Flow cell performance improvement method based on flow channel geometrical shape optimization

Abstract

The invention discloses a flow battery performance improvement method based on flow channel geometrical shape optimization, and provides a calculation formula of a performance optimal coefficient (POC) in order to solve the problem of multi-parameter coupling in a traditional flow channel design method. Through the formula, an optimal coefficient can be calculated according to geometric parameters (such as flow channel width, rib width, sectional area, diagonal length, flow velocity and the like) of the flow channel, and the optimal coefficient is used for quantifying the influence of different flow channel geometric shapes on the battery performance. The formula not only simplifies the complex flow channel design process, but also can accurately predict the performance of the geometric structure of the flow channel in practical application. By accurately controlling parameters such as runner width, rib width, flow velocity, pump power and the like, the energy loss can be reduced while the optimal battery performance is maintained.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow batteries, and in particular to a method for optimizing fluid flow characteristics by adjusting the aspect ratio of a flow field section while maintaining a constant flow field cross-sectional area. The method is applicable to the flow field optimization design of vanadium liquid flow batteries (VRFBs) to improve the overall performance and energy utilization efficiency of the battery. Background Art

[0002] Vanadium redox flow batteries (VRFBs) are a highly efficient energy storage technology widely used in renewable energy storage and grid regulation. However, factors such as electrolyte flow uniformity, mass transfer capacity, and pump power consumption significantly impact battery efficiency and lifespan. Traditional flow field designs primarily employ fixed structures such as serpentine, parallel, and staggered channels. However, these designs have limited adaptability under varying operating conditions, leading to problems such as local concentration polarization, high pressure loss, and uneven electrochemical reactions.

[0003] In their 2024 paper, "Flow field structure design for redox flow battery: Developments and Prospects," published in the Journal of Energy Storage, Lu et al. analyzed that when the inlet and outlet channels of a parallel flow field are directly connected, the pressure drop between the parallel channels is small, the electrolyte velocity in the porous electrode leads to weak mass transfer and large concentration polarization. In their 2022 paper, "Numerical study on serpentine design flow channel configurations for vanadium redox flow batteries," Ali et al. analyzed that the serpentine flow field structure has the highest concentration in the inlet region and the lowest concentration in the outlet region, due to the gradual consumption of reactants along the flow direction, and exhibits high polarization losses.

[0004] In the paper "Effect of flowfield geometry on hydrodynamics of flow in redox flow battery" published in "Energy Engineering" in 2022, Kumar et al. analyzed the staggered flow field structure and found that the electrolyte velocity is higher in the inlet and outlet channel areas, while the velocity is lower in the area where the electrolyte flows into the porous electrode at the tail end of the channel.

[0005] Previous studies have shown that optimizing flow channel geometry (e.g., changing the width and depth of the flow channel) can effectively improve electrolyte flow distribution and enhance electrode material utilization. However, when optimizing flow channel geometry, how to adjust the flow field while maintaining a constant cross-sectional area to ensure optimized fluid dynamics while reducing manufacturing complexity and cost remains a current technical challenge. This paper proposes a new optimization method to improve the flow field design of VRFBs and enhance overall energy conversion efficiency. Summary of the Invention

[0006] This paper provides a method for improving flow battery performance based on flow channel geometry optimization, specifically targeting the flow channel design of vanadium redox flow batteries (VRFBs). By systematically studying the impact of different flow channel geometric parameters on battery performance, the paper proposes an empirical formula that combines flow channel geometry parameters with battery performance indicators, providing a concise and effective way to optimize flow channel design to improve the battery's voltage efficiency and overall performance.

[0007] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0008] A method for improving the performance of a flow battery based on the optimization of flow channel geometry uses the following calculation formula to improve the performance of the flow battery. The formula calculates the optimal performance coefficient of the battery based on parameters including flow channel width, rib width, flow channel cross-sectional area, diagonal length, flow velocity, and pump power. The calculation formula is:

[0009]

[0010] Among them, W cha is the channel width, W rib is the rib width, S cha is the channel cross-sectional area, L dia is the channel diagonal length, V inlet is the inlet flow rate, η d is the overpotential difference, P pump is the pump power loss.

