Flow battery storage tank electrolyte self-balancing system
By using asymmetrically designed positive and negative electrode storage tanks and liquid level balancing pipes, combined with liquid addition ball valves and drain ball valves, the problem of electrolyte volume shift in vanadium redox flow batteries was solved, realizing automatic electrolyte adjustment and unattended operation, thus improving system stability and safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ZHANGJIAGANG DETAI ENERGY STORAGE EQUIP CO LTD
- Filing Date
- 2025-06-13
- Publication Date
- 2026-07-07
AI Technical Summary
In existing vanadium redox flow battery systems, the electrolyte volume shifts asymmetrically during charging and discharging, resulting in capacity imbalance. This requires manual intervention and sensor monitoring, making it impossible to achieve automated and unattended operation.
The positive and negative electrode storage tanks and liquid level balance pipes adopt an asymmetrical design. By setting a liquid level balance pipe with a specific height difference, the volume change characteristics of the electrolyte are used to achieve automatic adjustment. Combined with the design of the liquid addition ball valve and the drain ball valve, the self-balancing of the electrolyte is achieved.
It enables automatic adjustment of electrolyte and unattended operation, reduces manual intervention, improves system stability and safety, reduces environmental pollution risks, and enhances ease of operation and system automation.
Smart Images
Figure CN224472459U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of flow battery technology, and in particular relates to a self-balancing system for electrolyte in a flow battery storage tank. Background Technology
[0002] During the charging and discharging process of a vanadium redox flow battery (VRFB), the average oxidation state of vanadium ions in the electrolyte is approximately +2.5 in the initial state. After charging, the positive electrode side stores active material dominated by +4 and +5 vanadium ions, while the negative electrode side stores mainly +2 and +3 vanadium ions, stored in their respective electrolyte reservoirs. This change in valence state directly leads to a change in volume: during charging, the positive electrode side loses water due to oxidation, resulting in a decrease in volume; the negative electrode side absorbs water due to reduction, resulting in an increase in volume. During discharging, the opposite occurs, and the volume change trend reverses. However, in actual operation, this volume change exhibits a certain asymmetry, resulting in an irreversible cumulative shift towards the positive electrode. This shift is influenced by various factors, such as the material properties of the ion exchange membrane, electrolyte acidity, operating temperature, and charging / discharging strategy, and is a common phenomenon in vanadium redox flow battery systems. Typically, the volume shift per cycle is between 0.5% and 2.5%. As the number of cycles increases, the offset will gradually accumulate. Therefore, it is necessary to control it by dynamically replenishing the electrolyte or periodically rebalancing the electrolyte to maintain the stable operation of the system.
[0003] The commonly used method for electrolyte rebalancing control involves manually adjusting the distribution of electrolyte at both electrodes by opening or closing valves in the level balancing pipeline, based on changes in the capacity of the positive and negative electrolyte storage tanks, to achieve capacity balance. Because electrolyte volume shifts are inherently uncertain, this process typically relies on sensors for change alerts. However, sensor measurements are prone to error, requiring manual on-site verification before operation. Given the various uncertainties involved in system operation, the entire process requires continuous monitoring and intervention by experienced professionals, making fully automated and unattended operation currently impossible. Utility Model Content
[0004] The purpose of this utility model embodiment is to provide a self-balancing system for electrolyte in a flow battery storage tank, so as to solve the capacity imbalance problem caused by electrolyte volume shift during the charging and discharging process of vanadium redox flow batteries, and realize automatic adjustment and unattended operation.
[0005] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is a self-balancing system for electrolyte in a flow battery storage tank, comprising a negative electrode storage tank, a positive electrode storage tank, and a level balancing pipe; the negative electrode storage tank and the positive electrode storage tank have the same bottom shape, size, and height; the cross-sectional area of the positive electrode storage tank in at least one cross-sectional region is smaller than the cross-sectional area of the corresponding position of the negative electrode storage tank; a level balancing pipe is provided between the negative electrode storage tank and the positive electrode storage tank, with one end of the level balancing pipe connected to the positive electrode storage tank and the other end connected to the negative electrode storage tank.
[0006] Furthermore, the liquid level balancing pipe is arranged near the top of the side wall of the positive electrode storage tank and the negative electrode storage tank; the connection height between the liquid level balancing pipe and the positive electrode storage tank is 80% to 85% of the height of the positive electrode storage tank; the connection height between the liquid level balancing pipe and the negative electrode storage tank is 75% to 80% of the height of the negative electrode storage tank.
