A method for calculating a coefficient of a riser for a bipolar plate of a flow battery

Abstract

The application belongs to the technical field of energy storage, and particularly discloses a method for calculating a pole tube coefficient optimized bipolar plate interdigital flow channel for a liquid flow battery, which defines a pole tube coefficient, calculates the pole tube coefficient of the interdigital flow channel of the bipolar plate and the porous electrode between the flow channels in the liquid flow battery, and realizes the flow uniformity of the electrolyte in the porous electrode under low resistance. The method can make the electrolyte flow uniformly through the electrode, make the electrolyte fully contact with the electrode, thus fully and uniformly react, improve the electrochemical reaction speed, reduce the concentration polarization caused by the non-uniform flow and reaction, realize the flow uniformity of the electrolyte in the porous electrode under low resistance, improve the operation efficiency of the battery stack, inhibit the occurrence of the side reaction, improve the reliability of the liquid flow battery stack, prolong the service life of the liquid flow battery stack, and have an excellent application prospect.

Description

Technical Field

[0001] This invention relates to the field of battery energy storage technology, specifically to a calculation method for optimizing the bipolar plate interdigitated flow channel of an arm-loader used in flow batteries. Background Technology

[0002] Renewable energy sources such as solar and wind power suffer from intermittency and instability, making them unsuitable for direct grid connection. Based on the fundamental characteristics of renewable energy generation and output, a demand arises for practical, balanced power generation. To meet this demand, appropriate electrochemical energy storage devices must be integrated into the power grid.

[0003] Electrochemical energy storage boasts pollution-free operation, high efficiency, flexible power and energy characteristics to meet diverse grid functions, long cycle life, low maintenance costs, and is unrestricted by terrain or environment. It can directly store and release electrical energy, making it an ideal energy storage technology. Flow batteries, with their low cost, long lifespan, and high energy efficiency, are considered the future direction for large-scale electrochemical energy storage. Over the past 40 years of research and development, iron-chromium flow batteries have neared full commercialization and have been widely applied in emergency continuous power supply facilities, industrial batteries, electric traction, stand-alone applications, and load balancing.

[0004] In a flow battery, driven by a pump, the electrolyte flows through the channels within the bipolar plates to contact the electrodes and initiate an electrochemical reaction. Therefore, the uniformity of the electrolyte flow within the channels directly affects the contact and reaction process between the electrolyte and the electrodes, and also influences the resistance encountered by the electrolyte flow. Thus, there is an urgent need for a method to overcome the drawbacks of uneven electrolyte flow and high resistance in existing flow batteries, and to improve the problems of uneven and incomplete electrochemical reactions and high resistance within existing flow battery stacks. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a calculation method for optimizing the bipolar interdigitated flow channel of a flow battery using an arm-loaded arm. This method, coupled with simulation verification of the actual flow channel, achieves uniform electrolyte flow, ensuring uniform and sufficient contact between the electrolyte and electrodes for electrochemical reactions. This method allows for adjustments to the actual flow channel and flow rate based on the calculation and simulation results, saving time, manpower, and material costs, and solving the problems mentioned in the background section.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for calculating the optimization coefficient of the bipolar plate interdigitated flow channel in a flow battery, comprising the following steps:

[0007] S1. Calculate the pressure drop of the electrolyte flowing through the interdigitated channel.

[0008] S2. Calculate the pressure drop of the electrolyte flowing through the porous electrode in the flow channel.

[0009] S3. Define the loading arm coefficient and calculate the loading arm coefficient;

[0010] S4. By limiting the value of the loading arm coefficient, the uniformity of electrolyte flow in the flow channel is measured, and the actual flow channel and flow rate of the flow battery are optimized and adjusted.

[0011] Preferably, step S1 specifically includes the following:

[0012] S11, Definition Formula:

[0013] Where D e Let A be the equivalent diameter, A be the cross-sectional area of ​​the flow channel, and L be the wetted perimeter of the flow channel; let a and b be the width and height of the flow channel cross-section, respectively. Then A = ab, L = 2(a + b). Therefore,

[0014] S12, Define the formula:

[0015] Where Re is the Reynolds number, ρ is the fluid density, v1 is the electrolyte flow rate, d is the characteristic length, and η is the fluid viscosity coefficient;

[0016] S13. When Re < 2000, in the laminar flow region, the friction coefficient is...

