Batteries: thermoelectric and photoelectric – Photoelectric – Cells
Reexamination Certificate
1996-10-03
2002-01-08
Chapman, Mark (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Cells
C136S259000
Reexamination Certificate
active
06337437
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to thermophotovoltaic (TPV) power generators which convert infrared radiant energy to electric power using low bandgap photovoltaic cells.
An earlier filed copending application Ser. No. 08/702,184, now U.S. Pat. No. 5,865,906 disclosed a TPV generator including a platinum wire coil inserted in the flame of a burner and surrounded by a circuit of low bandgap TPV cells. In that unit, the heated coil glows and emits infrared energy. That infrared energy is received by the TPV cells and converted to electric power. Excess heat from the TPV cells is removed by convective air cooling through fins attached to the outside surface of the cell circuit. Variations of that basic small TPV generator include units having ceramic emitters with infrared emission spectrums matched to the TPV cells in place of the platinum wire coil.
An example of the units described in the earlier filed application have the following dimensions. An emitter has a diameter of about 0.5 inches and a height of about 1.5 inches. A 6 volt TPV circuit includes 24 cells and has a diameter of about 2 inches and a height of about 1.5 inches. The cell circuit is cooled by 24 radial fins. Each fin is about 3 inches tall and 2 inches long from tip to base. In the example, the complete TPV converter assembly is about 6 inches in diameter and three inches tall, not including the height of the fuel/air mixing tube. Generators made according to those specifications typically generate about 2 watts of electric power with a steady state cell operating temperature of 90 degrees Celsius.
Needs exist for TPV generators having increased power output while maintaining compact package sizes. Needs further exist for economically viable TPV cell generators having increased power per cell. Needs further exist for compact TPV generating units that are easily adaptable for use in a variety of potential applications.
SUMMARY OF THE INVENTION
The present invention is a compact electric power generating unit that provides for high power outputs. The unit includes a basic TPV converter assembly and a fan for improving cell cooling. The assembly includes a fuel/air mixing tube, an infrared emitter, a TPV cell circuit surrounding the emitter, cooling fins extending from the cell circuit and a cylinder enclosing the tube, emitter, cell circuit and cooling fins. A fan is positioned at a bottom of the cylinder for forced air cooling. When the fuel valve of the mixing tube is opened, the fuel/air mixture is ignited at the top of the cylinder. The resulting combustion heats the emitter. The heated emitter emits infrared radiation, which impinges on the TPV cells of the cell circuit and is converted to electric power. A portion or all of the generated electric power is delivered from the circuit to the fan. The fan, equipped with the constant power supply from the cell circuit, blows air upward past the cooling fins, thereby greatly improving cell cooling. Excess electric power converted by the cell circuit may be distributed for other useful purposes.
Relative to a TPV generator using only convective cooling, the present generator unit allows cooling fin length from tip to base to be halved and fin density to be quadrupled, such that about ten times more waste heat is removed. That allows for the production of ten times more electric power while not increasing the diameter of the unit beyond the dimensions of a unit with convective cooling. For example, for a 6 inch diameter generator, fin length in the present unit decreases from 2 inches to one inch, thereby allowing the cell circuit diameter to be increased from 2 inches to 4 inches. By doubling the circuit diameter, twice as many cells may be included in the circuit, thereby doubling the output voltage from 6 volts to 12 volts. Also, the emitter diameter of the present unit may be increased from 0.5 inch to 2.5 inches, providing for a five fold increase in emitter area and emitter power for a given emitter temperature.
The fan of the present unit provides benefits beyond enhanced cell cooling. As the fuel/air mixing tube is contained in the cylinder, the fan provides for an increase in combustion air flow, which in turn allows for an increase in fuel flow and results in increased emitter temperature. By increasing the emitter temperature, substantial increase in output electric power is realized.
The example of the present unit, including the TPV assembly, the cylinder and the fan at the base of the cylinder, provides for electric power outputs in the range of 20 watts. The fan itself consumes minimal electric power, in the range of 1 watt.
While the present forced air cooled TPV generator has a wide range of possible embodiments and applications, three preferred embodiments are immediately useful.
In one preferred embodiment, a fuel cylinder is located in the cylindrical enclosure beneath the fuel/air mixing tube and above the fan. The diameter of the fuel cylinder is preferably significantly less than the enclosure diameter, such that air from the fan passes upward around the fuel cylinder and past the fins for cell cooling. A handle is provided on the cylindrical enclosure for rendering the TPV generator easily portable. In a 20 watt version of that TPV generator including one pound of fuel, the approximate dimensions of the unit are 6 inches in diameter and 12 inches in height.
In a second preferred embodiment of the present invention, the TPV generator is secured to the inner surface of an exterior wall by a mounting bracket. A fused silica (glass) shield surrounds the emitter assembly and extends upward. The shield functions as a chimney and leads to a small exhaust hood which routes exhaust gases outward through an opening in the exterior wall. The small exhaust hood, which is preferably approximately 2 inches high and 4.5 inches wide, is hinged at its top to the wall, thereby allowing the hood to be easily lifted for igniting the generator.
A third preferred embodiment of the present generator is configured for use in recreational vehicles, sailboats, mountain cabins and other small living spaces where a large fuel (e.g., propane) cylinder is already present. A fuel line from the fuel source leads directly to the fuel/air mixing tube, thereby eliminating the need for housing a fuel cylinder in the generator enclosure. Other features, including a wall mount, chimney and exhaust hood may also be included. The removal of the fuel cylinder from inside the enclosure renders the TPV generator much more compact. The resultant wall mounted TPV generator is preferably only about 12 inches high from the bottom of the fan to the tip of the exhaust hood. That embodiment generates heat and light in addition to 20 watts of electric power and is easy to install.
In any of the embodiments the chimney and exhaust hood may be configured to remove only the combustion exhaust. In those cases the blown air that cools the fins, heats the enclosure. The blown air also circulates over the exhaust hood, transferring heat from the hood to the room. In embodiments where it is desired not to add heat to the room, the exhaust hood also conducts the blown air out of the room.
A thermophotovoltaic generator apparatus includes a thermophotovoltaic converter assembly, a fan positioned for generating an updraft from beneath the assembly, and a housing for enclosing the fan and the assembly. The assembly preferably includes a fuel source, a fuel/air combustion chamber connected to the fuel source for allowing hydrocarbon combustion. An infrared emitter in the combustion chamber emits infrared radiation when heated by combustion gases resulting from the hydrocarbon combustion in the combustion chamber. A receiver positioned around the infrared emitter receives the infrared radiation and converts the radiation to electric power. A heat shield positioned between the receiver and the infrared emitter prevents exhaust gases from contacting the receiver. The infrared emitter is preferably perforated, and the heat shield is preferably a fused silica heat shield that is t
Custard Paul D.
Fraas Lewis M.
Williams Douglas J.
Chapman Mark
JX Crystals Inc.
Narasimhan Meera P.
Wray James Creigton
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