Patent Application
20120270079
The present invention relates to flowing electrolyte batteries. In particular, although not exclusively, the invention relates to a bromine complex valve for a flowing electrolyte battery.
Batteries used in stand alone power supply systems are commonly lead-acid batteries. However, lead-acid batteries have limitations in terms of performance and environmental safety. For example, typical lead-acid batteries often have very short lifetimes in hot climate conditions, especially when they are occasionally fully discharged. Lead-acid batteries are also environmentally hazardous, since lead is a major component of lead-acid batteries and presents environmental challenges during manufacturing and disposal.
Flowing electrolyte batteries, such as zinc-bromine batteries, zinc-chlorine batteries, and vanadium flow batteries, offer the potential to overcome the above mentioned limitations of lead-acid batteries. In particular, the operational lifetime of flowing electrolyte batteries is not affected by deep discharge applications, and the energy to weight ratio of flowing electrolyte batteries is up to six times higher than that of lead-acid batteries.
A flowing electrolyte battery, like a lead acid battery, comprises a stack of cells that produce a total voltage higher than that of individual cells. But unlike a lead acid battery, cells in a flowing electrolyte battery are hydraulically connected through an electrolyte circulation path.
Referring to
To achieve high voltage, the zinc-bromine battery 100 further comprises a stack of cells connected in a bipolar arrangement. For example, a cell 135 comprises half cells 140, 145 including a bipolar electrode plate 155 and a micro porous separator plate 165. The zinc-bromine battery 100 then has a positive polarity end at a collector electrode plate 160, and a negative polarity end at another collector electrode plate 150.
A chemical reaction in a positive half cell, such as the half cell 145, during charging can be described according to the following equation:
2Br−→Br2+2e− Eq. 1.
Bromine is thus formed in half cells in hydraulic communication with the positive electrolyte circulation path 110 and is then stored in the positive bromine electrolyte tank 130. A chemical reaction in a negative half cell, such as the half cell 140, during charging can be described according to the following equation:
Zn2++2e−→Zn Eq. 2
A metallic zinc layer 170 is thus formed on the collector electrode plate 150 in contact with the negative electrolyte circulation path 105.
Chemical reactions in the half cells 140, 145 during discharging are the reverse of Eq. 1 and Eq. 2, which means that the complexed bromine stored in the positive bromine electrolyte tank 130 must be made available to the half cells 140 and 145. Typically, the complexed bromine settles at the bottom of positive bromine electrolyte (catholyte) tank 130 and, since it is undesirable to have complexed bromine circulating during charge, the positive electrolyte pump 120 will have an inlet which sits above this level so as to only draw aqueous bromine electrolyte into positive electrolyte circulation path 110. Therefore, a separate bromine complex pump 175 is required to draw complexed bromine from the bottom of the positive bromine electrolyte tank 130 and introduce it into positive electrolyte circulation path 110. As indicated, this pump will only be run during discharge.
Therefore, a fully operational zinc-bromine flowing electrolyte battery will have three separate pumps, or at least two pumps and an electrically operated valve, to ensure the two active electrolyte solutions and the complexed bromine are circulated efficiently and only at the appropriate time. A third pump will draw a significant current during the critical discharge phase of operation, reducing the total battery efficiency. An electrically operated valve may also draw a significant current. In either case an electrical device is employed to control complex bromine flow which may increase costs and complexity and reduce reliability and efficiency of the battery.
It is therefore an object of the invention to overcome or alleviate at least one of the aforementioned deficiencies in the prior art or at least provide a useful or commercially attractive alternative.
In one form, although it need not be the only or indeed the broadest form, the invention resides in a zinc-bromine flowing electrolyte battery comprising:
wherein, in use, preferential activation of either of the negative electrolyte pump or the positive electrolyte pump determines whether positive electrolyte only or a positive electrolyte and complexed bromine mix are circulated within the positive electrolyte circulation path.
Preferably, activation of at, least one of the negative electrolyte pump or the positive electrolyte pump results in pressure actuated switching of an electrolyte flow control mechanism.
Suitably, the electrolyte flow control mechanism comprises a positive electrolyte intake and a positive electrolyte/complexed bromine intake and pressure actuated switching of the electrolyte flow valve causes an increased volume of flow through one with respect to the other.
In a second form the invention resides in a method of regulating the flow of complexed bromine within a positive electrolyte circulation path of a zinc-bromine flowing electrolyte battery including the steps of:
In a third form the invention resides in an electrolyte flow control mechanism for a zinc-bromine flowing electrolyte battery comprising:
In a fifth form the invention resides in an electrolyte flow control mechanism for a zinc-bromine flowing electrolyte battery comprising:
To assist in understanding the invention and to enable a person skilled in the art to put the invention into practical effect, preferred embodiments of the invention are described below by way of example only with reference to the accompanying drawings, in which:
Those skilled in the art will appreciate that minor deviations from the symmetrical layout of components as illustrated in the drawings will not detract from the proper functioning of the disclosed embodiments of the present invention.
