Abstract:
The invention involves systems and methods of providing energy to land-based telemetry devices wherein the energy storage and power conditioning system is comprised of an input power supply, an energy storage element, an output supply and a control system. The input power supply provides energy to the output power supply and charges the energy storage element. The energy storage element is comprised of one or more UltraCaps and supplies energy to the output power supply at times of peak need and when the primary energy source to the input power supply is removed. The control system adjusts the voltage supplied to the energy storage element by the input power supply according to changes in the ambient temperature to compensate for changes in the internal equivalent series resistance of the UltraCaps caused by the change in ambient temperature. The output power supply provides energy to the land-based telemetry device. Adjusting the voltage supplied to the energy storage element helps extend the operating life of the UltraCaps.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/383,843, filed May 28, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to the field of data telemetry; and specifically to a system of method for storing energy for later use in electronic devices used in land-based telemetry. 
     2. Description of Related Art 
     Electronic metering and telemetry devices must accurately measure the flow or use of services, products or materials to external customers or internal processes. In addition to accurately measuring (“metering”) such quantities, the telemetry device must be able to transmit the measured quantity and other information to another device with a low margin of error in such transmission or receive information transmitted by another device. Often such transmission or receipt must occur when the telemetry device has lost its primary power source. Therefore, most electronic telemetry devices have a back-up power source and are designed with several common characteristics in mind, including: operating reliably and accurately over a wide temperature range; continuing to function for a limited time after the failure of the primary power source; operating continuously, reliably and without maintenance in excess of ten years; and being physically small enough for the desired application. Additionally, the telemetry device may consume peak power exceeding the instantaneous capability of the primary power source when the primary source is available or “on” and any back-up power source must be designed to supply this additional energy. 
     Although implementing each of these requirements separately poses some difficulty, it is extremely difficult to address all five simultaneously. The practical energy storage devices for these applications are batteries, electrolytic capacitors, and a class of capacitors commonly referred to as “Super” capacitors or “SuperCaps.” Generally, SuperCaps are capacitors with very high storage capacitance (e.g., on the order of one Farad, or higher). A drawback to SuperCaps is their very high “equivalent series resistance” or “ESR.” Recently, SuperCaps have been developed with intrinsically low ESR (e.g., on the order of less than one-half ohm DC resistance). These SuperCaps with low ESR are commonly referred to as “UltraCaps.” UltraCaps are commercially available from companies such as Cooper Electronic Technologies, a division of Cooper Industries, Ltd. (a Bermuda corporation, headquartered in Houston, Tex.) and Maxwell Technologies of San Diego, Calif. 
     Batteries are generally not a practicable solution to meet the above criteria because of their need for maintenance, their reduced life and because their operational characteristics are affected by temperature variations. SuperCaps (and to a lesser degree, UltraCaps), fail to operate consistently over wide variations in temperature. Furthermore, electrolytic capacitors are often large and bulky and rapidly discharge after a primary source power outage because of large leakage currents at high temperatures. 
     Because the life of batteries that are appropriate for these applications falls short of ten years and standard electrolytic capacitors are physically too large, it is more probable that the temperature performance of UltraCaps may be enhanced in some manner. Enhancing the performance of UltraCaps over a range of temperatures requires understanding the mechanisms that affect UltraCaps at temperature extremes: at low temperatures, the internal ESR of the capacitor increases notably, thereby decreasing the available energy at higher currents; and standard charging voltages at elevated operating temperatures may damage the internal materials of an UltraCap. 
     One way to address these issues is to operate the UltraCaps at a lower voltage at higher temperatures and to apply heat to the UltraCaps at low temperatures. This solution is problematic in that heating the UltraCaps requires additional energy that may not be available and operating the UltraCaps at a lower voltage requires an increase in the size or number of UltraCaps, in conflict with the need to keep the energy source small. Therefore, what is needed is an electronic metering and telemetry device and associated back-up power supply that simultaneously operates reliably and accurately over a wide temperature range; continues to function for a limited time after the failure of the primary power source; operates continuously, reliably and without maintenance in excess of ten years; is physically small enough for the desired application; and with a back-up power source capable of supplying additional energy when the telemetry device consumes peak power exceeding the instantaneous capability of the primary power source when the primary source is available or “on.” This invention demonstrates a method and system of meeting all of the design criteria using UltraCaps, while considering all of the device&#39;s shortcomings. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention is a system and method for using a class of capacitors known as “UltraCaps” to provide energy storage in electronic devices. In particular, the invention provides energy storage for land-based telemetry devices. Specifically, the invention measures ambient air temperature and changes the voltage applied to one or more UltraCaps connected in series based on the measured ambient temperature. 
     The invention involves two power supplies, an input power supply and an output power supply, and one or more UltraCaps. The input power supply receives power from a primary power source, supplies charging voltage to the UltraCaps, and supplies power to the output power supply. The output power supply receives power from the input power supply and/or the UltraCaps and provides a constant voltage output for use by the telemetry device for its operation. 
     One or more of a microprocessor, microcomputer, microcontroller, control circuit or other external means controls the power supplies. The external control system may be associated with an associated metering device or the telemetry device. One or more algorithms controls the input power supply such that a lower voltage is applied to the UltraCaps at higher temperatures to prevent damaging the UltraCaps and a higher voltage is applied at low temperatures to compensate for internal energy dissipation caused by higher ESR. At lower temperatures the higher voltages do not damage the UltraCaps and in no case does the applied voltage exceed the manufacturer&#39;s ratings for the UltraCap. 
