Patent Publication Number: US-2020295387-A1

Title: Fuel cartridge

Description:
BACKGROUND 
     Hydrogen gas has many industrial uses. For example, hydrogen gas can be used in chemical synthesis, as a forming gas, in fuel cells, for energy storage, and/or for applications calling for buoyancy. Previous approaches for utilizing hydrogen gas may involve storing compressed hydrogen gas in a storage tank. Such approaches may be limited in certain contexts by bulk and/or weight. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a fuel cell based power generator incorporating a fuel cartridge in accordance with one or more embodiments of the present disclosure. 
         FIG. 2  illustrates a block diagram of an example fuel cartridge in accordance with one or more embodiments of the present disclosure. 
         FIG. 3A  is a perspective view of an example fuel cartridge in accordance with one or more embodiments of the present disclosure. 
         FIG. 3B  is a schematic representation of an axial flow tube design in accordance with one or more embodiments of the present disclosure. 
         FIG. 3C  is a schematic representation of a radial flow tube design in accordance with one or more embodiments of the present disclosure. 
         FIG. 3D  is a schematic representation of a further radial flow tube design in accordance with one or more embodiments of the present disclosure. 
         FIG. 3E  is cross section block diagram of an alternative fuel cartridge in accordance with one or more embodiments of the present disclosure. 
         FIG. 3F  is a top cross-sectional view of the fuel cartridge of  FIG. 3E  in accordance with one or more embodiments of the present disclosure. 
         FIG. 3G  is a cross section view of a further fuel cartridge in accordance with one or more embodiments of the present disclosure. 
         FIG. 4  is a perspective view of another example fuel cartridge in accordance with one or more embodiments of the present disclosure. 
         FIG. 5  is a cross-sectional view of another example fuel cartridge in accordance with one or more embodiments of the present disclosure. 
         FIG. 6  is a cross-sectional view of another example fuel cartridge in accordance with one or more embodiments of the present disclosure. 
         FIG. 7  is a cross-sectional view of another example fuel cartridge in accordance with one or more embodiments of the present disclosure. 
         FIG. 8  is a cross-sectional view of another example fuel cartridge in accordance with one or more embodiments of the present disclosure. 
         FIG. 9  is a cross-sectional view of another example fuel cartridge in accordance with one or more embodiments of the present disclosure. 
         FIG. 10  is a cross-sectional view of another example fuel cartridge in accordance with one or more embodiments of the present disclosure. 
         FIG. 11  is a perspective view of another example fuel cartridge in accordance with one or more embodiments of the present disclosure. 
         FIG. 12  is a perspective view of the example fuel cartridge illustrated in  FIG. 11  showing a fan mounted to the fuel cartridge. 
         FIG. 13  is a block diagram of a specifically programmed system for executing control methods for a fuel cartridge according to one or more embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Devices and methods for providing a fuel cartridge are disclosed. One fuel cartridge includes an inlet valve, a plurality of fuel beds containing a hydride material, and an outlet valve, wherein each of the plurality of fuel beds is coupled to the inlet valve via an inlet manifold and wherein each of the plurality of fuel beds is coupled to the outlet valve via an outlet manifold. 
     An alternative fuel cartridge includes an inlet manifold and a plurality of fuel beds containing a hydride material. A first end of each of the fuel beds is coupled to the inlet manifold to receive wet hydrogen via the inlet manifold. An outlet manifold is coupled to a second end of each of the fuel beds to receive dry hydrogen from the fuel beds. The fuel beds are laterally spaced from each other providing space for flow of coolant fluid therebetween. Valves may be included in the inlet and outlet manifolds. 
     A method includes containing a granular hydride material and an inert gas in a plurality of parallel fuel beds of a fuel cartridge, passing water vapor from a first end of each of the plurality of fuel beds through a second end of each of the plurality of fuel beds, wherein hydrogen gas is generated by a respective reaction within each of the plurality of fuel beds, and passing the generated hydrogen gas, the inert gas, and a portion of the water vapor out of the fuel cartridge. 
     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 in some embodiments. The software may consist of computer executable instructions stored on computer readable media or computer readable storage device such as one or more non-transitory memories or other type of hardware based storage devices, either local or networked. 
     Further, such functions correspond to modules, which may be 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, turning such computer system into a specifically programmed machine. 
     Embodiments of the present disclosure include fuel cartridges. Fuel cartridges in accordance with embodiments of the present disclosure can produce hydrogen gas. Hydrogen gas produced by one or more embodiments herein can be used in chemical synthesis, as a forming gas, for energy storage, and/or for applications calling for buoyancy, among other uses. Such a cartridge is sometimes herein discussed as being configured for use in the example of powering an unmanned air system (UAS). It is noted, however, that such discussion is provided for example purposes and that embodiments of the present disclosure are not so limited. 
     Embodiments of the present disclosure can be a part of a fuel cell based power generator system. In the example of a UAS, such a fuel cell based power generator system can be capable of, for instance, providing 4-12 times the run time of state of the art lithium batteries. Some embodiments may, for example, provide six to twelve or more hours of flight time. 
     A fuel cell based power generator including one or more fuel cartridges in accordance with the present disclosure provides run time improvement and energy efficiency under specified load power profiles. Moreover, the fuel cell based power generator may be substantially lighter than prior energy storage devices and may have lower projected lifecycle costs, without compromising operation temperature range or environmental and safety performance. The improvement in runtime lies in the innovative fuel-cell technology and its fuel chemistry based on lithium aluminum hydride (LAH) that requires no net water consumption in order to sustain its operation, thus eliminating the need for a water fuel reservoir, which enables the energy source to be substantially smaller and lighter than other conventional chemical hydride or direct methanol fuel cells with on-board storage of water (fuel, diluent, or solvent). 
     In some embodiments, hydrogen is stored in the form of solid chemical hydride granules. These granules can be collected in packed beds. In some embodiments, the granules can be collected in fluidized beds. When not in use, the beds can be surrounded by inert gas(es) sealed in by valves on either side of the beds. Accordingly, embodiments herein obviate the need in previous approaches for regulators and avoid issues associated with containing high pressures. 
     In use, the valves are opened allowing a combination of water vapor and inert gas(es) to flow into the cartridge, where a manifold directs the combined gases through the beds. The water vapor reacts exothermically with the chemical hydride granules in the beds, converting the chemical hydride to solid chemical oxides and hydroxides, and producing hydrogen gas that is directed out of the cartridge by another manifold. 
     A temperature of the fuel cartridge can be controlled by conduction and/or convection. In some embodiments, heat is carried away from the fuel by a thermally conductive housing around, between, and/or through the beds. In some embodiments, a coolant (e.g., gas and/or liquid) can be flowed over some or all of the exterior of the cartridge to carry the heat away from the cartridge. In some embodiments, the cartridge can include a housing configured to provide cooling functions. For instance, in some embodiments, the cartridge housing can incorporate interface features for a fan and/or pump to circulate the coolant. In some embodiments, the cartridge housing can incorporate interface features for a fan duct or tubing to direct the coolant. In some embodiments, the cartridge housing can incorporate a manifold for directing the coolant around the cartridge. A temperature of the beds can be determined via temperature sensors inserted into the beds, and coolant flow properties, such as flow rate, can be controlled (e.g., in a closed loop) to regulate the bed temperature. 
