Abstract:
An improved system for generating electrical power using a fuel cell. More particularly, a system for generating hydrogen gas by reacting water vapor with a substantially non-fluid substance and transporting the generated hydrogen gas to the fuel cell which generates electrical power. Reacting water vapor with the non-fluid hydrogen generating substance rather than liquid water prevents caking of the non-fluid substance and deposition of byproducts onto the non-fluid substance that interfere with continued generation of hydrogen gas.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to an improved system for generating electrical power using a fuel cell. More particularly, the invention pertains to a system for generating hydrogen gas by reacting water vapor with a substantially non-fluid substance and transporting the generated hydrogen gas to the fuel cell which in turn generates electrical power. 
         [0003]    2. Description of the Related Art 
         [0004]    Similar to batteries, fuel cells function to produce electric power through chemical reactions. Rather than storing reactants as batteries do, fuel cells are operated by continuously supplying reactants to the cell. In a typical fuel cell, hydrogen gas acts as one reactant and oxygen as the other, with the two reacting at electrodes to form water molecules and releasing energy in the form of direct current electricity. This direct current electricity may then be converted into an alternating current. The system may produce electricity continuously as long as hydrogen and oxygen are provided. While oxygen is typically provided from the air, it is generally necessary to generate hydrogen gas from other compounds through controlled chemical reactions rather than storing hydrogen, because storing of hydrogen gas requires that it either be compressed or cryogenically cooled. As fuel cell technology evolves, so do the means by which hydrogen gas is generated for application with fuel cells. 
         [0005]    Currently, there are various methods which are known and employed for generating hydrogen gas. The predominant method is by a process known as reformation in which fossil fuels are broken down into their hydrogen and carbon products. However, this system is undesirable in the long term because it is dependent upon a non-renewable resource. Another method is electrolysis, in which hydrogen is split from water molecules. However, this method is not well suited for large scale applications, such as use in automobiles. Another means of generating hydrogen gas is by reversibly adsorbing and releasing hydrogen gas from metal hydrides or alloys through heating. While this method is useful, it is not preferred because the metal hydrides are typically very heavy, expensive and only release small quantities of hydrogen. Yet another means by which hydrogen gas is generated is through reactive chemical hydrides. This process involves chemically generating hydrogen gas from dry, highly reactive solids by reacting them with liquid water or acids. Chemicals especially suitable for this process are lithium hydride, calcium hydride, lithium aluminum hydride and sodium borohydride, each of which are capable of releasing plentiful quantities of hydrogen. The disadvantages associated with this method is that reaction products from the chemical and liquid water typically form a cake or pasty substance which interferes with further reaction of the reactive chemical with the liquid water or acid. 
         [0006]    It is of great interest in the art to provide a means by which hydrogen gas may be generated for use in fuel cells, without relying on non-renewable resources and without the disadvantages of each of the aforementioned methods. The present invention provides a solution to this problem. The invention provides an electrical power generator and a process for generating hydrogen gas for fueling a fuel cell. The electrical power generator comprises a water vapor generator at least partially filled with water vapor, at least one hydrogen gas generator connected to the water vapor generator, and a fuel cell connected to the hydrogen gas generator, the hydrogen generation chamber being at least partially filled with a substantially non-fluid substance which reacts with water vapor to generate hydrogen gas. The hydrogen gas generated may then be used as a “fuel” which allows the fuel cell to generate electrical power. The present invention improves upon the related art by reacting a water vapor with a substantially non-fluid substance to generate hydrogen gas rather than liquid water. By reacting a water vapor with the aforementioned non-fluid chemical substance, it has been found that the typical problems associated with reactive chemical hydrides are avoided, resulting in a more efficient system than those of the prior art. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention provides an electrical power generator comprising:
       a) a water vapor generator;   b) a hydrogen gas generator attached to the water vapor generator, said hydrogen generator containing a substantially non-fluid substance which reacts with water vapor to generate hydrogen gas; said hydrogen generator optionally being attached to said water vapor generator via at least one conduit; and   c) a fuel cell attached to the hydrogen gas generator; said fuel cell optionally being attached to said hydrogen gas generator via at least one conduit.       
 
         [0011]    The invention also provides a process for generating hydrogen gas for fueling a fuel cell comprising:
       a) directing water vapor from a water vapor generator to a hydrogen generator, said hydrogen generator being at least partially filled with a substantially non-fluid substance which reacts with water vapor to generate hydrogen gas; and   b) directing hydrogen gas and any residual water vapor from the hydrogen generator to a fuel cell.       
 
         [0014]    The invention further provides an improved process for generating electrical energy wherein water and hydrogen gas are directed from a water containing chamber to a fuel cell; and water and any residual hydrogen gas are directed from the fuel cell back to the water containing chamber; and water and hydrogen gas are directed through a hydrogen gas generator, which hydrogen gas generator is connected to each of the fuel cell and water containing chamber and which hydrogen gas generator is at least partially filled with a substance which reacts with water to generate hydrogen gas, wherein the improvement comprises contacting water in the form of water vapor with a substantially non-fluid substance which reacts with water vapor to generate hydrogen gas. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0015]      FIG. 1  is a schematic representation of an electrical power generator having a conduit and a separate return line. 
