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. In preferred embodiments of the present invention, the cobalt oxide doped emitter strongly emits infrared radiation in a wavelength interval between about 1 and 2.1 microns. The photovoltaic cells of the receiver are preferably of Ge cells, GaSb cells, In(1-z)Ga(z)As cells and Ga(1-x)In(x)Sb(1-y)As(y), where x and y range between 0 and 0.2 and z ranges between 0.3 and 0.7. A silica heat shield may be positioned between the emitter and the receiver when combustion heat sources are used for confining the combustion byproduct gases.
A method and structure for heat transport, cooling, sensing and power generation is described. A photonic bandgap structure (3) is employed to enhance emissive heat transport from heat sources such as integrated circuits (2) to heat spreaders (4). The photonic bandgap structure (3) is also employed to convert heat to electric power by enhanced emission absorption and to cool and sense radiation, such as infra-red radiation. These concepts may be applied to both heat loss and heat absorption, and may be applied to heat transport and absorption enhancement in a single device.
A method for powering a vehicle comprises, in one embodiment, receiving infrared radiation emitted as heat from a roadway surface, and converting energy of the infrared radiation to a form of energy that is useful for providing power to the vehicle. In another embodiment, a method for powering a vehicle comprises: insulating a first region of a road's surface with a material that transmits visible light but blocks infrared radiation, while leaving a second region of the surface uninsulated; conducting heat from portions of the road beneath the first region, to the second region; receiving infrared radiation emitted as heat from the second region; and converting energy of the infrared radiation to a form of energy that is useful for providing power to the vehicle.
The invention teaches a method and apparatus for the generation of electric power by recycling the heat generated by various industrial processes. Thermophotovoltaic cells are used to convert the heat radiated from the industrial apparatus used to perform the various processes into electricity. Arrays of thermophotovoltaic cells placed around the apparatus, which may optionally be surrounded by an infrared (IR) emitter. The emitter serves to convert the IR radiation of the initial heat source into IR radiation having a more uniform wavelength. The cell arrays are spaced outward from a convection barrier tube and a short pass filter that may be placed around the IR emitter. A heat sink may be placed outside of the perimeter formed by the array of thermophotovoltaic cells, this serves to cool the thermophotovoltaic arrays, and also increases the power density of the cells, which in turn improves the power generation capacity of the array.
A composite emitter (100) for a thermophotovoltaic cell and other applications, and a method of forming the composite emitter. The composite emitter includes a substrate (102) and a selective emitter layer (104) composed of at least one substantially pure ceramic oxide selective emitter material applied to the substrate using a thermal spraying method. The substrate is preferably made of a durable material such as a silicon-based material or a refractory metal oxide. In one embodiment, the selective emitter layer may be composed of two or more selective emitter materials. In another embodiment, the composite emitter may further include a reflective metal layer (106). The method includes providing a substrate and plasma spraying one or more selective emitter materials onto the substrate to a thickness of between about 10 microns and about 400 microns to form the selective emitter layer. Preferably, the selective emitter layer has an in situ density of between 80% and 95% of the bulk density of the selective emitter material used.
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. A modular photovoltaic converter circuit is complete with series connected low bandgap filtered cells, a heat spreader and high current-carrying mirror-shielded interconnects. An efficient but lightweight and short heat exchanger regenerator is fairly easy to fabricate by inserting an array of angled vanes through slits in a simple cylinder. One regenerator is formed with integrally extruded or machined fins on a high temperature SiC composite.