[0017] S14. When 4000 < Re < 10000, in the turbulent region, the friction coefficient is...

[0018] S15, Frictional pressure loss in the flow channel region, i.e., the pressure drop of the electrolyte flowing through the interdigitated flow channel. Where l1 is the flow channel length The average flow velocity is denoted as .

[0019] Preferably, step S2 specifically includes the following:

[0020] Pressure loss in the porous electrode region refers to the pressure drop of the electrolyte as it flows through the porous electrodes in the flow channels. Where l2 is the length of the electrolyte flow through the electrode, v2 is the flow rate of the electrolyte on the porous electrode surface, and k is the electrode permeability.

[0021] Preferably, in step S3, the loading arm coefficient is the pressure drop of the electrolyte flowing through the porous electrode between the flow channels. Pressure drop of electrolyte flowing through interdigitated channels The ratio, that is

[0022] Preferably, in step S4, the uniform distribution of electrolyte within the porous electrode under the interdigitated flow channel structure is guaranteed only when the loading arm coefficient is greater than 25.

[0023] The beneficial effects of this invention are as follows: This invention overcomes the drawbacks of uneven electrolyte flow and high resistance in existing flow batteries, improves the problems of uneven and insufficient electrochemical reaction and high resistance in existing flow battery stacks, and provides a calculation method for optimizing the bipolar plate interdigitated flow channel of the loading arm coefficient in flow batteries. This method, coupled with simulation verification of the actual flow channel, achieves low-resistance uniform electrolyte flow in a porous medium, ensuring uniform and sufficient contact between the electrolyte and electrodes for a complete reaction. The method of this invention is simple, simplifying the complex process of selecting flow channels, flow rates, and other conditions in reality through calculation and simulation. This saves manpower, material resources, and time costs, improves stack operating efficiency, reduces production costs, reduces resistance, improves the reliability of flow battery stacks, and extends the service life of flow battery stacks, demonstrating excellent application prospects. Attached Figure Description

[0024] Figure 1 This is a top view of the bipolar plate in Embodiment 1 of the present invention;

[0025] Figure 2 The velocity cloud diagrams at the center position of the porous electrode in the actual flow channel simulation of Examples 1 and 2 are shown, where (a) is Example 1 and (b) is Example 2.

[0026] Figure 3 The velocity cloud diagrams at the center position of the porous electrode in the actual flow channel simulation of Comparative Examples 1, 2, and 3 are shown. (a) is Comparative Example 1, (b) is Comparative Example 2, and (c) is Comparative Example 3.

[0027] In the figure, 1-porous electrode; 2-interdigitated flow channel; I1-flow channel length; I2-electrolyte flow length in the electrode; →-electrolyte flow direction. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention provides a technical solution: a calculation method for optimizing the interdigitated flow channel of a bipolar plate in a flow battery, wherein the bipolar plate is as follows: Figure 1As shown, the arrows indicate the direction of electrolyte flow. l1 and l2 are shown in the figure, where 1 is the porous electrode (covering the flow channel) and 2 is the interdigitated flow channel. The calculation method includes the following steps:

[0030] S1. Calculate the pressure drop of the electrolyte flowing through the interdigitated channel. Specifically, it includes the following:

[0031] S11, Definition Formula:

[0032] Where D e Let A be the equivalent diameter, A be the cross-sectional area of ​​the flow channel, and L be the wetted perimeter of the flow channel; let a and b be the width and height of the flow channel cross-section, respectively. Then A = ab, L = 2(a + b). Therefore,

[0033] S12, Define the formula:

[0034] Where Re is the Reynolds number, ρ is the fluid density, v1 is the electrolyte flow rate, and d is the characteristic length (in this patent, it is a rectangular flow channel, and the characteristic length is the equivalent diameter D). e ), where η is the fluid viscosity coefficient;

[0035] S13. When Re < 2000, in the laminar flow region, the friction coefficient is...

[0036] S14. When 4000 < Re < 10000, in the turbulent region, the friction coefficient is...

[0037] S15, Frictional pressure loss in the flow channel region, i.e., the pressure drop of the electrolyte flowing through the interdigitated flow channel. Where l1 is the flow channel length The average flow velocity is denoted as .