           [0016]      FIG. 2  is a schematic representation of an electrical power generator having neither a conduit nor a return line. 
           [0017]      FIG. 3  is a schematic representation of an electrical power generator having a conduit connecting each of the water vapor generator, the hydrogen gas generator and the fuel cell, and also having a pump, a tensile membrane within the water vapor generator and a thermal insulator around the fuel cell. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    An electrical power generator is provided which generates hydrogen gas through controlled reactions of water vapor with a substantially non-fluid substance, which hydrogen gas is then used to fuel a fuel cell. The electrical energy generated may be used to power miniature devices such as cellular phones or other hand held electronic devices, and ultimately may be suitable for use in larger scale systems such as fuel driven equipment and automobiles. 
         [0019]    A seen in  FIGS. 1-3 , the electrical power generator  10  broadly comprises at least one water vapor generator  12 , at least one hydrogen gas generator  14  attached to the water vapor generator  12  and a fuel cell  16  attached to the hydrogen gas generator  14 . The water vapor generator  12  is preferably a chamber that is at least partially filled with water in the form of either water vapor, liquid water or ice. The quantity of either liquid water or ice may vary and generally depends on the size of the water vapor generating chamber  12  and the application for which the power generator  10  is used. Should any liquid water be present within the water vapor generator  12 , the liquid water may be prevented from seeping out of the water vapor generator  12  by either porous plugs  24  or by a valve  26 . Porous plugs  24  comprise a porous material such as cotton or a polymeric fabric, which acts as a barrier to liquid water while allowing the passage of water vapor into and out of the water vapor generator  12 . 
         [0020]    Alternately, valve  26 , may regulate the passage of water vapor out of the water vapor generator  12  and prevent the seeping out of any liquid water. This embodiment is shown in  FIG. 2 . The valve  26  may be either a manually or electrically controlled valve. If the valve is controlled electrically, the initial power necessary to open the valve, causing an initial flow of water vapor from the water vapor generator  12  to the hydrogen gas generator  14 , is preferably supplied by power stored in a device  30 . The valve  26  may be directly electrically connected to the device  30  or to the fuel cell  16 , with the fuel cell then being electrically connected to the device  30 . The device  30  may alternately be attached to either the water vapor generator  12 , the hydrogen gas generator  14  or another element of the power generator  10 . Once the valve  26  is initially opened to allow water vapor out of the water vapor generator  12 , the power generated from the fuel cell  16  is then preferably used to supply the power for controlling the valve  26 . In the preferred embodiment of the invention, the device  30  comprises a battery. The opening and closing of the valve  26  is preferably controlled externally depending on when it s desired to generate hydrogen gas and fuel the fuel cell. 
         [0021]    In another embodiment, the power generator  10  is initially loaded with hydrogen gas within at least one of said water vapor generator  12 , hydrogen gas generator  14 , fuel cell  16  and said optional conduits  18  or return line  20 . This initial loading of hydrogen gas will travel to the fuel cell  16 , causing a reaction with oxygen gas within the fuel cell, and generating electricity. This electricity is then used to power the valve  26 . While valve  26  is only depicted in  FIG. 2 , it is intended that any embodiment of the present invention may include at least one valve  26 . 
         [0022]    The dimensions of the water vapor generator  12  are preferably very small in scale, but may also vary with respect to the use of the power generator  10 . In preferred small scale embodiments, the water vapor generator  12  is preferably from about 0.1 cm to about 1.0 cm in height, from about 0.1 cm to about 1.0 cm in width and from about 0.1 cm to about 1.0 cm in length. As seen in  FIG. 3 , optionally within the water vapor generator is a tensile membrane  32 . The tensile membrane  32  acts to exert pressure on water vapor within the water vapor generator  12  forcing the water vapor out of the water vapor generator  12  and toward the hydrogen gas generator  14 . The pressure within the water vapor generator  12  is preferably maintained at a pressure of slightly more than atmospheric pressure. Attached to the water vapor generator  12  is a hydrogen gas generator  14 . The hydrogen gas generator  14  is preferably in the form of a chamber and is at least partially filled with a substantially non-fluid substance which reacts with water vapor to generate hydrogen gas. Alternately, the hydrogen gas generator  14  may be an open area adjacent to the water vapor generator  12  suitable for retaining the non-fluid substance. Similar to the water vapor generator  12 , the dimensions of the hydrogen gas generator  14  will vary depending on the proposed use of the power generator  10 . When the hydrogen gas generator  14  comprises a chamber in a small scale application, it is preferably from about 0.1 cm to about 1.0 cm in height, from about 0.1 cm to about 1.0 cm in width and from about 0.1 cm to about 1.0 cm in length. 