[0011] Furthermore, the P pump is the pump loss power, calculated as follows:

[0012]

[0013] Furthermore, the flow channel width is 1.0-1.5 mm.

[0014] Furthermore, the width of the rib is 20%-30% of the width of the flow channel.

[0015] Furthermore, the cross-sectional area of ​​the channel is 1 mm 2.

[0016] Furthermore, the inlet flow rate is 120 ml / min to 180 ml / min.

[0017] Furthermore, the diagonal length of the channel is 1.41-1.64 mm.

[0018] Furthermore, the liquid flow battery structure includes a reaction area porous electrode (1), an electrolyte inlet (2), a rib area (3) between flow channels, and an electrolyte flow area flow channel (4), wherein the electrolyte flow area flow channel (4) is above the reaction area porous electrode (1), and the distance between two adjacent flow channels is the rib area (3).

[0019] Furthermore, the size of the porous electrode in the reaction area is 2×2 cm.

[0020] Furthermore, the width and height of the electrolyte inlet (2) vary with the size of the electrolyte flow channel (4), with the height being 1-1.5 mm and the width being 1-0.67 mm.

[0021] Compared with the prior art, the present invention has the following technical advantages:

[0022] (1) Create a quantitative analysis method for flow channel design, significantly improving design efficiency and accuracy

[0023] Compared with the flow channel design model in the prior art that relies on trial and error experiments or single parameter analysis, this invention has for the first time constructed an empirical formula system that integrates multi-dimensional geometric parameters such as flow channel width, rib width, cross-sectional area, diagonal length, flow rate, etc. By scientifically empowering the calculation of the optimal coefficient of battery performance (POC), the impact of complex flow channel structure on battery performance is converted into a quantifiable mathematical model, which completely changes the inefficient model of "repeated testing-gradual correction" in traditional design. It can provide engineers with accurate quantitative design tools to solve the core problems of fuzzy parameter correlation and insufficient prediction accuracy in the prior art.

[0024] (2) Construct a low-energy optimization strategy to achieve synergistic efficiency between electrochemical reaction and fluid mechanics

[0025] Existing flow battery flow channel designs often focus on optimizing a single performance indicator, making it difficult to balance electrochemical reaction efficiency and fluid transport energy consumption. The present invention proposes a breakthrough system optimization strategy based on flow channel geometric ratios. By precisely controlling the electrolyte flow morphology, it significantly reduces overpotential losses and pumping energy consumption while improving the uniformity of reactant distribution. The present invention achieves the dual goals of "mass transfer enhancement and energy consumption reduction" through geometric parameter optimization, breaking the inherent contradiction in existing technologies where performance improvement is accompanied by increased energy consumption, and provides a key technical path for the development of highly economical flow battery systems.

[0026] (3) Establish a cross-scale design theoretical framework to solve the problem of multi-physics field coupling prediction

[0027] In response to the industry pain points in the existing technology, such as the unclear influence of flow channel geometry on battery performance and the difficulty in quantifying the multi-parameter coupling effect, the present invention, through cross-validation of a large amount of experimental data and numerical simulation, reveals for the first time the intrinsic correlation mechanism between flow channel geometry parameters and electrochemical reactions, fluid flow, and mass transfer processes. The proposed empirical formula and optimization strategy can not only accurately predict key performance indicators such as energy efficiency and pressure loss under different flow channel structures, but also construct a cross-scale design theory system from microscopic mass transfer to macroscopic flow. This achievement fills the theoretical gap in the field of flow channel design for liquid flow batteries, provides a reusable methodology for the subsequent development of new flow channel structures, and completely changes the limitations of traditional design relying on experience accumulation, and promotes the paradigm shift of liquid flow battery design from "trial and error optimization" to "theory-guided design".

