An optimized design method for the flow channels of a flow battery

Abstract

The present invention relates to the technical field of flow batteries, and discloses a method for optimizing the design of flow channels of a flow battery. By using simulation software to separately change the resistance of the flow channels of each battery, a balance point can be found between balancing the leakage current and reducing the flow resistance. This method can more precisely control the resistance at the flow channels, avoiding the problem of excessive flow resistance caused by overall increasing the flow channel resistance. At the same time, this precise control can also reduce the energy loss and safety problems caused by excessive resistance. The simulation software can simulate the operation of the stack in a virtual environment, thereby discovering and solving potential problems in advance. This can not only save time and costs in actual operation, but also improve the reliability and safety of the stack. Generally speaking, compared with the prior art, the present invention can not only more precisely control the leakage current and flow resistance, improve the efficiency and lifespan of the stack, but also has the advantages of intelligence and broad application prospects.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of flow batteries, and particularly relates to a method for optimizing the design of flow channels of a flow battery. Background Art

[0002] A flow battery is a new type of energy storage technology that stores energy by converting electrochemical energy into chemical energy in a liquid electrolyte. Flow batteries have many advantages, such as intrinsic safety, long cycle life, and good scalability. However, when assembling a stack of flow batteries, there is a common problem, namely leakage current. Leakage current refers to the unexpected current flow in the battery pack, which can cause energy loss and safety problems. Existing solutions mainly reduce the leakage current by increasing the resistance at the flow channel. The flow channel is the channel through which the electrolyte flows in the flow battery. Increasing the resistance at the flow channel can reduce the leakage current. However, this approach also has some drawbacks. Although increasing the resistance at the flow channel can reduce the leakage current, it also leads to an increase in the flow resistance during the operation of the stack. Flow resistance refers to the resistance encountered by the liquid when flowing through the flow channel. Increasing the flow resistance will result in an increase in pump power consumption, that is, an increase in the energy required for the pump to work. In addition, excessive flow resistance will also affect the charge and discharge efficiency and life of the flow battery. Therefore, how to find a balance between reducing the leakage current and lowering the flow resistance is an urgent problem to be solved in the technical field of flow batteries. Summary of the Invention

[0003] In view of the deficiencies and defects existing in the prior art, the present invention provides a method for optimizing the design of flow channels of a flow battery. By using simulation software to calculate the leakage current of the stack, the balance between leakage and flow resistance is found, and while achieving the best system efficiency, the charge and discharge efficiency and life of the flow battery are improved.

[0004] The object of the present invention can be achieved by the following technical solutions.

[0005] A method for optimizing the design of flow channels of a flow battery includes the following steps.

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

[0007] S2, number all the batteries in sequence from 1 to N.

[0008] Update the equivalent flow channel resistance values of each battery: the equivalent flow channel resistance values of the batteries numbered 1 and N remain unchanged; the equivalent flow channel resistance value of the battery numbered X is 0; the equivalent flow channel resistance values of the batteries numbered X to N and the batteries numbered 1 to X both decrease and the degree of decrease is symmetric; where if N is even, then X = N / 2, (N / 2)+1, otherwise X = (N+1) / 2;

[0009] S3. Substitute the updated equivalent flow channel 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 specifications: If the leakage loss is less than the loss threshold, directly execute step S5; otherwise, increase the equivalent flow channel resistance values of the batteries with serial numbers 1 and N by Δr1 and then execute step S3.

[0011] S5. Calculate 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 it does not meet, decrease the equivalent flow channel resistance values of the batteries with serial numbers 1 and N by Δr2 and then jump to step S3; otherwise, execute step S6.

[0013] S6. Calculate the current corresponding flow channel structure parameters and output the flow channel optimization design scheme.

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

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

[0016] Preferably, the way of decreasing the equivalent flow channel resistance value in step S2 is arithmetic progression decrease or geometric progression decrease or decrease according to a preset function.

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

[0018] Preferably, Δr1 > Δr2.

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

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

[0021] In the formula, 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 in actual design and production.

[0023] Preferably, the average leakage current of the stack is obtained through the leakage model, and then the leakage loss is obtained by combining the number of stacks and the average voltage.