     In the event of a failure to the primary power source, the input power supply shuts down and power is furnished to the output power supply by one or more UltraCaps. The output power supply, in turn, provides power to the telemetry devices for a limited amount of time to enable the device to continue to receive and transmit information. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
     Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
     FIG. 1A is a simple exemplary block diagram of an energy storage and power condition system for metering and telemetry devices in an embodiment of the invention. 
     FIG. 1B is a more detailed exemplary block diagram of an energy storage and power conditioning system for an application in an embodiment of the invention. 
     FIG. 2 is an exemplary circuit diagram of an energy storage and power conditioning system for an application in an embodiment of the invention. 
     FIG. 3 is an exemplary detailed circuit diagram of an input power supply in an energy storage and power conditioning system for an application in an embodiment of the invention. 
     FIG. 4 is an exemplary detailed circuit diagram of an output power supply in an energy storage and power conditioning system for an application in an embodiment of the invention. 
     FIG. 5 is a graphical illustration of the change in equivalent series resistance of a Maxwell PC10 UltraCap over a change in temperature as such capacitors may be used in an embodiment of the invention. 
     FIG. 6 is a flowchart illustrating the steps of a control algorithm for controlling the output voltage of an input power supply for charging and supplying energy to an energy storage unit and output power supply in an embodiment of the invention. 
     FIG. 7 is a graphical illustration of the total charging voltage applied to an energy storage element comprised of six UltraCaps connected in series and the charging voltage applied to each UltraCap over a range of temperatures in an embodiment of the invention. 
     FIG. 8 is a graphical illustration of the worst-case ESR over a range of temperatures that can be expected for a Maxwell PC10 UltraCap after ten years use in an embodiment of the invention. 
     FIG. 9 is a graphical illustration of the required and minimum voltage that the energy storage element UltraCaps must be charged before a 40-byte message may be transmitted in an embodiment of the invention. 
     FIG. 10 is a graphical illustration of the amount of time required to charge a fully discharged energy storage element comprised of six Maxwell PC10 UltraCaps to a voltage sufficient to send a 256-byte message over a range of temperatures in an embodiment of the invention. 
     FIG. 11A is an overview flowchart illustrating the steps of a control process for determining the available energy of an energy storage unit to supply energy to a telemetry device for transmitting a message in an embodiment of the invention. 
     FIG. 11B is a more detailed flowchart illustrating the steps of a control process for determining the available energy of an energy storage unit to supply energy to a telemetry device for transmitting a message in an embodiment of the invention. 
     FIG. 12 is a graphical illustration of the worst-case and typical amount of time that the telemetry device may operate in the “receive” mode during a power failure and still have sufficient energy to transmit a 40-byte power fail message over a range of temperatures in an embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. 
     The present invention is described below with reference to block diagrams and flowchart illustrations of methods, apparatuses (i.e., systems) and computer program products according to an embodiment of the invention. It will be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, respectively, can be implemented by computer program instructions. These computer program instructions may be loaded onto a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions that execute on the computer or other programmable data processing apparatus create means for implementing the functions specified in the flowchart block or blocks. 
     These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means that implement the function specified in the flowchart block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. 
     Accordingly, blocks of the block diagrams and flowchart illustrations support combinations of means for performing the specified functions, combinations of steps for performing the specified functions and program instruction means for performing the specified functions. It will also be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, can be implemented by special purpose hardware-based computer systems that perform the specified functions or steps, or combinations of special purpose hardware and computer instructions. 
     FIG. 1A is a simplified exemplary overview of an apparatus  100  encompassing an embodiment of the invention in which a metering device  102  measures a quantity of a service, product or material by use of a sensor, transducer, optical reader, transformer, etc.  132  and provides the metered quantity to a telemetry device  104 . For example, the metering device  102  may measure the flow of electrical energy into a building or the flow of electrical energy into or out of an electrical generating facility, the flow of water, natural gas, propane, etc. into an area where such products are being used. Furthermore, the metering device  102  may be used to measure the quantity of a material or substance that is added during a manufacturing process. An energy storage/supply device  106  is connected to and supplies energy to the telemetry device  104 . Generally, a primary source of energy  110  is supplied to the energy storage/supply device  106  from, for example, the metering device  102 . An outside source  126  supplies energy to the metering device  102 . In other embodiments, the outside source  126  may connect directly to the energy storage/supply device  106  or it may connect to the telemetry device  104  with a subsequent feed to the energy storage/supply device  106 . Control and input signals  112  are transmitted to and from the metering device  102  and the energy storage/supply device  106 . Energy is supplied to the telemetry device  104  from the energy storage/supply device  106 . The energy storage/supply device  106  will continue to supply energy to the telemetry device  104  for a limited time after the failure of the primary source of energy  110 . Control and input signals  114  are transmitted to and from the telemetry device  104  and the energy storage/supply device  106 . Furthermore, control and input signals  116 , including the metered quantity, are transmitted to and from the metering device  102  and the telemetry device  104 . 
