Effects of heat transfer on characteristics of thermionic energy converter

Abstract

Photon enhanced thermionic emission (PETE) is a new concept in solar energy conversion, combining thermal and photovoltaic carrier excitations with thermionic emission. A solar-power-driven thermionic energy converter operates by illuminating the solar light condensed by a large-scale Fresnel lens to convert heat energy into electrical energy. By enhancing the efficiency of converting solar radiation into the emitter internal energy, the output power and efficiency of the thermionic energy converter can be greatly improved. In this study, using numerical simulations, the effects of emitter temperature and output characteristics on a thermionic energy converter were investigated. The results showed that the higher rate of the heating power represented the higher temperature of an emitter, as well as output current density, and efficiency. In addition, by reducing the diameter of a collector and thermal conductivity of insulation materials, or increasing the diameter of emitter, the temperature of emitter, output current density, and efficiency could be notably improved. It is also worth mentioning that the main factor that affected the emitter temperature in the process of heat transfer was heat conduction between solids. In conclusion, adequate illumination, reasonable size of collector and emitter, as well as appropriate insulation measurements could efficiently improve the output characteristics of thermionic energy converter.