Patent Publication Number: US-9901891-B2

Title: Membrane valve modulated gas generator

Description:
This application is a divisional of U.S. patent application Ser. No. 14/080,571, filed Nov. 14, 2013, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Some hydrogen generators generate hydrogen by reacting water vapor with a hydride fuel. The water vapor has been provided by different sources, such as ambient, a reservoir of water, or even as a byproduct of a chemical reaction such as in the case of fuel cells. When hydrogen is not required from the hydrogen generator, the supply of water vapor is shut off. The shut off has been accomplished by somewhat complex arrangements of valves. 
     SUMMARY 
     A device includes a case having a surface with a perforation and a cavity. A membrane is supported by the case inside the cavity and has an impermeable valve plate positioned proximate the perforation. The membrane is water vapor permeable and gas impermeable and flexes responsive to a difference in pressure between the cavity and outside the cavity to selectively allow water vapor to pass through the perforation into the cavity as a function of the difference in pressure. 
     A device includes a case having a surface with an array of perforations and a cavity containing a gas generating fuel. A membrane is supported by the case inside the cavity, the membrane having an array of impermeable valve plates, each positioned proximate a corresponding perforation. The membrane is water vapor permeable and gas impermeable and flexes responsive to a difference in pressure between the cavity and outside the cavity to move the plate to block the perforations via the valve plates when the pressure inside the cavity is greater, and to unblock the perforations when the pressure inside the cavity is lower than outside the cavity. 
     A method includes passing water vapor through a gas impermeable, water vapor permeable membrane to a gas producing fuel in a fuel container, responsive to a gas pressure in the container higher than pressure outside the container, moving a plate supported by the membrane towards a perforation in the container to impede passing of water vapor to the gas producing fuel, and responsive to a gas pressure in the container lower than pressure outside the container, moving the membrane and plate away from the perforation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram cross section representation of a fuel cartridge having a membrane based valve assembly according to an example embodiment. 
         FIG. 2  is a block diagram cross section representation of a portion of the fuel cartridge of  FIG. 1  showing the valve in an open position according to an example embodiment. 
         FIG. 3  is a block diagram cross section representation of a portion of the fuel cartridge of  FIG. 1  showing the valve in a closed position according to an example embodiment. 
         FIG. 4  is a block diagram cross section representation of an alternative fuel cartridge having a membrane based valve assembly according to an example embodiment. 
         FIG. 5  is a top view representation of a membrane having an array of valve plates according to an example embodiment. 
         FIG. 6  is a top view representation of a membrane having an array of interconnected valve plates according to an example embodiment. 
         FIG. 7  is a cross section representation of a power generator utilizing a gas generating cartridge having a membrane based valve assembly according to an example embodiment. 
         FIG. 8  is a portion of the power generator of  FIG. 7 . 
         FIG. 9  is a top view block representation of a manifold for the power generator of  FIGS. 7 and 8  according to an example embodiment. 
         FIG. 10  is a cross section representation of a power generator incorporating a membrane with a valve assembly according to an example embodiment. 
         FIG. 11  is a cross section representation of a portion of the power generator of  FIG. 10  according to an example embodiment. 
         FIG. 12  is a cross section representation of a portion of an alternative power generator according to an example embodiment. 
         FIG. 13  is a cross section representation of a power generator container having a power generator inserted according to an example embodiment. 
         FIG. 14  is a graph illustrating water vapor flow rate versus internal pressure of a membrane based valve assembly according to an example embodiment. 
         FIG. 15  is a block diagram of a computer system for implementing a controller according to an example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the present invention. The following description of example embodiments is, therefore, not to be taken in a limited sense, and the scope of the present invention is defined by the appended claims. 
     The functions or algorithms described herein may be implemented in software or a combination of software and human implemented procedures in one embodiment. The software may consist of computer executable instructions stored on computer readable media such as memory or other type of storage devices. Further, such functions correspond to modules, which are software, hardware, firmware or any combination thereof. Multiple functions may be performed in one or more modules as desired, and the embodiments described are merely examples. The software may be executed on a digital signal processor, ASIC, microprocessor, or other type of processor operating on a computer system, such as a personal computer, server or other computer system. 
       FIG. 1  is a cross sectional representation of a removable fuel cartridge  100 . Cartridge  100  comprises a case  110  (metal or polymer) containing a water-reactive gas generating fuel  112  in a cavity  113 . The cartridge  100  may be inserted into a gas consuming device, such as a power generator. In one embodiment the power generator comprises a fuel cell system and the generated gas comprises hydrogen. A side or face  115  of the case  110  is perforated  116 , and exposes a selectively permeable membrane  120  (water vapor permeable, atmospheric gas impermeable) which separates the fuel  112  from the ambient environment  122  outside the case  110 . 
     In one embodiment, the membrane  120  is positioned between the perforated face  115  and a permeable plate  125 , which may be perforated in one embodiment. The membrane  120  is flexible, and moves between the plate  125  and face  115  responsive to a difference in pressure between the cavity  113  and ambient  122 . The plate  125  and face  115  bound the movement of the membrane  120  in one embodiment such that the membrane is not unduly stressed via the difference in pressure that may develop. A typical gap may be up to a few hundred micron in some embodiments and more in others, depending on the lateral dimensions of the membrane. The membrane may be coupled to sides of the case  110  via adhesive on a perimeter of the membrane or other method to provide a seal that allows the difference in pressure to cause the membrane  120  to move transverse to the face  115 . 