     Either the telemetry device  104  or the metering device  102 , or both may have a microcomputer, microprocessor, microcontroller or control circuit ( 128 ) for the control of the energy storage/supply device  106  (the control device  128  is shown in this embodiment as being included within the metering device  102 ). The metering device may also include a temperature sensor  130  that is used by the control device  128  to adjust the output voltage of the energy storage/supply device  106 , according to the ambient temperature. In other embodiments, circuits or devices not associated with the telemetry device  104  or the metering device may control the energy storage/supply device  106 . As shown in FIG. 1B, the energy storage/supply device  106  is comprised of an input power supply  124 , one or more energy storage capacitors  118 , and an output power supply  120 . 
     In a preferred embodiment, the input power supply  124  is a switching voltage regulator such as a switched-mode power supply with a regulated output as is known in the art such as, for example, a Linear Technology LT1618, although other models or types of power supplies may be used. The input power supply  124  serves as a charger for the energy storage capacitors  118 , and is a constant voltage/constant current type charger. It also provides energy to the output power supply  120  when the primary source of energy  110  is supplying energy to the input power supply  124 . 
     The output power supply  120  may also be a switching voltage regulator, such as, for example, a National Semiconductor LM 2650 buck-type switching regulator, although other models and types of power supplies may be used. This device takes the varying voltage from the energy storage capacitors  118  and/or the input power supply  124  and produces a fixed voltage for use by the application. 
     The energy storage capacitors  118  are a form of capacitor generally known as UltraCaps characterized by a low ESR that allows high discharge currents. 
     The preferred embodiment of the invention includes one or more UltraCaps  118  connected in series to form an energy storage element. If a particular embodiment requires more than one UltraCap, then each UltraCap should have a resistor in parallel as shown in FIG.  2 . The resistors  202  in parallel to the UltraCaps  204  provides an even voltage distribution across each UltraCap  204  in a multi-capacitor arrangement although such a resistor is not required to practice the invention. Each resistor  202  in parallel to an UltraCap  204  should be of substantially equivalent resistance value so that the voltage will be divided equally across the capacitors  204 . Furthermore, in a multi-capacitor arrangement as shown in FIG. 2, the values (capacitance, voltage rating, etc.) of the capacitors (UltraCaps)  204  connected in series should be substantially equivalent for proper voltage distribution. 
     The energy storage element  206  in an exemplary embodiment of the invention as shown in FIG. 2 is comprised of UltraCaps C 1 , C 2 , C 3 , C 4 , C 5  and C 6   204  and each capacitor&#39;s paralleled resistor, R 5 , R 6 , R 7 , R 8 , R 9 , and R 10   202 , respectively. In a preferred embodiment such as that shown in FIG. 2, each of the capacitors  204  will be substantially equivalent in their rating values such as, for example, 10 Farads and 2.5 VDC, although capacitors of other values may be used. Resistors R 5 -R 10   202  will also be of substantially equivalent value such as, for example 10K ohms at 1% accuracy, although other values may be used. Resistors R 1   218  and R 2   220  form a voltage divider such as, for example, a 10:1 voltage divider, to allow an analog to digital converter (“ADC”) (not shown) to read the input power source&#39;s  234  bus voltage  226 . The digital bus voltage signal is then provided by the ADC to a microcomputer, microprocessor, controller or circuit  128  associated with the application in order to control the energy storage system  106 . Resistors R 3   222  and R 4   224  form a voltage divider such as, for example, a 10:1 voltage divider, to allow an ADC (not shown) to read the bus voltage  228  at the energy storage element  206 . The digital bus voltage signal of the energy storage element  206  is then provided by the ADC to a microcomputer, microprocessor, controller or circuit  128  associated with the application in order to control the energy storage system. In some embodiments, the invention may be practiced without the voltage dividers formed by R 1   218 , R 2   220  and R 3   222 , R 4   224 . 
     The output  208  of the input power supply  210  is connected to the positive terminal  212  of the energy storage element  206 , and the negative terminal  214  of the energy storage element  206  is connected to the circuit ground  216 , as is shown in FIG.  2 . 
     The input power supply  210 , as shown in FIG. 3 in more detail, has the following characteristics: the current input to the regulator is limited so as to not exceed the capabilities of the primary power supply; an input to the power supply, PFAIL_N, shuts down the power supply in the event the primary power source ceases to supply power. This input may be supplied in various instances by the primary power supply, by reducing the primary power source (e.g., by a voltage divider or a transformer) and supplying the reduced voltage primary power source to an ADC with the output of the ADC connected to the PFAIL_N input, or a circuit may be supplied that monitors the state of the primary power source and is asserted in the event the primary power source is no longer available; a multi-bit input that changes the output voltage based on the binary value of the input. In this instance, it is a two-bit binary input that changes dependent upon ambient air temperature and with the output values changing according to the two-bit binary input, and; the output of the input power supply operates in a current limited mode until the UltraCap is charged to the voltage determined from monitoring the ambient air temperature. This output current is limited by controlling the input current. 
     In an exemplary embodiment of the input power supply  210  of the invention as shown in FIG. 3, the input power supply  210  is comprised of U 1   302 , which in this particular embodiment is a Linear Technology LT1618 step-up DC converter that functions as a power switch for a single-ended primary inductance converter (“SEPIC”) type switching regulator. In this embodiment, capacitor C 9   304  is an input filter capacitor that keeps any large circulating AC currents at the input power supply close to the power supply. In this particular embodiment, for example, capacitor C 9   304  is rated 4.7 micro-Farad (“μF”) and 25 V, though capacitors rated differently may be used. Transformer T 1   306  serves as two coupled inductors of equal value. A torroidial inductor is used to minimize any stray magnetic fields. In this particular embodiment, for example, transformer T 1  is comprised of paralleled 50 micro-Henry (“μH”) torroidial inductors, though transformers of other ratings may be used. Resistors R 11   308  and R 15   310  are used to set the limit level for current control of the input current to