H.K. Kim, T.Y. Kim, O.C. Kwon
Keywords: combustion, thermophotovoltaic, photonic crystal structure
Summary:The demand for high-performance portable power sources is recently enhanced due to the increasing use of electronic devices. Portable power systems using the combustion of hydrocarbon fuels have been considered as a novel alternative to replace current secondary batteries due to the features of fast charging and high energy density. A thermophotovoltaic (TPV) power generating system converts thermal energy to electricity through photons. Primary elements of the TPV systems are a heat source, an emitter and photovoltaic cells (PVCs). Unlike other power generating devices using combustion, the TPV systems have simple structure and high efficiency without friction loss by moving parts. To enhance the efficiency of the TPV systems, there are several important design factors: stable burning in the combustor as a heat source, effective radiation from the emitter into PVCs and spectral matching between the emitter’s thermal radiation and the absorption wavelength of PVCs. Photonic crystal structure which can be applied on the emitter surface allows the precise control of electromagnetic wave properties and enlarges the photonic bandgap. In this study, the performance of the combustor that was developed for TPV systems in a previous study is experimentally evaluated. To estimate the combustor performance, combustion stability limits and temperature distribution along the emitter wall surface are measured. Two stability limits have been observed: the flashback limit and the blowout limit. With increasing fuel flow rate and stoichiometric ratio, the flame stability limits are extended. The average temperature of the emitter wall is high enough to obtain proper performance for a TPV system. Spectral emissive power and electrical power which are measured varying the distance from the emitter to a single PVC, to evaluate performance when the photonic crystal structure is applied on the emitter, indicate that they are enhanced with the photonic crystal structure compared with the conventional emitters.