Abstract: A small and light cylindrical thermophotovoltaic generator uses gaseous fuels, a counter flow heat exchanger, regenerator and low bandgap photovoltaic cells. In the fuel injection system, with preheated air from a recuperator, fuel combustion begins immediately when the fuel and air first meet. A hot and compact burn results from complete and rapid fuel and air mixing. A venturi necks down the air flow, and a chemically etched jet shim disk creates over 150 small fuel jet streams. The emitter geometric configuration provides good hot gas energy transfer to the IR emitter. Four alternate emitter configurations accomplish the good heat transfer. One emitter is a composite SiC with integrally formed internal fins which extend into the combustion chamber. The photovoltaic converter assembly has good spectral control, good high rate but lightweight heat removal and high current-carrying capability, while maintaining low parasitic IR absorption.

Abstract: Thermophotovoltaic (TPV) electric power generators have emitters with infrared (IR) outputs matched with usable wavelengths for converter cells. The emitters have durable substrates, optional refractory isolating layers, conductive refractory metal or inter-metallic emitter layers, and refractory metal oxide antireflection layers. SiC substrates have tungsten or TaSi2 emitter layers and 0.14 micron ZrO2 or Al2O3 antireflection layers used as IR emitters for GaSb converter cells in TPV generators.

Abstract: A three-layer solid infrared emitter having a spectral output matched to low bandgap TPV cells is provided. The three layers include inner and outer layers, and a core layer between the inner and outer layers. The core layer is of solid fiber reinforced undoped refractory oxide material. The inner layer of siC material absorbs radiation from the radiator, the core layer conducts heat from the inner layer to the outer layer. The core layer is a strengthening layer forming a diffuse reflector for stopping a shine-through of long wavelength radiation from the inner layer thereby preserving spectral selectivity in the outer layer. The emitter material may be cobalt doped, nickel doped, or combination of Ni or Co doped refractory oxides with erbia or a thin erbia selective emitter layer.

Abstract: A TPV cell apparatus with a base region of GaSb crystals. The GaSb crystals are of varying orientations and joined at grain boundaries. A surface region is provided on the GaSb crystals. The GaSb crystals are Tellurium doped N-type GaSb and the surface region is thin Zinc doped P-type GaSb cells. The surface region faces an infrared source. A bus region is connected to a metal grid connected which is in contact with the surface region of the cell. A continuous metal layer is in contact with the GaSb crystals. A multilayer coating is provided on a front side of the cell. The multilayer coating forms an infrared filter for transmitting convertible infrared energy to the cell and for reflecting as much of non-convertible infrared energy back to the IR source as possible. A TPV generator may be provided with the TPV cells.

Abstract: The TPV generator unit insert has air circulation fans that supply air for both TPV cell cooling and heat transfer and room air circulation. Combustion air is supplied by a blower and mixed with natural gas or propane in a mixing chamber. Fuel and air mixing is enhanced by injecting the fuel counter to the air flow in an air supply tube within the mixing chamber. The fuel and air mixture is then injected into a combustion chamber and burned. The hot combustion gases then heat an IR emitter. Infrared radiation from the emitter is then incident on TPV cells, where electricity is produced. The hot by-product gases then transfer heat to the circulating room air in an upper plenum prior to exiting the room through the flue pipe. The yellow-orange glow from the emitter is visible through a front glass window, which then produces a very aesthetically pleasing effect. The rectangular unit is designed to include at least two cell panels at front and at the back.

Abstract: A thermophotovoltaic generator apparatus includes a thermophotovoltaic converter assembly and a cooling fan positioned beneath the assembly for generating an updraft around the assembly. A fuel source is connected to the converter assembly by a fuel line. A new control system, which may include a non-metallic electrode for flame sensing and, regulates flow of fuel from the fuel source to the converter assembly. A housing encloses the cooling fan and the converter assembly. The converter assembly includes a fuel injector cup having a fuel inlet connected to the fuel source and a fuel outlet. A combustion chamber is positioned above the cup for receiving fuel from the fuel outlet and for allowing hydrocarbon combustion. A combustion fan is positioned between the cup and the cooling fan for generating an updraft into the combustion chamber. An infrared emitter is positioned around the combustion chamber for emitting infrared radiation when heated by combustion gases resulting from the hydrocarbon combustion.

Abstract: A thermophotovoltaic generator includes an infrared cobalt oxide doped refractory ceramic emitter having a broad power band region which is matched with the energy conversion band of a low bandgap thermophotovoltaic cell receiver. The generator is provided with a heat source or is constructed for mounting on a heat source or for holding a heat source, such as a radioisotope. The generator is compatible with any heat source, including, but not limited to, a hydrocarbon flame, nuclear reactors, and radioisotopes. The emitter is made of a refractory ceramic material such as cobalt oxide doped alumina or magnesia. The refractory compound of the emitter is preferably doped with a small number of substitutional ions to create a material for emitting near blackbody radiation in a wide wavelength band above a threshold energy level and a minimal amount of radiation at wavelengths longer than the threshold level.