[0007] Furthermore, the connection between the liquid level balance pipe and the positive electrode storage tank is higher than the connection between the liquid level balance pipe and the negative electrode storage tank, and the height difference accounts for 5% of the total height of the positive electrode storage tank or the negative electrode storage tank.
[0008] Furthermore, the positive electrode storage tank has a recessed structure on the top of the side near the negative electrode storage tank, and the liquid level balance pipe is located in the recessed area of the positive electrode storage tank.
[0009] Furthermore, the liquid level balancing pipe is connected to the positive storage tank via a positive electrode flange and to the negative storage tank via a negative electrode flange; the liquid level balancing pipe is equipped with a filling ball valve and a drain ball valve, the filling ball valve being located near the positive storage tank and the drain ball valve being located near the negative storage tank; a positive balance ball valve is located between the positive electrode flange and the filling ball valve, and a negative balance ball valve is located between the negative electrode flange and the drain ball valve.
[0010] Furthermore, the valve passages of the liquid filling ball valve and the drain ball valve are right-angled structures and are connected to the liquid level balance pipe by threaded fixing.
[0011] Furthermore, both the negative electrode storage tank and the positive electrode storage tank are provided with manhole flanges on their tops, and the manhole flanges are annular.
[0012] Furthermore, the positive electrode storage tank and the negative electrode storage tank are made of polyethylene, and the liquid level balance pipe is made of unplasticized polyvinyl chloride.
[0013] Compared with existing technologies, the advantages of this invention are a significant reduction in the need for manual intervention, enabling unmanned operation of electrolyte management in flow battery storage tanks. This invention employs asymmetrically designed positive and negative electrode storage tanks (made of PE) and a liquid level balancing pipe (made of UPVC) designed based on the volume change characteristics of the electrolyte during charging and discharging. This allows the invention to automatically adjust the volume difference between the positive and negative electrode electrolytes during long-term charge-discharge cycles, achieving electrolyte self-balancing without relying on sensor monitoring or manual calibration. Specifically, this invention utilizes the characteristic that the volume of the positive electrode electrolyte decreases and the volume of the negative electrode electrolyte increases during charging, and the opposite trend occurs during discharging. By setting up a liquid level balancing pipe with a specific height difference, the system can naturally redistribute the electrolyte, thereby avoiding the risk of decreased energy storage efficiency or equipment failure due to electrolyte volume shift. Furthermore, this invention provides a convenient electrolyte filling and emptying mechanism. The design of the filling ball valve and the emptying ball valve makes maintenance simpler and faster, while reducing the risk of environmental pollution.
[0014] In summary, this utility model not only improves the automation and stability of the system, but also enhances operational safety and environmental friendliness, demonstrating significant technological advancement and practical value. Attached Figure Description
[0015] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0016] Figure 1 This is a three-dimensional diagram of the electrolyte self-balancing system of the flow battery storage tank in this embodiment;
[0017] Figure 2 This is a top view of the self-balancing system of the electrolyte in the flow battery storage tank according to this embodiment;
[0018] Figure 3 This is a front view of the self-balancing system of the electrolyte in the flow battery storage tank according to this embodiment;
[0019] 1. Positive electrode flange; 2. Positive electrode balancing ball valve; 3. Negative electrode flange; 4. Negative electrode balancing ball valve; 5. Drain ball valve; 6. Liquid filling ball valve; 7. Liquid level balancing pipe; 8. Negative electrode storage tank; 9. Positive electrode storage tank; 10. Manhole flange. Detailed Implementation
[0020] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0021] like Figures 1-3 This embodiment provides a self-balancing electrolyte system for a flow battery storage tank, including a negative electrode storage tank 8, a positive electrode storage tank 9, and a level balancing pipe 7; as shown... Figure 1 In some specific embodiments, the negative electrode storage tank 8 and the positive electrode storage tank 9 have an asymmetrical structural design, but their bottom dimensions, shape, and height are the same. The positive electrode storage tank 9 has a recessed structure on the side near the negative electrode storage tank 8. When the negative electrode storage tank 8 and the positive electrode storage tank 9 have the same bottom dimensions and height (in this embodiment, it is a cuboid structure, but not limited to this shape), by adjusting the size of the cross-sectional area perpendicular to the width direction, the positive electrode electrolyte and the negative electrode electrolyte can form the required liquid level difference during operation, that is, the liquid level of the positive electrode electrolyte is higher than that of the negative electrode electrolyte. The recessed area on the positive electrode storage tank 9 not only facilitates the connection and installation of the liquid level balance pipe 7, but also serves as a platform to support and integrate other related components required after the negative electrode storage tank 8 and the positive electrode storage tank 9 are combined, improving the compactness and functionality of the overall structure. To achieve the required level difference between the positive and negative electrolytes, the cross-sectional area of the positive electrode storage tank 9 in at least one cross-sectional region is smaller than the cross-sectional area of the negative electrode storage tank 8 at the corresponding position. This design ensures dynamic adaptation to level changes during system operation, especially during charge-discharge cycles: during charging, the negative electrolyte level rises above the positive electrolyte level; while during discharging, the positive electrolyte level rises accordingly and exceeds the negative electrolyte level. This embodiment optimizes the dynamic response capability of the liquid level through a rational design of the storage tank geometry, thereby effectively improving the operational stability and energy conversion efficiency of the flow battery system.
