Abstract:
A device for generating hydrogen for power system based on hydrolysis aluminum assisted water split has a housing, a unit for containing aluminum in the housing, a unit for periodically bringing the aluminum and the electrolyte in contact for production of hydrogen, and a unit for the withdrawing the hydrogen to a power source.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to electric current sources based on fuel elements. 
         [0002]    Hydrogen is a “clean fuel” because it can be reacted with oxygen in hydrogen-consuming devices, such as a fuel cell or combustion engine, to produce energy and water. Virtually no other reaction byproducts are produced in the exhaust. As a result, the use of hydrogen as a fuel effectively solves many environmental problems associated with the use of petroleum based fuels. Safe and efficient storage of hydrogen gas is, therefore, essential for many applications that can use hydrogen. In particular, minimizing volume, weight and complexity of the hydrogen storage systems are important factors in mobile applications. 
         [0003]    The development of fuel cells as replacements for batteries in portable electronic devices, including many popular consumer electronics such as personal data assistants, cellular phones and laptop computers is dependent on finding a convenient and safe hydrogen source. The technology to create small-scale systems for hydrogen supply, storage and delivery has not yet matched the advancements in miniaturization achieved with fuel cells. 
         [0004]    A hydrogen fuel cell for portable applications needs to be compact and lightweight, have a high gravimetric hydrogen storage density, and be operable in any orientation. Additionally, it should be easy to match the control of the system&#39;s hydrogen flow rate and pressure to the operating demands of the fuel cell. 
         [0005]    The existing hydrogen storage options, which include compressed and liquid hydrogen, hydrided metal alloys, and carbon nanotubes, have characteristics which complicate their use in small consumer applications. For instance, compressed hydrogen and liquid hydrogen require heavy tanks and regulators for storage and delivery, metal hydrides require added heat to release their stored hydrogen, and carbon nanotubes must be kept pressurized. 
         [0006]    Alternatives for hydrogen storage and generation include the class of compounds known as chemical hydrides, such as the alkali metal hydrides, the alkali metal aluminum hydrides and the alkali metal borohydride. The hydrolysis reactions of many complex metal hydrides, including sodium borohydride, (NaBH4) have been commonly used for the generation of hydrogen gas. 
         [0007]    In those applications where a steady and constant supply of hydrogen is required, it is possible to construct hydrogen generation apparatus that control the contact of a catalyst with the hydride fuel. Such generators typically use a two-tank system, one for fuel and the other for discharged product. The hydrogen generation reaction occurs in a third chamber that contains a metal catalyst and connects the two tanks. However, such two-tank designs are not typically directionally independent or amenable to miniaturization. 
       SUMMARY OF THE INVENTION 
       [0008]    Accordingly, it is an object of the present invention to provide a device for and method of storage and generation of hydrogen for autonomous current sources based on fuel cells, which constitutes a further improvement of the existing solutions. 
         [0009]    In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a device for producing hydrogen for power sources, comprising a housing; means for containing electrolyte in said housing; means for containing aluminum in said housing; means for periodically bringing the aluminum and the electrolyte in contact for production of hydrogen; and means for the withdrawing the hydrogen to a power source. 
         [0010]    In accordance with the present invention, another feature of the present invention resides, briefly stated, in a method further comprising setting a predetermined pressure in said container so that when an interior of said housing is connected with a power source, a pressure which is lower than the said pressure is provided inside said container and the aluminum is brought in contact with the electrolyte, while after generation of hydrogen and withdrawal from said container when a pressure becomes again equal to the said pressure the aluminum and electrolyte are disengaged from one another and generation of hydrogen is stopped until a next cycle. 