       FIG. 1  is a schematic diagram of a fuel cell based power generator  100  in accordance with an embodiment of the present disclosure. In the embodiment shown in  FIG. 1 , power generator  100  includes a fuel cell  110  and a hydrogen generator  115 . 
     As used herein, the term “fuel cell” can, for example, refer to an electrochemical cell that converts chemical energy from a fuel into electricity through an electrochemical reaction. For example, hydrogen can be provided to fuel cell  110  such that hydrogen is consumed in an electrochemical reaction to produce electricity, as is further described herein. An ambient air path  120  is configured to run ambient air past a cathode side of the fuel cell  110 , via ambient air path portion  122 . The ambient air path  120  is part of a cathode loop, which includes all the paths that ambient air circulates through, including interiors of components the ambient air passes through. 
     A reaction in the fuel cell  110  generates electrical power and adds water as a by-product to the ambient air path portion  122 . This water is then provided to the hydrogen generator  115 , which contains one or more fuels that release hydrogen responsive to exposure to water, which may be in vapor form. As used herein, the term “hydrogen generator” refers to a device which contains one or more fuels that release hydrogen responsive to exposure to water, which may be in the form of humidity. 
     The hydrogen generator  115  provides the released hydrogen to a recirculating hydrogen path  125 , which splits into two parts at junction  127 . The two parts include a primary path  126  and a secondary path  128 . The primary path  126  recirculates released hydrogen back to hydrogen generator  115 . The secondary path  128  runs past the anode side of the fuel cell  110  to provide the hydrogen to the fuel cell  110 . The secondary path  128  is part of an anode loop, which includes all the paths that hydrogen recirculates through, including interiors of components the ambient air passes through. 
     Hydrogen from the recirculating hydrogen path  125  reacts with oxygen from the ambient air path  120  in fuel cell  110 , producing electrical power, water vapor, and heat as reaction byproducts. The byproducts on the cathode side of the fuel cell  110  are removed from the fuel cell by the air flowing within ambient airflow path  120 . Leftover hydrogen and any inert gases that leak/permeate into the anode loop over time continue through the recirculating hydrogen path  125 . 
     In some embodiments, a cooling mechanism  132 , such as a fan or liquid cooling loop, can be used with the fuel cell portion system to assist in the removal of heat. In such an embodiment, most of the heat generated in the fuel cell is removed via this liquid cooling loop and rejected to ambient via a heat exchanger and/or fan, represented in block form as part of the cooling mechanism  132 . 
     In some embodiments, as shown in  FIG. 1 , the secondary path  128  can include a purge valve  129  that purges inert gases (e.g. nitrogen, water vapor) that build up over time in the anode loop into an ambient airflow path portion  123  of the ambient airflow path  120 . These gases are purged periodically by actuating the purge valve  129 , for example, based on predetermined timing or a sensed parameter like fuel cell voltage or hydrogen concentration. In some embodiments, the valve may be slightly open most of the time to continuously remove the inert gases, with most of the hydrogen flowing to and being consumed by the anode of the fuel cell. 
     In some embodiments, the fuel cells provide current to a controller  135  that charges a Li-ion battery or batteries  130 . The controller  135  also provides power to a load, such as the UAS. In some implementations, the batteries can provide the ability to supply higher and more dynamic levels of power than simply utilizing the fuel cells directly, which can be slower to respond and not normally be able to provide high levels of power that may be required for operation of the UAS in a desired manner, such as accelerating sufficiently while carrying a load. 
     Controller  135  may comprise a microprocessor, circuitry, and other electronics to receive data representative of sensed pressure, temperature, and other parameters and utilize control algorithms, such as proportional/integral/derivative (PID) or other type of algorithms to control mechanisms to modify the parameters to meet one or more different setpoints. Controller  135  may also be referred to as a power management module or controller  135 . In some embodiments, control may be based on proportional controller. 
     In some embodiments, the fuel cell based power generator  100  has a system configuration (implemented in a X590 form factor battery package in one embodiment) and its operating principle is schematically depicted in  FIG. 1 . Hydrogen generator  115 , in various embodiments, is a replaceable and disposable “fuel-cartridge” unit that generates H 2  for a H 2 /oxygen proton exchange membrane (PEM) fuel cell  110 , and a permanent unit that, in some embodiments, includes PEM fuel cell  110 , Li-ion recharge battery  130  as an output stage to interface with an external load, and the controller  135  that controls electronic and fluidic control circuits (e.g., controlling one or more fluid movement apparatuses) to dynamically sense and optimize the power generator  100  under varying load and environmental conditions. 
     Ambient air serves as the fuel cell power generator  100  oxygen source, carrier gas for water vapor, and coolant gas for the fuel cell stack and H 2  generator. A first fluid movement apparatus (e.g., a fan)  140  draws in fresh air from ambient via an inlet  142  and circulates it over the cathode side of the fuel cell stack at  121  via the ambient air path or passage  120 . 
     Since the fuel cell  110  reaction is exothermic, the temperature of the fuel cell  110  increases and may be measured by a first temperature sensor  143  associated with fuel cell  110 , which is positioned to measure the temperature of the fuel cell  110 . The temperature sensor is shown in block form and may be placed anywhere such that it is thermally coupled to the fuel cell  110  to provide a reliable measurement of the temperature of the fuel cell  110 . Sensor  143  may comprise multiple temperature sensors. In one embodiment, one of the temperature sensors is coupled to provide data representative of the temperature proximate the anode, and another coupled to provide data representative of the temperature proximate the cathode of the fuel cell  110 . The temperature data is provided to the controller  135  for use in controlling to one or more setpoints. A fuel cell set point temperature of the fuel cell  110  is indicated as 60° C., which has been found to be a temperature at which the fuel cell  110  functions most efficiently. 
     In further embodiments, the set point may vary between 40° C. and 80° C., and may vary further depending on the configuration and specific materials utilized in fuel cell  110  and system  100 . Different optimal set points for the fuel cell may be determined experimentally for different fuel cells and may be found to be outside the range specified above. 
     The fuel cell temperature is modified via cooling mechanism  132  (e.g., liquid cooling loop with liquid pump, heat exchanger, and fan) under control of controller  135  that receives temperature information from first temperature sensor  143 . The first temperature sensor  143  may include separate temperature sensors to sense temperatures of both the anode side and cathode side of the fuel cell  110 . 
     In some embodiments, the fuel cell temperature and hydrogen generator temperature can be controlled separately. Separately controllable fans and or fluid pumps may be used for such independent control. The power management module may control various pressures and temperatures via the various mechanisms using one or more of PID control, proportional control, or other type of algorithm. Temperatures may be controlled within desired temperature ranges defined by upper and lower temperature thresholds. 
     While the fuel cell  110  is producing electrical power as well as heat, ambient air flowing within path  120  delivers oxygen to the fuel cell  110  cathode and removes water vapor generated by the reaction in the fuel cell  110 . The hot, humid air continues down path  120  to a first water exchanger  155 . The water exchanger  155  extracts water from the hot, humid ambient air and passes the extracted water into the hydrogen flow path  124  (anode loop). The hot, somewhat drier air continues down path  122 ′ to a second water exchanger  157 , where heat and water is passed into the cathode loop. This heat and water raise the temperature and humidity of the incoming ambient air, which improves fuel cell performance. After exiting the second water exchanger, the warm dry air is exhausted to the ambient at  160 . 
     Water exchanger  155 , and the operation of water exchanger  155 , is further described herein. For instance, water exchanger  155  can be a light-weight, low pressure-drop water exchanger, as will be further described herein. 