[0028] (4) Through simulation and experimental verification of different flow channel design schemes, the present invention further verifies the effectiveness of the optimized design. For example, a design with a flow channel width of 1.2 mm (SFW-12) was selected. Through experimental testing, at a flow rate of 120 ml / min, the battery voltage efficiency was 91.53%; and at a flow rate of 180 ml / min, the battery voltage efficiency increased to 92.34%. This design not only performs well in terms of electrolyte concentration distribution and flow rate distribution, but also significantly reduces the battery's overpotential difference and polarization loss, thereby improving the overall efficiency of the battery.

[0029] (5) The manufacturing difficulty of the liquid flow battery of the present invention is comparable to that of the prior art. However, after finding the optimal structure through the performance optimal coefficient formula proposed by the present invention, the overall efficiency of the battery can be improved, the cost can be effectively reduced, and the economic benefits can be improved.

[0030] (6) The present invention not only improves the electrochemical reaction efficiency of the flow battery, but also improves the stability of the system while reducing energy consumption by proposing a formula for the optimal performance coefficient and a method for optimizing the flow channel geometry. The optimized flow channel design can effectively improve the power density and energy conversion efficiency of the battery and reduce pump power consumption, providing reliable technical support for the efficient operation of the flow battery. The present invention breaks through the limitations of traditional flow battery design methods by optimizing the flow channel geometry and adopting an innovative formula for the optimal performance coefficient, providing a high-efficiency, low-energy flow battery flow channel optimization solution. This technology not only provides a theoretical basis for the design of flow batteries, but also has broad practical application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The design diagrams of the serpentine flow channel with six different widths are shown;

[0032] Figure 2 Schematic diagram of the serpentine flow field structure;

[0033] Figure 3 Schematic diagram of cross-section location. DETAILED DESCRIPTION

[0034] The present invention relates to a method for improving the performance of liquid flow batteries, specifically by optimizing the flow channel geometry to enhance the battery's power efficiency and energy conversion efficiency. Flow battery performance is significantly influenced by flow channel geometry, particularly factors such as channel width, depth, rib width, cross-sectional area, and flow rate. Proper design of these geometric parameters can significantly improve electrolyte flow distribution, reduce energy losses, and enhance the battery's overall efficiency.

[0035] First of all, the width of the flow channel is one of the most critical parameters in the design. The flow channel width directly determines the flow path of the electrolyte, affecting the flow rate of the electrolyte and the reaction efficiency of the battery. In the present invention, the flow channel width is designed to be between 1.0mm and 1.5mm. This range can effectively ensure the uniformity of the electrolyte flow and avoid the energy loss caused by too large or too small width. In addition, the rib width design is closely related to the flow channel width. The rib width usually accounts for 20% to 30% of the flow channel width. By reasonably configuring the ratio of rib width to flow channel width, the disturbance effect of electrolyte flow can be promoted, thereby improving the uniformity of electrolyte distribution on the electrode surface and in the porous material, enhancing the efficiency of the reaction and reducing the overpotential difference.

[0036] The cross-sectional area design of the flow channel is also crucial. In the present invention, the cross-sectional area of ​​the flow channel is set to 1mm 2 This setting ensures that the flow of the electrolyte is not overly restricted, and while increasing the flow rate, it avoids energy waste caused by an excessively large flow channel area. Optimizing the flow rate is also key to improving battery performance. Through experiments and simulation analysis, we found that when the flow rate ranges from 120ml / min to 180ml / min, the battery can achieve higher voltage efficiency and lower overpotential loss. In particular, at a flow rate of 180ml / min, the battery's voltage efficiency is significantly improved.

[0037] In addition to the flow channel geometry, the present invention also optimizes the diagonal length of the flow channel. The diagonal length of the flow channel affects the electrolyte flow path and the contact time of the electrolyte on the electrode surface. A longer diagonal helps increase the reaction time and area, thereby improving the battery's power density. However, an excessively long diagonal increases flow resistance, so the design needs to be considered in combination with the width and depth of the flow channel.

