Near-field thermionic-thermophotovoltaic energy converters

Abstract

We proposed a model of the coupling system composed of a vacuum thermionic power generator and a near-field thermophotovoltaic cell. The coupling system can simultaneously convert electrons and photons into electricity. Expressions for the efficiency and power output density of the coupling system are analytically derived. The influences of external and internal irreversible losses on the performance of the coupling system are discussed. The working temperature of the anode is calculated through an energy balance equation. The maximum efficiency and power output density of the coupling system are found to be obviously larger than those of a single vacuum thermionic power generator or a near-field thermophotovoltaic cell. Some parametric selective criteria are supplied and the boundaries of optimized parameters are determined. The results obtained here will be helpful to the optimal design and actual development of near-field thermionic-thermophotovoltaic cells.