KR20160075923A - Redox flow battery having reduced shunt loss - Google Patents

Abstract

The present invention relates to a redox flow battery and, more particularly, to a redox flow battery with reduced self-discharge that is attributable to a shunt current which is generated in and between stacks. This redox flow battery includes the stacks where unit cells are stacked with first and second electrolytes flowing with an ion exchange membrane interposed therebetween. This redox flow battery is provided with a tube-expanded flow path portion that is formed in parallel to a gravity direction in each fuel cell and is formed by an electrolyte flow path width being increased. A floating body is provided in the tube-expanded flow path portion and the floating body moves upward and downward in accordance with a flow velocity of the electrolyte.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a redox flow battery,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a redox flow cell, and more particularly, to a redox flow cell that reduces self-discharge due to a shunt current generated in a stack and between stacks.

A redox flow cell is a device that converts the chemical energy of an electrolyte solution into electric energy through a battery cell.

The operating voltage of the battery cell is about 1.0 to 1.7 V and has a relatively low voltage. Therefore, in order to increase the operating voltage, the cells are stacked in series to form a stack. The stack has a structure in which a plurality of battery cells are electrically connected in series and the electrolytes are shared in parallel.

The current flowing between the battery cells through the electrolyte solution sharing path is called a shunt current. Shunt currents occur inside or between stacks and cause self-discharge of the stack. Reduced energy stored in the stack even in a standby state in which redox flow cells are not operated by self-discharge.

On the other hand, a certain amount of energy must be stored in the stack in order to operate immediately in the standby state. To this end, the pump is operated intermittently to circulate the electrolyte, to discharge the electrolyte that has lost energy due to self-discharge, and to supply the electrolyte with energy. For this, the operation of the pump in the atmospheric state is eventually included in the energy loss.

The present invention is intended to reduce the shunt loss occurring between the inside of the redox flow cell stack and the stack, thereby reducing the self-discharge of the redox flow battery and improving the overall energy efficiency.

It is an object of the present invention to reduce the shunt loss occurring between the stack and the redox flow cell stack.

Another object of the present invention is to provide a redox flow battery capable of reducing shunt loss at the time of operation stop and reducing flow resistance at the time of operation by allowing the connection of the electrolyte between cells to be blocked at the time of operation stop .

The present invention relates to a redox-flow battery comprising a stack in which unit cells in which a first electrolyte and a second electrolyte flow through an ion-exchange membrane are stacked, the redox-flow battery being formed in parallel with the direction of gravity in each unit cell, And an expansion pipe portion formed in the expansion pipe portion, wherein the expansion pipe portion is provided with a body that moves up and down according to the flow rate of the electrolytic solution in the expansion pipe portion.

The main body preferably interrupts the flow of the electrolyte between the flow path portion and the baffle flow path portion in the stationary state of the redox flow cell.

The electrolytic solution flowing in the flow path portion of the phase expansion pipe has a flow in a direction of rising in the operating state and the supporting member is formed to have a specific gravity larger than that of the electrolyte solution and sinks to the lower portion of the expansion pipe portion in the stopped state, It may be configured to float by flow velocity,

Wherein the electrolytic solution flowing in the passage expanding conduit has a flow direction in which the electrolytic solution flows down in the operating state and the supporting body is formed to have a specific gravity smaller than that of the electrolytic solution so that the floating state is maintained at the upper portion of the expansion conduit, It may be configured to be lowered by the flow rate of the electrolytic solution.

At this time, it is more preferable to provide a stopper for limiting the rising / falling range of the main body within the expanded flow path portion.

The body may have a circular or polygonal profile in its longitudinal section, and it is further preferable that the body has guide means for maintaining a constant attitude when ascending and descending.

Wherein the guide means comprises a guide pin extended from one side of the body and inserted into the inlet side of the expanded flow path portion or a guide groove formed in the expanded flow path portion in contact with the body and the guide body, Lt; / RTI >

At this time, it is preferable that the thickness of the main body is formed to be smaller than the thickness of the expansion channel portion so that a clearance is formed between the surface of the main body and the surface of the expansion channel portion so that the lifting and lowering operation of the main body can be smoothly performed.

