System and method for automatically providing fuel to a fuel cell in response to a power failure in a primary power system

The present invention provides, in one embodiment, a system for providing fuel to a backup electrical fuel cell. In this particular embodiment, the system includes a sealed fuel container having a pierceable membrane with a container seal associated therewith, an acerate tube proximate the pierceable membrane, and an actuator. The actuator is coupled to the acerate tube and automatically drives the acerate tube through the pierceable membrane to provide fluid communication from the fuel container to the fuel cell in response to a failure of a primary electrical power system. The container seal is configured to form a seal about the acerate tube when the acerate tube pierces the pierceable membrane to prevent unnecessary loss of fuel, such as methanol, from the container. In alternative embodiments, the system may also include the primary power system and a backup electrical fuel cell that is electrically coupled to the primary power system.

TECHNICAL FIELD OF THE INVENTION
 The present invention is directed, in general, to a system and method for
 providing fuel to a fuel cell and, more specifically, to a system and
 method for automatically providing fuel to a fuel cell in response to a
 power failure in a primary power system.
 BACKGROUND OF THE INVENTION
 In our complex society today, numerous systems rely upon electrical power
 to function properly. Under normal circumstances, operating power is
 provided by the commercial AC power distribution system for heat, air
 conditioning, traffic lights, cooking, telecommunications, etc. Since
 many, if not all, major power distribution lines are located on poles or
 towers, a natural disaster, such as a tornado, hurricane, or blizzard,
 frequently causes the loss of commercial AC power. The failure of
 commercial AC power may constitute a significant danger to life or
 property depending upon the system impacted. For instance, failure of AC
 power supplying the lighting or air conditioning in a hospital or nursing
 home could readily result in loss of life. Therefore, backup power systems
 have been developed to assure that the loss of primary power does not
 seriously affect critical systems.
 The one critical system most often taken for granted is the
 telecommunications system. Significantly, when an emergency occurs,
 virtually everyone expects that telephone communications will remain
 unaffected. Clearly, this is essential since it is through the telephone
 that we normally summon medical or rescue aid. Therefore, because of this
 essential nature, the telecommunications system has been provided with a
 complex backup power system in the event of commercial AC power failure.
 Traditionally, backup electricity for telecommunications has been achieved
 by dispersing batteries throughout the telecommunications system to power
 the necessary switches, amplifiers, etc., of the system. These batteries,
 amounting to millions worldwide, are located in special rooms, in
 enclosures atop telephone poles, or even atop mountains, depending upon
 the local system needs. These batteries may be in place for years before a
 power failure requires them. Naturally, these batteries employ a very well
 understood and proven technology. However, the batteries require physical
 maintenance from time to time, and generally require a charging circuit to
 maintain them at a sufficiently charged state to perform their intended
 function. The power fraction, that is the power developed per unit of
 weight, is typically very low for lead-acid batteries because the
 components are inherently extremely heavy. Additionally, the lead is very
 toxic and, when the batteries are no longer useable, must be properly
 recycled. In flooded cell batteries, the acid electrolyte is also a
 significant hazard to those who must service the batteries, or to anyone
 who comes in contact with them. The very nature of charging lead-acid
 batteries from the commercial power system causes gassing and consumes
 some of the water that is a part of the electrolyte solution, thereby
 necessitating service. In the case of valve-regulated lead-acid (VRLA)
 batteries, including many types of "maintenance free" batteries, the
 electrolyte may not be serviceable and the batteries are permanently
 degraded. Additionally, because battery life and capacity are dependent on
 ambient temperature, the state of the electrolyte chemistry, and the
 condition of the grids, it is difficult and expensive to predict the
 battery reserve power available at any given time. However, experience has
 shown that telecommunication grade VRLA batteries in non-extreme
 environmental conditions exhibit a useful life of about four to five
 years, regardless of the manufacturer's claims.
 One alternative to batteries as a backup power source might be a generator
 powered by a liquid fuel. Significantly, the power fraction for liquid
 fuels is many times higher than that of lead-acid batteries. Such power
 generators for both AC and SC power generation are quite common; most are
 gasoline engine driven. Gasoline however has several disadvantages for a
 backup power system that may not be needed for several years. Gasoline is
 actually a mixture of several chemical compounds, each with its own
 volatility. Over even a short period, the lighter (high volatility)
 compounds evaporate more quickly, leaving the heavier components behind.
