Characteristic Research Of Selective Emitters For Thermophotovoltaic System

In the field of deep space exploration, it’s difficult to receive the sun’s rays, however, using radioisotope power systems can provide a stable power source for deep space detector. In this article, the characteristics of selective emitter of Thermophotovoltaic system will be analyzed and researched.Firstly, it is known that the band gap of erbium atom matching the forbidden band of GaSb photovoltaic cells well. On the basis of the theories of radiative transfer and energy balance, combined with the spectral analysis method for wavelength of radiation, the theoretical research of coating emitter is studied to obtain the optimization of coating thickness. The theoretical research has shown the excellent selective radiation characteristics which is based on erbium, it is suitable as a coating material for selective emitters. In the working temperature of 1500K, the emissivity of the coating emitter in wavelength of 1500nm has decreased as the increasing of the substrate’s emissivity, and increased with the increasing of coating thickness; and the spectrum efficiency of the coating emitter in wavelength of 1500nm is higher of the lower emissivity of the substrate. The maximum spectrum efficiency is showed in the selective emitter which coating thickness between 0.2 to 0.3 mm.Secondly, using the sol-gel method and the thermal chemical reaction method to prepare the coating emitters respectively, the research of sol-gel method shows that when the slurry prepared with the sol of 5% solid content and the alumina fiber of 40% mass fraction can obtain the sample with better surface morphology and can well combined with the substrate of coating samples; The research thermal chemical reaction method shows that the samples prepared with adding PEG2000 as dispersant and 5% PVA solution as binder, the adding amount between 5% to 6% and 50% of powder quality, respectively, with the final sintering temperature of 1500 degrees Celsius. The research of powder molding method of sample preparation shows that when adding 7% PVA solution as binder with adding amount between 9% to 11%, and the molding pressure is 8MP and ceramic thickness between 2.5 to 3.5 mm, the ceramic samples has had better radiation performance.Finally, measuring the emissivity of the coating preparations and the ceramic preparations, it shows that the spectrum efficiency of coating samples is higher when erbium content between 25% to 35%, among these samples, the highest efficiency is 16%; And the spectrum efficiency of ceramic samples is higher when erbium content between 30% to 35%, among these samples, the highest efficiency is close to 20%. Among all these samples, the average emissivity between 1.4 to 1.6 microns are greater than 0.3, and the highest can reach 0.44.