[0022] In some specific implementations, both the negative electrode storage tank 8 and the positive electrode storage tank 9 are equipped with annular manhole flanges 10 on their tops, which facilitates personnel to enter the tanks for pipeline assembly and quality inspection, improving the maintainability and ease of operation of the equipment and ensuring the safety and efficiency of internal operations.
[0023] In some specific embodiments, a liquid level balancing pipe 7 is provided in the recessed area of the positive electrode storage tank 9. One end of the liquid level balancing pipe 7 is connected to the positive electrode storage tank 9, and the other end is connected to the negative electrode storage tank 8 to achieve liquid level balance control between the two storage tanks. Specifically, the liquid level balancing pipe 7 is arranged near the top of the side wall of the positive electrode storage tank 9 and the negative electrode storage tank 8. Further, the connection height between the liquid level balancing pipe 7 and the positive electrode storage tank 9 is 80% to 85% of the height of the positive electrode storage tank 9, preferably 85%; while the connection height between the liquid level balancing pipe 7 and the negative electrode storage tank 8 is 75% to 80% of the height of the negative electrode storage tank 8, preferably 80%. Through the above structural design, while ensuring the effective volume of the storage tanks, it is possible to effectively prevent operational risks or safety hazards caused by excessively high electrolyte levels, and at the same time ensure the stability and controllability of the dynamic changes in liquid level during the charging and discharging process.
[0024] In some specific embodiments, the liquid level balancing pipe 7 is connected to the positive electrode storage tank 9 through the positive electrode connecting flange 1 and to the negative electrode storage tank 8 through the negative electrode connecting flange 3, so as to ensure the fixed sealing of the liquid level balancing pipe 7 with the positive electrode storage tank 9 and the negative electrode storage tank 8.
[0025] In some specific embodiments, the connection point between the liquid level balancing pipe 7 and the positive electrode storage tank 9 is higher than its connection point with the negative electrode storage tank 8, and the height difference accounts for 5% of the height of either the positive electrode storage tank 9 or the negative electrode storage tank 8. During charging, due to the phenomenon that the volume of the positive electrode material decreases while the volume of the negative electrode material increases, this embodiment provides a necessary liquid medium compensation mechanism. However, during discharging, the volume change trend is the opposite, with an irreversible cumulative shift towards the positive electrode. That is, when charging, the volume of the negative electrode electrolyte is larger than that of the positive electrode electrolyte, and when discharging, the volume of the positive electrode electrolyte is larger than that of the negative electrode electrolyte. However, at the end of each charge-discharge cycle, the volume of the positive electrode electrolyte is slightly larger than that of the negative electrode electrolyte again, and the volume of the positive electrode electrolyte continues to accumulate with the increase of the number of charge-discharge cycles. This phenomenon is irreversible. This embodiment, by connecting one end of the liquid level balancing pipe 7 to the higher positive electrode storage tank 9 and the other end to the lower negative electrode storage tank 8, helps to maintain the balance of the liquid level between the two storage tanks, while adapting to the irreversible volume changes that occur inside the battery over time.
[0026] In this embodiment, during the charging process, the positive electrolyte level gradually decreases, while the negative electrolyte level rises accordingly. However, since the negative electrolyte level will not exceed the height of the connection port of the level balance pipe 7 on the positive electrolyte storage tank 9 side, excessive backflow or overflow can be effectively prevented.