 This fuel condition makes starting the engine more difficult; as the
 longer the fuel stands, or the warmer the ambient temperature is, more of
 the lighter compounds evaporate. Also over time, the more complex organic
 compounds may break down into simpler compounds that are not as readily
 useable as fuel. While many liquid fuels are highly volatile and evaporate
 readily, one liquid fuel that is significantly more stable than gasoline
 is methanol (CH.sub.3 OH). Among the organic compounds, methanol is one of
 the simplest compounds, and therefore does not break down into other
 components. Although methanol will readily evaporate if left open to the
 atmosphere, it will remain stable for an extended period of time if kept
 in a well-sealed container.
 As with any system, liquid fuels have some drawbacks. In some respects,
 they are more difficult to handle and store than the typical battery,
 simply because they are liquid. Measuring the fuel remaining involves
 measuring a liquid volume. Because the fuel quantity is analog in nature,
 there are no readily established decision points for accomplishing a
 refueling. Also, some type of a pumping capability must be provided to
 move the fuel to the generator.
 Accordingly, what is needed in the art is a backup power system that takes
 advantage of the high power fraction of liquid fuels, methanol in
 particular, while providing: (a) an ease of handling the fuel, (b)
 elimination of fuel evaporation, (c) long shelf life fuel storage, (d)
 controlled quality of the liquid fuel, and (e) an easy decision point for
 refueling.
 SUMMARY OF THE INVENTION
 To address the above-discussed deficiencies of the prior art, the present
 invention provides, in one embodiment, a system for providing fuel to a
 backup electrical fuel cell, such as a generator. In this particular
 embodiment, the system includes a sealed fuel container having a
 pierceable membrane with a container seal associated therewith, an acerate
 tube proximate the pierceable membrane, and an actuator. The actuator is
 coupled to the acerate tube and automatically drives the acerate tube
 through the pierceable membrane to provide fluid communication from the
 fuel container to the fuel cell in response to a failure of a primary
 electrical power system. The container seal is configured to form a seal
 about the acerate tube when the acerate tube pierces the pierceable
 membrane to prevent unnecessary loss of fuel, such as methanol, from the
 container. In alternative embodiments, the system may also include the
 primary power system and a backup electrical fuel cell that is
 electrically coupled to the primary power system. Thus, this particular
 embodiment, provides a system that automatically provides fuel to a fuel
 cell in response to a failure of a primary electrical power system. As a
 primary electrical power system, such as a telecommunications power
 system, fails the present system senses the failure and automatically
 delivers fuel to a fuel cell, such as a generator, so that it, in turn,
 can provide an alternate source of electricity until the primary
 electrical power system is fully restored. The present invention,
 therefore, eliminates the need for constant servicing and maintenance that
 is typically required of conventional back-up power systems, such as
 batteries.
 In one particular embodiment, the system further comprises a controller
 that determines when the actuator drives the acerate tube. The actuator
 may be a variety of mechanical or electrical devices such as an electrical
 controller, a mechanical controller, or an electromechanical controller.
 In another aspect, the system may further comprise a sensor that is
 electrically coupled to the controller and configured to sense a fuel
 level within the fuel container and transmit a fuel signal to the
 controller. In such instances, the controller causes the actuator to drive
 the acerate tube upon receiving the fuel level signal.
 In another embodiment the sealed fuel container may comprise a plurality of
 sealed fuel containers each having a pierceable membrane. In such
 embodiments, the system further comprises an acerate tube proximate each
 of the pierceable membranes. This particular embodiment includes an
 embodiment where only one acerate tube is present in the system that can
 be automatically positioned, when needed, proximate each of the pierceable
 membranes. In those embodiments wherein there is a plurality of acerate
 tubes, each of the acerate tubes has an actuator coupled thereto that
 automatically drives the acerate tube through the pierceable membrane to
 provide fluid communication from each of the fuel containers to the fuel
 cell in response to a failure of the primary electrical power system.
 Alternatively, however, in those embodiments where just one acerate tube
 is present, only one actuator may be required to insert the acerate tube
 through the pierceable membrane.