the input power supply: the current limit is (0.050/R 11 ), if R 15   310  is 0 ohms. The current limit is (0.025/R 11 ), if R 15   310  is 2 mega-ohms. In this particular embodiment, R 15   310  must be either 0 or 2 mega-ohms. R 11   308  in this particular embodiment, for example, is 0.15 ohms at 5% accuracy, therefore the input current limit is 165 mA if R 15   310  is 2 mega-ohms and the input current limit is 330 mA if R 15   310  is 0 ohms. The use of a jumper, JP 4   336 , allows R 15   310  to quickly and easily be changed from 0 to 2 mega-ohms, and vice-versa. Capacitor C 7   312  couples the two windings of T 1   306  together. Note that if C 7   312  were omitted, the circuit would function as a conventional flyback converter. A flyback converter, however, would require a power-wasting snubber network to absorb the voltage kick from the leakage inductance of T 1   306 . Capacitor C 7   312  causes leakage inductance energy to go to the load, transformer T 1   306  must have a 1:1 ratio for this to work. In this particular embodiment, for example, capacitor C 7  is rated 1 μF and 25 V. Diode D 1   314  is an output rectifier. Because in this particular embodiment U 1   302  operates above 1 MHz, D 1   314  is a Schottky barrier rectifier. Capacitor C 10   316  serves as an output filter. In this particular embodiment, for example, C 10   316  is rated 4.7 μF and 25 V. Resistors R 12   318  and R 13   320  are feedback resistors for voltage sensing. In this particular embodiment, R 12   318  is rated 100K ohms at 1% accuracy and R 13  is rated 10K ohms at 1% accuracy. The R 12   318  to R 13   320  junction in this particular embodiment will be at 1.263 volts nominally when the voltage mode is controlling U 1   302 . Resistors R 16   322  and R 17   324  offset the output voltage by −1 volt and −2 volts, respectively, when the logic control signals SETV_ 0   326  and SETV_ 1   328  are set to a logical “1.” In this particular embodiment R 16   322  is 332K ohms and R 17   324  is 165K ohms with a logic level “1” of 3.3 volts. If the logic level is other than 3.3 volts, new values for these resistors ( 322 ,  324 ) will need to be determined. Capacitor C 11   330 , and resistor R 14   334  shape the frequency response of the input power supply to assure control loop stability. In this particular embodiment, C 11   330  is rated 0.033 μF and 25 V, and R 14   334  is rated 2K ohms at 5% accuracy. 
     Referring again to FIG. 2, the positive terminal  212  of the energy storage element  206  is also connected to the input of an output power supply  238 . The output power supply  238 , as shown in FIG. 4, has the following characteristics: the input voltage operating range should be set so that the upper limit is above the maximum voltage applied to the energy storage element and the lower limit should be set to the minimum usable voltage level of the storage element; the output voltage is set to a value appropriate for the particular application. 
     In an exemplary embodiment of the output power supply  238  of the invention as shown in FIG. 4, the output power supply  238  is comprised of U 2   402 , which in this particular embodiment is a National Semiconductor LM2650 buck-type switching regulator. Capacitors C 12   404  and C 13   406  are input filter capacitors designed to keep high frequency AC currents confined to areas near the chip  402 . In this embodiment, capacitors C 12   404  and C 13   406  are each rated 22 μF and 35 V. These filtering capacitors  404 ,  406  are less effective at above about 2 or 3 MHz. Therefore, capacitors C 14   408 , C 15   410 , and C 16   412  are used along with capacitors C 12   404  and C 13   406  to filter out higher-frequency AC currents, up to 20 MHz, or so. In this particular embodiment, capacitors C 14   408 , C 15   410  and C 16   412  are each rated 0.1 μF and 50 V. Device T 2   414  is, in this particular embodiment, a 50 μH torroidial inductor. Paralleling two windings of the inductor  414  reduces the DC resistance of the winding. Paralleling two 50 μH coils on the same core results in 50 μH overall inductance. A torroidial coil was chosen in this embodiment for its low stray magnetic field. Capacitor C 17   416  is part of a charge pump to allow proper gate drive and lower “ON” resistance of the pull-up MOSFET of the switching regulator  402  resulting in better efficiency. In this particular embodiment, capacitor C 17   416  is rated 0.1 μF and 50 V. The resistor R 23   418  sets the operating frequency, in this particular embodiment, to 200 KHz. This frequency was selected over the normal operating frequency of 90 KHz to reduce the inductor and capacitor physical sizes. In this particular embodiment, resistor R 23   418  is rated 24.9K ohms at 1% accuracy. 
     The operation of the overall circuit as shown in FIG. 2 is controlled by one or more control processes running on a microcomputer, microprocessor or microcontroller ( 128 ), although a dedicated control circuit may be used (collectively, the “control system”). Control signals that are input into the control system include, for example, the voltage of the primary power source  234 , V_MON  226 , the voltage applied to the energy storage element  206 , V_CAP  228 , and the ambient air temperature as provided by a temperature sensor  130 . Failure of the primary power source  234  results in shutdown of the input power supply  210  through the input control signal PFAIL_N  236 . As previously described, this signal may originate from the primary power source  234  or the control system. When the input power supply  210  shuts down, it no longer provides energy to the energy storage unit  206  or the output power supply  238 . Furthermore, energy from the energy storage unit  203  is prevented from feeding back into the primary power source  234  by the high impedance of the input power supply  210 . 
     The control system algorithms control the input power supply  210  such that Vout  208  is lower at higher temperatures to prevent damaging the UltraCaps  204  and Vout  208  is higher at low temperatures to compensate for internal energy dissipation within the capacitors  204  caused by higher ESR. As can be seen in FIG. 5, in a particular embodiment using UltraCaps  204  such as, for example, Maxwell PC10 capacitors, the ESR  502  varies greatly over temperature and in this instance ranges from approximately 0.28 ohms at −40 C to 0.10 ohms at 85 C, while the capacitance  504  remains relatively the same over the temperature range. The voltage output  208  of the input power supply  210  is adjusted for temperature through the use of the two control signals that are outputs from the control system, SETV_ 0   230 , and SETV_ 1   232 . At lower temperatures the higher voltages do not damage the UltraCaps  204  and in no case does the applied voltage exceed the manufacturer&#39;s ratings for the UltraCap  204 . In an exemplary preferred embodiment of the invention utilizing six Maxwell PC10 UltraCaps connected in series as the energy storage unit  206 , these control signals  230 ,  232  are set as shown in Table 1 (and in FIG. 2) for temperature compensation of the output voltage, Vout  208 , of the input power supply  210 . 
     
