US20070221205A1 - Self powered pelletized fuel heating device - Google Patents

Abstract

A self powered pelletized fuel heating device comprising a thermal electric generator (TEG) unit therein powering a typical collection of low voltage system components including a storage power unit. Non-typically, the heating device requires no external power supply and relies on thermodynamic principles using the pelletized fuel as a heat source. The TEG is configured and positioned optimally for conventional operation and installation requirements without modification to normal form or function.

Description

FIELD OF INVENTION
• The invention as disclosed here within consists of a pellet burning device for living/working area heating purposes. This device, also called a bio-mass burner, utilizes a thermoelectric generator (TEG) allowing the device to charge a self-contained battery system, thereby providing a stand-alone energy/heating system not requiring an external power source. The TEG pellet stove provides for both convenience and utility best reflected, but so far limited in present-day hybrid pellet stove heating units running a 12 VDC backup system for uninterrupted power supply function. Long power outages typical for many rural parts of the country prevent successful heating using conventional art.
BACKGROUND OF INVENTION
• The typical pellet burning device is a heating stove configured to stand freely within the room, venting through an exposed pipe or configured as an insert to fit snugly inside a fireplace, venting through the existing chimney. These pellet stoves have common components in varying complexities depending on the level of user requirements. Common components include a compartment to store pellets, and a feed conveyor system that moves pelletized fuel to a combustion chamber. The pellets are ignited manually or with a heating element within a small fire bowl. As the stove heats up, a blower is manually or automatically switched on to pass outside air through a heat exchange apparatus located in the upper parts of the combustion chamber and/or the air circulates around the combustion chamber as present in art like U.S. Pat. No. 6,336,449 Drisdelle, et al. Solid fuel burner for a heating apparatus.
• Drisdelle also states for information purposes and not related to this prior arts embodiments that;
• Because of the small amount of energy required, it is particularly desirable to use DC motors. Not only is such a system very safe, but it provides a further advantage that the system can be powered by a 12 volt battery in the event of an electrical power failure.”
• Drisdelle fails to address the external power dependence though points our other attributes intrinsic in the invention as presented here.
• Other prior art includes U.S. Pat. No. 5,429,110 Burke, et al. a Mobile pellet stove with thermal barrier and ventilated firepot which uses fresh air to cool internal electric and mechanical components but does not capture latent heat for self-generation as embodied in the present invention. The invention herein disclosed uses art as U.S. Pat. No. 5,123,360 Burke et al.; Pellet stove with enhanced air circulation efficiency describes a 12 VDC system, but unlike the invention presented here, the prior art relies on an external power source for recharging.
• In a more sophisticated configuration, the pellet stove is started and stopped by a thermostatic control unit. The thermostat operates conventionally as such; sends a signal to a control unit within the pellet stove; the control unit starts the feeder conveyer system to place a starter amount of pellets near the ignition element. Typically, a blower will fan hot air across the element to ignite the pellets.
• The typical pellet stove has a complex control system monitoring running temperatures and manual inputs. The control system usually changes both the speed of the pelletized fuel feeder system and blower fan speeds that heat the room and ignite pellets.
• Typically the control system requires 110V AC electricity, and/or a 12V DC battery source to run the associated blower fans and fuel feeder system apparatus. The typical configuration using a 12V volt DC battery source in conjunction with an 110V AC source serves as a backup system when the conventional 110V power source is interrupted. The typical hybrid backup period is from 5 to 10 hours of operation. The hybrid system also requires a regulator for charging the battery source during normal 110V AC operation.
• The conventional pellet stove requires a reliable energy source and can only ensure continued operation for a short period of time during emergency power-outages. Consumers typically compare pellet stove operation and reliability with that of a standard wood heating stove. Wood stoves also come in stand-alone and fireplace insert configuration and usually only require an 110V supply for an optional blower unit that helps to circulate warm air to the room. Statistics show a high percentage of wood stoves are purchased without blowers. This supports the idea that consumers of wood stoves require a high level of reliable operation and independence from outside power supplies.
