KR101878365B1 - Redox Flow Battery System - Google Patents

Abstract

The present invention relates to a redox flow battery system, and more particularly, to an energy reduction system for a redox flow battery system, in which an electrolytic cell or an electrolytic cell and a stack portion of a redox flow battery system are embedded in a ground with a low temperature change And a redox flow battery system in which installation space can be reduced and installation cost can be reduced.

Description

Redox Flow Battery System < RTI ID = 0.0 >

The present invention relates to a redox flow battery system, and more particularly, to an energy reduction system for a redox flow battery system, in which an electrolytic cell or an electrolytic cell and a stack portion of a redox flow battery system are embedded in a ground with a low temperature change And a redox flow battery system in which installation space can be reduced and installation cost can be reduced.

With global fossil fuels including petroleum, the world is experiencing serious climate change, restrictions on the use of fossil energy are intensifying. As a result, major industrialized countries such as the US, Japan, and Europe are strengthening regulations and support at the national level in relation to the energy industry. Academic and research institutes are conducting research on energy-related technology development and commercialization. We are working on new market development. The energy industry now combines ICT with innovation in distribution, trading and management technologies. New markets and industries are being created, such as renewable energy, energy management systems, virtual power plants, micro grids, and electric vehicles, and at the core are Energy Storage Systems (ESS).

The ESS is a system that stores power and supplies it when it is needed, thereby improving the efficiency of power use. When the electricity rate is low, it can be used at the peak time when the electricity rate is high after saving the electricity, which can bring innovation to the demand management. Solar power, and wind power, it is necessary to have an energy storage system that is independent of the location environment and natural conditions in large-scale solar power generation and wind power generation facilities. Production-consumption "paradigm that has to be consumed at the same time as production has been replaced by a" production-storage-consumption "paradigm. The use of ESS stabilizes the renewable power output and enhances the efficiency of energy utilization, and the major energy powerhouses are concentrating on the energy industry as a key growth engine.

ESS can be divided into battery type such as lithium battery, Nat yu uranium battery, redox flux battery, supercapacitor, and non-battery type such as positive water, compressed air storage and flywheel depending on the energy storage method. It can also be divided into frequency control, peak reduction, and new output stabilization depending on the application of ESS.

The lithium battery (LiB) stores energy by the lithium ion movement between the anode and the cathode, and it is advantageous to obtain high energy density and high energy efficiency. It can be divided into three parts: anode, cathode and electrolyte, and various kinds of materials can be used. Graphite is the most commonly used negative electrode. An oxide such as layered lithium cobalt oxide, a polyanion such as lithium iron phosphate (LiFePO4), lithium manganese oxide, spinel, etc. are used for the anode. The voltage, lifetime, capacity, and stability of the battery vary greatly depending on which material is used as the cathode, anode, and electrolyte. Recently, nanotechnology has been used to improve battery performance. However, it is difficult to implement a large-capacity cell because the price is high, but recently, a large-capacity cell implementation technology is being developed continuously.

Sodium-sulfur cells (NaS) store electricity in molten Na and S reactions. It has a long cycle life and high energy density, yet is inexpensive and has little self-discharge, making it suitable for high-capacity power storage systems. The NaS cell consists of a positive electrode (S), a negative electrode (Na), a solid electrolyte and a separator (Al2O3) (Figure 2). Since the cathode active material, sulfur, is an insulator, it must be impregnated with a carbon felt, which is a conductive material. Therefore, the performance of a battery greatly varies depending on the cathode material composition and characteristics.

A redox flow battery (RFB) is an electrochemical storage device in which the active energy in an electrolyte is charged and discharged by an oxidation / reduction reaction, and stores the chemical energy of the electrolyte directly as electrical energy. The electrolyte is stored in a liquid state in an external tank and is a flow cell that is supplied into the cell through the pump during the charge and discharge processes. The reaction is reversible electrochemical reaction. The active material itself has no lifetime limit. It has very low maintenance cost, operates at room temperature, and is suitable for high energy storage because of its environmental problems. The disadvantage is that the energy density and efficiency are low.