Abstract: A hydrocarbon fired room heater with thermophotovoltaic electric generator has high power outputs without cell overheating and failure. The unit includes a burner for generating a hydrocarbon flame, a catalytic emitter positioned in the hydrocarbon flame for emitting infrared radiation when heated by the flame, a receiver positioned around the catalytic emitter for receiving the infrared radiation and for converting the infrared radiation to electric power, an exhaust chimney positioned adjacent the receiver, and air draw ducts having uncovered tops, upper parts, and lower parts and positioned adjacent the chimney and the receiver for directing heat up and away from the receiver. The chimney is positioned directly above the top edge of the receiver, and the air draw ducts are positioned adjacent the receiver and chimney for defining air draw channels. Each air draw duct is a generally U-shaped member having a pair of side walls and a boundary wall extending between the side walls.

Abstract: A thermophotovoltaic generator provides a greater power output while maintaining a compact, simplistic structure. The generator includes a burner having adjustable fuel and air flows, an infrared radiation emitter suspended above the flame nozzle of the burner and a cylindrical receiver surrounding the emitter. The emitter is a conical infrared emitter connected to the burner by wires. The emitter is positioned above the burner nozzle such that the emitter is immersed in the generated hydrocarbon flame. The emitter material catalyzes combustion on its surface. Infrared energy radiated by the heated emitter is collected by a cylindrical receiver that completely encircles the emitter. The receiver includes a flexible circuit having an inner surface, an outer surface, opposite ends, top and bottom edges and bending regions. First and second rows of low bandgap cells are connected to the top and bottom edges of the circuit, respectively, away from the bending regions.

Abstract: A thermophotovoltaic generator includes a stainless steel heat exchanger, a ceramic heat exchanger, a mixing chamber, a combustion chamber, an igniter, an infrared radiation emitter with counterflow, and an array of thermophotovoltaic cells surrounding the emitter and tube. The generator possesses both high conductance for the combustion gases and efficient heat transfer from the hot combustion gases to the emitter. The thermophotovoltaic cells have an IR response at least out to 1.7 microns and are fitted with simple dielectric filters. The emitter is an SiC spine disc emitter that is surrounded by at least one fused silica heat shield. Preferably, the thermophotovoltaic cells are GaSb cells, the infrared radiation emitter is a SiC blackbody emitter, and the dielectric filter is designed to transmit for wavelengths less than 1.7 microns and to reflect wavelengths between 1.7 and 4.0 microns. The filter can transmit again beyond 4.

Abstract: Electric power generator has linear arrays of thermophotovoltaic cells spaced outwardly from a tubular IR emitter. Hot combustion products flow downward from a combustion zone between a central pillar and the IR emitter, and then upward between the emitter and a tubular IR transparent window. The cell arrays are spaced outward from a convection barrier tube and a short pass filter. A burner assembly at the top of the pillar has an alternating arrangement of accelerating air channels with large openings to the air supply and slowing mixing channels with small openings to the air supply. Radial fuel channels connect the central fuel supply with the peripheral mixing channels. Release of accelerated air creates turbulence in the combustion zone where the air and fuel further mix and are ignited. A cavity in the pillar supplies liquid fuels which are atomized by ultrasonic energy from a central rod. The atomized liquids are released through small holes into the combustion zone.

Abstract: A novel low-cost solar photovoltaic module using line-focus lenses and photovoltaic receivers incorporating high-performance photovoltaic cells is described. It consists of an array of linear arched Fresnel lenses with a linear photovoltaic cell receiver located along the focal line of each lens. The lens consists of a protective superstrate with molded silicone Fresnel grooves on its inner surface. The photovoltaic cell receiver consists of high efficiency cells interconnected in a string with a solid secondary optical element adhesive bonded to the cells. The entrance aperture of each secondary optical element is rectangular in shape and the optical secondaries are butted up against each other in a line to form a continuous entrance aperture along the focal line. In addition to providing more concentrated sunlight, the solid optical secondaries shield the cells against radiation damage.

Abstract: In the present invention, we describe a simple ceramic gas burner for use in a cylindrical thermophotovoltaic generator in which the burner and IR emitter section consist of three concentric ceramic tubes, with the largest tube being the outer exhaust tube. Fuel and a small amount of primary air are injected from the bottom of the smallest tube and exit at the top of the infrared emitter section where they combine with secondary air coming down through a second ceramic tube with an intermediate diameter open at the bottom of the emitter section. Ignition is initiated at the bottom of this air injector tube. After ignition, combustion then moves up to the top of the fuel injector tube. The exhaust gases then pass down from the top of the emitter section inside the mid diameter tube to the bottom end of the emitter section and then back up between the mid diameter tube and the outer tube to the top of the emitter section.