Preferably, the ratio of the maximum cross-sectional area of the expansion conduit to the maximum cross-sectional area of the body is in the range of 1: 0.5 to 1: 0.9.

It is possible to increase the shunt resistance by shutting off the electrolyte flow at the time of stopping the operation and to prevent the flow of the electrolyte at the time of operation It brings about an effect that does not give.

The redox flow cell according to the present invention includes an expansion flow path portion and a main body disposed therein. The redox flow path portion functions to reduce shunt loss by moving up and down depending on the flow of gravity, buoyancy, and electrolyte. Power supply and control device are not required.

Further, the redox flow battery according to the present invention can reduce the energy consumption of the electrolyte due to self-discharge by increasing the shunt resistance in the standby state, so that even if the electrolyte is not circulated in the standby state, It brings the effect.

1 is a conceptual diagram for explaining a shunt loss occurring in a redox flow cell,
FIG. 2 is a view illustrating an enlarged flow path portion for reducing shunt loss in a redox flow cell according to an embodiment of the present invention;
FIG. 3 and FIG. 4 are views showing the lifting and lowering of the body according to the operation state of the redox flow battery according to the first embodiment of the present invention, FIG.
FIG. 5 and FIG. 6 are views showing the lifting and lowering of the secondary body according to the operation state of the redox flow battery according to the second embodiment of the present invention, FIG.
FIG. 7 is a view showing a flow path portion and a body of the redox flow cell according to the third embodiment of the present invention,
FIG. 8 is a view illustrating an enlarged flow path portion and a body of a redox flow cell according to a fourth embodiment of the present invention,
FIG. 9 is a view showing a flow path portion and a main body of a redox flow cell according to a fifth embodiment of the present invention,
10 is a cross-sectional view taken along the line AA of Fig.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or preliminary meaning and the inventor shall properly define the concept of the term in order to describe its invention in the best possible way It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention. It should be noted that the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention, It should be understood that various equivalents and modifications are possible.

1 is a conceptual diagram for explaining shunt loss occurring in a redox flow cell.

The redox flow cell produces power using the redox reaction of the first electrolyte and the second electrolyte with the ion exchange membrane sandwiched therebetween. Since the voltage generated in one unit cell is low, a plurality of unit cells are stacked It is generally used.

The stack is formed by stacking a plurality of unit cells, and the electrolytic solution is supplied to each unit cell through a common supply passage as shown in the figure. Although not shown, Is recovered.

The shunt current is generated when the electrode unit of the unit cell constituting the stack is connected to the electrode unit of the adjacent cell and the electrolytic solution. The electrode of each unit cell is connected to the cell voltage The voltage difference will be generated as much as the voltage difference. This occurs because the unit cells constituting the stack are connected in series with each other.

Therefore, as the number of cells increases, the voltage difference gradually increases. If one cell voltage is 1.2V and a total of 10 cells are connected in series, the voltage difference between the electrodes located at both ends becomes 10.8V (1.2V * 9).

The shunt current changes according to the voltage difference of the cell and the electrolyte resistance.

The shunt current generated in the stack or between the stacks is composed of a complicated electric circuit model that occurs in multiple cells in a complex manner, but can be simply expressed as follows.

Shunt current: I = ΔV / R _s

Shunt _{resistance: R s = R * L /} A

* R _s : Shunt resistance

* R: electrolyte resistivity,

* L: length of electrolytic solution path between cell electrodes

* A: Cross-sectional area of electrolyte path between cell electrodes

As the shunt resistance increases, shunt current decreases and shunt loss can be reduced.

It is preferable that the width ratio of the flow path portion and the expanded flow path portion is in the range of 1: 2 to 1:10. If the width of the enlarged flow path portion is less than twice the width of the flow path portion, there may arise a problem that the flow resistance is increased due to the installation of the main body. If the width of the enlarged flow path portion exceeds 10 times the width of the flow path portion, It is difficult to block the flow.

Here, the path cross-sectional area means the cross-sectional area in the direction perpendicular to the flow direction of the electrolyte.

