WO2001094786A1

WO2001094786A1 - Submersible electrolyte circulation system

Info

Publication number: WO2001094786A1
Application number: PCT/US2001/018024
Authority: WO
Inventors: Gerd Tomazic
Original assignee: Powercell Corporation
Priority date: 2000-06-08
Filing date: 2001-06-04
Publication date: 2001-12-13
Also published as: AU2001275193A1; EP1287260A1; JP2003536021A

Abstract

A submersible circulation system comprising a motor (12), a first pump (38), a second pump (44) and a casing (62). The motor includes a shaft. The first and second pumps each have an impeller driven by the shaft of the motor. The casing encapsulates at least a portion of the motor to in turn permit the motor to operate while submersed in a fluid.

Description

TITLE OF THE INVENTION

SUBMERSIBLE ELECTROLYTE CIRCULATION SYSTEM

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed primarily to a circulation/pump system, and more particularly to a submersible circulation system, for example for circulating electrolyte of a battery. The system includes multiple pumps operating from a single motor. This invention is particularly well suited for, but not limited to, operation in the electrolyte of a zinc bromine battery.

2. Background Art

The use of pumps and motors to circulate fluid based material has long been used in the art. Such pumps are, for example, utilized to circulate electrolyte in a zinc/bromine battery. Generally, the type of pumps that are currently utilized for such applications comprise multiple pumps having a single impeller driven by a single motor. These motors are often positioned proximate to the electrolyte storage structure (generally a tank), and various pipes are utilized to attach the pump to the tank. In addition, multiple components and transfoπners are required to drive the motor, and in turn, the pumps. Such components, along with high power motors are generally necessary because the overall pump efficiencies are rather low (i.e. commonly 14%). The overall losses due to the circulation system lower the efficiency of the overall zinc/bromine battery.

Certain circulation system solutions have placed multiple pump impellers on a single motor drive shaft. While these solutions reduce the number of components that are necessary, such solutions nevertheless have drawbacks. In particular, such solutions rely on submerging the pumps within the electrolyte, but, due in part to the inefficiency of the motor along with the required components and transfomiers, the motor is nevertheless placed on the outside of the tank. In such a solution, the motor and the pumps are coupled with a shaft that extends through the tank. Such a solution requires the use of seals around the shaft of the motor to preclude leaking of the electrolyte about the opening in the tank which accepts the shaft. As a result, repair and maintenance on the circulation system is difficult and labor intensive. Specifically, pump replacement generally requires draining of the electrolyte and disassembly of the pumps from the motor.

Accordingly, it is an object of the invention to provide a pump, primarily for use in association with a zinc/bromine battery, which is submersible and which includes a plurality of impellers operating from a single motor.

It is likewise an object of the invention to increase the efficiency of the motor, to in turn, increase the efficiency of the overall circulation system.

SUMMARY OF THE INVENTION

The submersible circulation system of the present invention comprises a motor, a first pump, a second pump and a casing. The motor includes a shaft. The first pump and the second pump each include an impeller which is driven by the shaft of the motor. The casing encapsulates at least a portion of the motor. As such, the motor is permitted to operate while submersed in a fluid.

In a preferred embodiment, the system further includes a pressure compensation tube associated with at least one of the first pump and the second pump. The pressure compensation tube facilitating a uniform flow rate in the output of the pumps. In a preferred embodiment, the motor includes a rotor and an armature and one of the motor and the casing further including means for facilitating the passage of fluid between the rotor and armature. In such a preferred embodiment, the fluid passage facilitating means further comprises at least one uni-directionally oriented element associated with the surface of the rotor. The uni- directionally oriented element forcing electrolyte across the rotor between the rotor and the armature. In a preferred embodiment, the first and second pumps are positioned at opposite ends of the shaft of the motor. Preferably, the motor comprises a 12V DC variable frequency motor. In one embodiment, the motor efficiency of the motor approaches about 90%. In another embodiment, the efficiency of the circulation system approaches about 36%.

In another preferred embodiment, the system further includes means for controlling the circulation system. In one embodiment, the control means comprises a frequency controller wherein rotational speed of the motor can be controlled by changes in frequency.

In still another preferred embodiment, at least one of the first and second pumps include a valve which controls the quantity of fluid which can be pumped by the respective first and second pumps. In another embodiment, each of the first and second pumps include a valve to control the output of the respective pumps.

In yet another preferred embodiment, the casing comprises a unitized casing which unitizes the motor, the first pump and the second pump, to, in turn, facilitate positioning and replacement of same as a single unit. In one such embodiment, the casing comprises a polyolefin, such as polyethylene, polypropylene and the like.

