Abstract:
Use of a hydrogen-sensitive coating as a hydrogen detector is disclosed. The invention includes providing a hydrogen-sensitive coating on a surface to detect the presence of hydrogen in the vicinity of the surface. A fuel cell system having a hydrogen-sensitive coating is also disclosed.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to hydrogen detectors. More particularly, the present invention relates to the use of hydrogen-sensitive surface coatings to detect hydrogen in the vicinity of a vehicular fuel cell, hydrogen-fueled internal combustion engine or other system.  
       BACKGROUND OF THE INVENTION  
       [0002]     Fuel cell technology potentially provides clean and efficient energy for stationary and traction applications. A functioning fuel cell, as any other electrochemical device, requires a series of components that provide the key functions of reactant distribution (mass transport), catalytic reactivity, ionic separation, and current collection. A typical fuel cell system includes a fuel cell stack which includes multiple fuel cells arranged in a stacked configuration for the generation of electrical power. A hydrogen distribution line connects a hydrogen storage tank to the fuel cell stack. At least one regulator is typically provided in the hydrogen distribution line for controlling the distribution of gaseous hydrogen from the hydrogen storage tank to the fuel cell stack.  
         [0003]     Presently, the state of the art for hydrogen detection control in fuel cell and other systems falls into two categories: (1) active hydrogen sensors and (2) reliance on the structural integrity of the system. Active hydrogen sensors function only when DC power is applied and may lose sensitivity over time. Generally, the fluid integrity a hydrogen gas distribution system is checked after initial installation by running helium through the system.  
         [0004]     A passive hydrogen detection system which includes the use of a hydrogen-sensitive coating is needed for fuel cell and other systems.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention is generally directed to use of a hydrogen-sensitive coating as a hydrogen detector. According to the invention, a hydrogen-sensitive coating is provided on a surface to detect the presence of hydrogen in the vicinity of the surface. The present invention is further directed to a fuel cell system having a hydrogen-sensitive coating. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     The invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0007]      FIG. 1  is a schematic view of an illustrative fuel cell system in implementation of the present invention;  
         [0008]      FIG. 2  is a sectional view of a hydrogen storage tank, a line fitting extending from the tank and a hydrogen distribution line connected to the line fitting, with a hydrogen-sensitive coating provided on the tank, the line fitting and the hydrogen distribution line in implementation of the present invention;  
         [0009]      FIG. 3  is a sectional view of a regulator provided in the hydrogen distribution line, with a hydrogen-sensitive coating provided on the regulator housing, line fittings and hydrogen distribution line in implementation of the present invention;  
         [0010]      FIG. 4  is a sectional view of a portion of a fuel cell stack of the fuel cell system, with a hydrogen-sensitive coating provided on the hydrogen distribution line, hydrogen inlet fitting and wall of the fuel cell stack in implementation of the present invention;  
         [0011]      FIG. 4A  is a cross-sectional view of a surface, illustrating a hydrogen-sensitive coating embedded in the surface according to an alternative implementation of the invention; and  
         [0012]      FIG. 5  is a top view of a section of a hydrogen distribution line, with a hydrogen-sensitive coating provided on the hydrogen distribution line, more particularly illustrating a bright-colored region of the hydrogen-sensitive coating compared to the surrounding regions of the coating as indicative of the presence of hydrogen gas.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]     The present invention is generally directed to the use of a hydrogen-sensitive coating as a hydrogen detector in a fuel cell system. However, it is to be understood that the invention is not to be limited to use in fuel cell systems but is intended to include use in any system, application or industry in which hydrogen is stored, transported and otherwise used.  