 In another aspect of this particular embodiment, the system may further
 comprise a controller that determines when each of the actuators drives
 each of the acerate tubes. In alternative embodiments, the system may
 include a plurality of such controllers. The system may further include a
 sensor, electrically coupled to the controller, that is configured to
 sense a fuel level within the fuel container and transmit a fuel level
 signal to the controller. Again, the controller causes one of the
 actuators to drive one of the acerate tubes upon receiving the fuel level
 signal. As in other embodiments described above, the actuator may be an
 electrical controller, a mechanical controller, or an electromechanical
 controller.
 The present invention also provides a method for providing fuel to a backup
 electrical fuel cell. An advantageous method includes automatically
 driving an acerate tube proximate a pierceable membrane of a sealed fuel
 container with an actuator coupled to the acerate tube, piercing the
 pierceable membrane with the acerate tube, forming a seal about the
 acerate tube with a container seal associated with the pierceable membrane
 when the acerate tube pierces the membrane, and providing fluid
 communication from the fuel container to the fuel cell in response to a
 failure of a primary electrical power system.
 The foregoing has outlined, rather broadly, preferred and alternative
 features of the present invention so that those skilled in the art may
 better understand the detailed description of the invention that follows.
 Additional features of the invention will be described hereinafter that
 form the subject of the claims of the invention. Those skilled in the art
 should appreciate that they can readily use the disclosed conception and
 specific embodiment as a basis for designing or modifying other structures
 for carrying out the same purposes of the present invention. Those skilled
 in the art should also realize that such equivalent constructions do not
 depart from the spirit and scope of the invention in its broadest form.

DETAILED DESCRIPTION
 Referring initially to FIG. 1, illustrated is an isometric view of one
 embodiment of a liquid fuel storage and delivery system constructed
 according to the principles of the present invention. The liquid fuel
 storage and delivery system, generally designated 100, comprises a sealed
 fuel container 110, an acerate tube 120, and an actuator 130. In one
 embodiment, the fuel container 110 comprises a protective carton 111, a
 flexible bladder 112, a container seal 113, and a fuel sight gauge 115.
 The protective carton 111 may be manufactured of any suitable rigid
 material, e.g., heavy cardboard, plastic, hardboard, etc., which offers
 the desired degree of protection to the bladder 112 and its contents
 during shipping, handling, and storage. In one embodiment, the interior of
 the protective carton 111 may be communicated with ambient air pressure so
 that the fuel will flow out of the bladder 112 due to air pressure. In an
 alternative embodiment, a positive fuel head may be provided by a pressure
 bleed conduit taken from a pressure source, e.g., the pressure stage of a
 microturbine 140 to be described below, and fed into the cavity 114
 between the bladder 112 and the inside of a sealed protective carton. It
 should be noted that such a pressure source is available during starting
 even before the microturbine or engine is running. In yet another
 embodiment, the cavity 114 between the bladder 112 and the inside of the
 sealed protective carton 111 of the previous embodiment may be
 factory-pressurized with a suitable gas to provide a positive flow of
 fuel. In yet another alternative embodiment, the protective carton 111 may
 comprise a rigid shape with an integral, impermeable, pierceable membrane
 that is internally factory-pressurized with a gas. One who is skilled in
 the art will recognize that the shape and size of the protective carton
 111 may vary, or may even be absent, and is not a limiting factor of the
 present invention.
 In one advantageous embodiment, the flexible bladder 112 comprises an
 impermeable, pierceable membrane containing a liquid fuel, such a
 plastic-based or metalized film. In the illustrated embodiment, the
 container seal 113 is a flexible, rubber-like circular mass assembled by
 any suitable means, e.g., adhesive, thermoforming, etc., to the flexible
 bladder 112. One who is skilled in the art will readily recognize that the
 container seal 113 may also be any or all of: (a) integral to and formed
 of the same material as the flexible bladder 112, (b) manufactured of any
 material acceptable for the intended purpose, and (c) of any appropriate
 shape. In one particularly advantageous embodiment, the liquid fuel within
 the bladder 112 is methanol. In one advantageous embodiment, the fuel
 sight gauge 115 may be fluidly coupled to the bladder 112, providing a
 visual indication of fuel remaining within the container 110. To ease the
 decision making of replacing an "empty" container, a mark 116 may be
 inscribed on the container 110 or fuel sight gauge 115 to indicate a fuel
 level below which the container is considered empty. In this embodiment, a
 colorant may be added to the colorless methanol, if necessary, to show the
 remaining fuel level. One who is skilled in the art will readily envision
 other methods of determining fuel remaining within the container 110.