Embodiments of the present invention comprise control mechanisms for controlling the positive electrolyte and complexed bromine flow within the positive electrolyte circulation path of a zinc-bromine flowing electrolyte battery. Elements of the invention are illustrated in concise outline form in the drawings, showing only those specific details that are necessary for understanding the embodiments of the present invention, but so as not to clutter the disclosure with excessive detail that will be obvious to those of ordinary skill in the art in light of the present description.
In this patent specification, adjectives such as first and second, left and right, front and back, top and bottom, etc., are used solely to define one element or method step from another element or method step without necessarily requiring a specific relative position or sequence that is described by the adjectives. Words such as “comprises” or “includes” are not used to define an exclusive set of elements or method steps. Rather, such words merely define a minimum set of elements or method steps included in a particular embodiment of the present invention.
As shown in
Extending from electrolyte flow valve housing 220 is a positive electrolyte and complexed bromine inlet tube 225 which takes the form of a U-bend and ends at an upper extent in first inlet tube aperture 230. Located adjacent the lower extent of the U-bend of positive electrolyte and complexed bromine inlet tube 225 is complexed bromine inlet tube 235 into which complexed bromine can enter via second inlet tube aperture 240. Complexed bromine inlet tube 235 opens into the hollow interior of positive electrolyte and complexed bromine inlet tube 225.
As will be demonstrated later, positive electrolyte flow unit 200 will sit within a positive electrolyte tank (not shown in the figures) such that first inlet tube aperture 230 is submerged within and opens into the positive electrolyte but sits above the level of the complexed bromine. Second inlet tube aperture 240 is submerged within and opens into the complexed bromine which accumulates at the bottom of the positive electrolyte tank. This means that when positive electrolyte is drawn into positive electrolyte and complexed bromine inlet tube 225 through first inlet tube aperture 230, due to the action of the positive electrolyte pump, it flows past the end of complexed bromine inlet tube 235 which opens into positive electrolyte and complexed bromine inlet tube 225. At this point the positive electrolyte (aqueous) mixes with the complexed bromine, which has been drawn through complexed bromine inlet tube 235 due to the positive electrolyte pump pressure, and both enter electrolyte flow valve housing 220 through positive electrolyte and complexed bromine inlet tube 225.
Disposed adjacent positive electrolyte and complexed bromine inlet tube 225 on electrolyte flow valve housing 220 is a positive electrolyte inlet 245 which, in the embodiment shown in
Negative electrolyte valve control inlet 250 and positive electrolyte valve control inlet 255 are located adjacent one another on platform 210. Negative electrolyte valve control inlet 250 is connected to a high pressure outlet of a negative electrolyte pump of the zinc-bromine flowing electrolyte battery and positive electrolyte valve control inlet 255 is likewise connected to a high pressure outlet of the positive electrolyte pump. For the sake of clarity these connections are not shown in the figures but they result in a high pressure stream of negative electrolyte entering negative electrolyte valve control inlet 250 when the negative electrolyte pump is switched on, and a high pressure stream of positive electrolyte entering positive electrolyte valve control inlet 255 when the positive electrolyte pump is switched on. The effect of this high pressure supply of positive and/or negative electrolyte will be described in greater depth hereinafter.
Referring now to
Negative electrolyte valve control inlet 250 opens, at its lower extent, into a negative electrolyte chamber 260 which is defined by a negative electrolyte chamber base 265, a negative electrolyte chamber wall 270 and platform 210. In the embodiment shown, negative electrolyte chamber wall 270 takes the form of ribbed expandable bellows but any expandable chamber design may be appropriate. In the neutral position the lower extent of negative electrolyte valve control inlet 250 sits adjacent negative electrolyte chamber base 265 which is in contact at its lower surface with a bromine complex actuator 275. A bromine complex aperture 280 can be seen exposed through a bromine complex actuator recess 285 within bromine complex actuator 275 since the two are in alignment in
Below the position of bromine complex actuator recess 285 on bromine complex actuator 275 is a bromine complex actuator notch 290 which is shaped to receive a first angled face 295 of locking bar 300. Locking bar 300 is seen to sit such that, in the neutral position, first angled face 295 is not engaging bromine complex actuator notch 290 and so the potential movement of bromine complex actuator 275 is unrestricted.
