WO2002008494A1 - Fan flow sensor for proton exchange membrane electrolysis cell - Google Patents

Abstract

A fan flow sensor (70) for a hydrogen generating proton exchange member electrolysis cell includes a switching device (394) and a sail (380) disposed in communication with the switching device. The sail is configured to actuate the switching device in response to an airflow from a fan (368). The sail may be slidably or pivotally disposed on the switching device.

Description

FAN FLOW SENSOR FOR PROTON EXCHANGE MEMBRANE ELECTROLYSIS CELL

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefits of U.S. Provisional Patent Application Serial Number 60/219,525 filed July 20, 2000, and U.S. Patent Application Serial Number 09/842,617 filed April 25, 2001, the entire contents of both applications being incorporated herein by reference.

BACKGROUND

Electrochemical cells are energy conversion devices, usually classified as either electrolysis cells or fuel cells. Proton exchange membrane electrolysis cell can function as hydrogen generators by electrolytically decomposing water to produce hydrogen and oxygen gases. Referring to FIGURE 1, a section of an anode feed electrolysis cell of the prior art is shown generally at 10 and is hereinafter referred to as "cell 10." Reactant water 12 is fed into cell 10 at an oxygen electrode (anode) 14 to form oxygen gas 16, electrons, and hydrogen ions (protons). The chemical reaction is facilitated by the positive terminal of a power source 18 comiected to anode 14 and negative terminal of power source 18 connected to a hydrogen electrode (cathode) 20. Oxygen gas 16 and a first portion 22 of water are discharged from cell 10, while the protons and second portion 24 of the water migrate across a proton exchange membrane 26 to cathode 20. At cathode 20, hydrogen gas 28 is formed and removed, generally through a gas delivery line. The removed hydrogen gas 28 is usable in a myriad of different applications. Second portion 24 of water, which is entrained with hydrogen gas, is also removed from cathode 20.

An electrolysis cell system may include a number of individual cells arranged in a stack with reactant water 12 being directed through the cells via input and output conduits formed with the stack structure. The cells within the stack are sequentially arranged, and each one includes a membrane electrode assembly defined by a proton exchange membrane disposed between a cathode and an anode. The cathode, anode, or both may be gas diffusion electrodes that facilitate gas diffusion to proton exchange membrane. Each membrane electrode assembly, is in fluid communication with flow field adjacent to the membrane electrode assembly defined by structures configured to facilitate fluid movement and membrane hydration within each individual cell.

Power to the electrolysis cell is interrupted when, after sensing a condition such as a pressure variation in the gas delivery line, a control unit signals an electrical source that drives a reference voltage applied across a potentiometer to an extreme value. In such a system, the control unit is directly dependent upon the detection of a mass leak from the gas delivery line. Depending upon the preselected conditions of the system, when the power interruption capability is dependent upon the detection of a mass leak, a delay between the time that the leak occurs and the time at which the system is shut down may be experienced. Such systems do not provide early detection of potential problems but instead simply react to signals indicative of problems currently existing in the operation of the cell.

SUMMARY

A fan flow sensor for a gas generating proton exchange member electrolysis cell is disclosed. The fan flow sensor includes a switching device and a sail disposed in communication with the switching device. The sail is configured to actuate the switching device in response to an airflow from a fan.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a schematic representation of an anode feed electrolysis cell of the prior art.

FIGURE 2 is a schematic representation of a gas generating apparatus into which an electrolysis cell system may be incorporated.

FIGURE 3 is an exploded perspective view of a ventilation system of a gas generating apparatus.

FIGURE 4 is a perspective view of the ventilation system of FIGURE 3. FIGURES 5 A and 5B are exploded sectional views of sail/collar assemblies.

FIGURE 6 is an alternate configuration of a sail/collar assembly. FIGURES 7 A and 7B are alternate configurations of retainers disposed on spindles.

FIGURE 8 is an exploded perspective view of an alternate embodiment of a ventilation system of a gas generating apparatus.

FIGURE 9 is a perspective view of the ventilation system of FIGURE 8. FIGURE 10 is a plan view of the ventilation system of FIGURE 8.