     The extracted water from the ambient air path is then provided to the recirculating hydrogen path to create humid hydrogen (H 2 ) at  124 . This humid H 2  then flows to the hydrogen generator where water therein interacts with the fuel to generate additional hydrogen. 
     The hydrogen generator  115  also has a set point temperature at which it operates most efficiently. The temperature may be measured by sensing the temperature of the hydrogen as it exits the hydrogen generator  115  as represented by the position of a sensor  133 , which may be a temperature sensor and also may include a pressure sensor. The hydrogen generator experiences an exothermic reaction and has an optimal operating set point is shown as 80° C., but may vary from 60° C.-100° C. or outside the range depending on the composition of the hydrogen generator used. 
     The hydrogen generator temperature may be controlled by varying the speed of one or more cooling mechanisms  131  positioned to remove heat from the hydrogen generator. The cooling mechanism may be positioned on the outside of the hydrogen generator or positioned proximate the hydrogen generator to effect cooling of the hydrogen generator. For example, in some embodiments, the hydrogen generator temperature is modified by an external cooling mechanism (e.g., a fan, blower, etc.) positioned, for instance, on the surface of the generator. The cooling mechanism may be controlled via the controller  135  using PID or other control algorithms, such as proportional control. The hydrogen generator could also be cooled using a liquid cooling loop and associated liquid pump, heat exchanger, and fan. 
     The humid hydrogen  124  flows into the hydrogen generator  115 , where the water reacts with the fuel and generates hydrogen. The now dry hydrogen leaves the hydrogen generator and flows into blower  165 , which raises the pressure. 
     The higher pressure dry hydrogen then progresses down the path  125  to a split  127  where some of the dry H 2  enters a primary path  126  and some dry H 2  enters a secondary path  128 . 
     The secondary path  128  is located adjacent the anode side of the fuel cell to provide hydrogen to the fuel cell, while the primary path can be located further away from the fuel cell. This configuration allows for a large amount of hydrogen to recirculate continuously through the system in a hydrogen loop (to efficiently extract the water from the cathode via the ambient air path water exchanger  155 ) while flowing a smaller amount of hydrogen to the fuel cell via secondary path  128 . 
     The secondary path  128  can be a dead end with a purge valve  129  therein that allows inert gasses (e.g., nitrogen, water vapor) to be purged from the anode stream by actuating the valve periodically (e.g., based timing or a sensed parameter such as fuel cell voltage or oxygen concentration). Because some water vapor is included in the inert gas, it is desirable to purge the inert gas into the cathode stream  122  upstream of the primary water exchanger  155 , so that the water vapor can be recovered via water exchangers  155  and  157 . 
     The anode loop pressure as measured by sensor  133  is controlled by varying the blower  165  fan speed, which controls the amount of water recovered from through the water exchanger  155 , and hydrogen generated in the hydrogen generator  115 . Higher blower fan speeds lead to higher anode loop pressures, for example, pressures slightly above ambient pressure by 1-10 psig. 
     Steady state operation of the fuel cell based power generator can be achieved by: 
     1) Controlling cathode blower speed based on power demand from load; 
     2) Controlling anode blower speed based on anode loop pressure (e.g., measured via pressure sensor  133 ); 
     3) Controlling fuel cell cooling based on fuel cell temperature (e.g., via cooling mechanism  132 ); and/or 
     4) Controlling pump/fan speed control for cooling mechanism  131  (e.g., fan, blower, cooling loop, etc.) associated with the hydrogen generator (e.g., mounted on the outside of the hydrogen generator) based on hydrogen generator temperature. 
     In some embodiments, as air passes by the fuel cell stack  110  from the ambient air path  120  and the secondary path  128  of the recirculating hydrogen path  125 , oxygen and hydrogen are consumed by the fuel cell  110 , and water vapor and waste heat are removed by the ambient air at fuel cell cathode  121 . 
     The power generated in the fuel cell stack may be fed to controller  135  which may include power management circuitry. The circuitry conditions the power and provides it as electricity to a load as indicated by contacts  180 . 
     One or more sensors may measure, in addition to the temperature sensor previously described, humidity, and/or pressure throughout the system  100 . Data provided by the sensors, as well as the electrical load and/or charge state of the charge storage device  130  are used by the control controller  135  to determine and set the various fluid movement apparatus speeds to control the temperature of the elements to corresponding set points. Power management circuitry  135  can include a controller, as is further described herein. 
     Fuel consumption may also be monitored via controller  135  or other power monitoring device, and the remaining capacity may be displayed via a display on the fuel cell power generator packaging as driven by controller  135  in various embodiments. In some embodiments, greater than 95% fuel utilization may be achieved through an optimized LAH fuel formation (e.g., through one or more of porosity, particle size/distribution, rate enhancing additives, or other formulation characteristics). 
     In some embodiments, the LAH-water reaction generates heat (˜150 kJ/mol LAH, exothermic) leading to a rise in temperature in the fuel. The temperature may be monitored along with controlling the speed of the hydrogen generator cooling fan to maintain the temperature at a desired set point for optimal operation. 
     Electrochemical system power performance can substantially degrade at low temperatures (−40° C.) due to slower reaction kinetics and lower electrolyte conductivity. The hybrid fuel cell may avoid freezing problems by: 1) using water in vapor form, 2) adjusting airflow to prevent water vapor condensation, 3) using heat generated by the fuel cell stack and H 2  generator to regulate their temperatures, 4) Insulating certain system components, and 5) using electrically power heaters to control the temperature of certain system components. In some embodiments, noryl plastic packaging (e.g., consistent with the type used on the Saft BA5590) may be used. Many different types of plastics and/or other materials (e.g., that provide low weight yet sufficient tolerance to the operating parameters and environmental conditions of the generator) may be used. 
     Hydrogen generator  115  in some embodiments is a high-rate hydrogen generator suitable for man-portable power and micro air vehicle applications that provides four to five times the hydrogen of commercially available hydrogen sources of the same size and weight. Many different hydrogen producing fuels, such as LAH may be used. In further embodiments, the hydrogen producing fuel may, for example, include 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 combinations of one or more thereof. 
     The term “about” as used herein can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range, and includes the exact stated value or range. 
     The term “substantially” as used herein refers to a majority of, or mostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more, or 100%. 
     Hydrogen-Generating Composition for a Fuel Cell 
     In various embodiments, the present disclosure provides a hydrogen-generating composition for a fuel cell. 
     The hydrogen-generating composition reacts with water to generate hydrogen gas. The phase of the water contacted with the hydrogen-generating composition to generate the hydrogen gas can be any suitable phase, such as liquid water (e.g., in a pure state, diluted state, or such as having one or more compounds or solvents dissolved therein) or gaseous water (e.g., water vapor, at any suitable concentration). The generated hydrogen gas can be used as the fuel for a hydrogen-consuming fuel cell. 
     The hydrogen-generating composition can be in any suitable form. The hydrogen-generating composition can, for example, be in the form of a loose powder or a compressed powder. The hydrogen-generating composition can also be in the form of grains or pellets (e.g., a powder or grains compressed into pellets). The hydrogen-generating composition can have any suitable density, such as, for example, about 0.5 g/cm 3  to about 1.5 g/cm 3 , or about 0.5 g/cm 3  or less, or less than, equal to, or greater than about 0.6 g/cm 3 , 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4 g/cm 3 , or about 1.5 g/cm 3  or more. 