 In the illustrated embodiment, the acerate tube 120 is proximate the
 bladder 112 and the container seal 113. The acerate tube 120 is in fluid
 connection with a fuel control mechanism 145 of a microturbine 140 by a
 flexible conduit 125. The acerate tube 120 is configured to be driven by
 the actuator 130 into the bladder 112. In one embodiment, the actuator 130
 is a mechanical, spring-loaded device that holds the acerate tube 120 away
 from the container seal 113 so long as commercial electrical power is
 applied to a primary electrical power distribution system 150. Upon
 commercial power failure, the acerate tube 120 is released, and the
 spring-loaded device drives the acerate tube 120 through the permeable
 membrane of the bladder 112. As the acerate tube 120 passes through the
 container seal 113, the flexible container seal 113 constricts about the
 acerate tube 120 and prevents air or liquid from leaking around the
 acerate tube 120. With the opening of the acerate tube 120 within the
 bladder 112 and in contact with the fuel, the methanol fuel flows under
 ambient air pressure through a flexible conduit 125 to the microturbine
 140 or other electrical generating device, such as a fuel cell. The
 electrical output of the microturbine 140 is electrically connected to the
 electrical power distribution system 150. When provided with fuel, the
 microturbine 140 starts and powers the electrical power distribution
 system 150. One who is skilled in the art is familiar with methods for
 starting a microturbine 140. In a particularly advantageous embodiment the
 electrical power distribution system 150 supplies power to a
 telecommunications system, however, one who is skilled in the art will
 readily identify other applications.
 Referring now to FIG. 2, illustrated is a plan view of an alternative
 embodiment of the liquid fuel storage and delivery system of FIG. 1. In
 the illustrated embodiment, a liquid fuel storage and delivery system 200
 comprises a plurality of fuel containers 210a-210e, a corresponding
 plurality of acerate tubes 220a-220e, a corresponding plurality of
 actuators 230a-230e, and a controller 260. The operation and function of
 the plurality of acerate tubes 220a-220e, actuators 230a-230e, and fuel
 containers 210a-210e are analogous to the acerate tube 120, actuator 130,
 and fuel container 110, respectively, of FIG. 1. Although the system 200
 is described with five fuel containers 210a-210e, one who is skilled in
 the art will recognize that analogous systems may be constructed to employ
 a quantity of fuel containers ranging in number from a single container to
 n containers while remaining within the scope of the present invention. In
 this embodiment, any empty container 210a-210e may be removed and replaced
 with a new, sealed container while the fuel cell 140 is running on fuel
 from a different container 210. Because the containers 210a-210e remain
 sealed until needed, the hazard of fire during refueling is significantly
 reduced.
 In a particularly advantageous embodiment, the controller 260 is connected
 to: the primary electrical power distribution system 150, the actuators
 230a-230e, and a fuel level sensor 270. The fuel level sensor 270 is
 proximate the fuel containers 210a-210e so as to be able to measure and
 manage the fuel remaining in each container 210a-210e. In one embodiment,
 the fuel level sensor 210 may be a plurality of strain gauges or a
 segmented electronic scale that provides a quantity for each individual
 fuel container 210a-210e to the controller 260. One who is skilled in the
 art will readily conceive of other methods by which the fuel status may be
 ascertained. In one embodiment, the controller 260 is an electrical
 controller that electrically monitors the power status of the primary
 power distribution system 150 and the fuel remaining in the fuel
 containers 210a-210e so as to operate an appropriate actuator 230a-230e
 when primary electrical power fails. The controller 260 may also
 selectively operate a plurality of valves 233a-233e that control fuel flow
 to the microturbine 140 and limit fuel loss through evaporation into empty
 fuel containers. To provide for long term primary power outages, the
 system 200 may employ multiple fuel containers 210a-210e as shown. As each
 fuel container approaches empty, the controller 260 selects an unused fuel
 container to provide uninterrupted fuel to a microturbine 140.