[0024] Advantageous technical effects of the present invention: By using simulation software to individually change the resistance of each battery flow channel, a balance point can be found between balancing the leakage current and reducing the flow resistance. This method can more precisely control the resistance at the flow channel, avoiding the problem of excessive flow resistance caused by overall increasing the flow channel resistance. At the same time, this precise control can also reduce energy losses and safety issues caused by excessive resistance. The simulation software can simulate the operation of the stack in a virtual environment, thereby discovering and solving potential problems in advance. This can not only save time and costs in actual operation but also improve the reliability and safety of the stack. Generally speaking, compared with the prior art, the present invention can not only more precisely control the leakage current and flow resistance, improve the efficiency and lifespan of the stack, but also has an intelligent and broad application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0026] Figure 2 It is the comparison of leakage current distributions before and after optimization in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with 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] As Figure 1 shown, a method for optimizing the flow channel design of a 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 value R.

[0030] S2. Number all the batteries in sequence from 1 to N, and then calculate X according to the number of battery sections.

[0031] Update the equivalent flow channel resistance values of each battery: The equivalent flow channel resistance values of the batteries with serial numbers 1 and N remain unchanged; the equivalent flow channel resistance value of the battery with serial number X is 0; the equivalent flow channel resistance values of the batteries with serial numbers from X to N and the batteries with serial numbers from 1 to X both decrease and the degree of decrease is symmetric; where if N is even, then X = N / 2, (N / 2)+1, otherwise X = (N+1) / 2.

[0032] S3. Substitute the updated equivalent flow channel 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 channel resistance values of the batteries with serial numbers 1 and N by Δr1 and then execute step S3.

[0034] S5. Calculate 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 channel resistance values of the batteries with serial numbers 1 and N by Δr2 and jump to step S3; otherwise, execute step S6.

[0036] S6. Calculate the current corresponding flow channel structure parameters and output the flow channel optimization design scheme.

[0037] The leakage loss can be calculated through the leakage model. The leakage model is not clearly defined and is defined by those skilled in the art in combination with the prior art and actual situations. For example, substitute the updated equivalent flow channel resistance value R into the leakage model to obtain the average leakage current of the stack. Multiply the average leakage current of the stack, the number of stacks, and the average voltage of the stack to obtain the total leakage loss.

[0038] The following further illustrates the above flow channel optimization design method for the flow battery according to the embodiments.

[0039] For the same zinc-based flow battery, before executing this method, test the leakage current to obtain the leakage current distribution map, and then execute this method under the same conditions:

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

[0041] S2. Number all the batteries in the order from 1 to N, then calculate X = [20, 21] according to the number of battery sections.

[0042] Update the equivalent flow channel resistance values of each battery: the equivalent flow channel resistance values of the batteries with serial numbers 1 and 40 remain unchanged and are still ; 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 and the equivalent flow channel resistance values corresponding to the batteries with serial numbers 1 to 20 are equally proportionally decreasing and the decreasing degree is symmetric.

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

[0044] In S4, the loss threshold in the design index is 58 W. Since the current leakage loss is greater than the set threshold, increase the equivalent flow channel resistance values of the batteries with serial numbers 1 and 30 by 100 Ω on the original basis, and then return to execute step S3.

[0045] In S3, substitute the new equivalent flow channel resistance value into the leakage model, and the finally calculated leakage loss is 55 W.

[0046] In S4, since the leakage loss is less than the set threshold of 58 W, execute step S5.

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

[0048] 。

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

[0050] The set pressure loss threshold range is 0 - 65 kPa. 66.87 kPa does not meet this range. Decrease the equivalent flow channel resistance values of the batteries with serial numbers 1 and 30. To avoid excessive decrease resulting in the equivalent flow channel resistance value being lower than the initial value and causing the method to be unable to obtain the optimal solution, decrease the equivalent flow channel resistance value by 50 Ω, and return to execute step S3.

[0051] In S3, substitute the new equivalent flow channel resistance value into the leakage model, and the finally calculated leakage loss is 57 W.

[0052] In S4, since the leakage loss is less than the set threshold of 58 W, execute step S5.

[0053] In S5, calculate 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 execute step S6.

[0054] In S6, calculate the corresponding current flow channel structure parameter values, 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 appendix Figure 2 。

[0055] According to the comparison results, after using this method to optimize the leakage current distribution, the design threshold of the leakage loss is not exceeded, which can ensure the system efficiency of the stack. And after the leakage current distribution is uniform, the consistency of the current density distribution of each cell can be improved, thereby ensuring that the electrochemical reactions in each cell are consistent and extending the life of the stack. The above embodiments are illustrative of the specific implementation manners of the present invention, rather than limitations on the present invention. Those skilled in the relevant technical fields can also make various transformations and changes 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 N to X are both decreased and the equivalent flow path resistance values ​​of the batteries with serial numbers 1 to X are decreased 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 path resistance value according to the updated equivalent flow path resistance value 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. A flow battery flow channel optimization design method 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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