Pellet stove

Abstract

According to embodiments of the present invention, a pellet stove includes a firepot assembly with a bottom plate slideable along rails to move between a closed position during combustion in the firepot and an open position during ash removal. According to other embodiments, a firebox or combustion enclosure includes a plurality of airfoils formed on the inner and outer surfaces of the enclosure to facilitate heat exchange between exhaust gases flowing across the inner surface of the enclosure and air blown across the outer surface of the enclosure. According to some embodiments, the airfoils and enclosure are of integral unibody construction. According to yet other embodiments, a user sets parameters via a wall control unit, and a stove control unit receives the parameters and automatically controls fuel feed rate, ignition, convection blower, combustion blower, and/or firepot cleaning based on the one or more parameters.

1 . A firepot assembly for a pellet stove, comprising: 
 a combustion enclosure configured to house a solid fuel during combustion, the combustion enclosure comprising a first opening configured to receive the solid fuel and a second opening through which the solid fuel may be released after combustion;    a first rail;    a second rail;    a bottom plate configured to slide along the first rail and the second rail between a closed position in which the bottom plate substantially covers the second opening and an open position in which the bottom plate does not cover the second opening; and    a motor coupled to the bottom plate and configured to move the bottom plate between the closed position and the open position.    
   
   
       2 . The firepot assembly of  claim 1 , wherein the second opening comprises a bottom opening and a partial side opening, and wherein the bottom plate comprises a substantially flat portion configured to abut the bottom opening and a ramped portion configured to abut the partial side opening.  
   
   
       3 . The firepot assembly of  claim 1 , further comprising 
 a controller communicably coupled to the motor and configured to activate the motor at predetermined time intervals.    
   
   
       4 . The firepot assembly of  claim 1 , further comprising 
 a controller configured to receive information about the solid fuel, calculate a cleaning interval based on the information, and activate the motor after the cleaning interval based on calculation.    
   
   
       5 . The firepot assembly of  claim 1 , wherein the motor comprises a drive shaft, and wherein the drive shaft extends through a crank arm having a cam roller, the firepot assembly further comprising a lever arm pivotally mounted to a stationary pivot bracket, wherein the lever arm includes a channel at a distal end for receiving the cam roller, wherein a proximate end of the lever arm is pivotally connected to a plow arm coupled to a lower surface of the bottom plate, and wherein actuation of the crank arm causes the lever arm to pull the plow arm and move the bottom plate to the open position.  
   
   
       6 . A firebox for exchanging heat in a pellet stove, comprising: 
 an enclosure comprising side walls, a back wall, and a thermally conductive top wall, the enclosure at least partially enclosing a combustion site, wherein the thermally conductive top wall is at least partially slanted with respect to the back wall;    a first plurality of thermally conductive airfoils formed on an inner surface of the thermally conductive top wall; and    a second plurality of thermally conductive airfoils formed on an outer surface of the thermally conductive top wall, wherein the first plurality of thermally conductive airfoils is configured to absorb heat from the combustion site via convection, and wherein the second plurality of thermally conductive airfoils is configured to receive the heat via conduction from the first plurality of thermally conductive airfoils through the top wall and impart the heat via convection to a fluid surrounding the second plurality of thermally conductive airfoils.    
   
   
       7 . The firebox of  claim 6 , wherein the back wall is a thermally conductive back wall, the firebox further comprising: 
 a third plurality of thermally conductive airfoils formed on an inner surface of the thermally conductive back wall; and    a fourth plurality of thermally conductive airfoils formed on an outer surface of the thermally conductive back wall, wherein the third plurality of thermally conductive airfoils is configured to absorb the heat from the combustion site via convection, and wherein the fourth plurality of thermally conductive airfoils is configured to receive the heat via conduction from the third plurality of thermally conductive airfoils through the back wall and impart the heat via convection to a fluid surrounding the fourth plurality of thermally conductive airfoils.    
   
