A high-efficiency energy storage system and method based on bipolar membrane electrodialysis

Abstract

The application discloses a kind of high-efficiency energy storage system and method based on bipolar membrane electrodialysis, including multiple series setting bipolar membrane stack combination unit, electrode system, electrolyte circulation system, control system and auxiliary equipment.The application utilizes the water dissociation characteristics of bipolar membrane and the ion migration mechanism of electrodialysis, realizes the efficient storage and release of electric energy, is suitable for renewable energy storage, power grid peak shaving and distributed energy system and other fields, and significantly improves energy conversion efficiency, prolongs system life and reduces operating cost by optimizing membrane structure, improving system design and control strategy.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, specifically bipolar membrane electrodialysis, and more particularly to a high-efficiency energy storage system and method based on bipolar membrane electrodialysis (BPED). This invention utilizes the water dissociation characteristics of bipolar membranes and the ion migration mechanism of electrodialysis to achieve efficient storage and release of electrical energy, and is applicable to fields such as renewable energy storage, grid peak shaving, and distributed energy systems. Background Technology

[0002] With the rapid development of renewable energy sources (such as solar and wind power), energy storage technology has become crucial for addressing their intermittency and instability. Currently, common energy storage technologies include lithium-ion batteries, pumped hydro storage, and compressed air storage, but these technologies suffer from high costs, low efficiency, and significant environmental impact. Electrochemical energy storage technology has attracted widespread attention due to its high efficiency, flexibility, and environmental friendliness. Among these, electrodialysis and bipolar membrane electrodialysis technologies demonstrate enormous potential due to their unique ion migration mechanisms.

[0003] Electrodialysis (ED) is a technology that utilizes ion exchange membranes and electric fields to achieve directional ion migration, and it is widely used in water treatment, desalination, and energy storage. In the field of energy storage, electrodialysis technology achieves energy storage by converting electrical energy into chemical energy (such as the concentration difference of acid-base solutions). However, traditional electrodialysis technology has a low energy storage density, making it difficult to meet the needs of large-scale energy storage.

[0004] Bipolar membrane electrodialysis (BPED) is a technique that introduces a bipolar membrane into traditional electrodialysis. The bipolar membrane consists of a cation exchange layer and an anion exchange layer, and under the influence of an electric field, it can dissociate water molecules into H+. + and OH - The bipolar membrane generates ions, thus producing acid and alkali solutions, achieving a highly efficient conversion of electrical energy into chemical energy. Compared to traditional electrodialysis energy storage, the water dissociation characteristics of the bipolar membrane significantly improve energy conversion efficiency, and by generating high-concentration acid and alkali solutions, the energy storage density is significantly increased. Due to these characteristics, bipolar membrane electrodialysis energy storage technology is applicable to various application scenarios, including renewable energy storage and grid peak shaving. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a high-efficiency energy storage system and method based on bipolar membrane electrodialysis. This invention utilizes the water dissociation characteristics of bipolar membranes and the ion migration mechanism of electrodialysis to achieve efficient storage and release of electrical energy. It is applicable to fields such as renewable energy storage, grid peak shaving, and distributed energy systems. By optimizing the membrane structure, improving system design, and control strategies, it significantly improves energy conversion efficiency, extends system lifespan, and reduces operating costs.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention first provides a high-efficiency energy storage system based on bipolar membrane electrodialysis. The high-efficiency energy storage system includes multiple bipolar membrane stack units arranged in series, an electrode system, an electrolyte circulation system, a control system, and auxiliary equipment. Each bipolar membrane stack unit is composed of three layers: an anion exchange membrane, a bipolar membrane, and a cation exchange membrane. The electrode system includes an anode and a cathode. The voltage, current, and electrolyte flow rate are adjusted by the control system, and the system is kept stable by the auxiliary equipment.

[0007] As a preferred embodiment of the present invention, the electrolyte circulation system includes a salt chamber for storing a salt solution, an acid chamber for storing an acid solution, an alkali chamber for storing an alkali solution, a pump, and pipelines, the pipelines being connected to a bipolar membrane stack assembly unit.