• Evidence by U.S. Pat. No. 6,169,340 by Jones titled Electrical junction box for auxiliary power, Jones provides only for a level of independence from power outages with a small portable appliance plug to be used with a small convention generator.
• Marketing of the typical pellet stove; therefore, requires a different tact other than independence, thriftiness, and even reliability. Additionally, pellet stove construction complexity dictates a higher cost in comparison to wood stoves. The typical pellet stove requires an electrical plug nearby for operation. It may be required that the consumer rewire his or her home to supply power to the pellet stove.
• The hurdles for consumer acceptance are varied and substantial. Appeal for purchasing a pellet stove must rely on convenience type factors such as, less ash, cleaner burning, better controlled burning, easier lighting, cleaner and more reliable fuel, ease of fueling, ease of storage of fuel, and direct comparison to conventional heating systems. In many cases it is shown that a purchase decision typically is pivotal to obtaining independence from the 110V power grid, since the initial purchase price can be from $300 to $1500 more than a wood stove. The hybrid pellet stove provides some independence, allowing a few hours of continued operation during emergency power failure conditions but costs more and is more complex.
SUMMARY OF INVENTION
• An objective of the present invention is to provide all the conveniences of owning a pellet stove without the external power requirements. An essential embodiment of the invention provides for a self-contained power unit incorporated into the pellet stove. The power unit should be of tested and reliable configuration and proven to be of sufficient power for all operations. The pivotal consumer objection to purchasing a pellet stove is removed in the preferred environment of the present invention.
• Power requirements of a pellet stove allow for limited operation using a typical 12 VDC backup supply system. The typical 12 VDC backup system has no external charging circuit other than relying on the external power supply to run a re-charging circuitry only occurring during normal operation. The backup supply system optimally is required to run all internal components as in normal operation. The complexity of the control system increases since normal 110 VAC voltage is replaced with 12 VDC during the transition. Some operations may need to be controlled differently, since the 12 VDC backup system may not handle some power requirements, such as the lighting/ignition requirements as mentioned above. The control system also must compensate for slower blower fan operation during normal degradation of the 12 VDC battery supply; typically slowing pellet fuel feeder system to optimize normal burning with slowing blower fan operation. All the above mentioned complexities add to the cost of the control system.
• In a preferred embodiment of the invention, the self-contained power unit incorporates heat generated by the typical pellet stove to run all electrical systems. The self-contained power unit should be compact and efficient without restraining normal operations or heat conveyance to the room. In the preferred embodiment, the self-contained power unit should be unobtrusively located so that typical pellet stove configuration is not changed. Optimally, external package configuration as a freestanding or fireplace insert is not changed or modified in any way requiring additional installation considerations. In the preferred embodiment of the invention, the self-contained power unit is sealed and independent from other operational system functions within the pellet stove except for re-charging a stand-alone power supply once the stove starts to produce heat. A primary objective of this invention is to have the self-contained power unit re-charge a singular primary power source, such as a battery. The power unit is always on in the preferred embodiment, starting automatically once the stove produces heat and automatically slowing and stopping as the pellet stove cools and shuts down.
• Another objective of this invention is a self-contained power unit that is both functional, reliable and of an assembly using few parts and good engineering design. In this embodiment, the self-contained power unit charges a typical 12 VDC system wherein all controls, fans, blowers and feeder systems operate. There are no hybrid-powered circuitry requirements; thereby, reducing costs for such redundant systems. There are no external power requirements; therefore, no additional house wiring is required. In the preferred embodiment, the customers objections to external power source requirements are removed. An objective of this invention is to provide the convenience of a pellet stove with the independence of a wood stove.
• Other objectives, advantages and salient features of the invention will become apparent from the following detailed description, which taken in conjunction with the annexed drawings, discloses preferred embodiments of the invention.