FIGURE 11 is a perspective view of a tab on the sail of the ventilation system of FIGURE 8 illustrating the placement of magnets used for actuating a flow switch.

DETAILED DESCRIPTION

Referring to FIGURE 2, an exemplary embodiment of an electrolysis cell system is shown generally at 30 and is hereinafter referred to as "system 30." System 30 is suitable for generating hydrogen for use in gas chromatography, as a fuel, and for various other applications. It is to be understood that while the inventive improvements described below are described in relation to an electrolysis cell, the improvements are generally applicable to both electrolysis and fuel cells. Furthermore, although the description and figures are directed to the production of hydrogen and oxygen gas by the electrolysis of water, the apparatus is applicable to the generation of other gases from other reactant materials. Exemplary system 30 includes a water-fed electrolysis cell capable of generating gas from reactant water and is operatively coupled to a control system. Suitable reactant water is deionized, distilled water and is continuously supplied from a water source 32. The reactant water utilized by system 30 is stored in water source 32 and is fed by gravity or pumped through a pump 38 into an electrolysis cell stack 40. The supply line, which is preferably clear plasticizer-free tubing, includes an electrical conductivity sensor 34 disposed therewithin to monitor the electrical potential of the water, thereby determining its purity and ensuring its adequacy for use in system 30.

Cell stack 40 comprises a plurality of cells similar to cell 10 described above with reference to FIGURE 1 encapsulated within sealed structures (not shown). The reactant water is received by manifolds or other types of conduits (not shown) that are in fluid communication with the cell components. An electrical source 42 is disposed in electrical communication with each cell within cell stack 40 to provide a driving force for the dissociation of the water.

Oxygen and water exit cell stack 40 via a common stream and are ultimately returned to water source 32, whereby the water is recycled and the oxygen is vented to the atmosphere. The hydrogen stream, which contains water, exits cell stack 40 and is fed to a phase separation tank, which is a hydrogen/water separation apparatus 44, hereinafter referred to as "separator 44" where the gas and liquid phases are separated. This hydrogen stream has a pressure that is preferably about 250 pounds per square inch (psi), but which may be anywhere from about 1 psi to about 6000 psi. Some water is removed from the hydrogen stream at separator 44. The exiting hydrogen gas (having a lower water content than the hydrogen stream to separator 44) is further dried at 46, for example by a diffuser, a pressure swing absorber, or desiccant. Water with trace amounts of hydrogen entrained therein is returned to water source 32 through a low pressure hydrogen separator 48. Low pressure hydrogen separator 48 allows hydrogen to escape from the water stream due to the reduced pressure, and also recycles water to water source 32 at a lower pressure than the water exiting separator 44. Separator 44 also includes a release 50, which may be a relief valve, to rapidly purge hydrogen to a hydrogen vent 52 when the pressure or pressure differential exceeds a preselected limit.

Pure hydrogen from diffuser 46 is fed to a hydrogen storage 54. Valves 56, 58 are provided at various points on the system lines and are configured to release hydrogen to vent 52 under certain conditions. Furthermore, a check valve 60 is provided that prevents the backflow of hydrogen to diffuser 46 and separator 44. A ventilation system, shown below with reference to FIGURES 3 through 7B, is provided to assist in venting system gases when necessary. The ventilation system comprises a fan portion that continually purges the air in the enclosure of system 30. An airflow switch is mounted on the fan portion and is configured to interrupt the power to cell stack 40 in the event of a failure in the fan portion, thereby halting the production of hydrogen gas.

A hydrogen output sensor 64 is incorporated into system 30. Hydrogen output sensor 64 may be a pressure transducer that converts the gas pressure within the hydrogen line to a voltage or current value for measurement. However, hydrogen output sensor 64 can be any suitable output sensor other than a pressure transducer, including, but not limited to, a flow rate sensor, a mass flow sensor, or any other quantitative sensing device. Hydrogen output sensor 64 is interfaced with a control unit 66, which is capable of converting the voltage or current value into a pressure reading. Furthermore, a display means (not shown) may be disposed in operable communication with hydrogen output sensor 64 to provide a reading of the pressure, for example, at the location of hydrogen output sensor 64 on the hydrogen line. Control unit 66 is any suitable gas output controller, such as an analog circuit or a digital microprocessor.

