Patent Publication Number: US-2007099049-A1

Title: Subterranean fuel cell system

Description:
RELATED APPLICATION  
      This application claims priority under 35 U.S.C. §119 (e) to U.S. Provisional Patent Application No. 60/730,900, filed on Oct. 27, 2005. The entire disclosure of this provisional application is hereby incorporated by reference. 
    
    
     GENERAL FIELD  
      A subterranean fuel cell system comprising a fuel cell stack, a fuel storage container, balance-of-plants components, and fluid circuitry for supplying, exhausting, and/or circulating fluids.  
     BACKGROUND  
      A fuel cell system can comprise a fuel cell stack, a fuel storage container, and balance-of-plants components (pumps, humidifiers, filters, valves, pressure regulators, flow meters, etc.). An anode fluid circuit forms a flow path for anode gas (e.g., hydrogen) through the fuel cell stack and a cathode fluid circuit forms a flow path for cathode gas (e.g., air) through the fuel cell stack. A fuel cell system can be used to provide electrical power when central power plant electrical power is not available. For example, a fuel cell system can be used as backup power for traffic signal lights and/or railroad gates so that they will remain operational when conventional power is discontinued due to outages and/or transmission problems.  
     SUMMARY  
      A fuel cell system is provided that can be positioned within a subterranean well. The system can be constructed to be compact and self-contained, with minimal above-ground hoses, pipes, tubing and/or other plumbing. In this manner, the fuel cell system can be stored in a tamper-prohibiting location, will not occupy a large above-the-ground footprint and, for the most part, can be hidden from view. The ground can function as a heat sink for absorbing system heat and, if the relevant components are positioned below the frost line, an insulator for preventing freezing of reactant and/or cooling water. These and other features of the fuel cell system are fully described and particularly pointed out in the claims. The following description and annexed drawings set forth in detail certain illustrative embodiments, these embodiments being indicative of but a few of the various ways in which the principles may be employed. 
    
    
     DRAWINGS  
       FIG. 1  is a schematic drawing of a fuel cell system positioned within a subterranean well.  
       FIG. 2  is flow circuit showing the passage of cathode air through the fuel cell system.  
       FIG. 3  is a flow circuit showing the passage of hydrogen-containing fuel through the fuel cell system.  
       FIG. 4  is a flow circuit showing the passage of cooling fluids through the fuel cell system. 
    