The supercapacitor stores electricity by electrochemically adsorbing to the surface of the ion. A super capacitor is a capacitor having a very large capacitance. It is called an Ultra Capacitor or an ultra-high capacity capacitor in Korean. In academic terms, electrochemical or electrochemical capacitors are distinguished from conventional electrostatic or electrolytic capacitors. Unlike a battery using a chemical reaction, a supercapacitor uses a charge phenomenon by simple ion movement or surface chemical reaction to an electrode and an electrolyte interface. As a result, it can be rapidly charged and discharged, and has high charge / discharge efficiency and semi-permanent cycle life. Low energy density and high cost are disadvantages.

Among the various energy storage devices, a large-capacity secondary battery is expected to be a very powerful energy storage system. Among them, the Redox Flow Battery (RFB) has a very long life span of 20,000 cycles and 20 years, and it can design the output and energy completely independently, so that the long-term ESS 2 It is said to be one of the most promising technologies among car batteries.

Unlike existing rechargeable batteries, redox flow cells are an electrochemical storage device in which active material in an electrolyte is oxidized-reduced to charge and discharge electricity and stores electric energy as chemical energy of an electrolyte solution. Actual electrochemical reactions take place in the stack and operate by continuously circulating the electrolyte inside the stack using a fluid pump.

Normally a large capacity redox flow cell system places the stack and the electrolytic tank on the ground. In this case, the installation area is excessively increased and the installation cost is increased. In addition, there is a problem that the system is required to cool the electrolyte solution and the cooling process due to the rise in temperature during the charge / discharge of the battery, and the system efficiency is decreased and the operation cost is increased. For small systems, air is cooled using a heating plate, but in this case the efficiency of the pump is reduced. Also, when the system is operated during the summer, the temperature of the stack and the electrolytic cell is raised by the radiation heat. In winter operation, the pipe must be heated in order to maintain the electrolyte above the reference temperature (-5 ℃) There is a problem that system efficiency is lowered.

Overall, there is a need to improve the redox flow battery system to reduce the installation space of the system and effectively cope with temperature changes due to driving and the surrounding environment.

Korean Patent Publication No. 10-2014-0109615

SUMMARY OF THE INVENTION The present invention has been conceived to solve the above-described problems, and its object is to provide a redox flow cell in which an electrolytic cell and a stack portion are installed in an underground buried portion to reduce occupied space, System.

Still another object of the present invention is to provide an environmentally friendly redox flow battery system that prevents leakage of electrolyte in the underground buried portion.

It is still another object of the present invention to provide a highly efficient redox flow cell system capable of improving overall system efficiency through cooperation with other systems such as wind, solar, or tidal power.

The object is achieved by an electrolytic cell comprising an electrolytic solution containing a pair of oxidation-reduction active materials; A stack unit for storing and discharging electric power through an electrochemical reaction of the electrolytic solution; And a pump for transferring and circulating the electrolytic solution from the electrolytic bath to the inside of the stack portion, wherein the electrolytic bath or stack portion is installed in an underground buried portion, the stack portion includes a battery cell including an ion exchange membrane, Can be achieved by a redox flow cell system made by mixing polyether ether ketone (PEEK) or polybenzimidazole (PBI) and heteropolyacid (HPA).

At this time, the electrolytic cell and the stack portion may be vertically arranged.

In addition, the active material may be any one of vanadium / vanadium, zinc / bromine, iron / chromium, and zinc / air, and preferably, the active material may be vanadium / vanadium and zinc / bromine.

The electrolytic bath may be constituted by an electrolytic bath containing a cathode electrolytic solution and a cathode electrolytic solution, and coating means for preventing leakage of the electrolytic solution may be provided on a wall surface and a bottom surface of the underground buried portion.

The battery management system may include a battery management system for informing the charging and discharging states of the redox flow battery through an external interface and performing a protection function against overcharge or overdischarge, System.