Referring now to FIGURES 3 and 4, the ventilation system is shown generally at 62. Ventilation system 62 comprises a fan portion, shown generally at 68, and a fan flow sensor portion, shown generally at 70, disposed in operable communication with fan portion 68. Fan portion 68 and fan flow sensor portion 70 are mounted within the generator with a bracket 72. Fasteners 74 extending through bracket 72 enable fan portion 68 to be secured to bracket 72. Fan portion 68 comprises an impeller (not shown) rotatably mounted within a housing 76 and driven by a motor (not shown), which may be a 12 volt DC motor. The impeller provides ventilation within the enclosure of the generator via a continual purge of air at a rate such that if the full production of hydrogen were to leak into the enclosure, the hydrogen would be vented outside the enclosure and diluted to a very low concentration.

Fan flow sensor portion 70 comprises a switch housing, shown generally at 78, and a sail/collar assembly, shown generally at 80, in operable communication with switch housing 78. Sail/collar assembly 80 is configured to receive airflow from fan portion 68. Switch housing 78 includes a switching device (described below with reference to FIGURES 5A and 5B) mounted in a spindle 82 extending from an upper surface of a base member 84, which is mounted to a hub 79 of fan portion 68. Sail/collar assembly 80 is defined by a substantially planar sail 85 having a collar 86 extending either from an upper surface of sail 85 as shown or through the upper surface and a lower surface of sail 85. Collar 86 is received over spindle 82 such that slidable communication is maintained therebetween. A retainer 88 is disposed at an upper end of spindle 82 distal from base member 84.

In FIGURES 5A and 5B, fan flow sensor portion 70, particularly switch housing 78 and sail/collar assembly 80, are shown in greater detail. The switching device disposed within switch housing 78 is a reed switch, shown generally at 94, which is configured to function independent from the delivery line pressure of the hydrogen gas. In airflow switch 78, spindle 82 is fixedly mounted to base member 84 at a lower end thereof such that spindle 82 extends substantially perpendicularly from the upper surface of base member 84. Alternately, spindle 82 and base member 84 may be cast as a unitary piece. An opening 90 is formed within spindle 82 and extends therethrough to enable communication to be maintained between reed switch 94 disposed inside spindle 82 and a remotely located ventilation system control unit (not shown). Reed switch 94 is securely disposed within spindle 82 with a potting material 92. Potting material 92 provides a relief to stresses associated with the operation of switch housing 78 and is generally a solidified material such as an epoxy. An adhesive (not shown) may be applied to a lower surface of base member 84 to facilitate the attachment of switch housing 78 to hub 79 of the fan portion.

Reed switch 94 includes two separate flexible magnetic reeds 95a, 95b disposed adjacent to each other within an enclosure 96. The flexibility of reeds 95a, 95b enables reeds 95a, 95b to be magnetically biased together such that contact can be intermittently made therebetween and maintained upon the magnetic actuation of reed switch 94, which is effectuated by the placement of a magnet 98 in close proximity to reeds 95a, 95b. hi FIGURE 5 A, magnet 98 is shown as a bar magnet disposed longitudinally along the length of collar 86. In FIGURE 5B, magnet 98 is shown as a ring magnet disposed around collar 86. In either configuration, lead wires 100 extend from each reed 95a, 95b through potting material 92 and through opening 90 to provide electronic communication between reed switch 94 and the ventilation system control unit.

With respect to sail/collar assembly 80, collar 86 functions as a guide member to provide for the translational motion of sail 85 along spindle 82. Collar 86 is configured to be received over spindle 82 such that sail/collar assembly 80 is slidably disposed on spindle 82. Regardless of whether magnet 98 is a bar magnet, as is shown in FIGURE 5A, or a ring magnet, as is shown in FIGURE 5B, magnet 98 is disposed on the outer surface of collar 86; alternately, magnet 98 maybe insert- molded directly into collar 86. Magnet 98 is generally fabricated from a rare earth element such as neodymium. Both collar 86 and spindle 82 are radially dimensioned relative to each other to facilitate such slidable motion with a minimum amount of resistance generated by the contact of the outer surface of spindle 82 and the inner surface of collar 86. Both collar 86 and spindle 82 are likewise axially dimensioned relative to each other such that collar 86 can axially translate the length of spindle 82 to a point where reed switch 94 is unaffected by magnet 98.