Preferably, the circulation system further includes means for cooling the motor. In one such embodiment, the cooling means comprises an electrolyte fluid within which the pump is submersed. In one particular embodiment, the circulation system is provided for use in association with a zinc- bromine battery.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 of the drawings is a cross-sectional view of the circulation system of the present invention; and Fig. 2 of the drawings is a cross-sectional view of the circulation system of the present invention as submersed in a tanlc of electrolyte in a zinc/bromine battery.

BEST MODE FOR PRACTICING THE INVENTION

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will be described in detail, one specific embodiment with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated.

Circulation system 10 is shown in Fig. 1 as comprising motor 12, first pump 16, second pump 18, casing 20, control system 22 and passage 24. As shown in Fig. 2, circulation system 10 is designed so as to be submersible in electrolyte 40 contained in tank 14. While not specifically limited, circulation system 10 is primarily intended for use in a zinc/bromine battery for purposes of recirculating electrolyte. Of course, other applications where the advantages of a submersible circulation system may benefit from the present invention, are likewise contemplated.

Motor 12 includes shaft 30 which provides rotational output produced by the motor. Motor 12 preferably comprises a high efficiency DC motor which is capable of providing a desired output for powering the pumps. For example, motors can be utilized which are capable of achieving efficiencies of up to 90% with special magnets and the like. With such efficiencies, due to the relatively low output power that is needed, a brushless 12V DC motor can be used. The prior art has generally utilized only less efficient motors (i.e. motors with an efficiency of about 50%), which were generally required to operate at higher voltages, such as 24-36V, and transfomiers, such as jump-start transfomiers to provide the higher voltage for the motor. The present invention contemplates that, instead of such a transformer, a frequency transformer with low output can be used to change the rotational speed (i.e. by changing the frequency). By utilizing the higher efficiency motors and by maximizing the other components, an overall efficiency of the submersible pump can approach, or even exceed 36%. Current circulation systems for zinc/bromine batteries are on the order of 14% efficiency.

Motor 12 includes rotor 13 and armature 15. Rotor 13 is encapsulated by a plastic material, such as PE so as to preclude corrosion thereof when exposed to the zinc bromine electrolyte. As will be explained, the electrolyte is directed between the rotor and the armature of the motor.

First pump 16 is shown in Fig. 1 as comprising inlet 34, outlet 36 and impeller 38. Specifically, impeller 38 is attached to one end of shaft 30 of motor 12. As will be explained impeller 38 is powered by motor 12 and forces fluid, received from inlet 34, through outlet 36. It will be understood that various different shapes can be utilized for the impeller. It is contemplated that certain of these configurations will be of greater efficiency relative to others. Of course, various sizes for the pumps are likewise contemplated. As will be understood, the pumps are selected and configured so as to drive the specified quantity of fluid per specified time unit.

Second pump 18 is shown in Fig. 1 as comprising inlet 40, outlet 42 and impeller 44. Impeller 44, like impeller 38 is associated with shaft 30 of motor 12. Specifically, impeller 38 is positioned on the opposite side of the motor relative to impeller 44. As such, rotation of motor 12 rotates both impeller 38 and impeller 44. As will be explained below, impeller 44 receives fluid from inlet 40 and drives the fluid through outlet 42. It is likewise contemplated that the first and second pumps may be positioned on shaft 30 on the same side of motor 12. It is further contemplated that additional impellers (i.e. in excess of the two identified above) may be coupled to shaft 30 of motor 12.

Control system 22 is shown in Fig. 1 as comprising valves 50, 52, pressure compensation tube 53 and controller 54. Controller 54 controls the operation of valves 50, 52 and motor 12. Valves 50, 52 can be used to control the quantity of fluid that is directed through the pumps. Of course, while the valves are shown proximate each inlet, they may be positioned proximate each outlet, or, proximate both the inlet and the outlet. Pressure compensation tube 53 serves to insure uniform flow rate in both of the outlets. Controller 54 can control the relative position of each of the valves, and the operation (i.e. speed, torque) of motor 12. Due to the higher efficiencies of the preferred 12V motors, the required control circuitry of the controller for motor 12, can be quite simplified as compared to the controller for 24-36V motors.

Casing 20 is shown in Fig. 1 as comprising an encasement for the motor and the pumps. Casing 20 preferably comprises a lightweight material such as PE, while other materials are likewise contemplated for use. Specifically, casing 20 includes motor chamber 62 and pump chambers 64, 66. In other embodiments the casing may comprise several separate components which may or may not be attached together. By way of example, motor chamber 62 of casing 20 can be a separate/non- integrated member relative to pump chambers 64, 66. In such an embodiment, the casing comprises three components which may be attached together in various manners.