In addition, the redox flow battery system may include a power generation system and a power conversion system using at least one of wind, sunlight, and tidal power, and at least one of the power generation system and the power conversion system Can be installed.

In addition, it is possible to store surplus power produced from the power generation system and discharge the power when the power is insufficient, and the power conversion apparatus can convert the variable power produced by the power generation system into stable power.

According to the redox flow battery system according to an embodiment of the present invention, the electrolyzer or the electrolytic tank and the stack portion of the redox flow battery system are buried in the ground with little change in temperature during the year, thereby reducing energy required for heating and cooling, It is effective.

In addition, since the electrolytic cell or the stack part is installed in the underground part, the installation space can be reduced and the installation cost can be reduced. Further, the electrolytic cell and the stack part can be vertically arranged to further reduce the installation space.

Further, the system efficiency can be improved by constituting the electrolytic bath containing the anode electrolytic solution and the cathode electrolytic solution.

Further, coating means for preventing leakage of the electrolytic solution to the wall surface and the bottom surface of the underground buried portion are provided, so that an environmentally friendly system can be constituted.

In addition, a system having improved efficiency can be constructed by installing a wind power, solar light, or a tidal power generation system in a redox flow battery system and a power conversion device for converting variable power produced by the system into stable power.

In addition, at least one of the wind power, the solar light, the tidal power generation system, and the power conversion device is installed on the upper part of the underground buried part, thereby reducing installation space and reducing installation cost.

Also, a battery management system for informing the charging and discharging states of the redox flow battery through an external interface and performing a protection function against overcharge or overdischarge, and a control system for monitoring or controlling the states of the battery and the power inverter, The efficiency of the system can be improved.

1 is a schematic diagram of a redox flow cell system according to the prior art.
2 is a schematic diagram of a redox flow cell system according to an embodiment of the present invention.
3 is a graph showing changes in temperature of the electrolytic solution piping and the electrolyte tank during charge and discharge of the redox flow cell.
FIG. 4 is a graph showing the distribution of the ground temperature according to the depth of the ground.
5 and 6 are conceptual diagrams for explaining the operation principle of the redox flow cell.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings, which are intended to illustrate the present invention in a manner that allows a person skilled in the art to easily carry out the invention. And does not mean that the technical idea and scope of the invention are limited.

2 is a schematic diagram of a redox flow battery system according to an embodiment of the present invention. FIG. 3 is a graph showing the temperature change of the electrolytic solution pipe and the electrolyte tank during charging and discharging of the redox flow cell, FIG. 4 is a graph showing the ground temperature distribution according to the depth of the ground, Fig. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

The redox flow cell system according to an embodiment of the present invention includes an electrolytic bath containing an electrolytic solution containing a pair of oxidation-reduction active materials; A stack unit for storing and discharging electric power through an electrochemical reaction of the electrolytic solution; And a pump for transferring and circulating the electrolytic solution from the electrolytic bath to the inside of the stack portion.

Unlike conventional secondary batteries, redox flow batteries are an electrochemical storage device in which active materials in an electrolyte are redoxed and discharged to store chemical energy of an electrolyte directly as electrical energy.

The basic structure of the RFB is as shown in FIG. 5. The components include a tank storing different active materials having different oxidation states, a pump circulating the active material during charging and discharging, and a cell separated into an ion exchange membrane. As an active material, an electrolyte prepared by dissolving a transition metal such as V, Fe, Cr, Cu, Ti, Mn, and Sn in a strong acid aqueous solution is used. The prepared electrolyte is not stored in the cell but is stored in a liquid state in an external tank and is supplied into the cell through the pump during the charging and discharging process. In addition, the electrode used in the stack portion is an inactive electrode, and since the electrode itself reacts between the surface of the electrode and the electrolyte without chemical reaction, it has a long lifetime and is differentiated from the conventional battery. In addition, because it is a room temperature operation type, there are few factors promoting deterioration of battery material due to temperature, and the battery stack can be used for more than 20 years.