         [0011]    In the present invention the hydrogen production is performed by aluminum assisted water split in accordance with the following formula: 
         [0000]      2Al+6H2O[ in alkaline solution ]→2Al(OH) 3 +3H 2 ↑ 
         [0012]    As a result of reaction of aluminum with water in alkaline medium, a pure hydrated aluminum oxide is produced (AlOH 3 .nH 2 O) and hydrogen. The yield of hydrogen can be substantially 3.7%. Taking into consideration that a quantity of water required for reaction can be provided in half by a returned water generated in the electrochemical power system based on the fuel cell during the use of an energy device, the yield of hydrogen can reach 7-10%. The necessary condition of the reaction is a direct contact of all reactant (aqueous alkaline solution and aluminum) with each other. The quantity of produced hydrogen can be regulated by a magnitude of area of contact of the surfaces of particles of aluminum which interact with water. 
         [0013]    The aluminum can be used in any form, such as foil, sheet, wire, granules (pellets) of regular and irregular shape. It is important to provide an optimal area of surface of reaction and its completeness. It is important that one of the linear sizes of the used form of aluminum parts is small and does not exceed 0.1-1 mm. 
         [0014]    The important feature of the present invention is also the content of the electrolyte, in particular NaOH with addition of LiOH, NaInO 2  and Na 4 Ga 2 O 3 *nH2O. 
         [0015]    The required quantities include 4 M of NaOH with 1-10 Wt % of the above mentioned additives. 
         [0016]    The novel features of which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a view schematically showing a device for a hydrogen gas generation in accordance with the first embodiment of the present invention; 
           [0018]      FIG. 2  is a view schematically showing a device for a hydrogen gas generation in accordance with the second embodiment of the present invention; 
           [0019]      FIG. 3  is a view schematically showing a device for a hydrogen gas generation in accordance with the third embodiment of the present invention; 
           [0020]      FIG. 4  is a view showing a graph of hydrogen generation rate versus time for a hydrogen production by aluminum assisted water split according to the present invention; 
           [0021]      FIG. 5  is a view showing a graph of a total amount of hydrogen produced versus time for hydrogen production by aluminum assisted water split according to the present invention; 
           [0022]      FIG. 6  is a view showing a graph of a hydrogen output pressure versus time for a hydrogen production by aluminum assisted water split according to the present invention; and 
           [0023]      FIG. 7  is a view showing a graph of a hydrogen generation temperature versus time for hydrogen production by aluminum assisted water split according to the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    A device for hydrogen gas generation in accordance with one embodiment of the present invention is shown in  FIG. 1 . The device has a housing  10 , a unit for setting a controlling pressure  12 , a sealing unit  14  for sealing introduction of gas which sets the pressure, a unit  16  for sealing a pipe for supply of a generated hydrogen to a fuel cell, a unit  18  for sealing a removable lid of the device. The device further has a flexible bay  20  formed as an electrolyte container for accommodating electrolyte  22 . The device further has a container  30  with a portion of aluminum, and a unit  24  for sealing the container with aluminum. 
         [0025]    Reference numeral  26  identifies a unit of sealing a pipe for return of water from the fuel cell. The device further has unit  32  for filtration and withdrawal of generated hydrogen from the device, a flexible pipe  34  for withdrawal of the generated hydrogen from the flexible back  32 , a pipe  40  for supplying the generated hydrogen to a fuel cell, and a pipe  50  for return of water from the fuel cell into the device. 
         [0026]    The housing  10  can be composed of rigid material, for example from a thermoplastic material such as polyamide, ABC, and thermoreactive plastic material such as fluoroplastics or silicon elastomers. The container  20  for electrolyte is composed of an elastic material, for example from rubber EPDM or silicon rubber, and accommodates a required quantity of electrolyte needed for the chemical reaction. The container  30  with a portion of aluminum, the sealing unit  24 , and the unit for filtration and removal of generated hydrogen is located inside the container  20 . 