     In one embodiment, the membrane  120  comprises one or more valve plates  130  that move toward the perforations  116  when the pressure is higher inside the cavity  113 , and move away from the perforations when the pressure inside the cavity is lower than ambient  122 . In one embodiment, a gasket  135  is formed about the perforations which is compressible to form a seal with corresponding valve plates  130  when the difference in pressure causes the membrane to push the valve plates  130  into contact with the gasket. The gasket may be optional where the materials comprising the valve plates  130  and face  115  having perforations  116  form an adequate seal when pressed against each other by the different in pressure. The differences in pressure in some embodiments modulate up to few tenths of a pound per square inch in one embodiment. 
     In various embodiments, the number of perforations  116  in face  115  may vary between one and many, forming an array of perforations. Similarly, the number of valve plates may be the same as the number of perforations, and arranged in an array to mate with each corresponding perforation. In still further embodiments, one or more larger valve plates may be used such that each valve plate may cover multiple perforations. 
     In one embodiment, a gas permeable particulate filter  140  is positioned between fuel  112  and plate  125  to prevent fuel from clogging the perforations in the plate  125 . The fuel in various embodiments may be porous to allow the water vapor passing through the perforated face  115 , membrane  120  in areas other than those contain the valve plates  130 , plate  125 , and filter  140  to migrate through the fuel to generate more gas. The fuel porosity in one embodiment varies between approximately 15% and 20%. The porosity may be selected to allow adequate movement of gas and water vapor while at the same time providing a desired gas producing capability. 
     The gas also moves through the porous fuel  112  towards a gas exit  145 . The gas exit in different embodiments may be positioned on a side of the case  110  that may be plugged into a gas consuming device. While the gas exit  145  is shown about a middle of the side of the case  115 , it may be located in any convenient location on the case where the gas may be used. A check valve  150  may be coupled to the gas exit and be actuated by plugging the fuel container  100  into the gas consuming device. In still a further embodiment, a particulate filter  155  may be positioned about the check valve  150  and gas exit  145  to prevent the gas exit  145  from being clogged by fuel. Channels may be formed within cavity  113  to facilitate distribution of water vapor and generated gas in still further embodiments. 
       FIGS. 2 and 3  are partial cross sections illustrating the interaction of the valve plates  130  with the perforated plate  115 . At  200  in  FIG. 2 , when a low pressure occurs in chamber  113  due to gas being drawn out of the chamber for use, the resulting difference in pressure results in the membrane  120  being flexed toward the plate  125 , allowing water vapor to enter through perforations  116 , and pass through the membrane  120  at portions of the membrane not being covered by valve plates  130 . 
       FIG. 3  illustrates the interaction of the valve plates  130  with the perforated plate  115  when the pressure inside the chamber  113  is greater than ambient  116  pressure. The membrane is shown as being pushed toward the perforated plate  115 , causing the valve plates  130  to come into contact with the perforated plate  115 , optionally via the gasket  135 . As seen, the valve plates  130  are sized to be a little bit larger than the perforations  116  such that they serve to block flow of water vapor when contacting the perforations  116 . When generated gas is drawn out via gas exit  145 , the pressure decreases, allowing the valve plates to move away from the perforations  116  and once again allow water vapor to reach the fuel  112  through membrane  120 . The flexible membrane with valve plates thus serves to regulate the water vapor flow and hence gas generation response to the difference in pressure. 
     In one embodiment, the water vapor reacts with the fuel  112  to generate hydrogen. The hydrogen is provided via gas exit  145  when the cartridge  100  is inserted into a fuel cell based power generator. The power generator may also cause the check valve  150  to be opened when the cartridge is inserted, allowing the hydrogen to exit. 
       FIG. 4  is a cross section of an alternative gas generating cartridge  400 . Cartridge  400  also contains a water vapor membrane based valve arrangement as shown in  FIG. 1  which is numbered consistently with  FIG. 1 . In addition, a second water vapor membrane based valve arrangement is illustrated on a further side of the cartridge  400 . A side or face  160  is perforated as indicated at  165 . Similarly to face  115 , a gasket  170  may also be used, a similar membrane  175  may be positioned with valve plates  180  between the face  160  and a perforated plate  185 . A particulate filter  190  may also be positioned between the fuel  112  and the perforated plate  185 . Each of these elements operates similarly to the valve assembly shown on the other or opposite side of the case  110 . In further embodiments, more than two such assemblies may be utilized. 
       FIG. 5  is a top view of a membrane  500  representation. The membrane  500  in one embodiment supports an array of water and gas impermeable valve plates  510 . The membrane  500  may be formed of Dupont Nafion® material or Gore® PRIMEA® membrane material that is metalized to form the plates  510 . The valve plates may be formed of metal, such as gold, and may be patterned by deposition or otherwise formed on the membrane  500  in a position such that they will mate with the perforations in the perforated plate to form the water vapor valve assembly. Other materials, such as a polymer or plastic that is impermeable to gas may be used in further embodiments, and may be deposited, glued, or otherwise supported in position on the membrane  500 . 
