OCR Text |
Show electricity. Optical filters are generally used to minimize the unusable out-of-band radiant energy striking the P V cells. The portion of the energy absorbed by the P V cells that is not converted to electricity must be removed as waste heat. A recuperator is necessary to boost system efficiency by transferring the unused energy in the exhaust stream to the incoming combustion air. High efficiency is a Fiaurel: TPV system components primary goal of component design. For clarity, the following efficiencies are defined: PC A Efficiency: ePCA = Qelectric + Qemtter BER Efficiency: eBER = Qemtter + Qfuelinput System Efficiency: e5ysum = £PCA xeBER xerurusmc Qem.tter is defined as the net energy per unit time leaving the emitter surface. £p_-asitic is the electrical output used to power system components such as pumps, fans, fuel heaters, etc. Combustion efficiency refers to the completeness of combustion of the fuel to C O : and H2O. High C O emissions and soot emissions indicate less than 1 0 0 % combustion efficiency. Burner Design The design of the 500-watt portable power system is shown in Figure 2 and is detailed in earlier work (1,2). A cylindrical P C A surrounds a cylindrical B E R . The B E R incorporates a fuel feed system and vaporizer inside the annular recuperator. The burner in the center of the unit mixes preheated air and vaporized fuel to form a stable flame inside the radiator in the upper half of the unit. Hot combustion gas flows around the open end of the radiator, and through the annulus between the radiator and the emitter enclosure. O n the lower half of the unit, the hot gases enter a counter-flow heat exchanger (recuperator) to raise the temperature of the combustion air. The design goals for the TPV burner are: • Elevate the emitter temperature over 2400°F • Produce a uniform emitter temperature • Achieve reliable long-term burner operation using diesel fuel ^ 5 = = 5 5V Burner 2000°K, 3140°F Emitter 1700°K, 2600°F Filter Exhaust PV cell 2 |