Passive dual modulation regulator for hydrogen generation

Abstract

A passive dual modulation regulator is provided that is responsive to a pressure difference between a hydrogen side and an oxygen side of one or more proton exchange membrane (PEM) cells. The passive dual modulation regulator includes a flexible diaphragm that is clamped between hemispherical chambers along its periphery. A two-way valve assembly extends through the flexible diaphragm and includes opposing valve plugs for selectively closing the output ports of the respective hemispherical chambers. A large or continuous pressure imbalance between the hydrogen side and the oxygen side of the hydrogen generation system is avoided without any kind of active control input, and thus rupture of the PEM is completely avoided.

Description

Technical Field

[0001] The present invention relates to water electrolysis for generating hydrogen fuel using a proton exchange membrane stack. Background Art

[0002] Water electrolysis is the process of separating water into hydrogen and oxygen by applying electrical energy. Among existing electrolysis technologies, proton exchange membrane (PEM) electrolyzers use a proton exchange membrane as an ion conductor. The proton exchange membrane consists of a thin solid ion-conducting membrane rather than an aqueous solution as found in alkaline electrolyzers. The membrane conducts H + Ions (ie, protons) are transferred from the anode to the cathode and separate the hydrogen gas and the oxygen gas.

[0003] PEM electrolysis is generally preferred over alkaline electrolysis because no caustic electrolyte is used in PEM electrolysis. In addition, PEM electrolysis has faster ion transport due to the membrane (e.g., Nafion from DuPont), which is important under fluctuating conditions. In addition, alkaline cells suffer from cross-contamination because both gases (hydrogen and oxygen) and alkaline substances will be present in the output gas, requiring a scrubber to remove oxygen and alkaline contaminants from the hydrogen gas. This is particularly important because only 3% oxygen in hydrogen is enough to form an explosive mixture.

[0004] PEM electrolyzers include differential pressure designs and balanced pressure designs. In differential pressure or balanced pressure designs, pressure regulation of hydrogen gas and oxygen gas is extremely important for the efficiency and life of the PEM electrolyzer. Therefore, there is still a continuing need for improved pressure regulators for PEM electrolyzers. In particular, there is still a continuing need for improved pressure regulators for balancing oxygen gas and hydrogen gas without cross contamination. Summary of the invention

[0005] A passive dual modulating regulator is provided that responds to a pressure differential between the hydrogen side and the oxygen side of one or more PEM cells. The passive dual modulating regulator includes a flexible diaphragm that is clamped along its periphery between hemispherical chambers. A two-way valve assembly extends through the flexible diaphragm and includes opposing valve plugs for limiting and ultimately closing the output ports of the respective hemispherical chambers. A sustained pressure imbalance between the hydrogen side and the oxygen side of the hydrogen generation system is avoided without any kind of active control input, and thus rupture of the electrolyzer membrane is completely avoided.

[0006] In one embodiment, the opposite ends of the bidirectional valve assembly include an alignment rod, a valve plug, a valve stem, and a fender washer. The alignment rod is externally threaded at one end for attachment to the valve stem and securing the valve plug against the valve stem. The valve plug includes a beveled washer formed of silicone rubber and including a beveled engagement surface for engaging a matching valve seat that has been machined into the concave inner surface of each hemispherical chamber. The valve stem is internally threaded at the distal end for attachment to the alignment rod and is internally threaded at the proximal end for attachment to a headless screw that links each side of the valve assembly together.

[0007] Because the flexible diaphragm is sensitive even to small pressure differences, the high pressure side pushes the diaphragm toward the low pressure side to close the output port on the low pressure side. As the output port is closed and gas is continuously generated at the PEM cell, the pressure on the low pressure side will slowly accumulate. As the pressure equalizes, the output port gradually opens. Thus, the thin polymer membrane within each PEM cell is balanced on each side, thereby preventing rupture of the thin polymer electrolyte membrane.