     Membrane  500  in one embodiment, where not covered by valve plates as indicated at  520  is water vapor permeable and gas impermeable. Ionomer type membranes may be used in some embodiments. Example membrane materials include Nafion or PRIMEA membranes. 
       FIG. 6  is a top view of a membrane  600  representation. The membrane  600  in one embodiment supports an array of gas impermeable valve plates  610  that maybe interconnected by connectors  612  to provide additional structural integrity to the membrane as it flexes responsive to the difference in pressure. A perimeter band  620  may also be formed to provide additional structural integrity where the membrane  600  is attached to the case of the cartridge. The valve plates, connectors, and band may be formed of metal, such as gold, and may be patterned by deposition or otherwise formed on the membrane  600  in a position such that they will mate with the perforations in the perforated plate to form the water vapor valve assembly. Other materials, such as a polymer or plastic such as Kapton that is impermeable to gas may be used in further embodiments, and may be deposited, glued, or otherwise supported in position on the membrane  600 . Each of the elements may be formed of different materials in further embodiments. 
     Membrane  600  in one embodiment, where not covered by valve plates as indicated at  615  is water vapor permeable and gas impermeable. Ionomer type membranes may be used in some embodiments. Example membrane materials include Nafion or PRIMEA membranes. 
       FIG. 7  is a cross section representation of a device  700  to utilize a gas generating cartridge case  110 .  FIG. 8  is a blown up view of a portion of the device  700  and has reference numbers consistent with those used in  FIG. 7 . In one embodiment, device  700  includes a case  710  having a cavity  712  into which the cartridge  100  may be inserted. Case  710  may be formed of the same material as the cartridge case  110  in some embodiments, or other material suitably ridged. A gas channel or transport path  715  formed in the case  710  may extend from the gas exit  145  of case  110  and provide generated gas to a manifold  720  having multiple openings  722  to allow water vapor to reach case  110  and the gas generating fuel  112 . 
     In one embodiment, manifold  720  forms a structural wall of the case  710 , and also includes an array of channels  725  to provide gas to a membrane  730 , such as a fuel cell membrane electrode assembly. In one embodiment, the gas is hydrogen, which is provided to an anode side of the membrane  730 . The manifold sandwiches the membrane  730  to prevent hydrogen from leaking around the membrane, and also exposes a cathode side of the membrane to oxygen from ambient via openings  722 . Electricity is produced by the membrane along with water vapor which migrates toward the cartridge case  110  along with ambient water vapor to reach the fuel  112  and produce more hydrogen, as regulated by the membrane valve assembly in case  110  based on the difference in pressure. The electricity generated may be provided to an external device, or a device in which the device  700  is integrated into in further embodiments. 
     Management electronics  740  may be disposed anywhere in the device  700 , and is shown supported by a bottom plate  750  of device  700 , which may be a power generator in some embodiments. In one embodiment, management electronics  740  is a controller, such as a micro-controller that may be adapted to manage power generation and delivery, including a rechargeable battery, battery charging integrated circuit, etc. Electronics  740  may be separable, and alternatively, its functions may be provided by device such as a mobile device like a smart phone or touchpad for example. 
     The manifold  720  in one embodiment is illustrated in a top view representation in  FIG. 9 . Openings  722  are shown as round openings in one embodiment, with the channels  725  running between the openings  722  and containing fuel cell membranes  730  which may run the length of the channels  725  in one embodiment. Manifold  720  further includes an exhaust valve  735  which vents gas to ambient. The exhaust valve  735  may be solenoid controlled in one embodiment and may be used to exhaust nitrogen and other gases that may build up during operation. Exhaust valve  735  may also be actuated as a function of pressure, temperature or other sensed parameter or parameters in further embodiments. Also shown is check valve  150  from the case  110 . 
     The device  700  in one embodiment contains a check-valve and fuel cartridge interface  755  which automatically opens the check valve  150  when the cartridge case  110  is inserted into the device cavity  712 , allowing hydrogen to flow from the cartridge case  110  to the fuel cells  730 . In some embodiments, multiple valves may be provided on the cartridge case  110  with the device  700  having multiple interfaces  755 . 
     Device  700  in one embodiment is a fuel cell based power generator that utilizes hydrogen produced from a water reactive hydrogen generating fuel such as a hydride fuel. Production of hydrogen increases pressure in the case  110  while drawing hydrogen from the case reduces the pressure. When power is not drawn from the fuel cells, hydrogen is not drawn from the case  110  and the pressure inside the case increases as water vapor remaining in the case is used to create more hydrogen. The increased pressure pushes the membrane supported valve plates into a closed position with respect to the perforations, shutting off the supply of water vapor and leading to a decrease or cessation of hydrogen production. When power demands increase, the pressure is reduced, resulting in more water vapor being provided to the fuel  112  and the production of more hydrogen to provide to the fuel cells. An equilibrium pressure may be established dependent on the electrical load and ambient temperature and humidity. 