     In some embodiments, the hydrogen-generating composition is substantially free of elemental metals. In some embodiments, the hydrogen-generating composition can be substantially free of elemental aluminum. 
     Hydride 
     The hydrogen-generating composition may include one or more hydrides. The one or more hydrides can form any suitable proportion of the hydrogen-generating composition, such as about 50 wt % to about 99.999 wt %, about 70 wt % to about 99.9 wt %, about 70 wt % to about 90 wt %, or about 50 wt % or less, or less than, equal to, or greater than about 52 wt %, 54, 56, 58, 60, 62, 64, 66, 68, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 92, 94, 96, 98, 99, 99.9, 99.99, or about 99.999 wt % or more. 
     The hydride can be any suitable hydride, such that the hydrogen-generating composition can be used as described herein. The hydride can be a compound in which one or more hydrogen centers (e.g., one or more hydrogen atoms, or a group that includes one or more hydrogen atoms) having nucleophilic, reducing, or basic properties. 
     The hydrogen atom in the hydride can be bonded to a more electropositive element or group. For example, the hydrogen can be chosen from an ionic hydride (e.g., a hydrogen atom bound to an electropositive metal, such as an alkali metal or alkaline earth metal), a covalent hydride (e.g., compounds including covalently bonded hydrogen and that react as hydride, such that the hydrogen atom or hydrogen center has nucleophilic properties, reducing properties, basic properties, or a combination thereof), a metallic hydride (e.g., interstitial hydrides that exist within metals or alloys), a transition metal hydride complex (e.g., including compounds that can be classified as covalent hydrides or interstitial hydrides, such as including a single bond between the hydrogen atom and a transition metal), or a combination thereof. 
     The hydride can be chosen from magnesium hydride (MgH 2 ), lithium hydride (LiH), aluminum hydride (AlH 3 ), calcium hydride (CaH 2 ), sodium aluminum hydride (NaAlH 4 ), sodium borohydride (NaBH 4 ), lithium aluminum hydride (LiAlH 4 ), ammonia borane (H 3 NBH 3 ), diborane (B 2 H 6 ), palladium hydride, LaNi 5 H 6 , TiFeH 2 , and a combination thereof. The hydride can be chosen from lithium aluminum hydride (LiAlH 4 ), calcium hydride (CaH 2 ), sodium aluminum hydride (NaAlH 4 ), aluminum hydride (AlH 3 ), and a combination thereof. The hydride can be lithium aluminum hydride (LiAlH 4 ). 
     In some embodiments, the hydrogen-generating composition only includes a single hydride and is substantially free of other hydrides. In some embodiments, the hydrogen-generating composition only includes one or more hydrides chosen from lithium aluminum hydride (LiAlH 4 ), calcium hydride (CaH 2 ), sodium aluminum hydride (NaAlH 4 ), and aluminum hydride (AlH 3 ), and is substantially free of other hydrides. 
     In various embodiments, the hydrogen-generating composition only includes the hydride lithium aluminum hydride (LiAlH 4 ), and is substantially free of other hydrides. In some embodiments, the hydrogen-generating composition can be substantially free of simple hydrides that are a metal atom directly bound to a hydrogen atom. In some embodiments, the hydrogen-generating composition can be substantially free of lithium hydride and beryllium hydride. 
     In various embodiments, the hydrogen-generating composition can be substantially free of hydrides of aluminum (Al), arsenic (As), boron (B), barium (Ba), beryllium (Be), calcium (Ca), cadmium (Cd), cerium (Ce), cesium (Cs), copper (Cu), europium (Eu), iron (Fe), gallium (Ga), gadolinium (Gd), germanium (Ge), hafnium (Hf), mercury (Hg), indium (In), potassium (K), lanthanum (La), lithium (Li), magnesium (Mg), manganese (Mn), sodium (Na), neodymium (Nd), nickel (Ni), lead (Pb), praseodymium (Pr), rubidium (Rb), antimony (Sb), scandium (Sc), selenium (Se), silicon (Si), samarium (Sm), tin (Sn), strontium (Sr), thorium (Th), titanium (Ti), thallium (Tl), vanadium (V), tungsten (W), yttrium (Y), ytterbium (Yb), zinc (Zn), zirconium (Zr), hydrides of organic cations including (CH 3 ) methyl groups, or a combination thereof. In some embodiments, the hydrogen-generating composition can be substantially free of one or more of lithium hydride (LiH), sodium hydride (NaH), potassium hydride (KH), magnesium hydride (MgH 2 ), calcium hydride (CaH 2 ), lithium aluminum hydride (LiAlH 4 ), sodium borohydride (NaBH 4 ), lithium borohydride (LiBH 4 ), magnesium borohydride Mg(BH 4 ) 2 , sodium aluminum hydride (NaAlH 4 ), or mixtures thereof. 
     In various embodiments, the hydrogen-generating composition includes a metal hydride (e.g., an interstitial intermetallic hydride). Metal hydrides can reversibly absorb hydrogen into their metal lattice. The metal hydride can be any suitable metal hydride. 
     The metal hydride can, for example, be LaNi 5 , LaNi 4.6 Mn 0.4 , MnNi 3.5 Co 0.7 Al 0.8 , MnNi 4.2 Co 0.2 Mn 0.3 Al 0.3 , TiFe 0.8 Ni 0.2 , CaNi 5 , (V 0.9 Ti 0.1 ) 0.95 Fe 0.05 , (V 0.9 Ti 0.1 ) 0.95 Fe 0.05 , LaNi 4.7 Al 0.3 , LaNi 5-x Al x  wherein x is about 0 to about 1, or any combination thereof. The metal hydride can be LaNi 5-x Al x  wherein x is about 0 to about 1 (e.g., from LaNi 5  to LaNi 4 Al). The metal hydride can form any suitable proportion of the hydrogen-generating composition, such as about 10 wt % to about 99.999 wt %, or about 20 wt % to about 99.5 wt %, or about 10 wt % or less, or less than, equal to, or greater than about 15 wt %, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.5, 99.9, 99.99, or about 99.999 wt % or more. Any metal hydride that is described in U.S. Pat. No. 8,172,928, incorporated by reference herein in its entirety, can be included in the present hydrogen-generating composition. 
     The hydrogen-generating composition can include both a metal hydride (e.g., an interstitial intermetallic hydride, such as LaNi 5-x Al x  wherein x is about 0 to about 1), and a chemical hydride (e.g., an ionic hydride or a covalent hydride, such as magnesium hydride (MgH 2 ), lithium hydride (LiH), aluminum hydride (AlH 3 ), calcium hydride (CaH 2 ), sodium aluminum hydride (NaAlH 4 ), sodium borohydride (NaBH 4 ), lithium aluminum hydride (LiAlH 4 ), ammonia borane (H 3 NBH 3 ), diborane (B 2 H 6 ), palladium hydride, LaNi 5 H 6 , TiFeH 2 , and a combination thereof). 
     Metal Oxide 
     In various embodiments, the hydrogen-generating composition can include one or more metal oxides. In some embodiments, the hydrogen-generating composition can be free of metal oxides. The one or more metal oxides can form any suitable proportion of the hydrogen-generating composition, such as about 0.001 wt % to about 20 wt % of the hydrogen-generating composition, about 1 wt % to about 10 wt %, or about 0.001 wt % or less, or less than, equal to, or greater than about 0.01, 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, or about 20 wt % or more. 