         [0014]     Referring to the drawings, an illustrative fuel cell system in implementation of the present invention is generally indicated by reference numeral  10  in  FIG. 1 . In accordance with the present invention, various components of the fuel cell system  10  are coated with a hydrogen-sensitive coating  32 , as shown in  FIGS. 2-4  and will be hereinafter further described. Generally, the fuel cell system  10  includes a fuel cell stack  12  which is connected to a hydrogen storage tank  20  through a hydrogen distribution line  16 . The fuel cell stack  12  includes a fuel cell enclosure  13  which includes an interior surface  13   a  and an exterior surface  13   b , as shown in  FIG. 4 . Multiple fuel cells (not shown), which are electrically connected to each other in a stacked configuration, are contained inside the fuel cell enclosure  13 .  
         [0015]     A hydrogen inlet fitting  14  is provided on the fuel cell enclosure  13  to facilitate attachment of the hydrogen distribution line  16  to the fuel cell stack  12 . An oxidant gas inlet  34  is further provided on the fuel cell enclosure  13  to facilitate attachment of an oxidant gas distribution line  36  to the fuel cell stack  12 . At least one regulator  18  is typically provided in the hydrogen distribution line  16  to regulate the flow of hydrogen gas  38  from the hydrogen storage tank  20 , through the hydrogen distribution line  16  and to the fuel cell stack  12 . As shown in  FIG. 3 , the regulator  18  typically includes a regulator housing  19  which contains the functional regulator elements (not shown) of the regulator  18 . The regulator housing  19  includes an interior surface  19   a  and an exterior surface  19   b . A pair of line fittings  18   a  may extend from opposite ends of the regulator housing  19  and each receives a corresponding segment of the hydrogen distribution line  16 .  
         [0016]     As shown in  FIG. 2 , the hydrogen storage tank  20  typically includes a tank wall  22  which has an exterior surface  23  and an interior surface  24  and encloses a tank interior  26 . A line fitting  28  extends from the tank wall  22  and is connected to the hydrogen distribution line  16 . Accordingly, in operation of the fuel cell system  10 , hydrogen gas  38  is distributed from the hydrogen storage tank  20  through the line fitting  28 , the hydrogen distribution line  16 , the regulator or regulators  18  and the hydrogen inlet fitting  14  and into the fuel cell stack  12 , respectively.  
         [0017]     According to the present invention, a hydrogen-sensitive coating  32  is applied to the exterior surfaces of various components of the fuel cell system  10 . These may include, for example, the exterior surface  23  of the hydrogen storage tank  20  and/or the exterior surfaces of the line fitting  28 ; the hydrogen distribution line  16 ; the regulator and/or regulators  18 ; the hydrogen inlet fitting  14 ; and/or the fuel cell enclosure  13 , respectively. The hydrogen-sensitive coating  32  may be any type of pressure-sensitive coating or material which is known to those skilled in the art and utilizes luminescence to indicate static pressure on a surface. The pressure-sensitive coating indicates differences in atmospheric pressure on the surface by indicating a slight change in color in areas subjected to a high partial pressure of oxygen relative to the color of the coating on the adjacent areas subjected to low partial pressures of oxygen. The intensity of the color is proportional to the magnitude of the partial pressure of oxygen applied to the coating. In the event hydrogen is present, the hydrogen displaces the oxygen and changes the luminosity of the coating. The invention is also applicable to hydrogen-sensitive coatings which indicate a change upon reacting chemically with hydrogen.  
         [0018]     An example of a pressure-sensitive material which is suitable for carrying out the present invention is a pressure-sensitive paint (PSP) such as ISSI UNICOAT (trademark) available from ISSI (Innovative Scientific Solutions, Inc). However, it is to be understood that the invention may be carried out using any type of pressure-sensitive paint or other pressure-sensitive coating or material which is suitable for sensing the presence of hydrogen typically by increased hydrogen gas pressure. Preferably, the pressure-sensitive coating is of the type in which variations in brightness, intensity or darkness which are observed by the naked eye represent corresponding variations in gas pressure on the coating, with the brighter, more intense or darker areas representing the areas of higher hydrogen pressure than the surrounding areas. It has been found that PSP, when sealed in a Pyrex® flask, maintains a dull, flat grayish tone, when viewed through a color filter, during exposure to ambient air but changes to a bright orange hue upon exposure to hydrogen. Therefore, when PSP is used to coat a surface, the region or regions of hydrogen presence would be indicated by the presence of a bright orange spot or spots on the otherwise gray PSP when viewed through a color filter. However, the invention is also applicable to hydrogen-sensitive coatings which change color or intensity without the necessity of being viewed through a color filter.  