And the maximum path cross-sectional area of the expanding flow path portion means the largest path cross-sectional area of the path cross-sectional area of the expanded flow path portion.

On the other hand, the maximum cross-sectional area of the body means the largest cross-sectional area of the cross-sectional area in the direction perpendicular to the flow direction of the electrolyte of the body.

In the present invention, it is preferable that the ratio of the maximum cross-sectional area of the expanded passage portion to the maximum cross-sectional area of the body is 1: 0.5 to 1: 0.9. When the ratio of the maximum path cross-sectional area of the flow path portion to the maximum cross-sectional area of the body is less than 1: 0.5, it is difficult for the body to shut off the flow of the electrolyte solution in the flow path portion and the expansion path portion at the time of operation stop. There is a problem that the load on the pump must be increased due to an increase in resistance to the flow.

To increase the shunt resistance, the electrolyte path length (L) must be increased, the electrolyte path cross-sectional area (A) must be reduced, or the path of the electrolyte must be shut off. However, if the electrolyte path length (L) increases or the cross-sectional area (A) of the electrolyte path decreases, the fluid resistance increases, so the energy consumed to circulate the electrolyte must be increased.

The pump is used to circulate the electrolyte. Increasing the path length L or decreasing the cross-sectional area A of the path increases the energy consumed in the operation of the pump used to operate the redox flow cell, A deadly disadvantage occurs in that the efficiency of the doff-flow battery is deteriorated.

The present invention can prevent the flow of electrolytic solution by blocking the electrolyte when the electrolytic solution does not flow in the operation stopped state by providing a body in the flow path through which the electrolytic solution is supplied so that the shunt resistance value is increased and the shunt loss is reduced , And the flow of the electrolyte is opened when the battery is in operation.

FIG. 2 is a view illustrating a flow path portion for reducing shunt loss in a redox flow cell according to an embodiment of the present invention. Referring to FIG.

The redox flow cell has a continuous flow of electrolyte during operation and a pump for the flow of electrolyte. The width of the flow path is designed to maintain an appropriate flow rate and flow rate.

The expansion duct portion 100 means a portion having a width larger than the width of the flow passage portion 10 designed in this way.

The expansion passage portion 100 is formed in a direction parallel to the direction of gravity based on the state in which the redox flow battery is installed. The expansion channel portion 100 is formed in a direction parallel to the direction of gravity. This is because the support member 200 to be described later is capable of preventing gravity from flowing in the expansion channel portion 100, buoyancy caused by the electrolyte solution, To be able to descend and descend.

In addition, the redox flow battery according to the present invention includes a support body 200 inside the expansion flow path portion 100. The support body 200 has a predetermined shape and is formed to be able to move up and down according to the flow of the electrolytic solution in the expansion conduit channel portion 100.

During operation of the redox flow cell, the electrolyte 300 flows at the flow passage 100 through the flow passage 100, and when the operation stops, the flow passage 300 is filled with the electrolyte 300 without flowing .

Accordingly, the body 200 accommodated in the expansion pipe portion 100 is kept immersed in the electrolytic solution. For example, if the specific gravity of the body 200 is larger than the specific gravity of the electrolytic solution 300 and the operation is stopped, the gravity is larger than the buoyancy acting on the body 200, It will remain seated. Conversely, when the specific gravity of the support body 200 is smaller than the specific gravity of the electrolyte solution 300 and the operation is stopped, the buoyancy acting on the support body 200 is larger than the gravity, .

The supporting member 200 is preferably made of a material that does not react with the electrolyte solution, that is, a material that is not corroded by the electrolyte solution, since it must be operated for a long period of time in a state of being immersed in the electrolyte solution 300.

The material of the support 200 is preferably a plastic material such as PP, PE, PVDF, or PTFE having chemical resistance to the electrolyte, but is not limited thereto. The electrolyte 200 may be made of a material having chemical resistance to the electrolyte, Can be used in the present invention.

FIG. 3 and FIG. 4 are views showing the lifting and lowering of the body according to the operation state of the redox flow cell according to the first embodiment of the present invention.

