Maximum conversion efficiency of thermionic heat to electricity converters using pure tungsten as the emitter: A theoretical review

Abstract

In this work, analysis of the efficiency of a thermionic converter of heat to electricity is made in terms of the potential difference between the top of the potential barrier in the inter electrode space and the Fermi level of the
emitter, VE the potential drop across a load impedance connected in series to the converter, VL and the potential drop to the necessary electrical connection to the collector, VC. An expression for the maximum conversion efficiency has been developed. The expression yields optimum values of load impedance, collector lead geometry and emitter work function in terms of collector voltage, emitter temperature, effective emmissivity of the emitter for both the theoretical and practically obtained Richardson- Dushman constant for a Pure Tungsten, W metal surface. The results show that low value of collector voltage is required for a high efficiency; low radiation heat loss is required for a high conversion efficiency and relatively low values of emitter work function are required for maximum conversion efficiency at ordinary emitter temperature.