Since the cell stack (output) and the electrolyte tank (capacity) can be separated, the output and capacity can be freely designed and the installation site is limited. Since the electrolyte is supplied from the same tank, the charging state of each battery cell is the same, so no operation such as cell balancing is required, and the battery is operated at room temperature. Vanadium in the electrolytic solution can be semi-permanently recycled without generating exhaust gas such as CO 2, and can utilize resources effectively.

Large-capacity power storage cells should have high energy density and efficiency, have a long lifetime, and be safe and reliable. In order to develop RFB which has the advantages of energy density, durability and low cost, active materials and ion exchange membranes play the most important role in the performance of the battery. Therefore, high voltage redox couples are excellent in permselectivity of solvent and ion, This small ion exchange membrane must be secured. RFB is a cell in which the active material of the electrode is composed of a positive electrode electrolyte and a negative electrode electrolyte different in oxidation state in a solution state that is not a solid state as in a conventional battery. The electromotive force of RFB is a standard electrode potential E0 of a redox couple constituting a positive electrode electrolyte and a negative electrode electrolyte . ≪ / RTI >

Considering the electrode reaction and the electrolyte composition, the RFB redox couples that can actually be used are, first, Fe-Cr type. The main redox couples developed so far are Fe / Cr, V / V, V / Br, Zn / Br and Zn / Ce. In particular, vanadium can be oxidized in aqueous solutions such as V (II), V (III), VO2 + (IV), and VO2 + (V). VCl3, V2O5, and VOSO4 are used as active materials, but RFB composed of aqueous solution of VCl3 · HCl has a problem of generating chlorine gas. When it is composed of V2O5, it is not used because of low solubility. It is common to use a solution in which 2M VOSO4 is dissolved in 3M H2SO4. In this case, the oxidation number of the vanadium ion is +4

On the other hand, the inside of the stack is constituted by a plurality of battery cells. The battery cell comprises a membrane, which is an ion exchange membrane, first and second porous electrodes positioned between the membranes, first and second porous electrodes each fixing the first and second porous electrodes at the edges of the first and second porous electrodes, 2 flow frame, and an anode electrode and a cathode electrode respectively located outside the first and second porous electrodes.

In the two neighboring battery cells, the anode electrode and the cathode electrode are integrally formed, which is referred to as a bipolar plate. The first and second porous electrodes may be made of carbon felt, and the anode and cathode electrodes may be made of graphite. Four holes for circulating the electrolyte may be formed in the first and second flow frames.

In the first flow frame, one of the four holes is a positive electrode electrolyte inlet, the other is a cathode electrolyte outlet, and the other two are a cathode electrolyte hole. In the first flow frame, a flow path is formed between the anode electrolyte inlet and the first porous electrode and between the first porous electrode and the anode electrolyte outlet so that the anode electrolyte flows to the first porous electrode.

In the second flow frame, one of the four holes is a negative electrode electrolyte inlet, the other is a negative electrode electrolyte outlet, and the other two are positive electrode electrolyte through holes. In the second flow frame, a flow path is formed between the cathode electrolyte injection port and the second porous electrode and between the second porous electrode and the cathode electrolyte discharge port so that the cathode electrolyte flows to the second porous electrode.

Two kinds of redox couples (zinc-bromine or vanadium-vanadium, etc.) having different oxidation numbers included in the positive and negative electrode electrolytes are reacted at the first and second porous electrodes to charge and discharge. Specifically, charging is performed by an oxidation reaction, and a discharge is performed by a reduction reaction.

In RFB, ion exchange membranes are a key component in determining battery life and price. The ion exchange membranes applicable to RFB are: 1) high selective permeability of ions; 2) low electrical resistance; 3) low solute and solvent diffusion coefficient; 4) chemically stable; 5) 6) Nafion (DuPont), CMV, AMV and DMV (Asahi Glass) membranes are widely used.