[0038] In order to solve the multi-parameter coupling problem existing in the traditional flow channel design method, the present invention proposes a calculation formula for the performance optimization coefficient (POC). Through this formula, an optimal coefficient can be calculated based on the geometric parameters of the flow channel (such as flow channel width, rib width, cross-sectional area, diagonal length, flow rate, etc.), which is used to quantify the impact of different flow channel geometries on battery performance. This formula not only simplifies the complex flow channel design process, but also accurately predicts the performance of the flow channel geometry in actual applications. By precisely controlling parameters such as flow channel width, rib width, flow rate, pump power, etc., it is possible to reduce energy loss while maintaining optimal battery performance.

[0039] The calculation formula is:

[0040]

[0041] Among them, W cha is the channel width, W rib is the rib width, S cha is the channel cross-sectional area, L dia is the channel diagonal length, V inlet is the inlet flow rate, η d Overpotential difference

[0042] Among them, P pump is the pump loss power, calculated as follows:

[0043]

[0044] By adjusting the weight coefficients of various parameters, the flow channel geometry can be flexibly optimized under different battery design requirements.

[0045] This calculation formula provides a theoretical basis for optimizing the design of vanadium redox flow battery flow channel structures, further improving the battery's power density, energy conversion efficiency, and system stability. Experimental data validates the effectiveness of this formula, showing that the optimal design predicted by the formula significantly reduces the battery's overpotential losses, improves the battery's voltage efficiency, and reduces system energy consumption, demonstrating broad application prospects.

[0046] The following is explained with more specific examples.

[0047] Example

[0048] The embodiment of the present invention takes the vanadium redox flow battery (VRFB) as an example, combines the proposed calculation formula, optimizes the design of different flow channel geometries, and verifies their effects on battery performance. In this example, the present invention adopts six different widths of serpentine flow channel variable size design, ranging from 1.0mm to 1.5mm, such as Figure 1As shown, the specific values ​​of the flow channel dimensions are shown in Table 1, and the flow channel cross-sectional area (5) remains unchanged at 1mm 2 , studying its impact on battery voltage efficiency and pump power.

[0049] Table 1 Specific numerical values ​​of variable dimension parameters of six serpentine flow channels with different widths (unit: mm)

[0050]

[0051] Key components of the vanadium flow battery structure such as Figure 2 and Figure 3 As shown, it includes a porous electrode 1 in the reaction area, an electrolyte inlet 2, a rib area 3 between flow channels, a flow channel 4 in the electrolyte flow area, and a flow channel cross-sectional area 5.

[0052] Because the present invention is designed and optimized based on a battery cell, the flow channel 4 in the electrolyte flow area is above the porous electrode in the reaction area, and the distance between two adjacent flow channels is the rib area.

[0053] Reaction area porous electrode: 2×2cm, inlet width and height will vary with the flow channel size. Height range: 1-1.5mm, width range: 1-0.67mm

[0054] First, a design with a flow channel width of 1.2 mm (SFW-12) was selected as an optimization reference. Through simulation analysis, it was found that this design exhibited the best battery performance at different flow rates. When the flow rate was 120 ml / min, the battery voltage efficiency reached 91.53%; when the flow rate was increased to 180 ml / min, the battery voltage efficiency was further improved to 92.34%, as shown in Table 2. In addition, the SFW-12 design significantly reduced the battery's overpotential difference and polarization loss, maintained good current uniformity and reaction consistency, and avoided the problems of local overheating and excessive current density.

[0055] Table 2 Numerical values ​​of single cell voltage efficiency

[0056]

[0057]

[0058] When compared to other designs (such as SFW-10 and SFW-15), the SFW-12 performs particularly well, especially in terms of electrolyte concentration distribution and flow rate distribution. By optimizing the flow channel width and rib width ratio, strong under-rib convection is ensured, promoting uniform distribution of electrolyte within the porous electrode, and effectively improving the battery's power density and energy conversion efficiency. Through calculation and verification of empirical formulas, it was found that the performance of the SFW-12 design is highly consistent with the results predicted by the formula, providing effective theoretical support and practical basis for future battery design.