BRIEF DESCRIPTION OF DRAWINGS
• FIG. 1 is a perspective cross-sectional view of this TEG pellet stove.
• FIG. 2 is a perspective cross-sectional view of this TEG pellet stove in another embodiment.
DETAILED DESCRIPTION OF THE INVENTION
• Turning toFIG. 1, there is illustrated a TEG pellet stove in the spirit of the invention. Typical of conventional pellet stoves in a stand-alone configuration, the illustration points out a body (1) and a stand (1A) supporting the body. It should be noted that an insert pellet stove will not have a stand but a flange covering the outside and sealing the unit to the surface of the fireplace once installed. In the spirit of the invention, typical pellet stoves, both stand-alone and insert, are utilizing a TEG unit as described in these preferred embodiments.
• Turning again toFIG. 1, some of the typical pellet stove components are shown such as, a burn chamber door (2), a vent exhaust port (3), a removable ash collection tray (4), a pellet fuel reservoir (5), a pellet feed port (5A), a fire bowl burn area (6), an ignition and burn air port (A), an ignition element (6B), an ash grate (7), an insulated firewall (7A), a burn chamber (8), a cold chamber, a heat exchanger (9) and a heater air room vent. Conventional art, not distinctly shown, is a pellet feeder system connecting the pellet fuel reservoir to the pellet feed port. A typical pellet feeder system can be a rotating endless screw auger or conveyer belt configuration.
• In the spirit of the invention, a battery (10) is configured and charged by a control circuit (11). For simplicity, the control circuit includes all the typical pellet stove circuitry as, manual control switches, solid state logic circuits and connecting wires to fans, blows and pellet feeder systems typical of the art. The other components within a typical pellet stove include a blower motor (12), a cold fresh air intake (13) and a heater air channel (13A). Conventional art, not shown for clarity of illustration, is an ignition air supply system, typically a separate fresh blower motor and an addition air channel feeding the ignition air port. The ignition port can also serve as a burn port to support or sustain burning in the fire bowl, or typically, a second port located nearby can sustain combustion with fresh air. The control circuit (11) manages the ignition supply system, typically from a manual input or thermostatic control to feed a small portion of pellets to the fire bowl, start the ignition air and heat the element (6B). In the spirit of the invention, the general configuration and placement of these typical pellet stove components are relatively unchanged, allowing for easy placement of the inventions in the preferred embodiments.
• Positioned in a relatively uncluttered area within the conventional pellet stove and closely aligned vertically to the fire bowl burn area, is the thermal electric generator (14) (TEG). The positioning and configuration, as further shown and described below, is optimized to collect heat from rising hot air produced from the fire bowl burn area. In the art, an upward sustained operating temperature of 700 degrees F. is optimal for seebeck P-N configured solid sate devices as further described in this invention. An induction fin assembly (15) protrudes sufficiently into the flow of vertical rising hot air produced by the fire bowl burn area and aligned parallel and longitudinally to the flow of hot gases rising up towards the conventional heat exchanger above. In the preferred embodiment of the invention, the induction fin assembly is configured in a staggered formation allowing for easy flow of gas between individual fins while slightly redirecting flow of rising hot gases to evenly collect heat from the gas. The TEG, based on seebeck principles requires a hot thermal side for optimal efficiency, as represented by the invention in the induction fin assembly. Upper temperature operation limits for conventional TEG nodal array may require configuration with smaller induction fin assemblies of unit placement off-set from vertical rising hot gas. The placement may be set into, or part of the insulated firewall. Persons familiar in the art will optimize placement and size of the TEG based on empirical temperature collection within the burn chamber and adjacent to a cool air channel as further described in the invention. As illustrated, the induction fin assembly is attached and supported at the base by a conventional heat-sink mount (15B).
• Directly opposite and across the conventional insulated firewall (7A) is positioned a heat dissipation fin assembly (15A). This assembly is strategically aligned inside the heater air channel (13A). Cool air from outside the device is drawn in through the fresh air intake (13) by the blower motor (12) and forced down the heater air channel to cool the dissipation fin assembly, thus producing a heat gradient across the TEG assembly (14). The fin assembly (15A) mounts on a heat-sink mount (15C). In a preferred embodiment of the invention, the insulated firewall (7A) acts as a thermal resistor providing a heat gradient from the induction fin assembly to the dissipation fin assembly for higher TEG thermodynamic efficiencies. As in the art, thermal resistance layers (17) separate the heat dissipation fin assembly (15A) and the induction fin assembly (15). An embodiment of the invention uses the insulated firewall (7A) as an integral part of one the thermal resistance layers providing better TEG thermodynamic efficiencies and a cooler mechanical area for running components.