         [0027]    The unit  32  for filtration and removal of the generated of the united hydrogen is connected through the sealing unit  16  by the flexible pipe  34  with a pipe for supply of hydrogen  40  to the fuel cell. The device for setting controlling pressure  12  is connected through the sealing unit  14  to the housing  10 , and the pipe for return of water from the fuel cell  50  is connected to the housing  10  through the sealing unit  26 . The housing  10  is composed of two parts connected with one another by the sealing unit  18 . 
         [0028]    In the initial position the device formed as a cartridge does not have active components. In order to supply the components into the cartridge, it is necessary to open the housing  10  in the sealing unit  18  which can be formed as screw connection, a bayonet connection or another fast connection, to disconnect the sealing unit  24 , to pour aqueous solution, for example of 4 M Na OH with additives 1-10 Wt % LiOH, NaInO 2  and Na 4 Ga 2 O 3 *nH2O into the electrolyte container  20 , to place the container  30  with a portion of aluminum inside the container  20 , to seal the sealing unit  24 , to seal the housing  10 . 
         [0029]    For activation of the device, it is necessary to connect the pipe for supply of hydrogen  40  to the fuel cell, and the pipe for return of water  50  to a corresponding part of the fuel cell. 
         [0030]    After the connection of the pipe  40 , insufficient pressure, relative to pressure set by the unit  12  is provided. This leads to squeezing of the electrolyte container  20  which is composed of elastic material, and the electrolyte  22  is brought into contact with the aluminum in the container  30 , so that in accordance with the above mentioned reaction, generation of hydrogen starts. This process continues until the pressure inside the container  20  becomes equal to the pressure set by the setting unit  12 . After the pressures inside the elements  12  and  20  become equal, electrolyte and aluminum are disconnected, and reaction of generation of hydrogen automatically stops until a next cycle. The next cycle starts when the pressure of hydrogen in the fuel cell again becomes smaller than the pressure set by the unit  12 , and the process continues until a complete use of the reactants. As can be seen, the device formed as a cartridge can operate in any spatial orientation. 
         [0031]    After the complete use of the reactants, the device is disconnected from the fuel cell and is recharged. For this purpose the housing  10  is open in the sealing unit  18 , the sealing unit  24  is disconnected, the container  30  is removed from the container  20 , the spent solution of electrolyte is removed from the container  20 , and the container is washed, while the spent solution can be sent for recycling, a fresh solution specified herein above is introduced into the electrolyte container  20 , the container  30  with a portion of aluminum is introduced into the container  20 , the sealing unit  20  is sealed, the housing  20  is sealed, and the device is ready for next use. 
         [0032]      FIG. 2  shows another embodiment of the device in accordance with the present invention. The device has a housing  10 , a unit  12  for setting controlling pressure, a unit  14  for sealing introduction of gas that sets by pressure, a unit  16  for sealing a pipe for supply of generated hydrogen into a fuel cell, a unit  18  for sealing a removable lid of the device. Reference numeral  22  identifies electrolyte. The device further has a container  30  with a portion of aluminum, a unit  24  for sealing the aluminum container, a unit  26  for sealing a pipe for return of water from a fuel cell, a flexible pipe  34  for removal of generated hydrogen from the flexible bag. 
         [0033]    The device further has a pipe  40  for supplying generated hydrogen to the fuel cell, a pipe  50  for return of water from the fuel cell into the device. The device further has an internal bag  60  composed of a porous hydrophobic membrane which allows a passage of hydrogen a net  62  which can be formed as a plastic net and reinforced for providing a required gap between the internal bag  60  and a flexible bag  64 . The flexible bag  64  is impermeable for hydrogen and electrolyte. Reference numeral  66  identifies a unit for withdrawal of hydrogen from the device. 