     In one embodiment, the manifold  720  is generally planar in shape and may consist of multiple cells connected in series. The power management electronics  740  may include a rechargeable battery, such as a Li-ion battery manufactured by Saft America Inc. The battery may be used to power the electronics and may also provide additional power during periods of high demand or transient fluctuations in power demand. The battery may be recharged utilizing electricity generated by the fuel cell. Other rechargeable or non-rechargeable batteries may be used in further embodiments. One or more sensors  760  may be included at various portions of the device  700  and coupled to the electronics  740  to provide temperature and/or pressure information for use in controlling various features, such as exhaust valve  735 . A single sensor  760  is shown in block form in transport path  715  as an example of the one or more sensors. In further embodiments, the number and placement of sensors may vary as desired. In some embodiments the sensor  760  includes a least one of a temperature sensor pressure sensor, humidity sensor, and voltage sensor 
     The fuel  112  may be formed of many different hydrides such as combinations of chemical hydrides, and combinations of chemical hydrides and metal hydrides may be used for the hydrogen producing fuel, such as for example alane AlH 3 , LiAlH 4 , NaAlH 4 , KAlH 4 , MgAlH 4 , CaH 2 , LiBH 4 , NaBH 4 , LiH, MgH 2 , Li 3 Al 2 , CaAl 2 H 8 , Mg 2 Al 3 , alkali metals, alkaline earth metals, alkali metal silicides, or any combinations thereof that act as a water-reactive hydrogen-producing material that reacts with water vapor to produce hydrogen. 
     In one embodiment, the hydrogen producing fuel may be formed as pellets with a controlled porosity. The term pellet, is used in a broad sense to describe any shape or configuration of the hydride particles that occupy in the space allotted to the chemical hydride in the fuel source. Thus, the shape of the chemical hydride pellet is not critical. It may be a, layer, disk, tablet, sphere, or have no specific shape. The shape of the chemical hydride particles may be determined by the shape of the fuel source and the need to make the most efficient use of the space allotted to the chemical hydride. If appropriate, differently shaped chemical hydride pellets can be used within one fuel source. 
     The power generator may be formed in the size of a standard “AA”, “AAA”, “C”, or “D” cell (or any other battery size) that can be removed and replaced. In further embodiments, the power generator may be positioned within a device to be powered in a manner that allows access to the fuel container to remove and replace it with a new or recharged fuel container and also allows access to ambient for providing oxygen to the fuel cell. In one embodiment, manifold  720  may be covered with a water resistant membrane  770 , such as a Gortex® membrane to prevent damage to the device  700  if it is exposed to liquid water. Such a membrane may also be used in other embodiments. 
       FIG. 10  is a block cross section view of a fuel cell based power generator  1000 .  FIG. 11  is a blown up portion of the generator with numbering consistent with  FIG. 10 . In one embodiment, the power generator  1000  is formed with a self-modulated fuel container similar to that illustrated in  FIG. 1 . In one embodiment, generator  1000  comprises a case  1010  (metal or polymer) containing a water-reactive gas generating fuel  1012  in a cavity  1013 . A side or face  1015  of the case  1010  is perforated  1016 , and exposes a selectively permeable membrane  1020  (water vapor permeable, gas impermeable) which separates the fuel  1012  from the ambient environment  1022  outside the case  1010 . 
     In one embodiment, the membrane  1020  is positioned between the perforated face  1015  and a perforated plate  1025 . The membrane  1020  is flexible, and moves between the plate  1025  and face  1015  responsive to a difference in pressure between the cavity  1013  and ambient  1022 . The plate  1025  and face  1015  bound the movement of the membrane  1020  in one embodiment such that the membrane is not unduly stressed via the difference in pressure that may develop. The membrane may be coupled to sides of the case  1010  via adhesive on a perimeter of the membrane or other method to provide a seal that allows the difference in pressure to cause the membrane  1020  to move transverse to the face  1015 . 
     In one embodiment, the membrane  1020  comprises one or more valve plates  1030  that move toward the perforations  1016  when the pressure is higher inside the cavity  1013 , and move away from the perforations when the pressure inside the cavity is lower than ambient  1022 . In one embodiment, a gasket  1035  is formed about the perforations to form a seal with corresponding valve plates  1030  when the difference in pressure causes the membrane to push the valve plates  1030  into contact with the gasket. The gasket may be optional where the materials comprising the valve plates  1030  and face  1015  having perforations  1016  form an adequate seal when pressed against each other by the different in pressure. The differences in pressure in some embodiments modulate up to few tenths of a pound per square inch in one embodiment. 
     In various embodiments, the number of perforations  1016  in face  1015  may vary between one and many, forming an array of perforations. Similarly, the number of valve plates may be the same as the number of perforations, and arranged in an array to mate with each corresponding perforation. In still further embodiments, one or more larger valve plates may be used such that each valve plate may cover multiple perforations. 
     In one embodiment, a gas permeable particulate filter  1040  is positioned between fuel  1012  and plate  1025  to prevent fuel from clogging the perforations in the plate  1025 . The fuel in various embodiments may be porous to allow the water vapor passing through the perforated face  1015 , membrane  1020  in areas other than those contain the valve plates  1030 , plate  1025 , and filter  1040  to migrate through the fuel to generate more gas. The fuel porosity in one embodiment varies between approximately 15% and 20%. The porosity may be selected to allow adequate movement of gas and water vapor while at the same time providing a desired gas producing capability. 
