Abstract:
The present invention generally relates to a use of a thermoelectric module in conjunction with a fireplace or stove to generate electricity to run certain features or peripheral devices related to the stove or fireplace. The thermoelectrical module may be positioned between interior and exterior walls of the stove or fireplace outside and protected from the fire generated in the combustion chamber of the stove or fireplace. Power generated by the thermoelectric module may be used for various purposes such as powering a blower, a control unit such as a microprocessor, lights, back-up systems, ignition systems, and flame control devices. Furthermore, the power generated by the thermoelectric module may be saved in a power storage device such as a rechargeable battery or capacitor for a later use by various devices associated with fireplace or stove.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Technical Field  
         [0002]     The present invention generally relates to thermoelectric power and more specifically relates to generation of electric power for a fireplace using thermoelectric power.  
         [0003]     2. Related Art  
         [0004]     The popularity of gas burning stoves and fireplaces has increased significantly over the past several decades. Burning gas such as natural gas or propane is typically a much more efficient way of producing heat and far more clean and easy to control than burning wood, wood pellets, coal or oil. The efficiency and convenience of gas burning stoves and fireplaces is further enhanced by using such peripheral devices as a blower to circulate heated air through the room in which the stove or fireplace is placed, an ignition system to self-start the fire, back-up storage devices, and control systems that automatically or manually control various features of the stove or fireplace. Many of these devices require electrical power to operate and thus contribute to the cost of operating a gas stove or fireplace. Furthermore, in areas where electrical power is unavailable or expensive, many of these devices may not be an option for use with a gas stove or fireplace.  
         [0005]     Many known stoves and fireplaces have reduced heat generating efficiency because much of the heat produced escapes through the combustion exhaust system or into the structure surrounding the stove or fireplace rather than heating the intended air space around the stove or fireplace. Improving the heat generating efficiency of stoves and fireplaces is an objective for many manufacturers of these products.  
         [0006]     The use of thermoelectric modules to produce electricity using a heat source has been known for many years.  FIG. 1  schematically illustrates a typical thermoelectric module  1  that includes a number of alternate negative (N) and positive (P) type semiconductor thermo elements connected in series by metal interconnectors  2 ,  4  that are sandwiched between two electrically insulated but thermally conducting plates H, C. A heat source connected to plate H and a heat sink connected to plate C provide a temperature differential across the thermo elements that in turn generate a current (I) that can be delivered to an external load (W).  
         [0007]     Typically, increasing the temperature difference (ΔT) across a thermoelectric module will increase the power generated by the module within limits of the materials used and the configuration of the module. Those skilled in the art are aware that materials with a high figure-of-merit are preferred for use as thermo elements in a thermoelectric module. Heavily doped semi-conductors, such as tellurides of antimony and bismuth, are examples of materials with a high figure-of-merit value. Manufacturers of thermoelectric modules such as continue to make advances in the efficiency of thermoelectric modules by altering their designs or discovering new materials or combinations of materials that are most efficient.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention generally relates to the use of a thermoelectric module in conjunction with a fireplace or stove to generate electricity to run certain features or peripheral devices related to the stove or fireplace. A thermoelectric module may be positioned adjacent to an exterior wall of the stove or fireplace or between interior and exterior walls of the stove or fireplace so long as the module is protected from the fire in the combustion chamber. Power generated by the thermoelectric module may be used for various purposes such as powering a blower, a control unit, lights, sensors, ignition systems, and flame igniting and control devices. Furthermore, the power generated by the thermoelectric module may be saved in a power storage device such as a rechargeable battery or capacitor for a later use by devices listed above.  
         [0009]     One aspect of the invention relates to a thermoelectric fireplace that includes a combustion chamber enclosure having an outer surface and an inner surface defining a combustion chamber, an outer enclosure surrounding a portion of the combustion chamber enclosure, and a thermoelectric module positioned adjacent to the outer surface of the combustion chamber enclosure. In one embodiment, the thermoelectric also may be positioned between the combustion chamber enclosure and the outer enclosure. Heat generated in the combustion chamber in the combustion chamber enclosure is used by the thermoelectric module to generate power.  
         [0010]     Another aspect of the invention relates to a thermoelectric system configured to generate power in a fireplace. The thermoelectric system includes a combustion chamber enclosure and an outer enclosure. The thermoelectric system includes a thermoelectric module positioned adjacent to the combustion chamber enclosure and positioned between the combustion chamber enclosure and the outer enclosure. The thermoelectric module generates power using heat provided in the combustion chamber enclosure.  