     The metal oxide can be any suitable metal oxide, such that the hydrogen-generating composition can be used as described herein. The metal oxide can be zirconium (IV) oxide, hafnium (IV) oxide, titanium (IV) oxide, or a combination thereof. The metal oxide can be titanium (IV) oxide. 
     The hydrogen-consuming fuel cell can include an anode, a cathode, and an electrically-insulating ion-conducting electrolyte (e.g., a membrane, such as a proton exchange membrane, or PEM) separating the anode and cathode, wherein at least one of the anode or cathode undergoes a chemical reaction that consumes hydrogen and generates an electrical potential across the electrodes. In some embodiments, the cathode of the fuel cell consumes hydrogen gas and generates electrons and hydrogen ions. 
     The hydrogen ions can travel across the electrolyte to the cathode, while the electrons can travel to the cathode via an electrical circuit connecting the anode to the cathode. At the cathode, the hydrogen ions can react with oxygen gas and the electrons produced by the anode to form water. 
     The water vapor reacts with the chemical hydride fuel in the hydrogen generator, and generates hydrogen in an exothermic reaction. The hydrogen is carried to a PEM fuel cell as illustrated in  FIG. 1  to generate electrical power. 
     The hydrogen generator  115  may be contained in a replaceable and disposable (recyclable) cartridge such as a container. The hydrogen generator  115  may be cylindrical in geometry in some embodiments. 
     During the electrochemical reaction in fuel cell  110  that produces energy, water vapor, and heat as reaction byproducts, the ambient air within the path  120  is heated and water is added resulting in hot, wet air travelling through the path at  122 . 
     The water exchanger  155  extracts water from the hot, wet air within ambient air path at  123 , and exhausts hot, dry air outside the power generator  100  at exhaust  160 . The set point temperature, which in some embodiments is 60° C., may, for example, vary from 40° C. to 80° C. in some embodiments, or outside that range depending on the type of water exchanger utilized as first water exchanger  155 . The extracted water from the ambient air path  120  is provided to the anode loop  125  to release additional hydrogen at  124  from hydrogen generator  115 . Temperature sensors in the anode and cathode loops may be used to determine and control the water exchanger  155  temperature. One or more sensors may be positioned proximate outlets of the water exchanger to provide a temperature data to the controller  135 . 
     As shown in the embodiment of  FIG. 1 , the power generator  100  can also include one or more other water exchangers, such as second water exchanger  157 . Second water exchanger  157  transfers heat and water vapor to the incoming air at inlet  142 , which improves fuel cell performance. In some embodiments a single water exchanger which combines the functions of the first and second water exchangers (e.g. has separate flow paths for the anode and cathode loops) is used to save weight. 
     Once the released hydrogen travels from hydrogen generator  115  through anode loop  125 , it progresses to junction  127  where some of the hydrogen enters a primary path  126  to be recirculated and some hydrogen enters a secondary path  128  to be provided for the electrochemical reaction in fuel cell  110 . 
     As described above, the electrochemical reaction in fuel cell  110  can produce energy. In some embodiments, the fuel cell  110  charges a charge storage device  130 . The charge storage device can be a rechargeable battery such as a lithium-ion battery, a capacitor, or any other suitable charge storage device. In other words, charge storage device  130  is coupled to power generator  100  such that charge storage device  130  receives electricity generated by fuel cell  110 . 
     In some implementations, the charge storage device  130  can provide the ability to supply higher and more dynamic levels of power than simply utilizing the fuel cell  110  directly, which can be slower to respond and not normally be able to provide high levels of power that may be required for operation of a UAS in a desired manner, such as accelerating sufficiently while carrying a load. In the embodiment of  FIG. 1 , power generated by the fuel cell  110  can be provided for storage in one or more charge storage devices  130 , and/or provided directly to the load from the controller  135 . 
     As illustrated in  FIG. 1 , power generator  100  can include controller  135 . Controller  135  can provide inputs to power generator  100  such that power generator  100  can run optimally, producing power to be stored in charge storage device  130  for use by a UAS, for example. For example, controller/power management electronics can manage flow of power from the fuel cell to the load, and/or control other aspects of power generation (e.g., regulation of temperatures, pressures, flow rates, etc.) 
     Controller  135  can provide inputs to power generator  100  in various ways such that power generator  100  can optimally generate power, as are further described herein. For example, in some embodiments, controller  135  can provide inputs to power generator  100  based on a pressure in anode loop  125 . In some embodiments, controller  135  can provide inputs to power generator  100  based on a current draw by the load (e.g., a UAS) from charge storage device  130 . However, embodiments of the present disclosure are not limited to control schemes for power generator  100 . For example, controller  135  can provide inputs for other system controls. For instance, controller  135  can control the temperature of the fuel cell/hydrogen generator, pressure in the anode loop, flow in anode and cathode loops, state of charge of charge storage device, anticipated changes in load from the device the power source is powering, etc. 
     As described above, in some examples controller  135  can provide inputs to power generator  100  based on a pressure in anode loop  125 . Controller  135  can receive a pressure reading in anode loop  125 , where the pressure in anode loop  125  is based on the blower fan speed of blower  165 . 
     The pressure reading received by controller  135  can be the pressure in anode loop  126 . The pressure in anode loop  126  can be the absolute pressure or the gauge pressure relative to the local ambient pressure. For example, a sensor included in anode loop  125  can determine the pressure in anode loop  125  and transmit the pressure to controller  135 . The pressure in anode loop  126  can allow controller  135  to determine a speed of blower  165  in order to allow hydrogen generator  115 , fuel cell  110 , first water exchanger  155  and/or second water exchanger  157  to operate optimally, as is further described herein. That is, the speed of blower  165  can affect operating parameters of the hydrogen generator  115 , fuel cell  110 , first water exchanger  155  and/or second water exchanger  157  according to the operational scheme of power generator  100  as described above. 
     Controller  135  can determine whether the pressure in anode loop  125  exceeds a threshold pressure. As an example, the sensor in anode loop  125  can determine the pressure in anode loop  125  is 8 pounds per square inch (PSI). Controller  135  can compare the received pressure to a threshold pressure to determine whether the received pressure exceeds the threshold pressure. The threshold pressure can be a predetermined pressure stored locally in memory included in controller  135 . 
     The threshold pressure can be a pressure range. For example, the pressure range can include an upper threshold pressure and a lower threshold pressure. For instance, operation of power generator  100  may occur optimally at a particular pressure of the anode loop  125 , and the particular pressure of the anode loop  125  can fall within the threshold pressure range. That is, the particular pressure of the anode loop  125  can be within the lower threshold pressure and the upper threshold pressure. 
     In some examples, controller  135  can determine the pressure in anode loop  125  is less than the lower threshold pressure. For example, the lower threshold pressure can be 5 PSI, and the controller  135  can determine the received pressure in the anode loop  125  is 4 PSI. Accordingly, controller  135  can determine the pressure in anode loop  125  is less than the lower threshold pressure. 
     A drop in pressure in anode loop  125  can, in some examples, correspond to a higher power requirement by the load from charge storage device  130 . For example, in response to more power being drawn by the load (e.g., by a UAS), more energy from fuel cell  110  may be needed to meet the demand. As the rate of hydrogen being used by fuel cell  110  increases to generate more energy, the pressure in anode loop  125  can drop, causing the pressure to fall below the lower threshold pressure. 