Generally, the zinc bromide electrolyte acts as a lubricant and coolant between the rotor and the armature. To transport the lubricant between the rotor and the armature, casing 20 includes openings 55 for the electrolyte proximate the motor, and the coated rotor includes threads 51 of low depth or other uni-directionally oriented elements (i.e. grooves and the like) to essentially direct the flow of electrolyte from one end to the other end of the rotor. This lubricates and cools the rotor of the motor. In addition, it is contemplated that certain casings fully seal the motor and rotor from the electrolyte.

Casing 20 further includes control passage 24 which comprises a passage for the providing of electrical wiring to the motor. Such wiring includes wiring for the control systems, valves and the motor itself. Commonly, 8-gauge to 14-gauge wiring can be utilized for most applications. In operation, the system is first assembled by encasing motor 12 and pumps 6, 18 within casing 20. Specifically, motor 12 is placed within motor chamber 62 of casing 20 and the impellers are associated with pump chambers 64, 66 of casing 20. Once positioned, the casing is sealed, so that the motor is encapsulated and so that the impellers are properly positioned relative to the inlet and the outlet. Next, the entire encased circulation system, is merely dropped into the tanlc containing the electrolyte. Once positioned, the motor is activated by the user and the flow valves can be controlled so as to control the quantity of fluid that is circulated by the respective pumps. In addition, the pressure compensation tube facilitates a unifonn flow rate in both of the outlets.

As such, the assemblies can be fully assembled prior to introduction into the tank containing electrolyte. In addition, and most advantageously, should a problem with the motor or any other component of the system arise, the entire circulation system can be removed rather easily, and a substitute system can be positioned in its place. Accordingly, the down time, and the repair expertise that is required is limited. For example, and as can be seen in Fig.2, outlet 36, outlet 42, and control passage 24 can be integrally associated with tanlc cover 60. In such an embodiment, the entire circulation system can be dropped into tank 14 which includes the electrolyte. Of course, in other embodiments, the cover can be separate from the various passage outlets.

Moreover, by being positioned within the electrolyte, the electrolyte is forced to pass between the armature and the rotor (which is encapsulated in a PE material). In turn, the electrolyte serves to cool the rotor, thereby precluding overheating thereof. The cooling capacity of the electrolyte provides effective cooling benefits. Furthermore, encapsulization and submersion of the system within the electrolyte virtually eliminates the undesirable noise associated with such a circulatory system.

The foregoing description merely explains and illustrates the invention and the invention is not limited thereto except insofar as the appended claims are so limited, as those skilled in the art who have the disclosure before them will be able to make modifications without departing from the scope of the invention.

Claims

CLAIMSWhat is claimed is:

1. A submersible circulation system comprising:

- a motor having a shaft;

- a first pump having an impeller driven by the shaft of the motor;

- a second pump having an impeller driven by the shaft of the motor; and

- a casing which encapsulates at least a portion of the motor, so as to permit the motor to operate while submersed in a fluid.

2. The system of claim 1 wherein the first and second pumps are positioned at opposite ends of the shaft of the motor.

3. The system of claim 1 further including a pressure compensation tube associated with at least one of the first pump and the second pump, the pressure compensation tube facilitating a uniform flow rate in the output of the pumps.

4. The system of claim 1 wherein the motor includes a rotor and an armature, one of the motor and the casing further including means for facilitating the passage of fluid between the rotor and armature thereof.

5. The system of claim 4 wherein the fluid passage facilitating means further comprises at least one uni-directionally oriented element associated with the surface of the rotor, the uni-directionally oriented element forcing electrolyte across the rotor between the rotor and the armature.

6. The system of claim 1 wherein the motor comprises a 12V DC variable motor.

7. The system of claim 1 further including means for controlling the circulation system.

8. The system of claim 7 wherein the control means comprises a frequency controller wherein rotational speed of the motor can be controlled by changes in frequency.

9. The system of claim 1 wherein at least one of the first and second pumps include a valve which controls the quantity of fluid which can be pumped by the respective first and second pumps.

10. The system of claim 9 further including means for controlling the circulation system, wherein the controlling means includes means for controlling the valve associated with at least one of the first and second pumps.

11. The system of claim 1 wherein the casing comprises a unitized casing which unitizes the motor, the first pump and the second pump, to, in turn, facilitate replacement of same as a single unit.

12. The system of claim 1 further including means for cooling the motor.

13. The system of claim 12 wherein the cooling means comprises an electrolyte fluid within which the pump is submersed

14. The system of claim 1 wherein the casing comprises a PE material.

15. The system of claim 1 wherein the motor efficiency approaches about 90%.

16. The system of claim 1 wherein the efficiency of the circulation system approaches about 36%.

17. The system of claim 1 wherein the circulation system is provided for use in association with a zinc-bromine battery.