       
         
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Temp Range 
                 Vout 
                 SETV_1 
                 SETV_0 
               
               
                   
                   
               
             
             
               
                   
                 −40 C. to −20 C. 
                 15 V 
                 0 
                 0 
               
               
                   
                 −20 C. to 0 C. 
                 14 V 
                 0 
                 1 
               
               
                   
                  +0 C. to 30 C. 
                 13 V 
                 1 
                 0 
               
               
                   
                  30 C. to 85 C. 
                 12 V 
                 1 
                 1 
               
               
                   
                   
               
             
          
         
       
     
     An exemplary algorithm in pseudo-code for controlling the energy storage/energy supply device  106  in an embodiment of the invention is attached hereto as APPENDIX A and is completely incorporated herein. The pseudo code is provided in a format of pseudo “C” programming language. The algorithm generally performs the functions as described in the flowcharts of FIG.  6  and FIG.  11 . 
     FIG. 6 is a flowchart illustrating the steps of a control process for controlling the output voltage, Vout  208 , of an input power supply  210  for charging and supplying energy to an energy storage unit  206  and output power supply  238  in an embodiment of the invention. This process is executed on the control system and generally executes approximately once each minute to obtain the ambient air temperature and accordingly adjust the output voltage  208  of the input power supply  210  dependent upon the measured ambient air temperature. Table 1 provides the output voltages  208  for the given ambient air temperature in an exemplary embodiment of the invention. 
     The control process begins in Step  600 . In Step  602 , the ambient air temperature is measured by a temperature sensor and converted into a signal that is provided to the control system in order to determine the ambient air temperature. This measured ambient air temperature is compared to one or more predetermined temperature values in Steps  604 ,  608  and  612  in order to adjust the output voltage  208  of the input power supply  210  according to the measured ambient air temperature. In this particular embodiment, if the ambient air temperature is above 30 C, then the output voltage  208  is set at 12 volts (Step  606 ) and the process ends (Step  618 ); if the ambient air temperature is greater than 0 C, but less than or equal to 30 C, then the output voltage  208  is set at 13 volts (Step  610 ) and the process ends (Step  618 ); and, if the ambient air temperature is greater than −20 C, but less than or equal to 0 C, then the output voltage  208  is set at 14 volts (Step  614 ) and the process ends (Step  618 ). If the determination of Steps  604 ,  608  or  612  are negative, then the control process proceeds to Step  616 . In Step  616 , if the ambient air temperature is less than or equal to −20 C, then the output voltage  208  is set at 15 volts (Step  610 ) and the process ends (Step  618 ). 
     SPECIFIC EXAMPLE 
     As stated above, a specific embodiment of the invention has an energy storage element  206  comprised of six UltraCaps  204  connected in series. In this particular embodiment, design considerations for the invention include an expected life of at least 10 years with minimal failures, an average operating temperature of 55 C, a high temperature design limit of 85 C, and a low temperature design limit of −40 C. 
     As shown above in Table 1, the voltage applied to the energy storage unit  206  during charging (i.e., while the primary power source  234  is providing power to the input power supply  210 ) is regulated by the input power supply  210  according to the ambient temperature so as to minimize voltage-temperature stress on the UltraCaps  204 . As shown in FIG. 7, the total output voltage  702 , Vout, applied to all the UltraCaps  202  in the six series connected UltraCaps  202  in this embodiment by the input power supply  210  varies according to temperature. Likewise, the voltage  704  applied to each individual UltraCap varies according to the temperature. As FIG. 7 shows, the voltage applied to each UltraCap  204  in an embodiment of the energy storage unit  206  comprised of six UltraCaps  204  connected in series is 2.5 volts per UltraCap for a total Vout  208  of 15 volts when the ambient temperature is between −40 and −20 C; between −20 and 0 C, 2.33 volts are applied to each UltraCap  204  for a total Vout  208  of 14 volts; between 0 and 30 C, 2.16 volts are applied to each UltraCap  204  for a total Vout  208  of 13 volts, and; between 30 and 85 C, 2.00 volts are applied to each UltraCap  204  for a total Vout  208  of 12 volts. In this embodiment, resistors R 5 -R 10   202 , as shown in FIG. 2 are 10K ohm at 1% accuracy to encourage voltage equivalency across the series-connected UltraCaps. 
     In order to compensate for possible degradation over the life of the UltraCap, FIG. 8 shows the worst-case direct-current ESR that can be expected for each UltraCap after 10 years of service, depending upon temperature. This worst-case ESR is used for the design calculations of this embodiment. 