• A conventional part of the thermal electric generator (14) is a P-N nodal solid-state array (16). The P-N nodal arrangement is typically for best collecting thermo-excited electron flows. In the spirit of the invention, electrons flow from the thermal electric generator via a TEG recharging wire (18) connected directly between the P-N nodal array to the control circuit (11). In the preferred embodiment of the invention, the current captured from the TEG assembly is sufficient to charge a conventional battery (10) supplying operational power to all pellet stove components.
• In another embodiment of the present invention, a solar panel plug (19) is placed on the body (1) to access a conventional external solar photovoltaic array (not shown) for additional battery recharging during daylight hours in the event of heavy continuous operation and any other deteriorating system circumstances, as loss of battery (10) efficiency. The external photovoltaic array connects to the solar panel plug and to the control circuit (11) via a solar recharging wire (20) as illustrated.
• Turning toFIG. 2, an illustration shows a cross-sectional of a similar configured pellet stove with a Stirling Engine TEG assembly. The operating principles are mechanical rather then solid state to produce a current flow that recharges the battery (10) as described above. Stirling TEG engine principles are as follows; hot gases are sealed within a TEG assembly (15), heated bore (16) and cooled bore (17). In the preferred embodiment of the invention, the heated bore is positioned inside the heater head (16A) close and over the fire bowl burned area (6). In another embodiment of the invention, the heater head is finned to capture optimal amounts of heat from the rising gases. Those familiar with the art could configure and position the heater head to maximize thermal electric efficiencies.
• Positioned in and loosely fitted to the heated bore is a hot gas piston (15A). A cold gas piston (15B) is fitted loosely inside a cold bore (17). Surrounding and enclosing the cold bore is a cooled head (17A). The cooled head in the preferred embodiment has a radial array of cooling fins aligned longitudinally in the direction of intake air flow and sealed within a heater air channel (14). Forced fresh air is drawn from a fresh air intake (13) through a blower motor (12) to the heater air channel.
• In accordance with the configuration and assembly of a Stirling TEG, linkage (20) attaches from both hot and cold gas pistons then is swivel fitted to a first rotary disk (18) and to a second rotated disk (19). All linkage ends are rotationally connected between segments, at pistons and disks as illustrated, and moves about a fixed pivot (20A). The linkage attachment at the first rotary disk and at the second rotary disk is offset, thus driving both rotating disks about their fixed respective axises in operation. Connected to the second rotated disk (19) is a conventional low voltage generator (19A). The generator is connected directly to the control circuit via a TEG recharging wire (19B). The embodiment produces electrical current to recharge the battery within the invention; thereby, providing a stand-alone closed heating and electrical generating pellet stove.
• A solar panel plug (21) is placed on the body (1) to access a conventional external solar photovoltaic array (not shown) for additional battery recharging during daylight hours in the event of heavy continuous operation and any other deteriorating system circumstances, like loss of battery (10) efficiency. The external photovoltaic array connects to the solar panel plug and to the control circuit (11) via a solar recharging wire (21A) as illustrated.
• In another embodiment of the present invention, the linkages and rotating disks are replaced by rack and pinion driven rods and gears, well know in the art, upon which the low voltage generator is attached and spins to produce required electrical current to effectively recharge the battery (10) via the control circuit (11). In the spirit of the invention, the configured Stirling TEG can be reconfigured and reposition, as know in the art, inside the burn chamber (8). It is intended by this inventor that the general art existing for Stirling TEGs may be slightly altered to fit and function properly as illustrated.
• Although the invention has been described in conjunction with specific embodiments, it is evident that many alternatives and variations will be apparent to those skilled in the art and in light of the foregoing description. Accordingly, the invention is intended to embrace all of the alternatives and variations that fall within the spirit and scope of the appended claims.