Sail 85 is fixedly mounted to a lower end of collar 86. Alternately, sail 85 can be integrally formed with collar 86, e.g., collar 86 can be formed or molded with sail 85 such that sail/collar assembly 80 is a unitary piece. The dimensions of sail 85 substantially correspond with the dimensions of the opening in the fan portion through which airflow is generated by the rotation of the impeller. In particular, the peripheral dimensions of sail 85 correspond with the peripheral dimensions of the opening in the fan portion, thereby enabling sail 85 to register with the opening in the fan portion. Materials that may be used for the construction of sail 85 (and also for the construction of collar 86) include, but are not limited to, titanium, aluminum, high density polypropylene, polytetrafluoroethylene, nylon, and MYLAR.

Retainer 88 is a ring-shaped element dimensioned to be positioned over the upper end of spindle 82 and fixedly attached thereto. Retainer 88 prevents the axial translation of sail/collar assembly 80 beyond the upper end of spindle 82 and, more particularly, prevents the removal of sail/collar assembly 80 from spindle 82 altogether.

Referring now to FIGURE 6, another configuration of a sail/collar assembly is shown generally at 180. Sail/collar assembly 180 comprises a collar 186 and an associated magnet 198 similar to those described with reference to FIGURES 3, 4, 5 A, and 5B. Sail/collar assembly 180 further comprises a sail, shown generally at 185, having a deflective surface 187 disposed about the periphery of sail 185. Deflective surface 187 is dimensioned to be angled away from a flat planar surface 189 of sail 185 at an angle a, which is generally between about five and ten degrees. By incorporating deflective surface 187 into the architecture of sail 185, sail collar assembly 180 can experience additional lift as a result of airflow from the fan portion.

Referring now to FIGURES 7 A and 7B, additional configurations of switch housings are shown, hi a switch housing shown generally at 178 in FIGURE 7A, the retainer (as illustrated at 88 in FIGURES 3, 4, 5A, and 5B) can be reconfigured to define tabs 188 fixedly disposed on and extending laterally from the upper end of a spindle 182. Tabs 188 comprise protrusions extending normally from the surface of a spindle 182 to prevent the axial translation of a sail/collar assembly (not shown) beyond the upper end of spindle 182. Tabs 188 are, furthermore, flexible to allow the sail/collar assembly to be "snapped" onto spindle 182. Although two tabs 188 are illustrated, any number of tabs 188 can be disposed peripherally about the cross section of the upper end of spindle 182 to retain the sail/collar assembly thereon.

In a switch housing shown generally at 278 in FIGURE 7B, a retainer 288 is configured as a plug having a lip 289 and a plug portion 291. Once the sail/collar assembly (not shown) is inserted onto a spindle 282, plug portion 291 is inserted into an upper open end of a spindle 282. Lip 289 is dimensioned to overhang the outer perimeter of spindle 282, thereby retaining the sail/collar assembly thereon. The operation of fan flow sensor portion 70 is described with reference to FIGURES 3, 4, 5A, and 5B. The slidable communication maintained between sail/collar assembly 80 and spindle 82 provides for the actuation of reed switch 94. Reed switch 94 is electronically configured to interrupt the flow of electrical current to the cell stack in the event that the airflow generated by the impeller of fan portion 68 is impeded to any degree as a result of operational difficulties. At startup of the generator, sail/collar assembly 80 rests on spindle 82 adjacent base member 84. Magnet 98 provides communication between reeds 95a, 95b of reed switch 94 by causing reeds 95a, 95b to flex and remain in contact with each other. The contact maintained between reeds 95 a, 95b closes a circuit, thereby causing electronic communication to be maintained between reed switch 94 and the ventilation system control unit through lead wires 100. Upon rotation of the impeller, airflow is generated through fan portion 68, which causes sail 85 to slide via collar 86 up spindle 82 and lift away from base member 84. Upon proper functioning of fan portion 68, the lift experienced by sail 85 causes magnet 98 to be removed from the proximity of reed switch 94. Reeds 95a, 95b then relax and separate, thereby interrupting the continuity of the circuit and removing the signal to the cell stack that causes the interruption of power.