         [0034]    In the device shown in  FIG. 2  the housing  10  is also composed of rigid material as in the embodiment of  FIG. 1 . The container formed as a bag for electrolyte  64  is located inside the housing and composed of an elastic material such as EPDM rubber or silicon rubber with a supply of the electrolyte  22 , and the container with a portion of aluminum  30 . The internal bag  60  is composed of a gas permeable membrane known in the art and more permeable to hydrogen than water, such as silicon rubber, fluoropolymer, or any common hydrogen-permeable metal membrane, such as palladium-gold alloy membrane. Another bag  62  composed of a plastic mesh or net, for example of polyethylene or polypropylene fluoroplastic and another material which is resistant in alkali solutions, is provided between the elements  60  and  64  for obtaining a gap therebetween. The container  30  with a portion of aluminum and electrolyte  22  are introduced into the container  64  through the hermetically sealed window  24 . The unit for withdrawal of hydrogen  66  is arranged on the container  64  and connected by the flexible pipe  34 , which through the sealing unit  16  is connected with the pipe  40  for supply of hydrogen to the fuel cell. The unit  12  for setting controlling pressure and the pipe for return of water from the cell  50  are connected through the sealing unit  14  and the sealing unit  26  correspondingly to the housing  10 . The housing  10  is composed of two parts connected with one another by the sealing unit  18 . 
         [0035]    As in the previous embodiment, in the initial position there are no reactants in the device. It is then necessary to open the housing  10  in the area of the sealing unit  18 , to disconnect the sealing unit  24 , to introduce the electrolyte into the container  20 , to place the container  30  with a portion of aluminum into the container  60 - 64 , to seal the unit  24  and the housing  10 . 
         [0036]    In order to activate the device it is necessary to connect the device  40  for supply of hydrogen to the fuel cell and the pipe of  50  for return of water to the corresponding parts of the fuel cell. After the connection of the pipe  40  an insufficient pressure relative to the pressure set by the unit  12  is provided. This leads to squeezing of the composite container for electrolyte  60 - 64 , which is composed of the elastic material, the electrolyte  22  is brought in contact with aluminum in the container  30 , and hydrogen is generated in accordance with the above mentioned reaction. After equalization of the pressure inside the elements  20  and  64 , the electrolyte and aluminum are disengaged from one another and the reaction of generation of hydrogen automatically stops until the next cycle. The next cycle starts when pressure of hydrogen in the fuel cell again becomes lower than the pressure set by the unit  12 , and the process continues till full use of reactants. 
         [0037]    After the complete use of reactants the device is disconnected from the fuel cell and is recharged. For this purpose the housing  10  is open in the area of the sealing unit  18 , the sealing unit  24  is disconnected, the container  30  is removed from the composite container  60 - 64 , the electrolyte is removed from the container  20  and washed, and the spent solution is sent for recycling, a fresh solution of the electrolyte is introduced into the composite container  60 - 64 , the container  30  with the portion of aluminum is introduced into the composite container  60 - 64 , the unit  24  is sealed, and the housing  10  is sealed. 
         [0038]      FIG. 3  shows another embodiment of the present invention. The device for hydrogen generation has a housing  10 , a unit  12  for setting controlling pressure, a unit  14  for sealing introduction of gas which sets the pressure, a unit  16  for sealing a pipe for supply of generated hydrogen to a fuel cell, a unit  18  for sealing a removable lid of the device. Reference numeral  22  identifies electrolyte. The device further has a unit  76  for sealing the container with aluminum, a unit  26  for sealing a pipe for return of water from the fuel cell, a container  30  with a portion of aluminum, a pipe  40  for supply of generated hydrogen to the fuel cell, a pipe  50  for return of water from the fuel cell, a unit  70  for removal of hydrogen from the device, a cylinder  72  providing a displacement of aluminum container by means of a piston rod  78  under the action of the gas from the unit  12 , a piston  74 , and a unit for sealing the piston rod  78 . The device further has a flexible bag  80  which is impermeable for hydrogen and electrolyte. 