     The worst-case design scenario involves the need to provide enough energy to transmit a message via the telemetry device  104  after the failure of the primary power source  110  when the UltraCaps  204  are at the end of their serviceable life (approximately 10 years of use). Generally, it is assumed that the message to be transmitted during this power outage is 40-bytes in length. The required and minimum energy storage voltage to send a 40-byte message is also temperature dependent and is shown in FIG.  9 . Furthermore, upon initial start-up, or if the energy storage/supply device  106  has been without power for some time, then the UltraCaps  202  will likely have discharged and require a charge period before a message may be transmitted. This charge-up time is temperature-dependent as well and is shown in FIG.  10 . Note that this time shown in FIG. 10 is conservative in nature in that it is based on the charge needed to transmit a 256-byte message. 
     Assuming an application for metering the use or flow of electricity, the metering device  102  may be, for example, a Smart Meter™ as manufactured by Elster (formerly known as Asea Brown Boveri or ABB), and the telemetry device may be a Creatalink2 XT™, a ReFlex™ pager radio as manufactured by SmartSynch, Inc., both commercially available products. When the primary power source  110  to the energy storage/supply device  106  is “on,” the sending of data depends upon the power management by the microprocessor  128  and associated software in the Smart Meter™ module. Before sending a message, the microprocessor evaluates the temperature via a temperature sensor  130 , charge voltage  228 , and size of the message to be sent to determine if adequate energy is available. If the conditions are not met then the message is deferred until later. If a large block of data has just very recently been sent, then the transmitting of the next message may be deferred for up to 40 seconds. If the primary power source  110  has just been restored after an extended outage, then a delay of almost two minutes may occur before the message may be sent (reference FIG.  10 ). The software running on the control system will periodically check the charge voltage  228  via an analog to digital converter in the ReFlex™ pager radio. This process is further detailed in the flowchart of FIG. 11, as described below. 
     FIGS. 11A and 11B are flowcharts illustrating the steps of a control process for determining the available energy of an energy storage unit  206  to supply energy to a telemetry device  104  for transmitting a message in an embodiment of the invention. When transmitting a message, energy is supplied to the telemetry device  104  not only by the input power supply  210 , but also by the energy storage unit  206 . As described above, the energy storage unit  206  must be charged to a certain predetermined voltage where such predetermined value is dependent upon ambient air temperature in order to supply sufficient energy such that the telemetry device  104  is able to transmit a message. The algorithm described in FIGS. 1A and 1B returns a Boolean value of “OK.” If the energy storage unit  206  has sufficient energy to transmit the message, then OK is “true.” If the energy storage unit does not have sufficient energy to transmit the message, then OK is “false” and the control system waits a predetermined period of time and re-executes the algorithm to determine if the energy storage device  206  is charged to an adequate voltage. FIG  11 A is a general overview of the control process for determining if the energy storage unit  206  is sufficiently charge to transmit a message, depending upon the ambient temperature. The process begins at Step  1100 . In Step  1102 , the controller receives a request from the telemetry device to transmit a message. In Step  1104 , the controller determines the ambient air temperature. Depending upon the ambient air temperature, in Step  1106  the controller then checks the voltage of the energy storage unit  206  to determine if it is at or above a minimum voltage level that is established by the ambient air temperature. If the minimum voltage level of the energy storage unit  206  is met (Step  1108 ) then “OK” is set as “true” (Step  1110 ) and the process ends (Step  1116 ). If the minimum voltage level of the energy storage unit  206  is not met (Step  1108 ) then “OK” is set as “false” (Step  1112 ), the process delays (Step  1114 ) for a predetermined period of time, and the process ends goes to Step  1104  to check the ambient air temperature and begin again. 
     FIG. 11B is a more specific embodiment of the process described in FIG.  11 A. The process begins at Step  1150 . In Step  1152 , constants K 1 , K 2 , K 3 , and K 4  are set for curve fitting within the algorithm. In Step  1154 , “TEMP_C” is set as the ambient air temperature obtained from the temperature sensor. In Step  1156 , “V_CAP” is set as the voltage obtained from the energy storage unit. In Step  1158 , it is determined whether TEMP_C is greater than 20 C. If TEMP C is greater than 20 C, TEMP_C is set equal to 20 C for the purposes of these calculations (Step  1160 ) and the process proceeds on to Step  1162 ; if TEMP_C is less than or equal to 20 C, then the process also proceeds to Step  1162 . In Step  1162 , it is determined whether the length of the message to be transmitted (“LEN_MSG”) is less than 40 bytes. If LEN_MSG is less than 40 bytes, then in Step  1164  LEN_MSG is set equivalent to 40 bytes for the purpose of these calculations and the process proceeds on to Step  1166 . If LEN_MSG is equal to or greater than 40 bytes, then the process proceeds on to Step  1166 . In Step  1166 , the minimum voltage required to transmit a 40-byte message (“V_MIN — 40”), is calculated according to the formula: 
     