[0027] During discharge, the positive electrode electrolyte level gradually recovers to its initial height. Towards the end of discharge, influenced by the volume changes of the positive and negative electrode electrolytes, the positive electrode electrolyte level eventually rises slowly and exceeds the height of the level balance pipe 7. At this point, some electrolyte flows into the negative electrode storage tank 8 through the level balance pipe 7, thus achieving dynamic transfer and redistribution of electrolyte between the positive and negative electrodes. During this process, the average oxidation state of vanadium in both the positive and negative electrode electrolytes remains at approximately 2.5, which is beneficial for maintaining the system's chemical stability and electrochemical performance. This level balance mechanism achieves adaptive adjustment and automatic balancing of the electrolyte during charge-discharge cycles without external control, improving the system's operational stability and reliability.
[0028] In some specific embodiments, the liquid level balancing pipe 7 is also equipped with a liquid filling ball valve 6 and a drain ball valve 5, the valve passages of which are right-angled. The liquid filling ball valve 6 is located near the positive electrode storage tank 9 to facilitate the addition of liquid medium to the system; the drain ball valve 5 is located near the negative electrode storage tank 8 to drain the electrolyte in the liquid level balancing pipe 7 when necessary. Both the liquid filling ball valve 6 and the drain ball valve 5 are connected to the liquid level balancing pipe 7 by threaded fixing to ensure the stability and sealing of the connection. When the liquid level balancing pipe 7 needs to be replaced, the system can be isolated by closing the positive electrode balancing ball valve 2 and the negative electrode balancing ball valve 4, and the replacement operation of the liquid level balancing pipe 7 can be carried out conveniently and quickly by utilizing the design of the ball valve's live thread. In particular, before replacing the liquid level balancing pipe 7, if there is electrolyte in the pipe, the electrolyte can be completely drained by operating the drain ball valve 5 to avoid waste of electrolyte and potential environmental pollution. This design not only improves the efficiency of maintenance work but also ensures operational safety and meets environmental protection requirements. A positive balancing ball valve 2 is installed between the positive electrode flange 1 and the filling ball valve 6; similarly, a negative balancing ball valve 4 is installed between the negative electrode flange 3 and the drain ball valve 5, facilitating the replacement and adjustment of the liquid level balancing pipe 7 during later operation and maintenance. This implementation allows for flexible adjustment and replacement of the liquid level balancing pipe 7 without damaging the overall system structure, improving the system's maintainability and adaptability.
[0029] In some specific embodiments, the positive electrode storage tank 9 and the negative electrode storage tank 8 are made of polyethylene (PE), and the liquid level balance pipe 7 is made of unplasticized polyvinyl chloride (UPVC).
[0030] This implementation adopts an overflow self-balancing design, which, based on the inherent characteristics of electrolyte volume change during charging and discharging, achieves automatic adjustment and dynamic balance of the positive and negative electrode electrolyte volumes. It does not require the introduction of additional control logic or auxiliary equipment, has a simple structure, is highly efficient in operation, and effectively avoids the risk of self-discharge.
[0031] By rationally designing the dimensional parameters of the positive electrode storage tank 9 and the negative electrode storage tank 8, and while maintaining the same overall volume, a differentiated liquid level is set (the liquid level in the positive electrode storage tank 9 is higher than that in the negative electrode storage tank 8), thus constructing a height difference that meets the system's operational requirements. This height difference is determined through optimized calculations based on the volume change pattern during the electrochemical reaction process, ensuring the accuracy and stability of liquid level control.
[0032] During the charging phase, the negative electrode electrolyte changes from a high oxidation state (such as V) to a high oxidation state. 5+ ) reduced to a lower oxidation state (such as V) 2+ As the volume increases, the liquid level rises; meanwhile, the positive electrode electrolyte undergoes an oxidation reaction, changing from a low oxidation state (e.g., V) to a higher oxidation state. 2+ ) transforms into a higher oxidation state (such as V) 5 + As the volume decreases, the liquid level drops. Since the negative electrode liquid level will never exceed the height of the connection port of the liquid level balance pipe 7 on the positive electrode side, there is no phenomenon of electrolyte backflow into the positive electrode storage tank 9, thus avoiding self-discharge.