Claims (4)

1. A pellet stove for heating, comprising: a body,

a insulated firewall with thermal means separating an air tight burner chamber for pellet fuel burning therein producing heat, and a cold chamber with a fuel feed port communication between, said cold chamber includes a pellet fuel reservoir with attached transporting means to move pellet fuel to said feed port,

a fire bowl burn area positioned in said burn chamber near said feed port, and components comprising,

an ignition/burn means near said fire bowl,

a first and second blower motor supplying external air to said pellet stove through an cold fresh air intake with a first and second cold air channel feeding respectively to,

a heat exchanger means near said burn chamber and said ignition/burn means,

a hot air room vent to port circulated air from said heat exchanger and deliver air to room,

a control circuit to manage and operate said components,

a battery supplying power to said control circuit, blower motors, transporting means, and ignition/burn means,

a set of power wires attaching one to the positive side of said battery and one to negative side of said battery,

a thermal electric device positioned in said firewall extending opposite ends to said burn chamber and said cold chamber and further extending one end sealed inside said first cold air channel and receiving cold fresh air,

a thermal electric recharging wire connecting said thermal electric device to said control circuit,

whereby when said fuel is fed by said transporting means into said burn chamber and ignited to produce heat and controlled to a sustain burn with control circuit and said components, the said thermal electric device operates to charge said battery through said recharging wire, control circuit and said set of power wires.

2. The stove ofclaim 1 wherein said thermal electric device is solid-state seebeck principled device comprising,

an induction fin assembly position at said first end in said burn chamber,

a heat dissipation fin assembly position at said second end,

a first and second heat sink mount for respectively mounting said induction fin assembly and said heat dissipation assembly,

a first and second thermal resistance layer adjacent to and along said first and second heat sink mounts respectively at opposite sides to said induction fin assembly and said heat dissipation fin assembly,

a P-N nodal solid-sate array between and along said thermal resistance layers

whereby a heat gradient is produced across said P-N nodal array from said induction fin assembly to said heat dissipation assembly producing low voltage a potential across the said P-N nodal array feeding electrical current to said control circuit via said thermal electric recharging wire to charge said battery.

2. A stove inclaim 1 wherein said thermal electric device is a Stirling principled device with said body comprising,

a heat head position at first said end in said burn chamber,

a cooled heat position at second said end,

a heated bore and cooled bore respectively placed in said heat head and said cooled head each containing respectively a loosely fitted hot gas piston and loosely fitted cold gas piston, each positioned to stroke inline with said bores,

a first rotary disk and second rotating disk axially fixed respectively aligned inline with said heated bore and said cooled bore,

a fixed pivot,

a linkage having segments rotationally joined together and to said hot gas piston and said cold gas piston and inline with said bores,

a voltage generator affixed axially to said second rotating disk,

a recharging wire attaching said voltage generator to said control circuit,

whereby when said fuel is fed by said transporting means into said burn chamber and ignited to produce heat and controlled to a sustain burn with said control circuit and said components,

whereby said thermal electric device operates to charge said battery through said wire and said control circuit.

3. A stove claimed in2 and3 wherein said body comprising,

a solar photovoltaic array plug,

a solar recharging wire connecting said solar photovoltaic array plug to said control circuit,

whereby said solar photovoltaic array plug attached to a typical external photovoltaic array and collects current during daylight operation to recharge said battery via said solar recharging wire and said control circuit.

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