Abstract:
A method and apparatus for a natural gas filling station comprising a dispenser; a structure covering the dispenser and having a canopy top; at least one tank disposed on the canopy top, the tank having at least one gas therein comprising CNG or LNG; and at least one line between the tank and the dispenser for communicating the gas between the tank and the dispenser.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Field of the Invention 
         [0002]    U.S. natural gas production is increasing and the price of natural gas is currently lower than the price of gasoline or diesel fuel, leading to increasing interest in natural gas-based fuels for vehicles. The most common type of natural gas vehicle operates on compressed natural gas (CNG), but there is also an interest in liquefied natural gas (LNG) as a vehicle fuel, especially for commercial trucks because LNG, which is natural gas super-cooled to its liquid form, has a much higher energy density than CNG. Hydrogen is also emerging as an alternative fuel for vehicles and can be stored and provided in liquefied or gaseous form. In the case of compressed hydrogen (CH) the gas is kept under pressures to increase its storage density. For hydrogen to be in a fully liquid/cryogenic state (LH) without boiling at atmospheric pressure, it is cooled to −423° F. 
         [0003]    Description of the Related Art 
         [0004]    At CNG refueling stations, the natural gas is typically taken from the local gas utility&#39;s line at low pressure, compressed to around 3,600 pounds per square inch gauge (“psig”), and then stored in a vehicle&#39;s storage tanks at high pressure. For example, at a “fast-fill” CNG station, the combination of a relatively large compressor coupled with a high-pressure storage tank system fills the vehicle&#39;s storage tanks in about the same amount of time it takes to fuel a comparable petroleum vehicle. A typical fast-fill CNG station is shown in  FIG. 1 . Some of the major components of the fast-fill CNG station include an inlet gas line  10  (from a utility company); a dryer  15  to reduce the moisture content of the natural gas; and a natural gas compressor  20 . One example of a natural gas compressor  20  is an Ingersoll Rand compressor package, which includes a compressor, an electric motor, a motor starter, a cooler, and controls. The compressor package will increase the pressure of the natural gas in the inlet gas line  10  from about 5 pounds per square inch gauge (“psig”) up to about 5,000 psig. At least one storage vessel  25  is capable of holding natural gas at about 5,000 psig and supplying the natural gas to a gas dispenser  30  for dispensing to a vehicle&#39;s storage tanks. In the case of HG, the hydrogen is compressed from X bar to X bar and can then be pumped or delivered to a tank at the refueling station. 
         [0005]    LNG (or LH) stations are structurally similar to gasoline/diesel stations, because they both deliver a liquid fuel.  FIG. 2  illustrates some typical components of an LNG station, including a storage tank  50 , a pump  55  for transmitting the liquid fuel from the storage tank  50 , some type of a card reader  60  for charging a customer for the liquid fuel, and a dispenser  65  to carry the liquid fuel to a vehicle  70 . In the mobile fueling arrangement shown in  FIG. 2 , LNG is delivered by a tanker truck that contains metering and dispensing equipment onboard to fill the storage tank  50 . In the case of LH, the cooled gas is likewise delivered to a storage tank at the refueling station. 
         [0006]    In addition to expenses related to construction ($1 to $4 million, according to the Energy Information Administration), a fueling site like the ones shown in  FIGS. 1 and 2  require at least one storage tank as well as pumps/compressors. For this reason, there is interest in converting gasoline/diesel stations to those that can supply CNG/LNG. Current attempts to retro-fit existing stations have envisioned setting aside surface area for the tanks, compressors, pumps, and related equipment or even excavating the gasoline/diesel tanks and replacing them with tanks suitable for natural gas. These solutions are expensive and create a substantial change of the footprint of the filling station. 
         [0007]    There is a need, therefore, for a simple and efficient arrangement to convert or retro-fit a gasoline/diesel station into one that can also provide CNG and/or LNG, hydrogen or any other alternative fuel that would typically require a retro-fit. 
       SUMMARY OF THE INVENTION 
       [0008]    Embodiments of the invention generally relate to a natural gas filling station, comprising a dispenser; a structure covering the dispenser and having a canopy top; at least one tank disposed on the canopy top, the tank having at least one gas therein comprising CNG, LNG, CH, or LH; and at least one line between the tank and the dispenser to communicate the gas between the tank and the dispenser. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    So that the manner in which the above recited features of the invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0010]      FIG. 1  is a drawing of a prior art CNG filling station. 
           [0011]      FIG. 2  is a drawing of a prior art LNG filling station. 
           [0012]      FIG. 3  is a perspective view of a filling station that is constructed or retro-fit to provide CNG/LNG in addition to gasoline and diesel fuel, according to one aspect of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]      FIG. 3  is a perspective view of a filling station  100  that is constructed or retro-fit to provide CNG and/or LNG in addition to conventional fuels, such as gasoline and diesel fuel. While the Figure illustrates aspects of the invention involving CNG and LNG, it will be understood that the arrangement is equally effective for other liquefied or compressed gases, like CH, or LH. Like a typical filling station, the retro-fit filling station  100  includes one or more islands  101  having one or more dispensers  102 ,  105  provided thereon. In the embodiment shown, the dispensers  102  are constructed and arranged to provide CNG and/or LNG, while the other dispensers  105  provide conventional fuels, such as gasoline and diesel. Also, like conventional filling stations, the filling station  100  in  FIG. 3  includes a canopy  120  (or other similar type of support structure) to cover the dispensers  102 ,  105  and the vehicles being re-fueled using the dispensers  102 ,  105 . 