In the illustrated embodiment, the supporting body 200 has a specific gravity larger than that of the electrolyte solution 300, and the electrolyte solution 300 flows in a direction opposite to the gravity direction in the operating state.

3 shows the operation stop state, and the supporting body 200 is kept sinking to the lower portion (inlet portion) of the expansion pipe portion 100. [ In this state, the support body 200 closes the gap between the expansion passage portion 100 and the flow passage portion 10. If the electrolytic solution 300 is completely blocked, the electrical connection between the cells due to the electrolytic solution 300 is cut off, and no shunt loss occurs.

However, even if it is not completely blocked, since the cross-sectional area connected to the electrolyte 300 is very small, the shunt resistance increases and the shunt loss can be reduced.

For example, in the case where the thickness of the expansion pipe portion is 10 mm and the distance between the body 200 and the portion closest to the expansion pipe portion 100 is 0.1 mm, the cross-sectional area of the electrolyte at this portion is 10 mm * 0.1 mm * 2 2.0 mm < 2 >.

4 shows the operation state, and the electrolytic solution 300 has a flow rising. When the flow of the electrolytic solution 300 occurs, the secondary body 200 generates a drag due to the flow of the electrolyte other than gravity and buoyancy.

Drag:

* F _D : Drag

* ρ: Density

* v: Linear velocity of electrolyte

* C _D : drag coefficient

* A: Flow velocity direction cross-sectional area

Since the drag acts in a direction to push up the body 200, when the sum of drag and buoyancy becomes larger than gravity, the body 200 floats. As shown in FIG. 4, when the supporting body 200 floats, the path of the electrolytic solution is opened and the fluid resistance is reduced, so that the influence on the load of the pump is reduced.

4, the portion where the cross-sectional area of the electrolyte is the narrowest is the AA section crossing the body 200 in the radial direction. If the interval between the support body 200 and the expansion passage portion is 2 mm, the cross- 10mm * 2.0mm * 2, so it becomes 40.0mm2.

The present invention is configured such that the supporting body 200 is formed to move up and down so as to shut off the connection of the electrolyte solution 300 at the time of stopping the operation or to sharply reduce the cross sectional area of the electrolyte which greatly affects the shunt resistance of the electrolyte solution 300, And the flow of the electrolytic solution 300 is not obstructed at the time of operation.

In order to reduce the shunt loss, if the cross-sectional area of the passage is reduced, the resistance of the fluid increases. In this case, the power of the pump consumed for proper flow of the fluid must be increased. The shunt resistance is increased at the time of stopping the operation and the flow of the fluid is not obstructed at the time of operation by allowing the flow of the electrolyte solution to be blocked only at the time of stopping the operation.

In the present embodiment, although the longitudinal section of the support body 200 is shown as a circular plate having a circular cross section, it may have an elliptical cross section or may have a polygonal shape as will be described later. It is not particularly limited to the shape as long as it can ascend and descend within the portion and thereby the sectional area of the path can be adjusted.

The redox flow cell according to the present invention reduces the shunt loss by using an enlarged flow path portion and a main body provided therein, and the operation of the main body is performed by the flow of gravity, buoyancy and electrolyte. Therefore, no separate power supply or control device is required.

A structure in which the stack is disposed higher than the liquid level of the electrolyte storage tank for the purpose of reducing shunt loss has been employed so as to allow the electrolyte to be discharged to the electrolyte storage tank by its own weight at the time of stopping the operation. Of course, such a structure has the advantage that the electrolyte is naturally discharged into the electrolyte storage tank in the stack at the time of operation stop, thereby reducing the shunt loss. However, the pump power is increased by the amount corresponding to the height of the electrolyte storage tank and stack at the time of operation In order to switch from the operation stop state to the operation state, the electrolytic solution must be supplied to the empty stack, so that it can not be quickly switched to the operation state.

However, in the case of the present invention, since the stack need not be higher than the liquid level of the electrolyte storage tank, a weight structure for heightening the height of the stack is not required and the power of the pump is not required to be increased according to the height difference. So that it is possible to quickly switch to the driving state, and the position of the stack can be freely selected, thereby improving the degree of freedom of design.

