Batteries: thermoelectric and photoelectric – Photoelectric – Cells
Reexamination Certificate
1998-08-20
2001-09-04
Chapman, Mark (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Cells
Reexamination Certificate
active
06284969
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to thermophotovoltaic (TPV) generators. More particularly, the invention relates to a hydrocarbon fired thermophotovoltaic furnace having a non-fused silica tube.
BACKGROUND
Thermophotovoltaic (TPV) generators are combined with residential gas furnaces in a number of ways. One method is to treat the TPV unit as a first heat stage. This method requires that the single stage furnace be sized to handle the coldest days. To ensure that the furnace will be able to maintain the space temperature, the furnace is typically oversized. A TPV first stage that is 20% of the main furnace output is sufficient for 50% or more of the heating hours, and comfort is improved since the heat output more closely matches the space heat load. The furnace blower operates at a low rpm that matches the pressure output of the TPV generator. This operation is done with a PWM DC motor, a device that is already available in the HVAC industry. Two stage heat thermostats are commercially available. The TPV controls ensure safety of the hybrid system. The principal feature is enhanced comfort. Temperature swings are reduced at low loads, and continuous air movement also provides filtration. The TPV add-on serves as a backup furnace in the event there is a loss of power. The TPV unit is not able to satisfy the second stage load, but it at least maintains a significant space temperature relative to outdoor conditions. With the addition of electrical storage, full furnace output may be provided for a duration determined only by the amount of storage provided. The backup furnace may be done without using the TPV unit as a first stage, but the added value of a first stage operation makes the most sense.
The small, portable, cylindrical TPV generator provides electricity. A significant market exists for self-powered furnaces. A forced air self-powered furnace requires a 200 W DC blower and a 200 W electric generator to operate the blower. An infrared (IR) emitter and TPV cells provide electric power but require a new redesign for each different model furnace. Furthermore, the furnace requires 200 W of electricity, and a potential customer would have to purchase a new TPV powered furnace.
SUMMARY OF THE INVENTION
The present invention is a hydrocarbon fired thermophotovoltaic furnace having a non-fused silica tube. In a preferred embodiment, the furnace has an infrared emitter tube having a top end and a bottom end and a substantially transparent non-fused silica window tube having a closed top end. The window tube is positioned concentrically around the infrared emitter tube, and the infrared emitter tube is in fluid communication with the window tube. The window tube is preferably composed of Lucalox (alumina or Chromolux), magnesia, yterria, titania, spinel, stablized zirconia or yterria alumina garnet. In another preferred embodiment, the furnace has a radiator tube having a top end and a bottom end and an infrared emitter tube having a closed top end. The infrared emitter tube is positioned concentrically around the radiator tube, and the radiator tube is in fluid communication with the infrared emitter tube.
Fluid flows from the inner tube to the outer tube. For either of the above embodiments, either the top end of the inner tube is spaced from the closed top end of the outer tube to permit fluid to flow between the ends of the tubes or the top end of the inner tube abuts the closed top end of the outer tube and the inner tube has a plurality of holes formed therethrough.
The furnace has low bandgap cells positioned distally around the outer tube and has a plurality of dielectric filters individually positioned on each cell.
The furnace has a fuel tube axially aligned with and positioned below the inner tube. A fuel inlet is mounted at a base of the fuel tube, and a fuel injector is mounted at a top of the fuel tube. A venturi is positioned adjacent to and around the fuel injector. An axial fan is positioned below the venturi. The fan forces combustion air into the venturi. A photovoltaic array is preferably positioned around the outer tube for supplying electricity to the combustion air fan.
A combustion air tube surrounds the fuel tube and directs combustion air to the venturi. A combustion chamber is positioned beyond the fuel injector and the venturi. Ignitors positioned in a top end of the fuel injector start the combustion of the fuel. An exhaust conduit surrounds the outer tube and extends down along the combustion air tube.
A heat exchanger is connected to the exhaust conduit. Heat exchanger fins are positioned in the exhaust conduit and extend into the combustion air tube for preheating combustion air. The heat exchanger also includes a recuperator. The recoperatur has a recuperator tube with slots formed therein and arranged helically. Fins extend through the slots from outside the recuperator tube to inside the recurperator tube. Preferably, the recuperator fins are either trapezoidal or rectangular. The trapezoidal shaped recuperator fins have shoulders which abut an outside of the recuperator tube.
In a preferred embodiment, the fuel injector includes a generally hollow tube having an upper end and a lower end and a cup member press fit to the upper end of the hollow tube. The cup member has a central hole formed therein for receiving a fastener. A plurality of holes are also formed in the cup member. The holes are positioned radially around the central hole and are spaced equidistantly spaced from the central hole and from each other. An annular cup is positioned adjacent a top end of the cup member and a cap is positioned adjacent the annular cup opposite the cup member. A jet shim is positioned between the annular cup and the cap. The jet shim has a plurality of etched radial channels formed therein. Gaseous fuel flows through the etched radial channels between a flat upper rim of the cup member and a flat lower surface of the cap. The shim also has an inner hub held between a flat inner surface of the cup member and the flat lower surface of the cap.
Finally, the furnace includes means for attaching the furnace to an existing air duct system.
These and further objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification, with the drawings.
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Ferguson Lucian G.
Fraas Lewis M.
Mulligan William P.
Samaras John E.
Chapman Mark
Creighton Wray James
JX Crystals Inc.
Narasimhan Meera P.
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