[0008] In another embodiment, a hydrogen generation system is provided. The hydrogen generation system includes one or more PEM cells, an oxygen-water separator, a hydrogen-water separator, a hydrogen storage tank, and a passive dual modulation regulator. The hydrogen-water separator receives hydrogen gas and trace amounts of water from the cathode side of the PEM cell, and the hydrogen gas is extracted into the hydrogen output line. The oxygen-water separator is used as the main water reservoir for the PEM cell, and collects excess water carrying oxygen from the anode side of the PEM cell. The oxygen gas is then extracted from the oxygen-water separator into the oxygen output line. The passive dual modulation regulator is arranged between the hydrogen output line and the oxygen output line for maintaining a balanced pressure between the hydrogen side and the oxygen side of one or more PEM cells. The hydrogen output line is connected to a pressurized hydrogen storage tank, and the oxygen output line is connected to an oxygen valve and an oxygen meter for safely discharging the oxygen gas into the atmosphere.

[0009] In some embodiments, hydrogen fuel is directed to a gas grill having one or more hydrogen burners. The gas grill may be suitable for personal or commercial applications, such as restaurants or cafeterias. A gas grill operating on hydrogen gas is environmentally friendly because the hydrogen grill does not generate carbon emissions and operates directly from renewable energy sources, such as solar energy collected by photovoltaic cells. The hydrogen generation system and passive dual modulation regulator are not limited to cooking applications and may be used in other systems as needed, including emergency backup power systems, transportation systems, and propulsion systems.

[0010] These and other features and advantages of the present invention will become apparent from the following description of embodiments of the invention, when viewed in light of the accompanying drawings and appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic diagram of a hydrogen generation system according to one embodiment.

[0012] Figure 2 Graphics for use with Figure 1 The PEM cell is used in conjunction with a hydrogen generation system.

[0013] Figure 3 is with Figure 1 First exploded view of a passive dual modulation regulator used in conjunction with the system.

[0014] Figure 4 is with Figure 1 A second exploded view of a passive dual modulation regulator used in conjunction with the system.

[0015] Figure 5 is used for Figure 3 to Figure 4 Exploded side view of the diaphragm and valve assembly of a passive dual-modulation regulator.

[0016] Figure 6 is a first exploded view of a passive dual modulation regulator according to further embodiments.

[0017] Figure 7 yes Figure 6 Second exploded view of the passive dual modulation regulator. DETAILED DESCRIPTION

[0018] The current embodiment includes a passive dual modulation regulator that responds to the pressure difference between the hydrogen side and the oxygen side of one or more PEM cells to ensure that the PEM cells do not rupture. Large or sustained pressure imbalances between the hydrogen side and the oxygen side are avoided without any kind of active control input. However, before discussing the passive dual modulation regulator in detail, an exemplary hydrogen storage system with two PEM cells will now be described. Although the system is described below as generating hydrogen fuel for cooking applications, the passive dual modulation regulator is not limited to any one such system and can be used in other systems as desired.

[0019] First reference Figure 1The hydrogen generation system 10 according to an exemplary embodiment includes a distilled or deionized water source 12, an oxygen-water separator 14, a hydrogen-water separator 16, two PEM cells 18, 20, a hydrogen storage tank 22, a passive dual modulation regulator 24, and an oxygen valve 26 and an oxygen meter 28. The PEM cells 18, 20 may include any of a variety of commercially available PEM cells having a proton exchange membrane 32, an anode 34, and a cathode 36, which are generally Figure 2 At the anode 34 of each PEM cell, the feed water is electrochemically split into protons (H + ), electronic (e - ) and oxygen (O2). Protons are transported to cathode 36 via proton exchange membrane 32. Electrons leave anode 34 through an external power circuit that provides a driving force (cell voltage) for the reaction. At cathode 36, protons and electrons combine to produce hydrogen. Although not shown, hydrogen generation system 10 includes an energy source that generates a cell voltage for PEM cells 18, 20 connected in series. By way of non-limiting example, the energy source may be solar photovoltaic, solar thermal, or geothermal.