The body may have a specific gravity smaller than the specific gravity of the electrolyte or may be formed of a material having a specific gravity larger than the specific gravity of the electrolyte. The flow direction of the electrolyte may be parallel to the direction of the colonel or opposite to the direction of gravity.

For example, if the flow direction of the electrolytic solution is in the direction parallel to the direction of gravity, the floating body moves in the sinking direction due to the flow of the electrolyte, so that the specific gravity of the floating body is made smaller than the specific gravity of the electrolyte, When the flow of the electrolyte solution is generated, the flow of the fluid is reduced by the drag force, and the flow path portion of the expansion pipe can be opened.

Hereinafter, embodiments relating to the specific gravity of the subject and the operation of the subject according to the flow direction of the electrolyte will be described with reference to the drawings.

FIGS. 5 and 6 are views showing the lifting and lowering of the body according to the operation state of the redox flow cell according to the second embodiment of the present invention.

The second embodiment shown in the figure shows a case where the secondary body 200 has a specific gravity smaller than the specific gravity of the electrolyte solution 300 and the electrolyte solution 300 flows in the same direction as the gravity direction in the operating state.

5 shows the operation stop state, in which the support body 200 is floated in a state of being in close contact with the inlet portion of the expansion pipe portion 100. In this state, the shroud resistance increases due to the shape of the support body 200 blocking the inlet of the expansion passage portion 100.

6 shows the operation state of the electrolytic solution 300. Since the electrolytic solution 300 flows downward, when the electrolytic solution 300 flows, the body 200 generates a drag due to the flow of the electrolytic solution 300 in addition to gravity and buoyancy Since the direction of the drag force is the same as the direction of the gravity force, the sum of the gravity force and the drag force is greater than the buoyancy force, and the body 200 is lowered downward to increase the cross-sectional area of the path, thereby reducing the resistance to the flow of the electrolyte solution 300.

FIG. 7 is a view illustrating a flow path portion and a main body of a redox flow cell according to a third embodiment of the present invention. FIG.

In the third embodiment, like the first embodiment, the specific gravity of the body 210 is larger than the electrolyte 300 and flows in the direction in which the electrolyte 300 rises in the operating state.

The third embodiment is characterized in that it further includes a stopper 110 for restricting a lifted position of the support 210 in an operating state. Even if the body 210 rises due to the flow of the electrolyte 300, the body 210 can be stably fixed at a predetermined position by the stopper 110 so that the body 210 can move up and down more stably.

Although the shape and position of the stopper 110 are not limited in any way, it is necessary to avoid a shape in which the path cross-sectional area is excessively reduced or the flow resistance increases due to the stopper 110.

FIG. 8 is a view showing a flow path portion and a main body of a redox flow cell according to a fourth embodiment of the present invention. FIG.

In the fourth embodiment, like the first embodiment, the specific gravity of the body 220 is larger than that of the electrolytic solution and flows in a direction in which the electrolytic solution rises in the operating state.

The fourth embodiment further includes a guide pin 225 for allowing the support 220 to move up and down and maintain a constant posture.

As shown in the figure, the guide pin 225 does not come off the flow path portion 100 even when the support body 220 is lifted. Therefore, it is possible to prevent the body 220 from rotating unintentionally, and the body 220 only moves upward and downward while maintaining a constant posture.

FIG. 9 is a view showing a flow path portion and a body of a redox flow cell according to a fifth embodiment of the present invention, and FIG. 10 is a sectional view taken along line A-A of FIG.

FIG. 9 is a cross-sectional view of a state in which the upper surface of the baffle channel portion is removed, and in FIG. 10, the upper surface of the baffle channel portion is not removed.

The fifth embodiment has a guide protrusion 235 and a guide groove 135 for allowing the support body 230 to maintain a constant attitude while moving up and down.

A guide protrusion 235 is formed on the surface of the body 230 contacting the expansion pipe portion 100 and the guide groove 135 is formed in the expansion pipe portion 100 corresponding to the guide protrusion 235, ).