         [0039]    As before, the housing  10  is composed of a solid material, for example a plastic material. The container or bag for electrolyte  80  composed of an elastic material, for example of EPDM rubber or silicon rubber or plastic with the electrolyte  22  is located in the housing. The housing  10  is composed of two parts removably connectable by the sealing unit  18 . The electrolyte container  80  is connected to the housing  10  in the area of the sealing unit  18 . The unit for filtration and removal of hydrogen  70  with the pipe  40  for supply of hydrogen to the fuel cell and the device for regulating the position of the container  30  with aluminum relative to the level of the electrolyte  20  are located in an upper part of the housing  10 . This regulating device includes the unit  12  for setting a controlled pressure, the cylinder  72  with the piston  74 , the piston rod  78  and the sealing unit  76 , the pipe  50  for water return from the fuel cell through this sealing unit  26 . The pipe  50  for return of water from the fuel cell is connected to the housing  10  through the sealing unit  26 . 
         [0040]    As in the previous embodiments for introducing reactants it is necessary to open the housing  10 , to introduce the electrolyte into the container  80 , to connect the container  30  with aluminum to the piston rod  78  at a corresponding height, to seal the housing  10 . 
         [0041]    For activation of the device it is necessary to connect the pipe  40  for hydrogen to the fuel cell and the pipe  50  for water return to the corresponding part of the fuel cell. Immediately after the connection of the pipe  40  an insufficient pressure relative to the pressure set by the unit  20  is produced. This leads to lowering of the container  30  with aluminum till its contact with the electrolyte  22 , and they are brought in contact with one another, whereafter in accordance with the above mentioned reaction generation of hydrogen starts. The process will continue till the pressure inside the housing  10  equalizes with the pressure set by the unit  12 . After the equalization of the pressures the container  30  with aluminum connected to the piston rod  78  moves upwardly, the electrolyte and aluminum are disengaged with one another, and the reaction stops until a next cycle. The next cycle starts when the pressure of hydrogen in the fuel cell transmitted into the housing  10  is again less than the pressure set by the element  12 , and the process continues until complete use of the reagents. The device can work in a substantial vertical position +/−30°. After the use of the reactants the device is disconnected from the fuel cell and is recharged/replaced correspondingly. 
         [0042]    It should be mentioned that the container  30  for aluminum is configured so as to provide a contact of the electrolyte with the aluminum in the container. The container  7  can be formed as a mesh, net, etc, which allows the above mentioned contact. The important feature of the present invention is that the aluminum is provided in form of small particles with a thickness substantially not exceeding 0.1-1 mm. This provides a high degree of contact between the aluminum and the electrolyte and high efficiency of the process. 
         [0043]    The inventive device and method have been tested. An example is presented herein below just for illustration purposes and is not to be constructed as limitation of the present invention, since many deviations are possible without a parting of the spirit and scope of the invention. 
         [0044]    The device shown in  FIG. 3  is utilized here as an example. It was constructed to bench test of the invention. 300 ml of 4 M of solution NaOH with corresponding additives was introduced into the flexible bag  80 . 65 gram of industrial aluminum alloy 6061 was introduced into the container  30  as a band with a thickness of 1 mm, wound into a spiral with an outer diameter approximately 75 mm. The test was made for obtaining hydrogen in the quantity of approximately 180 liter with a flow rate approximately 0.65 liter per minute during approximately 5 hours. The results of this experiment are shown in  FIGS. 4 ,  5 ,  6  and  7 . 207,089 liter of hydrogen was produced with efficiency of 0.677 liter per minute during 5 hours. During the test a low pressure set by the self regulating system has observed inside the device as shown in  FIG. 6  and a corresponding calculated value of temperatures as shown in  FIG. 7 . It clearly shows that the device and method can be used as a hydrogen source for portable fuel cell power systems and also for industrial/residential power systems and electric vehicle operations. 
         [0045]    It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions and methods differing from the type described above. 
         [0046]    While the invention has been illustrated and described as embodied in a device for and method of storage and generation of hydrogen for autonomous current sources based on fuel cells, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
         [0047]    Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.