Means for maintaining desired liquid level between inter-connected tanks

Abstract

Means for maintaining level complementary electrolytes inflow battery tanks has first and second interconnected tanks 2, 3. The first tank 2 contains positive electrolyte, 2b, and the second tank containing negative electrolyte 3b. Both tanks have a void 2a and 3 a respectively, for air or other noble gases. The tanks themselves are connected by pipes; a lower tank connecting pipe 4, an upper tank connection pipe 5 with an inter-pipe connecting pipe 6 therebetween. The peak of the lower tank connection pipe 4a is designed to remain below the normal liquid level 7 of both tanks, in contrast to the upper tank connection pipe 5 which remains above the desired liquid level 7.

Claims

1. Means for maintaining level complementary electrolytes in a pair of flow battery tanks, the means comprising: a first tank, and a second tank, wherein the first and second tanks are connected by: a lower tank connection pipe configured to provide continuous fluid communication between the first and second tanks, and an upper tank connection pipe, wherein: the lower tank connection pipe and the upper tank connection pipe are connected by an inter-pipe connecting pipe, wherein the lower tank connection pipe is curved such that it has a high point between the first and second tanks, and wherein the inter-pipe connecting pipe connects to the lower tank connection pipe at the high point of the lower tank connection pipe.

2. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 1, wherein one of the first or second tanks houses a positive electrolyte, and the other of the first or second tanks houses a negative electrolyte with a cell stack located therebetween.

3. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 1, wherein the lower tank connection pipe is connected to both the first and second tanks below a desired liquid level of each of the first and second tanks.

4. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 1, wherein the lower tank connection pipe is adapted to have a bore diameter of 10 mm to 80 mm in order to minimise the volume of electrolyte which is relatively stagnant as a result of being in the lower tank connecting pipe.

5. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 1, wherein the lower tank connection pipe is adapted to be of sufficient volume so that it can accommodate substantially the entire volume of electrolyte moving between the first and second tanks in one charge or discharge half-cycle.

6. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 1, wherein the lower tank connecting pipe has a constant or varied bore size.

7. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 1, wherein the upper tank connection pipe is connected to both the first and second tanks above a desired liquid level.

8. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 1, wherein the upper tank connecting pipe has a larger diameter than the lower tank connecting pipe.

9. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 1, wherein the upper tank connecting pipe is adapted to act as an overflow pipe if the lower tank connecting pipe is blocked.

10. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 1, wherein the lower pipe, upper pipe and inter-pipe connecting pipe are in substantially the same plane.

11. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 1, wherein the upper tank connection pipe allows for movement of a gas blanket between the first and second tanks.

12. A vanadium redox flow battery having a pair of flow battery tanks and comprising a means for maintaining level complementary electrolytes in the pair of flow battery tanks as defined in claim 1.

13. A means for maintaining level complementary electrolytes in a pair of flow battery tanks, the means comprising: a first tank, and a second tank, wherein the first and second tanks are connected by: a lower tank connection pipe configured to provide continuous fluid communication between the first and second tanks, and an upper tank connection pipe, wherein: the lower tank connection pipe and the upper tank connection pipe are connected by an inter-pipe connecting pipe, wherein the lower tank connection pipe is substantially W shaped, the W shape having a saddle, wherein the saddle has a high point between the first and second tanks, and wherein the inter-pipe connecting pipe connects to the lower tank connection pipe at the high point of the saddle of the lower tank connection pipe.

14. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 13, wherein one of the first or second tanks houses a positive electrolyte, and the other of the first or second tanks houses a negative electrolyte with a cell stack located therebetween.

15. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 13, wherein the lower tank connection pipe is connected to both the first and second tanks below a desired liquid level of each of the first and second tanks.

16. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 13, wherein the lower tank connection pipe is adapted to have a bore diameter of 10 mm to 80 mm in order to minimise the volume of electrolyte which is relatively stagnant as a result of being in the lower tank connecting pipe.

17. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 13, wherein the lower tank connection pipe is adapted to be of sufficient volume so that it can accommodate substantially the entire volume of electrolyte moving between the first and second tanks in one charge or discharge half-cycle.

18. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 13, wherein the lower tank connecting pipe has a constant or varied bore size.

19. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 13, wherein the upper tank connection pipe is connected to both the first and second tanks above a desired liquid level.