     In one embodiment, a fuel cell proton exchange membrane (PEM)  1050  is supported by a further face  1060  of the power generator  1000 . Face  1060  has perforations or holes that allow the hydrogen to migrate to the fuel cell  1050 . The fuel cell  1050  receives hydrogen generated by fuel  1012  at an anode side facing the fuel  1012 , generates electricity, and exhausts water vapor resulting from the reaction to ambient. A cathode side of the fuel cell  1050  is facing ambient and receive oxygen from ambient. 
     In one embodiment, the fuel cell  1050  is sandwiched between rigid plates  1060  that have holes to allow oxygen and water vapor to pass to and from the fuel cell. The holes may or may not line up with the face  1055  perforations. A particulate filter  1070  may also be provided between the face  1055  and the fuel  1012  to prevent clogging of the perforations by loose fuel. The fuel cell membrane may be sealed at the sides of the case to prevent ambient water vapor from reaching the fuel from the fuel cell side of the power generator. 
     Power generator  1000  in one embodiment integrates the membrane valve, fuel cartridge and fuel cell into one monolithic unit. In such a unit, there is no need for gas seals or routing channels to couple the hydrogen generator to the fuel cell, dramatically simplifying the design of a power generator. Control electronics may also be integrated or separate. 
       FIG. 12  is a block diagram of an alternative fuel cell based power generator  1200  utilizing a membrane  1210  based valve plate  1212  arrangement to control water vapor provided to fuel responsive to pressure. A power generator  1200  case  1215  has a chamber  1220  defined by a bottom side  1225  that holds hydrogen producing fuel  1227 . A top side  1230  of case  1215  is permeable to gas and water vapor, and may also contain a liquid water impermeable membrane  1235 . The top side  1230  may be perforated or otherwise permeable in various embodiments. 
     Membrane  1210  is disposed inside case  1215  between the top side  1230  and the fuel  1227 , which may optionally have a particulate filter  1240  positioned to prevent migration of fuel toward membrane  1210 . Membrane  1210  is sandwiched between two structural support layers  1245  and  1250  that provide different functions for different parts of membrane  1210 . Support layer  1250  positioned between the membrane  1210  and fuel  1227  and is permeable to both water vapor and hydrogen. One portion of support layer  1245  forms a chamber  1255  with an opening  1260  that is exposed to water vapor migrating through top side  1230 . A first membrane portion  1265  of the membrane  1210  is disposed within the chamber  1255  and includes the valve plate  1212  that moves with the membrane responsive to pressure to engage with the opening  1260  and prevent water vapor from passing to the fuel  1227  when the pressure in the fuel chamber  1220  is higher than ambient. A gasket  1267  may be disposed on layer  1245  about the opening  1260  to engage the valve plate  1212  as it moves to restrict water vapor flow through opening  1260 . 
     A second membrane portion  1270  is patterned with anode and cathode catalysts, and acts as a membrane electrode assembly fuel cell membrane. Second membrane portion  1270  is positioned between support layer  1245  in an area where the support layers are permeable to water vapor and oxygen. Current collectors  1275  are shown contacting the second membrane portion  1270  to act as anode and cathode contacts. The current collectors  1275  may be patterned as conductive traces. In some embodiments, multiple chambers  1255  with membrane portions containing valve plates and second membrane portions form an array of valves and fuel cell membranes along a length and width of the membrane  1210 . In some embodiments, control electronics may also be integrated or separate. 
       FIG. 13  is a block cross section of a power generator container  1300  having a replaceable power generator  1200  inserted into a power generator container cavity  1310 , filling up the cavity in one embodiment. The power generator container  1300  contains a first side wall  1315  that is permeable to water vapor, and a gas permeable, liquid water impermeable membrane  1320  covering the wall to prevent particulates and liquid water from entering the generator  1200  and possibly reaching fuel  1227 . A back side  1325  is shown opposite an opening of cavity  1310 , and provides a stop when sliding the power generator  1200  into the cavity  1310 . No additional gas paths are needed in this embodiment, as power generator  1200  provides hydrogen directly to fuel cell  1270 . In one embodiment, control electronics  1330  are provided as previously described to both couple to electrodes of fuel cell  1270  for power transfer and potential storage. Container  1300  may also contain conductors between the control electronics  1330  and a connector  1350  on the power generator  1200  that mates with a mating connector  1355  on the power generator container  1300  when the power generator  1200  is plugged into the cavity  1310 . 
       FIG. 14  is a graph  1400  illustrating a proof of concept of a membrane with valve plate assembly according to an example embodiment. Water vapor flow rate in mol/second is shown on a y-axis, with internal pressure shown on an x-axis. A curve  1410  is annotated with the corresponding position of the valve. External pressure is atmospheric pressure, which appears to be just less than 15 psi. The valve appears to be open at a little less than 15 psi, and closed at 15 psi and greater. Note that some minimal flow still occurs when the valve is closed. 