       
           V _MIN — 40 =K 1/(TEMP —   C+K 3)+ K 2. 
       
     
     The required voltage (“V_MIN_N”) for a LEN_MSG greater than 40 bytes is determined in Step  1168  by the formula: 
     
       
           V _MIN —   N=V _MIN — 40+(LEN_MSG+40)/ K 4. 
       
     
     In Step  1170 , it is determined whether V_CAP is greater than V_MIN_N. If it is, Step  1172 , then OK is set as “true.” If V_CAP is less than or equal to V_MIN_N, Step  1174 , then OK is set as “false” and the process ends (Step  1176 ). 
     Referring back to FIG. 9, the V_Req — 40 curve  902  represents the required voltage charge for the energy storage unit  206  for sending a 40-byte message, depending upon temperature. The V —Min  40 curve  904  is the calculated minimum voltage charge for the energy storage element  206  for sending a 40-byte message from the formula used by the microprocessor in the Smart Meter TM (reference FIGS.  11 A and  11 B). The design criteria involves a transmit time of 292 milliseconds to send a 40 byte message (based on three tries for success), and; 1069 milliseconds to send a 256 byte message, also based on three tries for success. Assuming an ESR of 0.6 ohms per UltraCap  202  (worst case at −20 C), and 12 volts initial charge for all the UltraCaps  202  connected in series, the energy storage unit  206  reaches a minimum usable voltage of approximately 7 volts in 400 milliseconds, well in excess of the required 292 milliseconds to send a 40-byte message. 
     When the primary power source  110  is “off,” the sending of a power fail report with the power available also depends on power management by the microprocessor  128  in the Smart Meter TM module. The sending of the power fail report must be accomplished with the energy available in the energy storage element  206 . A critical issue in power fail reporting is the maximum amount of time that the telemetry device  104  may operate in the receive mode, while still retaining enough energy to transmit the power fail report. Good design practice calls for the power fail reporting software to attempt to send the power fail report even if the voltage is too low considering the ambient temperature and the message size. It is important that the telemetry device  104  be able to report a power failure to a parent utility so that the utility may investigate the outage and use such information for trouble determination and repair. 
     Table 2 shows the amount of time that the telemetry device  104  may be in receive mode before attempting to send a power fail report at various temperatures under worst case circumstances in this particular embodiment of the invention. Receive time is an important design criteria for sending a power fail report because the energy storage unit  206  must supply enough energy to the telemetry device  104  to complete receiving any incoming message an then have enough energy to transmit the power fail report. It is assumed that 200 milliseconds are required to transmit a 40-byte power failure message and that two tries are required for sending of the message. Other worst case assumptions include: assuming the UltraCaps  202  have been in use for 10 years and that their ESR has doubled from its initial values; the telemetry device  104  requires 1.4 amps at 5.5 volts to transmit; the output power supply  238  is 85% efficient and that the output power supply  238  will cease operating when its input voltage  228  is approximately 7.0 volts. 
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Worst-Case Scenario 
               
             
          
           
               
                 Ambient 
                 Initial 
                 ESR 
                 Tx Minimum 
                 Receive Time 
               
               
                 Temperature 
                 Volts 
                 Ohms 
                 Volts 
                 Seconds 
               