         [0014]    In the embodiment shown, the upper surface of the canopy  120  (e.g., the top of the canopy  120 ) is used to hold one or more tanks  125  containing CNG and/or LNG, and to hold one or more lines  127  that are available to and from the tanks  125  for receiving fuel (e.g., CNG and/or LNG) and for dispensing the fuel to the dispensers  102  and thus to vehicles underneath. In each retro-fit case, the canopy  120  can be reinforced as needed to safely bear the weight of the tanks  125  and their contents. In the case of CNG or CH, the load added to the canopy  120  is essentially limited to the weight of the tanks  125  themselves as a cubic meter of natural gas weighs only 0.714 kilograms. In the case of either CH or LH, relatively low energy content by volume necessitates relatively large tanks. For example, LH storage vessels are nominally 1,500-, 4,500-, 9,000-, and 20,000-gallon tanks. 
         [0015]    At an end of the canopy  120  is a superstructure  130  housing one or more compressors  135  related to CNG as described above in relation to  FIG. 1 . In addition to the compressors  135 , the upper surface of the canopy  120  and the superstructure  130  can hold a variety of equipment related to natural gas fuel including supply tanks and/or accumulators upstream of the compressors, as well as pumps, filters, dryers, etc. In one embodiment, one or more pumps  137  are disposed on the upper surface of the canopy  120  and constructed and arranged to pump LNG into one or more of the tanks  125  via one or more lines  139 . In this manner, no additional “real estate” is necessary for a conversion of a conventional gas/diesel filling station to one configured to supply natural gas. 
         [0016]    In the case of CNG, a line  126  runs from a utility line for supplying natural gas at a low pressure to the compressors  135  in the superstructure  130 , which compress the natural gas to a higher pressure, and another line  127  runs from the compressors  135  to one or more of the tanks  125  for storing and holding the compressed natural gas. In the case of LNG (or LH), the liquid fuel is typically delivered by truck and pumped into the tanks  125  provided for that fuel, via the pumps  137  and lines  139  for example. One or more flow control devices, such as valves, chokes, etc., as known in the art can be coupled to the lines  126 ,  137 ,  139  to control the flow of the gas, CNG, and/or LNG to and from the compressors  135 , the pumps  137 , the tanks  125 , and/or the dispensers  102  as needed. 
         [0017]    There are a number of advantages to designs like the one shown in  FIG. 3 . First, inherent problems associated with placing the tanks  125  on or below ground are avoided. For example, CNG or CH tanks, because they are filled with a gas, have necessarily been mounted at ground level because high floatation of the tanks requires substantial anchoring to prevent flotation when the tanks are buried in the ground. LNG or LH tanks can be more easily buried but in any case the ground must be excavated to hold the tanks that are necessarily well insulated and made from a material which can withstand the extreme cold (−260° F. for LNG and −423° F. for LH) of the liquefied natural gas they are holding. The placement of equipment on the top or upper surface of the canopy  120  is also an improvement from a safety standpoint as it removes the tanks from the already crowded area and confined space around a typical filling station, such as filling station  100 . Additionally, where the natural gas is lighter than air, putting the tanks  125  on the upper surface of the canopy  120  improves safety in the event of a leak occurring. Specifically, the natural gas will leak into the atmosphere at a location high above and away from individuals and vehicles at the filling station  100 , whereas if the tanks  125  were on or below ground, then individuals and vehicles are at risk of being directly exposed to the natural gas leak. The arrangement also increases efficiency as it permits the compressors  135  and tanks  125  to be closer to the dispensers  102  and the fueling point, thereby facilitating a quick-fill application. 
         [0018]    In addition to space savings and the avoidance of buried tanks, the infrastructure expense is greatly reduced on conversions of existing stations by not running the high pressure piping underground from the compressors  135  to the dispensers  102 . In the embodiment described and shown in  FIG. 3 , the piping (e.g., the lines  127 ) runs along the upper surface of the canopy  120  and down an existing upright. Finally, as stated above, because natural gas is lighter than air, having it above the fueling zone results in a safer design. 
         [0019]    In one embodiment, LH is delivered to a refueling station and pumped to an elevated tank as shown in the figures. Thereafter, the LH is converted to a gaseous state at around 5000 psi, possibly through the use of a vaporizer, and then delivered to a vehicle as CH. A typical installation normally consists of a tank, a vaporizer, and controls. While steam and electric vaporizers are occasionally used, the most widely employed vaporizers obtain heat from the surrounding air. These “ambient air” vaporizers are provided in arrays of many-finned tubes to provide vaporization. In some instances, vehicles are equipped with their own means for converting LH to CH, and in those instances, liquid hydrogen is pumped directly into the vehicle&#39;s tank. 
         [0020]    While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. For example, the embodiment shown and described presumes a retro-fit arrangement that provides alternative fuels, e.g., CH and/or LH, as well as conventional fuel. However, the design can be just as easily utilized in a new station, and the invention is not limited to one where different fuel types are available. Additionally, the essence of the invention is elevating equipment related to fuel at a filling station, and the principles of the invention are usable in any number of ways and are not strictly limited to the elevation of equipment by utilizing a canopy top.