20. The means for maintaining level complementary electrolytes in a pair of flow battery tanks, as claimed in claim 13, wherein the upper tank connecting pipe has a larger diameter than the lower tank connecting pipe.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) To help understanding of the invention, a specific embodiment thereof will now be described by way of example and with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a cross-sectional representation of a vanadium redox flow battery in accordance with the present invention and

(3) FIG. 2 shows the arrangement of FIG. 1, wherein one of the tanks has been punctured.

DETAILED DESCRIPTION OF THE INVENTION

(4) Referring to FIG. 1, a cross sectional view of a pair of electrolyte tanks can be seen fitted with a device in accordance with the preferred embodiment of the present invention 1. There is a positive electrolyte tank 2, and a negative electrolyte tank 3. Each respective tank has a portion filled with electrolyte, 2b, 3b and a portion is an air void 2a, 3a. The air void may be filled with argon, or other noble gas to form a blanket.

(5) Connected to both the positive electrolyte tank 2 and negative electrolyte tank 3 is a lower tank connection pipe 4. The lower tank connection pipe 4 is of high length:diameter ratio. Additionally, the lower tank connection pipe 4 is designed such that it has a high point 4a. The entirety of the lower tank connection pipe 4 and its peak 4a are designed to lie below the normal liquid level 7 of both tanks.

(6) In addition to the lower tank connection pipe 4 is an upper tank connection pipe 5. The upper tank connection pipe 5 may have a larger diameter than the lower tank connection pipe 4. As can be seen in FIG. 1, the upper tank connection pipe 5 connects to the positive electrolyte tank 2 and negative electrolyte tank 3 above the normal electrolyte level 7. The upper tank connection pipe 5 is capable of acting as an overflow pipe, in the event that the lower tank connection pipe 4 is blocked.

(7) In addition to the lower tank connection pipe 4 and upper tank connection pipe 5 there is an inter-pipe connecting pipe 6. The inter-pipe connecting pipe 6 connects the lower tank connection pipe 4 to the upper tank connection pipe 5. The connection is normally between the peak 4a of the first pipe 4, and the main body of the second pipe 5, this is substantially in the middle of the upper and lower pipes 5, 4. The inter-pipe connecting pipe is attached to the high point 4a of the first pipe 4 allows gas to escape via the inter-pipe connecting pipe 6 to enter the upper pipe 5 and thence the air gap 2a, 3a. The connecting pipe 6 is substantially vertical, although may be in other orientations in other embodiments.

(8) In a variant of the present invention, the lower tank connecting pipe 4 and/or the upper tank connecting pipe 5 may extend into one or both of the positive electrolyte tanks 2 and the negative electrolyte tank 3.

(9) The arrangement depicted in FIG. 1 is such that if either the positive electrolyte tank 2 or the negative electrolyte tank 3 were punctured, gas from the second pipe 5 could move into the first pipe 4 via the connecting pipe 6. The movement of gas in this manner prevents significant syphoning occurring. Such a scenario is depicted in FIG. 2.

(10) FIG. 2 differs from FIG. 1 in that the tank 3 has a puncture 8. There is a positive electrolyte tank 2 and a negative electrolyte tank 3. The electrolyte tanks 2, 3 are connected by both a first pipe 4 and a second pipe 5. The first pipe 4 has a peak 4a. A connecting pipe 6 joins the first pipe 4 and the second pipe 5.

(11) A dotted line 7 denotes the normal fill level of the tank. As a result of the puncture 8 in electrolyte tank 3, electrolyte leaks from the tank. The level in tank 3 drops until the fill area 3b of tank 3 is below the puncture 8. The inter-pipe connecting pipe 6 allows gas from the air gaps 2a, 3a of both tanks to enter the lower tank connecting pipe 4 and fill the void. This stops a syphon from forming, thereby reducing the total volume spilled. The tank should empty only down to level 9a, this corresponds to the lower part of the lower tank connecting pipe 4 at its peak 4a. Without the inter-pipe connecting pipe 6, a syphon would be formed in the lower tank connecting pipe 4, and the electrolyte tank 2 would continue to drain down to the demarcation 9b.

(12) In a variation of the present invention, the lower pipe and/or the upper pipe could extend into the electrolyte tanks. If either tank was punctured with the first pipe 4 extending into the body of the tank, the electrolyte level of the un-punctured tank would be lower as the siphon effect would last longer.

(13) The lower tank connecting pipe 4 is generally curved, with a high point 4a. The greater the difference between the lower pipe openings in the tank, and the peak 4a, the less impact syphoning will have on the tank emptying.

(14) The invention is not intended to be restricted to the details of the above described embodiments.