         [0011]     A further aspect of the invention relates to a method of generating power in a fireplace using a thermoelectric system that includes a thermoelectric module. The fireplace includes a combustion chamber enclosure having inner and outer surfaces and an outer enclosure surrounding the combustion chamber enclosure. The method includes positioning the thermoelectric module adjacent to the outer surface of the combustion chamber enclosure between the combustion chamber enclosure and the outer enclosure, heating the combustion chamber enclosure, transferring heat from the combustion chamber enclosure to the thermoelectric module, and generating power in the thermoelectric module from the transferred heat.  
         [0012]     A yet further aspect of the invention relates to a thermoelectric fireplace that includes a compression molded combustion chamber enclosure defining a combustion chamber, and a thermoelectric module positioned adjacent to the combustion chamber enclosure. The thermoelectric module is positioned relative to the combustion chamber enclosure so that heat generated in the combustion chamber is transferred to the thermoelectric module for the production of power.  
         [0013]     The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. Figures in the detailed description that follow more particularly exemplified embodiments of the invention. While certain embodiments will be illustrated and described, the invention is not limited to use in such embodiments. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The invention may be more completely understood in consideration of the following detailed description of various embodiments in the invention and in connection with accompanying drawings, in which;  
         [0015]      FIG. 1  is a schematic representation of a known power generating thermoelectric module;  
         [0016]      FIG. 2  is a perspective view of an example fireplace in which principles of the present invention may be applied;  
         [0017]      FIG. 3  is a perspective side view of the fireplace shown in  FIG. 2  with a portion of the fireplace outer enclosure removed to illustrate an example thermoelectric module and other aspects of the invention;  
         [0018]      FIG. 4  is a cross-sectional view of one example embodiment of the invention taken along cross-sectional indicators  4 - 4  shown in  FIG. 3 ;  
         [0019]      FIG. 5  is a cross-sectional view of another example embodiment of the invention taken along cross-sectional indicators  5 - 5  shown in  FIG. 3 ;  
         [0020]      FIG. 6  is a top perspective view of an example thermoelectric module of the invention in use with a compression molded combustion chamber enclosure; and  
         [0021]      FIG. 7  is a cross-sectional side view of another example embodiment of the invention with a heat source positioned in the fireplace plenum.  
         [0022]     While the invention is amenable to various modifications and alternate forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the invention is not limited to the particular embodiments described. On the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]     The invention is applicable to stoves and fireplaces that provide a heat source, and particularly to combustible gas fireplaces and stoves. The invention is directed to generating electrical power from heat provided by a stove or fireplace using a thermoelectric device. Power generated by the thermoelectric device may be used to power various features associated with the stove or fireplace. While the present invention is not so limited, appreciation of various aspects of the invention will be gained through a discussion of the examples provided below.  
         [0024]     Embodiments of the present invention may be used in conjunction with gas, electric or other types of heat sources that generate heat to provide a temperature differential across a thermoelectric module thereby generating electric power. While the example embodiments of the present invention provided below are described in conjunction with example fireplaces, the present invention is equally applicable to other systems or apparatuses such as furnaces and stoves that generate heat for the purpose of heating an air space such as a home or commercial building. Some example fireplaces that may be used in accordance with the present invention include a direct vent, a universal vent, a B-vent, a horizontal/vertical-vent, a dual direct vent, and a multisided unit having two or three glass panels as combustion chamber side panels.  
         [0025]     As used herein, the phrase “combustion chamber enclosure” may include any structure that at least partially encloses a space in which a flame is generated from combusting a material, solid or gas, or simulating a flame. The phrase “transferring heat” may include either convection or conduction heat transfer. A “thermoelectric module” as used herein will be more completely described below but generally relates to a device that generates electrical power in the presence of a temperature differential. A “heat source” may include, for example, an electric or gas heater.  
         [0026]     Referring to  FIGS. 2-5 , respective front, side and cross-sectional views of an example embodiment of a fireplace  10  is shown. Fireplace  10  includes an outer enclosure  11 , a combustion chamber enclosure  30 , and a thermoelectric system  50 . Outer enclosure  11  includes top, bottom, first and second side, and rear panels  12 ,  14 ,  16 ,  18 ,  20 . Outer enclosure  11  may also include a front surface  22  into which first and second vents  23 ,  24  are formed. Vents  23 ,  24  are used to draw air into and exhausting air from the internal space of fireplace  10 .  
         [0027]     Combustion chamber enclosure  30  includes first and second side panels  31 ,  47 , top and bottom panels  35 ,  39 , and rear panel  43 . As shown in  FIGS. 3-5 , first panel  31  includes outside and inside surfaces  32 ,  34 , top panel  35  includes inside and outside surfaces  36 ,  38 , bottom panel  39  includes inside and outside surfaces  40 ,  42 , and rear panel  43  includes an outside surface  44 .  