               
                   
               
             
          
           
               
                 −40 C. 
                 15 
                 0.90 
                 14.15 
                 48 
               
               
                 −30 C. 
                 15 
                 0.75 
                 13.00 
                 121 
               
               
                 −21 C. 
                 15 
                 0.60 
                 11.90 
                 184 
               
               
                 −20 C. 
                 14 
                 0.60 
                 11.90 
                 119 
               
               
                 −10 C. 
                 14 
                 0.53 
                 11.30 
                 151 
               
               
                  −1 C. 
                 14 
                 0.45 
                 10.70 
                 181 
               
               
                  0 
                 13 
                 0.45 
                 10.70 
                 120 
               
               
                  29 C. 
                 13 
                 0.40 
                 10.30 
                 140 
               
               
                  30 C. 
                 12 
                 0.40 
                 10.30 
                 83 
               
               
                  80 C. 
                 12 
                 0.40 
                 10.30 
                 83 
               
               
                   
               
             
          
         
       
     
     “Initial Volts” is the charge on the energy storage element  206  at the time of the power failure. “ESR Ohms” is the equivalent series resistance of each UltraCap  202  that comprises the energy storage element  206 , “Tx Minimum Volts” is the minimum voltage that will be required at the input  228  to the output power supply  238  in order to transmit the power fail message (at the given ambient temperature), and “Receive Time Seconds” is the amount of time that the telemetry device  104  may be in receive mode before sending the power fail message and with the energy storage element  206  retaining enough energy to transmit the power fail message. Note that the above values are dependent upon the devices used that comprise the energy storage/energy supply device  106  as well as the telemetry  104  and metering devices  102  and that the values above are only valid for this particular embodiment. 
     If the telemetry device  104  has just begun to receive a message at the time of the failure of the primary power source  234 , in this embodiment it may continue to receive such a message for be up to  76  seconds before the telemetry device  104  may transmit the power fail report. Therefore, the desired minimum Receive Time Seconds (for design purposes) is 76 seconds in this embodiment. Referring to Table 2 and FIG. 12, it can be seen that this minimum design criteria  1206  is met at all the evaluated temperatures other than at −40 C in this worst-case scenario  1202 . It is thought that the actual ESR of a 10-year-old UltraCap  202  will not approach the conservative values shown in Table 2 and thus the 76 second receive time requirement will not likely be violate at the −40 C ambient. 
     Table 3 shows the amount of time that the telemetry device  104  may be in receive mode before attempting to send a power fail report at various temperatures under typical operating circumstances in this particular embodiment of the invention. As above, it is assumed that 200 milliseconds are required to transmit a 40-byte power failure message and that two tries are required for sending of the message. Other assumptions include: a typical ESR value for each UltraCap  202 ; the telemetry device  104  requires 1.4 amps at 5.5 volts to transmit; the output power supply  238  is 85% efficient and that the output power supply  238  will cease operating when its input voltage  228  is approximately 7.0 volts. 
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Typical Scenario 
               
             
          
           
               
                 Ambient 
                 Initial 
                 ESR 
                 Tx Minimum 
                 Receive Time 
               
               
                 Temperature 
                 Volts 
                 Ohms 
                 Volts 
                 Seconds 
               
               
                   
               
             
          
           
               
                 −40 C. 
                 15 
                 0.45 
                 10.70 
                 247 
               
               
                 −30 C. 
                 15 
                 0.38 
                 10.15 
                 268 
               
               
                 −21 C. 
                 15 
                 0.30 
                 9.55 
                 304 
               
               
                 −20 C. 
                 14 
                 0.30 
                 9.55 
                 237 
               
               
                 −10 C. 
                 14 
                 0.27 
                 9.30 
                 250 
               
               
                  −1 C. 
                 14 
                 0.23 
                 9.05 
                 258 
               
               
                  0 
                 13 
                 0.23 
                 9.05 
                 197 
               
               
                  29 C. 
                 13 
                 0.20 
                 8.80 
                 207 
               
               
                  30 C. 
                 12 
                 0.20 
                 8.80 
                 150 
               
               
                  80 C. 
                 12 
                 0.20 
                 8.80 
                 150 
               
               
                   
               
             
          
         
       
     
     Note that the above values are also dependent upon the devises used that comprise the energy storage/energy supply device  106  as well as the telemetry  104  and metering devices  102  and that the values above are only valid for this particular embodiment. 
     The desired minimum Receive Time Seconds (for design purposes) is also 76 seconds in this embodiment. Referring to Table 3 and FIG. 12, it can be seen that this minimum design criteria  1206  is met at all the evaluated temperatures in this typical scenario  1204 . 
     Therefore, it can be seen that systems and methods are disclosed for storing and supplying energy in land-based telemetry applications. In particular, the present invention utilizes a form of capacitor known as UltraCaps as an energy storage element in concert with an input power supply and an output power supply to provide energy to a telemetry device that receives its information from a metering device. The present invention is designed for a minimum life of 10 years, is compact in size, has sufficient energy storage capabilities for the application, and has the ability to operate over a wide temperature range. 
     Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.