[0020] Reference again Figure 1 , a distilled or deionized water supply 12 (e.g., distilled municipal water) is fed to an oxygen-water separator 14. The feed water from the oxygen-water separator 14 is gravity fed to the anode surfaces of the first PEM cell 18 and the second PEM cell 20 via a supply line 30, where the feed water is separated into oxygen and hydrogen as described above. The oxygen-water separator 14 serves as the primary water reservoir for the PEM cells 18, 20, and collects excess water carrying oxygen from the anode side of the PEM cells 18, 20 via the oxygen line 30. The oxygen gas is then pumped from the oxygen-water separator 14 into an oxygen output line 44. The hydrogen-water separator 16 receives hydrogen gas and trace amounts of water from the cathode side of the PEM cells 18, 20 via a hydrogen line 38. The hydrogen gas is pumped into a hydrogen output line 42. A passive dual modulation regulator 24 is provided between a hydrogen output line 42 and an oxygen output line 44 for maintaining a balanced pressure between the hydrogen and oxygen sides of the PEM cells 18, 20. The hydrogen output line 42 is coupled to a pressurized hydrogen storage tank 22, and the oxygen output line 44 is coupled to an oxygen valve 26 and an oxygen meter 28 for safely discharging the oxygen gas to the atmosphere. Figure 1 Two PEM cells 18, 20 connected in series are shown, but other embodiments may include more or fewer PEM cells, such as a single PEM cell or three or more PEM cells.

[0021] As hydrogen fuel is produced, it is stored in a pressurized hydrogen tank 22. No compressor is required to pressurize the hydrogen tank 22. The PEM cells 18, 20 continue to produce gas until a pressure limit is reached, prompting actuation of the cut-off switch. Hydrogen is produced at twice the rate of oxygen, however, since the hydrogen side has a large tank 22 to fill and the oxygen side has no tank, the oxygen is released into the atmosphere. Once there is the slightest hydrogen pressure, the oxygen side will begin a regulated release of gas to maintain equal pressure on both sides. The hydrogen fuel can be directed to a gas grill having one or more hydrogen burners. The gas grill can be suitable for personal or commercial applications, such as restaurants or cafeterias. A gas grill that operates on hydrogen gas (rather than propane) is environmentally friendly because the hydrogen grill does not generate carbon emissions and can operate directly from renewable energy sources, such as solar energy collected by photovoltaic cells. The hydrogen generation system and passive dual modulation regulator are not limited to cooking applications and can be used in other systems as needed, including emergency backup power systems, transportation systems, and propulsion systems.

[0022] Reference now Figures 3 to 5 , illustrates a passive dual modulation regulator 24 according to an exemplary embodiment. The regulator 24 includes an outer shell formed by a first end cap 50 and a second end cap 52, which cooperate to define a spherical internal cavity that is divided into a hydrogen chamber and an oxygen chamber. The first end cap 50 includes an inlet 54 for receiving hydrogen gas from the hydrogen output pipeline 42, and includes an outlet 56 for discharging the hydrogen gas to the hydrogen storage tank 22. Similarly, the second end cap 52 includes an inlet 58 for receiving oxygen gas 60 from the oxygen output pipeline 44, and includes an outlet 60 for discharging the oxygen gas to the outlet valve 26. Each inlet 54, 58 is formed in a side opening in a rectangular flange 62, and each outlet 56, 60 is formed in a central opening in a hemispherical end wall 64. Thus, the hydrogen inlet 54 is in fluid communication with the hydrogen outlet 56 via the hemispherical hydrogen chamber 66 , and the oxygen inlet 58 is in fluid communication with the oxygen outlet 60 via the hemispherical oxygen chamber 68 .

[0023] The regulator 24 also includes a flexible diaphragm 70 sandwiched between the first end cap 50 and the second end cap 52 to separate the spherical interior cavity into a hemispherical hydrogen chamber 66 and a hemispherical oxygen chamber 68. A series of bolt openings 72 around the periphery of the flexible diaphragm 70 are aligned with bolt openings 74 in the first end cap 50 and the second end cap 52. The flexible diaphragm 70 is optionally formed of silicone rubber or other air-impermeable membrane material and includes a central orifice. The regulator also includes a valve assembly 76 that extends through the central orifice in the flexible diaphragm 70 for selectively closing the output ports 56, 60 of the hydrogen chamber 66 and the oxygen chamber 68. As shown in FIG. Figure 5, the opposite ends of the valve assembly 76 are joined together by grub screws 78 and include an alignment rod 80, a valve plug 82, a valve stem 84 and a Fender washer 86. The alignment rod 80 is externally threaded at one end for attachment to the valve stem 84 and is used to (a) maintain alignment of the valve assembly 76 and (b) secure the valve plug 82 against the valve stem 84. The valve plug 82 includes a beveled washer formed of silicone rubber and includes a 60 degree engagement surface 88 for engaging a matching 60 degree valve seat that has been machined into the concave inner surface of each hemispherical end wall 64. The valve stem 84 is internally threaded at the distal end for attachment to the threaded portion 90 of the alignment rod 80 and is internally threaded at the proximal end for attachment to the grub screw 78 that joins each side of the valve assembly 76 together.

