current corresponding to each battery, then square each value and multiply it with the equivalent flow path resistance value corresponding to the current battery to obtain 40 products, sum these 40 products and multiply them by the number of battery stacks 1 to calculate the total leakage loss, which is finally 59W.

[0044] S4, the loss threshold in the design index is 58W, and the current leakage loss is greater than the set threshold, so the equivalent flow channel resistance value of the battery numbered 1 and 30 is increased by 100Ω on the original basis, and then return to step S3.

[0045] S3, using the new equivalent flow path resistance value to substitute into the leakage model, the final calculated leakage loss is 55W.

[0046] S4, the leakage loss is less than the set threshold 58W, and step S5 is executed.

[0047] S5, calculating the pressure loss P corresponding to the current equivalent flow channel resistance value.

[0048] .

[0049] In the formula, the standard pressure loss coefficient k = 82kPa; the flow rate through the flow channel Q = 4.9m 3 / h.

[0050] The set pressure loss threshold range is 0~65kPa, and 66.87kPa does not meet this range. The equivalent flow path resistance values ​​of the batteries numbered 1 and 30 are reduced. In order to avoid excessive reduction that causes the equivalent flow path resistance value to be lower than the initial value, which causes the method to be unable to obtain the optimal solution, the equivalent flow path resistance value is reduced by 50Ω, and the process returns to step S3.

[0051] S3, using the new equivalent flow path resistance value to substitute into the leakage model, the final calculated leakage loss is 57W.

[0052] S4, the leakage loss is less than the set threshold 58W, and step S5 is executed.

[0053] S5, calculating the pressure loss P corresponding to the current equivalent flow channel resistance value as 64.24 kPa, which meets the set pressure loss threshold range, and executing step S6.

[0054] S6, calculate the current corresponding flow channel structure parameter value, output the flow channel optimization design scheme and test the leakage current distribution under this scheme, and compare it with the test results before the optimization design, see the attached Figure 2 .

[0055] According to the comparison results, after optimizing the leakage current distribution using this method, the design threshold of the leakage loss is not exceeded, which can ensure the system efficiency of the battery stack, and after the leakage current is evenly distributed, the consistency of the current density distribution of each battery can be improved, thereby ensuring that the electrochemical reaction in each battery remains consistent and extending the life of the battery stack. The above embodiments are descriptions of specific implementation methods of the present invention, rather than limitations of the present invention. Technicians in the relevant technical field can also make various changes and modifications to obtain corresponding equivalent technical solutions without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should be included in the patent protection scope of the present invention.

Claims

1. A flow battery flow channel optimization design method, characterized in that: The following steps are involved: S1, input the flow battery stack parameters and calculate the equivalent flow channel resistance R; S2, number all batteries in sequence from 1 to N; Update the equivalent flow path resistance value of each battery: the equivalent flow path resistance value of the batteries with serial numbers 1 and N remains unchanged; the equivalent flow path resistance value of the battery with serial number X is 0; the equivalent flow path resistance values ​​of the batteries with serial numbers X to N are both decreasing and the equivalent flow path resistance values ​​of the batteries with serial numbers 1 to X are decreasing symmetrically; if N is an even number, then X=N / 2, (N / 2)+1, otherwise X=(N+1) / 2; S3, substituting the updated equivalent flow path resistance value R into the leakage model to calculate the leakage loss; S4, compare the leakage loss with the loss threshold in the design index: if the leakage loss is less than the loss threshold, directly execute step S5; Otherwise, the equivalent flow channel resistance values ​​of the batteries numbered 1 and N are increased by Δr1 and then step S3 is executed; S5, calculating the pressure loss corresponding to the current equivalent flow channel resistance value according to R; Compare whether the pressure loss meets the set pressure loss range: if not, reduce the equivalent flow channel resistance of the batteries numbered 1 and N by Δr2 and then jump to step S3; otherwise, execute step S6; S6, calculating the current corresponding flow channel structure parameters and outputting the flow channel optimization design scheme.

2. A flow battery flow channel optimization design method according to claim 1, characterized in that: The flow battery includes but is not limited to an all-vanadium flow battery, a zinc-based flow battery, an iron-based flow battery, and a sodium polysulfide-bromine flow battery.

3. A flow battery flow channel optimization design method according to claim 1, characterized in that: Construct leakage model through Kirchhoff's law or equivalent circuit.

4. A flow battery flow channel optimization design method according to claim 1, characterized in that: In step S2, the equivalent flow channel resistance value decreases in an arithmetic or geometric manner or according to a preset function.

5. The method for optimizing the flow channel design of a liquid flow battery according to claim 1, characterized in that: The loss threshold in step S4 and the pressure loss range in step S5 are determined according to the design and production requirements of the fuel cell stack.

6. A flow battery flow channel optimization design method according to claim 1, characterized in that: Δr1>Δr2.

7. A flow battery flow channel optimization design method according to claim 1, characterized in that: The equivalent flow channel resistance is a physical quantity used to reflect the flow channel structure of the flow battery and the change in the resistivity of the electrolyte, and is calculated based on the flow battery stack parameters.

8. A flow battery flow channel optimization design method according to claim 1, characterized in that: The pressure loss corresponding to the current equivalent flow channel resistance value ; Where k is the standard pressure loss coefficient; Q represents the flow rate through the flow channel; ρ represents the fluid density.

9. A flow battery flow channel optimization design method according to claim 8, characterized in that: k is the pressure loss corresponding to the standard flow channel actually designed and produced.

10. The method for optimizing the flow channel design of a liquid flow battery according to claim 1, characterized in that: The average leakage current of the battery stack is obtained through the leakage model, and the leakage loss is calculated by combining the number of battery stacks and the average voltage.

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