In FIGURES 8 through 11, another exemplary embodiment of the ventilation system is shown generally at 362. Referring specifically to FIGURES 8 and 9, ventilation system 362 comprises a fan portion, shown generally at 368, and a fan flow sensor portion, shown generally at 370, disposed in operable communication with fan portion 368. As above, fan portion 368 and fan flow sensor portion 370 are mounted within the generator with a bracket 372 and fasteners 374. An impeller (not shown) rotatably mounted within a housing 376 of fan portion 368 provides the airflow of ventilation system 362. Fan flow sensor portion 370 comprises a switching device (which is a reed switch, shown generally at 394 in FIGURE 11), and a sail, shown generally at 380, configured to receive an airflow from fan portion 368. Referring to FIGURE 10, sail 380 is described in greater detail. Although sail 380 is illustrated as being a substantially L-shaped member of planar configuration having a pivotal leg 381 and a radial leg 383, it should be recognized that other shapes and configurations maybe utilized. Radial leg 383 is arcuately configured along an outer edge 385 thereof to conform to the inner edge of a circular opening disposed in bracket 372. A tab (shown below with reference to FIGURE 11) dimensioned to accommodate the attachment of one of the magnets of the switching device depends from a peripheral surface of pivotal leg 381 and extends substantially normally from the general plane of sail 380. Sail 380 is pivotally mounted to a hub 379 of the fan portion utilizing a piece of cloth/glass tape 387, which is capable of maintaining its adhesive properties in the high temperature environment characteristic of the generator. Hub 379 is supported on the fan portion by fan wiring channels 391. Referring to FIGURE 11, a switching device is shown generally at 378. Switching device 378 comprises the reed switch 394, which is substantially similar to reed switch 94 as shown in FIGURES 3 through 7B. Reed switch 394, in a manner similar to that as described above, includes two separate flexible magnetic reeds (not shown) disposed adjacent to each other within an enclosure. The flexibility of the magnetic reeds enables them to be magnetically biased together such that contact can be intermittently made therebetween and maintained upon magnetic actuation effectuated by the placement of at least one magnet 398a, 398b in close proximity to the reeds of reed switch 394.

Reed switch 394 is mounted in the fan wiring channel (as shown at 391 in FIGURE 10) on housing 376 and configured such that when the airflow generated by the impeller is impeded, the flow of electrical current to the cell stack is interrupted. At startup of the generator, sail 380 rests across the opening of fan portion 368. Magnet 398a disposed on the tab 393 is in close proximity with magnet 398b mounted adjacent reed switch 394. The proximity of magnets 398a, 398b causes a magnetic field to be generated across reed switch 394 that biases the flexible magnetic reeds together to close the circuit, thereby causing electronic communication to be maintained between reed switch 394 and the ventilation system control unit. Upon rotation of the impeller, airflow is generated through fan portion 368, which causes sail 380 to pivot about its connection to hub 379, lifting magnets 398a, 398b out of proximity with each other and causing the magnetic reeds to separate, thereby interrupting the continuity of the circuit and removing the signal to the cell stack that causes the interruption of power. Other configurations, e.g., one in which only a single magnet is utilized to bias the magnetic reeds together, may be incorporable into the ventilation system.

In either exemplary embodiment of the ventilation system, only the ventilation system needs to malfunction in order for the generator to be shut down during its operation. By configuring the system such that the interruption of power thereto is dependent upon the proper functioning of the ventilation system instead of the pressure delivery line, the cell stack can be shut down upon obstruction of the fan portion (or a similar problem) prior to any leakages of hydrogen gas. The cell stack and all of its associated components except for the ventilation system may, therefore, be in functioning order during the operation of the generator. Nevertheless, because the ventilation system operates independent of the delivery line pressure, malfunction or failure of either the fan portion or the switching device will close the circuit and cause a signal to be sent to the electrical source to interrupt the flow of electrical current to the cell stack, thereby shutting down operation of the generator.