       FIG. 15  is a block schematic diagram of a computer system  1500  to implement control electronics according to an example embodiment. The computer system  1500  may also take the form of an integrated circuit or commercially available microprocessor or microcontroller having fewer components than shown in  FIG. 15 . One example computing device in the form of a computer  1500 , may include a processing unit  1502 , memory  1503 , removable storage  1510 , and non-removable storage  1512 . Memory  1503  may include volatile memory  1514  and non-volatile memory  1508 . Computer  1500  may include—or have access to a computing environment that includes—a variety of computer-readable media, such as volatile memory  1514  and non-volatile memory  1508 , removable storage  1510  and non-removable storage  1512 . Computer storage includes random access memory (RAM), read only memory (ROM), erasable programmable read-only memory (EPROM) &amp; electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD ROM). Digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium capable of storing computer-readable instructions. Computer  1500  may include or have access to a computing environment that includes input  1506 , output  1504 , and a communication connection  1515 . The computer may operate in a networked environment using a communication connection to connect to one or more remote computers, such as database servers. The remote computer may include a personal computer (PC), server, router, network PC, a peer device or other common network node, or the like. The communication connection may include a Local Area Network (LAN), a Wide Area Network (WAN) or other networks. 
     Computer-readable instructions stored on a computer-readable medium are executable by the processing unit  1502  of the computer  1500 . A hard drive, CD-ROM, and RAM are some examples of articles including a non-transitory computer-readable medium. For example, a computer program  1518  capable of providing a generic technique to perform access control check for data access and/or for doing an operation on one of the servers in a component object model (COM) based system may be included on a CD-ROM and loaded from the CD-ROM to a hard drive. The computer-readable instructions allow computer  1500  to provide generic access controls in a COM based computer network system having multiple users and servers. 
     The following are sets of examples. Features from the various examples may be combined and interchanged in various embodiments. Membrane Valve Examples: 
     1. A device comprising: 
     a case having a surface with a perforation and a cavity; 
     a membrane supported by the case inside the cavity, the membrane having an impermeable valve plate positioned proximate the perforation, wherein the membrane is water vapor permeable and gas impermeable and flexes responsive to a difference in pressure between the cavity and outside the cavity to selectively allow water vapor to pass through the perforation into the cavity as a function of the difference in pressure. 
     2. The device of example 1 and further comprising a gasket positioned to mate between the perforation and the valve plate and form a seal between the valve plate and the perforation when the difference in pressure pushes the membrane and valve plate toward the perforation. 
     3. The device of any of examples 1-2 wherein the membrane is supported by the case at a perimeter of the membrane such that water vapor can only travel through the membrane to reach the cavity containing the gas generating fuel. 
     4. The device of any of examples 1-3 wherein the case further comprises a gas permeable plate positioned between the membrane and the cavity containing a gas generating fuel. 
     5. The device of example 4 and further comprising a particulate filter supported by the perforated plate to contain fuel particles within the cavity. 
     6. The device of any of examples 1-4 wherein the case further comprises an exit opening for gas generated from a gas generating fuel within the cavity responsive to water vapor. 
     7. The device of example 6 wherein the exit opening comprises a check valve. 
     8. The device of any of examples 1-7 and further comprising a hydride fuel disposed within the cavity to receive water vapor passed through the membrane. 
     9. The device of any of examples 1-8 wherein the case has an array of perforations and the membrane has a corresponding array of valve plates. 
     10. The device of example 9 wherein the array of valve plates are connected, forming a structurally reinforcing mesh on the membrane. 
     11. The device of example 10 wherein the mesh further comprises a perimeter band fastened to sides of the case and formed to facilitate movement of the membrane towards and away from the perforations of the case. 
     12. A device comprising: 
     a case having a surface with an array of perforations and a cavity containing a gas generating fuel; 
     a membrane supported by the case inside the cavity, the membrane having an array of impermeable valve plates, each positioned proximate a corresponding perforation, wherein the membrane is water vapor permeable and gas impermeable and flexes responsive to a difference in pressure between the cavity and outside the cavity to move the plate to block the perforations via the valve plates when the pressure inside the cavity is greater, and to unblock the perforations when the pressure inside the cavity is lower than outside the cavity. 
     13. The device of example 12 and further comprising: 
     a gasket positioned to mate between the perforation and the valve plate and form a seal between the valve plate and the perforation when the difference in pressure pushes the membrane and valve plate toward the perforation, wherein the membrane is supported by the case at a perimeter of the membrane such that water vapor can only travel through the membrane to reach the cavity containing the gas generating fuel; 
     wherein the case further comprises a perforated plate positioned between the membrane and the cavity containing the gas generating fuel; 
     a particulate filter supported by the perforated plate to contain fuel particles within the cavity; and 
     wherein the case further comprises an exit opening for gas generated from the fuel and water vapor. 
     14. The device of example 13 wherein the gas generating fuel comprises a hydride fuel disposed within the cavity to receive water vapor passed through the membrane. 
     15. The device of example 14 wherein the array of valve plates are connected, forming a structurally reinforcing mesh on the membrane. 
     16. The device of example 15 wherein the mesh further comprises a perimeter band fastened to sides of the case and formed to facilitate movement of the membrane towards and away from the perforations of the case. 