         [0023]    The substantially non-fluid substance within the hydrogen gas generator  14  preferably comprises a material in powder, granule or pellet form and is preferably an alkali metal, calcium hydride, lithium hydride, lithium aluminum hydride, sodium borohydride and combinations thereof. Suitable alkali metals non-exclusively include lithium, sodium and potassium. The preferred material for the non-fluid substance is sodium borohydride. The non-fluid substance is also preferably combined with a hydrogen generation catalyst to catalyze the reaction of the water vapor and the non-fluid substance. Suitable catalysts include non-exclusively include cobalt, nickel, ruthenium, magnesium and alloys and combinations thereof. 
         [0024]    Attached to the hydrogen gas generator  14  is a fuel cell  16 . Hydrogen powered fuel cells are well known in the art. The dimensions of the fuel cell  16  also depend on the intended use of the power generator  10 . In small scale applications, the fuel cell is preferably from about 0.1 cm to about 1.0 cm in height, from about 0.1 cm to about 1.0 cm in width and from about 0.1 cm to about 1.0 cm in length. As seen in  FIG. 3 , it is preferred that the fuel cell  16  is at least partially surrounded by a thermal insulator  28 . The thermal insulator  28  may comprise anything suitable to maintain the fuel cell above the freezing temperature of water. Suitable thermal insulators non-exclusively include insulators comprising a plastic foam. In addition to the thermal insulator, a heater  34  may be placed adjacent to or attached to the fuel cell  16  to maintain the temperature of the fuel cell and power generator  10  above the freezing temperature of water. In the preferred embodiment of the invention, the power generator  10  will be maintained at a temperature of from about −20° C. to about 50° C., more preferably from about 0° C. to about 50° C. and most preferably from about 20° C. to about 50° C. while in use. 
         [0025]    As seen in  FIGS. 1 and 3 , the water vapor generator  12  is preferably connected to the hydrogen generator  14  via at least one conduit  18 , and the hydrogen generator  14  is preferably connected to the fuel cell  16  via at least one conduit  18 . The conduits  18  may comprise anything sufficient to facilitate the transport of water vapor from the water vapor generator  12  to the hydrogen generator  14  and hydrogen gas from the hydrogen generator  14  to the fuel cell  16 . As seen in  FIG. 1 , in the preferred embodiment of the invention, the power generator  10  also includes a return line  20  that directs any residual water vapor and hydrogen gas from the fuel cell  16  back to the water vapor generator  12 . The return line  20  is preferably substantially identical to conduits  18 . As shown in  FIG. 2 , neither the conduits  18  nor the return line  20  are necessary elements for the efficient performance of the invention. In this embodiment, the water vapor generator  12  may be directly attached to the hydrogen gas generator  14  and the fuel cell  16  directly attached to the hydrogen gas generator  14 . 
         [0026]    It is further preferred that at least one pump  22  is coupled with the power generator  10  to pump hydrogen gas and water vapor between the water vapor generator  12  and the hydrogen gas generator  14 . The pump  22  is preferably electrically connected to and powered by the fuel cell  16 , with the pump optionally being powered initially by power stored in device  30 . It is also preferred that an inert gas is initially present within the water vapor generator  12 , hydrogen gas generator  14 , fuel cell  16  and in the optional conduits  18  and optional return line  20 . The inert gas assists in transporting water vapor and hydrogen gas to the fuel cell  16  and is preferably a gas selected from the group consisting of nitrogen, argon, combinations thereof and the like. 
         [0027]    In use, the water vapor generator  12  may generate water vapor in a variety of ways, such as by evaporation of liquid water from the water vapor generator  12 , by diffusion of water molecules into the air, by bubbling gas through the water, or by passing gas over the surface of the liquid water or the ice if present or over surfaces wetted by the water. Once the water vapor is generated it is directed from the water vapor generator  12  toward the hydrogen gas generator  16  either via diffusion, via pressure exerted by tensile membrane  32 , via a force generated by pump  22 , by a flow induced as water vapor is consumed in the hydrogen generator, or by flow induced as hydrogen is consumed by the fuel cell. The water vapor then passes through either the porous plugs  24  or open valve  26 , preferably into conduit  18  and then to the hydrogen gas generator  14  which is at least partially filled with the substantially non-fluid substance. Once the water vapor passes into the hydrogen gas generator  16 , the substantially non-fluid substance reacts with the water vapor, consuming water vapor to generate hydrogen gas. The hydrogen gas and any residual water vapor is then directed from the hydrogen gas generator  14  to the fuel cell  1 , preferably via another conduit  18 . Once the hydrogen gas reaches the fuel cell, the hydrogen gas is reacted with oxygen gas within the fuel cell, consuming the hydrogen gas to generate electricity. Subsequently, any residual water vapor and any residual hydrogen gas are transported from the fuel cell  16  back to the water vapor generator  12 , preferably via a return line  20 . 
         [0028]    While the present invention has been particularly shown and described with reference to preferred embodiments, it will be readily appreciated by those of ordinary skill in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. It is intended that the claims be interpreted to cover the disclosed embodiment, those alternatives which have been discussed above and all equivalents thereto.