[0038] S2. Calculate the pressure drop of the electrolyte flowing through the porous electrode in the flow channel. Specifically, it includes the following:

[0039] Pressure loss in the porous electrode region refers to the pressure drop of the electrolyte as it flows through the porous electrodes in the flow channels. Where l2 is the length of the electrolyte flow through the electrode, v2 is the flow rate of the electrolyte on the porous electrode surface, and k is the electrode permeability.

[0040] S3. Define and calculate the loading arm coefficient; the loading arm coefficient is the pressure drop of the electrolyte flowing through the porous electrode between the flow channels. Pressure drop of electrolyte flowing through interdigitated channels The ratio, that is

[0041] S4. By limiting the value of the loading arm coefficient, the uniformity of electrolyte flow within the flow channel is measured, and the actual flow channel and flow rate of the flow battery are optimized and adjusted. A loading arm coefficient greater than 25 is required to ensure uniform electrolyte distribution within the porous electrode under the interdigitated flow channel structure.

[0042] Example 1

[0043] A method for calculating the loading arm coefficient to optimize the bipolar interdigital flow channel in a flow battery is proposed. First, the loading arm coefficient is defined as the pressure drop of the electrolyte flowing through the porous electrodes in the flow channel. Pressure drop of electrolyte flowing through interdigitated channels The ratio, that is

[0044] Calculate pressure drop

[0045] 1) The cross-sectional width of the flow channel is a = 3.0 mm, the height is b = 9.0 mm, and the equivalent diameter is...

[0046] 2) Electrolyte density ρ = 1330 kg / m³ 3 The electrolyte flow velocity in the channel is v1 = 0.370 m / s, and the fluid viscosity coefficient is η = 0.002709 m·g·s. Laminar flow;

[0047] 3) Then the friction coefficient The flow channel length l1 = 0.5m. Pressure drop along the flow path

[0048] 4) The electrolyte flow length in the electrode is l2 = 22.5 mm = 0.0225 m, the electrolyte flow velocity on the porous electrode surface is v2 = 20 mm / s = 0.02 m / s, and the electrode permeability is k = 9.8 × 10⁻⁶. -11 ,

[0049] calculate This indicates that under this flow channel design and flow rate control, the electrolyte flow uniformity is good.

[0050] The actual flow channel was simulated using the fluid simulation software Ansys Fluent. The Navier-Stockes equation and the Brinkman equation were used to describe the momentum conservation of the electrolyte within the flow channel and porous electrode. Their respective expressions are as follows:

[0051]

[0052] In the formula: ρ is the electrolyte density, P is the pressure, μ is the electrolyte viscosity, ε is the electrode porosity, and κ is the electrode permeability. The initial parameter settings are shown in Table 1.

[0053] Table 1 Initial Parameter Settings

[0054]

[0055] Example 2

[0056] A method for calculating the loading arm coefficient to optimize the bipolar interdigital flow channel in a flow battery is proposed. First, the loading arm coefficient is defined as the pressure drop of the electrolyte flowing through the porous electrodes in the flow channel. Pressure drop of electrolyte flowing through interdigitated channels The ratio, that is

[0057] Calculate pressure drop

[0058] 1) The cross-sectional width of the flow channel is a = 3.0 mm, the height is b = 9.0 mm, and the equivalent diameter is...

[0059] 2) Electrolyte density ρ = 1330 kg / m³ 3 The electrolyte flow velocity in the channel is v1 = 0.370 m / s, and the fluid viscosity coefficient is η = 0.002709 m·g·s. Laminar flow;

[0060] 3) Then the friction coefficient The flow channel length l1 = 0.5m. Pressure drop along the flow path

[0061] 4) The electrolyte flow length in the electrode is l2 = 22.5 mm = 0.0225 m, the electrolyte flow velocity on the porous electrode surface is v2 = 20 mm / s = 0.02 m / s, and the electrode permeability is k = 9.8 × 10⁻⁶. -11 ,

[0062] calculate This indicates that under this flow channel design and flow rate control, the electrolyte flow uniformity is good.