 Alternatively, a plurality of fuel containers 210a-210e may be employed at
 remote sites to provide power in the event of multiple power failures over
 an extended period of time, e.g., several years, without an urgent need to
 replace expended fuel containers. One who is skilled in the art will
 readily recognize that alternative embodiments employing mechanical or
 electromechanical controllers are clearly within the scope and intent of
 the present invention. In yet another alternative embodiment, the
 controller 260 may also comprise a microprocessor that monitors the total
 fuel remaining and automatically sends an alert message to an attendant if
 the fuel level falls below a required minimum. Also, one who is skilled in
 the art will recognize that the controller 260 of the described system 200
 may be capable of distinguishing and tracking the fuel quantity within
 each container 210a-210e so as to compensate for an unexpectedly, empty
 container.
 Referring now to FIG. 3, illustrated is an alternative embodiment of the
 liquid fuel storage and delivery system of FIG. 2. In the illustrated
 embodiment, a liquid fuel storage and delivery system 300 comprises a
 plurality of fuel containers 310a-310e, an acerate tube 320, an actuator
 330, a controller 360, a positioner 380, and a positioning rail 390. The
 operation and function of the controller 360 and fuel containers 310a-310e
 are analogous to the controller 260 and fuel containers 210a-210e of FIG.
 2. Upon determination of a need for fuel, the controller 360: (a) selects
 a fuel container 310a-310e to provide fuel for the microturbine 140, (b)
 commands the positioner 380 to move the actuator 330 and the acerate tube
 320 proximate the selected fuel container 310a-310e along the positioning
 rail 390, and (c) commands the actuator 330 to drive the acerate tube 320
 to puncture the bladder of the selected fuel container 310a-310e. Although
 the illustrated embodiment details an electromechanical system, one who is
 skilled in the art will readily envision alternative methods of
 positioning the actuator 330 and acerate tube 320.
 Referring now to FIG. 4, illustrated is an alternative embodiment of the
 liquid fuel storage and delivery system of FIG. 3. In the illustrated
 embodiment, a liquid fuel storage and delivery system 400 comprises a
 plurality of fuel containers 410a-410e, an acerate tube 420, an actuator
 430, and a controller 460. The operation and function of the controller
 460 and fuel containers 410a-410e are analogous to the controller 360 and
 fuel containers 310a-310e of FIG. 3. Upon determination of the first need
 for fuel, the controller 460 commands the actuator 430 to advance the
 acerate tube 420 sufficiently to puncture the bladder of the first fuel
 container 410a, positioning the opening in the acerate tube 420 within the
 bladder. Upon determination of a second need for fuel, the controller 460
 commands the actuator 430 to advance the acerate tube 420 through the
 remaining wall of the bladder in the first fuel container 410a and
 sufficiently beyond to puncture the bladder of the second fuel container
 410b. Each successive fuel container 410c-410e may be accessed in a
 similar manner. Although the illustrated embodiment details an
 electromechanical system, one who is skilled in the art will readily
 envision alternative methods of positioning the actuator 430 and acerate
 tube 420.
 From the foregoing, it is readily apparent that the present invention
 provides a system for providing fuel to a backup electrical fuel cell. The
 system preferably includes a scaled fuel container having a pierceable
 membrane with a container seal associated therewith, an acerate tube
 proximate the pierceable membrane, and an actuator. The actuator is
 coupled to the acerate tube and automatically drives the acerate tube
 through the pierceable membrane to provide fluid communication from the
 fuel container to the fuel cell in response to a failure of a primary
 electrical power system. The container seal is configured to form a seal
 about the acerate tube when the acerate tube pierces the pierceable
 membrane to prevent unnecessary loss of fuel, such as methanol, from the
 container. In alternative embodiments, the system may also include the
 primary power system and a backup electrical fuel cell that is
 electrically coupled to the primary power system.
 Although the present invention has been described in detail, those skilled
 in the art should understand that they can make various changes,
 substitutions and alterations herein without departing from the spirit and
 scope of the invention in its broadest form.