While the disclosure has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this disclosure, but that the disclosure will include all embodiments falling within the scope of the appended claims.

What is claimed is:

Claims

1. A gas generating system, comprising: a reactant source; an electrolysis cell disposed in fluid communication with said reactant source; an electrical source disposed in communication with said electrolysis cell; a ventilation system disposed in communication with said electrolysis cell, said ventilation system comprising, a fan, a sail disposed in operable communication with said fan, said sail being movable in response to an airflow from said fan, and a switch disposed in operable communication with said sail and said electrical source.

2. The gas generating system of claim 1 wherein said sail is slidably movable in response to the airflow from said fan.

3. The gas generating system of claim 1 wherein said sail is pivotally movable in response to the airflow from said fan.

4. The gas generating system of claim 1 wherein said switch comprises a magnetically actuatable reed switch.

5. A hydrogen gas generator, comprising: a proton exchange membrane electrolysis cell; and a ventilation system disposed in fluid communication with said proton exchange membrane electrolysis cell, said ventilation system comprising, a fan portion, said fan portion being configured to produce an airflow; a switch disposed in electronic communication with said proton exchange membrane electrolysis cell, and a sail configured to receive the airflow from said fan portion, said sail being disposed in actuatable communication with said switch.

6. The hydrogen gas generator of claim 5 wherein said switch comprises a magnetically actuatable reed switch.

7. The hydrogen gas generator of claim 6 wherein said sail comprises a magnet disposed thereon.

8. The hydrogen gas generator of claim 7 wherein said sail is slidably movable in response to the airflow from said fan portion.

9. The hydrogen gas generator of claim 7 wherein said sail is pivotally movable in response to the airflow from said fan portion.

10. A fan flow sensor, comprising: a switching device; and a sail disposed in communication with said switching device, said sail being configured to actuate said switching device in response to an airflow from a fan.

11. The fan flow switch of claim 10 wherein said switching device is disposed within a spindle, said spindle having a first end disposed proximate a source of the airflow from the fan and a second end disposed distal from the source of the airflow from the fan, said spindle being dimensioned to accommodate slidable movement of said sail there along in response to the airflow from the fan.

12. The fan flow switch of claim 11 further comprising a collar disposed between said sail and said spindle, said collar being dimensioned and configured to facilitate the slidable movement between said sail and said spindle.

13. The fan flow switch of claim 11 further comprising a retainer disposed at said second end of said spindle.

14. The fan flow switch of claim 13 wherein said retainer is a ring-shaped element.

15. The fan flow switch of claim 13 wherein said retainer is a tab configured to protrude normally from a surface of said spindle.

16. The fan flow switch of claim 11 wherein said switching device is actuatable in response to a magnet disposed on said sail.

17. The fan flow switch of claim 16 wherein the magnet is insert-molded into a collar disposed on said sail.

18. The fan flow switch of claim 10 wherein said switching device is a reed switch.

19. The fan flow switch of claim 10 wherein said sail comprises a deflective surface disposed about a periphery thereof, said deflective surface being configured and dimensioned to deflect the airflow back toward the source of the airflow.

20. The fan flow switch of claim 10 wherein said switching device is mounted on a housing of the fan, said sail being pivotally mounted on the housing and pivotally movable in response to the airflow from the fan.

21. The fan flow switch of claim 20 wherein said switching device is actuatable in response to a magnet disposed on said sail.

22. The fan flow switch of claim 21 wherein the magnet is disposed on a tab depending from a peripheral surface of said sail.

23. The fan flow switch of claim 20 wherein said sail is pivotally mounted on a hub of the housing.

24. An electrolysis cell, comprising: means for generating a gas from a reactant source; and means for interrupting power to said means for generating hydrogen gas upon detection of a hydrogen gas leak.

25. The electrolysis cell of claim 24 wherein said means for interrupting power to said means for generating gas is a magnetically actuatable switching device.