The layout just described in relation to the positive electrolyte and complexed bromine flow control mechanism is repeated for the positive electrolyte only flow control mechanism. Positive electrolyte valve control inlet 255 opens, at its lower extent, into a positive electrolyte chamber 305 defined by a positive electrolyte chamber base 310, a positive electrolyte chamber wall 315 and platform 210. The lower extent of positive electrolyte valve control inlet 255 sits adjacent positive electrolyte chamber base 310 which is in contact at its lower surface with a positive electrolyte actuator 320. In the neutral position shown in
Below the position of positive electrolyte actuator recess 330 on positive electrolyte actuator 320 is a positive electrolyte actuator notch 335 adapted to receive a second angled face 340 of locking bar 300. It will now be apparent that locking bar 300 is free to slide to the left or right to engage with either of bromine complex actuator notch 290 or positive electrolyte actuator notch 335. Locking bar 300 is sized such that, in operation, either of bromine complex actuator 275 or positive electrolyte actuator 320 must be locked.
The downward motion of bromine complex actuator 275 causes the second angled face 340 of locking bar 300 to be forced into engagement with positive electrolyte actuator notch 335. Thus, when the positive electrolyte pump is subsequently activated and positive electrolyte from a high pressure fluid circuit exiting the positive electrolyte pump is introduced into positive electrolyte chamber 305 the change in internal pressure therein is unable to effect a downward movement of positive electrolyte actuator 320 due to a side wall of bromine complex actuator 275 preventing locking bar 300 from shifting leftwards to exit positive electrolyte actuator notch 335. This results in positive electrolyte aperture 325 being forced to remain open to the flow of positive electrolyte introduced through positive electrolyte inlet 245.
It should be clear that, in the embodiment shown in
The movement of positive electrolyte actuator 320 also causes the leftwards motion of locking bar 300 such that first angled face 295 of locking bar 300 engages with bromine complex actuator notch 290. Locking bar 300 is effectively locked in this position while the flow of high pressure positive electrolyte into positive electrolyte chamber 305 is maintained. This results in bromine complex actuator 275 being unable to move such that bromine complex actuator recess 285 is maintained in alignment with bromine complex aperture 280 thereby allowing the flow of both positive electrolyte and complexed bromine received from positive electrolyte and complexed bromine inlet tube 225 into bromine complex aperture 280. This will result in positive electrolyte and complexed bromine being pumped out of positive electrolyte flow unit 200 into the positive electrolyte circulation path. This embodiment of the flow control mechanism would, therefore, be appropriate for use during a discharge cycle of the zinc-bromine flowing electrolyte battery.
The embodiments of positive electrolyte flow unit 200 described in relation to
This movement of piston 435 brings it closer to angled face 440 and further movement is prevented when a positive electrolyte face 445 of piston 435 encounters the outer extent of angled face 440. Positive electrolyte face 445 and angled face 440 define a positive electrolyte chamber 450 into which positive electrolyte inlet 410 opens. Piston 435 has a head portion 455 which is reduced in size by comparison to the opposite end of piston 435 which presents negative electrolyte face 430 and so the surface area of positive electrolyte face 445 presented to positive electrolyte entering positive electrolyte chamber 450 from positive electrolyte inlet 410 is less than that presented by negative electrolyte face 430 to the negative electrolyte. This means that, when the negative electrolyte pump has been activated first, subsequent activation of the positive electrolyte pump will not cause piston 435 to move away from angled face 440 to any notable extent.
The position that piston 435 has been forced to take due to the influx of negative electrolyte is such that an unbroken flow path is created for positive electrolyte and complexed bromine to enter into a central chamber 460 through bromine complex inlet 420 and to exit via bromine complex outlet 415. Bromine complex outlet 415 leads to the positive electrolyte pump and so, in the embodiment shown in
The movement caused by the influx of positive electrolyte results in head portion 455 being positioned to block the flow of positive electrolyte and complexed bromine mix from central chamber 460 into bromine complex outlet 415. The positive electrolyte pump will receive only positive electrolyte from a separate source (not shown in the figures) and so the embodiment shown in
When the negative electrolyte pump is subsequently switched on, negative electrolyte passes into negative electrolyte inlet 405 and contacts negative electrolyte face 430 of piston 435. It will be appreciated that the negative electrolyte can only act against a restricted surface area of negative electrolyte face 430 due, in part, to the size of the bore of negative electrolyte inlet 405. The surface area of negative electrolyte face 430 receiving negative electrolyte is further restricted by negative electrolyte inlet seal 475 which surround the opening of negative electrolyte inlet 405 into negative electrolyte chamber 425. When negative electrolyte face 430 of piston 435 is forced against negative electrolyte inlet seal 475, as shown in
This results in the positive electrolyte generating a pressure across a much greater surface area of positive electrolyte face 445, and hence a greater force, than is being generated by negative electrolyte across negative electrolyte face 430. Thus, the subsequent activation of the negative electrolyte pump cannot overcome this force and so does not result in any substantial shift of piston 435 and the flow of complexed bromine through bromine complex valve 400 remains impeded.