[0008] As a preferred embodiment of the present invention, the control system includes a PLC and a real-time sensor monitoring system.

[0009] As a preferred embodiment of the present invention, both the anode and the cathode are made of titanium mesh coated with tantalum-iridium mixed metal oxide.

[0010] As a preferred embodiment of the present invention, the auxiliary equipment includes a circulating pump, valves, and sensors.

[0011] As a preferred embodiment of the present invention, the number of bipolar film stack combination units is 6-10.

[0012] As a preferred embodiment of the present invention, the membrane material of the bipolar membrane stack unit is perfluorosulfonic acid resin or polyether ether ketone.

[0013] The present invention also provides an operation method for the above-mentioned high-efficiency energy storage system based on bipolar membrane electrodialysis, wherein the operation method is divided into an energy storage process and a power generation process; The energy storage process is as follows: In charging mode, with external electrical energy input, the bipolar membrane dissociates water molecules into H+ under the influence of an electric field. + and OH - Ions, H + and OH -Ions migrate to the acid and base compartments respectively through cation exchange membranes and anion exchange membranes. In the acid and base compartments, H+... + and OH - Ions react with ions in the solution to generate acid and alkali solutions, realizing the conversion of electrical energy into chemical energy. The generated acid and alkali solutions are stored in the electrolyte circulation system, completing the energy storage process. The power generation process is as follows: In discharge mode, the stored acid and alkali solutions re-enter the bipolar membrane stack, and under the action of the reverse electric field, H... + and OH - Ions migrate in the opposite direction and recombine at the bipolar membrane interface to form water. The current generated by ion migration outputs electrical energy through an external circuit. The discharged solution returns to the electrolyte circulation system, completing the energy release process.

[0014] In a preferred embodiment of the present invention, 0.5-3 mol / L HCl solution, HNO3 solution, or H2SO4 solution is injected into the acid chamber, 0.5-3 mol / L NaOH solution is injected into the alkali chamber, and 0.35-1 mol / L NaCl solution, NaNO3 solution, or Na2SO4 solution is injected into the salt chamber; the electrolyte is a mixed solution of 0.1 mol / L K3[Fe(CN)6], 0.1 mol / L K4[Fe(CN)6], and 0.2 mol / L NaCl.

[0015] As a preferred embodiment of the present invention, during the energy storage process, the operating temperature is 10-60℃ and the charging current density is 20-1000A / m. 2 During power generation, the power generation current density is 20-1000 A / m. 2 The membrane voltage is 0.6-0.9V, and the power density is 5-8W / m³. 2 .

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1) The high-efficiency energy storage system of the present invention is environmentally friendly and pollution-free. The reverse bipolar membrane electrodialysis technology drives ion migration through an electric field without introducing other chemical substances. The whole process is clean and environmentally friendly and does not produce secondary pollution.

[0017] 2) The high-efficiency energy storage system of this invention utilizes waste salt or excess acid and alkali: the reverse bipolar membrane electrodialysis technology can utilize waste salt generated during industrial production to generate electricity, maximizing resource utilization. By optimizing system parameters, such as initial acid and alkali concentration, electrolyte mass fraction, and current density, system operating costs can be significantly reduced, improving economic efficiency. For example, when treating nanofiltration concentrated brine, the operating cost of the bipolar membrane electrodialysis process is lower than that of the traditional DTRO-evaporation crystallization process.

[0018] 3) Under optimized conditions, the high-efficiency energy storage system of this invention, compared with the reverse electrodialysis technology that utilizes salt energy difference for power generation, can achieve high voltage and high power density. Under conditions of acid-base concentration of 0.5-3 mol / L and salt chamber concentration of 0.35-1 mol / L, the membrane voltage is 0.6-0.9 V, and the power density can reach 5-8 W / m³. 2 .

[0019] 4) The high-efficiency energy storage system of the present invention is not only environmentally friendly and pollution-free, but also can effectively utilize waste salt or excess acid and alkali to generate electricity, thereby maximizing the utilization of resources. It has high economic feasibility and broad application prospects. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application 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 application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart of the high-efficiency energy storage system of the present invention.