In the case of a vanadium-based battery, an active material mixed with a transition metal element and a strong acid as an electrolyte is used, and thus a film having high acid resistance, oxidation resistance and selective permeability is required. When the Nafion membrane is applied to a vanadium battery, the energy efficiency is lowered due to the permeation of vanadium ions, and the life characteristic of the CMV membrane is lowered.

Microporous PVC separators, ultra-microporous filter membranes, CMV, AMV and other conductive polymers such as polyaniline and polypyrrole, Silica-filled PE, sulphonated polysulphone membranes, PE symmetric membranes and membranes crossed by asymmetric membranes It is possible

Ion exchange membranes using engineering plastic polymers can be applied to compensate for the disadvantages of Nafion membranes and to apply them in strong acid and high temperature regions. Polyethylene ether ketone (PEEK), polysulfone (PSF), and polybenzimidazole (PBI) are examples of engineering plastic polymers. These polymers are excellent in high temperature and acid resistance due to excellent manufacturability and high mechanical strength. In addition, HPA (heteropolyacid) can be added to improve the electrochemical and thermal properties, and ion exchange membranes can be fabricated and applied to polymer electrolyte membrane electrolysis (PEME).

On the other hand, it is effective to maintain the temperature of the electrolyte at -5 to 40 ° C. 3 is a graph showing the correlation between the electrolyte temperature, the operation time, and the stack voltage.

As shown in FIG. 1, the redox flow battery system of a large capacity is generally provided with a stack portion and an electrolytic tank on the ground. In this case, the installation area is excessively increased, the installation cost is increased, and the electrolytic solution cooling device and the cooling process are required due to the rise in temperature during charging / discharging of the battery, and the system efficiency is decreased and the operation cost is increased. Also, when the system is operated during the summer, the temperature of the stack and the electrolytic cell is raised by the radiation heat. In winter operation, the pipe must be heated in order to maintain the electrolyte above the reference temperature (-5 ℃) Thereby reducing system efficiency.

In order to solve the problem, the present invention is characterized in that an underground buried portion is installed in a redox flow cell system as shown in FIG. 2, and an electrolytic cell or a stack portion is buried underground. The depth of the underground buried portion should be deep enough to minimize the temperature difference due to seasonal changes, and preferably at least 5 m. At this time, in order to further increase the space efficiency, it is preferable that the electrolytic cell and the stack portion are vertically arranged.

When an electrolytic cell or a stack is buried in an underground part, the electrolytic solution leaks during operation and is absorbed into the ground surface, which may cause environmental pollution. To prevent this, a waterproof coating is applied to the wall and bottom of the underground part. Epoxy and PVC can be applied to the coating material.

In addition, the redox flow battery system may be provided with a battery management system that informs the charging and discharging states of the battery through an external interface and performs a protection function against overcharge or overdischarge.

The battery management system includes a battery system composed of a plurality of batteries, so that surplus energy provided from the system is stored in the battery system, and the energy stored in the battery system when a peak load or a system accident occurs . In addition to a battery system for energy storage, such a battery management device may include an air conditioning module (HVAC) for battery constant temperature and humidity, and a fire suppression module for preparing for fire.

It may also include a control system for monitoring or controlling the state of the battery and power converter of the redox flow battery system.

Hereinafter, a redox flow battery system in conjunction with a renewable energy generation system according to an embodiment of the present invention will be described in detail.

Generally wind turbines have demanding grid connection conditions. This is because wind turbines can cause serious instability in the connected system if they do not meet the set of link conditions set by the T & D company. Sudden drop in large-scale wind turbines due to sudden fluctuations in wind volume or unanticipated accidents and low output of wind turbines that do not support predicted demand can cause serious problems in the system, Can be more serious. In addition, since the transmission and distribution facilities for large-scale wind farms must be designed based on the maximum output of the generator, large-scale wind farms require huge investment in transmission and distribution facilities. Solar and tidal power generation is also very sensitive to the external environment, so independent power generation that is not connected to the external power grid is necessary to prepare for the after sunset and during the high and low tide periods.