[0033] During the discharge phase, the negative electrode electrolyte is re-oxidized, its volume decreases, and its level drops; while the positive electrode electrolyte volume recovers and gradually rises. Based on the asymmetric nature of the volume changes of the positive and negative electrode electrolytes, at the end of the discharge phase, the electrolyte level in the positive electrode storage tank 9 will exceed the height of the level balance pipe 7. The electrolyte will then flow naturally into the negative electrode storage tank 8 through the connecting pipe, achieving volume redistribution and level balance within the system. At this point, the electrolyte as a whole is in a near-average valence state (approximately V). 3 . 5 In the 2.5 valence state, the self-discharge tendency of the system is significantly reduced.
[0034] In addition, the flow of the positive electrode electrolyte to the negative electrode storage tank 8 also promotes the mixing of the two electrode electrolytes, which helps to further achieve the homogenization of the redox valence state and the stability of the system's electrochemical performance, thereby enhancing the operational consistency and long-term reliability of the entire energy storage system.
[0035] The above description is merely a preferred embodiment of this utility model and is not intended to limit the scope of protection of this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model are included within the scope of protection of this utility model.
Claims
1. A self-balancing system for the electrolyte in a flow battery storage tank, characterized in that, The negative electrode storage tank (8), the positive electrode storage tank (9), and the liquid level balance pipe (7) are provided. The negative electrode storage tank (8) and the positive electrode storage tank (9) have the same bottom shape, size, and height. The cross-sectional area of the positive electrode storage tank (9) in at least one cross-sectional area is smaller than the cross-sectional area of the negative electrode storage tank (8) at the corresponding position. A liquid level balance pipe (7) is provided between the negative electrode storage tank (8) and the positive electrode storage tank (9). One end of the liquid level balance pipe (7) is connected to the positive electrode storage tank (9), and the other end is connected to the negative electrode storage tank (8).
2. The self-balancing system for electrolyte in a flow battery storage tank according to claim 1, characterized in that, The liquid level balancing pipe (7) is arranged near the top of the side wall of the positive electrode storage tank (9) and the negative electrode storage tank (8); the connection height between the liquid level balancing pipe (7) and the positive electrode storage tank (9) is 80% to 85% of the height of the positive electrode storage tank (9); the connection height between the liquid level balancing pipe (7) and the negative electrode storage tank (8) is 75% to 80% of the height of the negative electrode storage tank (8).
3. The self-balancing system for the electrolyte in the liquid flow battery storage tank according to claim 2, characterized in that, The connection between the liquid level balance pipe (7) and the positive electrode storage tank (9) is higher than the connection between the liquid level balance pipe (7) and the negative electrode storage tank (8), and the height difference accounts for 5% of the total height of the positive electrode storage tank (9) or the negative electrode storage tank (8).
4. The self-balancing system for the electrolyte in the liquid flow battery storage tank according to claim 1, characterized in that, The positive electrode storage tank (9) has a recessed structure on the top of the side near the negative electrode storage tank (8), and the liquid level balance pipe (7) is located in the recessed area of the positive electrode storage tank (9).
5. The self-balancing system for the electrolyte in the liquid flow battery storage tank according to claim 1, characterized in that, The liquid level balancing pipe (7) is connected to the positive electrode storage tank (9) through the positive electrode connecting flange (1) and to the negative electrode storage tank (8) through the negative electrode connecting flange (3). The liquid level balancing pipe (7) is equipped with a liquid filling ball valve (6) and a drain ball valve (5). The liquid filling ball valve (6) is located near the positive electrode storage tank (9), and the drain ball valve (5) is located near the negative electrode storage tank (8). A positive electrode balancing ball valve (2) is provided between the positive electrode connecting flange (1) and the liquid filling ball valve (6), and a negative electrode balancing ball valve (4) is provided between the negative electrode connecting flange (3) and the drain ball valve (5).
6. The self-balancing system for the electrolyte in the liquid flow battery storage tank according to claim 5, characterized in that, The valve passages of the liquid filling ball valve (6) and the drain ball valve (5) are right-angled structures and are connected to the liquid level balance pipe (7) by threaded fixing.
7. The self-balancing system for the electrolyte in the liquid flow battery storage tank according to claim 1, characterized in that, Both the negative electrode storage tank (8) and the positive electrode storage tank (9) are provided with manhole flanges (10) on their tops, and the manhole flanges (10) are circular.
8. The self-balancing system for electrolyte in a flow battery storage tank according to claim 1, characterized in that, The positive electrode storage tank (9) and the negative electrode storage tank (8) are made of polyethylene, and the liquid level balance pipe (7) is made of unplasticized polyvinyl chloride.