         [0019]     As shown in  FIG. 2 , according to the present invention, the hydrogen-sensitive coating  32  may be coated on the exterior surface  23  of the tank wall  22 , the line fitting  28 , and/or the hydrogen distribution line  16 . As shown in  FIG. 3 , the hydrogen-sensitive coating  32  may additionally or alternatively be coated on the exterior surface  19   b  of the regulator housing  19  and/or the line fittings  18   a  of the regulator housing  19 . As shown in  FIG. 4 , the hydrogen-sensitive coating  32  may additionally or alternatively be applied to the exterior surface  13   b  and/or the hydrogen inlet fitting  14  of the fuel cell enclosure  13 . Preferably, however, the hydrogen-sensitive coating  32  is coated as a continuous layer on the exterior surface  23  and line fitting  28  of the hydrogen storage tank  20 ; the hydrogen distribution line  16 ; the line fittings  18   a  and exterior surface  19   b  of the regulator housing  19 ; and the hydrogen inlet fitting  14  and the exterior surface  13   b  of the fuel cell enclosure  13 .  
         [0020]     As shown in  FIG. 5 , in the event that hydrogen gas pressures from the hydrogen distribution line  16  are not normal, for example, during operation of the fuel cell system  10 , the hydrogen sensitive coating  32  indicates the location of the hydrogen by the presence of a bright or dark region  33 , at a point where the hydrogen is present, relative to the surrounding regions of the hydrogen-sensitive coating  32 . In like manner, the hydrogen-sensitive coating  32  indicates the presence of hydrogen from the fuel cell system  10  at the tank wall  22 , the line fitting  28 , the regulator housing  19 , the line fitting  18   a , the hydrogen inlet fitting  14  and/or the fuel cell enclosure  13 .  
         [0021]     An alternative application of the invention is shown in  FIG. 4A , in which the hydrogen-sensitive coating  32 , rather than being applied to an exterior surface, as was heretofore described with respect to  FIGS. 2-4 , is embedded in a surface  40 . The surface  40  may be, for example, the exterior surface  23  of the tank wall  22  of the hydrogen storage tank  20 ; the exterior surface of the line fitting  28 ; the exterior surface of the hydrogen distribution line  16 ; the exterior surface of the regulator housing  19 ; the exterior surface of the hydrogen inlet fitting  14 ; and/or the exterior surface  13   b  of the fuel cell enclosure  13  of the fuel cell system  10  which was heretofore described with respect to  FIGS. 1-4 . Alternatively, the surface  40  may be on a component in any system, application or industry in which hydrogen is stored, transported or otherwise used. Accordingly, the embedded hydrogen-sensitive coating  32  is suitable for detecting the presence of hydrogen in and/or around the surface  40  typically in the manner which was heretofore described with respect to  FIG. 5 .  
         [0022]     Referring next to  FIGS. 6 and 7 , in many fuel cell applications, the hydrogen storage tank  20  is contained inside a hydrogen storage tank box  44  for aesthetic purposes to normally conceal the hydrogen storage tank  20  from view. The hydrogen storage tank box  44  includes a box wall  45  which defines a box interior  46 . As shown in  FIG. 7 , a hydrogen-sensitive coating  32  is provided on at least one interior surface of the box wall  45 . Therefore, in the event of the presence of hydrogen in the hydrogen storage tank  20 , the hydrogen-sensitive coating  32  indicates the presence of hydrogen in the box interior  46  of the hydrogen storage tank box  44  when the hydrogen storage tank box  44  is opened.  
         [0023]     While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications can be made in the invention and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.