[0022] Figure 2 This is a schematic diagram of the internal membrane arrangement of the bipolar membrane unit of the present invention.

[0023] In the diagram, 1. Bipolar membrane stack; 2. Electrode system; 3. Electrolyte circulation system; 4. Control system; 5. Auxiliary equipment. Detailed Implementation

[0024] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings and embodiments.

[0025] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. The terms "first," "second," etc., used in this invention are for the convenience of describing the technical solutions of the invention and have no specific limiting effect; they are all general terms and do not constitute a limitation on the technical solutions of the invention. It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of this application can be combined with each other. In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, not to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Multiple technical solutions in the same embodiment, as well as multiple technical solutions in different embodiments, can be arranged and combined to form new technical solutions that do not contradict or conflict, all of which are within the scope of protection claimed by this invention.

[0026] See Figure 1 and Figure 2 This invention provides a high-efficiency energy storage system based on bipolar membrane electrodialysis. The high-efficiency energy storage system includes multiple bipolar membrane stack combination units arranged in series, an electrode system 2, an electrolyte circulation system 3, a control system 4, and auxiliary equipment 5. Each bipolar membrane stack combination unit is composed of three layers: an anion exchange membrane, a bipolar membrane, and a cation exchange membrane. The electrode system 2 includes an anode and a cathode. The voltage, current, and electrolyte flow rate are adjusted by the control system 4, and the system is kept stable by the auxiliary equipment 5. Multiple bipolar membrane stack combination units arranged in series form a bipolar membrane stack 1.

[0027] In this invention, the bipolar membrane stack 1 employs a highly selective, low-resistance bipolar membrane and an ion exchange membrane to improve ion migration efficiency. The bipolar membrane and ion exchange membrane utilize corrosion-resistant and pollution-resistant materials, such as perfluorosulfonic acid resin (Nafion) and polyether ether ketone (PEEK), to extend the membrane's service life. The bipolar membrane stack adopts a modular design, with each module containing 6-10 bipolar membrane units, facilitating system expansion and maintenance.

[0028] Electrode system 2, including an anode and a cathode, is used to provide an electric field to drive ion migration. The electrodes are made of titanium mesh coated with mixed metal oxides such as tantalum and iridium.

[0029] Electrolyte circulation system 3 uses a mixed solution of 0.1 mol / L K3[Fe(CN)6], 0.1 mol / L K4[Fe(CN)6], and 0.2 mol / L NaCl as the electrode water. The brine can be a 0.5-1 mol / L sodium chloride solution to improve ion migration rate and energy storage density. The electrolyte circulation system includes a salt chamber, an acid chamber, an alkali chamber, pumps, and piping, and is constructed using corrosion-resistant materials (such as polytetrafluoroethylene) to ensure long-term stable operation.

[0030] Control system 4 uses a PLC (Programmable Logic Controller) and sensors to monitor system parameters (such as voltage, current, electrolyte flow rate and temperature) in real time, and optimizes operating parameters through algorithms. The system supports automated operation mode and can automatically switch operating states according to energy storage and power generation needs.

[0031] Auxiliary equipment 5, including circulating pumps, valves, sensors, etc., is used to maintain stable system operation.

[0032] The electrode chamber is filled with a mixed solution of 0.1 mol / L K3[Fe(CN)6], 0.1 mol / L K4[Fe(CN)6], and 0.2 mol / L NaCl. The salt, acid, and alkali chambers are independent, each containing one of the three functional fluids: salt, acid, or alkali solution. Auxiliary equipment includes a circulation pump, valves, and a pump controller responsible for fluid circulation and flow control.

[0033] The acid chamber is filled with 0.5-3 mol / L HCl solution, HNO3 solution, or H2SO4 solution; the alkali chamber is filled with 0.5-3 mol / L NaOH solution; and the salt chamber is filled with 0.35-1 mol / L NaCl solution, NaNO3 solution, or Na2SO4 solution. The electrolyte is a mixed solution of 0.1 mol / L K3[Fe(CN)6], 0.1 mol / L K4[Fe(CN)6], and 0.2 mol / L NaCl.