[0024] As the pressure from the PEM cells 18, 20 increases, hydrogen and oxygen enter the regulator 24, but the hydrogen produced therein is twice as much as oxygen. Since the hydrogen side has a large storage tank 22 to be filled, and the oxygen side does not have a storage tank, the oxygen gas is initially released into the atmosphere without restriction. Once there is the slightest hydrogen pressure, the oxygen side will begin the modulated release of the gas to maintain equal pressure on both sides. Because the diaphragm 70 is sensitive even to a small pressure difference, the hydrogen side pushes the diaphragm 70 toward the oxygen side to close the oxygen output port 60 while allowing hydrogen gas to be transferred to the hydrogen storage tank 22. While oxygen is continuously generated at the PEM cells 18, 20, the pressure on the oxygen side will slowly accumulate (to match the pressure on the hydrogen side) due to the closure of the oxygen output port 60. When the pressure on the oxygen side reaches the pressure on the hydrogen side, the valve assembly is centered and allows gas flow at each output port 56, 60. The thin polymer membrane 32 within each PEM cell 18, 20 is balanced on either side, thereby preventing rupture of the membrane 32. Excess oxygen is vented through the outlet valve 26 to maintain a balanced pressure between the hydrogen side and the oxygen side.

[0025] Passive dual modulation regulators are not limited to Figures 3 to 5 The valve assembly may include other configurations as required. Figure 6 to Figure 7 , for example, the valve assembly may include a valve plug 82 extending from the flexible diaphragm 70 to the alignment rods 80 on either side of the flexible diaphragm. In this embodiment, the valve plug 82 is tapered, having a frustoconical geometry, for closing either output port 56, 60. For example, the valve plug 82 may include a 60 degree cone that mates with a 60 degree valve seat that has been machined into the concave inner surface of each hemispherical end wall 64.

[0026] We will now describe Figures 3 to 5 Passive dual modulation regulator Figure 1 to Figure 2A working example of a hydrogen generation system. The hydrogen generation system includes two PEM cells connected in series, which are powered by a 100W solar panel. The passive dual modulation regulator includes a valve assembly having a machined brass rod of 0.5 inches in diameter and 0.625 inches in length. The rod is internally threaded at each end. The valve assembly also includes a 0.25 inch diameter brass alignment rod, which is 1.1 inches in length, one of which is machined to 0.19 inches and is externally threaded. The alignment rod is screwed into the brass rod with a rubber bevel washer between the two. Two such assemblies are connected to a 0.25 inch x 28 headless screw, which extends through a 0.25 inch opening in a silicone rubber diaphragm. Two 1.5 inch steel Fender washers are used on either side of the diaphragm to prevent rupture of the diaphragm. The hydrogen generation system achieves a hydrogen delivery pressure of greater than 200PSI, with a flow rate between 320ml / min and 400ml / min. In contrast, commercially available hydrogen generators include hydrogen delivery pressures between 5PSI and 100PSI, have a flow rate of only 160ml / min, and cost several times that of the hydrogen generation system of the present invention. Thus, the present invention provides a commercially viable hydrogen fuel source that can run on renewable energy sources (e.g., solar energy) with significantly improved delivery pressures and flow rates over those found in existing systems.

[0027] It is worth noting that the numerical values ​​in the aforementioned working examples are exemplary and are not intended to be limiting. For example, the 200 psi in the aforementioned working examples was selected in view of economic and practical considerations, because existing propane tanks are typically rated at 200 psi. The hydrogen generation system can be configured to operate at higher delivery pressures (including pressures above 5000 psi) with only single-digit efficiency losses.

[0028] The above description is presented for illustrative purposes and should not be construed as an exhaustive description of all embodiments of the invention or to limit the scope of any claim to the specific elements illustrated or described in conjunction with the embodiment. For example, any reference to an element in the singular using the articles "a", "an", "the", or "said" should not be construed as limiting the element to the singular. In addition, the terms "upper", "lower", "above", "below", etc. are intended to make information clear when describing the embodiments as shown in the accompanying drawings, and should not be construed as limiting the relationship between the geometric features of the invention.