In order to solve the instability of electric power due to the problems of the renewable power generation system, hybrid power generation linked with ESS can be a solution. Some of the developed electricity is stored in the ESS. If the electricity is not generated, the electric power stored in the ESS can be supplied to supply electricity of a constant quality regardless of the external environment.

Surplus power produced by wind, solar, and tidal power generation systems is stored in the redox flow battery system. At this time, the electric power produced through the system flows into the redox flow battery through a power conditioning system, and a variable voltage caused by conditions such as variable wind speed (or flow rate) and irregular sunshine amount that can be generated in the renewal, Quality secondary energy having a constant voltage and a constant frequency characteristic so that low-quality primary energy having a variable frequency characteristic can be linked to a power system

The renewable power generation system can supply electric power to the system, the load, and the power conversion apparatus. The new and renewable power generation system may generate electric power to supply electric power necessary for consumption of the load, supply electric power necessary for charging the electric power conversion apparatus, or transfer electric power to the electric power generation system. The new and renewable generation system can deliver electric power to the system, the load or the power conversion apparatus under the control of the control unit.

In particular, the new and renewable power generation system is installed above the underground buried portion of the redox flow battery system, thereby reducing the distance between the installation site and the two systems, thereby reducing installation and maintenance costs.

The control unit may transmit or receive information necessary for charging / discharging electricity by using various communication methods including a system, a load, a power conversion device, and a solar cell, a wired or wireless communication method, and a PLC (power line communication) .

The control unit may transmit or receive the charge information of the system, the charge amount or the discharge amount measurement information for calculating the charge, and the purchase and expenditure information, which are the basis for charge / discharge, with each other.

In addition, the control unit can set charging and discharging criteria and criteria for purchase and sale through various charging and discharging criteria based on the charging information of the system as a reference for charging / discharging, and can remotely control the charging and discharging standards.

In addition, the control unit transmits information on a billing function, which is a function of automatically charging the sales amount by transmitting the amount and cost information of selling and purchasing the system and electric power (electricity) to the system by recognizing the user information, Transmission or reception with the system.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the invention, It is obvious that the claims fall within the scope of the claims.

Claims (12)

An electrolytic bath containing an electrolytic solution containing a pair of oxidation-reduction active materials;
A stack unit for storing and discharging electric power through an electrochemical reaction of the electrolytic solution; And
And a pump for transferring and circulating the electrolytic solution from the electrolytic bath into the stack portion,
The electrolytic bath or the stack unit is installed in the underground buried part,
Wherein the stack portion includes a battery cell including an ion exchange membrane,
The ion-
Wherein a polyether ether ketone (PEEK) or polybenzimidazole (PBI) is mixed with HPA (heteropolyacid). The method according to claim 1,
Wherein the electrolytic cell and the stack portion are vertically arranged. The method according to claim 1,
Wherein the active material is any one of vanadium / vanadium, zinc / bromine, iron / chromium, and zinc / air. The method of claim 3,
Wherein the active material is one of vanadium / vanadium and zinc / bromine. The method according to claim 1,
Wherein the electrolytic bath comprises an electrolytic bath containing a cathode electrolytic solution and a cathode electrolytic solution, respectively. The method according to claim 1,
And coating means for preventing leakage of the electrolyte solution is provided on a wall surface and a bottom surface of the underground buried portion. The method according to claim 1,
And a battery management system for informing the charging and discharging states of the redox flow battery through an external interface and performing a protection function against overcharge or overdischarge. The method of claim 7, wherein
And a control system for monitoring or controlling the state of the battery and the power conversion device. The method according to claim 1,
Wherein the redox flow battery system is provided with a power generation system and / or a power conversion system using at least one of wind, solar, and tidal power. 10. The method of claim 9,
Wherein at least one of the power generation system and the power conversion device is installed on the upper portion of the underground buried portion. 11. The redox flow battery system according to claim 9 or 10, wherein excess power generated from the power generation system is stored and discharged when the power is low. 11. The method according to claim 9 or 10,
Wherein the power conversion apparatus converts the variable power produced by the power generation system into stable power.

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