         [0028]     Thermoelectric system  50  may include a thermoelectric module  52 , heat sink  58  and leads  60 ,  62 . Thermoelectric module  52  may include the basic configuration shown in  FIG. 1 , including a plurality of thermo elements P, N connected in series with connectors  2 ,  4  and positioned between heat conductive plates H, C. Other thermoelectric module configurations may be used so long as the thermoelectric module  52  is capable of using heat to generate electrical power. Heat sink  58  may be configured as a plurality of ribs as shown in  FIG. 3 , or other structures that enhances heat dissipation to increase the temperature differential between opposing sides of thermoelectric module  52 .  
         [0029]     In another thermoelectric system embodiment shown in  FIG. 5 , a portion of the system, such as a heat sink  158 , may extend beyond the first side panel  16  and possibly even beyond an additional wall structure  80  positioned adjacent the fireplace  10 . Heat sink  158  may then be exposed to a colder environment than that area between the combustion chamber enclosure  30  and the outer enclosure  11 . For example, heat sink  158  may extend outside of a house where the fireplace resides so as to be exposed to cool/cold outdoor air. Such a configuration would create a much greater temperature differential across the thermoelectric module resulting in improved power output.  
         [0030]      FIGS. 3-4  illustrate thermoelectric system  50  mounted to outside surface  32  of first side panel  31  of the combustion chamber enclosure  30 . Thermoelectric system  50  is orientated with the thermoelectric module  52  secured to the combustion chamber enclosure  30  with the heat sink  158  positioned away from the combustion chamber enclosure.  FIG. 4  illustrates the entire thermoelectric system  50  positioned between combustion chamber enclosure  30  and the first side panel  16  and a removable side panel  28  of outer enclosure  11 . Similarly,  FIG. 5  illustrates that at least a portion of the thermoelectric system  150  is positioned between combustion chamber enclosure  30  and outer enclosure  11 . In other embodiments, the thermoelectric system may be mounted to the outside surfaces of the top, bottom, rear or second side panels  35 ,  39 ,  43 ,  47  of combustion chamber enclosure  30  for various reasons such as, for example, improving power generation efficiency or meeting the size and shape constraints of the fireplace.  
         [0031]     Fireplace  10  may include auxiliary features that typically operate using electrical power. For example, fireplace  10  includes an energy storage device  70 , a blower  72 , a control unit  74 , and an ignition system  26  (see  FIG. 1 ). Energy storage device  70  may be, for example, a capacitor or rechargeable battery. Preferably, energy storage device  70  is capable of being charged with power from thermoelectric system  50  so that some of the fireplace features can operate when there fireplace is not generating heat sufficient for the thermoelectric system to produce power.  
         [0032]     Blower  72  provides air circulation around the outside surface of combustion chamber  30  and within outer enclosure  11 . Blower  72  typically draws cool air in through the lower first vent  23  and exhausts heated air through the higher second vent  24  on the front surface  22  of fireplace  10 . In some embodiments, blower  72  may be configured solely for the purpose of cooling thermoelectric module  52  while a separate blower is used to circulate air into and out of the fireplace.  
         [0033]     Control unit  74  may individually control or may represent any of a number of different control features that may be used with a fireplace. For example, control unit  74  may be an ignition system control such as the ignition system disclosed in U.S. Pat. No. 6,520,199 (which is incorporated herein by reference in its entirety), a main flame valve control, a heat sensor control, a blower control, or a power allocation control unit. Control unit  74  may include a microprocessor that is programmable to, for example, automatically charge or discharge energy storage device  70 , turn on or off blower  72  at specified times during heating and cooling within combustion enclosure  30 , automatically turning on or off the main flame of the fireplace, maintaining the ignition system  26 , or manually igniting a pilot light of the fireplace (not shown).  
         [0034]      FIG. 3  illustrates hard wires extending between control unit  74 , blower  72  and energy storage device  70 . However, in other embodiments, other communication technology such as infrared, remote control or other wireless communication may be used to send and receive control signals from the control unit  74  and various electronically controlled devices of fireplace  10 .  
         [0035]     The thermoelectric systems  50 ,  150  shown in  FIGS. 3-5  may more efficiently generate power when blower  72  moves air across heat sink  58 ,  158  to increase the temperature differential across thermoelectric module  52 ,  152 . In these examples, blower  72  draws cool air in the direction B across a bottom portion of the combustion chamber enclosure  30 , moves the air in the vertical direction S across the thermoelectric system  50 ,  150 , and exhausts the air out from the fireplace the intended air space in front of the fireplace. Typically, the exhausted air is heated relative to the intake air by the time the air is exhausted from the fireplace, thus providing heating of the intended air space while at the same time cooling the thermoelectric module. In other embodiments, different types of cooling devices may be used in place of or in addition to a blower to cool the thermoelectric system. One example alternative cooling device is a closed-loop liquid-state cooling system.  