    
     DETAILED DESCRIPTION  
      Referring now to the drawings, and initially to  FIG. 1 , a fuel cell system  10  for positioning within a subterranean well W is shown. The well W can be cylindrical hole dug with readily available augers and preferably has a depth extending below the frost line F. This underground situating of fuel cell system  10  inhibits tampering efforts and does not monopolize above-the-ground space. Also, in many situations, fuel cell system  10  will be hidden from view and not noticed by casual observers. And, as is explained in more detail below, the ground can act both as a sink for absorbing system heat and an insulator for preventing freezing of reactant and/or cooling water.  
      The fuel cell system  10  comprises a capsule  12 , a fuel cell stack  14 , a fuel storage container  16 , a balance-of-plants (BOP) assembly  18 , and an electronics panel (or box)  20 . The capsule  12  is shaped and sized for positioning within the well W. The fuel cell stack  14 , the fuel storage container  16 , the BOP assembly  18  and the electronics panel  20  are contained within the capsule  12 .  
      The fuel cell stack  14  can comprise a series of proton exchange membrane fuel cells and, if so, system operation can be start quickly. This fuel cell type might be preferred because there are no corrosive fluid hazards and/or the thinness of the membrane electrode assemblies can contribute positively to system compactness. In the illustrated embodiment, the cathode fluid comprises air drawn from the surrounding environment and the fuel for the system  10  can be pressurized hydrogen. The fuel storage tank  16  includes a fill port  22  for periodic refilling.  
      The system  10  further comprises fluid circuitry for supplying, exhausting, and/or circulating fluids. The fluid circuitry includes an air inlet pipe  24 , a heat-exchanger tube  26 , an air exhaust chimney pipe  28 , and a water-separating manifold  30 . The cathode fluid (air) enters the system  10  through the inlet pipe  24  and exits the system  10  through the exhaust pipe  28 , and both of these pipe cans project above ground level G outside of the capsule  12 . The remaining fluid circuitry can be contained within the capsule  12  and/or within the subterranean surrounding the capsule  12  whereby external hoses, fittings, and other fluid plumbing is almost nonexistent.  
      An electrical connection is provided at each end of the fuel cell stack so as to form a complete circuit (through a load) and an electrical cable  24  is routed from the load to an appropriate medium outside the capsule  12 .  
      The capsule  12  comprises a tubular wall  40 , a top wall  42  and a bottom wall  44  defining an interior space. This interior space comprises an upper compartment  46 , an intermediate compartment  48 , and a lower compartment  50 . The fuel fill port  22  can be situated in the upper compartment  46  and the air inlet pipe  24  and the electrical cable  34  can (but need not) extend through this compartment  46 . The top wall  42  has a lidded construction whereby it can be opened to gain access to the upper compartment  46  (and thus the fuel fill port  22 ). A lock or other security measure can be employed to avoid the risk of tampering by unauthorized personnel.  
      The fuel storage container  16  is situated in the intermediate compartment  48 . At least some portions of the intermediate compartment  48 , and thus, the container  16  can be positioned above the frost line F. The container  16  can advantageously have an annular (in cross-section) shape following the circumference of the capsule  12 . The air inlet pipe  24  and/or the electrical cable  34  can extend through the open central passage of the annular container  16 .  
      The fuel cell stack  14 , the BOP assembly  18 , and the electronics panel  20  are situated in the lower compartment  50  and, in the illustrated embodiment, below the frost line F. The fuel cell stack  14  can be positioned on one side of the compartment  50  and both the BOP assembly  18  and the electronics panel  20  can be positioned on the other side. The water-separating manifold  30  can be positioned beneath these components and define a water collection pocket  52  in the lowermost region of the compartment  50 .  
      The BOP assembly  18  can comprise a plurality of planar layers assembled in face-to-face contact and joined together in a fluid tight manner. The layers can integrate fluid-conveying channels and/or fluid-interacting devices (pumps, humidifiers, filters, valves, pressure regulators, flow meters, etc.) to form the BOP fluid circuitry for the fuel cell system  10 .  
      In  FIG. 2 , the cathode air flow circuit is schematically shown. The BOP assembly  18  can include a filter  60 , a compressor  62 , and a humidifier  64 . Air is drawn by the compressor  62  through the inlet pipe  24  and through the filter  60 . The air discharged from the compressor  62  flows through the humidifier  64  and to the fuel cell stack  14 . In the fuel cell stack  14 , the anode/cathode reaction results in water being produced, this water being in a vapor state due elevated reaction temperatures. This water vapor (along with the pre-reaction humidity carried by the cathode and anode fluids) flows with the air in the cathode exhaust.  
      The exhaust air from the fuel cell stack  14  (and accumulated water vapor) passes to the heat-exchanger tube  26 . The tube  26  is coiled around the lower region of the capsule  12  with the surrounding ground serving as a heat sink to cool the air/vapor mixture. The cooled air then flows through water-separation manifold  30  on route to the chimney pipe  28  whereat it is exhausted to the environment. When passing through the water-separation manifold  30 , liquid water drops will fall into the collection pocket  52 . The collected water can be used to supply system humidifiers (e.g., cathode humidifier  64  introduced above and/or anode humidifier  70  introduced below). An emergency drain for the pocket  52  and/or a back-up water supply can also be incorporated into the system  10 .  
      In  FIG. 3 , the anode flow circuit is schematically shown. The hydrogen fuel is conveyed from the container  16 , through a humidifier  70  (in the BOP assembly  18 ) and to the fuel cell stack. The pressure of the fuel will typically be reduced upon exiting the container  16  or shortly thereafter (e.g., within the BOP assembly  18 ). Any water within the fuel cell (e.g., after operation ceases) will drain to the manifold  30  and then be collected in the pocket  52 .  
      In  FIG. 4 , the cooling fluid circuits are schematically shown. In the illustrated embodiment, a liquid (e.g., water) is used as the circulating medium and air is used to cool the water as it repeats the cycle through the fuel cell stack  14 . It may be noted that if the fuel cell stack  14  and the BOP assembly  18  are located below the frost line F, this will eliminate any risk of freezing, regardless of the season and/or weather conditions. The cooling air can (but does not have to) enter/exit the system  10  through the same passages as the cathode air, specifically air inlet pipe  24  and air exhaust pipe  28  in the illustrated embodiment. The cathode air and the cooling air can travel completely independent paths after entering and prior to exiting.  
      The cooling liquid can be circulated by a pump  80  through the fuel cell stack  14 , through a heat exchanger  82 , and then returned to a holding chamber  84  for repeat of the cycle. The cooling air is drawn through inlet pipe  24  by a compressor  86  and pushed through the heat exchanger  82  (wherein it absorbs heat from the circulating liquid) and then exits the system  10  through the exhaust pipe  28 . It may be noted that the air could itself be used to as the cooling medium if its heat-absorption qualities are sufficient in a particular fuel cell situation.  
      As was indicated above, the fuel cell stack  14  can comprise a series of proton exchange membrane fuel cells and the system  10  uses pressurized hydrogen gas as its anode fluid. However, other fuel-cell-system types (e.g., metal-to-air, solid oxide fuel, direct methanol, high temperature, etc.) and/or other fuels (e.g., liquid hydrogen, carbon monoxide, methanol, etc.) are possible and contemplated. Appropriate modifications to BOP components and the fluid circuitry may be necessary to accommodate fuel-cell-type and/or fuel changes, such as those involving the transport of fuel, the management of reaction water, leakage-sealing issues, and/or cooling cycles.  
      One may now appreciate that the subterranean fuel cell system  10  is tamper-prohibitive, compact, self-contained, space-saving, and can be adapted to have minimal above-ground hoses, pipes, tubing and/or other plumbing. Although the system has been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In regard to the various functions performed by the above described elements (e.g., components, assemblies, systems, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.