     17. A method comprising: 
     passing water vapor through a gas impermeable, water vapor permeable membrane to a gas producing fuel in a fuel container; 
     responsive to a gas pressure in the container higher than pressure outside the container, moving a plate supported by the membrane towards a perforation in the container to impede passing of water vapor to the gas producing fuel; and 
     responsive to a gas pressure in the container lower than pressure outside the container, moving the membrane and plate away from the perforation. 
     18. The method of example 17 and further comprising: 
     producing gas responsive to the water vapor reacting with the fuel in the container; and 
     providing the produced gas via a gas exit of the container. 
     19. The method of any of examples 17-18 wherein the perforation comprises an array of perforations, and the membrane comprises an array of plates corresponding to the array of perforations moving responsive to gas pressure with the membrane. 
     20. The method of example 19 wherein the gas producing fuel comprises a hydride that produces hydrogen that is supplied to a fuel cell. 
     Power Generator Having Hydrogen Manifold Examples: 
     1. A power generator comprising: 
     a cavity to accept a hydrogen producing fuel cartridge; 
     a channel to couple to and receive hydrogen from the fuel cartridge: 
     a manifold coupled to the channel to receive hydrogen from the channel, the manifold having an opening to receive oxygen and water vapor, the manifold being positioned to provide the water vapor to the cavity; 
     an array of fuel cell membranes supported by the manifold to receive hydrogen from the manifold and oxygen from the opening in the manifold. 
     2. The power generator of example 1 and wherein the array of fuel cell membranes is supported by the manifold in a position to provide water vapor to the cavity. 
     3. The power generator of any of examples 1-2 and further comprising a protrusion disposed within the cavity to engage a check valve of the fuel cartridge. 
     4. The power generator of any of examples 1-3 and further comprising an exhaust valve coupled to the manifold to controllably exhaust gas. 
     5. The power generator of example 4 and further comprising: 
     a sensor; and 
     a controller coupled to the sensor and to the exhaust valve to control the exhaust valve responsive to signals from the sensor. 
     6. The power generator of example 5 wherein the sensor comprises at least one of a temperature sensor pressure sensor, humidity sensor, and voltage sensor. 
     7. The power generator of any of examples 1-6 wherein the manifold comprises an array of hydrogen providing channels to distribute hydrogen to an anode side of each fuel cell membrane, and second openings to expose a cathode side of each fuel cell membrane to oxygen provided via the first openings. 
     8. The power generator of example 7 and further comprising a hydrogen producing fuel cartridge disposed within the cavity and coupled to the channel. 
     9. The power generator of any of examples 7-8 wherein the manifold has a planar structure, wherein the first openings comprise an array of air channels through the manifold, wherein the fuel cell membranes extend along the hydrogen providing channels separating the hydrogen from oxygen provided via the first openings, and wherein the manifold sandwiches the fuel cell membranes between an upper portion containing the hydrogen providing channels and a lower portion providing access to the oxygen. 
     10. The power generator of example 9 and further comprising: 
     a liquid water impermeable, gas and water vapor permeable membrane disposed between the cathode side of the fuel cell membranes and ambient; and 
     a vent coupled to the manifold to vent gas buildup in the manifold to the outside of the power generator. 
     11. A power generator comprising: 
     a cavity to accept a hydrogen producing fuel cartridge; 
     a channel to couple to receive hydrogen from the fuel cartridge; 
     a manifold coupled to the channel to receive hydrogen from the channel, the manifold having an opening to receive oxygen and water vapor, the manifold being positioned to provide the water vapor to the cavity; 
     an array of fuel cell membranes supported by the manifold to receive hydrogen from the manifold and oxygen from the opening in the manifold, wherein the manifold comprises an array of hydrogen providing channels to distribute hydrogen to an anode side of each fuel cell membrane, and a second opening to expose a cathode side of each fuel cell membrane to oxygen provided via the first opening; 
     an exhaust valve coupled to the manifold to controllably exhaust gas; 
     a sensor; and 
     a controller coupled to the sensor and to the exhaust valve to control the exhaust valve responsive to signals from the sensor. 
     12. The power generator of example 11 and wherein the array of fuel cell membranes is supported by the manifold in a position to provide water vapor to the cavity. 
     13 The power generator of any of examples 11-12 and further comprising a protrusion disposed within the cavity to engage a check valve of the fuel cartridge. 
     14. The power generator of example 12 wherein the manifold has a planar structure, wherein the first opening comprises an array of air channels through the manifold, wherein the fuel cell membranes extend along the hydrogen providing channels separating the hydrogen from oxygen provided via the array of air channels, and wherein the manifold sandwiches the fuel cell membranes between an upper portion containing the hydrogen providing channels and a lower portion providing access to the oxygen. 
     15. The power generator of example 14 and further comprising: 
     a liquid water impermeable, gas and water vapor permeable membrane disposed between the cathode side of the fuel cell membranes and ambient; and 
     a vent coupled to the manifold to vent gas buildup in the manifold to the outside of the power generator. 
     16. A method comprising: 
     inserting a fuel cartridge into a cavity of a power generator; 
     receiving hydrogen from the fuel cartridge into a hydrogen channel; 
     distributing the hydrogen to an anode side of an array of fuel cell membranes via a manifold having an array of hydrogen channels; 
     providing oxygen via an opening in the manifold to a cathode side of the array of fuel cell membranes to produce electricity; and 
     providing water vapor to the fuel cartridge having a hydride that produces hydrogen when exposed to the water vapor. 