         [0036]     Power generation using thermoelectric system  50  may be started in several different ways. Heat is generated in the combustion chamber enclosure  30  using, for example, a gas fed flame, or may be generated by another heat source positioned between the combustion chamber enclosure  30  and the outer enclosure  28 .  
         [0037]     The flame may be started with the ignition system  26  that includes, for example, a standing pilot light or a pilot light that that is manually or automatically controlled by control unit  74  using power powered stored in energy storage device  70 . As heat builds in or around the combustion chamber, the thermoelectric module  52  begins to draw heat from the heat source and converts that heat into electrical power. Control unit  74  may be used to power “on” the blower  72  either before or after the thermoelectric system  50  begins to generate electrical power by using energy stored in the storage device  70  or using energy produced by thermoelectric system  50 . As noted above, blowing air across the heat sink  58  (for example, using blower  72 ) improves the power output from the thermoelectric system, and thus it may be advantageous to begin air movement across the heat sink at a very early stage. In some embodiments, energy storage device  70  may include a capacitor that provides a surge of power to meet the start up energy requirements for blower  72 .  
         [0038]     Power generated by the thermoelectric system  50  may be used for powering other features not shown in the Figures such as, for example, lights in and around the fireplace, moving devices in and around the fireplace such as an simulated flame element (see U.S. patent application Ser. No. 09/941,400), a simulated fuel bed (see U.S. patent application Ser. No. 09/851,803), an ember out of a log (see U.S. patent application Ser. No. 10/463,175), a touch switch (see U.S. patent application Ser. No. 10/199,983), a proximity sensor (see U.S. patent application Ser. Nos. 10/120,890 and 10/119,474), moving a lenticular screen (see U.S. patent application Ser. No. 09/859,719), a thermostat, and other alarms and sensors such as a carbon monoxide sensor and an associated alarm (all of the above listed patent applications are incorporated herein by reference in their entirety). Another sensor and alarm system may monitor the thermoelectric system and provide notification when the thermoelectric system is overheating or is in need of repairs so that the user or possibly the control unit can shut down the fireplace to conduct diagnostics and/or repairs.  
         [0039]     Another example fireplace  200  that includes a thermoelectric system  250  is shown in  FIG. 6 . Fireplace  200  includes a combustion chamber enclosure  230  having an outer surface  232  and an inner surface  234  that defines a combustion chamber  229 . Thermoelectric system  250  may be mounted to or otherwise positioned adjacent to outer surface  232  so that thermoelectric system  250  can use heat from combustion chamber  229  to generated power. Combustion chamber enclosure  230  may include inorganic fibers, binders and fillers, and may be made by a compression molding method to provide a compression molded article as disclosed in U.S. Patent Application Publication No. 2003/0049575 A1, which is incorporated herein by reference.  
         [0040]     Thermoelectric system  250  may include the same or similar features as disclosed above, including a thermoelectric module  252 , a heat sink  258 , a control system (not shown), a power storage device (not shown), and a blower (not shown).  
         [0041]     In a yet further example fireplace  300  shown in  FIG. 7 , a heat source  51  that generates a temperature differential in the thermoelectric system  50  may be positioned between the combustion chamber enclosure  30  and the outer enclosure  28  of the fireplace  300 . For example, an electric heater and at least a portion of the thermoelectric module  52  of the thermoelectric system may be positioned between the combustion chamber enclosure and the outer enclosure.  
         [0042]     One example thermoelectric system for a fireplace produces a DC voltage of about 5 to 15 V and is capable of providing current of about 250 to 1000 mA. The amount of voltage produced has a roughly inverse relationship to the amount of current that can be drawn from the system. In one particular example, the system provides a DC voltage of about 13 V and a current of about 500 mA. The current and voltage specifications for a thermoelectric module may also vary depending on whether the thermo elements are arranged in series or in parallel.  
         [0043]     The thermoelectric system preferably includes two or more thermo elements or thermo plates connected in series or in parallel. One example thermoelectric system that provides sufficient power to run a blower and other basic electronic features for a standard residential gas fireplace includes five thermo plate connected in series, such as thermoelectric module Model No. TZ08119-02 made by Tellurex Corporation of Traverse City, Mich., U.S.A.  
         [0044]     The present invention should not be considered limited to the particular examples or materials described above, but rather should be understood to cover all aspects of the invention as fairly set out in the attached claims. Various modifications, equivalent processes, as well as numerous structures to which the present invention may be applicable will be readily apparent to those of skill in the art to which the present invention is directed upon review of the instant specification.