This configuration allows the guide protrusion 235 to move only on the guide groove 135, so that the support body 230 can move up and down along the guide groove 135 in a predetermined posture.

In the illustrated embodiment, the guide protrusion 230 is formed in the support body 230 and the guide groove 135 is formed in the expansion passage portion 100. Alternatively, a guide groove may be formed in the support body 230, A guide protrusion may be formed on the substrate 100.

At this time, the thickness t2 of the support body 230 is formed to be smaller than the thickness t1 of the expansion passage portion 100 so that a gap exists between the surface of the support body 230 and the inner surface of the expansion passage portion 100 And it is preferable that a clearance is also present between the guide protrusion 230 and the guide groove 135. The body 230 must move up and down according to the sum of the buoyancy force, the gravity force and the drag force so that when the frictional force between the surface of the body 230 and the surface of the expansion passage portion 100 becomes large, 230 can not smoothly move up and down. Therefore, it is preferable to form a clearance to allow the electrolytic solution to flow through the clearance so that the supporting body 230 can smoothly operate.

Meanwhile, in the illustrated embodiment, the guide protrusion 235 is provided on both sides of the supporting body 230, but the guide protrusion 235 may be provided on only one side.

In FIG. 8 and FIG. 9, guide pins, guide protrusions and guide grooves are used as guiding means for stable lifting and lowering operation of the body, but the guiding means is not limited to this type, Various forms can be applied.

It is to be understood that the above-described embodiments are to be considered in all respects as illustrative and not restrictive, and the scope of the present invention will be indicated by the appended claims rather than by the foregoing detailed description. It is intended that all changes and modifications that come within the meaning and range of equivalency of the claims, as well as any equivalents thereof, be within the scope of the present invention.

10:
100: Expansion duct part
110: Stopper
135: Guide groove
200, 210, 220, 230:
225: Guide pin
235: Guide projection

Claims (11)

A redox flow cell comprising a stack in which unit cells are stacked with a first electrolyte and a second electrolyte flowing through the ion exchange membrane,
Wherein each of the plurality of unit cells is provided with an expanding flow path portion formed in parallel with the gravity direction and formed by enlarging the width of the electrolyte flow path and having a body that moves up and down according to the flow rate of the electrolyte solution in the expanded flow path portion.
The method according to claim 1,
Wherein the main body cuts off the flow of the electrolyte between the flow path portion and the baffling flow path portion in the rest state of the redox flow cell.
The method according to claim 1,
The electrolytic solution flowing in the channel portion of the liquid crystal display has flow in a direction of rising in the operating state,
Wherein the floating body is formed to have a specific gravity greater than that of the electrolyte, and sinks to a lower portion of the expansion pipe portion when in a stopped state, and floats due to a flow rate of the electrolyte in an operating state.
The method according to claim 1,
The electrolytic solution flowing in the passage portion of the liquid phase expansion pipe has a flow in a direction of falling in the running state,
Wherein the floating body is formed to have a specific gravity smaller than that of the electrolyte so that the floating body remains floating on the upper portion of the expansion pipe portion in the stop state and falls in accordance with the flow rate of the electrolyte in the operation state.
The method according to claim 3 or 4,
And a stopper for restricting an up-down range of the main body within the expansion passage portion.
The method according to claim 1,
Wherein said body has a round or polygonal profile in its longitudinal section.
The method according to claim 1,
And guiding means for maintaining the attitude of said body to be maintained in a constant posture.
8. The method of claim 7,
Wherein the guide means is a guide pin extending from one side of the body and inserted into an inlet side of the expanded flow path portion.
8. The method of claim 7,
The guide means
And a guide groove and a guide protrusion which are formed to correspond to each other in the expanded passage portion contacting the body and the body.
The method according to claim 1,
Wherein the thickness of the body is smaller than the thickness of the flow path portion of the redistribution conduit.
The redox flow cell according to claim 1, wherein a ratio of a maximum cross-sectional area of the expansion passage portion to a maximum cross-sectional area of the main body is in a range of 1: 0.5 to 1: 0.9.

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