     In order to compensate for the rate of hydrogen being utilized by fuel cell  110  from hydrogen generator  115  increasing as a result of the increased load from the UAS, controller  135  can modify the speed of blower  165  to increase the hydrogen generation rate in the hydrogen generator. Controller  135  can modify the speed of blower  165  by increasing the blower speed such that blower  165  can provide more water vapor to the hydrogen generator  115 , which increases the hydrogen generation rate. Increasing the speed of blower  165  thus increases the pressure in anode loop  125  (e.g., to within the threshold pressure range as described above). As a result, operational parameters for various components of power generator  100  can be kept to within ideal operational limits. 
     In some examples, controller  135  can determine the pressure in anode loop  125  exceeds the upper threshold pressure. For example, the upper threshold pressure can be 12 PSI, and the controller  135  can determine the received pressure in the anode loop  125  is 14 PSI. Accordingly, controller  135  can determine the pressure in anode loop  125  has exceeded the upper threshold pressure. 
     An increase in pressure in anode loop  125  can, in some examples, correspond to a lower power requirement by the load or the charge storage device  130 . For example, in response to lower power being used by the load (e.g., by a UAS) or by charge storage device  130 , power may be required from fuel cell  110 . As the rate of hydrogen being used by fuel cell  110  decreases to generate less power for charge storage device  130 , the pressure in anode loop  125  can increase, causing the pressure to increase above the higher threshold pressure. 
     In order to compensate for the rate of hydrogen being utilized by fuel cell  110  from hydrogen generator  115  decreasing as a result of the decreased load from the UAS or charge storage device  130 , controller  135  can modify the speed of blower  165 . Controller  135  can modify the speed of blower  165  by decreasing the blower speed such that blower  165  can provide less water vapor to hydrogen generator  115 , which decreases the hydrogen generation rate. Decreasing the speed of blower  165  can correspondingly decrease the pressure in anode loop  125  (e.g., to within the threshold pressure range as described above). As a result, operational parameters for various components of power generator  100  can be kept to within ideal operational limits. 
     Although the lower threshold pressure is described above as being 5 PSI and the upper threshold pressure is described above as being 14 PSI, embodiments of the present disclosure are not so limited. For example, the upper and lower threshold pressures can be any other pressure value. In some examples, the pressure values of the upper and lower threshold pressures can vary based on the load (e.g., the UAS), the type of hydrogen fuel utilized by hydrogen generator  115 , among other parameters. 
     As described above, modifying the speed of blower  165  can affect operating parameters of various components of power generator  100 . For example, modifying the speed of blower  165  to modify the pressure in anode loop  125  can maintain an inlet and outlet relative humidity of fuel cell  110  within a predetermined range, maintain an inlet and outlet relative humidity of hydrogen generator  115  within a predetermined range, maintain an inlet and outlet relative humidity of first water exchanger  155  and/or second water exchanger  155  within a predetermined range, and/or a temperature of first water exchanger  155  and/or second water exchanger  155  within a predetermined range, among other operating parameters and/or other operating parameters of other components of power generator  100 . 
     Various sensors can be utilized to monitor components of power generator  100 . For example, the various components of power generator  100  can include temperature sensors that can transmit temperatures of hydrogen generator  115 , fuel cell  110 , and/or first water exchanger  155  and/or second water exchanger  157  to controller  135 . In some examples, controller  135  can maintain operating temperatures of the hydrogen generator  115 , fuel cell  110 , and/or first water exchanger  155  and/or second water exchanger  157  utilizing a fan and/or fans (e.g., operation of the fan/fans can lower the operating temperatures). In some examples, controller  135  can maintain operating temperatures of the hydrogen generator  115 , fuel cell  110 , and/or first water exchanger  155  and/or second water exchanger  157  utilizing a pump circulating cooling fluid to the components of power generator  100  (e.g., operation of the pump circulating the cooling fluid can lower the operating temperatures). 
     As described above, in some examples controller  135  can provide inputs to power generator  100  based on a current draw by the load (e.g., a UAS) from charge storage device  130 . Controller  135  can receive an amount of current draw from charge storage device  130  coupled to fuel cell  110 . As described above, the charge storage device  130  receives electricity generated by fuel cell  110  in response to hydrogen being provided to an anode of fuel cell  110 . Hydrogen can be supplied to the anode via blower  165  by way of anode loop  125  and secondary path  128 . 
       FIG. 2  illustrates a block diagram of an example fuel cartridge  200  in accordance with one or more embodiments of the present disclosure. The fuel cartridge  200  can be a portion of a larger system and/or device, such as the fuel cell based power generator discussed above in connection with  FIG. 1 , where it is embodied as the hydrogen generator  115 , for instance. It is noted, however, that embodiments herein are not limited to such implementations. 
     The fuel cartridge  200  includes an inlet valve  202  coupled to an inlet manifold  204 . Fuel cartridge  200  also includes a first filter  206 - 1 , a second filter  206 - 2 , a third filter  206 -N (sometimes cumulatively referred to as “filters  206 ” which include N filters where N is greater than 2, coupled to the inlet manifold  204 ). A first fuel bed  208 - 1 , a second fuel bed  208 - 2 , a third fuel bed  208 -N (sometimes cumulatively referred to as “fuel beds  208 ”) which includes N corresponding fuel beds coupled to the N filters  206 . A fourth filter  210 - 1 , a fifth filter  210 - 2 , a sixth filter  210 -N (sometimes cumulatively referred to as “filters  210 ”) includes N corresponding fuel beds coupled to the N filters  206 . An outlet manifold  212  is coupled to the N filters  210 . A valve  214  is coupled to the outlet manifold  212 . A coolant mover  216  and a heat exchanger  218  are coupled to cool the fuel cartridge. It is noted that while three filters  206 , three fuel beds  208 , and three filters  210  are shown, embodiments herein are not so limited. Similarly, where single quantities of components are shown (e.g., the valve  202 ), it is to be understood that different quantities may be used. 
     Fuel can be stored in the fuel beds  208  in the form of solid chemical hydride granules. In some embodiments, these granules can be packed in the beds  208 ; in some embodiments, the granules can be fluidized in the beds  208 . When not in use, the beds can be surrounded by inert gas(es) sealed in by the valves  206  and  210  on either side of the beds  208 . As previously discussed, the fuel can include one or more of a number of materials such as, for instance, a chemical hydride material. The filters  206  and the filters  210  can be gas-permeable screens, for instance, sized to allow the passage of water, water vapor, hydrogen gas, and/or other gases but prevent the passage of the fuel therethrough. 
     In use, the valve  202  can be opened allowing a combination of water vapor and inert gas(es) to flow into the inlet manifold  204 . The manifold  204  directs the combined gases through the filters  206  to, and then through, the fuel beds  208 . In the fuel beds  208  the water vapor reacts exothermically with the chemical hydride granules, converting the chemical hydride to solid chemical oxides and hydroxides, and producing hydrogen gas. The produced hydrogen gas (along with the inert gas(es) and unreacted water vapor) flows out of the fuel beds  208  past the filters  210  and is directed via the outlet manifold  212  through the valve  214  (also opened) and out of the fuel cartridge  200 . 
     Stated differently, a method for producing hydrogen gas can include containing a granular hydride material and an inert gas in a plurality of parallel fuel beds  208  of the fuel cartridge  200 , passing water vapor from a first end of each of the plurality of fuel beds (e.g., proximal to the inlet manifold  204 ) through a second end of each of the plurality of fuel beds (e.g., proximal to the outlet manifold  212 ), wherein hydrogen gas is generated by a respective reaction within each of the plurality of fuel beds  208 , and passing the generated hydrogen gas, the inert gas, and a portion of the water vapor out of the fuel cartridge  200 . 