[0063] The actual flow channel was simulated using the fluid simulation software Ansys Fluent. The Navier-Stockes equation and the Brinkman equation were used to describe the momentum conservation of the electrolyte within the flow channel and porous electrode. Their respective expressions are as follows:

[0064]

[0065] In the formula: ρ is the electrolyte density, P is the pressure, μ is the electrolyte viscosity, ε is the electrode porosity, and κ is the electrode permeability. The initial parameter settings are shown in Table 1.

[0066] Comparative Example 1

[0067] A method for calculating the loading arm coefficient to optimize the bipolar interdigital flow channel in a flow battery is proposed. First, the loading arm coefficient is defined as the pressure drop of the electrolyte flowing through the porous electrodes in the flow channel. Pressure drop of electrolyte flowing through interdigitated channels The ratio, that is

[0068] Calculate pressure drop

[0069] 1) The cross-sectional width of the flow channel is a = 8.0 mm, the height is b = 1.0 mm, and the equivalent diameter is...

[0070] 2) Electrolyte density ρ = 1330 kg / m³ 3 The electrolyte flow velocity in the channel is v1 = 0.391 m / s, and the fluid viscosity coefficient is η = 0.002709 m·g·s. Laminar flow;

[0071] 3) Then the friction coefficient The flow channel length l1 = 0.5m.

[0072] Pressure drop along the flow path

[0073] 4) The electrolyte flow length in the electrode is l2 = 11.58 mm = 0.01158 m, the electrolyte flow velocity on the porous electrode surface is v2 = 6.3 mm / s = 0.0063 m / s, and the electrode permeability is k =

[0074] calculate This indicates that under this flow channel design and flow rate control, the electrolyte flow uniformity is poor.

[0075] Comparative Example 2

[0076] A method for calculating the loading arm coefficient to optimize the bipolar interdigital flow channel in a flow battery is proposed. First, the loading arm coefficient is defined as the pressure drop of the electrolyte flowing through the porous electrodes in the flow channel. Pressure drop of electrolyte flowing through interdigitated channels The ratio, that is

[0077] Calculate pressure drop

[0078] 1) The cross-sectional width of the flow channel is a = 8.0 mm, the height is b = 1.0 mm, and the equivalent diameter is...

[0079] 2) Electrolyte density ρ = 1330 kg / m³ 3 The electrolyte flow velocity in the channel is v1 = 0.586 m / s, and the fluid viscosity coefficient is η = 0.002709 m·g·s. Laminar flow;

[0080] 3) Then the friction coefficient The flow channel length l1 = 0.5m.

[0081] Pressure drop along the flow path

[0082] 4) The electrolyte flow length in the electrode is l2 = 11.58 mm = 0.01158 m, the electrolyte flow velocity on the porous electrode surface is v2 = 9.4 mm / s = 0.0094 m / s, and the electrode permeability is k = 9.8 × 10⁻⁶ m / s. -11 ,

[0083] calculate This indicates that under this flow channel design and flow rate control, the electrolyte flow uniformity is poor.

[0084] Comparative Example 3

[0085] A method for calculating the loading arm coefficient to optimize the bipolar interdigital flow channel in a flow battery is proposed. First, the loading arm coefficient is defined as the pressure drop of the electrolyte flowing through the porous electrodes in the flow channel. Pressure drop of electrolyte flowing through interdigitated channels The ratio, that is

[0086] Calculate pressure drop

[0087] 1) The cross-sectional width of the flow channel is a = 8.0 mm, the height is b = 1.0 mm, and the equivalent diameter is...

[0088] 2) Electrolyte density ρ = 1330 kg / m³ 3 The electrolyte flow velocity in the channel is v1 = 0.781 m / s, and the fluid viscosity coefficient is η = 0.002709 m·g·s. Laminar flow;

[0089] 3) Then the friction coefficient The flow channel length l1 = 0.5m.

[0090] Pressure drop along the flow path

[0091] 4) The electrolyte flow length in the electrode is l2 = 11.58 mm = 0.01158 m, the electrolyte flow velocity on the porous electrode surface is v2 = 12.5 mm / s = 0.0125 m / s, and the electrode permeability is k = 9.8 × 10⁻⁶ m / s. -11 ,

[0092] calculate This indicates that under this flow channel design and flow rate control, the electrolyte flow uniformity is poor.

