Thermionic energy conversion (TEC) is the direct conversion of heat to electricity by the thermal (thermionic) emission of electrons from a very hot surface. Though historically pursued primarily for electricity production from nuclear sources in space applications, it has the potential to be used terrestrially for waste heat, solar, or nuclear energy conversion. To meet this objective, however, TEC must be enhanced to operate more efficiently at lower temperatures than historically possible. Microplasma thermionic energy conversion occurs when a microplasma (ionized gas) is ignited between a thermionic diode with an electrode spacing ~1-20 micrometers. This mode of operation could enable operation in inert gases, at near atmospheric pressures, and at lower temperatures - all necessary features for practical terrestrial application. Understanding of the fundamental interaction between thermionic emission and microplasmas will be advanced by this research in order to pave the way for microplasma-TEC devices. First principles theory and simulations will be used to reveal the inter-dependence between a microplasma and thermionic emission, and experiments will be conducted to confirm the enhancement of thermionic emission by a microplasma necessary to realize improved energy conversion efficiency. Carbon-based electrodes, including diamond and carbon nanotubes, will be synthesized using a microplasma jet processing technique and used as electrodes in microplasma-TEC experiments. In addition to the efficacy of microplasma-TEC being established by this research, fundamental studies will also advance the basic understanding of plasma/electrode coupling, where there are persistent questions that affect a wide variety of technologies from highintensity discharge lamps to arc-based materials deposition.
Direct thermal-to-electrical energy conversion can be used to convert solar, nuclear, and waste heat to electricity, and energy conversion technologies will play an important role in creating a more energy efficient and independent nation. The discoveries made by this research will lay the foundation for practical, terrestrial TEC devices that could become an essential part of the energy economy, greatly impacting energy security in the United States. Further, undergraduate students from underrepresented minorities will be engaged in this research early in their careers, creating a more effective undergraduate research experience and increasing the number that achieve graduate science and engineering degrees. Using a service-learning approach, outreach to the local K-8 youth in the community will be led by these undergraduates including the creation of a plasma exhibit for a community-wide science festival and a targeted, interactive outreach program on environmental science for middle school students. These undergraduate students will be exposed to the fulfilling nature of outreach and also inspire a large number of K-8 youth toward science and engineering, creating a perpetuating educational cycle in which each generation fosters the inspiration, excitement, and development of the next generation.