Claims

1. A passive dual modulation regulator, comprising: a first housing section and a second housing section, wherein each of the first housing section and the second housing section comprises a gas inlet and a gas outlet; a diaphragm clamped along its periphery between the first housing section and the second housing section, wherein a first chamber is positioned on a first side of the diaphragm and a second chamber is positioned on a second side of the diaphragm; and A valve assembly extending through the diaphragm and including a first valve plug aligned with a valve seat in the first housing section and including a second valve plug aligned with a valve seat in the second housing section, wherein a pressure differential between the first chamber and the second chamber causes the diaphragm to deflect toward an area of ​​lower pressure such that the valve assembly restricts and then seals the gas outlet for the first chamber or the second chamber to equalize pressure within the first chamber and the second chamber.

2. The regulator according to claim 1, wherein: The first housing section includes a first hemispherical end wall, and the second housing section includes a second hemispherical end wall.

3. The regulator according to claim 2, wherein: The gas outlet for the first housing section extends through the first hemispherical end wall, and wherein the gas outlet for the second housing section extends through the second hemispherical end wall.

4. The regulator according to claim 1, wherein: The first and second shell sections each include a flange plate defining the gas inlet for the corresponding shell section.

5. The regulator according to claim 1, wherein: The first valve plug includes a first beveled washer, and wherein the second valve plug includes a second beveled washer.

6. The regulator according to claim 1, wherein: The valve assembly comprises: a first alignment rod extending from the first valve plug; and A second alignment rod extends from the second valve plug.

7. The regulator according to claim 1, wherein: The valve assembly includes a first Fender washer on a first side of the diaphragm and a second Fender washer on a second side of the diaphragm.

8. The regulator according to claim 1, wherein: The diaphragm and the valve plug are each formed of an elastomeric material.

9. The regulator according to claim 1, wherein: The diaphragm is gas-impermeable and includes a central orifice for the valve assembly.

10. The regulator according to claim 9, wherein: The valve assembly includes a headless screw extending through the central aperture for attachment to the first valve stem and the second valve stem.

11. A hydrogen generation system comprising: Proton exchange membrane (PEM) batteries; an oxygen-water separator that receives oxygenated water from the anode side of the PEM cell and includes an output; a hydrogen-water separator that receives hydrogen-containing water from the cathode side of the PEM cell and includes an output; and a passive dual modulation regulator coupled to the output of the oxygen-water separator and the output of the hydrogen-water separator, the passive dual modulation regulator comprising: a diaphragm clamped between the first housing section and the second housing section; A bidirectional valve assembly extending through the diaphragm and including a first valve plug aligned with a valve seat in the first housing section and including a second valve plug aligned with a valve seat in the second housing section, wherein a pressure imbalance across the diaphragm causes the diaphragm to deflect toward the first valve seat or the second valve seat to equalize pressure within the passive dual modulation regulator.

12. The system of claim 11 further comprising a storage tank in fluid communication with the output of the hydrogen-water separator via the passive dual modulation regulator.

13. The system of claim 11, further comprising a source of distilled or deionized water in fluid communication with the PEM cell.

14. The system of claim 11, wherein: The first housing section includes a first flange and a hemispherical end wall, and The second housing section includes a second flange and a hemispherical end wall.

15. The system according to claim 11, wherein: The first valve plug includes a first beveled washer, and wherein the second valve plug includes a second beveled washer.

16. The system of claim 11, wherein: The two-way valve assembly comprises: a first alignment rod extending from the first valve plug; and A second alignment rod extends from the second valve plug.

17. The system of claim 11, wherein: The valve assembly includes a first Fender washer on a first side of the diaphragm and a second Fender washer on a second side of the diaphragm.

18. The system of claim 11, wherein: The diaphragm and the valve plug are each formed of an elastomeric material.

19. The system of claim 11, further comprising a bleed valve in fluid communication with the output of the oxygen-water separator via the passive dual modulation regulator.

20. The system of claim 11, wherein: The PEM cell is a first PEM cell, and the system further includes a second PEM cell connected in series with the first PEM cell.

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