[0034] That is, the strong electrolyte inorganic salts and corresponding acid-base combinations in this invention include the NaCl-HCl-NaOH combination, the NaNO3-HNO3-NaOH combination, and the Na2SO4-H2SO4-NaOH combination.

[0035] Preferably, the present invention uses a NaCl-HCl-NaOH combination.

[0036] In energy storage operation, after injecting salt, acid, and alkali solutions into the compartments, an external current is applied to the reactor, driving the directional migration of ions through an electrodialysis process. Cations move towards the cathode, and anions move towards the anode, increasing the concentration of the acid and alkali solutions and decreasing the concentration of the salt solution. This ultimately creates a significant pH difference across the bipolar membrane, converting electrical energy into stored chemical energy. The operating temperature is controlled between 10-60℃ (preferably 30℃), and the current density is adjusted appropriately based on the membrane area.

[0037] After switching from power generation to regeneration mode, the reverse electrodialysis process is driven by the pH difference across the bipolar membrane. The H+ in the acid chamber... + With the OH in the alkali chamber - Water is generated by binding in the intermediate layer of the bipolar membrane. Simultaneous redox reactions occur in the electrode chambers, with hydrogen produced at the cathode and oxygen at the anode. Electrons are then passed through an external circuit to generate an electrical current, with a preferred power generation current density of 20-1000 A / m³. 2 When the pH difference decreases to 9-10, reapply 20-1000 A / m. 2 The device is charged with current until the pH difference is restored, enabling multiple cycles of energy storage and power generation.

[0038] Example 1

[0039] This embodiment is an energy storage and power generation experiment based on the NaCl-HCl-NaOH system. The experimental setup consisted of a bipolar membrane energy storage system, with 10 pairs of bipolar membrane electrodialysis units connected in series within the reactor. Each pair of bipolar membranes had an effective electrodialysis area of ​​100 cm². 2 The energy storage system consists of anion exchange membrane, bipolar membrane, and cation exchange membrane stacked sequentially to form three compartments: salt, acid, and alkali. The electrode plates are made of titanium mesh coated with a tantalum-iridium mixed metal oxide. The anode and cathode compartments are filled with 0.1 mol / L K3[Fe(CN)6], 0.1 mol / L K4[Fe(CN)6], and 0.2 mol / L NaCl solutions. The salt compartment is filled with 0.5 mol / L NaCl solution, the acid compartment with 0.5 mol / L HCl solution, and the alkali compartment with 0.5 mol / L NaOH solution. The auxiliary system's circulation pumps are connected to each compartment and the storage container, and the circuit includes switches and loads.

[0040] During the experiment, the data closure switch was switched to energy storage mode, and 100 A / m was applied. 2 After charging at the specified current density for 1 hour, a stable pH difference was established across the bipolar membrane (acid side pH≈1, alkaline side pH≈13). Then, switching to power generation mode at 20 A / m... 2 Under current density discharge, the system operated stably for 4.2 hours, with a maximum output power of 0.65W and a total power generation of 2.73Wh. After discharging and recharging, and after 10 cycles, the system discharge time remained above 4 hours, and the power generation efficiency remained at 98% of the initial state, with no membrane damage or bulging.

[0041] Example 2

[0042] This embodiment is an energy storage and power generation experiment based on the Na2SO4-H2SO4-NaOH system. The experimental setup used the same membrane structure, electrode material, and number of electrodes connected in series as in Example 1, with an effective membrane area of ​​100 cm². 2 The salt chamber is filled with 0.5 mol / L Na2SO4 solution, the acid chamber with 0.5 mol / L H2SO4 solution, the alkali chamber with 0.5 mol / L NaOH solution, and the electrode chamber with 0.5 mol / L Na2SO4 solution, all equipped with the same circulation and circuit system.