Abstract: In the present invention, a thermophotovoltaic electric power generator is described. It contains low bandgap photovoltaic cells sensitive in the infrared out to at least 1.7 microns and a broadband infrared emitter with a shortpass IR filter located between the cells and the emitter to recycle the nonuseful IR back to the emitter. Several specific IR filter designs as well as filter/cell and filter/emitter combinations are described all of which improve the overall generator conversion efficiency.

Abstract: In the present invention, we describe a generic interchangeable thermophotovoltaic (TPV) receiver assembly that can be incorporated in a variety of large or small TPV generators. Our TPV receiver assembly contains low bandgap TPV cells series connected along a line on a thermally conductive circuit carrier. The circuit carrier is directly bonded to a parallel cooling channel. The cooling channel also supports and cools parallel mirror elements which concentrate infrared energy efficiently to the series connected cell string. The cell interconnections are hidden under the mirror elements. The mirror elements, cooling channel, circuit carrier, and series connected cell string together form a linear TPV receiver assembly with + and - terminals on either end. Identical receiver assemblies can be packed side by side each facing an infrared emitter in a large variety of TPV generator configurations.

Abstract: A photovoltaic (PV) cell with a single pn-junction is disclosed that is capable of functioning as both a current source and a bypass diode. The photovoltaic cell is made of material that has a low bandgap energy, 1.0 eV, or less. One version of the PV cell is formed of a GaSb wafer doped with Te to form an n-region; the Te concentration is between 6 and 10.times.10.sup.17 atoms/cm.sup.3. Multiple PV cells of this invention can be connected in series or in parallel or in tandem in a primary-booster tandem pair to form a circuit without the requirement of protecting the individual cells of the circuit with a separate bypass diode.

Abstract: Multiple low bandgap GaSb photovoltaic cell strings are mounted around the perimeter of a cylinder in parallel with the cylinder axis. These cell strings face radially inward and receive infrared (IR) radiation from a ceramic axial emitter and efficiently convert this radiation into DC electric power. Linear reflectors are associated with each cell string and serve to concentrate IR energy into the photovoltaic cells or to return it to the emitter. The ceramic emitter is heated from the inside by hydrocarbon combustion. A uniform temperature along the length of the emitter is maintained by staged addition of fuel in a special burner design. Regenerative air heating is also inherent in the burner design increasing its efficiency. Air for the combustion is supplied by a blower. Sliding contacts to the rotating shaft on the blower can be used for DC to AC conversion. The cell strings are cooled through a compact closed cycle convective liquid cooling loop.

Abstract: A novel low-cost solar photovoltaic module using line-focus lenses and photovoltaic receivers incorporating high-performance tandem cell-stacks is described. It consists of an array of linear arched Fresnel lenses with a linear tandem-cell receiver located along the focal line of each lens. The lens consists of a glass protective superstrate with molded silicone Fresnel grooves on its inner surface. The tandem cell receiver consists of high efficiency cell-stacks interconnected in a string with a secondary optical element adhesive bonded to each cell-stack. The entrance aperture of each secondary optical element is rectangular in shape and the optical secondaries are butted up against each other in a line to form a continuous entrance aperture along the focal line. Each optical secondary provides for sunlight concentration in two dimensions so that its base bonded to the cell-stack is smaller in both the direction along the focal line as well as perpendicular to it.

Abstract: Zinc diffusion procedures applicable for large scale manufacture of GaAs and GaSb cells used in tandem solar cells having a high energy conversion efficiency. The zinc doping and carrier concentration are restricted to be less than about 10.sup.19 /cm.sup.3 to obtain good light generated carrier collection and hence good short circuit currents. The amount of zinc that is available for diffusion during a drive-in heating step is restricted. Confinement of zinc and arsenic vapors during the heating step may be effected by use of a proximity source wafer or by an encapsulant layer. The zinc diffusion of GaSb is obtained by a homogeneous light diffusion that is followed by a patterned heavy diffusion to give low ohmic contact with the grid lines. Texture etching of the GaSb solar cell is also compatible with this diffusion process.

Abstract: A photovoltaic cell array involving rows and columns of tandem or stacked solar cell units composed of GaSa/GaSb associated with a radiation collector have produced measured energy conversion efficiencies of 31% AMO. The booster GaSb cell is manufactured by a process which produces a p-type diffusion region within an n-type substrate, has improved energy conversion efficiencies and can be mounted as part of a four terminal stacked solar cell unit.