     17. The method of example 16 wherein the water vapor is provided via the opening in the manifold from outside the power generator. 
     18. The method of any of examples 16-17 wherein the water vapor is provided via the cathode side of the fuel cell membranes. 
     19. The method of any of examples 16-18 and further comprising modulating the amount of water vapor that reaches the hydride via a differential pressure responsive water vapor permeable, gas impermeable flexible membrane having a valve plate that mates with an opening in the fuel cartridge. 
     20. The method of example 19 and further comprising venting excess gas from the array of hydrogen channels in the manifold. 
     Power Generator Having Integrated Membrane Valve Examples: 
     1. A power generator comprising: 
     a case having a surface with a perforation and a cavity containing a gas generating fuel; 
     a membrane supported by the case inside the cavity, the membrane having an impermeable valve plate positioned proximate the perforation, wherein the membrane is water vapor permeable and gas impermeable and flexes responsive to a difference in pressure between the cavity and outside the cavity to selectively allow water vapor to pass through the perforation to the fuel as a function of the difference in pressure; and 
     a fuel cell membrane supported by the case and positioned to receive hydrogen at an anode side of the fuel cell membrane and to receive oxygen from outside the power generator at a cathode side of the fuel cell membrane. 
     2. The power generator of example 1 and further comprising a first particulate filter disposed between the cavity and the membrane. 
     3. The device of any of examples 1-2 and further comprising a gasket positioned to mate between the perforation and the valve plate and form a seal between the valve plate and the perforation when the difference in pressure pushes the membrane and valve plate toward the perforation. 
     4. The device of any of examples 1-3 wherein the membrane is supported by the case at a perimeter of the membrane such that water vapor can only travel through the membrane to reach the cavity containing the gas generating fuel. 
     5. The device of any of examples 1-4 wherein the case further comprises a perforated plate positioned between the membrane and the cavity containing the gas generating fuel. 
     6. The device of example 5 and further comprising a particulate filter supported by the perforated plate to contain fuel particles within the cavity. 
     7. The device of any of examples 1-6 and further comprising a water reactive hydrogen generating fuel disposed within the cavity to receive water vapor passed through the membrane. 
     8. The device of any of examples 1-7 wherein the case has an array of perforations and the membrane has a corresponding array of valve plates. 
     9. The device of example 8 wherein the array of valve plates are connected, forming a structurally reinforcing mesh on the membrane. 
     10. The device of example 1 wherein the membrane comprises a catalyst patterned portion to form the fuel cell membrane. 
     11. The device of example 10 wherein water vapor produced by the fuel cell membrane is provided back to the fuel via perforation as selectively allowed by the membrane and valve plate. 
     12. The device of example 1 wherein the membrane and fuel cell membrane are positioned on opposite sides of the fuel. 
     13. A power generator comprising: 
     a case having a surface with an array of perforations and a cavity containing a gas generating fuel; 
     a membrane supported at a first side of the case inside the cavity, the membrane having an array of impermeable valve plates, each positioned proximate the perforations, wherein the membrane is water vapor permeable and gas impermeable and flexes responsive to a difference in pressure between the cavity and outside the cavity to selectively allow water vapor to pass through the perforations to the fuel as a function of the difference in pressure; and 
     a fuel cell membrane supported to receive hydrogen at an anode side of the fuel cell membrane and to receive oxygen from outside the power generator at a cathode side of the fuel cell membrane. 
     14. The power generator of example 13 and further comprising: a first particulate filter disposed between the cavity and the membrane; and a second particulate filter disposed between the cavity and the fuel cell membrane. 
     15. The power generator of any of examples 13-14 and further comprising an array of gaskets positioned to mate between the perforations and the valve plates and form a seal between the valve plates and the perforations when the difference in pressure pushes the membrane and valve plates toward the perforations. 
     16. The power generator of any of examples 13-15 wherein the membrane is supported by the case at a perimeter of the membrane such that water vapor can only travel through the membrane to reach the cavity containing the gas generating fuel. 
     17. The power generator of any of examples 13-16 wherein the case further comprises a perforated plate positioned between the membrane and the cavity containing the gas generating fuel, wherein the gas generating fuel comprises a hydride fuel. 
     18. A method comprising: 
     passing water vapor through a gas impermeable, water vapor permeable membrane to a gas producing fuel in a power generator: 
     responsive to a gas pressure in the container higher than pressure outside the power generator, moving a plate supported by the membrane towards a perforation in the power generator to impede passing of water vapor to the gas producing fuel: 
     responsive to a gas pressure in the power generator lower than pressure outside the power generator, moving the membrane and plate away from the perforation; 
     providing gas produced by the gas producing fuel reacting with the water vapor to a fuel cell membrane; and 
     providing oxygen to the fuel cell membrane and exhausting water vapor produced by a reaction between hydrogen and oxygen away from the power generator. 
     19. The method of example 18 wherein the perforation comprises and array of perforations, and the membrane comprises an array of plates corresponding to the array of perforations moving responsive to gas pressure with the membrane. 
     20. The method of example 19 wherein the fuel cell membrane comprises catalyst coated portions of the membrane.