   
       8 . The firebox of  claim 6 , wherein the fluid is air, the firebox further comprising: 
 a convection blower configured to blow the air over the plurality of airfoils on the outer surface of the top wall.    
   
   
       9 . The firebox of  claim 6 , wherein each airfoil of the second plurality of thermally conductive airfoils comprises: 
 a leading edge;    a trailing edge narrower than the leading edge;    a base; and    a tip which is narrower than the base.    
   
   
       10 . The firebox of  claim 9 , wherein each airfoil of the second plurality of thermally conductive airfoils is configured to permit laminar flow of the fluid over each airfoil of the second plurality of thermally conductive airfoils.  
   
   
       11 . The firebox of  claim 6 , further comprising: 
 a fuel opening through which a fuel passes from an outside of the enclosure to the combustion site; and    an exhaust opening through which exhaust gases pass from the combustion site to the outside.    
   
   
       12 . The firebox of  claim 11 , further comprising: 
 a one-piece hopper positioned at least partially over the top wall and configured to hold the fuel, the one-piece hopper comprising a chute through which the fuel falls into the fuel opening.    
   
   
       13 . The firebox of  claim 6 , wherein the first plurality of thermally conductive airfoils and the second plurality of thermally conductive airfoils are formed integrally with the top wall.  
   
   
       14 . The firebox of  claim 7 , wherein the first plurality of thermally conductive airfoils and the second plurality of thermally conductive airfoils are formed integrally with the top wall, wherein the third plurality of thermally conductive airfoils and the fourth plurality of thermally conductive airfoils are formed integrally with the back wall, and wherein the side walls and the back wall are formed integrally with the top wall.  
   
   
       15 . A pellet stove control system comprising: 
 a wall control unit providing a user interface through which a user sets one or more parameters related to operation of the pellet stove; and    a stove control unit communicably coupled with the wall control unit, the stove control unit receiving the one or more parameters from the wall control unit and automatically controlling fuel feed rate, ignition, convection blower, combustion blower, and firepot cleaning of the pellet stove, based at least in part on the one or more parameters.    
   
   
       16 . The pellet stove control system of  claim 15 , wherein the one or more parameters are selected from a group consisting of: temperature, time of day, day of week, fuel type, automatic mode, and manual mode.  
   
   
       17 . The pellet stove control system of  claim 15 , wherein the stove control unit comprises a machine-readable medium, the machine-readable medium containing instructions executable by the stove control unit to: 
 feed a predetermined amount of biomass fuel into the firepot;    ignite the biomass fuel;    start the combustion blower;    detect a flame for the biomass fuel; and    based at least in part on the detection, feed additional amounts of the biomass fuel into the firepot at an increasing rate while concurrently increasing a speed of the combustion blower until a predetermined heat output is achieved.    
   
   
       18 . The pellet stove control system of  claim 15 , wherein the stove control unit comprises a machine-readable medium, the machine-readable medium containing instructions executable by the stove control unit to: 
 receive information about a fuel type;    determine a cleaning frequency based on the fuel type;    initiate an auto clean process based on the cleaning frequency; and    re-ignite the fuel.    
   
   
       19 . The pellet stove control system of  claim 15 , further comprising a memory, the memory comprising parametric data for one or more fuel types, the parametric data for each of the one or more fuel types including one or more fixed parameters selected from the group consisting of: feed rate, auger speed, combustion fan speed, minimum temperature during burn, maximum temperature during burn, soft start low feed speed, soft start feed speed, soft start feed time, soft start blower speed, rise temperature during soft start, pot temperature after soft start, maximum number of ignition retries, auto clean pulse interval, start up feed charge speed, ignition time, snapshot time, snapshot temperature rise differential, cool down time, start up vacuum test combustion blower speed, start up ignition combustion blower speed, shutdown combustion blower speed, vacuum pressure threshold, drop tube maximum temperature, and power table data.