[0059] The innovation of this invention lies in proposing an empirical formula that combines flow channel geometry parameters with battery performance indicators, providing a new approach to optimizing flow channel design in redox flow batteries (particularly vanadium redox flow batteries). This empirical formula takes into account factors such as flow channel width, rib width, flow channel cross-sectional area, diagonal length, and flow velocity. By assigning different weighting coefficients, it comprehensively calculates the battery's optimal performance coefficient (POC). This formula not only simplifies the complex calculations in the flow channel design process, but also accurately predicts and optimizes battery performance under different flow channel geometries.

[0060] Furthermore, through detailed experimental and numerical simulation analysis of different flow channel geometries, this paper proposes a new optimization strategy: by optimizing flow channel geometry ratios, electrolyte flow and reactant distribution are optimized, reducing overpotential losses and energy consumption, and improving the battery's power efficiency. This innovation improves the electrochemical reaction and mass transfer performance of the flow battery while reducing the system's energy consumption and pump power requirements, thus possessing significant practical application value.

[0061] By proposing and verifying this empirical formula, the present invention solves the difficult problem of predicting the impact of different geometric structures in flow channel design on battery performance, especially achieving breakthroughs in improving energy efficiency, reducing pressure loss and optimizing electrolyte flow, providing a theoretical basis and technical support for the design and optimization of liquid flow batteries.

Claims

1. A method for improving the performance of a flow battery based on flow channel geometry optimization, characterized in that: The following calculation formula is used to improve the performance of the flow battery. The formula calculates the optimal performance coefficient of the battery based on parameters including flow channel width, rib width, flow channel cross-sectional area, diagonal length, flow rate, and pump power. The calculation formula is: Among them, W cha is the channel width, W rib is the rib width, S cha is the channel cross-sectional area, L dia is the channel diagonal length, V inlet is the inlet flow rate, η d is the overpotential difference, P pump is the pump power loss.

2. The method for improving flow battery performance based on flow channel geometry optimization according to claim 1, characterized in that: The P pump is the pump loss power, calculated as follows:

3. The method for improving flow battery performance based on flow channel geometry optimization according to claim 1, characterized in that: The flow channel width is 1.0-1.5 mm.

4. The method for improving flow battery performance based on flow channel geometry optimization according to claim 1, characterized in that: The width of the rib is 20%-30% of the width of the flow channel.

5. The method for improving flow battery performance based on flow channel geometry optimization according to claim 1, characterized in that: The channel cross-sectional area is 1 mm 2 .

6. The method for improving flow battery performance based on flow channel geometry optimization according to claim 1, characterized in that: The inlet flow rate is 120 ml / min to 180 ml / min.

7. The method for improving flow battery performance based on flow channel geometry optimization according to claim 1, characterized in that: The diagonal length of the channel is 1.41-1.64 mm.

8. The method for improving flow battery performance based on flow channel geometry optimization according to claim 1, characterized in that: The liquid flow battery structure comprises a reaction region porous electrode (1), an electrolyte inlet (2), a rib region (3) between flow channels, and an electrolyte flow region flow channel (4). The electrolyte flow region flow channel (4) is above the reaction region porous electrode (1), and the distance between two adjacent flow channels is the rib region (3).

9. The method for improving flow battery performance based on flow channel geometry optimization according to claim 8, characterized in that: The size of the porous electrode in the reaction area is 2×2 cm.

10. The method for improving flow battery performance based on flow channel geometry optimization according to claim 1, characterized in that: The width and height of the electrolyte inlet (2) vary with the size of the electrolyte flow channel (4), with the height being 1-1.5 mm and the width being 1-0.67 mm.

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