[0093] like Figure 2 , Figure 2 In the figures (a) and (b), the velocity contour maps of the center position of the porous electrode in the actual flow channel simulation of Examples 1 and 2 are respectively. Figure 3 In (a), (b), and (c) (which are velocity contour plots of the center position of the porous electrode in the actual flow channel simulation of Comparative Examples 1, 2, and 3, respectively), it can be found that... Figure 2 The velocity distribution in the electrolyte is more uniform. That is, under the flow channel design and flow rate control in Examples 1 and 2, the calculated loading arm coefficient is >25, and the actual flow channel simulation verifies that the electrolyte can flow uniformly through the porous electrode at this time.

[0094] In summary, this invention provides a calculation method for optimizing the loading arm coefficient of the bipolar interdigitated flow channel in a flow battery. This method calculates the loading arm coefficient of the bipolar interdigitated flow channel within the flow battery, supplemented by flow channel simulation and actual flow channel verification, to improve the uniformity of electrolyte flow within the bipolar plate. The method of this invention enables the electrolyte to flow uniformly through the electrodes, ensuring sufficient contact between the electrolyte and the electrodes, thereby facilitating a full and uniform reaction, increasing the electrochemical reaction rate, reducing concentration polarization caused by uneven flow and reaction, achieving uniform electrolyte flow within the porous electrodes at lower resistance, improving the operating efficiency of the battery stack, suppressing side reactions, enhancing the reliability of the flow battery stack, and extending its service life, demonstrating excellent application prospects.

[0095] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0096] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0097] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0098] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0099] The terms "first" and "second" used in the embodiments are merely to distinguish similar objects and do not represent a specific ordering of objects. It is understood that "first" and "second" can be interchanged in a specific order or sequence where permitted. It should be understood that the objects distinguished by "first" and "second" can be interchanged where appropriate so that the embodiments described herein can be implemented in an order other than those illustrated or described herein.

[0100] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calculating the optimization coefficient of the bipolar plate interdigitated flow channel in a flow battery, characterized in that, Includes the following steps: S1. Calculate the pressure drop of the electrolyte flowing through the interdigitated channel. S2. Calculate the pressure drop of the electrolyte flowing through the porous electrode in the flow channel. S3. Define and calculate the loading arm coefficient; the loading arm coefficient is the pressure drop of the electrolyte flowing through the porous electrode between the flow channels. Pressure drop of electrolyte flowing through interdigitated channels The ratio, that is S4. By limiting the value of the loading arm coefficient, the uniformity of electrolyte flow in the flow channel is measured, and the actual flow channel and flow rate of the flow battery are optimized and adjusted; it is limited that the uniform distribution of electrolyte in the porous electrode under the interdigitated flow channel structure can only be guaranteed when the loading arm coefficient is greater than 25.

2. The calculation method for optimizing the bipolar plate interdigitated flow channel of the loading arm for a flow battery according to claim 1, characterized in that: Step S1 specifically includes the following: S11, Define the formula: Where D e Let A be the equivalent diameter, A be the cross-sectional area of ​​the flow channel, and L be the wetted perimeter of the flow channel; let a and b be the width and height of the flow channel cross-section, respectively. Then A = ab, L = 2(a + b). Therefore, S12, Define the formula: Where Re is the Reynolds number, ρ is the fluid density, v1 is the electrolyte flow rate, d is the characteristic length, and η is the fluid viscosity coefficient; S13. When Re < 2000, in the laminar flow region, the friction coefficient is... S14. When 4000 < Re < 10000, in the turbulent region, the friction coefficient is... S15, Frictional pressure loss in the flow channel region, i.e., the pressure drop of the electrolyte flowing through the interdigitated flow channel. Where l1 is the flow channel length The average flow velocity is denoted as .

3. The calculation method for optimizing the bipolar plate interdigitated flow channel of the loading arm for a flow battery according to claim 1, characterized in that: Step S2 specifically includes the following: Pressure loss in the porous electrode region refers to the pressure drop of the electrolyte as it flows through the porous electrodes in the flow channels. Where l2 is the length of the electrolyte flow through the electrode, η is the fluid viscosity coefficient, v2 is the flow velocity of the electrolyte on the porous electrode surface, and k is the electrode permeability.

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