The embodiments of a bromine complex valve 400 shown in FIG.'s 7A to 7C are particularly suitable for zinc-bromine battery flow systems which operate at relatively high pump pressures as a certain minimum pressure is required to overcome the sliding O-ring friction provided by the use of sliding O-rings 465 and 470 on piston 435. These O-rings effectively seal the negative and positive electrolyte inlets 405 and 410, respectively, from central chamber 460.
An actuator 525 is connected at its upper extent to the underside of chamber base 520 and at its lower extent ends in an inlet platform 530. Inlet platform 530, in
In the embodiment shown in
The effect of switching on the negative electrolyte pump first is to have negative electrolyte entering negative electrolyte chamber 510 and expanding chamber wall 515 which results in chamber base 520 being forced downwards. This moves actuator 525, and thus inlet platform 530 and sliding sleeve 555 with it, to leave the inlet holes of sliding sleeve 555 aligned with the solid exterior of second positive electrolyte flow tube 560 thereby preventing the ingress of positive electrolyte therethrough. Positive electrolyte can only enter the positive electrolyte pump through positive electrolyte inlet 535 and so second positive electrolyte flow tube 560 and bromine complex inlet tube 565 are bypassed. The negative pressure exerted by the positive electrolyte pump, once it is subsequently switch on, is insufficient to overcome the downward force exerted by the negative electrolyte in negative electrolyte chamber 510 due to the size of the gap already formed between inlet platform 530 and positive electrolyte inlet 535 and the influx of positive electrolyte therein.
This results in only positive electrolyte being pumped into the positive electrolyte circulation path and so the embodiment shown in
The position of inlet platform 530 means that attached sliding sleeve 555 is moved generally upwards in relation to its position in
This results in a positive electrolyte and complexed bromine mix being pumped into the positive electrolyte circulation path and so the embodiment shown in
When the negative electrolyte pump is subsequently switched on the downward force generated on actuator 525 by the influx of negative electrolyte into negative electrolyte chamber 510 is not sufficient to displace inlet platform 530 from within groove 580 of positive electrolyte inlet 535 due to the suction force between the two components generated by the negative pressure in first positive electrolyte flow tube 540 and the large difference between the surface area of inlet platform 530 and chamber base 520.
The embodiments of a positive electrolyte flow unit 500 described in
It will be appreciated that a number of embodiments of positive electrolyte and complexed bromine flow control mechanisms have been described herein. They all operate to afford control over whether the positive electrolyte pump will pump positive electrolyte only or a positive electrolyte and complexed bromine mix into the positive electrolyte circulation path. The control is achieved simply by the choice of which of the positive electrolyte pump or the negative electrolyte pump is activated first.
The invention described herein obviates the need for a third pump dedicated to pumping complexed bromine or a dedicated electrically operated valve and so offers savings in manufacturing costs as well as enabling the zinc-bromine flowing electrolyte battery to be more compact and have an improved overall efficiency. Further savings are likely for the consumer due to improved reliability of the battery resulting from reduced complexity through dispensing with the need for the third pump and reducing of the amount of complex electronics required.
The above description of various embodiments of the present invention is provided for purposes of description to one of ordinary skill in the related art. It is not intended to be exhaustive or to limit the invention to a single disclosed embodiment. As mentioned above, numerous alternatives and variations to the present invention will be apparent to those skilled in the art of the above teaching. Specifically, wherein certain embodiments have components such as expandable chambers, inlet chambers and the like which have been described as receiving either of a negative electrolyte flow or a positive electrolyte flow it will be appreciated that tubing supplying such flow may simply be swapped over such that those chambers would now receive the opposite of their former negative or positive electrolyte flow. The main implication such a change would have would be that the order in which the negative or positive electrolyte pumps need to be started to achieve a desired outcome may be reversed. Given the present disclosure, such a change and the implications thereof would be easily comprehended by a person of skill in the art.
Accordingly, while some alternative embodiments have been discussed specifically, other embodiments will be apparent or relatively easily developed by those of ordinary skill in the art. Accordingly, this patent specification is intended to embrace all alternatives, modifications and variations of the present invention that have been discussed herein, and other embodiments that fall within the spirit and scope of the above described invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009905358 | Nov 2009 | AU | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/AU2010/001430 | 10/27/2010 | WO | 00 | 7/16/2012 |