     The reaction in the fuel beds  208  is exothermic and temperature regulation may be desired. A cooling mechanism, (e.g., the coolant mover  216 ) can provide a flow of coolant. In some embodiments, the flow of coolant can pass by and/or along a housing, indicated as a cartridge boundary by broken line  213 , of one or more of the fuel beds  208  contacting the housing. The housing can conduct heat from the interior of the fuel beds  208  to the coolant, thereby acting as the heat exchanger  218  and carrying heat away from the fuel beds  208 . The housing can be made from aluminum and/or aluminum nitride. In some embodiments, the housing can be made from a polymer. In some embodiments, the housing can be made from a polyester resin. In some embodiments, the housing can be made from biaxially-oriented polyethylene terephthalate (BoPET). In some embodiments, the housing can be made from a material having ultra-high thermal conductivity to weight ratio. In some embodiments, the housing can be made from a multi-layer laminate including a first metal layer separated from a second metal layer by a pyrolytic graphite sheet (PGS). In further embodiments, the fuel beds, and/or housing may be formed using a fiber reinforced polymer. 
     A structure, geometry, and/or arrangement of the housing defining the fuel beds  208  can be selected to allow the flow of coolant past, along, and/or between the fuel beds  208 . In some embodiments, the coolant mover  216  includes a fan configured to direct air coolant past and/or along the fuel beds  208 . In some embodiments, the coolant mover  216  includes a pump configured to direct liquid coolant past and/or along the fuel beds  208 . Note that in some embodiments, the coolant mover  216  is separate from the cartridge and may be adapted to mate with replaceable cartridges to provide for movement of coolant through heat exchanger  218 . The heat exchanger  218  may be integrated with the cartridge or alternatively removably couplable to a replaceable cartridge. 
     In some embodiments, the housing can provide cooling functions. For instance, in some embodiments, the housing can incorporate interface features for a fan and/or pump to circulate the coolant. In some embodiments, the housing can incorporate interface features for a fan duct or tubing to direct the coolant. In some embodiments, the housing can incorporate a manifold for directing the coolant around the fuel cartridge  200 . A temperature of the fuel beds  208  can be determined via one or more temperature sensors. For example, in some embodiments, a temperature sensor is inserted into an interior of one or more of the fuel beds  208 . In some embodiments, a temperature sensor  220  is used to determine a temperature associated with an outer surface of the fuel cartridge  200 . Based on determined temperature, coolant flow properties, such as flow rate, can be controlled (e.g., in a closed loop) to regulate the fuel bed temperature (e.g., maintain the fuel bed temperature within a particular temperature range). 
     Fuel cartridges in accordance with embodiments herein can include a heating mechanism. Such a mechanism may be activated to initiate and/or accelerate the reactions occurring in the fuel beds  208 , for instance. The heating mechanism may be powered via battery  130  and controlled via controller  135 . 
       FIG. 3A  is a perspective view of an example fuel cartridge in accordance with one or more embodiments of the present disclosure. As shown in  FIG. 3 , the fuel cartridge can include a plurality of cylindrical (e.g., tubular) fuel beds  308  connected at a first end to an inlet manifold  304  and connected at a second end to an outlet manifold  312 . The manifolds are shown as blocks for simplicity of illustration but will include one or more passages to couple to the tubular fuel beds  308  to provide water in a first end of the tubes and remove generated hydrogen from the tubes. The fuel beds  308  can be parallel. The fuel beds  308  can be spaced apart such that air is permitted to flow in the spaces between the fuel beds  308 . In the example illustrated in  FIG. 3A , air can be forced in a direction orthogonal to the fuel beds  308  (e.g., orthogonal to an elongate axis of the fuel beds  308 ). A filter or screen  328  at the top and bottom of each tube to keep the fuel granules in place, but allow gas to flow in and out with minimal impedance. 
       FIGS. 3B, 3C, and 3D  are schematic representations of radial and axial fuel bed designs in the shape of tubes or rods that may be utilized in the array/manifold structure of  FIG. 3A . The axial flow fuel tube design shown in  FIG. 3B , a cylindrical structure, may have a fuel tube diameter of: 10 mm to 50 mm and a fuel tube length of: 50 mm to 500 mm in one embodiment. The fuel tubes have thin, light-weight outer shells that are at least substantially gas impermeable in some embodiments to contain the hydrogen generated therein and provide the hydrogen to the hydrogen path via the outlet manifold. The tubes also allow heat to be convected away by the coolant flowing over the outside of the tubes without interfering with hydrogen generation and allowing the control of the temperature of the tubes and fuel therein to be maintained within a narrow desired temperature range of 40-100C. or 60-80C. 
     The radial flow fuel tube design of  FIG. 3C  has toroid shape with a gas permeable side screens  326  and a fuel tube diameter of: 10 mm to 50 mm and a fuel tube length of: 50 mm to 500 mm. The “side screens” may be porous/perforated layers that contains the fuel and allows gas to flow (radially) through it into outer flow channel  327 . 
     The radial flow fuel tube design of  FIG. 3D  has a toroid shape with a bottom screen  328 . Packaging materials for the fuel tubes include thin polymers and metals compatible with the fuel. 
     Wet hydrogen is shown by arrow  335  as entering each of the tubes at one end of the tube, contacting the LAH fuel  340 , and exiting at the other end of the tubes as dry hydrogen. In  FIG. 3C , the wet hydrogen flows axially through the inner flow channel  329 , and then radially though a first side screen  326  into the fuel, then through a second side screen, into the outer flow channel  327 , and then axially out the bottom as dry hydrogen. The fuel tube design avoids a large pressure drop over time and helps maintain a flatter hydrogen generation response, as opposed to a high rate of hydrogen production at the beginning of the hydrogen producing life of the fuel tubes followed by a significantly lower rate over time. The design also provides for better utilization of the fuel, as water vapor is distributed more evenly in the fuel, resulting higher average reaction rates and greater fuel utilization above the minimal cutoff rate. 
       FIG. 3E  is a cross section block diagram of a fuel cartridge  350  according to an example embodiment. The fuel cartridge  350  includes multiple tubes or rods of fuel indicated at  352 . Each rod is coupled at first ends to a first manifold  354  having an inlet  355  and multiple outlets  357  that are coupled to provide wet hydrogen to the first ends of the fuel rods  352 . The second ends of the fuel rods  352  are coupled to inlets  358  of a second manifold  359 . Second manifold  359  provides dry hydrogen to the anode loop via an outlet  360  for provision to the fuel cell. Filters  362 , represented by broken lines, may be place at the first and second ends of the fuel rods to screen out particles that may foul or clog hydrogen and water vapor flow within the fuel rods. 
     In one embodiment, the packaging of the fuel rods is impermeable to water vapor and other gases that might impair operation of the hydrogen generating capability of the fuel in the fuel rods. In addition, the manifolds hold the fuel rods in place in a spaced apart manner to allow fluid to flow between the tubes to remove heat generated by the hydrogen producing reaction with the water vapor. A pump or fan  365  may be positioned at a side to blow fluid across the tubes to remove the heat. The fan  365  may be supported by the manifolds such that fluid moved by the fan flows through the openings between the rods and exits the fuel cartridge to efficiently remove heat without encountering significant resistance such that the fan may be low power and light in weight. 
