Combination Solar and Combustion Heater

Abstract

Substituting a solar concentrator for a conventional burner for heating is desirable. However, the sun's energy is diurnal and cannot be counted upon even during daylight hours. To ensure heating is available, a backup conventional combustor can be provided. According to the present disclosure, a heat exchanger element of the heater assembly is directly acted upon by solar rays via a solar concentrator and by combustion. The heat exchanger acts as the combustion holder. Fuel provided to the outside of the heat exchanger is adjusted based on the demanded for heating and the amount of insolation achieved via the solar concentrator. The heat exchanger can be part of a conventional heater or a heat pump for heating water.

1 . A heater assembly, comprising:
 a window having an outer surface and an inner surface;   a solar concentrator having a collection area many times greater than an area of the window wherein most of the sun rays that impact the solar concentrator are reflected onto the outer surface of the window;   a heat exchanger that is arranged closer to the inner surface of the window; and   a fuel-and-air delivery chamber defined by the inner surface of the window, a first surface of the heat exchanger, and a side wall of the delivery chamber with an inlet for fuel and air defined in the side wall of the delivery chamber; and   a combustion chamber defined by a second surface of the heat exchanger, a side wall of the combustion chamber, and a bottom wall with an outlet for exhaust gases defined in one of the side wall and the bottom wall of the combustion chamber.   
     
     
         2 . The assembly of  claim 1  wherein the heat exchanger comprises at least one tube arranged in a spiral with a distance between adjacent tubes displaced less than or equal to a quench distance of the fuel and air. 
     
     
         3 . (canceled) 
     
     
         4 . The assembly of  claim 13 , further comprising: an ignitor disposed in the combustion chamber. 
     
     
         5 . The assembly of  claim 4 , further comprising:
 a fuel supply duct coupled to an inlet of the fuel-and-air delivery chamber;   an air supply duct coupled to the inlet of the fuel-and-air delivery chamber;   a fuel valve disposed in the fuel supply duct; and   an electronic control unit electronically coupled to the fuel valve and the ignitor.   
     
     
         6 . The assembly of  claim 5  wherein the heat exchanger comprises at least one tube adapted to carry a working fluid, the tube is arranged in a spiral, and the tube has an inlet and an outlet, the assembly further comprising: a temperature-measuring device disposed in the outlet of the tube. 
     
     
         7 . The assembly of  claim 6 , further comprising: an electronic control unit (ECU) electronically coupled to the temperature measuring device and the fuel valve wherein the ECU controls the fuel valve based on the temperature at the outlet of the tube. 
     
     
         8 . The assembly of  claim 1  wherein the window and the heat exchanger are substantially flat and parallel to each other. 
     
     
         9 . The assembly of  claim 1  wherein the solar concentrator comprises:
 a concave reflective parabolic ring adapted to reflect incoming solar rays onto the window; 
 a convex reflective parabolic disk disposed opposite the upper surface of the window; and 
 a concave reflective parabolic bowl disposed inside the reflective parabolic ring wherein the parabolic bowl is adapted to reflect incoming solar rays onto the parabolic disk and the parabolic disk is adapted to reflect incoming solar rays from the parabolic bowl onto the window. 
 
     
     
         10 . A heater assembly, comprising:
 a solar concentrator;   a heat exchanger comprising at least one tube; and   a window arranged between the solar concentrator and the heat exchanger; wherein:
 the at least one tube is adapted to conduct a working fluid; 
 the solar concentrator is arranged to direct the sun's rays onto the heat exchanger; and 
   the heat exchanger is adapted to stabilize combustion at an outer surface of the heat exchanger when provided a combustible mixture of air and fuel and after combustion has been initiated wherein the heat exchanger is disposed within a chamber defined by:
 a window arranged substantially parallel to the heat, a side wall, and a bottom wall; and 
 the chamber is separated by the heat exchanger into a fuel-and-air delivery chamber and a combustion chamber. 
   
     
     
         11 . The assembly of  claim 10  wherein
 the window is arranged substantially parallel to the heat exchanger. 
 
     
     
         12 . The assembly of  claim 11  wherein:
 the fuel-and-air delivery chamber defines a fuel-and-air inlet; 
 the combustion chamber defines an exhaust outlet; and 
 the combustion chamber has an ignitor disposed therein. 
 
     
     
         13 . The assembly of  claim 10 , wherein the at least one tube comprises:
 a first tube arranged in a first spiral with an inlet at the center of the first spiral and an outlet at the periphery of the first spiral;   a second tube arranged in a second spiral with an inlet at the center of the second spiral and an outlet at the periphery of the second spiral;   the first and second spirals are entwined with a distance between adjacent tubes being less than a quench distance throughout the spiral; and   the outlets of the first and second tubes are arranged substantially diametrically opposed from each other.   
     
     
         14 . The assembly of  claim 10  wherein the at least one tube comprises a plurality of tubes with a distance between adjacent tubes being less than a quench distance of the combustible fuel and air. 
     
     
         15 . The assembly of  claim 10  wherein the solar concentrator is substantially parabolic, the assembly further comprising:
 a positioning system to move one of: a mirror of a heliostat, the solar concentrator, and the heater assembly so that available rays from the sun are directed into the solar concentrator substantially parallel to a central axis of the solar concentrator; 
 a fuel delivery system having a valve to meter an amount of fuel provided to the fuel-and-air delivery chamber; 
 an air delivery system for metering air provided to the fuel-and-air delivery chamber; and 
 an electronic control unit electronically coupled to the valve, the ignitor, and the positioning system. 
 
     
     
         16 . A method to operate a heater assembly having a solar concentrator and a heat exchanger adapted to stabilize combustion, the method comprising:
 positioning one of: a heliostat proximate the solar concentrator, the solar concentrator, and the heater assembly to cause solar rays to impact the heat exchanger;   determining a present heating demand; and   supplying fuel and air to the heat exchanger when the solar energy is insufficient to provide the heating demand;   determining the present heating demand; and   adjusting the fuel and air flow rate to provide the desired heating demand.   
     
     
         17 . The method of  claim 16 , further comprising:
 actuating the ignitor when a temperature of the heat exchanger is below the ignition temperature of the fuel and air proximate the heat exchanger.   
     
     
         18 . (canceled) 
     
     
         19 . The method of  claim 16 , further comprising:
 determining whether the fuel valve is nearly turned off; and   commanding the fuel valve to close when it is determined that the fuel valve is nearly turned off.   
     
     
         20 . The method of  claim 16 , further comprising: positioning a mirror of the heliostat substantially parallel to the heat exchanger when it is determined that it is night time.