[0043] Experimental procedures and data are presented at 100 A / m 2 After charging at a current density of 1 hour, the pH difference across the bipolar membrane stabilized at 12 units. Switching to 20 A / m... 2 Under current density discharge, the system operated stably for 3.5 hours, with a maximum output power of 0.52W and a total power generation of 1.82Wh. After 10 cycles, the discharge duration decreased to 2.8 hours, and the power generation efficiency decreased to 80% of the initial state.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A high-efficiency energy storage system based on bipolar membrane electrodialysis, characterized in that, The high-efficiency energy storage system includes multiple bipolar membrane stack units arranged in series, an electrode system, an electrolyte circulation system, a control system, and auxiliary equipment. Each bipolar membrane stack unit is composed of three layers: an anion exchange membrane, a bipolar membrane, and a cation exchange membrane. The electrode system includes an anode and a cathode. The control system adjusts the voltage, current, and electrolyte flow rate, and the auxiliary equipment maintains stable system operation.

2. The high-efficiency energy storage system based on bipolar membrane electrodialysis according to claim 1, characterized in that, The electrolyte circulation system includes a salt chamber for storing a salt solution, an acid chamber for storing an acid solution, an alkali chamber for storing an alkali solution, a pump, and pipelines connected to a bipolar membrane stack assembly unit.

3. The high-efficiency energy storage system based on bipolar membrane electrodialysis according to claim 1, characterized in that, The control system includes a PLC and a real-time sensor monitoring system.

4. The high-efficiency energy storage system based on bipolar membrane electrodialysis according to claim 1, characterized in that, Both the anode and cathode are made of titanium mesh coated with a tantalum-iridium mixed metal oxide.

5. The high-efficiency energy storage system based on bipolar membrane electrodialysis according to claim 1, characterized in that, The auxiliary equipment includes a circulation pump, valves, and sensors.

6. The high-efficiency energy storage system based on bipolar membrane electrodialysis according to claim 1, characterized in that, The number of bipolar membrane stack assembly units is 6-10.

7. The high-efficiency energy storage system based on bipolar membrane electrodialysis according to claim 1, characterized in that, The membrane material of the bipolar membrane stack unit is perfluorosulfonic acid resin or polyether ether ketone.

8. A highly efficient energy storage operation method based on bipolar membrane electrodialysis, characterized in that, The operation method is divided into an energy storage process and a power generation process; The energy storage process is as follows: In charging mode, with external electrical energy input, the bipolar membrane dissociates water molecules into H+ under the influence of an electric field. + and OH - Ions, H + and OH - Ions migrate to the acid and base compartments respectively through cation exchange membranes and anion exchange membranes. In the acid and base compartments, H+... + and OH - Ions react with ions in the solution to generate acid and alkali solutions, realizing the conversion of electrical energy into chemical energy. The generated acid and alkali solutions are stored in the electrolyte circulation system, completing the energy storage process. The power generation process is as follows: In discharge mode, the stored acid and alkali solutions re-enter the bipolar membrane stack, and under the action of the reverse electric field, H... + and OH - Ions migrate in the opposite direction and recombine at the bipolar membrane interface to form water. The current generated by ion migration outputs electrical energy through an external circuit. The discharged solution returns to the electrolyte circulation system, completing the energy release process.

9. The efficient energy storage operation method based on bipolar membrane electrodialysis according to claim 8, characterized in that, The acid chamber is filled with 0.5-3 mol / L HCl solution, HNO3 solution, or H2SO4 solution; the alkali chamber is filled with 0.5-3 mol / L NaOH solution; and the salt chamber is filled with 0.35-1 mol / L NaCl solution, NaNO3 solution, or Na2SO4 solution. The electrolyte is a mixed solution of 0.1 mol / L K3[Fe(CN)6], 0.1 mol / L K4[Fe(CN)6], and 0.2 mol / L NaCl.

10. The efficient energy storage operation method based on bipolar membrane electrodialysis according to claim 8, characterized in that, During energy storage, the operating temperature is 10-60℃, and the charging current density is 20-1000A / m³. 2 During power generation, the power generation current density is 20-1000 A / m. 2 The membrane voltage is 0.6-0.9V, and the power density is 5-8W / m³. 2 .

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