Increasing the Efficiency of a Thermionic Engine Using a Negative Electron Affinity Collector

Report No. ARL-RP-0470
Authors: Joshua R. Smith
Date/Pages: January 2014; 14 pages
Abstract: Most attention to improving vacuum thermionic energy conversion device (TEC) technology has been on improving electron emission with little attention to collector optimization. A model was developed to characterize the output characteristics of a TEC where the collector features negative electron affinity. According to the model, there are certain conditions for which the space charge limitation can be reduced or eliminated. The model is applied to devices comprised materials reported in the literature, and predictions of output power and efficiency are made, targeting the sub-1000K hot-side regime. By slightly lowering the collector barrier height, an output power of around 1 kW, at e20% efficiency for a reasonably sized device (~0.1 m2 emission area) can be achieved. VC 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.4826202]
Distribution: Approved for public release
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Last Update / Reviewed: January 1, 2014