     In some embodiments, the first manifold inlet and the second manifold outlet may include valves  368  to selectively allow gas to flow through the manifolds and fuel rods. The valves may be iris valves or other types of suitable large conductance valves. The inlet and outlet may be configured to mate with the anode loop in a manner that opens valves  368  to allow hydrogen flow upon insertion of the fuel cartridge  350 . The valves  368  operate to preserve the hydrogen producing fuel during transport and storage by preventing air and humidity from entering the manifolds and fuel rods. 
     The rod spacing may be done in in an array like pattern  370  as shown in top cross-sectional view in  FIG. 3F , with columns or rods  353  staggered, or otherwise arranged to provide good heat removal by the fluid without significantly restricting the fluid flow. Such a staggered column array facilitates a high hydrogen density fuel cell which may be light in weight. 
       FIG. 3G  is a cross sectional view of a further fuel cartridge  380  with the same reference numbers of like parts the same as those used for fuel cartridge  350 . In fuel cartridge  380 , the first manifold  381  inlet  382  is in line with the rods, as is the second manifold  383  outlet  384 . 
       FIG. 4  is a perspective view of another example fuel cartridge in accordance with one or more embodiments of the present disclosure. As shown in  FIG. 4 , the fuel cartridge can include a plurality of stacked rectangular (e.g., slab-shaped) fuel beds  408 . No manifolds are illustrated in  FIG. 4  so as not to obscure embodiments of the present disclosure. The fuel beds  408  can be spaced apart such that air is permitted to flow through spaces between the fuel beds  408 . As shown in the example illustrated in  FIG. 4 , the housing of the fuel beds  408  can include cooling fins  409 . The fins can provide structural strength to the cartridge while allowing fluid to pass through ducts between the fuel beds  408  and conducting heat away from the fuel beds  408  to the passing fluid. The fins  409  may be constructed with a shape similar to that of corrugated cardboard, with airflow facilitated through the openings transverse to the fuel beds  408 . Other arrangements of fuel beds and/or ducts can be provided through different housing configurations, such as those illustrated in  FIGS. 5-10 , which are included for purposes of illustration and are not to be taken in a limiting sense. 
       FIG. 5  is a cross-sectional view of another example fuel cartridge in accordance with one or more embodiments of the present disclosure.  FIG. 6  is a cross-sectional view of another example fuel cartridge in accordance with one or more embodiments of the present disclosure.  FIG. 7  is a cross-sectional view of another example fuel cartridge in accordance with one or more embodiments of the present disclosure.  FIG. 8  is a cross-sectional view of another example fuel cartridge in accordance with one or more embodiments of the present disclosure.  FIG. 9  is a cross-sectional view of another example fuel cartridge in accordance with one or more embodiments of the present disclosure.  FIG. 10  is a cross-sectional view of another example fuel cartridge in accordance with one or more embodiments of the present disclosure. 
     The examples illustrated in  FIGS. 5, 6, 7, 8, 9, and 10  each include different housing configurations that define different shapes and configurations of fuel beds and ducts. That is, the examples illustrated in  FIGS. 5, 6, 7, 8, 9, and 10  respectively include housings  519 ,  619 ,  719 ,  819 ,  919 , and  1019 . These housings  519 ,  619 ,  719 ,  819 ,  919 , and  1019  respectively enclose a plurality of fuel beds  508 ,  608 ,  708 ,  808 ,  908 , and  1008 . The housings  519 ,  619 ,  719 ,  819 ,  919 , and  1019  respectively enclose a plurality of ducts  520 ,  620 ,  720 ,  820 ,  920 , and  1020 . The housings may also be coupled to manifolds at each end of the fuel beds to transport wet hydrogen from the anode loop into and through the beds, and transport dry hydrogen back to the anode loop. 
     As shown in  FIGS. 5-10 , fuel beds in accordance with the present disclosure can be provided in different cross-sectional shapes including, for example, rectangular, square, hexagonal, triangular, and irregular. These examples are not to be taken in a limiting sense and embodiments herein are not limited to a particular shape and/or configuration. Fuel beds can be adjacent to one another in some embodiments and separated by ducts in other embodiments. Fuel beds can be arranged in ring configurations. Fuel beds can be located central to a fuel cartridge in some embodiments. Fuel beds can be located on the periphery of a fuel cartridge in some embodiments. Each of the fuel beds can be separated from other fuel beds by at least one duct. The different configurations can each provide unique thermal performances and/or flow characteristics. Flow of coolant can be parallel and/or substantially in line with hydrogen flow. Flow of coolant can be substantially orthogonal to hydrogen flow. 
       FIG. 11  is a perspective view of another example fuel cartridge in accordance with one or more embodiments of the present disclosure.  FIG. 12  is a perspective view of the example fuel cartridge illustrated in  FIG. 11  showing a fan mounted to the fuel cartridge. The fuel cartridge shown in  FIGS. 11 and 12  may be analogous to the cartridge illustrated in  FIG. 6 , for instance. Accordingly, the inlet manifold  1104  obscures the fuel beds while airflow is permitted through a plurality of substantially-triangular ducts  1120 . The air flow can be provided by a fan  1216 , which may be mounted to an exterior surface of the inlet manifold  1104 . 
       FIG. 13  is a block diagram of a specifically programmed system for executing control methods for a fuel cartridge according to one or more embodiments of the present disclosure. In the embodiment of  FIG. 13 , a hardware and operating environment of the system includes a general purpose computing device in the form of a computer  1303  (e.g., a microcontroller, personal computer, workstation, or server), including one or more processing units  1380  and memory  1381 . There may be only one or there may be more than one processing unit  1380 , such that the processor of computer  1303  comprises a single central-processing unit (CPU), or a plurality of processing units, commonly referred to as a multiprocessor or parallel-processor environment. In various embodiments, computer  1303  is a conventional computer, a distributed computer, or any other type of computer. 
     The memory can also be referred to as simply memory, and, in some embodiments, includes read-only memory (ROM), random-access memory (RAM). Memory can be stored on a computing device, a memory device, or a computer readable medium, such as a memory stick, CD, tape, or other suitable medium or storing data and/or computing device executable instructions. 
     A number of executable instruction types  1383  can be stored in memory. For example, memory  1382  can include an operating system, one or more application programs, other program modules, and data stored in memory (e.g., for use by one or more programs)  1384 . Programming for implementing one or more processes or method described herein may be resident on any one or number of these computer-readable media. 
     In further embodiments, power management and control electronics include one or more temperature and power output sensors that are used by the control electronics to maintain operating temperatures. These sensors can provide sensor data  1386  as inputs into the computing device  1303  for use by one or more programs therein via executable instructions  1383  executed by processor  1381  or to be stored in memory  1382  for use by another computing device. 
     The control electronics may be configured to maintain design points for such temperatures and/or power output. Instructions  1388  to adjust one or more components of a system (e.g., system  100  of  FIG. 1 ) can be sent via one or more outputs  1387 . Such outputs can be via a wired connection between the computing device and one or more other components of the system or can be communicated via a wireless connection. 
     Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art will appreciate that any arrangement calculated to achieve the same techniques can be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments of the disclosure. 
     It is to be understood that the above description has been made in an illustrative fashion, and not a restrictive one. Combination of the above embodiments, and other embodiments not specifically described herein will be apparent to those of skill in the art upon reviewing the above description.